title: Anion-driven conformational polymorphism in homochiral helical coordination polymers.
abstract: Three homochiral 3D frameworks are assembled based on periodically ordered arrays of helices built from axial chiral 3,3'-bipyridine-5,5',6,6'-tetramethyl-2,2'-dimethoxy-1,1'-biphenyl ligands and linearly coordinated Ag(I) ions. The aggregation behavior of silver salts and the ditopic ligand in solutions was investigated by a variety of techniques, including (1)H NMR, UV-vis, CD, GPC and MALDI-TOF. The cationic polymer skeleton exhibits an unprecedented conformational polymorphism in the solid-state, folding into two-, three- and four-fold helices with NO(3)(-), PF(6)(-) and ClO(4)(-) as the counteranion, respectively. The two-fold helices cross-link via argentophilic Ag-Ag interactions to form sextuple helices, which lead to a three-dimensional (3D) chiral framework. The three-fold or four-fold helices, on the other hand, self-associates in pairs to form three-dimensional tubular architectures. This anion-dependent self-assembly behavior can be rationalized by considering the sizes, geometries and binding abilities of the counteranions and subsequent chain conformation to minimize steric repulsions and maximize secondary interactions.
authors.affiliation: School of Chemistry and Chemical Technology and State Key Laboratory of Metal Matrix Composites, Shanghai Jiao Tong University, Shanghai 200240, China.
authors.forename: Guozan
authors.initials: G
authors.lastname: Yuan
authors.forename: Chengfeng
authors.initials: C
authors.lastname: Zhu
authors.forename: Yan
authors.initials: Y
authors.lastname: Liu
authors.forename: Weimin
authors.initials: W
authors.lastname: Xuan
authors.forename: Yong
authors.initials: Y
authors.lastname: Cui
mesh_terms: D000838:Anions / Q000737:chemistry*; D001713:Biphenyl Compounds / Q000737:chemistry; D002850:Chromatography, Gel; D018360:Crystallography, X-Ray; D008024:Ligands; D008958:Models, Molecular; D008968:Molecular Conformation; D009942:Organometallic Compounds / Q000737:chemistry*; D011108:Polymers / Q000737:chemistry*; D012834:Silver / Q000737:chemistry; D013057:Spectrum Analysis; D013237:Stereoisomerism; D013379:Substrate Specificity
chemical_list: D000838:Anions; D001713:Biphenyl Compounds; D008024:Ligands; D009942:Organometallic Compounds; D011108:Polymers; D012834:Silver; C010574:biphenyl