Polymer complexes: XLXII-interplay of coordination π-π Stacking and hydrogen bonding in supramolecular assembly of [sulpha drug derivatives-N,S:N,O] complexes

Article abstract of DOI:10.1016/j.saa.2010.07.011

A novel series of nickel(II) polymer complexes of 5-sulphadiazineazo-3- phenylamino-2-thio-4-thiazolidinone (HL₁), 5-sulphamethazine-3- phenylamino-2-thioxo-4-thiazolidinone (HL₂), 5-sulphamethoxazole-3- phenylamino-2-thioxo-4-thiazo

Full text of DOI:10.1016/j.saa.2010.07.011

Spectrochimica Acta Part A 77 (2010) 755–766
Contents lists available at ScienceDirect
Spectrochimica Acta Part A: Molecular and
Biomolecular Spectroscopy
journal homepage: www.elsevier.com/locate/saa
Polymer complexes: XLXII-interplay of coordination ␲–␲ stacking and hydrogen
bonding in supramolecular assembly of [sulpha drug derivatives-N,S:N,O]
ଝ
complexes
a,∗
a
b
b
A.Z. El-Sonbati , M.A. Diab , M.M. El-Halawany , N.E. Salam
a
Chemistry Department, Faculty of Science (Demiatta), Mansoura University, Demiatta, Egypt
Department of Mathematical and Physical Sciences, Faculty of Engineering, Mansoura University, Mansoura, Egypt
b
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 20 February 2010
Accepted 12 July 2010
A
4
5
novel series of nickel(II) polymer complexes of 5-sulphadiazineazo-3-phenylamino-2-thio-
-thiazolidinone (HL1), 5-sulphamethazine-3-phenylamino-2-thioxo-4-thiazolidinone (HL2),
-sulphamethoxazole-3-phenylamino-2-thioxo-4-thiazolidinone (HL3), 5-sulphacetamide-3-phenyl-2-
thioxo-4-thiazolidinone (HL4) and 5-sulphaguanidine-3-phenylamino-2-thioxo-4-thiazolidinone (HL5)
were prepared and characterized. IR spectra show that HLn (n = 1–5) is coordinated to the metal ion
in a neutral tetradentate manner with NSNO donor sites of NH (hydrazone’s), NH (3-phenylamine),
carbonyl group and Ph-NH. The title [Ni3(HLn)2(␮-OAc)2(OAc)4]n consists of three Ni(II) atoms linked
by interchain ␲–␲ interaction are observed between aromatic rings of two ligands (HLn) which are
further doubly bridged two adjacent nickel atoms by acetate group. The geometrical structures of these
complexes are found to be octahedral. The nature of bonding and the stereochemistry of the complexes
Keywords:
Azo sulpha drug
Supramolecular structures
Trinuclear polymeric Ni(II) complexes
Spectroscopy
Thermal analysis
1
have been deduced from elemental analyses, thermal, infrared, H NMR, electronic spectra, magnetic
susceptibility and conductivity measurements. The richness of electronic spectral in these complexes is
also supporting evidence for the trinuclearity of the Ni(II) polymer complexes.
©
2010 Elsevier B.V. All rights reserved.
1
. Introduction
and to act as complex ligands for rare metal ions other metallic
elements.
Particular attention has recently paid to the synthesis and study
The coordination chemistry of sulpha drug and their azo deriva-
tives have much attention by virtue of their applicability as
potential ligands for large number of metal ions [7–10]. The metal
chelates thus produced have wide applications in the dye industry,
as analytical reagents for the microdetermination of metals and
in biological uses [11]. Different methods were reported for the
synthesis of azo sulpha drugs [5–10]. The electronic and infrared
(IR) spectra of a large number of azo sulpha drugs were inves-
tigated for structure elucidation [8–10]. It was confirmed that
these compounds exist mainly as a chelated hydrazo-keto struc-
ture but under the influence of high electron accepting substituents
and in highly polar solvents, the azo sulpha drug compound was
liable to exist in hydrazone-azo tautomeric equilibrium [5–7].
Nuclear magnetic resonance was used as a tool to determine
the tautomeric forms of 5-sulphadiazineazo-3-phenyl-2-thioxo-4-
of the tetradentate Schiff bases and their complexes. This is due to
a variety of reasons, not the least of which is their crucial role in
some biological processes such as the biological function of bac-
terorhodospin [1]. These complexes are used in some chemical
processes as catalyst and also as biological models in understand-
ing the structure of biomolecules and biological processes [2,3]. In
continuation of our studies on the ligating properties of the het-
erocyclic nitrogen–sulphur and/or nitrogen–oxygen compounds
and their azo dyes [4–21], El-Sonbati and his school [4–21] have
prepared and investigated several novel solid polymer complexes
and/or transition metal complexes in recent years. Azo dyes have
played a key role in our understanding of the coordination chem-
istry of transition metal ions. Transition metal polymer complexes
of tetradentate azo dye are always of interest [4–21] since they
exhibit a marked tendency to oligomerise, thus leading to novel
structural types, to display a wide variety of magnetic properties
thiazolidinone [HL ], 5-sulphamethazineazo-3-phenyl-2-thioxo-
1
4-thiazolidinon [HL ], 5-sulphamethoxoleazo-3-phenyl-2-thioxo-
2
4
4
4
-thiazolidinone [HL ], 5-sulphacetamideazo-3-phenyl-2-thioxo-
3
-thiazolidinon [HL ], 5-sulphaguanidineazo-3-phenyl-2-thioxo-
4
-thiazolidinone [HL5] and several related azo heterocyclic in
dimethylformamide [10].
Of late, a large number of complexes of rhodanine azo sulpha
drugs have been prepared and characterized by magnetic and spec-
ଝ
Abstracted from the Ph.D. work of Salam.
Corresponding author. Tel.: +20 60081581; fax: +20 502254000.
E-mail address: elsonbatisch@yahoo.com (A.Z. El-Sonbati).
∗
1
386-1425/$ – see front matter © 2010 Elsevier B.V. All rights reserved.
doi:10.1016/j.saa.2010.07.011

