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

Interest in the applicability of fluctuation theorems to the thermodynamics of single molecules in external potentials has recently led to calculations of the work and total entropy distributions of Brownian oscillators in static and time-dependent electromagnetic fields. These calculations, which are based on solutions to a Smoluchowski equation, are not easily extended to a consideration of the other thermodynamic quantity of interest in such systems - the heat exchanges of the particle alone - because of the nonlinear dependence of the heat on a particle's stochastic trajectory. In this paper, we show that a path integral approach provides an exact expression for the distribution of the heat fluctuations of a charged Brownian oscillator in a static magnetic field. This approach is an extension of a similar path integral approach applied earlier by our group to the calculation of the heat distribution function of a trapped Brownian particle, which was found, in the limit of long times, to be consistent with experimental data on the thermal interactions of single micron-sized colloids in a viscous solvent. © 2011 IOP Publishing Ltd and SISSA.

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Journal of Statistical Mechanics: Theory and Experiment

Single-molecule thermodynamics: The heat distribution function of a charged particle in a static magnetic field

Calcium levulinate (4-ketopentanoate) is used as an oral and parenteral source of calcium. We hypothesized that levulinate is converted in the liver to 4-hydroxypentanoate, a new drug of abuse, and that this conversion is accelerated by ethanol oxidation. We confirmed these hypotheses in live rats, perfused rat livers, and liver subcellular preparations. Levulinate is reduced to (R)-4-hydroxypentanoate by a cytosolic and a mitochondrial dehydrogenase, which are NADPH- and NADH-dependent, respectively. A mitochondrial dehydrogenase or racemase system also forms (S)-4-hydroxypentanoate. In livers perfused with [13C5]levulinate, there was substantial CoA trapping in levulinyl-CoA, 4-hydroxypentanoyl-CoA, and 4-phosphopentanoyl-CoA. This CoA trapping was increased by ethanol, with a 6-fold increase in the concentration of 4-phosphopentanoyl-CoA. Levulinate is catabolized by 3 parallel pathways to propionyl-CoA, acetyl-CoA, and lactate. Most intermediates of the 3 pathways were identified by mass isotopomer analysis and metabolomics. The production of 4-hydroxypentanoate from levulinate and its stimulation by ethanol is a potential public health concern. © 2011 by The American Society for Biochemistry and Molecular Biology, Inc.

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Journal of Biological Chemistry

Metabolism of levulinate in perfused rat livers and live rats: Conversion to the drug of abuse 4-hydroxypentanoate

To study defect origin of ferromagnetism, hollow spheres are better candidates as they are less agglomerated and has both sides of the wall free, as compared to nanoparticles and thin films respectively. Our results show improved magnetic properties of GaN, ZnAl2O4 and MgO hollow spheres over their earlier reported nanoparticle counterparts. Photoluminescence spectroscopy supports our magnetic findings. © 2011 Elsevier B.V. All rights reserved.

Chemical Physics Letters

Ferromagnetism in thin-walled hollow spheres of non-magnetic inorganic materials

The role played by polyethylene-like oligomers in transducing external tensile forces to benzocyclobutene mechanophores is investigated computationally. It is demonstrated that the oligomer chains do indeed exert a notable influence on the force dependence of the activation energies of both conrotatory and disrotatory ring-opening processes of a cis 1,2-disubstituted benzocyclobutene. This opens the doorway to tuning the properties of mechanoresponsive materials not only by changing the properties of the mechanophore itself, but also by tailoring the force-transducing chain molecules attached to it. Furthermore, it is found that these chains even have a profound impact on the topology of the force-transformed potential energy surface in the vicinity of conrotatory transition states. Hitherto unexpected and most striking is the phenomenon that some of these conrotatory transition states are found to drive the system to disrotatory products. © 2011 The Royal Society of Chemistry.

Journal of Materials Chemistry

On the role of polymer chains in transducing external mechanical forces to benzocyclobutene mechanophores

Ultrafast photoinduced electron transfer (PET) from N,N-dimethylaniline (DMA) to coumarin dyes in a room-temperature ionic liquid (RTIL, [pmim][BF 4]) and in a mixed micelle containing the RTIL and a triblock copolymer, (PEO)20-(PPO)70-(PEO)20, (Pluronic P123) is studied using femtosecond upconversion. A Marcus-like inversion in the rate of PET is observed in neat RTIL. This is attributed to high viscosity and nanostructuring of the RTIL. Diffusion and the rate of PET in the neat RTIL are slower than those in the RTIL-P123 mixed micelle. The coumarin dyes exhibit faster electron transfer and translational diffusion (anisotropy decay) in the RTIL-P123 mixed micelle compared to that in the P123 micelle. © 2011 American Chemical Society.

