l- and d-[LnZn(IN)3(C2H4O2)]n (Ln = Eu, Sm, and Gd): Chiral Enantiomerically 3D 3d–4f Coordination Polymers Constructed by Interesting Butterfly-like Building Units and −[Ln-O-Zn]n– Helices

A total of six three-dimensional chiral coordination compounds l- and d-[LnZn(IN)3(C2H4O2)]n (Ln = Eu, Sm, and Gd; HIN = isonicotinic acid) have been successfully synthesized under hydrothermal conditions without any chiral auxiliary and characterized by IR, TG, elemental analyses, and solid-state circular dichroism spectra. The structures of 1–6 were determined by single-crystal X-ray structural analysis, which shows that l-[LnZn(IN)3(C2H4O2)]n (Ln = Eu (1), Sm (2), and Gd (3)) crystallize in space group P6522 and are levogyrate. The chiral frameworks of l-[LnZn(IN)3(C2H4O2)]n are constructed from l-helical Ln-O-Zn cluster chains, while adjacent l-type helical −[Ln-O-Zn]n– chains are connected through IN– ligands. d-[LnZn(IN)3(C2H4O2)]n (Ln = Eu (4), Sm (5), and Gd (6)) crystallize in space group P6122, and their chiral frameworks consist of d-helical Ln-O-Zn cluster chains. The observed second-harmonic generation efficiencies of [EuZn(IN)3(C2H4O2)]n, [SmZn(IN)3(C2H4O2)]n, and [GdZn(IN)3(C2H4O2)]n are 0....