Research Article Mechanisms of Laser-Induced Reactions of ...downloads.hindawi.com/journals/ijp/2014/874102.pdf · Research Article Mechanisms of Laser-Induced Reactions of Stacked

Research ArticleMechanisms of Laser-Induced Reactions ofStacked Benzene Molecules A Semiclassical DynamicsSimulation and CASSCF Calculation

Kunxian Shu1 Jie Zhao1 Shuai Yuan1 Yusheng Dou2 and Glenn V Lo2

1 Institute of Bioinformatics Chongqing University of Posts and Telecommunications Chongqing 400065 China2Department of Physical Sciences Nicholls State University PO Box 2022 Thibodaux LA 70310 USA

Correspondence should be addressed to Shuai Yuan yuanshuaicqupteducn and Yusheng Dou yushengdounichollsedu

Received 8 May 2014 Accepted 27 June 2014 Published 27 October 2014

Academic Editor Fuli Li

Copyright copy 2014 Kunxian Shu et al This is an open access article distributed under the Creative Commons Attribution Licensewhich permits unrestricted use distribution and reproduction in any medium provided the original work is properly cited

The response to ultrashort laser pulses of two stacked benzene molecules has been studied by semiclassical dynamics simulationtwo typical pathways were found following excitation of one of the benzene molecules by a 25 fs (FWHM) 47 eV photon With afluence of 4049 Jm2 the stacked molecules form a cyclobutane benzene dimer the formation of the two covalent bonds linkingtwo benzenes occurs asynchronously after the excimer decays to electronic ground stateWith a fluence of 4326 Jm2 only one bondis formed which breaks about 50 fs after formation followed by separation into the two molecules The deformation of benzenering is found to play an important role in the bond cleavage

1 Introduction

The photocycloaddition reactions of unsaturated doublebond complexes are of theoretical interest because thesereactions are involved in DNA photodamage [1ndash4] andorganic synthesis [5 6] The best known examples are the[2 + 2] photocycloaddition (forming either cyclobutanes orfour-membered heterocycles) and excited state [4 + 4] cyclo-additions that produce cyclooctadiene compounds

Although quite (thermally) stable benzene moleculescan become quite reactive when being photoexcited theycan be transformed to benzvalene [7 8] and fulvene whenbeing excited to the first singlet (119878

1) excited state or to

Dewar benzene [9 10] when being excited to the secondsinglet (119878

2) excited state Benzene can be involved in a

photocycloaddition reaction with an alkene molecule Thereactions can be classified into three categories [5 6] [2+ 2] (or ortho) [3 + 2] (or meta) and [4 + 2] (or para)photocycloadditions Photocycloadditions of benzene and analkene are usually triggered by the photoexcitation of thebenzene molecule If the 119878

1state of benzene is involved

only meta addition is allowed to occur in a concertedfashion according to molecular orbital symmetry rules [1112] The formation of ortho- and para-cycloadducts can be

interpreted as being due to (i) charge transfer processes(ii) nonconcerted mechanism and (iii) excitation to the 119878

2

state Clifford et al found [13] that for the benzene plusethylene system cycloadditions could take place from 119878

1state

without barrier through a conical intersection (CI) which iscommon to all three cycloadductsThis low energy CI resultsfrom the formation of one CndashC bond between benzene andethylene Their subsequent studies [14] suggest that CI seambetween 119878

1and 119878

0could control chemical selectivity in the

photocycloaddition of benzene and ethyleneCycloadditions [4 + 2] and [4 + 4] are also observed

between polycondensed aromatic compounds such as naph-thalene anthracene and their derivatives The [4 + 2]cycloaddition (photo-Diels-Alder reaction) [15ndash18] is fre-quently observed with naphthalene derivatives [4 + 4]photocycloadditions are often observed in two-arene systemswhich are connected by a saturated bridge (such as ndashCH

2ndash

CH2ndashCH2ndash or ndashCH

2ndashOndashCH

2ndash) These bridge aromatic sys-

tems canundergo intramolecular [4 + 4] photocycloadditionsto form ldquobiplanemersrdquo inwhich the two120587 systems are stackedface-to-face [19]

To date the mechanism of cycloaddition among aro-matic ring compounds has not been clearly characterized

Hindawi Publishing CorporationInternational Journal of PhotoenergyVolume 2014 Article ID 874102 11 pageshttpdxdoiorg1011552014874102

2 International Journal of Photoenergy

Rogachev and coworkers [20] performed a series of calcula-tions involving benzene dimers in the ground state but nostudies have been made on the photochemical dimerizationof benzene In this paper we studied photoinduced [2 +2] cycloaddition of two-benzene system by semiclassicaldynamic simulation The simulation results provide detaileddynamics features for this process from photon excitation tothe formation of product The geometry at the conical inter-section (CI) between the first singlet (119878

1) excited state and

ground state (1198780) was optimized by using completed active

space self-consistent field (CASSCF)method to comparewithother theoretical results

2 Methodology

21 Semiclassical Dynamics Simulation We carried outthe dynamics simulations using the semiclassical electron-radiation-ion dynamics (SERID) method In this approachthe valence electrons are calculated by the time-dependentSchrodinger equation while both the radiation field and themotion of the nuclei are treated by the classical approxi-mation A detailed description of this technique has beenpublished elsewhere [21 22] and only a brief review isgiven here The one-electron states are updated by solvingthe time-dependent Schrodinger equation at each time step(typically 005 femtoseconds in duration) in a nonorthogonalbasis

119894ℏ120597Ψ119895

120597119905= Sminus1 sdotH sdot Ψ

119895 (1)

where S is the overlap matrix for the atomic orbitals Thelaser pulse is characterized by the vector potential A whichis coupled to the Hamiltonian via the time-dependent Peierlssubstitution

119867119886119887(X minus X1015840) = 119867

0

119886119887(X minus X1015840) exp( 119894119902

ℏ119888A sdot (X minus X1015840))

(2)

here119867119886119887(XminusX1015840) is the Hamiltonian matrix element for basis

functions 119886 and 119887 on atoms at X and X1015840 respectively and 119902 =minus119890 is the charge of the electron

The Hamiltonian matrix elements overlap matrix ele-ments and repulsive energy are calculated with the density-functional based tight bonding (DFTB) method The DFTBmethod does have essentially the same strengths and lim-itations as time-dependent density-functional theory (TD-DFT) In particularly the bonding is well described butthe excited state energies are typically too low For thisreason we matched the effective central photon energy ofthe laser pulse to the relevant density-functional (rather thanexperimental) excitation energy and this should not adverselyaffect the interpretation of the results This model has beenused in biologically relevant studies such as photoinduceddimerization of thymine [23] and cytosine [24] via [2 + 2]photocycloaddition reaction All the results were found to beconsistent with experimental observations The formation ofcyclobutane pyrimidine dimer may provide good referencesfor [2 + 2] photocycloaddition of benzene

In this technique forces acting on nucleus or ions arecomputed by the Ehrenfest equation

119872119897

1198892119883119897120572

1198891199052

= minus1

2sum119895

Ψ+

119895sdot (

120597H120597119883119897120572

minus 119894ℏ1

2

120597S120597119883119897120572

sdot120597

120597119905) sdot Ψ119895minus120597119880rep

120597119883119897120572

(3)

where119880rep is effective nuclear-nuclear repulsive potential and119883119897120572= ⟨119883119897120572⟩ is the expectation value of the time-dependent

Heisenberg operator for the 120572 coordinate of the nucleuslabeled by 119897 (with 120572 = 119909 119910 119911) Equation (3) is obtained byneglecting the second and higher order terms of the quantumfluctuations119883 minus ⟨119883

119897120572⟩ in the exact Ehrenfest theorem

The present ldquoEhrenfestrdquo principle is complementary toother methods based on different approximations such asthe full multiple spawning model developed by the Ben-Nun and Martınez [25] The limitation of this method isthat the simulation trajectory moves along a path dominatedby averaging over all the terms in the Born-Oppenheimerexpansion [26 27]

Ψtotal

(119883119899 119909119890 119905) = sum

119894

Ψ119899

119894(119883119899 119905) Ψ119890

119894(119909119890 119883119899) (4)

rather than following the time evolution of a single potentialenergy surface which is approximately decoupled fromall theothers [26ndash29] (Here119883

119899and 119909

119890represent the sets of nuclear

and electronic coordinates resp and the Ψ119890119894are eigenstates

of the electronic Hamiltonian at fixed 119883119899) The strengths

of the present approach include retention of all of the 3119873nuclear degrees of freedom and the incorporation of the laserexcitation as well as the subsequent deexcitation at an avoidedcrossing near a conical intersection

22 CASSCF Multiconfigurational self-consistent field(MCSCF) is a method in quantum chemistry used to gene-rate qualitatively correct reference states of molecules incases where Hartree-Fock (HF) and DFT are not adequate(eg for molecular ground states which are quasidegeneratewith low lying excited states or in bond breaking situations)It uses a linear combination of configuration state functions(CSF) or configuration determinants to approximate theexact electronic wavefunction of an atom or molecule In anMCSCF calculation the set of coefficients of both the CSFsor determinants and the basis functions in the molecularorbitals are varied to obtain the total electronic wavefunctionwith the lowest possible energy This method can be consi-dered a combination of configuration interaction (where themolecular orbitals are not varied but the expansion of thewave function are varied) and Hartree-Fock (where there isonly one determinant but the molecular orbitals are varied)A particularly important MCSCF approach is the CASSCFwhere the linear combination of CSFs includes all that arisefrom a particular number of electrons in a particular numberof orbitals [30 31]

In this research the CASSCF ab initio computationsused a 12-electron and 12-orbital active space involving all

International Journal of Photoenergy 3

1998400 2

998400

3998400

4998400

5998400

6998400

1 23

456

374 A375 A

(a)

1

1

998400 2

2

998400

minus184∘C1ndashC2ndashC1

998400ndashC2998400=

(b)

