Department of Chemistry

Indian Institute of Technology Palakkad&nbsp;(IIT Palakkad or IIT PKD) is a public autonomous&nbsp;engineering&nbsp;and&nbsp;research&nbsp;institute located in&nbsp;Palakkad,&nbsp;Kerala. It was&nbsp;one of the five new&nbsp;IITs&nbsp;proposed in the&nbsp;2014 Union budget of India. The campus was inaugurated on 3 August 2015. The institute has 94 faculty, 978 students, and 63 non-teaching staffs.

IT Palakkad currently offers four-year Bachelor of Technology (B.Tech) and two years MS programmes in 8 different engineering disciplines including&nbsp;Computer Science, Electrical, Mechanical, Civil among others.

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IIT Palakkad

In an objective to synthesize metallaheteroboranes containing heavier chalcogen atoms, we performed the reaction of dimetallaborane analogues of pentaborane(9) with various chalcogen sources. As a result, the thermolysis of nido-[1,2-(Cp∗RuH)2B3H7], 1 (Cp∗ = η5-C5Me5) with mixture of S and Se powder was carried out, that led to the isolation of half sandwich dimetallaheteroborane arachno-[(1,2-Cp∗Ru)2B2H6S2], 2. On the other hand, the reaction of nido-1 with diorganyldichalcogenide ligands, [Ph2E2] afforded chalcogen bridged half sandwich complexes [(2,3-Cp∗Ru)2B3H6(μ-η1-EPh)], 4a-c (4a: E = S; 4b: E = Se and 4c: E = Te). Compound 2 can be derived from a closo-snub disphenoid by removing a 5-connect vertex followed by the removal of a 3-connect vertex. Compound 4a-c can be described as nido-square pyramidal structures, isoelectronic and isostructural with nido-1. All the compounds have been characterized by mass spectrometry, 1H, 11B and 13C spectroscopy. Further, the geometry of compounds 2, 3, 4b and 4c were unequivocally established by crystallographic analysis. © 2014 Elsevier B.V. All rights reserved.

World University root node

Journal of Organometallic Chemistry

Diruthenium analogues of Hexaborane(12) and Pentaborane(9): Synthesis and structural characterization of [(1,2-Cp∗Ru)2B2H6S2] and [(2,3-Cp∗Ru)2B3H6(μ-η1-EPh)], (E = S, Se and Te) (Cp∗ = η5-C5Me5)

A fast and facile electrochemical sensor for the detection of an important anti-cancer drug, 5-fluorouracil, is fabricated using a gold nanoparticle decorated multiwall carbon nanotube (GNP-MWCNT) composite modified electrode. GNP-MWCNT composite has been prepared by a simple one-pot synthesis in the presence of chitosan, which acts as a reducing as well as stabilizing agent. Synthesized GNP-MWCNT is characterized by UV-Visible spectroscopy, Raman spectroscopy, XRD analysis and FESEM for the structural and chemical properties of nanocomposite, and the size of the gold nanoparticles is determined to be ∼30 nm by different methods. The electrochemical capability of the fabricated GNP-MWCNT composite modified electrode for the detection of 5-FU is examined by cyclic voltammetry, electrochemical impedance analysis and differential pulse voltammetry. The nanoAu decorated carbon nanotube electrode is found to be efficient for electrocatalytic oxidation of 5-FU. Peak current of the DPVs exhibited a linear relationship against 5-FU over a wide concentration range of 0.03-10 μM with a low-detection-limit (3σ/b) of 20 nM, and the analysis time is as low as 25 s. Practical utility of the developed GNP-MWCNT nanocomposite biosensor has been demonstrated for the detection of 5-FU directly from artificial urine and pharmaceutical formulations with good recovery limits. © 2015 Elsevier Ltd.

Electrochimica Acta

Biopolymer Stabilized Nanogold Particles on Carbon Nanotube Support as Sensing Platform for Electrochemical Detection of 5-Fluorouracil in-vitro

Supramolecular assemblies that help to preorganize reactant molecules have played an important role in the development of concepts related to the control of excited-state processes. This has led to a persistent search for newer supramolecular systems (hosts), and this review briefly presents our work with octa acid (OA) to a host to control excited-state processes of organic molecules. Octa acid, a water-soluble host, forms 1:1, 2:1, and 2:2 (host-guest) complexes with various organic molecules. A majority of the guest molecules are enclosed within a capsule made up of two molecules of OA whereas OA by itself remains as a monomer or aggregates. Luminescence and 1H NMR spectroscopy help to characterize the structure and dynamics of these host-guest complexes. The guest molecule as well as the host-guest complex as a whole undergoes various types of motion, suggesting that the guests possess freedom inside the confined space of the octa acid capsule. In addition, the confined guests are not isolated but are able to communicate (energy, electron, and spin) with molecules present closer to the capsule. The host-guest complexes are stable even on solid surfaces such as silica, clay, α-Zr phosphate, TiO2, and gold nanoparticles. This opens up new opportunities to explore the interaction between confined guests and active surfaces of TiO2 and gold nanoparticles. In addition, this allows the possibility of performing energy and electron transfer between organic molecules that do not adsorb on inert surfaces of silica, clay, or α-Zr phosphate. The results summarized here, in addition to providing a fundamental understanding of the behavior of molecules in a confined space provided by the host OA, are likely to have a long-range effect on the capture and release of solar energy. © 2014 American Chemical Society.

