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FT-IR and Raman spectroscopic and quantum chemical studies of zinc halide complexes with 2,2′-biquinoline
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Vibrational Spectroscopy 48 (2008) 238–245 www.elsevier.com/locate/vibspec
FT-IR and Raman spectroscopic and quantum chemical studies of zinc halide complexes with 2,20 -biquinoline Aysen E. Ozel a,*, Serda Kecel a, Sevim Akyuz b b
a Istanbul University, Faculty of Science, Department of Physics, Vezneciler, 34134 Istanbul, Turkey Istanbul Kultur University, Faculty of Science and Letters, Department of Physics, Atakoy Campus, 34156 Istanbul, Turkey
Received 18 July 2007; received in revised form 22 January 2008; accepted 23 January 2008 Available online 6 February 2008
Abstract The molecular structure, vibrational frequencies and the corresponding vibrational assignment of Zn(biq)X2 (X = Cl and Br; biq = 2,20 biquinoline) have been studied by employing the hybrid density functional theory (B3LYP) method and the complete basis set (DFT) method together with the 6-31G(d,p) basis set for X = Cl and Br. The FT-IR (400–4000 cm1) and Raman (100–3200 cm1) spectra of compounds were recorded and compared with that of the calculated spectra, which allowed authors to assign most of the observed bands. It was demonstrated that cis conformer is suitable for the Zn(biq)X2 compounds. The fundamental vibrational modes were characterized by their total energy distribution. The coordination effects on vibrational wavenumbers of biq were discussed in detail. # 2008 Elsevier B.V. All rights reserved. Keywords: Ab initio calculations; DFT; 2,20 -Biquinoline; Halide complexes; Vibrational frequencies
1. Introduction Quinoline family compounds are of great interest in pharmaceutical industry and widely used as parent compounds for making drugs [1], especially anti-malarial medicines [2]. 2,20 -Biquinoline (abbreviated as biq) is a interesting dimmer and used for the preparation of sensitizers for solar cell studies [3]. These molecules are also widely employed as a ligand with any metal cations. Zinc is one of the most abundant transition metal in human bodies. It is rich in the brain [4], and also plays significant and indispensable roles in biological systems. The IR spectroscopic studies on Zn(ClO4)2 [5], dichlorodioxochromium(VI) [6] and palladium, platinum and rhodium complexes of biq [7] were previously reported. In these studies, however, only some important vibrational modes of the ligand were given. The crystal data on biq [8] and W(CO)4(biq) [9], Re(CO)3(biq)Cl complexes [10] have been reported. Recently surface enhanced Raman spectra of biq [11,12] were reported. The vibrational wavenumbers of free biq were calculated by ab initio, DFT and force field refinement methods [13,14].
* Corresponding author. Tel.: +90 212 4555826; fax: +90 212 5190834. E-mail address: [email protected] (A.E. Ozel). 0924-2031/$ – see front matter # 2008 Elsevier B.V. All rights reserved. doi:10.1016/j.vibspec.2008.01.010
In our previous studies, experimental and theoretical spectroscopic investigations on quinoline and biq have been reported [14,15], and now we wish to extend our investigations to coordinated biq for predicting the coordination sensitive modes of biq. To the best of our knowledge, no ab initio and DFT calculation have been reported in the literature on zinc halide complexes with 2,20 -biquinoline. The aim of this study is to analyse the influence of the formation of bidentate coordination through both ring nitrogens on the vibrational wavenumbers of biq. For this purpose, vibrational wavenumbers of free and coordinated biq molecules were calculated by using the same method and the same basis sets. Moreover, determination of the wavenumbers particularly arising from metal–ligand and metal–halide bonds vibrations has a separate interest. 2. Experimental and computational details All chemicals used were reagent grade (Merck and Sigma). The Zn(biq)X2 (X = Cl and Br) complexes were prepared by adding slightly more than 1 mol of biq solution in ethanol to 1 mol of zinc halide solution using constant stirring. The precipitate was filtered, washed with ethanol, and dried at room temperature. The C, H, N analyses were carried out for both
A.E. Ozel et al. / Vibrational Spectroscopy 48 (2008) 238–245
samples. Anal. (%) calcd for Zn (C18H12N2)Cl2; C, 55.02; H, 3.08; N, 7.14. Found: C, 54.95; H, 3.1; N, 7.12. Calcd for Zn (C18H12N2)Br2; C, 44.86; H, 2.51; N, 5.82. Found: C, 44.90; H, 2.4; N, 5.80. The IR spectra of nujol mulls or KBr discs were recorded on a Jasco 300E FT-IR spectrometer (2 cm1 resolution) between 400 and 4000 cm1 spectral region. The Raman spectra of the samples were taken with a JY Jobin Yvon Horiba HR(800) spectrometer using 632.8 nm excitation from a He–Ne laser in the 3200–100 cm1 region with 4 cm1 resolution. All computational studies were carried out with the Gaussian03 package program [16]. The geometry of the title compounds in the ground state were optimized using DFT with B3LYP [17] exchange correlation function and the 6-31G(d,p) basis set. The addition of diffuse functions to the 6-31G(d,p) basis set did not introduce any principal changes in the calculated frequencies and IR intensities. To the best of our knowledge, no crystallographic study has been reported on zinc halide complexes with biq. Therefore, the optimized geometry of the title compounds were obtained by using single crystal data of biq [8] and for Zn–N and Zn–X bonds; and the X-ray results of Zn halide complexes of nicotinamide [18,19], as the initial geometric parameters. Tetrahedral arrangement around Zn atom were applied. Harmonic vibrational wavenumbers and infrared intensities were calculated at the same level of theory to characterize the stationary points. The total energy distribution (TED) of the vibrational modes of the molecules was calculated by using parallel quantum mechanics solutions (PQS) program [20] and the fundamental vibrational modes were characterized by their total energy distribution. 3. Results and discussion The Zn(biq)X2 (X = Cl and Br) complexes have been prepared for the first time and vibrational assignment were performed in comparison with these of calculated results. In solid state, 2,20 -biquinoline molecule is known to be in trans coplanar configuration [21], however cis form occurs on formation of complexes with metal ions [6,7,11,12]. When no symmetry restrictions were imposed during the geometry optimizations, the minima located at molecular potential energy surface corresponded to C1 symmetry for both complexes. The results for ZnBr2 complex were found to be slightly different from C2v symmetry, therefore we tried to constrain both structures to C2v symmetry. When we took into account C2v symmetry of the title compounds, although Zn(biq)Br2 complex gave no negative eigenvalue, one imaginary frequency was found for Zn(biq)Cl2 complex indicating that the structure found for Zn(biq)Cl2 complex was not a minimum energy structure. Thus, the optimized geometry parameters for C1 symmetry were taken for Zn(biq)Cl2 and for C2v symmetry were taken for Zn(biq)Br2 complex. On the other hand, initial frequency calculations of both the cis and trans conformer of Zn(biq)X2 compound at interring torsion 08 and 1808, respectively, were also done, but the calculated results demonstrated that the minima on the molecular potential energy hypersurfaces corresponds to cis
239
