title: Arrays of Molecular Rotors with Triptycene Stoppers: Surface Inclusion in Hexagonal Tris(o-phenylenedioxy)cyclotriphosphazene.
abstract: A new generation of rod-shaped dipolar molecular rotors designed for controlled insertion into channel arrays in the surface of hexagonal tris(o-phenylenedioxy)cyclotriphosphazene (TPP) has been designed and synthesized. Triptycene is used as a stopper intended to prevent complete insertion, forcing the formation of a surface inclusion. Two widely separated (13)C NMR markers are present in the shaft for monitoring the degree of insertion. The structure of the two-dimensional rotor arrays contained in these surface inclusions was examined by solid-state NMR and X-ray powder diffraction. The NMR markers and the triptycene stopper functioned as designed, but half of the guest molecules were not inserted as deeply into the TPP channels as the other half. As a result, the dipolar rotators were distributed equally in two planes parallel to the crystal surface instead of being located in a single plane as would be required for ferroelectricity. Dielectric spectroscopy revealed rotational barriers of ∼4 kcal/mol but no ferroelectric behavior.
authors.affiliation: †Institute of Organic Chemistry and Biochemistry, Academy of Sciences of the Czech Republic, Flemingovo nám. 2, 16610 Prague, Czech Republic.
authors.forename: Jiří
authors.initials: J
authors.lastname: Kaleta
authors.forename: Paul I
authors.initials: PI
authors.lastname: Dron
authors.forename: Ke
authors.initials: K
authors.lastname: Zhao
authors.forename: Yongqiang
authors.initials: Y
authors.lastname: Shen
authors.affiliation: §Department of Inorganic Chemistry, Faculty of Science, Charles University in Prague, Hlavova 2030, 12840 Prague, Czech Republic.
authors.forename: Ivana
authors.initials: I
authors.lastname: Císařová
authors.forename: Charles T
authors.initials: CT
authors.lastname: Rogers
authors.affiliation: †Institute of Organic Chemistry and Biochemistry, Academy of Sciences of the Czech Republic, Flemingovo nám. 2, 16610 Prague, Czech Republic.
authors.forename: Josef
authors.initials: J
authors.lastname: Michl