Fulltext

Langmuir

Supramolecular photochemistry in solution and on surfaces: Encapsulation and dynamics of guest molecules and communication between encapsulated and free molecules

In this report, we have explored the acid-base bifunctional catalytic activity of iron oxohydroxides (FeOOH) by catalyzing deacetalization and Henry condensation reactions successively in a single pot. The crystalline polymorphs of FeOOH, namely goethite (α FeOOH), akaganèite (β FeOOH), lepidocrocite (γ FeOOH) and δ FeOOH, were chemically prepared and tested for the catalytic activity. All the polymorphs of FeOOH exhibited acid-base bifunctional catalytic activity. The relative selectivity for products varied with the polymorphs of FeOOH. Whereas α FeOOH produced benzaldehyde in high yield, the polymorphs β FeOOH, γ FeOOH and δ FeOOH showed high selectivity for trans-β-nitrostyrene. In addition, β FeOOH also exhibited a unique activity towards the formation of 1,3-dinitro-2-phenylpropane. The difference in the catalytic activity of FeOOH polymorphs was explained based on the strength and density of acidic and basic active sites on the surface. Selectivity for the products was tuned by changing the synthesis parameters of the catalysts and reaction conditions. © The Royal Society of Chemistry.

Catalysis Science and Technology

Tunable acid-base bifunctional catalytic activity of FeOOH in an orthogonal tandem reaction

A combined experimental and quantum-chemical study of a series of homometallic metallaheteroboranes [(Cp∗M)2E6B2H2] (M = Rh or RuH; E = S or Se; Cp∗ = η5-C5Me5), which are analogues of 1,3-bishomocubane, is reported. The thermolysis of nido-[(Cp∗Rh)2B3H7] (1) in the presence of S or Se powder in toluene yielded bishomocubane clusters [(Cp∗Rh)2(μ-E)2(μ3-E)4B2H2], (3: E = S; 4: E = Se). In a similar fashion, the treatment of nido-[(Cp∗RuH)2B3H7] (2) with S or Se powder in p-xylene yielded [(Cp∗Ru)2(μ-E)2(μ3-E)4B2H2] (5: E = S; 6: E = Se) and [(Cp∗Ru)2(μ3-Se)(μ4-Se)B3H5] (7). One of the noteworthy features of 3-6 is the presence of an electron-precise trichalcogenoborato ligand. All of the compounds have been characterized by mass spectrometry; IR spectroscopy; and 1H, 11B and 13C NMR spectroscopy. The structures of 3, 4, 6 and 7 were established unequivocally by X-ray crystallographic analysis. Quantum-chemical calculations by DFT methods for 3, 4 and 6 showed reasonable agreement with the experimentally observed structural parameters. The large HOMO-LUMO gaps are consistent with the high stabilities of these complexes. Copyright © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

European Journal of Inorganic Chemistry

Electron‐Precise 1, 3‐Bishomocubanes–A Combined Experimental and Theoretical Study

Selective and discriminative detection of -NO2 containing high energy organic compounds such as picric acid (PA), 2,4,6-trinitrotoluene (TNT) and dinitrotoluene (DNT) has become a challenging task due to concerns over national security, criminal investigations and environment protections. Among various known detection methods, fluorescence techniques have gained special attention in recent time. A wide variety of fluorescent chemosensors have been developed for nitroaromatic explosive detection. In this review article, we provide an overview of the recent developments made in small molecule-based turn-off fluorescent sensors for nitroaromatic explosives with special focus on organic and H-bonded supramolecular sensors. The fluorescent sensors discussed in this review are classified and organized according to their functionality and their recognition of nitroaromatics by fluorescence quenching. © The Royal Society of Chemistry 2015.

