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Local Cyclic Voltammetry of a Langmuir-Blodgett Film on Water. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2024; 40:2562-2566. [PMID: 38276954 DOI: 10.1021/acs.langmuir.3c02743] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/27/2024]
Abstract
An electrochemical Langmuir-Blodgett trough that permits an examination of local redox processes in a layer floating on the surface of water with a scanning tunneling microscopy-tip ultramicroelectrode has been constructed and tested on a layer of 1,1'-dicarbooctadecyloxyferrocene.
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2
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Catalytic C−C/C−H Bond Activation Relay for Synthesis of Fluorescent Naphthoquinolizinium Salts. European J Org Chem 2023. [DOI: 10.1002/ejoc.202300153] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/03/2023]
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3
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Electrochemistry of Tetrathiafulvalene Ligands Assembled on the Surface of Gold Nanoparticles. Molecules 2022; 27:molecules27217639. [PMID: 36364465 PMCID: PMC9659269 DOI: 10.3390/molecules27217639] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2022] [Revised: 10/31/2022] [Accepted: 11/02/2022] [Indexed: 11/09/2022] Open
Abstract
The synthesis of a tetrathiafulvalene (TTF) derivative, S-[4-({4-[(2,2′-bi-1,3-dithiol-4-ylmethoxy)methyl] phenyl}ethynyl)phenyl] ethanethioate, suitable for the modification of gold nanoparticles (AuNPs), is described in this article. The TTF ligand was self-assembled on the AuNP surface through ligand exchange, starting from dodecanethiol-stabilized AuNPs. The resulting modified AuNPs were characterized by TEM, UV-Vis spectroscopy, and electrochemistry. The most suitable electrochemical method was the phase-sensitive AC voltammetry at very low frequencies of the sine-wave perturbation. The results indicate a diminishing electronic communication between the two equivalent redox centers of TTF and also intermolecular donor–acceptor interactions manifested by an additional oxidation wave upon attachment of the ligand to AuNPs.
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4
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Electrochemical test of flexibility of pyridine terminated molecular rods. Electrochim Acta 2022. [DOI: 10.1016/j.electacta.2022.140377] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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5
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Synthesis of (Di)thiahelicenes and Dithiophenohelicenes by [2+2+2] Cycloisomerisation of Alkynes. Helv Chim Acta 2022. [DOI: 10.1002/hlca.202100225] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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6
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On the Supra-LUMO Interaction: Case Study of a Sudden Change of Electronic Structure as a Functional Emergence. Chemistry 2021; 27:17889-17899. [PMID: 34761431 DOI: 10.1002/chem.202103136] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2021] [Indexed: 11/07/2022]
Abstract
The synergistic functioning of redox-active components that emerges from prototypical 2,2'-di(N-methylpyrid-4-ylium)-1,1'-biphenyl is described. Interestingly, even if a trans conformation of the native assembly is expected, due to electrostatic repulsion between cationic pyridinium units, we demonstrate that cis conformation is equally energy-stabilized on account of a peculiar LUMO (SupLUMO) that develops through space, encompassing the two pyridiniums in a single, made-in-one-piece, electronic entity (superelectrophoric behavior). This SupLUMO emergence, with the cis species as superelectrophore embodiment, originates in a sudden change of electronic structure. This finding is substantiated by insights from solid state (single-crystal X-ray diffraction) and solution (NOE NMR and UV-vis-NIR spectroelectrochemistry) studies, combined with electronic structure computations. Electrochemistry shows that electron transfers are so strongly correlated that two-electron reduction manifests itself as a single-step process with a large potential inversion consistent with inner creation of a carbon-carbon bond (digital simulation). Besides, absence of reductive formation of dimers is a further indication of a preferential intramolecular reactivity determined by the SupLUMO interaction (cis isomer pre-organization). The redox-gated covalent bond, serving as electron reservoir, was studied via atropisomerism of the reduction product (VT NMR study). The overall picture derived from this in-depth study of 2,2'-di(N-methylpyrid-4-ylium)-1,1'-biphenyl proves that trans and cis species are worth considered as intrinsically sharply different, that is, as doubly-electrophoric and singly-superelectrophoric switchable assemblies, beyond conformational isomerism. Most importantly, the through-space-mediated SupLUMO may come in complement of other weak interactions encountered in Supramolecular Chemistry as a tool for the design of electroactive architectures.
