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Your search keyword '"Payra, Pramatha"' showing total 17 results
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17 results on '"Payra, Pramatha"'

3. Existence of colloidal primitive building units exhibiting memory effects in zeolite growth compositions

Author

Rani, V. Radha, Singh, Ramsharan, Payra, Pramatha, and Dutta, Prabir K.

Subjects
Chemistry, Physical and theoretical -- Research, Crystallization -- Analysis, Memory (Computers) -- Research, Zeolites -- Chemical properties, Semiconductor memory, Chemicals, plastics and rubber industries
Abstract

The study aims on clear, stable mother liquors obtained after completion of crystallization of nanocrystalline sodalite, zeolite A, and zeolite Y. It is observed that during nanocrystalline zeolite synthesis, there are specific primary particles throughout the crystalline process that can grow to form viable nuclei if provided with a source of nutrients.

Published
2004

4. Synthesis and characterization of the dimethyl-substituted bisbenzimidazole ligand and its manganese complex

Author

Kwok, Wai Him, Zhang, Huichang, Hung, Shao-ching, Payra, Pramatha, Chan, Michael K., Duan, Maosheng, Skrzypczak-Jankun, E, Johnston, Dean H., and Gallucci, Judith

Subjects
Porphyrins -- Research, Porphyrins -- Chemical properties, Methyl groups -- Research, Methyl groups -- Chemical properties, Chemistry
Abstract

The dimethyl-substituted bisbenzimidazole ligand (Me(sub 2)BBZ) has structural similarities to porphyrins and phthalocyanines, one major difference is its inherent non-planarity. The Mn - Me(sub 2)-BBZ structure reveals a distinct two dimensional 'staircase' lattice and the metal ions within this lattice display weak antiferromagnetic interactions.

Published
2000

5. Structural trends in first-row transition-metal bis(benzimidazole) complexes

Author

Payra, Pramatha, Zhang, Huichang, Wai Him Kwok, Maosheng Duan, Gallucci, Judith, and Chan, Michael K.

Subjects
Metal ions -- Research, Metal ions -- Magnetic properties, Metal ions -- Chemical properties, Porphyrins -- Chemical properties, Porphyrins -- Research, Chemistry
Abstract

The structures of a periodic series of dimethyl-substituted bis(benzimidazole) Me2BBZ complexes bound to Mn(II), Fe(II), Co(II), Ni(II) and Cu(II) are determined to examine the effects of the metal-ion binding on the magnitude of this nonplanarity. The results indicate that the relative sizes of the metal ion and the Me2BBZ ligand cavity have profound effects on the structural features of the metal-ligand complex.

Published
2000

7. Fundamental Studies of Crystal Growth of Microporous Materials

Author

Singh, Ramsharan, Doolittle, John, Jr, Payra, Pramatha, Dutta, Prabir K, George, Michael A, Ramachandran, Narayanan, and Schoeman, Brian J

Subjects
Chemistry And Materials (General)
Abstract

Microporous materials are framework structures with well-defined porosity, often of molecular dimensions. Zeolites contain aluminum and silicon atoms in their framework and are the most extensively studied amongst all microporous materials. Framework structures with P, Ga, Fe, Co, Zn, B, Ti and a host of other elements have also been made. Typical synthesis of microporous materials involve mixing the framework elements (or compounds, thereof) in a basic solution, followed by aging in some cases and then heating at elevated temperatures. This process is termed hydrothermal synthesis, and involves complex chemical and physical changes. Because of a limited understanding of this process, most synthesis advancements happen by a trial and error approach. There is considerable interest in understanding the synthesis process at a molecular level with the expectation that eventually new framework structures will be built by design. The basic issues in the microporous materials crystallization process include: (a) Nature of the molecular units responsible for the crystal nuclei formation; (b) Nature of the nuclei and nucleation process; (c) Growth process of the nuclei into crystal; (d) Morphological control and size of the resulting crystal; (e) Surface structure of the resulting crystals; and (f) Transformation of frameworks into other frameworks or condensed structures.

Published
2003

11. Structural, magnetic and catalytica properties of a self-recognized micro-oxo-bridged diiron(III) bis(benzimidazole) complex

Author

Payra, Pramatha, Shao-Ching Hung, Wai Him Kwok, Johnston, Dean, Gallucci, Judith, and Chan, Michael K.

Subjects
Ligands -- Research, Metal complexes -- Research, Benzimidazoles -- Magnetic properties, Benzimidazoles -- Chemical properties, Benzimidazoles -- Structure, Chemistry
Abstract

The synthesis and characterization of a diiron mu-oxo-bridged Me2-BBZ complex, [Fe(Me2BBZ)OFe(Me2BBZ)](ClO4)(sub 4)(H2))(sub 3)(CH3CH)(sub 3) (1), that provides indirect support for this hypotheses is described. The results highlight the steric differences between the phenyl(benzimidazole) and Schiff-base portions of the ligand, features that could be important in chiral recognition of ligands and in differentiating substrate trajectories as required for asymmetric catalysis.

Published
2001

12. Coupling of catalyses by carbonyl clusters and dehydrogenases: Reduction of pyruvate to L-lactate by dihydrogen

Author

Bhaduri, Sumit, Mathur, Pradeep, Payra, Pramatha, and Sharma, Krishna

Subjects
Dehydrogenases -- Observations, Lactate dehydrogenase -- Observations, Chemistry
Abstract

A platinum cluster has been used in the catalytic reduction of NAD+ to NADH by dihydrogen. The reaction is extended using the enzyme L-lactate dehydrogenase (L-LDH), incorporating the reduction of pyruvate to L-lactate. It was found that there was no reaction in the absence of any one of the components of salt, L-LDH or NAD+, or if (Bu(sub4)N)(sub2)(Pt(sub12)(CO)(sub24)) is used instead of the salt.

Published
1998

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