title: Equilibrium shift in solution: molecular shape recognition and precipitation of a synthetic double helix using helicene-grafted silica nanoparticles.
abstract: Chiral silica nanoparticles (70 nm) grafted with (P)-helicene recognized the molecular shape of double helix and random coil (P)-ethynylhelicene oligomers in solution. A mixture of the (P)-nanoparticles and double helix precipitated much faster than a mixture of the (P)-nanoparticles and random coil, and the precipitate contained only the double helix. The mixture of the (P)-nanoparticles and (P)-ethynylhelicene pentamer reversibly dispersed in trifluoromethylbenzene upon heating at 70 °C and precipitated upon cooling at 25 °C. When a 10:90 equilibrium mixture of the double helix and random coil in solution was treated with the (P)-nanoparticles, the double helix was precipitated in 53% yield and was accompanied by equilibrium shift.
authors.affiliation: Department of Organic Chemistry, Graduate School of Pharmaceutical Sciences, Tohoku University, 6-3 Aoba, Sendai 980-8578 (Japan), Fax: (+81) 22-795-6811.
authors.forename: Masamichi
authors.initials: M
authors.lastname: Miyagawa
authors.forename: Wataru
authors.initials: W
authors.lastname: Ichinose
authors.forename: Masahiko
authors.initials: M
authors.lastname: Yamaguchi
mesh_terms: D053758:Nanoparticles / Q000737:chemistry*; D010316:Particle Size; D011083:Polycyclic Compounds / Q000737:chemistry*; D012822:Silicon Dioxide / Q000737:chemistry*; D012996:Solutions / Q000737:chemistry; D013237:Stereoisomerism; D013696:Temperature
chemical_list: D011083:Polycyclic Compounds; D012996:Solutions; C560958:ethynylhelicene; C031660:helicenes; D012822:Silicon Dioxide
keywords: equilibrium shift; helicenes; nanoparticles; precipitation; recognition