Synthesis and characterization of nine complexes formed from the reaction of metal ion salts (chloride or acetate) of
Mn2+, Co2+, Ni2+, Cu2+, Zn2+ and Cd2+ (I – IX) and 4-aminopyridine (4Am) with variable stoichiometric ratios were studied and
their chemical structures were discussed. The prepared complexes were characterized by different chemical and physical
techniques. The antimicrobial activity of the studied complexes was tested against representative bacteria and fungi. The
results suggested the high - to - moderate activities against the tested organisms compared to ampicillin taken as a standard
drug. The cytotoxic activities of some selected complexes were tested against Lung carcinoma cells A-549 cell line. The
results obtained showed that the complexes are considered to have high to moderate activity. The catalytic activity of Ni(4AM)
(1:4) complex was tested for the removal of orange G (OG+) dye from waste water sample where almost complete removal of
the dye was performed after 90 min. Molecular modeling and quantum chemical parameters of the Mn2+, Co2+, Ni2+ and Zn2+
complexes were studied and calculated. Also, the total density function, deformation density function and frontier orbital
energy were determined using DFT method