Theoretical characterization of single-electron iodine-bond weak interactions in CH3…I-Y(Y = BH2, H, CH3, C2H3, C2H, CN, NC) systems

Abstract

Iodine-involved single-electron halogen bonds (SEXBs) weak interactions in the systems of CH3…I-Y(Y = BH2, H, CH3, CH=CH2, C≡CH, CN, NC) were investigated for the first time using B3LYP/6-311++G(d,p) and MP2/aug-cc-pVTZ computational levels (the relativistic effective core potential basis set of Lanl2dz was used on iodine atom). The interaction energies between two moieties with basis set super-position error corrections for the seven complexes are −0.57, −1.36, −3.80, −2.17, −4.49, −6.33 and −8.64 kJ mol−1 (MP2/aug-cc-pVTZ), respectively, which shows that SEXBs interactions are all weak. Natural bond orbital theory analysis revealed that charges flow from CH3 to the I-Y moiety. The total amount of natural bond orbital charge transfer (Δ NC) from the CH3 radical to I-Y increases in the order CH3…IBH2 < CH3…IH ≈ CH3…ICH3 ≈ CH3…IC2H3 < CH3…ICCH < CH3…ICN < CH3…INC. Atoms-in-molecules theory was used to investigate the topological properties of the bond critical points in the seven SEXB structures.