Difluorodiazirine (CF2N2): A comparative quantum mechanical study of the first triplet and first singlet excited states

摘要

3,3'-Difluorodiazirine is a precursor of difluorocarbene radical (:CF2) which is used in organic synthesis and photo affinity labelling. This molecule possesses no dipole moment in the ground electronic state (S-0) but has a significant dipole moment (of magnitude similar to 0.97 D) in both its first (triplet, T-1) and second (singlet S-1) excited states. These equal dipole moments are shown to originate from widely differing atomic polarization and inter-atomic charge transfer terms (defined by the Quantum Theory of Atoms in Molecules (QTAIM)). The calculated vertical/adiabatic excitation energies for the T-1 and S-1 states are 2.81/2.63 and 3.99/3.78 eV, respectively. Geometries, vibrational frequencies, atomic charges and spin populations, and the localization-delocalization matrices (LDMs) (Matta, J. Comput. Chem. 35 (2014) 1165) of the excited states are compared with those of the ground state. All calculations have been conducted at the (U) QCISD/aug-cc-pVTZ level of theory. (C) 2016 Elsevier B.V. All rights reserved.