Structure and vibrational assignment of bis(4-amino-3-penten-2-onato) nickel(II). A density functional theoretical study

Article abstract of DOI:10.1016/j.molstruc.2011.05.008

Bis(4-amino-3-penten-2-onato) nickel(II), (Ni(APO)₂), and its NH deuterated analog, Ni(DAPO)₂, were synthesized and their molecular structure and vibrational assignments were investigated by means of density functional theory (DFT) calculations. The molecular stability was investigated by applying the NBO and geometry calculations. The harmonic vibrational frequencies of Ni(APO)₂ and Ni(DAPO)₂ were obtained at the B3LYP level using 6-311G basis set. The calculated geometrical parameters and vibrational frequencies were compared with the experimental results. The measured vibrational band frequencies were interpreted in terms of the calculated vibrational normal modes. The scaled theoretical frequencies and the structural parameters were found to be in good agreement with the experimental data.

Full text of DOI:10.1016/j.molstruc.2011.05.008

Journal of Molecular Structure 997 (2011) 117–125
Contents lists available at ScienceDirect
Journal of Molecular Structure
journal homepage: www.elsevier.com/locate/molstruc
Structure and vibrational assignment of bis(4-amino-3-penten-2-onato)nickel(II).
A density functional theoretical study
c
a
d
M. Jamialahmadi a, S.F. Tayyari b, , M.H. Habibi , M. Yazdanbakhsh , R.E. Sammelson
⇑
a Chemistry Department, Ferdowsi University of Mashhad, Mashhad 91775-1436, Iran
b Department of Chemistry, Neyshabur Branch, Islamic Azad University, Neyshabur, Iran
c Department of Chemistry, University of Isfahan, Isfahan 81746-73441, Iran
d Department of Chemistry, Ball State University, Muncie, IN 47306-0445, USA
a r t i c l e i n f o
a b s t r a c t
Article history:
Bis(4-amino-3-penten-2-onato) nickel(II), (Ni(APO)2), and its NH deuterated analog, Ni(DAPO)2, were
synthesized and their molecular structure and vibrational assignments were investigated by means of
density functional theory (DFT) calculations. The molecular stability was investigated by applying the
NBO and geometry calculations. The harmonic vibrational frequencies of Ni(APO)2 and Ni(DAPO)2 were
obtained at the B3LYP level using 6-311G⁄ basis set. The calculated geometrical parameters and vibra-
tional frequencies were compared with the experimental results. The measured vibrational band fre-
quencies were interpreted in terms of the calculated vibrational normal modes. The scaled theoretical
frequencies and the structural parameters were found to be in good agreement with the experimental
data.
Received 27 January 2011
Received in revised form 4 May 2011
Accepted 5 May 2011
Available online 11 May 2011
Keywords:
Bis(4-amino-3-penten-2-onato)nickel(II)
FT-IR spectroscopy
FT-Raman spectroscopy
Vibrational assignment
Density functional theory
Ó 2011 Elsevier B.V. All rights reserved.
1. Introduction
2. Experimental
In recent years, the use of amine and imine complexes based on
late transition metals as active and selective catalysts for the poly-
merization of a-olefins has received a great deal of attention [1–7].
The APO ligand was synthesized according to Lacey [12]. This
ligand was added to an aqueous solution of nickel (II) acetate
and Ni(APO)2 was obtained as a precipitate. This precipitate was
purified by crystallization from a chloroform solution. Anal. Found:
C, 47.52; H, 6.42; N, 10.66; Ni, 23.19 Calc.: NiC10H16O2N2: C, 47.11;
H, 6.33; N, 10.99; Ni, 23.02%. M.p. 245 °C, 1H NMR (CDCl3,
100 MHz, reference: solvent residual peak, d 7.24 ppm): d 9.66(b,
2H, NH), d 4.83(s, 2H, CH), d 1.84(s, 6H, CH3CO), d 1.58(s, 6H,
CH3CN).
The late transition metal complexes, because of their less oxophilic
nature relative to early transition metal complexes, are generally
considered to be more tolerant toward polar media and polar func-
tional groups and thus make them possible targets for the develop-
ment of catalysts for polar monomer polymerizations [5,8].
Ni is known to be an excellent catalyst for many processes. He
and Wu [9] synthesized and characterized a series of bis(b-ketoa-
mino)nickel(II) complexes and investigated the effects of catalyst
structure and polymerization conditions on the polymerization
activity of methyl methacrylate using bis(b-ketoamino)nickel(II)/
methylaluminoxane (MAO) as catalytic systems [10].
According to Gurr’s study [11], the unit cell of bis(4-amino-3-
penten-2-onato) nickel(II) [hereafter abbreviated as Ni(APO)2], is
orthorhombic, space group Ccca, and the unit cell dimensions are
a = 16.7, b = 15.1, c = 13.5 Å. In this research, the complex was pre-
pared in high purity and experimental data were compared with
the theoretical calculation results.
The NH deuterated analog of Ni(APO)2, referred to as Ni(DAPO)2,
was prepared according to the literature [13].
The infrared spectra in the region 500–4000 cmÀ1 were re-
corded on a Bomem MB-154 Fourier transform spectrophotometer
using KBr pellets and CHCl3 and CH2Cl2 solutions. The spectra were
collected with a resolution of 2 cmÀ1 by signal averaging the re-
sults of 15 scans.
