title: Solvent induced helical aggregation in the self-assembly of cholesterol tailed platinum complexes.
abstract: Three alkynylplatinum(ii) bipyridyl complexes in which two cholesterol groups are combined with a bipyridyl group via alkyl chains and amido bonds were designed and synthesized. The complexes have different lengths of ethylene glycol chains at the para-position of 1-phenylethyne. All three complexes can self-assemble to gel networks in DMSO, while only the morphology of 1a without an ether chain shows a well-defined right-handed helical structure in layer packing mode. However, 1c with long ethylene glycol chains forms perfect regular left-handed helical structures in aqueous ethanol solution while the volume percentage of water is less than 5% (v/v). As the ratio of water increases, the chirality changes from a left-handed helix to a right-handed helix and the packing mode alters from a monolayer structure to a hexagonal structure. As the ratio of water further increases to greater than 50% (v/v), the structure of the assembly finally transforms into bilayer vesicles. The process of the morphology transition is traced by circular dichroism spectra, powder X-ray diffraction, SEM and TEM images. The result indicates that a polar solvent (water) acts as a trigger to change the self-assembly of the chiral structures of the complex due to the strong hydrophobic interaction between cholesterol groups and the balance of the hydrophobicity and hydrophilicity of the solvent environment.
authors.affiliation: Department of Chemistry and Concerted Innovation Center of Chemistry for Energy Materials, Fudan University, 220 Handan Road, Shanghai 200433, China. yitao@fudan.edu.cn.
authors.forename: Yueyuan
authors.initials: Y
authors.lastname: Mao
authors.forename: Keyin
authors.initials: K
authors.lastname: Liu
authors.forename: Luyan
authors.initials: L
authors.lastname: Meng
authors.forename: Liang
authors.initials: L
authors.lastname: Chen
authors.forename: Liming
authors.initials: L
authors.lastname: Chen
authors.forename: Tao
authors.initials: T
authors.lastname: Yi
mesh_terms: D000114:Acetylene / Q000031:analogs & derivatives* / Q000737:chemistry; D002784:Cholesterol / Q000737:chemistry*; D004121:Dimethyl Sulfoxide / Q000737:chemistry; D000431:Ethanol / Q000737:chemistry; D015394:Molecular Structure; D010984:Platinum / Q000737:chemistry*; D012997:Solvents / Q000737:chemistry*
chemical_list: D012997:Solvents; C044736:phenylacetylene; D000431:Ethanol; D010984:Platinum; D002784:Cholesterol; D000114:Acetylene; D004121:Dimethyl Sulfoxide