Theoretical treatment of the electronic circular dichroism spectrum and the optical rotatory power of H2S2

The electronic circular dichroism spectrum and the optical rotatory power of dihydrogen disulfide are investigated at CI ab initio level. The calculation of the optical rotatory power is performed by a variation-perturbation method including electronic correlation and ensuring gauge invariance. Application to dihydrogen disulfide shows that its optical rotatory power is weak and is essentially due to the first lowest spectroscopic states. Moreover, the correlation between the optical rotatory power and the conformation of the molecule is studied and shows the importance of the lone pairs of sulphur atoms in the optical properties of the disulfide compounds. The investigation of the optical rotatory power as a function of the wavelength of incident light enables us to recover the experimental law of Biot, and its sign agrees well with experimental data on compounds of the same family (R2S2). (C) 1998 Elsevier Science B.V.