The structures of o-di(pyrrolyl-2-formamido)phenylene (PFP) and its halide anion complex in DMSO were optimized by density functional theory B3LYP method at the LANL2DZ level. The conformation change of the host and the supramolecular interaction between the host and the halide anion, in the formation of the complex, have been investigated by analyzing the geometric parameters, charge population, frontier orbital, binding energy and thermodynamic parameters. The results show that anion recognition of PFP is spontaneous. The frontier orbital of the host interacts with that of the guest anion in the formation of the complex, and the electron is transferred from HOMO of halide anion to LUMO of the host. Moreover, PFP:F^－ is most stable among the complexes PFP:X^－ (X^－＝F^－, Cl^－, Br^－, I^－), which agrees well with the experimental results of anion recognition of PFP reported in the literature. At last, if a host molecule con-taining multi-groups of pyrrolyl-2-formamido with the size of cup-shaped meatus appropriately regulated can be designed, the halide anion recognition of the host molecule will be improved.

Key words: o-di(pyrrolyl-2-formamido)phenylene, anion recognition, density functional theory