Synthesis, characterization and antimicrobial studies of Schiff base complexes

Journal of Molecular Structure 1097 (2015) 129–135

Contents lists available at ScienceDirect

Journal of Molecular Structure journal homepage: www.elsevier.com/locate/molstruc

Synthesis, characterization and antimicrobial studies of Schiff base complexes Hina Zafar a, Anis Ahmad b, Asad U. Khan b, Tahir Ali Khan a,⇑ a b

Division of Inorganic Chemistry, Department of Chemistry, Aligarh Muslim University, Aligarh 202002, India Department of Ophthalmology, Storm Eye Institute, Medical University of South Carolina, Charleston, South Carolina, United States

h i g h l i g h t s

g r a p h i c a l a b s t r a c t

 Transitional metal complexes.

Antibacterial, XRD pattern and energy minimized cylindrical bonded 3-dimensional molecular structure of Schiff base [C15H20N4MCl2] complex, where M = Fe(II), Co(II), Ni(II), Cu(II) and Zn(II).

 Octahedral geometry around the

metal ions.  XRD.  Antibacterial study by disc diffusion

method.

a r t i c l e

i n f o

Article history: Received 20 November 2014 Received in revised form 25 April 2015 Accepted 27 April 2015 Available online 14 May 2015 Keywords: Schiff base complexes Octahedral geometry Spectral studies Antimicrobial studies

a b s t r a c t The Schiff base complexes, MLCl2 [M = Fe(II), Co(II), Ni(II), Cu(II) and Zn(II)] have been synthesized by the template reaction of respective metal ions with 2-acetylpyrrole and 1,3-diaminopropane in 1:2:1 M ratio. The complexes have been characterized by elemental analyses, ESI – mass, NMR (1H and 13C), IR, XRD, electronic and EPR spectral studies, magnetic susceptibility and molar conductance measurements. These studies show that all the complexes have octahedral arrangement around the metal ions. The molar conductance measurements of all the complexes in DMSO indicate their non-electrolytic nature. The complexes were screened for their antibacterial activity in vitro against Gram-positive (Streptococcus pyogenes) and Gram-negative (Klebsiella pneumoniae) bacteria. Among the metal complexes studied the copper complex [CuLCl2], showed highest antibacterial activity nearly equal to standard drug ciprofloxacin. Other complexes also showed considerable antibacterial activity. The relative order of activity against S. Pyogenes is as Cu(II) > Zn(II) > Co(II) = Fe(II) > Ni(II) and with K. Pneumonia is as Cu(II) > Co(II) > Zn(II) > Fe(II) > Ni(II). Ó 2015 Elsevier B.V. All rights reserved.

Introduction ⇑ Corresponding author at: Division of Inorganic Chemistry, Department of Chemistry, Aligarh Muslim University, Aligarh 202002, India. E-mail address: [email protected] (T.A. Khan). http://dx.doi.org/10.1016/j.molstruc.2015.04.034 0022-2860/Ó 2015 Elsevier B.V. All rights reserved.

Hugo Schiff in 1864 [1a,b] described the condensation reaction between an aldehyde and amine leading to the formation of a Schiff base. Characteristically Schiff base provides geometrical

130

H. Zafar et al. / Journal of Molecular Structure 1097 (2015) 129–135

cavity control for host–guest interaction and modulation of its lipophilicity offers remarkable selectivity, sensitivity and stability for a specific metal ion [2a–c,3]. Schiff bases have been used as ligands, can coordinate to transition and main group metals [3–6]. A very large number of coordination compounds with the diimine Schiff base ligand and its substituted derivatives have been reported [4,7]. The chelating structures, moderate electron donation and easy tunable electronic and steric effects proved Schiff bases as versatile ligands capable of stabilizing different metals in various oxidation states with unusual structural features and controlling the performance of metals in variety of useful catalytic transformations [3,8]. Schiff bases have been extensively employed in the understanding of molecular processes occurring in biochemistry, material science, hydrometallurgy, catalysis and separation phenomena [3,9a,b,10]. Schiff-bases are considered as a very important class of organic compounds, having wide applications in many biological aspects, proteins, visual pigments, enzymic aldolization and decarboxylation reactions. Moreover, some Schiff’s bases and their metal complexes exhibit antibiotic, antiviral and antitumor agents, activities [11–13a,b]. It has been suggested that the azomethine linkage is responsible for the biological activities of Schiff bases such as, antitumour, antibacterial, antifungal and herbicidal activities [11,14]. We have a long term interest in synthesis and characterization of transition metal complexes of a wide variety [15–17] and recently also studies their biological properties [18–21]. Herein, we report the Schiff base complexes, MLCl2 [M = Fe(II), Co(II), Ni(II), Cu(II) and Zn(II)] which were also studied for their antimicrobial properties.

