ABSTRACT
Stress-related anxiety disorders and anxiety-like behavior in post-traumatic stress disorder (PTSD) are associated with altered neurocircuitry pathways, neurotransmitter systems, and the activities of monoamine and glucocorticoid-metabolizing enzymes. Resveratrol, a natural polyphenol, is recognized for its antioxidant, anti-inflammatory, and antipsychiatric properties. Previous studies suggest that resveratrol reduces anxiety-like behavior in animal PTSD models by downregulating key enzymes such as 11ß-hydroxysteroid dehydrogenase type 1 (11ß-HSD-1) and monoamine oxidases (MAOs). However, the underlying mechanisms remain unclear. In this study, we explored the efficacy of resveratrol in treating stress-induced anxiety using a chronic predator stress model in rats. Resveratrol was administered intraperitoneally at 100 mg/kg following a 10-day stress exposure, and anxiety behavior was assessed with an elevated plus maze. Our results indicated that stress-related anxiety correlated with increased activities of brain MAO-A, MAO-B, and hepatic 11ß-HSD-1, alongside elevated oxidative stress markers in the brain and liver. Resveratrol treatment improved anxiety behavior and decreased enzyme activities, oxidative stress, and hepatic damage. We demonstrate that resveratrol exerts antianxiogenic effects by modulating glucocorticoid and monoamine metabolism in the brain and liver. These findings suggest resveratrol's potential as a therapeutic agent for anxiety disorders, warranting further clinical investigation.
ABSTRACT
The development of an efficient hydrogen generation strategy from aqueous protons using sunlight is a current challenge aimed at the production of low-cost, easily accessible, renewable molecular hydrogen. For achieving this goal, non-noble metal containing and highly active catalysts for the hydrogen evolution reaction (HER) are desirable. Octahedral tantalum halide clusters {Ta6(µ-X)12}2+ (X = halogen) represent an emerging class of such HER photocatalysts. In this work, the photocatalytic properties of octahedral aqua tantalum bromide clusters toward HER and in acid and homogeneous aqueous conditions were investigated. The [{Ta6Bri12}Bra2(H2O)a4]·4H2O (i = inner ligand; a = apical ligand) compound is revealed to be an efficient precatalyst in acid (HBr) conditions and with methanol as the sacrificial agent. A response surface methodology (RSM) study was applied for the optimization of the HER conditions, considering the concentrations of both additives (methanol and HBr) as independent variables. An optimal H2 production of 11 mmol·g-1 (TON = 25) was achieved, which displays exceptional catalytic properties compared to regular Ta-based materials. The aqua tantalum bromide clusters assist in the photocatalytic hydrogen generation in agreement with energy-conversion schemes, and plausible active catalytic species and a reaction mechanism were proposed from computational and experimental perspectives.
ABSTRACT
The generation of hydrogen (H2) using sunlight has become an essential energy alternative for decarbonization. The need for functional nanohybrid materials based on photo- and electroactive materials and accessible raw materials is high in the field of solar fuels. To reach this goal, single-step synthesis of {Ta6Bri12}@GO (GO = graphene oxide) nanohybrids was developed by immobilization of [{Ta6Bri12}Bra2(H2O)a4]·4H2O (i = inner and a = apical positions of the Ta6 octahedron) on GO nanosheets by taking the advantage of the easy ligand exchange of the apical cluster ligands with the oxygen functionalities of GO. The nanohybrids were characterized by spectroscopic, analytical, and morphological techniques. The hybrid formation enhances the yield of photocatalytic H2 from water with respect to their precursors and this is without the presence of precious metals. This enhancement is attributed to the optimal cluster loading onto the GO support and the crucial role of GO in the electron transfer from Ta6 clusters into GO sheets, thus suppressing the charge recombination. In view of the simplicity and versatility of the designed photocatalytic system, octahedral tantalum clusters are promising candidates to develop new and environmentally friendly photocatalysts for H2 evolution.
ABSTRACT
Synthetic procedures providing straightforward access to the whole family of Nb and Ta halide clusters with terminal cyanide ligands have been developed. Corresponding [M6X12(CN)12]4- (M = Nb, Ta; X = Cl, Br) can be accessed by ligand-exchange procedures from K4Nb6X18 (X = Cl, Br) and Bu4NCN, (Et4N)2[Ta6Cl18] and Bu4NCN and from [Ta6Br12(H2O)4Br2]·4H2O and KCN in moderate to high yields (50-80%). The products were isolated as Bu4N salts. The compounds were investigated both experimentally and by quantum chemistry, revealing correlations between structural, electrochemical, electrostatic, electronic, and topological features as a function of type of metal, halide, and charge.
ABSTRACT
Ta powder reacts with I2 at 650 °C with the formation of Ta6I14, which belongs to the family of {M6(µ-X)12} clusters. It undergoes aquation with the formation of the intensely colored [Ta6I12(H2O)6]2+. The crystal structure was determined for [Ta6I12(H2O)6](BPh4)2·xH2O (Ta-Ta 2.9322(6) Å, Ta-I 2.8104(7) Å, Ta-O 2.3430(5) Å). With DMF, [Ta6I12(DMF)6]I2·xDMF was isolated (Ta-Ta 2.9500(2) Å, Ta-I 2.8310(4) Å, Ta-O 2.2880(7) Å). Cyclic voltammetry of [Ta6I12(H2O)6]2+ shows two consecutive quasi-reversible one-electron oxidations (E1/2 0.61 and 0.92 V vs Ag/AgCl). Reaction of Ta6I14 with Bu4NCN yields (Bu4N)4[Ta6I12(CN)6]·xCH3CN (Ta-Ta 2.9777(4) Å, Ta-I 2.8165(6) Å, Ta-C 2.2730(7) Å). Quantum chemical calculations reproduce well the experimental geometry of the aqua complex and show the essentially Ta-centered nature of both the HOMO and LUMO. The long-term stability of [Ta6I12(H2O)6]2+ solutions can be greatly enhanced in the presence of polystyrenesulfonate (PSS), which forms nanoparticle associates with the aqua complex in water (ca. 1 cluster per 3 PSS monomeric units).