Uric acid monohydrate--a new urinary calculus phase.

In our laboratory more than 100,000 urinary calculi have been analysed since 1972. Amongst this huge sample, 15 specimens originating from a total of eight patients were observed showing similar characteristics but escaping unambiguous identification with any of the substances that have been described so far in urinary concrements. Therefore, the unknown substance was submitted to a more extended analytical regimen. Structural analysis by x-ray crystallography turned out to be most successful, identifying the unknown material as uric acid monohydrate. Uric acid monohydrate crystallizes in the monocline space group P2(1)/c. Within the crystal, uric acid and water molecules form continuous layers by hydrogen bonds. This is in contrast to uric acid in its water free and its dihydrate forms, which both crystallize by forming 3-dimensional networks To the best of our knowledge , the existence of a monohydrate form of uric acid has not been reported so far. Accordingly, this is the first report on uric acid monohydrate as a urinary stone component. The frequency of only 0.015% in our survey indicates that uric acid monohydrate is rarely the main component in concrements, in contrast to uric acid and uric acid dihydrate with frequencies of 10% and 6%, respectively. The infrared spectrum of uric acid monohydrate is very similar to that of the other crystal forms of uric acid. Because of this similarity and its low frequency, uric acid monohydrate may have been overlooked as a component of urinary concrements. X-ray diffraction allows for better differentiation in routine stone analysis. All samples of uric acid monohydrate were found by solid state NMR spectroscopy to be highly contaminated by amorphous material. This material consisted of long aliphatic chains reminiscent of lipids and fatty acids, respectively. Concrements consisting of other forms of uric acid or urate lacked this amorphous component. Therefore, a role of this aliphatic material has to be taken into consideration when discussing the conditions that may favour the rare formation of concrements from uric acid monohydrate. As for as the metabolic situation of the affected patients is concerned, no common peculiarities became evident by a retrospective survey.

Boron-diindomethene (BDI) dyes and their tetrahydrobicyclo precursors--en route to a new class of highly emissive fluorophores for the red spectral range.

The X-ray crystallographic, optical spectroscopic, and electrochemical properties of a newly synthesized class of boron-diindomethene (BDI) dyes and their tetrahydrobicyclo precursors (bc-BDP) are presented. The BDI chromophore was designed to show intensive absorption and strong fluorescence in an applicationary advantageous spectral range. Its modular architecture permits fusion of a second subunit, for example, a receptor moiety to the dye's core to yield directly linked yet perpendicularly prearranged composite systems. The synthesis was developed to allow facile tuning of the chromophore platform and to thus adjust its redox properties. X-ray analysis revealed a pronounced planarity of the chromophore in the case of the BDIs, which led to a remarkable close packing in the crystal of the simplest derivative. On the other hand, deviation from planarity was found for the diester-substituted bc-BDP benzocrown that exhibits a "butterfly"-like conformation in the crystal. Both families of dyes show charge- or electron-transfer-type fluorescence-quenching characteristics in polar solvents when equipped with a strong donor in the meso-position of the core. These processes can be utilized for signaling purposes if an appropriate receptor is introduced. Further modification of the chromophore can invoke such a guest-responsive intramolecular quenching process, also for receptor groups of low electron density, for example, benzocrowns. In addition to the design of various prototype molecules, a promising fluoroionophore for Na+ was obtained that absorbs and emits in the 650 nm region and shows a strong fluorescence enhancement upon analyte binding. Furthermore, investigation of the remarkable solvatokinetic fluorescence properties of the "butterfly"-like bc-BDP derivatives suggested that a second intrinsic nonradiative deactivation channel can play a role in the photophysics of boron-dipyrromethene dyes.

A charge transfer-type fluorescent molecular sensor that "lights up" in the visible upon hydrogen bond-assisted complexation of anions.

A charge transfer-type fluorescent molecular sensor consisting of a bisamidopyridine receptor and two styryl base chromophores shows H(2)PO(4)(-) and acetate-enhanced fluorescence due to the conversion of weak intramolecular hydrogen bonds into strong ones in the host-guest ensemble.

Monoalkylated 4'-aryl-substituted terpyridines.

1-Methyl-2-[4-phenyl-6-(pyridinium-2-yl)pyridin-2-yl]pyridinium diperchlorate, C(22)H(19)N(3)(2+).2ClO(4)(-), (I), and 2-[4-(methoxyphenyl)-2,2'-bipyridin-6-yl]-1-methylpyridinium iodide, C(23)H(20)N(3)O(+).I(-), (II), both crystallize in the monoclinic space group P2(1)/c. In contrast with the monocharged molecule of (II), the doubly charged molecule of (I) contains an additional protonated pyridine ring. One of the two perchlorate counter-anions of (I) interacts with the cation of (I) via an N-H.O hydrogen bond. In (II), two molecules related by a centre of symmetry are connected by weak pi-pi interactions, forming dimers in the crystal structure.

Phenanthroline complexes of zinc and calcium carbamates.

Bis(N,N-di-n-butyldithiocarbamato-kappa2S,S')(1,10-phenanthroline-kappa2N,N')zinc(II) ethanol hemisolvate, [Zn(C9H18NS2)2(C12H8N2)].0.5C2H6O, (I), and bis(N,N-di-n-hexyldithiocarbamato-kappa2S,S')bis(1,10-phenanthroline-kappa2N,N')calcium(II), [Ca(C13H26NS2)2(C12H8N2)2], (II), are mixed-ligand complexes. In the first compound, the Zn atom has a distorted octahedral coordination, while in the second compound, the Ca atom is eight-coordinate, with four S and four N atoms forming a highly distorted cube.

Two polymorphic forms of 2,5-bis(4-methoxycarbonylphenyl)-1,3,4-oxadiazole.

The title compound [systematic name: dimethyl 4,4'-(1,3,4-oxadiazole-2,5-diyl)diphenylenedicarboxylate], C(18)H(14)N(2)O(5), crystallizes under similar conditions in two different orthorhombic crystalline forms. In both forms, the molecule consists of two equivalent parts. In form 1, these parts are related by a twofold axis of space group Pbcn, and in form 2, by a mirror plane of space group Cmc2(1). The O atom of the oxadiazole ring occupies a special position on the twofold axis and on the mirror plane in forms 1 and 2, respectively.