Reaction of [(arene)MCl₂]₂ with bidentate 4, 5-diazafluorene-9-one (dafo) and derived Schiff base ligands (L1–L3) in the presence of ammonium hexafluorophosphate yielded mononuclear cationic complexes having general formula [(arene)MLCl]PF₆ {M = Ru, arene = benzene (1, 5, 9); M = Ru, arene = p-cymene (4, 8); M = Rh, arene = Cp^* (2, 6, 10); M = Ir, arene = Cp^* (3, 7, 11); L = 4, 5-diazafluorene-9-one(L1), N-(4, 5-diazafluoren-9-ylidene)aniline (L2), N-(4, 5-diazafluoren-9-ylidene)phenyl hydrazine (L3)}.All these complexes were isolated as hexafluorophosphate salts and characterized by spectral and analyticaltechniques such as FT-IR, UV-vis, NMR spectroscopy and ESI-Mass spectrometry. Complexes 1-3 werecharacterized by X-ray crystallographic studies, which indicated NN0 bidentate coordination of the ligandsthrough pyridine nitrogen atoms of the ligand. To evaluate the biological properties of these complexes,antibacterial and antioxidant experiments have been carried out. The complexes 8, 9 and 11 exhibitedantibacterial activity against Gram-positive bacteria. Results also show that the compounds possess prominentantioxidant activity against DPPH radicals.