Fourier transform infrared spectrum, vibrational analysis and structural determinations of the trans-bis(glycine)nickel(II) complex by means of the RHF/6-311G and DFT:B3LYP/6-31G and 6-311G methods

Article abstract of DOI:10.1016/j.saa.2006.11.055

The trans-bis(glycine)nickel(II) complex was synthesized, and the Fourier transform infrared spectra in the regions 4000-370 cm^-1 and 700-30 cm^-1 were measured. Band deconvolution analysis and the second derivative of the infrared spectrum were also performed. The determination of the geometrical structure in the trans position of the glycine ligands around Ni(II) for the trans-bis(glycine)nickel(II) complex as well as the vibrational assignment were assisted by RHF/6-311G and by Density Functional Theory calculations, DFT:B3LYP/6-31G and 6-311G basis sets. A full discussion of the framework vibrational modes was done using as criteria the geometry study of distorted structures generated for the vibrational modes. Incidentally, Normal Coordinate Analysis was carried out for the Ni(N)₂(O)₂ structural fragment. The calculated DFT spectra in the high- and low-energy regions agree with the observed ones.

Full text of DOI:10.1016/j.saa.2006.11.055

Available online at www.sciencedirect.com
Spectrochimica Acta Part A 68 (2007) 1370–1378
Fourier transform infrared spectrum, vibrational analysis and structural
determinations of the trans-bis(glycine)nickel(II) complex by means of
the RHF/6-311G and DFT:B3LYP/6-31G and 6-311G methods
c
a,∗
Joanna Maria Ramosa,∗, Otavio Versianeb,c, Judith Felcman , Claudio A. Tellez Soto
´
a Instituto de Qu´ımica, Departamento de Qu´ımica Inorgaˆnica-UFF, Morro de Valonguinho s/n, Nitero´i 24210-150, RJ, Brazil
b Centro Federal de Educac¸a˜o Tecnolo´gica de Qu´ımica de Nilo´polis (CEFETEQ), Rio de Janeiro, RJ, Brazil
c Departamento de Qu´ımica, PUC-Rio, Ga´vea, Rio de Janeiro, RJ, Brazil
Received 5 September 2006; accepted 22 November 2006
Abstract
The trans-bis(glycine)nickel(II) complex was synthesized, and the Fourier transform infrared spectra in the regions 4000–370 cm−1 and
700–30 cm−1 were measured. Band deconvolution analysis and the second derivative of the infrared spectrum were also performed. The determi-
nation of the geometrical structure in the trans position of the glycine ligands around Ni(II) for the trans-bis(glycine)nickel(II) complex as well as
the vibrational assignment were assisted by RHF/6-311G and by Density Functional Theory calculations, DFT:B3LYP/6-31G and 6-311G basis
sets. A full discussion of the framework vibrational modes was done using as criteria the geometry study of distorted structures generated for the
vibrational modes. Incidentally, Normal Coordinate Analysis was carried out for the Ni(N)2(O)2 structural fragment. The calculated DFT spectra
in the high- and low-energy regions agree with the observed ones.
© 2007 Elsevier B.V. All rights reserved.
Keywords: trans-Bis(glycine)nickel(II) complex; Structure and vibrational spectra; DFT:B3LYP/6-311G and 6-31G basis sets
1. Introduction
The principal purpose of the present work is to obtain
more information about the [Ni(Gly)2] complex through the
FT-infrared spectrum and to perform a full assignment of the
observed bands, particularly in the low-energy region, which
is of high interest to inorganic chemists. To reach this goal the
Density Functional Theory (DFT) will be used in the obtainment
of the geometrical structure of the trans-bis(glycine)nickel(II)
isomer, in order to perform the vibrational spectra calculations
and the theoretical assignment. As we have proposed in other
works [4,5], for a better understanding of the coupled degree of
the different vibrational internal coordinates in the composition
of the normal mode, we have studied here the distorted geometry
generated by each normal mode.
The infrared spectrum of metal–glycine complexes was
object of study by many researchers, and the results were
compiled in two excellent monographs [1,2]. Considering the
earlier Normal Coordinate Analysis performed by Condrate
and Nakamoto [3], we have observed that the 3n − 6 = 51
normal modes in the [Ni(Gly)2] complex were not included
in the calculation. Such calculations were performed using a
1:1 (metal/ligand) model of 3n − 6 = 24 normal modes using a
set of 21 observed wave numbers. In that model it is noticeable
that only symmetrical Ni–N and Ni–O stretching were used.
Today, however, with modern FT-IR spectrophotometers, it is
possible to obtain IR spectra with better resolution, and there
are excellent computational resources that allow obtaining the
second derivative spectrum and performing band deconvolution
analysis (BDA).
2. Experimental
2.1. Synthesis of the trans-bis(glycine)nickel(II) complex:
[Ni(Gly)2]
∗
Corresponding author.
