Spectral and Antimicrobial Screening of Cu(II), Ni(II) and Co(II) Coordination Compounds with Nitrogen Oxygen and Sulphur Containing Tridentate Schiff Base

Introduction

Schiff base ligands and their metal complexes exhibit numerous biocidal    activities^1-2, such as antitumour³, antibiotic⁴ and antiviral⁵. Schiff bases have attracted the interest of many chemists due to their ability to coordinate with various metal ions and also their reactions with microbial DNA and inhibiting tumor growth⁶, which have been reported by several workers in the past. Such ligands have unusual configuration, structural liability and are sensitive to molecular environment. As a continuation of our interest in the field of the chemistry of, the present communication deals with the synthesis, spectral and antimicrobial studies of Co(II), Ni(II) and Cu(II) complexes with Schiff bases derived from condensation of 2-ethyl –[3-(hydroxy propyl)]-3,1(4H) quinazoline -4 one with semcarbazide/thiosemicarbazide hydrochloride.

Experimental

All the used chemicals and reagent used were analytical grade. The solvents were used without any purification, the metal contents were determined using standard procedures¹². IR spectra of ligand and complexes over the region 4000-200 cm^-1 were recorded on Parkin Elmer’s model577 spectrometer using KBR disc. Molar conductivity of the complexes were measured at room temperature by using systronics conductivity meter model 303 in DMF. Magnetic susceptibility was carried out by Gouy’s method at room temperature using Hg[Co(NCS)4] as standard. Electronic spectra over the region 10000-25000 cm^-1 were recorded by Cary 2390 spectrometer using 10^-3m DMF solution of complexes.

Preparation of the ligand EHPQS/EHPQT

A suspension of 2-ethyl-[(hydroxy propyl)]- 3, 1(4H) quinazoline-4-one was allowed to react with semicarbazide/ thiosemicarbazide  hydrochloride dissolved in 10ml ethanolic solution acetate. The mixture was heated on water bath for 4h, after cooling and slow evaporation the compounds, EHPQS/EHPQT as colourless prismatic needles was formed. The compounds were recrystallised with methanol. M.P. 201± 1⁰C for EHPQ and 209± 1⁰C for compound EHPQT.

Preparation of the Complexes

The complex of Cu(II), Ni(II) and Co(II) were synthesize by refluxing ethanolic solution of respective metal acetates(o.oo1m) to the Schiff base ligands (0.002m) EHPQS/EHPQT dissolved in minimum volume of ethanol. Partial removal of the solvent and cooling to room temperature gave coloured complexes which was filtered, washed thoroughly with ethanol and finally dried.

Results And Discussion

Both the ligands and their complexes are air and moisture free crystalline solids. The complexes are intensively coloured. The complexes are insoluble in common inorganic solvent and only soluble in DMF. The elemental analysis data concur well with the proposed formulae for the ligands and stoichiometry of the proposed structure of complex [M(EHPQS/ EHPQT)­­₂].

A broadband observed in ligands, EHPQS/ EHPQT at 3450 cm^-1 is broadened and has shifted to a lower frequency region at 3400 cm^-1 on the complexation with metal ion proposing coordination of alcoholic oxygen by deprotonation^13,14.IR spectra of the both ligands EHPQS/ EHPQT show a broad band at         3200 cm^-1 assigned to n_N-H. This band remains unperturbed on complexation that indicates non-involvement of either terminal or secondary amino group in coordination.

The IR spectra of the ligands EHPQS/ EHPQT show strong band at 1570 cm^-1 assigned n_C=N. This band also shifts to lower wave number by 20-25 cm^-1 suggesting participation of azomethine linkage with metal ion. The IR Spectra of the ligand EHPQS shows a strong and broad band at 1740cm^-1assigned n_C=O. This band undergoes red shift on complexation indicating the involvement carbonyl oxygen in coordination. The IR Spectrum of lligand EHPQT show a strong band at 790cm^-1assigned to n_C=S. This band is shifted  to lower frequency region after complex formation indicating linkage of thione sulphur atom to the metal ion. Metal ligand vibration are generally observed in the far IR region and usually give valuable information regarding the bonding of ligand to the metal ion. The appearance of the three bands in the far IR regions at 575-525, 475-435 and 405-385 cm^-1 assigned to n_M-O, n_M-S and n_M-N band respectively.

The coordination with azomethine Nitrogen/N atom of NH₃/ pyridine/ a, b and g-picolines as well coordination of alcoholic oxygen by deportation is supported by appearance to above mentioned three bands in the Far IR region. The above argument is further supported by the low value of the molar conductance of the complexes in the range 5.4-8.3 ohm^-1 cm² mol^-1 which proposes non-electrolytic nature of the complexes.

