Synthesis, Crystal Structures and Photosensitizing Activities of Ni(II) and Pd(II) Heteroleptic Dithiolate–dppf Complexes

New heteroleptic complexes, [M(dithiolate-dppf)] (M=Ni(II) 1,Pd(II) 2, dithiolate=2-(methylene-1,1′-dithiolato)-1,3-indandione (L1); Pd(II) 3, 2-(methylene-1,1′-dithiolato)-5,5′-dimethylcyclohexane-1,3-dione (L2); dppf = 1,1′-bis(diphenylphosphino)ferrocene) have been synthesized and characterized by elemental analysis, spectroscopy (IR, UV-Vis., 1H, 13C and 31P NMR) and cyclic voltammetry. X-ray crystallography revealed distorted square planar geometry with P2MS2 cores in 1–3, displaying M⋯H−C intramolecular anagostic interactions. Complexes 1–3 show luminescent characteristics in CH2Cl2 solution at room temperature emanating from the MLCT charge-transfer state. Based on their optical and electrochemical properties, the sensitizing activities of 1–3 have been explored; the Ni complex 1 has shown significant light to electrical energy conversion efficiency with η value of 0.78%. All the three complexes with σrt, 10−6-10−7 S cm−1 and Ea=1.00-1.35 eV are weakly conducting but show semiconducting characteristic in the 303–363 K temperature range.