Dinuclear cyclometalated platinum (II) complexes: Synthesis,photophysics, and monomolecular electroluminescence

Two novel dinuclear platinum (II) complexes of (C₁₂Rppy)₂Pt₂(dipic) (R = H and F) were synthesized and characterized, where C₁₂Rppy is a 2-phenylpyridine derivative modified with dodecyloxy groups and dipic is a bi-picolinic acid derivative linked by biphenyl unit. Their physical, surface morphologies and optoelectronic properties, as well as molecular orbitals calculation were investigated. Intense excimer emission for both dinuclear platinum (II) complexes were observed in their neat films rather than in their dichloromethane solution under photo-excitation. In contrary, these dinuclear platinum (II) complexes exhibited a stronger monomolecular emission instead of excimer emission in their doped single-emissive-layer polymer light-emitting devices (PLEDs) under electric field owing to the effect of two alkyloxy groups in the ligand of 2-phenylpyridine. Better electroluminescent emission with a maximum current efficiency of 1.3 cd/A and a maximum luminance of 1407 cd/cm² was observed in the (C₁₂Hppy)₂Pt₂(dipic)-doped devices. To our best knowledge, the performance of (C₁₂Rppy)₂Pt₂(dipic) (R = H and F) is among the top values for the solution-processed dinuclear platinum (II) complex-based PLEDs reported so far.