arrangement of the biq. The calculated geometric parameters for the two model systems are summarized in Table 1. The optimized structure and atoms numbering of Zn(biq)X2 complexes are shown in Fig. 1. As seen from Table 1, the N2ZnX2 part of the compounds are in distorted tetrahedral configuration. In both cases, the Zn–X and Zn–N bond pairs are ˚ (for ZnCl2) and 2.317 A ˚ found to be the same: Zn–X = 2.222 A ˚ ˚ (for ZnBr2); and Zn–N = 2.085 A (for ZnCl2) and 2.099 A (for ZnBr2). It should be noted that the calculated value of BrZnBr angle (126.38) is larger than ClZnCl angle (123.88) whereas NZnN angles are 79.38 and, 78.98 for Zn(biq)Cl2 and Zn(biq)Br2, respectively. The vibrational wavenumbers, calculated IR intensity and a complete assignment of the fundamental modes according to their total energy distribution and comparison between calculated and experimental results, are given in Table 2. Experimental data of the SERS study of 2,20 -biquinoline [12], in which adsorbed biq molecules on a silver colloidal surface were shown to coordinate silver atoms through both the nitrogen atoms in the cis form, were included in Table 2 for comparison. The differences between the calculated and the experimental values for the same mode are often attributed to the neglect of anharmonicity and incomplete inclusion of electronic correlation effects. In order to correct overestimation between unscaled wavenumbers and observed frequencies, The vibrational frequencies were scaled with a factor of 0.9614 [22]. Fig. 2 represents the experimental Raman spectra of Zn(biq)X2 complexes. Free biq is in trans form, therefore IR active vibrations are Raman inactive, and vice versa. However, when it involves in complex formation it turns to cis conformation. As seen in Table 2, in Zn(biq)X2 frequencies, several vibrational modes are observed in both IR and Raman spectra. The calculated IR spectra of free and coordinated biq together with experimental IR spectrum of Zn(biq)Br2 complex is shown in Fig. 3. Calculated IR spectra of Zn(biq)X2 complexes are found to be in agreement with those of experimental IR spectra. Raman spectra of the Zn(biq)X2 (X = Cl and Br) complexes show two bands at 343 and 306 cm1, and 288 and 230 cm1, respectively, which can be attributed to n(Zn–Cl) and n(Zn–Br) vibrational modes (see Fig. 4). These modes were observed at 343 and 304 cm1, and 302 and 225 cm1, at Raman spectra of nicotinamide complexes of ZnCl2 and ZnBr2, respectively [23], and 345 and 330 cm1, and 300 and 295 cm1 at the IR spectra of Pd(biq)Cl2 and Pd(biq)Br2 complexes, respectively [7]. Zn– N stretching vibrations of the complexes were calculated at 190 and 157 cm1 for Zn(biq)Cl2 (DFT/B3LYP 6-31G(d,p)) and 182 and 157 cm1 for Zn(biq)Br2 (see Table 2). In the case of Zn(nicotinamide)2X2 (X = Cl or Br) complexes, Zn–N (nicotinamide) stretching modes were observed at 236 and 202 cm1 for X = Cl and 200 and 184 cm1 for X = Br [23]. In the Raman spectra of Zn(biq)X2 compounds however, only one band around 200 cm1 was observed, which can be attributed to Zn– N stretching vibration (see Fig. 4). In the case of pyridine–metal complexes, ring stretching modes around 1400–1600 cm1 and ring breathing mode are known as coordination sensitive modes and increase in
240
A.E. Ozel et al. / Vibrational Spectroscopy 48 (2008) 238–245
Table 1 Optimized geometry parameters of Zn(biq)X2 complex (X = Cl and Br) obtained by B3LYP/6-31G(d,p) density functional calculations
R(1,2) R(1,6) R(1,7) R(2,3) R(2,13) R(3,4) R(3,14) R(4,5) R(4,25) R(5,6) R(5,28) R(6,33) R(7,8) R(7,12) R(8,9) R(8,33) R(9,10) R(9,19) R(10,11) R(10,18) R(11,12) R(11,15) R(12,16) R(17,18) R(17,20) R(17,21) R(18,22) R(19,20) R(19,23) R(20,24) R(25,26) R(25,31) R(26,27) R(26,32)
Cl
Br
1.417 1.330 1.491 1.374 1.082 1.414 1.086 1.430 1.418 1.364 1.418 2.085 1.331 1.418 1.364 2.084 1.430 1.418 1.414 1.418 1.374 1.086 1.082 1.376 1.418 1.085 1.086 1.376 1.084 1.085 1.376 1.086 1.418 1.085
1.418 1.330 1.491 1.374 1.082 1.414 1.086 1.430 1.418 1.364 1.418 2.099 1.330 1.418 1.364 2.099 1.430 1.418 1.414 1.418 1.374 1.086 1.082 1.376 1.417 1.085 1.086 1.376 1.084 1.085 1.376 1.086 1.417 1.085
R(27,28) R(27,29) R(28,30) R(33,34) R(33,35) A(2,1,6) A(2,1,7) A(6,1,7) A(1,2,3) A(1,2,13) A(3,2,13) A(2,3,4) A(2,3,14) A(4,3,14) A(3,4,5) A(3,4,25) A(5,4,25) A(4,5,6) A(4,5,28) A(6,5,28) A(1,6,5) A(5,6,33) A(1,7,8) A(1,7,12) A(8,7,12) A(7,8,9) A(9,8,33) A(8,9,10) A(8,9,19) A(10,9,19) A(9,10,11) A(9,10,18) A(11,10,18) A(10,11,12)
Cl
Br
1.376 1.085 1.084 2.222 2.219 121.4 122.6 116.0 119.3 120.7 119.9 120.3 120.3 119.4 117.3 123.6 119.1 121.0 119.7 119.3 120.7 125.2 116.0 122.5 121.4 120.7 125.2 121.0 119.3 119.7 117.3 119.1 123.5 120.3
1.376 1.085 1.084 2.317 2.317 121.4 122.4 116.2 119.3 120.7 119.9 120.3 120.4 119.4 117.3 123.5 119.2 121.0 119.6 119.4 120.7 125.0 116.2 122.4 121.3 120.7 125.0 121.0 119.4 119.6 117.3 119.2 123.5 120.3
A(10,11,15) A(12,11,15) A(7,12,11) A(7,12,16) A(11,12,16) A(18,17,20) A(18,17,21) A(20,17,21) A(10,18,17) A(10,18,22) A(17,18,22) A(9,19,20) A(9,19,23) A(20,19,23) A(17,20,19) A(17,20,24) A(19,20,24) A(4,25,26) A(4,25,31) A(26,25,31) A(25,26,27) A(25,26,32) A(27,26,32) A(26,27,28) A(26,27,29) A(28,27,29) A(5,28,27) A(5,28,30) A(27,28,30) A(6,33,8) A(6,33,34) A(6,33,35) A(8,33,34) A(8,33,35)
Cl
Br
119.4 120.3 119.3 120.7 119.9 120.4 120.0 119.5 120.1 118.9 120.9 119.6 119.0 121.3 120.9 119.5 119.5 120.1 118.9 120.9 120.4 120.0 119.5 120.9 119.5 119.5 119.6 119.1 121.3 79.3 109.2 113.2 109.3 113.2
119.4 120.4 119.3 120.7 119.9 120.4 120.0 119.5 120.1 118.9 120.9 119.6 119.2 121.1 121.0 119.4 119.5 120.1 118.9 120.9 120.4 120.0 119.5 121.0 119.4 119.5 119.6 119.2 121.1 78.9 110.4 110.4 110.4 110.4
A(34,33,35) A(7,8,33) A(1,6,33) D(6,1,2,3) D(2,1,7,8) D(2,1,7,12) D(6,1,7,8) D(6,1,7,12) D(3,4,5,28) D(25,4,5,6) D(3,4,25,31) D(4,5,6,33) D(28,5,6,33) D(5,6,33,8) D(5,6,33,34) D(5,6,33,35) D(33,8,9,10) D(33,8,9,19) D(9,8,33,6) D(9,8,33,34) D(9,8,33,35) D(8,9,10,18) D(19,9,10,11) D(11,10,18,22) D(33,6,1,7) D(33,6,1,2) D(33,8,7,12) D(33,8,7,1) D(7,8,33,6) D(7,8,33,34) D(7,8,33,35) D(1,6,33,8) D(1,6,33,34) D(1,6,33,35)
Cl
Br
123.8 113.8 113.8 0.1 179.7 0.2 0.2 179.3 179.2 179.6 0.3 172.6 7.7 177.7 75.47 66.9 172.9 7.3 177.5 75.6 66.7 179.6 179.2 0.3 7.0 173.5 173.8 6.7 7.9 98.8 118.8 8.1 98.8 118.9
126.3 114.3 114.3 0.0 180.0 0.0 0.0 180.0 180.0 180.0 0.0 180.0 0.0 180.0 72.2 72.2 180.0 0.0 180.0 72.2 72.2 180.0 180.0 0.0 0.0 180.0 180.0 0.0 0.0 107.8 107.8 0.0 107.8 107.8
R, A and D characters represent bond, angle and dihedral angle type of coordinates, respectively.
wavenumber upon coordination through the ring nitrogen [24]. Similar effect was also observed in the case of 2,20 -biquinoline complexes [7,11,12]. The 1800–400 cm1 region of the FT-IR spectrum of Zn(biq)Cl2 complex is shown in Fig. 5, together with that of solid biq. As seen in Fig. 5, the vibrational modes of biq compounds show the characteristic upward shifts for the
coordinated ligand, with respect to the free molecule. In order to find the coordination sensitive vibrational bands of biq, we have compared the unscaled wavenumbers of calculation of same level of theory for free biq with those of biq halide complexes.As seen from Table 2, similar shifts are also observed in theoretic calculations. Coordination sensitive
Fig. 1. Optimized geometries and atoms numbering of Zn(biq)Cl2 (C1) (a) and Zn(biq)Br2 (C2v ) (the same numbering scheme applied to both complexes).
Table 2 Calculated and experimental wavenumbers of Zn(biq)Cl2 and Zn(biq)Br2 complexes Assign.
Solid biq IR, exp.
SER a
Zn(biq)X2 X = Cl IR, nexp.
