The construction of molecular systems capable of photoinduced multielectron charge transfer: a photochemical analysis of the reactivity of [(CN)₅Fe^II-(CN)-Pt^IV(L)₄-(NC)-Fe^II(CN)₅]^4-(LNH₃, ethylenediamine)

The title trinuclear complexes are synthesized by the redox reaction of [Fe(CN)₆]^3- and [PtL₄]²⁺ (A: LNH₃; B: L= 1 2 ethylenediamine). Both of these complexes exhibit an intervalence charge transfer (IT) band in the visible region of the optical spectrum. The energy of this transition is strongly dependent on temperature, as well as solvent. The energy of the IT band shifts by -17.3±1.1 and -14.4±0.7 cm^-1/K for A and B, respectively, within the temperature range of 0-45 °C. This shift is attributed to the temperature dependent redox potential of the [Fe(CN)₆]^4-/3- moiety. The solvent dependence of the IT energy correlates with the electron-accepting ability of the solvent, and thus, the degree of H bonding between the solvent and the cyanide lone pairs. The nature of the solvent also affects the photodissociation quantum yield. This effect is reported in detail for A in a DMSO/water solvent mixture. The results can be interpreted using the Marcus-Hush charge transfer theory, which proves to be applicable to these systems capable of multielectron charge transfer.