(0.01 mM DMSO) were recorded on a JEOL JES FA-200 EPR spectrometer at room temperature. Magnetic susceptibility were carried out at 25 °C using a Faraday balance. The electrical conductivities were obtained with a systronics type 302 conductivity bridge equilibrated at 25 ± 0.0 °C using 10 3 M solution in DMSO. The [FeLCl2] complex was characterized by X-ray diffraction. The XRD pattern and different parameters were collected with a Rigaku, Mini Flex II powder diffractometer using X-ray radiation. The antibacterial activity of the synthesized compounds was completed by the disc diffusion method and broth dilution methods [24,25].

Materials and methods

ESI-mass spectra

Metal salts (all Merck) were commercially available pure samples. The 2-acetylpyrrole (Merck) and 1,3-diamino propane (Otto Chemical Pvt. Ltd.) were used as received. Methanol used as the solvent was of A.R. grade.

Mass spectra of Fe(II), Co(II), Ni(II), Cu(II) and Zn(II), complexes showed m/z peaks at 382.04, 386.00, 384.00 391.69 and 392.11 that corresponded to C15H20N4FeCl2, C15H20N4CoCl2, C15H20N4NiCl2 C15H20N4CuCl2 and C15H20N4ZnCl2 moieties, respectively. The proposed molecular formulae of synthesized complexes were

Results and discussion A new series of Schiff base complexes, MLCl2, [Fe(II), Co(II), Ni(II), Cu(II) and Zn(II)] have been prepared by the reaction of 2-acetylpyrrole and 1,3-diaminopropane in presence of respective metal salt in 2:1:1 M ratio as shown in Scheme 1. All the complexes were stable in atmosphere and dissolve in DMF (N,N-Dimethylformamide) and DMSO (Dimethyl sulfoxide). The molar conductance measurements (Table 1) for all the complexes indicate that they are non-electrolytes in DMSO. The formation of complexes was further ascertained on the basis of results of elemental analyses, molecular ion peak in ESI-mass spectra (Table 1), characteristic bands in the FT-IR (Table 2), and resonance signals in the NMR (1H and 13C) spectra. The overall geometry of the complexes was inferred from the magnetic susceptibility, XRD, electronic and EPR spectra.

Synthesis of the complexes In this synthesis of complexes, MLCl2, [M = Fe(II), Co(II), Ni(II), Cu(II) and Zn(II), L = ligand] 25 ml of a methanolic solution of the respective metal salt (5 mmol) was placed in a three necked round bottom flask, then methanolic solutions of 2-acetylpyrrole (10 mmol) and 1,3-diaminopropane (5 mmol) were added drop wise with continuous stirring in 1:2:1 M ratio. The resulting mixture was stirred for about 4 h and the solid product obtained, was filtered, washed several times with methanol and dried in vacuo.

MCl 2 Metal salt

CH3

N H

H2N

O

NH2

1,3-diaminopropane

2-acetylpyrrole Measurements

Stirring The elemental analyses for carbon, hydrogen and nitrogen were obtained from the Sophisticated Analytical Instrumental Facility, Chandigarh India. The 1H and 13C NMR spectra were recorded on a JEOL GSX 300 MHz FX-1000 spectrometer using DMSO-d6 as a solvent and tetramethylsilane (Me4Si) as an internal standard. The IR spectra were recorded in the region 4000–400 cm 1 by using FT-IR Perkin Elmer spectrometer (2400) and in the region 700–30 cm 1 by using FT-IR/FIR Perkin Elmer (Frontier) spectrometer. Electrospray ionization-mass spectra (ESI-MS) of the complexes were recorded on a Q-Tof micro mass spectrometer from Guru Nanak Dev University (Amritsar, India). Metal and chloride ions were determined volumetrically [22] and gravimetrically [23a,b], respectively. The electronic spectra of the compounds in DMSO were recorded on a Pye-Unicam 8800 spectrophotometer at room temperature. The EPR spectra in solid and solution

H3C

MeOH

N Cl

N

CH3

M N H

Cl

N H

Scheme 1. Suggested structure of Schiff base complexes of the type MLCl2, where, [M = Fe(II), Co(II), Ni(II), Cu(II) and Zn(II)]; L = ligand].

