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Michael A. Giardello

Bio: Michael A. Giardello is an academic researcher from California Institute of Technology. The author has contributed to research in topics: ROMP & Ring-opening metathesis polymerisation. The author has an hindex of 8, co-authored 20 publications receiving 2809 citations.

Papers
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Journal ArticleDOI
TL;DR: This procedure provides a nonhazardous alternative to distillations and vacuum transfers and does not require undue supervision or cooling, yet allows for the rapid collection of large quantities of extremely pure solvents on demand.

2,663 citations

Patent
04 Feb 2000
TL;DR: In this paper, the authors describe a density modulator composed of one or more density modulators dispersed in a polymer matrix where the matrix is prepared by the metathesis of an olefin monomer using a ruthenium or osmium metal carbene catalyst.
Abstract: The invention discloses a composition comprising one or more density modulators dispersed in a polymer matrix wherein the matrix is prepared by the metathesis of an olefin monomer using a ruthenium or osmium metal carbene catalyst. The composition may use a catalyst of formula (I) wherein: M is ruthenium or osmium; X and X1 are either the same or different and are any anionic ligand; L and L1 are either the same or different and are any neutral electron donor; R and R1 are either the same or different and are each independently hydrogen or a substituent selected from the group consisting of C?1?-C20alkyl, C2-C20alkenyl, C2-C20alkynyl, aryl, C1-C20 carboxylate, C1-C20alkoxy, C2-C20alkenyloxy, C2-C20alkynyloxy, aryloxy, C2-C20alkoxycarbonyl, C1-C20alkylthio, C1-C20alkylsulfonyl and C1-C20alkylsulfinyl, wherein each of the substituents is substituted or unsubstituted. The density modulators are selected from the group consisting of metallic density modulators, microparticulate density modulators and macroparticulate density modulators.

66 citations

Journal ArticleDOI
TL;DR: The first synthesis of a newly found naturally occurring anti-malarial nonenolide was described in this article, where a pivotal step in the synthesis is the ring-closing metathesis of a dienoic ester prepared by coupling an acid and alcohol that were stereoselectively synthesized from (S)-α-hydroxy-γ-butyrolactone and 1,2-O-isopropylidene d -glyceraldehyde, respectively.

58 citations

Patent
30 Aug 2002
TL;DR: In this paper, a novel composition comprising porous materials infused with polymers obtained from metathesis reactions, for example, ROMP derived polymers and ADMET-derived polymers.
Abstract: The present invention relates to novel compositions comprising porous materials infused with polymers obtained from metathesis reactions, for example ROMP derived polymers and ADMET derived polymers. The invention further relates to cyclic olefin monomer formulations, including ruthenium or osmium carbene metathesis catalysts, useful for the infusion of porous materials. Also disclosed are methods for preparing the porous materials infused with cyclic olefin resin formulations.

29 citations

Patent
17 Jun 2012
TL;DR: In this paper, a ring opening metathesis polymerization (ROMP) composition is proposed to improve the adhesion of resin compositions to substrate materials, pre-treating substrate materials with adhesion promoters containing isocyanate groups, and adding a hydroperoxide gel modifier to a ROMP polymerizable resin composition to control gel formation of the polymerizing resin.
Abstract: This invention relates to compositions and methods for improving the adhesion of resin compositions to substrate materials, pre-treating substrate materials to improve the adhesion of resin compositions to the substrate materials, and/or controlling gel formation of resin compositions. More particularly, the invention relates to compositions and methods for improving the adhesion of ring opening metathesis polymerization (ROMP) compositions to substrate materials using adhesion promoters containing isocyariate groups in a resin composition. The invention also relates to methods for improving the adhesion of resin compositions to substrate materials by pre-treating substrate materials with adhesion promoters containing isocyanate groups. The invention further relates to a method of providing a gel- modified ROMP composition, in which a hydroperoxide is added to a ROMP polymerizable resin composition in order to control gel formation of the polymerizing resin. An improved ROMP composition is further disclosed, comprising a cyclic olefin, a ROMP metathesis catalyst, an adhesion promoter, and an added hydroperoxide gel modifier. The polymer products produced via ROMP reactions of the invention may be utilized for a wide range of materials and composite applications. The invention has utility in the fields of catalysis, organic synthesis, and polymer and materials chemistry and manufacture.

18 citations


Cited by
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Journal ArticleDOI
01 Dec 2006-Carbon
TL;DR: In this article, a number of functionalized graphite oxides were prepared by treatment of graphite oxide (GO) with organic isocyanates, which can then be exfoliated into functionalized graphene oxide nanoplatelets that can form a stable dispersion in polar aprotic solvents.