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Electrochemical Cleavage of Carbon‐Chlorine Bonds in Multiply Bridge‐Chlorinated Bicyclo[1.1.1]pentane‐1,3‐dicarboxylic Acids. ChemElectroChem 2021. [DOI: 10.1002/celc.202100987] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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8
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Electrochemical Cleavage of Carbon‐Chlorine Bonds in Multiply Bridge‐Chlorinated Bicyclo[1.1.1]pentane‐1,3‐dicarboxylic Acids. ChemElectroChem 2021. [DOI: 10.1002/celc.202100372] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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9
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Front Cover: Electrochemical Cleavage of Carbon‐Chlorine Bonds in Multiply Bridge‐Chlorinated Bicyclo[1.1.1]pentane‐1,3‐dicarboxylic Acids (ChemElectroChem 17/2021). ChemElectroChem 2021. [DOI: 10.1002/celc.202100988] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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10
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Helquats as Promoters of the Povarov Reaction: Synthesis of 1,2,3,4‐Tetrahydroquinoline Scaffolds Catalyzed by Helicene‐Viologen Hybrids. Chempluschem 2020. [DOI: 10.1002/cplu.202000552] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
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11
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Front Cover: Helquats as Promoters of the Povarov Reaction: Synthesis of 1,2,3,4‐Tetrahydroquinoline Scaffolds Catalyzed by Helicene‐Viologen Hybrids (ChemPlusChem 10/2020). Chempluschem 2020. [DOI: 10.1002/cplu.202000565] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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12
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Helquats as Promoters of the Povarov Reaction: Synthesis of 1,2,3,4-Tetrahydroquinoline Scaffolds Catalyzed by Helicene-Viologen Hybrids. Chempluschem 2020; 85:2212-2218. [PMID: 32400944 DOI: 10.1002/cplu.202000151] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2020] [Revised: 04/29/2020] [Indexed: 01/10/2023]
Abstract
Helquats (HQs) are structurally linked to helicenes and viologens, and they represent an attractive field of research in chemistry and medicinal chemistry. In the present work they were used as catalysts for the synthesis of 1,2,3,4-tetrahydroquinolines in good yields by the Povarov reaction. The substrate scope and the capability of different helquats to promote Povarov reactions are demonstrated. Studies to elucidate mechanistic details revealed that helquats act as single-electron transfer oxidants through a cation-radical mechanism. The screening of the catalytic activity of HQs confirmed that an active HQ must have a LUMO energy below -8.67 eV and the standard redox potential higher (less negative) than -1.2 V vs. the ferrocene/ferrocenium redox couple.
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13
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Electron Storage System Based on a Two-Way Inversion of Redox Potentials. J Am Chem Soc 2020; 142:5162-5176. [DOI: 10.1021/jacs.9b12762] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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14
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Electrochemical characterization of the artificial metalloenzyme papain-[(η6-arene)Ru(1,10-phenanthroline)Cl]+. J Electroanal Chem (Lausanne) 2020. [DOI: 10.1016/j.jelechem.2020.113882] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
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15
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Straightforward Synthesis and Properties of Highly Fluorescent [5]‐ and [7]‐Helical Dispiroindeno[2,1‐
c
]fluorenes. Angew Chem Int Ed Engl 2019; 58:17169-17174. [DOI: 10.1002/anie.201908348] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2019] [Revised: 09/03/2019] [Indexed: 01/19/2023]
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17
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The Impact of Huge Structural Changes on Electron Transfer and Measurement of Redox Potentials: Reduction of ortho-12-Carborane. J Phys Chem B 2019; 123:9668-9676. [PMID: 31626548 DOI: 10.1021/acs.jpcb.9b08151] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
A massive structural change accompanies electron capture by the 1,2-dicarba-closo-dodecaborane cage molecule (1). Bimolecular electron transfer (ET) by pulse radiolysis found a reduction potential of E0 = -1.92 V vs Fc+/0 for 1 and rate constants that slowed greatly for ET to or from 1 when the redox partner had a potential near this E0. Similarly, two electrochemical techniques could detect no current at potentials near E0, finding instead peaks or polarographic waves near -3.1 V, which is 1.2 V more negative than E0. Voltammetry could determine rate constants, but only near -3.1 V. DigiSim simulations can describe the irreversible voltammograms but require electrochemical rate constants near 1 × 10-10 cm/s at E0, a factor of 10-10 relative to molecules undergoing facile ET. This factor of 10-10 compared to ∼10-5 for bimolecular ET presents a puzzle. This puzzle can be understood as a manifestation of one of the "Frumkin Effects" in which only part of the applied voltage is available to drive ET at the electrode.
