title: Single-crystal-to-single-crystal topochemical polymerizations of a terminal diacetylene: two remarkable transformations give the same conjugated polymer.
abstract: Host-guest chemistry was used to prepare a cocrystal of a dipyridyl substituted oxalamide host and a resorcinol derivative of a terminal diacetylene. X-ray crystallography revealed that the molecules assemble into a triple-helix with the diacetylene functionalities aligned in the center of the helix. Upon heating, the diacetylenes polymerize to give the corresponding polymer. In a second experiment, the X-ray structure of the crystalline hydrate of the same diacetylene also showed a suitable alignment of the diacetylene functionalities. These crystals polymerize at only 50 degrees C with the C1 carbon end of the diacetylene undergoing an unprecedented 2.4 A inward swinging movement. This results in a remarkable 9% increase in crystal density. These are the first structurally characterized polymerizations of any terminal diacetylene. A detailed comparison of the two sets of structural changes offers an interesting insight into the precise trajectories of polymerization reactions.
authors.affiliation: Department of Chemistry, State University of New York, Stony Brook, New York 11794-3400, USA.
authors.forename: Xi
authors.initials: X
authors.lastname: Ouyang
authors.forename: Frank W
authors.initials: FW
authors.lastname: Fowler
authors.forename: Joseph W
authors.initials: JW
authors.lastname: Lauher