Crystallographic Studies of Ternary Chalcogenides and Organic Semiconductors

Abstract: X-ray diffraction methods have been used to study the crystal structure of different compounds, both organic and inorganic. The inorganic compounds were all synthesized by solid state reactions. A new compound, Re4As6S3, was synthesized and its structure was solved by Rietveld methods. Re4As6S3 is a cluster compound described by a rock-salt-type arrangement of ReAsS3- and As5- clusters. This structure is related to thiospinel with space-group F43m. In a further search for related systems, new intercalation compounds based on NbS2 and Al or Zn were found. The new compound with approximate stoichiometry Zn1/3NbS2 consists of layers of trigonal prismatic NbS6 with inclusion of Zn in the octahedral sites between these layers. The inclusion of yttrium in the antiferromagnet manganese telluride (MnTe) was observed, and magnetic measurements indicate strong antiferromagnetic interactions between unpaired spins created by the inclusion of yttrium. Single-crystal diffraction studies of organic semiconductors were carried out on crystals grown as part of a collaborative research project between Bell Laboratories (USA), Columbia University (USA) and the medical University of Silesia (Poland). The aim of this project is to better understand electronic charge transport in organic semiconductors. The crystal structures of two molecules with formula C42H30 and C42H26 that crystallized during the growth of rubrene (C42H28) crystals by vapour phase methods, were studied. The influence of substituents on molecular packing and hence on the charge transport was examined in different crystal structures of halogen substituted tetracene and hexacene-quinone. Finally the crystal structures of four quinoline and thiazine derivatives related to pentacene were studied. Unlike pentacene which is flat, all these molecules were butterfly molecules with five fused rings. Here, substituents strongly influence not only the packing of the molecules but also the butterfly angle.