Synthesis, Molecular and Electronic Structure, and TDDFT and TDDFT-PCM Study of the Solvatochromic Properties of (Me₂Pipdt)Mo(CO)₄ Complex (Me₂Pipdt = <i>N</i>,<i>N</i>‘-Dimethylpiperazine-2,3-dithione)

The synthesis, spectroscopic, and structural characterization of the (Me2Pipdt)Mo(CO)4 complex (Me2Pipdt = N,N‘-piperazine-2,3-dithione) are presented in this paper. The title complex crystallizes in the P21/n space group with a = 25.541(3) Å, b = 10.3936(14) Å, c = 10.9012(12) Å, β = 92.261(9)°, V = 2891.6(6) Å3, and Z = 8. Gas- and solution-phase structural and electronic features of (Me2Pipdt)Mo(CO)4 and Me2Pipdt have been investigated using density functional theory. The molecular structure underscores the flexibility of the NC(S)C(S)N fragment in both the free ligand and the metal complex. On the basis of structural, spectroscopic, and theoretical results, the bidentate ligand in (Me2Pipdt)Mo(CO)4 is considered to be in the dithione, not dithiolate, form. Time-dependent density functional theory has been used for the investigation of the excited states and solvatochromic properties of (Me2Pipdt)Mo(CO)4. The calculated vertical excitation energies in solution are consistent with the experimental data, showing that the metal-to-ligand charge-transfer transitions, in both the visible and UV regions, dominate over the ligand-based π−π* transitions.