Publications by authors named "Chullikkattil P Pradeep"

31 Publications

Post-functionalization through covalent modification of organic counter ions: a stepwise and controlled approach for novel hybrid polyoxometalate materials.

Dalton Trans 2020 Sep;49(35):12174-12179

School of Basic Sciences, Indian Institute of Technology Mandi, Mandi 175005, Himachal Pradesh, India.

Post-functionalization of Class I type polyoxometalate-organic hybrids through covalent modification of the organic counter ions in a step-wise and controlled manner is reported for the first time. The properties of the post-functionalized hybrids have been studied and compared with those of their parent hybrids revealing marked differences in properties.
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http://dx.doi.org/10.1039/d0dt01410aDOI Listing
September 2020

Facile Synthesis of an Organic Solid State Near-Infrared-Emitter with Large Stokes Shift via Excited-State Intramolecular Proton Transfer.

ACS Omega 2018 Oct 29;3(10):14341-14348. Epub 2018 Oct 29.

School of Basic Sciences, Indian Institute of Technology Mandi, Kamand 175 005, Himachal Pradesh, India.

An organic solid-state near-infrared (NIR)-emitter (λ = 738 nm) exhibiting large Stokes shift (Δλ = 293 nm) through the excited-state intramolecular proton transfer phenomenon has been synthesized and characterized. The present discovery points to the possibility of achieving a new family of solid-state NIR emitters starting from simple aldehyde and amine precursors.
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http://dx.doi.org/10.1021/acsomega.8b02116DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6645307PMC
October 2018

Crystal structure and Hirshfeld surface analysis of -2-[2-(4-chloro-phen-yl)-3,4-di-hydro-2-1-benzo-pyran-4-yl-idene]hydrazine-1-carbo-thio-amide.

Acta Crystallogr E Crystallogr Commun 2019 May 25;75(Pt 5):707-710. Epub 2019 Apr 25.

School of Basic Sciences, Indian Institute of Technology Mandi, Mandi-175005, Himachal Pradesh, India.

In the title compound, CHNOSCl, a Schiff base derivative of a thio-semicarbazide with a flavanone, the 4-chlorophenyl ring is inclined to the benzene ring of the chromane ring system by 30.72 (12)°. The pyran ring has an envelope conformation with the methine C atom as the flap. The mean plane of the thio-urea unit is twisted with respect to the benzene ring of the chromanone ring system, subtending a dihedral angle of 19.78 (19)°. In the crystal, mol-ecules are linked by two pairs of N-H⋯S hydrogen bonds, forming inversion dimers enclosing (8) ring motifs, which are linked to form ribbons propagating along the -axis direction. The inter-molecular contacts in the crystal have been analysed using Hirshfeld surface analysis.
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http://dx.doi.org/10.1107/S2056989019005073DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6505591PMC
May 2019

A chemosensor for micro- to nano-molar detection of Ag and Hg ions in pure aqueous media and its applications in cell imaging.

Dalton Trans 2017 Oct;46(41):14201-14209

Department of Chemistry, S.S.V.P.S's L. K. Dr P. R. Ghogrey Science College, Dhule-424 001, MS, India.

The pyridine substituted thiourea derivative PTB-1 was synthesized and characterized by spectroscopic techniques as well as by single crystal X-ray crystallography. The metal ion sensing ability of PTB-1 was explored by various experimental (naked-eye, UV-Vis, fluorescence, mass spectrometry and H NMR spectroscopy) and theoretical (B3LYP/6-31G**/LANL2DZ) methods. PTB-1 exhibited a highly selective naked-eye detectable color change from colorless to dark brown and UV-Vis spectral changes for the detection of Ag with a detection limit of 3.67 μM in aqueous medium. The detection of Ag ions was achieved by test paper strip and supported silica methods. In contrast, PTB-1 exhibited a 23-fold enhanced emission at 420 nm in the presence of Hg ions with a nano-molar detection limit of 0.69 nM. Finally, the sensor PTB-1 was applied successfully for the intracellular detection of Hg ions in a HepG2 liver cell line, which was monitored by the use of confocal imaging techniques.
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http://dx.doi.org/10.1039/c7dt02524fDOI Listing
October 2017

Engineering Multifunctionality in Hybrid Polyoxometalates: Aromatic Sulfonium Octamolybdates as Excellent Photochromic Materials and Self-Separating Catalysts for Epoxidation.

