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

Room temperature photolysis of a triply-bridged borylene complex, [(μ3-BH)(Cp*RuCO)2(μ-CO)Fe(CO)3] (1 a; Cp*=C5Me5), in the presence of a series of alkynes, 1,2-diphenylethyne, 1-phenyl-1-propyne and 2-butyne led to the isolation of unprecedented vinyl-borylene complexes (Z)-[(Cp*RuCO) 2(μ-CO)B(CR)(CHR′)] (2: R, R′=Ph; 3: R=Me, R′=Ph; 4: R, R′=Me). This reaction permits a hydroboration of alkyne through an anti-Markovnikov addition. In stark contrast, in the presence of phenylacetylene, a metallacarborane, closo-[1,2-(Cp*Ru) 2(μ-CO)2{Fe2(CO)5}-4-Ph-4,5- C2BH2] (5 a), is formed. A plausible mechanism has been proposed for the formation of vinyl-borylene complexes, which is supported by density functional theory (DFT) methods. Furthermore, the calculated 11B NMR chemical shifts accurately reflect the experimentally measured shifts. All the new compounds have been characterized in solution by mass spectrometry and IR, 1H, 11B and 13C NMR spectroscopies and the structural types were unequivocally established by crystallographic analysis of 2, 5 a and 5 b. Unique metal-borylene complexes: Photolysis of a triply bridged borylene complex [(μ3-BH) (Cp*RuCO)2(μ-CO)Fe(CO)3] (Cp*= η5-C5Me5) with various internal alkynes led to hydroboration yielding new vinyl-borylene complexes (see figure). A plausible mechanism has been proposed for the formation of vinyl-borylene complexes, which is supported by density functional theory (DFT) methods. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

World University root node

Chemistry–A European Journal

Syntheses and Characterization of New Vinyl‐Borylene Complexes by the Hydroboration of Alkynes with [(μ3‐BH)(Cp*RuCO)2(μ‐CO)Fe(CO)3]

The synthesis, structural characterization and reactivity of new bridged borylene complexes are reported. The reaction of [{Cp*CoCl}2] with LiBH4×THF at -70°C, followed by treatment with [M(CO)3(MeCN)3] (M=W, Mo and Cr) under mild conditions, yielded heteronuclear triply bridged borylene complexes, [(μ3-BH) (Cp*Co)2(μ-CO)M(CO)5] (1-3; 1: M=W, 2: M=Mo, 3: M=Cr). During the syntheses of complexes 1-3, capped-octahedral cluster [(Cp*Co)2(μ-H)(BH)4{Co(CO)2}] (4) was also isolated in good yield. Complexes 1-3 are isoelectronic and isostructural to [(μ3-BH)(Cp*RuCO)2(μ-CO){Fe(CO) 3}] (5) and [(μ3-BH)(Cp*RuCO)2(μ-H) (μ-CO){Mn(CO)3}] (6), with a trigonal-pyramidal geometry in which the μ3-BH ligand occupies the apical vertex. To test the reactivity of these borylene complexes towards bis-phosphine ligands, the room-temperature photolysis of complexes 1-3, 5, 6 and [{(μ3-BH) (Cp*Ru)Fe(CO)3}2(μ-CO)] (7) was carried out. Most of these complexes led to decomposition, although photolysis of complex 7 with [Ph2P(CH2)nPPh2] (n=1-3) yielded complexes 9-11, [3,4-(Ph2P(CH2)nPPh 2)-closo-1,2,3,4-Ru2Fe2(BH)2] (9: n=1, 10: n=2, 11: n=3). Quantum-chemical calculations by using DFT methods were carried out on compounds 1-3 and 9-11 and showed reasonable agreement with the experimentally obtained structural parameters, that is, large HOMO-LUMO gaps, in accordance with the high stabilities of these complexes and NMR chemical shifts that accurately reflected the experimentally observed resonances. All of the new compounds were characterized in solution by using mass spectrometry, IR spectroscopy and 1H, 13C and 11B NMR spectroscopy and their structural types were unequivocally established by crystallographic analysis of complexes 1, 2, 4, 9 and 10. Love can build a bridge: The thermolysis of [M(CO)3(MeCN)3] (M=W, Mo, Cr) with an in situ generated cobaltaborane that was obtained from [{Cp*CoCl}2] and [LiBH4×THF] yielded heterometallic bridged borylenes [(μ3-BH)(Cp*Co) 2(μ-CO)M(CO)5] (see figure). © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

New Heteronuclear Bridged Borylene Complexes That Were Derived from [\{Cp*CoCl\}2] and Mono‐MetalCarbonyl Fragments

We previously reported that a novel metabolic pathway functionally catabolizes 4-hydroxy-2(E)-nonenal (HNE) via two parallel pathways, which rely heavily on β-oxidation pathways. The hypothesis driving this report is that perturbations of β oxidation will alter the catabolic disposal of HNE, favoring an increase in the concentrations of HNE and HNE-modified proteins that may further exacerbate pathology. This study employed Langendorff perfused hearts to investigate the impact of cardiac injury modeled by ischemia/reperfusion and, in a separate set of perfusions, the effects of elevated lipid (typically observed in obesity and type II diabetes) by perfusing with increased fatty acid concentrations (1 mM octanoate). During ischemia, HNE concentrations doubled and the glutathione-HNE adduct and 4-hydroxynonanoyl-CoA were increased by 7- and 10-fold, respectively. Under conditions of increased fatty acid, oxidation to 4-hydroxynonenoic acid was sustained; however, further catabolism through β oxidation was nearly abolished. The inhibition of HNE catabolism was not compensated for by other disposal pathways of HNE, rather an increase in HNE-modified proteins was observed. Taken together, this study presents a mechanistic rationale for the accumulation of HNE and HNE-modified proteins in pathological conditions that involve alterations to β oxidation, such as myocardial ischemia, obesity, and high-fat diet-induced diseases. © 2013 Elsevier Inc. All rights reserved.