After a detailed study of the diagram distribution curves of
glycine and of the solubility curve of Ni(OH)2, the pH and
E-mail addresses: joannamaria@uol.com.br (J.M. Ramos),
tellez@vm.uff.br (C.A. Te´llez Soto).
1386-1425/$ – see front matter © 2007 Elsevier B.V. All rights reserved.
doi:10.1016/j.saa.2006.11.055

J.M. Ramos et al. / Spectrochimica Acta Part A 68 (2007) 1370–1378
1371
concentration limits of glycine were determined in order to
carry out the trans-bis(glycine)nickel(II) synthesis. According
to the results, 4 mmol of glycine (NH2CH2COOH) (0.3002 g)
and 2 mmol of nickel nitrate were mixed in a porcelain cap-
sule. The mixture was heated to 70 ◦C for 2 h and then dissolved
in deionized water under stirring and heating for 1 h. After the
complete dissolution of the solid mixture, KOH 1 mol/L was
added slowly with the purpose of obtaining pH 6.0. The solu-
tion was stored in a glass vessel for 4 days. After this time, the
solution was concentrated slowly in a Becker under constant
stirring. At this stage the volume of the solution was reduced
to 10 mL. When this solution was freezing to 4 ◦C, a fine green
solid precipitated slowly. The product was purified with a solu-
tion of water, ethanol and nitric acid (10 mL of deionized water,
85 mL of ethanol and 5 mL of HNO3 1 mol/L). After separation
the precipitate was dried and stored in desiccators containing
granulated CaCl2. The yield was of the order of 69% [6].
2.2. Elemental analysis
Elemental analyses of the complexes were performed by a
CHN Sinc EA 1110 analyzer. The values found are (the the-
oretical composition is in parentheses): C, 22.99% (23.22%);
H, 3.85% (3.87%); N, 13.69% (13.55%); O, 31.05% (30.96%).
Ni was analyzed by atomic absorption spectrometry using a
Varian-1106 spectrophotometer, yielding the experimental value
of 28.39% (28.40%).
Fig. 1. Infrared spectra of the [Ni(Gly)2] complex in the regions of
4000–370 cm−1 and 650–50 cm−1
.
2.3. FT-IR spectrum
ences in the bond angle parameters (Condrate and Nakamoto’s
values are in parentheses): <NNiO, 87.73◦ (85.80◦); <NiOC,
116.71◦ (105.00◦); <OCC, 112.81◦ (130.00◦); <OC O, 125.79◦
(114.80◦). Selected bond lengths and bond angles are given in
Table 1. Full [Ni(Gly)2] complex structure is given in Fig. 2.
The FT-IR spectra of solid trans-bis(glycine)nickel(II) com-
plex were recorded on a Perkin Elmer 2000 FT-IR spectrometer.
Data were collected with a resolution of 4 cm−1. Scanning speed
0.2 cm−1 s−1 and 120 scans were performed. The solid sample
was measured as a KBr pellet in the 4000 –370 cm−1 spectral
range, and in the 710–30 cm−1 region as a polyethylene pellet.
Observed and calculated infrared spectra are given in Fig. 1.
3.1. Vibrational assignments
Vibrational assignments were carried out with the aid of
Density Functional Theory calculations. Traditional Normal
3. Optimization of the geometrical parameters
Ab initio optimization of the geometrical parameters, and
hence structural analysis of the trans-bis(glycine)nickel(II)
complex, [Ni(Gly)2], was carried out employing DFT levels
[7–9,13] with B3LYP/6-31G and with B3LYP/6-311G basis
sets, and the RHF/6-311G procedure. Due to the proxim-
ity of the values found in the calculations, in the discussion
we will take as reference principally the DFT:B3LYP/6-31G
results. The calculated B3LYP/6-31G stabilization energy was:
E(RB + HF − LYP) = −2075.7277591 AU. The calculated bond
˚
lengths for the two Ni–N bonds were: 1.909 and 1.830 A. Con-
˚
drate and Nakamoto [3] use the values of 2.09 A for the Ni–N
˚
bond distance, and of 2.08 A for the Ni–O distance. For the
C O, C–O, N–C, C–C ring bond distances the calculated values
˚
were: 1.236, 1.340, 1.502 and 1.539 A, respectively. Condrate
and Nakamoto use the following C O, C–O, N–C and C–C
geometrical parameters for the Ni(II)–glycine complex: 1.29,
1.25, 1.42 and 1.50 A, respectively. Also, we found differ-
Fig. 2. DFT:B3LYP/6-31G calculated structure of the [Ni(Gly)2] complex
showing atom numbering.
˚

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J.M. Ramos et al. / Spectrochimica Acta Part A 68 (2007) 1370–1378
Table 1
3.1.1. NH and CH stretching
Geometrical parameters for the trans-bis(glycine)nickel(II) complex obtained
by the DFT/B3LYP:6-31G procedure
In all we expect to observe four bands pertaining to the asym-
metric and symmetric N–H stretching normal modes. Among a
large band centered on 3333 cm−1, we can identify absorption
Bond angles (◦)
˚
Atoms i, j
Bond lengths (A)
Atoms i, j, k
bands at 3437, 3346, 3296, 3189, 2982, 2986 and 2856 cm−1
.
