The role of heteratoms in defining the conformation in conjugated structures is discussed.

A combination of NMR spectroscopy, mass spectrometry and chemical synthesis was used to elucidate the two-step hydrolytic decomposition pathway of the slow-release hydrogen sulfide (H 2 S) donor GYY4137 and the key decomposition product was also prepared by an independent synthetic route. The (dichloromethane-free) sodium salt of the phosphonamidodithioate GYY4137 was also produced as a pharmaceutically more acceptable salt. In contrast with GYY4137 and its sodium salt, the decomposition product did not generate H 2 S or exert cytoprotective or anti-inflammatory effects in oxidatively stressed human Jurkat T-cells and LPS-treated murine RAW264.7 macrophages. The decomposition product represents a useful control compound for determining the biological and pharmacological effects of H 2 S generated from GYY4137. ARTICLE Journal NameThis journal is © The Royal Society of Chemistry 2012 † X-Ray crystallographic data of 3 were collected on a Bruker APEXII CCD diffractometer mounted at the window of a Bruker FR591 rotating anode (MoKα, λ = 0.71073 Å) and equipped with an Oxford Cryosystems Cryostream device. Data were processed using the COLLECT package 24 and unit cell parameters were refined against all data. An empirical absorption correction was carried out using SADABS. 25 crystal structure was solved by direct methods and refined on Fo 2 by full-matrix leastsquares refinements using SHELX-97 program suite. 26 Graphics were generated using OLEX2. 27 The corresponding CIF has been deposited with the Cambridge has been deposited with the Cambridge Crystallographic Data Centre (Deposition number CCDC 1053548). Crystallographic data of 3: a = 24.2051 (3) Å, b = 8.9799(2) Å, c = 17.2946(3) Å, α = 90°, β = 101.412(1) °, γ = 90°; V = 3684.82(11) Å 3 , Monoclinic, C2/c, Z = 8, ρcalc = 1.357 Mg/m 3 ; µ = 0.391 mm − − − −1 ; T = 120(2) K; θmax = 27.47 o , 26236 measured reflections, 4230 unique reflections [Rint = 0.0416], 3784 with F 2 > 2σ, R(F, F 2 >2σ) = 0.0329; Rw(F 2 , all data) = 0.0804, GoF = 1.065.§ The rate of decomposition of aqueous solutions of GYY4137 3 proved to be too slow to monitor satisfactorily by NMR spectroscopy. Solutions in "wet" organic solvents such as acetone or chloroform however, revealed a substantially faster rate of hydrolysis. We suggest that this may be attributable to an intimate ion pair effect, which renders the phospinodithioate salt in substantially less polar solvents, more reactive towards nucleophilic attack at phosphorus than the solvated anion in pure water. ‡ All graphs are plotted with mean +/-standard deviation. In all cases, the mean values were calculated from data taken from at least six separate experiments. Where significance testing was performed, ANOVA with post-hoc t-test was used; *p < 0.05. Electronic Supplementary Information (ESI) available: (i) Experimental procedures and characterisation data for the hydrolysis pathway and compounds prepared. (ii) Experimental procedures for cell culture, H2S generation, cytotoxicity assays and LPS treatment of RAW264.7 cells. See

A series of heterometallic coordination clusters (CCs) [Ni(II)2Ln(III)2(L1)4Cl2(CH3CN)2] 2CH3CN [Ln = Y (1Y), Sm (1Sm), Eu (1Eu), Gd (1Gd), or Tb (1Tb)] were synthesized by the reaction of (E)-2-(2-hydroxy-3-methoxybenzylidene-amino)phenol) (H2L1) with NiCl2·6(H2O) and LnCl3·x(H2O) in the presence of Et3N at room temperature. These air-stable CCs can be obtained in very high yields from commercially available materials and are efficient catalysts for the room-temperature domino ring-opening electrocyclization synthesis of trans-4,5-diaminocyclopent-2-enones from 2-furaldehyde and primary or secondary amines under a non-inert atmosphere. Structural modification of the catalyst to achieve immobilization or photosensitivity is possible without deterioration in catalytic activity.

Eight dithiolato-, diselenolato-, and mixed S,Se-Fe2(CO)6 complexes based on peri-substituted naphthalene and phenanthrene dichalcogenides are prepared by oxidative insertion of Fe3(CO)12 into the dichalcogen bonds of 2,7-dimethoxynaphtho­[1,8-cd]­[1,2]­dithiole, three naphtho­[1,8-cd]­[1,2]­diselenoles, two naphtho­[1,8-cd]­[1,2]­thiaselenoles, phenanthro­[1,10-cd]­[1,2]­dithiole, and phenanthro­[1,10-cd]­[1,2]­diselenole. Complexes are characterized by 1H, 13C NMR, UV/vis, and IR spectroscopy and by X-ray analysis. The effect of replacing sulfur with selenium, incorporating electron-donating groups (2,7-di-tert-butyl, 2,7-dimethoxy) on the naphthalene ring system, and changing the degree of conjugation in the aromatic backbone (naphthalene vs phenanthrene) on the reduction potential is evaluated by cyclic voltammetry. The electrocatalytic activity of these [FeFe]-hydrogenase synthetic mimics for proton reduction in the presence of increasing concentrations of p-TsOH is investigated. Diselenolate-based [FeFe]-complexes show enhanced catalytic activity for proton reduction compared with their sulfur congeners.