Migration Reaction of a Silyl Group from a Phosphorus to a Carbonyl Oxygen in a Molybdenum Coordination Sphere

The reaction of Cp anion, [C 5 H 4 CH 2 CH 2 P(TMS)Mes] m with (CH 3 CN) 3 Mo(CO) 3 leads to the formation of [( m 5 --C 5 H 4 CH 2 CH 2 --P(TMS)Mes)Mo(CO) 3 ] m , which then reacts with MeI to give a metallaphosphacyclopropane complex with silyl migration.     

Practical one-pot conversion of aryl bromides and β-bromostyrenes into aromatic nitriles and cinnamonitriles

Various aryl bromides were efficiently converted into the corresponding aromatic nitriles in good yields by the treatment with Mg turnings and subsequently DMF, followed by treatment with molecular iodine and aq NH₃. The same treatment of aryl bromides, which are weakly reactive to Mg turnings, with ⁱPrMgCl·LiCl and subsequently DMF, followed by the treatment with molecular iodine and aq NH₃ also afforded the corresponding aromatic nitriles in good yields. On the other hand, when N-formylpiperidine was used instead of DMF, p-substituted β-bromostyrenes were converted into the corresponding p-substituted cinnamonitriles, i.e., α,β-unsaturated nitriles, in good to moderate yields by the same procedure. The reactions were carried out by means of a simple experimental procedure and did not require any toxic metal cyanides or expensive rare metals. Therefore, the present reactions are practical and environmentally benign one-pot methods for the preparation of aromatic nitriles, cinnamonitriles, and aliphatic nitriles from aryl bromides, β-bromostyrenes, and alkyl bromides, respectively, through the formation of Grignard reagents and their DMF or N-formylpiperidine adducts.     

Molecular Recognition by Cyclophane/Guanidinium Supramolecular Receptor Embedded at the Air-Water Interface

In order to develop a supramolecular receptor through a self-assembling process, a site-specific host and an inclusion-type host were mixed as a Langmuir monolayer, and guest binding and pressure-induced fluorescence emission were investigated. A guanidinium amphiphile and several cyclophanes carrying hydrophobic moieties were used as the host molecules; molecular recognition of an aqueous fluorescent guest, 6-p-toluidino-2-naphthalenesulfonic acid (TNS) by binary mixed receptor monolayers was evaluated by a surface pressure-molecular area (π-A) isotherm and a surface fluorescence measurement. An apparent increase in fluorescence intensity was observed when the mixed monolayers of the guanidinium and cyclophane amphiphiles were compressed on an aqueous TNS solution. In contrast, single-component monolayers of the guanidinium or the cyclophane did not show a significant increase in fluorescence emission. In the mixed monolayers, the guest TNS would be bound to the interface by strong electrostatic interaction with the guanidinium, and inclusion of the formed complex probably suppresses the quenching effect in polar medium and/or self-quenching. Experiments with various mixing ratios of these components suggest selective formation of an equimolar cooperative receptor of the guanidinium and the cyclophane. Investigation of the cyclophane structures by fluorescence emission and a competitive binding experiment with another guest were also carried out.     

Nearly perfect triplet-triplet energy transfer from Wannier excitons to naphthalene in organic-inorganic hybrid quantum-well materials

We report the observation of extremely efficient energy transfer (greater than 99%) in an organic-inorganic hybrid quantum-well structure consisting of perovskite-type lead bromide well layers and naphthalene-linked ammonium barrier layers. Time-resolved photoluminescence measurements confirm that the transfer is triplet-triplet Dexter-type energy transfer from Wannier excitons in the inorganic well to the triplet state of naphthalene molecules in the organic barrier. Using measurements in the 10-300 K temperature range, we also investigated the temperature dependence of the energy transfer.     

Structural Investigation of Hesperetin-7-O-Glucoside Inclusion Complex with β-Cyclodextrin: A Spectroscopic Assessment

Flavonoids are biologically active natural products of great interest for their potential applications in functional foods and pharmaceuticals. A hesperetin-7-O-glucoside inclusion complex with β-cyclodextrin (HEPT7G/βCD; SunActive^® HCD) was formulated via the controlled enzymatic hydrolysis of hesperidin with naringinase enzyme. The conversion rate was nearly 98%, estimated using high-performance liquid chromatography analysis. The objective of this study was to investigate the stability, solubility, and spectroscopic features of the HEPT7G/βCD inclusion complex using Fourier-transform infrared (FTIR), Raman, ultraviolet–visible absorption (UV–vis), ¹H- and ¹³C- nuclear magnetic resonance (NMR), differential scanning calorimetry (DSC), liquid chromatography/mass spectroscopy (LC–MS), scanning electron microscopy (SEM), and powdered X-ray diffraction (PXRD) spectroscopic techniques including zeta potential, Job’s plot, and phase solubility measurements. The effects of complexation on the profiles of supramolecular interactions in analytic features, especially the chemical shifts of β-CD protons in the presence of the HEPT7G moiety, were evaluated. The stoichiometric ratio, stability, and solubility constants (binding affinity) describe the extent of complexation of a soluble complex in 1:1 stoichiometry that exhibits a greater affinity and fits better into the β-CD inner cavity. The NMR spectroscopy results identified two different configurations of the HEPT7G moiety and revealed that the HEPT7G/βCD inclusion complex has both –2S and –2R stereoisomers of hesperetin-7-O-glucoside possibly in the –2S/–2R epimeric ratio of 1/1.43 (i.e., –2S: 41.1% and –2R: 58.9%). The study indicated that encapsulation of the HEPT7G moiety in β-CD is complete inclusion, wherein both ends of HEPT7G are included in the β-CD inner hydrophobic cavity. The results showed that the water solubility and thermal stability of HEPT7G were apparently increased in the inclusion complex with β-CD. This could potentially lead to increased bioavailability of HEPT7G and enhanced health benefits of this flavonoid.     

The enzymatic degradation of commercial biodegradable polymers by some lipases and chemical degradation of them

Biodegradable polyesters, poly(butylene succinate adipate) (PBSA), poly(butylene succinate) (PBS), poly(ethylene succinate) (PES), poly(butylene succinate)/poly(caprolactone) blend (HB02B) and poly(butylene adipate terephthalate) (PBAT), were evaluated about degradability for enzymatic degradation by lipases and chemical degradation in sodium hydroxide solution. In enzymatic degradation, PBSA was the most degradable by lipase PS, on the other hand, PBAT containing aromatic ring was little degraded by eleven kinds of lipases. In 1N NaOH solution, degradation rate of PES with ethylene unit was extremely fast, in comparison with other polyesters. Interestingly the degradation rate of PBSA in enzymatic degradation by lipase PS was faster than in chemical degradation.