Structural, spectroscopic and theoretical studies on dixanthogens: (ROC(S)S)2, with R = n-propyl and isopropyl

Abstract

Structural and conformational properties of two dixanthogen molecules, [CH₃(CH₂)₂OC(S)S]₂ and [(CH₃)₂CHOC(S)S]₂, have been analyzed using a combined experimental and theoretical approach, with data obtained from structural X-ray diffraction methods, IR, Raman and UV-visible spectroscopies, and DFT calculations. [(CH₃)₂CHOC(S)S]₂ crystallizes in the monoclinic P2₁/c space group with a = 9.735(1) Å, b = 12.588(3) Å, c = 12.131(2) Å, β = 112.65(1)°, and Z = 4 molecules per unit cell. The interactions in the crystal were modelled and interpreted by NBO analysis. [CH₃(CH₂)₂OC(S)S]₂ is liquid at room temperature, and the vibrational spectra were satisfactorily explained in terms of the equilibrium between three conformers, originating from the rotation of the two terminal CH₃– groups, in agreement with the DFT predictions. The electronic spectra of both dixanthogens were assigned with the assistance of the TD-DFT calculations.