Synthesis, physical characterization, antibacterial activity and thermodynamic studies of five coodrdinate cobalt(III) Schiff base complexes

S Esmaielzadeh,L Azimian,Z Zare

doi:10.4314/bcse.v30i2.5

S Esmaielzadeh, L Azimian + Show 1 more

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https://doi.org/10.4314/bcse.v30i2.5

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Abstract

Some five-coordinated cobalt(III) complexes were synthesized and characterized using elemental analysis, 1 H NMR and IR spectra. The formation constants and the thermodynamic parameters were measured spectrophotometrically for the 1:1 adduct formation of [Co(Chel)(PBu 3 )]ClO 4 .H 2 O where Chel = cd3OMesalen, cd4OMesalen, cd5OMesalen: methyl-2-{[1-methyl-2-(2-hydroxy-3-, 4-, 5-methoxyphenyl)methylidynen-itrilo]ethyl}amino-1-cyclopentene-dithiocarboxylate, as acceptors, with some linear and cyclic amines as donors, in different solvents at constant ionic strength (I = 0.1 M NaClO 4 ), and at various temperatures (T = 283-313 K). The results revealed that the formation constants of the Co(III) Schiff base complexes toward a given amines donor are as follow: [Co(cd4OMesalMeen)(PBu 3 )] + > [Co(cd3OMesalMeen)(PBu 3 )] + > [Co(cd5OMesalMeen)(PBu 3 )] + . The trend of the formation constants of the donors (amines) toward a given cobalt(III) complex is as follow: Im > 4-MeIm > BzIm and n-butylamine > sec-butylamine > tert-butylamine. Also the effect of the solvents on the formation constants of a given cobalt(III) Schiff base complex toward a given donor are as follow: CH 3 CN > DMF > EtOH. The ligands and their cobalt complexes have been screened for their antibacterial activities. All the free Schiff base ligands exhibit higher antibacterial activity than the cobalt(III) complexes. KEY WORDS : Cobalt (III) Schiff base complex, Thermodynamic parameters, Amines, Antibacterial activity Bull. Chem. Soc. Ethiop. 2016 , 30(2), 209-220. DOI: http://dx.doi.org/10.4314/bcse.v30i2.5

Highlights

For a long time tetradentate Schiff base complexes of transition metal ions have attracted many researchers interest in the field of coordination chemistry [1,2,3,4]
Though a large number of papers have appeared on metal complexes with Schiff base derived from aromatic aldehydes and substituted amines with N4 and N2O2 coordination sphere [5,6,7,8], only few publications exist on Schiff bases containing sulfur donor ligands
Following our earlier studies on the coordination behavior, here we report the formation constants for three Co(III) Schiff base complexes with three cyclic amine donors Im, 4-MeIm and BzIm

Summary

INTRODUCTION

For a long time tetradentate Schiff base complexes of transition metal ions have attracted many researchers interest in the field of coordination chemistry [1,2,3,4]. This paper describes thermodynamic studies of five coordinated cobalt(III) complexes in equilibrium with amines as the sixth ligand in ethanol, CH3CN and DMF as solvents. Yield: 56%; m.p.: 301 oC; 1H NMR (400 MHz, DMSO-d6, r.t., TMS, δ ppm): 0.85 (3H, d, Me), 1.28-1.62 (9H, t, P-CH3), 1.94-2.03 (18H, m, P(CH2)3), 2.54 (2H, m, H4'), 2.96 (3H, s, SMe), 3.04-3.20 (4H, m, H3',5'), 3.65 (2H, d, Hen), 3.86 (3H, s, OMe), 4.42 (1H, m, Hen), 6.74 (1H, dd, H4), 6.80 (1H, d, H5), 6.91 (1H, d, H6), 8.56 (1H, s, CH=N); IR (KBr, cm-1): 456 (νCo-N), 579 (νCo-O), 737 (νC-S), 1094 (νClO4), 1180 (νC-S+νC-N), 1246 (νC-O), 1444 (νC=C aromatic), 1607, 1614 (νC=N), 2930 (νC-H), 3420 (νO-H); UV-Vis (DMF) Found: C, 48.34, H, 7.32, N, 3.64, S, 8.58%

C H H OMe

RESULTS AND DISCUSSION

CONCLUSION