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Front Cover: Chiroptical Redox Switching of Tetra‐Cationic Derivatives of Azoniahelicenes (ChemElectroChem 12/2019). ChemElectroChem 2019. [DOI: 10.1002/celc.201900762] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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19
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Chiroptical Redox Switching of Tetra‐Cationic Derivatives of Azoniahelicenes. ChemElectroChem 2019. [DOI: 10.1002/celc.201900761] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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21
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Kinetics of radical dimerization. Simple evaluation of rate constant from convolution voltammetry and faradaic phase angle data. Electrochim Acta 2019. [DOI: 10.1016/j.electacta.2019.01.119] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
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22
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Abstract
We report the electron paramagnetic resonance spectra of the radical cation and radical anion of 1,2,2,3-tetramethyl-2,3-dihydro-1 H-naphtho[2,3- d]imidazole-4,9-dione (1) and its doubly 13C labeled analogue 2, of interest for singlet fission. The hyperfine coupling constants are in excellent agreement with density functional theory calculations and establish the structures beyond doubt. Unlike the radical cation 1•+, the radical anion 1•- and its parent 1 have pyramidalized nitrogen atoms and inequivalent methyl groups 15 and 16, in agreement with the calculations. The distinction is particularly clear with the labeled analogue 2•-.
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Intense redox-driven chiroptical switching with a 580 mV hysteresis actuated through reversible dimerization of an azoniahelicene. Chem Commun (Camb) 2018; 53:9059-9062. [PMID: 28737778 DOI: 10.1039/c7cc04903j] [Citation(s) in RCA: 27] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
Electrochemical reduction of an azoniahelicene affords a dimer, accompanied by a strong change in the electronic circular dichroism. The fast dimerisation event leads to a >500 mV shift of the oxidation potential, affording a large area of bistability, where the chiroptical signal only depends on the redox history.
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Ferrocenyl helquats: unusual chiral organometallic nonlinear optical chromophores. Dalton Trans 2017; 46:1052-1064. [PMID: 28050611 DOI: 10.1039/c6dt04347j] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
Three new dipolar cations have been synthesised, containing ferrocenyl (Fc) electron donor groups attached to helquat (Hq) acceptors. These organometallic Hq derivatives have been characterised as their TfO- salts by using various techniques including NMR and electronic absorption spectroscopies and electrochemical measurements. UV-vis spectra show multiple intense low energy absorptions attributable to intramolecular charge-transfer (ICT) excitations. Each compound displays a reversible Fc+/0 redox process, together with two reversible one-electron reductions of the Hq fragment. Molecular quadratic nonlinear optical (NLO) responses have been determined by using hyper-Rayleigh scattering at 1064 nm, and Stark (electroabsorption) spectroscopic studies on the visible absorption bands. The obtained first hyperpolarizabilities β are moderate, consistent with the relatively short π-conjugation lengths between the Fc and attached pyridinium group. A single-crystal X-ray structure has been solved for one of the complexes as its PF6- salt, revealing a centrosymmetric packing in the triclinic space group P1[combining macron]. Density functional theory (DFT) and time-dependent DFT calculations indicate that the lowest energy absorption bands have mainly metal-to-ligand charge-transfer character. The donor orbitals involved in the electronic transitions forming the next lowest energy ICT band also have substantial contributions from the Fe atom. Good agreement between the simulated and experimental UV-vis absorption spectra is achieved by using the PBE0 functional with the 6-311++G(d)/LANL2DZ mixed basis set, and the theoretical β values are reasonably large. Oxidation of the Fc unit is predicted to cause the βtot value to decrease by more than 80% in one of the complexes.
