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Motohiro Tomizawa - One of the best experts on this subject based on the ideXlab platform.

  • nereistoxin and cartap neurotoxicity attributable to direct block of the insect nicotinic receptor channel
    Journal of Agricultural and Food Chemistry, 2003
    Co-Authors: Motohiro Tomizawa
    Abstract:

    Nereistoxin (NTX) (4-dimethylamino-1,2-Dithiolane) is the naturally occurring prototype for cartap [the bis(thiocarbamate) derivative of the NTX dithiol], which is generally regarded as a proinsecticide reverting to NTX. The aim of this study is to define the target site(s) for Dithiolanes and dithiol esters. The affinity of [3H]NTX was not suitable for binding assays with honeybee (Apis mellifera) head membranes. However, NTX and cartap are equally potent, direct-acting, and competitive displacers of [3H]thienylcyclohexylpiperidine binding at the noncompetitive blocker (NCB) site of the Apis nicotinic acetylcholine receptor (nAChR)/channel. NTX also binds at the Apis [3H]imidacloprid agonist site, but cartap does not. As candidate metabolic pathways, sequential N-desmethylation and S-oxidation of NTX progressively reduce its potency at the NCB site and toxicity to houseflies. A P450 inhibitor reduces the toxicity of NTX and enhances it with cartap. Surprisingly, cartap is not just a pro-NTX but instead d...

  • nereistoxin and cartap neurotoxicity attributable to direct block of the insect nicotinic receptor channel
    Journal of Agricultural and Food Chemistry, 2003
    Co-Authors: Seog-jong Lee, Motohiro Tomizawa
    Abstract:

    Nereistoxin (NTX) (4-dimethylamino-1,2-Dithiolane) is the naturally occurring prototype for cartap [the bis(thiocarbamate) derivative of the NTX dithiol], which is generally regarded as a proinsecticide reverting to NTX. The aim of this study is to define the target site(s) for Dithiolanes and dithiol esters. The affinity of [(3)H]NTX was not suitable for binding assays with honeybee (Apis mellifera) head membranes. However, NTX and cartap are equally potent, direct-acting, and competitive displacers of [(3)H]thienylcyclohexylpiperidine binding at the noncompetitive blocker (NCB) site of the Apis nicotinic acetylcholine receptor (nAChR)/channel. NTX also binds at the Apis [(3)H]imidacloprid agonist site, but cartap does not. As candidate metabolic pathways, sequential N-desmethylation and S-oxidation of NTX progressively reduce its potency at the NCB site and toxicity to houseflies. A P450 inhibitor reduces the toxicity of NTX and enhances it with cartap. Surprisingly, cartap is not just a pro-NTX but instead directly induces inhibitory neurotoxicity by blocking the nAChR/channel, whereas NTX may have dual NCB and agonist targets.

Robert M Waymouth - One of the best experts on this subject based on the ideXlab platform.

  • 1 2 Dithiolane derived dynamic covalent materials cooperative self assembly and reversible cross linking
    Journal of the American Chemical Society, 2017
    Co-Authors: Xiangyi Zhang, Robert M Waymouth
    Abstract:

    The use of Dithiolane-containing polymers to construct responsive and dynamic networks is an attractive strategy in material design. Here, we provide a detailed mechanistic study on the self-assembly and gelation behavior of a class of ABA triblock copolymers containing a central poly(ethylene oxide) block and terminal polycarbonate blocks with pendant 1,2-Dithiolane functionalities. In aqueous solution, these amphiphilic block copolymers self-assemble into bridged flower micelles at high concentrations. The addition of a thiol initiates the reversible ring-opening polymerizations of Dithiolanes in the micellar cores to induce the cross-linking and gelation of the micellar network. The properties of the resulting hydrogels depend sensitively on the structures of 1,2-Dithiolanes. While the methyl asparagusic acid-derived hydrogels are highly dynamic, adaptable, and self-healing, those derived from lipoic acid are rigid, resilient, and brittle. The thermodynamics and kinetics of ring-opening polymerization ...

