Complexing properties of some pyrimidines

Article abstract of DOI:10.1080/15257770500379090

The synthesis of transition metal barbiturate, and thiobarbiturate complexes containing different functional groups of variable electronic character with Co^II, Ni^II, Cu^II, Pd ^II, and Pt^II have been pr

Full text of DOI:10.1080/15257770500379090

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Complexing Properties of Some
Pyrimidines
Mamdouh S. Masoud a , Sawsan S. Haggag a & Ekram A. Khalil a
a Chemistry Department , Faculty of Science, Alexandria University ,
Alexandria, Egypt
Published online: 20 Aug 2006.
To cite this article: Mamdouh S. Masoud , Sawsan S. Haggag & Ekram A. Khalil (2006) Complexing
Properties of Some Pyrimidines, Nucleosides, Nucleotides and Nucleic Acids, 25:1, 73-87
To link to this article: http://dx.doi.org/10.1080/15257770500379090
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Nucleosides, Nucleotides, and Nucleic Acids, 25:73–87, 2006
Copyright ꢀ Taylor & Francis Group, LLC
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ISSN: 1525-7770 print / 1532-2335 online
DOI: 10.1080/15257770500379090
COMPLEXING PROPERTIES OF SOME PYRIMIDINES
Mamdouh S. Masoud, Sawsan S. Haggag, and Ekram A. Khalil
Chemistry Department, Faculty of Science, Alexandria University, Alexandria, Egypt
2
The synthesis of transition metal barbiturate, and thiobarbiturate complexes containing different
2
functional groups of variable electronic character with CoII , NiII , CuII , PdII , and PtII have been
prepared. The stereochemistry and the mode of bonding of the complexes were determined by elemental
analysis and electronic and vibrational spectra together with their magnetic moment values. Electronic
spin resonance of copper complexes were recorded. The Racah parameter of some cobalt and nickel
complexes were calculated. Some of the complexes are of mixed stereochemistry. All the PdII or PtII
complexes are of square planar geometries.
INTRODUCTION
Pyrimidines are one of the most important compounds due to their bi-
ological activity and are involved in the structure of nucleic acid in living
systems.[1,2] The nucleic acid is related to antimetabolites used in anticar-
cinogenic chemotherapy.[3] Compounds containing nitrogen and sulphur
as donor atoms have an important role to play as anticancer and antiviral
agents.[4,5] Barbiturates are used as hypnotic drugs and produce depres-
sive effect on the central nervous system.[6] The metal ions involved with
pyrimidine nucleus-lead to an understanding of the complex biological pro-
cesses occurring in living systems. In our laboratory, studies were reported on
the structural chemistry of pyrimidine compounds and the transition metal
complexes.[7−17] The structural chemistry of organic ligands (Figures 1 and
2) and their transition metal complexes are the aims of this manuscript.
The scope of this investigation includes the characterization of the synthe-
sized multidentate ligands, and their cobalt, nickel, copper, palladium, and
platinum through elemental analysis, spectral (UV-Vis, IR and ESR), Racah
parameter of (cobalt and nickel) complexes, and magnetic susceptibility
measurements.
Accepted 1 July 2005.
Address correspondence to Mamdouh S. Masoud, Chemistry Department, Faculty of Science,
Alexandria University, Alexandria, Egypt. E-mail:
73

74
M. S. Masoud et al.
EXPERIMENTAL
Synthesis of Organic Compounds
The azo compounds (1) were prepared using the usual diazotization
process.[8] (X: -H, -NO2, -Cl, -COOH, -CH[3], -OH). 5-(3-Aldehydo pheny-
lazo) thiobarbituric compound was treated with hydroxylamine hydrochlo-
ride at room temperature, in the mole ratio (1:1) to obtain 5-(3-aldoxime
arylazo) thiobarbituric acid (X: = NOH). The condensed products (2) were
prepared by refluxing the corresponding acids [(BA) or (SBA)] with the de-
sired aldehyde (benzaldehyde and salicylaldehyde) dissolved in 30 mL diox-
ane. The obtained compounds were filtered off, crystallized from ethanol,
then dried in a vacuum desiccator over P4O10. Their analytical data are col-
lected in Table 1.
A general skeleton for the prepared compound is given as follows:
X = -H
5-(arylazo)barbituric
-H(BA)
acid Y = -H 5-(3-benzilidence) barbituric acid
-Bzd (BA)
X = -NO2
X = -Cl
5-(3-nitroarylazo)barbituric
-NO2 (BA)
5-(3-chloroarylazo)barbituric
-Cl(BA)
acid Y = -H 5-(3-benzilidine) thiobarbituric acid
-Bzd (SBA)
acid Y = -OH 5-(3-salicylidine) barbituric acid
-Sal (BA)
X = -COOH 5-(3-carboxyarylazo)barbituric acid Y = -OH 5-(3-salicylidine) thiolarbituric acid
-COOH(BA) -Sal (SBA)
5-(3-aldehydoarylazo)barbituric acid
X = -CHO
CHO(BA)
X = -CH3
5-(-3-tolyarylyazo)barbituric acid
5-(-3-hydoroxyarlyazo)barbituric acid
5-(3-aldoximarylazo)thiobarbituric acid
-CH3(BA) X = -OH
-OH(BA) X = (=NOH)
= NOH(SBA)
-BA
-Bzd
= barbituric acid
= benzilidine
-SBA
-Sal
= thiobarbituric acid
= salicylidene