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27
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Linquats: Synthesis, Characterization, and Properties of Linear Extended Diquats. Chemistry 2016; 22:12154-9. [PMID: 27405657 DOI: 10.1002/chem.201600819] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2016] [Indexed: 11/08/2022]
Abstract
We report an innovative synthetic route to linear extended diquats (linquats). Our approach is short and efficient and features a highly modular reaction sequence based on two-fold quaternization followed by the key intramolecular [2+2+2] alkyne cycloaddition. The physico-chemical properties of four new linquats were characterized by spectroscopic methods, X-ray crystallography, and electrochemistry complemented by information obtained from DFT calculations. Electron deficient N-heteroaromatic cations with linear extended diquat motif with high electron affinities have been recently recognized as attractive n-type semiconductors for chemical and biological sensing. Their advantageous redox properties such as very fast reversible electron transfers make the title compounds interesting for applications.
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Importance of the Anchor Group Position (ParaversusMeta) in Tetraphenylmethane Tripods: Synthesis and Self-Assembly Features. Chemistry 2016; 22:13218-35. [DOI: 10.1002/chem.201602019] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2016] [Indexed: 11/06/2022]
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29
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Electrochemical Hydrogen Oxidation in Toluene/LiCB11
Me12
: H2
as a Surrogate for Lithium Metal? ChemElectroChem 2015. [DOI: 10.1002/celc.201500332] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
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The Scope of Direct Alkylation of Gold Surface with Solutions of C1-C4 n-Alkylstannanes. J Am Chem Soc 2015; 137:12086-99. [PMID: 26327466 PMCID: PMC4704782 DOI: 10.1021/jacs.5b07672] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2015] [Indexed: 12/25/2022]
Abstract
Treatment of cleaned gold surfaces with dilute tetrahydrofuran or chloroform solutions of tetraalkylstannanes (alkyl = methyl, ethyl, n-propyl, n-butyl) or di-n-butylmethylstannyl tosylate under ambient conditions causes a self-limited growth of disordered monolayers consisting of alkyls and tin oxide. Extensive use of deuterium labeling showed that the alkyls originate from the stannane and not from ambient impurities, and that trialkylstannyl groups are absent in the monolayers, contrary to previous proposals. Methyl groups attached to the Sn atom are not transferred to the surface. Ethyl groups are transferred slowly, and propyl and butyl rapidly. In all cases, tin oxide is codeposited in submonolayer amounts. The monolayers were characterized by ellipsometry, contact angle goniometry, polarization modulated IR reflection absorption spectroscopy, X-ray photoelectron spectroscopy, and electrochemical impedance spectroscopy with ferrocyanide/ferricyanide, which revealed a very low charge-transfer resistance. The thermal stability of the monolayers and their resistance to solvents are comparable with those of an n-octadecanethiol monolayer. A preliminary examination of the kinetics of monolayer deposition from a THF solution of tetra-n-butylstannane revealed an approximately half-order dependence on the bulk solution concentration of the stannane, hinting that more than one alkyl can be transferred from a single stannane molecule. A detailed structure of the attachment of the alkyl groups is not known, and it is proposed that it involves direct single or multiple bonding of one or more C atoms to one or more Au atoms.
