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<Dateiname>.ppt
Zentrum für Festkörperchemie
&Neue
Materialien
Columbus 2010 Columbus 2010
Large Amplitude Motions:
Revealing Information TransferAlong Conjugated Systems
Jens-Uwe Grabow, Hilkka Saal, Isabelle Kleiner,
Angela R. Hight-Walker, Jon T. Hougen und Walther Caminati
Dipartimento di Chimica “G.Ciamician” Universita’ di Bologna
Institut für Physikalische Chemie & Elektrochemie
National Institute of Standards and Technology – Gaithersburg, MD
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<Dateiname>.ppt
Zentrum für Festkörperchemie
&Neue
Materialien
Columbus 2010
4362
1232
132
126
2int
2222224224
2222
62
int
6sin},{3cos},{}3sin,{6cos
)}(,{)(2
)2
()(22
2)6cos1(2
1
pFpPPPVpPPPPDpPPVpPFH
PPPPPPPPPPH
PCB
APPCB
PCB
H
pFPVFpH
HHHHH
mamcbbcaJbaabccJJ
cbaKcbJaKaJKJcd
aeffcbR
aT
cdRT
Benzotrifluoride: V6 internal rotation
Torsion
Rotation
Centrifugal Distorsion
Torsion Rotation Interaction
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<Dateiname>.ppt
Zentrum für Festkörperchemie
&Neue
Materialien
Columbus 2010
Benzotrifluoride: V6 internal rotation barrier with 7 digit accuracy
barrier to internal rotation V6 = 3.229948(3) cm-1
Vadim V. Ilyushin, Laura B. Favero, Walther Caminati, Jens-Uwe Grabow,
ChemPhysChem, accepted.
the heavy-top case of benzotrifluride:
A
A
A
E
Ev=0
v=1
v=2
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<Dateiname>.ppt
Zentrum für Festkörperchemie
&Neue
Materialien
Columbus 2010
Coaxial oriented Beam-Resonator Arrangement (COBRA)
Fabry-Perot resonator
resonatortuning
FT
FID
Impulse
polarization pulse:
coherence between
rotating molecular dipoles
oscillating macroscopic
dipole moment:
electromagnetic field at frequencies
of molecular transitions
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<Dateiname>.ppt
Zentrum für Festkörperchemie
&Neue
Materialien
Columbus 2010
“coaxially oriented beam resonator arrangement“(COBRA) FTMW-Spectrometer
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<Dateiname>.ppt
Zentrum für Festkörperchemie
&Neue
Materialien
Columbus 2010
para-tolualdehyde:Information Transfer Through Conjugated bonds?
V6 vs. V3 barrier to internal rotationWalther Caminati, Angela R. Hight-Walker, Jon T. Hougen, Isabelle Kleiner,
Hilkka Saal, Jens-Uwe Grabow, to be published.
Will the methyl group know about the asymmetry?
H
O
C1
3
2
1 2
3
1
2
3
Top view: Side view:along internal rotation axis
aldehyde group introduces asymmetry:
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<Dateiname>.ppt
Zentrum für Festkörperchemie
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Materialien
Columbus 2010 Columbus 2010
Internal rotation: Permutation-Inversion (PI) group
theoretical considerations
-CH3 top:
C3 permutation-inversion symmetry: C3
-C6H4-CHO frame:
Cs point group symmetry: E,
Molecular symmetry group: G6
H1
Cl
H3H2
C3 axis
C3 E C3 C3²
E (123) (123)² = (132)
A1 1 1 1
E 1 *
1 *
H. C. Longuet-Higgins, Mol. Phys. 6 (1963), 445.J. T. Hougen, J. Chem. Phys. 37 (1962), 1433; J. Chem. Phys. 39 (1963), 358.
