Preparation, spectral and biological investigation of formaldehyde-based ligand containing piperazine moiety and its various polymer metal complexes

Article abstract of DOI:10.1016/j.saa.2011.06.012

A novel tetradentate salicylic acid-formaldehyde ligand containing piperazine moiety (SFP) was synthesized by condensation of salicylic acid, formaldehyde and piperazine in presence of base catalyst, which was subjected for the preparation of coordination polymers with metal ions like manganese(II), cobalt(II), copper(II), nickel(II) and zinc(II). All the synthesized polymeric compounds were characterized by elemental analysis, IR, ¹H NMR and electronic spectral studies. The thermal stability was determined by thermogravimetric analysis and thermal data revealed that all the polymer metal complexes show good thermal stability than their parent ligand. Electronic spectral data and magnetic moment values revealed that polymer metal complexes of Mn(II), Co(II) and Ni(II) show an octahedral geometry while Cu(II) and Zn(II) show distorted octahedral and tetrahedral geometry respectively. The antimicrobial screening of the ligand and coordination polymers was done by using Agar well diffusion method against various bacteria and fungi. It was evident from the data that antibacterial and antifungal activity increased on chelation and all the polymer metal complexes show excellent antimicrobial activity than their parent ligand.

Full text of DOI:10.1016/j.saa.2011.06.012

Spectrochimica Acta Part A 81 (2011) 290–295
Contents lists available at ScienceDirect
Spectrochimica Acta Part A: Molecular and
Biomolecular Spectroscopy
journal homepage: www.elsevier.com/locate/saa
Preparation, spectral and biological investigation of formaldehyde-based ligand
containing piperazine moiety and its various polymer metal complexes
Shamim Ahmad Khan, Nahid Nishat∗, Shadma Parveen, Raza Rasool
Materials Research Laboratory, Department of Chemistry, Jamia Millia Islamia, New Delhi 110025, India
a r t i c l e i n f o
a b s t r a c t
Article history:
A novel tetradentate salicylic acid–formaldehyde ligand containing piperazine moiety (SFP) was synthe-
sized by condensation of salicylic acid, formaldehyde and piperazine in presence of base catalyst, which
was subjected for the preparation of coordination polymers with metal ions like manganese(II), cobalt(II),
copper(II), nickel(II) and zinc(II). All the synthesized polymeric compounds were characterized by ele-
mental analysis, IR, 1H NMR and electronic spectral studies. The thermal stability was determined by
thermogravimetric analysis and thermal data revealed that all the polymer metal complexes show good
thermal stability than their parent ligand. Electronic spectral data and magnetic moment values revealed
that polymer metal complexes of Mn(II), Co(II) and Ni(II) show an octahedral geometry while Cu(II) and
Zn(II) show distorted octahedral and tetrahedral geometry respectively. The antimicrobial screening of
the ligand and coordination polymers was done by using Agar well diffusion method against various
bacteria and fungi. It was evident from the data that antibacterial and antifungal activity increased on
chelation and all the polymer metal complexes show excellent antimicrobial activity than their parent
ligand.
Received 6 April 2011
Received in revised form 2 June 2011
Accepted 13 June 2011
Keywords:
Formaldehyde-based ligand
Coordination polymers
Condensation
Thermogravimetric analysis
Agar well diffusion method and
antimicrobial activity
© 2011 Elsevier B.V. All rights reserved.
1. Introduction
properties [6–8]. This includes the search for potential appli-
cations of these new materials [9]. There is also evidence that
The synthesis and characterization of metal complexes with
bioactive organic ligands to produce novel potential chemother-
apeutic agents is rapidly developing. Of particular note is the
pressing need for new antibacterials to replace those losing their
effectiveness because of the fast development of microorgan-
isms’ resistance [1]. Thus, the discovery of new antimicrobial
compounds or increasing the effectiveness of previously known
drugs is important [2]. Several antibacterial polymers have
been synthesized by immobilization of low-molecular-weight
antibacterial agents to polymers [3]. The controlled aggregation
of small coordination-complex based building blocks to form
larger architectures is of great interest in both metal–ligand and
polyoxometalate chemistry [4]. Particularly, the ability to use both
ligand design and adjustment of reaction conditions to understand
and control the aggregation processes is crucial. The combination
of these approaches should yield the best chance of synthesizing
sophisticated, potentially functional, complexes and clusters [5].