Inorg Chem 2017 Sep 17;56(17):10325-10336. Epub 2017 Aug 17.

School of Basic Sciences, Indian Institute of Technology Mandi , Kamand 175 005, Himachal Pradesh, India.

Engineering multifunctionality in hybrid polyoxometalates (hybrid POMs) is an interesting but scarcely explored topic. Herein, we set about engineering two important materials properties, viz., photochromism and self-separating catalysis, in a hybrid POM by modulating the counterion motif. A series of six aromatic sulfonium counterions have been developed on the basis of an aromatic sulfonium counterion motif that allows structural and electronic fine-tuning by changing substituents at multiple locations. Using the aromatic sulfonium counterions and sodium molybdate, six new aromatic sulfonium octamolybdate hybrids (1-6) having formulas (HPDS)[MoO] (1), (HMPDS)[MoO] (2), (MPDS)[MoO] (3), (APDS)[MoO] (4), (AMPDS)[MoO] (5), and (MAPDS)[MoO] (6) (where HPDS = (4-hydroxyphenyl)dimethylsulfonium, HMPDS = (4-hydroxy-2-methylphenyl)dimethylsulfonium, MPDS = (4-methoxyphenyl)dimethylsulfonium, APDS = (4-(allyloxy)phenyl)dimethylsulfonium, AMPDS = (4-(allyloxy)-2-methylphenyl)dimethylsulfonium and MAPDS = (4(methacryloyloxy)phenyl)dimethylsulfonium) have been synthesized, and their structures were confirmed by single crystal X-ray diffraction and ESI-MS analyses. Hybrids 1-6 acted as good solid-state photochromic materials exhibiting color change from white to purple under UV illumination (350 nm), and we show here that the photochromic properties of hybrids 1-6 could be modulated by changing the substitutions on the counterion motif. A coloration kinetic half-life (t) of 0.33 min was achieved with this class of hybrid POMs. Hybrids 1-6 exhibited excellent self-separating catalytic properties toward the epoxidation of olefins, yielding up to 99% epoxide product with good selectivity in short time. The substituents on the aromatic sulfonium counterions helps to fine-tune the electronic, lipophilic, and solubility properties of the hybrids and thereby their catalytic properties. Moreover, we used ESI-MS analyses to understand the mechanism of catalysis exhibited by octamolybdates 1-6 in the presence of HO, and we succeeded in identifying a hitherto undetected intermediate, tetraperoxo-octamolybdates, shedding more light on the epoxidation mechanism.
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http://dx.doi.org/10.1021/acs.inorgchem.7b01143DOI Listing
September 2017

Polyarylenesulfonium Salt as a Novel and Versatile Nonchemically Amplified Negative Tone Photoresist for High-Resolution Extreme Ultraviolet Lithography Applications.

ACS Appl Mater Interfaces 2017 01 27;9(1):17-21. Epub 2016 Dec 27.

School of Basic Sciences and ‡School of Computing and Electrical Engineering, Indian Institute of Technology Mandi , Kamand 175 005, Himachal Pradesh, India.

The present report demonstrates the potential of a polyarylenesulfonium polymer, poly[methyl(4-(phenylthio)-phenyl)sulfoniumtrifluoromethanesulfonate] (PAS), as a versatile nonchemically amplified negative tone photoresist for next-generation lithography (NGL) applications starting from i-line (λ ∼ 365 nm) to extreme ultraviolet (EUV, λ ∼ 13.5 nm) lithography. PAS exhibited considerable contrast (γ), 0.08, toward EUV and patterned 20 nm features successfully.
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http://dx.doi.org/10.1021/acsami.6b10384DOI Listing
January 2017

Multifunctional Zn(II) Complexes: Photophysical Properties and Catalytic Transesterification toward Biodiesel Synthesis.

Inorg Chem 2016 Aug 20;55(15):7492-500. Epub 2016 Jul 20.

School of Basic Sciences, Indian Institute of Technology Mandi , Kamand 175 005, Himachal Pradesh, India.

