Elucidating the Mechanism of Tetrahydrofuran-Diol Formation through Os(VI)-Catalyzed Oxidative Cyclization of 5,6-Dihydroxyalkenes Ligated by Citric Acid.

A computational study is reported here on the mechanism of tetrahydrofuran (THF)-diol formation from the Os(VI)-catalyzed oxidative cyclization of 5,6-dihydroxyalkene ligated with citric acid and in the presence of BroÌ·nsted acid. Initiated by Os(VI) dioxo citrate formation, coordination of co-oxidant pyridine-N-oxide (PNO) and protonation of its oxo group generate the active catalyst. The catalytic cycle commences through successive steps, including dihydroxyalkene addition to the active catalyst in a concerted mechanism to form hexacoordinated alkoxy-protonated PNO-complexed Os(VI) bisglycolate as a turnover-limiting step (TLS), cyclization to Os(IV) THF-diolate, reoxidation to Os(VI) THF-diolate, and hydrolysis via a dissociative mechanism to furnish the THF-diol and regenerate the active species, sustaining the catalytic cycle through an Os(VI)/Os(IV) cycle. Despite the overall exergonic nature of catalytic cycle (ΔGrcycle = -45.0 kcal/mol), the TLS is accelerated by the formation of an open-valence 16-electron Os(VI) intermediate but decelerated by the undesired formation of a saturated/hexacoordinate 18-electron Os(VI) intermediate. BroÌ·nsted acid plays crucial roles in the formation of Os(VI) citrate and the active catalyst, impediment of the second cycle, and the cyclization step. Additionally, besides its role as a co-oxidant, and in the presence of acid, PNO is found to assist the insertion of dihydroxyalkene and, importantly, in releasing the THF-diol to regenerate the active intermediate.

A theoretical investigation for improving the performance of non-fullerene organic solar cells through side-chain engineering of BTR non-fused-ring electron acceptors.

In the current quantum chemical study, indacenodithiophene donor core-based the end-capped alterations of the reference chromophore BTR drafted eight A2-A1-D-A1-A2 type small non-fullerene acceptors. All the computational simulations were executed under MPW1PW91/6-31G (d, p) level of DFT. The UV-Vis absorption, open circuit voltage, electron affinity, ionization potential, the density of states, reorganization energy, orbital analysis, and non-covalent interactions were studied and compared with BTR. Several molecules of our modeled series BT1-BT8 have shown distinctive features that are better than those of the BTR. The open circuit voltage (VOC) of BT5 has a favorable impact, allowing it to replace BTR in the field of organic solar cells. The charge carrier motilities for proposed molecules generated extraordinary findings when matched to the reference one (BTR). Further charge transmission was confirmed by creating the complex with a PM6 donor molecule. The remarkable dipole moment contributes to the formation of non-covalent bond interactions with chloroform, resulting in superior charge mobility. Based on these findings, it can be said that every tailored molecule has the potential to surpass chromophore molecule (BTR) in OSCs. So, all tailored molecules may enhance the efficiency of photovoltaic cells due to the involvement of potent terminal electron-capturing acceptor2 moieties. Considering these obtained results, these newly presented molecules can be regarded for developing efficient solar devices in the future.

Simulation study of a practical approach to enhance cadmium removal via biological treatment by controlling the concentration of MLSS.

The fate of cadmium at the Muharram Aisha wastewater treatment plant in Karbala governorate, Iraq was studied using the TOXCHEM model. Cadmium, a known carcinogen, and is considered one of the most dangerous heavy metals and high concentrations, greater than permissible limits, were found in the treated wastewater. The plant operates using an activated sludge system and this was modeled via TOXCHEM with a sensitivity analysis carried out on the extended aeration system. Prior to analysis, the model was calibrated and validated for cadmium, with the adjustments leading to a mean square error (RMSE) and correlation coefficient (R) of 0.0001 and 0.81, respectively. The mass balance of cadmium in the Muharram Aisha treatment plant was found to be 4832.44 g/day (37.1726%) in the treated wastewater and 8164.52 g/day (62.804%) in the sludge, which indicated that the mix liquor suspended solid (MLSS) was the most sensitive factor. The sensitivity to cadmium was analyzed via MLSS in the extended aeration system and the results o indicated that the higher the MLSS concentration (mg/L), the greater the removal of cadmium in the treated wastewater. It was found that increasing the MLSS through a biological treatment method reduced the concentration of cadmium without the need for additional of any (potentially harmful) chemical treatments. The plant was subsequently operated for a period of 5 months with the MLSS increased from 1500 to 4500 mg/L, and this reduced the concentration of cadmium in the wastewater from 0.36 to 0.01 mg/L as a consequence. This research demonstrates how the novel application of TOXCHEM can be a useful tool in the reduction of heavy metal contamination in the environment.

Exploration of the in vitro antiviral activity of a series of new pyrimidine analogues on the replication of HIV and HCV.

BACKGROUND: In continuation of our search for new anti-HIV and anti-HCV agents, the suggestion, synthesis and structure elucidation of a new series of 2,6-diamino-4-alkylthio- or (2-benzylhydrazinyl)-5-p-chlorophenylazopyrimidines), 2,6-diamino-4-(2-benzylhydrazinyl)-5-(aryl-[1,1'-biphenyl]-4-yl)pyrimidines, 2,6-diamino-4-(aryl)-5-(aryl[1,1'-biphenyl]-4-yl) pyrimidines), 6-(aryl)-1,3-dimethyl-5-nitro pyrimidine-2,4-dione and 6-amino-4-methoxy-N,N-dimethyl-6-arylpyrimidines were described. METHODS: The anti-HIV-1 (strain IIIB) and HIV-2 (strain ROD) activity of the newly synthesized pyrimidine analogues was evaluated in vitro in human MT-4 cells using the MT-4/MTT assay. Similarly, the same compounds were evaluated in vitro for their selective antiviral activity against HCV in the Huh 5-2 replicon system (type 1b, Con1 strain). RESULTS: None of the tested compounds exhibited inhibition of HIV-1 and HIV-2 replication in cell culture. Even though many compounds yielded a 50% effective concentration in the HCV replicon system with selectivity indexes up to 6.9, none of the compounds matched the selection criteria of a selective inhibitor of virus replication in this assay (that is, >70% inhibition at concentrations that do not elicit an anti-metabolic effect on the host cells). CONCLUSIONS: Structural modification of these compounds might optimize their anti-HCV activity by introducing diverse and potent functional groups at the pyrimidine backbone, like nitrile residue. Because of the nature of the molecules, these new derivatives will also be evaluated for their potential anti-HIV activity.