Journal of Molecular Structure 1058 (2014) 308–317

Contents lists available at ScienceDirect

Journal of Molecular Structure

journal homepage: www.elsevier .com/locate /molstruc

Structure and vibrational assignment of bis(benzoylacetonato)copper(II)

0022-2860/$ - see front matter � 2013 Elsevier B.V. All rights reserved.http://dx.doi.org/10.1016/j.molstruc.2013.11.018

⇑ Corresponding author. Tel.: +98 511 8780216.E-mail address: sftayyari@gmail.com (S.F. Tayyari).

Mohammad Vakili a, Sayyed Faramarz Tayyari b,⇑, Mahnoosh Hakimi-Tabar a, Abdo-Reza Nekoei c,Saeideh Kadkhodaei d

a Department of Chemistry, Ferdowsi University of Mashhad, Mashhad 91775-1436, Iranb Department of Chemistry, Shahrood Branch, Islamic Azad University, Shahrood, Iranc Department of Chemistry, Shiraz University of Technology, Shiraz 71555-313, Irand Department of Chemistry, Mashhad Branch, Islamic Azad University, Mashhad, Iran

h i g h l i g h t s

� Vibrational band assignments for bis(benzoylacetonato)copper are performed.� Experimentally shown that the trans isomer is predominant in the sample.� The metal–O bond strength increases by substituting of CH3 by C6H5 group.� Metal–O stretching frequency is related to the metal–O bond length.

a r t i c l e i n f o

Article history:Received 3 October 2013Received in revised form 7 November 2013Accepted 7 November 2013Available online 14 November 2013

Keywords:Vibrational assignmentDFT calculationCopper(II) benzoylacetonate complexFT-Raman spectrumFT-IR spectrum

a b s t r a c t

Fourier transform Raman (3200–150 cm�1) and infrared (4000–100 cm�1) spectral measurements havebeen made for the solid copper (II) benzoylacetonate, Cu(bzac)2 and, for comparison, copper (II) acetyl-acetonate, Cu(acac)2. The molecular electronic energies, equilibrium geometries, IR and Raman spectra,and the internal coordinates for the vibrational modes have been computed for the cis and trans struc-tures of Cu(bzac)2 at the B3LYP/6-311G* level of theory. Potential energy distribution (PED) and normalmode analysis have also been performed. A complete assignment of the observed band frequencies hasbeen proposed. Comparing of observed and calculated vibrational spectra suggests that the predominantisomer in the sample is the trans isomer.

To realize the effect of CH3 substitution by phenyl group on the structure, metal–O bond strength, andvibrational spectra, the geometrical parameters and vibrational wavenumbers of Cu(acac)2 were also cal-culated at the same level of theory. The calculated vibrational frequencies were compared with the exper-imental results. All of the measured IR and Raman bands were interpreted in terms of the calculatedvibrational modes. The metal–O bond strength was investigated by geometry calculations and spectro-scopic results. All theoretical and vibrational spectroscopic studies confirm stronger metal–ligand bondin Cu(bzac)2 than that in Cu(acac)2.

� 2013 Elsevier B.V. All rights reserved.

1. Introduction

The metal complexes of b-diketones and especially those ofacetylacetone are well known and have been extensively studied[1–7]. The investigation of the structures and properties of metalcomplexes of b-diketones is of significant importance because ofa variety of potential applications. These compounds can be usedin preparation of supported catalysts and as precursors of hetero-geneous catalysts [8–11]. These complexes have various applica-tions in industry, such as organic electroluminescent technology,luminescent materials, sensors for bioinorganic applications, and

luminescent labels in bioaffinity assays [12,13]. Because of theirhigh formation constant, b-diketonate complexes can be used indetermination of trace metals. Many 1,3-diketones have foundincreasing use as metal extractants [14–16] and some of their me-tal (lanthanon) chelates have found applications either as NMRshift reagents [17–21] or in laser technology [12,13].

The assignments of vibrational wavenumbers of copper (II) ace-tylacetonate, Cu(acac)2, have been reported by several workers.Nakamoto [22] assigned the IR band frequencies based on a normalcoordinate analysis, whereas Junge and Musso [6] assigned the IRband frequencies of several metal acetylacetonate complexes,including Cu(acac)2 based on the 13C, 18O, and 2H substitution fre-quency shifts. Raissi et al. [23] used density functional theory (DFT)calculations to assign the vibrational band frequencies. However,there are many discrepancies between the assignments reported

M. Vakili et al. / Journal of Molecular Structure 1058 (2014) 308–317 309

by these workers. In the case of copper (II) benzoylacetonate,Cu(bzac)2, a few IR bands have been considered by Nakamotoet al. [24] and David et al. [25]. To the best of our knowledge, thereis no report in the literature discussing the full assignments ofvibrational frequencies (except some tentative assignments forthe IR spectrum by Nakamoto et al [24]), the theoretical structure,and the Raman spectrum for the Cu(bzac)2 complex. In the presentwork, by the aid of DFT computations the observed vibrationalband frequencies of Cu(bzac)2 are assigned and the results arecompared with those of the Cu(acac)2 and copper(II) dibenzoylme-thane, Cu(dbm)2 [26], complexes to give a clear understanding ofsubstitution effect of phenyl groups (in b-position) on the struc-ture, stability, and CuAO bond strength of the complex. Moreover,since there are many discrepancies between the observed vibra-tional wavenumbers and assignments for Cu(acac)2 in the previ-ously published papers [6,22,23], we also attempted to obtain acomplete assignment based on quantum mechanical calculationsfor this complex in addition to that for Cu(bzac)2. In addition,due to coupling of different vibrations in the normal modes, poten-tial energy distribution (PED) and normal mode analysis have alsobeen carried out to determine the contributions of bond oscillatorsin each normal mode.

The aim of the present work is to predict the structure andvibrational spectra (harmonic wavenumbers, potential energy dis-tribution (PED), and relative intensities for Raman and IR spectra)of cis and trans isomers of Cu(bzac)2 and Cu(acac)2 by means ofdensity functional theory (DFT) calculations, to estimate thestrength of metal–oxygen bond. Comparing the geometricalparameters and vibrational spectra of Cu(bzac)2 with those ofCu(acac)2 and Cu(dbm)2 gives a clear understanding of substitutioneffect of phenyl groups (in b-position) on the structure of this sys-tem. Also, the experimental vibrational spectroscopies have beenemployed as evidences for the quantum mechanical computed re-sults. Finally, the obtained assignments and band frequencies willbe compared with the previous results.

2. Experimental

Cu(acac)2 was prepared according to the literature [27] andsimilar procedure was used for preparation of Cu(bzac)2 complex.The precipitated Cu(bzac)2 was recrystallized from CH2Cl2 solution.Calc. for C20H18CuO4: C,62.17; H,4.66. Anal. Found: C,62.91; H,4.91.

The infrared spectra in the region 4000–500 cm�1 were recordedon a Bomem MB-154 Fourier transform spectrophotometer usingKBr pellets and CCl4 solution. The spectra were collected with a res-olution of 2 cm�1 by signal averaging the results of 15 scans.

