Unprecedented NH2-MIL-101(Al)/n-Bu4NBr system as solvent-free heterogeneous catalyst for efficient synthesis of cyclic carbonates via CO2 cycloaddition.

Amine-functionalised framework NH2-MIL-101(Al) was synthesized using a solvothermal and microwave method and characterized by PXRD, FT-IR, TGA, SEM-EDX, and BET surface area analysis. The desolvated framework, in the presence of co-catalyst tetrabutylammonium bromide (TBAB), acted as an excellent heterogeneous catalyst for the solvent-free cycloaddition of carbon dioxide (CO2) with epoxides, affording five-membered cyclic carbonates. Using styrene oxide, the NH2-MIL-101(Al)/TBAB system showed more than 99% conversion, affording 96% yield and 99% selectivity with a turn over frequency of 23.5 h-1. This validated the synergistic effect of the quaternary ammonium salt during CO2 cycloaddition. The catalyst could be recycled at least five times without a noticeable loss in activity, while leaching test showed no leached Al3+ ions throughout the reaction. Thorough analysis of the reaction parameters showed that the optimum conditions for obtaining the maximum yield and highest selectivity were 120 °C and 18 bar of CO2 for 6 h. The outstanding conversion and selectivity were maintained for a range of aliphatic and aromatic epoxides, corroborating the duel benefit of the micro-mesoporous system with amine functionality, which offered easy access for reactant molecules with diverse sizes, and provided inspiration for future CO2 cycloaddition catalytic systems. We also propose a rationalized mechanism for the cycloaddition reaction mediated by NH2-MIL-101(Al) and TBAB based on literature precedent and experimental outcome.

ß-Cyclodextrin-Assisted Intervalence Charge Transfer in Mixed-Valent [2]Rotaxane Complexes Having Metal Centers Linked by an Interrupted π-Electron System.

FeII to RuIII electron transfer is initiated by the inclusion of saturated bridging ligands into the ß-cyclodextrin (CD) cavity of [2]rotaxane complexes and is observed as an intervalence charge transfer (IVCT) band in the electronic spectra. The rotaxanes are synthesized by using RuIII and FeII complexes as stoppers, ß-CD as the cyclic molecular head, and 4,4'-bipyridine derivatives with interrupted π-electron system as the bridging ligand between the metal centers.

Montmorillonite Poly-L-Lactide Microcomposites of Procainamide for controlled drug delivery: In vitro and In vivo evaluation.

The research work reported in this paper is extension of our previous findings related to intercalation of procainamide hydrochloride, an antiarrythmia drug in interlayer gallery of Na(+)-clay (montmorillonite). The microcomposite particles prepared from procainamide-montmorillonite hybrid and poly L-lactide were characterised by scanning electron microscope and atomic force microscopy analysis. In vitro drug release study in simulated intestinal fluid showed controlled release pattern up to ~72 h and significant reduction in the drug release in gastric environment. In vivo pharmacokinetics and biodistribution in rats showed that the plasma/tissue drug levels were within therapeutic window as compared with free drug. The data from toxicity biomarker estimations and clinical biochemistry/haematological parameters showed significant reduction in drug toxicity when formulated in montmorillonite/poly L-lactide as compared with free drug, which is of considerable value in achieving improved therapy with reduced side effects.

Montmorillonite-Alginate Composites as a Drug delivery System: Intercalation and In vitro Release of Diclofenac sodium.

Diclofenac sodium and alginate was intercalated into montmorillonite to form uniform sized beads by gelation method. The structure and surface morphology of the synthesized composite beads were characterized by powdered X-ray diffraction, Fourier transform infrared spectroscopy, thermo gravimetric analysis and scanning electron microscopy. Diclofenac release kinetics of the composite in simulated intestinal fluid medium (pH 7.4) and effect of montmorillonite content on the in vitro release of diclofenac from diclofenac-montmorillonite-alginate composites bead was investigated by UV/Vis spectrophotometer. Diclofenac encapsulation efficiency in the montmorillonite-alginate composites bead increases with an increase in the montmorillonite content. The control release of diclofenac from diclofenac-montmorillonite-alginate composites beads was observed to be better as compared to diclofenac-alginate beads.