Using 4-substituted derivatives of phenol-based compartmental Schiff-base hydroxyl-rich ligand, four multifunctional binuclear Zn(II) complexes have been synthesized and characterized. The photophysical properties of these complexes were explored in the solid state, in solutions, and in poly(methyl methacrylate) (PMMA) matrix, which revealed their good potential as tunable solid state emitters. Some of these complexes acted as efficient catalysts for the transesterification of esters and canola oil showing their potential in biodiesel generation. Mechanistic investigations using ESI-MS revealed that the transesterification catalyzed by these complexes proceeds through two types of acyl intermediates.
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http://dx.doi.org/10.1021/acs.inorgchem.6b00804DOI Listing
August 2016

Benzimidazole Based 'Turn on' Fluorescent Chemodosimeter for Zinc Ions in Mixed Aqueous Medium.

J Fluoresc 2016 Jul 4;26(4):1439-45. Epub 2016 Jun 4.

School of Basic Sciences, Indian Institute of Technology, Mandi, Himachal Pradesh, 175001, India.

Benzimidazole based compound 3 is designed and synthesized. The compound 3 is evaluated as fluorogenic sensor for metal ions in mixed aqueous solutions. Among all the metal ions tested, the compound 3 selectively senses Zn(2+) ions. The imine bond of 3 gets cleaved by Zn(2+) ions. Thus, 3 behave as 'turn on' fluorescent chemodosimeter for Zn(2+) ions with limit of detction in micromolar range. Furthurmore, we demonstated that 3 can detect Zn(2+) ions in cells of Allium cepa. Graphical Abstract Benzimidazole based ligand 3 is designed and synthesized which behave as chemodosimeter for Zn(2+) ions. We further demonstrated that 3 can detect Zn(2+) ions in cells of Allium cepa.
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http://dx.doi.org/10.1007/s10895-016-1836-xDOI Listing
July 2016

Patterning highly ordered arrays of complex nanofeatures through EUV directed polarity switching of non chemically amplified photoresist.

Sci Rep 2016 Mar 15;6:22664. Epub 2016 Mar 15.

School of Basic Sciences, Indian Institute of Technology Mandi, Mandi - 175005, India.

Given the importance of complex nanofeatures in the filed of micro-/nanoelectronics particularly in the area of high-density magnetic recording, photonic crystals, information storage, micro-lens arrays, tissue engineering and catalysis, the present work demonstrates the development of new methodology for patterning complex nanofeatures using a recently developed non-chemically amplified photoresist (n-CARs) poly(4-(methacryloyloxy)phenyl)dimethylsulfoniumtriflate) (polyMAPDST) with the help of extreme ultraviolet lithography (EUVL) as patterning tool. The photosensitivity of polyMAPDST is mainly due to the presence of radiation sensitive trifluoromethanesulfonate unit (triflate group) which undergoes photodegradation upon exposure with EUV photons, and thus brings in polarity change in the polymer structure. Integration of such radiation sensitive unit into polymer network avoids the need of chemical amplification which is otherwise needed for polarity switching in the case of chemically amplified photoresists (CARs). Indeed, we successfully patterned highly ordered wide-raging dense nanofeatures that include nanodots, nanowaves, nanoboats, star-elbow etc. All these developed nanopatterns have been well characterized by FESEM and AFM techniques. Finally, the potential of polyMAPDST has been established by successful transfer of patterns into silicon substrate through adaptation of compatible etch recipes.
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http://dx.doi.org/10.1038/srep22664DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4791541PMC
March 2016

Aromatic Sulfonium Polyoxomolybdates: Solid-State Photochromic Materials with Tunable Properties.

Chemistry 2015 Dec 10;21(51):18557-62. Epub 2015 Nov 10.

School of Basic Sciences, Indian Institute of Technology Mandi, Mandi 175005, Himachal Pradesh (India) http://faculty.iitmandi.ac.in/∼pradeep/.