Chemical Communications

π-Electron rich small molecule sensors for the recognition of nitroaromatics

Equimolar combination of a series of binuclear half-sandwich p-cymene ruthenium(II) building units [Ru2(μ-η4-C 2O4)(MeOH)2(η6-p-cymene) 2](OTf)2 [1a](OTf)2, [Ru2(μ- η4-N,N′-diphenyloxamidato)( MeOH)2(η6-p- cymene)2](OTf)2 [1b](OTf)2 and [Ru 2(μ-η4-C6H2O 4)(MeOH)2(η6-p-cymene)2](OTf) 2 [1c](OTf)2 separately with imidazole-based ditopic ligands (L1-L2) in methanol yielded a series of tetranuclear metallamacrocycles [2-7](OTf)4, respectively [L 1 = 1,4-bis(imidazole-1-yl)benzene; L2 = 4,4′-bis(imidazole-1-yl)biphenyl; OTf- = O3SCF3 -]. Similarly, the reaction of [Ru2(μ- η4-C2O4)(MeOH)2(η 6-pcymene)2](OTf)2 [1a](OTf)2 with a triazine-based tritopic ligand 1,3,5-tris(imidazole-1-yl)triazine (L 3) in 3:2 M ratio afforded an unexpected tetranuclear macrocycle [8](OTf)4 instead of an expected trigonal prismatic cage [8a](OTf)6. All the self-assembled macrocycles [2-8](OTf)4 were isolated in moderate to high yields and were fully characterized by multinuclear [1H, 19F] NMR, IR and electrospray ionization mass spectrometry (ESI-MS). In addition, X-ray diffraction study on the single crystals of [3](OTf)4 and [8](OTf)4 also indicated the formation [2+2] self-assembled macrocycles. Despite the possibility of formation of different conformational isomeric macrocycles (syn-and anti) and polymeric product due to free rotation of ligand sites of imidazole linkers, the selective formation of single conformational isomer (anti) as the only product is quite interesting. Furthermore, the photo-and electrochemical properties of these assemblies have been studied using UV/Vis absorption and cyclic voltammetry analysis. © 2013 Elsevier B.V. All rights reserved.

Self-assembly of discrete metallamacrocycles employing half-sandwich octahedral diruthenium(II) building units and imidazole-based ligands

4-Hydroxy-2-( E)-nonenal (4-HNE) is one of the major lipid peroxidation product formed during oxidative stress. At high concentrations, 4-HNE is cytotoxic and exerts deleterious effects that are often associated with the pathology of oxidative stress-driven disease. Alternatively, at low concentrations it functions as a signaling molecule that can activate protective pathways including the antioxidant Nrf2-Keap1 pathway. Although these biphasic signaling properties have been enumerated in many diseases and pathways, it has yet to be addressed whether 4-HNE has the capacity to modulate oxidative stress-driven lipid peroxidation. Here we report an auto-regulatory mechanism of 4-HNE via modulation of the biological oxidant nitric oxide (NO). Utilizing LPS-activated macrophages to induce biological oxidant production, we demonstrate that 4-HNE modulates NO levels via inhibition of iNOS expression. We illustrate a proposed model of control of NO formation whereby at low concentrations of 4-HNE a negative feedback loop maintains a constant level of NO production with an observed inflection at approximately 1μM, while at higher 4-HNE concentrations positive feedback is observed. Further, we demonstrate that this negative feedback loop of NO production control is dependent on the Nrf2-Keap1 signaling pathway. Taken together, the careful regulation of NO production by 4-HNE argues for a more fundamental role of this lipid peroxidation product in normal physiology. © 2014 The Authors.

Redox Biology

Identification of a negative feedback loop in biological oxidant formation fegulated by 4-hydroxy-2-(E)-nonenal

Disulfide bridges are no longer considered to merely stabilize protein structure, but are increasingly recognized to play a functional role in many regulatory biomolecular processes. Recent studies have uncovered that the redox activity of native disulfides depends on their C-C-S-S dihedrals, χ2 and χ′2. Moreover, the interplay of chemical reactivity and mechanical stress of disulfide switches has been recently elucidated using force-clamp spectroscopy and computer simulation. The χ2and χ′2 angles have been found to change from conformations that are open to nucleophilic attack to sterically hindered, so-called closed states upon exerting tensile stress. In view of the growing evidence of the importance of C-C-S-S dihedrals in tuning the reactivity of disulfides, here we present a systematic study of the conformational diversity of disulfides as a function of tensile stress. With the help of force-clamp metadynamics simulations, we show that tensile stress brings about a large stabilization of the closed conformers, thereby giving rise to drastic changes in the conformational free energy landscape of disulfides. Statistical analysis shows that native TDi, DO and interchain Ig protein disulfides prefer open conformations, whereas the intrachain disulfide bridges in Ig proteins favor closed conformations. Correlating mechanical stress with the distance between the two α-carbons of the disulfide moiety reveals that the strain of intrachain Ig protein disulfides corresponds to a mechanical activation of about 100 pN. Such mechanical activation leads to a severalfold increase of the rate of the elementary redox .SN2 reaction step. All these findings constitute a step forward towards achieving a full understanding of functional disulfides. © 2014 Anjukandi et al.

PLoS ONE

The effect of tensile stress on the conformational free energy landscape of disulfide bonds

A series of novel Cp*-based (Cp*=η5-C 5Me5) agostic, bis(σ-borate) and boratrane complexes have been synthesized from diruthenium and dirhodium analogues of pentaborane(9). The synthesis and structural characterization of the first neutral ruthenadiborane(6) analogue are also reported. This new route offers a very efficient method for the isolation of bis(σ-borate) and agostic complexes from diruthenapentaborane(9). © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.