A solid hybrid molecular material containing 1-butyl 3-methyl imidazolium cations and Keggin anions of phosphotungstic acid has been synthesized. It is fully characterized by CHN analysis, FTIR, XRD, UV-Vis-NIR DRS, 31P MAS NMR, TGA and SEM. The FTIR spectrum of the compound shows the fingerprint vibrational bands of both Keggin molecular anions and imidazolium cations. The aromatic C-H stretch region (2700-3250 cm-1) of imidazolium cation is split due to the interaction between the ring C-H and bulky Keggin anion. The red-shift in the UV-Vis spectra and the downfield 31P MAS NMR chemical shift also confirm the electrostatic interaction between the ions in the compound. Near IR spectral region (1000-2500 nm) shows the elimination of water in the compound which is hydrophobic. © Indian Academy of Sciences.

Gangavarapu Ranga Rao

Department Of Chemistry

1-BUTYL 3-METHYL IMIDAZOLIUM BROMIDE

CHN ANALYSIS

Electrostatic interactions

FTIR SPECTRUMS

HYBRID MOLECULAR MATERIALS

IMIDAZOLIUM CATIONS

KEGGIN ANIONS

MAS-NMR

MOLECULAR ANIONS

MOLECULAR MATERIAL

NEAR IR

PHOSPHOTUNGSTIC ACID

PHOSPHOTUNGSTIC ACIDS

POLYOXOMETALATE ANIONS

vibrational bands

Acids

Flow interactions

Fourier transform infrared spectroscopy

Ionic liquids

Ionization of liquids

Negative ions

nuclear magnetic resonance

Nuclear magnetic resonance spectroscopy

Positive ions

Reconnaissance aircraft

SULFUR COMPOUNDS

Ions

Fulltext

IIT Madras is a public technical and research university located in Chennai, Tamil Nadu. Founded in 1959, it is recognised as an Institute of National Importance.

IIT Madras has been ranked as the top engineering institute in India for four years in a row by the National Institutional Ranking Framework of the MHRD

It currently offers undergraduate, postgraduate and research degrees across 16 disciplines in Engineering, Sciences, Humanities and Management. About 596 faculty belonging to science and engineering departments and centres of the Institute are engaged in teaching, research and industrial consultancy.

IIT Madras

Journal of Chemical Sciences

Abstract: Polyoxometalate (POM) based gels are synthesized by reacting POMs with an excess of caprolactam. These POM-entrapped caprolactam gels are thermoreversible and possess good mechanical strength. The gelation of POMs in caprolactam matrix brought the gel acidity similar to the physiological pH. The cytotoxicity studies on SCC 131 cell lines using these gels show 50% of cell death in the range of 2 to 6 mM concentration in 48 h. The supramolecular caprolactam matrix with active protons and the redox property of POMs are responsible for the cytotoxicity effect. Graphical Abstract: SYNOPSIS Two thermoreversible, hydrophilic gels containing Keggin-type polyoxometalates are synthesized by gradually increasing the caprolactam to polyoxometalate mole ratio. They both have physiological pH and show cytotoxicity effect on SCC 131 head and neck cancer cell lines within 24 hours.[Figure not available: see fulltext.] © 2018, Indian Academy of Sciences.

Polyoxometalate entrapped caprolactam gels and their cytotoxicity study

Polyoxometalate-based materials are gaining importance in the fields of heterogeneous catalysis and materials chemistry. In this context, we have synthesized (H(CL)2)3PMo and (H(CL)2)3PW novel hybrid materials using phosphomolybdic acid (PMoA) and phosphotungstic acid (PWA) as a source of Keggin anions, respectively, and ε-caprolactam (CL). The caprolactam molecules have undergone lactam–lactim tautomerisation in the presence of heteropolyacids forming cationic dimers. The hybrid materials are characterized by FTIR, XRD analyses, TGA, DSC, SEM and UV–DRS techniques. From single crystal X-ray analysis of (H(CL)2)3PMo, we find that the protonated caprolactam dimers replaced the protonated water molecules (H5O2+) from hexahydrated state of heteropolyacids. These materials show increased band gaps in the semiconducting region, due to decrease in the crystallite size. The cyclic voltammograms recorded by immobilizing these materials on 6 mm glassy carbon electrodes have shown three consecutive two-electron redox couples. © 2017 Elsevier Ltd

Polyhedron

Hydrophobic supramolecular assemblies of Keggin anions with lactam-lactim cationic tautomers

12-Tungstophosphoric acid supported on montmorillonite K10 (PWA/mont-K10) catalysed Pechmann condensation reaction was reported. The catalyst was characterized by XRD, FTIR, UV-Vis DRS, surface area and pore size analysis, TGA and acidity by DRIFTS using pyridine. The morphology of the catalyst was studied by SEM. The activity of mont-K10, mont-KSF, SO 2- 4/ZrO 2, 12-tungstophosphoric acid, and PWA/mont-K10 was investigated by condensation reaction of resorcinol with ethyl acetoacetate in the absence of solvent. Effect of molar ratio, amount of catalyst, reaction temperature and time on the yield of 7-hydroxy-4-methylcoumarin had been investigated on PWA/mont-K10. PWA/mont-K10 catalysed condensation of ethyl acetoacetate with phenol and a few substituted phenols had also been carried out to yield corresponding coumarins. The recycled catalyst showed reduced activity after single use. 15 wt% PWA on mont- K10 was found to be effective for synthesis of coumarin derivatives without employing any solvent. © Springer Science+Business Media, LLC 2011.

