The effect of substituents on the fluorescent properties of Para-phenylenevinylene

Semi-empirical AM I method and density function theory were used to study the electronic structures and spectroscopic characteristics of the luminescent material analogous to PPV (para-phenylenevinylene) oligomers attached to different substituents. It was indicated that the LUMO-HOMO energy gaps were changed distinctly by means of the electron-donating effect, conjugated effect and steric effect. The fluorescent wavelength in the fluorescent spectrum, the main absorption peaks in the electronic spectra and the chief bands in the IR spectra for the complexes were red-shifted, relative to those of the parent molecule, owing to the extension of the conjugated system, the shrink of the energy gap and the weakening of the C=C bonds, respectively. The C-13 chemical shifts were also moved obviously when the substituents on the matrix were changed.