Free Radical Biology and Medicine

4-Hydroxy-2(E)-nonenal (HNE) catabolism and formation of HNE adducts are modulated by β oxidation of fatty acids in the isolated rat heart

Three π-electron rich fluorescent supramolecular polymers (1-3) have been synthesized incorporating 2-methyl-3-butyn-2-ol groups in reasonable yield by employing Sonagashira coupling. They were characterized by multinuclear NMR (1H, 13C), ESI-MS and single crystal X-ray diffraction analyses [1 = 1-(2-methyl-3-butyn-2-ol)pyrene; 2 = 9,10-bis(2-methyl-3-butyn-2- ol)anthracene; 3 = 1,3,6,8-tetrakis(2-methyl-3-butyn-2-ol)pyrene]. Single crystal structures of 1-3 indicated that the incorporation of hydroxy (-OH) groups on the peripheral of the fluorophores helps them to self-associate into an infinite supramolecular polymeric network via intermolecular hydrogen bonding interactions between the adjacent discrete fluorophore units. All these compounds showed fluorescence characteristics in chloroform solution due to the extended π-conjugation and were used as selective fluorescent sensors for the detection of electron deficient nitroaromatics. The changes in photophysical properties of fluorophores (1-3) upon complex formation with electron deficient nitroaromatic explosives were studied in chloroform solution by using fluorescence spectroscopy. All these fluorophores showed the largest quenching response with moderate selectivity for nitroaromatics over various other electron deficient/rich aromatic compounds tested (Chart 1). Analysis of the fluorescence titration profile of 9,10-bis(2-methyl-3-butyn-2-ol)anthracene fluorophore (2) with 1,3,5-trinitrotoluene/2,4-dinitrotoluene provided evidence that this particular fluorophore detects nitroaromatics in the nanomolar range [2.0 ppb for TNT, 13.7 ppb for DNT]. Moreover, sharp visual color change was observed upon mixing nitroaromatic (DNT) with fluorophores (1-3) both in solution as well as in solid phase. Furthermore, the vapor-phase sensing study of thin film of fluorophores (1-3) showed efficient quenching responses for DNT and this sensing process is reproducible. Selective fluorescence quenching response including a sharp visual color change for nitroaromatics make these tested fluorophores (1-3) as potential sensors for nitroaromatic compounds with a detection limit of ppb level. © 2013 The Royal Society of Chemistry.

Fulltext

RSC Advances

Electron rich supramolecular polymers as fluorescent sensors for nitroaromatics

Recent force microscopy measurements on the mechanically activated cleavage of a protein disulfide bond through reaction with hydroxide ions revealed that for forces greater than 0.5 nN, the acceleration of the reaction rate is substantially reduced. Here, using ab initio simulations, we trace this 'reactivity switch' back to a dual role played by the mechanical force, which leads to antagonistic effects. On the one hand, the force performs work on the system, and thereby accelerates the reaction. On the other hand, the force also induces a conformational distortion that involves the S-S-C-C dihedral angle, which drives the disulfide into a conformation that is shielded against nucleophilic attack because of steric hindrance. The discovery of force-induced conformational changes that steer chemical reactivity provides a new key concept that is expected to be relevant beyond this specific case, for example in understanding how 'disulfide switches' regulate protein function and for the rational design of mechanoresponsive materials. © 2013 Macmillan Publishers Limited. All rights reserved.

Nature Chemistry

The Janus-faced role of external forces in mechanochemical disulfide bond cleavage

The FASEB Journal

Catabolism of 4‐hydroxy‐2(E)‐nonenal (HNE) via omega oxidation in perfused rat livers

The mechanism and the role of KOtBu in an enantioselective NHC-catalyzed Stetter reaction between p-chlorobenzaldehyde and N-acylamido acrylate is established using DFT(M06-2X) methods. The Gibbs free energies are found to be significantly lower for transition states with explicit bound KOtBu as compared to the conventional pathways without the counterions. An intermolecular proton transfer from HOtBu to the prochiral carbon is identified as the stereocontrolling step. The computed enantioselectivities are in excellent agreement with the experimental results. © 2013 American Chemical Society.

Organic Letters

N-heterocyclic carbene catalyzed asymmetric intermolecular stetter reaction: Origin of enantioselectivity and role of counterions

PEDIATRIC ANESTHESIA

Hypospadias surgery and locoregional anesthesia

Chemical Communications

Erratum: Chloride sensing via suppression of excited state intramolecular proton transfer in squaramides (Chemical Communications (2013) 49 (1633-1635) DOI: 10.1039/c3cc38767d)