Platinum(II) Complexes of Tridentate ‐Coordinating Ligands Based on Imides, Amides, and Hydrazides: Synthesis and Luminescence Properties

Abstract

Abstract Five Pt(II) complexes are described in which the metal ion is bound to anionic ‐coordinating ligands. The central, deprotonated N atom is derived from an imide Ar−C(=O)−NH−C(=O)−Ar {PtL 1–2 Cl; Ar=pyridine or pyrimidine}, an amide py−C(=O)−NH−CH 2 −py {PtL 3 Cl}, or a hydrazide py−C(=O)−NH−N=CH−py {PtL 4 Cl}. The imide complexes PtL 1–2 Cl show no significant emission in solution but are modestly bright green/yellow phosphors in the solid state. PtL 3 Cl is weakly phosphorescent. PtL 4 Cl is formed as a mixture of isomers, bound through either the amido or imino nitrogen, the latter converting to the former upon absorption of light. Remarkably, the imino form displays fluorescence in solution, λ 0,0 =535 nm, whereas the amido shows phosphorescence, λ 0,0 =624 nm, τ=440 ns. It is highly unusual for two isomeric compounds to display emission from states of different spin multiplicity. The amido‐bound PtL 4 Cl can act as a bidentate ‐coordinating ligand, demonstrated by the formation of bimetallic complexes with iridium(III) or ruthenium(II).