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

Spectrochimica Acta Part A 81 (2011) 290–295

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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

Article history: 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

a b s t r a c t 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, 1 H 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. © 2011 Elsevier B.V. All rights reserved.

1. Introduction The synthesis and characterization of metal complexes with bioactive organic ligands to produce novel potential chemotherapeutic 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 microorganisms’ 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 characterization 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

properties [6–8]. This includes the search for potential applications of these new materials [9]. There is also evidence that the transition metal complexes in polymer matrices show relatively 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 characterization 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

∗ Corresponding author. Tel.: +91 11 2682 3254; fax: +91 11 2684 0229. E-mail address: nishat [email protected] (N. Nishat). 1386-1425/$ – see front matter © 2011 Elsevier B.V. All rights reserved. doi:10.1016/j.saa.2011.06.012

Piperazine (s.d. fine-chem. Ltd), Salicylic acid, formaldehyde, (37% aqueous solution), sodium hydroxide (Merck)

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and Manganese(II) acetate tetrahydrate Mn(CH3 COO)2 ·4H2 O, Cobalt(II) acetate tetrahydrate Co(CH3 COO)2 ·4H2 O, Nickel(II) acetate tetrahydrate Ni(CH3 COO)2 ·4H2 O, Cooper(II) acetate monohydrate Cu(CH3 COO)2 ·H2 O, and Zinc(II) acetate dihydrate Zn(CH3 COO)2 ·2H2 O (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 purified 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).

AMU. In this work Escherichia coli, Bacillus subtilis, Staphylococcus aureus, Pseudomonas flourescence, Salmonella typhi, Candida albicans, Aspergillus niger and Microsporum canis were used to investigate 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 sterilized 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 compound 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).

3. Synthesis

3.4. Characterization

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 containing 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 stirring. 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 chromatography (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%.

The elemental analysis of metal coordinated polymers was carried 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 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. Proton nuclear magnetic resonance spectra were recorded on a Jeol GSX 300 MHz FX-1000 FT NMR spectrometer using DMSO as a solvent 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 temperature. Apart from these the antimicrobial activity of all synthesized compounds was also determined against various selected microorganisms 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 tetrahydrate (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 distilled 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 carried out in two steps, in the first step salicylic acid reacts with formaldehyde in (1:1) molar ratio. While in the second step 2hydroxy-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 insolubility 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

OH

O N

O

N

HO

OH OH

Scheme 1. Suggested structure of SFP ligand.

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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O

O

HO CH2 OH

+

OH

O

H2C

OH

OH 2-hydroxybenzoic acid

formaldehyde

2-hydroxy-5-(hydroxymethyl)benzoic acid H N

O HO CH2

OH OH

+

N H piperazine

OH

O CH2 N

O

N CH2

OH OH

HO

Metal Acetate

Metal Acetate

O X M X

O

O

O CH2 N

N CH2

O H

O O H

X

O M'

M X

O CH2 N

N CH2

O O H

O H

M'

M= Mn(II), Co(II), Ni(II) and Cu(II) M'=Zn(II)

X=H2O Scheme 2. Proposed reaction scheme for SFP ligand and its polymer metal complexes.

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 measurements. 4.1. FT-IR spectra 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

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 C O stretching vibration of salicylic acid at 1635 cm−1 of SFP ligand 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 polymers 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.

Table 1 Analytical data of coordination polymers of SFP ligand. Compounds

SFP [Mn(II)–SFP(H2 O)2 ]n [Co(II)–SFP(H2 O)2 ]n [Ni(II)–SFP(H2 O)2 ]n [Cu(II)–SFP(H2 O)2 ]n [Zn(II)–SFP]n

Empirical formula

C20 H22 N2 O6 [MnC20 H24 N2 O8 ]n [CoC20 H24 N2 O8 ]n [NiC20 H24 N2 O8 ]n [CuC20 H24 N2 O8 ]n [ZnC20 H20 N2 O6 ]n

Formula weight of repeating units

386.40 475.35 479.34 479.10 483.95 449.79

Yield (%)

79 70 85 79 80 75

Calculated (found) (%) C

H

N

M

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)

– 11.56 (11.58) 12.29 (12.36) 12.25 (12.31) 13.13 (13.15) 14.54 (14.59)

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Table 2 The IR spectral bands and their assignments for SFP ligand and its polymer metal complexes. Compounds

Assignments

SFP SFP–Mn(II) SFP–Co(II) SFP–Ni(II) SFP–Cu(II) SFP–Zn(II)

4.2.

1H

(–OH)

CH (asym–sym)

C O

C C

(C–O)

M–O

(C–N)

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

– 530m 537m 525m 530m 533m

1390 1373w 1370w 1365w 1367w 1370w

NMR spectra

The 1 H 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 ligand 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 indicate the presence of –CH2 –CH2 –groups of the piperazine moiety and a resonance signal appeared at 3.1 is due to proton of benzylic methylene group. The results of 1 H NMR spectra reveal that the piperazine moieties are attached to the salicylic acid with the methylene groups of formaldehyde.