The Far-IR spectra of CsBr pellets of Ni(APO)2 in the
600–150 cmÀ1 region were obtained by using a ThermoNicolet
NEXUS 870 FT-IR spectrometer equipped with a DTGS/polyethylene
detector and a solid substrate beam splitter. The spectra were
collected with a resolution of 2 cmÀ1 by averaging the results of 64
scans.
The FT-Raman spectra in the region 3200–200 cmÀ1 were
⇑
recorded employing
Bomem MB-154 Fourier transform Raman spectrometer operating
a 180° back-scattering geometry and a
Corresponding author. Tel.: +98 9153103538.
E-mail address: sftayyari@hotmail.com (S.F. Tayyari).
0022-2860/$ - see front matter Ó 2011 Elsevier B.V. All rights reserved.
doi:10.1016/j.molstruc.2011.05.008

118
M. Jamialahmadi et al. / Journal of Molecular Structure 997 (2011) 117–125
Table 1
at the 1064 nm excitation line of a Nd:YAG laser. It was equipped
with a ZnSe beam splitter and a TE cooled InGaAs detector. Ray-
leigh filtration was afforded by a set of two holographic technology
filters. The spectra were accumulated for 2500 scans with a resolu-
tion of 2 cmÀ1. The laser power at the sample was 500 mW.
Selected experimental (X-ray) and calculated geometrical parameters for Bis-(4-
amino-3-penten-2-ono)nickel(II) (bond lengths in Å, bond angles in °).
APOb
a
Parameter
Ni(APO)2
Cis
X-ray
Ni(acac)2
Bond lengths
Trans
NiAO
NiAN
OAC
NAC
C9AC10
C7AC10
C6AC14
C8AC16
NAH
1.865
1.859
1.274
1.318
1.406
1.395
1.511
1.513
1.014
1.091
1.081
1.853
1.857
1.287
1.306
1.420
1.385
1.510
1.512
1.014
1.091
1.083
1.845
1.843
1.337
1.299
1.405
1.342
1.475
1.536
0.796
0.960
0.961
1.876
1.273
1.401
1.504
3. Method of analysis
1.238
1.348
1.445
1.375
1.522
1.505
1.005
All the computations in the present study were performed using
GAUSSIAN 03 software package [14] and NBO 5.0 [15] programs.
The geometry optimization and vibrational frequencies are per-
formed at the B3LYP level using 6-311G⁄ basis set.
Raman activities were computed by numerical differentiation of
dipole derivatives with respect to the electric field, using standard
GAUSSIAN 03 procedures (Freq = Raman) and default options.
Vibrational assignments are based on comparison of calculated
and observed Raman and IR frequencies and activities. The pro-
posed assignments are further corroborated by noting the deute-
rium isotopic shifts of different bands and their predicted shifts
by the same theoretical methods. The assignment of the calculated
wavenumbers is aided by the animation option of the GaussView
3.0 graphical interface for Gaussian programs [14,16], which gives
a visual representation of the shape of the vibrational modes.
C14AH
C11AH13
1.083
Bond angles
O2ANiAO3
O2ANiAN5
84.66
176.8
92.17
90.99
179.58
93.37
86.63
85.30
178.0
94.33
86.11
93.6
O2ANIAN4
N4ANiAN5
O2AC6AC11
O2AC6AC14
N4AC8AC11
N4AC8AC16
C16AC8AC11
C6AC11AC8
NiANAH
179.83
125.56
114.03
121.83
120.07
120.41
123.01
114.86
116.12
118.77
124.99
114.71
122.83
118.45
120.30
122.33
118.52
112.62
118.62
0.72
123.87
116.05
123.76
116.97
120.03
124.37
121.45
111.39
118.20
2.74
123.5
119.5
122.4
116.0
121.6
123.1
CANAH
4. Results and discussion
C8AC11AH13
H4AN4ANiAN5
O2ANiAN5AH5
H17AC17AC9AN5
HAC14AC6AO2
cDEgas
118.2
0.5
2.752
179.729
4.1. Molecular geometry
158.022
179.020
27.45
129.43
156.37
According to the theoretical DFT calculations, two configura-
tions are possible for Ni(APO)2. These are recognized as trans and
cis configurations and are shown in Fig. 1. The optimized geomet-
rical parameters of trans Ni(APO)2 are summarized in Table 1. The
theoretical calculations in the gas phase indicate that the trans
configuration is considerably more stable than the cis configura-
tion (about 27.45 kJ molÀ1), which is not in agreement with the
X-ray result of Gurr [11]. According to the X-ray crystallography,
the cis configuration is prominent. This is most likely due to the ne-
glect of solvent effects in our theoretical calculations, which is cer-
tainly important (but not easily incorporated) for Ni(APO)2
complex systems [17,18]. However, Bradbury et al. [19] have
shown that Ni(APO)2 is predominantly trans in solution with the
cis and trans isomers in rapid equilibrium at room temperature,
therefore both vibrational frequencies and molecular geometry is
dependent on the chemical environment. This isomerization prob-
ably occurs by twisting to produce a pseudo-tetrahedral interme-
diate of the type discussed by Holm and O’Connor [20].
Calculations in solution phase show that the energy difference
between the cis and trans isomers decreases considerably (about
D
Esolution
13.07
a
b
c
Data from [21].
Calculated at B3LYP/6-311G⁄.
D
E = Ecis À ETrans in kJ molÀ1
.
14.4 kJ molÀ1), compared to that in the gas phase. Unfortunately
there is no way to predict the energy difference in the solid state.