Figure 1 Conformation and atomic labeling for the stacked benzene system

the 120587-orbitals of two benzene moieties All the geometrieswere optimized using the 6ndash31G(d) basis set in Gaussian09software package [32] To enhance calculation efficiency thegeometry at the decay time in simulation trajectory waspicked as the initial guess for CI optimization

3 Results and Discussions

From the reported experiments and ab initio calculations [33ndash37] the ground state of two stacked benzenes can have twonearly isoenergetic stable structures (T-shaped and slipped-parallel) and a less stable sandwich structure Electrostaticinteraction stabilizes theT-shaped structure while dispersionstabilizes the slipped-parallel structure The initial structureused in our calculations shown in Figure 1 is slipped parallelPrimed and unprimed labels are used to differentiate atoms inthe twomoleculesWe fixed the C

1ndashC1

1015840 andC2ndashC2

1015840 distancesbased on the geometries of [2 + 2] cycloaddition of hexatomicpyrimidine base [23 24]

To obtain ground state equilibrium configurations of twobenzene-system the simulationwas run at room temperaturefor 1000 fs an ldquoequilibratedrdquo geometry was taken at twentyequal time intervals over the 1000 fs time period and eachone was excited with the laser pulse to generate the trajec-tories A 25 fs FWHM laser pulse with a Gaussian profileand 47 eV photon energy was applied to the top benzenemoleculeThe selected photon energy matches the calculatedHOMO-LUMOenergy gapAfluence between 10 and 50 Jm2was randomly chosen for this study This fluence results inan electronic excitation but the forces produced do not breakany bonds The same laser pulse (Case 1 4049 Jm2 fluenceCase 2 4326 Jm2 fluence) is used for all 20 trajectories onerepresentative trajectory is reported in this paper The othertrajectories have similar results with the representative one

Figure 2 shows the HOMOminus1 HOMO LUMO andLUMO+1 for the equilibrated structure computed by the

DFTB approximation Based onWoodward-Hoffmann rulesthe formation of cyclobutane benzene dimer is a symmetry-forbidden reaction when both molecules are at the electronicground states or have one electron promoted from theHOMO to the LUMO However the reaction is symmetry-allowed when one molecule is at electronic ground state andanother one has one electron excited from the HOMO tothe LUMO These are evident from the molecular orbitaldiagram

Case 1 Formation of cyclobutane benzene dimerIn this section we present and discuss the simulation

results for the formation of cyclobutane benzene dimer Sixsnapshots taken from the simulation at different times areshown in Figure 3 Figure 3(a) represents electronic excita-tion of the top molecule in the equilibrated geometry at 0 fsThe excited molecule is distorted (Figure 3(b)) and movestoward the unexcited molecule (Figure 3(c)) The unexcitedmolecule is deformed due to the approach of the excitedmolecule (Figure 3(d)) At 770 fs C

1ndashC1

1015840 bond has beenformed (Figure 3(e)) The second bond C

2ndashC2

1015840 is formedat 1000 fs (Figure 3(f)) The structure of cyclobutane benzeneremains stable by the end of the simulation

The variations with time of the lengths of the C1ndashC2

and C1

1015840ndashC2

1015840 bonds and the distances of C1ndashC1

1015840 and C2ndashC2

1015840

are presented in Figure 4 Both C1ndashC2and C

1

1015840ndashC2

1015840 bondsare double bonds in the benzene molecules but becomesingle bonds in the benzene dimer The C

1ndashC2bond length

starts at about 14 A typical for a C=C double bond in anarene and then lengthens after the laser pulse is appliedThe excited benzene molecule approaches the unexcitedbenzene molecule and influences its structure as shown bythe increase in the C

1

1015840ndashC2

1015840 bond length after 200 fs Bothbond lengths increase to about 15 A after 600 fs because ofthe formation of the cyclobutane benzene dimer and theyremain at this length until the end of the simulation Both


(a) (b)

(c) (d)

Figure 2The diagrams of the (a) HOMOminus1 (b) HOMO (c) LUMO and (d) LUMO+ 1 of two stacked benzene molecules at the equilibratedgeometry

distances roughly remain at their initial values by 200 fs andstart to decrease thereafter The C

1ndashC1

1015840 distance decreasesto below 15 A at about 770 fs The C

2ndashC2

1015840 distance drops toabout 21 A at about 830 fs retains this value for 170 fs andthen drops to about 15 A at about 1000 fs This is the time forthe formation of the cyclobutane benzene dimer

The variations with time of the HOMOminus1 HOMOLUMO and LUMO+1 energies are shown in Figure 5 alongwith the time-dependent population of the orbitals Notethat the HOMO and HOMOminus1 are initially two identicalHOMOs of the benzene monomer molecules and the LUMOand LUMO+1 are initially two identical LUMOs of the twomolecules before laser excitation Figure 5(a) shows that thereis an abrupt change in the LUMO energy soon after applica-tion of the laser pulseTheHOMO and LUMO levels find oneclose approach with avoided crossings with the energy gapsbeing 004 eV at 770 fs Figure 5(b) shows that by the end ofthe laser pulse (which is 50 fs) about 1 electron is excited from

the HOMO to the LUMO consistent with the promotion ofone benzene molecule to an electronically excited state Thecoupling between the HOMO and LUMO as observed inFigure 5(a) leads to notable electronic transitions from theLUMO to theHOMOThis deexcitation eventually brings themolecule to the electronic ground state It can be seen fromFigure 6 that shortly after the coupling both the LUMO andHOMO levels move toward their initial values After 1000 fswhen the formation of the cyclobutane benzene dimer iscompleted these two energy levels only show fluctuationsabout constants values which are essentially the same as theirinitial values On the other hand the LUMO+1 andHOMOminus1levels only show slight variations during the reaction sincethey are the LUMO and HOMO of the unexcited moleculerespectively

Case 2 Formation and subsequent cleavage of only one 120590-bond between the two benzene molecules


h

(a) (b) (c)

(d) (e) (f)

Figure 3 Snapshots taken from the simulation of two stacked benzene molecules at (a) 0 (b) 300 (c) 700 (d) 740 (e) 770 and (f) 1000 fsThe molecule at the top is subjected to the irradiation of a 25 fs (fwhm) laser pulse with a fluence of 4049 Jsdotmminus2 and photon energy of 47 eVThis trajectory leads to the formation of cyclobutane benzene dimer and is briefly defined as Case 1

135

140

145

150

155

160

165

170

Bond

leng

th(A

)

0 500 1000 1500Time (fs)

C1ndashC2

C1998400ndashC2

998400

(a)

0 500 1000 1500

15

20

25

30

35

40

Time (fs)

Bond

leng

th(A

)

C1ndashC1998400

C2ndashC2998400

(b)

Figure 4The variations with time of (a) C1ndashC2and 119862

1

1015840ndashC2

1015840 bond lengths and (b) the lengths between the C1and C

2atoms and the C

1

1015840 andC2

1015840 atoms in two stacked benzene molecules in Case 1

The simulation results presented in this section show thatunder the laser irradiation two molecules form a 120590 bondbetween the C

1and C

1

1015840 atom sites However this 120590 bond onlyhas a lifetime of several ten femtoseconds and breaks shortlyafter it is formed

Six snapshots taken from the simulation at different timesare shown in Figure 6 One finds that at 930 fs two moleculeshave already formed a chemical bond between the C

1and

C1

1015840 atoms (Figure 6(d)) but the bondbreaks shortly thereafterand the two molecules move away from each other (Figures6(e) and 6(f))

The variations with time of the C1ndashC2and C

1

1015840ndashC2

1015840

bond lengths are plotted in Figure 7(a) The C1ndashC2bond

stretches in length soon after the laser pulse is applied dueto the excitation of electrons from the HOMO to LUMO andshrinks to its original length shortly after 900 fs when the


Orb

ital e

nerg

y (e

V)

minus2

minus3

minus4

minus5

minus6

minus7

0 500 1000 1500Time (fs)

HOMOLUMOLUMO+1

HOMOminus1

(a)

0

0 500 1000 1500

00

05

10

15

20

Elec

troni

c pop

ulat

ion

Time (fs)

HOMOLUMOLUMO+1

HOMOminus1

(b)

Figure 5The variationswith time of (a) orbital energies and (b) time-dependent populations of theHOMOminus1 HOMO LUMO and LUMO+1of two benzene molecules in Case 1

(a) (b) (c)

(d) (e) (f)

Figure 6 Snapshots taken from the simulation of two stacked benzene molecules at (a) 0 (b) 350 (c) 790 (d) 930 (e) 960 and (f) 1100 fsThe molecule at the top is subjected to the irradiation of a 25 fs (fwhm) laser pulse with a fluence of 4326 Jsdotmminus2 and photon energy of 47 eVThis trajectory results in the breaking of C

1ndashC1

1015840 bond and is briefly defined as Case 2

bond linking two benzene molecules is broken However theC1

1015840ndashC2

1015840 bond shows little variation since excitation A sharpjump up and down in the C

1

1015840ndashC2

1015840 bond length during 900to 1000 fs indicates the formation and breakage of the bondbetween two benzene molecules The variations with time ofthe C

1ndashC1


1015840 distances are plotted in Figure 7(b)for this process Both distances do not exhibit significant

changes until 400 fs but show a decrease afterwards due tothe interaction between two close molecules The C

1ndashC1

1015840

distance becomes about 15 A at about 930 fs indicating theformation of a CndashC 120590-bond Immediately after that thedistances between the C

1and C

1

1015840 atoms and the C2and C

2

1015840

atoms increase quickly because twomolecules separated fromeach other


130

135

140

145

150

155

160

0 500 1000 1500Time (fs)

Bond

leng

th(A

)

C1ndashC2

C1998400ndashC2

998400

(a)

0 500 1000 1500

15

20

25

30

35

40

Time (fs)

Bond

leng

th(A

)

