Source of materialUnder stirring, 1.4 g (0.01 mol) 2-hydroxy-3-nitropyridine was dissolved in 2 ml fuming H 2SO4 (50 % SO3 content). 1.5 ml mixture ® = 1.6 g/ml) of oleum with fuming HNO 3 was added slowly and kept below 40°C. The solution was stirred at RT for 1 h and slowly rised to 90°C in 2 h, followed by keeping at 90°C for additional 4 h. The solution was cooled to RT and poured on 20 g ice. 1.05 g (75 %) pale yellow needles were obtained. Single crystals suitable for X-ray diffraction analysis were isolated after several weeks from aqueous solution (m.p. 175-176°C). DiscussionPyridone and hydroxypyridine are tautomeric organic molecules. The calculation of two tautomeric forms of unsubstituted hydroxypyridine, benzoid and quinoid structures, resulted in the difference of energies. The benzoid form is slightly more preferable than the quinoid form [1]. Nitropyridine and its derivatives have been paid much attention due to their practical applications: 2-hydroxy-3,5-dinitropyridine is extremely important as an intermediate for oxidative dyestuffs, medicines or agrochemicals [2]. Also some derivatives of the nitropyridine have nonlinear optics property [3]. A variety of substituted nitropyridine compounds are used as herbicidal chemicals to control the growth of undesired plants [4]. 2-Hydroxyl-3,5-dinitropyridine and its metal complexes have higher explosion temperature and lower sensitivity. So, they are used as energetic catalysts for solid propellants in order to adjust and improve their trajectory properties [5]. The atoms of nitropyridone moiety (including N3, O4, O5) display an almost coplanar configuration with a mean deviation to the least-squares plane of 0.0134 Å. The plane through N2, O2 and O3 has a dihedral angle of 12.5°with the above-mentioned plane. The C2N2, C2C3 and C4C5 distances are 1.462(3) Å, 1.363(4) Å and 1.360(3) Å, respectively, which agree well with the corresponding distance in compound 3-nitro-2-pyridone [6]. The distances 1.456(3) Å for C1C2 and 1.390(4) Å for C3C4 are slightly longer than the respective distances in 3-nitro-2-pyridone (1.439(3) Å and 1.371(4) Å, respectively), while the distances of 1.223(3) Å for C1O1 and 1.325(4) Å for C5N1 are slightly shorter than the corresponding distances in the same compound (1.236(3) Å and 1.339(4) Å, respectively) [6].

Source of materialSodium hydroxide (1.2 g, 0.03 mol) was added slowly to 5-mercapto-1-phenyltetrazole (5 g, 0.03 mol) in 20 ml of dry DMSO. The reaction mixture was stirred at 80°C for 1 h. Then 1.4 ml (0.015 mol) of 1,3-dichloropropane was added in portions to the solution and resulted in the formation of grey suspension. figure, top) and its centrosymmetric equivalent. The benzene ring and tetrazole ring planes form a dihedral angle of 110.6°. The CN distances are 1.346(4) Å for C4N1 and 1.326(4) Å for C4N4, which agree well with the corresponding distances for 1,6-bis(1-phenyl-1H-tetrazol-5-ylthio)hexane (1.318(2) Å and 1.349(2) Å [5]) and 1,3-bis(1-methyl-1H-tetrazol-5-ylthio)propane (1.329(2) Å and 1.334(2) Å [6]). While the C4S1 distance (1.729(4) Å) agrees with the corresponding distance in 1,6-bis(1-phenyl-1H-tetrazol-5-ylthio)hexane (1.732(2) Å [5]), the corresponding distance is shorter with 1.817(2) Å in 1,3-bis(1-methyl-1H-tetrazol-5-ylthio)propane [6]. The C4S1C1 and C11S2C3 bond angles are 101.4(2)°a nd 100.5(2)°, respectively. The N2N1C5C6 and N6N5 C12C17 torsion angles are 67.4(5)°and 53.6(5)°, respectively. In addition, two kinds of aromatic p-p stacking interactions occur between parallel phenyl rings and tetrazolyl rings, respectively (figure, bottom). There exists a strengthening part of the p-p stacking interactions by inter hydrogen bonds. So, the distances between the tetrazolyl rings centroids are 3.325 Å and 3.333 Å. Also, parallel phenyl rings are stacked with their centroids separated by 3.782 Å. The molecules are assembled into a two-dimensional sheet structure by the hydrogen bonds and aromatic stacking interactions mentioned above.

Source of materialA solution of 0.2 g (0.8 mmol) of 1,3-bis(3,5-dimethylpyrazol-1-yl)propan-2-ol (Hdpzhp) [1] in 20 ml of methanol was treated with 32 mg (0.8 mmol) of NaOH and stirred further for 30 min at room temperature. This ligand solution was combined with a solution of 0.178 g (0.8 mmol) of CuBr 2 in 20 ml of methanol and stirred further for 1 h. The resulting dark blue solution was filtered and allowed to stand at RT. Large dark blue single crystals suitable for X-ray diffraction were formed after a few days. Elemental Analysis: found C, 39.79 %; H, 5.12 %; N, 13.58 %; calc. for C 28H46Br2Cu2N8O4 C, 39.77 %; H, 5.48 %; N, 13.25 %. DiscussionCopper proteins with a type-3 site, like hemocyanin and the enzymes tyrosinase and catechol oxidase are important dioxygenprocessing proteins [2][3][4][5][6]. These metallo-enzymes, which use molecular oxygen from air as the primary oxidant, are generally considered as very sophisticated catalysts. Their reactions are very fast and highly efficient while operating under mild conditions with high substrate specificity, regio-selectivity and yield, and having mostly water as the only ¢waste¢ product [7]. The title crystal structure consists of a [Cu 2(MeOH)2(dpzhp)2] 2+ cation and two Br anions. The cation is a dinuclear copper complex coordinated by two methanol molecules and two molecules of ligand bridged to each other by means of two alkoxo oxygen atoms. The Cu1Cu1A distance is 3.030(2) Å, which agrees well with the corresponding distances of 2.990. Each copper ion is coordinated by two nitrogen atoms and two oxygen atoms of two ligands in a distorted square-planar environment. The average terminal CuN(pyrazole) distance (1.961 Å) is comparable to that reported [1] and the average bridging CuO(alcoholic hydroxy) bond distance (1.925 Å) is similar to those of reported complexes. In this complex, the N1Cu1N3 and Cu1O1O1¢ angles are 102.3(2)°and 76.2(2)°. The axial Cu1Br1 and Cu1O2(methanol) distances are 3.948(2) Å and 2.757(7) Å, respectively. The oxygen atoms of the methanol groups contact the Br atoms through OH···Br hydrogen bonds (3.214(6) Å) in a molecular layer.