Phase composition and morphological characterization of human kidney stones using IR spectroscopy, scanning electron microscopy and X-ray Rietveld analysis.

Pathological calcification in human urinary tract (kidney stones) is a common problem affecting an increasing number of people around the world. Analysis of such minerals or compounds is of fundamental importance for understanding their etiology and for the development of prophylactic measures. In the present study, structural characterization, phase quantification and morphological behaviour of thirty three (33) human kidney stones from eastern India have been carried out using IR spectroscopy (FT-IR), powder X-ray diffraction (PXRD) and scanning electron microscopy (SEM). Quantitative phase composition of kidney stones has been analyzed following the Rietveld method. Based on the quantitative estimates of constituent phases, the calculi samples have been classified into oxalate (OX), uric acid (UA), phosphate (PH) and mixed (MX) groups. Rietveld analysis of PXRD patterns showed that twelve (36%) of the renal calculi were composed exclusively of whewellite (calcium oxalate monohydrate, COM). The remaining twenty one (64%) stones were mixture of phases with oxalate as the major constituent in fourteen (67%) of these stones. The average crystallite size of whewellite in oxalate stones, as determined from the PXRD analysis, varies between 93 (1) nm and 202 (3) nm, whereas the corresponding sizes for the uric acid and struvite crystallites in UA and PH stones are 79 (1)-155 (4) nm and 69 (1)-123(1) nm, respectively. The size of hydroxyapatite crystallites, 10 (1)-21 (1) nm, is smaller by about one order of magnitude compared to other minerals in the kidney stones. A statistical analysis using fifty (50) kidney stones (33 calculi from the present study and 17 calculi reported earlier from our laboratory) revealed that the oxalate group (whewellite, weddellite or mixture of whewellite and weddellite as the major constituent) is the most prevalent (82%) kidney stone type in eastern India.

2,4-Dimethyl-1,3-thiazole-5-carboxylic acid: an X-ray structural study at 100 K and Hirshfeld surface analysis.

The crystal structure of the title thiazolecarboxylic acid derivative, C(6)H(7)NO(2)S, (I), has been determined from single-crystal X-ray analysis at 100 K. In the crystal packing, an interplay of O-H···N and C-H···O hydrogen bonds connects the molecules to form C(6)R(2)(2)(8) polymeric chains, which are further linked via weak C-H···O hydrogen bonds into a two-dimensional supramolecular framework. The relative contributions of different interactions to the Hirshfeld surface in (I) and a few related thiazolecarboxylic acid derivatives indicate that the H···H, N···H and O···H contacts can account for about 50-70% of the total Hirshfeld surface area in this class of compound.

Tris(hydroxymethyl) aminomethane salt of ramipril: synthesis, structural characterization from X-ray powder diffraction and stability studies.

Tris(hydroxymethyl) aminomethane (tris) salt of API ramipril was synthesized, and characterized by FTIR, TG-DSC and ab initio X-ray powder structure analysis. The compound, ramipril-tris (II), crystallizes in the monoclinic space group P2(1) with a=24.3341(15), b=6.4645(5), c=9.5357(7) Å, ß=96.917(3)° and V=1489.1(3) Å(3). The crystal structure has been determined from laboratory X-ray powder diffraction data using direct space global optimization strategy (simulated annealing) followed by the Rietveld refinement. A network of intermolecular OH…O, CH…N and CH…O hydrogen bonds between the ramipril-ramipril, tris-tris and ramipril-tris components in the compound generates a two-dimensional molecular assembly in (110) plane. A comparative study of solid-state stabilities of ramipril-tris (II) with that of ramipril (I) and ramipril-erbumine (III) indicates that ramipril-tris (II) is the most stable one among the three, and the conversion to impurity D after 72 h at 80 °C is only 1.5%. The solution phase analysis at different pH values also reveals a greater stability of ramipril-tris (II) over ramipril (I).

Lamivudine hemihydrate.