C1ndashC1998400

C2ndashC2998400

(b)

Figure 7 The variations with time of (a) C1ndashC2and C

1

1015840ndashC2


2atoms and the C

1

1015840 andC2


Orb

ital e

nerg

y (e

V)

0 500 1000 1500Time (fs)

minus2

minus3

minus4

minus5

minus6

minus7

HOMOLUMOLUMO+1

HOMOminus1

(a)

0 500 1000 1500

00

05

10

15

20

Elec

troni

c pop

ulat

ion

Time (fs)

HOMOLUMOLUMO+1

HOMOminus1

(b)


The variations of the HOMOminus1 HOMO LUMO andLUMO+1 energies as a function of time are shown inFigure 8(a) and the time-dependent populations of theHOMO and LUMO are shown in Figure 8(b) An avoidedcrossing between the HOMO and LUMO levels is foundwith the energy gaps being 005 eV at 605 fs This avoidedcrossing leads to notable electronic transition from theLUMO to HOMO which eventually directs the excimer tothe electronic ground state

31 Discussion It is seen from Figures 4 5 7 and 8 thatthe formation of the C

1ndashC1


1015840 bonds has a crucial

impact on the nonadiabatic transition of the excimer to theelectronic ground state In addition the deformation of thebenzene ring especially the deformation of the benzene ringsat C1 C2 C1

1015840 andC2

1015840 atoms sites also has a notable influenceon the nonadiabatic transition of the excimer to ground stateTo understand this a comparison between the C

5ndashC6ndashC1ndash

C2and C

5

1015840ndashC6

1015840ndashC1

1015840ndashC2

1015840 dihedral angles and the energy gapbetween the HOMO and LUMO for each case is plotted inFigure 9 The deformation of the benzene ring at the C

1 C2

C1

1015840 and C2

1015840 atoms sites is represented by these two dihedralangles It is seen that for each case the minimum of theenergy gap is in line with a sharp rise of the C

5

1015840ndashC6

1015840ndashC1

1015840ndashC2

1015840


0

1

2

3

4

5

6En

ergy

(eV

)

0 300 600 900 1200 1500Time (fs)

40

30

20

10

0

minus10

minus20

minus30

minus40

minus50

Dih

edra

l ang

les(

∘)

ΔE(LUMO-HOMO)C5ndashC6ndashC1ndashC2 C5

998400ndashC6998400ndashC1

998400ndashC2998400

(a)

Ener

gy (e

V)

0

1

2

3

4

5

6

0 300 600 900 1200 1500Time (fs)

40

30

20

10

0

minus10

minus20

minus30

minus40

minus50

Dih

edra

l ang

les(

∘)



998400ndashC2998400

(b)

Figure 9 Comparison between the C5ndashC6ndashC1ndashC2and C

5

1015840ndashC6

1015840ndashC1

1015840ndashC2

1015840 dihedral angles and the energy gap between the HOMO and LUMOof two stacked benzene molecules (a) Case 1 and (b) Case 2

dihedral angle and a sharp dip in the C5ndashC6ndashC1ndashC2dihedral

angle suggesting that in both cases the deformation of thebenzene ring plays an important role in the nonadiabatictransition of the excimer to ground state

In Case 2 the C1ndashC1

1015840 bond between two benzenes isbroken about 50 fs after its formation To understand howthe structural deformation of the benzene ring impacts thecleavage of the C

1ndashC1

1015840 bond it is worthwhile to the comparethe distances between the C

1and C

1

1015840 atoms and the C2

and C2

1015840 atoms and the C5ndashC6ndashC1ndashC2and C

5

1015840ndashC6

1015840ndashC1

1015840ndashC2

1015840

dihedral angles For the formation of the cyclobutane ben-zene dimer the dihedral angle of C

5

1015840ndashC6

1015840ndashC1

1015840ndashC2

1015840 is almostconstant before 680 fs (ie just before the formation of theC1ndashC1

1015840 bond) and then quickly decreases to minus30∘ Afterthat this dihedral angle fluctuates around its initial valueuntil the end of simulation On the other hand the dihedralangle of C

5ndashC6ndashC1ndashC2has a relatively smaller change in

amplitude In particular during 770 to 1050 fs in which theC1ndashC1

1015840 bond is formed and C2ndashC2

1015840 is not bonding thevalue of C

5ndashC6ndashC1ndashC2dihedral angle is dominantly positive

This suggests movement of C1and C

2towards the bottom

molecule enhancing the likelihood of C2ndashC2

1015840 bonding ForCase 2 however the C

5ndashC6ndashC1ndashC2dihedral angle oscillates

between minus30∘ and 30∘ after formation of the C1ndashC1

1015840 bondThis strong vibration deters the formation of a bond betweenthe C

2and C

2

1015840 and also makes the C1ndashC1

1015840 bond unstableWe therefore conclude that the forces produced by thedeformation of the benzene ring at C

1site break the C

1ndashC1

1015840

bond and prevent the formation of the cyclobutane benzenedimer

The time evolution of the net charge of the excitedbenzene molecule (benzene 1) in Cases 1 and 2 is shownin Figures 10(a) and 10(c) respectively Figure 10(b) isan expanded view of Figure 10(a) from 600 to 1100 fswith C

1ndashC1


1015840 distances shown for comparisonFigure 10(d) is an expanded view of Figure 10(c) from 800to 1000 fs with C

1ndashC1


1015840 distances also shown for

comparison For the formation of the cyclobutane benzenedimer (Case 1) although electrons hop frequently betweenthe two benzene molecules from 700 to 1000 fs it canbe hardly defined as ldquocharge transfer staterdquo overall Onlyat 770 fs when the avoided crossing occurs a zwitterionis clearly formed However the excited benzene moleculealmost immediately returns to electric neutrality In thezwitterionic geometry C

1and C

1

1015840 atoms are linked by a120590 chemical bond with length of 158 A while the C

2and

C2

1015840 distance is 266 A A ldquobonded-intermediaterdquo is almostimmediately formed as the C

2ndashC2

1015840 distance shortens from26 to about 21 A After 1000 fs the bonded-intermediate hasconverted into the cyclobutane benzene dimer because ofC2ndashC2

1015840 bonding In Case 2 as shown in Figures 10(c) and10(d) the zwitterionic exists for about 20 fs and then C

1ndashC1

1015840

bond is broken The bonded-intermediate is not observed inCase 2

The molecular geometry at the avoided crossing of bothcases is shown in Figure 11 with a few critical geometryparameters indicated The distances of C

1ndashC1


1015840

of Case 1 are 158 and 266 A respectively The interatomicdistances of Case 2 are 157 and 261 A respectively Figures11(a) and 11(b) are not significantly different It suggests thatthe electronic decay point which is bonded-intermediatestructure may lead to either [2 + 2] photoaddition productor reversal depending on the vibrations of C

1 C2 C1

1015840 andC2

1015840 atomsThe interatomic distances of C

1ndashC1


1015840 are164 A and 260 A respectively (as seen in Figure 12) byusing CASSCF optimization for the 119878

11198780CI of two-benzene

system It is worth noting that the C3ndashC2

1015840 distance in the CIgeometry is only 221 A which is far less than that obtained inour semiclassical dynamics simulations (both Cases 1 and 2)This CASSCF geometry is very similar to the CI of benzeneand ethylene system calculated by Clifford and coworkers[13] Decay from this CI point may lead to either [2 + 2][2 + 3] or [2 + 4] photoaddition product although formation


0 500 1000 1500

Net

char

ge o

f ben

zene

1

Case 1

Time (fs)

10

05

00

minus05

minus10

(a)

600 700 800 900 1000 1100

Zwitterionic 15

20

25

30

35

Bonded-intermediate

Net

char

ge o

f ben

zene

1

10

05

00

minus05

minus10

Time (fs)

Dist

ance

s(A)

C1ndashC1998400

C2ndashC2998400

(b)

0 500 1000 1500

Net

char

ge o

f ben

zene

1

Case 2

Time (fs)

10

05

00

minus05

minus10

(c)

800 850 900 950 1000

Zwitterionic

Net

char

ge o

f ben

zene

1

10

05

00

minus05

minus10

Time (fs)

15

20

25

30

35

Dist

ance

s(A)

C1ndashC1998400

C2ndashC2998400

(d)

Figure 10The net charge of benzene 1 molecule of (a) Case 1 and (c) Case 2 Here (b) is the detail of (a) from 600 to 1200 fs and both C1ndashC1

1015840

and C2ndashC2

1015840 distances are inserted to compare (d) is the expanded scale of (c) from 800 to 1000 fs and both C1ndashC1


1015840 distances inthat case are inserted

of [2 + 3] product seems most probable because of the shortC3ndashC2

1015840 distanceClassical photoinduced [2 + 2] cycloadditions proceed

via a cyclic transition state and are concerted reactionsin which bond breaking and bond formation take placesimultaneously and no intermediate state is involved Butfor the photoinduced [2 + 2] dimerization of benzenes oursimulation results show that theC

1ndashC1


1015840 bond for-mations are nonconcertedThe CASSCF calculation suggeststhat two stacked benzenes decay to the electronic groundstate via the CI when the formation of the C

1ndashC1

1015840 bondoccurs and that the C

2ndashC2

1015840 distance is longer than C1ndashC1

1015840

at the CI Therefore the Woodward-Hoffmann rules do notapply Our simulations suggest the formation of a ldquobonded-intermediaterdquo at avoided crossing it involves a charge separa-tion leading to a zwitterion and a ldquobonded-intermediaterdquoThebonded-intermediate is a necessary intermediate for forming[2 + 2] product Otherwise the zwitterion could reverse toreactant with the breaking of the C

1ndashC1

1015840 bond

4 Conclusions

In this paper we report a semiclassical dynamics simulationstudy of the response to ultrashort laser pulses of stackedbenzene molecules The simulation uncovered two differentreaction paths leading to the formation of two differentproducts The first leads to the formation of cyclobutanebenzene dimer and the second eventually returns back toreactants after deactivation The simulation results can besummarized as follows

