Faculty Publications
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Item Entropy stabilized multicomponent oxides with diverse functionality–a review(Taylor and Francis Ltd., 2022) Salian, A.; Mandal, S.Over the last few years, high-entropy oxides (HEOs) are subjected to considerable scientific scrutiny due to their exceptional characteristics, tunable properties displaying remarkable performance including colossal dielectric constant, low electrical and thermal conductivity, high-temperature phase stability, excellent magnetic, structural optical properties and extraordinary catalytic behavior. The single-phase crystal structure of multicomponent oxides is stabilized via configurational entropy (S config). An incrementation in the number of elements magnifies S config which dominates the free energy landscape, overcomes enthalpy in Gibb’s free energy, and reaches a maximum magnitude while entire elements are in equiatomic fractions. Therefore, accurate control of configurational entropy is the main motive force used to achieve phase pure HEOs by the incorporation of more than four cations in the system in equiatomic proportions with random distributions. HEOs are becoming hotcakes in the field of research as it emphasizes on compositions proximally near the centers of the multicomponent phase diagram, where unexpected behaviors can be anticipated. Thus, presenting a crucial research frontier for the material scientists to explore. As the novel design approach of entropy stabilization is still immature, these new oxide candidates can be engineered for practical applications in batteries, capacitors, nuclear reactors, and thermal barrier coatings. This review addresses the properties like electrochemical, electrical, magnetic, mechanical, catalytic, thermal, etc., of HEOs to date, with additionally focusing on their classification, theoretical predictions, and fundamental understanding of entropy engineering including entropy dominated phase stabilization effect. © 2021 Taylor & Francis Group, LLC.Item Supramolecular synthons in noncovalent synthesis of a class of gelators derived from simple organic salts: Instant gelation of organic fluids at room temperature via in situ synthesis of the gelators(2009) Das, U.K.; Trivedi, D.R.; Adarsh, N.N.; Dastidar, P.(Chemical Equation Presented) The supramolecular synthon approach has been employed to synthesize noncovalently a series of low molecular mass organic gelators (LMOGs) derived from benzylammonium salts of variously substituted benzoic acids. The majority of the salts (75%) prepared showed interesting gelation properties. Instant gelation of an organic fluid, namely methyl salicylate, was achieved at room temperature by using most of the gelator salts by in situ synthesis of the gelators. Table top rheology and scanning electron microscopy (SEM) were used to characterize the gels. Single crystal X-ray diffraction studies revealed the presence of both 1D and 2D supramolecular synthons. X-ray powder diffraction (XRPD) studies indicated the presence of various crystalline phases in the fibers of the xerogels. By using these data, a structure-property correlation has been attempted and the working hypothesis for designing the gelator has been reinforced. © 2009 American Chemical Society.Item Synthesis, crystal structure, and spectral analysis of antimony thiourea tetra chloride(2010) Mahesha Upadhya, K.; Udayashankar, N.K.The synthesis of antimony thiourea tetra chloride (ATTC) single crystals by solution technique at room temperature is reported. The complex crystallizes in the orthorhombic space group Pnma with four formula units ofSb[CS(NH 2)2]2Cl3·Cl in the unit cell. The structure has been solved by direct methods and refined to a final-R value of 0.0393. The synthesized crystals are characterized by FT-IR, UV-visible and TGA-DTA techniques. Copyright © Taylor & Francis Group, LLC.Item Synthesis, characterization and antimicrobial activity of novel ethyl 1-(N-substituted)-5-phenyl-1H-pyrazole-4-carboxylate derivatives(2012) Chandrakantha, B.; Isloor, A.M.; Shetty, P.; Isloor, S.; Malladi, S.; Fun, H.