title: Room-temperature monoclinic and low-temperature triclinic phase-transition structures of meso-octamethylcalix[4]pyrrole-dimethyl sulfoxide (1/1).
abstract: Crystals of the title complex, C28H36N4*C2H6OS, undergo a phase transition between room temperature and 198 K, as determined by X-ray diffraction techniques. A monoclinic form is observed at room temperature, while a triclinic modification is found at 198 K, with Z' changing from 1 to 2. Differential scanning calorimetry (DSC) of the calixpyrrole-dimethyl sulfoxide complex revealed a series of phase changes between 273 and 243 K. The transition from the room-temperature monoclinic form to the low-temperature triclinic form is reversible, as determined by changes in the cell dimensions from remeasuring selected reflections at room temperature and at temperatures below 223 K. The uncomplexed calix[4]pyrrole molecule shows no phase changes occurring between room temperature and 233 K, the low-temperature limit of the DSC.
authors.affiliation: Department of Chemistry and Biochemistry, University of Texas at Austin, Austin, TX 78712, USA. vmlynch@mail.utexas.edu
authors.forename: V M
authors.initials: VM
authors.lastname: Lynch
authors.forename: P A
authors.initials: PA
authors.lastname: Gale
authors.forename: J L
authors.initials: JL
authors.lastname: Sessler
authors.forename: D
authors.initials: D
authors.lastname: Madeiros
mesh_terms: D002152:Calorimetry, Differential Scanning; D003460:Crystallization; D018360:Crystallography, X-Ray; D008958:Models, Molecular; D015394:Molecular Structure; D011758:Pyrroles / Q000737:chemistry*; D013696:Temperature
chemical_list: D011758:Pyrroles; C447542:meso-octamethylcalix(4)pyrrole-dimethyl sulfoxide