Conformational effect of 2,6-bis(imidazol-1-yl) pyridine on the self-assembly of 1D coordination chains: spontaneous resolution, supramolecular isomerism, and structural transformation

The achiral 2,6-bis(imidazol-1-yl)pyridine (L) was used as the ditopic organic tecton for the formation of coordination polymers with Zn(II) ions. Hydrothermal reaction between L and ZnX2 (X = Br, Cl) afforded spontaneous resolved double helical motifs in ZnLCl2 center dot 0.5H(2)O (and ZnLBr2 center dot 0.25H(2)O . In the homochiral crystals of and , the helices are of M-helicity, whereas, in and , they are of P-helicity. In contrast, solvothermal reaction between L and ZnCl2 in dried DMF afforded achiral ZnLCl2 , which exhibits a zigzag polymeric motif. An achiral polymorph which contains 2(1) helical chains was obtained in wet DMF. The formation of different 1D motifs was related to the conformations of L. All these compounds were characterized by infrared spectroscopy, elemental analyses, and single-crystal X-ray diffraction. As revealed by thermal gravimetric analysis and powder X-ray diffraction study, the homochiral motif in was stable even upon removal of guest water molecules. Contrastingly, structural transformation from is possible upon hydration.