Synthesis and light-emitting properties of platinum-containing oligoynes and polyynes derived from oligo(fluorenyleneethynylenesilylene)s

A series of blue-light-emitting oligo(fluorenyleneethynylenesilylene)s (OFESs) of the general formula HC≡CRC≡C(EC≡CRC≡C)mEC≡CRC≡CH (E = SiPh2, SiMe2, or SiMe2-SiMe2; m = 0-2; R = 9,9-dihexylfluorene-2,7-diyl) and their phosphorescent platinum-containing oligoynes and polyynes were synthesized and characterized. The solution properties and regiochemical structures of this new structural class of organosilicon-based polyplatinayne polymers {trans-[-Pt(PBu3)2C≡CRC≡C(EC≡ CRC≡C)mEC≡CRC≡C-]n) were studied with IR and NMR (1H,13C,29Si, and31P} spectroscopy. The optical absorption and photoluminescence spectra of these metallopolymers were examined and compared with their discrete oligomeric model complexes. Our studies led to a novel approach of using the sp3-silyl moiety as a conjugation interrupter to limit the effective conjugation length in metal polyynes, which could boost the phosphorescence decay rates essential for light-energy harvesting from the triplet excited state. The influence of the heavy platinum atom and the group 14 silyl unit possessing different side-group substituents on the thermal and phosphorescence properties was investigated in detail. We also established the goal of studying the evolution of the lowest singlet and triplet excited states with chain length m of OFESs and the nature of E in these metallopolymers. This work indicated that the phosphorescence emission efficiency harnessed through the heavy-atom effect of platinum in the main chain did not change very much with oligomer chain length m but generally decreased with the E group in the order SiMe2> SiMe2-SiMe2> SiPh2.