The structure of (S)-(-)-4-(2-benzimidazolyl)-4-hydroxybutyric acid formed during mammalian metabolism of the fungicide 2-(2-furyl)benzimidazole.

During metabolism of the fungicide 2-(2-furyl)benzimidazole (FB) in mammals, an optically active compound, metabolite A, was isolated. This compound, a principal metabolite in the biological degradation of FB, was isolated from the urine of horse and dog. When studied by IR, NMR, MS, CD and electrophoretic techniques, the metabolite proved to be the zwitterionic form of (S)-(-)-4-(2-benzimidazolyl)-4-hydroxybutyric acid. The synthesized optical active compound was in every respect identical with metabolite A. The suggested structure has been completely verified by the current investigation of its crystal structure, based on single crystal diffraction data collected at the synchrotron MAX II in Lund, Sweden. In an earlier determination, a related compound, 3-benzimidazolylpropionic acid (Ercan et al. 1996) was suggested to be non-zwitterionic. The present studies have shown that the latter compound too is zwitterionic and that the conclusions presented were apparently based on some erroneously proposed hydrogen positions.

Comparative study of the high-pressure behavior of As, Sb, and Bi.

The high-pressure behavior of the heavier group 15 elements As, Sb, and Bi was investigated by means of ab initio density functional calculations employing pseudopotentials and a plane wave basis set. The high-pressure structural sequence of these elements is distinguished by the occurrence of the Bi-III structure, which is a complex, incommensurately modulated, host-guest structure. We approximated this structure by a supercell which reproduced the experimentally established pressure stability ranges of the host-guest structure for the different elements extremely well. With pressure we find an increasing admixture of d states (s-d hybridization) in the occupied levels of the electronic structure of As, Sb, and Bi. However, the s-d mixing remains at a low level. Thus, the emergence of a complex intermediate pressure structure cannot be explained by a pressure-induced altered valence state for these elements. Instead, it is argued that the Bi-III structure is a consequence of a delicate interplay between the electrostatic and the band energy contribution to the total energy. In the intermediate pressure range of heavier group 15 elements, both important parts of the total energy account equally for structural stability.

A new urolith in four cats and a dog: composition and crystal structure.

A previously unreported urolith is presented. The concrement was found in the bladder of four Persian cats and one collie dog. It contained potassium, magnesium and phosphorus, all determined by chemical analysis. The infrared spectrum of the X-ray-dense urolith displayed absorption bands in the phosphate region. A single absorption maximum at 930 cm(-1) indicated the presence of inorganic pyrophosphate. A single crystal structure determination of the urolith has been performed. The results obtained are consistent with the formula [K(1.0)Mg(1.5)](4+)[P(2)O(7)](4-.)(H(2)O)(5), which corresponds to 11.5% K, 10.7% Mg and 18.2% P. The structure contains negatively charged slabs of composition MgP(2)O(7) small middle dot(H(2)O)(2)(2-)alternating with positively charged, hydrated Mg(2+) and K(+) ions. The observed P(2)O(7) is that of a distorted eclipsed syn conformation, which is the most common geometry in the solid state according to a statistical analysis of known structural data. A simple numerical descriptor has been derived, classifying observed X(2)O(7) conformations. It is suggested that some genetic enzymatic dysfunction of pyrophosphate-hydrolysing alkaline phosphatase might cause the formation of this unusual urolith.

Synthesis, Structure, and Photophysical Properties of Novel Ruthenium(II) Carboxypyridine Type Complexes.

A series of Ru(II) compounds and salts have been synthesized: [Ru(6-carboxylato-bpy)(2)] (5), [Ru(6-carboxylato-bpy)(tpy)]PF(6) (9), [Ru(tpy)(2)](PF(6))(2) (8), and [Ru(bpy)(2)(Pic)]PF(6) (11), where 6-carboxy-bpy (1) = 6-carboxy-2,2'-bipyridine, tpy (2) = 2,2':6',2"-terpyridine, and Pic = 2-carboxylatopyridine. The compounds have been characterized by NMR, electrospray mass spectrometry (ESI-MS), cyclic voltammetry, absorption and emission spectroscopy (at 100, 140, and 298 K), and single-crystal X-ray diffraction (complex 5). Complex 5 crystallizes in the monoclinic system, space group P2(1)/n, formula RuC(22)H(14)N(4)O(4).C(2)H(5)OH, with a = 11.088(3) Å, b = 11.226(3) Å, c = 35.283(9) Å, beta = 91.41(2) degrees, and Z = 8. A linear dependence on the number of coordinated carboxylato groups and the electrochemical redox potentials was found, ca. 0.4 V lower reduction potential for the oxidation step (Ru(II/III)) per carboxylate group. Also, to the best of our knowledge, these are the first examples (9, 11) of mononuclear Ru(II) complexes containing a carboxypyridine-ruthenium moiety displaying any luminescence emission.