1–2
1–20
1–4
1–3
2–5
20–19
5–6
19–16
16–22
22–26
6–3
1.844
1.853
1.917
1.918
1.335
1.327
1.537
1.543
1.523
1.459
1.502
1.501
1.526
1.502
1.501
1.244
1.238
1.459
1.459
0.971
0.975
1.022
1.017
1.027
1.021
1.094
1.090
1.088
1.089
1.092
1.089
2–1–3
2–1–4
2–1–20
1–2–5
3–1–4
86.89
92.88
179.16
117.22
179.64
93.83
108.66
108.09
112.53
86.39
These bands can be assigned according to DFT results to the
vibrational modes νas(NH), νs(NH), νs(NH), νas(CH), νas(CH),
νs(CH) and νs(CH), respectively. The second derivative spec-
trum shows bands at 3430, 3347, 3288 and 3176, 2971, 2921 and
2854 cm−1. When we apply the Bellamy Williams relationship
[14] for primary amines ν(aꢀ) = 345.5 + 0.876ν(aꢀꢀ) to the exper-
imental band found at 3347 cm−1 and to the obtained value by
means of deconvolution analysis found at 3419 cm−1, we obtain
the values of 3356 and 3340 cm−1, which can be correlated with
the observed band at 3346 cm−1. Correlations among the FT-
IR bands, the calculated second derivative and BDA bands are
given in Table 1. The DFT calculated bands for these NH and
CH stretching vibrational modes are in good agreement with
experimental ones. Second derivative infrared spectrum in the
region between 3800 and 2600 cm−1 is depicted in Fig. 3 joined
with the second derivative spectrum.
3–1–20
1–3–6
1–3–13
1–3–14
4–1–20
1–4–16
1–4–17
1–4–18
1–20–19
2–5–6
2–5–15
6–3–13
6–3–14
3–6–5
107.54
109.58
110.18
115.99
112.92
125.89
110.60
109.42
108.81
108.76
110.50
107.54
113.59
107.42
106.14
111.83
108.12
108.49
121.11
109.81
109.91
108.96
105.78
109.13
109.77
112.05
110.50
109.77
6–4
6–7
6–3
16–4
19–21
5–15
7–8
22–26
8–9
26–27
4–18
4–17
3–13
3–14
7–11
7–10
22–23
22–24
16–25
6–12
3–6–7
3–6–12
13–3–14
16–4–17
16–4–18
4–16–19
4–16–22
4–16–25
17–4–18
6–5–15
5–6–7
5–6–12
7–6–12
6–7–8
6–7–10
6–7–11
8–7–10
8–7–11
10–7–11
3.1.2. C O stretching
Observing the geometrical structure of the trans-
bis(glycine)Ni(II) complex depicted in Fig. 2, we can
infer one asymmetrical and one symmetrical C O stretching.
As it is well known, the band absorption of carbonyl groups
is located in the region of ∼1700–1500 cm−1, commonly in a
Coordinate Analysis based on the well-known FG-matricial
Wilson–Elꢀyashevich method [10–12] was also carried out for
the Ni(N2)(O2) framework of C2v symmetry (the N–Ni–N and
O–Ni–O calculated bond angles had a small distortion of 180◦,
so the inversion center is absent) to assist in the vibrational
assignment of the harmonic wave numbers.
For the discussion of the vibrational assignment, we will
take the DFT values corrected by a scale factor of 0.9613 as
a base of comparison with the 38 experimental wave numbers
of the infrared spectrum joined to the second derivative and
with the band deconvolution analysis of the [Ni(Gly)2] com-
plex. For an accurate description of the normal modes in the
metal–ligand spectral range, as we have proposed in other works
[4,5,15–20], we use the Percentage of Deviation of the Geo-
metrical Parameters (PDGP) from the equilibrium position. The
PDGP can be also normalized to obtain the percentage of par-
ticipation of each internal vibrational coordinate that describes
the framework vibrations.
Fig. 3. Infrared spectra of the [Ni(Gly)2] complex in the regions of
1300–900 cm−1 and 700–400 cm−1
.

J.M. Ramos et al. / Spectrochimica Acta Part A 68 (2007) 1370–1378
1373
higher energy region than the absorption bands pertaining to
the HNH bending vibrational modes. In the infrared spectrum
we observe two bands at 1656 and at 1606 cm−1. The second
derivative of the spectrum and the band deconvolution analysis
include values at 1638 and at 1643 cm−1, respectively. By
means of the DFT procedure with B3LYP/6-311G and 6-31G
basis sets we can assign the experimental band found at
1656 cm−1 (IR) to the νs(C O) vibrational mode. The bands
found at 1638 and at 1643 cm−1 by means of the second
derivative and band deconvolution can be assigned as the
νas(C O) vibrational mode. The match between calculated and
experimental values for the ν(C O) stretching was excellent.
