DETERMINATION OF THE EXCITED-STATE GEOMETRY OF NSO-CONTAINING COMPOUNDS BY MEANS OF THE PRE RESONANCE RAMAN EFFECT - STUDY ON BIS(SULFINYLAMINO)SULFANE, S(NSO)(2)

The study of the pre resonance Raman effect of bis(sulfinylamino)sulfa ne, S(NSO)(2), was performed in order to obtain information about the electronic excited state geometry of the molecule. The structure and c onformation of S(NSO)(2) were determined by ab initio calculations (HF /3-21G, HF/6-31G, HF/3-21G with an additional set of d-functions at t he nitrogens, alpha(d)=0.8, HF/6-21G, HF/6-31G* and MP2/6-31G*). The molecule possesses C-2V symmetry with both S=O bonds in syn (cis) posi tion with respect to the S-N bonds. The vibrational spectra were also investigated. A complete assignment of the observed bands is proposed and correlated with results arising from theoretical calculations. Sub sequently, a normal coordinate analysis is performed with the experime ntal data. Excited state geometries of S(NSO)(2) were determined from experimental data using an expression relating the Raman intensities t o the frequencies of the normal modes and the dimensionless displaceme nts. It takes also into account both the difference in the electronic energy between the minimum of the fundamental state potential surface and the minimum of the excited state potential surface and the energy of the incident radiation. The excitation profile was calculated for t he six incident radiations. Both, transferability of the R-N=S-O confi guration and ability of the pre resonance Raman effect studies to give results related to the molecular geometries were tested again. (C) 19 97 Elsevier Science S.A.