Homochiral zinc phosphonates with layered and open framework structuresusing polycarboxylate as second linkers

摘要

Reactions of zinc sulfate and (R)- or (S)-(1-phenylethylamino)methylphosphonic acid (pempH2) in thepresence of 1,4-benzenedicarboxylic acid (H_2bdc) result in homochiral enantiomers (R)- and(S)-[Zn_4(pempH)_4(bdc)_2].2H_2O(1). When H_2bdc is replaced by 1,2,4,5-benzenetetracarboxylic acid(H_4btec), enantiomers(R)-and (S)-[Zn_3(pempH)_2(btec)(H_2O)_2]?H_2O(2) are obtained. Compounds 1have a layer structure in which the chiral inorganic double chains, made up of corner-sharing {Zn04}and {PO_3C} tetrahedra, are connected by bdc~(2-).While in compounds 2, chiral chains of zincphosphonate are each connected to their four equivalent neighbors through btec~(4-)linkages, resulting inan open framework structure. All these compounds are optically active, exhibiting second harmonicgeneration (SHG) responses 0.2 or 0.8 times that of urea.