Kinetic investigations of the mechanism of dihydrogen driven catalytic reduction of methylene blue, safranine O, methyl viologen and ferricyanide using platinum carbonyl cluster anions (Chini-clusters) as catalyst

[Bu4N]2[Pt12(CO)24] (1) catalyses the selective reduction of electron acceptors (S), methylene blue (MB+), safranine O (Saf+), methyl viologen (MV2+) and ferricyanide by dihydrogen. Macroscopic rate investigations for the cationic substrates in DMF, and for ferricyanide in DMSO have been carried out. In all cases, kobs is given by k1 [S] + k2, indicating that there are two catalytic cycles. In one of them, the formation of a complex between S and [Pt12(CO)24]2- in the rate determining step (rate constant k1) is followed by electron transfer and/or other fast steps. In the other catalytic cycle, the rate determining step (rate constant k2) involves formation of the solvated cluster anion [Pt12(CO)24]2-. The solvated cluster then undergoes fast reduction by dihydrogen and other reactions. The relative contributions of these two cycles depend on the substrate, and for MB+, Saf+, MV2+ and [Fe(CN)6]3- the contribution of the second cycle is about 99%, 55%, 77% and 97%, respectively. Both k1 and k2 of ferricyanide are about three orders of magnitude smaller than those of the cationic electron acceptors. The rates of reduction of MB+ and Saf+ have also been studied in the presence of added water. Rates increase as the presence of water provides an additional pathway for the reduction of [Pt12(CO)24]2- to [Pt9(CO)18]2-

Plastic is a global menace. Do we have enough data?

Plastic waste ends up in the ocean through run-off and rivers which affects the marine ecosystem. Continuous increase in the production of plastics and polymers have exacerbated this problem. Here we report marine plastic pollution with reference to India and Chennai (the capital of Tamil Nadu, South India). In particular, Tamil Nadu has a long coastline and the plastic waste reaching it through rivers and land run-off, and dumped ghost fishing gear, causes serious problems to the flora and fauna as well as livelihood of the fishing communities across the region. Despite various studies, there remains an uncertainty about the quantity of macro and micro plastic waste reaching the oceans and the consequences of marine plastic pollution, locally as well as globally

Some aspects of the chemistry of platinum carbonyl clusters

Different aspects of the work carried out on the Chini-clusters are reviewed here. These are: (1) the uses of platinum clusters for the synthesis of hetero-metal clusters, (2) platinum clusters as mediators in pH-driven transport of sodium ions and electrons through a liquid membrane, and (3) asymmetric hydrogenation of a-ketoesters with cluster derived heterogeneous catalysts

Molecular orbital calculations on [HRu<SUB>3</SUB>(CO)<SUB>9</SUB>(PhNCO)]<SUP>-</SUP> and related clusters

Molecular orbital calculations (EHMO) have been performed on five ruthenium carbonyl clusters considered to be involved in the reductive carbonylation of nitrobenzene. The bonding in the isocyanate cluster, [HRu3(CO)9(HNCO)]-, is shown to arise mainly from the interaction between the LUMO of HNCO and HOMO of the [HRu3(CO)9]- fragment. The relative stabilities of this cluster, two of its isomers and the CO-eliminated cluster [HRu3(CO)9(HN)]-, are also commented upon. The calculated results are in accordance with empirical kinetic data

Development of Next-Generation Fluorescent Turn-On Sensor to Simultaneously Detect and Detoxify Mercury in Living Samples

Strategies for simultaneous detection and detoxification of Hg^(2+) using a single sensor from biological and environmental samples are limited and have not been realized in living organisms so far. We report a highly selective, small molecule “turn-on” fluorescent sensor, PYDMSA, based on the cationic dye Pyronin Y (PY) and chelating agent meso-2,3-dimercaptosuccinic acid (DMSA) for the simultaneous detection and detoxification of inorganic mercury (Hg^(2+)). After Hg^(2+) detection, concomitant detoxification was carried out with sufficient efficacy in living samples, which makes the sensor unique. PYDMSA exhibits high selectivity for Hg^(2+) over other competing metal ions with an experimental detection limit of ∼300 pM in aqueous buffer solution. When PYDMSA reacts with Hg2+, the CS–C^9 bond in the sensor gets cleaved. This results in the “turn-on” response of the fluorescence probe with a concomitant release of one equivalent of water-soluble Hg^(2+)–DMSA complex which leads to a synchronous detoxifying effect. The sensor by itself is nontoxic to cells in culture and has been used to monitor the real-time uptake of Hg^(2+) in live cells and zebrafish larvae. Thus, PYDMSA is a unique sensor which can be used to detect and detoxify mercury at the same time in living samples

Biodegradation of polymers

186-193Exhaustive studies on the degradation of plastics have been carried out in order to overcome the environmental problems associated with synthetic plastic waste. Recent work has included studies of the distribution of synthetic polymer-degrading microorganisms in the environment, the isolation of new microorganisms for biodegradation, the discovery of new degra­dation enzymes, and the cloning of genes for synthetic polymer-degrading enzymes. Under ambient conditions, polymers are known to undergo degradation, which results in the deterioration of polymer properties, characterized by change in its molecular weight and other physical properties. In this paper mainly the biodegradation of synthetic polymers such as polyethers, polyesters, polycaprolactones, polylactides, polylactic acid, polyurethane, PVA, nylon, polycarbonate, polyimide, polyacrylamide, polyamide, PTFE and ABS have been reviewed. Pseudomonas species degrade polyethers, polyesters, PVA, polyimides and PUR effectively. No microorganism has been found to degrade polyethylene without additives such as starch. None of the biodegradable techniques has become mature enough to become a technology yet

Effect of natural products on commercial oral antidiabetic drugs in enhancing 2-deoxyglucose uptake by 3T3-L1 adipocytes

Objective: The management of diabetes with insulin and synthetic oral hypoglycemic drugs (OHDs) can produce serious side effects and in addition fails to prevent diabetes-related complications in many patients. A new diabetes management strategy is needed that is more effective and has fewer side effects. Methods: This paper analyzes the dose- and time-dependent effect of three phytochemicals: berberine, arecoline and vanillic acid, and two antidiabetic drugs: 2,4-thiazolidinedione (TZD) and metformin, on the uptake of 2-deoxyglucose (2DG) by 3T3-L1 adipocytes. The interactions of the phytochemicals with the OHDs were analyzed with isobolograms and the combination index. Results: TZD and berberine increased 2DG uptake by 3.3-fold (with respect to control) at 15 µM and 25 µM, respectively. The same concentrations of arecoline and vanillic acid increased 2DG uptake by 3.2-and 2.9-fold, respectively, when compared with the basal level. Berberine and arecoline acted synergistically with both the OHDs, whereas vanillic acid had an additive interaction with TZD and an antagonistic interaction with metformin. Arecoline significantly increased the translocation of GLUT4 via the PPARγ pathway, whereas berberine and vanillic acid did this via the AMPK-dependent pathway. Conclusions: These phytochemicals significantly reduced the expression of the enzymes involved in fatty acid and cholesterol synthesis, indicating that they might help prevent the secondary complications of diabetes. The current study suggests that berberine and arecoline could allow dosage reduction of OHDs, which could also lead to a reduction in the toxicity and side effects caused by OHDs