131

H. Zafar et al. / Journal of Molecular Structure 1097 (2015) 129–135 Table 1 m/z values, analytical and physical data of the complexes. Complexes

m/z found (calc.)

Color

Found (calc.) % M

C

H

N

[FeLCl2] C15H20N4FeCl2

382.04 (383.04)

Brown

14.23 (14.35)

47.00 (47.03)

5.91 (5.26)

14.54 (14.63)

22.2/205

[CoLCl2] C15H20N4CoCl2

386.00 (386.13)

Light green

15.10 (15.26)

46.00 (46.61)

5.91 (5.17)

14.81 (14.51)

20.2/210

[NiLCl2] C15H20N4NiCl2

384.00 (385.89)

Pink

15.25 (15.20)

46.69 (46.68)

5.86 (5.24)

14.79 (14.52)

25.5/220

[CuLCl2] C15H20N4CuCl2

391.69 (390.75)

Dark green

16.25 (16.26)

46.25 (46.19)

5.89 (5.15)

14.80 (14.33)

27.5/215

[ZnLCl2] C15H20N4ZnCl2

392.11 (392.61)

Off white

16.55 (16.66)

45.10 (45.88)

5.11 (5.13)

14.22 (14.27)

22.0/250

Table 2 IR spectral data of the complexes (cm

1

).

Molar conductivity (ohm 1 cm2 mol 1)/m.p. (°C)

IR spectra

Complexes

m(NAH)

m(C@N)

m(CAH)

d(CAH)

m(MAN)

m(MACl)

[FeLCl2] [CoLCl2] [NiLCl2] [CuLCl2] [ZnLCl2]

3215 3210 3220 3220 3210

1520 1500 1530 1510 1505

2920 2920 2910 2915 2920

1460 1450 1465 1458 1440

450 410 410 420 430

270 285 290 280 290

The IR spectra give some important information regarding formation of the Schiff base complexes. The main bands and their assignments are listed in Table 2. The IR spectra for all the complexes exhibit a medium intensity band in the region 1500– 1530 cm 1 which may be assigned [26] to a coordinated imine m(C@N) stretching vibration. Another band which appeared in the region 3210–3220 cm 1 may be ascribed [27] to the coordinated NAH stretching vibrations of pyrrole ring. A weak absorption band in the region 2810–2815 cm 1 may be assigned to the CH3 stretching vibration [16]. The bands appearing in the regions 2910–2920 cm 1 and 1440–1465 cm 1 in all complexes may be due to m(CAH) and d(CAH), respectively [16]. A medium intensity band in the 400–450 cm 1 has been assigned to the m(MAN) stretching vibration [18]. In the chloro complexes the bands appearing in the region 270–290 cm 1 are assigned to the m(MACl) stretching vibration [18,20].

1

H and

13

C NMR spectra

The 1H NMR data for Zn(II) complex (Table 3) recorded in DMSO-d6 show a sharp signal at d2.37 ppm which may be assigned to the [28] methyl protons (ACH3; 6H). Furthermore, other chemical shift in the region d1.93–1.99 ppm which may be assigned [16] to the secondary amino (NACH2AC; 6H) protons of the 1,3-diamino propane moiety. Other multiplet observed in the range d5.025–5.351 ppm may be attributed [29,30] to the pyrrole protons. A broad signal observed at d7.019 ppm may be ascribed [30a,b] to the pyrrole ring (CANAHAC; 2H) protons.

Table 3 H NMR spectral data of the Schiff base [ZnLCl2] complex d (ppm).

1

Complex

NACH2AC (6H) d (m)

ACH3 group (6H) d (s)

NAH (2H) d (s)

Pyrrole ring d (m)

[ZnLCl2]

1.93–1.99

2.37

7.019

5.02–5.35

Where (s) = singlet and (m) = multiplet.

