Solid-state characterization of Felodipine-Soluplus amorphous solid dispersions.

The aim of the current study is to develop amorphous solid dispersion (SD) via hot melt extrusion technology to improve the solubility of a water-insoluble compound, felodipine (FEL). The solubility was dramatically increased by preparation of amorphous SDs via hot-melt extrusion with an amphiphilic polymer, Soluplus® (SOL). FEL was found to be miscible with SOL by calculating the solubility parameters. The solubility of FEL within SOL was determined to be in the range of 6.2-9.9% (w/w). Various techniques were applied to characterize the solid-state properties of the amorphous SDs. These included Fourier Transform Infrared Spectrometry spectroscopy and Raman spectroscopy to detect the formation of hydrogen bonding between the drug and the polymer. Scanning electron microscopy was performed to study the morphology of the SDs. Among all the hot-melt extrudates, FEL was found to be molecularly dispersed within the polymer matrix for the extrudates containing 10% drug, while few small crystals were detected in the 30 and 50% extrudates. In conclusion, solubility of FEL was enhanced while a homogeneous SD was achieved for 10% drug loading.

Synthesis, characterization, photophysical properties, and catalytic activity of an SCS bis(N-heterocyclic thione) (SCS-NHT) Pd pincer complex.

Treatment of 1,3-bis(3'-butylimidazolyl-1'-yl)benzene diiodide with elemental sulfur in the presence of a base produced a bis(N-heterocyclic thione) (NHT) pincer ligand precursor. Its reaction with PdCl2(CH3CN)2 produced chloro[1,3-bis(3'-butylimidazole-2'-thione-κ-S)benzene-κ-C]palladium(ii), a 6,6-fused ring SCS-NHT palladium pincer complex. This air stable compound is, to our knowledge, the first SCS pincer complex that utilizes N-heterocyclic thione (NHT) donor groups. The molecular structures of the ligand precursor and the palladium complex were determined by X-ray crystallography and computational studies provided insight into the interconversion between its rac and meso conformations. The photophysical properties of the complex were established, and its catalytic activity in Suzuki, Heck, and Sonogashira cross-coupling reactions was evaluated.

Noncovalent interactions in microsolvated networks of trimethylamine N-oxide.

The effects of the formation of hydrogen-bonded networks on the important osmolyte trimethylamine N-oxide (TMAO) are explored in a joint Raman spectroscopic and electronic structure theory study. Spectral shifts in the experimental Raman spectra of TMAO and deuterated TMAO microsolvated with water, methanol, ethanol, and ethylene glycol are compared with the results of electronic structure calculations on explicit hydrogen-bonded molecular clusters. Very good agreement between experiment and theory suggests that it is the local hydrogen-bonded geometry at TMAO's oxygen atom that dominates the structure of the extended hydrogen-bonded networks and that TMAO's unique stabilizing abilities are a result of the "indirect effect" model. Natural bonding orbital (NBO) calculations further reveal that hyperconjugation results in vibrational blue shifts in TMAO's C-H stretching region when solvated and a red shift in methanol's C-H stretching region when hydrogen bonding with TMAO.