Structure and vibrational assignment of beryllium acetylacetonate

Spectrochimica Acta Part A 73 (2009) 342–347

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Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy journal homepage: www.elsevier.com/locate/saa

Structure and vibrational assignment of beryllium acetylacetonate Sayyed Faramarz Tayyari a,∗ , Tayyebeh Bakhshi a , Maryam Ebrahimi b , Robert Erik Sammelson c a

Chemistry Department, Ferdowsi University of Mashhad, Mashhad 91775-1436, Iran WatLab, Department of Chemistry, University of Waterloo, Waterloo, Ont., Canada N2L 3G1 c Department of Chemistry, Ball State University, Muncie, IN 47306-0445, USA b

a r t i c l e

i n f o

Article history: Received 14 November 2008 Received in revised form 12 February 2009 Accepted 19 February 2009 Keywords: Beryllium acetylacetonate DFT calculations Fourier transform IR and Raman spectra Anharmonicity

a b s t r a c t The structure of beryllium acetylacetonate, Be(acac)2 , was fully optimized at the B3LYP (using the 6-31G*, 6-311G*, and 6-311++G(3df,2p) basis sets), Hartree–Fock, and the Möller–Plesset (using the 6-31G* basis set) levels. The frequency and intensity of the vibrational bands of Be(acac)2 and its 1,3,5-13 C; 2,4-13 C; 32 H; 3-2 H–2,4-18 O derivatives were obtained at the B3LYP level using 6-311G* basis set. We also calculated the anharmonic frequencies at the B3LYP/6-311G* level of theory for Be(acac). The calculated frequencies are compared with the experimental Fourier transform IR and Raman spectra. All of the measured IR and Raman bands were interpreted in terms of the calculated vibrational modes. The scaled theoretical frequencies and the structural parameters are in excellent agreement with the experimental data. Analysis of the vibrational spectra indicates a strong coupling between the chelated ring modes. Four bands at the 1042, 826, 748, and 480 cm−1 are found to be mainly due to the metal–oxygen stretching motions. © 2009 Elsevier B.V. All rights reserved.

1. Introduction The investigation of the structures and properties of metal ␤-diketonates is of significant importance because of a variety of potential applications. These compounds can be used in the preparation of supported catalysts and as precursors of heterogeneous catalysts [1–4]. Volatility of some acetylacetonates makes possible their utilization in thin film formation, with magnetic, electrical, and high-temperature superconductor properties, by metalorganic chemical vapor deposition techniques [4,5]. Beryllium ␤-diketones can be used in order to obtain polymeric compounds [3,6]. The beryllium(II) acetylacetonate complex is widely used for the determination of trace amounts of beryllium ions in biological samples and analytical chemistry [7–9]. The principal uses for beryllium and its compounds are in the manufacturing of electrical components, nuclear reactors, aerospace applications, chemicals, ceramics, and X-ray tubes [10,11]. Beryllium and its compounds are very toxic, especially to the lung, skin, and eyes, and at high concentration can cause death. There are only a few studies about beryllium and its compounds [12]. A few studies on the molecular structure and properties of beryllium acetylacetonate, Be(acac)2 , have been reported. Gas-phase electron diffraction (GED) study of Be(acac)2 was performed by Shibata et al. [13]. The structure of Be(acac)2 [14] and beryllium malonaldehyde (Be(mda)2 )

∗ Corresponding author. Tel.: +98 5118780216; fax: +98 5118438032. E-mail address: [email protected] (S.F. Tayyari). 1386-1425/$ – see front matter © 2009 Elsevier B.V. All rights reserved. doi:10.1016/j.saa.2009.02.027

[15] was also investigated by quantum mechanical calculations. These studies and X-ray crystallographic results [16] predict the D2 d symmetry for Be(acac)2 . The infrared spectrum of Be(acac)2 in the 1600–600 cm−1 is studied by Nakamoto et al. [17] and Junge and Musso [18]. Junge and Musso [18] assigned the IR band frequencies of Be(acac)2 by considering the 13 C, 18 O, and 2 H labeling of the ligand atoms. These results are very useful for interpretation of the vibrational spectra of Be(acac)2 . According to our knowledge, there is no report on the Far-IR and Raman spectra of this compound in the literature. The aim of the present work is the reassignment of the vibrational spectra [harmonic and anharmonic wavenumbers, and relative intensities for Raman and IR spectra] of Be(acac)2 in the 4000–100 cm−1 region by means of anharmonic density functional theory (DFT) calculations. The calculated vibrational frequencies are compared with those observed experimentally. The calculated band assignment at the DFT level is also compared with that given by Nakamoto et al. [17], based on normal coordinate analysis, and Junge and Musso [18], based on isotopic substitutions. The calculated geometrical parameters are compared with the X-ray and gas phase electron diffraction, GED, results. 2. Experimental Be(acac)2 was prepared and purified according to the method described in the literature [19]. The IR spectra were recorded on a Bomem B-154 Fourier transform spectrophotometer in the region 4000–600 cm−1 by averaging