(1) In both reactions the distances between the C1and

C1

1015840 atoms have a great impact on the formation of theavoided crossings which lead to the deactivation ofthe photoexcitedmolecule Radiationless transforma-tion of both cases occurs when the C

1and C

1

1015840 atomsform a covalent bond

(2) In the first reaction the formation of the two chemicalbonds is asynchronous and a time lag is 230 fs A


C1

C2

C3

C4C5

C6

195∘

158 A

266 A336 A

C9984002

C9984001

C2ndashC1ndashC1998400ndashC2

998400=

(a)

216∘

157 A

261 A346 A

C9984002

C9984001

C2

C3

C1


998400=

(b)

Figure 11 The molecular geometry at avoided crossing of (a) Case 1 and (b) Case 2

221 A

292 A260 A

164 A

C1

C2

C4

C3

C1998400

C2998400

Figure 12 The geometry of conical intersection by CASSCF(1212)6ndash31g(d) optimization

bonded-intermediate is observed before the forma-tion of cyclobutane dimer

(3) In the second reaction only one bond is formedbetween two benzene molecules This bonded-inter-mediate exists for only 50 fs and possesses significantzwitterionic character The final product is two sepa-rated benzenemoleculesThedeformation of benzenering plays an important role in the breaking of thisbond

Conflict of Interests

The authors declare that there is no conflict of interestsregarding the publication of this paper

Acknowledgments

This work is supported by the National Natural ScienceFoundation of China (Grant no U1330138 and no 21203259)and the Natural Science Foundation Project of CQ CSTC(cstc2011jjA00009) and Project of the Science TechnologyFoundation of Chongqing Education Committee China(nos KJ120516 and KJ120521)

References

[1] R Beukers A P M Eker and P H M Lohman ldquo50 yearsthymine dimerrdquo DNA Repair vol 7 no 3 pp 530ndash543 2008

[2] C E Crespo-Hernandez B Cohen and B Kohler ldquoBasestacking controls excited-state dynamics in A-T DNArdquo Naturevol 436 pp 1141ndash1144 2005

[3] C T Middleton K de la Harpe C Su Y K Law C E Crespo-Hernandez and B Kohler ldquoDNA excited-state dynamics fromsingle bases to the double helixrdquo Annual Review of PhysicalChemistry vol 60 pp 217ndash239 2009

[4] M Boggio-Pasqua G Groenhof L V Schafer H Grubmullerand M A Robb ldquoUltrafast deactivation channel for thyminedimerizationrdquo Journal of the American Chemical Society vol129 no 36 pp 10996ndash10997 2007

[5] N Hoffmann ldquoPhotochemical reactions as key steps in organicsynthesisrdquo Chemical Reviews vol 108 pp 1052ndash1103 2008

[6] U Streit and C G Bochet ldquoThe arene-alkene photocycloaddi-tionrdquo Beilstein Journal of Organic Chemistry vol 7 pp 525ndash5422011

[7] K E Wilzbach J S Ritscher and L Kaplan ldquoBenzvalene thetricyclic valence isomer of benzenerdquo Journal of the AmericanChemical Society vol 89 no 4 pp 1031ndash1032 1967

[8] L Kaplan and K E Willzbach ldquoPhotolysis of benzene vaporBenzvalene formation at wavelengths 2537ndash2370Ardquo Journal ofthe American Chemical Society vol 90 no 12 pp 3291ndash32921968


[9] E E van Tamelen and S P J Pappas ldquoChemistry of dewarbenzene 125-Tri-t-butylbicyclo[220]Hexa-25-dienerdquo Journalof the American Chemical Society vol 84 pp 3789ndash3791 1962

[10] E E van Tamelen and S P Pappas ldquoBicyclo[220]hexa-25-diene [3]rdquo Journal of the American Chemical Society vol 85 no20 pp 3297ndash3298 1963

[11] D Bryce-Smith ldquoOrbital symmetry relationships for thermaland photochemical concerted cycloadditions to the benzeneringrdquo Journal of the Chemical Society D no 14 pp 806ndash8081969

[12] J A van der Hart J J C Mulder and J Cornelisse ldquoFunnelsand barriers in the photocycloaddition of arenes to alkenes anddienesrdquo Journal of Photochemistry and Photobiology A vol 86no 1ndash3 pp 141ndash148 1995

[13] S CliffordM J Bearpark F BernardiM OlivucciM A Robband B R Smith ldquoConical intersection pathways in the pho-tocycloaddition of ethene and benzene a CASSCF study withMMVB dynamicsrdquo Journal of the American Chemical Societyvol 118 no 31 pp 7353ndash7360 1996

[14] J J Serrano-Perez F de Vleeschouwer F de Proft D Mendive-Tapia M J Bearpark and M A Robb ldquoHow the conical inter-section seam controls chemical selectivity in the photocycload-dition of ethylene and benzenerdquo Journal of Organic Chemistryvol 78 no 5 pp 1874ndash1886 2013

[15] J J McCullough ldquoPhotoadditions of aromatic compoundsrdquoChemical Reviews vol 87 no 4 pp 811ndash860 1987

[16] D Dopp ldquoPhotocycloaddition with captodative alkenesrdquo inOrganic Physical and Materials Photochemistry V Rama-murthy and K S Schanze Eds vol 6 of Molecular andSupramolecular Photochemistry pp 101ndash148 Marcel DekkerNew York NY USA 2000

[17] KMizunoHMaeda A Sugimoto andK Chiyonobu ldquoMolec-ular and supramolecular photochemistryrdquo in Understandingand Manipulating Excited-State Processes V Ramamurthy andK S Schanze Eds vol 8 p 127 Marcel Dekker New York NYUSA 2001

[18] D Dopp C Kruger H R Memarian and Y-H Tsay ldquo14-pho-tocycloaddition of 120572-morpholinoacrylonitrile to 1-acylnaph-thalenesrdquo Angewandte Chemie International Edition in Englishvol 24 no 12 pp 1048ndash1049 1985

[19] H Meier and D Cao ldquoOptical switches with biplanemersobtained by intramolecular photocycloaddition reactions oftethered arenesrdquo Chemical Society Reviews vol 42 pp 143ndash1552013

[20] A Y Rogachev X-D Wen and R Hoffmann ldquoJailbreakingbenzene dimersrdquo Journal of the American Chemical Society vol134 no 19 pp 8062ndash8065 2012

[21] Y Dou B R Torralva and R E Allen ldquoSemiclassical electron-radiation-ion dynamics (SERID) and cis-trans photoisomeriza-tion of butadienerdquo Journal of Modern Optics vol 50 no 15ndash17pp 2615ndash2643 2003

[22] Y Dou B R Torralva and R E Allen ldquoGas phase absorptionspectra and decay of triplet benzene benzene-d

6 and toluenerdquo

Chemical Physics Letters vol 392 no 4 pp 352ndash358 2004[23] W Zhang S Yuan A Li Y Dou J Zhao and W Fang

ldquoPhotoinduced thymine dimerization studied by semiclassicaldynamics simulationrdquoThe Journal of Physical Chemistry C vol114 no 12 pp 5594ndash5601 2010

[24] S Yuan W Zhang L Liu Y Dou W Fang and G V LoldquoDetailed mechanism for photoinduced cytosine dimerizationa semiclassical dynamics simulationrdquo The Journal of PhysicalChemistry A vol 115 no 46 pp 13291ndash13297 2011

[25] M Ben-Nun and T J Martınez ldquoAb Initio quantum moleculardynamicsrdquo Advances in Chemical Physics vol 121 pp 439ndash5122002

[26] W Domcke D R Yarkony and H Koppel Eds ConicalIntersections Electronic Structure Dynamics and SpectroscopyWorld Scientific Singapore 2004

[27] M Baer Beyond Born-Oppenheimer Electronic NonadiabaticCoupling Terms and Conical Intersections Wiley-InterscienceHoboken NJ USA 2006

[28] M J Bearpark F Bernardi S CliffordMOlivucciM A Robband T J Vreven ldquoThe lowest energy excited singlet states andthe cis-trans photoisomerization of styrenerdquo Journal of theAmerican Chemical Society vol 101 no 2 pp 3841ndash3847 1997

[29] B G Levine and T J Martınez ldquoIsomerization through conicalintersectionsrdquo Annual Review of Physical Chemistry vol 58 pp613ndash634 2007

[30] J Frank Introduction to Computational Chemistry John Wileyamp Sons Chichester UK 2007

[31] C J Cramer Essentials of Computational Chemistry JohnWileyamp Sons Chichester UK 2002

[32] M J Frisch G W Trucks H B Schlegel et al Gaussian 09Revision D01 Gaussian Wallingford Conn USA 2010

[33] S Tsuzuki ldquoInteractions with aromatic ringsrdquo Structure andBonding vol 115 pp 149ndash193 2005

[34] K C Janda J C Hemminger J S Winn S E Novick S JHarris and W Klemperer ldquoBenzene dimer a polar moleculerdquoThe Journal of Chemical Physics vol 63 no 4 pp 1419ndash14211975

[35] J M Steed T A Dixon and W Klemperer ldquoMolecularbeam studies of benzene dimer hexafluorobenzene dimer andbenzene-hexafluorobenzenerdquo The Journal of Chemical Physicsvol 70 no 11 pp 4940ndash4946 1979

[36] E Arunan and H S Gutowsky ldquoThe rotational spectrum stru-cture anddynamics of a benzene dimerrdquoTheJournal of ChemicalPhysics vol 98 no 5 pp 4294ndash4296 1993

[37] W Scherzer O Kratzschmar H L Selzle and E W SchlagldquoStructural isomers of the benzene dimer from mass selectivehole-burning spectroscopyrdquo Zeitschrift fur Naturforschung Avol 47 pp 1248ndash1252 1992

