Supramolecular structure, stereochemistry and substituents effect on the spectral studies of novel ruthenium complexes

Novel complexes of Ru(III) with 5-(4-alkylphenylazo)-2-thioxo-4-thiazolidinone (HLn) have been prepared and characterized by elemental analysis, thermogravimetric analysis (TGA), 1H NMR, magnetic susceptibility and electronic spectral techniques. Tentative structures for the complexes are proposed. The important infrared (IR) bands and the main 1H NMR signals are assigned and discussed relative to the molecular structure. The spectra show that all complexes are octahedral in which chloride is attached to the metal ion. The spectral data were utilized to compute the important ligand field parameters B, β and Dq. The B-values suggest a strong covalency in the metal–ligand σ-bond and the Dq-values indicate a medium strong ligand field. Results show that the β-depends greatly upon the electronegativity of the donor atoms and the ligand structure and also the effect of the p-substituent groups. The ligands act as a monobasic (bis/tris-bidentate chelating agent) coordinating through NN and OH groups by replacement of a proton from the latter group there by forming a six-membered. Stability of these complexes has been investigated and a considerable interest has also been focused on the synthesis of the azo compounds and its metal complex due to its wide potential applications. In p-azo-rhodanine intramolecular OH⋯N hydrogen bonds have detected.

► HLn behaves as a chelating bidentate monobasic ligand.
► HLn bonding through azodye (NN) and enolic oxygen atom after deprotonation.
► The ligand field parameters were calculated using various energy level diagrams.
► The present study revealed octahedral geometry around Ru(III)-complexes.