A normal coordinate analysis on chlorambucil and thioguanine has been carried out with a set of symmetry coordinates following Wilson's F -G matrix method. The potential constants evaluated for these molecules are found to be in good agreement with literature values thereby confirming the vibrational assignments. To check whether the chosen set of vibrational frequencies contribute maximum to the potential energy associated with the normal coordinates of the molecule, the potential energy distribution has been evaluated.

The FTIR and FT Raman spectra of dacarbazine were recorded in the regions 4000-400 and 3500-100 cm -1 , respectively. The optimized geometry, wavenumber, polarizability and several thermodynamic properties of dacarbazine were studied using ab initio Hartree-Fock, MP2 and DFT methods. A complete vibrational assignment aided by the theoretical harmonic wavenumber analysis was proposed. The calculated harmonic vibrational frequencies were compared with experimental FTIR and FT Raman spectra. Based on the comparison between calculated and experimental results and the comparison with related molecules, assignments of fundamental vibrational modes were made. The X-ray geometry and experimental frequencies were compared with the results of theoretical calculations.

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Single crystals of urea thiourea mercuric sulphate (UTHS) and urea thiourea mercuric chloride (UTHC), semi-organic nonlinear optical materials, were grown by lowtemperature solution growth technique by slow evaporation method using water as the solvent. Good quality single crystals were grown within three weeks. The nonlinear nature of the crystals was confirmed by SHG test. The UV-Vis spectrum showed the transmitting ability of the crystals in the entire visible region. FTIR spectrum was recorded and vibrational assignments were made. The degree of dopant inclusion was ascertained by AAS. The TGA-DTA studies showed the thermal properties of the crystals.

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The Fourier transform Raman and Fourier transform infrared (FT-IR) spectra of thioguanine have been recorded. Ab initio and density functional computations of the vibrational (IR) spectrum, the molecular geometry, Highest Occupied Molecular Orbital (HOMO)-Lowest Unoccupied Molecular Orbital (LUMO) energy gaps and polarizabilities were studied. On the basis of the comparison between calculated and experimental results and the comparison with related molecules, assignments of fundamental vibrational modes are examined. The observed and simulated spectra were found to be well comparable. The electronic transition energies and intensities of spectral lines were carried out using TDDFT and ZINDO methods.

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