Diazaborolyl-boryl push-pull systems with ethynylene-arylene bridges as %26apos;turn-on%26apos; fluoride sensors

作者：Weber Lothar^*; Eickhoff Daniel; Kahlert Jan; Boehling Lena; Brockhinke Andreas; Stammler Hans Georg; Neumann Beate; Fox Mark A

来源：Dalton Transactions, 2012, 41(34): 10328-10346.

DOI：10.1039/c2dt30438d

Two linear pi-conjugated systems with 1,3-diethyl-1,3,2-benzodiazaborolyl [C6H4(NEt)(2)B-] as a donor group and dimesitylboryl (-BMes(2)) as acceptor were synthesised with -ethynylene-phenylene-(-C C-1,4-C6H4-, 3) and -ethynylene-thiophene-(-C C-2,5-C4H2S-12) bridges between the boron atoms. An assembly (20) consisting of two diazaborolyl-ethynylene-phenylene-boryl units, [C6H4(NCy)-(N%26apos;)B-C C-1,4-C6H4-BMes(2)] joined via a 1,4-phenylene unit at the nitrogen atoms (N%26apos;) of the diazaborolyl units was also synthesised. The three push-pull systems, 3, 12 and 20, form salts on fluoride addition with the BMes(2) groups converted into (BMes(2)F)(-) anions. The molecular structures of 3, 12 and (NBu4)(12 center dot F) were elucidated by X-ray diffraction analyses. The borylated systems 3, 12 and 20 show intense blue luminescence in cyclohexane with quantum yields (Phi(fl)) of 0.99, 0.44 and 0.94, respectively, but weak blue-green luminescence in tetrahydrofuran (Phi(fl) = 0.02-0.05). The charge transfer nature of these transitions is supported by TD-DFT computations with the CAM-B3LYP functional. Addition of tetrabutylammonium fluoride to tetrahydrofuran solutions of 3 and 20 resulted in strong violet-blue luminescence with emission intensities up to 46 times more than the emission intensities observed prior to fluoride addition. Compounds 3 and 20 are demonstrated here as remarkable %26apos;turn-on%26apos; fluoride sensors in tetrahydrofuran solutions.

• 出版日期2012