Journal of Porous Materials

PWA/montmorillonite K10 catalyst for synthesis of coumarins under solvent-free conditions

A molecular salt with formula [BmIm]3[PMo12O40]3- has been prepared using room temperature ionic liquid and phosphomolybdic acid. The material is characterized by single-crystal X-ray diffraction. The compound crystallizes in orthorhombic system with space group Pca21. It is also characterized by CHN analysis, 31P MAS NMR, UV-vis DRS and near-IR methods. Thermal stability of the compound is investigated by TGA, IR and PXRD methods. Near-IR shows the loss of water of crystallization by the Keggin ions of phosphomolybdic acid bonded with ionic liquid. © 2008 Elsevier Masson SAS. All rights reserved.

Solid State Sciences

Synthesis and characterization of 1-butyl 3-methyl imidazolium phosphomolybdate molecular salt

The nature of the Keggin ions of tungstophosphoric acid interacting with Ce0.5Zr0.5O2 solid solution has been investigated. The vibrational study shows additional IR features at 1051 and 957 cm-1 which are correlated to the primary Keggin anions interacting with Lewis sites involving Ce4+ and Zr4+ ions, and thus affecting the P-O and W=Oterminal bonds. The IR study indicates the formation of interfacial Ce4+-O-W and Zr4+-O-W bonds. The chemisorbed Keggin molecular layers on Ce0.5Zr0.5O 2 show activity towards conversion of acetophenone to styrene by Meerwein-Ponndorf-Verley reduction followed by dehydration. The activity is correlated with the relative intensities of IR peaks at 1051 and 957 cm -1 of the perturbed Keggin molecular layers. © 2007 Springer Science+Business Media, LLC.

Catalysis Letters

Investigation of 12-tungstophosphoric acid supported on Ce 0.5Zr0.5O2 solid solution

A white colour IL-SiWA hybrid molecular material has been synthesized using 1-butyl 3-methyl imidazolium bromide ionic liquid and silicotungstic acid. The material is found to dissolve in polar organic solvent such as DMSO, but not in water. It is characterized by CHN analysis, FTIR, XRD, UV-vis DRS, TGA and SEM. The FTIR spectra indicate the formation of a hybrid compound showing fingerprint vibrational bands of both Keggin ions of silicotungstic acid and imidazolium ions. There is a strong evidence of interaction between the Keggin anions and imidazolium cations from the UV-vis DR spectra and the splitting of imidazolium C-H bands in the IR spectrum of the IL-SiWA. The near IR shows loss of crystallization water from heteropoly acid when it reacts with ionic liquid forming the hybrid molecular material. © 2008 Elsevier B.V. All rights reserved.

Materials Chemistry and Physics

Synthesis and characterization of hybrid molecular material prepared by ionic liquid and silicotungstic acid

The interaction of 20 wt% 12-tungstophosphoric acid with Cex Zr1 - x O2 solid solutions has been studied by PXRD, FTIR, FT-Raman, H2-TPR, NH3-TPD, diffuse reflectance UV-vis-NIR, and 31P MAS NMR techniques. The study indicates that the Keggin anions are attached to Lewis metal ion centres and anion vacancies on Cex Zr1 - x O2 supports through W{double bond, long}O terminal bonds. The Keggin units at the interface are chemically perturbed as indicated by non-intrinsic IR bands observed at 958 cm-1 (W{double bond, long}Oter bond), and 1052, 1102 cm-1 (P{single bond}O bond). NH3-TPD shows that the Keggin anions fixed to Lewis sites and/or oxygen ion vacancies decrease the ammonia uptake on Cex Zr1 - x O2 solid solutions. H2-TPR shows modified redox behaviour of Cex Zr1 - x O2 solid solutions due to the simultaneous reduction of ceria, decomposition of Keggin anions and the reduction of WO3. The broadening of 31P MAS NMR and DR-UV-vis-NIR spectra demonstrate the existence of chemical interactions between the Keggin anions and Cex Zr1 - x O2 supports. © 2008 Elsevier Inc. All rights reserved.

Journal of Colloid and Interface Science

Interaction of Keggin anions of 12-tungstophosphoric acid with Cex Zr1 - x O2 solid solutions

CeO2-ZnO composite catalysts prepared by amorphous citrate method have been investigated for cyclohexanol dehydrogenation and hydrogen transfer reactions. The precursors and catalysts have been characterized by TGA, CHN analysis, XRD, UV-vis-NIR diffuse reflectance, SEM and acid-base measurements. The amorphous precursors in citrate process contain one molecule of citric acid per Ce4+ or Zn2+ ions. Structural studies of composite oxides indicate the presence of individual oxide phases along with non-equilibrium solid solutions in a limited composition range. The composite oxides contain low coordination Ce3+ and Ce4+ sites. Cyclohexanone was obtained as main product for cyclohexanol transformation reaction carried out over these mixed oxide catalysts due to dehydrogenation on basic sites. The presence of ceria in the composite oxide enhances the surface area and acid-base properties facilitating the dehydrogenation process. At low ceria content, the CeO2-ZnO composite oxide catalysts show higher catalytic activity for both cyclohexanol dehydrogenation and hydrogen transfer reactions due to higher basicity, surface area and smaller crystallite sizes. Hydrogen transfer activity is found to be higher on CeO2(10%)-ZnO catalyst prepared by citrate method compared to the catalyst prepared by decomposition from acetate precursor. This study demonstrates the promoting effect of ceria in CeO2-ZnO catalysts for reactions involving acid-base sites. © 2005 Elsevier B.V. All rights reserved.

Journal of Molecular Catalysis A: Chemical

Promoting effect of ceria on the physicochemical and catalytic properties of CeO2-ZnO composite oxide catalysts

Investigation of hybrid molecular material prepared by ionic liquid and polyoxometalate anion

Journal	Journal of Chemical Sciences
ISSN	02534134
Open Access	Yes