3095w 3074w 3064w 3056w 3046m 3042w 3036w 3028sh 3008w 2997w 2988w 2975w 1618m 1594vs 1595R 1588sh 1554m 1549m 1534w 1508R 1497vs 1474w 1459R 1458w 1449w 1431w 1420m 1374R 1354w 1327m 1323w 1300w 1247w 1245R 1213m 1205R 1144m 1141sh 1129m 1112R
3054
1590 1559
1508
1463
1430 1380 1343
1241 1221 1166
1144
3118m 3111w 3089m 3081w 3067w 3062w 3059w 3057w 3036sh 3031w 3026w 3021w 1617m 1599m 1585m 1585m 1558w 1554w 1545w 1509vs 1490w 1476w 1464w 1456w 1451w 1434m 1431sh 1381m 1367m – 1338m 1317w 1261w 1253w 1215m – 1164w 1155w 1145s –
X = Br R, nexp.
3066w
1620m 1599m 1585m 1566w 1512m 1505w 1469s 1462w
1440w 1388vs 1352w 1334vs 1315m 1276m 1255m 1224w – 1175w – – –
IR, nexp. 3117m 3111w 3087m 3079sh 3070w 3063sh 3059w 3054w 3039w 3030w 3027sh 3020w 1616m 1594m 1588m 1585m 1559w 1553w 1540w 1509vs
Zn(biq)Cl2 DFT/B3LYP 6-31G(d,p)
Zn(biq)Br2 DFT/B3LYP 6-31G(d,p)
TED% Zn(biq)Cl2 DFT/B3LYP/6-31G(d,p)
Unsc., ncal.
Scaled, ncal.
(I)
Unsc., ncal.
Scaled, ncal.
(I)
3248 3233 3223 3223 3213 3213 3202 3202 3194 3193 3188 3188 1673 1672 1649 1641 1627 1604 1562 1559 1512 1503 1477 1472 1425 1421 1401 1384 1355 1351 1330 1292 1283 1260 1254 1203 1191 1189 1177 1169
3123 3108 3099 3099 3089 3089 3078 3078 3071 3070 3065 3065 1608 1607 1585 1578 1564 1542 1502 1499 1454 1445 1420 1415 1370 1366 1347 1331 1303 1299 1279 1242 1233 1211 1206 1157 1145 1143 1132 1124
7.91 0.53 3.35 9.83 3.81 21.57 12.95 10.53 9.70 7.26 1.35 1.26 9.20 8.41 61.5 17.8 2.36 17.03 0.05 136.4 0.05 5.03 19.32 11.70 7.50 46.6 41.7 20.31 2.12 1.81 1.24 2.60 4.09 3.14 18.56 3.82 6.73 1.19 7.46 15.27
3249 3234 3226 3226 3214 3214 3202 3202 3193 3193 3188 3188 1673 1673 1650 1642 1627 1604 1562 1559 1513 1503 1477 1472 1425 1420 1401 1386 1355 1349 1329 1292 1283 1260 1254 1204 1192 1189 1177 1169
3124 3109 3101 3101 3090 3090 3078 3078 3070 3070 3065 3065 1608 1608 1586 1579 1564 1542 1502 1499 1455 1445 1420 1415 1370 1365 1347 1333 1303 1297 1278 1242 1233 1211 1206 1158 1146 1143 1132 1124
8.69 0.52 5.20 0.49 1.07 32.41 12.80 9.45 10.25 7.40 1.63 1.43 8.16 9.21 58.28 18.05 2.23 16.48 0.09 133.20 0.05 5.55 19.18 11.68 5.84 45.94 38.31 20.78 1.52 1.36 1.72 2.35 4.48 2.96 17.96 4.07 6.52 0.88 6.44 15.30
R, nexp.
3058w
1621w 1600m 1586m 1564w 1514m
1476w 1465w 1457vw 1449vw 1434s 1431w 1382s 1366m
1473s 1461w
1439w 1431w 1388vs 1345w
1338m 1316m 1268w 1253w 1215m – 1184w 1155m 1145s –
1337vs 1316m 1277m 1256w 1225m – 1176w – 1143w –
3218 3217 3213 3206 3203 3202 3189 3188 3180 3179 3175 3175 1674 1673 1653 1646 1610 1597 1552 1549 1516 1503 1468 1464 1412 1410 1386 1385 1350 1337 1302 1279 1270 1247 1246 1181 1178 1177 1171 1160
nCH(98) nCH(95) nCH(97) nCH(97) nCH(98) nCH(98) nCH(96) nCH(95) nCH(93) nCH(91) nCH(96) nCH(96) nCC(60) + dCCH(3) nCC(60) + dCCH(3) nCC(50) + nNC(9) + dCCH(6) nCC(45) + dCCH(7) nCC(47) + nNC(13) nCC(45) + nNC(15) nCC(33) + dCCH(20) nCC(41) + dCCH(3) nCC(23) + nNC(13) + dCCH(23) nCC(18) + nNC(10) + dCCH(24) nCC(20) + dCCH(40) nCC(12) + dCCH(36) nCC(63) + nCN(12) nCC(65) + nCN(8) nNC(13) + nCC(8) + dCCH(17) nCC(37) + nNC(32) + dCCH(11) nCC(16) + nNC(38) + dCCH(10) nNC(36) + dCCH(12) nCC(32) + dCCH(10) nCC(22) + dCCH(51) nCC(35) + dCCH(32) nCC(32) + dCCH(23) nCC(45) + nNC(4) + dCCH(14) nCC(11) + dCCH(64) nCC(12) + dCCH(57) dCCH(56) nCC(24) + dCCH(50) nCC(16) + dCCH(42)
A.E. Ozel et al. / Vibrational Spectroscopy 48 (2008) 238–245
nCH nCH nCH nCH nCH nCH nCH nCH nCH nCH nCH nCH nCC nCC nCC nCC nCC nCC nCC nCC nCC dCCH dCCH dCCH nCC nCC nCC nCC nNC nNC nCC dCCH nCC nCC nCC dCCH dCCH dCCH dCCH dCCH
Free biq (cis) DFT/B3LYP 631G(d,p) Unsc., ncal.
241
242
Table 2 (Continued ) Assign.
Solid biq IR, exp.
SER a
Zn(biq)X2 X = Cl
Unsc., ncal.
Scaled, ncal.
(I)
(I)
1135w – – – 1019w – – – 971w – – – 890w – – –
1132m 1106m 1048w 1048w 1021w 1021w 997w 988w 973m 957m – – 892w 873m 873m –
1134w – – – 1018w – – – 970w – – – 892w – – –
1148 1110 1042 1041 1002 1002 993 989 968 967 967 949 901 891 890 862
1167 1132 1050 1047 1009 1009 996 991 989 971 969 968 906 885 882 849
1122 1088 1009 1007 970 970 958 953 951 934 932 931 871 851 848 816
8.18 19.35 0.30 0.69 0.02 0.19 3.67 5.51 0.03 1.51 0.01 18.35 0.27 1.71 0.27 0.12
1167 1131 1050 1048 1008 1007 996 989 987 966 966 965 906 881 877 841
1122 1087 1009 1008 969 968 958 951 949 929 929 928 871 847 843 809
7.96 18.79 0.30 0.88 0.02 0.00 3.07 5.29 0.00 1.50 17.70 0.00 0.20 4.28 0.00 0.00
– –
– 843w
– –
844 837
840 838
808 806
89.41 1.49
837 837
805 805
1.43 84.80
804m 791m
834s – 785s 750s
– 806m 790m – 699w – – – – – 622w – – 535w 528w – 497w 472w 424w 398w
810 803 785 783 779 765 721 676 658 630 619 567 555 537 529 523 493 491 471 418
809 800 799 798 780 760 706 671 667 647 635 563 559 546 535 517 499 498 496 429
778 769 768 767 750 731 679 645 641 622 610 541 537 525 514 497 480 479 477 412
1.72 0.63 27.05 18.65 0.00 34.39 0.31 7.21 1.54 1.09 3.35 0.08 0.00 0.33 0.03 2.62 1.66 0.26 9.05 0.07
808 800 798 798 776 755 700 671 666 646 635 561 558 546 535 516 497 496 496 428
777 769 767 767 746 726 673 645 640 621 610 539 536 525 514 496 478 477 477 411
2.01 25.86 18.20 0.00 0.00 37.65 0.00 6.63 1.97 0.98 3.16 0.10 0.00 0.38 0.04 2.39 1.58 0.00 8.49 0.02
nCC GHCCC GHCCC nCC GHCCC GHCCC GHCCN dCCC GCCCN dCCC dCCC dCCC GCCCC dCCC dCCC GCCCC GCCCC GCCCC dCCC dCCC
830m 789m 766m 737m – – – 646w 641w 625m 614sh – – – 520w 499w 484w 473m – –
835s – 784s 751s – – – 658m 649w 633w 622m – – – 525w 502w 489m 471w – –
698w – – – – – 626w – – 537w 524w – 491w 475w 423w 400w
– – 658m 649w 634w 622m – – – 525w 501m 488m 472w – –
nCC(21) + dCCH(36) nCC(27) + nNC(16) + dCCH(8) nCC(65) nCC(67) GHCCH(60) + GCCCC(3) + GCCCH(14) GHCCH(60) + GCCCC(3) + GCCCH(14) GHCCH(37) + GCCCH(36) nCN(6) + nCC(24) + dCCC(11) + dCCH(6) GHCCH(33) + GCCCH(39) GHCCH(43) + GCCCH(12) GHCCH(42) + GCCCH(8) dCNC(13) + dCCC(14) nCC(13) + dCCC(22) GHCCC(29) + GHCCN(12) + GHCCH(8) GHCCC(30) + GHCCN(12) + GHCCH(9) GHCCC(42) + GCCCC(12) + GNCCN(3) + GCNCC(10) GHCCC(53) + GHCCN(11) nCC(9) + nNC(6) + dCCC(38) + dCCn(10) + dCCH(6) nCC(52) + dCCC(6) GHCCC(26) + GCCCC(3) + GCCCN(9) GHCCC(20) + GCNCC(9) nCC(57) GHCCC(65) + GHCCN(9) GHCCC(60) + GHCCN(6) GHCCC(9) + GHCCN(14) + GNCCN(4) nCC(10) + dCCC(33) GHCCN(7) + GCCCC(10) + GCCCN(26) dCCC(32) + dCCN(8) nCC(8) + dCCC(40) dCCC(19) + dNCC(16) + dCNZn(7) GCCCC(25) + GCCCH(9) nCC(20) + dCCC(27) + dNCC(8) nCC(15) + dCCC(29) + dNCC(12) GCCCC(24) + GCCCH(8) + GCCNZn(6) GCCCC(26) + GCCCH(14) GCCCC(18) + GCCCN(3) nCC(9) + dCCC(25) + dNCC(10) dCCC(27) + dNCC(19) + dCNZn(7)
A.E. Ozel et al. / Vibrational Spectroscopy 48 (2008) 238–245
1135m 1106m 1049w 1049w 1022w 1022w 998w 989w 973m 957m – – 892w 873m 873m – – 843w
533
Scaled, ncal.