Table 2
Experimental FT-IR spectrum and calculated DFT:B3LYP/6-31G vibrational wave numbers (wn) for the [Ni(Gly)2] complex
DFT:B3LYP/6-31G calculated wn
and IR intensitiesa
DFT scaled
values × 0.9613
FT-IR (% T)
2d
BDA
Approximate assignment
3549 (12.00)
3548 (41.44)
3469 (3.84)
3469 (15.76)
3153 (11.07)
3153 (14.08)
3095 (2.41)
3094 (15.64)
1740 (0.53)
1730 (952.00)
1719 (10.72)
1718 (134.70)
1518 (5.91)
1517 (13.24)
1383 (0.35)
1383 (6.63)
1336 (2.57)
1335 (10.80)
1269 (15.96)
1263 (311.34)
1177 (4.95)
1171 (351.32)
1167 (0.96)
1167 (253.84)
1018 5.85)
1017 (1.68)
961 (1.61)
3412
3412
3335
3335
3031
3031
2975
2974
1673
1663
1652
1652
1459
1458
1329
1329
1284
1283
1220
1214
1131
1126
1122
1122
979
979
924
919
868
865
776
750
702
680
584
577
515
503
482
460
439
3437
3430
3478
3419
3343
3280
3176
2969
2934
2851
1659
1643
1602
1572
1444
1415
1383
νas(NH)
νas(NH)
νs(NH)
νs(NH)
νas(CH)
νas(CH)
νs(CH)
νs(CH)
νs(C O) + δ(CCO)
νas(C O) + δ(CCO)
δ(HNH)sciss
δ(HNH)sciss
δ(HCH)sciss
3346
3296
3189
2982
2936
2856
1656
3347
3288
3176
2971
2921
2854
1658
1638
1604
1565
1442
1416
1382
1606
1578
1438
1410
1384
δ(HCH)wagg
δ(HCH)wagg
δ(HCH)wagg + δ(HNH)twist
δ(HCH)twist + δ(HNH)twist
δ(HCH)twist + δ(HNH)twist
νs(CC) + νs(C O)
νas(CC) + νas(C O)
δ(HNH)wagg
δ(HNH)wagg + δ(HCH)twist
δ(HNH)twist + δ(HCH)twist
δ(HNH)twist + δ(HCH)twist
νas(CN)
1311
1301
1268
1237
1181
1120
1110
1044
981
950
939
922
882
849
826
791
737
695
646
600
546
523
1179
1178
1107
1043
978
1108
1049
969
942
915
882
νs(CN)
928
872
838
ρ(CH2) + δ(HNH)wagg
ρ(CH2) + δ(HNH)wagg
νas(CC)
νs(CC)
ρ(NH2)
ρ(NH2)
δ(CCO)anel
ρ(NH2)
νas(NiN) + νas(NiO) + ν(CC)
νs(NiN) + ν(CC) + δ(NiNC)
νas(NiN) + δ(NiNC); νas(NiN)
δ(NiNC) + νs(NiN)
δ(ONiO) + δ(NNiN)
δ(CC O) + νs(NiN); ν (NiN)
νas(NiO) + δ(CC O); νas(NiO)
δ(ONiN) + δ(NiOC) + δ(NiNC); δ(ONiN)
νs(NiO) + δ(CC O);ν (NiO) + δ(ONiO)
δ(ONiN) + δ(NiNC); δ(ONiN)
δ(ONiO) + δ(NNiO); δ(NNiN) + δ(ONiO) + ν(NiO)
Torc¸a˜o; δ(ONiO) + ν(NiO) + δ(NNiN)
Torsion
Torsion
Torsion
Torsion
Torsion
956 (1.35)
903 (69.50)
900 (0.398)
807 (39.21)
780 (30.31)
730 (7.62)
707 (0.91)
608 (50.63)
600 (4.57)
556 (1.79)
523 (1.63)
501 (14.87)
479 (0.17)
457 (28.81)
404 (1.22)
377 (0.22)
272 (0.03)
215 (0.13)
147 (14.81)
134 (20.30)
103 (0.33)
95 (10.41)
79 (24.34)
824
739
690
646
596
548
522
486
694
651
597
561
519
489
452
415
384
350
285
206
159
120
451
450
405
365
346
295
216
152
121
90
s
388
362
261
207
141
129
99
89
354
291
s
149
124
95
76
34
60
35
56
38
62
35 (4.84)
In bold characters are the NCA results for the NiN2O2 fragment.
a
IR intensity in K m/mol units.

1374
J.M. Ramos et al. / Spectrochimica Acta Part A 68 (2007) 1370–1378
Condrate and Nakamoto [3] had informed a single value of
1610 cm−1 for one of the ν(C O) stretching, leaving aside
the vibrational assignment for the second ν(C O) stretching
predicted for the carbonyls.