Submit your manuscripts athttpwwwhindawicom

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Inorganic ChemistryInternational Journal of

Hindawi Publishing Corporation httpwwwhindawicom Volume 2014

International Journal ofPhotoenergy


Carbohydrate Chemistry

International Journal of


Journal of

Chemistry


Advances in

Physical Chemistry

Hindawi Publishing Corporationhttpwwwhindawicom

Analytical Methods in Chemistry

Journal of

Volume 2014

Bioinorganic Chemistry and ApplicationsHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

SpectroscopyInternational Journal of


The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Medicinal ChemistryInternational Journal of


Chromatography Research International


Applied ChemistryJournal of



Theoretical ChemistryJournal of


Journal of

Spectroscopy

Analytical ChemistryInternational Journal of


Journal of


Quantum Chemistry


Organic Chemistry International

ElectrochemistryInternational Journal of



CatalystsJournal of


Rogachev and coworkers [20] performed a series of calcula-tions involving benzene dimers in the ground state but nostudies have been made on the photochemical dimerizationof benzene In this paper we studied photoinduced [2 +2] cycloaddition of two-benzene system by semiclassicaldynamic simulation The simulation results provide detaileddynamics features for this process from photon excitation tothe formation of product The geometry at the conical inter-section (CI) between the first singlet (119878

1) excited state and

ground state (1198780) was optimized by using completed active

space self-consistent field (CASSCF)method to comparewithother theoretical results

2 Methodology

21 Semiclassical Dynamics Simulation We carried outthe dynamics simulations using the semiclassical electron-radiation-ion dynamics (SERID) method In this approachthe valence electrons are calculated by the time-dependentSchrodinger equation while both the radiation field and themotion of the nuclei are treated by the classical approxi-mation A detailed description of this technique has beenpublished elsewhere [21 22] and only a brief review isgiven here The one-electron states are updated by solvingthe time-dependent Schrodinger equation at each time step(typically 005 femtoseconds in duration) in a nonorthogonalbasis

119894ℏ120597Ψ119895

120597119905= Sminus1 sdotH sdot Ψ

119895 (1)

where S is the overlap matrix for the atomic orbitals Thelaser pulse is characterized by the vector potential A whichis coupled to the Hamiltonian via the time-dependent Peierlssubstitution

119867119886119887(X minus X1015840) = 119867

0

119886119887(X minus X1015840) exp( 119894119902

ℏ119888A sdot (X minus X1015840))

(2)

here119867119886119887(XminusX1015840) is the Hamiltonian matrix element for basis

functions 119886 and 119887 on atoms at X and X1015840 respectively and 119902 =minus119890 is the charge of the electron

The Hamiltonian matrix elements overlap matrix ele-ments and repulsive energy are calculated with the density-functional based tight bonding (DFTB) method The DFTBmethod does have essentially the same strengths and lim-itations as time-dependent density-functional theory (TD-DFT) In particularly the bonding is well described butthe excited state energies are typically too low For thisreason we matched the effective central photon energy ofthe laser pulse to the relevant density-functional (rather thanexperimental) excitation energy and this should not adverselyaffect the interpretation of the results This model has beenused in biologically relevant studies such as photoinduceddimerization of thymine [23] and cytosine [24] via [2 + 2]photocycloaddition reaction All the results were found to beconsistent with experimental observations The formation ofcyclobutane pyrimidine dimer may provide good referencesfor [2 + 2] photocycloaddition of benzene

In this technique forces acting on nucleus or ions arecomputed by the Ehrenfest equation

119872119897

1198892119883119897120572

1198891199052

= minus1

2sum119895

Ψ+

119895sdot (

120597H120597119883119897120572

minus 119894ℏ1

2

120597S120597119883119897120572

sdot120597

120597119905) sdot Ψ119895minus120597119880rep

120597119883119897120572

(3)

where119880rep is effective nuclear-nuclear repulsive potential and119883119897120572= ⟨119883119897120572⟩ is the expectation value of the time-dependent

Heisenberg operator for the 120572 coordinate of the nucleuslabeled by 119897 (with 120572 = 119909 119910 119911) Equation (3) is obtained byneglecting the second and higher order terms of the quantumfluctuations119883 minus ⟨119883

119897120572⟩ in the exact Ehrenfest theorem

The present ldquoEhrenfestrdquo principle is complementary toother methods based on different approximations such asthe full multiple spawning model developed by the Ben-Nun and Martınez [25] The limitation of this method isthat the simulation trajectory moves along a path dominatedby averaging over all the terms in the Born-Oppenheimerexpansion [26 27]

Ψtotal

(119883119899 119909119890 119905) = sum

119894

Ψ119899

119894(119883119899 119905) Ψ119890

119894(119909119890 119883119899) (4)

rather than following the time evolution of a single potentialenergy surface which is approximately decoupled fromall theothers [26ndash29] (Here119883

119899and 119909

119890represent the sets of nuclear

and electronic coordinates resp and the Ψ119890119894are eigenstates

of the electronic Hamiltonian at fixed 119883119899) The strengths

of the present approach include retention of all of the 3119873nuclear degrees of freedom and the incorporation of the laserexcitation as well as the subsequent deexcitation at an avoidedcrossing near a conical intersection

22 CASSCF Multiconfigurational self-consistent field(MCSCF) is a method in quantum chemistry used to gene-rate qualitatively correct reference states of molecules incases where Hartree-Fock (HF) and DFT are not adequate(eg for molecular ground states which are quasidegeneratewith low lying excited states or in bond breaking situations)It uses a linear combination of configuration state functions(CSF) or configuration determinants to approximate theexact electronic wavefunction of an atom or molecule In anMCSCF calculation the set of coefficients of both the CSFsor determinants and the basis functions in the molecularorbitals are varied to obtain the total electronic wavefunctionwith the lowest possible energy This method can be consi-dered a combination of configuration interaction (where themolecular orbitals are not varied but the expansion of thewave function are varied) and Hartree-Fock (where there isonly one determinant but the molecular orbitals are varied)A particularly important MCSCF approach is the CASSCFwhere the linear combination of CSFs includes all that arisefrom a particular number of electrons in a particular numberof orbitals [30 31]

In this research the CASSCF ab initio computationsused a 12-electron and 12-orbital active space involving all


1998400 2

998400

3998400

4998400

5998400

6998400

1 23

456

374 A375 A

(a)

1

1

998400 2

2

998400


998400ndashC2998400=

(b)





1ndashC1








1ndashC1


2ndashC2



and C1

1015840ndashC2



1015840


1

1015840ndashC2


1ndashC2bond length


1

1015840ndashC2



(a) (b)

(c) (d)



1ndashC1


2ndashC2






h

(a) (b) (c)

(d) (e) (f)


135

140

145

150

155

160

165

170

Bond

leng

th(A

)

0 500 1000 1500Time (fs)

C1ndashC2

C1998400ndashC2

998400

(a)

0 500 1000 1500

15

20

25

30

35

40

Time (fs)

Bond

leng

th(A

)

C1ndashC1998400

C2ndashC2998400

(b)


1

1015840ndashC2


2atoms and the C

1

1015840 andC2



1and C

1



1and

C1



1

1015840ndashC2

1015840




Orb

ital e

nerg

y (e

V)

minus2

minus3

minus4

minus5

minus6

minus7

0 500 1000 1500Time (fs)

HOMOLUMOLUMO+1

HOMOminus1

(a)

0

0 500 1000 1500

00

05

10

15

20

Elec

troni

c pop

ulat

ion

Time (fs)

HOMOLUMOLUMO+1

HOMOminus1

(b)


(a) (b) (c)

(d) (e) (f)


1ndashC1



1015840ndashC2


1

1015840ndashC2


1ndashC1




1ndashC1

1015840


1and C

1


2

1015840



130

135

140

145

150

155

160

0 500 1000 1500Time (fs)

Bond

leng

th(A

)

C1ndashC2

C1998400ndashC2

998400

(a)

0 500 1000 1500

15

20

25

30

35

40

Time (fs)

Bond

leng

th(A

)

C1ndashC1998400

C2ndashC2998400

(b)


1

1015840ndashC2


2atoms and the C

1

1015840 andC2


Orb

ital e

nerg

y (e

V)

0 500 1000 1500Time (fs)

minus2

minus3

minus4

minus5

minus6

minus7

HOMOLUMOLUMO+1

HOMOminus1

(a)

0 500 1000 1500

00

05

10

15

20

Elec

troni

c pop

ulat

ion

Time (fs)

HOMOLUMOLUMO+1

HOMOminus1

(b)




1ndashC1




1015840 andC2



C2and C

5

1015840ndashC6

1015840ndashC1

1015840ndashC2


1 C2

C1

1015840 and C2


5

1015840ndashC6

1015840ndashC1

1015840ndashC2

1015840


0

1

2

3

4

5

6En

ergy

(eV

)

0 300 600 900 1200 1500Time (fs)

40

30

20

10

0

minus10

minus20

minus30

minus40

minus50

Dih

edra

l ang

les(

∘)



998400ndashC2998400

(a)

Ener

gy (e

V)

0

1

2

3

4

5

6

0 300 600 900 1200 1500Time (fs)

40

30

20

10

0

minus10

minus20

minus30

minus40

minus50

Dih

edra

l ang

les(

∘)



998400ndashC2998400

(b)


5

1015840ndashC6

1015840ndashC1

1015840ndashC2






1ndashC1


1and C

1


and C2


5

1015840ndashC6

1015840ndashC1

1015840ndashC2

1015840


5

1015840ndashC6

1015840ndashC1

1015840ndashC2









2towards the bottom






2and C

2



1site break the C

1ndashC1

1015840



1ndashC1



1ndashC1




1and C

1


2and

C2


2ndashC2



1ndashC1

1015840



1ndashC1


1015840


1 C2 C1

1015840 andC2


1ndashC1







0 500 1000 1500

Net

char

ge o

f ben

zene

1

Case 1

Time (fs)

