title: Polymorphism in pentacene.
abstract: Pentacene, C(22)H(14), crystallizes in different morphologies characterized by their d(001)-spacings of 14.1, 14.5, 15.0 and 15.4 A. We have studied the crystal structure of the 14.1 and 14.5 A d-spacing morphologies grown by vapour transport and from solution. We find a close correspondence between the 14.1 A structure reported by Holmes, Kumaraswamy, Matzeger & Vollhardt [Chem. Eur. J. (1999), 5, 3399-3412] and the 14.5 A structure reported by Campbell, Monteath Robertson & Trotter [Acta Cryst. (1961), 14, 705-711]. Single crystals commonly adopt the 14.1 A d-spacing morphology with an inversion centre on both molecules in the unit cell. Thin films grown on SiO(2) substrates above 350 K preferentially adopt the 14.5 A d-spacing morphology, with a slightly smaller unit-cell volume.
authors.affiliation: Solid State Chemistry Laboratory, Materials Science Centre, University of Groningen, Nijenborgh 4, NL-9747 AG Groningen, The Netherlands.
authors.forename: C C
authors.initials: CC
authors.lastname: Mattheus
authors.forename: A B
authors.initials: AB
authors.lastname: Dros
authors.forename: J
authors.initials: J
authors.lastname: Baas
authors.forename: A
authors.initials: A
authors.lastname: Meetsma
authors.forename: J L
authors.initials: JL
authors.lastname: de Boer
authors.forename: T T
authors.initials: TT
authors.lastname: Palstra