3.1.3. HNH and HCH bending
In general terms, these HNH and HCH bending vibrations are
considered as characteristic wave numbers. As usual, we can dif-
ferentiate scissoring, wagging, twisting and rocking vibrations
within the –CH2 and –NH2 groups. In the infrared spectrum we
can observe four bands at 1578, 1438, 1410 and at 1384 cm−1
,
which can be correlated with the scaled DFT:B3LYP/6-31G
values: 1652, 1459, 1452 and 1329 cm−1. These bands can be
assignedprincipallyto δ(HNH)sciss, δ(HNH)sciss, δ(HCH)sciss
and δ(HCH)sciss, respectively. In the infrared spectrum, accord-
ing the DFT calculations, the infrared bands found at 1384,
1120, and at 1110 cm−1 can be assigned to the δ(HNH)wagg
vibrationalmodes. Vibrationalassignmentsfortheδ(HCH)wagg
are doubtful due to the strong coupling. Wave numbers found
at 1311 and at 1268 cm−1 can be assigned in both cases
to the coupled modes δ(HCH)twist + δ(HNH)twist. Rocking
vibrations according to the RHF/DFT calculations can be
assigned as: 922 cm−1 to ρ(CH)2 + δ(HNH)wagg; 882 cm−1
to ρ(CH)2 + δ(HNH); 791 cm−1 to ρ(NH)2; 646 cm−1 to the
ρ(NH)2 vibrational mode. Fig. 3 shows the infrared spectrum
together with the second derivative in the 2000–1000 cm−1 spec-
tral region. A full description of the assignment of these modes
is given in Table 2.
Fig. 4. Infrared spectrum in the low-energy region of the [Ni(Gly)2] complex
showing the second derivative band positions.
3.1.4. CN, CO and CC stretching vibrations
1700 and 600 cm−1 we can find several bending descriptions,
and in the low-energy region between ∼600 and ∼200 cm−1
we can describe the metal–ligand normal modes. Almost below
200 cm−1 we found the torsion normal modes. From a visual
approximate description of the normal modes we have chosen
the region between 650 and 200 cm−1 in this study as the region
in which the metal–ligand vibrations have greater participation.
As we have pointed out, in an earlier work on the trans-
bis(glycine)Ni(II) complex, Condrate and Nakamoto [3] used
a single 1:1 metal/ligand geometrical model for the descrip-
tion of the normal modes and further assignment. This approach
neglected half of the Ni–N, Ni–O, N–C and C–C stretching, and
half of the bending inside the structural planes of the two five-
member rings. In the above referenced work, only the observed
wave numbers found at 439 and at 290 cm−1 could be assigned
to the vibrational modes ν(NiN) and ν(NiO), respectively. In the
same work the normal modes pertaining to the –NH2, –CH2 and
to the –C O groups are only partially described.
A natural and considerable mixture of the internal coordi-
nates describing isolated C–N, C–O, C–C stretching is found
in the normal modes and is physically meaningful. For the
trans-bis(glycine)Ni(II) complex, the following infrared cou-
pled bands can be assigned principally as: 950 (IR) cm−1 as
νas(CN); 939 cm−1 as νs(CN); 849 cm−1 as νas(CC); 826 cm−1
as νs(CC). No assignment can be done to the main contributions
of the νas(CO) and νs(CO) modes, which are naturally coupled
by the rings formed by the glycine ligands around the central
cation Ni(II). Fig. 4 shows the infrared spectrum and its second
derivate in the region of 1000–370 cm−1
.
3.1.5. Skeletal framework vibrations
As we have pointed out in other publications [4,5], a clear
identification of the metal–ligand vibrations is not straight-
forward due to the higher mixture of the different internal
coordinates that take part in the description of the normal mode.
With the purpose of better understanding this energy region and
with the aim of obtaining a better assignment of the low-energy
vibrational bands, in this work we studied the distorted geome-
try of each normal mode analyzing the extension to which the
equilibrium configuration parameters are dislocated.
A first assumption in this study has been taken from the
well-known“High/LowFrequencySeparationMethod”[10,21].
In the vibrational spectrum we have clearly four well defined
regions: in the higher region between 3500 and 2850 cm−1, the
–CH, –NH and other stretching occur. In the region between
In this work, for consistency, we carried out the Normal
Coordinate Analysis for the Ni(O)2(N)2 fragment assuming a
C2v symmetry due to the small angle distortion between the
N–Ni–N and the O–Ni–O angles. The used wave numbers
in the calculations are those indicated by the Density Func-
tional Theory through the semi-empiric method based on the
Hartree–Fock–Rotham (RHF) equations.
For the description of the normal modes below 650 cm−1
we will describe the most accurate assignment we were able
to deduce through the study of the distorted geometries of

J.M. Ramos et al. / Spectrochimica Acta Part A 68 (2007) 1370–1378
1375
the normal modes described by the ab initio RHF/6-311G,
DFT:B3LYP/6-311G and DFT:B3LYP/6-31G procedures. Our
goal was to identify which bond lengths and bond angle bend-
ing parameters had the greater participation in the description of
the normal mode. The results presented below obey the follow-
ing nomenclature: in bold characters we write the experimental
observations in the infrared spectrum; the second derivative
values are indicated as 2nd d, and BDA indicates the band
deconvolution analysis values. The abbreviation corr. means
that the calculated wave number by the DFT:B3LYP/6-31G
procedure was scaled by 0.9613. The percentage (%) indi-
cates the percentage variation of the bond lengths and bond
angle.
