UV-Induced Unimolecular Photochemistry of Diketene Isolated in Cryogenic Inert Matrices

This article presents a detailed comprehensive investigation of the ortho fluoro- and chloro- substituted benzoic acids both, as isolated molecules and in the crystalline phase. Quantum chemical calculations performed within the density functional theory (DFT) formalism are used to investigate the potential energy landscapes of the molecules, taking into special consideration the effects of the interactions between the carboxylic group and the ortho halogen substituents, as well as the nature of these later on the structure and properties of the investigated systems. The structures of the relevant conformers of the molecules are discussed in comparative terms, and used to rationalize experimental data obtained for the compounds in the gas phase and isolated in low-temperature inert matrices. The UV-induced photofragmentation reactions of two of the compounds isolated in cryogenic inert matrices were studied as illustrative cases. The structures of the crystals reported previously in the literature are revisited and discussed also in a comparative basis. Particular emphasis is given to the analysis of the intermolecular interactions in the different crystals, using Hirshfeld surface analysis, the CE-B3LYP energy decomposition model and the HOMA index, and to their correlation with thermodynamic data.

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Critical points in ethylcellulose matrices: Influence of the polymer, drug and filler properties

Acta Pharmaceutica ◽

10.2478/acph-2013-0005 ◽

2013 ◽

Vol 63 (1) ◽

pp. 115-129 ◽

Cited By ~ 9

Author(s):

Celia Cifuentes ◽

Ángela Aguilar-de-Leyva ◽

Ali R. Rajabi-Siahboomi ◽

Isidoro Caraballo

Keyword(s):

Drug Release ◽

Release Kinetics ◽

Polymer Particle ◽

Compression Pressure ◽

Formulation Factors ◽

Inert Matrices ◽

Main Components ◽

First Time ◽

Viscosity Polymer ◽

Global Influence

Percolation theory has been applied to study the drug release behaviour in multicomponent inert matrices containing ethylcellulose as a matrix forming polymer. Global influence of major formulation factors such as polymer viscosity, polymer particle size, drug and filler solubility and porosity of the tablets in drug release kinetics has been studied for the first time. Batches containing three viscosity grades of Ethocel™, microcrystalline cellulose (MCC) and lactose as fillers, a lubricant and flow aid mixture and three drugs with different solubility have been manufactured. For some batches, compression pressure was varied in order to obtain matrices with five levels of initial porosity. The behaviour of inert matrices was explained based on the percolation ranges of the main components of the formulation. The effect of the porosity percolation threshold was observed and the existence of a tricoherent drug-polymer-filler system is hypothesized.

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Electron spin resonance studies of oriented NO2 and NF2 in inert matrices at low temperatures

Canadian Journal of Chemistry ◽

10.1139/v70-130 ◽

1970 ◽

Vol 48 (5) ◽

pp. 805-817 ◽

Cited By ~ 24

Author(s):

C. A. McDowell ◽

H. Nakajima ◽

P. Raghunathan

Keyword(s):

Electron Spin Resonance ◽

Electron Spin ◽

Low Temperatures ◽

Hyperfine Splitting ◽

Preferential Orientation ◽

Paramagnetic Species ◽

Host Matrix ◽

Argon Matrix ◽

Spin Resonance ◽

Inert Matrices

Preferentially oriented NO2 and NF2 in inert matrices have been studied in some detail by electron spin resonance methods at 4.2 °K. Methods are discussed which may optimize the degree of preferential orientation of the paramagnetic species in appropriate matrices. The results demonstrate that while neon is the best host matrix for orienting NO2, argon is to be preferred for NF2. The g-values and hyperfine splitting data have been accurately determined and are compared with earlier values. Motional processes are suggested to explain the spectra obtained for NF2 in an argon matrix in the temperature range 4–30 °K.

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