Electronic Spectra and magnetic Moments of the Complexes

Electronic spectra of the Co(II) complexes exhibits three bands in the region 10200-10300 cm^-1, 15400-15800 cm^-1 and 22100-22400 cm^-1 assigned to the transitions, ⁴T_1g(F) ® ⁴T_2g(F), ⁴T_1g(F) ® ⁴A_2g (F) and ⁴T_1g(F) ® ⁴T_1g(P) respectively indicate an octahedral^21,22 geometry for Co(II) complexes which is supported by the magnetic moment value in the range 4.85-4.89 B.M. The Ni(II) complexes exhibit three absorption bands at 12600 ,17500 and 25000 cm^-1 assignable to ³A_2g(F) ® ³T_2g(F), ³A_2g(F) ® ³T_1g(F) and ³A_2g(F) ® ³T_1g(P) transitions respectively in an octahedral environment. The proposed octahedral geometry of Ni(II) complexes supported by the magnetic susceptibility value in the range 3.16-3.20 BM. The Cu(II) complexes exhibit two spectral bands in the region 13500-13650 cm^-1 and 17950-18200 cm^-1 assigned to ²E_g ® ²T_2g and C. T. bands respectively which proposed distorted octahedral²⁶ geometry. The magnetic susceptibility value for Cu(II) complexes are found in the range 1.84-1.87 B.M.^23,24

Table 1:  Colour, Molar mass, Analytical, Magnetic susceptibility, Electronic spectra, molar conductance and Decomposition temperature of the complexes

Compounds (Colour)	Molar Mass	% Analysis found (calculated)				meff B. M.	l max electronic cm-1	DT    oC	Wm ohm-1 cm2 mol-1
		M	C	N	H
EHPQS(Colourless)	274		60.29 (60.96)	27.04 (27.13)	6.14 (6.20)
EHPQT(Colourless)	290		66.80 (66.97)	25.39 (25.51)	5.77 (5.83
[Co(EHPQS)2](Brown)	606.93	9.62 (9.70)	51.22 (51.40)	22.89 (23.06)	5.21 (5.27)	4.85	10200, 15800, 22400	217	7.6
[Ni(EHPQS)2](Red)	606.71	9.58 (9.67)	51.88 (52.08)	22.88 (23.01)	5.21 (5.27)	3.16	12600, 17300, 25400	210	7.1
[Cu(EHPQS)2](Sky Blue)	611.54	10.30 (10.39)	50.83 (51.01)	22.78 (22.89)	5.18 (5.23)	1.84	13500, 18200	218	8.3
[Co(EHPQT)2](Brownish red)	638.93	9.14 (9.22)	48.62 (48.83)	21.80 (21.91)	4.93 (5.00)	4.89	10300, 15400, 22100	222	7.9
[Ni(EHPQT)2](Brick red)	638.71	9.12 (9.19)	48.64 (48.84)	21.79 (21.91)	4.95 (5.01)	3.20	12300, 17500, 25200	202	5.9
[Cu(EHPQT)2](Blue)	643.54	9.80 (9.87)	48.36 (48.48)	21.64 (21.75)	4.93 (4.97)	1.87	13650, 17950	226	5.4

 

Table 2: IR spectral bands of ligand DDOQH and its metal complexes.

Compounds	nO-H	nN-H	nC=O	nC=N	nC=S
EHPQS	3450 s,b	3260 b	1740 s,b	1570 s,b
EHPQT	3430 s,b	3260 b		1560 s,b	790 s,b
[Co(EHPQS)2]	3420 m,b	3260 b	1720 m,b	1555 m,b
[Ni(EHPQS)2]	3430 m,b	3260 b	1715 m,b	1550 m,b
[Cu(EHPQS)2]	3425 m,b	3260 b	1720 m,b	1550 m,b
[Co(EHPQT)2]	3405 m,b	3260 b		1540 m,b	770 m,b
[Ni(EHPQT)2]	3400 m,b	3260 b		1535 m,b	765 m,b
[Cu(EHPQT)2]	3400 m,b	3260 b		1535 m,b	765 m,b

 

Figure 1:  [M(EHPQS)2 ] / [ M(EHPQT)2] X = oxygen or sulphur; R = n-propyl, R’ = ethyl   Click here to View figure

 

Antimicrobial Activity

Ligands EHPQS/ EHPQT and their metal complexes of Co(II), Ni(II) and Cu(II) were evaluated against Gram positive bacteria, staphylococcus aureus and Gram negative bacterial Escherichia coli. The susceptibility of certain strains of bacteria the ligand and their metal complexes were evaluated by measuring the size of bacteriostatic diameter through paper disc plate method²⁷. The metal complexion shows better inhibition as compared to their ligands. It might be due to complexion of metal ions with Schiff base ligands. Such metal complexes might be inhibiting the enzyme activity of the bacterial system. Antimicrobial activity data for the ligand and their metal complexes are given in Table-3

Table 3: Antimicrobial activity of Schiff base ligands and their metal complexes

Ligand/ Complexes	S. aureus	E.Coli.
EHPQS	8	6
EHPQT	9	7
[Co(EHPQS)2]	15	12
[Ni(EHPQS)2]	16	12
[Cu(EHPQS)2]	17	14
[Co(EHPQT)2]	18	15
[Ni(EHPQT)2]	20	17
[Cu(EHPQT)2]	22	19

Conclusions

On the basis of analytical and spectral data the tentative structure of the complexes of the type [M(EHPQS)₂] and [M(EHPQT)₂] are proposed to be octahedral in nature. The synthesized Schiff bases, EHPQS/EHPQT acts as uninegative tridentate ligand. The metal ions are coordinated through alcoholic oxygen by deprotonation and azomethine.