The Far-IR spectra in the region 600–100 cm�1 were obtainedusing a Thermo Nicolet NEXUS 870 FT-IR spectrometer equippedwith a DTGS/polyethylene detector and a solid substrate beam split-ter with use of polyethylene disks. The spectrum was collected witha resolution of 2 cm�1 by signal averaging the results of 32 scans.

The FT-Raman spectra in the region 3200–100 cm�1 were re-corded employing a 180� backscattering geometry and a BomemMB-154 Fourier transform Raman spectrometer. The instrumentwas equipped with a ZnSe beam splitter and a TE cooled InGaAsdetector. Excitation wavelength at 1064 nm was obtained from aNd/YAG laser. Rayleigh filtration was afforded by a set of two holo-graphic technology filters. The spectra were accumulated for 1500scans with a resolution of 2 cm�1. The laser power at the samplewas 500 mW.

3. Method of analysis

All the computations are performed using Gaussian 09W [28]software. The geometry optimization, vibrational frequencies, the

internal coordinates of Cu(acac)2, and the cis and trans isomersof Cu(bzac)2 are obtained at the B3LYP [29,30] level, using 6-311G* basis set. Raman activities were computed at the same levelof calculation, using standard procedures (Freq = Raman).

A normal coordinate analysis was carried out to provide a com-plete description of the fundamental vibrational wavenumbers forthe molecules. For this purpose, the full set of 138 standard inter-nal coordinates containing 51 redundancies for the Cu(acac)2 com-plex is defined as given in Table S1 (Supplementary material). Fromthese a non-redundant set of local symmetry coordinates was con-structed by a suitable linear combination of internal coordinatesfollowing the recommendation of Pulay et al. [31]. The combina-tion coordinates and symmetry coordinates are given in Table S2(Supplementary material). The potential energy distributions(PEDs) were obtained using the calculated symmetry coordinates.

By combining the results of the GaussView 4.1.2 program [32]with symmetry considerations and potential energy distribution(PED) the vibration descriptions were made with a high degreeof accuracy. Vibrational assignments are based on comparison ofcalculated and observed Raman and IR frequencies and intensities.

Acetonitrile was selected for studying the isomerisation in solu-tion following the SCRF/PCM method [33]. In this method the soluteis embedded in the dielectric medium surrounded by a cavityshaped in the form of the solute [34,35]. The van der Waals radiisuggested by Bondi [36] were adopted for atoms. In this level of cal-culation the specific solute–solvent effects are not taken into ac-count and the obtained solvation energies correspond to theelectrostatic contributions, which, still, play a dominant role in tau-tomerization reactions [37].

4. Results and discussion

4.1. Molecular geometry

To explore the effects of phenyl group on the metal–ligandstrength, the optimized geometrical parameters of Cu(bzac)2 andCu(acac)2 are calculated at the B3LYP/6-311G* level of theory.

Theoretically, two configurations are possible for Cu(bzac)2.These are recognized as trans and cis configurations (Fig. 1), which,according to the calculations, have Ci and C2 symmetries, respec-tively. Theoretical calculations in the gas phase indicate that theenergy difference between cis and trans isomers is negligible(0.32 kcal mol�1), which reduces to 0.11 kcal mol�1 in the CH3CNsolution. Zero point energy (ZPE) corrections in the gas phase notmuch change this energy difference (0.34 kcal mol�1). Therefore,from the theoretical point of view, the coexistence of both cisand trans isomers of Cu(bzac)2 in the sample is suggested. How-ever, the vibrational frequency investigations suggest that thetrans isomer in the sample is predominant and rule out the pres-ence of the cis isomer, which will be discussed in Section 4.2.3.

Since, excellent results have been obtained for similar com-pounds by using the B3LYP/6-311G* level [38–40], this level of cal-culation is used in this work. The selected calculated geometricalparameters for Cu(bzac)2, Cu(acac)2, and Cu(dbm)2 for comparison,are listed in Table 1. Some important geometrical parameters andvibrational band frequencies related to the MAO bond strengthfor these complexes are also collected in Table 2.

The comparison between geometry of cis and trans isomersshows that the steric hindrance between two phenyl groups inthe cis isomer causes the dihedral angle between the phenylgroups and chelated ring in the cis isomer to be larger than thatin the trans isomer. Therefore, it is expected that the conjugationbetween the phenyl group and chelated ring in the cis isomer isless than that in the trans isomer. According to Table 1, in bothcis and trans isomers of Cu(bzac)2, substitution of one of themethyl groups in each ligand and all methyl groups in Cu(dbm)2

Fig. 1. Cis and Trans configurations and atom numbering of Cu(bzac)2.

Table 1Some selected geometrical parameters of Cu(acac)2, Cu(bzac)2, and Cu(dbm)2,calculated at B3LYP/6-311G* level of theory (bond lengths in Å, bond angles in �).

Cu(acac)2 Cu(bzac)2 Cu(dbm)2 [26]

Cis Trans

Bond distances (Å)CuAO2 1.925 1.922 1.923 1.919CuAO1 1.925 1.923 1.920 1.919C1AO1 1.270 1.274 1.274 1.275C2AO2 1.270 1.271 1.272 1.275C1ACa 1.403 1.406 1.407 1.405C2ACa 1.403 1.403 1.402 1.404CAPh – 1.496 1.496 1.496CACH3 1.511 1.511 1.511 –O� � �O 2.769 2.761 2.760 2.754Bond angles (�)O2CuO1 91.9 91.8 91.8 91.6C2O2Cu 127.2 127.0 126.8 127.8C1O1Cu 127.2 128.2 128.3 127.8CaC1O1 125.2 124.1 124.1 124.6CaC2O2 125.2 125.6 125.7 124.6C2CaC1 123.1 123.3 123.3 123.4Ua – 16.9 12.2 19.3

a U, dihedral angle between phenyl and chelated rings.

310 M. Vakili et al. / Journal of Molecular Structure 1058 (2014) 308–317

with phenyl groups results in decreasing the CuAO bond distancesand increasing the C@C and C@O bond lengths, compared with thecorresponding values in Cu(acac)2. As it is shown in Table 2, theshorter CuAO bond length suggest more stability of Cu(bzac)2

and Cu(dbm)2 complexes than Cu(acac)2. This conclusion is inagreement with the vibrational spectra observations, which arediscussed in Section 4.2.

4.2. Vibrational analysis

The infrared spectra of Cu(bzac)2 in the solid phase and CCl4

solution is shown in Fig. 2. For comparison, the IR and Raman

Table 2Comparing several properties related to the Cu–ligand strength for Cu(acac)2,Cu(bzac)2, and Cu(dbm)2.a

Cu(acac)2 Cu(bzac)2b Cu(dbm)2

c

CuAO 1.925 1.922 1.919CAO 1.403 1.404 1.405CACa 1.270 1.273 1.275O� � �O 2.769 2.760 2.754mCO 1578 1554 1545maOACuAO 613 628 656msOACuAO 450 543 567

a Bond lengths in Å; frequencies in cm�1; ma, and ms are asymmetry and sym-metry stretching, respectively.

b The averaged geometrical parameters for cis and trans are given.c Data from [26].

spectra of the titled compound and Cu(acac)2 in the solid stateare compared in Figs. 3 and 4, respectively. The theoretical andexperimental vibrational frequencies and their assignments alongwith PED for Cu(bzac)2 and Cu(acac)2 are given in Tables 3 and 4,respectively.

