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Density functional calculations at the B3LYP/6-31G* level were performed for perylene tetracarboxylic dianhydride (PTCDA) and its potential derivatives modified by replacing the two anhydride ether groups with B-, N-, S-, and Se-containing groups, as well as for perylene monomer and dimer structures. The predicted infrared (IR) and Raman spectroscopic properties of PTCDA have been compared with the observed experimental spectra and available theoretical data. In addition, the isotope effect on the Raman and IR spectra of PTCDA by the replacement of all H atoms by deuterium isotopes, as well as the estimated UV-vis properties of PTCDA and its modified derivatives, based on the results of the time-dependent DFT method have been also presented. It was shown that the formation of polyperinaphthalene films affects strongly the predicted theoretically IR, Raman and UV-vis spectra of the precursor PTCDA. © 2005 Wiley Periodicals, Inc. Int J Quantum Chem, 2005 [ABSTRACT FROM AUTHOR]

The present article discusses the results of density functional calculations obtained using B3LYP functional and the standard 6-31G* basis sets for mono-, di-, and triethylamines (MEA, DEA, and TEA, respectively) and their H-bonded complexes with water molecules. In particular, the origin of the observed experimentally clear red shift for methylene νC&bond;H mode due to the nanosecond laser T-jump in TEA/H2O system is validated theoretically by explicit consideration of related infrared (IR) and Raman peaks appeared at the C&bond;H absorbance region. All theoretical calculations were performed with full geometry optimizations without imposing any constraints, and followed by direct harmonic frequency calculations. The effects of nonspecific and specific solvations were accounted for using simple Onsager model and explicit water molecules. It was shown that the former continuum model does not strongly perturb the observed spectral changes in the C&bond;H region because of shallow potential energy surface for the interacting subsystems. Both the structural changes in geometry and electron redistribution as a result of H-bonding were found to be main factors to explain the observed experimental spectral changes in IR and Raman spectra. © 2005 Wiley Periodicals, Inc. Int J Quantum Chem, 2005 [ABSTRACT FROM AUTHOR]