HALOCOBALOXIMES CONTAINING COORDINATED PYRAZINE, PYRAZINE CARBOXYLIC ACID AND PYRAZINE CARBOXAMIDE: MICROWAVE ASSISTED SYNTHESIS, CHARACTERIZATION AND ANTIBACTERIAL ACTIVITY

Authors: S. Martina, C. Revathia, A. Dayalana*, N. Mathivananb and V. Shanmugaiyab

aDepartment of Chemistry, Loyola College (Autonomous), Chennai-600 034, India;bCentre for Advanced Studies in Botany, University of Madras, Chennai-600 025, India.;E-mail: dayalansgp@gmail.com

About nine cobaloximes of the type Trans -[Co(dmgH)₂(B)X] , where     dmgH^- = Dimethylglyoximate, X^- = Cl^- , Br^- or I^-  and   B = Pyrazine, Pz (1 to 3 ) , Pyrazine  carboxylic acid , PzCA (4 to 6) or    Pyrazine carboxamide , PzAM (7 to 9)  were prepared and characterized by elemental analysis, TG/DTA , FABMS UV-visible, IR and NMR spectra. The ligands and their cobaltI(III) complexes were screened against  microorganisms for their antibacterial activity and compared against tetracycline as standard. The free ligands viz., Pz , PzCA and PzAM showed antibacterial activity in the order : Pz >   PzCA >  PzAM  whereas, the free equatorial ligand dmgH ₂ was found to be inactive against all  the bacteria tested. The cobaloximes were  found to be more active than the corresponding pyrazine and its derivatives as axial ligand in the complexes . Bromocobaloximes are found to be more active than   chloro- and iodocobaloximes with the antibacterial activity order for the axial halides as   Br^- > I ^- > Cl^-   for complexes having axial pyrazine ; whereas , a slightly different trend viz.,  I^-  >  Br^-   > Cl^-  was noticed for halocobaloximes containing axial pyrazine carboxylic acid or  pyrazine carboxamide.

Keywords : Cobalt(III) complexes , Cobaloximes, Pyrazine , Pyrazine carboxylic acid , Pyrazine carboxamide , Antibacterial activity of metal complexes.