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Synthesis, Magneto-Spectral, Electrochemical, Thermal Characterization and Antimicrobial Investigations of Some Nickel(II) Complexes of Hydrazones of Isoniazid
Synthesis, Magneto-Spectral, Electrochemical, Thermal Characterization and Antimicrobial Investigations of Some Nickel(II) Complexes of Hydrazones of Isoniazid
Journal of the Korean Chemical Society. 2009. Dec, 53(6): 683-692
Copyright © 2009, The Korean Chemical Society
  • Received : May 18, 2009
  • Accepted : October 28, 2009
  • Published : December 20, 2009
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About the Authors
Surendra Prasad
Division of Chemical Sciences, Faculty of Science, Technology and Environment, The University of the South Pacific, Suva, Fiji
ram_agarwal54@yahoo.com (Ram K. Agarwal)
Ram K. Agarwal
Department of Chemistry, Lajpat Rai Postgraduate College, Sahibabad, Ghaziabad 201005, India
ram_agarwal54@yahoo.com (Ram K. Agarwal)

Abstract
The synthesis of a novel series of nickel(II) complexes with new ligands derived from hydrazones of isoniazid have been reported in present work. The complexes have general compositions [Ni(L) 2 X 2 ] or [Ni(L) 3 ](ClO 4 ) 2 {L = N-isonicotinamido-furfuraldimine (INH-FFL), N-isonicotinamido-3',4',5'-trimethoxybenzaldimine (INH-TMB) or N-isonicotinamido-cinnamalidene (INH-CIN) and X = Cl - , NO 3 - , NCS - or CH 3 COO - }. The ligands hydrazones behave as neutral bidentates (N and O donor) through the carbonyl oxygen and azomethine nitrogen. The new complexes with octahedral geometry have been characterized by elemental analysis, molecular weight determinations, magnetic susceptibility/moment, thermogravimetric, electrochemical and spectroscopic studies viz . infrared and electronic spectra. On the basis of conductivity measurements in nitrobenzene (PhNO 2 ) solution the [Ni(L) 2 X 2 ] and [Ni(L) 3 ](ClO 4 ) 2 complexes have been found to be non-electrolytes and 1:2 electrolytes, respectively. Thermal properties have also been investigated, which support the geometry of the complexes. Antibacterial and antifungal properties of nickel(II) complexes and few standard drugs have also been examined and it has been observed that the complexes have moderate antibacterial activities.
Keywords
INTRODUCTION
The multifarious role of the transition metal complexes in biochemistry have been playing potentially for the development of new chemistry with metal ligand system. This has stimulated enormous interest in synthesis of transition metal complexes with Schiff bases of nitrogen and oxygen donor due to the wide range of pharmacological activities of such compounds. 1 Schiff bases derived from condensation of primary amines and carbonyl group of an aldehyde or ketone by elimination of water molecule, are known to have a nitrogen atom with a lone pair of electrons in its functional group (>C=N-), and used as ligands with a variety of metal ions. Many of these complexes may serve as models for biologically important species. In addition, they present a vast variety of biological activities ranging from anti-tumour, fungicide, bactericide, anti-inflamatory and anti-viral activities. 2 We have recently published some lanthanide(III) complexes of semicarbazones 3 and oxovanadium(IV), 4 , 5 platinum(II), 6 cobalt(II) and nickel(II) 2 , 7 complexes of thiosemicarbazones derived from 4-aminoantipyrine. The antibacterial and antifungal properties of the thiosemicarbazone ligands and their cobalt(II), 2 , 7 nickel(II) 7 and oxovanadium(IV) 5 complexes have also been examined.
