A density functional computation of few mixed 1,3 -dithia-2-arsacyclopentane ( 1,3-D-2-A ) derivative s with sulfur and oxygen donor legends such as thiobenzoic acid, and benzoic acid, have been performed with the obj ective of exploring their electronic, structural and spectral behavior. While complexes with thiobenzoic acid are abbreviated as compound1, the complexes with benzoi c acid are termed as compound2. The geometrical parameters, band gap and assignment of important vi bration frequencies are reported. The As-S (ligand s) bond length 2.409 is slightly higher than As-S (1, 3-D-2 -A) bond length. The two ring namely benzene and 1 , 3-D-2-A are not co-planer. The C-S and C-O bonds are greater t han C-C bond. In the two molecules under considera tion As-S bond is > As-O bond. The total energies of the two compounds are found to -3851.61 a.u and -3530.86 a .u. suggesting sulfur complex to be much more stable co mpared to oxygen complex. On the other hand compou nd2 is more polar than compound1. The energy gap in the two complexes is found to be 4.33 and 4. 77 eV resp ectively. An important feature of the two complexes is that w hile 1 exists in only one stable form the compound 2 undergoes rotation about O2-C3 and O2-As bonds to produce one more conformer in which benzene ring is cis to the 1, 3- dithia -2-arsacyclopetane group. The compound 2 is stabilized by hydrogen bonding.