The Experts below are selected from a list of 26145 Experts worldwide ranked by ideXlab platform
Bernold Hasenknopf - One of the best experts on this subject based on the ideXlab platform.
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Exploring the utility of organo-polyoxometalate hybrids to inhibit SOX transcription factors
Cell regeneration (London England), 2014Co-Authors: Kamesh Narasimhan, Bernold Hasenknopf, Emmanuel Lacote, Kévin Micoine, Serge Thorimbert, Edwin Cheung, Ralf JauchAbstract:SOX transcription factors constitute an attractive target class for intervention with small molecules as they play a prominent role in the field of regenerative biomedicine and cancer biology. However, rationally engineering specific inhibitors that interfere with transcription factor DNA interfaces continues to be a monumental challenge in the field of transcription factor chemical biology. Polyoxometalates (POMs) are inorganic compounds that were previously shown to target the high-mobility group (HMG) of SOX proteins at nanomolar concentrations. In continuation of this work, we carried out an assessment of the selectivity of a panel of newly synthesized organo-polyoxometalate hybrids in targeting different transcription factor families to enable the usage of Polyoxometalates as specific SOX transcription factor drugs. The residual DNA-binding activities of 15 different transcription factors were measured after treatment with a panel of diverse Polyoxometalates. Polyoxometalates belonging to the Dawson structural class were found to be more potent inhibitors than the Keggin class. Further, organically modified Dawson Polyoxometalates were found to be the most potent in inhibiting transcription factor DNA binding activity. The size of the Polyoxometalates and its derivitization were found to be the key determinants of their potency. Polyoxometalates are highly potent, nanomolar range inhibitors of the DNA binding activity of the Sox-HMG family. However, binding assays involving a limited subset of structurally diverse Polyoxometalates revealed a low selectivity profile against different transcription factor families. Further progress in achieving selectivity and deciphering structure-activity relationship of POMs require the identification of POM binding sites on transcription factors using elaborate approaches like X-ray crystallography and multidimensional NMR. In summary, our report reaffirms that transcription factors are challenging molecular architectures and that future polyoxometalate chemistry must consider further modification strategies, to address the substantial challenges involved in achieving target selectivity.
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Exploring the utility of organo-polyoxometalate hybrids to inhibit SOX transcription factors
Cell Regeneration, 2014Co-Authors: Kamesh Narasimhan, Bernold Hasenknopf, Emmanuel Lacote, Kévin Micoine, Serge Thorimbert, Edwin Cheung, Ralf JauchAbstract:SOX transcription factors constitute an attractive target class for intervention with small molecules as they play a prominent role in the field of regenerative biomedicine and cancer biology. However, rationally engineering specific inhibitors that interfere with transcription factor DNA interfaces continues to be a monumental challenge in the field of transcription factor chemical biology. Polyoxometalates (POMs) are inorganic compounds that were previously shown to target the high-mobility group (HMG) of SOX proteins at nanomolar concentrations. In continuation of this work, we carried out an assessment of the selectivity of a panel of newly synthesized organo-polyoxometalate hybrids in targeting different transcription factor families to enable the usage of Polyoxometalates as specific SOX transcription factor drugs.
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Regioselective Double Organic Functionalization of Polyoxotungstates through Electrophilic Addition of Aromatic Isocyanates to [P2W17O61(SnR)](7-)
European Journal of Inorganic Chemistry, 2013Co-Authors: Kévin Micoine, Emmanuel Lacote, Serge Thorimbert, Max Malacria, Bernold HasenknopfAbstract:The direct attachment of several different organic molecules to a single polyoxometalate remains a challenge in the field of functionalized Polyoxometalates. In this paper, we show that an organotin-functionalized Dawson-type polyoxotungstate [P2W17O61(SnR)]7 reacts with aromatic isocyanates ArNCO to yield new doubly functionalized compounds [P2W17O61(SnR)(CONHAr)]6. Both organic moieties, Ar and R, can be varied independently; we have tested nine Ar and three R groups. Therefore, this synthetic methodology represents a way to graft two distinct functional molecules directly onto a polyoxometalate.
