Phosphorescent organoplatinum(II) D2A2 metallacycles: synthesis, self-assembly, and photophysical properties

AbstractA pair of organoplatinum(II) metallacycles, M1 and M2, was self-assembled by combining one of two donor molecules, cis-[Pt(dhim)2(C≡CC5H4N)2] (D1; dhim = 1,3-dihexyl-2-H-imidazole-2-yelidene) and Pt(tbbpy)(C≡CC5H4N)2 (D2; tbbpy = 4,4′-di-tert-butyl-2,2′-bipyridine), with an acceptor precursor, Pt(tbbpy)(OTf)2 (A1; OTf = CF3SO3−), 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 CH2Cl2 for M2). Both metallacycles were characterized by 1H NMR, FT-IR, and FT-ICR-MS techniques that support D2A2 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. Photophysical studies of M1 and M2 reveal that the metallacycles display triplet emission bands at 4...