Two Copper-Containing Polyoxometalate-Based Metal-Organic Complexes as Heterogeneous Catalysts for the C-H Bond Oxidation of Benzylic Compounds and Olefin Epoxidation.

Using a one-pot assembly method, two novel copper-containing Keggin-type polyoxometalates (POMs)-based metal-organic complexes, that is, [CuII2(pbba)2NO3-(H2O)2(PW12O40)]·3H2O [PW12-Cu-pbba, H2pbba = 1,1'-(1,4-phenylene-bis(methylene))-bis(pyridine-3-carboxylic acid)] and [CuII2(pbba)2(H2O)2(GeW12O40)]·3H2O (GeW12-Cu-pbba), were successfully synthesized. These two complexes are isostructural, differing only in their POM components. They are applicable as heterogeneous catalysts for the C-H bond oxidation of benzylic compounds and olefin epoxidation under mild conditions, with oxygen as the oxidant and isobutyraldehyde as the coreductant. The catalytic activity of PW12-Cu-pbba was superior to that of GeW12-Cu-pbba. Under the optimal conditions, PW12-Cu-pbba catalyzed the oxidation of indane into 1-indanone with an 81% yield and >99% selectivity within 48 h. As heterogeneous catalysts, both complexes demonstrated excellent recoverability and high stability and could be stably reused five times without significant activity loss.

Modifying Parallel Excitations into One Framework for C(sp3)─H Bond Activation with Energy Combined More Than Two Photons.

Natural photosynthesis enzymes utilize energies of several photons for challenging oxidation of water, whereas artificial photo-catalysis typically involves only single-photon excitation. Herein, a multiphoton excitation strategy is reported that combines parallel photo-excitations with a photoinduced electron transfer process for the activation of C(sp3)─H bonds, including methane. The metal-organic framework Fe3-MOF is designed to consolidate 4,4',4″-nitrilotrisbenzoic units for the photoactivation of dioxygen and trinuclear iron clusters as the HAT precursor for photoactivating alkanes. Under visible light irradiation, the dyes and iron clusters absorbed parallel photons simultaneously to reach their excited states, respectively, generating 1O2 via energy transfer and chlorine radical via ligand-to-metal charge transfer. The further excitation of organic dyes leads to the reduction of 1O2 into O2 •- through a photoinduced electron transfer, guaranteeing an extra multiphoton oxygen activation manner. The chlorine radical abstracts a hydrogen atom from alkanes, generating the carbon radical for further oxidation transformation. Accordingly, the total oxidation conversion of alkane utilizing three photoexcitation processes combines the energies of more than two photons. This new platform synergistically combines a consecutive excited photoredox organic dye and a HAT catalyst to combine the energies of more than two photons, providing a promising multiphoton catalysis strategy under energy saving, and high efficiency.

Rational regulation of transition metals in polyoxometalate hybrids without noble metal assistance for efficient light-driven H2 production.

Four new rationally designed polyoxometalate (POM)-based hybrids are reported with a maximum photocatalytic hydrogen evolution rate of 12245.59 µmol g-1 h-1, which outperform all known POM-based metal-organic photocatalysts.

Selective synthesis and application to the synthesis of (E)-fluorovinyl nucleosides.

A selective method for synthesizing (E)-fluorovinyl was developed. Novel acyclic (E)-fluorovinyl versions of neplanocin A were designed and selectively synthesized as potential antiviral agents. The condensation of the bromide 7 with the nucleosidic bases (5-FU, C, A, G) and the deprotection afforded the desired acyclic fluorovinyl nucleosides. The synthesized compounds 11, 12, 13, and 16 were evaluated for their antiviral activity. The guanine derivative 16 showed toxicity-dependent anti-HIV-1 activity in MT-4 cells.

Nanomemulsion of megestrol acetate for improved oral bioavailability and reduced food effect.

Megestrol acetate (MGA) belongs to the BCS class II drugs with low solubility and high permeability, and its oral absorption in conventional dosage form MGA microcrystal suspension (MGA MS) is very limited and greatly affected by food. In this study, MGA nanoemulsion (MGA NE) was formulated based on solubility, phase-diagram and release studies. Then oral bioavailability of MGA NE and MGA MS was evaluated. A randomized two-way crossover trial was conducted on six male dogs under fed and fasting conditions. Blood concentrations of MGA were analyzed using LC-MS/MS. MGA NE yielded 5.00-fold higher oral bioavailability in fasting conditions and displayed more stable absorption profiles after food intake compared with MGA MS.