Crystal structure prediction of LiBeH3 using ab initio total-energy calculations and evolutionary simulations.

The stable crystal structure of LiBeH(3) is predicted on the basis of ab initio total-energy calculations using density-functional theory and an extended database of candidate structures and using global optimizations based on an evolutionary algorithm. At the level of density-functional theory, a CaSiO(3)_1-type structure with space group P2(1)/c, containing BeH(4) tetrahedra linked in chains, is the ground-state structure of LiBeH(3) (alpha-LiBeH(3)). It is found to be lower in energy than the structures proposed in previous studies. The analysis of the electronic structure shows that alpha-LiBeH(3) is an insulator with a band gap of about 4.84 eV and exhibits strong covalent bonding in the BeH(4) tetrahedral complexes. Calculations at finite temperatures and high pressures suggest that at T=408 K and ambient pressure a structural transition from alpha-LiBeH(3) (CaSiO(3)-type) to a YBO(3)-type structure with space group Cmcm occurs and that at a pressure of 7.1 GPa alpha-LiBeH(3) undergoes a pressure-induced structural transition from the alpha-phase to a MgSiO(3)-type structure with space group C2/c. The calculated enthalpies of formation (-45.36 and -30.12 kJ/mol H(2) without and with zero-point energy corrections) are in good agreement with the experimental result, indicating that LiBeH(3) is a potential hydrogen storage material with low activation barriers for hydrogen desorption.

Synthesis of C-5'-alkyl substituted 17-spirofuran 19-norsteroids.

A number of new steroidal 17-spirofuran derivatives of the 19-nor series containing Me, Et or (i)Pr-substituents in the heterocyclic moiety has been prepared, which are expected to have a strong progestagenic activity. The proposed approach made use of the 1-3-dipolar cycloaddition of low-molecular nitrile oxides with steroidal acetylenic alcohols followed by transformation of the isoxazole side chain.

[1,5-bis(1-methyl-1H-tetrazol-5-yl-kappaN)-3-oxopentane-kappaO]dichlorocopper(II).

The title compound, [CuCl2(C8H14N8O)], is the first structurally characterized molecular chelate complex of a binuclear N-substituted tetrazole. The Cu atom is five-coordinate, with an approximately square-pyramidal geometry. The equatorial positions of the pyramid are occupied by two Cl atoms and two N atoms from the ligand molecule; the O atom of the ligand lies in the axial position. Each complex is connected to four others via weak C-H...Cl and C-H...N interactions, forming sheets parallel to the (010) plane.

2-(1H-tetrazol-1-yl)benzoic acid.

In the title compound, C8H6N4O2, the tetrazole and benzene rings are planar to within 0.001 (1) and 0.007 (1) A, respectively. These rings are not coplanar in the molecule, the dihedral angle between them being 52.90 (4) degrees. Molecules are connected together by O-H...N and C-H...O hydrogen bonds, forming two-dimensional networks parallel to the xz plane with van der Waals interactions between them.

4-Nitro-2-(1H-tetrazol-1-yl)phenol.

There are two symmetry-independent molecules in the unit cell of the title compound, C(7)H(5)N(5)O(3). The tetrazole and phenyl rings are essentially planar and are not coplanar in either molecule [dihedral angles 30.2 (1) and 7.0 (1) degrees]. In the structure, four molecules are connected by O-H...N bridges, forming four-membered molecular aggregates which are linked together by a complex three-dimensional hydrogen-bond network.