A new aromatic sulfonium counter-ion motif for polyoxometalate (POM) clusters with potential for structural and electronic fine-tuning has been designed. Its two derivatives 4-hydroxyphenyl dimethylsulfonium triflate (HPDST) and 4-(allyloxy)phenyl dimethylsulfonium triflate (APDST) exhibit ionic liquid behaviors under ambient conditions. HPDST and APDST are used to develop a series of aromatic sulfonium POM hybrids (HPDS/APDS)n[XMo12 O40] (HPDS and APDS are the cations of HPDST and APDST, respectively; X=P or Si; n=3 or 4), which are tested for photochromic behavior. On exposure to UV light, these POM hybrids undergo color change from yellow to green/blue. The coloration kinetics half lives (t1/2) are less for APDS-based hybrids than for HPDS-based hybrids, suggesting that alkyl substitution on the phenolic group helps to fine-tune the electron availability on the sulfonium moiety and hence to control the photochromic behavior of the POM hybrids. The t1/2 values of these hybrids are considerably lower than those of the reported aliphatic sulfonium POM hybrids. We have also demonstrated the application of photoreduced POM hybrids as catalysts for the reduction of 4-nitrophenol to 4-aminophenol.
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http://dx.doi.org/10.1002/chem.201503574DOI Listing
December 2015

Self-assembly of triangular polyoxometalate-organic hybrid macroions in mixed solvents.

Chem Commun (Camb) 2015 May;51(41):8630-3

Department of Polymer Science, University of Akron, Akron, Ohio, USA 44325.

Triangular-shaped inorganic-organic hybrids with three polyoxometalate (POM) clusters as polar head groups are found to self-assemble into blackberry structures in water-acetone solvent mixtures containing 65-95 vol% acetone. The driving force for the self-assembly of the hybrids is shown to originate from the electrostatic counterion-cluster interactions.
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http://dx.doi.org/10.1039/c5cc02003dDOI Listing
May 2015

New polyoxometalates containing hybrid polymers and their potential for nano-patterning.

Chemistry 2015 Jan 27;21(5):2250-8. Epub 2014 Nov 27.

School of Basic Sciences, Indian Institute of Technology Mandi, Mandi 175 001, Himachal Pradesh (India).

Two new polyoxometalate (POM)-based hybrid monomers (Bu4 N)5 (H)[P2 V3 W15 O59 {(OCH2 )3 CNHCO(CH3 )CCH2 }] (2) and (S(CH3 )2 C6 H4 OCOC(CH3 )=CH2 )6 [PV  2Mo10 O40 ] (5) were developed by grafting polymerizable organic units covalently or electrostatically onto Wells-Dawson and Keggin-type clusters and were characterized by analytical and spectroscopic techniques including ESI-MS and/or single-crystal X-ray diffraction analyses. Radical initiated polymerization of 2 and 5 with organic monomers (methacryloyloxy)phenyldimethylsulfonium triflate (MAPDST) and/or methylmethacrylate (MMA) yielded a new series of POM/polymer hybrids that were characterized by (1) H, (31) P NMR and IR spectroscopic techniques, gel-permeation chromatography as well as thermal analyses. Preliminary tests were conducted on these POM/polymer hybrids to evaluate their properties as photoresists using electron beam (E-beam)/extreme ultraviolet (EUV) lithographic techniques. It was observed that the POM/polymer hybrid of 2 with MAPDST exhibited improved sensitivity under EUV lithographic conditions in comparison to the MAPDST homopolymer resist possibly due to the efficient photon harvesting by the POM clusters from the EUV source.
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http://dx.doi.org/10.1002/chem.201405369DOI Listing
January 2015

Cyanide induced self assembly and copper recognition in human blood serum by a new carbazole AIEE active material.

Mater Sci Eng C Mater Biol Appl 2014 Oct 19;43:418-23. Epub 2014 Jul 19.

Indian Institute of Technology, Mandi, Himachal Pradesh, 175001, India. Electronic address:

New carbazole based AIEE material is synthesized with fluoro group which shows ESIPT induced AIEE in H2O:THF (80:20, v/v). The material selectively recognizes Cu(2+) and CN(-) ions in contrasting modes with detection limits of 5 × 10(-6)Mol L(-1) and 12×10(-5)Mol L(-1) respectively and acts as a dual action chemosensor. The recognition of copper has also been observed in human serum, thus facilitating the detection of increased level of free Cu(2+) ions and its quantification in human serum.
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http://dx.doi.org/10.1016/j.msec.2014.07.041DOI Listing
October 2014

Imatinib intermediate as a two in one dual channel sensor for the recognition of Cu²⁺ and I⁻ ions in aqueous media and its practical applications.

Dalton Trans 2014 Sep;43(35):13299-306

School of Chemical Sciences, North Maharashtra University, P. B. No. 80, Jalgaon - 425 001, M.S., India.