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56
A.Z. El-Sonbati et al. / Spectrochimica Acta Part A 77 (2010) 755–766
Fig. 1. Structure of ligands (HLn).
tral studies [8–17]. In our laboratories the coordination behaviour,
chemical equilibria, nuclear and electron paramagnetic resonance
and the solution chemistry of transition and inner transition metal
As a part of our ongoing work [5–21] in the area of supramolec-
ular assembly of polymer complexes based on aromatic and/or
aliphatic amine sulpha drugs, we report herein the synthesis,
of HL –HL5 are prepared and studies. However, no structural and
characterization, structure of HL –HL5 (Fig. 1) and properties
1
1
coordinating studies in solid and solution have been reported for
azodyes containing both rhodanine and sulpha drug functional
groups except references [4–6,11–14]. The existing literatures on
the coordination chemistry of these ligands are obscure.
Although a few papers are available on the transition metal
complexes of sulphonamides, there is no previous work on the
complexes of azosulphonamide except for the reported synthesis
and characterization of 5-sulphadiazineazo-3-phenyl-2-thioxo-4-
of hydrazone’s nickel supramolecular polymer complexes of the
general formula [Ni (HLn) (␮-OAc) (OAc) ]n. The most probable
3
2
2
4
coordination, semicoordination and hydrogen bonds related to
inclusion phenomena, guest exchange and molecular based nickel
will be discussed more in detail.
As part of a continuing program on the synthesis and character-
ization of bi/tetradentate heterobi/trinuclear complexes. This work
is of interest because of the magnetic and electronic properties
of the complexes which are formed. This kind of investigation is
fundamentally important to the structural estimation of various
metalloenzymes.
thiazolidinone [HL ], 5-sulphamethazineazo-3-phenyl-2-thioxo-
1
4
4
4
4
-thiazolidinon [HL ], 5-sulphamethoxoleazo-3-phenyl-2-thioxo-
2
-thiazolidinone [HL ], 5-sulphacetamideazo-3-phenyl-2-thioxo-
3
-thiazolidinon [HL ], 5-sulphaguanidineazo-3-phenyl-2-thioxo-
4
-thiazolidinone [HL5] in our laboratories [4–21].
2. Experimental
As part of our ongoing work [16–21] in the area of supramolec-
ular assembly of polymer complexes based on aromatic and/or
aliphatic amine sulpha drugs, we report herein the synthesis, char-
2.1. Synthesis of the ligand
acterization and structure of HL –HL5 and properties of the first
example of hydrazone nickel supramolecular polymer complexes
The experimental technique has been described previously
[4–10,16–21]. 3-Phenylamino-2-thioxo-4-thiazolidinone was pre-
pared according to the previously reported method [9–19]. The
standard chemical sulpha drug was used without any further purifi-
cation.
1
[
Ni (HLn) (␮-OAc) (OAc) ]n based on coordination, semicoor-
3 2 2 4
dination and hydrogen bonds, which are of current interest due
to their potential application related to inclusion phenomena,
guest exchange and molecular based nickel. Further studies are
in progress involving other d- and/or f-metals and different
stoichiometries in order to obtain a reasonable explanation and a
better insight into this field of magnetic interactions. Recently, El-
Sonbati [7,10,16] published a paper on rare earth/d-block ions with
2.2. Preparation of 5-sulphadiazine
azo-3-phenyl-2-thioxo-4-thiazolidinone [4–10,16–21]
A solution of the appropriate sulphadiazine, sulphamethazine,
sulphamethozale, sulphacetamide and sulphaguanidine (0.01 mol)
in 30 ml hydrochloric acid (30%, v/v) was treated with a cold
saturated solution of sodium nitrite (0.015 mol), with stirring in
ice-bath for 15 min after that the cold solutions were added to
a cold solution of rhodanine (3) (0.01 mol) in ethanol (30 ml)
containing 2.0 g of sodium acetate. The reaction mixtures were
5
-sulphadiazineazo-3-phenyl-2-thioxo-4-thiazolidinone [HL ], 5-
1
sulphamethazineazo-3-phenyl-2-thioxo-4-thiazolidinone [HL ],
2
5
-sulphamethoxoleazo-3-phenyl-2-thioxo-4-thiazolidinone
[
[
[
HL ], 5-sulphacetamideazo-3-phenyl-2-thioxo-4-thiazolidinone
3
HL ], 5-sulphaguanidineazo-3-phenyl-2-thioxo-4-thiazolidinone
4
HL5].

