On the electronic structure of the ground state of cyclopentoxy. The case for a two coupled state description

Abstract

Previous descriptions of the cyclopentoxy radical have considered the ground state as an isolated electronic state; however, the doublet ground and first excited states of the cyclopentoxy radical arise from three electrons in the oxygen 2pπ orbitals, yielding states that may not be adequately described by a single state model. In this work, a prelude to the determination of the photoelectron spectrum of cyclopentoxide, the electronic structure of the ground and first excited state of cyclopentoxy is studied. Both axial and equatorial structures are considered. The ground state is found to have an axial configuration. Conical intersections of the ground and excited state potential energy surfaces in both axial and equatorial nuclear configurations are found, with the minimum energy axial (equatorial) conical intersection lying within ∼515 (260)cm−1 of the axial (equatorial) ground state minimum. The barriers to axial–equatorial interconversion and to ring opening are estimated. The implications for the simulation of the cyclopentoxide photoelectron spectrum are discussed.