Electronic spectra of oxocomplexes of Re(V) with thiolato ligands

TD-DFT investigation of triple-stranded helicates with bis(benzene-o-dithiolato) ligands

The electronic spectra of triple-stranded complexes of Ti(IV) with bis(benzene-o-dithiolato) ligands (H(4)-L(1)=1,2-bis(2,3-dimercaptobenzamido)ethane; H(4)-L(2)=1,2-bis(2,3-dimercaptobenzamido)benzene) were investigated at the TD-DFT level of theory employing B3LYP/LANL2DZ. The influence of the nature (aliphatic or aromatic) of the spacer bridging both {Ti(S(2)C(6)H(3))(3)} units on the absorptive features of the dinuclear complexes was also studied. B3LYP/LANL2DZ leads to spectra accounting for four absorption bands. At the lowest-energy region, the most important transitions are due to ligand-to-metal charge transfer (LMCT), in which out-of-plane ligand-centered orbitals and titanium-based MOs are involved. In going to the blue-region, a third band was detected with excitations showing an important contribution from ligand-to-ligand charge transfer (LLCT) and indeed, a combined LMCT+LLCT character has been considered. This observation seems to arise from a decrease in the metallic character of the LUMO-derivatives involved in the excitations. The origin of the absorption band at the highest-energy part of the spectrum is assigned to a LLCT. The influence of the nature of the spacer on the molar absorption coefficients (ɛ) for this band has been clearly observed. The complex bearing aliphatic spacer shows ɛ of about 5 E+4 M(-1) cm(-1), while the one containing an aromatic spacer present a value of ɛ of about 2 E+5 M(-1) cm(-1).

Time-dependent density functional theory investigation of the electronic spectra of hexanuclear chalcohalide rhenium(III) clusters

The UV-vis spectra of the hexanuclear chalcohalide rhenium(III) clusters of formula [Re(6)S(8)X(6)](4-) (X(-) = Cl(-), Br(-), I(-)) were investigated at the time-dependent density functional theory (TD-DFT) level employing B3LYP, PBE1PBE, and the double-hybrid B2PLYP functional in combination with the LANL2DZ basis set. We were able to reproduce the red shift experimentally observed when the halide changes from chloride to iodide. However, some discrepancies between experimental results and theory were found. First, we did not observe a remarkable dependence of the experimental ill-resolved bands on the solvent. Indeed, similar spectra were obtained taken CH(2)Cl(2) or CH(3)CN as solvents into account. Second, all calculations explained the origin of the band peaked at the low-energy region in contraposition with the one experimentally assumed by R. Long et al. (J. Am. Chem. Soc. 1996, 118, 4603), and theoretically made available by Arratia-Pérez et al. (J. Chem. Phys. 1999, 110, 2529). These authors have proposed a ligand-to-cluster charge transfer (LCCT) for all title complexes. Our findings undoubtedly allow such origin to be discarded. While the HGGA functionals lead to a cluster-to-halide ligand charge transfer (CLCT), an intracluster charge transfer (ICCT) has been considered by employing B2PLYP. This contribution showed B2PLYP in the presence of the solvent to be the best performer in studying the UV-vis spectra of large complexes of rhenium(III) containing the Re-S bond. We strongly recommended the use of the double-hybrid B2PLYP in studying UV-vis spectrum of rhenium complexes of size making the computational cost affordable. We expect that our work stimulates new experimental and theoretical investigations of the title complexes to confirm our assignment.