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 the context of generating reactive organic radical cations within a confined capsule and exploring photoinduced electron transfer from encapsulated organic molecules to organic and inorganic acceptors through an organic molecular wall, we have investigated electron transfer from the upper excited state (S2) of azulene (Az) and guaiazulene (GAz) enclosed within an octa acid (OA) capsule to water-soluble 4,4′-dimethyl viologen2+ (MV2+) and pyridinium+ (Py+) salts or colloidal TiO2. S2 fluorescence of OA encapsulated Az and GAz was quenched by electron acceptors such as MV2+ and Py+ salts. That electron transfer is responsible for S2 fluorescence quenching was established by recording the transient absorption spectrum of the MVâ-+ in the femtosecond time regime. Femtosecond time-resolved fluorescence experiments suggested that the time constant for the forward and reverse electron transfer from encapsulated Az and GAz to MV2+ is 4 and 3.6 ps, and 55.7 and 36.9 ps, respectively. The observed S2 fluorescence quenching by colloidal TiO2 in aqueous buffer solution is attributed to electron transfer from encapsulated Az and GAz to TiO2. Lack of quenching by the wider band gap material ZrO2 supported the above conclusion. FT-IR-ATR experiments confirmed that OA capsules containing Az and GAz can be adsorbed on TiO2 films, and excitation of these resulted in S2 fluorescence quenching. The observations presented here are important in the context of establishing the value of OA type cavitands where charge separation and donor shielding are critical. © 2017 American Chemical Society.

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Journal of Physical Chemistry C

Ultrafast Electron Transfer from Upper Excited State of Encapsulated Azulenes to Acceptors across an Organic Molecular Wall

Self-assembly has proven to be a powerful tool for the construction of complex superstructures. The assembly of monomers into supramolecular architectures via non-covalent interactions is chiefly directed by the molecular structures, their functional groups, and environmental conditions. The principal advantage of non-covalent interactions is reversibility, which allows the assembly of monomers into supramolecular structures in situ depending on the local conditions. In addition, the supramolecular approach provides a degree of control over self-assembly at the molecular level, thereby influencing the macroscopic level and facilitating tuning of the bulk material properties. This review discusses the meritorious examples of supramolecular materials constructed through the molecular assembly process, guided by the classical principles of supramolecular chemistry. Furthermore, this year (2017) marks the 50th anniversary of supramolecular chemistry in honor of the first example of supramolecular structure reported by Charles J. Pedersen and the achievements in the area of supramolecular chemistry ever since. Many breakthrough developments in the past few decades have been achieved through multidisciplinary research. Supramolecular chemistry has played an extensive role in bridging chemical, physical, and biological sciences together. These interdisciplinary studies benefit our understanding of individual and hybrid systems. The supramolecular approach has emerged as a toolkit with remarkable capability for the assembly of rationally designed building blocks, which precisely organize in three-dimensional space to form intricate molecular assemblies as well as bulk material with functional properties. Because of such potential, supramolecular chemistry has emerged as a platform for the discovery of new systems and/or novel applications for existing ones. This field also holds great promise for advancement in the discovery of a vast array of systems that can be utilized in material chemistry, nanomaterials, soft materials, light-emitting devices, delivery agents, sensors, etc. Self-assembly of molecules through reversible noncovalent interactions has proven to be an attractive tool for the constructions of various supramolecular structures. Such methods are actively emerging as key methods for the development of novel materials for potential applications. The availability of a variety of building blocks offers endless possibilities for the construction of a wide variety of supramolecular materials. This review highlights the examples of functional materials formed through noncovalent molecular assembly process utilising supramolecular chemistry principles. © 2017 Elsevier Inc.

Fulltext

Chem

Supramolecular Chemistry: A Toolkit for Soft Functional Materials and Organic Particles

We report here a novel one-pot synthetic strategy for the synthesis of a family of N-alkyl-1,8-naphthalimide based Tröger's bases via a nucleophilic substitution reaction of a common 'precursor' (or a 'synthon') N-aryl-1,8-naphthalimide Tröger's base heated at 80 °C in neat aliphatic primary amine, in overall yield of 65-96%. This methodology provides an efficient and one-step facile route to design 1,8-naphthalimide derived Tröger's base structures in analytically pure form without the use of column chromatography purification, that can be used in medicinal chemistry and as supramolecular scaffolds. We also report the formation of the corresponding anhydride, and the crystallographic analysis of two of the resulting products, that of the N-phenyl-4-amino-1,8-naphthalimide and the anhydride derived Tröger's bases. © 2017 The Royal Society of Chemistry.

