Ponnambalam Venuvanalingam

Bio: Ponnambalam Venuvanalingam is an academic researcher from Bharathidasan University. The author has contributed to research in topics: Ab initio & HOMO/LUMO. The author has an hindex of 27, co-authored 141 publications receiving 2258 citations. Previous affiliations of Ponnambalam Venuvanalingam include University of South Carolina & Madurai Kamaraj University.

Tuning nonlinear optical and optoelectronic properties of vinyl coupled triazene chromophores: a density functional theory and time-dependent density functional theory investigation

Abstract: Triazenes are a unique class of polyazo compounds containing three consecutive nitrogen atoms in an acyclic arrangement and are promising NLO candidates. In the present work, a series of 15 donor-π-acceptor type vinyl coupled triazene derivatives (VCTDs) with different acceptors (−NO2, −CN, and −COOH) have been designed, and their structure, nonlinear response, and optoelectronic properties have been studied using density functional theory and time-dependent density functional theory methods. B3LYP/6-311g(d,p) optimized geometries of the designed candidates show delocalization from the acceptor to donor through a π-bridge. Molecular orbital composition analysis reveals that HOMO is stabilized by the π-bridge, whereas acceptors play a major role in the stabilization of LUMO. Among the three acceptors, nitro derivatives are found to be efficient NLO candidates, and tri- and di-substituted cyano and carboxylic acid derivatives also show reasonably good NLO response. The effect of solvation on these propertie...

Interaction of anthraquinone dyes with lysozyme: evidences from spectroscopic and docking studies.

Abstract: The interaction between lysozyme and anthraquinone dyes such as Alizarin Red S, Acid blue 129 and Uniblue was studied using steady state, time resolved fluorescence measurements and docking studies. Addition of anthraquinone dyes effectively quenched the intrinsic fluorescence of lysozyme. Fluorescence quenching of lysozyme by dyes has revealed the formation of complex. The number of binding sites (n) and binding constant (K) for all the three dyes was calculated by relevant fluorescence quenching data. Based on Forster's non-radiative energy transfer theory, distance (r(0)) between the donor (lysozyme) and acceptor (dyes) as well as the critical energy transfer distance (R(0)) has also been calculated. The interaction between dyes and lysozyme occurs through static quenching mechanism as confirmed by time resolved spectroscopy. The conformational change of lysozyme has been analyzed using synchronous fluorescence measurement. Finally, docking studies revealed that specific interactions were observed with the residue of Trp 62.

Hydrogenolysis of sorbitol over Ni and Pt loaded on NaY

Abstract: The hydrogenolysis of sorbitol (15% aqueous solution) was carried out at 60 bar pressure at 220 °C in a stirred batch reactor using Ni–NaY (2, 4, 6 wt.% Ni) with and without added Pt(1 wt.%). 1,2-Propanediol was the major product over Ni–NaY and glycerol was the main product over Pt(1 wt.%)–NaY. The addition of 1 wt.% Pt to the Ni-catalysts had only a marginal effect on conversion and selectivity of the catalysts. Addition of Ca(OH)2 as the promoter to both Ni and Pt catalysts increased the conversion significantly without any significant effect on selectivity.

Water-Soluble Mono- and Binuclear Ru(η6-p-cymene) Complexes Containing Indole Thiosemicarbazones: Synthesis, DFT Modeling, Biomolecular Interactions, and In Vitro Anticancer Activity through Apoptosis

Abstract: Indole thiosemicarbazone ligands were prepared from indole-3-carboxaldehyde and N-(un)substituted thiosemicarbazide. The Ru(η6-p-cymene) complexes [Ru(η6-p-cymene)(HL1)Cl]Cl (1) and [Ru(η6-p-cymene)(L2)]2Cl2 (2*) were exclusively synthesized from thiosemicarbazone (TSC) ligands HL1 and HL2, and [RuCl2(p-cymene)]2. The compounds were characterized by analytical and various spectroscopic (electronic, FT-IR, 1D/2D NMR, and mass) tools. The exact structures of the compounds (HL1, HL2, 1, and 2*) were confirmed by single-crystal X-ray diffraction technique. In complexes 1 and 2*, the ligand coordinated in a bidentate neutral (1)/monobasic (2*) fashion to form a five-membered ring. The complexes showed a piano-stool geometry around the Ru ion. While 2* existed as a dimer, 1 existed as a monomer, and this was well explained through free energy, bond parameter, and charge values computed at the B3LYP/SDD level. The intercalative binding mode of the complexes with calf thymus DNA (CT DNA) was revealed by spectrosc...

Enhanced photocatalytic degradation of azo dyes using nano Fe3O4

Abstract: Nanosized magnetic Fe3O4 synthesized via sonochemical route was used as a photocatalyst for the degradation of azo dyes, methyl red and congo red. The novelty of the photo catalyst is its easy recovery by magnetic force and its recycling ability due to its long-term stability, in addition to its cost effectiveness, non-toxicity and non-carcinogenicity. A detailed feasibility study has been carried out on the photocatalytic degradation of the azo dyes at various pH and at various concentrations of photocatalyst, dye and H2O2. The presence of photocatalyst is found to significantly accelerate the degradation of azo dyes and the optimal dosage is found to be 0.075 and 0.2 g/l for methyl red and congo red, respectively. Langmuir–Hinshelwood kinetic analysis revealed pseudo-first-order kinetics for the photocatalytic degradation of the dyes and the degradation products were identified using spectral analysis. The degradation study revealed the following order of reactivity: Photo-Fe3O4 > Photo-H2O2 > Fe3O4 > H2O2.

Ab initio calculation of vibrational absorption and circular dichroism spectra using density functional force fields

Abstract: : The unpolarized absorption and circular dichroism spectra of the fundamental vibrational transitions of the chiral molecule, 4-methyl-2-oxetanone, are calculated ab initio. Harmonic force fields are obtained using Density Functional Theory (DFT), MP2, and SCF methodologies and a 5S4P2D/3S2P (TZ2P) basis set. DFT calculations use the Local Spin Density Approximation (LSDA), BLYP, and Becke3LYP (B3LYP) density functionals. Mid-IR spectra predicted using LSDA, BLYP, and B3LYP force fields are of significantly different quality, the B3LYP force field yielding spectra in clearly superior, and overall excellent, agreement with experiment. The MP2 force field yields spectra in slightly worse agreement with experiment than the B3LYP force field. The SCF force field yields spectra in poor agreement with experiment.The basis set dependence of B3LYP force fields is also explored: the 6-31G* and TZ2P basis sets give very similar results while the 3-21G basis set yields spectra in substantially worse agreements with experiment. jg

‘Click’ Chemistry in Polymer and Materials Science

Abstract: The modification of polymers after the successful achievement of a polymerization process represents an important task in macromolecular science. Cycloaddition reactions, among them the metal catalyzed azide/alkyne ‘click’ reaction (a variation of the Huisgen 1,3-dipolar cycloaddition reaction between terminal acetylenes and azides) represents an important contribution towards this endeavor. They combine high efficiency (usually above 95%) with a high tolerance of functional groups and solvents, as well as moderate reaction temperatures (25–70 °C). The present review assembles recent literature for applications of this reaction in the field of polymer science (linear polymers, dendrimers, gels) as well as the use of this and related reactions for surface modification on carbon nanotubes, fullerenes, and on solid substrates, and includes the authors own publications in this field. A number of references (>100) are included.