Ligand-Controlled Redox and Photophysical Properties in Photoluminescent Tris-Heteroleptic Ru(II) Pyridyl-Phosphonium...

The ability to tune the redox and photophysical properties of transition metal complexes is crucial for expanding their functional scope across diverse applications. Such modulation is commonly achieved through rational ligand design and the deliberate assembly of heteroleptic complexes featuring tailored coordination environments. However, the selective synthesis of tris-heteroleptic metal complexes featuring three different bidentate ligands remains a major challenge in coordination chemistry. These specific architectures are still rarely reported in the literature, largely due to their synthetic complexity and the lack of general, reliable protocols for their preparation. In this general context, we present an efficient synthetic strategy for the preparation of octahedral tris-heteroleptic Ru(II) phosphonium ylide complexes incorporating three distinct chelating ligands. The isolated pyridyl-phosphonium ylide Ru(II) complexes exhibit intense and tunable photoluminescence, with emission profiles spanning a broad spectral window from sky blue to near-infrared, along with a wide range of redox potentials. The successful isolation of these well-defined Ru species highlights the crucial influence of ligand electronic and steric properties on the excited-state behavior of the metal center.