However, this large energy shift may be consistence with the lower
energy of the cis form in the solid state.
As it is shown in Table 2, the calculated bond lengths of CAO
and C7AC10 are longer and CAN and C9AC10 are shorter than the
corresponding values in APO. This results show that the resonance
in Ni(APO)2 has increased relative to APO. The calculated NiAO dis-
tance in Ni(APO)2 is 1.882 Å that is shorter and, therefore, stronger
than the similar bond in bis (acetylacetonato) nickel(II) (Ni(acac)2)
[21].
As Table 1 shows, the geometrical parameters are close to
the previously determined structural X-ray parameters [11]. The
15
14
15
16
2
1
3
5
7
6
7
3
5
4
8
12
13 11
10
10 12
9
13 11
1
9
8
6
2
4
17
16
17
14
Cis
Trans
Fig. 1. Cis and Trans configurations and atom numbering of Ni(APO)2.

M. Jamialahmadi et al. / Journal of Molecular Structure 997 (2011) 117–125
119
Table 2
and the NAC bond order is considerably greater than the corre-
sponding bond orders in APO. These results confirm that resonance
in chelated ring of Ni(APO)2 is more than in that of APO. Compar-
ison between cis and trans isomers represents that OAC, NiAN, and
C9AC10 bond orders in the trans isomer are less than and NAC,
NiAO, and C7AC10 bond orders are greater than cis isomer. The
high value of LP(2)O4 ? r⁄ (NiAO2) (305.1 kJ molÀ1) and LP(2)
Selected Wiberg bond orders for Trans and Cis Ni(APO)2 calculated at B3LYP/6-311G⁄
level of theory.
Bond
Trans
Cis
APO
NiAO
NiAN
OAC
0.3284
0.3779
1.2785
1.5507
1.4524
1.2479
1.0183
1.0225
0.9241
0.3013
0.4034
1.3122
1.3121
1.4213
1.2746
1.0177
1.0231
0.9242
1.6169
1.2810
1.1846
1.5159
1.0040
1.0336
0.9284
1.6169
1.2810
NAC
C11
?
r⁄ (O2AC6) (196.07 kcal molÀ1) energies, in the trans isomer
C7AC10
C9AC10
C7AC15
C8AC16
and LP(2)O2 ? r⁄ (NiAN5) (66.94 kcal molÀ1) and LP(2)C11
?
r⁄
(N4AC8) (kJ molÀ1) energies, in the cis isomer indicates that these
interactions play an important role in the mentioned bond orders.
The charge distribution calculated by the NBO method and the
Mulliken charges for optimized geometries of APO, and cis and
trans isomers of Ni(APO)2 are tabulated in Table 3. As this data
indicates, the less charge difference over O and N atoms in trans
isomer is caused by higher conjugation of NiAO and NiAN with
CAO and CAN in the trans isomer compared with that in the cis
isomer.
C
10AH
Table 3
Selected Natural and Mulliken charges (e) for optimized cis and trans Ni(APO)2 and
APO.
Natural charges
Trans
Mulliken charges
Trans Cis
1.025550
À0.560052
À0.798333
0.384594
Cis
1.12693
À0.69471
À0.78843
0.50791
APO
4.3. Vibrational analysis
Ni
O
N
C6
1.12024
1.033365
À0.513777
À0.809356
0.376900
À0.73248
À0.76367
0.49235
À0.64784
À0.74366
0.53593
The infrared spectra of Ni(APO)2 in the solid phase and CH2Cl2
solution are shown in Figs. 2 and 3. The far infrared spectrum of
the titled compound in the solid phase is shown in Fig. 4. Fig. 5 rep-
resents the Raman spectrum of Ni(APO)2. The theoretical and
experimental IR and Raman band frequencies in the solid phase
and CHCl3 and CH2Cl2 solutions for cis and trans configurations
and their assignments are given in Table 4. Table 5 shows the the-
oretical and experimental IR band frequencies in the solid phase
for Ni(DAPO)2 along with their assignments. Figs. 6 and 7 show
the comparison between the infrared spectra of Ni(APO)2 and Ni
(DAPO)2 in the solid phase.
The calculated fundamental wavenumbers are compared with
the experimental results in the 3400–150 cmÀ1 region. The calcu-
lated frequencies are slightly higher than the observed values for
the majority of the normal modes. Two factors may be responsible
for the discrepancies between the experimental and computed
spectra of Ni(APO)2. The first is caused by the environment. DFT
calculations have been done at the gas phase, and experimental
data are obtained from solid complex. The second reason for this
discrepancy is the fact that the experimental values are anhar-
monic frequencies while the calculated values are harmonic
frequencies. However, simple scaling of the theoretical wavenum-
C8
0.31202
0.31084
0.30206
0.422570
0.414127
C10
H12
C14
C16
À0.45672
À0.45919
À0.44913
À0.438046
À0.449172
0.19974
0.20014
0.19792
0.182754
0.185978
À0.60833
À0.5993
À0.61366
À0.60002
À0.63875
À0.59718
À0.664854
À0.695745
À0.660902
À0.697576
NAH and CAH bond lengths are longer than the corresponding
a
values obtained by X-ray. X-ray diffraction cannot measure the
bond lengths including H atom and an electronegative element,
such as O or N, exactly. Therefore, the length of such bonds mea-
sured by X-ray spectroscopy is shorter than the actual bond length.
