Four new compounds, 3-methoxy-2-hydroxybenzaldehyde S-ethylisothiosemicarbazone (H2L), (3-methoxy-2-hydroxybenzaldehyde S-ethyl-isothiosemicarbazonato-N,N0,O)-(1-methylimidazole)-nickel(II) (1), (3-methoxy-2-hydroxybenzaldehyde S-ethyl-isothiosemicarbazonato-N,N0,O)-(pyridine)-nickel(II) (2) and cis-dioxo-dimethylsulfoxide-(3-methoxy-2-hydroxybenzaldehyde S-ethyl-isothiosemicarbazonato- N,N0,O)-molybdenum(VI) (3), have been synthesized and characterized by molar conductivity, FT-IR, UV–Vis, 1H NMR, elemental analysis and X-ray crystal structures. The crystal structure of H2L reveals that the NH2 and S–R moieties are in cis positions with respect to each other, and the molecule adopts the Z configuration. The ligand is bonded to the central metals as a binegatively tridentate agent. The Ni(II) atom adopts square planar geometry with this ligand, with the 1-methylimidazole and pyridine ligands occupying the remaining position in complexes 1 and 2 respectively. The Mo(VI) center in complex 3 is six coordinated by the ligand, two oxido groups and one DMSO molecule. The Density Functional Theory approach has been successfully used for the investigation of the ground state, frequency assignment and natural bond analysis.

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