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20 scans with a resolution of 2 cm−1 . The spectra were measured as a KBr pellet and in CCl4 and CS2 solutions. The Far-IR spectra in the region 600–100 cm−1 were obtained using a Thermo Nicolet NEXUS 870 FT-IR spectrometer equipped with a DTGS/polyethylene detector and a solid substrate beam splitter. The spectrum of the polyethylene pellet was collected with a resolution of 2 cm−1 by averaging the results of 64 scans. The FT-Raman spectra were recorded employing a 180◦ backscattering geometry and a Bomem MB-154 Fourier transform Raman spectrometer. The instrument was equipped with a ZnSe beam splitter and a TE cooled InGaAs detector. Rayleigh filtration was afforded by two sets of two holographic technology filters. The spectra were accumulated for 500 scans with a resolution of 2 cm−1 . The laser power at the sample was 400 mW. 3. Method of analysis The molecular equilibrium geometry and vibrational transitions of Be(acac)2 were computed with the Gaussian 03 [20] software system. The Becke’s three-parameters (B3) [21] exchange functional with the correlation functional of Lee, Yang, and Parr (LYP) [22,23] with the 6-31G*, 6-311G*, and 6-311++G(3df,2p) basis sets were used for optimizing the structure. To compare the accuracy of several different computational methods, the geometry of Be(acac)2 was further optimized at the HF and MP2 levels, using the 6-31G* basis set. The B3LYP/6-311G* level was used for calculating the vibrational frequencies and IR and Raman intensities. In order to assign the observed vibrational transitions, anharmonic frequency calculations [24–26] were performed for Be(acac) using the B3LYP functional and 6-311G* basis set. The assignment of the experimental frequencies are based on the observed band frequencies and intensities in the infrared and Raman spectra confirmed by establishing one to one correlation between observed and theoretically calculated frequencies. The assignment of the calculated wavenumbers is aided by the animation option of the GaussView 3.0 graphical interface for Gaussian programs [27], which gives a visual representation of the shape of the vibrational modes. 4. Results and discussion 4.1. Molecular geometry The optimized geometrical parameters of Be(acac)2 are summarized in Table 1 and its geometry along with the atom numbering system is shown in Fig. 1. For comparison, the GED [13] and X-ray diffraction results [16] are also given in Table 1. It can be clearly

Fig. 1. Structure and atom numbering system for Be(acac)2 .

observed from Table 1 that the calculated geometrical parameters are somewhat sensitive to the choice of level and basis sets. The results obtained at the B3LYP, using 6-311G* and 6-311++G(3df,2p) basis sets, are in excellent agreement with the experimental data. The only exception is the C2 C1 H bond angle, which the calculated value (112–113◦ ) is considerably different from the corresponding experimental value (106.0 ± 1◦ ) reported by Shibata et al. [13]. This disagreement could be due to the assumption of the CH3 position taken by Shibata et al. in their interpretation of the electron diffraction results [13]. It appears that Shibata et al. assumed an eclipsed conformation for the CH3 groups with respect to the oxygen atoms. According to our calculations, both methyl groups are staggered with respect to the oxygen atoms and the energy difference between the staggered and eclipsed conformers is 10–13 kJ/mol (see Table 1). 5. Vibrational analysis The Fourier transform infrared spectra of Be(acac)2 in the solid phase and in solution are shown in Fig. 2. The solid state Raman spectrum of Be(acac)2 is given in Fig. 3. Lorentzian function is utilized for deconvolution of the infrared spectrum of Be(acac)2 in the 1700–900 cm−1 region and the results are shown in Fig. 4. The anharmonic and unscaled and scaled harmonic calculated frequencies, Raman, and IR intensities at the BLYP/6-311G* level along with the experimental results and their assignments are listed in Table 2.

