J-type aggregation of a simple merocyanine skeleton: Spectral features and structure of 4-amino-6-oxopyrimidine

The absorption and fluorescence spectral properties of 4-amino-6-oxopyrimidine (1), which has a simple streptopolymethine merocyanine skeleton, clearly showed that the molecule 1 formed the aggregate 1(n), and showed an exciton band, appearing at an absorption of 350 nm due to the red-shifted HOMO-LUMO transition. Upon light irradiation of the exciton band, a fluorescence band at 398 ran (Phi(FL) = 0.10) was observed, and its decay lifetimes were determined. Based on these spectral features, the aggregated 1(n) was found to be formed by J-type aggregation. The molecular orientation 1 in the crystal was revealed as being both parallel pi-pi stacking and hydrogen bonding chains. (C) 2007 Elsevier B.V. All rights reserved.