Mascarenhas, E.J.; Fondell, M.; Büchner, R.; Eckert, S.; Vaz da Cruz, V.; Föhlisch, A.: The Role of the Lowest Excited Triplet State in Defining the Rate of Photoaquation of Hexacyanometalates. The Journal of Physical Chemistry Letters 15 (2024), p. 241-247
10.1021/acs.jpclett.3c02775
Open Access Version
Abstract:
Photosolvation is a type of ligand substitution reaction started by irradiation of a solution with light, triggering the replacement of a ligand with a molecule from the solvent. The excited state is created through many possible pathways. For the class of hexacyanides of groups 8 and 9 of the periodic table, irradiation in the ligand field band is followed by intersystem crossing to the lowest excited triplet state, which we propose to mediate the photoaquation reaction in this class of complexes. In this study, we present time-resolved X-ray absorption data showing indications of the triplet intermediate state in the cobalt(III) hexacyanide complex and we discuss general aspects of the photoaquation reaction in comparison with reported data on the isoelectronic iron(II) hexacyanide. Quantum chemical calculations are analyzed and suggest that the nature of the lowest excited triplet state in each complex can explain the drastically different rate of reactions observed.