75

76

Complexing Properties of Some Pyrimidines
Preparation of Metal Complexes
77
An ammoniacal solution of the metal (II) chloride (Co, Ni, Cu, Pd and Pt)
(0.1 mol) was mixed with the organic compounds (1, 2) (0.1 mol), which are
dissolved in dioxane. The reaction mixture was boiled under reflux for 1 hr.,
then left overnight, whereupon the complex is precipitated. The complexes
(Table 1) were separated by filtration, washed several times with water, and
dried in vacuum over P4O10.
Analysis and Instruments
The analytical data are collected in Table 1. All the complexes do not
contain anions with the melting point above 300◦C. Metal contents were
determined as described previously.[18] The Pd[II] content was determined
gravimetrically as the dimethylglyoximato complex.[18] C, H, and N analyses
were made by the chemistry department, Faculty of Science, Cairo University.
Electronic spectral measurements of the solid complexes were recorded us-
ing a Pye Unicam Spectrophotometer Model SP 1750 and Cary Model 14. The
solvents used for studying the Racah parameters are of spectroquality grade.
IR spectra were taken as KBr disc using SP 2000 Pye Unicam instrument
covering the 200–4000 cm−1 range. ESR spectra of the copper complexes
were measured at 298 K using a Varian E-12 instrument (X-band) spectrom-
eter (2,2-diphenyl-1-picryl hydrazone) was used as an external standard. Mo-
lar magnetic susceptibilities, corrected for diamagnetism using Pascal’s con-
stants, were determined at room temperature (298 K) using Gouy’s method.
The apparatus was calibrated with Hg [Co (SCN)4].
Stereochemistry of the Complexes
Cobalt Complexes.
The analytical data shown in Table 1 indicated
three different stoichiometries (metal: ligand nH2O). However, most of the
complexes are with large number of water molecules. From the spectral and
magnetic moment values, the complexes are classified to three categories
(Table 1):
1. Pure Td obtained from -CHO (BA), -Bzd(SBA), -Sal(SBA), and -Bzd(SBA)
compounds. All of them are with the electronic transition of the type
4
4A2g → T(P).[13]
2. Pure Oh depicted from -NO2 (BA) and -Cl(BA) compounds, with the
4
4
4
4
transitions ν3 = Tlg → Tlg (P) and ν2 = Tlg → A2g.[5−7]
3. An equilibrium between Td and Oh geometries obtained from -OH (BA)
complex, with the electronic transitions 4A2 → T1 (P), 4Tlg (F) → A2g
4
4
(F), and 4Tlg (F) → Tlg(P).[6,7]
4