-K.In the present study, a novel series of Pyrazole derivatives (3a-m) were synthesized by condensing ethyl-3-(dimethylamino)-2-(phenylcarbonyl)prop-2- enoate with different aromatic and aliphatic hydrazines. These newly synthesized compounds were characterized by NMR, mass spectral, IR spectral studies as well as by C, H, and N analyses. All the newly synthesized compounds were screened for their antibacterial properties against Staphylococcus aureus, Bacillus subtilis, Escherichia coli, and Pseudomonas aeruginosa. Among the screened samples, 3c, 3f, 3k, and 3l have showed excellent antibacterial activity against all the tested bacterial strains as compared to the standard drug Ceftriaxone. Few of the compounds were found to be biologically potent. Molecular structure of compound 3i was confirmed by single crystal X-ray analysis. © Springer Science+Business Media, LLC 2011.Item Synthesis and anti-inflammatory evaluation of some new 3,6-disubstituted-1, 2,4-triazolo-[3,4-b]-1,3,4-thiadiazoles bearing pyrazole moiety(2012) Malladi, S.; Isloor, A.M.; Shetty, P.; Fun, H.-K.; Telkar, S.; Mahmood, R.; Isloor, N.In the present study, a new series of 3,6-disubstituted- 1,2,4-triazolo-[3,4-b]-1,3,4-thiadiazoles (4aj) have been synthesized by condensing 3-substituted-4-amino-5- mercapto-1,2,4-triazoles (1a-b) with various 3-substitutedpyrazole- 4-carboxylic acids (3a-e) in the presence ofPOCl3. The structures of newly synthesized compounds were characterized by elemental analysis, IR, 1H NMR, 13CNMR, and mass spectroscopic studies. Structure of the compound 4b was also confirmed by recording the single crystal X-ray structure. All the synthesized compounds were screened for their anti-inflammatory activities by carrageenan induced paw edema method. Anti-inflammatory screening indicated that, compounds 4d, 4e, and 4h were found to be biologically active whereas remaining compounds showed poor antiinflammatory activity. Also molecular docking studies were also performed for compounds which showed good antiinflammatory activity. © Springer Science+Business Media, LLC 2011.Item Synthesis, structural analysis and solvatochromic behaviour of 4,6-bis (4-butoxyphenyl)-2-methoxynicotinonitrile mesogen(2013) Ahipa, T.N.; Kumar, V.; Vasudeva Adhikari, A.V.In this communication, we report the synthesis and characterisation of a new luminescent liquid crystalline material, 4,6-bis (4-butoxyphenyl)-2-methoxynicotinonitrile (3). We have confirmed its structure by Fourier transform infrared and 1H nuclear magnetic resonance spectroscopy, elemental analysis and X-ray single crystal diffraction studies. The newly synthesised compound crystallises in a monoclinic system with the space group C2/c and its cell parameters are found to be a = 25.181(4) Å, b = 15.651(4)Å, c = 12.703(19) Å, V = 4880.4 (16) Å, Z = 8. The results indicate that the presence of weak CH... O and CH... N hydrogen bonding as short-range intermolecular interactions are responsible for the formation of its crystal assembly. The measured torsion angle shows the existence of a distorted structure for the molecule wherein 4-butoxyphenylene ring substituent at the fourth position of the central pyridine ring forms a torsion angle ?[C(4), C(3), C(10), C(19)] of 40.55°. Its liquid crystalline behaviour was investigated with the aid of polarised optical microscopy and differential scanning calorimetry. The study reveals that the compound displays a broad nematic phase in the range of 78-112°C. Further, solution phase optical studies indicate that it is a blue light emitter in different non-polar and polar organic solvents at a concentration of 10-5M. © 2013 Copyright Taylor and Francis Group, LLC.Item Design and regioselective synthesis of trifluoromethylquinolone derivatives as potent antimicrobial agents(Elsevier Masson SAS infos@masson.fr 62 rue Camille Desmoulins Issy les Moulineaux Cedex 92442, 2013) Garudachari, B.; Isloor, A.M.; Satyanarayana, M.N.; Fun, H.