Organic and Biomolecular Chemistry

One-pot facile synthesis of 4-amino-1,8-naphthalimide derived Tröger's bases: Via a nucleophilic displacement approach

In this work, we report the synthesis and electrode applications of iron-carbon nanohybrid particles prepared by carbonization of a nanocomposite of FeOOH nanoneedles and melamine-formaldehyde resin. The chemical composition and microstructure of the material have been characterized using ICP-AES, FT-IR, XRD, FESEM, TEM and XPS. The supercapacitor properties of the MF-Fe-C are studied in detail. A thorough comparison of the supercapacitor performances of MF-Fe-C and bare MF-C has been carried out through detailed electrochemical characterisations employing both two and three-electrode techniques. The nanohybrid showed an enhanced energy density of 127.75 WhKg−1, specific capacitance of ∼408 F g−1 at 1 mVs−1 scan rate, and excellent cyclic stability even after 1000 charge-discharge cycles, making it an intriguing material for high energy density supercapacitor devices. [Figure not available: see fulltext.] © 2017, Springer-Verlag Berlin Heidelberg.

Journal of Solid State Electrochemistry

Iron-carbon nanohybrid particles as environmentally benign electrode for supercapacitor

Development of sustainable catalytic systems for fundamentally important synthetic transformations and energy storage applications is an intellectually stimulating challenge. Catalytic dehydrogenation of feedstock chemicals, such as alcohols and amines to value-Added products with the concomitant generation of dihydrogen is of much interest in the context of hydrogen economy and is an effective alternative to the classical oxidation reactions. Despite a number of homogeneous catalysts being identified for the acceptorless dehydrogenation, the use of high price and limited availability of precious metals and poor recovery of the catalyst have spurred interest in catalysis with more earth-Abundant alternatives, especially iron. However, no report has described a reusable iron-based heterogeneous catalyst for oxidant-free and acceptorless dehydrogenation reactions. Here we replace expensive noble metal catalysts with an inexpensive, benign, and sustainable nanoscale iron catalyst for the efficient acceptorless dehydrogenation of N-heterocycles and alcohols with liberation of hydrogen gas. © 2017 The Author(s).

Nature Communications

Iron-based nanocatalyst for the acceptorless dehydrogenation reactions

Mycotoxin are small (MW ~700 Da), toxic secondary metabolites produced by fungal species that readily colonize crops and contaminate them at both pre- and post-harvesting. Among all, aflatoxins (AFs) are mycotoxins of major significance due to their presence in common food commodities and the potential threat to human health worldwide. Based on the severity of illness and increased incidences of AFs poisoning, a broad range of conventional and analytical detection techniques that could be useful and practical have already been reported. However, due to the variety of structural analogous of these toxins, it is impossible to use one common technique for their analysis. Numerous recent research efforts have been directed to explore alternative detection technologies. Recently, immunosensors and aptasensors have gained promising potential in the area of sample preparation and detection systems. These sensors offer the advantages of disposability, portability, miniaturization, and on-site analysis. In a typical design of an aptasensor, an aptamer (ssDNA or RNA) is used as a bio-recognition element either integrated within or in intimate association with the transducer surface. This review paper is focused on the recent advances in electrochemical immunoand aptasensing platforms for detection of AFs in real samples. © 2017 by the authors.

Chemosensors

Recent advances in electrochemical-based sensing platforms for aflatoxins detection

