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

Abstract

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 ZnLCl2.0.5H2O (1) and ZnLBr2.0.25H2O (2). In the homochiral crystals of 1a and 2a, the helices are of M-helicity, whereas, in 1b and 2b, they are of P-helicity. In contrast, solvothermal reaction between L and ZnCl2 in dried DMF afforded achiral ZnLCl2 (3a), which exhibits a zigzag polymeric motif. An achiral polymorph 3b which contains 21 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 1 was stable even upon removal of guest water molecules. Contrastingly, structural transformation from 3a or 3b to 1 is possible upon hydration.

Crystal structure of 3,5-bis(imidazole-1-yl)pyridine, C11H9N5

“…The asymmetric unit contains one molecule of the title compound, which is constructed by one pyridine and two imidazole moieties. All three rings of BIP are exactly not planar, and the angles between the pyridine and imidazole ring planes are 38.30°and 14.12°, respectively, which are larger than those for 2,6-bis(imidazole-1-yl)pyridine [9]. Additionally, the two imidazole rings of BIP are not equivalent expressed by the different bond lengths and angles.…”

Spontaneous Resolution of Chiral Polyoxometalate‐Based Compounds Consisting of 3D Chiral Inorganic Skeletons Assembled from Different Helical Units

“…[23] For compounds 1 a-2 b, we investigated methods of generating initial chiral units without a chiral auxiliary, transferring the chiral units into homochiral structures of higher dimensionalities, and inducing spontaneous resolution. Offering further insight into the nature of these intricate architectures, we found that the Ni cations are coordinated to six different groups, namely two different VO 4 (V1 and V2) tetrahedra, two different bbi ligands, and two water molecules (O2W and O3W), via covalent linkages in 1 a and 1 b.…”

Imidazole and Azo-Based Schiff Bases Ligands as Highly Active Antifungal and Antioxidant Components

“…In addition, imidazoles constitute an entire or partial part of the binding sites of various transition metal ions such as Ni 2+ , Cu 2+ , or Zn 2+ in a large number of metalloproteins and have thus been utilized as effective ligands to chelate these transition metals. For example, imidazole based ligands have been used to afford tetranuclear copper(II) and nickel(II) metal complexes, [7] copper(II) or zinc(II) coordination polymers, [8] 1D coordination chains, [9] tripodal metal complexes, [10] and many other complexes used for treatment of Wilson and Menkes diseases [11]. On the other hand, azobenzene [12,13] and its numerous derivatives are currently used as dyes and represent 60-70 % of the world production of "absorbing molecules" [14].…”