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Regioselective Double Organic Functionalization of Polyoxotungstates through Electrophilic Addition of Aromatic Isocyanates to [P2W17O61(SnR)]7–†
European Journal of Inorganic Chemistry, 2013Co-Authors: Kévin Micoine, Emmanuel Lacote, Serge Thorimbert, Max Malacria, Bernold HasenknopfAbstract:The direct attachment of several different organic molecules to a single polyoxometalate remains a challenge in the field of functionalized Polyoxometalates. In this paper, we show that an organotin-functionalized Dawson-type polyoxotungstate [P2W17O61(SnR)]7– reacts with aromatic isocyanates ArNCO to yield new doubly functionalized compounds [P2W17O61(SnR)(CONHAr)]6–. Both organic moieties, Ar and R, can be varied independently; we have tested nine Ar and three R groups. Therefore, this synthetic methodology represents a way to graft two distinct functional molecules directly onto a polyoxometalate.
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Chirality in Polyoxometalate Chemistry
European Journal of Inorganic Chemistry, 2008Co-Authors: Bernold Hasenknopf, Emmanuel Lacote, Kévin Micoine, Serge Thorimbert, Max Malacria, René ThouvenotAbstract:The increasing use of Polyoxometalates in the fields of material sciences, catalysis, and biology has raised the interest in chirality of such systems. This review provides a summary of the different strategies followed: i) chirality in solid-state arrangements, ii) chiral polyoxometalate frameworks, and iii) chiral polyoxometalate–organic hybrids. Through the discussion of selected examples, an outline for future work is drawn. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)
Kévin Micoine - One of the best experts on this subject based on the ideXlab platform.
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Exploring the utility of organo-polyoxometalate hybrids to inhibit SOX transcription factors
Cell regeneration (London England), 2014Co-Authors: Kamesh Narasimhan, Bernold Hasenknopf, Emmanuel Lacote, Kévin Micoine, Serge Thorimbert, Edwin Cheung, Ralf JauchAbstract:SOX transcription factors constitute an attractive target class for intervention with small molecules as they play a prominent role in the field of regenerative biomedicine and cancer biology. However, rationally engineering specific inhibitors that interfere with transcription factor DNA interfaces continues to be a monumental challenge in the field of transcription factor chemical biology. Polyoxometalates (POMs) are inorganic compounds that were previously shown to target the high-mobility group (HMG) of SOX proteins at nanomolar concentrations. In continuation of this work, we carried out an assessment of the selectivity of a panel of newly synthesized organo-polyoxometalate hybrids in targeting different transcription factor families to enable the usage of Polyoxometalates as specific SOX transcription factor drugs. The residual DNA-binding activities of 15 different transcription factors were measured after treatment with a panel of diverse Polyoxometalates. Polyoxometalates belonging to the Dawson structural class were found to be more potent inhibitors than the Keggin class. Further, organically modified Dawson Polyoxometalates were found to be the most potent in inhibiting transcription factor DNA binding activity. The size of the Polyoxometalates and its derivitization were found to be the key determinants of their potency. Polyoxometalates are highly potent, nanomolar range inhibitors of the DNA binding activity of the Sox-HMG family. However, binding assays involving a limited subset of structurally diverse Polyoxometalates revealed a low selectivity profile against different transcription factor families. Further progress in achieving selectivity and deciphering structure-activity relationship of POMs require the identification of POM binding sites on transcription factors using elaborate approaches like X-ray crystallography and multidimensional NMR. In summary, our report reaffirms that transcription factors are challenging molecular architectures and that future polyoxometalate chemistry must consider further modification strategies, to address the substantial challenges involved in achieving target selectivity.
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Exploring the utility of organo-polyoxometalate hybrids to inhibit SOX transcription factors
Cell Regeneration, 2014Co-Authors: Kamesh Narasimhan, Bernold Hasenknopf, Emmanuel Lacote, Kévin Micoine, Serge Thorimbert, Edwin Cheung, Ralf JauchAbstract:SOX transcription factors constitute an attractive target class for intervention with small molecules as they play a prominent role in the field of regenerative biomedicine and cancer biology. However, rationally engineering specific inhibitors that interfere with transcription factor DNA interfaces continues to be a monumental challenge in the field of transcription factor chemical biology. Polyoxometalates (POMs) are inorganic compounds that were previously shown to target the high-mobility group (HMG) of SOX proteins at nanomolar concentrations. In continuation of this work, we carried out an assessment of the selectivity of a panel of newly synthesized organo-polyoxometalate hybrids in targeting different transcription factor families to enable the usage of Polyoxometalates as specific SOX transcription factor drugs.