The dihedral angle HAC17AC9AN5 has deviated from planar
structure, by about 22°. However, in X-ray structure, this angle is
129.4, which shows about 50° deviation from planar. This result
is also consistent with the crystal effects on the structure of the
molecules.
4.2. NBO analysis
The calculated Wiberg bond orders for APO, and cis and trans
Ni(APO)2 are collected in Table 2. This data shows that in both
cis and trans Ni(APO)2 the OAC bond order is significantly less than
bers according to the equation mobsd
satisfactory agreement with the set of the observed wavenumbers.
= amtheor generally leads to
Values of
a for high and low frequencies are used from Ref. [22].
0.14
0.12
0.10
0.08
0.06
0.04
0.02
0.00
Ni(APO)2
.… Ni(APO)2 in CH 2Cl2
3400
3200
3000
2800
2600
Wavenumbers (cm-1)
Fig. 2. Infrared spectrum of Ni(APO)2, in the solid phase and in solution, in the 3500–2600 cmÀ1 region.

120
M. Jamialahmadi et al. / Journal of Molecular Structure 997 (2011) 117–125
0.25
0.20
0.15
0.10
0.05
0.00
-0.05
Ni(APO)2
.… Ni(APO)2 in CH2Cl2
1600
1400
1200
1000
800
600
Wavenumbers (cm-1)
Fig. 3. Infrared spectrum of Ni(APO)2, in the solid phase and in solution, in the 1700–600 cmÀ1 region.
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
700
600
500
400
300
Wavenumbers (cm -1
)
Fig. 4. Far infrared spectrum of Ni(APO)2, in the solid phase.
10
8
6
4
2
0
1600
1400
1200
1000
800
600
400
Wavenumbers (cm-1)
Fig. 5. Raman spectrum of Ni(APO)2, in the solid phase, in the 1700–250 cmÀ1 region.
4.3.1. 3500–1700 cmÀ1 region
strong band is observed at 3287 cmÀ1. However, in CHCl3 and
CH2Cl2 this band shifts to 3346 and 3343 cmÀ1, respectively. The
corresponding band in the deuterated analog appears at
2431 cmÀ1. The red shift of about 50 cmÀ1 for this band in the solu-
tion, with respect to the solid phase, confirms the presence of a
In this region the CAH and NH stretching frequencies are
expected to be observed. The NH stretching bands are usually
appeared in the 3500–3100 cmÀ1 region upon complexation
[23,24]. In the infrared spectrum of Ni(APO)2 in the solid phase a

M. Jamialahmadi et al. / Journal of Molecular Structure 997 (2011) 117–125
121
Table 4
Fundamental band assignment of Ni(APO)2.
Theoretical
Gas
Experimental
Assignment
Solution
FsC(IIR
IR
Raman
Solid
No.
FsT(IIR, AR)
FsC(IIR, AR)
FsT(IIR
)
)
Solid
3287(s)
CHCl3
CH2Cl2
1
2
3
4
5
6
7
8
9
3405(33,1)
3405(0,126)
3068(1,220)
3068(34,5)
2999(44,21)
2999(7,134)
2989(46,4)
2989(1,138)
2970(29,1)
2970(0,206)
2966(36,0)
2966(0,193)
2917(0,625)
2916(35,0)
2916(0234)
2916(51,2)
1619(0,47)
1612(381,0)
1531(0,25)
1528(530,0)
1504(173,0)
1495(0,16)
1470(0,36)
1469(150,1)
1461(10,1)
1461(7,26)
1458(0,25)
1458(22,0)
1448(260,0)
1437(0,41)
1398(0,33)
1391(30,0)
1388(0,24)
1385(11,0)
1380(0,7)
1368(142,0)
1234(7,0)
1219(0,23)
1179(61,0)
1174(0,23)
1041(0,0)
1041(0,0)
1035(0,26)
1032(27,1)
1031(3,0)
1031(14,0)
1026(0,6)
1026(16,0)
953(0,21)
953(4,0)
3385(4,6)
3379(0,143)
3075(1,227)
3074(35,3)
3000(2143)
3000(49,8)
2998(6,122)
2997(32,39)
2973(30,181)
2973(1,4)
2964(41,148))
2963(1,29)
2919(29,431)
2919(10,11)
2912(38,366)
2912(7,29)
1599(0,40)
1586(526,130)
1562(305,0)
1546(11,5)
1496(308,5)
1488(3,16)
1478(17,13)
1478(0,12)
1466(4,22)
1462(166,2)
1456(15,8)
1456(0,19)
1443(378,29)
1436(12,21)
1433(32,6)
