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Luminescent and Ionochromic Polyiminofluorene with Conjugated Terpyridine Substituent Groups
Author(s) -
Rabindranath Aravinda Raman,
Maier Anna,
Schäfer Mathias,
Tieke Bernd
Publication year - 2009
Publication title -
macromolecular chemistry and physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.57
H-Index - 112
eISSN - 1521-3935
pISSN - 1022-1352
DOI - 10.1002/macp.200800542
Subject(s) - chemistry , terpyridine , acetonitrile , diimine , monomer , quantum yield , polymerization , zinc , substituent , titration , polymer chemistry , pentamer , photochemistry , conjugated system , homoleptic , perchlorate , metal , polymer , medicinal chemistry , fluorescence , inorganic chemistry , organic chemistry , catalysis , biochemistry , physics , quantum mechanics , ion
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 510 nm, and the quantum yield Φ 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.