Structure of Zone-Cast HBC−C12H25 Films

• Published in: Journal of the American Chemical Society Vol. 127; no. 32; pp. 11288 - 11293
• Main Authors: Breiby, Dag W, Bunk, Oliver, Pisula, Wojciech, Sølling, Theis I, Tracz, Adam, Pakula, Tadeusz, Müllen, Klaus, Nielsen, Martin M
• Format: Journal Article
• Language: English
• Published: Washington, DC American Chemical Society 17.08.2005
• Subjects: Condensed matter: structure, mechanical and thermal properties; Exact sciences and technology; Physics; Solid surfaces and solid-solid interfaces; Surface structure and topography; Surfaces and interfaces; thin films and whiskers (structure and nonelectronic properties); Molecular packing; Crystal orientation; Grazing incidence; XRD; Polycyclic aromatic compound; Experimental study; Lattice parameters; Organic compounds; Surface structure
• ISSN: 0002-7863; 1520-5126
• DOI: 10.1021/ja042355e

The structure of a thin zone-cast film of the hexa-n-dodecyl-substituted hexa-peri-benzocoronene (HBC) has been investigated using grazing incidence X-ray diffraction. A model with an orthorhombic unit cell containing two molecules accounts well for the observations. The molecules are arranged in a “herringbone” structure resembling the packing observed for unsubstituted HBC. The molecular disk planes are oriented perpendicularly to the substrate, rotated by approximately 39° about the film normal. The relatively long side chains of dodecyl were found to be in an ordered interdigitated state. The aliphatic side chains and the aromatic HBC-cores segregate to form regular vertical domains spanning the film thickness. For in-plane rocking scans a discrete orientation distribution is observed with peaks at regular angle intervals. We interpret this as a grain boundary effect induced by alkyl chain stacking faults.