In recent years, intense research efforts on synthesis and char-
acterization of metal–organic coordination polymers has led to
significant advances in both their theoretical description and the
search for novel electronic, optical, magnetic, and physicochemical
the transition metal complexes in polymer matrices show rela-
tively interesting chemical and catalytic reactivity towards various
small gas molecules. This reactivity has been shown to take place
under relatively mild conditions that are different from those of
the corresponding free transition metal complexes or those in
inorganic oxide-supported systems [10–12]. The characterization
of ion-containing polymers has been the subject of numerous
investigations. It has been demonstrated that the thermophysical
properties of ligands can be modified by coordination to transition
metal complexes [13–15]. The investigation of biological activity
of the synthesized SFP ligand and its polymer metal complexes
towards two kind of organism chosen for the investigation, i.e.
fungus and bacterium.
According to present article, we describe the synthesis and char-
acterization of a novel SFP ligand and its polymer metal complexes
containing Mn(II), Co(II), Ni(II), Cu(II) and Zn(II) metal ions. In this
SFP ligand the position of two salicylic acid are linked with linear
aliphatic chain of formaldehyde and piperazine unit at its first and
fifth carbon atom as shown in Scheme 1.
2. Experimental
2.1. Materials and strains
∗
Piperazine (s.d. fine-chem. Ltd), Salicylic acid, formalde-
hyde, (37% aqueous solution), sodium hydroxide (Merck)
Corresponding author. Tel.: +91 11 2682 3254; fax: +91 11 2684 0229.
E-mail address: nishat nchem08@yahoo.com (N. Nishat).
1386-1425/$ – see front matter © 2011 Elsevier B.V. All rights reserved.
doi:10.1016/j.saa.2011.06.012

S.A. Khan et al. / Spectrochimica Acta Part A 81 (2011) 290–295
291
AMU. In this work Escherichia coli, Bacillus subtilis, Staphylococ-
cus aureus, Pseudomonas flourescence, Salmonella typhi, Candida
albicans, Aspergillus niger and Microsporum canis were used to inves-
tigate the bacteriological and antifungal activities of the SFP ligand
and its polymer metal complexes. Accordingly agar well diffusion
method, bacteria were incubated on Muller Hinton Agar (Difco) and
yeast on Sabouraud Dextrose Agar (Difco). The SFP ligand and its
polymer metal complexes (100 ␮g/ml) were dissolved in DMF. A
circular well was made at the centre of each petri dish with a ster-
ilized steel borer. Then 0.1 ml of each test solution was added to
the well and incubated at about 37 ◦C for 24 h and yeast sample
were incubated 30 ◦C for 72 h. The experiment was repeated three
times simultaneously under the same conditions for each com-
pound and the mean value obtained for the three wells was used
to calculate the zone of growth inhibition of each sample. DMF was
used for the positive control only. The resulting inhibition zones
on the dish were measured in mm, and compared with Kanamycin
as a standard drug for the antibacterial activity and Miconazole for
antifungal activity (Tables 5 and 6).
OH
O
N
N
O
OH
HO
OH
Scheme 1. Suggested structure of SFP ligand.
and Manganese(II) acetate tetrahydrate Mn(CH3COO)2·4H2O,
Cobalt(II) acetate tetrahydrate Co(CH3COO)2·4H2O, Nickel(II)
acetate tetrahydrate Ni(CH3COO)2·4H2O, Cooper(II) acetate
monohydrate Cu(CH3COO)2·H2O, and Zinc(II) acetate dihydrate
Zn(CH3COO)2·2H2O (Qualigens fine chemicals) were used without
further purification. Solvents such as acetone, methanol, diethyl
ether, dimethylformamide (DMF), dimethylsulfoxide (DMSO) (s.d.
fine-chem. Ltd), ethanol (Jiangsu Hauxi International), were puri-
fied by standard procedures before use. All the microorganisms
were provided by the culture collection centre of Microbiology
Laboratory, Department of Microbiology (A.M.U. Aligarh).
