Theoretical study of the lowest electronic transitions of sulfur-bearing mesoionic compounds in gas-phase and in dimethyl sulfoxide

Using the TD-DFT approach in combination with B3LYP and PBE1PBE hybrid functionals we have calculated the n–π∗ and π–π∗ electronic transitions of sulfur-bearing mesoionic compounds in gas-phase and in DMSO. The solvent effects have been included using the PCM method. The calculations show large hypsochromic shifts for these two lowest transitions in going from gas-phase to DMSO, specially for the weak n–π∗ transition. For the compound 4-phenyl-5-(p-chlorophenyl)-1,3,4-thiadiaolium-2-thiolate the TD-B3LYP/6-311+G(2d,p) and [TD-PBE1PBE/6-311+G(2d,p)] models predict for the intense π–π∗ transition in DMSO absorption wavelengths of 413.50 nm and [394.59 nm] in good agreement with the available experimental result around of 408 nm.