R, nexp.
– 840m
616
Unsc., ncal.
TED% Zn(biq)Cl2 DFT/B3LYP/6-31G(d,p)
IR, nexp.
GHCCC dCCC
782
Zn(biq)Br2 DFT/B3LYP 6-31G(d,p)
R, nexp.
1120sh 1105w 1057w 1053w 1018R 1018R 994w 978w 954m 945m 936m – – 870m 867m –
951
X = Br
Zn(biq)Cl2 DFT/B3LYP 6-31G(d,p)
IR, nexp. dCCH nCC nCC nCC GHCCH GHCCH GHCCH nCC GCCCH GHCCH GHCCH dCCC dCCC GHCCC GHCCC GHCCC
1023b
Free biq (cis) DFT/B3LYP 631G(d,p) Unsc., ncal.
– – – – – – –
– – – – – – –
– 332w 343w 332w 306w – –
– – – – – –
– 332w 288w 281w 230m – –
405 405 – 329 – 280 241
413 408 350 338 311 282 275
397 392 336 325 299 271 264
7.74 0.03 66.5 0.00 34.8 3.23 0.29
413 407 336 307 281 276 242
397 391 323 295 270 265 233
8.28 0.00 0.00 45.18 3.00 7.42 15.58
GCCCC GCCCC nNZn GCCCC nNZn GCCNC GZnNCC dXZnX dXZnX
– –
– –
– – 199w
– – –
– – 198w
202 186
240 196 190 182 157 116 114 103 85
231 188 183 175 151 112 110 99 82
3.97 5.56 2.86 0.00 12.99 0.14 0.28 2.39 8.85
237 193 182 171 157 117 98 96 56
228 186 175 164 151 112 94 92 54
2.20 4.73 0.00 0.32 8.48 0.00 0.01 0.00 5.15
GXZnNC dXZnN
75 44
72 42
11.9 0.01
54 44
52 42
4.81 0.00
GXZnNC
43
41
0.37
34
33
1.01
GZnNCC
26
25
0.13
15
14
0.00
GXZnNC
20
19
1.52
5
5
0.08
(I) = computed IR intensities; R = Raman; IR = infrared; unsc. = unscaled. The scaling factor is 0.9614 taken from Ref. [22]. a Taken from Ref. [12]. b Taken from Ref. [11].
GCCCC(38) GCCCC(37) nXZn(100) GCCCC(18) + GCCNC(8) + GNZnNC(6) nXZn(94) nNZn(22) + dCCC(19) + dCCN(25) nCC(19) + nNC(7) + nNZn(21) + dCCC(8) + dCCN(8) GCCCC(14) + GZnNCC(8) GCCCC(22) + GCCNC(16) nCC(3) + nNZn(27) + dCNZn(16) + dNZnN(14) GCCCC(30) + GCCNC(10) nNZn(42) + dCNZn(15) GCCCC(19) + GCCNC(21) + GZnNCC(3) dXZnN(14) + GZnNCC(16) + GXZnNC(8) dZnNC(14) + dCCC(6) + dXZnN(14) + dXZnX(15) nNZn(14) + dCNZn(7) + dXZnN(9) + dXZnX(22) + GXZnNC(6) nNZn(8) + dCNZn(3) + dXZnN(25) + GXZnNC(54) dXZnN(16) + GNZnNC(12)GCCNC(12) + GCCCH(6) + GZnNCC(8) + GCCCC(13) dXZnN(8) + GCCNC(3) + GZnNCC(6) + GCCCC(4) + GXZnNC(39) dXZnN(6) + GCCCC(5) + GCCNC(13) + GNCCN(7) + GZnNCC(32) + GXZnNC(28) GXZnNC(51) + GZnNCC(16) + GNZnNC(10)
A.E. Ozel et al. / Vibrational Spectroscopy 48 (2008) 238–245
GCCCC GCCCC nXZn GCCCC nXZn dCCN dCCC + nCC
243
244
A.E. Ozel et al. / Vibrational Spectroscopy 48 (2008) 238–245
Fig. 2. Experimental Raman spectra of Zn(biq)X2 complexes.
Fig. 4. The 410–140 cm1 region of the Raman spectra of Zn(biq)Br2 (top) and Zn(Biq)Cl2 (bottom) complexes. *Zn–X stretching and **Zn–N stretching modes are indicated.
Fig. 5. The 1800–400 cm1 region of the FT-IR spectrum of solid biq (a) and Zn(biq)Cl2 complex (b).
modes of biq are marked as bold (Table 2). These shifts in are found to be only slightly depend on the halide groups but mainly result as an interaction between biq molecule and metal. 4. Summary and conclusion The structural parameters, IR wavenumbers and intensities of the fundamental bands of Zn(biq)X2 complexes were calculated using the DFT(B3LYP) methods using standart 631G(d,p), basis set for X = Cl and Br. DFT methods yield a good definition of the vibrational modes of Zn(biq)X2 halides. The comparison between calculated wavenumbers of free and coordinated biq enable us to predict coordination sensitive modes. Acknowledgements Fig. 3. Calculated IR spectra (B3LYP/6-31G(d,p)) of free biquinoline (a), Zn(biq)Cl2 (b) and Zn(biq)Br2 (c) complexes and the experimental IR spectrum of Zn(biq)Br2 (d).
This work was supported by the Research fund of the University of Istanbul. Project number UDP 918/18042007. The micro-Raman spectra were recorded at Istanbul Technical
A.E. Ozel et al. / Vibrational Spectroscopy 48 (2008) 238–245
University, Department of Metallurgical and Materials Engineering. We thank Professor Mustafa Urgen for allowing us to use his laboratory and Dr. Devrim Sam for recording the spectra. References [1] S. Sakai, K. Minoda, G. Saito, S. Akagi, A. Ueno, F. Fukuoka, GANN 46 (1955) 605. [2] R. Vlahov, St. Parushev, J. Vlahov, P. Nickel, G. Snatzke, Pure & Appl. Chem. 62 (1990) 1303. [3] K. Kalyanasundaram, M. Gra¨tzel, Coord. Chem. Rev. 177 (1998) 347. [4] A.I. Bush, Curr. Opin. Chem. Biol. 4 (2000) 184. [5] A. Morsali, A.R. Mahjoub, A. Ramazani, J. Coord. Chem. 57 (2004) 347. [6] M. Trpkovska, B. Soptrajanov, L. Pejov, J. Mol. Struct. 654 (2003) 21. [7] M.H. Zaghal, H.A. Qaseer, Trans. Met. Chem. 16 (1991) 39. [8] K. Folting, L.L. Merritt, Acta Crystallogr. B 33 (1977) 3540. [9] A.O. Youssef, M.M.H. Khalil, R.M. Ramadan, A.A. Soliman, Trans. Met. Chem. 28 (2003) 331. [10] B. Machura, R. Kruszynski, Polyhedron 26 (2007) 3336. [11] J. Chowdhury, M. Ghosh, T.N. Misra, Spectrochim. Acta A 56 (2000) 2107. [12] S. Kim, S.W. Joo, Vib. Spect. 39 (2005) 74. [13] S. Yurdakul, M. Yurdakul, J. Mol. Struct. 834–836 (2007) 555.
