Sarvesh Kumar Pandey

Effect of current density and grain refining agents on pulsed electrodeposition of nanocrystalline nickel

Abstract Nanocrystalline nickel was electrodeposited on copper substrate using a Watt’s bath at a temperature of 50°C. The effect of pulsed current density (up to 1·5 A cm−2) and role of organic additives (namely saccharin and sodium citrate) in the deposition bath was evaluated for rendering grain refinement. The deposited samples were characterised for current efficiency, colonial morphology, crystallite size, texture, coercivity and nanomechanical properties (such as Young’s modulus and hardness). Results were compared with deposition using direct current, and utilising annealed Cu substrate. The smallest crystallite size of 22 nm was obtained, and the lowest coercivity equaled 22 Oe for the sample deposited using pulsed current with the peak current density 1 A cm−2 and 10 g L−1 saccharin addition. Annealing of the substrate has shown to increase the Young’s modulus of electrodeposited Ni by 10·2%, which increases further by 14·4% with saccharin addition when compared to those of deposits without saccharin addition.

The aromaticity and electronic properties of monosubstituted benzene, borazine and diazadiborine rings: an ab initio MP2 study

A comparative Møller–Plesset perturbation theory-based study to analyze the substituent’s effect on the aromaticity and electronic properties of benzene, borazine and diazadiborine has been performed considering electron-donating groups (EDGs) such as –NH2 and –CH3 as well as electron-withdrawing groups (EWGs) such as –NO2 and –CF3 at various positions. The lowest energy structures of all monosubstituted rings follow the same trend of NICS values such that there is slight change in the aromaticity due to EDGs and EWGs. However, N-substituted borazine rings are more aromatic but less stable than B-substitution. More interestingly, the aromaticity of substituted diazadiborine rings increases with the increase in the energy of the isomers due to change in the position of substituent. Therefore, the aromaticity does not account for the relative stability of these species. The electronic properties of lowest energy isomers of benzene, borazine and diazadiborine are affected by the substituent in accordance with the aromaticity. For instance, the substitution of EDGs decreases and that of EWGs increases the ionization potential for all ring systems. The electronic properties of –NO2 (strong EDG)-substituted rings are particularly noticeable due to their large electrophilic index values and larger ionization potentials. This comprehensive report is intended to provide new insights into the energetics, aromaticity and related properties of substituted six-membered homocyclic as well as heterocyclic rings.

Stability versus aromaticity in mono-hydroxylated borazine, 1,2-azaborine and 1,3,2,4-diazadiborine

ABSTRACT We have performed ab initio MP2/aug-cc-pVDZ computations to analyse the relative stability of −OH substituted borazine, azaborine and diazadiborine rings and their aromaticity by calculating nucleus independent chemical shift (NICS), its tensor component (NICSzz) harmonic oscillator model of aromaticity and para delocalisation index values. B-substituted rings are energetically more stable than N-substitution which was found to be associated with the increase in the polarity of BN bond due to lone pair–antibond interactions. This increase in polarity causes to reduce the aromaticity of B-substituted rings and increase their stability. On the contrary, N-substituted rings are destabilised due to repulsion between lone pairs of N and O atoms, which causes to shift the lone pair of N toward B atom. This causes to increase the cyclic delocalisation within the ring and consequently, the aromaticity increases. In the systems studied here, the aromaticity does not cause any significant stabilisation, but increases with the decrease in the stability. These findings may provide further insights into the relation between stability and aromaticity of substituted six-membered heterocyclic rings.

BO2-functionalized B3N3C54 heterofullerene as a possible candidate for molecular spintronics and nonlinear optics

BO2-substituted B3N3C54 heterofullerene was studied using density functional theory, and its electronic, magnetic and nonlinear optical properties are discussed. The substitution was considered at the B and N sites of the heterofullerene, in lower and higher spin states. We notice that BO2 substitution at the B sites of B3N3C54 heterofullerene leads to interesting properties, such as a smaller energy gap (0.66 eV) and a high spin magnetic moment (3 μ B). The density-of-states curves, molecular orbitals and spin density surfaces have been used to explain these facts. In addition, the first-order mean hyperpolarizability of B3N3C54 heterofullerene has been found to be significantly large (3.6 × 103 a.u.), which is due to smaller transition energy in the crucial excited state. This is reflected by the absorption spectra calculated using the time-dependent density functional theory method. These findings may be exploited to design novel materials for possible spintronic and electro-optical applications.

