Spectral Studies of H-Aggregate of D-π-A Molecule

D-π-A molecules bearing strong electron donor and acceptor, 5-(4-N,N-dimethyl amino-benzylidene)-(1H, 3H)-2,4,6-pyrimidinetrione(AB₁) and 5-(4-N, N-dioctadecylaminobenzylidene)-(1H, 3H)-2,4,6-pyrimidinetrione(AB₁₈) were synthesized and their spectral properties were investigated. For AB₁ and AB₁₈ their UV-visible absorption spectra in cyclohexane and surface photovoltage spectra show peaks at 450 nm due to the formation of H-aggregate, which underwent a blue-shift about 30 nm than that of monomer intramolecular charge transfer(ICT) band in chloroform. The fluorescence emission band of excimer of H-aggregate in solid and at a high concentration in chloroform solution occurs at 620 nm and near 610 nm, respectively. The band at 620 nm underwent a red-shift about 3 000 cm^-1 than that of monomer. In addition, intermolecular π-π interactions of such D-π-A molecules possesing strong electron donor and acceptor are discussed.