78
M. S. Masoud et al.
Nickel Complexes.
The analytical data shown in Table 1 indicate three
different stoichiometries (metal: ligand nH2O), depending on the sub-
stituents. The great similarities between the electronic absorption spectra
of these complexes, either in position or in intensity, suggest similar stere-
ochemistry, except-Bzd(SBA) and -Sal(BA).[19] The electronic spectra gath-
ered with the µeff values of the azo complexes containing -NO2 (BA), -Cl(BA),
-COOH(BA), -CHO(BA), -CH3(BA), -OH(BA), and -Sal(SBA) groups, sug-
gest the presence of different geometries, viz. tetrahedral and square
planar.[7,8] Some of the complexes are with +1 and/or +2 oxidation states
of nickel.
The diamagnetic property and the electronic spectra of -Bzd(SBA) and
-Sal(BA) complexes suggest their existence in square planar geometry, and
the ligands are of strong field property to quench the distribution of charge
density,[19] with the possible existence of Ni1 in -Bzd(SBA). The unusual data
for this complex permit the assumption for association where spin quenching
occurs. The 2:1 nH2O nickel orange complexes are obtained from the -
Cl(BA) and -COOH(BA) azo ligands. The first gives two bands at 30,303
and 23,529 cm−1 in a broad feature, while the second gives only one intense
band at 264,550 cm−1. The broad nature of the longer wavelength band of
the chloro complex is argued to the presence of more than d-d transition.[19]
However, the absence of this band in the carboxy complex is probably due
to its existence in an associated structure through intramolecular hydrogen
bond.
Copper Complexes.
The copper complexes (Table 1) derived from
-NO2(BA), -CHO(BA), -OH(BA), and -Sal(SBA) have a tetrahedral ge-
ometry. However, -Cl(BA), -Me(BA), -Sal(BA), -(COOH), and -Bzd(BA)
exist in a dynamic equilibrium between the fourth and fifth coordinate
(structure 3) and that -Bzd(SBA) is with tetragonal distorted octahedral
stereochemistry.[20]
Additional information is derived from electron spin resonance data. The
temperature has no effect on the spectrum of all complexes except that of the
copper -Sal(SBA). The increase in temperature leads to decrease the G and
ꢁgꢂ values by 0.1 and 0.01, respectively. However, g remains the same and
⊥
gꢃꢃ is decreased by 0.03 unit on increasing the temperature, which agreed
with an orbitally non-degenerate ground state. ꢁgꢂ values lie in the range

Complexing Properties of Some Pyrimidines
79
TABLE 2 Electronic Spectral Resonance Data for Copper
Complexes (298 K)
Copper complexes
g11
g
⊥
ꢁgꢂ
G
gs
Cu-Cl(BA)
2.207 2.185
2.189 2.176
2.190 2.175
2.194 2.175
2.210 2.176
2.190 2.070
2.190
2.180
2.180
2.180
2.190
2.110
—
—
2.210
2.220
1.120
1.070
1.080
1.108
1.190
2.710
—
Cu-NO2(BA)
Cu-COOH(BA)
Cu-CHO(BA)
Cu-OH(BA)
Cu-CH3(BA)
Cu-Bzd(BA)
Cu-Bzd(SBA)
Cu-Sal(SBA)
—
—
—
—
2.175
2.180
—
2.270 2.180
2.300 2.180
1.500
1.600a
aThe experiment was done at −170 K.
2.11–2.22. All the complexes exhibit an axial elongated type spectrum with
dx2-y2 ground state (g and g//) except those of -Bzd(BA) and -Bzd(SBA),
⊥
where only one g value is obtained (2.175 and 2.180, respectively). The latter
two cases of copper (II) complexes may exist in dynamic or pseudo rotational
types of Jahn–Teller distortion.[21]
The ESR spectra of -Sal(SBA) and -CH3(BA) complexes are of a broad
nature and with strong covalency in bonding. All the complexes have much
lower G values (G
4) due to strong interaction between copper and the
active centers of the organic compounds. However, no hyperfine structure
is seen and no absorption is observed at 1600 Gauss to assign the Ms =
2
transitions in the copper (II) dimer. In general, the spectra showed a very
intense sharp absorption band at ≈3100 G that arises from the copper (II)
ions in a spin state S = 1/2. The -Bzd(BA) and -Bzd(SBA) copper complexes
give no change in the ESR pattern (Table 2).
Palladium Complex.
The great similarity of the electronic spectral
band and the diamagnetic property of these complexes (Table 1) lead to a
similar stereochemistry with square planar geometry.[22,23] The 1:4. 4H2O Pd-
(SBA) complex gives two electronic absorption bands at 29,940 and 24,631
cm−1. The slight change in the position of the spectral bands from -(BA) and
-(SBA) palladium complexes is due to the change in the electronegativity of O
and S atoms[8] (Table 1). The 1:1 Pd-H[BA] gives two intense bands at 26,455
and 17,544 cm−1. The longer wavelength is due to strong conjugation in the
complex with the presence of the azo chromophore. These bands are of
spin allowed d-d transition. The tridentate nature of the organic compound
with possible Pd-Pd interaction gathered with its diamagnetic property are
consistent with square planar geometry in 1:1H-(BA), = NOH(SBA), and -
Sal(SBA) palladium complex. In 1:3 and 1:4 Pd complexes, the square planar
geometry of (BA), (SBA), -NO2 (BA) azo palladium complexes lead to biden-
tate behavior of the first two ligands on complexation. These complexes are
hydrogen-bonded with the other ligand and water molecules.

