1. Contribution from the Physical and Theoretical Chemistry Laboratory, Oxford University, South Parks Road, Oxford OX1 3QZ, United Kingdom; School of Science and the Environment, Coventry University, Priory Street, Coventry CV1 5FB, United Kingdom; Dyson Perrins Laboratory, Oxford University, South Parks Road, Oxford OX1 3QY, United Kingdom; and Department of Chemistry, University of Bath, Claverton Down, Bath BA2 7AY, United Kingdom