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Abstract: Electrochemical measurements on pincer ligands bis‐N‐(2,5‐dimethoxyphenyl)pyridine‐2,6‐dicarbothioamide (pdcta) and 6‐(4,7‐dimethoxy‐2‐benzothiazolyl)‐N‐(2,5‐dimethoxyphenyl)‐2‐pyridinecarbothioamide (pbcta) in N,N‐dimethylformamide (DMF) and dimethylsulfoxide (DMSO) on a glassy carbon working electrode revealed sulfur centred electrochemical processes. Spectroscopic, elemental and electrochemical analyses indicated that pdcta coordinated to Pd(II) via a κ3‐SNS mode to give 1 whereas pbcta coordinated via a κ3‐SNN mode to give 2. Electrochemical measurements in DMF indicated that the reduction of Pd(II)→Pd(0) proceeded in a concerted manner in the 2, whereas reduction was resolved into the Pd(II)→Pd(I)→Pd(0) in the case of 1. In the presence of p‐toluenesulfonic acid, both palladium complexes displayed electro‐catalytic proton reduction in DMF, with associated overpotentials calculated to be 97 mV and 156 mV for 1 and 2, respectively. The data suggests that the κ3‐SNS pincer ligand enhances the activity of the Pd(II) towards proton reduction relative to 1. [ABSTRACT FROM AUTHOR]

This study assessed the relative merits of the Derjaguin-Landau-Verwey-Overbeek and Sogami-Ise theories for the description of the electrostatic interaction between like-charged colloid particles in an electrolyte solution, which differ qualitatively in their predictions of the nature of this interaction. The former implies a repulsion at all distances with a screened-Coulomb (or Yukawa-type) dependence on distance, whereas the latter leads to an electrolyte-mediated, long-range attraction. The Sogami-Ise result for the interaction potential depends critically on the notion that the electrostatic parts of the Helmholtz and Gibbs energies of an electrolyte solution are different. By elaborating on the thermodynamic implications of this assumption, it was determined that it leads to a conflict with well-established results, in particular the relation between osmotic pressure and solvent chemical potential, already at the Debye-Hückel level. For this reason alone, the Sogami-Ise theory is untenable. The condensation and ordering phenomena observed with charged colloids in low-ionic.strength solutions, which the Sogami-Ise theory was originally designed to explain, can be interpreted without the need to resort to longrange electrostatic attraction, as has been demonstrated in previously published work. [ABSTRACT FROM AUTHOR]

Mikanolide [systematic names: 1,10:2,3-diepoxy-6,8-dihydroxy-11-vinylgermacr-4-ene 12,14-di-γ-lactone and 7,10a-dimethyl-1a,1b,2a,6a,7,9a,10,10a-octahydro-4H-6,3-methenofuro[3,2-c]bisoxireno[f,h]oxacycloundecin-4,8(6H)-dione], C15H14O6, derived from a variety of Mikania micrantha growing in Portland, Jamaica, contains a methylcyclodecane ring fused to an unsaturated planar α,γ-lactone, an envelope-type near-planar vinyl-β,γ-lactone and two epoxide moieties. The crystal packing shows stacks of mikanolide molecules interlocked via a network of non-classical C-H…O hydrogen bonds between the lactone units. [ABSTRACT FROM AUTHOR]

The article presents information on the structure of 7-Acetyl-12-methoxyhorminone. A horminone derivative with the systematic name 7-acetyl-12-methoxyabieta-8,12-diene-11,14- dione, C23H32O5, was isolated from Hyptis verticillata from Jamaica. The Hyptis genus has approximately 400 species and is a member of the Labiatae family growing mostly in the tropical Americas. A number of these species possess significant biological activities, including mycotoxinic, phytotoxinic, teratogenic, and antifertility properties. Hyptis verticillata is widely used in folklore medicine as a treatment for itching, insect stings and rheumatoid arthritis.