Table 1 Selected theoretical and experimental geometrical parameters for Be(acac)2 .a . A Bond length (Å) Be–O C–O C2 –C3 C1 –C2 C1 –H Bond angles (◦ ) OBeO BeOC OC2 C1 C2 C1 H C2 C3 C4 OC2 C3 E (kJ/mol)

B 1.620 1.272 1.400 1.503 1.087

106.4 123.3 116.2 112.5 121.0 123.0 10.9

C 1.626 1.276 1.402 1.505 1.090

106.3 123.2 116.0 112.8 121.0 123.2 10.9

D 1.636 1.295 1.413 1.520 1.093

106.9 122.8 115.9 112.5 120.9 123.3 11.4

E 1.623 1.295 1.413 1.504 1.082

105.5 123.5 115.7 112.6 120.9 123.7 13.0

X-ray [16] 1.629 1.286 1.400 1.503 1.091

107.5 122.0 115.3 112.8 121.0 123.7 12.4

1.62(2) 1.26(1) 1.39(2) 1.50(5)

107(1) 123(1) 117(1)

GED [13] 1.615(6) 1.270(4) 1.397(4) 1.499(5) 1.093(11) 106.0(10) 123.4(9) 116.3(10) 106.1(23)

121(1) 123(1)

a A, B, and C calculated at the B3LYP level using 6-311++G(3df,2p), 6-311G*, and 6-31G* basis sets, respectively; D and E stand for calculations at the MP2 and HF levels, respectively, using 6-31G* basis set; GED, gas-phase electron diffraction; E, E(eclipsed) − E(gauche).

344

Table 2 Fundamental band assignment of Be(acac)2 .a . Symmetry

Experimental

F1

F2

F3

IIR

AR

3212 3212 3132 3132 3132 3098 3098 3098 3043 3043 3043 1650 1621 1572 1515 1499 1498 1490 1489 1489 1454 1416 1416 1412 1328 1323 1221 1070 1069 1063 1058 1057 1042 985 981 951 833 792 755 699 681 663 573 571 494 480 446 424 277 273 237 228 193

3084 3084 3008 3008 3008 2975 2975 2975 2922 2922 2922 1593 1565 1518 1463 1448 1446 1438 1438 1438 1404 1367 1367 1363 1282 1277 1179 1033 1033 1027 1021 1021 1006 963 960 930 815 776 739 684 667 649 560 559 484 469 436 415 271 267 232 223 189

3085 3085 2978 2977 2978 2958 2963 2963 2950 2950 2943 1609 1589 1530 1478 1460 1459 1442 1451 1451 1423 1383 1383 1380 1293 1290 1191 1048 1045 1043 1038 1033 1023 987 965 932 812 748 732 691 670 657 563 557 490 474 441 419 274 271 232 221 192

0 19 0 1 86 19 0 0 0 3 16 0 997 481 26 0 210 17 0 0 340 0 3 38 0 80 14 0 0 244 0 15 7 31 0 10 570 15 38 0 0 25 0 0 2 0 0 8 0 1 1 0 0

176 1 238 5 3 1 366 0 769 38 3 22 4 5 9 12 18 16 12 0 2 33 51 2 32 18 5 0 0 0 26 0 1 2 15 0 0 0 1 5 0 3 4 0 3 14 5 0 0 0 0 1 1

IR solid

Assignments IR CCl4

3110(5)

3097(1)

2997(7) 2997(7) 2964(7)

3000(2) 3000(2) 2972(1)

R solid

TW

3102(5)

CH␣ CH␣ a CH3 a CH3 a CH3 a CH3 a CH3 a CH3 s CH3 s CH3 s CH3 s C.—. .O + s C.—. .C.—. .C s C.—. .O + s C.—. .C.—. .C s C.—. .C.—. .C + ıCH ı CH +  C.—. .P

2997(5)

2962(8) 2921(38) 2926(6) 2926(6)

2926(3) 2926(3)

1576(70) 1531(100) 1462(17)

1583(71) 1531(100) 1460(10)

1448(6) 1437(20)

1444(17) 1422(13)

– 1392(87)

– 1398(73)

1362(36)

1362(1)

1299(23) 1191(4)

1299(8) 1185(3)

1042(40)

1041(13)

1602(2) 1569(1) 1523(1)

a

1444(4) 1444(4) 1432(6) 1432(6) – 1392sh 1369(28) 1369(28) 1299(50) 1299(50) 1188(11)

1032(14) 1036(23) 1012(17) 960(11)

1037(20) 1013(4) 960(3)

935(19) 826(59) 781(15) 748(17)

