Solid solutions La1-xSrxCo1-yFeyO3-z (0 < x <= 1, 0 less than or equal to y less than or equal to 1) fabricated by ceramic technology in air from fused nitrates were characterized by X-ray powder diffraction and thermal analysis. The oxygen nonstoichiometry of the synthesized samples was determined by iodimetric titration. ne calculation scheme for the apparent activation energy of oxygen exchange was refined to include the structural and chemical degradation of the solid solutions in question. Thermogravimetry was employed to study oxygen exchange in the solid solutions. SrCo0.8Fe0.2O3-z (ss) was shown to be the only oxygen-conducting composition of SrCo1-yFeyO3-z solid solutions. The substitution of lanthanum fer strontium was shown to raise the activation energy of oxygen conductivity.

The structural data for the closo-monocarboranes CBn-1Hn- (n = 6-12), closo-dicarboranes C2Bn-2Hn (n = 6-12), closo-azadodecaborane HNB11H11, decaborane-14 B10H14, and azadicarboranes nido-10,7,8-NC2B8H11 and arachno-1,8,11-NC2B8H13 were invoked to estimate the bond energies, enthalpies of formation, and energies of three-dimensional (or spherical) aromaticity for these compounds. The calculations are based on the equations of the structural- thermodynamical model. This work is a continuation of our systematic investigations into the effect of heteroatom (carbon, nitrogen, or fluorine) on the extent of electron delocalization in the cage clusters and, hence, on the thermodynamic stability of boranes.

The trends in:the changes of the average equilibrium internuclear boron-boron distances <(R)over bar(e)>(BB) in the BnLnk clusters (n = 4-12; k = 0 or -2; and L = H, F, Cl, Br, or I) are considered.:It is shown that <(R)over bar(e)>(BB) changes as <(R)over bar(e)>(BB) = *R-e(BB) + aln(1/2 + A(t)) with the increase in cluster size, where A(t) = m/n is the topological factor dependent on the number m of bonds and number n of atoms in the core cluster B-n. The <(R)over bar(e)>(BB) value increases with increasing electronegativity of ligand L in respect to the hydrogen atom. On passing from k = -2 to k = 0, <(R)over bar(e)>(BB) also increases. The ab initio quantum-chemical Hartree-Fock LCAO MO calculations of the B4H4, B6H62-, B4F4, B6F62-, and B6F6 systems are performed using the STO-3G basis set. A new relationship is obtained between the equilibrium internuclear distance <(R)over bar(e)>(BB) and the nu(BB) frequency in the LR spectra of fluoro-substituted closo-dodecaborates.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.