  • 1,2-Dithiolane-Derived Dynamic, Covalent Materials: Cooperative Self-Assembly and Reversible Cross-Linking
    2017
    Co-Authors: Xiangyi Zhang, Robert M Waymouth
    Abstract:

    The use of Dithiolane-containing polymers to construct responsive and dynamic networks is an attractive strategy in material design. Here, we provide a detailed mechanistic study on the self-assembly and gelation behavior of a class of ABA triblock copolymers containing a central poly­(ethylene oxide) block and terminal polycarbonate blocks with pendant 1,2-Dithiolane functionalities. In aqueous solution, these amphiphilic block copolymers self-assemble into bridged flower micelles at high concentrations. The addition of a thiol initiates the reversible ring-opening polymerizations of Dithiolanes in the micellar cores to induce the cross-linking and gelation of the micellar network. The properties of the resulting hydrogels depend sensitively on the structures of 1,2-Dithiolanes. While the methyl asparagusic acid-derived hydrogels are highly dynamic, adaptable, and self-healing, those derived from lipoic acid are rigid, resilient, and brittle. The thermodynamics and kinetics of ring-opening polymerization of the two Dithiolanes were investigated to provide important insights on the dramatically different properties of the hydrogels derived from the two different Dithiolanes. The incorporation of both Dithiolane monomers into the block copolymers provides a facile way to tailor the properties of these hydrogels

  • structurally dynamic hydrogels derived from 1 2 Dithiolanes
    Journal of the American Chemical Society, 2015
    Co-Authors: Gregg A Barcan, Xiangyi Zhang, Robert M Waymouth
    Abstract:

    The design and generation of adaptable materials derived from structurally dynamic polymers provides a strategy for generating smart materials that can respond to environmental stimuli or exhibit self-healing behavior. Herein we report an expedient organocatalytic ring-opening polymerization of cyclic carbonates containing pendant Dithiolanes (trimethylene carbonate/Dithiolane, TMCDT) from poly(ethylene oxide) diols to generate water-soluble triblock (ABA) copolymers containing a central poly(ethylene oxide) block and terminal Dithiolane blocks. Hydrogels generated from the triblock copolymers and a cross-linking dithiol exhibited dynamic behavior as a result of the reversible ring opening of the pendant 1,2-Dithiolanes. These materials exhibit self-healing behavior, can be injected through a syringe, and rapidly recover their mechanical properties after a severe strain deformation. The dynamic properties of these gels can be modulated with the number of Dithiolane units, pH, and temperature.

  • Structurally Dynamic Hydrogels Derived from 1,2-Dithiolanes
    2015
    Co-Authors: Gregg A Barcan, Xiangyi Zhang, Robert M Waymouth
    Abstract:

    The design and generation of adaptable materials derived from structurally dynamic polymers provides a strategy for generating smart materials that can respond to environmental stimuli or exhibit self-healing behavior. Herein we report an expedient organocatalytic ring-opening polymerization of cyclic carbonates containing pendant Dithiolanes (trimethylene carbonate/Dithiolane, TMCDT) from poly­(ethylene oxide) diols to generate water-soluble triblock (ABA) copolymers containing a central poly­(ethylene oxide) block and terminal Dithiolane blocks. Hydrogels generated from the triblock copolymers and a cross-linking dithiol exhibited dynamic behavior as a result of the reversible ring opening of the pendant 1,2-Dithiolanes. These materials exhibit self-healing behavior, can be injected through a syringe, and rapidly recover their mechanical properties after a severe strain deformation. The dynamic properties of these gels can be modulated with the number of Dithiolane units, pH, and temperature

Heinz Heimgartner - One of the best experts on this subject based on the ideXlab platform.

  • a novel application of 2 silylated 1 3 Dithiolanes for the synthesis of aryl hetaryl substituted ethenes and dibenzofulvenes
    Beilstein Journal of Organic Chemistry, 2017
    Co-Authors: Grzegorz Mlostoń, Paulina Pipiak, Roza Hamerafaldyga, Heinz Heimgartner
    Abstract:

    Trimethylsilyldiazomethane (TMS-CHN2) reacts readily with hetaryl thioketones to give sterically crowded 2-trimethylsilyl-4,4,5,5-tetrahetaryl-1,3-Dithiolanes with complete regioselectivity at −75 °C as well as at rt. Thiofluorenone, a relatively stable and highly reactive aryl thioketone, yields upon treatment with TMS-CHN2 at −60 °C the corresponding 1,3,4-thiadiazoline. This unstable cycloadduct undergoes decomposition at ca. −45 °C and the silylated thiocarbonyl S-methanide generated thereby is trapped with complete regioselectivity by aryl or hetaryl thioketones forming also sterically crowded 2-trimethylsilyl-1,3-Dithiolanes. The obtained 1,3-Dithiolanes, by treatment with an equimolar amount of TBAF in a one-pot procedure, are converted in high yields into hetaryl/aryl-substituted ethenes or dibenzofulvenes, respectively, via a cycloreversion reaction of the intermediate 1,3-Dithiolane carbanion. The presented protocol offers a new, highly efficient approach to tetrasubstituted ethenes and dibenzofulvenes bearing aryl and/or hetaryl substituents.

