In-depth investigation of the iodine-nitrogen interaction mechanism using ab initio and density functional theory calculations

In this paper, we systematically investigate the interactions of I₂ with several representative nitrogen-containing building units (NBUs) using high-precision ab initio and density functional theory calculations. Our findings reveal that the binding strengths of I₂ with NBUs are positively correlated with the hybridization degrees of N-2p electrons. Further energy analyses indicate that the I-N orbital interaction determines the binding strength to a great extent. Especially for I₂@NBU(sp³), its σn binding orbital formed by the σ orbital of I₂ and the n orbital of NBU(sp³) exhibits nearly perfect orbital overlap. QTAIM analyses identify the unique partially covalent feature of I-N bonds in I₂@NBU(sp²/sp³) and the pure ionic feature in I₂@NBU(sp). The I-N orbital interactions lead to remarkable electron reorganizations in I₂@NBUs. Moreover, we demonstrate that the binding strengths between NBUs and I₂ can be effectively regulated through introducing electron-donating/electron-withdrawing functional groups. This study deepens the fundamental understanding of iodine coordination chemistry.