A Combined Computational and Spectroelectrochemical Study of Platinum-Bridged Bis-Triarylamine Systems

The character of the electronic transitions in the ultraviolet–visible–near infrared (UV–vis–NIR) spectra of platinum-bis­(alkynyl) bridged, bis-triarylamine mixed-valence systems trans-[Pt­(CCC₆H₄NAr₂)₂ (PR₃)₂]ⁿ⁺ (R = ethyl, Ar = C₆H₄CH₃-4 (1) or C₆H₄OCH₃-4 (2); R = Ph, Ar = C₆H₄CH₃-4 (3) or C₆H₄OCH₃-4 (4), n = 0, 1, 2) has been determined from a combination of spectroscopic measurement and density functional theory calculations. The hybrid functional BLYP35 in combination with a suitable solvent model (i.e., conductor-like screening model (COSMO)) has been used to model the UV–vis–NIR and IR spectroscopic properties of [1–4]⁺, to confirm the description of [1–4]⁺ as examples of metal-bridged organic mixed-valence compounds, and to assign the principal features of the electronic spectra, including the triarylamine-based intervalence charge transfer transition located in the NIR region. The successful modeling of the charge distribution within the system demonstrates the utility of the BLYP35-COSMO protocol as a tool for use in the study of intramolecular charge transfer properties in mixed-valence complexes.