Abstract Novel heteroleptic Co(II) and Zn(II) complexes of a Schiff base derived from 2-amino-4,6-dihydroxypyrimidine and 2-hydroxy-1-napthaldehyde were synthesized and characterized by percentage metal and elemental (CHN) analyses, FTIR, UV-VIS and 1H- and 13C-NMR spectroscopies, magnetic susceptibility, melting point and molar conductance measurements. The proposed molecular formula [M(L)(L’)OAc] {M= Co and Zn; L=Schiff base and L’= 2,2’-Bipyridine} for the complexes were consistent with the spectral, elemental and percentage metal data. The electronic and room temperature magnetic susceptibility values were corroborative of octahedral geometry for the heteroleptic divalent complexes. In addition, the room temperature magnetic susceptibility showed a spin crossover from high to low spin within the octahedral environment for Co(II) complex, while the CHN data indicate 1:1:1 molar ratio of the metal ions to the ligands. Low values of molar conductance in dimethylsuphoxide (DMSO) established the non-electrolytic nature of the complexes. The antimicrobial studies of the Schiff base, 2,2’-bipyridine and their heteroleptic complexes screened in vitro against S. aureus, P. aeruginosa, E. coli, B. cereus, P. mirabilis and K. oxytoca; and Aspergillus flevus, Aspergillus niger and R. stolonifer displayed moderate-good activities. Remarkably, the synthesized compounds showed broad spectrum activity against tested microbes with inhibitory zones of 5.5-26.0 mm proving their potentials as broad-spectrum microbial agents. Also, the antioxidant activities of the ligands and their heteroleptic complexes were determined in vitro by DPPH methods. The obtained values were mostly comparable/higher to that of the standard, ascorbic acid (55.03%) suggesting a similar pathway for their antioxidant activities and proving their potentials as probable anticancer agents.
Keywords Antioxidant, heteroleptic complexes, broad-spectrum, non-electrolytic and naphthaldehyde.