3.4. Characterization
3. Synthesis
The elemental analysis of metal coordinated polymers was car-
ried out on Perkin Elmer Model-2400 [IIT, Roorkee]. The metal
content of the SFP ligand were determined by complexometric
titration against EDTA after decomposing with concentrated nitric
3.1. Synthesis of ligand SFP
The SFP ligand containing salicylic acid, piperazine and
formaldehyde was prepared according to the procedure [16] in
which salicylic acid (0.01 mol) and formaldehyde (0.01 mol) of (1:1)
molar ratio was taken in 250 ml three necked round bottom flask
equipped with thermometer condenser and magnetic stirrer con-
taining dimethyl formamide (DMF) (∼50 ml) as a solvent. One or
two drop of 40% aqueous NaOH was added in this reaction mixture
and the temperature rose up to 70 ◦C for 3 h with continuous stir-
ring. After that (0.01 mol) of piperazine solution in 25 ml DMF was
added to this system and stirred again for about 1 h up to 90–100 ◦C.
The progress of reaction was monitored by thin layered chromatog-
raphy (TLC). The reaction mixture was cooled and precipitated into
50/50 (v/v) water/acetone mixture. The solid cream color product
(SFP-ligand) was filtered, and reprecipitated from DMF in ethanol,
followed by filtering and washing repeatedly with distilled water
and acetone, and dried in a vacuum oven to remove the solvent
(DMF and ethanol), the yield was 79%.
acid. The FT-IR spectra were recorded over the (4000–400 cm−1
)
range on a Perkin Elmer infrared spectrophotometer model 621
using KBr pellets. The UV–vis spectra were carried on a Perkin Elmer
Lambda EZ-201 spectrophotometer using DMSO as a solvent. Pro-
ton nuclear magnetic resonance spectra were recorded on a Jeol
GSX 300 MHz FX-1000 FT NMR spectrometer using DMSO as a sol-
vent and tetramethylsilane (TMS) as an internal standard. Thermal
behavior [thermogravimetric analysis – TGA] of all the synthesized
polymeric compounds was determined on a TA analyzer 2000 in
nitrogen atmosphere. TGA was carried out at a heating rate of 20
and 10 ◦C min−1, respectively. The solubility of the SFP ligand and
its metal complexes was tested in various solvents at room temper-
ature. Apart from these the antimicrobial activity of all synthesized
compounds was also determined against various selected microor-
ganisms from the Microbiological Laboratory of A.M.U.
3.2. Synthesis of polymer metal complexes
4. Results and discussion
All the polymer metal complexes were prepared by using
equimolar ratio (1:1) of SFP ligand and metal salts. The synthetic
route (Scheme 2) for the preparation of polymer metal complex of
Mn(II) is given as: A hot solution of manganese(II) acetate tetrahy-
drate (2.45 g, 0.01 mol in 10 mL DMF) was added to a solution of
SFP ligand (3.86 g, 0.01 mol in 20 ml DMF). The reaction mixture
was refluxed at 80 ◦C for 3 h with constant stirring. It turned brown
which was precipitated in distilled water. Finally the product was
filtered, washed with distilled water, alcohol and acetone and dried
in a vacuum desiccator on calcium chloride, the yield was 70%.
A similar procedure was adopted for the synthesis of the other
polymer metal complexes such as SFP–Co(II), SFP–Ni(II) SFP–Cu(II)
and SFP–Zn(II), their yields were between 75 and 85% and the
obtained product was found to be soluble in DMF and DMSO and
insoluble in most of the other common organic solvents and dis-
tilled water.
The analytical data of the SFP ligand and its polymer metal
complexes and some physical properties are listed in Table 1.
