Crystal chemistry of the 4,4'-dimethyl-2,2'bipyridine/copper bromide system.

The reaction of 4,4'-dimethyl-2,2-bipyridine (henceforth dmbp) with copper(I) and/or copper(II) bromide under a wide variety of conditions has led to the isolation of 10 different crystalline materials. These include one Cu(I) salt, [Cu(dmbp)(2)]Br (a distorted tetrahedral Cu species and a lattice Br(-) ion); two mixed valence Cu(I,II) compounds, [Cu(dmbp)(2)Br][CuBr(2)] (discrete 5-coordinated Cu(II) and linear Cu(I) species) and Cu(dmbp)(2)BrCu(2)Br(3) (linked 5-coordinate Cu(II) and trigonal planar Cu(I) species); and seven Cu(II) compounds, (dmbp)CuBr(2) (stacked planar monomers), [(dmbp)CuBr(2)](2)(five coordinate bibridged dimers), (dmbp)Cu(2)Br(4) (stacked planar bibridged dimers), (dmbp)CuBr(2)(DMSO) (five coordinate monomers), [Cu(dmbp)(2)Br]OH.5(1)/(2)H(2)O and [Cu(dmbp)(2)Br](Br/OH).5(1)/(2)H(2)O (five coordinate monomers), and (dmbpH(2))CuBr(4).H(2)O (distorted tetrahedral monomers). The crystal structure determinations of these materials are reported. A common thread in their structural chemistry is the supramolecular architecture developed through interdigitation of the dmbp rings on neighboring molecular species. The interdigitation leads to layer structures in many of the materials. The distances between the interdigitated dmbp rings are in the range 3.4-3.7 A. The Cu(dmbp)(2)Br(+) species exhibits an exceptionally large distortion from tetrahedral geometry due to deviation of the dihedral angle between the mean planes of the Cu(dmbp) fragments from 90 degrees. The Cu(dmbp)(2)Br(+) cations have distorted trigonal bipyramidal geometry, the Br(-) ion occupying an equatorial position. The length of the Cu-Br bond in the Cu(dmbp)(2)Br(+) species is correlated with the change in dihedral angle between the planes of the two dmbp ligands. The mono-dmbp complexes show a greater variation in coordination geometry for the Cu(II) species, including distorted trigonal bipyramidal and augmented square planar 4 + 1 and 4 + 2 coordination.

Bis(2,3-dimethylquinoxalinium) tribromocuprate(I).

The title compound, (C10H11N2)2[CuBr3], contains layers of planar monoprotonated cations. Isolated trigonal-planar [CuBr3]2- anions are hydrogen bonded to cations in adjacent layers, providing three-dimensional stability to the crystal structure.

Structure of an isoxazole amino ester.

2'-(N-Methylamino)-2-methylpropyl 5-methyl-3-phenylisoxazole-4-carboxylate hydroiodide, C16H21N2O3+.I-, Mr = 416.26, orthorhombic, Pna21, a = 23.293 (7), b = 10.276 (3), c = 7.971 (1) A, V = 1908.0 (8) A3, Z = 4, Dx = 1.448 g cm-3, Mo K alpha, lambda = 0.71069 A, mu = 17.1 cm-1, F(000) = 832, T = 293 K, R = 0.0610 for 1846 unique observed reflections with F greater than 3 sigma. In the title compound, the isoxazole ring is distorted only slightly from planarity, with C(3) being 0.045 A out of the mean plane. Steric interactions force the isoxazole ring out of planarity with both the phenyl ring and the ester carbonyl O(2), which show dihedral angles of 34.9 (9) degrees and 47.2 (7) degrees, respectively. The N(2) amino methyl group is oriented approximately anti to the ester carbonyl O(2). The minimum iodide to nitrogen distance is from I to N(2)', 3.46 (2) A.

Cardioactivity and solid-state structure of two 4-isoxazolyldihydropyridines related to the 4-aryldihydropyridine calcium-channel blockers.

Diethyl 2,6-dimethyl-4-(5-ethyl-3-phenylisoxazol-4-yl)-1,4-dihydroyprid ine-3,5- dicarboxylate (5) and diethyl 2,6-dimethyl-4-(5-isopropyl-3-phenylisoxazol-4-yl)-1,4-dihydropyri dine-3,5- dicarboxylate (6) were synthesized, and their molecular structures were determined by X-ray crystallography. In compound 5, which has an ethyl group at the C5 position of the isoxazole ring, the deviation from planarity in the dihydropyridine (DHP) ring is the smallest of all known DHP derivatives. The dihedral angle between the aromatic ring (the isoxazole) and the DHP ring, which is approximately 90 degrees in similar biologically active dihydropyridines, is somewhat smaller (82.7 degrees and 85.2 degrees, respectively) in these two compounds. In both compounds, one of the ester groups is coplanar with the DHP ring while the other one is out of plane by 14.7 degrees (ethyl) and 18.8 degrees (isopropyl). Both 5 and 6 were found to be vasodilators in the Langendorff assay. The potency of 6 on cardiac flow was similar to that of nifedipine; however, that of 5 was considerably attenuated. Since isoxazolyl analogue 6 lacks the significant negative inotropic activity associated with nifedipine, 6 offers promise as an antihypertensive or antianginal agent.