Avijit Kumar Paul

The use of hydrothermal methods in the synthesis of novel open-framework materials

The preparation of inorganic compounds, exhibiting open-framework structures, by hydrothermal methods has been presented. To illustrate the efficacy of this approach, few select examples encompassing a wide variety and diversity in the structures have been provided. In all the cases, good quality single crystals were obtained, which were used for the elucidation of the structure. In the first example, simple inorganic network compounds based on phosphite and arsenate are described. In the second example, inorganic-organic hybrid compounds involving phosphite/arsenate along with oxalate units are presented. In the third example, new coordination polymers with interesting structures are given. The examples presented are representative of the type and variety of compounds one can prepare by careful choice of the reaction conditions.

The illustrative use of thiosulfate in the formation of new three-dimensional hybrid structures

Examples of 3D cadmium thiosulfate based inorganic–organic hybrid compounds have been shown to be active photocatalysts using sunlight.

Charge Density Analysis of a Pentaborate Ion in an Ammonium Borate: Toward the Understanding of Topological Features in Borate Minerals

Structural and charge density distribution studies have been carried out on a single crystal data of an ammonium borate, [C(10)H(26)N(4)][B(5)O(6)(OH)(4)](2), synthesized by solvothermal method. Further, the experimentally observed geometry is used for the theoretical charge density calculations using the B3LYP/6-31G** level of theory, and the results are compared with the experimental values. Topological analysis of charge density based on the Atoms in Molecules approach for B-O bonds exhibit mixed covalent/ionic character. Detailed analysis of the hydrogen bonds in the crystal structure in the ammonium borate provides insights into the understanding of the reaction pathways that could result in the formation of borate minerals. The net atomic charges and electrostatic potential isosurfaces also give additional input to evaluate chemical and physical properties in such systems.

Design, synthesis, characterization, antimicrobial evaluation and molecular modeling studies of some dehydroacetic acid-chalcone-1,2,3-triazole hybrids

A series of new dehydroacetic acid chalcone-1,2,3-triazole hybrids as potential antimicrobial agents was designed, synthesized and characterized by FTIR, NMR and HRMS spectral techniques. All the synthesized compounds were screened in vitro against four bacterial strains (Staphylococcus epidermidis, Bacillus subtilis, Escherichia coli and Pseudomonas aeruginosa) and two fungal strains (Aspergillus niger and Candida albicans). The antimicrobial results indicated that some of the compounds showed remarkable activities comparable to the standard drugs. Most of the compounds exhibited better efficacy compared to the DHA, which is itself an antimicrobial agent. The synergistic effect in biological activity was observed when DHA, chalcone and 1,2,3-triazole are conjugated. The molecular modeling studies of compound 5j into E. coli topoisomerase II DNA gyrase B were also performed.

Novel amine templated three-dimensional zinc-organophosphonates with variable pore-openings

Five new amine-templated zinc-organophosphonate compounds have been synthesized hydrothermally in the presence of zinc, 1-hydroxyethane-1,1-diphosphonic acid (H4hedp) as the diphosphonate ligand and different aliphatic amines. All the five compounds have three-dimensional open-framework structures, which are formed by the connectivity between zinc ions and diphosphonate ligands, and the biprotonated amines are present inside the open-channels. Five different amines, namely ethylenediamine (EDA), diethylenetriamine (DETA), 1,2-diaminopropane (1,2-DAP), 1,3-diaminopropane (1,3-DAP) and diazobicyclooctane (DABCO), have been used to obtain three different classes of framework structures, and such types of amine-templated frameworks are observed for the first time in the family of organophosphonates. Compound I, [C2N2H10][Zn3(hedp)2]·H2O, and compound II, [C4N3H15][Zn3(hedp)2], have similar framework structures, though these compounds have been synthesized in the presence of EDA and DETA, respectively. Compound III, [C3N2H12][Zn3(hedp)2], and compound IV, [C3N2H12][Zn3(hedp)2], have the same molecular formula and framework structures; however, their amines are different, i.e. 1,2-DAP and 1,3-DAP, respectively. Compound V, [C6N2H14][Zn3(hedp)2], forms a different three-dimensional framework from the above structures in the presence of DABCO. By varying the amine molecules from EDA to 1,2-DAP or DABCO, the ring size can be tuned from 4-, 5-, 6-, and 8-membered to only 6-, and 8-membered. All the compounds have also been characterized by powder XRD, IR spectroscopy, and TGA. The luminescence properties of compounds I–V have also been studied.

Identification of selection parameters for evaluating superior rice hybrids

Forty eight popular rice hybrids were studied to find out suitable genetic parameters for evaluation of an elite rice hybrid. The experiment was conducted during kharif 2012 and 2013 at Zonal Research Station, Chianki (Birsa Agricultural University, Ranchi), Palamau. A wide spectrum of variability was observed for all the characters in both the years. High genotypic coefficient of variation was observed for grains/panicle followed by test weight, grain yield and tillers/plant both for the years. High heritability percent was observed for days to 50% flowering, test weight and grain yield during kharif, 2012 and 2013. Days to 50% flowering days to maturity, grains/panicle and test weight had high positive significant association with grain yield whereas plant height, panicles/sq. m and tillers/plant showed positive significant correlation with grain yield at genotypic level. High positive direct effect was noted for test weight followed by grains/panicle, days to 50% flowering, days to maturity and plant height. Based on the results of the present study on correlation and path analysis, the characters i.e. grains/panicle, test weight, days to 50% flowering and days to maturity influenced the grain yield either directly or indirectly in hybrid rice for improving the grain yield.

Comparative Studies on Optical and Electronic Behavior of Lanthanide-based Coordination Polymers: Synthesis, Structure, Absorption-Emission and Magnetic Properties

A series of lanthanide(III) based coordination polymers have been synthesized using chelidamic acid (CA) as a ligand,

Crystal structure of bis­(piperazin-1-ium-κN4)bis­(thio­sulfato-κS)zinc(II) dihydrate

[\hbox {Ln}(\hbox {C}_{7}\hbox {H}_{2}\hbox {NO}_{5})(\hbox {H}_{2}\hbox {O})_{3}].\hbox {H}_{2}\hbox {O}