Phosphorescent organoplatinum(II) D 2 A 2 metallacycles: synthesis, self-assembly, and photophysical properties

A pair of organoplatinum(II) metallacycles, M1 and M2 , was self-assembled by combining one of two donor molecules, cis -[Pt(dhim) 2 (C≡CC 5 H 4 N) 2 ] ( D1 ; dhim = 1,3-dihexyl-2-H-imidazole-2-yelidene) and Pt(tbbpy)(C≡CC 5 H 4 N) 2 ( D2 ; tbbpy = 4,4′-di-tert-butyl-2,2′-bipyridine), with an acceptor precursor, Pt(tbbpy)(OTf) 2 ( A1 ; OTf = CF 3 SO 3 − ), respectively. Both donor molecules exhibit an idealized 90° angle between the coordination vectors of their ethynylpyridine moieties.

When mixed with A1 , coordination-driven self-assembly occurs at 50 °C (4 days in acetonitrile for M1 and 18 h in CH 2 Cl 2 for M2 ). Both metallacycles were characterized by 1 H NMR, FT-IR, and FT-ICR-MS techniques that support D 2 A 2 self-assembly of molecular squares. The structure of building block D1 was determined by X-ray diffraction, confirming the expected square coordination geometry and 90° orientation of the pyridyl coordination vectors.