Structure and chiroptical properties of platinum(II) complexes with chiral BINOL ligands

Abstract An enantiomeric pair of novel platinum(II) complexes, coordinated with two chiral 1,1′-bi-2-naphthol (BINOL) ligands and a 4,4′-di-tert-butyl-2,2′-bipyridine ligand, were synthesized. X-ray crystallographic analysis revealed that both BINOLs serve as monodentate ligands, with their uncoordinated hydroxyl groups forming intramolecular hydrogen bonds. These hydrogen bonds enforce an obtuse dihedral angle between the two naphthalene rings. In solution, circular dichroism (CD) and circularly polarized luminescence (CPL) spectra attributable to the binaphthyl moieties were observed, with the signs of the CD and CPL signals being reversed owing to the unique structure of the binaphthyl units. In contrast, in the solid state, the Pt complex exhibited aggregation-induced enhanced phosphorescence.