两个具有强双光子荧光的有机硼化合物

以二米基硼为电子受体, 苯乙烯基噻吩为共轭桥, 合成了两个新的稳定的有机硼化合物: 反式,反式-2-二米基 硼-5-{2-4-(2-噻吩乙烯基)苯基]乙烯基}噻吩(1)和反式,反式-1,4-二-2-(5-二米基硼噻吩)乙烯基]苯(2). 前者为不对称结构的偶极分子, 后者为对称的A-π-A型四极分子. 对称性不同的化合物表现出不同的双光子吸收性质. 对于偶极分子1, 单双光子吸收达到的激发态能级接近, 而对于四极分子2, 双光子吸收达到的激发态则比单光子吸收所达到的激发态高出0.35 eV. 在波长为710到 900 nm范围的飞秒脉冲激光激发下, 化合物1和2在THF溶液中都可以发出很强的绿色上转换荧光 (1, λ_max＝505 nm; 2, λ_max＝513 nm). 用双光子荧光法测得A-π-A型化合物2在775 nm处的双光子吸收截面达1340 GM.

Two Organoboron Compounds with Strong Two-photon Excited Fluorescence

Two new stable organoboron compounds with dimesitylboryl group as electron acceptor and styrylthiophene as conjugated bridge have been synthesized, which are named trans,trans-2-dimesityl- boryl-5-(2-(4-(2-(thien-2-yl)vinyl)phenyl)vinyl)thiophene (1) and trans,trans-1,4-bis2-(5-dimesitylborylthien-2-yl)vinyl]benzene (2). The former is asymmetrical dipolar molecule and the latter is symmetrical A-π-A type quadrupolar molecule. The compounds with different symmetry exhibit different two-photon absorption properties. To dipolar molecule 1, the energy levels of the excited states by single- and two-photon absorption processes are very close, but to quadrupolar molecule 2, the level of the excited state by two-photon absorption is about 0.35 eV higher than that by single-photon absorption. Pumped by laser pulses from 710 to 900 nm in femtosecond regime, both compounds 1 and 2 showed strong green up-converted fluorescence in THF solution with λ_max＝505 nm for 1 and λ_max＝513 nm for 2. Under the excitation of 775 nm light, the two-photon absorption cross-section of 2 was measured to be 1340 GM by two-photon fluorescence method.