  • A novel application of 2-silylated 1,3-Dithiolanes for the synthesis of aryl/hetaryl-substituted ethenes and dibenzofulvenes
    Beilstein-Institut, 2017
    Co-Authors: Grzegorz Mlostoń, Paulina Pipiak, Róża Hamera-fałdyga, Heinz Heimgartner
    Abstract:

    Trimethylsilyldiazomethane (TMS-CHN2) reacts readily with hetaryl thioketones to give sterically crowded 2-trimethylsilyl-4,4,5,5-tetrahetaryl-1,3-Dithiolanes with complete regioselectivity at −75 °C as well as at rt. Thiofluorenone, a relatively stable and highly reactive aryl thioketone, yields upon treatment with TMS-CHN2 at −60 °C the corresponding 1,3,4-thiadiazoline. This unstable cycloadduct undergoes decomposition at ca. −45 °C and the silylated thiocarbonyl S-methanide generated thereby is trapped with complete regioselectivity by aryl or hetaryl thioketones forming also sterically crowded 2-trimethylsilyl-1,3-Dithiolanes. The obtained 1,3-Dithiolanes, by treatment with an equimolar amount of TBAF in a one-pot procedure, are converted in high yields into hetaryl/aryl-substituted ethenes or dibenzofulvenes, respectively, via a cycloreversion reaction of the intermediate 1,3-Dithiolane carbanion. The presented protocol offers a new, highly efficient approach to tetrasubstituted ethenes and dibenzofulvenes bearing aryl and/or hetaryl substituents

Fourmigué Marc - One of the best experts on this subject based on the ideXlab platform.

  • Introducing Selenium in Single-Component Molecular Conductors Based on Nickel Bis(dithiolene) Complexes
    'American Chemical Society (ACS)', 2021
    Co-Authors: Hachem Hadi, Jeannin Olivier, Fourmigué Marc, Barrière Frédéric, Cui Hengbo, Kato Reizo, Lorcy Dominique
    Abstract:

    International audienceTwo selenated analogues of the all-sulfur single-component molecular conductor [Ni(Et-thiazdt)(2)] (Et-thiazdt = N-ethylthiazoline-2-thione-4,5-dithiolate) have been prepared from their precursor radical-anion complexes. Replacement of the thione by a selenone moiety gives the neutral [Ni(Et-thiazSedt)(2)] complex. It adopts an unprecedented solid-state organization (for neutral nickel complexes), with the formation of perfectly eclipsed dimers and very short intermolecular Se···Se contacts (81% of the van der Waals contact distance). Limited interactions between dimers leads to a large semiconducting gap and low conductivity (σ(RT) = 1.7 × 10(-5) S cm(-1)). On the other hand, going from the neutral [Ni(Et-thiazdt)(2)] dithiolene complex to the corresponding [Ni(Et-thiazds)(2)] diselenolene complex gives rise to a more conventional layered structure built out of uniform stacks of the diselenolene complexes, different, however, from the all-sulfur analogue [Ni(Et-thiazdt)(2)]. Band structure calculations show an essentially 1D electronic structure with large band dispersion and a small HOMO-LUMO gap. Under high pressures (up to 19 GPa), the conductivity increases by 4 orders of magnitude and the activation energy is decreased from 120 meV to only 13 meV, with an abrupt change observed around 10 GPa, suggesting a structural phase transition under pressure

  • Halogen bonded metal bis(dithiolene) 2D frameworks
    'Royal Society of Chemistry (RSC)', 2020
    Co-Authors: Hachem Hadi, Jeannin Olivier, Fourmigué Marc, Barrière Frédéric, Lorcy Dominique
    Abstract:

