Platinum(II) diimino complexes with 1,3-propanedithiol: Synthesis and spectral characterization

Two new platinum(II) diimino complexes with 1,3-propanedithiolate ion (Pdt( 2-)), [Pt(Diimine)(Pdt)] (Diimine = 1,10-phenanthroline or 2,2'-bipyridine) , are synthesized and spectrally characterized. It is established that the medium-intensity [3000-4000 l/(mol cm)] absorption bands of the [Pt(Diimine )(Pdt)] solutions in the range 450-550 nm are caused by two energetically c lose electronic transitions. It is shown that these charge-transfer transit ions occur from the molecular orbitals composed of the orbitals of central atom and orbitals of the thiolate sulfur atoms to the vacant pi* orbital of the diimine ligand, {Pt/S} --> (Diimine). Absorption band in the range 600 -638 nm [similar to 500 l/(mol cm)] is assigned to the singlet-triplet char ge-transfer transition. The 1,3-propanedithiolate ion is found to exhibit a tangible trans-effect.