80
M. S. Masoud et al.
Platinum Complexes. The prepared platinum complexes (Table 1) are
of [1:1. nH2O) derived from -(BA), -(SBA), and -H(BA), and (1:4 . nH2O)
derived from -CH3(BA), and -Sal(SBA). The ground state of PtCl42− with D4h
symmetry is 1A1g. Three stronger spin-allowed and the three spin-forbidden
d-d transitions are as follows:
1
3A2g: 1A1g → A2g(ν1 = 21, 000 cm−1, ε = 15)
1
3B2g: 1A1g → B2g(ν2 = 25, 000 cm−1, ε = 59)
1
3E2g: 1A1g → Eg(ν3 = 30, 2000 cm−1, ε = 64)
The first band is reasonably assigned to the spin-forbidden transition be-
cause of its low intensity. The third and fourth bands are due to spin-allowed
transitions, dz2 → dx2-y2 (1A2g) and dxz, dyz → dx2-y2 (1Eg), respectively.[7]
3
3
The second band can be assigned to a spin-forbidden, E2g or A2g , and
the other to a spin-allowed [dz2 → dx2-y2 (1B2g)] transition. Although
the intensity of a spinforbidden band is much weaker than that of a spin-
allowed, the platinum complexes give fairly strong spin-forbidden bands
owing to a strong spin-orbit interaction. However, band 2 is assigned to a
spin-forbidden transition.[24] The prepared platinum complexes (Table 1)
are of (1:2. nH2O) derived from -(BA), -(SBA), and -H(BA), and (1:4. nH2O)
2−
derived from -CH3(BA) and -Sal(SBA). The ground state of PtCl4 with
3
1
D4h symmetry is A1g. The band A2g due to transition of A1g → A2g (ν1
= 21,000 cm−1) (ε = 15) is of a spin-forbidden transition. The intensity of
spin-forbidden is much weaker than that of a spin-allowed, so the platinum
complexes give fairly strong spin-forbidden bands owing to a strong spin or-
bit interaction.[7] The 1:2 Pt-(SBA) and Pt-(BA) complexes absorb at 29,240
and 19,920 and 29,240 cm−1, respectively, where the former complex ex-
ists in a more stabilized and conjugated structure than the latter due to the
difference in electronegativity between oxygen and sulphur atoms. The 1:2
Pt-H(BA) complex absorbs at 24,390 cm−1.
The absence of anions in the synthesized complexes, suggest that PtIV
is subjected to reduction, where PtII is formed. The electronic spectra of
the platinum complexes (Table 1) suggest square planar geometry with D4h
symmetry.
The infrared spectra of the metal complexes with those of the free lig-
ands, the vibrational frequency of coordinated functional group (e.g., νO−H
,
−
νC=O, νC=N, νC=S, νCOO and νN=N), are affected with different degrees
depending on the strength of π interaction occurring between the metal
ion and π electron of functional group.[19] Some of the carbonyl bands
disappeared and others are slightly shifted, probably due to tautomerization
to the enol form followed by complexation through the deprotonaion pro-
cess. The shift in C N bands suggested the C N is involved in coordination.

