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Interchain-Solvent-Induced Chirality Change of 1D Helical Chains:  From Achiral to Chiral Crystallization

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posted on 02.04.2007, 00:00 by Long Jiang, Xiao-Long Feng, Cheng-Yong Su, Xiao-Ming Chen, Tong-Bu Lu
Three helical supramolecular stereoisomers of meso-2, Δ-2, and Δ-3 with the formula of cis-[Ni(f-rac-L)][Ni(CN)4] were successfully constructed based on the [Ni(f-rac-L)2+ and [Ni(CN)4]2- building blocks (L = 5,5,7,12,12,14-hexamethyl-1,4,8,11-tetraazacyclotetradecane). In all three supramolecular stereoisomers, cis-[Ni(f-rac-L)]2+ cations are alternately bridged by [Ni(CN)4]2- anions through two cis (in meso-2 and Δ-2) or trans (in Δ-3) cyano groups to form one-dimensional (1D) helical chains of cis-[Ni(f-rac-L)][Ni(CN)4]. In meso-2, the right/left-handed chirality of the originally formed chain is transferred oppositely to adjacent chains through the interchain hydrogen-bonding interactions of hexameric water clusters, leading to the formation of meso-2 with a central symmetrical space group, P21/n, in which the 1D helical chains are packed in an alternating right- and left-handed chirality. In Δ-2 and Δ-3, the right/left-handed chirality of the original chain is transferred uniformly to adjacent chains through the zipper-like interchain hydrophobic interactions, resulting in the formation of Δ-2 and Δ-3 with chiral space groups of P212121 and P3121, respectively, in which all of the 1D helical chains are arranged in the same right/left-handed chirality.