The remarkable biological activity of acid hydrazides R-CO-NH-NH 2 , their aroyl hydrazones, R-CO-NH-N=CH-R' and their mode of chelation with transition metal ions present in the living systems had been of significant interest in past. 8 , 9 It is believed that the -CO-NH-N=C< moiety of hydrazone imparts biological characteristics to this class of compounds. The coordination compounds of aroylhydrazones have been reported to act as enzyme inhibitors and are useful due to their pharmacological applications. 10 - 12 Isoniazid is a drug of proven therapeutical importance and is used against a wide spectrum bacterial ailments viz ., tuberculosis. Hydrazones derived from the condensation of isoniazid with pyridine aldehydes have been found to show better antitubercular activity than isoniazid. 13 Thus in the past we and other researchers have reported transition metal coordination compounds of hydrazones of isoniazid. 14 - 16 In continuation of our most recent work on hydrazones of isoniazid complexes of cobalt(II), 17 - 18 the present work describes the synthesis, magneto-spectral, electrochemical, thermal and biological studies of a novel series of fifteen Ni(II) complexes of N-isonicotinamido-furfuralaldimine (INH-FFL) ( . 1 ), N-isonicotinamido-3',4',5'-trimethoxybenzaldimine (INH-TMB), ( . 2 ) and N-isonicotinamido-cinnamalidene (INHCIN) ( . 3 ).
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N-Isonicotinamido-furfuraldimine (INH-FFL).
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N-Isonicotinamido-3',4',5'-trimethoxybenzaldimine (INH-TMB).
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N-Isonicotinamido-cinnamalidene (INH-CIN).
EXPERIMENTAL SECTION
- Materials
All the nickel(II) salts, i.e. , NiX 2 ․nH 2 O (X = Cl - , NO 3 - or CH 3 COO - ) were obtained from BDH and were used as received. Ni(NCS) 2 was prepared by mixing NiCl 2 (in ethanol) and ethanolic solution of potassium thiocyanate in 1:2 molar ratio. The precipitated KCl was filtered off and the filtrate having Ni(NCS) 2 was used immediately for complex formation. 7 Ni(ClO 4 ) 2 was prepared by the addition of an ethanolic solution of sodium perchlorate into NiCl 2 solution. White precipitate of NaCl was filtered off and the filtrate containing Ni(ClO 4 ) 2 was used as such for complex formation. 7
- Synthesis of schiffs bases; INH-FFL, INH-TMB and INH-CIN
All the three hydrazones of isoniazid viz . INHFFL, INH-TMB and INH-CIN were synthesized by the following general method reported elsewhere. 16 Isonicotinic acid hydrazide (INH) (0.01 mol) was dissolved in 10 mL of 95% ethanol. To this solution respective aromatic aldehyde, i.e. , furfural, 3',4',5'-trimethoxybenzaldehyde or cinnamaldehyde (0.01 mmol) was added in 95% ethanol (10 mL). The mixture was refluxed on a water bath for ~ 2 h. The partial removal of solvent on a water bath followed by cooling produced crystalline product, which was suction filtered, washed with cold ethanol and dried over P 4 O 10 under vacuum (yd. 80%).
- Synthesis of nickel(II) complexes;[Ni(L)2X2] and [Ni(L)3](ClO4)2
A general method has been used for the synthesis of the nickel(II) complexes. 7 A hot ethanolic solution of the corresponding nickel(II) salt was mixed with a hot ethanolic solution of the corresponding hydrazone (in molar ratio 1:2 and 1:3 for [Ni(L) 2 X 2 ] and [Ni(L) 3 ](ClO 4 ) 2 complexes, respectively). The reaction mixture was refluxed on a water bath for ~ 2 h. On cooling at room temperature, the coloured complexes precipitated out in each case. They were filtered, recrystalized, washed with ethanol and dried over P 4 O 10 under vacuum.
- Instrumentation, analysis and physico-chemical measurements
Nickel contents of the complexes were determined complexometrically with EDTA using erichrome black-T as an indicator after decomposing the complexes with conc. H 2 SO 4 and H 2 O2 7 . The chlorine was estimated by Volhard’s method. 19 The thiocyanate was estimated by titrating slightly acidic solution of the complex with standard silver nitrate solution. The perchlorate was estimated by the method reported in our previous work. 7 The percentage of nitrogen was determined by Kjeldahl method. The molecular weight of the complexes was determined cryoscopically in freezing nitrobenzene using a Beckmann thermometer of accuracy of ± 0.01 ℃.