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Regioselective Double Organic Functionalization of Polyoxotungstates through Electrophilic Addition of Aromatic Isocyanates to [P2W17O61(SnR)](7-)
European Journal of Inorganic Chemistry, 2013Co-Authors: Kévin Micoine, Emmanuel Lacote, Serge Thorimbert, Max Malacria, Bernold HasenknopfAbstract:The direct attachment of several different organic molecules to a single polyoxometalate remains a challenge in the field of functionalized Polyoxometalates. In this paper, we show that an organotin-functionalized Dawson-type polyoxotungstate [P2W17O61(SnR)]7 reacts with aromatic isocyanates ArNCO to yield new doubly functionalized compounds [P2W17O61(SnR)(CONHAr)]6. Both organic moieties, Ar and R, can be varied independently; we have tested nine Ar and three R groups. Therefore, this synthetic methodology represents a way to graft two distinct functional molecules directly onto a polyoxometalate.
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Regioselective Double Organic Functionalization of Polyoxotungstates through Electrophilic Addition of Aromatic Isocyanates to [P2W17O61(SnR)]7–†
European Journal of Inorganic Chemistry, 2013Co-Authors: Kévin Micoine, Emmanuel Lacote, Serge Thorimbert, Max Malacria, Bernold HasenknopfAbstract:The direct attachment of several different organic molecules to a single polyoxometalate remains a challenge in the field of functionalized Polyoxometalates. In this paper, we show that an organotin-functionalized Dawson-type polyoxotungstate [P2W17O61(SnR)]7– reacts with aromatic isocyanates ArNCO to yield new doubly functionalized compounds [P2W17O61(SnR)(CONHAr)]6–. Both organic moieties, Ar and R, can be varied independently; we have tested nine Ar and three R groups. Therefore, this synthetic methodology represents a way to graft two distinct functional molecules directly onto a polyoxometalate.
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Chirality in Polyoxometalate Chemistry
European Journal of Inorganic Chemistry, 2008Co-Authors: Bernold Hasenknopf, Emmanuel Lacote, Kévin Micoine, Serge Thorimbert, Max Malacria, René ThouvenotAbstract:The increasing use of Polyoxometalates in the fields of material sciences, catalysis, and biology has raised the interest in chirality of such systems. This review provides a summary of the different strategies followed: i) chirality in solid-state arrangements, ii) chiral polyoxometalate frameworks, and iii) chiral polyoxometalate–organic hybrids. Through the discussion of selected examples, an outline for future work is drawn. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)
Serge Thorimbert - One of the best experts on this subject based on the ideXlab platform.
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Exploring the utility of organo-polyoxometalate hybrids to inhibit SOX transcription factors
Cell regeneration (London England), 2014Co-Authors: Kamesh Narasimhan, Bernold Hasenknopf, Emmanuel Lacote, Kévin Micoine, Serge Thorimbert, Edwin Cheung, Ralf JauchAbstract:SOX transcription factors constitute an attractive target class for intervention with small molecules as they play a prominent role in the field of regenerative biomedicine and cancer biology. However, rationally engineering specific inhibitors that interfere with transcription factor DNA interfaces continues to be a monumental challenge in the field of transcription factor chemical biology. Polyoxometalates (POMs) are inorganic compounds that were previously shown to target the high-mobility group (HMG) of SOX proteins at nanomolar concentrations. In continuation of this work, we carried out an assessment of the selectivity of a panel of newly synthesized organo-polyoxometalate hybrids in targeting different transcription factor families to enable the usage of Polyoxometalates as specific SOX transcription factor drugs. The residual DNA-binding activities of 15 different transcription factors were measured after treatment with a panel of diverse Polyoxometalates. Polyoxometalates belonging to the Dawson structural class were found to be more potent inhibitors than the Keggin class. Further, organically modified Dawson Polyoxometalates were found to be the most potent in inhibiting transcription factor DNA binding activity. The size of the Polyoxometalates and its derivitization were found to be the key determinants of their potency. Polyoxometalates are highly potent, nanomolar range inhibitors of the DNA binding activity of the Sox-HMG family. However, binding assays involving a limited subset of structurally diverse Polyoxometalates revealed a low selectivity profile against different transcription factor families. Further progress in achieving selectivity and deciphering structure-activity relationship of POMs require the identification of POM binding sites on transcription factors using elaborate approaches like X-ray crystallography and multidimensional NMR. In summary, our report reaffirms that transcription factors are challenging molecular architectures and that future polyoxometalate chemistry must consider further modification strategies, to address the substantial challenges involved in achieving target selectivity.
