Luminescent and Ionochromic Polyiminofluorene with Conjugated Terpyridine Substituent Groups

摘要

Poly(N-(4-(2,2':6,2 ''-terpyridyl)phenyl)imino-2,7-fluorenylene P1-2 was prepared upon palladium-catalyzed polycondensation of 2,7-dibromo-9,9-di-n-hexylfluorene 1 and 4'-(4-aminophenyl)-2,2':6,2 ''-terpyridine 2 with 80 yield. MALDI-TOF spectroscopy indicated a maximum degree of polymerization of 14, the most abundant species being the pentamer and the hexamer. P1-2 is highly fluorescent in solution. The emission maximum in chloroform is 5 10 nm, and the quantum yield Phi(f) is 55. UV/Vis titration of P1-2 with zinc acetate and iron(II) perchlorate indicates formation of metal-terpyridine (tpy) 1:2 (bis)complexes. Since formation of the (bis)complex is accompanied by cross-linking, the polymer slowly precipitates, especially in non-polar solvents. Comparative titration of monomer 2 with zinc acetate proceeds under sharp increase of photoluminescence intensity until a metal-tpy 2:1 ratio is reached. We assume the formation of two zinc (mono) complexes, one with the tpy and the other one with the amino group of 2. CV analysis of P1-2 in acetonitrile indicates three quasi-reversible oxidation processes with mid-potentials of 0.45, 0.50 and 0.95 V versus SCE due to oxidation of the backbone nitrogen atoms, while the reduction at -2.6 V is irreversible. The strong ionochromism renders P1-2 useful as highly sensitive and specific fluorimetric chemosensor.