title: ESR study of molecular dynamics and orientation of TEMPO included in organic 1-D nanochannel.
abstract: A mixture of 2,2,6,6-tetramethyl-1-piperidinyloxyl (TEMPO) radical and 2,2,6,6-tetramethyl-1-piperidine (TEMP) was included into organic 1-D nanochannels of tris(o-phenylenedioxy)cyclotriphosphazene (TPP) crystal. Dilution of the paramagnetic TEMPO radical was achieved with excess TEMP, thereby isolating a TEMPO molecule in the nanochannel. For inclusion compounds of TPP with TEMPO and TEMP (TEMPO/all guest compounds = 0.017, and 0.15), temperature-dependent electron spin resonance (ESR) spectra were observed to investigate their molecular dynamics and orientation. In the temperature range from 112 K to room temperature, the spectra depended remarkably on the temperature. Temperature dependence was well interpreted by uniaxial rotation, suggesting that TEMPO molecules undergo uniaxial rotation about a channel axis with a molecular orientation in which the N-O bond in the nitroxide group is perpendicular to the channel axis. The activation energy of uniaxial rotation was evaluated as 4.5 +/- 0.3 kJ mol(-1).
authors.affiliation: The Museum of Osaka University, Osaka University, Osaka, 560-0043, Japan.
authors.forename: Hirokazu
authors.initials: H
authors.lastname: Kobayashi
authors.forename: Takahiro
authors.initials: T
authors.lastname: Ueda
authors.forename: Keisuke
authors.initials: K
authors.lastname: Miyakubo
authors.forename: Taro
authors.initials: T
authors.lastname: Eguchi
authors.forename: Atsushi
authors.initials: A
authors.lastname: Tani
mesh_terms: D003497:Cyclic N-Oxides / Q000737:chemistry*; D004578:Electron Spin Resonance Spectroscopy / Q000379:methods; D006571:Heterocyclic Compounds / Q000737:chemistry*; D006860:Hydrogen Bonding; D008956:Models, Chemical; D015394:Molecular Structure; D049329:Nanostructures / Q000737:chemistry*; D009943:Organophosphorus Compounds / Q000737:chemistry*; D010880:Piperidines / Q000737:chemistry; D011789:Quantum Theory; D013696:Temperature
chemical_list: C528764:2,2,6,6-tetramethyl-1-piperidine; D003497:Cyclic N-Oxides; D006571:Heterocyclic Compounds; D009943:Organophosphorus Compounds; D010880:Piperidines; C528765:tris(o-phenylenedioxy)cyclotriphosphazene; C003959:TEMPO