An imatinib intermediate, 6-methyl-N-[4-(pyridin-3-yl)pyrimidin-2-yl]benzene-1,3-diaminepyridopyrimidotoluidine (PPT-1), was developed for the colorimetric sensing of Cu(2+) ions in aqueous solution. With Cu(2+), the receptor PPT-1 showed a highly selective naked-eye detectable color change from colorless to red over the seventy other tested cations. The colorimetric sensing ability of PPT-1 was successfully utilized in the preparation of test strips and supported silica for the real samples analysis to detect Cu(2+) ions from 100% aqueous environment. Moreover, the iodide-sensing ability of receptor PPT-1 was explored among the ten examined anions.
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http://dx.doi.org/10.1039/c4dt01516aDOI Listing
September 2014

A fluorescence 'turn-on' chemodosimeter for selective detection of Nb5+ ions in mixed aqueous media.

Dalton Trans 2013 Sep 24;42(36):12819-23. Epub 2013 Jun 24.

School of Basic Sciences, Indian Institute of Technology Mandi, Himachal Pradesh 175001, India.

Based on the mechanism of hydrolytic cleavage of Schiff bases, a 1-aminopyrene based fluorescent chemodosimeter, 3, is reported for the selective detection of Nb(5+) ions in solution. Among the 21 metal ions tested, the chemodosimeter shows a selective fluorogenic 'turn-on' response toward Nb(5+) ions in mixed aqueous media.
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http://dx.doi.org/10.1039/c3dt50914aDOI Listing
September 2013

Au microparticles mediated construction of a logic based dual channel molecular keypad lock.

Dalton Trans 2013 Jun;42(21):7514-8

Assistant Professor, School of Basic Sciences, Indian Institute of Technology, Mandi-175001, Himachal Pradesh, India.

New melamine based ligand with pyrene as a fluorophore is synthesized and characterized. The sequential addition of Au(3+) ions and ascorbic acid to the solution of in EtOH-H2O (9.5 : 0.5 v/v) generates gold microparticles (AuMPs). However, the particle size distribution and fluorescence behaviour on sequential additions are different and contribute to the construction of a new logic based molecular dual channel keypad lock system.
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http://dx.doi.org/10.1039/c3dt50495fDOI Listing
June 2013

Exploring the interplay between ligand derivatisation and cation type in the assembly of hybrid polyoxometalate Mn-Andersons.

Small 2013 Jul 7;9(13):2316-24. Epub 2013 Feb 7.

WestCHEM, School of Chemistry, University of Glasgow, University Avenue, Glasgow, G12 8QQ, UK.

Herein a library of hybrid Mn-Anderson polyoxometalates anions are presented: 1, [(MnMo6 O18 )((OCH2 )3 -C-(CH2 )7 CHCH2 )2 ](3-) ; compound 2, [(MnMo6 O18 )((OCH2 )3 C-NHCH2 C16 H9 )2 ](3-) ; compound 3, [(MnMo6 O18 )((OCH2 )3 C-(CH2 )7 CHCH2 )1 ((OCH2 )3 C-NHCH2 C16 H9 )1 ](3-) ; compound 4, [(MnMo6 O18 )((OCH2 )3 C-NHC(O)CH2 CHCH2 )2 ](3-) and compounds 5-9, [(MnMo6 O18 )((OCH2 )3 C-NHC(O)(CH2 )x CH3 )2 ]), where x = 4, 10, 12, 14, and 18 respectively. The compounds resulting from the cation exchange of the anions 1-9 to give TBA (a) and DMDOA (b) salts, and additionally for compounds 1, 2 and 3, tetraphenylphosphonium (PPh4 ) (c) salts, are explored at the air/water interface using scanning force microscopy, showing a range of architectures including hexagonal structures, nanofibers and other supramolecular forms. Additionally the solid-state structures for compounds 1c, 2c, 4a, 6a, 9a, are presented for the first time and these investigations demonstrate the delicate interplay between the structure of the covalently derivatised hybrid organo-clusters as well as the ion-exchange cation types.
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http://dx.doi.org/10.1002/smll.201202510DOI Listing
July 2013

Organic-soluble lacunary {M2(P2W15)2} polyoxometalate sandwiches showing a previously unseen αββα isomerism.