Journal of Physical Chemistry B

Marcus-like inversion in electron transfer in neat ionic liquid and ionic liquid-mixed micelles

Several π-electron rich fluorescent aromatic compounds containing trimethylsilylethynyl functionality have been synthesized by employing Sonogashira coupling reaction and they were characterized fully by NMR ( 1H, 13C)/IR spectroscopy. Incorporation of bulky trimethylsilylethynyl groups on the peripheral of the fluorophores prevents self-quenching of the initial intensity through π-π interaction and thereby maintains the spectroscopic stability in solution. These compounds showed fluorescence behavior in chloroform solution and were used as selective fluorescence sensors for the detection of electron deficient nitroaromatics. All these fluorophores showed the largest quenching response with high selectivity for nitroaromatics among the various electron deficient aromatic compounds tested. Quantitative analysis of the fluorescence titration profile of 9,10-bis(trimethylsilylethynyl)anthracene with picric acid provided evidence that this particular fluorophore detects picric acid even at ppb level. A sharp visual detection of 2,4,6-trinitrotoluene was observed upon subjecting 1,3,6,8-tetrakis(trimethylsilylethynyl)pyrene fluorophore to increasing quantities of 2,4,6-trinitrotoluene in chloroform. Furthermore, thin film of the fluorophores was made by spin coating of a solution of 1.0 × 10 -3 M in chloroform or dichloromethane on a quartz plate and was used for the detection of vapors of nitroaromatics at room temperature. The vapor-phase sensing experiments suggested that the sensing process is reproducible and quite selective for nitroaromatic compounds. Selective fluorescence quenching response including a sharp visual color change for nitroaromatics makes these fluorophores as promising fluorescence sensory materials for nitroaromatic compounds (NAC) with a detection limit of even ppb level as judged with picric acid. © 2011 The Royal Society of Chemistry.

Fluorescence and visual sensing of nitroaromatic explosives using electron rich discrete fluorophores

Fluorescence correlation spectroscopy (FCS) has been used to study the formation of large nanotube aggregates involving γ-cyclodextrin (γ-CD) and coumarin 153 (C153). It is observed that the length of a γ-CD:C153 nanotube aggregate is ∼770 nm. This is ∼480 times larger than the length of a 1:1 γ-CD:C480 complex (∼1.6 nm) and ∼950 times that of a γ-CD. This implies that 950 γ-CD units are noncovalently attached in the γ-CD:C153 aggregate. Binding constants (Kb) of both the dyes to γ-CD were obtained from the fluctuation in fluorescence intensity. The rate of association and dissociation are obtained from the inverse of τoff and τon, respectively. The binding constant for the 1:1 γ-CD:C480 complex is ∼1000 M-1. The burst integrated fluorescence lifetime (BIFL) histogram reveals presence of three distinct lifetime 1.8 ns (18%), 2.8 ns (69%), 3.2 ns (13%). These three lifetimes correspond to C153 present in bulk water and at the end and middle of the γ-CD:C153 nanotube aggregate, respectively. The lifetime of C480 in the 1:1 γ-CD:C480 complex is found to be 3.7 ns. © 2011 American Chemical Society.

Study of γ-cyclodextrin host-guest complex and nanotube aggregate by fluorescence correlation spectroscopy