10

05

00

minus05

minus10

(a)

600 700 800 900 1000 1100

Zwitterionic 15

20

25

30

35

Bonded-intermediate

Net

char

ge o

f ben

zene

1

10

05

00

minus05

minus10

Time (fs)

Dist

ance

s(A)

C1ndashC1998400

C2ndashC2998400

(b)

0 500 1000 1500

Net

char

ge o

f ben

zene

1

Case 2

Time (fs)

10

05

00

minus05

minus10

(c)

800 850 900 950 1000

Zwitterionic

Net

char

ge o

f ben

zene

1

10

05

00

minus05

minus10

Time (fs)

15

20

25

30

35

Dist

ance

s(A)

C1ndashC1998400

C2ndashC2998400

(d)


1015840

and C2ndashC2







1ndashC1



1ndashC1


2ndashC2


1015840


1ndashC1

1015840 bond

4 Conclusions



C1


1and C

1




C1

C2

C3

C4C5

C6

195∘

158 A

266 A336 A

C9984002

C9984001


998400=

(a)

216∘

157 A

261 A346 A

C9984002

C9984001

C2

C3

C1


998400=

(b)


221 A

292 A260 A

164 A

C1

C2

C4

C3

C1998400

C2998400






Acknowledgments


References
























6 and toluenerdquo


























Journal of

Chemistry


Advances in

Physical Chemistry



Journal of

Volume 2014














Journal of

Spectroscopy



Journal of


Quantum Chemistry






CatalystsJournal of


1998400 2

998400

3998400

4998400

5998400

6998400

1 23

456

374 A375 A

(a)

1

1

998400 2

2

998400


998400ndashC2998400=

(b)





1ndashC1








1ndashC1


2ndashC2



and C1

1015840ndashC2



1015840


1

1015840ndashC2


1ndashC2bond length


1

1015840ndashC2



(a) (b)

(c) (d)



1ndashC1


2ndashC2






h

(a) (b) (c)

(d) (e) (f)


135

140

145

150

155

160

165

170

Bond

leng

th(A

)

0 500 1000 1500Time (fs)

C1ndashC2

C1998400ndashC2

998400

(a)

0 500 1000 1500

15

20

25

30

35

40

Time (fs)

Bond

leng

th(A

)

C1ndashC1998400

C2ndashC2998400

(b)


1

1015840ndashC2


2atoms and the C

1

1015840 andC2



1and C

1



1and

C1



1

1015840ndashC2

1015840




Orb

ital e

nerg

y (e

V)

minus2

minus3

minus4

minus5

minus6

minus7

0 500 1000 1500Time (fs)

HOMOLUMOLUMO+1

HOMOminus1

(a)

0

0 500 1000 1500

00

05

10

15

20

Elec

troni

c pop

ulat

ion

Time (fs)

HOMOLUMOLUMO+1

HOMOminus1

(b)


(a) (b) (c)

(d) (e) (f)


1ndashC1



1015840ndashC2


1

1015840ndashC2


1ndashC1




1ndashC1

1015840


1and C

1


2

1015840



130

135

140

145

150

155

160

0 500 1000 1500Time (fs)

Bond

leng

th(A

)

C1ndashC2

C1998400ndashC2

998400

(a)

0 500 1000 1500

15

20

25

30

35

40

Time (fs)

Bond

leng

th(A

)

C1ndashC1998400

C2ndashC2998400

(b)


1

1015840ndashC2


2atoms and the C

1

1015840 andC2


Orb

ital e

nerg

y (e

V)

0 500 1000 1500Time (fs)

minus2

minus3

minus4

minus5

minus6

minus7

HOMOLUMOLUMO+1

HOMOminus1

(a)

0 500 1000 1500

00

05

10

15

20

Elec

troni

c pop

ulat

ion

Time (fs)

HOMOLUMOLUMO+1

HOMOminus1

(b)




1ndashC1




1015840 andC2



C2and C

5

1015840ndashC6

1015840ndashC1

1015840ndashC2


1 C2

C1

1015840 and C2


5

1015840ndashC6

1015840ndashC1

1015840ndashC2

1015840


0

1

2

3

4

5

6En

ergy

(eV

)

0 300 600 900 1200 1500Time (fs)

40

30

20

10

0

minus10

minus20

minus30

minus40

minus50

Dih

edra

l ang

les(

∘)



998400ndashC2998400

(a)

Ener

gy (e

V)

0

1

2

3

4

5

6

0 300 600 900 1200 1500Time (fs)

40

30

20

10

0

minus10

minus20

minus30

minus40

minus50

Dih

edra

l ang

les(

∘)



998400ndashC2998400

(b)


5

1015840ndashC6

1015840ndashC1

1015840ndashC2






1ndashC1


1and C

1


and C2


5

1015840ndashC6

1015840ndashC1

1015840ndashC2

1015840


5

1015840ndashC6

1015840ndashC1

1015840ndashC2









2towards the bottom






2and C

2



1site break the C

1ndashC1

1015840



1ndashC1



1ndashC1




1and C

1


2and

C2


2ndashC2



1ndashC1

1015840



1ndashC1


1015840


1 C2 C1

1015840 andC2


1ndashC1







0 500 1000 1500

Net

char

ge o

f ben

zene

1

Case 1

Time (fs)

10

05

00

minus05

minus10

(a)

600 700 800 900 1000 1100

Zwitterionic 15

20

25

30

35

Bonded-intermediate

Net

char

ge o

f ben

zene

1

10

05

00

minus05

minus10

Time (fs)

Dist

ance

s(A)

C1ndashC1998400

C2ndashC2998400

(b)

0 500 1000 1500

Net

char

ge o

f ben

zene

1

Case 2

Time (fs)

10

05

00

minus05

minus10

(c)

800 850 900 950 1000

Zwitterionic

Net

char

ge o

f ben

zene

1

10

05

00

minus05

minus10

Time (fs)

15

20

25

30

35

Dist

ance

s(A)

C1ndashC1998400

C2ndashC2998400

(d)


1015840

and C2ndashC2







1ndashC1



1ndashC1


2ndashC2


1015840


1ndashC1

1015840 bond

4 Conclusions



C1


1and C

1




C1

C2

C3

C4C5

C6

195∘

158 A

266 A336 A

C9984002

C9984001


998400=

(a)

216∘

157 A

261 A346 A

C9984002

C9984001

C2

C3

C1


998400=

(b)


221 A

292 A260 A

164 A

C1

C2

C4

C3

C1998400

C2998400






Acknowledgments


References
























6 and toluenerdquo


























Journal of

Chemistry


Advances in

Physical Chemistry



Journal of

Volume 2014














Journal of

Spectroscopy



Journal of


Quantum Chemistry






CatalystsJournal of


(a) (b)

(c) (d)



1ndashC1


2ndashC2






h

(a) (b) (c)

(d) (e) (f)


135

140

145

150

155

160

165

170

Bond

leng

th(A

)

0 500 1000 1500Time (fs)

C1ndashC2

C1998400ndashC2

998400

(a)

0 500 1000 1500

15

20

25

30

35

40

Time (fs)

Bond

leng

th(A

)

C1ndashC1998400

C2ndashC2998400

(b)


1

1015840ndashC2


2atoms and the C

1

1015840 andC2



1and C

1



1and

C1



1

1015840ndashC2

1015840




Orb

ital e

nerg

y (e

V)

minus2

minus3

minus4

minus5

minus6

minus7

0 500 1000 1500Time (fs)

HOMOLUMOLUMO+1

HOMOminus1

(a)

0

0 500 1000 1500

00

05

10

15

20

Elec

troni

c pop

ulat

ion

Time (fs)

HOMOLUMOLUMO+1

HOMOminus1

(b)


(a) (b) (c)

(d) (e) (f)


1ndashC1



1015840ndashC2


1

1015840ndashC2


1ndashC1




1ndashC1

1015840


1and C

1


2

1015840



130

135

140

145

150

155

160

0 500 1000 1500Time (fs)

Bond

leng

th(A

)

C1ndashC2

C1998400ndashC2

998400

(a)

0 500 1000 1500

15

20

25

30

35

40

Time (fs)

Bond

leng

th(A

)

C1ndashC1998400

C2ndashC2998400

(b)


1

1015840ndashC2


2atoms and the C

1

1015840 andC2


Orb

ital e

nerg

y (e

V)

0 500 1000 1500Time (fs)

minus2

minus3

minus4

minus5

minus6

minus7

HOMOLUMOLUMO+1

HOMOminus1

(a)

0 500 1000 1500

00

05

10

15

20

Elec

troni

c pop

ulat

ion

Time (fs)

HOMOLUMOLUMO+1

HOMOminus1

(b)




1ndashC1




1015840 andC2



C2and C

5

1015840ndashC6

1015840ndashC1

1015840ndashC2


1 C2

C1

1015840 and C2


5

1015840ndashC6

1015840ndashC1

1015840ndashC2

1015840


0

1

2

3

4

5

6En

ergy

(eV

)

0 300 600 900 1200 1500Time (fs)

40

30

20

10

0

minus10

minus20

minus30

minus40

minus50

Dih

edra

l ang

les(

∘)



998400ndashC2998400

(a)

Ener

gy (e

V)

0

1

2

3

4

5

6

0 300 600 900 1200 1500Time (fs)

40

30

20

10

0

minus10

minus20

minus30

minus40

minus50

Dih

edra

l ang

les(

∘)



998400ndashC2998400

(b)


5

1015840ndashC6

1015840ndashC1

1015840ndashC2






1ndashC1


1and C

1


and C2


5

1015840ndashC6

1015840ndashC1

1015840ndashC2

1015840


5

1015840ndashC6

1015840ndashC1

1015840ndashC2









2towards the bottom






2and C

2



1site break the C

1ndashC1

1015840



1ndashC1



1ndashC1




1and C

1


2and

C2


2ndashC2



1ndashC1

1015840



1ndashC1


1015840


1 C2 C1

1015840 andC2


1ndashC1







0 500 1000 1500

Net

char

ge o

f ben

zene

1

Case 1

Time (fs)