Table 4 C NMR spectral data of the Schiff base [ZnLCl2] complex d (ppm).

13

Fig. 1. Mass spectra of the Schiff base complexes; (a) [CoLCl2] and (b) [NiLCl2].

confirmed by comparing their molecular formula weights with respective m/z values (Table 1) that are in good agreement for these complexes (Fig. 1).

Complex

C@N d (s)

ACH3

ACH2 d (s)

ACH d (s)

Pyrrole ring carbon d (m)

[ZnLCl2]

170.10

30.21

60.20

70.19

108.1, 113.0,127.1,125.80

Where (s) = singlet and (m) = multiplet.

132

H. Zafar et al. / Journal of Molecular Structure 1097 (2015) 129–135

The 13C NMR spectrum of the [ZnLCl2] complex gave signals characteristics of different carbon atoms (Table 4) that appeared at their appropriate positions expected for proposed structure. However, the positions of resonance signals were found to be slightly downfield shifted [29,30a,b] in complex. The zinc complex shows a sharp signal corresponding to the azomethine carbon at d 155 ppm and the signals for ACH2 and ACH carbons appear at d60.20 and d70.19 ppm, respectively. Other chemical shifts for pyrrole ring carbons appeared at their appropriate positions [9b]. Conductivity measurements The molar conductivities of the complexes were recorded in 10 3 M DMSO. The reported values of molar conductances in DMSO for 1:1 electrolytes are in the range 51.5–59.2 ohm 1 cm2 mol 1 [31]. The observed molar conductances of Fe(II), Co(II), Ni(II) and Cu(II) complexes are in the range 20.20–27.5 ohm 1 cm2 mol 1 (Table 1) which are much lower than 1:1 electrolytes in the same solvent indicating non-electrolytic nature for these complexes. Thus two Cl groups are non-ionized and remain inside the coordination sphere. Magnetic susceptibility measurements The magnetic moment values (Table 5) for the Fe(II), Co(II), Ni(II) and Cu(II) complexes are in support of octahedral geometry around metal ions. The magnetic moment values for Fe(II) and Co(II) complexes corresponding to high spin octahedral configuration which indicate that the ligand field is weak. Nickel(II) with d8 configuration has two unpaired electrons in both high spin and low spin (weak or strong ligand field) octahedral arrangements. However, it generally shows a tendency to form octahedral complexes with weak field ligands and square planar complexes with strong field ligands in which all electrons are paired. Since the ligand field is weak thus it is probable that Ni(II) may assume an octahedral geometry rather than square planar. The observed magnetic moment for Ni(II) complex is 3.19 B.M. which is close to the spin only magnetic moment value (2.83 B.M.) for two unpaired electrons [15,32]. Deviation from spin only magnetic value may be due to spin–orbital coupling. This result is in strong support of octahedral geometry for Ni(II) complex. Electronic spectra and ligand field parameters

Fig. 2. EPR spectra of the [CuLCl2] complex at room temperature: (a) in solid state and (b) in solution (0.01 mM DMSO).

Table 5 Magnetic moments (leff), electronic spectral bands (cm

1

) with their assignments, ligand field parameters (10 Dq, B, b) and EPR data for the complexes.

Complexes

leff (B.M.)

Spectral bands (cm

[FeLCl2]

5.25

[CoLCl2]

4.10

[NiLCl2] [CuLCl2]

3.19 1.79

In weak octahedral crystal-fields only one spin-allowed transition is permitted for the Fe(II) ion [33]. The electronic spectrum of the Fe(II) complex exhibited weak intensity band at 18,200 cm 1 which may be assigned to the 5T2g?5Eg transition consistent with an octahedral geometry around the Fe(II) ion. The electronic spectrum of Co(II) complex exhibited two bands at 17,400 cm 1 and 19,100 cm 1 assignable to 4TIg(F)?4T1g(P) and

1

)

Assignments

10 Dq (cm

18,200

5

–

17,400 19,100

4

21,800 20,200

3

19,200 16,100

2

T2g?5Eg T1g (F)?4T1g (P) T1g (F)?4A2g (F)

1

)