There is a noticeable disagreement between the band wave-numbers of the previously published Raman spectrum [23] ofCu(acac)2 complex and the present Raman spectrum shown inFig. 4 and listed in Table 4. For instance, the Raman bands at3076, 2921, 1577, 1363, 1278, 1187, 1025, 939, 783, 688, 562,450, 409 and 208 cm�1 in the present Raman spectrum ofCu(acac)2 were reported at 3064, 2909, 1566, 1356, 1270, 1179,1013, 928, 769, 676, 550, 437, 396 and 194 cm�1, respectively, byRaissi et al. [23]. These discrepancies indicate that probably the ori-ginal file of the Raman spectrum of Cu(acac)2 has not been avail-able to these authors, they may extracted the wavenumbers froma hard copy of the spectrum. We also observed some discrepanciesbetween our IR wavenumbers and those reported by Raissi et al.[23], see Table 4. Recently, similar situation has been reportedfor another work of Raissi et al. [39]. In addition to the vibrationalwavenumbers, there are also many discrepancies between our cal-culated PED and those reported by Raissi et al. [23]. Unfortunatelythese authors did not state how they calculated the PEDs.

The calculated fundamental wavenumbers are compared withthe experimental results. The calculated frequencies are slightlyhigher than the corresponding observed values for the majorityof the normal modes. Two factors may be responsible for the dis-crepancies between the experimental and computed spectra ofCu(bzac)2 and Cu(acaca)2. The first is caused by the environment.The DFT calculations have been done at the gas phase while theexperimental data are obtained at the condensed phases. The sec-ond reason for these discrepancies is the fact that the calculated

Fig. 2. The IR spectra of Cu(bzac)2 in CCl4 solution (—) and in solid phase (� � �).

Fig. 3. The IR spectra of Cu(bzac)2 (—) and Cu(acac)2 (� � �) in the solid state (in the1650–260 cm�1 range).

Fig. 4. The Raman spectra of Cu(bzac)2 (—) and Cu(acac)2 (� � �) in the solid state (inthe 1650–100 cm�1 range).

M. Vakili et al. / Journal of Molecular Structure 1058 (2014) 308–317 311

values are harmonic frequencies but the experimental values con-tained anharmonic vibrational frequencies.

The overestimation of computed wavenumbers is quite system-atic and could be corrected by applying appropriate scaling factors[38–40]. In Tables 3 and 4 the calculated harmonic frequencies arescaled by different scaling factors for the regions above and below2000 cm�1, recommended by Tayyari et al. [40]. As it is indicated inthese tables, excellent agreement exists between observed andscaled calculated wavenumbers.

4.2.1. Vibrational irreducible representationAccording to the C2 and Ci symmetries for cis and trans

Cu(bzac)2 complexes, respectively, the 3N-6 = 123 vibrationalmodes can be classified among the symmetry species:

for C2 symmetry : Cvib ¼ 62aðIR&RÞ þ 61bðIR&RÞfor Ci symmetry : Cvib ¼ 60agðRÞ þ 63auðIRÞ

The 81 normal modes of Cu(acac)2 span the representation of 13ag (R), 12 b1g (R), 8 b2g (R), 6 b3g (R), 7 au, 9 b1u (IR), 13 b2u (IR), 13b3u (IR) species of D2h symmetric group.

4.2.2. Band assignment4.2.2.1. CHa stretching. We expect to observe the vibrational bandfrequencies due to the CHa stretching at about 3100 cm�1 [5,38–41]. According to the calculated results in Cu(bzac)2, m CHa in

the IR and Raman spectra of Cu(bzac)2, in the solid phase, is ob-served at 3100 and 3098 cm�1, respectively. The correspondingband in Cu(acac)2, Cu(dbm)2 [26], and bzac [41] is observed at3077, 3134, and 3109 cm�1, respectively. Therefore, it seems thatby successive substitution of methyl groups by phenyl the CHastretching shows a blue shift of about 20–30 cm�1.

4.2.2.2. The CH stretching of phenyl and methyl groups. Assignmentsfor the phenyl group vibrational modes are given in Wilson’s nota-tion [42]. The CH stretching modes of the phenyl and methylgroups are expected to occur in the 3100–3000 cm�1 and 3000–2900 cm�1 region, respectively [43–45]. In the Raman spectrumof Cu(bzac)2 five bands are observed at 3089, 3069, 3061, 3044,and 3021 cm�1 which are attributed to the 2, 20b, 20a,7b, and 13normal modes of phenyl groups, respectively. All of these vibra-tions have weak scattering intensity in the Raman spectrum. Alsothree bands are observed in the Raman spectrum of Cu(bzac)2 at2996, 2968, and 2922 cm�1 that the first two bands are assignedto the asymmetric and the latter is assigned to the symmetricCAH stretching of the CH3 group. The corresponding bands inCu(acac)2 were observed at 3005, 2970, and 2922 cm�1.

4.2.2.3. 1700–1000 cm�1 Region. In this region, in addition to the CHdeformation and rocking, CHa in plane bending, and the CACstretching modes, we also expect to observe the bands due to theC@C and C@O stretching motions.

In Cu(bzac)2, the very strong Raman band at 1598 cm�1 is as-signed to 8a of the phenyl group, which is somewhat coupled withthe asymmetric C@C@O stretching. According to the calculations,the band at 1590 and 1554 cm�1 are arisen from coupling between8b and asymmetric C@C@O stretching vibrations. The strong IRband at 1578 cm�1 of Cu(acac)2 is attributed to the asymmetricC@C@O stretching (31%) coupled to the asymmetric CH3 deforma-tion (18%) and CACH3 bending (19%) (a B3u species). This band isassigned by Raissi et al. to symmetric C@O stretching (65%) [23].Our assignment is in better agreement with the Nakamoto’s work[22], which assigned this band to the C@O and C@C stretchingvibrations. The strong band in the IR spectrum of Cu(bzac)2 at1554 cm�1is assigned to the asymmetric C@C@O stretching cou-pled with 8b. Therefore, the asymmetric C@C@O stretching isstrongly coupled with both 8a and 8b. The corresponding band inCu(dbm)2 appears at 1545 cm�1. Therefore, it seems that by substi-tution of the methyl groups by phenyl groups, increasing of reso-nance effect, the asymmetric C@C@O stretching wavenumberreduces.

The strong IR band at 1516 cm�1 is assigned to the symmetricC@C@O stretching strongly coupled with dCHa and 19a. The StrongIR band in Cu(acac)2 at 1554 cm�1 is assigned to asymmetricC@C@C stretching (15%) coupled to CH3 deformation, dCHa, andCACH3 stretching vibrations. Nakamoto [22] considered this bandas a combination band. The band at 1487 cm�1 in the IR spectrumof Cu(bzac)2 complex is assigned to the 19b of the phenyl ringsstrongly coupled to the asymmetric CH3 deformation.

