Sub-100 fs time-resolved, broadband transient absorption spectroscopy is used to study ultrafast radiationless relaxation dynamics of near-infrared, metal-centered (MC), Laporte-forbidden electronic excited states of CuCl42-, CuBr42-, and IrBr62- in solution. It was found that the addition of water to acetonitrile solutions efficiently quenches the third excited MC state of CuCl42- (8300 cm-1 above the ground state) and the first excited MC state of IrBr62- (5000 cm-1 above the ground state). The quenching mechanisms involve the diffusion-controlled formation of a short-lived encounter complex, [CuCl4H2O]2-, and the long-distance dipole-dipole energy transfer to water molecules in the case of IrBr62-. The comparison between the radiationless dynamics of the lowest-energy MC states for CuCl42- and CuBr42- (5000 cm-1 above the ground state) yielded insights into the topology of the involved potential energy surfaces, Jann-Teller distortions, and the dynamics through conical intersections connecting the first excited and ground electronic states.

Ultrafast radiationless relaxation dynamics of low-energy near-infrared excited electronic states of Cu(II) and Ir(IV) complexes

255th National Meeting (2018)

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