The vibrational wavenumbers of guanidinium hydrogenselenate were calculated using Gaussian03 software package at different levels and the fundamental modes are assigned. The predicted infrared and Raman activities are reported. The first hyperpolarizability is calculated and the guanidinium hydrogenselenate is an attractive object for future studies of non linear optics. The calculated wavenumbers and geometrical parameters are in agreement with the reported experimental values.

The vibrational wavenumbers of dimethyl sulfoxide molecule were calculated using Gaussian03 software package at different levels and the fundamental modes are assigned. The predicted infrared and Raman activities are reported. The first hyperpolarizability is calculated and the dimethyl sulfoxide molecule is an attractive object for future studies of non linear optics. The calculated wavenumbers and geometrical parameters are in agreement with the reported experimental values.

The geometrical parameters of 4-Chloro-N-(3-chlorophenyl)benzamide were calculated theoretically using Gaussian03 set of quantum chemistry codes. The obtained geometrical parameters are compared with the reported XRD structure of 4-Chloro-N-(3-chlorophenyl)benzamide. The bond lengths and bond angles calculated theoretically agree with the reported values.

Metal-free phthalocyanines(H 2 Pc) and its derivatives are an important organic electro and photo active material with remarkable chemical stability and flexibility offering considerable interest for many intensive applications.The complexity of the molecule makes the vibrational study of the Raman spectrum difficult.A vibrational assignment of the frequencies in the F.T Raman spectrum of H 2 Pc has been made in comparison with its metal derivatives, other related porphyrin, pyrrole, indole and orthosubsituted benzene structures.

The vibrational wavenumbers of 3-pyridine carboxaldehyde were calculated using Gaussian03 software package at different levels and the fundamental modes are assigned.The predicted infrared and Raman activities are reported.The first hyperpolarizability is calculated and the title compound is an attractive object for future studies of non linear optics.The calculated wavenumbers are in agreement with the reported experimental values.

The vibrational wavenumbers of N-(2,4-Dichlorophenyl)benzamide were calculated using Gaussian03 software package and the fundamental modes are assigned. The predicted infrared, Raman activities, force constants and polarization rations are reported. The first hyperpolarizability is calculated and the N-(2,4-Dichlorophenyl) benzamide is an attractive object for future studies of non linear optics. The calculated geometrical parameters are in agreement with the reported experimental values.

The vibrational wavenumbers of Lithium trifluoromethanesulfonate were calculated using Gaussian03 software package at different levels and the fundamental modes are assigned. The predicted infrared intensities, Raman activities and first hyperpolarizability are reported. The calculated wavenumbers and geometrical parameters are in agreement with the reported experimental values.