• Amit Kumar

      Articles written in Journal of Chemical Sciences

    • A quantum-classical simulation of the nuclear dynamics in NO$^-_2$ and C6H$^+_6$ with realistic model Hamiltonian

      Subhankar Sardar Amit Kumar Paul Satrajit Adhikari

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      We perform the nuclear dynamics simulation to calculate the broad band as well as better resolved (a) photodetachment spectra of nitrogen dioxide anion (NO$^-_2$), and (b) photoelectron spectra of benzene radical cation (C6H$^+_6$) with degeneracy among the electronic states using our parallelized time dependent discrete variable representation approach. For this purpose, we first consider a theoretical model that describes the photodetachment spectrum originating due to the Franck-Condon (FC) transition from the anionic ground state to the conically intersecting $\widetilde{X}^2 A_1 - \widetilde{A}^2 B_2$ electronic manifold of the neutral NO2, whereas two multi-state, multi-mode model Hamiltonians of C6H$^+_6$ with degeneracy among the electronic states are explored for its’ photoelectron spectra. The dynamics of C6H$^+_6$ has been carried out with two Hamiltonians: (a) one consists with four states and nine modes, and (b) the other is constituted with three states and seven modes. Since the electronic states of both the systems are interconnected by several conical intersections in the vicinity of the FC region, it would be challenging to persue the dynamical calculation due to the impact of non-adiabaticity among the electronic states. The spectral profiles obtained with the advent of TDDVR approach show reasonably good agreement with the results obtained by other theoretical methodologies and experimental measurements.

    • SN2-type ring opening of substituted-𝑁-tosylaziridines with zinc (II) halides: Control of racemization by quaternary ammonium salt

      Manas K Ghorai Deo Prakash Tiwari Amit Kumar Kalpataru Das

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      Quaternary ammonium salt mediated highly regioselective ring opening of aziridines with zinc(II) halides to racemic and non-racemic 𝛽-halo amines in excellent yield and selectivity is described. The reaction proceeds via an SN2-type pathway and the partial racemization of the starting substrate and the product was effectively controlled by using quaternary ammonium salts to afford the enantioenriched products (er up to 95:5).

    • Cu(II) complexes of glyco-imino-aromatic conjugates in DNA binding, plasmid cleavage and cell cytotoxicity

      Amit Kumar Atanu Mitra Amrendra Kumar Ajay Manoj Kumar Bhat Chebrolu P Rao

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      Binding of metal complexes of C2-glucosyl conjugates with DNA has been established by absorption and fluorescence studies. Conformational changes occurred in DNA upon binding have been studied by circular dichroism. All these studies are suggestive that the metal complexes bind to DNA through intercalation. Binding of di-nuclear copper complex 5 was found to be stronger when compared to the other complexes studied. Copper complexes were found to cleave the plasmid DNA in the absence of oxidizing or reducing agent, whereas, zinc complexes do not cleave. Metal complexes have shown toxicity to the HeLa and MCF-7 cell lines.Morphological studies, western blot and FACS analysis are suggestive of apoptotic cell death induced by the metal complexes. Di-nuclear copper complexes were found to be better as compared to the mononuclear ones in binding, plasmid cleavage and also in causing more cell death.

    • Exploration of the structural features and magnetic behaviour in a novel 3-dimensional interpenetrating Co(II)-based framework

      Soumyabrata Goswami Amit Kumar Mondal Sanjit Konar

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      A new Co(II)-based three-dimensional (3D) framework having the molecular formula [Co(C4O4)(4-bpmh))H2O)2]n·2nH2O·2nMeOH·(1)(4-bpmh = N, N-bis-pyridin-4-ylmethylene-hydrazine) has been synthesized using a mixed ligand system and characterized by elemental analysis, IR spectroscopy, thermogravimetric analysis, single crystal X-ray diffraction and variable temperature magnetic study. The framework is constructed by the bridging squarate (C4O2−4) and N, N-bis-pyridin-4-ylmethylene-hydrazine (4-bpmh) ligands and interpenetration of the 2D grid-like frameworks at definite angles gives rise to 2D$\to$3D inclined polycatenation with sql/Shubnikov tetragonal plane net topology. Extensive non-covalent interactions (H-bonding as well as 𝜋$\cdots$𝜋 interactions) are also observed which stabilises the 3D arrangement. Additionally, complex 1 contains 1D channels of large dimensions (10.91 × 11.78 Å2) that runs along the b-axis. Variable temperature DC magnetic susceptibility study reveals dominant spin–orbit coupling effect typical of the 4T1g ground state of octahedral high-spin Co(II) ion at a higher temperature range.

    • A quinoline based pH sensitive ratiometric fluorescent sensor: Structure and spectroscopy

      Soma Mukherjee Amit Kumar Paul Helen Stoeckli-Evans

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      A new quinoline based hydrazone was synthesized via a condensation reaction and characterized by NMR, mass and single crystal X-ray diffraction studies. It was investigated for suitability as a reversible ratiometric fluorescent pH sensor in acidic pH region. The sensor exhibits intramolecular charge transfer (ICT) type photophysical changes upon protonation of the quinoline ring. No significant interference on emission behavior was observed in the presence of various metal ions.

    • Structure, luminescence and antimicrobial properties of mononuclear silver(I) complexes of pyridine 2-carboxamide

      Sutapa Joardar Shounak Roy Suvendu Samanta Amit Kumar Dutta

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      Two Ag(I) complexes, [Ag(HL)2]ClO4 (1) and [Ag(HL)2]NO3·H2O (2), where HL is pyridine 2– carboxamide, have been synthesized and characterized by various spectroscopic techniques. The X-ray crystal structural analyses indicate that both the complexes consist of slightly distorted square planar silver(I) ions and ligand-supported weak Ag⋯Ag metallophilic interactions. Both the complexes show photoluminescence in solid state and acetonitrile solution at room temperature. Antimicrobial studies have been performed with these silver(I) complexes against various gram +ve, gram −ve bacterial and fungal species.

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