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Kinetics of Multielectron Transfers and Redox-Induced Structural Changes in N-Aryl-Expanded Pyridiniums: Establishing Their Unusual, Versatile Electrophoric Activity. J Am Chem Soc 2015; 137:11349-64. [DOI: 10.1021/jacs.5b05545] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
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32
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The Use of Cobalt-Mediated Cycloisomerisation of Ynedinitriles in the Synthesis of Pyridazinohelicenes. Chemistry 2014; 20:8477-82. [DOI: 10.1002/chem.201402312] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2014] [Indexed: 11/07/2022]
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33
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Intense Chiroptical Switching in a Dicationic Helicene-Like Derivative: Exploration of a Viologen-Type Redox Manifold of a Non-Racemic Helquat. J Am Chem Soc 2014; 136:10826-9. [DOI: 10.1021/ja500220j] [Citation(s) in RCA: 69] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
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34
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Atrazine-based self-assembled monolayers and their interaction with anti-atrazine antibody: building of an immunosensor. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2013; 29:16084-16092. [PMID: 24313270 DOI: 10.1021/la404029j] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
As a part of our objective to build an immunosensor for the detection of the pesticide atrazine (ATZ) in environmental samples, we studied the self-assembling process of the disulfide derivative of the pesticide atrazine on a gold substrate. Atrazine-based self-assembled monolayers were characterized by ellipsometry, scanning tunneling microscopy, polarization-modulation infrared reflection-absorption spectroscopy (PM IRRAS), X-ray photoelectron spectroscopy and quartz crystal microbalance (QCM) measurements. Two different time constants for the adsorption process were observed, depending on the experimental method used. The QCM data reflect adsorption kinetics of the original disulfide compound, whereas ellipsometry and ex situ PM IRRAS refer to the formation of thiolate (ATZS) monolayers. In situ QCM data demonstrated the suitability of such monolayers for the detection of atrazine in aqueous samples. Exposure of the ATZS sensing surface to an anti-atrazine antibody (anti-ATZ IgG) resulted in complete coverage of the surface by antibody, whereas approximately half of the antibody molecules were displaced from the QCM sensor surface by further addition of atrazine into the solution.
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35
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On the Physicochemical Properties of Pyridohelicenes. Chemistry 2013; 20:877-93. [DOI: 10.1002/chem.201204410] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2012] [Revised: 10/04/2013] [Indexed: 11/08/2022]
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36
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Alkylation of Gold Surface by Treatment with C18H37HgOTs and Anodic Hg Stripping. J Am Chem Soc 2013; 135:5669-77. [DOI: 10.1021/ja3117125] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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37
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Tetrathiafulvalene-Oligo(para-phenyleneethynylene) Conjugates: Formation of Multiple Mixed-Valence Complexes upon Electrochemical Oxidation. Chemistry 2013; 19:6108-21. [DOI: 10.1002/chem.201102868] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2011] [Revised: 01/08/2013] [Indexed: 11/06/2022]
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38
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Abstract
Single-molecule conductance in a series of extended viologen molecules was measured at room temperature using a gold-molecule-gold scanning tunneling microscopy break junction arrangement. Conductance values for individual molecules change from 4.8 ± 1.2 nS for the shortest compound to 2.9 ± 1.0 nS for the compound with six repeating units and length of 11 nm. The latter value is almost 3 orders of magnitude higher than that reported for all-carbon-based aromatic molecular wires of comparable length. On the basis of the length of the molecules, an attenuation factor of only 0.06 ± 0.004 nm(-1) (0.006 ± 0.0004 Å(-1)) was obtained. To the best of our knowledge, this is the smallest value reported for the conductance attenuation in a series of molecular wires.