Complexing Properties of Some Pyrimidines
81
Most of the νN=N bands are not affected by complexation, except in (Cu,
Co-CHO), (Ni, Cu-COOH), and (CO, Ni-Cl). The νNH, νOH, νOH, νN−H, and
νC−O are affected on coordination which suggests that the oxygen and ni-
trogen and/or S atoms are considered as centers for complexation. In few
cases, the ligand may act as bidentate, as in structure (4). The tridentate
behavior exists in most complexes where the azo group is not involved in
the chelation, structure (5). The ligands act as mixed bidentate-tridentate,
where the azo group is either involved, structure (6), or is not involved struc-
ture (7)) and structure (8). Moreover, the ligand acts as a tri-tridentate,
structure (9).
The electronic absorption spectra of cobalt complexes are recorded
in presence of different solvents to trace the possible adducts formed,[25]
beside the calculation of Racah parameters, to know the geometry of
new species and their strengths.[26] The calculations of the ligand field
parameters are as follows:
ꢀ
ꢁ
10 Dq = ν2 − ν1, B = 2ν12 − ν1ν2 /(12ν2 − 27ν1)
10 Dq = 2ν1 − ν3 + 15B, B = 1/30[−(2ν1 − ν3)
ꢀ
ꢁ
1/2
− ν12 + ν32 + ν1ν3
]
ꢂ
10 Dq = 1/3(2ν2 − ν3) + 5B, B = 1/510 7(ν3 − 2ν2)
ꢃ
ꢄꢅ
3 81ν32 − 16ν2(ν2 − ν3)
10 Dq = ν2 − ν1, B = (ν2 + ν3 − 3ν1)/15
The data are collected in Table 3, where the followings are given: Most of
the B parameter, whichisthe measureoftheelectron-electronrepulsionterm
which is lower in complexes (Table 3), than in the free ion (985 cm−1), with β
values lower than unity, assume largely covalent bonds between the organic
ligand and the metal ion.[25] The -NO2 complex with ν2/ν1 values in the
presence of all basic solvents lie between 1.86 and 2.08 suggests that complex-
solvent interaction still has an Oh structure. However, the ν2/ν1 value 1,2-
dichloro ethane is 1.45 to identify the tetrahedral geometry. The chloro
complex remains of Oh geometry, irrespective of the basic solvents used.
The methods used to calculate the Racah parameters in presence of
different solvents for nickel complexes are as follows:
ꢀ
ꢁꢆ
10Dq = ν1, B = 2ν12 + 2ν22 − 3ν1ν2 (15ν2 − 27ν1)
ꢀ
ꢁꢆ
10Dq = ν1, B = 2ν12 = ν32 − 3ν1ν3 (15ν3 − 27ν1)
10Dq = ν1, B = (ν2 + ν3 − 3ν1)/15
ꢃ
ꢄ
1/2
10Dq = ν1, B = 1/75 3ν1 25(ν3 − ν2)2 − 16ν12

82

83

84
M. S. Masoud et al.
TABLE 4 Racah Parameters for the Solvent Effects on the Electronic Spectra of Nickel
Complexes
Method of
Complex/media
calculation
ν
ν
ν
3
B
β
ν /ν
2 1
1
2
Ni-COOH (BA)
Butylamine
γ Picoline
DMF
(a)
(a)
(a)
(c)
13,200
12,857
12,500
11,900
18,750
19,250
19,250
20,400
24,750
23,917
24,500
24,750
565
704
796
630
0.55
0.68
0.77
0.61
1.42
1.49
1.54
1.71
Pyridine
Ni-No2(BA)
DMSO
DMF
(b)
(c)
(c)
(c)
(c)
(c)
7,250
1000
9000
9500
9000
9500
13,750
17,750
14,750
15,125
15,125
15,125
24,000
25,000
23,500
23,250
23,500
25,500
968
850
750
658
775
808
0.93
0.81
0.72
0.63
0.74
0.77
1.89
1.78
1.64
1.59
1.68
1.59
Pyridine
α Picoline
β Picoline
γ Picoline
Ni-CHO(BA)
DMSO
(a)
(c)
(a)
(c)
(c)
(d)
12,000
10,700
9375
16,500
15,000
14,500
24,500
22,500
441
333
431
360
792
878
0.43
0.32
0.42
0.35
0.77
0.84
1.38
1.40
DMF
Pyridine
1,2-Dichloroethane
Ni-Cl(BA)
Butylamine
γ Picoline
Pyridine
25,500
26,666
1.55
2.01
8000 16,125
(c)
(c)
(c)
9500
9625
9400
16,550
16,837
15,100
24,500
24,250
25,250
837
814
743
0.81
0.79
0.72
1.74
1.75
1.61
Ni-OH(BA)
α Picoline
β Picoline
γ Picoline
DMSO
(c)
(c)
(c)
(b)
(c)
(c)
9250
9750
9625
7750
7750
8000
15,875
16,750
15,125
16,417
15,000
13,750
22,875
23,417
23,375
24,500
22,600
22,125
733
728
642
953
957
792
0.70
0.69
0.61
0.91
0.92
0.76
1.73
1.72
1.57
2.12
1.93
1.72
DMF
Pyridine
Ni-Sal(BA)
Butylamine
Propylalmine
α Picoline
Pyridine
(a)
(a)
(a)
(a)
12,500
12,000
12,500
10,000
18,500
18,750
18,000
15,500
25,500
24,750
24,500
24,250
650
829
570
660
0.63
0.80
0.55
0.64
1.48
1.56
1.44
1.55
Ni-Bzd(SBA)
Butylamine
DMSO
DMF
Pyridine
(c)
(c)
(b)
(a)
7500
7000
7250
11,500
12,000
13,000
18,000
18,500
17,375
26,830
467
633
575
683
0.45
0.61
0.55
0.56
1.53
1.71
1.79
1.76
7500 13,250
The β values are less than unity (Table 4), suggesting a largely cova-
lent bond between the organic ligand and nickel.[27] The electronic ab-
sorption spectra of nickel complexes were consistent with the formation
in tetragonal distorted octahedral geometry in case of -NO2, -COOH, -CHO,
and -OH (in case of γ -picoline only), octahedral geometry in -OH substi-
tuted ligand in most solvents, Ni-Sal (BA) complex in pyridine, α-picoline,