2,103 citations

Journal ArticleDOI
24 Aug 2006-Nature
TL;DR: Amine link groups are used to form single-molecule junctions with more reproducible current–voltage characteristics and it is found that the conductance for the series decreases with increasing twist angle, consistent with a cosine-squared relation predicted for transport through π-conjugated biphenyl systems.
Abstract: Since it was first suggested1 that a single molecule might function as an active electronic component, a number of techniques have been developed to measure the charge transport properties of single molecules2,3,4,5,6,7,8,9,10,11,12. Although scanning tunnelling microscopy observations under high vacuum conditions can allow stable measurements of electron transport, most measurements of a single molecule bonded in a metal–molecule–metal junction exhibit relatively large variations in conductance. As a result, even simple predictions about how molecules behave in such junctions have still not been rigorously tested. For instance, it is well known13,14 that the tunnelling current passing through a molecule depends on its conformation; but although some experiments have verified this effect15,16,17,18, a comprehensive mapping of how junction conductance changes with molecular conformation is not yet available. In the simple case of a biphenyl—a molecule with two phenyl rings linked by a single C–C bond—conductance is expected to change with the relative twist angle between the two rings, with the planar conformation having the highest conductance. Here we use amine link groups to form single-molecule junctions with more reproducible current–voltage characteristics19. This allows us to extract average conductance values from thousands of individual measurements on a series of seven biphenyl molecules with different ring substitutions that alter the twist angle of the molecules. We find that the conductance for the series decreases with increasing twist angle, consistent with a cosine-squared relation predicted for transport through π-conjugated biphenyl systems13.

1,266 citations

Journal ArticleDOI
TL;DR: The origins of the observed substituent effects as well as the implications of these studies for the design and implementation of new olefin metathesis catalysts and substrates are discussed in detail.
Abstract: This report details the effects of ligand variation on the mechanism and activity of ruthenium-based olefin metathesis catalysts. A series of ruthenium complexes of the general formula L(PR3)(X)2RuCHR1 have been prepared, and the influence of the substituents L, X, R, and R1 on the rates of phosphine dissociation and initiation as well as overall activity for olefin metathesis reactions was examined. In all cases, initiation proceeds by dissociative substitution of a phosphine ligand (PR3) with an olefinic substrate. All of the ligands L, X, R, and R1 have a significant impact on initiation rates and on catalyst activity. The origins of the observed substituent effects as well as the implications of these studies for the design and implementation of new olefin metathesis catalysts and substrates are discussed in detail.

1,016 citations

Journal ArticleDOI
TL;DR: Structural characterization of a high spin iron(0) alkyne and a bis(silane) sigma-complex has been accomplished and in combination with isotopic labeling studies provides insight into the mechanism of both catalytic C-H and catalyticC-Si bond formation.
Abstract: Reduction of the five-coordinate iron(II) dihalide complexes (iPrPDI)FeX2 (iPrPDI = ((2,6-CHMe2)2C6H3NCMe)2C5H3N; X = Cl, Br) with sodium amalgam under 1 atm of dinitrogen afforded the square pyramidal, high spin iron(0) bis(dinitrogen) complex (iPrPDI)Fe(N2)2. In solution, (iPrPDI)Fe(N2)2 loses 1 equiv of N2 to afford the mono(dinitrogen) adduct (iPrPDI)Fe(N2). Both dinitrogen compounds serve as effective precatalysts for the hydrogenation and hydrosilation of olefins and alkynes. Effecient catalytic reactions are observed with low catalyst loadings (≤0.3 mol %) at ambient temperature in nonpolar media. The catalytic hydrosilations are selective in forming the anti-Markovnikov product. Structural characterization of a high spin iron(0) alkyne and a bis(silane) σ-complex has also been accomplished and in combination with isotopic labeling studies provides insight into the mechanism of both catalytic C−H and catalytic C−Si bond formation.

718 citations

Journal ArticleDOI
25 Nov 2011-Science
TL;DR: A photoredox-catalyzed C–H arylation reaction for the construction of benzylic amines is discovered, an important structural motif within pharmaceutical compounds that is not readily accessed via simple substrates.
Abstract: Serendipity has long been a welcome yet elusive phenomenon in the advancement of chemistry. We sought to exploit serendipity as a means of rapidly identifying unanticipated chemical transformations. By using a high-throughput, automated workflow and evaluating a large number of random reactions, we have discovered a photoredox-catalyzed C–H arylation reaction for the construction of benzylic amines, an important structural motif within pharmaceutical compounds that is not readily accessed via simple substrates. The mechanism directly couples tertiary amines with cyanoaromatics by using mild and operationally trivial conditions.

667 citations