Transition-metal complexes bearing biaryl-2,2'-diyl ligands tend to show intense luminescence. However, difficulties in synthesis have prevented their further functionalization and practical applications. Herein, a series of platinum(II) complexes bearing biaryl-2,2'-diyl ligands, which have never been prepared in air, were synthesized through transmetalation and successive cyclometalation of biarylboronic acids. This approach does not require any air- or moisture-sensitive reagents and features a simple synthesis even in air. The resulting (Et4 N)2 [Pt(m,n-F2 bph)(CN)2 ] (m,n-F2 bph=m,n-difluorobiphenyl-2,2'-diyl) complexes exhibit intense green emissions with high quantum efficiencies of up to 0.80 at 298 K. The emission spectral fitting and variable-temperature emission lifetime measurements indicate that the high quantum efficiency was achieved because of the tight packing structure and strong σ-donating ability of bph.
Keywords: ligand design; ligand effects; luminescence; metallacycles; photophysics; platinum.
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