A new lamivudine hydrate, namely, cis-4-amino-1-(2-hydroxymethyl-1,3-oxathiolan-5-yl)pyrimidin-2(1H)-one hemihydrate, C(8)H(11)N(3)O(3)S.0.5H(2)O, has been synthesized and structurally characterized by both powder and single-crystal X-ray diffraction studies. The hemihydrate crystallizes in the Sohnke space group P2(1), with the asymmetric unit comprising four lamivudine and two water molecules. An extensive network of intermolecular hydrogen bonds involving both lamivudine and solvent water molecules generates a three-dimensional supramolecular architecture. The structural data and crystal packing of the present lamivudine hemihydrate are compared with those of other hydrated and anhydrous forms of lamivudine.

N,N'-Dicyclohexyl-N-[4-(1H-indol-3-yl)butanoyl]urea.

The title compound, C(25)H(35)N(3)O(2), is a novel urea derivative. Pairs of intermolecular N-H...O hydrogen bonds join the molecules into centrosymmetric R(2)(2)(12) and R(2)(2)(18) dimeric rings, which are alternately linked into one-dimensional polymeric chains along the [010] direction. The parallel chains are connected via C-H...O hydrogen bonds to generate a two-dimensional framework structure parallel to the (001) plane. The title compound was also modelled by solid-state density functional theory (DFT) calculations. A comparison of the molecular conformation and hydrogen-bond geometry obtained from the X-ray structure analysis and the theoretical study clearly indicates that the DFT calculation agrees closely with the X-ray structure.

Oxo-vanadium(IV) dihydrogen phosphate: preparation, magnetic study, and heterogeneous catalytic epoxidation.

A layered oxo-vanadium(IV) dihydrogen phosphate, {VO(H2PO 4)2} n has been synthesized hydrothermally and characterized by several physicochemical methods. Single-crystal X-ray analysis (crystal system, tetragonal; space group, P4/ ncc; unit cell dimensions, a = b = 8.9632(4), c = 7.9768(32) A) of {VO(H2PO4) 2} n reveals that the compound has an extended two-dimensional structure. The VO2+ moieties are connected through bridging H 2PO4 (-) ions, and this type of connection propagates parallel to the crystallographic ab plane which gives rise to a layered structure. The layers are staked parallel to the crystallographic c axis with a separation between the layers of ca. 4.0 A. Magnetic susceptibility of {VO(H2PO4)2} n has been measured in the temperature range 2-300 K on a SQUID magnetometer. The magnetic property of {VO(H2PO4)2} n is explicable in the light of a two-dimensional quantum Heisenberg antiferromagnet model. Magnetic pathways are available through the dihydrogen-phosphato bridges within the layer and provide for weak antiferromagnetic interactions. Notably {VO(H2PO4)2} n catalyzes the epoxidation reaction of alkenes with tert-BuOOH in acetonitrile medium under heterogeneous condition.

Two (E)-2-arylidene-1,4-di-p-tosyl-1,2,3,4-tetrahydroquinoxaline compounds: supramolecular frameworks built with C-H...O and C-H...pi(arene) hydrogen bonds and pi-pi stacking interactions.

The pyrazine ring in two N-substituted quinoxaline derivatives, namely (E)-2-(2-methoxybenzylidene)-1,4-di-p-tosyl-1,2,3,4-tetrahydroquinoxaline, C(30)H(28)N(2)S(2)O(5), (II), and (E)-methyl 2-[(1,4-di-p-tosyl-1,2,3,4-tetrahydroquinoxalin-2-ylidene)methyl]benzoate, C(31)H(28)N(2)S(2)O(6), (III), assumes a half-chair conformation and is shielded by the terminal tosyl groups. In the molecular packing of the compounds, intermolecular C-H...O hydrogen bonds between centrosymmetrically related molecules generate dimeric rings, viz. R(2)(2)(22) in (II) and R(2)(2)(26) in (III), which are further connected through C-H...pi(arene) hydrogen bonds and pi-pi stacking interactions into novel supramolecular frameworks.

