Anion binding properties of N-confused porphyrins at the peripheral nitrogen

Ni(II), Pd(II), and Cu(II) complexes of N-confused porphyrin (NCP) exhibit anion binding properties through a hydrogen bonding interaction at the peripheral NH of confused pyrrole ring. The binding constants of the tetrakis(pentafluorophenyl)-NCP metal complexes (1-M, M = Ni, Pd, Cu) for various halide anions in CH2Cl2 increase in the order of F- > Cl- > Br- > I-, respectively. Zwitterionic resonance form of the NCP complexes as well as interactions between halide anions and a pentafluorophenyl group are suggested to be important for efficient anion binding.