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Exploring the utility of organo-polyoxometalate hybrids to inhibit SOX transcription factors
Cell Regeneration, 2014Co-Authors: Kamesh Narasimhan, Bernold Hasenknopf, Emmanuel Lacote, Kévin Micoine, Serge Thorimbert, Edwin Cheung, Ralf JauchAbstract:SOX transcription factors constitute an attractive target class for intervention with small molecules as they play a prominent role in the field of regenerative biomedicine and cancer biology. However, rationally engineering specific inhibitors that interfere with transcription factor DNA interfaces continues to be a monumental challenge in the field of transcription factor chemical biology. Polyoxometalates (POMs) are inorganic compounds that were previously shown to target the high-mobility group (HMG) of SOX proteins at nanomolar concentrations. In continuation of this work, we carried out an assessment of the selectivity of a panel of newly synthesized organo-polyoxometalate hybrids in targeting different transcription factor families to enable the usage of Polyoxometalates as specific SOX transcription factor drugs.
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Regioselective Double Organic Functionalization of Polyoxotungstates through Electrophilic Addition of Aromatic Isocyanates to [P2W17O61(SnR)](7-)
European Journal of Inorganic Chemistry, 2013Co-Authors: Kévin Micoine, Emmanuel Lacote, Serge Thorimbert, Max Malacria, Bernold HasenknopfAbstract:The direct attachment of several different organic molecules to a single polyoxometalate remains a challenge in the field of functionalized Polyoxometalates. In this paper, we show that an organotin-functionalized Dawson-type polyoxotungstate [P2W17O61(SnR)]7 reacts with aromatic isocyanates ArNCO to yield new doubly functionalized compounds [P2W17O61(SnR)(CONHAr)]6. Both organic moieties, Ar and R, can be varied independently; we have tested nine Ar and three R groups. Therefore, this synthetic methodology represents a way to graft two distinct functional molecules directly onto a polyoxometalate.
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Regioselective Double Organic Functionalization of Polyoxotungstates through Electrophilic Addition of Aromatic Isocyanates to [P2W17O61(SnR)]7–†
European Journal of Inorganic Chemistry, 2013Co-Authors: Kévin Micoine, Emmanuel Lacote, Serge Thorimbert, Max Malacria, Bernold HasenknopfAbstract:The direct attachment of several different organic molecules to a single polyoxometalate remains a challenge in the field of functionalized Polyoxometalates. In this paper, we show that an organotin-functionalized Dawson-type polyoxotungstate [P2W17O61(SnR)]7– reacts with aromatic isocyanates ArNCO to yield new doubly functionalized compounds [P2W17O61(SnR)(CONHAr)]6–. Both organic moieties, Ar and R, can be varied independently; we have tested nine Ar and three R groups. Therefore, this synthetic methodology represents a way to graft two distinct functional molecules directly onto a polyoxometalate.