Salicylic acid containing formaldehyde in piperazine (SFP) was
obtained by the condensation process. The reaction was car-
ried out in two steps, in the first step salicylic acid reacts with
formaldehyde in (1:1) molar ratio. While in the second step 2-
hydroxy-5-(hydroxymethyl)benzoic acid and piperazine undergo
condensation and forms SFP ligand. The SFP ligand and polymer
metal complexes were soluble in DMF and DMSO and insoluble in
most of the common organic solvents such as benzene, methanol,
ethanol and water. The polymer metal complexes were obtained by
the reaction of SFP ligand with metal acetate in DMF in (1:1) molar
ratio. All the polymer metal complexes were colored and obtained
in good yield. Various facts such as the nature of the SFP ligand, high
thermal stability and metal to SFP ligand ratio (1:1) and insolubil-
ity of the polymer metal complexes in common organic solvents
suggest their polymeric nature [17]. Elemental analysis, physical
properties and IR data provide good evidence that the compounds
are polymeric [18]. The insolubility of the polymer metal complexes
in common organic solvents does not permit the determination of
the molecular weight. The elemental analysis (Table 1) showed that
3.3. Preparation of microbial cultures
The microorganisms used in the study were provided by the
culture collection centre of the Microbiological Laboratory of the

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S.A. Khan et al. / Spectrochimica Acta Part A 81 (2011) 290–295
O
O
HO CH2
OH
OH
OH
2-hydroxybenzoic acid
O
H2C
+
OH
formaldehyde
HO CH2
2-hydroxy-5-(hydroxymethyl)benzoic acid
H
N
O
OH
OH
+
N
H
piperazine
OH
O
O
CH2
N
N
CH2
OH
HO
OH
Metal Acetate
Metal Acetate
O
O
O
O
CH2
N
N
CH2
CH2
N
N
CH2
X
X
O
O
O
O
M'
M'
M
X
M
X
O
H
O
H
O
H
O
H
M= Mn(II), Co(II), Ni(II) and Cu(II)
M'=Zn(II)
X=H O
2
Scheme 2. Proposed reaction scheme for SFP ligand and its polymer metal complexes.
polymers is the presence of more broadened bands in the region of
3300–3450 cm−1 for the coordination polymer, as the oxygen of the
O–H group of the ligand forms a coordination bond with the metal
ions [19–21]. This is explained by the fact that water molecules
might have strongly absorbed to the polymer sample during their
formation. Another noticeable difference is the band due to the
SFP ligand to metal ratio in all the polymer metal complexes was
1:1, in good agreement with the calculated values. The structure of
SFP ligand and its polymer metal complexes was also confirmed by
IR, proton NMR, UV–visible and magnetic susceptibility measure-
ments.
C
O stretching vibration of salicylic acid at 1635 cm−1 of SFP lig-
4.1. FT-IR spectra
and which is shifted to lower frequency. The band at 1285 cm−1
of SFP ligand assigned to in-plane OH deformation, [22] is shifted
towards higher frequency in the spectra of the coordination poly-
mers due to the formation of metal–oxygen bonds. This has been
further confirmed by a band at 525–537 cm−1 corresponding to
C–O–M stretching [23]. Thus, all these characteristic features of
the IR studies suggest the proposed structure of the coordination
polymer as shown in Scheme 2.
The infrared spectra of the SFP ligand and their polymer metal
complexes are presented in Table 2. They resemble each other in
their general shape, but the comparison of the IR spectrum of the
parent ligand (SFP) with those of its coordination polymers has
revealed certain characteristics differences.
One of the significant differences to be expected between the
IR spectrum of the parent ligand (SFP) and its metal coordinated
Table 1
Analytical data of coordination polymers of SFP ligand.
Compounds
Empirical formula
Formula weight of repeating units
Yield (%)
Calculated (found) (%)
C
H
N
M
SFP
C20H22N2O6
386.40
475.35
479.34
479.10
483.95
449.79
79
70
85
79
80
75
62.17 (62.26)
50.53 (50.62)
50.11 (50.24)
50.14 (50.30)
49.64 (49.80)
53.41 (53.40)
5.74 (5.72)
5.09 (4.99)
5.05 (4.97)
5.05 (5.10)
5.00 (4.99)
4.48 (4.50)
7.25 (7.31)
5.89 (5.85)
5.84 (5.83)
5.85 (5.91)
5.79 (5.79)
6.23 (6.23)
–
[Mn(II)–SFP(H2O)2]n
[Co(II)–SFP(H2O)2]n
[Ni(II)–SFP(H2O)2]n
[Cu(II)–SFP(H2O)2]n
[Zn(II)–SFP]n
[MnC20H24N2O8]n
[CoC20H24N2O8]n
[NiC20H24N2O8]n
[CuC20H24N2O8]n
[ZnC20H20N2O6]n
11.56 (11.58)
12.29 (12.36)
12.25 (12.31)
13.13 (13.15)
14.54 (14.59)

S.A. Khan et al. / Spectrochimica Acta Part A 81 (2011) 290–295
293
Table 2
The IR spectral bands and their assignments for SFP ligand and its polymer metal complexes.