933(6) 828(31) 770m* 748w

956(16) 937(3)

697(8) – 661(14)

496m♣

661(9) – – 495m♣

661(11) 565(17)

443vw 420s

443vw 418s

494(32) 480(100) 441(53) 419(12)

279vw 244vw 225vw 193wbr

277w 244w – –

227w 177,sh#

3

Ref. [17]

Ref. [18]

C C C O

s C.—. .O a C.—. .C.—. .C

C O + ıCCH

ıa CH3

ıa CH3

c C.—. .O

ıs CH3

ıs CH3

C C + C–CH3 ıC–C–H

s C.—. .C.—. .C

 + Be–O

Be–O + CH3

CH3 rock

CH3 Complicated mode

C–CH3 + C O ıC–CH3 + Be–O C–C–H

Complicated mode ? C–C–H ␯Be–O



ıC–CH3 + Be–O

z

ıa CH3 ıa CH3 ıa CH3 ıa CH3 ıa CH3 a C.—. .O + a C.—. .C.—. .C ıs CH3 ıs CH3 ıs CH3 s C.—. .C.—. .C + s C–CH3 s C.—. .C.—. .C + s C–CH3 ıC–C–H CH3 CH3 s Be–O +  + CH3 CH3 CH3 CH3 ıC.—. .C.—. .C + CH3 +ıO–Be–O ıC.—. .C.—. .C + CH3 +ıO–Be–O a C–CH3 ␯s O–Be–O(o.p.) +  C–C–H ␯a O–Be–O ıC.—. .C.—. .O C.—. .C.—. .O ıC.—. .C.—. .O  s O–Be–O ıO–Be–O  + ıC–CH3 ıC–CH3 ıC–CH3 O–Be–O

O–Be–O AA–Be–AA

ıC–C–H

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A1 B2 A1 E B2 E B1 A2 A1 B2 E A1 B2 E E A1 B2 E B1 A2 E A1 B2 E A1 B2 E B1 A2 B2 A1 E E B2 A1 E B2 E E A1 E B2 B1 A2 E A1 B2 E A1 B2 E B1 A1

Theoretical

a F1 , theoretical frequency at B3LYP/6-311G*; F2 , theoretical frequency scaled by 0.9603, 0.9655, and 0.9786 for the 3200–1700, 1700–1000, and below 1000 cm−1 regions, respectively; F3 , calculated anharmonic frequency; IIR and AR , IR intensity (in kM/mol) and Raman activity (Å4 /amu), respectively; TW, this work; the relative intensities are given in parentheses, , stretching; ı, in-plane bending; , out-of-plane bending; , in-plane ring deformation; , out-of-plane ring deformation; , torsion; *, in CS2 solution; ♣, different scale below 600 cm−1 ; #, different scale below 200 cm−1 .

E A2 B1 A2 E B1 E

161 153 95 93 83 54 44

157 150 93 91 81 53 43

154 148 70 71 65 47 24

0 0 0 0 2 0 4

1 0 0 0 0 7 4

162w 146w – – 67w –

160vw – – – 66w –

157,w – 88,m – 64,sh 59,s 51,sh

C–CH3 C–CH3

CH3

CH3

CH3

AA–Be–AA AA–Be–AA

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Fig. 2. Infrared spectra of Be(acac)2 .

Fig. 3. Raman spectrum of Be(acac)2 in the solid phase.

No imaginary frequency is obtained in all theoretical calculations, which confirms the convergence of the calculations. The observed and corresponding calculated isotopic frequency shifts are collected in Table 3. As shown in Table 3, with a few exceptions, the calculated isotopic frequency shifts are in excellent agreement with the corresponding observed data [18]. The major discrepancies are obtained for the 2,4-13 C derivative, which could be attributed to the presence of an appreciable amount of the 2-13 C derivative in the experimental sample.

Fig. 4. The deconvoluted IR spectrum of Be(acac)2 in the CCl4 solution.

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Table 3 The calculated and observed isotopic frequency shifts for Be(acac)2 .a . Freq. (cm−1 )

1583 1531 1444 1398 1362 1299 1185 1041 1013 960 933 828 770 748 661 a b c d

3-2 H

1,3,5-13 C b

2,4-13 C b

3-2 H–2,4-18 O b

Theo.

Exp.

Theo.

Exp.

Theo.

Exp.

c

Theo.