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Chirality in Polyoxometalate Chemistry
European Journal of Inorganic Chemistry, 2008Co-Authors: Bernold Hasenknopf, Emmanuel Lacote, Kévin Micoine, Serge Thorimbert, Max Malacria, René ThouvenotAbstract:The increasing use of Polyoxometalates in the fields of material sciences, catalysis, and biology has raised the interest in chirality of such systems. This review provides a summary of the different strategies followed: i) chirality in solid-state arrangements, ii) chiral polyoxometalate frameworks, and iii) chiral polyoxometalate–organic hybrids. Through the discussion of selected examples, an outline for future work is drawn. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)
Emmanuel Lacote - One of the best experts on this subject based on the ideXlab platform.
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Exploring the utility of organo-polyoxometalate hybrids to inhibit SOX transcription factors
Cell regeneration (London England), 2014Co-Authors: Kamesh Narasimhan, Bernold Hasenknopf, Emmanuel Lacote, Kévin Micoine, Serge Thorimbert, Edwin Cheung, Ralf JauchAbstract:SOX transcription factors constitute an attractive target class for intervention with small molecules as they play a prominent role in the field of regenerative biomedicine and cancer biology. However, rationally engineering specific inhibitors that interfere with transcription factor DNA interfaces continues to be a monumental challenge in the field of transcription factor chemical biology. Polyoxometalates (POMs) are inorganic compounds that were previously shown to target the high-mobility group (HMG) of SOX proteins at nanomolar concentrations. In continuation of this work, we carried out an assessment of the selectivity of a panel of newly synthesized organo-polyoxometalate hybrids in targeting different transcription factor families to enable the usage of Polyoxometalates as specific SOX transcription factor drugs. The residual DNA-binding activities of 15 different transcription factors were measured after treatment with a panel of diverse Polyoxometalates. Polyoxometalates belonging to the Dawson structural class were found to be more potent inhibitors than the Keggin class. Further, organically modified Dawson Polyoxometalates were found to be the most potent in inhibiting transcription factor DNA binding activity. The size of the Polyoxometalates and its derivitization were found to be the key determinants of their potency. Polyoxometalates are highly potent, nanomolar range inhibitors of the DNA binding activity of the Sox-HMG family. However, binding assays involving a limited subset of structurally diverse Polyoxometalates revealed a low selectivity profile against different transcription factor families. Further progress in achieving selectivity and deciphering structure-activity relationship of POMs require the identification of POM binding sites on transcription factors using elaborate approaches like X-ray crystallography and multidimensional NMR. In summary, our report reaffirms that transcription factors are challenging molecular architectures and that future polyoxometalate chemistry must consider further modification strategies, to address the substantial challenges involved in achieving target selectivity.
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Exploring the utility of organo-polyoxometalate hybrids to inhibit SOX transcription factors
Cell Regeneration, 2014Co-Authors: Kamesh Narasimhan, Bernold Hasenknopf, Emmanuel Lacote, Kévin Micoine, Serge Thorimbert, Edwin Cheung, Ralf JauchAbstract:SOX transcription factors constitute an attractive target class for intervention with small molecules as they play a prominent role in the field of regenerative biomedicine and cancer biology. However, rationally engineering specific inhibitors that interfere with transcription factor DNA interfaces continues to be a monumental challenge in the field of transcription factor chemical biology. Polyoxometalates (POMs) are inorganic compounds that were previously shown to target the high-mobility group (HMG) of SOX proteins at nanomolar concentrations. In continuation of this work, we carried out an assessment of the selectivity of a panel of newly synthesized organo-polyoxometalate hybrids in targeting different transcription factor families to enable the usage of Polyoxometalates as specific SOX transcription factor drugs.
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Regioselective Double Organic Functionalization of Polyoxotungstates through Electrophilic Addition of Aromatic Isocyanates to [P2W17O61(SnR)](7-)
European Journal of Inorganic Chemistry, 2013Co-Authors: Kévin Micoine, Emmanuel Lacote, Serge Thorimbert, Max Malacria, Bernold HasenknopfAbstract:The direct attachment of several different organic molecules to a single polyoxometalate remains a challenge in the field of functionalized Polyoxometalates. In this paper, we show that an organotin-functionalized Dawson-type polyoxotungstate [P2W17O61(SnR)]7 reacts with aromatic isocyanates ArNCO to yield new doubly functionalized compounds [P2W17O61(SnR)(CONHAr)]6. Both organic moieties, Ar and R, can be varied independently; we have tested nine Ar and three R groups. Therefore, this synthetic methodology represents a way to graft two distinct functional molecules directly onto a polyoxometalate.