A.Z. El-Sonbati et al. / Spectrochimica Acta Part A 77 (2010) 755–766
757
Table 1
Analytical data of nickel(II) polymer complexes of (HLn) (for molecular structure see Fig. 2).b.
a
Compoundsc
Exp. (Calcd.)%
C
Compositions
H
N
S
Metal
HL1
1
HL2
2
HL3
3
HL4
4
46.8 (47.0)
40.1 (40.0)
48.7 (48.9)
44.5 (44.3)
46.9 (46.7)
39.8 (39.7)
45.2 (45.4)
38.7 (38.8)
42.3 (42.7)
37.0 (36.8)
2.9 (3.1)
3.1 (3.2)
3.9 (4.1)
3.9 (4.0)
3.1 (3.3)
3.3 (3.3)
3.1 (3.3)
3.4 (3.3)
3.4 (3.6)
3.3 (3.3)
19.8 (20.2)
13.1 (12.7)
18.7 (19.0)
13.6 (13.9)
17.5 (17.2)
11.2 (11.5)
15.9 (15.6)
9.8 (10.1)
20.2 (19.8)
12.8 (13.1)
19.0 (18.6)
13.3 (13.6)
20.0 (19.7)
12.8 (13.1)
21.0 (21.4)
13.4 (13.6)
20.9 (21.3)
13.4 (13.6)
–
11.7 (12.0)
–
12.1 (11.8)
–
11.7 (11.3)
–
12.3 (12.5)
–
12.3 (12.0)
[(Ni)3(HL1)2(␮-OAc)2(OAc)4]n
[(Ni)3(HL2)2(␮-OAc)2(OAc)4]n
[(Ni)3(HL3)2(␮-OAc)2(OAc)4]n
[(Ni)3(HL4)2(␮-OAc)2(OAc)4]n
[(Ni)3(HL5)2(␮-OAc)2(OAc)4]n
HL5
5
22.1 (21.9)
13.7 (13.4)
a
Microanalytical data as well as metal estimations are in good agreement with the stoichiometry of the proposed complexes.
The excellent agreement between calculated and experimental data supports the assignment suggested in the present work.
HL1–HL5 are the ligands as given in Fig. 1.
b
c
stirred in ice-bath for 1 h. The solid products that formed were
3. Results and discussion
filtered off, washed with cold water, dried and crystallized from
the solvent to give that 5-sulphadiazineazo-3-phenyl-2-thioxo-4-
3.1. The ligand
thiazolidinone [HL ], 5-sulphamethazineazo-3-phenyl-2-thioxo-
1
4
4
4
4
-thiazolidinon [HL ], 5-sulphamethoxoleazo-3-phenyl-2-thioxo-
Classic keto-hydrazones pigments are prepared by an aqueous
diazotization and coupling procedure, which lead directly to a pure
product in high yield and in a physical form suitable for appli-
cation [23]. However, attempts to prepare compounds using this
standard method either failed completely or gave a low yield of
a highly impure product, probably due to the instability of the
sulpha drug heterocyclic diazonium salts in hydrochloric acid solu-
tion at pH sufficiently high to allow coupling to take place. In the
present study, it was found that reasonable yields of the hydra-
zone pigments containing sulpha drug heterocyclic and rhodanine
could be easily obtained when the diazotization was finished in
pyridine and the coupling was carried out in potassium hydroxide
solution.
2
-thiazolidinone [HL ], 5-sulphacetamideazo-3-phenyl-2-thioxo-
3
-thiazolidinon [HL ], 5-sulphaguanidineazo-3-phenyl-2-thioxo-
4
-thiazolidinone [HL5] (see Fig. 1). The analytical data confirmed
the expected compositions (Table 1). The ligand was also charac-
terized by H NMR and IR spectroscopy.
1
2.3. Synthesis of the complexes
3
A hot solution of Ni(II), (0.01 mol) in EtOH (30 cm ) was added
3
to the appropriate ligands (0.022 mol) in EtOH (30 cm ). Polycrys-
talline solid complexes were immediately formed in each case. The
reaction mixture was then maintained at the reflux temperature
The dye prepared in this study may exist in tautomeric
forms as shown. Its analogs have been demonstrated conclusively
from a series of investigations using a variety techniques, such
as IR, and NMR, that 5-sulphadiazineazo-3-phenyl-2-thioxo-4-
for 1 1 h to ensure complete reaction. The solid complexes were fil-
2
tered off and washed several times with EtOH, followed by Et O,
and dried in vacuum over P O5.
2
2
thiazolidinone [HL ], 5-sulphamethazineazo-3-phenyl-2-thioxo-
1
4
4
4
4
-thiazolidinon [HL ], 5-sulphamethoxoleazo-3-phenyl-2-thioxo-
2
-thiazolidinone [HL ], 5-sulphacetamideazo-3-phenyl-2-thioxo-
2
.4. Measurements
3
-thiazolidinon [HL ], 5-sulphaguanidineazo-3-phenyl-2-thioxo-
4
-thiazolidinone [HL5] exist exclusively in keto-hydrazone form
C, H, and N microanalyses were carried out at the Cairo
in solution [5–8]. The two six-membered intermolecular hydro-
gen bonding rings are possible in the keto-hydrazone tautomer
University Analytical Center, Egypt. The metal content in the
polymer complexes was estimated by standard methods. The
(see Fig. 2), but only one six-membered rings is conceivable in
metal content in the polymer complexes was estimated by stan-
dard methods [7–10]. The 1H NMR spectrum was obtained with
the multiple conformations of the azo-enol form perhaps explain-
ing the greater prevalence of the keto-hydrazone tautomer. The
infrared spectra of HLn, and in particular the position of the car-
bonyl stretching vibrations, have been of considerable importance
in establishing that the compounds exist exclusively in the keto-
hydrazone form. The solid state IR spectra of the synthesized
pigments show a single carbonyl absorption band appearing at
a Jeol FX90 Fourier transform spectrometer with DMSO-d6 as
the solvent and TMS as an internal reference. Infrared spec-
tra were recorded using Perkin-Elmer 1340 spectrophotometer.
Ultraviolet–visible (UV–vis) spectra of the polymer were recorded
in nuzol solution using a Unicam SP 8800 spectrophotometer. The
magnetic moment of the prepared solid complexes was deter-
mined at room temperature using the Gouy method. Mercury(II)
−
1
1
675 cm
consistent with a keto-hydrazone form with exten-
sive two six-membered intramolecular hydrogen bonding, and this
has been confirmed by a number of previous published data of
keto-hydrazones analogous and also according to El-Sonbati et al.
(
tetrathiocyanato)cobalt(II), [Hg{Co(SCN) }], was used for the cali-
4
bration of the Gouy tubes. Diamagnetic corrections were calculated
from the values given by Selwood [22] and Pascal’s constants.
[
5–8]. In the 1H NMR spectra of HLn, the NH (hydrazone’s), NH
Magnetic moments were calculated using the equation ꢀ
2
thermobalance. Ten milligram samples were heated at a rate of
1
ple holder was boat-shaped, 10 mm × 5 mm × 2.5 mm deep; the
temperature measuring thermocouple was placed within 1 mm of
the holder.
=
eff
coor. 1/2
(3-phenylamine) and Ph-NH and NH C protons appear as broad
singlets at 8.9–12, 9.0–11.9 ppm, respectively. These NMR data con-
firm that the HLn exists in solution as keto-hydrazone. The infrared
.84[TꢁM
]
. TG measurements were made using a Du Pont 950
◦
0 C/min in a dynamic nitrogen atmosphere (70 ml/min); the sam-
spectra of the ligands showed the characteristic bands for ꢂ(SO ),
2
ꢂ(C N), ꢂ(NH), ꢂ(N N) values. The 1H NMR spectra of the lig-
ands showed characteristic proton signals of –SO NH, –C (NH) and
2