Exp.b

−5 −24 −4d −1 −3 −3 −341 −4 −3 −20 +13 −4 −202 −4 0

−10 −28 −11 −2 −2 −1 −328 −5 n.a. −21 +5 −4 −198 −6 0

−3 −25 −3 −7 −10 −3 −1 −11 −9 −19 −19 −3 −3 −2 −11

−3 −22 0 −4 n.a. −1 0 −4 −8 −21 −10 −2 −2 −1 −6

−42 −20 −4 −27 −1 −37 −8 −3 −10 0 −7 −1 −1 0 −1

−15 −8c −8 −29 n.a. −32 −4c −1 −2c −1 −4c −1 −1 0 −1

−23 −25 −2d −15 −5 −7 −348 −18 −15 −28 +7 −9 −204 −15 −10

−25 −31 −11 −13 −6 −5 −334 −18 n.a. −27 n.a. −8 −200 −16 −9

Theo. is calculated at the B3LYP/6-311G* level and Exp. the observed isotopic frequency shifts in cm−1 ; n.a., not available. Data from Ref. [18]. These bands are probably caused by only one 13 C substituted derivative at either 2- or 4-position. These bands are mixed with the 1455 cm−1 band.

The calculated frequencies are slightly higher than the observed values for the majority of the normal modes. Two factors may be responsible for the discrepancy between the experimental and computed spectra of Be(acac)2 . The first is caused by the environment. The second reason for this discrepancy is the fact that the experimental values are anharmonic frequencies while the calculated values are harmonic frequencies. As it is shown in Table 2, the calculated anharmonic frequencies are in excellent agreement with experimental results. A scaling factor could be also used to convert harmonic to anharmonic frequencies, but more precautions may be needed in this case since the extent of anharmonicity is not the same for all regions of vibrational spectra. This is also shown in Table 2. 5.1. Vibrational irreducible representation According to D2 d symmetry for the Be(acac)2 complex, the 3N − 6 = 81 vibrational modes can be classified among the symmetry species: vib = 13A1 (R) + 6A2 + 7B1 (R) + 13B2 (IR & R) + 21E(IR & R) 5.2. Band assignment 5.2.1. CH˛ stretching region The two normal modes due to the CH␣ stretching belong to A1 and B2 symmetry species. Comparing the previous assignments of acetylacetone [28], aluminum acetylacetonates [29], and considering the theoretical results, one expects to observe the CH␣ stretching at about 3100 cm−1 . The Raman spectrum of Be(acac)2 shows a band at 3102 cm−1 , which is assigned to this mode. The corresponding bands in aluminum acetylacetonates, Al(acac)3 , [29] and acetylacetone [28] are observed at 3092 and 3098 cm−1 , respectively. 5.2.2. Methyl group stretching Twelve CH stretching modes of four methyl groups can be divided into: 2A1 (R) + 1A2 + 1B1 (R) + 2B2 (IR & R) + 3E(IR & R) symmetry type. The CH stretching modes of the CH3 groups are expected to occur in the 3000–2900 cm−1 region [28,29]. Three bands are observed in the Raman spectrum at 2997, 2962, and 2921 cm−1 . The latter is strong and the others have weak scattering intensity in the Raman spectrum. By considering our calculated Raman intensities and comparing them with the reported results