1398(39,5)
1389(7,21)
1388(0,0)
1382(19,17)
1380(5,0)
1247(7,18)
1233(4,8)
1198(11,11)
1186(13,6)
1042(4,4)
1042(0,0)
1037(1,19)
1033(24,0)
1031(27,3)
1030(0,0)
1026(15,1)
1024(1,0)
958(1,25)
957(1,0)
935(12,0)
928(0,2)
753(96,0)
745(0,0)
722(7,16)
698(12,2)
691(2,0)
675(16,3)
662(0,0)
637(69,0)
612(7,0)
559(0,2)
3402(48)
3402(9)
3070(2)
3070(45)
3002(0)
3002(74)
2995(53)
2995(23)
2972(21)
2972(17)
2963(54)
2963(2)
2920(0)
2919(42)
2915(0)
2915(74)
1606(0)
1602(607)
1519(0)
1516(753)
1486(352)
1483(0)
1459(1)
1458(320)
1449(17)
1449(11)
1447(27)
1447(6)
1427(621)
1421(0)
1394(0)
1387(46)
1384(0)
1379(14)
1376(0)
1366(273)
1230(19)
1216(0)
1177(109
1174(0)
1039(0)
1028(0)
1033(0)
1029(27)
1029(48)
1028(1)
1026(34)
1026(0)
951(0)
3393(8)
3392(6)
3072(6)
3072(41)
3001(29)
3001(47)
2996(35)
2995(35)
2975(26)
2975(21)
2965(34)
2965(21)
2919(21)
2919(17)
2915(65)
2915(8)
1593(39)
1582(680)
1553(350)
1529(110)
1483(587)
1479(9)
1469(94)
1465(78)
1451(52)
1447(26)
1447(36)
1446(188)
1438(150)
1418(76)
1416(631)
1403(94)
1386(2)
1386(0)
1376(5)
1375(7)
1244(2)
1230(12)
1196(28)
1184(31)
1038(2)
1037(2)
1035(6)
1031(23)
1028(33)
1027(6)
1026(44)
1024(13)
955(6)
3346(s)
3343(s)
3288(w)
3288
3082(w)
3082
m
m
m
m
m
m
m
m
m
m
m
m
m
m
m
m
m
m
m
m
NAH
NAY
3079(w)
2994(w)
2988(w)
2956(w)
2927(w)
(⁄)
(⁄)
CH
CH
a
a
3001(w)
2985(w)
2996(w)
2981(w)
aCH3
aCH3
aCH3
aCH3
aCH3
aCH3
aCH3
aCH3
sCH3
sCH3
sCH3
sCH3
sCAO,
aCAO,
2964(w)
2957(w)
2925(w)
2962(w)
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
2927(vw)
2917(s)
2908(m)
2908
2908
1597(w)
2920(m)
2919(w)
2922(w)
m
m
sCAN(i. p.), dCH
aCAN(o. p.), dCH
a
a
1591(s)
1597(s)
1597(s)
1542(w)
aCACAC, dCH
aCACAC, dCH
a
a
, dNH
, dNH
m
m
1552(s)
1523 (s)
1516(m)
1513(s)
1515(w)
1515 (s)
dCH3,
dCH3,
daCH3
daCH3
daCH3
daCH3
daCH3
daCH3
m
m
aCACAN,
aCACAN,
aCACAO
aCACAO
1483(w)
1470(s)
1485(s)
1476 (s)
1469(m)
1467(w))
1466(m)
1460(m)
1462(m)
1460(m)
1454(w)
1455(w)
1442(m)
1458(m)
1434(s)
1436(s)
daCH3,
daCH3,
m
m
aC@CAN,
aC@CAN,
m
m
aCAC@O
aCAC@O
1441(w)
1401(m)
1392(sh)
1388(vs)
c
CH3,
m
sCAC@C
1391(m)
1374(m)
1411(s)
dsCH3,
dsCH3
mCACH3
1391(w)
1383(m)
1377(s)
1377(sh)
1375(m)
dCH3, mCACH3
dNH, dCH
dNH, dCH
dNH, dCH
dNH, dCH
a
a
a
a
, dsCH3
, dO@CAC
,
,
1352(m)
1248(w)
1350(vs)
(⁄)
1350(s)
1225(w)
m
m
C@CAC(i.p.)
C@CAC(o.p.)
1227(m)
1182(m)
1185(m)
1172(m)
1025(m)
1172(m)
1024(m)
dCH
dCH
a
a
, dNH
, dNH
p
p
q
p
p
q
q
q
CH3
CH3
CH3, dCAC@C
CH3
CH3
CH3, dCAC@C
CH3
CH3
1034(m)
1032(m)
1032(m)
1023(m)
954(s)
dCAC@C,
dCAC@C,
q
q
CH3
CH3
951(11)
930(62)
923(0)
767(227)
764(0)
953(6)
931(45)
924(4)
752(165)
747(1)
729(12)
710(32)
696(1)
953(w)
935(m)
933(26,0)
925(0,2)
780(137,0)
776(0,3)
737(3,0)
735(0,1)
943(m)
(⁄)
941(m)
(⁄)
D
D
ring,
ring,
m
m
CACH3
CACH3
814 (vsbr)
c
c
c
c
m
m
m
CH
a
a
a
a
,
,
,
,
c
c
c
c
NH
NH
NH
NH
810 (w)
766(w)
CH
CH
CH
736(0)
735(0)
767 (vw)
756 (m)
733(9,0)
729(18)
703(0)
677(37)
635(77)
624(0)
622(0)
532(0)
526(0)
483(64)
465(0)
449(4)
409(0)
374(2)
358(10)
316(13)
(⁄)
(⁄)
(⁄)
aNANiAN, dC@CAN
sNANiAN,
aOANiAO
704(0,17)
681(21,0)
640(38,0)
626(0,1)
625(0,5)
531(0,0)
678(0)
704(w)
msOANiAO(i.p.)
669(34)
635(105)
607(10)
602(0)
534(0)
532(0)
470(71)
469(1)
446(7)
416(0)
370(1)
681(m)
659(m)
(⁄)
651(m)
C
C
ring
623(vw)
m
c
c
m
m
sOANiAO,
CACH3
CACH3
aOANiAO,
sOANiAO,
msNANiAN(o.p.)
