Exploring the synthesis of infinite helical chains with 2-carboxycinnamic acid

Abstract

The hydrothermal reactions of Cd(NO3)2, 2-ccm and secondary N,N-ligands gave rise to four coordination polymers, [Cd(ccm·L·xH2O)·yH2O]n, [ccm = 2-carboxycinnamic acid, L = 2,2′-bipyridine, x = y = 1 (1); 1,10-phenanthroline, x = y = 1 (2); 1,3-di(4-bipy)propane, x = y = 1 (3) and 4,4′-bipyridine, x = 0, y = 4 (4)]. The structures of the resulting complexes appear to be tuned by secondary ligands. When the secondary ligands change from terminal ligands, via flexible bridging ligands, to rigid bridging ligands, the resulting compounds are observed to self-assemble into single-stranded helical chains (1 and 2), double-stranded zigzag chains (3) and 2D networks (4), respectively. This result provides a useful strategy to manipulate the design and synthesis of helical structures.