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Vibrational Spectroscopy 48 (2008) 238–245 www.elsevier.com/locate/vibspec
FT-IR and Raman spectroscopic and quantum chemical studies of zinc halide complexes with 2,20 -biquinoline Aysen E. Ozel a,*, Serda Kecel a, Sevim Akyuz b b
a Istanbul University, Faculty of Science, Department of Physics, Vezneciler, 34134 Istanbul, Turkey Istanbul Kultur University, Faculty of Science and Letters, Department of Physics, Atakoy Campus, 34156 Istanbul, Turkey
Received 18 July 2007; received in revised form 22 January 2008; accepted 23 January 2008 Available online 6 February 2008
Abstract The molecular structure, vibrational frequencies and the corresponding vibrational assignment of Zn(biq)X2 (X = Cl and Br; biq = 2,20 biquinoline) have been studied by employing the hybrid density functional theory (B3LYP) method and the complete basis set (DFT) method together with the 6-31G(d,p) basis set for X = Cl and Br. The FT-IR (400–4000 cm1) and Raman (100–3200 cm1) spectra of compounds were recorded and compared with that of the calculated spectra, which allowed authors to assign most of the observed bands. It was demonstrated that cis conformer is suitable for the Zn(biq)X2 compounds. The fundamental vibrational modes were characterized by their total energy distribution. The coordination effects on vibrational wavenumbers of biq were discussed in detail. # 2008 Elsevier B.V. All rights reserved. Keywords: Ab initio calculations; DFT; 2,20 -Biquinoline; Halide complexes; Vibrational frequencies
1. Introduction Quinoline family compounds are of great interest in pharmaceutical industry and widely used as parent compounds for making drugs [1], especially anti-malarial medicines [2]. 2,20 -Biquinoline (abbreviated as biq) is a interesting dimmer and used for the preparation of sensitizers for solar cell studies [3]. These molecules are also widely employed as a ligand with any metal cations. Zinc is one of the most abundant transition metal in human bodies. It is rich in the brain [4], and also plays significant and indispensable roles in biological systems. The IR spectroscopic studies on Zn(ClO4)2 [5], dichlorodioxochromium(VI) [6] and palladium, platinum and rhodium complexes of biq [7] were previously reported. In these studies, however, only some important vibrational modes of the ligand were given. The crystal data on biq [8] and W(CO)4(biq) [9], Re(CO)3(biq)Cl complexes [10] have been reported. Recently surface enhanced Raman spectra of biq [11,12] were reported. The vibrational wavenumbers of free biq were calculated by ab initio, DFT and force field refinement methods [13,14].
* Corresponding author. Tel.: +90 212 4555826; fax: +90 212 5190834. E-mail address: [email protected] (A.E. Ozel). 0924-2031/$ – see front matter # 2008 Elsevier B.V. All rights reserved. doi:10.1016/j.vibspec.2008.01.010
In our previous studies, experimental and theoretical spectroscopic investigations on quinoline and biq have been reported [14,15], and now we wish to extend our investigations to coordinated biq for predicting the coordination sensitive modes of biq. To the best of our knowledge, no ab initio and DFT calculation have been reported in the literature on zinc halide complexes with 2,20 -biquinoline. The aim of this study is to analyse the influence of the formation of bidentate coordination through both ring nitrogens on the vibrational wavenumbers of biq. For this purpose, vibrational wavenumbers of free and coordinated biq molecules were calculated by using the same method and the same basis sets. Moreover, determination of the wavenumbers particularly arising from metal–ligand and metal–halide bonds vibrations has a separate interest. 2. Experimental and computational details All chemicals used were reagent grade (Merck and Sigma). The Zn(biq)X2 (X = Cl and Br) complexes were prepared by adding slightly more than 1 mol of biq solution in ethanol to 1 mol of zinc halide solution using constant stirring. The precipitate was filtered, washed with ethanol, and dried at room temperature. The C, H, N analyses were carried out for both
A.E. Ozel et al. / Vibrational Spectroscopy 48 (2008) 238–245
samples. Anal. (%) calcd for Zn (C18H12N2)Cl2; C, 55.02; H, 3.08; N, 7.14. Found: C, 54.95; H, 3.1; N, 7.12. Calcd for Zn (C18H12N2)Br2; C, 44.86; H, 2.51; N, 5.82. Found: C, 44.90; H, 2.4; N, 5.80. The IR spectra of nujol mulls or KBr discs were recorded on a Jasco 300E FT-IR spectrometer (2 cm1 resolution) between 400 and 4000 cm1 spectral region. The Raman spectra of the samples were taken with a JY Jobin Yvon Horiba HR(800) spectrometer using 632.8 nm excitation from a He–Ne laser in the 3200–100 cm1 region with 4 cm1 resolution. All computational studies were carried out with the Gaussian03 package program [16]. The geometry of the title compounds in the ground state were optimized using DFT with B3LYP [17] exchange correlation function and the 6-31G(d,p) basis set. The addition of diffuse functions to the 6-31G(d,p) basis set did not introduce any principal changes in the calculated frequencies and IR intensities. To the best of our knowledge, no crystallographic study has been reported on zinc halide complexes with biq. Therefore, the optimized geometry of the title compounds were obtained by using single crystal data of biq [8] and for Zn–N and Zn–X bonds; and the X-ray results of Zn halide complexes of nicotinamide [18,19], as the initial geometric parameters. Tetrahedral arrangement around Zn atom were applied. Harmonic vibrational wavenumbers and infrared intensities were calculated at the same level of theory to characterize the stationary points. The total energy distribution (TED) of the vibrational modes of the molecules was calculated by using parallel quantum mechanics solutions (PQS) program [20] and the fundamental vibrational modes were characterized by their total energy distribution. 3. Results and discussion The Zn(biq)X2 (X = Cl and Br) complexes have been prepared for the first time and vibrational assignment were performed in comparison with these of calculated results. In solid state, 2,20 -biquinoline molecule is known to be in trans coplanar configuration [21], however cis form occurs on formation of complexes with metal ions [6,7,11,12]. When no symmetry restrictions were imposed during the geometry optimizations, the minima located at molecular potential energy surface corresponded to C1 symmetry for both complexes. The results for ZnBr2 complex were found to be slightly different from C2v symmetry, therefore we tried to constrain both structures to C2v symmetry. When we took into account C2v symmetry of the title compounds, although Zn(biq)Br2 complex gave no negative eigenvalue, one imaginary frequency was found for Zn(biq)Cl2 complex indicating that the structure found for Zn(biq)Cl2 complex was not a minimum energy structure. Thus, the optimized geometry parameters for C1 symmetry were taken for Zn(biq)Cl2 and for C2v symmetry were taken for Zn(biq)Br2 complex. On the other hand, initial frequency calculations of both the cis and trans conformer of Zn(biq)X2 compound at interring torsion 08 and 1808, respectively, were also done, but the calculated results demonstrated that the minima on the molecular potential energy hypersurfaces corresponds to cis
239