According to the Nakamoto et al. [22] and our assignments, themedium band at 1354 cm�1 in the IR spectrum of Cu(acac)2 isattributed to the symmetric deformation of methyl groups (dsCH3),whereas David et al. assigned this band to the dCHa coupled withmaC@C [25]. The corresponding band is observed at 1355 cm�1 forCu(bzac)2. The daCH3 modes of Cu(acac)2 and Cu(bzac)2 are ob-served at about 1460 and 1410 cm�1. The medium IR band andstrong Raman band at about 1290 cm�1 in the Cu(bzac)2 spectraare attributed to the C@Ca@C symmetric stretching coupled tomode 14 of the phenyl groups and dsCH3. The corresponding IRband for Cu(acac)2 appears at 1275 cm�1. The corresponding bandin Cu(dbm)2 also appears at 1290 cm�1 [26].

Table 3Fundamental band assignments of Cu(bzac).a

Theoretical Experimental Characterization of normal modes with PED (%)

Trans Cis IR IR R

s.s Fs I,IR RA s.s Fs I,IR RA Solid CCl4 Solid

ag 3100 0 165 A 3101 1 164 3098(vw) mCHa(56), mCHph(16)au 3100 25 0 B 3100 24 5 3100(vw) 3099(vw) mCHa(56), mCHph(16)ag 3084 0 151 B 3085 1 2 3089(vw) mCHph(80)au 3084 11 0 A 3085 7 177 3082(vw) 3084(vw) 3089 mCHph(80)ag 3068 0 234 A 3068 0 243 3069(vw) 2(75). mCHa(10)au 3068 26 0 B 3068 28 5 3064(sh) 3068(vw) 3069 2(75). mCHa(10)ag 3057 0 449 A 3058 71 300 3064 3062(vw) 3061(vw) 20a(84)au 3057 86 0 B 3058 8 73 3064 3062 3061 20a(84)au 3045 36 0 A 3046 3 182 3042(vw) 3040(vw) 3044(vw) 7b(82)ag 3045 0 317 B 3046 33 110 3042 3040 3044 7b(76)ag 3035 0 114 A 3036 0 54 3026(sh) 3026(sh) 3021(vw) 13(81)au 3035 0 0 B 3036 0 58 3026 3026 3021 13(81)ag 3004 0 168 A 3005 1 165 2996(vw) maCH3(77)au 3004 52 0 B 3004 48 11 2989(vw) 3003(vw) maCH3(77)au 2977 23 0 B 2977 23 235 2968(vw) 2964(vw) 2968(w) maCH3(77)ag 2977 0 209 A 2976 0 0 2968 maCH3(77)ag 2923 0 480 A 2922 25 543 2920(vw) 2926(vw) 2922(vw) msCH3(89)au 2922 28 0 B 2922 6 6 2920(vw) 2926(vw) 2922(vw) msCH3(89)ag 1613 0 515 A 1613 2 274 1598(vs) 8a(69), maCACAO(10)au 1612 14 0 B 1612 7 219 1602(sh) 1599(sh) 1598 8a(83), maCACAO(10)ag 1606 0 248 A 1606 13 99 1602 1599 1598 8b(52), maCACAO(13)au 1599 283 0 B 1599 284 14 1590(m) 1590(m) 1598 8b(58), maCACAO(10)ag 1579 0 63 A 1580 13 20 1562(w) 8b(54), maCACAO(14)au 1567 1020 0 B 1568 953 51 1554(vs) 1557(s) 8b(39), maCACAO(19), daCH3(11)au 1522 1195 0 A 1523 1025 112 1516(vs) 1520(vs) 19a(19), dCHa(20), msCCO(20), daCH3(12)ag 1521 0 199 B 1520 78 59 1516 19a(21), dCHa(20), msCCO(19), daCH3(12)au 1495 93 0 A 1495 99 17 1508(sh) 19a(71)ag 1495 0 36 B 1494 0 10 1489(vw) 19a(75)au 1478 170 0 A 1478 123 4 1487(s) 1488(m) daCH3(44), 19b(27), maCACAO(11)ag 1473 0 6 B 1472 81 3 1487 1488 daCH3(52), 19b(21)au 1457 21 0 B 1456 16 8 1462(m) 1455(m) daCH3(84)ag 1457 0 25 A 1456 6 18 1450(vw) daCH3(87)au 1453 271 0 A 1454 147 2 1462 1455 19b(42), daCH3(39}ag 1452 0 10 B 1451 56 3 1462 1455 1450(vw) 19b(52), daCH3(29)au 1427 553 0 A 1428 535 27 1411(m) 1397(vs) 1411(vw) 19b(33), daCH3(30), maCACAO(18)ag 1406 0 25 B 1406 18 0 1370(sh) 1369(sh) daCH3(34), 19b(23), maCACAO(22)ag 1381 0 64 A 1382 31 61 1355(m) 1361(sh) 1355(w) dsCH3(81)au 1381 31 0 B 1381 1 1 1355(m) 1361(sh) dsCH3(81)ag 1330 0 10 A 1330 2 8 1333(vw) 3(86)au 1330 1 0 B 1329 1 1 1339(sh) 3(86)ag 1309 0 111 A 1309 0 66 1309(m) 14(61)au 1308 51 0 B 1307 50 27 1310(m) 1308(vw) 1309 14(61)ag 1281 0 589 A 1281 29 374 1288(m) 1291(w) 1290(s) 14(36), maCAC@C(21), dsCH3(14)au 1279 159 0 B 1279 99 126 1288 1288 18a(36), maCAC@C(21), dsCH3(14)au 1215 105 0 A 1214 96 80 1212(m) 1210(m) 1212(mw) 9a(22), dCHa(24), dsCH3(16)ag 1212 0 93 B 1211 2 0 1212 9a(22), dCHa (24), dsCH3(16)ag 1183 0 8 A 1183 3 6 1189(w) 9a(71)au 1182 28 0 B 1181 16 1 1181(w) 1180(vw) 9a(71)au 1161 3 0 A 1161 1 13 1155(w) 1157(vw) 1156(w) 15(87)ag 1161 0 18 B 1161 1 5 1155 1157 1156 15(87)au 1108 17 0 A 1109 3 28 1107(vw) 1108(vw) 1108(vw) 18a(48), qCH3(15), msCACAO(13)ag 1107 0 42 B 1107 17 7 1107 1108 1108(vw) 18a(48), qCH3(15), msC-C-O(13)au 1081 20 0 A 1081 14 0 1070(w) 1071(vw) 1073(vw) 18b(76)ag 1081 0 2 B 1081 2 1 18b(82)au 1036 16 0 B 1036 16 0 1028(m) qCH3(54), cCCCC(24)ag 1036 0 1 A 1036 0 0 qCH3(54), cCCCC(25)ag 1030 0 40 A 1030 17 29 1028 1030(w) 18a(63), qCH3(17)au 1030 35 0 B 1030 14 3 1028 1028 1030 18a(64), qCH3(18)au 1016 34 0 A 1018 12 17 1009(w) 1009(vw) 18a(17), qCH3(48)ag 1015 0 17 B 1015 16 1 1009 1009 18a(18), qCH3(47)ag 997 0 165 A 997 3 122 1001(vs) 12(83)au 997 8 0 B 996 3 16 1000(w) 1000(vw) 1001 12(78)ag 983 0 1 A 981 1 2 990(vw) 5(91)au 983 4 0 B 979 3 1 985(vw) 990(sh) 5(91)ag 966 0 35 A 966 1 31 962(w) 5(23), qCH3(23), dCCC(10), dCCO(10)au 963 37 0 B 963 31 2 958(w) 961(vw) 5(23), qCH3(23), dCCC(10), dCCO(10)ag 954 0 2 A 953 1 2 17a(91)au 954 0 B 952 3 0 17a(91)au 919 2 0 A 917 0 1 922(vw) 925(vw) 17b(86)ag 919 0 2 B 917 2 1 922 925 17b(86)au 848 26 0 A 848 24 6 856(mw) 856(vw) 853(vw) 6a(34). mCAC(14), dCO(13)

