Alok K. Mukherjee

Oxoperoxo molybdenum(VI) and tungsten(VI) and oxodiperoxo molybdate(VI) and tungstate(VI) complexes with 8-quinolinol: synthesis, structure and catalytic activity

A solution obtained by dissolving MoO3 in a moderate excess of H2O2 reacts with 8-quinolinol (QOH) to give [MoO(O2)(QO)2] (1), but, when the same reaction is conducted with a large excess of H2O2, an anionic complex is formed, which reacts with PPh4Cl to give the corresponding salt [MoO(O2)2(QO)][PPh4] (2·PPh4). Freshly prepared WO3 behaves the same way and, depending on the amount of H2O2 used, as above, produces either [WO(O2)(QO)2] (3) or [WO(O2)2(QO)][PPh4] (4·PPh4), respectively. Crystallographic analyses reveal the coordination geometries around the metal center in these complexes to be distorted pentagonal bipyramids. These compounds show interesting catalytic properties in the oxidation of alcohols using H2O2 as the terminal oxidant. In the case of aromatics, including benzylic and cinnamylic alcohols, the oxidation occurs selectively, affording aldehydes or ketones with reasonably high turnover numbers. Taking benzyl alcohol as a representative case, a probable mechanism of the alcohol-to-aldehyde conversion mediated by the prepared catalysts is suggested. The oxidation of aliphatic primary alcohols, under the same conditions, does not show the above selectivity: the reaction yields the corresponding aldehydes as well as carboxylic acids. The work was also extended to study the catalytic activity towards the oxidation of phenol and various sulfides and amines using the same oxidants.

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.

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.

Acemetacin polymorphs: a rare case of carboxylic acid catemer and dimer synthons

Acemetacin is the first example of an API polymorph with a carboxylic acid catemer and dimer O–H⋯O synthons. The auxiliary stabilization to the catemer motif from stronger C–H⋯O and C–Cl⋯O interactions compared to those in the dimer structure is discussed for a polymorph pair. The crystal structure of the stable dimer polymorph was solved by structure determination from powder X-ray diffraction data (SDPD).

Synthesis, chemical characterization, structural data and solid state behaviour of N, N′-diethyl-1, 2-ethanediamine complexes of nickel(II) thiocyanate

Abstract [NiL 2 (NCS) 2 ]·H 2 O ( 1 ) and [NiL 2 (NCS) 2 ] ( 2 ) (L = N, N′-diethyl-1, 2-ethanediamine) have been synthesized from solution. The species 1 on deaquation transforms to [NiL 2 (NCS) 2 ] ( 1a ) which subsequently undergoes an irreversible exothermic phase transition (118–142°C; Δ H = −3.8kJ mol −1 ) accompanied by a pinkish-blue to blue thermochromism producing an isomer [NiL 2 (NCS) 2 ] ( 1b ). The pinkish-blue species 2 on heating shows an endotherm (82–120°C; Δ H =kJ mol −1 ) yielding the species 1b . Single crystal X-ray structure analyses of 1 and 2 have been carried out. The metal atoms in both the complexes, lying at crystallographic inversion centres, display distored octahedral geometries with four amine nitrogen atoms defining the equatorial plane and two isothiocyanato groups in trans axial positions.

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.

Thermochromism in copper(II) complexes: thermal, spectroscopic, solid-state broadline 1H NMR and room-temperature single-crystal x-ray analysis of bis(N,N′-dimethyl-1,2-ethanediamine)copper(II) dinitrate

Abstract The complex bis(N,N′-dimethyl-1,2-ethanediamine)copper(II) dinitrate, Cu (NN′-dmen)2(NO3)2, undergoes a first-order thermochromic phase transition at ca 148°C, changing from blue-violet to blue. The low-temperature phase has been characterized by X-ray crystallography. The copper ion possesses distorted (4+2) octahedral geometry with two five-membered chelate rings, in the δλ conformation, forming the CuN4 plane [CuN = 2.000(6) and 2.033(7) A] and oxygens from the two nitrate groups weakly coordinated in the two axial coordination sites [CuO = 2.506(8) A]. The broad-line 1H NMR indicates the onset of a dynamic disorder of diamine chelate rings at the phase transition temperature region. The electronic spectrum broadens on phase transition.

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.

Syntheses of [Ni2(dien)2(NCS)4(H2O)] and [Ni(aepn)(NCS)2]n ((dien = bis(2-aminoethyl)amine and aepn = N-(2-aminoethyl)-1,3-propanediamine): single crystal structure analysis and thermal behaviour in the solid state

Abstract [Ni 2 (dien) 2 (NCS) 4 (H 2 O)] ( 1 ) and [Ni(aepn)(NCS) 2 ] n ( 2 ) (where dien = bis(2-aminoethyl)amine and aepn = N -(2-aminoethyl)-1,3-propanediamine) have been synthesised from solution. Single crystal X-ray structure analyses of 1 and 2 reveal that the metal atoms in both the complexes display distorted octahedral geometry with the triamine coordinating facially in 1 and meridionally in 2 . The dinuclear [Ni 2 (dien) 2 (NCS) 4 (H 2 O)] unit in 1 is bridged via a thiocyanate moiety while in 2 the nickel(II) octahedra form a polymeric chain. The species 1 on deaquation at ∼ 165°C followed by cooling yields a conglomerated mass ( 1a ). The species 2 melts at ∼ 230°C which on cooling yields conglomerated mass ( 2a ). Both 1a and 2a are amorphous; the former reverts to 1 in a humid atmosphere.

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.