Santu Chakraborty

Structural and microstructural characterization of bioapatites and synthetic hydroxyapatite using X‐ray powder diffraction and Fourier transform infrared techniques

Bioapatite, the main constituent of mineralized tissue in mammalian bones and teeth, is similar in structure and composition to calcium hydroxyapatite (HAP), Ca10(PO4)6(OH)2. The crystallographic analyses of four bioapatites of human-, goat- and rabbit-bone and human-teeth origin, and one synthetic HAP prepared via microwave irradiation, have been carried out using X-ray powder diffraction techniques. Fourier transform infrared spectra and Rietveld analyses indicate partial replacement of PO43− ions by CO32− ions in all bioapatites.

Structural and microstructural characterization of human kidney stones from eastern India using IR spectroscopy, scanning electron microscopy, thermal study and X-ray Rietveld analysis

Structural and microstructural characterizations of eight human kidney stones (KS1–KS8) from eastern India have been carried out using IR spectroscopy, X-ray powder diffraction, scanning electron microscopy and thermogravimetric methods. An X-ray diffraction phase quantification revealed that three of the renal stones (KS1–KS3) were composed exclusively of calcium oxalate monohydrate (COM) and the remaining five (KS4–KS8) contained varying amounts of calcium oxalate dihydrate (40.1–53.0 wt%) and hydroxyapatite (1.3–17.3 wt%), in addition to the COM phase. The crystalline structure of COM (whewellite) at the atomic scale was redetermined through an X-ray powder diffraction study at room temperature using Rietveld analysis. Thermogravimetric analysis of KS1 reveals that COM (whewellite) is stable up to around 439 K, above which temperature anhydrous calcium oxalate is formed. The oxalate transforms to calcium carbonate at 751 K and finally to calcium oxide above 969 K. It should be emphasized that meaningful statistics in total number or gender specificity cannot be achieved with eight kidney stones.

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.

Ab initio structure determination of anhydrous sodium alendronate from laboratory powder X-ray diffraction data†

Sodium alendronate, a member of bisphosphonate class of compounds commonly used for treatment of generalized bone disorders, exists in various hydrated forms. Dehydration of sodium alendronate trihydrate has been studied using variable temperature X-ray powder diffraction technique. The crystal structure of anhydrous sodium alendronate, prepared by heating the trihydrate sodium alendronate at 150 degrees C, has been determined from X-ray powder data using direct space global optimization technique for structure solution, followed by the Rietveld refinement. The structure of the anhydrous form of sodium alendronate is compared with that of the trihydrate form, which was determined previously from single crystal X-ray diffraction data. Both anhydrous and trihydrate sodium alendronate crystallize in monoclinic system with space group P2(1)/n. The crystal structure of the anhydrous sodium alendronate is built by edge-sharing of NaO(6) octahedra into a two-dimensional molecular sheet in the (011) plane, whereas in the trihydrate compound, one-dimensional chain along the (010) direction is generated by corner sharing of NaO(6) octahedra.

Syntheses, spectroscopic and X-ray structure analyses of two dioxouranium (VI) complexes : supramolecular framework built from O-H...O, C-H...O and stacking interactions

Abstract Two dioxouranium(VI) complexes, [UO2(PBHA)2(DMSO)] (I) and [UO2(SALOP)(H2O)] (II), PBHA = N-phenyl benzohydroxamate, DMSO = dimethyl sulfoxide, SALOP = N,N′-bis (salicylidene)-o-phenylene diaminate have been synthesized, and characterized by spectroscopic and X-ray studies. Both compounds (I) and (II) crystallize in orthorhombic system with space group Pbca. The molecules in (I) are linked by intermolecular C–H…O hydrogen bonds into 32-membered tetrameric clusters (U4C12O8N4H4), which are further connected via uranyl oxygen atoms forming a three-dimensional supramolecular framework. In (II), intermolecular O—H…O hydrogen bonds between molecules related by inversion and translation generate infinite zigzag chains of R22(8) rings running along the [010] direction. The parallel chains are interlinked through C—H…O hydrogen bonds producing a complex supramolecular architecture in (II).

Synthesis and structure analysis of cyclodehydration product of piroxicam: A metabolite detected in dogs and monkeys

We report here a novel synthesis of 6-methyl-6H-7-oxopyrido[1,2-a]pyrimido[5,4-c]-1,2-benzothiazine-5,5-dioxide or cyclodehydration product of piroxicam, a metabolite detected in dogs and monkeys that was synthesized in 6% yield earlier. The reaction of benzoyl chloride with piroxicam in the presence of triethylamine afforded the piroxicam metabolite in good yield. A comparison of spectral data of the synthesized compound with the reported values remained inconclusive. The structure of the compound was confirmed unambiguously by single-crystal X-ray analysis.

Crystal and molecular structure analysis of 4-o-(4-methoxybenzoyl)- 2-methyl-N-(2-pyridal)-2H-1,2-benzothiazine-3-carboxamide-1,1- dioxide from laboratory X-ray powder data

4-o-(4-methoxybenzoyl)-2-methyl-N-(2-pyridal)-2H-1,2-benzothiazine-3-carboxamide-1,1-dioxide, C23H19N3O6S (I), a piroxicam derivative has been synthesized and characterized by X-ray powder structure analysis. The molecules of (I) are linked through pairs of intermolecular N–H···O and C–H···O hydrogen bonds forming centrosymmetric dimeric R22(14)(M) and R22(22)(N) rings which combine to form infinite one-dimensional MNMN… chain along the [2¯11] direction. The C–H···π (arene) hydrogen bonds interlink the parallel chains into two-dimensional sheets lying in the (102) plane. These sheets are further connected through intermolecular C–H···O and C–H···N bonds, so generating a three-dimensional framework structure in (I).

A comparative study of crystal structure of a Cu(II) dicyanamide compound determined independently from X-ray powder-and single-crystal analyses

Abstract The dicyanamido diethelenetriamine copper (II) compound, C8H13CuN9 (I), has been synthesized, and structurally characterized independently using X-ray powder- and single-crystal diffraction data. The direct methods program package EXPO-2004 has been used for structure solution from laboratory powder diffraction data. Intermolecular N—H···N hydrogen bonds in (I) generate R22(16) rings, which are fused forming molecular columns propagating along the [100] direction. Further linking of parallel columns through N—H···N hydrogen bonds results into a three-dimensional supramolecular network.

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, β=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).

{4-Bromo-2-[2-(5-bromo-2-oxido­benzyl­idene­amino­methyl)­phenyl­imino­methyl]­phenolato-κ4O,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.