7
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A.Z. El-Sonbati et al. / Spectrochimica Acta Part A 77 (2010) 755–766
Fig. 2. Structure of the model hydrogen bond dimers ligand.
1
NH proton signals. The obtained IR spectra, H NMR and elemental
3.3. Composition and general characteristics
2
analytical data agree well with the formulae of HLn. The proposed
structure for the ligand is shown in Fig. 2.
The Ni(II) polymeric complexes, were prepared by different sul-
pha drug-hydrazone and Ni(II). Syntheses of the five polymeric
complexes were essentially the same and involved mildly heating
and stirring of stoichiometric amounts of the appropriate sulpha
drug ligand and a slight excess of Ni(II) acetate in ethanol solvent.
Removal of solvent under vacuum gave the corresponding products
in good yields. They are stable in solution as well as in the dry state
under ambient conditions. These metal(II) polymer complexes eas-
ily dissolved in aprotic solvents like DMF and DMSO. The increased
high solubility might be due to the substituted group on the ring
and methyl groups of sulpha drug which increase the repulsion
force and reduce the aggregation of molecules. But their solubility
decrease in strong polar solvents such as methanol, ethanol and
water, because different groups and other substituted groups are
lipophilic and weakly polar. The elemental analytical data, IR spec-
3.2. Metal complexes
Following the successful preparation of the ligands, attention
was direct towards the chemical behaviour of the ligands towards
nickel acetate. When a mixture of ligands in dry ethanol was reacted
with nickel acetate in dry ethanol, a change in colour was observed
and the complex compounds precipitated. The products were puri-
fied by washing with dry ethanol, and gave elemental analyses
compatible with the suggested formulae given in Table 1 according
to the following general equation:
3
Ni(OAc) + 2HLn → [(Ni) (HLn) (OAc) ]n (where HLn
2
3
2
6
=
= tertradentate hydrazone, n = 1–5)