531(0,4)
530(0,1)
477(41,0)
470(0,14)
450(4,8)
420(0,1)
369(1,0)
357(6,0)
324(7,0)
524(0,4)
489(37,0)
468(0,22)
451(2,0)
410(0,3)
376(2,0)
485(vs)
456(s)
492(s)
487(s)
m
m
aNANiAN
sNANiAN
479(vs)
daCACH3
daCACH3
m
aNANiAN, dOANiAO
dNANiAN, dOANiAO
NANiAN, OANiAO
361(6,0)
327(6,0)
351(8)
316(15)
361(m)
315(w)
c
c
(continued on next page)

122
M. Jamialahmadi et al. / Journal of Molecular Structure 997 (2011) 117–125
Table 4 (continued)
Theoretical
Gas
Experimental
Assignment
Solution
FsC(IIR
IR
Raman
Solid
No.
FsT(IIR, AR)
FsC(IIR, AR)
FsT(IIR
)
)
Solid
CHCl3
CH2Cl2
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
285(0,3)
267(0,6)
262(1,0)
215(0,5
209(3,0)
169(0,2)
164(3,0)
148(0,1)
129(0,3)
113(5,0)
110(0,1)
107(3,0)
52(0,0)
282(1,2)
270(0,3)
253(1,5)
214(0,4)
196(0,0)
157(6,1)
157(0,0)
143(0,0)
111(1,0)
105(0,3)
92(4,0)
285(0)
265(0)
262(2)
213(0)
199(6)
165(0)
159(4)
136(0)
118(0)
111(8)
105(6)
97(0)
283(2)
273(1)
248(3)
214(0)
196(0)
156(1)
155(9)
137(0)
112(2)
107(0)
102(8)
63(0)
278(s)
265(s)
D
msNANiAN,
msOANiAO(o.p.)
dCACH3
m
c
s
s
s
s
s
APOANiAAPO
NANiAN, dOANiAO
196(s)
CH3,
CH3,
CANANi,
CAOANi,
CH3
c
c
CAC@C
CAC@C
c
c
CACH3
CACH3
dAPOANiAAPO
75(0,2)
49(1,3)
46(0,0)
38(1,0)
s
s
c
s
s
CH3
APO
48(0)
39(6)
37(0)
37(0)
41(1)
37(0)
31(1)
28(1)
46(1,0)
35(0,0)
34(2,0)
APOANiAAPO, sCH3
CH3
CH3
25(0,0)
Fs., theoretical frequency calculated at the UB3LYP/6-311G⁄ level, scaled by 0.9600 and 0.9781 for the 2000–3600 cmÀ1 and below 1700 cmÀ1 regions, respectively.); C,
Cis; T, Trans; IIR, IR intensity (in kM/mol); and AR, Raman activity (Å4/amu), the relative intensities are given in parentheses; v, very; s, strong; m, medium; w, weak; sh,
shoulder; (⁄), solvent band overlap,
, stretching; d, in-plane bending; , out-of-plane bending; , in-plane ring deformation; , out-of-plane ring deformation; , torsion;
in-plane rocking, , out-of-plane rocking; i.p, in phase; o.p. out of phase.
a
m
c
D
C
s
q,
p
weak intermolecular hydrogen bond in the solid phase. Archer [25]
reported a band at 3285 cmÀ1 without any band assignment. The
corresponding band in Cu(APO)2 in the solid phase is observed at
3290 cmÀ1 [26]. The infrared band at 3079 cmÀ1 and Raman band
which is somewhat coupled to the NAH in-plane bending. The
corresponding band in Cu(APO)2 [26], acetylacetone, AA, [27], mag-
nesium acetylacetonate, Mg(acac)2, [21], and beryllium acetylace-
tonate, Be(acac)2, [28] is observed at 1180, 1173, 1198, and
1191 cmÀ1, respectively.
at 3082 cmÀ1 are assigned to the CH stretching and a series of
a
weak bands, which are observed in the 2994–2920 cmÀ1 range,
are assigned to the asymmetric and symmetric CH3 stretching.
These bands did not change significantly upon deuteration.
4.3.3. Below 1000 cmÀ1
In this region, one expects to observe CACH3 stretching, NAH,
and CAH out-of-plane bending, in-plane, and out-of-plane ring
deformations. Archer [25] reported eight bands in this region:
950, 935, 810, 790, 755, 710, 680, and 650 cmÀ1. The strong Raman
band at 954 cmÀ1 is assigned to the CAC@C bending which is cou-
pled with the CH3 rocking. The infrared band at 935 cmÀ1 in the so-
lid phase is related to the in-plane ring deformation which is
coupled with CACH3 stretching. The solid state infrared broad
4.3.2. 1700–1000 cmÀ1 region
This is the most significant region of spectra. Beside the CH3 and
NH deformation and rocking frequencies, CACH3 stretching, and
CH in-plane bending modes, four bands are expected to be ob-
served in this region per ligand in relation to the chelated ring
modes which are attributed to the CAO, CAC, C@C, and CAN
stretching movements. Since there are two ligands per molecule,
it is expected that these vibrational modes to be appeared as in-
phase and out-of-phase vibrational modes. The infrared spectrum
bands at 814 and 767 cmÀ1 are assigned to the CH and NH out-
a
of-plane bending modes. Upon deuteration, these bands move to
757 and 538 cmÀ1. According to the theoretical calculations the
of Ni(APO)2 in the solid phase showed a strong band at 1591 cmÀ1
.