312 M. Vakili et al. / Journal of Molecular Structure 1058 (2014) 308–317

Table 3 (continued)

Theoretical Experimental Characterization of normal modes with PED (%)

Trans Cis IR IR R

s.s Fs I,IR RA s.s Fs I,IR RA Solid CCl4 Solid

ag 845 0 5 B 845 1 0 856 856 853 6a(36). mCAC(13), dCO(12)ag 837 0 4 A 837 1 4 832(vw) 10a(86)au 837 2 0 B 836 1 1 834(vw) 835(vw) 10a(86)au 797 2 0 B 796 1 2 796(vw) 797(vw) 10b(76), C(20)ag 797 0 4 A 796 1 2 797 10b(73), C(24)au 758 78 0 B 762 74 0 773(m) 11(24), cCHa(48)ag 757 0 2 A 762 0 1 774(vw) 11(24), cCHa(48)au 708 117 0 B 709 120 1 707(m) 710(w) 11(52), C(37)ag 707 0 2 A 708 0 0 11(54), C(39)au 692 38 0 A 691 6 4 692(w) 695(vw) 694(vw) 6a(53), dCO(10)ag 690 0 8 B 690 25 2 692 695 694 6a(53), dCO(10)au 686 40 0 A 686 0 0 683(m) 687(vw) 11(98)ag 686 0 1 B 686 41 1 683 687 11(77)au 625 26 0 A 625 28 3 628(m) 630(vw) 6b(39), maCuAO(11), dCACH3(29)ag 621 0 12 B 621 0 4 618(vw) 6b(74), C(17)au 617 12 0 A 618 11 7 613(sh) 612(vw) 618 6b(45), dCACH3(25), maCuAO(11)au 589 1 0 B 590 1 4 599(vw) 597(vw) 602(vw) cCACH3(52), 16b(19), maCuAO(11)ag 588 0 6 A 589 0 1 602 cCACH3(61), 16b(21)ag 583 0 4 B 586 8 0 599 597 602 dCH3ACAO(67), 6b(11), maCuAO(8)au 561 52 0 A 554 16 32 555(w) 554b 6b(50), msCuAO(15), dCH3ACAO(14)ag 543 0 38 B 550 47 0 541(mw) 6b(50), msCuAO(15), dCH3ACAO(14)au 460 40 0 A 459 7 12 457(w) 460 6b(55), D(22)ag 451 0 10 B 454 19 0 449(vw) 16b(61), D(21)au 442 18 0 A 439 8 11 440(vw) 442 16b(72)ag 425 0 14 B 426 12 1 431(w) 16b(37), dCACACH3(10)au 405 0 0 A 404 0 0 16a(94)ag 405 0 1 B 404 0 1 402(vw) 16a(93)au 376 21 0 A 372 0 14 374(m) 374(m) dCAph(34), maCuAO(17), dphACAC(13)ag 328 0 10 B 332 21 6 331(w) dCAph(54), maCuAO(15)au 305 1 0 A 308 0 2 dCAph(38), maCuAO(11)ag 305 0 4 B 300 6 0 314(w) dCAph(32), dOACuAO(10), dCACH3(27)au 285 66 0 B 285 51 1 282(s) 286(s) dCAph(19), maCuAO(18), dCAOACu(17), dOACuAO(13)au 254 3 0 A 255 0 1 mCAph(32), maCuAO(11), dCACH3(22), dCO(21)au 245 25 0 B 248 26 0 266(m) cOACuAO(51), cCAph(37)ag 203 0 7 A 205 0 4 219(w) cCAph(41), cCCCC(35)au 194 5 0 B 198 4 3 217(s) 201(w) cCAph(32), cCCCC(51)ag 192 0 12 B 178 2 5 177(w) dbzACuAbz(100)ag 169 0 9 A 175 0 14 177 dbzACu-bz(94)au 154 0 0 A 155 0 1 154(w,sh) sOACuAO(59), cCACH3(30)ag 145 0 1 B 147 0 1 sOACuAO(63), cCACH3(39)au 142 2 0 A 138 2 3 147(w) sOACuAO(14), dCAph(23), cCACH3(39)ag 98 0 1 A 100 0 0 sCH3(77), cCO(13)au 97 0 0 B 96 0 2 sCH3(72), cCAph(13), cCO(12)ag 88 0 6 B 90 1 3 dCAph(52), dCO(25). msCuAO(10)au 72 1 0 A 74 0 1 sCH3(56), cCO(15), cCAph(10)ag 70 0 1 A 71 0 3 sCH3(41), cCO(31), cCAph(11)ag 61 0 4 B 69 0 1 cCO(65), cCAph(27)au 44 0 0 A 39 0 4 dbzACuAbz(100)au 32 2 0 B 34 2 0 sph(32), cCH3COCu(40)ag 26 0 11 A 27 0 10 s-ph(100)au 21 0 0 A 19 0 1 s-ph(75)au 12 0 0 B 17 1 2 cphCOAphCO(90)

a s.s., symmetry species; Fs stands for scaled (by 0.9600 and 0.9781 for higher and lower than 2000 cm�1) wavenumbers calculated at the B3LYP/6-311G(d); I.IR, infraredintensity in KM/mol; AR, Raman scattering activities in A4/amu; m, stretching; d, in-plane bending; c, out-of-plane bending; q, in-plane rocking; p, out-of-plane bending; s,torsion; s, strong; m, medium; w, weak; vw, very weak; and sh, shoulder.

b Below 500 cm�1 has different scale; ph, phenyl.

M. Vakili et al. / Journal of Molecular Structure 1058 (2014) 308–317 313

The 1212 cm�1 in the Cu(bzac)2 spectra is assigned to dCHa (24%),which is strongly coupled with 9a (22%) and dsCH3 (16%). dCHa inCu(acac)2 complex appears at considerably lower wavenumber,1189 cm�1. The blue shift of this band in Cu(bzac)2 is partly causedby coupling with 9a. This frequency shift is in good agreement withthe results of the present DFT calculations. The corresponding bandin Cu(dbm)2 observed at 1232 cm�1. Therefore, as it was observedfor the CHa stretching, by successive substitution of the phenylgroups, the in-plane bending also shows a blue shift of about20 cm�1 per each phenyl group substitution. Part of this frequency

shift is caused by coupling with the phenyl groups vibrationalmodes, such as 9a, and part of it may be also caused by increasingthe resonance between the chelated ring and phenyl groups.