arrangement of the biq. The calculated geometric parameters for the two model systems are summarized in Table 1. The optimized structure and atoms numbering of Zn(biq)X2 complexes are shown in Fig. 1. As seen from Table 1, the N2ZnX2 part of the compounds are in distorted tetrahedral configuration. In both cases, the Zn–X and Zn–N bond pairs are ˚ (for ZnCl2) and 2.317 A ˚ found to be the same: Zn–X = 2.222 A ˚ ˚ (for ZnBr2); and Zn–N = 2.085 A (for ZnCl2) and 2.099 A (for ZnBr2). It should be noted that the calculated value of BrZnBr angle (126.38) is larger than ClZnCl angle (123.88) whereas NZnN angles are 79.38 and, 78.98 for Zn(biq)Cl2 and Zn(biq)Br2, respectively. The vibrational wavenumbers, calculated IR intensity and a complete assignment of the fundamental modes according to their total energy distribution and comparison between calculated and experimental results, are given in Table 2. Experimental data of the SERS study of 2,20 -biquinoline [12], in which adsorbed biq molecules on a silver colloidal surface were shown to coordinate silver atoms through both the nitrogen atoms in the cis form, were included in Table 2 for comparison. The differences between the calculated and the experimental values for the same mode are often attributed to the neglect of anharmonicity and incomplete inclusion of electronic correlation effects. In order to correct overestimation between unscaled wavenumbers and observed frequencies, The vibrational frequencies were scaled with a factor of 0.9614 [22]. Fig. 2 represents the experimental Raman spectra of Zn(biq)X2 complexes. Free biq is in trans form, therefore IR active vibrations are Raman inactive, and vice versa. However, when it involves in complex formation it turns to cis conformation. As seen in Table 2, in Zn(biq)X2 frequencies, several vibrational modes are observed in both IR and Raman spectra. The calculated IR spectra of free and coordinated biq together with experimental IR spectrum of Zn(biq)Br2 complex is shown in Fig. 3. Calculated IR spectra of Zn(biq)X2 complexes are found to be in agreement with those of experimental IR spectra. Raman spectra of the Zn(biq)X2 (X = Cl and Br) complexes show two bands at 343 and 306 cm1, and 288 and 230 cm1, respectively, which can be attributed to n(Zn–Cl) and n(Zn–Br) vibrational modes (see Fig. 4). These modes were observed at 343 and 304 cm1, and 302 and 225 cm1, at Raman spectra of nicotinamide complexes of ZnCl2 and ZnBr2, respectively [23], and 345 and 330 cm1, and 300 and 295 cm1 at the IR spectra of Pd(biq)Cl2 and Pd(biq)Br2 complexes, respectively [7]. Zn– N stretching vibrations of the complexes were calculated at 190 and 157 cm1 for Zn(biq)Cl2 (DFT/B3LYP 6-31G(d,p)) and 182 and 157 cm1 for Zn(biq)Br2 (see Table 2). In the case of Zn(nicotinamide)2X2 (X = Cl or Br) complexes, Zn–N (nicotinamide) stretching modes were observed at 236 and 202 cm1 for X = Cl and 200 and 184 cm1 for X = Br [23]. In the Raman spectra of Zn(biq)X2 compounds however, only one band around 200 cm1 was observed, which can be attributed to Zn– N stretching vibration (see Fig. 4). In the case of pyridine–metal complexes, ring stretching modes around 1400–1600 cm1 and ring breathing mode are known as coordination sensitive modes and increase in
240
A.E. Ozel et al. / Vibrational Spectroscopy 48 (2008) 238–245
Table 1 Optimized geometry parameters of Zn(biq)X2 complex (X = Cl and Br) obtained by B3LYP/6-31G(d,p) density functional calculations
R(1,2) R(1,6) R(1,7) R(2,3) R(2,13) R(3,4) R(3,14) R(4,5) R(4,25) R(5,6) R(5,28) R(6,33) R(7,8) R(7,12) R(8,9) R(8,33) R(9,10) R(9,19) R(10,11) R(10,18) R(11,12) R(11,15) R(12,16) R(17,18) R(17,20) R(17,21) R(18,22) R(19,20) R(19,23) R(20,24) R(25,26) R(25,31) R(26,27) R(26,32)
Cl
Br
1.417 1.330 1.491 1.374 1.082 1.414 1.086 1.430 1.418 1.364 1.418 2.085 1.331 1.418 1.364 2.084 1.430 1.418 1.414 1.418 1.374 1.086 1.082 1.376 1.418 1.085 1.086 1.376 1.084 1.085 1.376 1.086 1.418 1.085
1.418 1.330 1.491 1.374 1.082 1.414 1.086 1.430 1.418 1.364 1.418 2.099 1.330 1.418 1.364 2.099 1.430 1.418 1.414 1.418 1.374 1.086 1.082 1.376 1.417 1.085 1.086 1.376 1.084 1.085 1.376 1.086 1.417 1.085
R(27,28) R(27,29) R(28,30) R(33,34) R(33,35) A(2,1,6) A(2,1,7) A(6,1,7) A(1,2,3) A(1,2,13) A(3,2,13) A(2,3,4) A(2,3,14) A(4,3,14) A(3,4,5) A(3,4,25) A(5,4,25) A(4,5,6) A(4,5,28) A(6,5,28) A(1,6,5) A(5,6,33) A(1,7,8) A(1,7,12) A(8,7,12) A(7,8,9) A(9,8,33) A(8,9,10) A(8,9,19) A(10,9,19) A(9,10,11) A(9,10,18) A(11,10,18) A(10,11,12)
Cl
Br
1.376 1.085 1.084 2.222 2.219 121.4 122.6 116.0 119.3 120.7 119.9 120.3 120.3 119.4 117.3 123.6 119.1 121.0 119.7 119.3 120.7 125.2 116.0 122.5 121.4 120.7 125.2 121.0 119.3 119.7 117.3 119.1 123.5 120.3
1.376 1.085 1.084 2.317 2.317 121.4 122.4 116.2 119.3 120.7 119.9 120.3 120.4 119.4 117.3 123.5 119.2 121.0 119.6 119.4 120.7 125.0 116.2 122.4 121.3 120.7 125.0 121.0 119.4 119.6 117.3 119.2 123.5 120.3
A(10,11,15) A(12,11,15) A(7,12,11) A(7,12,16) A(11,12,16) A(18,17,20) A(18,17,21) A(20,17,21) A(10,18,17) A(10,18,22) A(17,18,22) A(9,19,20) A(9,19,23) A(20,19,23) A(17,20,19) A(17,20,24) A(19,20,24) A(4,25,26) A(4,25,31) A(26,25,31) A(25,26,27) A(25,26,32) A(27,26,32) A(26,27,28) A(26,27,29) A(28,27,29) A(5,28,27) A(5,28,30) A(27,28,30) A(6,33,8) A(6,33,34) A(6,33,35) A(8,33,34) A(8,33,35)
Cl
Br
119.4 120.3 119.3 120.7 119.9 120.4 120.0 119.5 120.1 118.9 120.9 119.6 119.0 121.3 120.9 119.5 119.5 120.1 118.9 120.9 120.4 120.0 119.5 120.9 119.5 119.5 119.6 119.1 121.3 79.3 109.2 113.2 109.3 113.2
119.4 120.4 119.3 120.7 119.9 120.4 120.0 119.5 120.1 118.9 120.9 119.6 119.2 121.1 121.0 119.4 119.5 120.1 118.9 120.9 120.4 120.0 119.5 121.0 119.4 119.5 119.6 119.2 121.1 78.9 110.4 110.4 110.4 110.4
A(34,33,35) A(7,8,33) A(1,6,33) D(6,1,2,3) D(2,1,7,8) D(2,1,7,12) D(6,1,7,8) D(6,1,7,12) D(3,4,5,28) D(25,4,5,6) D(3,4,25,31) D(4,5,6,33) D(28,5,6,33) D(5,6,33,8) D(5,6,33,34) D(5,6,33,35) D(33,8,9,10) D(33,8,9,19) D(9,8,33,6) D(9,8,33,34) D(9,8,33,35) D(8,9,10,18) D(19,9,10,11) D(11,10,18,22) D(33,6,1,7) D(33,6,1,2) D(33,8,7,12) D(33,8,7,1) D(7,8,33,6) D(7,8,33,34) D(7,8,33,35) D(1,6,33,8) D(1,6,33,34) D(1,6,33,35)
Cl
Br
123.8 113.8 113.8 0.1 179.7 0.2 0.2 179.3 179.2 179.6 0.3 172.6 7.7 177.7 75.47 66.9 172.9 7.3 177.5 75.6 66.7 179.6 179.2 0.3 7.0 173.5 173.8 6.7 7.9 98.8 118.8 8.1 98.8 118.9
126.3 114.3 114.3 0.0 180.0 0.0 0.0 180.0 180.0 180.0 0.0 180.0 0.0 180.0 72.2 72.2 180.0 0.0 180.0 72.2 72.2 180.0 180.0 0.0 0.0 180.0 180.0 0.0 0.0 107.8 107.8 0.0 107.8 107.8
R, A and D characters represent bond, angle and dihedral angle type of coordinates, respectively.
wavenumber upon coordination through the ring nitrogen [24]. Similar effect was also observed in the case of 2,20 -biquinoline complexes [7,11,12]. The 1800–400 cm1 region of the FT-IR spectrum of Zn(biq)Cl2 complex is shown in Fig. 5, together with that of solid biq. As seen in Fig. 5, the vibrational modes of biq compounds show the characteristic upward shifts for the
coordinated ligand, with respect to the free molecule. In order to find the coordination sensitive vibrational bands of biq, we have compared the unscaled wavenumbers of calculation of same level of theory for free biq with those of biq halide complexes.As seen from Table 2, similar shifts are also observed in theoretic calculations. Coordination sensitive
Fig. 1. Optimized geometries and atoms numbering of Zn(biq)Cl2 (C1) (a) and Zn(biq)Br2 (C2v ) (the same numbering scheme applied to both complexes).