Dalton Trans 2012 Sep 23;41(33):10000-5. Epub 2012 Jul 23.

WestCHEM, School of Chemistry, University of Glasgow, Joseph Black Building, University Avenue, Glasgow G12 8QQ, UK.

New polyoxometalate 'sandwiches' have been formed where two [P(2)W(15)O(56)](12-) lacunary Dawson clusters encapsulate two transition metal ions to give clusters with the general formula [M(II)(2)(P(2)W(15)O(56))(2)](20-) (where M = Mn, Co, and Ni respectively), [Fe(III)(2)(P(2)W(15)O(56))(2)](18-), and [Cu(II)(4)(P(2)W(15)O(56))(2)](16-). The Mn, Co, and Ni clusters exhibit a hitherto unseen αββα isomeric geometry and all five compounds are associated with tetrabutylammonium cations which allow for their dissolution in non-aqueous solvent.
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http://dx.doi.org/10.1039/c2dt30616fDOI Listing
September 2012

Controllable self-assembly of organic-inorganic amphiphiles containing Dawson polyoxometalate clusters.

Chemistry 2012 Jun 22;18(26):8157-62. Epub 2012 May 22.

Department of Chemistry, Lehigh University, Bethlehem, PA 18015, USA.

An organic-inorganic molecular hybrid containing the Dawson polyoxometalate, ((C(4)H(9))(4)N)(5)H[P(2)V(3)W(15)O(59)(OCH(2))(3)CNHCOC(15)H(31)], was synthesized and its surfactant-like amphiphilic properties, represented by the formation of bilayer vesicles, were studied in polar solvents. The vesicle size decreases with both decreasing hybrid concentration and with increasing polarity of the solvent, independently. The self-assembly behavior of this hybrid can be controlled by introducing different counterions into the acetonitrile solutions. The addition of ZnCl(2) and NaI can cause a gradual decrease and increase of vesicular sizes, respectively. Tetraalkylammonium bromide is found to disassemble the vesicle assemblies. Moreover, the original counterions of the hybrid can be replaced with protons, resulting in pH-dependent formation of vesicles in aqueous solutions. The hybrid surfactant can further form micro-needle structures in aqueous solutions upon addition of Ca(2+) ions.
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http://dx.doi.org/10.1002/chem.201200362DOI Listing
June 2012

Cation induced structural transformation and mass spectrometric observation of the missing dodecavanadomanganate(IV).

Dalton Trans 2012 Sep 17;41(33):9859-62. Epub 2012 May 17.

WestCHEM, School of Chemistry, University of Glasgow, Joseph Black Building, University Avenue, Glasgow, UK.

The heteropolyvanadate cluster [(n-C(4)H(9))(4)N](4)[Mn(IV)V(12)O(34)]·2CH(3)CN has been isolated by cation exchange from K(10)[(Mn(IV)V(11)O(32))(2)]·20H(2)O. The structural transformation has been confirmed by X-ray single crystal structure determination and cryospray ionization mass spectrometry measurements.
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http://dx.doi.org/10.1039/c2dt30627aDOI Listing
September 2012

Amphiphilic properties of dumbbell-shaped inorganic-organic-inorganic molecular hybrid materials in solution and at an interface.

Langmuir 2011 Aug 30;27(15):9193-202. Epub 2011 Jun 30.

Department of Chemistry, Lehigh University, Bethlehem, Pennsylvania 18015, USA.

Five novel dumbbell-shaped polyoxometalate (POM)-based inorganic-organic-inorganic molecular hybrids are investigated both in polar solvents and at interfaces for potential amphiphilic properties, which are compared with those of conventional surfactants. These hybrids with the general formula {P(2)V(3)W(15)}(2)-bis(TRIS)-linker are formed by linking two Wells-Dawson-type clusters, [P(2)V(3)W(15)O(62)](9-), with different linear bis(TRIS) linker ligands between the two TRIS moieties. Laser light scattering (LLS) studies reveal the presence of self-assembled vesicular structures in water/acetone mixed solvents, and the vesicle size increases with increasing acetone content, suggesting a charge-regulated process. The elastic constants, which are used to calculate the bending energy during vesicle formation, reveal that the organic ligands play an important role in determining the self-assembly process and that the hybrids do demonstrate amphiphilic behavior at the water/air interface. Furthermore, it is shown that some of the hybrids form monolayers at the interface, with an average molecular area that can be correlated with their organic linkers, as determined from their π-A isotherms. Finally, the hybrids not only display amphiphilic behavior akin to that of a surfactant but also exhibit an unusually high entropy contribution to vesicle formation as a result of their unique large, polar head groups, complex organic linkers, and their special molecular architectures as well as because of the involvement of the amphiphilic tetrabutylammonium (TBA) counterions.
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http://dx.doi.org/10.1021/la2013914DOI Listing
August 2011

