Current Applications of Computational Chemistry in JACS

Article discussing molecules, mechanisms, and materials and current applications of computational chemistry in the Journal of the American Chemical Society (JACS)

Structural Conformers of (1,3-Dithiol-2-ylidene)ethanethioamides: The Balance Between Thioamide Rotation and Preservation of Classical Sulfur-Sulfur Hypervalent Bonds

The reaction of N-(2-phthalimidoethyl)-N-alkylisopropylamines and S2Cl2 gave 4-N-(2-phthalimidoethyl)-N-alkylamino-5-chloro-1,2-dithiol-3-thiones that quantitatively cycloadded to dimethyl or diethyl acetylenedicarboxylate to give stable thioacid chlorides, which in turn reacted with one equivalent of aniline or a thiole to give thioanilides or a dithioester. Several compounds of this series showed atropisomers that were studied by a combination of dynamic NMR, simulation of the signals, conformational analysis by DFT methods, and single crystal X-ray diffraction, showing a good correlation between the theoretical calculations, the experimental values of energies, and the preferred conformations in the solid state. The steric hindering of the crowded substitution at the central amine group was found to be the reason for the presence of permanent atropisomers in this series of compounds and the cause of a unique disposition of the thioxo group at close-to-right angles with respect to the plane defined by the 1,3-dithiole ring in the dithiafulvene derivatives, thus breaking the sulfur–sulfur hypervalent bond that is always found in this kind of compounds.Ministerio de Economıá y Competitividad, Spain (Project CTQ2012- 31611), Junta de Castilla y León, Consejería de Educación y Cultura y Fondo Social Europeo (Project BU246A12-1), and the European Commission, Seventh Framework Programme (Project SNIFFER FP7-SEC-2012-312411

Structure of Mycobacterium tuberculosis RuvA, a protein involved in recombination

RuvA, a protein from M. tuberculosis H37Rv involved in recombination, has been cloned, expressed, purified and analysed by X-ray crystallography

Semiquinone-Bridged Bisdithiazolyl Radicals as Neutral Radical Conductors

Semiquinone-bridged bisdithiazolyls <b>3</b> represent a new class of resonance-stabilized neutral radical for use in the design of single-component conductive materials. As such, they display electrochemical cell potentials lower than those of related pyridine-bridged bisdithiazolyls, a finding which heralds a reduced on-site Coulomb repulsion <i>U</i>. Crystallographic characterization of the chloro-substituted derivative <b>3a</b> and its acetonitrile solvate <b>3a</b>·MeCN, both of which crystallize in the polar orthorhombic space group <i>Pna</i>2₁, revealed the importance of intermolecular oxygen-to-sulfur (CO···SN) interactions in generating rigid, tightly packed radical π-stacks, including the structural motif found for <b>3a</b>·MeCN in which radicals in neighboring π-stacks are locked into slipped-ribbon-like arrays. This architecture gives rise to strong intra- and interstack overlap and hence a large electronic bandwidth <i>W</i>. Variable-temperature conductivity measurements on <b>3a</b> and <b>3a</b>·MeCN indicated high values of σ­(300 K) (>10^–3 S cm^–1) with correspondingly low thermal activation energies <i>E</i>_act, reaching 0.11 eV in the case of <b>3a</b>·MeCN. Overall, the strong performance of these materials as <i>f</i> = ¹/₂ conductors is attributed to a combination of low <i>U</i> and large <i>W</i>. Variable-temperature magnetic susceptibility measurements were performed on both <b>3a</b> and <b>3a</b>·MeCN. The unsolvated material <b>3a</b> orders as a spin-canted antiferromagnet at 8 K, with a canting angle ϕ = 0.14° and a coercive field <i>H</i>_c = 80 Oe at 2 K

Metal Complexes of Bridging Neutral Radical Ligands: pymDTDA and pymDSDA

Metal complexes of the 4-(2′-pyrimidyl)-1,2,3,5-dithiadiazolyl (pymDTDA) neutral radical ligand and its selenium analogue (pymDSDA) are presented. The following series of metal ions has been studied using M(hfac)2 as the coordination fragment of choice (hfac = 1,1,1,5,5,5 hexafluoroacetylacetonato): MnII, CoII, NiII, and ZnII. The binuclear cobalt and nickel complexes of pymDTDA both exhibit ferromagnetic (FM) coupling between the unpaired electrons on the ligand and the metal ion, while the binuclear zinc complex of pymDTDA is presented as a comparative example incorporating a diamagnetic metal ion. The binuclear manganese complex of pymDTDA, reported in a preliminary communication, is compared to the pymDSDA analogue, and new insight into the magnetic behavior reveals that intermolecular magnetic coupling, mediated by chalcogen− oxygen contacts, gives rise to a significant increase in the χT product at low temperature. Surprisingly, the binuclear nickel complex of pymDSDA forms dimers in the solid state, as do the mononuclear complexes of cobalt and nickel with pymDTDA. In addition, mixed mononuclear/binuclear complexes of Mn- and Zn(pymDTDA) have been identified