former is assigned to the CH out-of-plane bending and the latter
a
According to the theoretical calculations, this bond is assigned
to the out-of-phase CAO and CAN stretching. The corresponding
in-phase band in the Raman spectrum was observed at
1597 cmÀ1. Two strong infrared bands observed at 1485 and
1552 cmÀ1 in the solid phase. The former is due to the in-plane
bending of CH3 and the latter is assigned to the asymmetric CAC@C
is related to the ND out-of-plane bending. The infrared bands at
681 and 659 cmÀ1 are assigned to the asymmetric OANiAO
stretching and out-of-plane ring deformation, respectively. The
very strong infrared and Raman bands at 485 and 479 cmÀ1 are
assigned to the asymmetric and symmetric OANiAO stretching
(coupled with the NANiAN stretching), respectively. The corre-
sponding bands in Cu(APO)2 were reported to be occurred at 466
and 464 cmÀ1 [26]. The two infrared bands at 315 and 196 cmÀ1
are assigned to the OANiAO and NANiAN out-of-plane bending
modes, respectively.
stretching which is coupled with the CH and NH in-plane bending
a
modes. The latter shifts to about 1515 cmÀ1 in the CHCl3 and
CH2Cl2 solutions. Upon deuteration, the 1552 cmÀ1 band shifts to
1514 cmÀ1. This result suggests that the intermolecular hydrogen
bond disappears in solution. Disappearing of this band in the IR
spectrum of deuterated compound supports this assignment.
The strong infrared band at 1523 cmÀ1 is attributed to the CH3
deformation coupled with the asymmetric CACAO and CACAN
stretching modes. This band shifts to about 1515 cmÀ1 in the CHCl3
and CH2Cl2 solutions. Upon deuteration, this band shifts to
1514 cmÀ1. The strong infrared band at 1434 cmÀ1 is also associ-
ated to the asymmetric CH3 bending which is coupled with the
asymetric C@CAN and CAC@O stretching. The corresponding band
in Cu(APO)2 was observed at 1435 cmÀ1 [26]. The very strong infra-
red bond at 1388 cmÀ1 is attributed to symmetric CH3 bending.
5. Conclusion
According to the theoretical DFT calculations, the trans configu-
ration in the gas phase is more stable than cis (about
27.45 kJ molÀ1). But, in solution, the energy difference between
the cis and trans isomers decreases about 14.4 kJ molÀ1. The calcu-
lated bond lengths of CAO, and C9AC10 (Table 1) are longer and
CAN and C@C(O) are shorter than the corresponding ones in
APO. These results show that resonance in Ni(APO)2 is increased
compared with APO. The NiAO distance in Ni(APO)2 is 1.86 Å,
The 1185 cmÀ1 band is assigned to the CH in-plane bending mode
a

M. Jamialahmadi et al. / Journal of Molecular Structure 997 (2011) 117–125
123
Table 5
Fundamental band assignment of Ni(DAPO)2.
No.
Theoretical
Trans
Experimental
Assignment
Cis
Fs
IRsolid
Fs
IIR
AR
IIR
AR
1
2
3
4
5
6
7
8
9
3068
3068
2999
2999
2989
2989
2970
2970
2966
2966
2917
2916
2916
2916
2493
2493
1616
1608
1520
1519
1498
1494
1468
1468
1461
1461
1458
1458
1445
1436
1391
1391
1384
1384
1312
1305
1215
1209
1041
1040
1040
1039
1031
1030
1029
1028
966
961
950
949
926
920
747
746
695
672
670
653
648
607
569
549
530
524
487
465
447
408
374
360
318
1
221
5
23
132
4
139
1
206
0
193
625
0
234
2
3075
3074
3000
3000
2998
2997
2973
2973
2964
2963
2919
2919
2912
2912
2478
2472
1597
1583
1534
1530
1494
1488
1477
1477
1463
1461
1456
1456
1442
1430
1389
1389
1383
1383
1324
1316
1218
1213
1054
1046
1042
1042
1032
1030
1030
1027
992
967
957
956
933
926
743
742
688
672
664
656
649
592
533
531
520
475
466
448
435
418
368
356
315
1
35
2
49
6
32
30
1
40
1
29
10
38
7
228
3
143
8
3082(w)
m
m
m
m
m
m
m
m
m
m
m
m
m
m
m
m
m
m
m
m
m
m
CH
CH
a
a
34
43
8
46
1
29
0
36
0
0
35
0
51
31
0
0
376
0
668
81
0
1
122
9
8
0
2994(w)