Design and synthesis of "dumb-bell" and "triangular" inorganic-organic hybrid nanopolyoxometalate clusters and their characterisation through ESI-MS analyses.

Chemistry 2011 Jun 18;17(27):7472-9. Epub 2011 May 18.

WestCHEM, Department of Chemistry, The University of Glasgow, G12 8QQ, UK.

A series of tris(hydroxymethyl)aminomethane (TRIS)-based linear (bis(TRIS)) and triangular (tris(TRIS)) ligands has been synthesised and were covalently attached to the Wells-Dawson type cluster [P(2)V(3)W(15)O(62)](9-) to generate a series of nanometer-sized inorganic-organic hybrid polyoxometalate clusters. These huge hybrids, with a molecular mass similar to that of small proteins in the range of ≈10-16 kDa, were unambiguously characterised by using high-resolution ESI-MS. The ESI-MS spectra of these compounds revealed, in negative ion mode, a characteristic pattern showing distinct groups of peaks corresponding to different anionic charge states ranging from 3(-) to 8(-) for the hybrids. Each peak in these individual groups could be unambiguously assigned to the corresponding hybrid cluster anion with varying combinations of tetrabutylammonium (TBA) and other cations. This study therefore highlights the prowess of the high-resolution ESI-MS for the unambiguous characterisation of large, nanoscale, inorganic-organic hybrid clusters that have huge mass, of the order of 10-16 kDa. Also, the designed synthesis of these compounds points to the fact that we were able to achieve a great deal of structural pre-design in the synthesis of these inorganic-organic hybrid polyoxometalates (POMs) by means of a ligand design route, which is often not possible in traditional "one-pot" POM synthesis.
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http://dx.doi.org/10.1002/chem.201100257DOI Listing
June 2011

Assembly of modular asymmetric organic-inorganic polyoxometalate hybrids into anisotropic nanostructures.

J Am Chem Soc 2010 Nov;132(44):15490-2

WestCHEM, School of Chemistry, University of Glasgow, Joseph Black Building, UK.

Three organic-inorganic hybrid Mn-Anderson polyoxometalates (POMs), with both symmetrical and asymmetrical appended groups, have been synthesized, identified using electrospray mass spectrometry, and isolated using an approach that allows the three AA, BB, and AB compounds to be structurally characterized. Investigation of the self-assembly of the hybrids on hydrophilic surfaces reveals the formation of nanofibres with characteristics that reflect the nature of the substitution of the POM yielding a route to the programmed assembly of anisotropic hybrid nanostructures.
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http://dx.doi.org/10.1021/ja1066338DOI Listing
November 2010

Cations in control: crystal engineering polyoxometalate clusters using cation directed self-assembly.

Dalton Trans 2010 Oct 18;39(40):9443-57. Epub 2010 Aug 18.

Department of Chemistry, University of Glasgow, Glasgow, G12 8QQ, UK.

The synthetic engineering of anionic polyoxometalate (POM) clusters with predefined properties tailored to specific applications is a great challenge using routine "one-pot" POM syntheses. Under such conditions, difficulties often arise from the multitude of complex reaction pathways and self-assembly processes occurring in solution. In this respect the major role of the charge balancing cations cannot be ignored, in fact such cations are crucial, both in the assembly of the building blocks, linkage to the overall cluster, and then assembly into the bulk material. Further, the role of the cation facilitating the selective crystallization of a particular cluster type cannot be divorced from the reaction process since the crystallization process itself can help pull "virtual" building blocks into being. This perspective briefly outlines our efforts towards engineering novel POM based materials, highlighting the use of large organic cations as "Shrink-wrapping" agents to isolate new POM clusters, frameworks and cage compounds. Central to this perspective is the hypothesis that, in the case of POM cluster assembly, the mechanism and various equilibria which define the clusters can be controlled by the selective crystallisation using cation control. Consequently, this indicates that the process of crystallisation can have a profound effect on self-assembly at the molecular level. We therefore propose that the crystallization process itself may define the molecular structure of the cluster leading to the conundrum, which came first, the cluster or the crystal of the cluster?
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http://dx.doi.org/10.1039/c0dt00325eDOI Listing
October 2010

The construction of high-nuclearity isopolyoxoniobates with pentagonal building blocks: [HNb27O76]16- and [H10Nb31O93(CO3)]23-.

