title: Dipolar molecular rotors in the metal-organic framework crystal IRMOF-2.
abstract: Rotating polar linker groups in the cubic metal-organic framework single crystal known as IRMOF-2 were investigated for freedom of motion, response to an external electric field, and effects of dipole-dipole interactions. The crystals consist of octahedrally coordinated zinc oxide clusters linked by the bromoterephthalate group, which contains a rotatable bromo-p-phenylene moiety. We confirmed the rotation by dielectric spectroscopy and found a 7.3 kcal mol(-1) barrier. The non-polar analog, IRMOF-1, containing terephthalic acid, was used as a control system. DFT and MP2 computations of the rotational barrier yield results in agreement with the observation, with B3LYP/SDD being the best. A Monte Carlo analysis of the equilibrium polarization fluctuations was used to assess the possibility of polar ordering and the potential for electro-optic applications.
authors: Department of Physics, University of Colorado, Boulder, USA.
authors: Erick B
authors: EB
authors: Winston
authors: Peter J
authors: PJ
authors: Lowell
authors: Jaroslav
authors: J
authors: Vacek
authors: Jana
authors: J
authors: Chocholousová
authors: Josef
authors: J
authors: Michl
authors: John C
authors: JC
authors: Price