DYNAMICS OF INTERSYSTEM CROSSING PROCESSES IN SOLUTION FOR 6-COORDINATE D5, D6, AND D7 SPIN-EQUILIBRIUM METAL-COMPLEXES OF IRON(III) IRON(II), AND COBALT(II)

Intersystem crossing rates for 14 (low-spin) ⇌(high-spin) spin-equilibrium metal complexes of six-coordinate iron-(II) (1A⇌5TΔS=2),iron(III) (2T⇌6A; ΔS=2), and cobalt(II) (2E⇌4T; ΔS=1) have been investigated in solution by Raman laser temperature-jump kinetics. Measurable first-order rate constants for the forward (K1) and reverse (K-1) processes range from 4×105to 2×107s-1, with four of the complexes having rate constants too large to measure (≥2×107 s-1) by the technique. The results are interpreted in terms of a model in which the spin multiplicity change is treated as an internal electron-transfer reaction. © 1978, American Chemical Society. All rights reserved.