Table 2 Calculated and experimental wavenumbers of Zn(biq)Cl2 and Zn(biq)Br2 complexes Assign.
Solid biq IR, exp.
SER a
Zn(biq)X2 X = Cl IR, nexp.
3095w 3074w 3064w 3056w 3046m 3042w 3036w 3028sh 3008w 2997w 2988w 2975w 1618m 1594vs 1595R 1588sh 1554m 1549m 1534w 1508R 1497vs 1474w 1459R 1458w 1449w 1431w 1420m 1374R 1354w 1327m 1323w 1300w 1247w 1245R 1213m 1205R 1144m 1141sh 1129m 1112R
3054
1590 1559
1508
1463
1430 1380 1343
1241 1221 1166
1144
3118m 3111w 3089m 3081w 3067w 3062w 3059w 3057w 3036sh 3031w 3026w 3021w 1617m 1599m 1585m 1585m 1558w 1554w 1545w 1509vs 1490w 1476w 1464w 1456w 1451w 1434m 1431sh 1381m 1367m – 1338m 1317w 1261w 1253w 1215m – 1164w 1155w 1145s –
X = Br R, nexp.
3066w
1620m 1599m 1585m 1566w 1512m 1505w 1469s 1462w
1440w 1388vs 1352w 1334vs 1315m 1276m 1255m 1224w – 1175w – – –
IR, nexp. 3117m 3111w 3087m 3079sh 3070w 3063sh 3059w 3054w 3039w 3030w 3027sh 3020w 1616m 1594m 1588m 1585m 1559w 1553w 1540w 1509vs
Zn(biq)Cl2 DFT/B3LYP 6-31G(d,p)
Zn(biq)Br2 DFT/B3LYP 6-31G(d,p)
TED% Zn(biq)Cl2 DFT/B3LYP/6-31G(d,p)
Unsc., ncal.
Scaled, ncal.
(I)
Unsc., ncal.
Scaled, ncal.
(I)
3248 3233 3223 3223 3213 3213 3202 3202 3194 3193 3188 3188 1673 1672 1649 1641 1627 1604 1562 1559 1512 1503 1477 1472 1425 1421 1401 1384 1355 1351 1330 1292 1283 1260 1254 1203 1191 1189 1177 1169
3123 3108 3099 3099 3089 3089 3078 3078 3071 3070 3065 3065 1608 1607 1585 1578 1564 1542 1502 1499 1454 1445 1420 1415 1370 1366 1347 1331 1303 1299 1279 1242 1233 1211 1206 1157 1145 1143 1132 1124
7.91 0.53 3.35 9.83 3.81 21.57 12.95 10.53 9.70 7.26 1.35 1.26 9.20 8.41 61.5 17.8 2.36 17.03 0.05 136.4 0.05 5.03 19.32 11.70 7.50 46.6 41.7 20.31 2.12 1.81 1.24 2.60 4.09 3.14 18.56 3.82 6.73 1.19 7.46 15.27
3249 3234 3226 3226 3214 3214 3202 3202 3193 3193 3188 3188 1673 1673 1650 1642 1627 1604 1562 1559 1513 1503 1477 1472 1425 1420 1401 1386 1355 1349 1329 1292 1283 1260 1254 1204 1192 1189 1177 1169
3124 3109 3101 3101 3090 3090 3078 3078 3070 3070 3065 3065 1608 1608 1586 1579 1564 1542 1502 1499 1455 1445 1420 1415 1370 1365 1347 1333 1303 1297 1278 1242 1233 1211 1206 1158 1146 1143 1132 1124
8.69 0.52 5.20 0.49 1.07 32.41 12.80 9.45 10.25 7.40 1.63 1.43 8.16 9.21 58.28 18.05 2.23 16.48 0.09 133.20 0.05 5.55 19.18 11.68 5.84 45.94 38.31 20.78 1.52 1.36 1.72 2.35 4.48 2.96 17.96 4.07 6.52 0.88 6.44 15.30
R, nexp.
3058w
1621w 1600m 1586m 1564w 1514m
1476w 1465w 1457vw 1449vw 1434s 1431w 1382s 1366m
1473s 1461w
1439w 1431w 1388vs 1345w
1338m 1316m 1268w 1253w 1215m – 1184w 1155m 1145s –
1337vs 1316m 1277m 1256w 1225m – 1176w – 1143w –
3218 3217 3213 3206 3203 3202 3189 3188 3180 3179 3175 3175 1674 1673 1653 1646 1610 1597 1552 1549 1516 1503 1468 1464 1412 1410 1386 1385 1350 1337 1302 1279 1270 1247 1246 1181 1178 1177 1171 1160
nCH(98) nCH(95) nCH(97) nCH(97) nCH(98) nCH(98) nCH(96) nCH(95) nCH(93) nCH(91) nCH(96) nCH(96) nCC(60) + dCCH(3) nCC(60) + dCCH(3) nCC(50) + nNC(9) + dCCH(6) nCC(45) + dCCH(7) nCC(47) + nNC(13) nCC(45) + nNC(15) nCC(33) + dCCH(20) nCC(41) + dCCH(3) nCC(23) + nNC(13) + dCCH(23) nCC(18) + nNC(10) + dCCH(24) nCC(20) + dCCH(40) nCC(12) + dCCH(36) nCC(63) + nCN(12) nCC(65) + nCN(8) nNC(13) + nCC(8) + dCCH(17) nCC(37) + nNC(32) + dCCH(11) nCC(16) + nNC(38) + dCCH(10) nNC(36) + dCCH(12) nCC(32) + dCCH(10) nCC(22) + dCCH(51) nCC(35) + dCCH(32) nCC(32) + dCCH(23) nCC(45) + nNC(4) + dCCH(14) nCC(11) + dCCH(64) nCC(12) + dCCH(57) dCCH(56) nCC(24) + dCCH(50) nCC(16) + dCCH(42)
A.E. Ozel et al. / Vibrational Spectroscopy 48 (2008) 238–245
nCH nCH nCH nCH nCH nCH nCH nCH nCH nCH nCH nCH nCC nCC nCC nCC nCC nCC nCC nCC nCC dCCH dCCH dCCH nCC nCC nCC nCC nNC nNC nCC dCCH nCC nCC nCC dCCH dCCH dCCH dCCH dCCH
Free biq (cis) DFT/B3LYP 631G(d,p) Unsc., ncal.
241
242
Table 2 (Continued ) Assign.
Solid biq IR, exp.
SER a
Zn(biq)X2 X = Cl
Unsc., ncal.
Scaled, ncal.
