Structures and photoluminescence of dinuclear platinum(II) and palladium(II) complexes with bridging thiolates and 2,2′-bipyridine or 2,2′∶6′,2″-terpyridine ligands

Abstract

A series of mononuclear and dinuclear platinum(II) thiolates with 2,2′-bipyridine (bpy) and 2,2′∶6′,2″-terpyridine (terpy) ligands having emissive LLCT (ligand-to-ligand charge-transfer) excited states were prepared and characterized by X-ray diffraction analyses. The [M₂(dtbpy)₂(NS)₂][ClO₄]₂ (M = Pt or Pd; dtbpy = 4,4′-di-tert-butyl-2,2′-bipyridine, NS^– = pyridine-2-thiolate) complexes are isostructural to each other with intramolecular Pt· · ·Pt and Pd· · ·Pd distances being 2.917(2) and 2.891(4) Å, respectively. Assignment of LLCT absorption bands for the platinum(II) complexes was based on the shift in absorption energy with the substituents on the diimine and thiolate ligands. In the solid state or in solution at room temperature the platinum(II) complexes show photoluminescence with λ_max ranging from 603 to 710 nm. The Pt^II· · ·Pt^II and/or ligand–ligand interactions are not primarily responsible for the emissions of the dinuclear platinum(II) thiolates which have intramolecular metal–metal separations greater than 2.9 Å.