The conductivity measurements were performed using a Toshniwal conductivity bridge with a dip type cell operated at 220 volts. All the measurements were done at room temperature in nitrobenzene. The magnetic measurements on powder form of the complexes were carried out at room temperature on Evans magnetic balance using anhydrous copper sulfate for calibration. The infrared spectra of the complexes were recorded on a Perkin Elmer FT-IR infrared spectrophotometer model521 in CsI in the range of 4000 - 200 cm -1 . Diffused reflectance spectra of the solid complexes were recorded on a Beckmann DK-2A spectrophotometer at CDRI Lucknow, India. Thermogravimetric analyses of the complexes were performed on Perkin Elmer Pyris Diamond in static air with unlidded small platinum boat sample holder at IIT Roorkee, India. The heating rate was 6 ℃ min -1 . The antibacterial and antifungal activities of the representative nickel(II) complexes and standard drugs (ampicillin and tetracycline) were screened by following the methods reported elsewhere. 2 , 7
RESULTS AND DISCUSSION
The reaction of nickel(II) salts with INH-FFL, INH-TMB and INH-CIN, resulted in the formation of [NiX 2 (L) n ] (X = Cl - , NO 3 - , NCS - or CH 3 COO - , n = 2 and L = INH-FFL, INH-TMB or INH-CIN) and [Ni(L) n ]X 2 (X = ClO 4 - , n = 3, and L = INH-FFL, INH- TMB or INH-CIN. The analytical data of present complexes are presented in 1 . The complexes were quite stable and could be stored for several weeks without any appreciable change. The complexes did not have sharp melting points, but decomposed on heating beyond 250 ℃. The complexes were generally soluble in common organic solvents.
The molar conductance of the nickel(II) complexes in nitrobenzene are presented in 1 . The chloro, nitrato, isothiocyanato and acetato complexes of the type [NiX 2 (L) n ] were essentially nonelectrolytes in nitrobenzene, while the perchlorato complexes of the type [Ni(L) n ]X 2 dissociated in nitrobenzene and behaved as 1:2 electrolytes. The molecular weights determined cryoscopically in nitrobenzene are also given in 1 . The results are in good agreement with conductance data.
Analytical, conductivity, molecular weight and magnetic moment data of nickel(II) complexes of hydrazones of isoniazid.
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OAc: CH3COOINH-
- Magnetic susceptibility
Nickel(II) has the electronic configuration 3d8 and should exhibit magnetic moment higher thanexpected for two unpaired electrons in octahedral (2.8 - 3.2 BM) and tetrahedral (3.4 - 4.2 BM) complexes, whereas its square planar complexes would be diamagnetic. This increase the magnetic moment value from that of the spin only value has been considered it to be due to some ‘mixing in’ of upper state via spin-orbit coupling. The paramagnetism observed for the present series of complexes ranges from 2.6 - 3.2 BM ( 1 ) which is consistent with the octahedral stereochemistry of the complexes. 7
- Infrared spectra
Key infrared bands (cm-1) of nickel(II) complexes of hydrazones of isoniazid.
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Key infrared bands (cm-1) of nickel(II) complexes of hydrazones of isoniazid.
