The novel azo-azomethine ligand incorporating oxygen and nitrogen donating atoms was designed and prepared. Additionally, a series of metal complexes derived from this azo-azomethine ligand namely, 2-(((1H-1,2,4-triazol-5-yl)imino)methyl)-5-((4-nitrophenyl)diazenyl)phenol formulated as [Ru(HL)2Cl(H2O)].4H2O, [M(HL)XYZ(H2O)].nH2O, (where M=Fe3+, Ni2+, Co2+, Mn2+, Cu2+(8-10), Zn2+ or UO22+; X= Cl, CH3COO or NO3; Y= Cl, H2O or 0; Z=H2O or 0; n= 2, 0 or 7, [VO(H2L)2(H2O)].SO4 and [Cu(H2L)2(H2O)2].SO4 were synthesized. The azo-azomethine ligand and its metallic chelates were structurally characterized based on thermal, elemental analyses and spectroscopic tools (Infrared, electronic absorption, nuclear magnetic resonance) as well as mass spectrometry, magnetic susceptibility, and molar conductivity measurements. The global reactivity descriptors, molecular electrostatic potential image, optimized geometry, lowest un-occupied and highest occupied molecular orbital (LUMO & HOMO) of the molecules were studied basing on density functional theory level (DFT) using B3LYP method and 6-311G.(d,p) basis set. The measurements were explored that the azo-azomethine ligand (H2L) performed as monobasic or neutral bidentate ligand bonded the cations via the protonated/deprotonated phenolic oxygen atom and azomethine nitrogen atom adopting tetrahedral or distorted octahedral geometries around the cations. The in vitro microbicide activity showed that the azo-azomethine ligand (H2L) was inactive while the complexes have a moderate inhibitory effect and some complexes showed activities close to the effect of standard drugs used.