A Quantum Theory of Atoms-in-Molecules Perspective and DFT Study of Two Natural Products: Trans-Communic Acid and Imbricatolic Acid

The topological features of the charge densities, ρ(r), and the chemical reactivity of two most biologically relevant and chemically interesting scaffold systems i.e. trans-communic acid and imbricatolic acid have been determined using density functional theory. To identify, characterize, and quantify efficiently, the non-covalent interactions of the atoms in the molecules have been investigated quantitatively using Baders quantum theory of atoms-in-molecules (QTAIM) technique. The bond path is shown to persist for a range of weak H···H as well as C···H internuclear distances (in the range of 2.0–3.0 A). These interactions exhibit all the hallmarks of a closed-shell weak interaction. To get insights into both systems, chemical reactivity descriptors, such as HOMO–LUMO, ionization potential, and chemical hardness, have been calculated and used to probe the relative stability and chemical reactivity. Some other useful information is also obtained with the help of several other electronic parameters, which are closely related to the chemical reactivity and reaction paths of the products investigated. Trans-communic acid seems to be chemically more sensitive when compared with imbricatolic acid due to its experimentally observed higher half-maximal inhibitory concentration (bioactivity parameter) value, which is in accordance with its higher chemical reactivity as theoretically predicted using density functional theory-based reactivity index. The quantum chemical calculations have also been performed in solution using different solvents, and the relative order of their structural and electronic properties as well as QTAIM-based parameters show patterns similar to those observed in gas phase only. This study further exemplifies the use and successful application of the bond path concept and the quantum theory of atoms-in-molecules.

Anion-controlled geometrically different Cu(II) ion-based coordination polymers and green synthetic route for copper nanoparticles: a combined experimental and computational insight

Abstract The Cu(II) ion-based polymeric complexes [Cu(2,2′-bpy).(N3)2]n (I), [Cu2(2,2′-bpy)2.(N3)4]n (II), and monomeric complex [Cu(2,2′-bpy).(NO3)2].5H2O (III) have been synthesized with rigid (–N3) and aromatic (2,2′-bpy = 2,2′-bipyridyl) ligand. The rigid azide group is responsible for the formation of 1-D extended structures in complexes I and II where as in the case of complex III, a monomeric complex is formed due to lack of a bridging group like –N3, resulting in limitation in dimensionality. The thermal stability of the 1-D complexes is comparatively higher than monomeric complex III. Hirshfeld surface analysis has also been applied to investigate other weak interactions and compared with the results from single-crystal X-ray data. Due to the presence of paramagnetic metal centers and long metal···metal distances in complexes I and II and presence of lattice water molecules in complex III, decrease in luminescence intensities have been observed. To attain further insights into the aforementioned interesting species, some chemical concepts such as highest occupied molecular orbital–lowest unoccupied molecular orbital gap, electronic chemical potential, chemical hardness, and electrophilicity index, identified as a derivative of electronic energy, have also been emphasized employing the quantum chemical calculations in the framework of the density functional theory method using the M06-2X/ 6-31G** level of study. Further, these complexes have been used to synthesize copper nanoparticles by applying a green synthetic route.

Spectroscopic analyses, intra-molecular interaction, chemical reactivity and molecular docking of imerubrine into bradykinin receptor

Imerubrine, a biologically active natural product, is one of the initial members of tropoloisoquinolines and biosynthetically related to the more common azafluoranthene alkaloids. We perform a comprehensive quantum chemical analysis on imerubrine using density functional theory at B3PW91/6-311 + G(d,p) level. The equilibrium molecular structure of imerubrine has been obtained. The weak intra-molecular C–H⋯O interactions are recognized, characterized and quantified by quantum theory of atoms in molecule and relaxed force constants. The chemical reactivity of imerubrine is explained and discussed with the help of highest occupied molecular orbital, lowest unoccupied molecular orbital and molecular electro static potential surfaces as well as a number of reactivity descriptors. The infrared spectrum of imerubrine has been calculated and the vibrational modes have been assigned on the basis of the potential energy distribution with the highest possible accuracy. The nuclear magnetic resonance spectra of imerubrine have been calculated, analyzed and compared with available experimental data. A good agreement between experimental and calculated values has been observed. The molecular docking of imerubrine into B1 bradykinin receptor (PDB ID: 1HZ6) shows that it is capable to bind with the receptor and hence, it can act as an effective bradykinin receptor agonist.