• 358 (RHF), 370 (DFT/311G), 377 (DFT/31G), 362
(corr.), 354 (IR), 346 (2nd d), 350 (BDA) cm−1. RHF:
ν(NiN) 21.4% + ν(NiO) 20.7%; DFT (311G): ν(NiO)
19.6% + δ(NiOC) 15.7% + ν(NiN) 14.6% + δ(NCC) 12.6%;
DFT (31G): νs(NiO) 8.6% + δ(CC O) 76%.
• 261 (RHF), 278 (DFT/311G), 272 (DFT/31G), 261
(corr.), 295 (2nd d), 285 (BDA) cm−1. RHF: δ(ONiN)
18.6% + δ(NiOC) 13.4% + ν(NiN) 14.4%; DFT (311G):
δ(ONiN) 26.4% + δ(NiNC) 10.8% + δ(ONiO) 14.3%; DFT
(31G): δ(ONiN) 39% + δ(NiNC) 12%.
• 242 (RHF), 254 (DFT/311G), 215 (DFT/31G), 207
(corr.), 216 (2nd d), 206 (BDA) cm−1. RHF: δ(ONiN)
19% + δ(NiOC) 18% + δ(ONiO) 16%; DFT (311G): δ(ONiN)
20% + δ(ONiO) 9%; DFT (31G): δ(ONiO) 36.5% + δ(NNiO)
33.1%.
• 647 (RHF), 608 (DFT/311G), 608 (DFT/31G), 584 (corr.),
600 (IR), 596 (2nd d), 597 (BDA) cm−1. RHF: νas(NiO)
14% + ν(CC) 13.6% + δ(ONiN) 10.5%; DFT (311G):
νas(NiN) 16.6% + ν(CC) 14.7% + ν(NiO) 14.5% + δ(NCC)
11.4%.; DFT (31G): νas(NiN) 17.7% + νas(NiO)
13.8% + ν(CC) 13.4%.
The approximate assignment for the 3n − 6 = 51 normal
vibrations are presented in Table 2. Fig. 4 shows infrared spec-
trum between 670 and 70 cm−1 combined with the spectral
second derivative. Fig. 5 shows the band deconvolution anal-
ysis for the [Ni(Gly)2] complex in the region between 700 and
50 cm−1. Fig. 6 displays the distorted geometry of the normal
modes for the metal–ligand vibrations obtained through the free
Chemkraft program [22].
• 642 (RHF), 600 (DFT/311G), 600 (DFT/31G), 577 (corr.),
546 (IR), 550 (2nd d), 561 (BDA) cm−1. RHF: ν(CC)
14.3% + ν(NiO) 10.8% + δ(NiNC) 10%; DFT (311G): ν(CC)
14.3% + δ(NiNC) 14.1% + ν(NiO) 11.5% + δ(NCC) 11.4%;
DFT (31G): ν(CC) 13.8% + δ(NiNC) 11% + νs(NiN) 10.6%.
• 573 (RHF), 552 (DFT/311G), 556 (DFT/31G), 534
(corr.), 523 (IR), 522 (2nd d), 519 (BDA) cm−1
.
RHF: νas(NiN) 14.9% + δ(NiNC) 14.3%; DFT (311G):
νas(NiN) 28.8% + δ(OCC) 28.5%; DFT (31G): νas(NiN)
35.7% + δ(NiNC) 13%.
• 563 (RHF), 515 (DFT/311G), 523 (DFT/31G), 503
(corr.), 486 (2nd d) cm−1. RHF: δ(NiOC) 18.4% + δ(NCC)
17.8% + δ(OCC) 12.8% + ν(NiN) 11.2%; DFT (311G):
δ(NiNC) 25.1% + νs(NiN) 22.4%; DFT (31G): δ(NiNC)
28.4% + νs(NiN) 21%.
• 507 (RHF), 497 (DFT/311G), 501 (DFT/31G), 482
(corr.), 489 (BDA) cm−1. RHF: νas(NiN) 29.9% + δ(OCC)
17.3% + δ(NiNC)
28.8% + νas(NiO)
15.9%;
18.8%;
DFT
DFT
(311G):
(31G):
δ(OCC)
δ(ONiO)
41% + δ(NNiN) 30.8%.
• 492 (RHF), 478 (DFT/311G), 479 (DFT/31G), 460 (corr.),
451 (IR), 450 (2nd d), 452 (BDA) cm−1. RHF: νs(NiN)
15.4% + δ(NiOC) 14.7% + δ(OCC) 13.4%; DFT (311G):
νs(NiN) 29% + δ(OCC) 27%; DFT (31G): ν(NiN) 19.2% + δ
(CC O) 59%.