The effect of a room temperature ionic liquid (RTIL) on the conformational dynamics of a protein, human serum albumin (HSA), is studied by fluorescence correlation spectroscopy (FCS). For this, the protein was covalently labeled by a fluorophore, 7-dimethylamino-3-(4-maleimidophenyl)-4-methylcoumarin (CPM). On addition of a RTIL ([pmim][Br]) to the native protein, the diffusion coefficient (Dt) decreases and the hydrodynamic radius (Rh) increases. This suggests that the RTIL ([pmim][Br]) acts as a denaturant when the protein is in the native state. However, addition of [pmim][Br] to a protein denatured by GdnHCl causes an increases in Dt and decrease in R h. This suggests that in the presence of GdnHCl addition of RTIL helps the protein to refold. In the native state, the conformational dynamics of protein is described by three distinct time constants: ∼3.6 ± 0.7, ∼29 ± 4.5, and 133 ± 23 μs. The faster components (∼3.6 ± 0.7 and ∼29 ± 4.5 μs) are ascribed to chain dynamics of the protein, while the slowest component (133 μs) is responsible for interchain interaction or concerted motion. On addition of [pmim][Br], the conformational dynamics of HSA becomes slower (∼5.1 ± 1, ∼43.5 ± 2.8, and ∼311 ± 2.3 μs in the presence of 1.5 M [pmim][Br]). The time constants for the protein denatured by 6 M GdnHCl are 3.2 ± 0.4, 34 ± 6, and 207 ± 38 μs. When 1.5 M [pmim][Br] is added to the denatured protein (in 6 M GdnHCl), the time constants become ∼5 ± 1, ∼41 ± 10, and ∼230 ± 45 μs. The lifetime histogram shows that, on addition of GdnHCl to HSA, the contribution of the shorter lifetime component decreases and vanishes at 6 M GdnHCl. The shorter lifetime component immediately reappears after addition of RTIL to unfolded HSA. This suggests recoiling of the unfolded protein by RTIL. © 2011 American Chemical Society.

An FCS study of unfolding and refolding of CPM-labeled human serum albumin: Role of ionic liquid

Synthesis of a series of two-dimensional metallamacrocycles via coordination-driven self-assembly of a shape-selective PtII 2-molecular building unit incorporating carbazole-ethynyl functionality is described. An equimolar (1:1) combination of a Pt II2-organometallic 90° acceptor, 1, with rigid linear ditopic donors (La and Lb) afforded [4 + 4] self-assembled octanuclear molecular squares, 2 and 3, in quantitative yields, respectively [La = 4,4′-bipyridine; Lb = trans-1,2-bis(4-pyridyl) ethylene]. Conversely, a similar treatment of 1 with an amide-based unsymmetrical flexible ditopic donor, Lc, resulted in the formation of a [2 + 2] self-sorted molecular rhomboid (4a) as a single product [L c = N-(4-pyridyl)isonicotinamide]. Despite the possibility of several linkage isomeric macrocycles (rhomboid, triangle and square) due to the different connectivity of Lc, the formation of a single and symmetrical molecular rhomboid (4a) as the only product is an interesting observation. All the self-assembled macrocycles (2, 3 and 4a) were fully characterized by multinuclear NMR (1H and 31P) and ESI-MS analysis. Further structural insights about the size and shape of the macrocycles were obtained through energy minimization using density functional theory (DFT) calculations. Decoration of the starting carbazole building unit with Pt-ethynyl functionality enriches the assemblies to be more π-electron rich and luminescent in nature. Macrocycles 2 and 3 could sense the presence of electron deficient nitroaromatics in solution by quenching of the initial intensity upon gradual addition of picric acid (PA). They exhibited the largest quenching response with high selectivity for nitroaromatics compared to several other electron deficient aromatics tested. © 2011 The Royal Society of Chemistry.

Dalton Transactions

Coordination-driven self-assembly of 2D-metallamacrocycles using a shape-selective PtII2-organometallic 90° acceptor: Design, synthesis and sensing study

Design and synthesis of three novel [2 + 2] self-assembled molecular rectangles 1-3via coordination driven self-assembly of predesigned Pd(ii) ligands is reported. 1,8-Diethynylanthracene was assembled with trans-Pd(PEt3)2Cl2 in the presence of CuCl catalyst to yield a neutral rectangle 1via Pd-C bond formation. Complex 1 represents the first example of a neutral molecular rectangle obtained via C-Pd coordination driven self-assembly. A new Pd2II organometallic building block with 180° bite-angle 1,4-bis[trans-(ethynyl) Pd(PEt3)2(NO3)]benzene (M2) containing ethynyl functionality was synthesized in reasonable yield by employing Sonagashira coupling reaction. Self-assembly of M2 with two organic clip-type donors (L2-L3) afforded [2 + 2] self-assembled molecular rectangles 2 and 3, respectively [L2 = 1,8-bis(4-pyridylethynyl)anthracene; L3 = 1,3-bis(3-pyridyl) isophthalamide]. The macrocycles 1-3 were fully characterized by multinuclear NMR and ESI-MS spectroscopic techniques, and in case of 1 the structure was unambiguously determined by single crystal X-ray diffraction analysis. Incorporation of Pd-ethynyl bonds helped to make the assemblies π-electron rich and fluorescent in nature. Complexes 1-2 showed quenching of fluorescence intensity in solution in presence of nitroaromatics, which are the chemical signatures of many commercially available explosives. © 2011 The Royal Society of Chemistry.