How to enhance the effective spin-reversal barriers of two-coordinate Co(ii) imido complexes with [CoN]+ core? a theoretical investigation

Abstract

Complete-active-space self-consistent field (CASSCF) calculations combined with different active spaces have been performed on four novel two-coordinate Co(II) imido complexes with the [CoN]⁺ core for the short CoN bond. The computational demand of the selected CAS (11, 8) for all complexes is acceptable, and it also gives the most accurate results compared with the experiments. CAS (11, 8) calculations show that shortening the CoN bond would result in the decrease of the total orbital angular momentum L, and then the weakening of the spin–orbit coupling interaction. However, the energy level splittings for different CoN bonds are almost close to each other due to the continuously increasing crystal field around Co(II). Thus, the decrease of the axial symmetry is the most important factor on the lower energy barriers for two-coordinate Co(II) imido complexes with shorter CoN bonds. Breaking the [CoN]⁺ core through lengthening the CoN bonds for two-coordinate Co-based complexes is a good choice to enhance the energy barrier.