Compounds
Assignments
ꢀ(–OH)
CH (asym–sym)
ꢀC
O
ꢀC
C
ꢀ(C–O)
ꢀM–O
ꢀ(C–N)
SFP
3440s
3420b
3410b
3412b
3415b
3425b
2920–2850
2920–2850
2920–2850
2920–2850
2920–2850
2920–2850
1635s
1625s
1629s
1622s
1623s
1630s
1460m
1450m
1445m
1443m
1447m
1452m
1285s
1290s
1287s
1292s
1284s
1295s
–
1390
SFP–Mn(II)
SFP–Co(II)
SFP–Ni(II)
SFP–Cu(II)
SFP–Zn(II)
530m
537m
525m
530m
533m
1373w
1370w
1365w
1367w
1370w
4.2. 1H NMR spectra
In the 1H NMR spectra of SFP–Zn(II) the signal for the pro-
tons of –COOH group disappeared, suggesting the participation of
–COOH proton to the metal centre in the formation of COO–M and
the protons of phenolic –OH group were shifted towards down
field at 3.81 ppm, due to the coordination of phenolic oxygen with
metal and a significant shifting in all the peaks was observed which
confirm the formation of polymer metal complexes. The peak of
aromatic protons became broad due to the intermolecular interac-
tion towards the metal ion and variation in the ␲-electron density
around the protons.
The 1H NMR spectra of SFP ligand and its polymer complex
of Zn(II) are shown in Figs. 1 and 2. The aromatic protons show
multiple resonance signals between 6.70 and 7.85 ppm for SFP lig-
and and SFP–Zn(II), respectively. The singlet corresponding to one
proton at 10.6 ppm is assigned to –COOH group and a resonance
signals appeared at 5.10 ppm is due to the proton of phenolic –OH
group [24] where as the resonance signal found at 2.46 ppm indi-
cate the presence of –CH2–CH2–groups of the piperazine moiety
and a resonance signal appeared at 3.1 is due to proton of ben-
zylic methylene group. The results of 1H NMR spectra reveal that
the piperazine moieties are attached to the salicylic acid with the
methylene groups of formaldehyde.
4.3. Magnetic moments and electronic spectra
Magnetic moments (ꢁeff) of the polymeric metal complexes are
given in Table 3. Examining these data reveals that all coordination
polymers other than that of Zn(II) are paramagnetic while that of
Zn(II) is diamagnetic.
The electronic spectra of manganese(II) chelate show three
weak bands at 14,083 cm−1
which have been assigned to the transition A1g → T1g (G),
, , ,
19,178 cm−1 and 24,498 cm−1
6
4
4
6
4
6A1g → T2g(G) and A1g(F) → T1g(F) respectively, suggesting an
octahedral structure of SFP–Mn(II) polymer metal complex. The
electronic spectra of Co(II) polymer metal complex shows three
bands at 15,280 cm−1, 19,078 cm−1, and 23,430 cm−1 which have
been assigned to the transitions 4T1g(F) → T2g
,
4T1g(F) → A2g, and
4
4
4
4T1g(F) → T1g(P) respectively. The value of the ligand field split-
ting energy (10 Dq), Racah interelectronic repulsion parameter (B),
nephelauxetic ratio (ˇ) and ˇ% are presented in Table 3 and are
consistent with values for an octahedral structure. The Ni(II) poly-
mer metal complex gave three bands at 10,816 cm−1, 17,025 cm−1
and 25,302 cm−1 corresponding to the transition 3A2g(F) → T2g(F),
3
3A2g(F) → T1g(F) and 3A2g(F) → T1g(P) respectively. The electronic
3
3
spectra of the Cu(II) polymer metal complex [25] exhibit a band at
15,700 cm−1 assigned to the 2Eg → T2g transition considering an
2
Fig. 1. 1H NMR spectra of SFP ligand.
octahedral geometry. A strong charge transfer band is observed at
25,380 cm−1 As the spectrum of the Zn(II) polymer metal complex
is not well resolved, it is not interpreted but its ꢁeff values shows
that it is diamagnetic as expected.