A.Z. El-Sonbati et al. / Spectrochimica Acta Part A 77 (2010) 755–766
759
Table 2
Electronic spectral data of trinuclear nickel(II) polymer complexes.
Nickel(II) polymer complexes derived from
d–d
Charge transfer
a
b
b
b
b
b
5
5
5
5
5
-Sulphadiazineazo-3-phenyl-2-thioxo-4-thiazolidinone (HL1)
-Sulphadiazineazo-3-phenyl-2-thioxo-4-thiazolidinone (HL2)
-Sulphadiazineazo-3-phenyl-2-thioxo-4-thiazolidinone (HL3)
-Sulphadiazineazo-3-phenyl-2-thioxo-4-thiazolidinone (HL4)
-Sulphadiazineazo-3-phenyl-2-thioxo-4-thiazolidinone (HL5)
10,158, 13,785, 16,390
9808, 14,120, 15,190
9540, 11,758, 14,200
10,030, 13,240, 14,485
10,465, 14,690, 16,665
26,310 , 33,333
a
25,310 , 31,750
a
23,800 , 29,415
a
27,023 , 32,780
a
27,023 , 33,333
a
Intra-ligand charge transfer transition (␲–␲*) and (n–␲*).
tra of the Ni(II) polymer complexes agree well with their formulae.
The metal-to-ligand ratio of the nickel(II) polymer complexes was
found to be 3:2, but all the Ni(II) polymer complexes have two
additional bridged coordinated acetate molecules. So the Ni(II) ions
appear to be five and hexa-coordinated with the SNON-neutral
tetradentate ligands and the bridged coordinated acetate, and the
geometry is octahedral for Ni(II) ion [6,9,24]. Fig. 3 shows the sug-
gested structures of the trinuclear Ni(II) polymer complexes.
of 2.82–2.73 B.M. which is normally observed for octahedral coor-
dinated nickel(II) ions due to the presence of strong nickel–nickel
interaction.
3.6. Electronic spectra of the ligands and their Ni(II) polymer
complexes
−
1
HL –HL5 exhibits bands at 26,350–26,150 cm (CS) (n → ␲*),
1
−
1
−1
3
0,460–30,250 cm
(CO) (n → ␲*), 32,980–3100 cm
(H-
3.4. Molar conductance
−1
bonding and association), 40,240–39,890 cm (phenyl) (ph-ph*,
␲
–␲*) [10,16] and the strong absorption band observed at
◦
The molar conductance values in DMF at 25 C for the polymeric
−1
≈29,610–30,303 cm is attributed to (n → ␲*) electronic transi-
complexes were found to be low. The relatively low values indi-
cate the non-electrolytic nature of these complexes [8]. This can be
accounted for by the sates faction of the bi-valency of the metal by
the acetate. Hence the six acetates in Ni(II) complexes are in the
coordination sphere. This implies the coordination of the anions to
the metal ion centers. The analytical data and the molar conduc-
tance measurements of the polymeric complexes reveal that six
anions are coordinated to the three metal atoms in all complexes
tion of hydrazone (–C N–NH–) group involving conjugation and
delocalization electronic system of the ligand [26]. This result of
the absorption band is shorter than that observed in arylhydrazone
compounds based on the phenylamine unit in the literature.
An obvious reason for the hypsochromic shift is the reduction
of the ␲ electronic density of sulpha drug ring relative to the
corresponding phenyl ring. These shifts or the disappearance
of the bands are indicative of coordination of the ligands are
indicative of coordination of the ligands to Ni(II). Electronic spectra
of five trinuclear polymeric complexes were obtained in DMF
medium (Table 2). The electronic spectra of all the complexes
exhibit three features: (i) one or two peaks is assigned to the
intraligand charge transfer transition (␲–␲*), (ii) an intense peak
is due to ligand-to-metal charge transfer transition, and (iii) the
d–d transition for the Ni(II) polymer complexes show three main
bands which is characteristic of Ni(II) in the 5/6 coordination
environment [27,28]. Although the appearance of the spectra
bear similarities with those for octahedrally Ni(II) ions, the three
[
see Table 1].
3
.5. Magnetic data of the polymeric Ni(II) complexes
The subnormality in magnetic moments has been ascribed to
antiferromagnetism which is due to the interaction between elec-
tronic spins on neighboring metal ions. It is generally accepted that
mechanism of the exchange interaction involves the mutual pairing
of electronic spins via some form of orbital overlap. Antiferromag-
netic exchange may be metal–metal interaction or superexchange.
Metal–metal interaction involves direct overlap of orbitals con-
taining the unpaired electrons, which influences the magnetic
behaviour where as superexchange involves the interaction of
electrons with opposite spins on the two interacting ions via an
intermediate diamagnetic anions(s) which results ineffective pair-
ing leading to a minimum number of unpaired spins in the ground
state of the system. Both the mechanisms seem to be operative in
the polymeric complexes of HLn [25]. In all the prepared nickel(II)
complexes, one of the nickel(II) ion in the thion compartment is
six coordinated, and the other in the hydrazone compartment is
five coordinated. The effective magnetic moment values for the
nickel(II) polymer complexes at room temperature are in the range
bands 3A2g → T2g(P), A2g → T1g(F), A2g → T1g(P) to the spin
3
3
3
3
3
8
allowed transition of an octahedrally d [27,28] ion would be a
misinterpretation. Further the higher molar extinction coefficients
of the absorption band maxima in fact indicate a square pyramidal
or trigonal bipyramidal coordination environment of at least one
of the Ni(II) ions [27,28]. The richness of electronic spectral in
these complexes is also supporting evidence for the trinuclearity of
the Ni(II) polymer complexes [29]. The electronic spectral studies
inferred that an in red shift of the d–d transition of Ni(II) ion in
the ligand HL1 to HL3 and HL4 to HL5. This is due to the flexibility
of sulpha drug ring that is imparted by the distortion of geometry
of the polymer complexes due to the increase in sulpha drug ring
size, which causes more distortion of the geometry [30,31].
3.7. On the structure of the used ligands
The considered ligands are neutral molecules with acidic and
basic sites. The interaction of these reactive sites within a given
molecule determines its conformation (Fig. 2). Such interaction,
when it takes place between neighboring molecules, serves to
maintain the ligand in a condensed state, for instance, in the solid
state or to form complexes with other analog molecules and salts
(discussed below).
Since series ligands concerns rhodanine azo sulpha drug sub-
stituted R (Fig. 1), the available proton on C N–NH (hydrazone)
Fig. 3. Structure of the model Ni(II) polymer complexes.