The IR spectrum of Cu(acac)2 shows a medium band at1020 cm�1, which is assigned to the CH3 rocking (61%) coupledto C@C@C bending (35%). However, Raissi et al. [23] assigned thisband to the CH3 rocking coupled to C@C@O. The correspondingbands in Cu(bzac)2 are observed at 1028 and 1009 cm�1, whichthe former is coupled with CCCC out of plane bending and the lat-ter is coupled to the 18a.

Table 4Vibrational assignments, experimental, and calculated wavenumbers (in cm�1) of Cu(acac)2.a

Theoretical Experimental Assignment

No Sym. Freq IIR AR IR (Solid) R (Solid) This work Ref. [22] Ref. [24] Ref. [25] Ref. [23]

1 ag 3078 0 217 3077(mw) mCHa(65), maCH3(9) mCHa(98)2 b3u 3078 33 0 3077(w) mCHa(65), maCH3(9) mCH mCHa(98)3 b2u 3005 3 0 maCH3(80), maCACAO(10) maCH3(i.p)(93)4 b1g 3005 0 7 maCH3(79), maCACAO(10) maCH3 (i.p)(91)5 ag 3005 0 314 3001(w) maCH3(76) maCH3(i.p)(93)6 b3u 3005 92 0 3005(w) maCH3(76) maCH3(i.p)(91)7 b1u 2977 47 0 2970(w) maCH3(77) maCH3(o.p.)(91)8 b2g 2977 0 0 maCH3(77) maCH3(o.p.)(91)9 b3g 2976 0 376 2970(w) maCH3(77) mCH3 maCH3(o.p.)(91)10 au 2976 0 0 maCH3(77) maCH3(o.p.)(91)11 ag 2922 0 781 2921(m) msCH3(90) msCH3(96)12 b3u 2922 14 0 2922(w) msCH3(90) msCH3(96)13 b2u 2922 37 0 2922(w) msCH3(90) msCH3(96)14 b1g 2922 0 17 2921(m) msCH3(90) mCH3 msCH3(96)15 ag 1610 0 79 1580(w) maC@C@O(31), daCH3(18), dCACH3(19) msC@O(65)16 b3u 1591 1073 0 1578(vs) msC@C@O(31), daCH3(18), dCACH3(19) mC@O,mC@C mC@C maC@O msC@O(65)17 b2u 1524 640 0 1554(s) 1551(vw) maC@C(15),dCH3(24),dCHa(25),mCACH3(13) Combination mC� � �O ma(C2@C3,C3@C4)(49),dCHa(27)18 b1g 1522 0 1 maCC(15),dCH3(24),dCHa(25),mCACH3(13) ma(C2@C3,C3@C4)(49), dCHa(27)19 b2u 1488 141 0 1532(s) daCH3(76), maCCO mC� � �O, mC� � �C mC� � �O msC@O daCH3(53), dCHa(17)20 b1g 1480 0 3 daCH3(78), maCCO daCH3(58), dCHa(15)21 ag 1464 0 38 1430(w,br) daCH3(86) daCH3(78)22 b3u 1463 158 0 1460(mw) daCH3(85) dCH, mC� � �C msC@C daCH3(78)23 b1u 1457 32 0 1460(mw) daCH3(92) dCH, mC� � �C msC@C daCH3(86)24 b2g 1457 0 39 1430 daCH3(93) daCH3(86)25 b3g 1456 0 12 1430 daCH3(95) daCH3(86)26 au 1456 0 0 daCH3(95) daCH3(86)27 b2u 1433 549 0 1416(m) daCH3(63),maC@O(19), maCCaC(14) ddCH3 ddCH3 mC@O, dCH maC@O(57), daCH3(21)28 b1g 1410 0 0 daCH3(61),maC@O(20), maCCaC(17) maC@O(45), daCH3(19)29 ag 1382 0 53 1370(mw) dsCH3(87) dsCH3(75)30 b3u 1382 1 0 dsCH3(87) dsCH3(75)31 b2u 1380 61 0 1354(m) dsCH3(87) dsCH3 dsCH3 dCH, maC@C dsCH3(77)32 b1g 1380 0 0 dsCH3(88) dsCH3(77)33 ag 1272 0 45 1278(m) msCCC(10),mCACH3(14),daCH3(41),dCO(15) as(C2@C3,C3@C4)(56), dsCH3(9)34 b3u 1271 64 0 1275(m) msCCC(10),mCACH3(14),daCH3(41), dCO(15) mCACH3, mC� � �C mCACH3, mC@C maC@C, maCACH3 ms(C2@C3,C3@C4)(56), dsCH3(9)35 b2u 1202 39 0 1189(m) dCHa(29),mCACH3(10),daCH3(12) dCH,mCACH3 dCH dCHa(73)36 b1g 1198 0 33 1187(m) dCHa(29),mCACH3(10),daCH3(12),dOC(10) dCHa(73)37 b3g 1044 0 0 pCH3(66) pCH3(78)38 au 1044 0 0 pCH3(63) pCH3(78)39 ag 1033 0 2 1023(w) qCH3(62), dCCaC(36) qCH3(59), dC@C@O(12)40 b1u 1031 35 0 1020(m) pCH3(77) qrCH3 qrCH3 pCH3(77)41 b2g 1030 0 0 pCH3(76) pCH3(77)42 b3u 1030 47 0 1020 qCH3(61), dCCaC(35) qCH3(59), dC@C@O(12)43 b2u 1023 12 0 1020 qCH3(85), dCHa(7) qCH3(57), dCHa(21)44 b1g 1021 0 0 qCH3(85), dCHa(7) qCH3(57), dCHa(21)45 ag 951 0 18 939(m) dCCaC(55), qCH3(36) maCAAMe(31), qCH3(26), dCHa(21)46 b3u 949 11 0 dCCaC(55), qCH3(36) maCAMe(31), qCH3(26), dCHa(21)47 b2u 929 26 0 937(m) maCAMe(90) mC� � �C, mC� � �O mC� � �O, mCAMe mCAMe(38), qCH3(23), dCCC(12)48 b1g 923 0 4 maCAMe(90) mCAMe(38), qCH3(23), dCCC(12)49 b1u 777 36 0 782(s) cCHa(77) pCH3 dCH cCHa(94)50 b2g 776 0 0 779(w) cCHa(77) cCHa (94)51 b3u 667 22 0 685(s) dOCMe(98) mCAMe, R.defo.,mCuAAO R.defo., mCuAO D(51), dCAMe(25)52 ag 664 0 9 686(mw) dOCMe(98) D(51), dCAMe(25)53 b1u 662 20 0 652(mw) C(75), cCAMe(23) mCAMe, mCuAO C(71)

314M

.Vakili

etal./Journal

ofM

olecularStructure

1058(2014)

