The excited state of 4-(β,β-dicyanovinyl)-3-methyl-N-methyl-N-benzylaniline (DCBA) in two types of molecular crystals, orange and yellow crystals, are investigated. These crystals were structurally analyzed by means of X-ray diffraction techniques. In each crystal, DCBA forms one-dimensional infinite chain by π-interactions between the 4-(β,β-dicyanovinyl)aniline planes. The orange crystal involves only one type of infinite chain. On the other hand, interestingly, the yellow crystal contains two kinds of different infinite chains, which are distinguished by the degree of π-overlap between the neighboring molecules. Only the crystalline forms of DCBA show fluorescence. The fluorescence time decay of the orange crystal contains only one decay component and its lifetime was 52.7 ns. On the other hand, that of the yellow crystal consists of two decay components, and the lifetimes were 7.0 and 16.8 ns. In each crystal, the number of the decay components are in agreement with the number of the independent infinite chains. The nature of the excited states is investigated by use of simple ab initio STO-3G molecular orbital (MO) calculations. It is suggested from the MO calculations that the delocalized excited states are formed in the orange crystal, on the other hand, the excited states of the yellow crystal are characterized by the localized excitation.
All Science Journal Classification (ASJC) codes
- Physical and Theoretical Chemistry