From Lead(II) Dithiocarbamate Precursors to a Fast Response PbS Positive Temperature Coefficient Thermistor.

PbS submicron crystals were formed by thermolysis of two different lead dithiocarbamate complexes. These precursors were readily synthesized and fully characterized, and in situ synchrotron powder diffraction experiments were performed to characterize their decomposition. The structure and purity of resultant PbS was examined using scanning electron and transmission electron microscopies, powder X-ray diffraction, and infrared spectroscopy. Submicron crystalline PbS was used to create a new PbS thermistor with excellent sensitivity and an ultrarapid thermal response time.

Inhibitory Kinetics of Azachalcones and their Oximes on Mushroom Tyrosinase: A Facile Solid-state Synthesis.

A solid-state-based mechanochemical process was used to synthesize novel azachalcones and their oximes as tyrosinase inhibitors. Their inhibitory activities on mushroom tyrosinase using l-3,4-dihydroxyphenylalanine as a substrate were investigated. Two of the novel oxime derivatives synthesized were seen to be more potent than the positive control, kojic acid. Both the compounds 1b and 2b inhibited the diphenolase activity of tyrosinase in a dose-dependent manner with their IC50 values of 15.3 and 12.7 µm, respectively. The kinetic analysis showed that their inhibition mechanism was reversible. Both the novel oxime compounds displayed competitive inhibition with their Ki values of 5.1 and 2.5 µm, respectively. This method minimizes waste disposal problems and provides a simple, efficient, and benign method for the synthesis of novel tyrosinase inhibitors for use as skin-whitening agents or as anti-browning food additives.

Evaluation of Novel Chalcone Oximes as Inhibitors of Tyrosinase and Melanin Formation in B16 Cells.

A series of hydroxy-substituted chalcone oxime derivatives were synthesized. These compounds were then evaluated for their inhibitory activities on tyrosinase and melanogenesis in murine B16F10 melanoma cells. The structures of the synthesized compounds were confirmed by (1) H NMR, (13) C NMR, FTIR, and HRMS. Two of the compounds exhibited much higher tyrosinase inhibitory activities (IC50 values of 4.77 and 7.89 µM, respectively) than the positive control, kojic acid (IC50 : 22.25 µM). Kinetic studies revealed them to act as competitive tyrosinase inhibitors with their Ki values of 5.25 and 8.33 µM, respectively. Both the compounds inhibited melanin production and tyrosinase activity in B16 cells. Docking results confirmed that the active inhibitors strongly interacted with the mushroom tyrosinase residues.

Azachalcones: a new class of potent polyphenol oxidase inhibitors.

A library of potent inhibitors of polyphenol oxidase and their structure activity relationships are described. Azachalcone derivatives were synthesized and tested for their tyrosinase inhibitory activity. Their inhibitory activities on mushroom tyrosinase using l-DOPA as a substrate were investigated. Two compounds that are the reduction congeners of the pyridinyl azachalcones strongly inhibited the enzyme activity and were more potent than the positive control kojic acid.

catena-Poly[[copper(I)-µ-2,6-bis-[4-(pyridin-2-yl)thia-zol-2-yl]pyridine] hexa-fluoridophosphate acetonitrile monosolvate] from single-crystal synchrotron data.

The title complex, {[Cu(C21H13N5S2)]PF6·CH3CN} n , was formed immediately on adding together a methanol solution containing copper(I) ions and a methanol solution of 2,6-bis-[4-(pyridin-2-yl)thia-zol-2-yl]pyridine. Crystallographic studies of the complex reveal a coordination polymer with the ligand acting as a bis-(bidentate) ligand with the pyridine N atom not coordinating a metal centre. The Cu(I) atom is four-coordinate with approximately tetra-hedral stereochemistry: the N4 donor set is provided by bipyridine-like moieties of the two heterocyclic ligands. Parallel chains of the coordination polymer run along the b-axis direction with the disordered (0.50:0.50 occupancy ratio) PF6 (-) anions and acetonitrile solvent mol-ecules located between the chains.