B (cm

1

)

b

EPR parameters g||

g\

G

–

–

–

–

–

13,220

696

0.62

–

–

–

14,120

710

0.68

–

–

–

–

–

–

2.16

2.06

2.66

4

A2g(F)?3T1g (F) A2g(F)?3T1g (P)

3

BIg?2Eg B1g?2B2g

2

H. Zafar et al. / Journal of Molecular Structure 1097 (2015) 129–135

133

The ligand field parameters 10 Dq and B calculated from the electronic spectra [36a,b] for the Co(II) and Ni(II) complexes are listed in Table 5. The nephelauxetic parameter (b) was calculated by using the relation: b = B(complex)/B(free ion), where B(free ion) for Co(II) is 1120 cm 1 and for Ni(II) is 1041[36c,36d]. The values of b which lie in the range 0.62–0.68 indicate appreciable covalent character of the metal–ligand bond. The observed values of 10 Dq are well within the range reported for the octahedral complexes [36c,e,f]. The values of the Racah parameter (B) are within 696–710 cm 1 (<971 cm 1) which suggest overlapping of metal–ligand orbitals [36d,e]. There is considerable reduction in the values of Racah parameters (B) in the complexes in comparison to the free metal ions which also indicate appreciable covalent character of the metal–ligand bond [36a–d]. Further pairing energy (P) for Co(II) is 22,500 cm 1 [36a,b,e] which is much higher than the observed value for D0 (13220 cm 1). Thus, D0 < P, indicate formation of the high spin octahedral complex as confirmed by magnetic moment data (Table 5). Fig. 3. XRD pattern for [FeLCl2] Schiff base complex.

EPR spectra

Table 6 The XRD parameters for [FeLCl2] complex. Identification complex Empirical formula Formula weight Wave length Crystal system (powder) Lattice parameter Lattice parameter 2h min–max Lattice type

[FeLCl2] C15H20N4FeCl2 382.04 (g mol 1) 1.5417498 Å Hexagonal a = 4.42368 Å, b = 4.4268 Å, c = 5.9179 Å Alpha = 90°, beta = 90°,gamma = 120° 10–70.00 P

4

TIg(F)?4A2g(F) transitions, respectively, corresponding to an octahedral geometry around Co(II) ion [34]. The electronic spectrum of Ni(II) complex exhibited two bands at 21,800 cm 1 and 20,200 cm 1 attributed to 3A2g(F)?3T1g(F) and 3A2g(F)?3T1g(P) transitions, respectively, characteristic of an octahedral environment for Ni(II) complex [15,34]. The electronic spectrum of Cu(II) complex showed a broad band at 19,200 cm 1 with a shoulder at 16,100 cm 1 assigned to 2B1g?2Eg and 2B1g?2B2g transitions, respectively [35] corresponding to distorted octahedral geometry. This geometry is further corroborated from EPR study of Cu(II) complex.

The EPR spectra of the copper(II) complex (Fig. 2) in solid state and in solution (DMSO) were recorded at room temperature from which, g|| and g\ values were calculated. It was observed that EPR spectra were almost identical in solid state and in solution. It is known that with g|| > g\ the unpaired electron in tetragonally distorted octahedral and square planar complexes lies in the dx2 y2 orbital giving 2B1g as the ground state [33,35]. The observed g|| and g\ values (Table 5) are 2.16 and 2.06, respectively, thus for this complex g|| > g\ which support the fact that the ground state of Cu(II) is predominantly 2B1g having unpaired electron in the dx2 y2 orbital. The unpaired electron will lie predominantly in the dx2 y2 orbital and two electrons in the dz2 orbital resulting in tetragonally distorted octahedral geometry for copper(II) complex. It is known that for an ionic environment g|| > 2.3, which for a covalent environment g|| < 2.3 [37]. The observed g|| value for the copper complex is less than 2.3 in agreement with the covalent character of the metal–ligand bond.