Oxo- and oxoperoxo-molybdenum(VI) complexes with aryl hydroxamates: synthesis, structure, and catalytic uses in highly efficient, selective, and ecologically benign peroxidic epoxidation of olefins.

A solution obtained by dissolving MoO3 in H2O2 reacts separately with secondary hydroxamic acids (viz., N-benzoyl N-phenyl hydroxamic acid (BPHAH), N-benzoyl N-ortho-, -meta-, -para-tolyl hydroxamic acids, (BOTHAH, BMTHAH, and BPTHAH, respectively), and N-cinnamoyl N-phenyl hydroxamic acid (CPHAH) affording [MoO(O2)(BPHA)2] (1), [MoO(O2)(BOTHA)2] (2), [MoO(O2)(BMTHA)2] (3), [MoO(O2)(BPTHA)2] (4), and [Mo(O)2(CPHA)2](5), respectively. The O and O2 are situated cis to each other in 2-4, but in each case, they are disordered and distributed over four sites. This disorder does not exist in the 6-coordinate cis dioxo complex 5, to which crude MoO(O2)(CPHA)2 (5') was converted during recrystallization. An aqueous molybdate solution readily reacts with all those hydroxamic acids producing [Mo(O)2(hydroxamate)2] (6). While 2, 3, and 4 possess a very distorted pentagonal bipyramidal structure, 5 has a distorted octahedral geometry. In the solid state, as well as in solution, 5 exists as two apparently enantiomerically related molecules differing in the orientation of the pendant phenyl rings. To emphasize that the formation and structural uniqueness of 5 compared to 1-4 is caused by the influence of the cinnamoyl residue, one compound of the 6 series, namely, [Mo(O)2(BPHA)2] (6A), was structurally characterized to prove directly that the special stereochemical properties of 5 rely on the special electronic structure of CPHA- ligand. Complexes 1-5, as well as 6, show high potential and selectivity as catalysts in the epoxidation of olefins at room temperature in the presence of NaHCO3 as a promoter and H2O2 as a terminal oxidant. A comparative epoxidation study has been performed to determine the relative efficiency of the catalysts. To make the epoxidation method cost effective, a study to optimize the use of H2O2 has also been performed. To obtain evidence in favor of our suggested mechanism to this homogeneous olefin --> epoxide conversion, it was necessary to synthesize a peroxo-rich compound, namely, [MoO(O2)2BMTHA]- (7), but the attempted synthesis culminated in the isolation of [MoO(O2)2(C6H5COO)]- (8), obviously, via the hydrolysis of coordinated BMTHA.

[4-Bromo-2-[2-(5-bromo-2-oxidobenzylideneaminomethyl)phenyliminomethyl]phenolato-kappa4O,N,N',O']nickel(II).

In the title complex, [Ni(C(21)H(14)Br(2)N(2)O(2))], the Ni(II) atom is coordinated by the two imine N and two phenolate O atoms of the Schiff base ligand in a tetrahedrally distorted square-planar geometry. The Ni-N and Ni-O distances are within the ranges expected for Ni-Schiff base derivatives. Intermolecular C-H...O hydrogen bonds link the molecules into centrosymmetric dimers, forming R(2)(2)(12) (A) and R(2)(2)(10) (B) rings. These dimers combine to form a supramolecular ABAB... aggregate which propagates along the [100] direction.

Highly efficient epoxidation method of olefins with hydrogen peroxide as terminal oxidant, bicarbonate as a co-catalyst and oxodiperoxo molybdenum(VI) complex as catalyst.

A combination of the newly synthesized and structurally characterized compound, [MoO(O2)2(saloxH)](saloxH2= salicylaldoxime) as catalyst, H2O2 as terminal oxidant and NaHCO3 as co-catalyst when stirred in CH3CN (10 cm3) at room temperature (rt) shows a very pronounced efficiency epoxidation of olefinic compounds, the method being green and economical.

Macrocyclic Cu(II)(2), Cu(II)(4), Ni(II)(3), and Ni(II)(4) Complexes: Magnetic Properties of Tetranuclear Systems.