The remaining coordination of the metal ion is satisfied by either carbonyl oxygen of semicarbozone moiety or thione sulphur of thiosemicarbozone moiety. All these observations put out together lead us to propose the complex of Co(II) and Ni(II) to have octahedral geometry whereas geometry of Cu(II) complexes is proposed to be distorted octahedral geometry as shown in Fig.1.

Acknowlwdgement

We express our sincere thanks to professor D. C. Baluni, Professor and Head, Postgraduate Dept. of zoology, RDS college, Muzaffarpur. One of another (BKR) is grateful to university Grant commission New Delhi for financial support.

References

1. Westcott, S.A. Transition Met. Chem. 30, 411(2005).
2. Singh R.B and Ishi H., Crit., Rev. Anal. Chem., 22, 381(1991).
3. Wang M, Wang L.F, Li.Y.Z, Li, Q.X, Xu, Zd and Qu. D.Q, Transition Met. Chem, 26, 307(2001).
4. Gulerman N.N., Rollas. S. and Erdeniz, H.J. Pharma., Sci., 26, 1(2011).
5. Transconi. P, Albertini. R, Bonati, A. Agila, P.P. Dall, Lunghi P and Pinelli. S, Bionorg. Met. Chem., 8, 154(2000).
6. Clereq De and Verpoort F, Macromolecules, 35, 8943(2002).
7. Rai B.K. and Anand Rahul, Asian J. Che,., 25, 480(2013).
8. Rai B.K. Thakur Amrita and Divya, Asian J. Chem, 25, 583(2013).
9. Rai B.K, Vidhyarthi S.N., Kumari Punam, kumara Suman, Kumari Lakshmi and Singh Rajkishore, Asian J. Chem., 25, 941(2013).
10. Rai B.K. and Kumar Arum, Asian J. Chem., 25, 1160(2013).
11. Rai B.K., J. Indian Chem. Vogel. A.I., A textbook of quantitative Chemical Analysis, Soc; 90, 105(2013).
12. Vogel, A. I., A. Textbook of Quantitative  Chemical Analysis. Revised by B. Denny, R.C. Barens, J.D. and Thomas M, Person education, 2008.
13. Shaymal A., Maurya M.R., Synth. React. Inorg. Met. Org. Chem. 39, 974(974) 1961.
14. Kemp William “Organic Spectroscopy”, 3^rd Edan, Polgrave, New York, Silverstein R.M. and Webster F.X., “Spectrometric Identification of Organic Compound”¹⁴ 6^th Edan, John Wiley and Sons, 109(2008).
15. Tuif, Turka K.I, gerbeley N.V., Russ J. Inorg. Chem., 22, 1497, 1977.
16. Rana A., Dinda R., Sengupta P., Ghosh S., and Falvello Larry, Polyhedron, 21, 1023(2002).
17. Borras J., Alznet G., Gonzatez-Alvarez M, Estevan F, Macias B, Liu Gonzatez M, and Cast Ai Polyhedron, 26, 5009(2007).
18. Agarwal R.K., Agarwal H., and Chakraborti I, Synth, React. Inorg. Metal-org., Chem., 25, 679(1995).
19. Ferraro J.R., “Low frequency vibration of Inorganic and Coordination compound”, plenum Press, New York.
20. Geary W.J., Coord. Chem., Rev., 7, 81(1971).
21. Mane P.S., Sirodhar S.G., Arbad B.R. and Chondekar T.K., Indian J. Chem., Sect. A, 40 648(2000).
22. Lever A.B.P., “Inorganic Electronic Spectroscopy”, Elseciere Amsterdam, 395(1968). C.K. Jorgenson, Acta Chem., Scand., 19, 887(1966).
23. Figgis B.N., “Introduction to Ligand field”, Wiley Eastern Ltd., New Delhi 279(1976).
24. Carlin R.L. and Van Dryneveldt A.J., “Magnetic properties of transition metal compounds”, Springer Verlag, New York, 1977.
25. Mishra A.P., Khare M. and Gautam S.K, Synth. React. Inorg. Metal-Org. Chem.; 32, 1485(2002).
26. Sacooni L., Transition Met. Chem., 4, 212(1968).
27. Mukhurjee P.K, Saha K, Giri S.N., Pal M. and Saha B.P., Indian J. Microbiology, 35(1995).

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