    International audienceHalogenated metal dithiolene complexes have been designed together with halogen bond acceptor sites in order to favor halogen bonding interactions between these electroactive architectures. For the synthesis, we explored the reactivity of the protected N-tert-butyl-1,3-thiazoline-2-thione-4,5-dithiolate ligand towards DMSO and I-2 and successfully prepared the appropriate protected 2-iodo-1,3-thiazole-4,5-dithiolate ligand, (I-tzdt). Nickel and gold monoanionic complexes, [M(I-tzdt)(2)](-1) (M = Au, Ni), have been synthesized and the Au complexes were isolated in the solid state in their trans and cis isomers. The trans-Ni and trans-Au complexes are isostructural and X-ray diffraction analysis confirmed the occurrence of short and directional IS halogen bonding interactions leading to 2D metal bis(dithiolene) frameworks with channels hosting the counterions. On the other hand, additional chalcogen center dot center dot center dot chalcogen interactions are observed for the cis-Au complex, transforming the 2D into a 3D network

  • Hydrogen bonding interactions in single component molecular conductors based on metal (Ni, Au) bis(dithiolene) complexes
    'Royal Society of Chemistry (RSC)', 2020
    Co-Authors: Hachem Hadi, Fourmigué Marc, Bellec Nathalie, Lorcy Dominique
    Abstract:

    International audienceIntroduction of hydrogen bonding (HB) interactions in single component conductors derived from nickel and gold bis(dithiolene) complexes is explored with the 2-alkylthio-1,3-thiazole-4,5-dithiolate (RS-tzdt) with R = CH2CH2OH through the preparation of the neutral [Ni(HOEtS-tzdt)2]0 (closed-shell) and [Au(HOEtS-tzdt)2]˙ (radical) complexes. At variance with many other radical gold dithiolene complexes which have a strong tendency to dimerize in the solid state, [Au(HOEtS-tzdt)2]˙ crystallizes into uniform stacks interconnected by strong O-HN HB involving the nitrogen atom of the thiazole ring. [Au(HOEtS-tzdt)2]˙ is isostructural with its neutral, closed-shell nickel analog [Ni(HOEtS-tzdt)2]0, a rare situation in this metal bis(dithiolene) chemistry. It demonstrates how the strength of the HB directing motif can control the overall structural arrangement to stabilize the same structure despite a different electron count. The nickel complex behaves as a band semiconductor with weak room temperature conductivity (1.6 × 10-5 S cm-1), while the gold complex is described as a Mott insulator with a three orders of magnitude improved conductivity (6 × 10-2 S cm-1)

  • Dinuclear Cp* cobalt complexes of the 1,2,4,5-benzenetetrathiolate bischelating ligand.
    'American Chemical Society (ACS)', 2008
    Co-Authors: Nomura Mitsushiro, Fourmigué Marc
    Abstract:

    International audienceThe dinuclear Cp*Co dithiolene complex [Cp*Co(btt)CoCp*] ( 1) is prepared in high yield from the reaction of the bis(dibutyltin) complex of 1,2,4,5-benzenetetrathiolate (btt) with 2 equiv of [Cp*Co(CO)I 2]. Mononuclear complexes are also obtained from 1,2,4,5-tetrakis(isopropylthio)benzene ( 2) and sodium in pyridine, from benzo[1,2- d;4,5- d ']bis(1,3-Dithiolane-2,6-dione) ( 3) and ( t )BuOK in tetrahydrofuran, or from benzo[ d]-1,3-Dithiolane-2-one ( 7) and ( t )BuOK to afford respectively 4a, 4b, and [Cp*Co(bdt)] ( 6), while [Cp*Co(dmit)] ( 8) is obtained by literature methods. The X-ray structures of the dinuclear complex 1 and the mononuclear complexes 4a and 6 were determined. They are all characterized by Cp* . . . btt face-to-face intermolecular interactions, leading to a recurrent 4-fold symmetry motif. The cyclic voltammograms of the [Cp*Co(dithiolene)] complexes performed in CH 2Cl 2 show reversible Co (III) to Co (II) reduction but irreversible oxidation waves. The large potential difference between the two reduction waves of the bimetallic complex 1 (269 mV) indicates a stable mixed-valence Co (III)-Co (II) state for the reduced [Cp*Co(btt)CoCp*] (-) anion. Upon trimethyl phosphite addition, the mono-P(OMe) 3 adduct [ 1.P(OMe) 3] exhibits a red shift of the low-energy absorption band to the IR region (856 nm, = 13 000 M (-1).cm (-1)), while [ 8.P(OMe) 3] exhibits a 150 nm blue shift. The stability constants of these P(OMe) 3 adducts were determined from UV-vis spectroscopic titration experiments, with, for example, log( K/mol (-1).dm (3)) values of 3.1 and 0.52 for the mono- and bis-adduct of 1, respectively. The electrochemical investigation of 1 and 8 in excess phosphite shows a strong current enhancement upon oxidation, attributable to the catalytic generation of the radical cation P(OMe) 3 (*+)

