James C. Stark

Synthetic, Structural, and Electrical Aspects of Molecular and Polymeric Selenium and Tellurium Materials

Abstract The physical and structural concepts concerning organochalcogen-based anisotropic organic metals are summarized, and the rationales which motivate synthetic activity in new selenium and tellurium materials are presented. An overview of our approach to new aromatic molecular and polymeric materials involving direct thermal reaction of new alkali chalcogenide reagents with unactivated aromatic halides is given, and recent applications to the synthesis of tetraselenonaphth-alene (TSeN) and new transition metal diselenolenes based on o-benzenediselenolate (bds) are noted. The crystal and molecular structures of TSeN and (nC4Hg)4N+ Ni(bds)2′ have been determined, as well as their electronic absorption and electron spin resonance spectra and cyclic voltammetric behavior. The reaction of cis-dichloroethylene and sodium diselenide leads to a polymer to which the repeat sequence ←Se-CH=CH-CH-CR-Se→ is assigned, based on elemental analysis and infrared spectrum.

The Crystal Structure of Tetratellurotetracene (TTeT) and Polymorphism of Tetraselenotetracene (TSeT)

Abstract The crystal structure of TTeT has been determined; salient features include a linear chain structure and very short intermolecular Te-Te contacts. A previously unreported polymorph of TSeT was found to be isomorphous to TTeT. These data, taken with the reported data for TTT, indicate a series of three crystals each with a lattice constant which is approximately twice the van der Waals radius of the chalcogen.

Studies of the Solid State Properties of Molecular and Supramolecular Selenium and Tellurium Materials

Abstract A three dimensional volume packing analysis of the crystal structures of quasi-one-dimensional ion-radical solids of the type (D)2 ∔ X− is presented. It is found that the (TMTSF)2 ∔ X−(X ≠ NO3) solids are loosely packed when compared with solids where D is an aromatic hydrocarbon. It is suggested that (TMTSF)2 ∔ X−(X ≠ NO3) are formed under conditions of kinetic control. A direct, broadly applicable approach to the synthesis of aromatic molecular (e.g. tetratellurotetracene (TTeT) and bis-(2-naphthyl)ditelluride) and supramolecular (e.g. poly-p-phenylene selenide (PPSe) and -telluride) materials is outlined. Our initial studies (powder data) of the structural and room temperature electrical properties of solids derived from TTeT and PPSe by electron transfer are summarized. The crystal and molecular structures of two forms of bis-(2-naphthyl) ditelluride have been determined using single crystal methods, and conformational polymorphism was observed.

Magnetic Studies of New Linear Chain Transition Metal Diselenolenes

Abstract The o-benzenediselenolate dianion(bds) reacts with transition metal dichlorides(Co, Ni, Cu) to give new transition metal diselenolenes isolated as tetra-n-butylammonium salts. These materials have been characterized by elemental analysis, cyclic voltammetry, electronic spectroscopy, x-ray diffraction, ESR and static magnetic susceptibility. The crystal structure of (n-C4H9)4 N+Ni(bds)2 reveals a mixed chain structure. This report primarily presents the results of studies of the magnetic properties of Co, Ni and Cu diselenolenes as revealed by ESR and static magnetic susceptibility techniques.