Ultrafast Photochemistry of [Cr(NCS)6](3-) Complex in Dimethylsulfoxide and Dimethylformamide upon Excitation into Ligand-Field Electronic State.

The ultrafast photochemistry of the [Cr(NCS)6](3-) complex upon excitation to the (4)T2 ligand-field (LF) state was studied in dimethylsulfoxide (DMSO) and N,N-dimethylformamide (DMF) in a wide temporal range (100 fs - 9 ms) by a combination of femtosecond and nanosecond transient absorption spectroscopy techniques and supported by quantum-chemical DFT/TD-DFT calculations. The initially excited (4)T2 state undergoes intersystem crossing to the vibrationally hot (2)E state with time constants of 1.1+/-0.2 and 1.8+/-0.1 ps in DMSO and DMF, respectively. Vibrational relaxation occurs in the same timescale and takes 1-5 ps. A major part of [Cr(NCS)6](3-) complex in the (2)E state undergoes intersystem crossing to the ground state with time constants 65+/-5 and 85+/-5 ns in DMSO and DMF, respectively. A minor part of electronically excited [Cr(NCS)6](3-) undergoes irreversible photochemical decomposition. In DMSO, the photolysis of [Cr(NCS)6](3-) complex results in single or double thiocyanate ion release followed by the coordination of the solvent molecules with time constant of 1+/-0.2 ms.