7
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A.Z. El-Sonbati et al. / Spectrochimica Acta Part A 77 (2010) 755–766
and/or C–OH (enolic) is involved in an intramolecular hydrogen
bond interaction with the carbonyl and/or azo group. This has been
confirmed by H NMR data [10] and IR spectra [5–10]. Such interac-
tion stabilizes an “S”-shaped conformation of C S, NH (hydrazone)
and C O groups, three donor sites rich in electron density. This con-
former could be appropriate for complex formation through the S
atom because it remains practically free of steric impediment from
the substituent groups and excludes the possibility of a chelating
effect of both donor sites in the coordination process.
plexes shows that the decomposes in four steps. The peaks at
◦
∼162 C due to the liberation of coordinated a acetate ion. The sec-
1
ond stage corresponds to the loss of two bridged acetato molecules
◦
and also methyl groups in the temperature range 225–235 C. The
third step represents the decomposition of the remaining acetate
group CO . As the temperature is increased, TGA curves of Ni(II)
2
polymer complexes exhibit a not rather sharp decomposition tem-
◦
◦
perature at about 300 C and 240 C, respectively, which may be due
to the loss of one ligand molecule, and exhibit a progressive mass
loss above the decomposition temperature, which may be due to
the mass loss of the second ligand of the polymer complexes. The
3.8. Thermal properties of the Ni(II) polymer complexes
fourth step of decomposition occurs within the temperature range
◦
3
80–570 C, associated with peaks, which may corresponding to
It can be see that the TGA curves of the Ni(II) azo sulpha drug
◦
the degradation of a small quantity of organic part of the chelates
polymer complexes show no any mass loss up to 135 C, indicating
the absence of water and any other adsorptive solvent molecules in
the coordination sphere. The thermogram of Ni(II) polymer com-
and the possible nickel oxide at the final temperature above
◦
5
00 C.
Fig. 4. 1H NMR chemical shift (DMSO-d6) (ppm vs. TMS), (a) HL1 and (b) HL1 with D2O.

A.Z. El-Sonbati et al. / Spectrochimica Acta Part A 77 (2010) 755–766
761
3
.9. IR spectra and mode of bonding
The infrared spectra of ligands exhibit strong to medium
−
1
broad bands in the frequency range 3295–2950 cm . These
bands can be attributed to intramolecular hydrogen bonded
–NH group and also, the sulphonamide NH stretching vibra-
IR spectra of five Ni(II) polymer complexes are very similar to
each other, except some light shifts and intensity change of a few
vibration bands caused by different ligands, which indicate that
the complexes have similar structures. However, there are some
significant changes between the Ni(II) polymer complexes and their
free ligands for chelation as expected. The coordination mode and
sites of the ligands to the Ni(II) ions were investigated by comparing
the infrared spectra of the free ligands with its Ni(II) polymeric
complexes.
tion of HL –HL5 [6–10]. Furthermore, all ligands exhibit
strong band at 1730–1710 cm , this is due to ꢃC O [6–8].
a
1
−
1
The discussed infrared features beside the band appeared at
−
1
1640–1600 cm can guide to assume the presence of C N struc-
ture through resonating phenomena [6–11,32–34]. Such class of
compounds is with different types of hydrogen bonding systems
[6–11,35,36].
Fig. 5. 1H NMR chemical shift (DMSO-d6) (ppm vs. TMS), (a) HL2 and (b) HL2 with D2O.

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1
2
3
. H-bonding of the type O–H· · ·N between the –OH group and
The following features for some of the prepared complexes are
observed:
–
N
N– group (Fig. 2C).
. H-bonding of the type N–H· · ·O between the –NH (hydrazone)
group and C O group (Fig. 2D).
. Intermolecular hydrogen bonding of the O–H· · ·N (Fig. 2E)
or N–H· · ·O (Fig. 2F) type of one molecule to another
one.
1
. The infrared spectra of the free ligands show no character-
istic absorption assignable to antisymmetric and symmetric
stretching vibration of aniline NH2 function of sulphonamide
groups, respectively. El-Sonbati et al. [4–10] and Kana-
4
. The [(2)-Fig. 2D] case is more favoured than (i). This is due to the
−
1
presence of a broad band located at 870–970 cm which could
be taken as a good evidence for the intermolecular hydrogen
bonding (Fig. 2D). This is illustrated in Fig. 2.
garaj and Rao [33] had observed these bands at 3467 and
−1
3
378 cm , respectively. This confirms the formation of the azo
compounds.
Fig. 6. 1H NMR chemical shift (DMSO-d6) (ppm vs. TMS), (a) HL3 and (b) HL3 with D2O.

