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.

In order to suppress excimer emission and obtain monomolecular electroluminescent (EL) for dinuclear platinum (II) complexes, both dinuclear platinum complexes of the (C12Rppy)2Pt2(dipic) (R = H and F) were prepared. Excimer emission of both dinuclear platinum (II) complexes in the devices was effectively suppressed by attaching two long chain alkyloxy groups into the cyclometalated ligand of 2-phenylpyridineFigure optionsDownload as PowerPoint slideHighlights
► Both dinuclear platinum complexes (C12Rppy)2Pt2(dipic) (R = H and F) were synthesized.
► We investigated the optophysical properties of the platinum complexes.
► Intense monomolecular emission instead of excimer emission in PLEDs under electric field.
► High-efficiency performances were obtained for these dinuclear platinum complexes in PLEDs.