Cadmium bis(4-pyridylformyl)piperazine coordination polymers: layered nets and a novel 3,5-connected binodal lattice

Abstract

Slow diffusion of aqueous solutions of cadmium salts with methanolic solutions of bis(4-pyridylformyl)piperazine (4-bpfp) generated crystalline coordination polymer phases whose dimensionality and topology are determined largely by the nature of the counteranion. [CdCl₂(4-bpfp)]_n (1) and [Cd(NO₃)₂(4-bpfp)]_n (2) both possess 2-D coordination polymer layers via ligation of pyridyl nitrogen and amide carbonyl oxygen atoms. {[Cd(H₂O)₂(4-bpfp)](ClO₄)₂·4-bpfp·3H₂O}_n (3) forms similar layer motifs, but with unligated perchlorate anions and 4-bpfp molecules in the interlamellar regions. Use of the more basic sulfate anion produced {[Cd(SO₄)(4-bpfp)(H₂O)]·H₂O}_n (4), which has cadmium sulfate polymeric layers linked into a novel 3,5-connected binodal lattice with (4.6²)(4.6⁶8³) topology by tethering 4-bpfp ligands. All species undergo blue-violet luminescence on exposure to ultraviolet light.