A.Z. El-Sonbati et al. / Spectrochimica Acta Part A 77 (2010) 755–766
763
−
1
−1
splitted strong spectral bands at 1435 and 1520 cm combined
2
. The strong band observed at ∼1110–1120 cm may be assigned
to ꢃ(N–N) vibration modes [9] is affected on complexation. It is
blue shifted and appeared as a weak band.
−
1
with the tracing of a strong bands at 1230 cm characteristic of
NH stretching vibration. All these data with lack of the ꢃC–O of
enol in the IR spectrum leads us to assume the structure (Fig. 2D)
for this compounds.
−1
3
. In all complexes 3490–3150 cm
is observed. Such region is
attributed to different probabilities: (a) it is due to either free
OH or NH (b) bonded-OH group or –NH group or (c) due to the
presence of coordinated water molecules.
. The spectra of ligands do not show absorption characteristic of
the N N function owing to the formation of the hydrazone. The
sharp, medium intensity band of C N (hydrazone) appears at
5. The spectra exhibits a very strong band at ∼1720 cm−1. This is a
powerful indicative to ꢃC O.
6. In all complexes 3480–3130 cm
−
1
4
is observed. Such region is
attributed to –NH group (3-phenylamine).
7. A remarkable feature is given, where the ꢂCH of the free lig-
−1
∼
1625–1610 cm for ligands. This is rather confirmed from the
and vanished on complexation, to point, again the probable C
bonding [39].
N
observation of Karabatoses et al. [37] and El-Sonbati et al. [38]
where the hydrazone form is more than the azo structure for sim-
ilar compounds. This is also proved by the appearance of N N in
8. The phenyl ring vibration appears at 1480–1510 cm−1. Band
−
1
−1
at 2930–3030 cm for the ligands and at ∼2970 cm for the
Fig. 7. 1H NMR chemical shift (DMSO-d6) (ppm vs. TMS), (a) HL4 and (b) HL4 with D2O.

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64
A.Z. El-Sonbati et al. / Spectrochimica Acta Part A 77 (2010) 755–766
−
1
complexes are assigned to ꢃ(C–H) vibration of the aromatic
system.
. Introduction of a hydrazo group instead of N N leads to a change
in the coordination mode of the azo group from the azo-nitrogen
to the amine nitrogen (NH) (Fig. 2).
frequency by ∼50 cm in the complexes, pointing to the coor-
dination of the sulphur to Ni(II) atom.
−
1
9
11. The presence of ꢂ(CH COO) absorption bands at ∼1534 cm
3
−
1
and ∼1422 cm in the IR spectra of complexes suggests that
the acetate group is coordinated to Ni(II) ion in ring bridge, in
a bidentate form [40,41] (see Fig. 3).
1
2. The spectra of the complexes show two bands in the region
This hydrogen bonding interaction will prevent the hydrazone
−
1
1
420–1435 and 1215–1260 cm
assigned to ꢂas and ꢂ
s
group from rearranging to the energetically more favourable N-
coordination mode. This behaviour has been observed with other
metal azo compounds that contained the substituent C N–NH
instead of C O in the vicinity of the azo group.
stretching vibration of acetate group. The correlation between
the positions of the antisymmetric and symmetric stretching
vibration of the acetate group and the type of coordina-
tion of this group was earlier studied [41]. It was concluded
from these studies that the frequency difference between
the two carboxyl stretches of ionic acetate groups is usu-
−
1
0. An intensive strong band at 845 cm 1 in the free ligand spec-
trum is due to ꢃ(C S) which has been found to shift to lower
Fig. 8. 1H NMR chemical shift (DMSO-d6) (ppm vs. TMS), (a) HL5 and (b) HL5 wit D2O.

