Arindam Chakraborty

Potential use of some metal clusters as hydrogen storage materials—a conceptual DFT approach

Structure, stability and reactivity of several metal clusters with or without hydrogen doping were studied using standard ab initio and density functional theory (DFT) calculations. Conceptual DFT-based reactivity descriptors and the associated electronic structure principles lend additional support towards understanding the stability of metal clusters upon hydrogen doping. Related aromaticity was analyzed through nucleus-independent chemical shift values. Site selectivity towards electrophilic and nucleophilic attacks were analyzed in terms of the corresponding local reactivity descriptors. Most of the metal clusters have the capacity to trap hydrogen molecules.

Bonding, aromaticity, and structure of trigonal dianion metal clusters.

Various isomers of the trigonal dianion metal clusters, X  32− , X = Be, Mg, Ca, and their mono‐ and disodium complexes are optimized at the B3LYP/6‐311+G(d) level. Different conceptual density functional theory based reactivity descriptors as well as the induced magnetic field values are calculated to understand the stability and aromaticity of these systems. Possibility of bond stretch isomerism is explored. Genetic algorithm results lend additional insights into the structures of these isomers.

On the Regio and Stereo Selective Formylations of Acyclic Alpha Methylene Ketones towards Vilsmeier Haack Reagent

Abstract The regio and stereo selectivities of Vilsmeier Haack reaction of ketomethylene compounds have been predicted. The possible mechanistic pathway has also been proposed.

Synthetic studies towards furosesquiterpenes: Construction of linearly-fused AB trans- and AB cis-furo[3,2-b]-and furo[2,3-b] decalins

Abstract Linearly fused furo[2,3-b]- and furo[3,2-b] decalin systems with cis trans ring junctions are present in several furosesquiterpenes obtained from marine sponges. A short and efficient synthesis of this ring system is described starting from Hagemans ester (1). The method has been extended for the synthesis of compound 8 and 14 via the diketones 5,6 and 12 respectively.

Trapping of noble gases (He–Kr) by the aromatic H3+ and Li3+ species: a conceptual DFT approach

The stability, reactivity and aromaticity of clusters of various noble gas atoms trapped in aromatic H3+ and Li3+ rings are studied at the B3LYP/6-311+G(d) and MP2/6-311+G(d) levels of theory. Electrophilicity, a gain in energy and nucleus-independent chemical shift values lend additional insights into the overall behavior of these clusters.

Aromaticity in all-metal annular systems: the counter-ion effect

The effect of counterions on the bonding, stability and aromaticity of trigonal dianion metal clusters has been analyzed through the behavior of various conceptual density functional theory based reactivity descriptors and the nucleus independent chemical shift calculated at different levels of theory, comprising one-determinant approaches and beyond (QCISD, CASSCF(8,8) and NEVPT2), for a proper benchmarking. Although several important insights into the counter-ion effects are obtained, much needs to be done in order to have a transparent idea therein.

Stability and aromaticity of nH2@B12N12 (n=1–12) clusters

Standard ab initio and density functional calculations are carried out to determine the structure, stability, and reactivity of B12N12 clusters with hydrogen doping. To lend additional support, conceptual DFT-based reactivity descriptors and the associated electronic structure principles are also used. Related cage aromaticity of this B12N12 and nH2@B12N12 are analyzed through the nucleus independent chemical shift values.

A conceptual density functional study of structure, bonding, reactivity and the possibility of bond-stretch isomerism in some neutral sulfur clusters, S n (n=3-8)

Geometries of different isomers of various neutral sulfur clusters, S n (n=3–8) are optimized at the B3LYP/6-311+G* level of theory. Their stability and aromaticity behavior are analyzed in terms of the conceptual density functional theory-based reactivity descriptors and the associated electronic structure principles. The nucleus-independent chemical shift lends additional support. Possibility of bond-stretch isomerism in these clusters is explored.

Studies on furoterpenes: Stereoselective total synthesis of (±)-Ambliol-A and Dendrolasin

Abstract (±)-Ambliol-A ( 1 ) is totally synthesised with high stereoselectivity starting from α-ionone and [3-(3′-furyl)propyl]triphenylphosphonium bromide ( 3 ). In another attempt utilising 3 with the commercially available ketone 11 the total synthesis of Dendrolasin ( 12 ) has also been achieved.

Thermal stability and fire retardancy of polyurea and epoxy nanocomposites using organically modified magadiite

The purpose of this study is to investigate the effect of the surface modification of a layered silicate (magadiite) on the flammability of both polyurea and amine-cured epoxy resin. Based on the surface chemistry of magadiite, both quaternary alkyl ammonium and silane modifier can be employed for the organo-modification. Nanocomposites of both polymers were prepared via ultrasound-assisted in situ polymerization. Dispersion of magadiite was investigated through X-ray diffraction and high-resolution transmission electron microscopy. Thermal stability and flammability were evaluated by thermogravimetric analysis and cone calorimetry, respectively. The addition of small amount of magadiite resulted in significant improvements in flame resistance with not much change in thermal stability for both polymers. Ammonium-modified magadiite improves the flame resistance, whereas silane modification helps to increase time to ignition of both polymers.