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Abstract: Structure and properties of the radical cations of “bridged” amidoesters (functional groups separated by 0–4 methylene groups and the corresponding dimethyl-substituted amides) were investigated by EPR, optical absorption spectroscopy and DFT calculations. The EPR spectra and thermal reactions of these species are similar. Meanwhile, for amidoesters with 2–4 methylene groups, the methylene “bridge” is involved in photochemistry, which can be explained by specific conformation of amidoester radical cations determined by interaction between the functional groups. [Copyright &y& Elsevier]

The radical cations of piperazine, morpholine, thiomorpholine, and thioxane were investigated by electron paramagnetic resonance (EPR) and electron−nuclear double resonance (ENDOR) spectroscopy in a solid Freon matrix. Optimized geometry and magnetic parameters of the radical cations were calculated using a density functional theory (DFT)/Perdew−Burke−Ernzerhof (PBE) method. Both experimental and theoretical results suggest that all the studied species adopt chair (or distorted chair) conformations. No evidence for the boat conformers with intramolecular σ*-bonding between heteroatoms were obtained. In the cases of morpholine and thioxane, the oxygen atoms are characterized by relatively small spin populations, whereas a major part of spin density is located at N and S atoms, respectively. The thiomorpholine radical cation exhibits nearly equal spin population of N and S atoms. In most cases (except for thioxane), the calculated magnetic parameters agree with the experimental data reasonably well. [ABSTRACT FROM AUTHOR]

Spectroscopic characteristics and X-ray induced transformations of the HCN... CO2 complex in solid Ar and Kr matrices were studied by FTIR spectroscopy and ab initio calculations at the CCSD(T) level. The complexwas prepared by deposition of the HCN/CO2/Ng gas mixtures (Ng = Ar or Kr). The comparison of the experiment and calculations prove formation of a linear, H-bonded NCH... OCO complex with a substantial red shift of the C-H stretching band and a blue shift of the H-C-N bending band in respect to the monomer. This result is in contrast with the previous gas-phase observations, where only T-shape complex was found. Irradiation of deposited matrices leads to formation of CN radicals and HNC molecules and subsequent annealing results in appearance of H2CN and trans-HCNH in both matrices plus HKrCN in the case of Kr. In the presence of CO2, the strongest absorption of trans-HCNH radical demonstrates an additional blue-shifted (by 6.4 cm-1) feature, which was assigned to the N-coordinated complex of this radical with CO2 on the basis of comparison with calculations. To our knowledge, it is the first experimentally observed complex of this radical. No evidence was found for HKrCN... CO2 complex, which was explained tentatively by steric hindrance. [ABSTRACT FROM AUTHOR]

The radical cations of aminoamides Me2N(CH2) n C(O)NMe2 and aminoethers Me2N(CH2) n OMe reveal selective photoinduced intramolecular H transfer from methylene bridge at a specific chain length (n = 3). [Copyright &y& Elsevier]

The radical cation (RC) of methoxyacetone exhibits a delocalization of spin density between two oxygen atoms with considerable spin population on methylene hydrogen atoms, which results in the selective deprotonation of this RC. [Copyright &y& Elsevier]