The infrared data of the ligands, INH-FFL, INHTMB and INH-CIN, and their nickel(II) complexes are presented in 2 . The infrared frequencies in the present ligands associated with amide group (carbonyl-oxygen), azomethine-nitrogen (C=N) and heterocyclic nitrogen are expected to be influenced on complex formation with metal ion have been discussed. Generally, all amides show two absorption bands: (i) the carbonyl absorption band near 1640 cm -1 known as amide-I band and (ii) strong band in the 1600 - 1500 cm -1 region, known as amide-II band. The amide-I band in INH-derivatives, however, appeared at 1655 cm -1 . 20 , 21 In the infrared spectra of the complexes, a considerable negative shift in ν (C=O) was observed indicating a decrease in the stretching force constant of (C=O) as a consequence of coordination through the carbonyl oxygen atom of the free base. The amide-II band appeared at the normal position in the NH-deformation rather than C-N link. In all these ligands the absorptions at 1540 - 1530 cm -1 have been assigned to amide-II absorptions. The NH stretching absorption in free ligands occurs at ~ 3300 and 3220 cm -1 which remain unaffected after complexation. This precludes the possibility of coordination through imine-nitrogen atom. Another important band occurs in 1590 - 1585 cm -1 range is attributed to ν (C=N) (azomethine) mode. 22 , 23 In spectra of all the complexes this band is shifted to lower wave number and appears in 1550 - 1525 cm -1 region, respectively indicating the involvement of N-atom of the azomethine group in coordination. 22 , 24 The strong bands observed at 1575 - 1520 cm -1 and 1080 - 1000 cm -1 are tentatively assigned25 to asymmetric and symmetric ν (C=C) + ν (C=N) of pyridine ring. The pyridine ring breathings and deformations remained practically unchanged in frequency and band intensities revealing non-involvement of pyridine-nitrogen and metal bond. The overall infrared spectral evidence suggests that the present ligands act as bidentate ligand and coordinate through amide-oxygen and azomethine-nitrogen atoms forming a five membered chelate ring. In far infrared spectral region, the bands in these ligands are practically unchanged in these complexes. Some new bonds with medium to weak intensities appeared in the regions 450 - 380 cm -1 in the complexes under study, which are tentatively assigned to ν (Ni-N)/ ν (Ni-O) modes. 14 - 16 , 26
- Anions
In all the perchlorato complexes, the presence of the ν 3 (1100 - 1090 cm -1 ) and ν 4 (625 - 620 cm -1 ) bands indicates that the T d symmetry of ClO 4 - is maintained in these complexes. This observation suggested the presence of ClO 4 - outside the coordination sphere in perchlorato complexes. 27 The three fundamental absorption in [Ni(NCS) 2 (L) 2 ] (L = INH-FFL, INH-TMB or INH-CIN) complexes i.e. C-N stretching ( ν 1 ), C-S stretching ( ν 3 ) and NC- S bending ( ν 2 ) were identified at 2040 - 2035, 845 - 830 and 470 - 465 cm -1 region, respectively. These frequencies are associated with the terminal N-bonded isothiocyanate ions. 7 , 28
In nitrato complexes, the infrared spectral data indicate the occurrence of two strong absorption bands in the regions 1555 - 1500 cm -1 and 1310 - 1295 cm -1 which are attributed to ν 4 and ν 1 modes of vibratioins of the covalently bonded nitrate groups, respectively. This suggests that nitrate groups are present inside the coordination sphere. 29 Distinction between monodentate and bidentate nitrate is usually difficult. However, by applying Lever’s separation method, 30 a separation of 15 - 25 cm -1 in the combination bands ( ν 1 + ν 4 ) in the 1800 - 1700 cm -1 region conclude the monodentate nitrate coordination. Other bands appeared at ~1040 ( ν 2 ), 810 ( ν 6 ) and 7335 cm -1 ( ν 3 / ν 5 ) due to nitrate groups.
The ν asym (COO - ) of free acetate ions are at ~1560 cm -1 and 1416 cm -1 respectively. In the unidentate complex, ν (C=O) is higher than ν asym (COO - ) and ν (C-O) is lower than ν asym (COO - ). As a result the separation between the two ν (CO) is much larger in unidentate complexes than free ion. The opposite trend is observed in the bidentate complexes, the separation between the ν (CO) is smaller than that of free ion in this case. In the bridging complexes, however, two ν (CO) are close to the free ion values. The present complexes show infrared absorption frequency bands corresponding to ν asym (COO - ) and ν sym(COO - ) at ~ 1610 and 1370 cm -1 respectively. These observations indicate that both the acetate groups in present complexes are unidentate. 7 , 31
- Electronic spectra
Six coordinated nickel(II) complexes exhibit a spectrum involving three spin-allowed transitions to 3 T 2g (F) ( ν 1 ), 3 T 1g (F) ( ν 2 ) and 3 T 1g (P) ( ν 3 ) from the ground state 3 A 2g (F). These occur in 7000 - 11000 cm -1 ( ν 1 ), 15000 - 19000 cm -1 ( ν 2 ) and 25000 - 29000 cm -1 ( ν 3 ) regions respectively. In the present complexes, the electronic spectra was very similar to each other and consists of bands in 8200 - 10990, 15100 - 17700 and 20000 - 20800 cm -1 ( 3 ), which clearly indicated the octahedral stereochemistry of the complexes 7 . The band maxima, their assignments, the calculated nephelauxetic effect (β) and the ligand field parameters B and D q for some representative chelate complexes are presented in 3 . 32
Electronic spectral bands (cm-1) and lignad field parameters of nickel(II) complexes of INH-FFL and INH-TMB.