A series of N,O-ketimine supported gallium and digallane complexes have been synthesized and structurally characterized. The mono(ketiminate) gallium dichloride [OCMeCHCMeN(Dipp)]GaCl2, 2 (Dipp=2,6-iPr2C6H3) and bis(ketiminate) gallium chloride [OCMeCHCMeN(Dipp)]2GaCl, 3 were isolated from the reaction of GaCl3 with 1 and 2 equivalents of lithiated ketimine, [OCMeCHCMeN(Dipp)]Li, 1 respectively. Treatment of 1 with ‘‘GaI’’ yielded diiodobis(ketiminate) digallane complex [OCMeCHCMeN-(Dipp)]2Ga2I2, 4. To the best of our knowledge, compound 4 is the first report on N,O-ketiminate ligand supported stable heteroleptic digallane(II) complex. The frontier molecular orbital analysis and a high Wiberg Bond Index (WBI) values support the strong interaction between the gallium centers in 4. In an attempt to synthesize alkyl substituted Ga complexes, we carried out the reaction of ketimine ligand with GatBu2Cl (1:1 ratio) that generated the adduct [OCMeCHCMeN(H)(Dipp)]GatBu2Cl, 5. In a similar fashion, dialkyl gallium complex [OCMeCHCMeN(Dipp)]GatBu2, 6 was obtained from the reaction of 1 with GatBu2Cl. All the compounds have been charecterized by 1H, 13C NMR and mass spectroscopy. The molecular structures of complexes 2–5 have also been determined by single crystal X-ray diffraction analysis. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

ChemistrySelect

Synthesis, Structure and Chemistry of Mono‐ and Digallane Complexes Supported by N,O‐Ketimine Ligand

A versatile and cost-effective aptamer-based fluorescence quenching assay is described for the detection of the mycotoxin zearalenone (ZEN). Exfoliated functional graphene oxide (FGO) of high water-dispersibility is adopted as an effective fluorescence quencher of the fluorescence of FAM. Quenching properties of graphite, graphene oxide (GO) and FGO were investigated, and FGO is found to be the most efficient quencher. FGO therefore was used in an aptamer-based detection format that allows ZEN to be determined in the concentration range of 0.5 to 64 ng·mL−1 with a limit of detection of 0.5 ng·mL−1. The aptamer assay has good repeatability and reproducibility (n ≥ 4). Selectivity of the aptamer assay against a set of possible interferents is substantiated. This aptasensing assay was successfully applied to the determination of ZEN in (spiked) alcoholic beverage samples, beer and wine, and recovery values in the range of 87 to 96% were obtained for the determination of ZEN at levels as low as 1–16 ng mL−1. [Figure not available: see fulltext.]. © 2017, Springer-Verlag GmbH Austria.

Microchimica Acta

Aptamer-based zearalenone assay based on the use of a fluorescein label and a functional graphene oxide as a quencher

In response to the urgent need for new antibiotic development strategies, antimicrobial peptides (AMPs) and other synthetic polymers are being actively investigated as promising alternatives to traditional antibiotics. Although most AMPs display lytic activity against several types of bacteria, they have poor toxicology profiles and are susceptible to proteolysis in vivo. While many synthetic variants have been created to mimic AMPs by tuning the hydrophobic to cationic ratio of the side-chain groups, few have decoupled the effects of charge from hydrophobicity in discrete systems, and none have investigated the effect of backbone hydrophobicity. We recently developed a rapid and efficient approach for the assembly of synthetic sequence-defined oligothioetheramides (oligoTEAs) that are resistant to protease activity. Our oligoTEA assembly scheme allows direct access to the oligomer backbone, which enables precise tuning of oligoTEA hydrophobicity while keeping charge constant. In this study, we synthesized a new class of antibacterial oligoTEAs (AOTs) with precise control over backbone hydrophobicity and composition. Our studies suggest that AOTs lyse cells via membrane permeabilization and that hydrophobicity and macromolecular conformation are key properties that regulate AOT activity. Some of our AOTs show highly promising antibacterial activity (MIC 0.5-5 μM) against clinically relevant pathogens in the presence of serum, with little to no toxicity against RBCs and HEK293 cells. Taken together, our data identify design parameters and criteria that may be useful for assembling the next generation of potent and selective AOTs. © 2017 American Chemical Society.

ACS Chemical Biology

Sequence-Defined Backbone Modifications Regulate Antibacterial Activity of OligoTEAs

The reaction of carbon dioxide with α-siloxy silanes assisted by cesium fluoride is studied by means of DFT calculations with the B97D functional. Different mechanistic models are examined, including explicit introduction of cationic counterions and solvent molecules. The reaction is confirmed to proceed through carbanionic intermediates generated by Brook rearrangement, a carbon-to-oxygen transfer of a silyl group. The cesium cation is shown to play a critical role in stabilizing the key transition state. © 2017, Springer-Verlag Berlin Heidelberg.