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Regioselective Double Organic Functionalization of Polyoxotungstates through Electrophilic Addition of Aromatic Isocyanates to [P2W17O61(SnR)]7–†
European Journal of Inorganic Chemistry, 2013Co-Authors: Kévin Micoine, Emmanuel Lacote, Serge Thorimbert, Max Malacria, Bernold HasenknopfAbstract:The direct attachment of several different organic molecules to a single polyoxometalate remains a challenge in the field of functionalized Polyoxometalates. In this paper, we show that an organotin-functionalized Dawson-type polyoxotungstate [P2W17O61(SnR)]7– reacts with aromatic isocyanates ArNCO to yield new doubly functionalized compounds [P2W17O61(SnR)(CONHAr)]6–. Both organic moieties, Ar and R, can be varied independently; we have tested nine Ar and three R groups. Therefore, this synthetic methodology represents a way to graft two distinct functional molecules directly onto a polyoxometalate.
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Chirality in Polyoxometalate Chemistry
European Journal of Inorganic Chemistry, 2008Co-Authors: Bernold Hasenknopf, Emmanuel Lacote, Kévin Micoine, Serge Thorimbert, Max Malacria, René ThouvenotAbstract:The increasing use of Polyoxometalates in the fields of material sciences, catalysis, and biology has raised the interest in chirality of such systems. This review provides a summary of the different strategies followed: i) chirality in solid-state arrangements, ii) chiral polyoxometalate frameworks, and iii) chiral polyoxometalate–organic hybrids. Through the discussion of selected examples, an outline for future work is drawn. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)
Ronny Neumann - One of the best experts on this subject based on the ideXlab platform.
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Dioxygen in Polyoxometalate Mediated Reactions
Chemical reviews, 2017Co-Authors: Ira A. Weinstock, Roy E. Schreiber, Ronny NeumannAbstract:In this review article, we consider the use of molecular oxygen in reactions mediated by Polyoxometalates. Polyoxometalates are anionic metal oxide clusters of a variety of structures that are soluble in liquid phases and therefore amenable to homogeneous catalytic transformations. Often, they are active for electron transfer oxidations of a myriad of substrates and upon reduction can be reoxidized by molecular oxygen. For example, the phosphovanadomolybdate, H5PV2Mo10O40, can oxidize Pd(0) thereby enabling aerobic reactions catalyzed by Pd and H5PV2Mo10O40. In a similar vein, Polyoxometalates can stabilize metal nanoparticles, leading to additional transformations. Furthermore, electron transfer oxidation of other substrates such as halides and sulfur-containing compounds is possible. More uniquely, H5PV2Mo10O40 and its analogues can mediate electron transfer-oxygen transfer reactions where oxygen atoms are transferred from the polyoxometalate to the substrate. This unique property has enabled correspond...
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On the effect of ion pairing of Keggin type polyanions with quaternary ammonium cations on redox potentials in organic solvents
Physical chemistry chemical physics : PCCP, 2016Co-Authors: Bo Chen, Ronny NeumannAbstract:The electrochemical properties of Keggin type Polyoxometalates Qn[XW12O40] (X = P, Si, B; Q = n-tetraoctylammonium and n-trioctylmethylammonium) in organic solvents were investigated in order to understand the interrelation between the redox potentials, solvents and ion pairing. A logarithmic correlation between the dielectric constant of the solvent (e ranged from 4.8 to 46.6) and the reduction potential of the [PW12O4]3−/[PW12O4]4− couple was found. This reduction potential increased significantly when the surface charge of the polyoxometalate went from 3− to 5−. The investigation of the ion pairing properties by diffusion NMR revealed the presence of intimate ion pairs in less polar solvents (e.g. dichloromethane) and less compact ion pairs in more polar solvents (e.g. DMSO). Using a V atom within the polyoxometalate an NMR experiment showed that a n-trioctylmethyl ammonium cation bonded to the polyoxometalate anion more intimately than a n-tetraoctyl ammonium cation.
