Structure elucidation of highly polar basic degradants by on-line hydrogen/deuterium exchange hydrophilic interaction chromatography coupled to tandem mass spectrometry

A hydrophilic interaction liquid chromatography (HILIC) method was used to separate a commonly used pharmaceutical starting material, 4-aminomethylpyridine (4-AMP), and its degradants. The structures of the major degradants were characterized and elucidated without prior isolation by accurate mass measurement, MS/MS analysis and on-line hydrogen/deuterium (H/D) exchange experiments. The mass spectra obtained from H/D exchange experiments are particularly useful to differentiate structural isomers, to elucidate the fragmentation pathways, and to aid in structure elucidation in the absence of MS/MS fragmentation information. The impact of deuterium oxide and temperature on HILIC separation has also been explored here. The integration of H/D exchange with HILIC has been described here for the first time and has been demonstrated to be a powerful structure elucidation tool via the study of degradants in 4-AMP.     

Synthesis,Structure and Magnetic Phase Transitions of the Manganese Succinate Hybrid Framework,Mn(C4H4O4)

An anhydrous manganese succinate, Mn(C₄H₄O₄), has been synthesised hydrothermally and studied by single‐crystal X‐ray diffraction. It adopts a succinate pillared structure in which layers of corner‐sharing MnO₆ octahedra alternate with sheets that contain chains of edge‐sharing octahedra. This unique 3D framework structure contains highly distorted MnO₆ octahedra, which are made possible by the lack of ligand field stabilisation energy for the high‐spin Mn²⁺ ion. Attempts to dope the structure with other divalent transition‐metal ions were accordingly unsuccessful. Magnetic susceptibility and heat capacity measurements indicate that Mn(C₄H₄O₄) undergoes antiferromagnetic ordering below 12 K, with a second antiferromagnetic transition at approximately 6 K. These two antiferromagnetic phases undergo further transitions in applied fields, underlining the subtle magnetic behaviour that is possible in inorganic–organic frameworks of this structural complexity.     

Controlled hydrothermal growth of ZnO nanostructures by sequestering the Zn metal ions with the chelating agent EDTA

In the present work, a controlled growth of ZnO nanostructures by manipulating Zn metal ion concentration by the chelating action of ethylene diaminetetra acetic acid in hydrothermal method is studied. EDTA produces metal–chelate complex by the formation of bidentate ligand with Zn²⁺ in the solution and diminishes the reactivity of Zn metal cations. Concentration of EDTA in the mother solution was varied in different ranges like 3, 5 and 10 mM while retaining the zinc metal salt and the NaOH concentration the same. Three different morphologies of wurtzite structured ZnO nanostructures such as nanorods-bunch, separate/discrete uniformly sized hexagonal nanorods and tapered flower petals like shapes are achieved by 3, 5 and 10 mM strengths of EDTA, respectively. The medium concentration 5 mM of EDTA is found to have moderate control over producing ZnO nanostructures of uniform diameter and a high aspect (length to diameter) ratio. An array of vertically aligned free standing ZnO nanorods with uniform spacing is successfully achieved by the addition of 5 mM of EDTA in the mother solution and the same is studied for its fluorescence property at an excitation of 325 nm and it has exhibited a characteristic UV emission of ZnO around 383 nm.     

Mechanical properties of hybrid inorganic-organic framework materials: establishing fundamental structure-property relationships

The mechanical properties of hybrid framework materials, including both nanoporous metal-organic frameworks (MOFs) and dense inorganic-organic frameworks, are discussed in this critical review. Although there are relatively few studies of this kind in the literature, major recent advances in this area are beginning to shed light on the fundamental structure-mechanical property relationships. Indeed research into the mechanical behavior of this important new class of solid-state materials is central to the design and optimal performance of a multitude of technological applications envisaged. In this review, we examine the elasticity of hybrid frameworks by considering their Young's modulus, Poisson's ratio, bulk modulus and shear modulus. This is followed by discussions of their hardness, plasticity, yield strength and fracture behavior. Our focus is on both experimental and computational approaches. Experimental work on single crystals and amorphized monoliths involved primarily the application of nanoindentation and atomic force microscopy to determine the elastic moduli and hardness properties. The compressibility and bulk moduli of single crystals and polycrystalline powders were studied by high-pressure X-ray crystallography in the diamond anvil cell, while in one instance spectroscopic ellipsometry has also been used to estimate the elastic moduli of MOF nanoparticles and deposited films. Theoretical studies, on the other hand, encompassed the application of first principles density-functional calculations and finite-temperature molecular dynamics simulations. Finally, by virtue of the diverse mechanical properties achievable in hybrid framework materials, we propose that a new domain be established in the materials selection map to define this emerging class of materials (137 references).     

Towards enhanced ligand-centred photoluminescence in inorganic-organic frameworks for solid state lighting

Three novel inorganic-organic framework compounds containing the organic chromophore ligand 9-fluorenone-2,7-dicarboxylic acid (abbreviated H(2)FDC) and barium (BaFDC), cadmium (CdFDC) and manganese (MnFDC), respectively, have been synthesized and evaluated for their use as phosphor materials for solid state lighting and other applications. The results are compared with two earlier reported structures containing the same ligand with calcium (CaFDC) and strontium (SrFDC). The barium- and cadmium-containing compounds both show blue excited, yellow photoluminescence, while the manganese structure does not. The trends in luminescent efficiency for the Ba, Cd, Ca, and Sr derivatives are discussed in relation to crystallographic, optical, and low-temperature specific heat considerations.