for acetylacetone [28] and aluminum acetylacetonates [29], the band at 2921 cm−1 is assigned to s CH3 and the bands at 2997 and 2964 cm−1 are assigned to the in-plane and out-of-plane asymmetric CH3 stretching modes, respectively. 5.2.3. 1700–1000 cm−1 region In this region, in addition to the CH3 deformation and rocking and also the CH in plane bending modes, we expect to observe four bands due to the C.—. .O and C.—. .C stretching modes. The Raman spectrum of Be(acac)2 shows two very weak bands at 1602 and 1569 cm−1 , which the former is inactive and the latter is very strong in the IR spectrum. This result is in excellent agreement with the calculation, which attributes the former to the A1 and the latter to the B2 species of the s C.—. .O + s C.—. .C.—. .C. The assignment for the former, as far as we know, has not been reported, but the latter is assigned by Nakamoto et al. [17] to C.—. .C and by Junge and Musso [18] to s C.—. .O. The very strong IR band at about 1530 cm−1 , which according to the theoretical calculation belongs to E species, is assigned to asymmetric C.—. .C.—. .C stretching coupled strongly to the C H in-plane bending mode. This band is assigned by Nakamoto et al. [17] to s C.—. .O and by Junge and Musso [18] solely to a C.—. .C.—. .C. Junge and Musso observed a low frequency shift of 22 cm−1 upon 1,3,5-13 C substitution and 28 cm−1 upon 3-2 H substitution, which are in good agreement with our calculations (25 and 24 cm−1 , respectively). The corresponding Raman band appears as a very weak band at 1523 cm−1 . The weakness of this band in the Raman spectrum has been considered [30,31] to be a measure of delocalization of the ␲-system of the chelated ring. The very strong IR band at 1398 cm−1 is attributed to the asymmetric C.—. .O stretching strongly coupled to the asymmetric C.—. .C.—. .C stretching. This band was assigned by Nakamoto et al. [17] to the asymmetric CH3 bending and by Junge and Musso [18] solely to the asymmetric C.—. .O stretching. The Raman spectrum shows a strong band at 1299 cm−1 . According to our theoretical calculations, this band belongs to A1 species of s C.—. .C + s C CH3 . The corresponding IR band appears as a sharp band with medium intensity and belongs to E species. Junge and Musso [18] assigned this band solely to s C.—. .C.—. .C but Nakamoto et al. [17] attributed this band to C.—. .C + C CH3 . The band at 1185 cm−1 is assigned to the C–H in-plane bending and is in agreement with the Nakamoto et al. [17] and Junge and Musso [18] assignments. The Strong IR band at about 1040 cm−1 is assigned to the symmetric Be-O stretching coupled to one of the

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ring deformation modes, which is in agreement with the Nakamoto et al. assignment. 5.3. Below 1000 cm−1

347

cies were compared with the experimental data in the solid state and solution. A satisfactory reproduction of the experimental frequencies and isotopic frequency shifts is obtained. Acknowledgments

In this region, one expects to observe C–CH3 and Be–O stretching, CH out of plane bending, and in plane and out of plane ring deformation modes. The infrared spectrum shows two bands at 960 and 935 cm−1 . According to the theoretical calculations, we assigned the band at 960 cm−1 to the C.—. .C.—. .C bending that is coupled to the CH3 rocking and O Be O bending. This band is assigned neither by Nakamoto et al. nor by Junge and Musso. The corresponding Raman band, which belongs to A1 species, occurs at 956 cm−1 . The 935 cm−1 band is assigned to the asymmetric C CH3 stretching. This band is assigned by Nakamoto et al. to C CH3 + C O. However, Junge and Musso considered this band as a complicated mode. The very strong band at 826 cm−1 is assigned to the B2 species of Be–O stretching. Junge and Musso did not assign this band but Nakamoto et al. considered this band as ␦C-CH3 + Be–O. The IR spectrum of Be(acac)2 indicates a medium band at 781 cm−1 which, according to the theoretical calculations, belongs to E species of the CH␣ out-of-plane bending. This assignment is in agreement with those of Nakamoto et al. [17] and Junge and Musso [18]. According to the calculation results, the 748 cm−1 band is assigned to the asymmetric Be–O stretching (E species). This band is assigned by Nakamoto et al. [17] to one of the out of plane ring deformations and by Junge and Musso [18] to the Be–O stretching. The 661 cm−1 band is attributed to one of the in-plane ring deformations. This band is assigned by Nakamoto et al. to the out of plane ring deformation and by Junge and Musso to the C CH3 in-plane bending and Be–O stretching. The two strong Raman bands at 480 and 441 cm−1 are assigned to the symmetric Be–O stretching (A1 ) and O–Be–O bending (B2 ), respectively. The stretching of the former band does not involve any movement of the metal; and therefore, its frequency may be useful in estimation of the metal–oxygen bond strength. The very strong infrared band at 418 cm−1 is assigned to the E species of C–CH3 in-plane bending coupled to the in-plane ring deformation. The infrared band at 245 cm−1 and the Raman band at 228 cm−1 are assigned to O–Be–O out-of-plane bending and O–Be–O torsion, respectively. 6. Conclusion The structural parameters of Be(acac)2 were calculated at the DFT level using B3LYP functional with 6-31G*, 6-311G*, and 6311++G(3df,2p) basis sets. For comparison, these calculations were also performed at the RHF/6-31G* and RMP2/6-31G* levels of theory. The results obtained at the B3LYP/6-311G* and B3LYP/6311++G(3df,2p) levels are in excellent agreement with the X-ray and GED experimental data. The harmonic and anharmonic vibrational frequencies, IR and Raman intensities of the vibrational bands were calculated at the B3LYP/6-311G* level. The predicted frequen-

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