10

05

00

minus05

minus10

(a)

600 700 800 900 1000 1100

Zwitterionic 15

20

25

30

35

Bonded-intermediate

Net

char

ge o

f ben

zene

1

10

05

00

minus05

minus10

Time (fs)

Dist

ance

s(A)

C1ndashC1998400

C2ndashC2998400

(b)

0 500 1000 1500

Net

char

ge o

f ben

zene

1

Case 2

Time (fs)

10

05

00

minus05

minus10

(c)

800 850 900 950 1000

Zwitterionic

Net

char

ge o

f ben

zene

1

10

05

00

minus05

minus10

Time (fs)

15

20

25

30

35

Dist

ance

s(A)

C1ndashC1998400

C2ndashC2998400

(d)


1015840

and C2ndashC2







1ndashC1



1ndashC1


2ndashC2


1015840


1ndashC1

1015840 bond

4 Conclusions



C1


1and C

1




C1

C2

C3

C4C5

C6

195∘

158 A

266 A336 A

C9984002

C9984001


998400=

(a)

216∘

157 A

261 A346 A

C9984002

C9984001

C2

C3

C1


998400=

(b)


221 A

292 A260 A

164 A

C1

C2

C4

C3

C1998400

C2998400






Acknowledgments


References
























6 and toluenerdquo


























Journal of

Chemistry


Advances in

Physical Chemistry



Journal of

Volume 2014














Journal of

Spectroscopy



Journal of


Quantum Chemistry






CatalystsJournal of


h

(a) (b) (c)

(d) (e) (f)


135

140

145

150

155

160

165

170

Bond

leng

th(A

)

0 500 1000 1500Time (fs)

C1ndashC2

C1998400ndashC2

998400

(a)

0 500 1000 1500

15

20

25

30

35

40

Time (fs)

Bond

leng

th(A

)

C1ndashC1998400

C2ndashC2998400

(b)


1

1015840ndashC2


2atoms and the C

1

1015840 andC2



1and C

1



1and

C1



1

1015840ndashC2

1015840




Orb

ital e

nerg

y (e

V)

minus2

minus3

minus4

minus5

minus6

minus7

0 500 1000 1500Time (fs)

HOMOLUMOLUMO+1

HOMOminus1

(a)

0

0 500 1000 1500

00

05

10

15

20

Elec

troni

c pop

ulat

ion

Time (fs)

HOMOLUMOLUMO+1

HOMOminus1

(b)


(a) (b) (c)

(d) (e) (f)


1ndashC1



1015840ndashC2


1

1015840ndashC2


1ndashC1




1ndashC1

1015840


1and C

1


2

1015840



130

135

140

145

150

155

160

0 500 1000 1500Time (fs)

Bond

leng

th(A

)

C1ndashC2

C1998400ndashC2

998400

(a)

0 500 1000 1500

15

20

25

30

35

40

Time (fs)

Bond

leng

th(A

)

C1ndashC1998400

C2ndashC2998400

(b)


1

1015840ndashC2


2atoms and the C

1

1015840 andC2


Orb

ital e

nerg

y (e

V)

0 500 1000 1500Time (fs)

minus2

minus3

minus4

minus5

minus6

minus7

HOMOLUMOLUMO+1

HOMOminus1

(a)

0 500 1000 1500

00

05

10

15

20

Elec

troni

c pop

ulat

ion

Time (fs)

HOMOLUMOLUMO+1

HOMOminus1

(b)




1ndashC1




1015840 andC2



C2and C

5

1015840ndashC6

1015840ndashC1

1015840ndashC2


1 C2

C1

1015840 and C2


5

1015840ndashC6

1015840ndashC1

1015840ndashC2

1015840


0

1

2

3

4

5

6En

ergy

(eV

)

0 300 600 900 1200 1500Time (fs)

40

30

20

10

0

minus10

minus20

minus30

minus40

minus50

Dih

edra

l ang

les(

∘)



998400ndashC2998400

(a)

Ener

gy (e

V)

0

1

2

3

4

5

6

0 300 600 900 1200 1500Time (fs)

40

30

20

10

0

minus10

minus20

minus30

minus40

minus50

Dih

edra

l ang

les(

∘)



998400ndashC2998400

(b)


5

1015840ndashC6

1015840ndashC1

1015840ndashC2






1ndashC1


1and C

1


and C2


5

1015840ndashC6

1015840ndashC1

1015840ndashC2

1015840


5

1015840ndashC6

1015840ndashC1

1015840ndashC2









2towards the bottom






2and C

2



1site break the C

1ndashC1

1015840



1ndashC1



1ndashC1




1and C

1


2and

C2


2ndashC2



1ndashC1

1015840



1ndashC1


1015840


1 C2 C1

1015840 andC2


1ndashC1







0 500 1000 1500

Net

char

ge o

f ben

zene

1

Case 1

Time (fs)

10

05

00

minus05

minus10

(a)

600 700 800 900 1000 1100

Zwitterionic 15

20

25

30

35

Bonded-intermediate

Net

char

ge o

f ben

zene

1

10

05

00

minus05

minus10

Time (fs)

Dist

ance

s(A)

C1ndashC1998400

C2ndashC2998400

(b)

0 500 1000 1500

Net

char

ge o

f ben

zene

1

Case 2

Time (fs)

10

05

00

minus05

minus10

(c)

800 850 900 950 1000

Zwitterionic

Net

char

ge o

f ben

zene

1

10

05

00

minus05

minus10

Time (fs)

15

20

25

30

35

Dist

ance

s(A)

C1ndashC1998400

C2ndashC2998400

(d)


1015840

and C2ndashC2







1ndashC1



1ndashC1


2ndashC2


1015840


1ndashC1

1015840 bond

4 Conclusions



C1


1and C

1




C1

C2

C3

C4C5

C6

195∘

158 A

266 A336 A

C9984002

C9984001


998400=

(a)

216∘

157 A

261 A346 A

C9984002

C9984001

C2

C3

C1


998400=

(b)


221 A

292 A260 A

164 A

C1

C2

C4

C3

C1998400

C2998400






Acknowledgments


References
























6 and toluenerdquo


























Journal of

Chemistry


Advances in

Physical Chemistry



Journal of

Volume 2014














Journal of

Spectroscopy



Journal of


Quantum Chemistry






CatalystsJournal of


Orb

ital e

nerg

y (e

V)

minus2

minus3

minus4

minus5

minus6

minus7

0 500 1000 1500Time (fs)

HOMOLUMOLUMO+1

HOMOminus1

(a)

0

0 500 1000 1500

00

05

10

15

20

Elec

troni

c pop

ulat

ion

Time (fs)

HOMOLUMOLUMO+1

HOMOminus1

(b)


(a) (b) (c)

(d) (e) (f)


1ndashC1



1015840ndashC2


1

1015840ndashC2


1ndashC1




1ndashC1

1015840


1and C

1


2

1015840



130

135

140

145

150

155

160

0 500 1000 1500Time (fs)

Bond

leng

th(A

)

C1ndashC2

C1998400ndashC2

998400

(a)

0 500 1000 1500

15

20

25

30

35

40

Time (fs)

Bond

leng

th(A

)

C1ndashC1998400

C2ndashC2998400

(b)


1

1015840ndashC2


2atoms and the C

1

1015840 andC2


Orb

ital e

nerg

y (e

V)

0 500 1000 1500Time (fs)

minus2

minus3

minus4

minus5

minus6

minus7

HOMOLUMOLUMO+1

HOMOminus1

(a)

0 500 1000 1500

00

05

10

15

20

Elec

troni

c pop

ulat

ion

Time (fs)

HOMOLUMOLUMO+1

HOMOminus1

(b)




1ndashC1




1015840 andC2



C2and C

5

1015840ndashC6

1015840ndashC1

1015840ndashC2


1 C2

C1

1015840 and C2


5

1015840ndashC6

1015840ndashC1

1015840ndashC2

1015840


0

1

2

3

4

5

6En

ergy

(eV

)

0 300 600 900 1200 1500Time (fs)

40

30

20

10

0

minus10

minus20

minus30

minus40

minus50

Dih

edra

l ang

les(

∘)



998400ndashC2998400

(a)

Ener

gy (e

V)

0

1

2

3

4

5

6

0 300 600 900 1200 1500Time (fs)

40

30

20

10

0

minus10

minus20

minus30

minus40

minus50

Dih

edra

l ang

les(

∘)



998400ndashC2998400

(b)


5

1015840ndashC6

1015840ndashC1

1015840ndashC2






1ndashC1


1and C

1


and C2


5

1015840ndashC6

1015840ndashC1

1015840ndashC2

1015840


5

1015840ndashC6

1015840ndashC1

1015840ndashC2









2towards the bottom






2and C

2



1site break the C

1ndashC1

1015840



1ndashC1



1ndashC1




1and C

1


2and

C2


2ndashC2



1ndashC1

1015840



1ndashC1


1015840


1 C2 C1

1015840 andC2


1ndashC1







0 500 1000 1500

Net

char

ge o

f ben

zene

1

Case 1

Time (fs)

10

05

00

minus05

minus10

(a)

600 700 800 900 1000 1100

Zwitterionic 15

20

25

30

35

Bonded-intermediate

Net

char

ge o

f ben

zene

1

10

05

00

minus05

minus10

Time (fs)

Dist

ance

s(A)

C1ndashC1998400

C2ndashC2998400

(b)

0 500 1000 1500

Net

char

ge o

f ben

zene

1

Case 2

Time (fs)

10

05

00

minus05

minus10

(c)

800 850 900 950 1000

Zwitterionic

Net

char

ge o

f ben

zene

1

10

05

00

minus05

minus10

Time (fs)