C3 group
H1
H2H3
H
O
C1
3
2
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<Dateiname>.ppt
Zentrum für Festkörperchemie
&Neue
Materialien
Columbus 2010 Columbus 2010
tunnel-pathways, tunnel-Hamilton matrix,energy level split diagram K=0, vt=0
symmetric matrix, 2 eigenvalues:
W1= W(A1)=H11+2HE
W2=W3=W(E1)=H11-HE
Htunneling: rotation of CH3-group
H11
H11
H11
HE HE
HE
3 (feasible) equivalent
tunneling pathways in total:
H1
Cl
H3H2
C3 axis
H1
H2H3
Γ(G6)
J0J
E1
A1
2Htunneling
Htunneling
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<Dateiname>.ppt
Zentrum für Festkörperchemie
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Materialien
Columbus 2010
V6/V3- torsional barrier
0 50 100 150 200 250 300 3500
5
10
15
20
25
30
V3=25.09 cm
-1, V
6= -5 cm
-1
V3=23.79 cm-1, V
6=+5 cm-1
V3=24.47 cm-1, V
6= 0 cm-1
En
ergy
(cm
-1)
Angle (degrees)
perfect fit to torsional groundstate (vt=0) spectrum archieved
for different contributions
to the barrier
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<Dateiname>.ppt
Zentrum für Festkörperchemie
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Materialien
Columbus 2010 Columbus 2010
free internal rotor – high barrier torsion
m = 0
|m| = 1
|m| = 2
|m| = 3
|m| = 4
A
A
A
E
E
Evt = 2
vt = 1
vt = 0
E
V
0 ∞
gi = 2 gi = 3
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<Dateiname>.ppt
Zentrum für Festkörperchemie
&Neue
Materialien
Columbus 2010
“free jet“ (FJ)absorption mm-wave setup
Side View
Top View
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<Dateiname>.ppt
Zentrum für Festkörperchemie
&Neue
Materialien
Columbus 2010
“free jet“ (FJ)Absorptions-Millimeterwellen-Spektrometer
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<Dateiname>.ppt
Zentrum für Festkörperchemie
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Materialien
Columbus 2010
FJ-A-MMW vs. COBRA-FT-MW spectrometer
FJ-A-MMW COBRA-FT-MW
Jet Temperature
~20 K
~ 2 K
Sweep Rate 10 GHz/day 0.2 GHz/day
Relative Line Intensity
Nearly Boltzmanian
Altered
Resolution 0.2 MHz 3 kHz (10-7 cm-1)
Accuracy 0.050 MHz 0.3 kHz (10-8 cm-1)
Sensitivity 10-7 - 10-8 cm-1 10-10 - 10-12 cm-1
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<Dateiname>.ppt
Zentrum für Festkörperchemie
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Materialien
Columbus 2010
para-tolualdehyde: J = 34 33 a R-band
T 50 K required broken diffusion pump heaters!
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<Dateiname>.ppt
Zentrum für Festkörperchemie
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Columbus 2010
0 60 120 180 240 300 3600
20
40
60
80
100
m=±3
m=±4
m=±2
m=±1
m=0
E,vt=2
A,vt=2
A,vt=1
E,vt=1
E,vt=0
A,vt=0
V3=24.5 cm
-1, V
6=0
Ene
rgy
(cm
-1)
Angle (degrees)
low-barrier torsional energy level diagram
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<Dateiname>.ppt
Zentrum für Festkörperchemie
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Materialien
Columbus 2010
para-tolualdehyde:reduced energy level diagram for m = +/- 3
E – (1/2)(B+C)J(J+1)
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<Dateiname>.ppt
Zentrum für Festkörperchemie
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Materialien
Columbus 2010
para-tolualdehyde:Information Transfer Through Conjugated bonds!
nlm CONSTANT OPERATOR VALUE STD DEV 202 A 0.166516196839980 0.000006112879081
B 0.032937322496368 0.000000063427868 C 0.027601452277977 0.000000064713936 DAB -0.002971620212815 0.000002362977471
211 RHORHO 0.030970392251857 0.000027764172184 220 F 5.490882492526767 0.003675124595046
V3 28.369747250217017 0.016741884821443 404 DJ 0.000000000766043 0.000000000002449
DJK -0.000000001773117 0.000000000020899 DK 0.000000040780968 0.000000002059929 ODELN 0.000000000152421 0.000000000001598 ODELK 0.000000002114823 0.000000000235953
413 ALV 0.000000004455893 0.000000000607588 AK1 0.000000241437257 0.000000041691112 ODELTA -0.000000067481273 0.000000015991851 C4 0.000000007123842 0.000000004163024
422 GV 0.000000119369360 0.000000034361650 AK2 0.000013649424323 0.000003574497292 DELTA -0.000009595953284 0.000001553935395 C1 0.000000455984320 0.000000016495752 FV -0.000009370236146 0.000000061416459 ODAB -0.000073087515674 0.000002201896216
431 AK3 0.000240896878198 0.000019336762283 440 V6 -5.328585545552866 0.025635841540561
AK4 -0.013457652989215 0.000793909144900 642 AMV -0.000000029064949 0.000000005471985
BK1 -0.000003052251718 0.000001041520361 C3 -0.000000161746243 0.000000005990665
DELTAB 0.000002198996436 0.000000272705423
result of global fit
to ~800 transitions in
5 different torsional states
at experimental accuracy
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<Dateiname>.ppt
Zentrum für Festkörperchemie
&Neue
Materialien
Columbus 2010
para-tolualdehyde:Information Transfer Through Conjugated bonds!
barrier to internal rotation: V3 = 28.3 >> V6 = 5.3 cm-1
the methyl group does know about the orientation of thealdehyde group hiding in the plane - but not from sterical hindering!
H
O
C1
3
2
Top view: Side view:along internal rotation axis
1 2
3
1
2
3
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<Dateiname>.ppt
Zentrum für Festkörperchemie
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Columbus 2010
AcknowledgementAcknowledgement
Deutsche Forschungsgemeinschaft (DFG)
Land Niedersachsen
Deutscher Akademischer
Austauschdienst (DAAD)
Università di Bologna
Minister of Education, Italy