Table 7 MIC and MBC results of complexes with positive control ciprofloxacin. Complexes

Gram positive bacteria Streptococcus pyogenes

Gram negative bacteria Klebsiella pneumonia

MIC

MBC

MIC

MBC

[FeLCl2] [CoLCl2] [ NiLCl2] [CuLCl2] [ZnLCl2] Standard ciprofloxacin

>100 >100 100 >25 >25 6.28

100 >100 >100 >50 >50 12.55

>100 100 >50 50 >100 6.35

>50 >100 100 >100 >50 12.60

MIC (lg/ml) = minimum inhibitory concentration, i.e. the lowest concentration of the compound to inhibit the growth of bacteria completely; MBC (lg/ml) = minimum bacterial concentration, i.e., the lowest concentration of the compound for killing the bacteria completely.

Fig. 4. Zone of inhibition (in mm) of the complexes tested against S. pyogenes and K. pneumoniae.

134

H. Zafar et al. / Journal of Molecular Structure 1097 (2015) 129–135

Fig. 5. Antibacterial activity of (a) [FeLCl2], (b) [CoLCl2], (c) [NiLCl2], (d) [CuLCl2] and (e) [ZnLCl2] shown by well-diffusion method.

X-ray diffraction analysis The X-ray powder diffraction (XRD) was used to determine the type of structure ordering of the Schiff base complexes. The XRD pattern of the complex [FeLCl2] recorded from polycrystalline sample exhibited some sharp peaks in the spectrum (Fig. 3) correlated to the crystalline behavior of Schiff base complex. Other parameters were calculated in Table 6. Biological activity Antibacterial studies The newly prepared complexes were screened for their antibacterial activity against Streptococcus pyogenes and Klebsiella pneumoniae bacterial strains by disc diffusion method [24,25]. Standard inoculums (1–2  107 CFU/ml 0.5 McFarland standards) were spread onto the surface of sterile agar plates. The discs measuring 6 mm in diameter were prepared using Whatman No. 1 filter paper and were sterilized by dry heat at 140 °C for 1 h. The sterile discs previously soaked in a known concentration of the test compounds were placed in the nutrient agar medium. Ciprofloxacin (30 lg) was used as positive control, while the disc poured in DMSO was used as negative control. The plates were inverted and incubated for 24 h at 37 °C. The susceptibility was assessed on the basis of the diameter of the zone of inhibition against Gram-positive and Gram-negative strains of bacteria. Inhibition zones were measured and compared with the controls (Table 7 and Fig. 4). Minimum inhibitory concentrations (MICs) were determined by the broth micro dilution method. The nutrient broth, which contained logarithmic serially two fold diluted

amount of test compound and controls were inoculated with approximately 5  105 CFU/ml of actively dividing bacteria cells. The cultures of the bacterial strains were incubated for 24 h at 37 °C and the growth was monitored visually and spectrophotometrically. The lowest concentration (highest dilution) required to arrest the growth of bacteria was regarded as minimum inhibitory concentration (MIC). To obtain the minimum bacterial concentration (MBC), 0.1 ml volume was taken from each tube and spread on agar plates displayed in Fig. 5. The number of CFU was counted after 17–24 h of incubation at 35 °C. MBC was defined as the lowest drug concentration at which 99.9% of the inoculums were killed. The MIC and MBC are given in Table 7. The investigation of antibacterial screening data revealed that all tested compounds showed moderate to good antibacterial activity. Among the metal complexes studied the copper complex [CuLCl2], showed highest antibacterial activity against S. pyogenes and K. Pneumonia nearly equal to standard drug ciprofloxacin. Other complexes also showed considerable antibacterial activity. The relative order of activity against S. Pyogenes is as Cu(II) > Zn(II) > Co(II) = Fe(II) > Ni(II) and with K. Pneumonia is as Cu(II) > Co(II) > Zn(II) > Fe(II) > Ni(II). The observed highest antibacterial activity of Cu(II) complex is quite remarkable. This behavior of copper is in agreement with the earlier studies [18,20,33,38]. The role of copper in biological systems is quite significant. Except the role of copper as an essential trace element, it exhibits considerable biological action forming complexes which can promote nucleic acid cleavage and, therefore, are used as metallodrugs to cause DNA damage [39]. The earlier reports reveal that copper(II) complexes exhibit stronger DNA binding propensity [40] as compared to other transition metal complexes. This is due to the

