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

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) A, b = 12.588(3) A, c = 12.131(2) A, 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.