(I)
(I)
1135w – – – 1019w – – – 971w – – – 890w – – –
1132m 1106m 1048w 1048w 1021w 1021w 997w 988w 973m 957m – – 892w 873m 873m –
1134w – – – 1018w – – – 970w – – – 892w – – –
1148 1110 1042 1041 1002 1002 993 989 968 967 967 949 901 891 890 862
1167 1132 1050 1047 1009 1009 996 991 989 971 969 968 906 885 882 849
1122 1088 1009 1007 970 970 958 953 951 934 932 931 871 851 848 816
8.18 19.35 0.30 0.69 0.02 0.19 3.67 5.51 0.03 1.51 0.01 18.35 0.27 1.71 0.27 0.12
1167 1131 1050 1048 1008 1007 996 989 987 966 966 965 906 881 877 841
1122 1087 1009 1008 969 968 958 951 949 929 929 928 871 847 843 809
7.96 18.79 0.30 0.88 0.02 0.00 3.07 5.29 0.00 1.50 17.70 0.00 0.20 4.28 0.00 0.00
– –
– 843w
– –
844 837
840 838
808 806
89.41 1.49
837 837
805 805
1.43 84.80
804m 791m
834s – 785s 750s
– 806m 790m – 699w – – – – – 622w – – 535w 528w – 497w 472w 424w 398w
810 803 785 783 779 765 721 676 658 630 619 567 555 537 529 523 493 491 471 418
809 800 799 798 780 760 706 671 667 647 635 563 559 546 535 517 499 498 496 429
778 769 768 767 750 731 679 645 641 622 610 541 537 525 514 497 480 479 477 412
1.72 0.63 27.05 18.65 0.00 34.39 0.31 7.21 1.54 1.09 3.35 0.08 0.00 0.33 0.03 2.62 1.66 0.26 9.05 0.07
808 800 798 798 776 755 700 671 666 646 635 561 558 546 535 516 497 496 496 428
777 769 767 767 746 726 673 645 640 621 610 539 536 525 514 496 478 477 477 411
2.01 25.86 18.20 0.00 0.00 37.65 0.00 6.63 1.97 0.98 3.16 0.10 0.00 0.38 0.04 2.39 1.58 0.00 8.49 0.02
nCC GHCCC GHCCC nCC GHCCC GHCCC GHCCN dCCC GCCCN dCCC dCCC dCCC GCCCC dCCC dCCC GCCCC GCCCC GCCCC dCCC dCCC
830m 789m 766m 737m – – – 646w 641w 625m 614sh – – – 520w 499w 484w 473m – –
835s – 784s 751s – – – 658m 649w 633w 622m – – – 525w 502w 489m 471w – –
698w – – – – – 626w – – 537w 524w – 491w 475w 423w 400w
– – 658m 649w 634w 622m – – – 525w 501m 488m 472w – –
nCC(21) + dCCH(36) nCC(27) + nNC(16) + dCCH(8) nCC(65) nCC(67) GHCCH(60) + GCCCC(3) + GCCCH(14) GHCCH(60) + GCCCC(3) + GCCCH(14) GHCCH(37) + GCCCH(36) nCN(6) + nCC(24) + dCCC(11) + dCCH(6) GHCCH(33) + GCCCH(39) GHCCH(43) + GCCCH(12) GHCCH(42) + GCCCH(8) dCNC(13) + dCCC(14) nCC(13) + dCCC(22) GHCCC(29) + GHCCN(12) + GHCCH(8) GHCCC(30) + GHCCN(12) + GHCCH(9) GHCCC(42) + GCCCC(12) + GNCCN(3) + GCNCC(10) GHCCC(53) + GHCCN(11) nCC(9) + nNC(6) + dCCC(38) + dCCn(10) + dCCH(6) nCC(52) + dCCC(6) GHCCC(26) + GCCCC(3) + GCCCN(9) GHCCC(20) + GCNCC(9) nCC(57) GHCCC(65) + GHCCN(9) GHCCC(60) + GHCCN(6) GHCCC(9) + GHCCN(14) + GNCCN(4) nCC(10) + dCCC(33) GHCCN(7) + GCCCC(10) + GCCCN(26) dCCC(32) + dCCN(8) nCC(8) + dCCC(40) dCCC(19) + dNCC(16) + dCNZn(7) GCCCC(25) + GCCCH(9) nCC(20) + dCCC(27) + dNCC(8) nCC(15) + dCCC(29) + dNCC(12) GCCCC(24) + GCCCH(8) + GCCNZn(6) GCCCC(26) + GCCCH(14) GCCCC(18) + GCCCN(3) nCC(9) + dCCC(25) + dNCC(10) dCCC(27) + dNCC(19) + dCNZn(7)
A.E. Ozel et al. / Vibrational Spectroscopy 48 (2008) 238–245
1135m 1106m 1049w 1049w 1022w 1022w 998w 989w 973m 957m – – 892w 873m 873m – – 843w
533
Scaled, ncal.
R, nexp.
– 840m
616
Unsc., ncal.
TED% Zn(biq)Cl2 DFT/B3LYP/6-31G(d,p)
IR, nexp.
GHCCC dCCC
782
Zn(biq)Br2 DFT/B3LYP 6-31G(d,p)
R, nexp.
1120sh 1105w 1057w 1053w 1018R 1018R 994w 978w 954m 945m 936m – – 870m 867m –
951
X = Br
Zn(biq)Cl2 DFT/B3LYP 6-31G(d,p)
IR, nexp. dCCH nCC nCC nCC GHCCH GHCCH GHCCH nCC GCCCH GHCCH GHCCH dCCC dCCC GHCCC GHCCC GHCCC
1023b
Free biq (cis) DFT/B3LYP 631G(d,p) Unsc., ncal.
– – – – – – –
– – – – – – –
– 332w 343w 332w 306w – –
– – – – – –
– 332w 288w 281w 230m – –
405 405 – 329 – 280 241
413 408 350 338 311 282 275
397 392 336 325 299 271 264
7.74 0.03 66.5 0.00 34.8 3.23 0.29
413 407 336 307 281 276 242
397 391 323 295 270 265 233
8.28 0.00 0.00 45.18 3.00 7.42 15.58
GCCCC GCCCC nNZn GCCCC nNZn GCCNC GZnNCC dXZnX dXZnX
– –
– –
– – 199w
– – –
– – 198w
202 186
240 196 190 182 157 116 114 103 85
231 188 183 175 151 112 110 99 82
3.97 5.56 2.86 0.00 12.99 0.14 0.28 2.39 8.85
237 193 182 171 157 117 98 96 56
228 186 175 164 151 112 94 92 54
2.20 4.73 0.00 0.32 8.48 0.00 0.01 0.00 5.15
GXZnNC dXZnN
75 44
72 42
11.9 0.01
54 44
52 42
4.81 0.00
GXZnNC
43
41
0.37
34
33
1.01
GZnNCC
26
25
0.13
15
14
0.00
GXZnNC
20
19
1.52
5
5
0.08
(I) = computed IR intensities; R = Raman; IR = infrared; unsc. = unscaled. The scaling factor is 0.9614 taken from Ref. [22]. a Taken from Ref. [12]. b Taken from Ref. [11].
GCCCC(38) GCCCC(37) nXZn(100) GCCCC(18) + GCCNC(8) + GNZnNC(6) nXZn(94) nNZn(22) + dCCC(19) + dCCN(25) nCC(19) + nNC(7) + nNZn(21) + dCCC(8) + dCCN(8) GCCCC(14) + GZnNCC(8) GCCCC(22) + GCCNC(16) nCC(3) + nNZn(27) + dCNZn(16) + dNZnN(14) GCCCC(30) + GCCNC(10) nNZn(42) + dCNZn(15) GCCCC(19) + GCCNC(21) + GZnNCC(3) dXZnN(14) + GZnNCC(16) + GXZnNC(8) dZnNC(14) + dCCC(6) + dXZnN(14) + dXZnX(15) nNZn(14) + dCNZn(7) + dXZnN(9) + dXZnX(22) + GXZnNC(6) nNZn(8) + dCNZn(3) + dXZnN(25) + GXZnNC(54) dXZnN(16) + GNZnNC(12)GCCNC(12) + GCCCH(6) + GZnNCC(8) + GCCCC(13) dXZnN(8) + GCCNC(3) + GZnNCC(6) + GCCCC(4) + GXZnNC(39) dXZnN(6) + GCCCC(5) + GCCNC(13) + GNCCN(7) + GZnNCC(32) + GXZnNC(28) GXZnNC(51) + GZnNCC(16) + GNZnNC(10)
A.E. Ozel et al. / Vibrational Spectroscopy 48 (2008) 238–245
GCCCC GCCCC nXZn GCCCC nXZn dCCN dCCC + nCC
243
244
A.E. Ozel et al. / Vibrational Spectroscopy 48 (2008) 238–245
Fig. 2. Experimental Raman spectra of Zn(biq)X2 complexes.
Fig. 4. The 410–140 cm1 region of the Raman spectra of Zn(biq)Br2 (top) and Zn(Biq)Cl2 (bottom) complexes. *Zn–X stretching and **Zn–N stretching modes are indicated.
Fig. 5. The 1800–400 cm1 region of the FT-IR spectrum of solid biq (a) and Zn(biq)Cl2 complex (b).
modes of biq are marked as bold (Table 2). These shifts in are found to be only slightly depend on the halide groups but mainly result as an interaction between biq molecule and metal. 4. Summary and conclusion The structural parameters, IR wavenumbers and intensities of the fundamental bands of Zn(biq)X2 complexes were calculated using the DFT(B3LYP) methods using standart 631G(d,p), basis set for X = Cl and Br. DFT methods yield a good definition of the vibrational modes of Zn(biq)X2 halides. The comparison between calculated wavenumbers of free and coordinated biq enable us to predict coordination sensitive modes. Acknowledgements Fig. 3. Calculated IR spectra (B3LYP/6-31G(d,p)) of free biquinoline (a), Zn(biq)Cl2 (b) and Zn(biq)Br2 (c) complexes and the experimental IR spectrum of Zn(biq)Br2 (d).
This work was supported by the Research fund of the University of Istanbul. Project number UDP 918/18042007. The micro-Raman spectra were recorded at Istanbul Technical
A.E. Ozel et al. / Vibrational Spectroscopy 48 (2008) 238–245
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