ISSN:
1089-7690
Source:
AIP Digital Archive
Topics:
Physics
,
Chemistry and Pharmacology
Notes:
Computer simulation of concerted molecular reorientation in terms of lattice potential energy, has been used to rationalize disorder in the room-temperature structure of the perylene–pyromellitic dianhydride molecular complex. A trial structure, based on the simulated disorder of rigid moieties, is not inconsistent with single-crystal x-ray diffractometer data, whereas unconstrained refinement allowing for anisotropic thermal motion converges to a chemically dubious configuration. The disordered trial structure was obtained by simulating gear-like, in-plane concerted rotation of planar molecules as a function of van der Waals lattice energy. Subminima in the potential energy surface were interpreted as possible contributing forms in the disordered arrangement. The total lattice-energy manifold was not explored and positional disorder was not taken into account. The trial structure therefore reflects the main features of the disorder (R=0.14), but is still inadequate to account for all disorder effects measured crystallographically. Vibration analysis as a function of temperature is shown to be an unreliable probe to distinguish between dynamic and static disorder effects.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1063/1.450108
