A. Wallace Cordes

Characterization of a mononuclear copper carboxylate complex: Bis(acetylsalicylato)bis(pyridine)copper(II)

Abstract The preparation, spectral properties, and crystal structure of a mononuclear copper(II) complex of acetylsalicylate and pyridine are reported. The complex exists as bis(acetylsalicylato)bis(pyridine)copper(II) both in the solid state and in chloroform solution. The crystal is monoclinic, space group P21/n, with a = 17.823(5), b = 10.903(4), c = 6.598(2) A, β = 95.74(2)°. The final refinement used 1472 observed reflections and gave an R of 0.046. The copper atom is surrounded by four atoms in a trans square planar arrangement with two short CuO distances of 1.949(3) A and two CuN distances of 2.003(4) A. Two longer CuO distances of 2.623(3) A are made with the remaining oxygen atoms of the aspirin carboxylate groups.

A MOLECULE LIKE SODIUM

The use of neutral π-radicals as building blocks for molecular conductors holds both appeal and challenge. Such systems obviate the need for counterions, as charge transfer is not required to generate charge carriers. Essentially an array of π-radicals should function like atoms in an elemental metal, e.g., sodium, affording a half-filled energy band. Most radicals, however, tend to dimerize, and even when association can be suppressed the resulting low bandwidth W, coupled with a high on-site Coulomb repulsion U, leads to a Mott insulating state. We are pursuing the design and synthesis of stable heterocyclic thiazyl radicals, with a view to generating stable, crystalline materials with a high W/U ratio. The search for these new radicals, the molecular analogues of sodium, is the subject of this presentation.

A π-stacked 1,2,3-dithiazolyl radical. Preparation and solid state characterization of (Cl2C3NS)(ClC2NS2)

Crystals of (Cl2C3NS)(ClC2NS2), an isothiazolyl-substituted 1,2,3-dithiazolyl radical, consist of evenly spaced, slipped pi-stacks; magnetic and conductivity measurements indicate the material is a Mott insulator with sigma RT = 2 x 10(-7) S cm-1.

Five-coordinate copper(II) complexes of GEM-N3P3Ph2(dmpz)4

Abstract 2,2-Diphenyl-4,4,6,6-tetrakis(3,5-dimethyl-1-pyrazolyl)cyclotriphosphazene, N 3 P 3 Ph 2 (dmpz) 4 ( 2 ), forms mononuclear five-coordinate complexes N 3 P 3 Ph 2 (dmpz) 4 ·CuX 2 [X  Cl ( 3 ) and Br ( 4 )] with copper(II) halides. The structure of dichloromethane solvate of the chloro derivative, N 3 P 3 Ph 2 (dmpz) 4 ·CuCl 2 , has been determined by single crystal X-ray diffraction. The metal exists in a distorted trigonal bipyramidal geometry and the ligand 2 acts as an N 3 capping tridentate ligand with two non-geminal pyrazolyl pyridine and one cyclotriphosphazene ring nitrogen and two chloride ions complete the trigonal bipyramidal environment. The spectroscopic (IR, UV-vis and EPR) characterization of the complexes is also reported.

Preparation and Solid State Characterization of 4,4'-Bis(1,2,3,5-dithiadiazolyl)

The reaction of oxamidrazone with sulfur dichloride affords 4,4′-bis(1,2,3,5-dithiadiazolium) dichloride, which can be reduced with triphenylantimony to the corresponding bis(1,2,3,5-dithiadiazolyl) diradical; the solid state structure and transport properties of the dimer [S2N2CCN2S2]2are reported.

Preparation and molecular sturcture of 1-chloro-3,5-diphenyl-1,2,4,6-thiatriazine; reduction of Ph2C2N3SCl and the e.s.r. spectrum of the Ph2C2N3S)· radical

The reaction of benzamidine wiht S3N3Cl3 yields 1-chloro-3,5-diphenyl-1,2,4,6-thiatriazine, whose molecular structure has been determined by X-ray crystallography; reduction of Ph2C2N3SCl with triphenylantimony yields the radical species (Ph2C2N3S)· characterized by its e.s.r. spectrum.

1,2,3,5-Dithiadiazolyls and 1,2,3,5-diselenadiazolyls; stacking and packing of π-dimers

1,2,3,5-Dithiadiazolyl and 1,2,3,5-diselenadiazolyl radicals bearing a 2,5-difluorophenyl substituent crystallize as π-stacked dimers. In the S-compound the dimer stacks adopt a pinwheel arrangement about a 41 axis with a series of close trans-columnar S---S contacts. In the Se-compound the dimer stacks are packed in a non-centric dovetailed arrangement. The preference for the latter pattern is dictated by structure-making intermolecular F---Se contacts

Structure–property trends in π-stacked dithiazolo-dithiazolyl conductors

The resonance stabilized dithiazolo-dithiazolyl radical 1b adopts a slipped π-stack structure exhibiting weak 1-D ferromagnetic coupling; variable temperature conductivity measurements indicate σRT = 2 × 10−6 S cm−1.

Heterocyclic Thiazyl and Selenazyl Radicals; Synthesis and Applications in Solid State Architecture

Abstract A wide range of heterocyclic sulfur-nitrogen and selenium-nitrogen radicals have been characterized in recent years. Synthetic routes to these materials are summarized, and the modes of association which they exhibit in the solid state are illustrated. The potential use of these radicals as building blocks for low-dimensional molecular conductors is outlined, and some strategies for generating specific solid state architectures are explored. Recent attempts to prepare conductive materials from custom-built bifunctional 1, 2, 3, 5-dithia- and diselenadiazolyls are described.

Stereochemical consequences of transannular S–Cl ⋯ S interactions in sulphur nitrogen chemistry; preparation and structure of [(Me2N)2C2N4S2Cl]+[Cl3]–

The oxidation of 3,7-bis(dimethylamino)-1,5-dithia-2,4,6,8-tetrazocine yields the S-chloro salt [(Me2N)2C2N4S2Cl]+[Cl3]–, whose crystal and molecular has been determined by X-ray crystallography; the molecular structure of the cation and the cation–anion contacts are related to the stereochemistry of chlorination of transannular sulphur–sulphur interactions in cyclothiazenes.