• 483 (RHF), 453 (DFT/311G), 457 (DFT/31G), 439
(corr.), 405 (2nd d), 415 (BDA) cm−1. RHF: νaas(NiO)
23.1% + δ(ONiN) 019.2%; DFT (311G): νas(NiN)
22.9% + δ(ONiN)
18.5%;
DFT
(31G):
νas(NiO)
33% + δ(CC O) 23%.
• 418 (RHF), 405 (DFT/311G), 404 (DFT/31G), 388
(corr.), 365 (2nd d), 384 (BDA) cm−1. RHF: δ(ONiN)
23% + δ(NiOC) 14.9% + δ(NiNC) 12.9% + νas(NiN) 10.6%;
DFT (311G): δ(ONiN) 23.6% + δ(NiOC) 17.1% + δ(NCC)
12.7%;
21.4% + δ(NiNC) 21%.
DFT
(31G):
δ(ONiN)
28.1% + δ(NiOC)
Fig. 5. Band deconvolution analysis spectrum in the low-energy region of the
[Ni(Gly)2] complex.

1376
J.M. Ramos et al. / Spectrochimica Acta Part A 68 (2007) 1370–1378
Fig. 6. (a and b) Distorted geometries of the framework normal modes considered in the NCA.

J.M. Ramos et al. / Spectrochimica Acta Part A 68 (2007) 1370–1378
1377
3.1.6. Normal Coordinate Analysis
that the visual computerized picture of each normal mode pro-
vided only a rough approach of its characterization, and hence
we studied the deviation of each bond and angle of the distorted
structure for a best indication of which bond or angle, within the
definition of an internal coordinate, had greater participation in
the molecular vibration.
A Normal Coordinate Analysis through the Wilson–
Elꢀyashevich GF matricial method for the framework
Ni(O)2(N)2 structure was carried out, and from the results we
obtained the valence force constants for the Ni–N and Ni–O
stretching.
Based on the probable assignment given by the DFT results
analysis of the distorted geometry of the normal modes, a set
of representative wave numbers of the framework vibrations
was selected. For the construction of the G matrix, we used the
geometrical parameters that describe the skeletal Ni(O)2(N)2
structure, for which we assumed a C2v symmetry. A modified
valence force field was used where the initial force constants
were obtained through the relation Fii = λii/Gii. Here, Gii repre-
sents the diagonal elements of the kinematics coefficient matrix.
Force constants were adjusted to yield the best wave number fit
by a least square method [23,24]. The agreement among the
nine observed and calculated wave numbers is within 0.1%.
Due to natural restrictions of the approximation, the νas(NiN)
and νs(NiN) normal modes appear to have little vibrational cou-
pling. The valence force constant value for the Ni–N stretching
Acknowledgements
´
C.A. Tellez Soto and J. Felcman would like to thank CNPq
for the financial assistance and research grant, and Professor Dr.
was: fNi–N = 1.59 mdyn A−1. The wave numbers observed at 522
˚
´
Jose Walkimar de Carneiro Mesquita for kindly allowing the
and at 451 cm−1 were assigned to νas(NiN) and νs(NiN), respec-
tively. The bands observed at 405 and at 354 cm−1 were assigned
principally to the νas(NiO) and νs(NiO) vibrational modes.
DFT calculations that were carried out on his computer faci-
lities.
−1
˚
The valence force constant value was: fNiO = 1.04 mdyn A
.
References
In Table 2 the selected wave numbers and the approximate
assignment obtained through the Normal Coordinate Analysis
are shown in bold characters.
[1] K. Nakamoto, Infrared and Raman Spectra of Inorganic and Coordination
Compounds, fourth ed., Wiley, New York, 1986.
[2] S.R. Ferraro, Low-frequency Vibrations of Inorganic and Coordination
Compounds, Plenum Press, New York, 1971.
4. Conclusions
[3] R.A. Condrate, K. Nakamoto, J. Chem. Phys. 42 (7) (1965) 2590.
[4] C.A. Te´llez Soto, E. Hollauer, M.A. Mondrago´n, V.M. Castan˜o, Spec-
trochim. Acta A 60 (2004) 2171.
[5] C.A. Te´llez Soto, E. Hollauer, M.A. Mondrago´n, V.M. Castan˜o, Spec-
trochim. Acta A 57 (2001) 993.
[6] O. Versiane, S´ıntese e caracterizac¸a˜o de complexos envolvendo os
aminoa´cidos serina, glicina, a´cido aspa´rtico e a´cido guanidoace´tico e
os ´ıons meta´licos Co(II), Ni(II) e Cu(II), Tese de doutorado, PUC-Rio,
2005.
[7] R.G. Parr, W. Yang, Density Functional Theory of Atoms and Molecules,
Oxford University Press, Oxford, 1989.
Based on an accurate study of the species distribution dia-
grams for glycine, and on the solubility curve of Ni(OH)2 (molar
concentration versus pH elemental analyses of the complexes
were performed by a CHN Sinc EA 1110 analyzer), we were
able to determine the molar concentrations for glycine and for
Ni(NO3)2, and the pH limits for the synthesis of the trans-
bis(glycine)nickel(II) complex.