Angew Chem Int Ed Engl 2010 ;49(1):113-6

WestCHEM, Department of Chemistry, The University of Glasgow, University Avenue, Glasgow G12 8QQ, UK.

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http://dx.doi.org/10.1002/anie.200903970DOI Listing
March 2010

Synthesis of modular "inorganic-organic-inorganic" polyoxometalates and their assembly into vesicles.

Angew Chem Int Ed Engl 2009 ;48(44):8309-13

WestCHEM, Department of Chemistry, The University of Glasgow, University Avenue, Glasgow G12 8QQ, Scotland, UK.

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http://dx.doi.org/10.1002/anie.200903070DOI Listing
February 2010

A functional hybrid polyoxometalate framework based on a 'trilacunary' heteropolyanion [(P4W6O34)2Co2Na2(H2O)2]18-.

Dalton Trans 2009 Sep 9(33):6483-6. Epub 2009 Jul 9.

WestCHEM, Department of Chemistry, University of Glasgow, Joseph Black Building, University Avenue, Glasgow, UK G12 8QQ.

Using multifunctional organocations a novel heteropolyanion, [(P4W6O34)2Co2Na2(H2O)2]18-, with unprecedented structural features, has been observed, and extension of these clusters from molecules into 1D chains occurs through a dimeric cobalt species, with this material exhibiting reversible colour/magnetic susceptibility changes upon dehydration.
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http://dx.doi.org/10.1039/b907410dDOI Listing
September 2009

Micropatterned surfaces with covalently grafted unsymmetrical polyoxometalate-hybrid clusters lead to selective cell adhesion.

J Am Chem Soc 2009 Feb;131(4):1340-1

WestCHEM Department of Chemistry, Joseph Black Building, University of Glasgow, University Avenue, Glasgow, G12 8QQ UK.

Mn-Anderson based polyoxometalate clusters with different terminal groups have been patterned successfully onto self-assembled monolayer (SAM) using microcontact printing. Studies of the interactions between the designed SAMs and human fibroblast (hTERT-BJ1) cells have been reported, and it was observed that cells attach and spread efficiently for monolayer presenting a terminal aromatic pyrene platform with a polyoxometalate Mn-Anderson cluster as linker, demonstrating the crucial role played by the polyoxometalate metal oxide cluster as an intermediary in cell adhesion to the surface.
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http://dx.doi.org/10.1021/ja807091vDOI Listing
February 2009

"Bottom-up" meets "top-down" assembly in nanoscale polyoxometalate clusters: self-assembly of [P4W52O178](24-) and disassembly to [P3W39O134](19-).

J Am Chem Soc 2008 Nov 21;130(45):14946-7. Epub 2008 Oct 21.

WestCHEM, Department of Chemistry, The University of Glasgow, Glasgow G12 8QQ, UK.

The pH-controlled assembly/disassembly of a nanoscale {P4W52O178}24- cluster at pH 2 to a {P4W44O152}20- cluster at pH 3-5 via a {P3W39O134}19- cluster species at pH 2-3 to finally give {P2W19O69(OH2)}14- at pH 6 is reported. This process can be traced in the solid state crystallographically and in solution using dynamic light scattering studies.
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http://dx.doi.org/10.1021/ja806596jDOI Listing
November 2008

Supramolecular metal oxides: programmed hierarchical assembly of a protein-sized 21 kDa [(C16H36N)19{H2NC(CH2O)3P2V3W15O59}4]5- polyoxometalate assembly.

Angew Chem Int Ed Engl 2008 ;47(23):4388-91

WestCHEM, Department of Chemistry, The University of Glasgow, University Avenue, Glasgow G12 8QQ, UK.

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http://dx.doi.org/10.1002/anie.200800431DOI Listing
July 2008
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