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activation of molecular oxygen Polyoxometalates and liquid phase catalytic oxidation
Inorganic Chemistry, 2010Co-Authors: Ronny NeumannAbstract:In this Forum Article, we discuss the use of dioxygen (O2) in oxidations catalyzed by Polyoxometalates. One- and two-electron-transfer oxidation of organic substrates is catalyzed by H5PV2Mo10O40 and often occurs via an outer-sphere mechanism. The reduced polyoxometalate is reoxidized in a separate step by O2 with the formation of water. H5PV2Mo10O40 also catalyzes electron transfer−oxygen transfer reactions. Here, in contrast to the paradigm that high-valent oxo species are often stronger oxygen-transfer species than lower-valent species, the opposite occurs. Thus, oxygen transfer from the catalyst is preceded by electron transfer from the organic substrate. The monooxygenase-type reduction of O2 with Polyoxometalates is also discussed based on the formation of a stable iron(III) hydroperoxide compound that may have implications for the oxidation of other lower-valent Polyoxometalates such as vanadium(IV)- and ruthenium(II)-substituted Polyoxometalates. Finally, the formation of hybrid compounds through ...
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strategies for oxidation catalyzed by Polyoxometalates at the interface of homogeneous and heterogeneous catalysis
ChemInform, 2006Co-Authors: Maxym Vazylyev, Dorit Slobodarozner, Adina Haimov, Galia Maayan, Ronny NeumannAbstract:A basic premise behind the use of Polyoxometalates in oxidation chemistry is the fact that Polyoxometalates are oxidatively stable. This, a priori, leads to the conclusion that for practical purposes Polyoxometalates would have distinct advantages over widely investigated organometallic compounds that are vulnerable to decomposition due to oxidation of the ligand bound to the metal center. Since polyoxometalate synthesis is normally carried out in water by mixing the stoichiometrically required amounts of monomeric metal salts and adjusting the pH to a specific acidic value many structure types are accessible by variation of the reaction stoichiometry, replacement of one or more addenda atoms with other transition or main group metals, and pH control. The structural variety available has enabled the use of Polyoxometalates as catalysts for oxidation of hydrocarbons and functionalized organic substrates (alcohols, amines, sulfides, etc.) with a wide range of oxygen donors ranging from molecular oxygen, hydrogen peroxide, nitrous oxide, ozone, alkyl hydroperoxides, periodate, sulfoxide and others. The wide purview of oxidation reactions is enabled because the structural variety leads to oxidation through a number of different mechanistic motifs. From a synthetic organic point of view, the most applicable uses of Polyoxometalates as catalysts involve the “green” oxygen donors – hydrogen peroxide and molecular oxygen. Since practical applications are in hand in this area, practical considerations concerned with catalyst recycle and/or recovery and the elimination of environmentally problematic solvents are also coming to the forefront. In this paper, we will present some of our activities in the area of “catalyst engineering” for catalytic synthetic applications by Polyoxometalates including: (a) catalytic mesoporous solids from organic-polyoxometalate hybrid materials, (b) fluorous phase Polyoxometalates with and without fluorous solvents and (c) the use of aqueous biphasic media for oxidation with hydrogen peroxide.
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Applications of Polyoxometalates in Homogeneous Catalysis
Polyoxometalate Molecular Science, 2003Co-Authors: Ronny NeumannAbstract:This chapter will present an overview on the use of Polyoxometalates as catalysts in homogeneous reaction media. This is not meant to be a comprehensive review as several such reviews are already available covering material up to the last few years [1], but rather an attempt to describe, also to non-practitioners, the general principles involved in this important field of application of polyoxometalate chemistry. This chapter will cover first more briefly the use of Polyoxometalates as acid catalysts and then the use of Polyoxometalates in oxidation catalysis. The discussion of oxidation catalysis will emphasize both general principles involved in the activation of oxidants and oxygen donors and the specific use of Polyoxometalates in this context. Emphasis will be on oxidative transformations involving hydrocarbons and much of the description and discussion will be concentrated on research carried out in our group (my apologies in advance to those whose research was not completely covered).