Thiocarbamoyl Disulfides as Inhibitors of Urease and Ammonia Monooxygenase: Crystal Engineering for Novel Materials

The environmental sustainability of soil nitrogen fertilization is essential for the primary production of food for an expanding human population. In this framework, the control of soil enzymatic activities that impact the release of N-based compounds either in the atmosphere or in the underground waters is critical. The two enzymes that act as key players in the biogeochemical cycle of nitrogen are urease and ammonia monooxygenase (AMO), respectively, nickel- and copper-dependent enzymes. This article reveals the high efficacy of three molecules of the thiurams family, namely, thiram (tetramethylthiuram disulfide, TMTD), disulfiram (tetraethylthiuram disulfide, TETD), and tetraisopropylthiuram disulfide (TIPTD) as inhibitors of both the activities of jack bean (Canavalia ensiformis) urease (JBU) and Nitrosomonas europaea AMO. The water solubility of these compounds was significantly improved by the preparation of three novel inclusion complexes of beta-cydodextrin with TMTD, TETD, and TIPTD by mechanochemical synthesis, using green technology. The resulting beta-CD.thiuram complexes beta-CD.TMTD, (beta-CD)(2)-TETD, and (beta-CD)(2).TIPTD were all characterized by powder X-ray diffraction, thermogravimetric analysis, and solid-state NMR. A conformational polymorph of TIPTD was also detected and isolated via hot stage microscopy, and structurally characterized by single-crystal X-ray diffraction. Biological tests of enzymatic inhibition performed on JBU and AMO with the beta-CD.thiuram complexes showed the same inhibition efficacy as the isolated molecules, suggesting that the active species is, in all cases, the free thiuram, likely in equilibrium with the adduct in solution. These results have a great potential for improving the nitrogen use efficiency of soil fertilizers for a greener environment

Mechanochemical reactivity inhibited, prohibited and reversed by liquid additives: examples from crystal-form screens

We demonstrate that liquid additives can exert inhibitive or prohibitive effects on the mechanochemical formation of multi-component molecular crystals, and report that certain additives unexpectedly prompt the dismantling of such solids into physical mixtures of their constituents. Computational methods were employed in an attempt to identify possible reasons for these previously unrecognised effects of liquid additives on mechanochemical transformations

Synthesis, characterization and reactivity of new complexes of titanium and zirconium containing a potential tridentate amidinato-cyclopentadienyl ligand

Group 4 metal complexes [M(eta(5)-C5Me4SiMe2-eta(1)-N-2R)(NMe2)(2)] (R = pyridine, pyrazine, pyrimidine, thiazole, M = Ti; R = pyridine, thiazole; M = Zr) containing the tetramethylcyclopentadienyldialkylsilyl bridged amidinato as pendant ligand, were synthesized and characterized by elemental analysis, solution H-1, C-13 and N-15 NMR spectroscopy and experimental C-13 and N-15 CPMAS in the solid state. The crystal structures of [Ti(eta(5)-C5Me4SiMe2-eta(1)-N-2R)(NMe2)(2)] (R = pyridine 2a, pyrazine 2b, pyrimidine 2c, thiazole 2d) were determined by single crystal X-ray diffraction studies. All compounds exhibit a distorted tetrahedral geometry, with the ansa-monocyclopentadienyl-amido ligands acting in a bidentate mode. The [M(eta(5)-C5Me4SiMe2-eta(1)-N-2R)(NMe2)(2)] (R = pyridine, thiazole; M = Zr, Ti) complexes are ethylene polymerization catalysts in the presence of MAO and they are active precursors in regioselective catalytic hydroamination operating with an anti-Markovnikov mechanism

Production of dibutyl carbonate by insertion of CO2 in titanium(IV) tetrabutoxide

The species resulting from insertion of 12CO2 and 13CO2 into titanium(IV) butoxide is for the first time fully characterized by means of infrared and nuclear magnetic resonance spectroscopy. Results show formation of Ti-monobutylcarbonate, that easily undergoes nucleophilic attack by an aliphatic amine. The hydrolysis of the resulting species produces butylcarbamate and dibutylcarbonate as the only main products. Characterization results of the carbonate-like adduct, along with its reactivity with amine molecules open the route to new ways of CO2 utilization as building block for valuable organic compounds

From unexpected reactions to a new family of ionic co-crystals: the case of barbituric acid with alkali bromides and caesium iodide.

Pressing solid barbituric acid with KBr to prepare samples for IR spectroscopy leads to formation of an ionic co-crystal, in which the co-former is a classical ionic salt; co-crystal formation is also obtained with the other alkali bromides (LiBr, NaBr, RbBr and CsBr) and with caesium iodide. The simultaneous presence of alkali and halide ions affects the dissolution properties of barbituric acid in water