The CHN–O elemental analysis shows a very good agree-
ment between the obtained and the calculated percentages of
the C, N, O and H atoms. Atomic absorption analysis for Ni also
reveals a very good agreement between the experimental and the
calculated quantities within the percentage composition of the
[Ni(Gly)2] complex.
Accurate analysis of the infrared spectra, one in the
4000–370 cm−1 region, the other in the low-energy region
between 650 and 50 cm−1, was carried out, including the second
derivative spectra and band deconvolution analysis. The selec-
tion rules indicate that all the normal modes are also active in the
infrared and Raman spectra, but due to sample decomposition
the FT-Raman spectrum was not carried out.
Theoretical structural analysis through the DFT procedure
has shown that the most probable and stable structure for the
[Ni(Gly)2] complex is with the trans position for the glycine
ligands around the Ni atom in the central skeletal square plane
structure. The spatial geometry for the [Ni(Gly)2] complex was
carried out, and starting from the most probable structure the
vibrational spectra were calculated with the aim of assisting in
the vibrational assignment.
[8] A.D. Becke, J. Chem. Phys. 98 (1993) 1372.
[9] M.J. Frisch, G.W. Trucks, H.B. Schlegel, G.E. Scuseria, M.A. Robb, J.R.
Cheeseman, V.G. Zakrzewski Jr., J.A. Montgomery, R.E. Stratmann, J.C.
Burant, S. Dapprich, J.M. Millam, A.D. Daniels, K.N. Kudin, M.C. Strain,
O. Farkas, J. Tomasi, V. Barone, N.M. Cossi, R. Cammi, B. Mennucci, C.
C¸ Pomelli, C. Adamo, S. Clifford, J. Ochterski, G.A. Peterson, P.Y. Ayala,
Q. Cui, K. Morokuma, D.K. Malick, A.D. Rabuck, K. Raghavachari, J.B.
Foresman, J. Cioslowski, J.V. Ortiz, A.G. Baboul, B.B. Stepanov, G. Liu, A.
Liashenko, P. Piskorz, I. Komaromi, R. Gomperts, R.L. Martin, D.J. Fox, T.
Keith, M.A. Al-Laham, C.Y. Peng, A. Nanayakkara, C. Gonza´lez, M. Chal-
lacombe, P.M.W. Gill, B. Johnson, W. Chen, M.W. Wong, J.L. Andresw,
C. Gonza´lez, M. Head-Gordon, E.S. Repogle, J.A. Pople, Gaussian 98,
Revision A. 7, Gaussian Inc., Pittsburgh, PA, 1998.
[10] E.B. Wilson, J.C. Decius P.C., Molecular Vibrations. The Theory of
Infrared and Raman Vibrational Spectra, McGraw-Hill, New York,
1955.
[11] M.A. Elꢀyashevich, Doklady AN SSSR 28 (1940) 605.
[12] M.A. Elꢀyashevich, Zh. Fiz. Khim. 14 (1940) 1381.
[13] J.B. Foresman, E. Frisch, Exploring Chemistry with Electronic Structure
Methods, second ed., Gaussian Inc., Pittsburg, 1996.
[14] L.J. Bellamy, R.L. Williams, Spectrochim. Acta 9 (1957) 341.
[15] C.A. Te´llez Soto, E. Hollauer, M.I. Pais da Silva, M.A. Mondrago´n, I.
Haiduc, M. Curtui, Spectrochim. Acta A 57 (2001) 1149.
[16] C.A. Te´llez Soto, J. Go´mez L, M.A. Mondrago´n, V.M. Castan˜o, G. Mena
R, Vib. Spectrosc. 9 (1995) 279.
[17] C.A. Te´llez Soto, D.N. Ishikawa, Rev. Soc. Qui. Mex 44 (2) (2000) 139.
Aiming to obtain the best interpretation of the DFT vibra-
tional analysis through the Gaussian program [9], we thought

1378
J.M. Ramos et al. / Spectrochimica Acta Part A 68 (2007) 1370–1378
[18] C.A. Te´llez Soto, D.N. Ishikawa, J.G. Lara, Spectrosc. Lett. 31 (2) (1998)
313.
[19] C. Te´llez, G. D´ıaz, J. Mol. Struct. 77 (1981) 213.
[20] C. Te´llez, Acta Sud. Am. Qui. 3 (1983) 139.
[21] K.H. Schmidt, A. Muller, Coord. Chem. Rev. 19 (1976) 41.
[22] Chemcraft software <http://www.chemkraftprog.com/order.htlm>.
[23] J.H. Schachtsneider, R.G. Snyder, Spectrochim. Acta 19 (1963) 117.
[24] J.H. Schachtsneider, Vibrational Analysis of Polyatomic Molecules,
Tech. Rep. No. 57–65, Shell Development Company, Emerville, CA,
1964.