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Acceptor-Substituted Ferrocenium Salts as Strong, Single-Electron Oxidants: Synthesis, Electrochemistry, Theoretical Investigations, and Initial Synthetic Application. Chemistry 2012; 18:12267-77. [DOI: 10.1002/chem.201201499] [Citation(s) in RCA: 50] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2012] [Indexed: 11/09/2022]
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40
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Spectroelectrochemical determination of the electron consumption. Anal Chim Acta 2011; 697:23-6. [DOI: 10.1016/j.aca.2011.04.033] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2011] [Revised: 04/18/2011] [Accepted: 04/19/2011] [Indexed: 11/26/2022]
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41
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Correlation of the formation constant of ferrocene–cyclodextrin complexes with dielectric properties of the aqueous DMSO solution. J Organomet Chem 2011. [DOI: 10.1016/j.jorganchem.2011.01.007] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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42
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Abstract
A modular approach to the construction of monocationic quaternary N-heteroaromatic frameworks was developed capitalizing on a direct pyridine-type nitrogen quaternization followed by metal-catalyzed [2+2+2] cycloaddition with gaseous acetylene. The flexibility of the route is demonstrated on 12 diverse scaffolds based on pyridinium, quinolinium, thiazolium, benzothiazolium, imidazolium, and pyrimidinium. Electrochemical study revealed a quinolinium redox system with two electrochemically distinct forms that are interconverted by a homogeneous chemical reaction triggered by fast electron transfers (reduction at -0.7 V and oxidation at -0.05 V).
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Inclusion complex of α-cyclodextrin and the extended viologen dication: a model of an insulated molecular wire. J INCL PHENOM MACRO 2010. [DOI: 10.1007/s10847-010-9897-y] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
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46
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On the adsorption of extended viologens at the electrode|electrolyte interface. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2010; 26:17232-17236. [PMID: 20936835 DOI: 10.1021/la1034239] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
Extended viologens represent a group of organic molecules intended to be used as molecular wires in molecular electronic devices. Adsorption properties of a novel series of extended viologen molecules were studied at the mercury electrode|electrolyte interface. These compounds form compact monolayers around the potential of zero charge with a constant differential capacitance value of 2.5 ± 0.2 μF cm(-2) independent of temperature, length of the molecule, and its bulk concentration. At more negative potentials their reduction in the adsorbed state takes place. We showed that the adsorption process is diffusion controlled and time needed to fully cover the electrode surface is independent of the electrode potential. A modified Koryta equation was employed for the calculation of the surface concentration of the adsorbates leading to the value of 5.3 × 10(-11) mol cm(-2) for the shortest wire and to 1.6 × 10(-11) mol cm(-2) for the longest one. Based on the space filling model and the differential capacitance value in the compact film region, it was postulated that these molecules lay flat on the electrode surface.
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Voltammetry of hypoxic cells radiosensitizer etanidazole radical anion in water. Bioelectrochemistry 2010; 78:118-23. [DOI: 10.1016/j.bioelechem.2009.08.008] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2009] [Revised: 07/27/2009] [Accepted: 08/15/2009] [Indexed: 11/26/2022]
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Host–Guest interaction of pesticide bifenox with cyclodextrin molecules. An electrochemical study. ACTA ACUST UNITED AC 2010. [DOI: 10.1135/cccc2009509] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
The reduction of nitroaromatic compound bifenox (methyl 5-(2,4-dichlorophenoxy)-2-nitrobenzoate) was studied in aprotic solvents in the absence or presence of cyclodextrin (CD) molecules of different cavity sizes. βCD and γCD form complexes with bifenox in DMSO with the complex formation constants (5 ± 2) × 102 M–1 [βCD–bifenox] and (3 ± 1) × 102 M–1 [γCD–bifenox], respectively. Bifenox yields a relatively stable anion radical in dimethyl sulfoxide, which is further reduced at more negative potentials by an overall addition of three electrons and four protons to the corresponding phenylhydroxylamine. In the presence of βCD the first reduction wave of bifenox becomes irreversible, it is shifted towards more positive potentials and the uptake of more than one electron is observed (up to four electrons during the exhaustive electrolysis). The first reduction wave of bifenox is not affected by the addition of glucose confirming that a simple availability of protons from the OH groups is not the main factor in further transformation of anion radical in the presence of βCD. The complex formation with βCD facilitates the protonation and additionally protects the molecule from disintegration into 2,4-dichlorophenol. A yield of 2,4-dichlorophenol decreases in the order βCD, γCD and αCD, respectively.
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