2987(w)
aCH3
aCH3
aCH3
aCH3
aCH3
aCH3
aCH3
aCH3
sCH3
sCH3
sCH3
sCH3
NAD
NAD
aCAO,
aCAO,
123
39
181
4
148
29
431
11
367
29
3
66
40
0
3
5
2954(w)
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
2927(w)
2917(m)
0
6
1
0
2431(s)
1587(s)
55
48
0
32
0
m
m
aCAN(o.p.), dCH
aCAN(o.p.), dCH
a
a
526
420
46
220
2
16
1
1
136
15
0
359
16
4
1
25
0
aCAC@C, dCH
aCAC@C, dCH
aCAC@O,
aCAC@O,
a
a
1514(s)
1496(s)
0
4
maCAC@N(o.p.), daCH3, dCH
a
a
14
42
1
16
14
12
41
3
8
19
8
8
28
4
20
2
16
0
1
15
0
0
4
0
15
1
0
0
15
0
25
0
1
2
0
0
13
8
0
1
0
0
0
4
0
0
15
7
maCAC@N(o.p.), daCH3, dCH
1460(m)
1460(m)
daCH3
daCH3
daCH3
daCH3
daCH3
daCH3
daCH3,
daCH3,
dsCH3
dsCH3
dsCH3
dsCH3
2
26
24
0
1450(m)
1448(m)
1437(s)
22
300
0
0
m
m
aC@CAN,
aC@CAN,
m
m
aCAC@O
aCAC@O
42
31
0
0
18
6
0
0
19
0
0
0
19
0
0
0
1
0
7
28
0
0
4
0
0
0
0
14
0
1
11
0
2
0
4
0
22
0
3
0
1430(m)
0
15
11
0
1392(vs)
0
1
dC@CAC,
dC@CAC,
dCH
mCACH3, dND, dCH
a
a
63
31
0
2
1
27
0
18
0
18
0
18
0
0
6
34
0
51
0
24
5
0
4
0
0
75
0
1
0
36
0
2
0
2
32
18
8
3
27
4
0
4
28
0
10
5
5
2
1
13
1
49
0
13
9
2
10
0
8
0
3
68
39
0
4
0
0
1
6
4
1303(s)
1198(w)
mCACH3, dND, dCH
a
a
CH3
,
,
m
m
CACH3
CACH3
dCH
p
p
q
p
p
q
p
q
1022(m)
CH3, dND
CH3, dC@CAC, ND
CH3
CH3
CH3, dCH
a
CH3
CH3, dCH
a
953(w)
934(w)
922(w)
757(w)
682(w)
664(w)
dND,
dND,
dCAC@C,
dND,
D
D
c
c
m
m
m
q
q
CH3, dCACAN,
m
CACH3,
m
aNANiAN
CH3,
CH3
CACH3, dCAC@C,
mCACH3, dCAC@C, msNANiAN
q
m
m
sNANiAN
ring,
ring,
m
m
CACH3
CACH3
CH
CH
a
a
aOANiAO,
sOANiAO,
aOANiAO,
m
m
m
aNANiAN, dND
sNANiAN, dND
aNANiAN, dND, cCACH3
C
C
m
c
c
c
c
m
m
sOANiAO, msNANiAN(o.p.)
ND
ND
CACH3
CACH3
aOANiAO,
sOANiAO
538(w)
480(s)
maNANiAN
3
1
0
0
daCACH3
daCACH3
m
sOANiAO,
dOANiAO, dNANiAN
OANiAO, NANiAN
msNANiAN
6
4
0
0
0
c
c
(continued on next page)

124
M. Jamialahmadi et al. / Journal of Molecular Structure 997 (2011) 117–125
Table 5 (continued)
No.
Theoretical
Experimental
Assignment
Trans
Fs
Cis
Fs
IRsolid
IIR
AR
IIR
AR
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
284
267
262
214
206
168
163
146
128
113
109
106
51
0
0
1
0
3
0
3
0
0
5
0
3
0
1
0
2
3
6
0
4
0
1
0
1
3
0
1
0
0
0
0
0
281
1
0
1
0
0
0
6
0
1
0
4
0
1
0
1
0
2
2
5
4
0
0
0
0
0
3
0
2
3
0
0
0
dAPOANiAAPO
dCACH3
dCACH3
D
269
253
213
192
156
155
143
110
104
92
m
sNANiAN,
msOANiAO(o.p.)
dCACH3
m
s
s
s
APOANiAAPO
CANANi,
CAOANi,
CH3
c
c
CACH3
CACH3
dAPOANiAAPO
73
49
46
38
s
s
c
s
s
CH3,
CH3,
APOANiAAPO
CH3
CH3
s
s
APOANiAAPO
APOANiAAPO
45
35
34
25
a Fs., theoretical frequency calculated at the UB3LYP/6-311G⁄ level, scaled by 0.9600 and 0.9781 for the 2000–3600 cmÀ1 and below 1700 cmÀ1 regions, respectively.); IIR, IR
intensity (in kM/mol); v, very; s, strong; m, medium; w, weak; sh, shoulder; br, broad; (⁄), solvent band overlap,
, stretching; d, in-plane bending; , in-plane ring
m
c, D
deformation;
C
, out-of-plane ring deformation;
s
, torsion;
q
, in-plane rocking,
p, out-of-plane rocking; i.p, in phase; o.p. out of phase.
0.12
0.10
0.08
0.06
0.04
0.02
0.00
-0.02
Ni(APO)2
.… Ni(DAPO)2
3400
3200
3000
2800
2600
2400
2200
Fig. 6. Comparison between the infrared spectra of Ni(APO)2 and Ni(DAPO)2 in the solid phase in the 3500–2200 cmÀ1 region.
0.25
0.20
0.15
0.10
0.05
0.00
Ni(APO)2
.… Ni(DAPO)2
1600
1400
1200
1000
800
Fig. 7. Comparison between the infrared spectra of Ni(APO)2 and Ni(DAPO)2 in the solid phase in the 1700–700 cmÀ1 region.
which is longer and, therefore, weaker than the corresponding
bond in Ni(acac)2.
The scaled calculated and observed frequencies, except for NAH
vibrational band frequencies, are in excellent agreement. The red

M. Jamialahmadi et al. / Journal of Molecular Structure 997 (2011) 117–125
125
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