A binuclear tetraprotonated macrocyclic complex [Mg(2)(L(2)-H(4))(NO(3))(2)](NO(3))(2).6H(2)O (1) has been obtained by template condensation of 4-methyl-2,6-diformylphenol and 1,2-diaminoethane in the presence of magnesium acetate and nitrate. Complex 1 on reduction with NaBH(4), followed by the removal of magnesium, yields the 36-membered octaaminotetraphenol macrocyclic ligand H(4)L(1). The replacement of magnesium in 1 with copper(II) leads to the formation of the binuclear complex [Cu(2)L(3)(ClO(4))(2)] (2) derived from the [2+2] cyclization product of 4-methyl-2,6-diformylphenol and 1,2-diaminoethane. From H(4)L(1) a series of tetranuclear nickel(II) complexes 5-8 with the core cation [Ni(4)L(1)(&mgr;(2)-X)(2)(&mgr;(2)-H(2)O)(2)](2+) (X = NCS, N(3), OAc, or Cl) have been synthesized and characterized. The trinuclear complex [Ni(3)L(1)(acac)(2)(H(2)O)(2).2H(2)O (9), obtained by reacting nickel(II) acetylacetonate with H(4)L(1), on treatment with nickel(II) perchlorate produces the tetranuclear compound [Ni(4)L(1)(acac)(2)(H(2)O)(4)](ClO(4))(2) (10). Variable-temperature (4-300 K) magnetic susceptibility measurements have been carried out for the tetracopper(II) complex [Cu(4)L(1)(H(2)O)(4)](ClO(4))(4) (3) and the tetranickel(II) complexes [Ni(4)L(1)(&mgr;(3)-OH)(&mgr;(2)-H(2)O)(2)(ClO(4))](ClO(4))(2).2CH(3)COCH(3).H(2)O (4), [Ni(4)L(1)(&mgr;(2)-NCS)(2)(&mgr;(2)-H(2)O)(2)](ClO(4))(2).2CH(3)CN (5), [Ni(4)L(1)(&mgr;(2)-N(3))(2)(&mgr;(2)-H(2)O)(2)](ClO(4))(2).2CH(3)OH (6), [Ni(4)L(1)(&mgr;(2)-OAc)(2)(&mgr;(2)-H(2)O)(2)](ClO(4))(2).2H(2)O (7), and [Ni(4)L(1)(&mgr;(2)-Cl)(2)(&mgr;(2)-H(2)O)(2)]Cl(2).4H(2)O (8). The X-ray structure of 5 has been determined. The complex (C(50)H(70)N(12)O(14)Cl(2)S(2)Ni(4)) crystallizes in the triclinic space group P&onemacr; with a = 11.794(6) Å, b = 12.523(4) Å, c = 12.794(5) Å, alpha = 117.28(5) degrees, beta = 96.38(4) degrees, gamma = 109.65(3) degrees, and Z = 1. In the asymmetric unit each of the nickel(II) centers with distorted octahedral geometry is triply-bridged by a phenoxide group, a water molecule, and a N-bonded thiocyanate and these metal centers are further bridged to their symmetry-related counterparts by another phenoxide group. The experimental susceptibility data have been analyzed using appropriate Heisenberg spin coupling models (H = -2J(ij)()S(i)().S(j)()) and the best-fit spin exchange parameters obtained are as follows: J = -288(3) cm(-)(1) (3); J(1) = -8.1(2) cm(-)(1), J(2) = -10.2(2) cm(-)(1) (4); J(1) = -34.5(1.0) cm(-)(1), J(2) = -9.5(2.0) cm(-)(1) (5); J(1) = -34(1) cm(-)(1), J(2) = 11(2) cm(-)(1) (6); J(1) = -30(1) cm(-)(1), J(2) = -7.0(1.5) cm(-)(1) (7); J(1) = -32(1) cm(-)(1), J(2) = -4(1) cm(-)(1) (8).