308–317

54 b2g 659 0 0 654(vw) C(75), cCAMe(23) C(71)55 b2u 606 38 0 613(mw) maOACuAO(92) R. defo., mCuAO O.P D(61), dCAMe(19)56 b1g 559 0 0 maOACuAO(90) D(59), dCAMe(18)57 au 553 0 0 cCAAMe(95) C(67)58 b3g 552 0 4 562(m) cCAMe(95) C(67)59 b3u 456 81 0 455(s)# msOACuAO(92) mCuAO, mCAMe mCuAO msCuAO(49), dCAMe(23)60 ag 440 0 59 448(vs) msOACuAO(93) msCuAO(49), dCAMe(23)61 b2u 428 12 0 430(m) D(95) R. defo. O.P msCuAO(48), dCAMe(18)62 b1g 401 0 1 407(w) D(96) msCuAO(48), dCAMe(18)63 b2u 332 0 0 dOACuAO(96) D(61), dCAMe(17)64 b3u 292 48 0 289(m) dOACuAO(97) dCuAO D(64), dCAMe(15)65 ag 255 0 0 dCAMe(96) D(51), dCAMe(21)66 b3u 250 2 0 dCAMe(95) D(51), dCAMe(21)67 b1u 247 35 0 264(m) cacac-Cu-acac(95) C(70), dCAMe(10)68 b1g 207 0 12 209(sh) maOACuAO(90) D(54), dCAMe(14)69 ag 192 0 22 202(s) macac-Cu-acaca(92) D(54), dCAMe(14)70 b2g 156 0 1 163(w) cCCaC(65), cCH3(29) C(46), dCAMe(19)71 b1u 155 0 0 cCCaC(65), cCH3(29) C(46), dCAMe(19)72 au 153 0 0 cOACuAO(96) C(53), dCAMe(15)73 b3g 139 0 0 cOACuAO(90) C(57), dCAMe(18)74 b2g 91 0 3 132(m) sOACuAO(94) C(57), dCAMe(18)75 au 89 0 0 sCH3(92) sCH3(83)76 b3g 89 0 0 s CH3(92) sCH3(83)77 b2u 87 2 0 dacac-Cu-acacia(90) D(38), dCAMe(26)78 b1u 78 3 0 sCH3(94) sCH3(76)79 b2g 69 0 1 sOACuAO(92) sCH3(76)

Lattice mode?80 b1u 32 3 0 cacac(90) s(OCuOC)(31), s(CCOCu)(23)81 au 30 0 0 sacac(96) s(OCuOC)(39), s(CCOCu)(19)

a See footnote of Table 3; Me, methyl; R. defo., ring deformation.

M.V

akiliet

al./Journalof

Molecular

Structure1058

(2014)308–

317315

Fig. 5. The comparison of theoretical and experimental Far-IR spectra of Cu(bzac)2.

Fig. 6. The comparison of theoretical and experimental Raman spectra of Cu(bzac)2

in the 500–150 cm�1 range.

316 M. Vakili et al. / Journal of Molecular Structure 1058 (2014) 308–317

The strong Raman band at 1001 cm�1 is attributed to the 12vibration of phenyl groups.

4.2.2.4. Below 1000 cm�1 region. In this region of spectra, the in-plane and out-of-plane ring deformations of the phenyl and che-lated rings, the CAMe and CAPh bending, OACuAO stretchingand bending, and CHa out-of-plane bending modes are expectedto be observed.

According to the calculated results and comparing with theCu(acac)2 and benzoyl acetone vibrational frequencies [41], themedium strong IR band at 773 cm�1 is mainly the CHa out-of-planebending mode (cCHa), which is coupled to one of the vibrationalmodes of the phenyl groups, 11. In the IR spectra of benzoylacetone[41] and Cu(acac)2, the cCHa vibration appears as a medium strongband at 764 and 782 cm�1, respectively. These frequency shifts arein good agreement with the results of the theoretical calculations.The IR spectrum of Cu(bzac)2 indicates a band at 707 cm�1, which,according to the theoretical calculations, is assigned to the out-of-plane deformation of the chelated ring and it is coupled to the 11vibrational mode of the phenyl groups. The corresponding modein the IR spectra of Cu(acac)2 is observed at 652 cm�1, which iscoupled to cCAMe. This band has been attributed to in-planebending ring deformation coupled to the CACH3 in-plane bendingmotion by Raissi et al. [23].

The IR band at 628 cm�1 is attributed to the maOACuAO modein Cu(bzac)2. This vibrational mode is coupled to 6a vibrationalmode of the phenyl rings. The corresponding band in Cu(acac)2

and Cu(dbm)2 [26] appears at 613 and 656 cm�1, respectively.These frequency shifts are in excellent agreement with the resultsof the theoretical calculations and O–metal bond strength.

The theoretical and experimental IR and Raman spectra ofCu(bzac)2 in the 100–500 cm�1 region are compared in Figs. 5and 6, respectively. According to these figures, both IR and Ramanspectra indicate that the trans isomer is the prominent isomer inthe sample. In these spectra those bands which rules out the exis-tence of the cis isomer in the sample are shown by asterisks. In thisregion of spectra, the IR bands at 374 and 282 cm�1 and the Ramanband at 331 cm�1 are somewhat involved in the CuAO stretching.

The 450 cm�1 band observed in the Raman spectrum ofCu(acac)2 is assigned to the symmetric OACuAO stretching vibra-tion (ag symmetry species). Since the metal atom is not moving inthis mode of vibration, it could be used as a measure for O-metalbond strength of different complexes of metals with the same li-gand. The corresponding band for Cu(bzac)2 and Cu(dbm)2 [26] isobserved at considerably higher frequencies, 543 and 567 cm�1,respectively, which suggests stronger CuAO band in Cu(dbm)2

and Cu(bzac)2 than in Cu(acac)2.Based on our Far-IR observations and the theoretical calcula-

tions, the OACuAO in-plane bending mode for Cu(bzac)2 andCu(dbm)2 [26] complexes is observed at 282 and 280 cm�1, respec-tively. The corresponding band for Cu(acac)2 is observed at289 cm�1. The assignment for Cu(acac)2 is in agreement with thethat given by Nakamoto et al. [22].

5. Conclusion

The molecular structure and vibrational spectra of cis and transisomers of Cu(bzac)2 and Cu(acac)2 complexes have been studiedand compared with those of Cu(dbm)2. Any differences betweentheir calculated energies and dipole moments for the cis and transisomers are not significant. However, comparing of calculated andobserved vibrational spectra suggests that the trans isomer is thepredominant isomer in the sample.

The IR and Raman spectra of the Cu(bzac)2 and Cu(acac)2 com-plexes have been recorded. Detailed assignments for the recordedIR and Raman spectra of both target complexes have been pre-sented and resolve some of their previously publishedassignments.

Comparing the calculated geometrical parameters and experi-mental vibration spectra of Cu(bzac)2 with those of Cu(acac)2 andCu(dbm)2 show the following trend in the CuAO bond strengthin these compounds:

CuðdbmÞ2 > CuðbzacÞ2 > CuðacacÞ2

Appendix A. Supplementary material

Supplementary data associated with this article can be found, inthe online version, at http://dx.doi.org/10.1016/j.molstruc.2013.11.018.

References

[1] K. Nakamoto, A.E. Martell, J. Chem. Phys. 32 (1960) 588.[2] K. Nakamoto, P.J. McCarthy, A. Ruby, A.E. Martell, J. Am. Chem. Soc. 83 (1961)

1272–1276.[3] K. Nakamoto, Y. Morimoto, A.E. Martell, J. Am. Chem. Soc. 83 (1961) 4533–

4536.[4] M. Mikami, I. Nakagawa, T. Shimanouchi, Spectrochim. Acta Part A 23 (1967)

1037–1053.[5] S.F. Tayyari, H. Raissi, Z. Ahmadabadi, Spectrochim. Acta Part A 58 (2002)

2669–2682.[6] H. Junge, H. Musso, Spectrochim. Acta 24A (1968) 1219–1230.[7] V. Tsaryuk, V. Zolin, J. Legendziewicz, R. Szostak, J. Sokolnicki, Spectrochim.

