We have applied femtosecond time-resolved absorption spectroscopy in an effort to elucidate the dynamics and mechanism of excited-state evolution in [Cr(bpy)3]3+. Whereas other Cr(III) complexes that we have studied exhibit intersystem crossing times of t < 100 fs for the 4T2 ---> 2E conversion (including [Cr(phen)3]3+, a molecule whose steady-state spectroscopic properties are nearly identical to those of [Cr(bpy)3]3+), the same process in [Cr(bpy)3]3+ is more than an order of magnitude slower (t = 2.15 � 0.1 ps). This attenuation in the rate of ISC is attrbuted to mixing between the 4T2 ligand-field state and nearby intraligand excited states; this mixing results in the creation of additional spin restrictions on excited-state evolution in this system. The details of this model will be presented, along with ultrafast data acquired on closely related compounds whose kinetics provide additional support for this emerging picture of excited-state dynamics in Cr(III) polypyridyl complexes.

Influence of electronic-state mixing on ultrafast dynamics: The curious case of [Cr(bpy)<sub>?3</sub>?]<sup>?3+</sup>?

245th National Meeting (2013)

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Influence of electronic-state mixing on ultrafast dynamics: The curious case of [Cr(bpy)?3?]?3+?

Influence of electronic-state mixing on ultrafast dynamics: The curious case of [Cr(bpy)_?3?]^?3+?