-K.; Pavithra, N.; Kulal, A.Three series of new trifluoromethyl substituted quinolone derivatives were synthesized (4a-f, 6a-f and 8a-f) from corresponding substituted anilines by multi-step reactions. The regioselective alkylation with different alkyl halides were carried out by approaching two different routes to get the final products in good yield. Newly synthesized compounds were characterized by spectral study and also by C, H, N analyses. Three dimensional structure of 2b and 4b were also confirmed by single crystal X-ray studies. The final compounds (4a-f, 6a-f and 8a-f) were screened for their in-vitro antibacterial and antifungal activity by well plate method (zone of inhibition). The results revealed that, compounds 4a, 6b, 6c and 8e showed significant antibacterial activity as compared to the standard drug Ciprofloxacin. The compound 8a was found to be a potent antifungal agent. © 2013 Elsevier Masson SAS. All rights reserved.Item 2-Methoxypyridine derivatives: Synthesis, liquid crystalline and photo-physical properties(Royal Society of Chemistry, 2014) Ahipa, T.N.; Vasudeva Adhikari, A.V.We herein report the design and synthesis of fourteen new bent shaped luminescent mesogens carrying a pyridine core substituted with various polar groups. They possess a slightly non-planar bent conformation with various intermolecular interactions, as evidenced by their single crystal X-ray diffraction study, and exhibit an ambient to elevated temperature liquid crystalline phase (N or Colr), which has been confirmed by differential scanning calorimetry, polarized optical microscopy, and powder X-ray diffraction techniques. In these compounds, the nature of polar substituents influences significantly the formation of the mesophase over a wide thermal range. The appearance of the nematic phase is due to the presence of the lateral CN group attached to the pyridine core and the terminal F or Cl substituent. The formation of a rectangular columnar phase is attributed to the absence of the lateral CN group in the pyridine core and the presence of the terminal Br, NO2 or 4-pyridyl group. © 2014 The Royal Society of Chemistry and the Centre National de la Recherche Scientifique.Item Structure-property relationship of sol-gel electrospun ZnO nanofibers developed for ammonia gas sensing(Academic Press Inc. apjcs@harcourt.com, 2014) Senthil, T.; Anandhan, S.Zinc oxide (ZnO) based nanomaterials have been used in various gas sensors due to the wide band gap (3.37. eV), large exciton binding energy and high mobility of charge carriers of ZnO. In this work, nanocrystalline ZnO nanofiber mats were synthesized through combined sol-gel electrospinning techniques followed by calcination, in which poly(styrene- co-acrylonitrile) and zinc acetate were used as the binder and precursor, respectively. Average diameter of the ZnO nanofibers decreased from 400 to 60. nm, while their grain size and crystallinity were enhanced by increasing the calcination temperature. Morphology and structure of the ZnO nanofiber mats were characterized by high resolution transmission electron microscopy, scanning electron microscopy, Fourier transform infrared spectroscopy and X-ray diffraction. ZnO nanofiber mats were found to be superhydrophilic (contact angle was close to 0°) by contact angle measurements. The sensitivity of these ZnO nanofibers in detecting gaseous ammonia was tested using an indigenous set up. Due to their high surface area and superhydrophility, these ZnO nanofiber mats were highly sensitive in sensing gaseous ammonia and the sensitivity of these mats increased as a function of their calcination temperatures. © 2014 Elsevier Inc.Item One-pot synthesis of new triazole - Imidazo[2,1-b][1,3,4]thiadiazole hybrids via click chemistry and evaluation of their antitubercular activity(Elsevier Ltd, 2015) Ramprasad, J.; Nayak, N.; Udayakumar, U.; Yogeeswari, P.; Sriram, D.A new series of triazole-imidazo[2,1-b][1,3,4]thiadiazole hybrids (6a-s, 7a) were designed by a molecular hybridisation approach and the target molecules were synthesized via one pot click chemistry protocol. All the intermediates and final molecules were characterised using spectral methods and one of the target compounds (6c) was analysed by the single crystal XRD study. The derivatives were screened for their antimycobacterial activity against Mycobacterium tuberculosis H37Rv strain. Two compounds, 6f and 6n, demonstrated significant growth inhibitory activity against the bacterial strain with a MIC of 3.125 ?g/mL. The presence of chloro substituent on the imidazo[2,1-b][1,3,4]thiadiazole ring and ethyl, benzyl or cyanomethylene groups on the 1,2,3-triazole ring enhance the inhibition activity of the molecules. The active compounds are not toxic to a normal cell line which signifies the lack of general cellular toxicity of these compounds. © 2015 Elsevier Ltd. All rights reserved.