15

20

25

30

35

Dist

ance

s(A)

C1ndashC1998400

C2ndashC2998400

(d)


1015840

and C2ndashC2







1ndashC1



1ndashC1


2ndashC2


1015840


1ndashC1

1015840 bond

4 Conclusions



C1


1and C

1




C1

C2

C3

C4C5

C6

195∘

158 A

266 A336 A

C9984002

C9984001


998400=

(a)

216∘

157 A

261 A346 A

C9984002

C9984001

C2

C3

C1


998400=

(b)


221 A

292 A260 A

164 A

C1

C2

C4

C3

C1998400

C2998400






Acknowledgments


References
























6 and toluenerdquo


























Journal of

Chemistry


Advances in

Physical Chemistry



Journal of

Volume 2014














Journal of

Spectroscopy



Journal of


Quantum Chemistry






CatalystsJournal of


130

135

140

145

150

155

160

0 500 1000 1500Time (fs)

Bond

leng

th(A

)

C1ndashC2

C1998400ndashC2

998400

(a)

0 500 1000 1500

15

20

25

30

35

40

Time (fs)

Bond

leng

th(A

)

C1ndashC1998400

C2ndashC2998400

(b)


1

1015840ndashC2


2atoms and the C

1

1015840 andC2


Orb

ital e

nerg

y (e

V)

0 500 1000 1500Time (fs)

minus2

minus3

minus4

minus5

minus6

minus7

HOMOLUMOLUMO+1

HOMOminus1

(a)

0 500 1000 1500

00

05

10

15

20

Elec

troni

c pop

ulat

ion

Time (fs)

HOMOLUMOLUMO+1

HOMOminus1

(b)




1ndashC1




1015840 andC2



C2and C

5

1015840ndashC6

1015840ndashC1

1015840ndashC2


1 C2

C1

1015840 and C2


5

1015840ndashC6

1015840ndashC1

1015840ndashC2

1015840


0

1

2

3

4

5

6En

ergy

(eV

)

0 300 600 900 1200 1500Time (fs)

40

30

20

10

0

minus10

minus20

minus30

minus40

minus50

Dih

edra

l ang

les(

∘)



998400ndashC2998400

(a)

Ener

gy (e

V)

0

1

2

3

4

5

6

0 300 600 900 1200 1500Time (fs)

40

30

20

10

0

minus10

minus20

minus30

minus40

minus50

Dih

edra

l ang

les(

∘)



998400ndashC2998400

(b)


5

1015840ndashC6

1015840ndashC1

1015840ndashC2






1ndashC1


1and C

1


and C2


5

1015840ndashC6

1015840ndashC1

1015840ndashC2

1015840


5

1015840ndashC6

1015840ndashC1

1015840ndashC2









2towards the bottom






2and C

2



1site break the C

1ndashC1

1015840



1ndashC1



1ndashC1




1and C

1


2and

C2


2ndashC2



1ndashC1

1015840



1ndashC1


1015840


1 C2 C1

1015840 andC2


1ndashC1







0 500 1000 1500

Net

char

ge o

f ben

zene

1

Case 1

Time (fs)

10

05

00

minus05

minus10

(a)

600 700 800 900 1000 1100

Zwitterionic 15

20

25

30

35

Bonded-intermediate

Net

char

ge o

f ben

zene

1

10

05

00

minus05

minus10

Time (fs)

Dist

ance

s(A)

C1ndashC1998400

C2ndashC2998400

(b)

0 500 1000 1500

Net

char

ge o

f ben

zene

1

Case 2

Time (fs)

10

05

00

minus05

minus10

(c)

800 850 900 950 1000

Zwitterionic

Net

char

ge o

f ben

zene

1

10

05

00

minus05

minus10

Time (fs)

15

20

25

30

35

Dist

ance

s(A)

C1ndashC1998400

C2ndashC2998400

(d)


1015840

and C2ndashC2







1ndashC1



1ndashC1


2ndashC2


1015840


1ndashC1

1015840 bond

4 Conclusions



C1


1and C

1




C1

C2

C3

C4C5

C6

195∘

158 A

266 A336 A

C9984002

C9984001


998400=

(a)

216∘

157 A

261 A346 A

C9984002

C9984001

C2

C3

C1


998400=

(b)


221 A

292 A260 A

164 A

C1

C2

C4

C3

C1998400

C2998400






Acknowledgments


References
























6 and toluenerdquo


























Journal of

Chemistry


Advances in

Physical Chemistry



Journal of

Volume 2014














Journal of

Spectroscopy



Journal of


Quantum Chemistry






CatalystsJournal of


0

1

2

3

4

5

6En

ergy

(eV

)

0 300 600 900 1200 1500Time (fs)

40

30

20

10

0

minus10

minus20

minus30

minus40

minus50

Dih

edra

l ang

les(

∘)



998400ndashC2998400

(a)

Ener

gy (e

V)

0

1

2

3

4

5

6

0 300 600 900 1200 1500Time (fs)

40

30

20

10

0

minus10

minus20

minus30

minus40

minus50

Dih

edra

l ang

les(

∘)



998400ndashC2998400

(b)


5

1015840ndashC6

1015840ndashC1

1015840ndashC2






1ndashC1


1and C

1


and C2


5

1015840ndashC6

1015840ndashC1

1015840ndashC2

1015840


5

1015840ndashC6

1015840ndashC1

1015840ndashC2









2towards the bottom






2and C

2



1site break the C

1ndashC1

1015840



1ndashC1



1ndashC1




1and C

1


2and

C2


2ndashC2



1ndashC1

1015840



1ndashC1


1015840


1 C2 C1

1015840 andC2


1ndashC1







0 500 1000 1500

Net

char

ge o

f ben

zene

1

Case 1

Time (fs)

10

05

00

minus05

minus10

(a)

600 700 800 900 1000 1100

Zwitterionic 15

20

25

30

35

Bonded-intermediate

Net

char

ge o

f ben

zene

1

10

05

00

minus05

minus10

Time (fs)

Dist

ance

s(A)

C1ndashC1998400

C2ndashC2998400

(b)

0 500 1000 1500

Net

char

ge o

f ben

zene

1

Case 2

Time (fs)

10

05

00

minus05

minus10

(c)

800 850 900 950 1000

Zwitterionic

Net

char

ge o

f ben

zene

1

10

05

00

minus05

minus10

Time (fs)

15

20

25

30

35

Dist

ance

s(A)

C1ndashC1998400

C2ndashC2998400

(d)


1015840

and C2ndashC2







1ndashC1



1ndashC1


2ndashC2


1015840


1ndashC1

1015840 bond

4 Conclusions



C1


1and C

1




C1

C2

C3

C4C5

C6

195∘

158 A

266 A336 A

C9984002

C9984001


998400=

(a)

216∘

157 A

261 A346 A

C9984002

C9984001

C2

C3

C1


998400=

(b)


221 A

292 A260 A

164 A

C1

C2

C4

C3

C1998400

C2998400






Acknowledgments


References
























6 and toluenerdquo


























Journal of

Chemistry


Advances in

Physical Chemistry



Journal of

Volume 2014














Journal of

Spectroscopy



Journal of


Quantum Chemistry






CatalystsJournal of


0 500 1000 1500

Net

char

ge o

f ben

zene

1

Case 1

Time (fs)

10

05

00

minus05

minus10

(a)

600 700 800 900 1000 1100

Zwitterionic 15

20

25

30

35

Bonded-intermediate

Net

char

ge o

f ben

zene

1

10

05

00

minus05

minus10

Time (fs)

Dist

ance

s(A)

C1ndashC1998400

C2ndashC2998400

(b)

0 500 1000 1500

Net

char

ge o

f ben

zene

1

Case 2

Time (fs)

10

05

00

minus05

minus10

(c)

800 850 900 950 1000

Zwitterionic

Net

char

ge o

f ben

zene

1

10

05

00

minus05

minus10

Time (fs)

15

20

25

30

35

Dist

ance

s(A)

C1ndashC1998400

C2ndashC2998400

(d)


1015840

and C2ndashC2







1ndashC1



1ndashC1


2ndashC2


1015840


1ndashC1

1015840 bond

4 Conclusions



C1


1and C

1




C1

C2

C3

C4C5

C6

195∘

158 A

266 A336 A

C9984002

C9984001


998400=

(a)

216∘

157 A

261 A346 A

C9984002

C9984001

C2

C3

C1


998400=

(b)


221 A

292 A260 A

164 A

C1

C2

C4

C3

C1998400

C2998400






Acknowledgments


References
























6 and toluenerdquo


























Journal of

Chemistry


Advances in

Physical Chemistry



Journal of

Volume 2014














Journal of

Spectroscopy



Journal of


Quantum Chemistry






CatalystsJournal of


C1

C2

C3

C4C5

C6

195∘

158 A

266 A336 A

C9984002

C9984001


998400=

(a)

216∘

157 A

261 A346 A

C9984002

C9984001

C2

C3

C1


998400=

(b)


221 A

292 A260 A

164 A

C1

C2

C4

C3

C1998400

C2998400






Acknowledgments


References
























6 and toluenerdquo


























Journal of

Chemistry


Advances in

Physical Chemistry



Journal of

Volume 2014














Journal of

Spectroscopy



Journal of


Quantum Chemistry






CatalystsJournal of
















6 and toluenerdquo


























Journal of

Chemistry


Advances in

Physical Chemistry



Journal of

Volume 2014














Journal of

Spectroscopy



Journal of


Quantum Chemistry






CatalystsJournal of










Journal of

Chemistry


Advances in

Physical Chemistry



Journal of

Volume 2014














Journal of

Spectroscopy



Journal of


Quantum Chemistry






CatalystsJournal of

Documents

Research Article Mechanisms of Laser-Induced Reactions of ...downloads.hindawi.com/journals/ijp/2014/874102.pdf · Research Article Mechanisms of Laser-Induced Reactions of Stacked