Spectral studies of H-aggregate of D-pi-A molecule

D-pi -A molecules bearing strong electron donor and acceptor, 5-(4-N,N-dime thyl amino-benzylidene)-(1H,3H)-2,4,6-pyrimidinetrione (AB(1)) and 5-(4-N,N -dioctadecylaminobenzylidene)-(1H,3H)-2,4,6-pyrimidinetrione (AB(18)) were synthesized and their spectral properties were investigated. For ABI and AB 18, their UV-visible absorption spectra in cyclohexane and surface photovol tage spectra show peaks at 450 nm due to the formation of H-aggregate, whic h underwent a blue-shift about 30 nm than that of monomer intramolecular ch arge transfer(ICT) band in chloroform. The fluorescence emission band of ex cimer of K-aggregate in solid and at a high concentration in chloroform sol ution occurs at 620 nm and near 610 nm, respectively. The band at 620 nm un derwent a red-shift about 3 000 cm(-1) than that of monomer. In addition, i ntermolecular pi-pi interactions of such D-pi -A molecules possesing strong electron donor and acceptor are discussed.