  • [CpNi(dithiolene)] (and diselenolene) neutral radical complexes.
    'American Chemical Society (ACS)', 2006
    Co-Authors: Nomura Mitsushiro, Cauchy Thomas, Geoffroy Michel, Adkine Prashant, Fourmigué Marc
    Abstract:

    International audienceVarious preparations of the neutral radical [CpNi(dddt)] complex (dddt = 5,6-dihydro-1,4-dithiin-2,3-dithiolate) were investigated with CpNi sources, [Cp2Ni], [Cp2Ni](BF4), [CpNi(CO)]2, and [CpNi(cod)](BF4), and dithiolene transfer sources, O=C(dddt), the naked dithiolate (dddt(2-)), the monoanion of square-planar Ni dithiolene complex (NBu4)[Ni(dddt)2], and the neutral complex [Ni(dddt)2]. The reaction of [CpNi(cod)](BF4) with (NBu4)[Ni(dddt)2] gave the highest yield for the preparation of [CpNi(dddt)] (86%). [CpNi(ddds)] (ddds = 5,6-dihydro-1,4-dithiin-2,3-diselenolate), [CpNi(dsdt)] (dsdt = 5,6-dihydro-1,4-diselenin-2,3-dithiolate), [CpNi(bdt)] (bdt = 1,2-benzenedithiolate), and [CpNi(bds)] (bds = 1,2-benzenediselenolate) were synthesized by the reactions of [Cp2Ni] with the corresponding neutral Ni dithiolene complexes [Ni(ddds)2]2, [Ni(dsdt)2], [Ni(bdt)2], and [Ni(bds)2], respectively. The five, formally Ni(III), radical complexes oxidize and reduce reversibly. They exhibit, in the neutral state, a strong absorption in the NIR region, from 1000 nm in the dddt/ddds/dsdt series to 720 nm in the bdt/bds series with epsilon values between 2500 and 5000 M(-1) cm(-1). The molecular and solid state structures of the five complexes were determined by X-ray structure analyses. [CpNi(dddt)] and [CpNi(ddds)] are isostructural, while [CpNi(dsdt)] exhibits a closely related structure. Similarly, [CpNi(bdt)] and [CpNi(bds)] are also isostructural. Correlations between structural data and magnetic measurements show the presence of alternated spin chains in [CpNi(dddt)], [CpNi(ddds)], and [CpNi(dsdt)], while a remarkably strong antiferromagnetic interaction in [CpNi(bdt)] and [CpNi(bds)] is attributed to a Cp...Cp face-to-face sigma overlap, an original feature in organometallic radical complexes

Yuliang Li - One of the best experts on this subject based on the ideXlab platform.

  • synthesis crystal structure and third order nonlinear optical behavior of a novel dimeric mixed ligand zinc ii complex of 1 3 dithiole 2 thione 4 5 dithiolate
    European Journal of Inorganic Chemistry, 2002
    Co-Authors: Deqing Zhang, Yinglin Song, Chuanlang Zhan, Yuliang Li
    Abstract:

    Metal bis-dithiolene complexes have aroused more and more interest over the past decades due to their potential applications as precursors for electrical conductors and superconductors;[1] the optical properties of these compounds are also very interesting. For example, in 1972 Drexhage and co-workers discovered that transition metal dithiolene complexes are very stable to intense irradiation in the nearinfrared region and are particularly suitable for Q-switching lasers.[2,3] Recently, more and more symmetrical bis-dithiolene complexes with third-order optical nonlinearity or optical limiting effects have been explored.[4] Because of the large values of their third-order nonlinear susceptibility χ(3) [1a,5] and negative molecular first hyperpolarizability(β),[1a,6] unsymmetrical dithiolene complexes have also become promising candidates for nonlinear optical materials. Herein we report the synthesis, crystal structure and thirdorder nonlinear optical behavior of a novel dimeric mixedligand zinc(II) complex of 1,3-dithiole-2-thione-4,5-dithiolate (dmit) [Zn(dmit)(2,2 -bpy)]2 (1). To the best of our knowledge, this is the first example of a dimeric mixed-ligand complex of dmit.