4.4. Thermogravimetric analysis
The thermal behavior of the coordination polymers was investi-
gated by thermalgravimetric analysis (TGA). TGA data of all samples
are presented in Table 4 and the thermograms are shown in Fig. 3.
The initial degradation temperature of the coordination polymers,
as well as the non-chelated, SFP ligand, is about 25–50 ◦C. A very
slight decrease in weight loss (2–3%) depicted from the thermo-
gram in the temperature range 25–150 ◦C for the parent ligand,
may be attributed to loosely bonded moisture. However, the grad-
ual weight loss that initially occurred below 150 ◦C in all of the
coordination polymers may be due to removal of hydrated water,
where the loss obtained in the range of 150–200 ◦C might be due
to metal-coordinated water molecules [26]. The rate of decomposi-
tion for the entire coordination polymer is initially low up to 150 ◦C
Fig. 2. 1H NMR spectra of SFP–Zn.

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S.A. Khan et al. / Spectrochimica Acta Part A 81 (2011) 290–295
Table 3
Magnetic susceptibility and electronic spectra of SFP ligand and its polymer metal complexes.
Abbreviation
Magnetic moment (BM)
Electronic spectral data
Electronic transition
10 Dq
B
ˇ
ˇ%
Geometry
Assignment (cm−1
)
6
SFP–Mn(II)
SFP–Co(II)
SFP–Ni(II)
5.29
4.72
3.20
24,498
19,178
14,083
23,430
19,078
15,280
25,302
17,025
10,816
25,380
15,700
–
4Tlg(F) ← Alg(F)
5200
867
0.87
0.69
0.90
976
755
10
13
31
Octahedral
Octahedral
Octahedral
6
4T2g(G) ← Alg(F)
4Tlg(G) ← 6Alg(F)
4
4Tlg(P) ← Tlg(F)
11,710
12,080
4
4A2g(F) ← Tlg(F)
4
4T2g(F) ← T1g(F)
3
3Tlg(P) ← A2g(F)
3
3Tig(F) ← A2g(F)
3
3T2g(F) ← A2g(F)
SFP–Cu(II)
SFP–Zn(II)
2.06
Charge-transfer
–
–
–
–
–
–
–
–
Distorted Octahedral
Tetrahedral
2T2g
–
←
2Eg
Diamagnetic
Table 4
Thermal properties of SFP ligand and its polymer metal complexes.
Compounds
Weight left (%) at the indicated temperature (◦C)
Characteristic weight left
100
200
300
400
500
600
700
(%) at 800 ◦
C
SFP
93
98
95
92
96
96
88
96
90
89
95
95
43
59
58
51
60
51
35
50
49
42
51
41
25
45
41
35
46
36
14
36
31
26
38
30
9
24
20
16
25
19
2
16
13
7
18
11
SFP–Mn(II)
SFP–Co(II)
SFP–Ni(II)
SFP–Cu(II)
SFP–Zn(II)
and gradually increases to a maximum in the range of 250–600 ◦C at
which almost 70–85% loss in weight occurred. The remarkable dif-
ference is observed in the thermal degradation of the parent ligand
anditscoordinationpolymer. TheSFPligandfollowsa two-step[27]
mode as compared to a single-step thermal degradation of the five
coordination polymers. In SFP ligand the first slow step of thermal
degradation in the range of 260–340 ◦C may be due to the decom-
position of a more labile aliphatic bridge present between the two
salicylic acid units and the second step of thermal degradation may
be in the salicylic acid, initiated at 500 ◦C, with a rapid weight loss
at around 550 ◦C and completed at 700 ◦C.
Table 5
Antibacterial activity of SFP ligand and its polymer metal complexes.
