Formation of Hetero-binuclear Pt(II)-M(II) Complexes Based on (2-(1 H-Tetrazol-5-yl)phenyl)diphenylphosphine Oxide...

Novel hetero-binuclear platinum complexes (HBC-Pt(II)-M(II), M = Ca(II), Mg(II), Zn(II), and Cd(II)) have been synthesized by the reaction of the corresponding precursors [Pt(ppy)(μ-Cl)]₂ with (2-(1 H-tetrazol-5-yl)phenyl)diphenylphosphine oxide (TTPPO). The X-ray structures of the complexes show that two ancillary ligands TTPPO in the square-planar Pt(II) moiety act as a quadridentate chelating agent for the other metal center, eventually forming a distorted octahedral configuration. There are no significant π-π interactions and Pt-M metallophilic interactions in the crystal lattice, due to the steric hindrances associated with the rigid octahedral structure together with the bulky TTPPO. Consequently, HBC-Pt-M complexes show monomer emission characteristics with quantum yields up to 59% in powder, suggesting their great potential for practical applications. DFT and TD-DFT calculations on HBC-Pt-Zn reveal that the phosphorescence can be ascribed to intraligand charge transfer (³ILCT) combined with some metal-to-ligand charge transfer (³MLCT) in the Pt(ppy) moiety, which is consistent with the observations from the photophysical investigations.