NO (v‘ ‘ = 0) Rotational Distributions from the Photodissociation of Organometallic Nitrosyls in the Charge Transfer Region

Abstract

The photodissociations of two metal nitrosyl compounds, Co(CO)3NO and Mn(CO)4NO, were studied at 450 nm, in the metal-to-nitrosyl charge-transfer region for both compounds. The rotational distributions of free NO in the v‘ ‘ = 0 vibrational state were determined by laser-induced fluorescence excitation. A Surprisal Analysis shows that the NO population distributions display a dynamical bias toward lower rotation in both compounds. The similarity between the NO rotational distributions is surprising, considering that Co(CO)3NO was expected to dissociate through a bent transition state and Mn(CO)4NO was not. The spin−orbit populations of the NO products (2Π1/2 and 2Π3/2) are equally populated in both compounds, indicating that the electronic surfaces that produce these two states are strongly coupled at the transition state. An upper limit of the M−NO bond dissociation energy is estimated at 52 kcal/mol from the rotational assignments.