Zones diameter showing complete growth inhibition (mm)a
Compounds
E. coli
P. flourescence
B. subtilis
S. aureus
S. typhi
SFP
16
15
19
17
21
19
16
20
17
16
23
18
19
17
17
18
21
18
15
21
18
16
20
17
14
17
17
17
20
18
SFP–Mn(II)
SFP–Co(II)
SFP–Ni(II)
SFP–Cu(II)
SFP–Zn(II)
a
14–15 mm: significant activity; 7–13 mm: moderate activity;
These results revealed that all the polymer metal complexes
show higher thermal stability than the SFP ligand due to the
insertion of metal ions into the polymeric chain as a result of
chelation. Another factor that may be responsible for the enrich-
ment of the thermal stability of the polymer metal complexes
is the increase in the molecular weight due to the joining of
two different polymer chains. The order of thermal stability pre-
dicted amongst these five coordination polymers and SFP ligand
are Cu–SFP > Mn–SFP > Co–SFP > Ni–SFP > Zn–SFP > SFP-ligand.
of inhibition for bacterial growth around the wells. The results of
activity were expressed as inactive, mild, moderate, and high. The
results are summarized in Tables 5 and 6. The results reveal that all
the compounds exhibited antibacterial and antifungal activities to
a certain extent.
All the synthesized compounds were screened for their antibac-
terial activity against E. coli, B. subtilis, S. aureus, P. flourescence,
S. typhi and for their antifungal activity against C. albicans, A.
niger and M. canis. All the compounds generally showed good
antibacterial activity, but more significantly antifungal activity was
observed against most of the strains. A marked enhancement of
activity was exhibited in all the polymer metal complexes against
all the bacterial/fungal strains. It was evident from the data that
4.5. Antimicrobial studies
The antibacterial and antifungal activities of the SFP ligand and
its polymer metal complexes were identified based on the zone
Table 6
Antifungal activity of SFP ligand and its polymer metal complexes.
Compounds
Zones diameter showing complete
growth inhibition (mm)a
C. albicans
M. canis
A. niger
SFP
13
14
15
20
21
19
15
12
13
21
22
20
16
13
17
19
22
19
SFP–Mn(II)
SFP–Co(II)
SFP–Ni(II)
SFP–Cu(II)
SFP–Zn(II)
a
Fig. 3. Thermograms of SFP ligand and its polymer metal complexes.
14–22 mm: significant activity; 7–13 mm: moderate activity.

S.A. Khan et al. / Spectrochimica Acta Part A 81 (2011) 290–295
295
the antimicrobial activity of all the polymeric compounds was
increased on coordination. The chelation/coordination reduces the
polarity of the metal ion by partial sharing of its positive charge with
the donor groups, and possibly ꢂ-electron delocalization within the
whole chelate ring [28]. This process thus increases the lipophilic
nature of the central metal atom [29], which, in turn, favors its
greater penetration through the bacterial wall of the microor-
ganisms, thus killing them more effectively [30]. It has also been
observed that the solubility, conductivity and dipole moment are
also influenced by the presence of metal ions; these could be
the significant factors responsible for increasing the hydrophobic
character and liposolubility of the molecule, hence enhancing the
biological activity.
The results of antibacterial activity reveal that the SFP–Cu(II)
showed the highest antibacterial and antifungal activity than other
polymer metal complexes. This result may have been due to the
higher stability constant of Cu(II) than the other polychelates [31].
According to the stability constant, the Cu(II) ion was made up
of stronger interactions with N and O donor atoms, by which its
lipophilic nature was increased.
Third World Academy of Sciences, Italy” for UV–Visible spectropho-
tometer EZ-201 (PerkinElmer) through research grant scheme No.
00-047 RG/CHE/AS.
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5. Conclusion
SFP ligand and its polymer metal complexes of Mn(II), Co(II),
Ni(II), Cu(II) and Zn(II) metal ion in basic medium were prepared
successfully. These polymer metal complexes showed octahedral
geometries except zinc, as depicted by the electronic spectra, and
the thermal analysis (TGA) of the complexes elucidated the com-
position, the number and nature of water molecules. The presence
of the water molecules in polymer metal complex generated two
decomposition steps which indicate a different bonding charac-
ter of water molecules as ligands. The following decomposition
step in the case of this compound could be associated with forma-
tion of a stable intermediate with SFP-ligand, coordinated to metal
ion. The thermal stability of SFP–Cu(II) is better amongst coordina-
tion polymers. The fairly good antimicrobial activities exhibited by
these polymer metal complexes may help them to find potential
application as effective antimicrobial coating materials.
Acknowledgements
Shamim A. Khan is thankful to UGC (New Delhi, India) for finan-
cial assistance. The authors express their sincere thanks to “The