A Series of Coordination Polymers Exhibiting Dual Chiral Features and Diverse Interhelical Interactions

With the aim of integrating the inherent chirality of ligand and the chirality induced by conformational twists of the asymmetric skeleton of the ligand upon its coordination, (1R,3S)-1,2,2-trimethyl-3-{[5-(2-hydroxy)phenyl-1,3,4-oxadiazol-2-yl]}cyclopentanecarboxylic acid (H2L) was prepared from the acylation reaction of chiral camphoric acid with salicylhydrazide. The reactions of H2L with transition metal ions gave five coordination polymers {[Co(L)(py)2]·DMF} n (1), {[Ni(L)(py)2]·DMF} n (2), [Cu(L)(py)] n (3), [Zn2(L)2(py)2] n (4), and [Cd2(L)2(py)2] n (5). Complexes 1 and 2 show only right-handed helical chains with homochiral helical discrimination by interhelical nonclassic hydrogen bonds C–H···O. However, 3–5 contain right-handed and left-handed helical chains simultaneously, which are arranged alternately and interact with each other by π···π interactions for 3 and by interchain M–O–M linkage for 4 and 5, respectively. The chiralities of these compounds derive from the inherent chirality of the ligand, as well as from the conformational twists of the asymmetric ligand skeleton. The results also reveal the role of different metal ions in the construction of chiral coordination polymers. The fluorescent studies revealed emission bands assigned to intraligand transmission for complexes 1–5.