二氰基乙烯基并三噻吩的光谱行为

The Spectroscopic Behavior of Dicyanovinyldithienothiophenes

本文设计合成了两种二氰基乙烯基并三噻吩化合物,即2-二氰基乙烯基二噻吩并[3,2-b:2′,3-′d]噻吩(DCTT)与2-二氰基乙烯基二噻吩并[2,3-b:3′,2-′d]噻吩(DCST).研究了介质极性对吸收与发射光谱行为的影响,考察了化合物的分子结构与其发光能力的关系.溶剂效应显示化合物DCST随介质的极性增加,分子内电荷转移态(ICT)的荧光发射峰位红移现象更为明显,展示出较大的Stokes位移.化合物DCTT随介质的极性增加,发光行为表现出负的溶致变色效应,与"能级邻近效应"有关.溶剂效应说明了DCTT分子中并三噻吩部分给出电子的能力较弱,而DCST分子中的并三噻吩部分给出电子的能力较强,是导致二者ICT态的发光能力的差异的主要原因.

Two conjugated D-A compounds, 2-dicyanovinlydithieno[3, 2-b：2′, 3′-d ] thiophene （DCTT） and 2-dicyanovinlydithieno[2,3-b ： 3′, 2′-d ] thiophene （DCST） were synthesized and char- acterized. The relationship between the emission properties and molecular structures was studied by investigation of solvent effect for DCTT and DCST. Both title compounds show intramolecular charge transfer （ICT） state emission. With the increase of polarity of solvents, DCST shows ICT emission with strong red shift and larger Stokes shift. However, DCTT shows weak red shift but negative solvatochromism： an increase of quantum yields from ICT emission, which may due to the Proximity effect between the transitions of π-π＊ and n-π＊. Such emission difference between DCTT and DCST shows that the ICT state could be occurred in both compounds, but charge separation might not be formed easily between moiety of thieno[ 3,2-b：2′, 3′-d ] thiophene and moiety of dicyanovinyl in DCIT, however, formed easily between moiety of thieno[2,3-b ： 3′, 2′-d ] thiophene and moiety of dicyanovinyl in DCST.