Theoretical investigation of the reaction mechanism for formation of pyridinyl formimidamide ancillary ligand in the synthesis of a new class of iridium(III) complexes

Abstract

In this study, density functional theory (DFT) calculations were performed to explore the reaction mechanism for the formation of a silver-formimidamide intermediate complex in the synthesis pathway of a novel cyclometallated iridium(III) complex bearing a pyridine-formimidamide ancillary ligand. The purpose of this study is to provide a detailed explanation of how the cyclic carbene ancillary ligand of (2-(4-methylbenzyl)-1H-1,2,4-triazol-1-yl)pyridine, MBpyta converted into acyclic (E)-N-cyano-N-(4-methylbenzyl)-N'-(pyridin-2-yl) formimidamide, CNMBpyfa when undergoing complexation with chloro-bridged iridium(III) dimer [{Ir(F2ppy)2(µ-Cl)}2]. The calculated results showed that the role of silver(I) oxide and the electron-withdrawing effect of the starting ligand in reactants triggered the two stages of deprotonation of two carbons in the starting triazolium salt precursor. Geometrical optimization reveals that the crystal structure of complex Ir(F2ppy)2(CNMBpyfa) has the lowest electronic energy compared to other designated ancillary ligand positions, confirming that the experimental data represent the most stable state of the synthesized complex