Chiral Strandberg‐Type Molybdates [(RPO3)2Mo5O15]2− as Molecular Gelators: Self‐Assembled Fibrillar Nanostructures with Enhanced Optical Activity

Carraro, Mauro; Sartorel, Andrea; Scorrano, Gianfranco; Maccato, Chiara; Dickman, Michael H.; Kortz, Ulrich; Bonchio, Marcella

doi:10.1002/anie.200801629

Cited by 118 publications

(67 citation statements)

References 37 publications

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“…These latter can be exploited for the development of new POM-based extended assemblies. [12] Thus, the protecting groups in 1 and 2 were removed by using classic procedures: 1 was treated with diethylamine (Scheme 2, pathway a) to obtain [{NH 2 CH(CH 3 )PO} 2 (γ-SiW 10 O 36 )] 4-(3), whereas 2 was reduced with H 2 by using a Pd/C catalyst (Scheme 2, pathway b) to yield the corresponding reduced heteropolyblue [{NH 2 CH(CH 3 )PO} 2 (γ-SiW 10 O 36 )]…”

Section: Resultsmentioning

confidence: 99%

“…Hydrogen bonding is a key tool for POM stabilization in the catalytic activation of hydrogen peroxide [2b] and/or evolving in supramolecular architectures. [12] In this respect, the design of suitable H-bonding patterns can boost the chirality transfer from the organic pendant arm to the inorganic envelope of the polyoxometalate through multiple noncovalent interactions. The reaction has shown to be of general scope, as -phenylalanine was also grafted onto 5 to give [ (9).…”

Section: Resultsmentioning

confidence: 99%

“…[10] In this respect, surface-appended organic moieties carrying suitable functional groups are introduced to foster the extended organization of the POM molecular units. [7,11,12] This strategy was successfully employed to obtain polymerizable, [13] dendrimeric, [14] and supramolecular derivatives. [15] Moreover, a tailored hybrid modification of POMs is instrumental for their grafting onto surfaces and onto nanoparticles, [16] for their embedding into polymeric membranes, [17] and for the introduction of organic or organometallic residues for advanced catalytic applications.…”

Section: Introductionmentioning

confidence: 99%

“…The induced helicity of the hybrid fibrils results from the expression of chirality at the supramolecular level. [12] We present herein the synthesis and characterization of new chiral polyoxotungstophosphonates, in enantiopure form, derived from the covalent functionalization of lacunary Keggin-type precursors.…”

Section: Introductionmentioning

confidence: 99%

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Optically Active Polyoxotungstates Bearing Chiral Organophosphonate Substituents

et al. 2009

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Divacant Keggin-type polyoxotungstates [γ-XW10O36]8– with X = Si or Ge, were functionalized with chiral phosphoryl groups. The hybrid compounds [(R*PO)2(γ-XW10O36)]4– with R = N-protected aminoalkyl groups or O-protected amino acid derivatives, were isolated. The solution characterization of the products was performed by different techniques: 183W, 31P, 13C, and 1H NMR spectroscopy, electrospray ionization mass spectrometry, UV/Vis spectroscopy, and circular dichroism (CD). The experimental data confirm the covalent grafting of the organic moieties onto the polyanionic surface. A chirality transfer, from the pendant organic arm to the inorganic framework is apparent from CD studies. Multiple Cotton effects were observed in the region of charge-transfer transitions pertaining to W–O bonds. Furthermore, the 183W NMR spectra are consistent with the expected C2 symmetry, resulting from introduction of two organic stereocenters. The title complexes were used in the presence of hydrogen peroxide to perform the oxidation of methyl p-tolyl sulfide. Implications for the design of enantioselective catalysts based on these derivatives are discussed

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Optically Active Polyoxotungstates Bearing Chiral Organophosphonate Substituents

et al. 2009

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“…[21] However originally, anisotropic DeSOM gels were first synthesized by Hasenknopf group using a Mn-Mo 6 type POM complex with bipridine and Pd 2+ . [22] [23] More recently, using Mn-Mo 6 type POMs with two dendritic poly(urethane amide) wings Nankai group showed interesting DeSOM formation that can act as pH sensitive gelators and form hybrid organogels of self-assembled hybrid nano-ribbons. [24] Apart from the above class of DeSOMs, it is to be noted that a body of venerable literature exploring catalytic acitivity of POMs has time and again employed diverse chemical means in addition to those as mentioned above for designing high surface area DeSOMs and the methods have been used for heterogenization of POM catalysts.…”

Section: Introductionmentioning

confidence: 99%

“SOFT OXOMETALATES” (SOMs): A VERY SHORT INTRODUCTION

Roy

2011

Comments on Inorganic Chemistry

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PolyoxometalatesUpdate based on the original article by Michael T. Pope,Encyclopedia of Inorganic Chemistry© 2005, John Wiley & Sons, Ltd.

