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141.
A three-dimensional potential energy surface (PES) for the Br(-)-H(2) complex is computed using the ab initio CCSD(T) method and an extended basis set. The PES has two equivalent minima at the linear geometries (equilibrium interfragment distance R(e)=3.34 A and interaction energy D(e)=670 cm(-1)) separated by the barrier at the T-shaped configuration (interfragment distance R(e)=4.03 A and barrier height of 610 cm(-1)). Ab initio points are fitted to a flexible analytical form and used in the variational rovibrational energy level calculations. Simulated infrared spectra of the Br(-)-H(2) and Br(-)-D(2) complexes in the monomer stretching excitation region are in good agreement with the measured ones. Nonstatistical intensity ratios of the complexes of para- and ortho-monomers are qualitatively explained by monomer ligand exchange reactions. Predissociation of the complexes containing vibrationally excited monomers is analyzed and shown to proceed through the near-resonant vibration-to-rotation energy transfer. For complexes involving Br(-) and the HD monomer, two energetically low-lying states are predicted, corresponding predominately to the Br(-)-DH and Br(-)-HD isomeric forms. The results demonstrate the close similarity of the bromide containing complexes to their analogs containing the chloride anion.  相似文献   
142.
143.
We have measured the bimolecular contribution (relaxivity) R1 (M(-1) s(-1)) to the spin-lattice relaxation rate for the protons of H2 and H2@C60 dissolved in organic solvents in the presence of paramagnet nitroxide radicals. It is found that the relaxation effect of the paramagnets is enhanced 5-fold in H2@C60 compared to H2 under the same conditions. 13C relaxivity in C60 induced by nitroxide has also been measured. The resulting value of R1 for 13C is substantially smaller relative to the 1H relaxation in H2@C60 than expected solely on the basis of the smaller magnetic moment of 13C. The observed values of R1 have been analyzed quantitatively using an outer-sphere model for bimolecular spin relaxation to extract an encounter distance, d, as the dependent variable. The resulting values of d for H2 and (13)C60 are similar to the sum of the van der Waals radii for the radical and the corresponding molecule. The value of d for (1)H2@C60 is substantially smaller than the corresponding van der Waals estimates, corresponding to larger than expected values of R1. A possible explanation for the enhanced relaxivity is a contribution from hyperfine coupling. Based on the results reported here, it seems that not only is the hydrogen molecule in H2@C60 not insulated from magnetic contact with the outside world but also the interaction with paramagnets is even stronger than expected based on distance alone.  相似文献   
144.
145.
Intramolecular mobility of spin-labelled terephthaloyl chloride and 1,10-decanediol copolymer in solution was investigated using a polymer in which the label was rigidly attached to the main chain methylene groups. Correlation times and effective segmental dimensions were measured, as were the frequency and amplitude of the high-frequency torsional vibrations of the main chain monomer units. The amplitude of high-frequency torsional vibrations was shown to increase with increasing temperature.  相似文献   
146.
The quantum yields of photolysis of organomercury compounds in different organic solvents have been measured. It was shown that the quantum yields of photolysis of nitro derivatives of mercury compounds and the symmetric (methylnaphtyl)mercury compound are equal to unity. The photolysis of halo derivatives of benzylmercury proceeds with lower quantum yields as compared with photolysis of analogous dibenzylmercury derivatives. The quantum yields of photolysis of organomercury compounds are almost independent of the solvent.  相似文献   
147.
Zero-point energies (ZPE) of intermolecular, non-bonded vibrations and isotope effects, induced by noncovalent interactions, are computed for paramagnetic molecules. They appear to be not significant for complexation of HO2 and oxygen with C–H bonds and results to isotope effect, which deviates from unit by 5–10%. However, ZPE and isotope effects in complexes of HO2 and nitroxyl radicals with water are larger and reach 50–70%. The largest effect, about 12, is found for complexation of hydrogen atom with water. Complexation of nitroxyl and peroxy radicals by hydrogen bonds is accompanied by transfer of spin density of unpaired electron from radical to the ligand molecules and induces high field paramagnetic shifts of the ligand NMR lines. It evidences that the spin transfer via intermolecular bonds occurs by mechanism of spin polarization.  相似文献   
148.
The adsorption, desorption, impact, and associative heterogeneous recombination rate coefficients are determined for atomic oxygen in the temperature range between 500 and 2000 K on the basis of quantum chemical data on the energy of interaction of atomic and molecular oxygen with the clusters that model an α-Al203 surface. These coefficients are used to calculate the heterogeneous recombination probabilities and the heat fluxes to the surface under the conditions similar to those of the MESOX facility.  相似文献   
149.
Oligomeric copperdiorganosiloxanes differing in organic environment at the silicon atoms and in the Si/Cu ratio were synthesized. The magnetic properties of all compounds were shown to deviate from the Curie law. Unlike rigid chain oligomers characterized by antiferromagnetic interaction, coordination metal oxide clusters linked by flexible chain siloxane fragments exhibit ferromagnetic properties. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 1691–1694, September, 1999.  相似文献   
150.
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