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Electronic spectral bands (cm-1) and lignad field parameters of nickel(II) complexes of INH-FFL and INH-TMB.
- Thermogravimetric studies
Thermoanalytical results of some representative complexes of the type [Ni(L) 2 X 2 ] where L = INHFFL and X = Cl - , NO 3 - or NCS - , are given in 4 . Thermal curves clearly suggested the absence of any water molecule in these complexes. During 160 - 290 ℃ temperature range the weight loss corresponds to 36.32 - 39.34% indicate the loss of one molecule of INH-FFL, while second ligand molecule evaporated off at ~400 ℃. Finally, at ~600 ℃, NiO formation takes place. Almost similar thermogravimetric curves were obtained with the same end product, NiO, which may be represented by the following equations ( cf . 4 ):
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Thermoanalytical results obtained for nickel(II) complexes of INH-FFL.
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Thermoanalytical results obtained for nickel(II) complexes of INH-FFL.
Antifungal and antibacterial activities of nickel(II) complexes of INH-FFL and INH-CIN.
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Antifungal and antibacterial activities of nickel(II) complexes of INH-FFL and INH-CIN.
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- Biological properties
The study of the biological i.e. antibacterial and antifungal properties of transition metal complexes with ligands of biological importance have recently been of great interest. 1 , 2 , 5 , 7 , 33 - 41 Thus in the present studies, the antibacterial activities of the nickel(II) complexes and standard drugs (ampicillin and tetracycline) were also screened by agar-cup method in DMF solvent at a concentration of 50 μg mL -1 . The results were checked against gram positive bacteria B. subtilis and S. aureus and gram negative bacteria E. coli and S. typhi and reported in 5 . The diameters of zone of inhibition (in mm) of the standard drug ampicillin against gram positive bacteria B. subtilis and S. aureus and gram negative bacteria E. coli and S. typhi were found to be 24, 22, 17 and 16 respectively, while tetracycline gave 18, 17, 21 and 22 respectively. Under identical conditions, 5 shows that all the nickel(II) complexes of hydrazones of isoniazid have moderate antibacterial activities against these bacteria. These complexes were also screened for their antifungal activities against two fungi ( A. niger and C. albicans ). The results are presented in 5 which show that almost all the complexes studied showed nearly the same extent of activity but they are less active compared to salicylic acid. These complexes appear to be efficient antifungal agents.
CONCLUSION AND STEREOCHEMISTRY OF THE COMPLEXES
The conductance, molecular weight determinations and other experimental analyses of the chloro, nitrato, thiocyanato and acetato nickel(II) complexes of INH-FFL, INH-TMB and INH-CIN, suggest that the complexes are non-ionic in nature and do not dissociate in nitrobenzene. Thus in the case of [Ni(L) 2 X 2 ] (X = Cl - , NO 3 - , NCS - or CH 3 COO - ; L = INH-FFL, INH-TMB and INH-CIN), the coordination number of Ni(II) is found to be six. The 1:2 electrolytic nature of the perchlorato complexes suggests that two perchlorate ions are present outside the coordination sphere and hence, the coordination number of nickel(II) in [Ni(L) 3 ](ClO 4 ) 2 , is found to be six.
The overall experimental evidences thus show that the studied nickel(II) complexes, [Ni(L) 2 X 2 ] and [Ni(L) 3 ](ClO 4 ) 2 , display a coordination number six and presumably have an octahedral environment around the metal ion. The proposed structures of these complexes are shown in . 4 .
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Probable structures of [Ni(L)2X2] and [Ni(L)3] (ClO4)2.
Acknowledgements
The authors are thankful to URC of the University of the South Pacific for supporting finance for this research through Project Nos. 6395-1321 and 6394-1321 (6C127-1321 and 6C126-1321) and Dr. Abdul Mohammed Hatha, Lecturer, Department of Biology, FST, USP for assisting in studying the biological properties of the compounds.
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