A.Z. El-Sonbati et al. / Spectrochimica Acta Part A 77 (2010) 755–766
765
Table 3
conductance measurements. It was observed that coordination of
anions with metal was effected by number of coordination sites,
which was further confirmed by molar conductance.
The geometries of the polymer complexes are also affected by
number of coordination sites and ligand (HLn) has four coordination
sites and formed different geometrical complexes with different
anions. Polymer complexes of ligands are compared and it observes
that these complexes are five/six coordinated in nickel acetate com-
plexes. It proved direct effect of coordination sites on complexation
1
H NMR chemical shift of HL1–HL5 (ppm vs. TMS).a.
Compound
NH hydrazone
NH (3-phenylamine)
and ph-NH
CH
NH C
HL1
HL2
HL3
HL4
HL5
11.64
9.98
11.65
12.0
9.50 and 9.2
9.35 and 8.95
11.45 and 9.18
11.8 and 9.18
9.18 and 8.9
4.25
3.45
3.45
3.40
3.45
–
–
–
–
11.6
8.90
a
The excellent agreement experimental data supports the assignment suggested
in the present work.
(Table 1).
The purpose for the synthesizing bis-azo/hydrazo drug rhoda-
nine polymeric complexes was as a model for the active site of the
enjume and also a good model for the physical properties of the
protein active sites.
The sulphonamide NH does not participate in bonding due to
structure complication.
ally in the interval ∼165 cm−1, longer values were found for
monodentate and lower values for bidentate groups [40]. Cor-
−1
respondingly, the split of 170–199 cm in complexes indicate
monodentate acetate. This is supported by results of Ryde
[
42].
1
3. Kanagaraj and Rao [33] and El-Sonbati et al. [9,10,16]
had assigned the bands appear as medium to sharp
1
2
. It is also clear has a high affinity for chelation with metal ions
under study accordance to the increasing charge density of the
metal ion and hence to the increasing of their coordination
affinities.
−1
−1
bands at 1345–1340 cm [ꢂasym(SO )] and 1090–1085 cm
2
[
(ꢂsym(SO )] with splits (due to hydrogen bonding) and the
2
stretching vibration band; ꢂ(NH), of the sulphonamide group,
which found at 3358–3375 cm
ꢂ
tion in agreement with the fact that this group was not involved
in the coordination.
−1
in the free ligands. The
. The formula [(Ni) (HLn) (␮-OAc) (OAc) ]n (Fig. 3) has been
3
2
2
4
asym(SO ) and ꢂsym(SO ) remained unaffected upon coordina-
2
2
proposed on the basis of analytical and various physico-
chemical data. The hydrazone is bonded to the metal ion in
bis-tetradentate fashion through carbonyl oxygen, NH (hydra-
zone), NH (rhodanine) and sulphur (thione rhodanine) groups
as inferred from IR and 1H NMR spectra.
3
.10. 1H NMR spectra
3
. These results also confirm the non-reactivity of the R group in
coordination (see Figs. 2 and 3).
The proton magnetic resonance of the ligands (Figs. 4a–8a,
Table 3) and complexes have been recorded in DMSO-d6 using
TMS as the internal standard. The broad signal exhibited by the
ligands can be assigned to intramolecular hydrogen bonded proton
of NH (hydrazone) (8.9–12 ppm), NH(3-phenylamine) and Ph-NH
4. The calculations show that HLn studied exist in a molecular
form with the intramolecular O–HN form.
5. The present study demonstrates perfectly an application of IR
spectra and molecular modeling in revealing not only the mul-
tiple inter/intramolecular of ␲–␲ stacking among the aromatic
groups as well as the hydrophobic interactions among hydro-
gen bonding species between hydrazide moieties involving in
a series of novel hydrazide based azo drug derivatives.
6. We have synthesized and fully characterized five (complexes
1–5) new Lewis bas adducts of bis-metal(II) polymeric nature.
7. Evidence for all polymeric nature come from its solubility prop-
erties and the metal complex to ligand stoichiometry which is
shown to be 3:2 from the elemental analysis. IR spectroscopy
provides partial evidence that the ligand and/or acetate is act-
ing as a bridge, and that bridging occurs through both the S
and NH from side and through O and NH (hydrazone) from the
other side besides to OAc.
(
9.0–11.9 ppm) and NH C (≈8.9 ppm) were not affected by dilution
and disappear in the presence of D O (Figs. 4b–8b) and the first
2
and third bands also disappear in uranyl complexes and the sec-
ond shifted to ∼8.8 ppm indicating the coordination of the nitrogen
atoms with the metal ion according to El-Sonbati et al. [8–10]. Fur-
ther, the CH (3.4–4.25 ppm) signal vanishes and a new NH and C
N
signal appears upon complexation i.e. change from azo to hydrazo
form. The chemical shift due to aromatic ring protons appear at
ı = 7.8–8.3 ppm in the ligands. The spectrum of HL1 exhibits a sin-
glet at ca. ı 2.45 ppm equivalent to the 6H of two methyl groups.
3.11. Mode of coordination of ligand
The free amide group (NH) in HL has a planer structure with
8. It is clear that all the three bonding sites (3-NH, CO and hydrazo
group) would introduce certain steric restrictions and hence
either both the hydrazo nitrogen and the carbonyl group would
coordinate or the NH group of 3-phenylamine and the carbonyl
group would coordinate. The coordination of NH group of 3-
phenylamine and the carbonyl group seems unlikely in view of
the large size of chelated ring (see Fig. 2).
9. The effect of electron withdrawing substituents to ligands in
their polymeric nickel complexes enhance the stabilities of
these complexes owing to the decrease of electron density at
the metal central atom and thus the increase the positive charge
on the metal. This effect results in decreasing reactivity. In con-
trast, the electron donating substituents increase the electron
density at the metal leading to decreased stability of the metal
chelates.
certain resonance stabilization energy [34]. The amide nitrogen
2
coordination without deprotonation will change the sp hybridiza-
tion of the nitrogen atom into an sp3 hybridization with loss of
the stabilization energy as well as the planar structure. On the
other hand, the carbonyl–oxygen-coordination will require only
the donation of a lone pair of electrons to a metal without change in
hybridization and loss of the resonance energy. Therefore, oxygen-
coordination is more favoured than nitrogen-coordination for a
non-deprotonated HLn group. The result of the present study as well
as our results [1–9] obtained so far various metal chelates support
completely the above view.
4
. Conclusion
A series of Ni(II) polymer complexes with ligands (HL1–5
)
10. It is also clear has a high affinity for chelation with metal ions
under study accordance to the increasing charge density of the
metal ion and hence to the increasing of their coordination
affinities.
have been prepared and fully characterized. The characteristics of
the prepared polymer complexes are discussed. The coordination
behaviour of the anions is also discussed on the basis of IR and molar

7
66
A.Z. El-Sonbati et al. / Spectrochimica Acta Part A 77 (2010) 755–766
1
1. The ligand is exhibiting biambidenticity. It behaves as a
tetradentate SNON in Ni(II) complexes. All the nickel polymeric
complexes are paramagnetic but they are strikingly showing
subnormal magnetic moments probably due to metal–metal
interaction and superexchange phenomena.
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5
[
4
Further studies with the title ligand, using different metal ions,
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58 (2002) 1623.
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The purpose for the synthesizing bis-azo/hydrazo drug rhoda-
nine polymeric complexes was as a model for the active site of
the enjume and also a good model for the physical properties of
the protein active sites. An octahedral geometry was suggested for
all the complexes. All the complexes show subnormal magnetic
moments. The richness of electronic spectral in these complexes is
also supporting evidence for the trinuclearity of the Ni(II) polymer
complexes. These complexes are used in some chemical processes
as catalyst and also as biological models in understanding the struc-
ture of biomolecules and biological processes.
21] A.T. Mubarak, A.Z. El-Sonbati, A.A. El-Bindary, R.M. Issa, H.M. Kera, Appl.
Organomet. Chem. 20 (2006) 819.
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