Acta Part A 61 (2005) 185–191.

M. Vakili et al. / Journal of Molecular Structure 1058 (2014) 308–317 317

[8] H.H. Murray, Appl. Clay Sci. 17 (2000) 207–221.[9] J. Guzman, B.C. Gates, Angew. Chem., Int. Ed. 42 (2003) 690–693.

[10] V.D. Vreshch, A.B. Lysenko, A.N. Chernega, J. Sieler, K.V. Domasevitch,Polyhedron 24 (2005) 917–926.

[11] E. Fujii, A. Tomozawa, H. Torii, R. Takayama, M. Nagaki, T. Narusawa, Thin SolidFilms 352 (1999) 85–90.

[12] H. Samuelson, A. Lempicki, J. Chem. Phys. 39 (1963) 110–112.[13] R.G. Charles, E.P. Riedel, J. Inorg. Nucl. Chem. 28 (1966) 3005–3018.[14] H.C. Arora, G.N. Rao, Indian J. Chem. 11 (1973) 488–489.[15] A. Roy, K. Nag, Indian. J. Chem. 15A (1977) 474–476.[16] G.N. Rao, H.C. Arora, J. Inorg. Nucl. Chem. 39 (1977) 2057–2060.[17] C.C. Hinckley, J. Am. Chem. Soc. 91 (1969) 5160–5162.[18] W.D. Horrocks, J.P. Sipe, J. Am. Chem. Soc. 93 (1971) 6800–6804.[19] J. Selbin, N. Ahmad, N. Bhacca, Inorg. Chem. 10 (1971) 1383–1387.[20] S.J. Lyle, A.D. Witts, Inorg. Chim. Acta 5 (1971) 481–484.[21] J.R. Campbell, Aldrichim. Acta 4 (1971) 55–65.[22] K. Nakamoto, Infrared and Raman Spectra of Inorganic and Coordination

Compounds, Part B: Applications in Coordination, Organometallic, andBioinorganic Chemistry, sixth ed., Wiley-Interscience, New York, 2000.

[23] H. Raissi, A.R. Nowroozi, F. Farzad, M.S. HosseiniBojd, J. Spectrochim. Acta PartA 62 (2005) 343–352.

[24] K. Nakamoto, Y. Morimoto, A.E. Martell, J. Phys. Chem. 66 (1962) 346–348.[25] L. David, C. Craciun, O. Cozar, V. Chis�, C. Agut, D. Rusu, M. Rusu, J. Mol. Struct.

563–564 (2001) 573–578.[26] M. Hakimi-Tabar, in: M.Sc., Thesis, Ferdowsi University of Mashhad, 2012.[27] T. Moeller, Inorganic Syntheses, vol. 5, McGraw-Hill, Book Co. Inc., New York,

1957, p. 108.[28] M.J. Frisch, G.W. Trucks, H.B. Schlegel, G.E. Scuseria, M.A. Robb, J.R. Cheeseman,

G. Scalmani, V. Barone, B. Mennucci, G.A. Petersson, H. Nakatsuji, M. Caricato,X. Li, H.P. Hratchian, A.F. Izmaylov, J. Bloino, G. Zheng, J.L. Sonnenberg, M.Hada, M. Ehara, K. Toyota, R. Fukuda, J. Hasegawa, M. Ishida, T. Nakajima, Y.Honda, O. Kitao, H. Nakai, T. Vreven, J.A. Montgomery, Jr., J.E. Peralta, F. Ogliaro,M. Bearpark, J.J. Heyd, E. Brothers, K.N. Kudin, V.N. Staroverov, R. Kobayashi, J.

Normand, K. Raghavachari, A. Rendell, J.C. Burant, S.S. Iyengar, J. Tomasi, M.Cossi, N. Rega, J.M. Millam, M. Klene, J.E. Knox, J.B. Cross, V. Bakken, C. Adamo,J. Jaramillo, R. Gomperts, R. E. Stratmann, O. Yazyev, A.J. Austin, R. Cammi, C.Pomelli, J.W. Ochterski, R.L. Martin, K. Morokuma, V.G. Zakrzewski, G.A. Voth,P. Salvador, J.J. Dannenberg, S. Dapprich, A.D. Daniels, O. Farkas, J.B. Foresman,J.V. Ortiz, J. Cioslowski, D.J. Fox, Gaussian 09, Revision A.02, Gaussian Inc.,Wallingford CT, 2009.

[29] A.D. Becke, J. Chem. Phys. 98 (1993) 5648–5652.[30] C. Lee, W. Yang, R.G. Parr, Phys. Rev. B 37 (1988) 785–789.[31] P. Pulay, G. Fogarasi, F. Pang, J.E. Boggs, J. Am. Chem. Soc. 101 (1979) 2550–

2560.[32] GaussView 4. 1. 2, Gaussian Inc., Pittsburg, PA, 2006.[33] J. Tomasi, M. Persico, Chem. Rev. 94 (1994) 2027.[34] J.L. Pascual-Ahuir, E. Silla, J. Tomasi, R. Bonaccorsi, J. Comp. Chem. 8 (1987)

778.[35] B. Mennucci, J. Tomasi, J. Chem. Phys. 106 (1997) 5151.[36] A. Bondi, J. Phys. Chem. 68 (1964) 441.[37] V. Barone, C. Adamo, J. Phys. Chem. 99 (1995) 15062.[38] M. Jamialahmadi, S.F. Tayyari, M.H. Habibi, M. Yazdanbakhsh, S. Kadkhodaei,

R.E. Sammelson, J. Mol. Struct. 985 (2011) 139–147.[39] S.F. Tayyari, M. Ghafari, M. Jamialahmadi, B. Chahkandi, B.O. Patrick, Y.A.

Wang, J. Mol. Struct. 1045 (2013) 20–28.[40] S.F. Tayyari, T. Bakhshi, S.J. Mahdizadeh, S. Mehrani, R.E. Sammelson, J. Mol.

Struct. 938 (2009) 76–81.[41] S.F. Tayyari, J.S. Emampour, M. Vakili, A.R. Nekoei, H. Eshghi, S. Salemi, M.

Hassanpour, J. Mol. Struct. 794 (2006) 204–214.[42] E.B. Wilson Jr., Phys. Rev. 45 (1934) 706.[43] P. Pulay, X. Zhou, G. Fogarasi, in: R. Fausto (Ed.), Recent Experimental and

Computational Advances in Molecular Spectroscopy, Kluver Academic,Netherlands, 1993, pp. 88–111.

[44] S.F. Tayyari, F. Milani-Nejad, Spectrochim. Acta Part A 56 (2000) 2679–2691.[45] N.B. Colthup, L.H. Daly, S.E. Wiberley, Introduction to Infrared and Raman

pectroscopy, Academic Press, London, 1975.