H. Zafar et al. / Journal of Molecular Structure 1097 (2015) 129–135

fact that the later 3d transition metal ions, specially Cu(II), which are classified as ‘‘borderline’’ between ‘hard’ (a-class) and ‘soft’ (b-class) metals show more affinity for both the heterocyclic bases as well as phosphate group in contrast to ‘soft’ (b-class) metals like Pt(II). Therefore, there appears enhancement in their binding strength with DNA. Conclusion A new series of Schiff base transition metal complexes of the type MLCl2 [M = Fe(II), Co(II), Ni(II), Cu(II) or Zn(II), L = ligand] was synthesized and characterized employing various physico-chemical methods. These studies show octahedral geometry around the metal ions. After characterization further studied were carried out for their antibacterial activities. The complexes were screened in vitro against S. pyogenes and K. pneumonia bacteria. All the complexes showed considerable antimicrobial activity and specially copper(II) complex [CuLCl2] showed highest antibacterial activity which is nearly equal to the standard drug ciprofloxacin. These studies presented here provide a new structural type for the development of novel antibacterial agents. Acknowledgments The Chairman, Department of Chemistry, Aligarh Muslim University, Aligarh, India, is acknowledged for providing necessary research facilities. The author HZ thanks University Grants Commission, New Delhi, for the financial support. References [1] (a) V.T. Kasumov, F. Koksal, Spectrochim. Acta Part A Mol. Biomol. Spectrosc. 61 (2005) 225–231; (b) M.D. Hobday, T.D. Smith, Coord. Chem. Rev. 9 (1972/1973) 331. [2] (a) R.H. Holm, G.W. Everett, A. Chakravorty, Progr. Inorg. Chem. 7 (1966) 83– 214; (b) D. Pletcher, H. Thompson, J. Electroanal. Chem. 464 (1999) 168–175; (c) S. Zolezzi, E. Spodine, A. Decinti, Polyhedron 21 (2002) 55–59. [3] M. Shakir, N. Shahid, N. Sami, M. Azam, A.U. Khan, Spectrochim. Acta Part A 82 (2011) 31–36. [4] A. Carey, Organic Chemistry, fifth ed., McGraw-Hill, New York, 2003. [5] S.M. Abdullah, G.G. Mohamed, M.A. Zayed, M.S. Abou El-Ela, Spectrochim. Acta Part A Mol. Biomol. Spectrosc. 73 (2009) 833–840. [6] H. Kim, H.K. Lee, A.Y. Choi, S. Jeon, Bull. Kor. Chem. Soc. 28 (2007) 538. [7] H.H. Sabah, Der. Phar. Chem. 6 (2) (2014) 38–41. [8] S. Chandra, L.K. Gupta, S. Agrawal, Trans. Met. Chem. 32 (2007) 558–563. [9] (a) B. Singh, U. Srivastava, Synth. Reac. Inorg. Met.-Org. Chem. 18 (1988) 515– 521; (b) A. Castineiras, R. Carballo, T. Perez, Polyhedron 20 (2001) 441–448. [10] A. Hanaa, E. Boraeya, R.M. Abdel-Rahman, E.M. Atia, K.H. Hilmy, Cent. Eur. J. Chem. 8 (2010) 820–833. [11] D. Kumar, Sandhya, J. Chem. Pharm. Res. 6 (2014) 746–750.

