Experimental and TDDFT characterization of the light-induced cluster-to-iron charge transfer in the (ferrocenylethynyl)-substituted trinuclear platinum derivative [Pt3(mu-PBu(t)2)3(CO)2(C[triple bond]C-Fc)]+.

The reaction between Pt(3)(mu-PBu(t)(2))(3)(CO)(2)Cl (2) and ethynylferrocene, in the presence of catalytic amounts of CuI, gives Pt(3)(mu-PBu(t)(2))(3)(CO)(2)C[triple bond]CFc (1), characterized by X-ray crystallography and representing a rare example of the sigma-coordination of an alkynyl moiety to a cluster unit. In a dichloromethane (CH(2)Cl(2)) solution, compound 1 undergoes three consecutive one-electron oxidations, the first of which is assigned to the ferrocene-centered Fe(II)/Fe(III) redox couple. Spectroelectrochemistry, carried out on a solution of 1, shows the presence of a broad band in the near-IR region, growing after the electrochemical oxidation, preliminarily associated with a metal-to-metal charge transfer toward the Fe(III) ion of the ferrocenium unit. Density functional theory (DFT) has been employed to analyze the ground- and excited-state properties of 1 and 1(+), both in the gas phase and in a CH(2)Cl(2) solution. Vertical excitation energies have been computed by the B3LYP hybrid functional in the framework of the time-dependent DFT approach, and the polarizable continuum model has been used to assess the solvent effect. Our results show that taking into account the medium effects together with the choice of an appropriate molecular model is crucial to correctly reproducing the excitation spectra of such compounds. Indeed, the nature of the substituents on P atoms has been revealed to have a key role in the quality of the calculated spectra.