Pope¹,

Kortz²

2012

Encyclopedia of Inorganic and Bioinorganic Chemistry

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The class of complexes known as polyoxometalates (POMs) is predominantly populated by polyoxoanions of high‐valent (d 0 , d 1 ) transition metals of groups 5 and 6 that typically incorporate some 5‐50 metal centers in structures of high symmetry. In most cases, the metal atoms occupy {MO 6 } octahedra that share vertices and edges. However, recent reports of POMs that incorporate square‐planar {Pd II O 4 } and hexagonal‐bipyramidal {U VI O 2 (η 2 − O 2 ) 2 (OH) 2 } building blocks indicate that further expansion of the field is in progress. The descriptive chemistry of many polyoxomolybdates and polyoxotungstates dates from the last third of the nineteenth century but it was not until the mid‐twentieth century that structural principles and the aqueous equilibria controlling the formation of POMs from monomeric oxoanions began to be recognized and quantified. That additional heteroatoms (metallic or nonmetallic) can be incorporated into the structures of, especially, polymolybdates and tungstates accounts for the enormous and rapidly developing variety of structures and possible applications of POMs. Four general types of POM structure, based on the mode of incorporation of the heteroatom(s), are described and it is shown how these can lead to hybrid organo‐POM complexes and to functionalization of POMs. Certain POM structures are reducible to mixed‐valence “heteropoly blue” versions, and those incorporating domains of paramagnetic heteroatoms can exhibit single‐molecule magnetic properties. The possibility that Mo VI and W VI can occupy a seven‐coordinate {O = M(O 6 )} polyhedron in POMs was first observed in [Mo 36 O 112 (H 2 O) 8 ] 8− {Mo 36 }; subsequent work has led to the development of other macrosized POMs including rings {Mo 154 }, hollow icosahedral “Keplerates” {Mo 60 W 72 }, and the “blue hedgehog” {Mo 368 }. Aqueous and aqueous‐organic solutions of such macro‐POMs spontaneously form hollow spherical vesicular structures (“blackberries”) with diameters typically 90 nm, with inter‐POM separations of 1 nm, depending upon the dielectric constant of the solvent. The various properties of POMs (such as large size, high molecular weight, solubility in polar and nonpolar solvents, electron and proton transfer and storage capacity, high thermal stability) have sparked applications in several fields, most notably in catalysis, both heterogeneous and homogeneous. Other applications include their use as electron‐dense staining and imaging agents, and their antiviral and antitumoral activity. Unconventional POMs are mainly represented by polyoxopalladates(II) and polyperoxodioxouranates(VI), which are also isolated from aqueous media. Unlike the early transition‐metal‐based POMs, the palladate structures are terminated by heteroatom groups and may also contain an internal heteroatom. The class of polyperoxodioxouranates(VI) isolated from more alkaline media frequently have fullerene‐like structures based on hexagonal bipyramidal bipyramids linked by η 2 ‐peroxo groups and hydroxo, oxalato, diphosphato, or diphosphonato bridges.

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Chiral Strandberg‐Type Molybdates [(RPO₃)₂Mo₅O₁₅]²⁻ as Molecular Gelators: Self‐Assembled Fibrillar Nanostructures with Enhanced Optical Activity

Cited by 118 publications

References 37 publications

Optically Active Polyoxotungstates Bearing Chiral Organophosphonate Substituents

Optically Active Polyoxotungstates Bearing Chiral Organophosphonate Substituents

“SOFT OXOMETALATES” (SOMs): A VERY SHORT INTRODUCTION

PolyoxometalatesUpdate based on the original article by Michael T. Pope,Encyclopedia of Inorganic Chemistry© 2005, John Wiley & Sons, Ltd.

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