135

[12] M. Shakir, A. Abbasi, M. Azam, A.U. Khan, Spectrochim. Acta Part A 79 (2011) 1866–1875. [13] (a) A.A. Abou-Hussein, W. Linert, Spectrochim. Acta Part A Mol. Biomol. Spectrosc. 117 (2014) 763–777; (b) P. Jogi, M. Padmaja, K.V.T.S. Pavan Kumar, C. Gyanakumari, J. Chem. Pharm. Res. 4 (2012) 1389–1397. [14] S. Chandra, X. Sangeetika, Spectrochim. Acta Part A Mol. Biomol. Spectrosc. 60 (2004) 147–153. [15] T.A. Khan, S. Naseem, R. Hajra, M. Shakir, Synth. React. Inorg. Met.-Org. Chem. 40 (2010) 861–868. [16] T.A. Khan, S. Naseem, S.N. Khan, A.U. Khan, M. Shakir, Spectrochim. Acta Part A 73 (2009) 622–629. [17] T.A. Khan, S.S. Ghani, S. Naseem, J. Coord. Chem. 63 (2010) 4411–4420. [18] T.A. Khan, H. Zafar, S.N. Khan, A.U. Khan, Synth. React. Inorg. Met.-Org. Chem. Nano-Met. Chem. 45 (2015) 1175–1183. [19] A. Kareem, H. Zafar, A. Sherwani, M. Owais, T.A. Khan, J. Mol. Struct. 1075 (2014) 17–25. [20] H. Zafar, A. Kareem, A. Sherwani, M. Owais, T.A. Khan, J. Mol. Struct. 1079 (2015) 337–346. [21] H. Zafar, A. Kareem, A. Sherwani, O. Mohammad, M.A. Ansari, H.M. Khan, T.A. Khan, J. Photochem. Photobiol., B 142 (2015) 8–19. [22] A.I. Vogel, A Text Book of Quantitative Inorganic Analysis, third ed., Longman, 1961. [23] (a) C.N. Reilly, R.W. Schmidt, F.A. Sadek, J. Chem. Ed. 36 (1959) 619; (b) N.P. Singh, N. Srivastava, J. Serb. Chem. Soc. 77 (2012) 627–637. [24] R. Cruickshank, J.P. Duguid, B.P. Marmion, R.H.A. Swain, twelfth ed., Medical Microbiology, vol. 2, Churchill Livingstone, London, 1975, pp. 196–202. [25] A.H. Collins, in: Microbiological Methods, second ed., Butterworth, London, 1976. [26] S. Ilhan, H. Temel, R. Ziyadanogullari, M. Sekerci, Trans. Met. Chem. 32 (2007) 584. [27] A. Mellouki, R. Georges, M. Herman, D.L. Snavely, S. Leytner, Chem. Phys. 220 (1997) 31. [28] M. Shakir, Y. Azim, H.T.N. Chisti, S. Parveen, Spectrochim. Acta Part A 65 (2006) 490–496. [29] R.J. Abraham, R.D. Lakker, K.M. Smith, J.F. Unsworth, J. Chem. Perkin Trans. 2 (1974) 1004. [30] (a) R.G. Parker, J.D. Robets, J. Org. Chem. 35 (1979) 996; (b) Richard A. Jones, The Chemistry of Heterocyclic Compounds, Pyrroles, John Wiley & Sons, 2009, p. 570. [31] W. Geary, Coord. Chem. Rev. 7 (1971) 81–122. [32] J.E. Weder, C.T. Dillon, T.W. Hambley, B.J. Kennedy, P.A. Lay, Coord. Chem. Rev. 232 (2002) 95–126. [33] A.P. Mishra, P. Gupta, J. Chem. Pharm. Res. 3 (2011) 150–161. [34] S. Chandra, L.K. Gupta, Spectrochim. Acta Part A 61 (2005) 1181–1188. [35] V.P. Singh, Spectrochim. Acta Part A 71 (2008) 17–22. [36] (a) C.K. Jørgensen, ‘‘Aspects of Ligand Field Theory’’, Amsterdam, 1971, pp. 645–669 (chapter 18).; (b) A.B.P. Lever, Coord. Chem. Rev. 4 (1968) 119; (c) C.K. Jørgensen, Absorption Spectra and Chemical Bonding in Complexes, Pergamon Press, London, 1962; (d) S. Chandra, P. Pipil, J. Inorg. Chem. 3 (2013) 109–115; (e) M.M. Kamal, Z.A. Ahmed, A.A.M. Aly, Synth. React. Inorg. Met.-Org. Chem. 21 (1991) 99–113; (f) F. Rafat, K.S. Siddqi, M.Y. Siddiqi, Polish J. Chem. 81 (2007) 313–326. [37] J. A. Weil, J. R Bolton, J.E Wertz, Wiley-Inter Science, New York, 2001. [38] N. Pravin, N. Raman, Eur. J. Med. Chem. 85 (2014) 675–687. [39] S. Tabassum, M. Afzal, F. Arjmand, J. Photochem, Photobiol. B 115 (2012) 63– 72. [40] Y. Zhang, L. Zhang, L. Liu, J. Guo, D. Wu, G. Xu, X. Wang, D. Jia, Inorg. Chim. Acta 363 (2010) 289–293.