Complexing Properties of Some Pyrimidines
85
-(BA)
M
=
Pd, X = 2 moles (BA)
-
M = Co a = b = c = H2O
Pt, X = zero
NO2(BA)
M = Ni a = H2O
M = Cu a = ------
M = Cu a = H2O
M = Ni a = H2O
M = Cu a = H2O
x = 5H2O
b = c = x = zero
b = -----
-(SBA)
M
=
Pd, X = 2 moles (SBA)
+4 H2O
-CI(BA)
-
CHO(BA)
c = x = zero
b = c = zero
= 2H2O
Pt, X = zero
-
b = ----
CH3(BA)
-
OH(BA)
-
c = x = zero
b = c = x = H2O
b = c = x = zero
-H(BA)
M
=
Pt, X = 7 H2O
M = Ni a = H2O
M = Cu a = mono-
/2
bidentate
legand
Bzd(BA)
M
Pd, X = 6 H2O
-
M = Co a = ----
b = c = x = zero
b = c = x = zero
CH3(BA) = Pt, X = 2 moles-
Bzd(SBA)
M = Cu a = b = c
= x = H2O
CH3(BA) + H2O
-
M = Co a = H2O
Sal(SBA)
-
M
Pd, X = -NO2(BA) +H2O
M = Ni a = ----
M = Cu a = ----
M = Pd a = Pd
b = c = x = zero
b = c = x = zero
b = c = x = zero
b = c = x = zero
b = c = x = H2O
NO2(BA) =
-(SBA)
M
=
Pt, X = 2 moles -
-H(BA)
Sal(SBA)
= NOH(SBA) M = Pd a = Pd
M = Pd a = H2O
Sal(SBA)
C-Mixed bidentate-tridentate ligand

86
M. S. Masoud et al.
propylamine, and butylamine solvents. The Ni-Bzd(S) complex forms
adducts with butylamine, DMSO, DMF, and pyridine solvents with the trac-
ing of square pyramidal geometry. However, the (ν2/ν1) values in presence
of DMSO, DMF, and pyridine solvents are in the range of 1.71–1.79, which
suggests the possible existence of Oh geometry. So the following equilibrium
is established: square pyramidal ↔ octahedral.[22,26,27] The eg electrons will
become σ-antibonding, and spend some time on the organic compound.
The t2g electrons may become π-bonding or antibonding and spend some
time on the organic moiety. So, a small amount of the σ and π electron
density on the metal may be transferred into the ligand. Such delocalization
will increase the mean distance between the d electrons to reduce the value
of β.[23] For -NO2 (BA) complex, the most distorted complex is that in pres-
ence of α and γ picolines solvents, while the least distorted is that studied in
DMSO. Similarly, the nickel Cl-(BA) complex gives adducts with butylamine,
γ picoline, and pyridine solvents, which are of a tetragonal distorted octa-
hedral geometry. The butylamine-nickel adduct gives more split bands, and
nickel pyridine adduct is the most distorted, probably due to possible ex-
istence of some sort of isomerization. This is subject to change the bond
length, and the bond angle gathered with the variation in the population in
the electron density in such a system.[27] A similar situation is reached for
the -COOH(BA) and -CHO(BA) complexes. The nickel -OH(BA) complex
gives octahedral adducts with pyridine, DMF, DMSO, and α and β picolines.
However, the γ picoline adduct has a tetragonal distorted geometry. The
nickel Sal(BA) complex with pyridine, α picoline, propylamine, and buty-
lamine formed octahedral adducts. The ν3 and ν2 bands in the presence
of propylamine and butylamine bases are of a split nature. The ν1 band in
the presence of propylamine is splitted, while that in the presence of buty-
lamine is of a broad nature, so such trend is related to the chain length of the
amine.
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