Fig. 1.

1

H NMR spectra of SFP ligand.

In the 1 H NMR spectra of SFP–Zn(II) the signal for the protons 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 interaction towards the metal ion and variation in the ␲-electron density around the protons. 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 , 19,178 cm−1 , and 24,498 cm−1 , which have been assigned to the transition 6 A1g → 4 T1g (G), 6 A → 4 T (G) and 6 A (F) → 4 T (F) respectively, suggesting an 1g 2g 1g 1g 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 4 T1g (F) → 4 T2g , 4 T1g (F) → 4 A2g , and 4 T (F) → 4 T (P) respectively. The value of the ligand field split1g 1g 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) polymer metal complex gave three bands at 10,816 cm−1 , 17,025 cm−1 and 25,302 cm−1 corresponding to the transition 3 A2g (F) → 3 T2g (F), 3 A (F) → 3 T (F) and 3 A (F) → 3 T (P) respectively. The electronic 2g 1g 2g 1g spectra of the Cu(II) polymer metal complex [25] exhibit a band at 15,700 cm−1 assigned to the 2 Eg → 2 T2g transition considering an 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

Fig. 2.

1

H NMR spectra of SFP–Zn.

The thermal behavior of the coordination polymers was investigated 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 thermogram in the temperature range 25–150 ◦ C for the parent ligand, may be attributed to loosely bonded moisture. However, the gradual 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 decomposition for the entire coordination polymer is initially low up to 150 ◦ C

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Table 3 Magnetic susceptibility and electronic spectra of SFP ligand and its polymer metal complexes. Abbreviation

SFP–Mn(II)

Magnetic moment (BM)

5.29

SFP–Co(II)

4.72

SFP–Ni(II)

3.20

SFP–Cu(II)

2.06

SFP–Zn(II)

Diamagnetic

Electronic spectral data Electronic transition

Assignment (cm−1 )

24,498 19,178 14,083 23,430 19,078 15,280 25,302 17,025 10,816 25,380 15,700 –

4

Tlg (F) ← 6 Alg (F) T2g (G) ← 6 Alg (F) 4 Tlg (G) ← 6 Alg (F) 4 Tlg (P) ← 4 Tlg (F) 4 A2g (F) ← 4 Tlg (F) 4 T2g (F) ← 4 T1g (F) 3 Tlg (P) ← 3 A2g (F) 3 Tig (F) ← 3 A2g (F) 3 T2g (F) ← 3 A2g (F) Charge-transfer 2 T2g ← 2 Eg –

10 Dq

B

ˇ

ˇ%

Geometry

5200

867

0.90

10

Octahedral

11,710

0.87

976

13

Octahedral

12,080

0.69

755

31

Octahedral

–

–

–

–

Distorted Octahedral

–

–

–

–

Tetrahedral

4

Table 4 Thermal properties of SFP ligand and its polymer metal complexes. Compounds

SFP SFP–Mn(II) SFP–Co(II) SFP–Ni(II) SFP–Cu(II) SFP–Zn(II)

Weight left (%) at the indicated temperature (◦ C)

Characteristic weight left

100

200

300

400

500

600

700

(%) at 800 ◦ C

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

and gradually increases to a maximum in the range of 250–600 ◦ C at which almost 70–85% loss in weight occurred. The remarkable difference is observed in the thermal degradation of the parent ligand and its coordination polymer. The SFP ligand follows a 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 decomposition 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. 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 enrichment 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 predicted amongst these five coordination polymers and SFP ligand are Cu–SFP > Mn–SFP > Co–SFP > Ni–SFP > Zn–SFP > SFP-ligand. 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 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 SFP–Mn(II) SFP–Co(II) SFP–Ni(II) SFP–Cu(II) SFP–Zn(II)

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

a

14–15 mm: significant activity; 7–13 mm: moderate activity;

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 antibacterial 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 Table 6 Antifungal activity of SFP ligand and its polymer metal complexes. Compounds

SFP SFP–Mn(II) SFP–Co(II) SFP–Ni(II) SFP–Cu(II) SFP–Zn(II) Fig. 3. Thermograms of SFP ligand and its polymer metal complexes.

a

Zones diameter showing complete growth inhibition (mm)a C. albicans

M. canis

A. niger

13 14 15 20 21 19

15 12 13 21 22 20

16 13 17 19 22 19

14–22 mm: significant activity; 7–13 mm: moderate activity.

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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 -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 microorganisms, 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. 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 composition, 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 character of water molecules as ligands. The following decomposition step in the case of this compound could be associated with formation of a stable intermediate with SFP-ligand, coordinated to metal ion. The thermal stability of SFP–Cu(II) is better amongst coordination 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 financial assistance. The authors express their sincere thanks to “The

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