Theoretical study on reaction mechanism of synthesis of iridium complexes having cyclometalated acyclic diaminocarbene ancillary ligands.

DFT calculations at the M06-2X level were performed to explore the reaction mechanism for the synthesis of the new cyclometalated iridium(III) complexes with acyclic diaminocarbene ancillary ligands. The solvent effects of the reaction systems have been considered by a single-point energy calculation using the SMD model in the experimental conditions of CH2Cl2 solvent. The calculated results show that the reaction consists of two main steps: the first step is the hydrogen transfer between the two N atoms, and the next step is the closed-loop process of the Ir atom and the aromatic ring ortho to release the HCl molecule. The reaction has a relatively low activation free energy of 17.1-23.2 kcal mol-1, indicating that it is easy to occur under the experimental conditions of Na et al. At the same time, it was found that the aryl para-CF3 substituent has higher reactivity than the corresponding reactant of the NO2 substituent.