Coordination polymers in selective separation of cations and anions: A series of rarely observed all helical three-dimensional coordination polymers derived from various chiral amino acid based bis-pyridyl-bis-amide ligands

Abstract

A series of Cu^II coordination polymers [{Cu(μL1)₂Br₂}·2H₂O]_∞CP1, [{Cu(μL2)2·H₂O·Br}·Br·4H₂O]_∞CP2, [{Cu(μL3)₂Br₂}·2H₂O]_∞CP3, [{Cu(μL3)₂Cl₂}·2H₂O]_∞CP4, derived from bis-pyridyl-bis-amide ligands having a natural l-amino acid backbone have been synthesized and characterized by single crystal X-ray diffraction. Environmentally relevant cations (Cu^II) and anions (Br^–) have been separated selectively from complex mixtures of cations (Cu^II, Co^II, and Zn^II) and anions (Br^–, NO₃^–, SO₄^2–, ClO₄^– and BF₄^–) via an in situ crystallization technique in separate experiments, respectively. Such separation of cations by in situ crystallization of coordination polymers represents the first example in the literature.