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Jeanluc Bredas - One of the best experts on this subject based on the ideXlab platform.
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a new class of Mixed Valence systems with orbitally degenerate organic redox centers examples based on hexa rhenium molecular prisms
Journal of the American Chemical Society, 2006Co-Authors: Peter H Dinolfo, Veaceslav Coropceanu, Jeanluc Bredas, Joseph T HuppAbstract:The ligand-centered Mixed-Valence (LCMV) properties of two supramolecular complexes are reported: triangular prisms of the form ([Re(CO)3]2X)3-μ,μ‘,μ‘ ‘-[tPyTz]2, where X is 2,2‘-bisbenzimidazolate (1) or a pair of benzylthiols (2), and tPyTz is tri-(4-pyridyl)-1,3,5-triazine. Cyclic voltammetry demonstrates that the redox-accessible bridging ligands, tPyTz, are reduced in sequential, one-electron reactions. The singly reduced prisms, which represent an unusual type of Mixed-Valence compound in which the tPyTz ligands themselves are the redox centers, show intense, broad intervalance transfer (IT) bands in the NIR, consistent with highly coupled MV species. Electroabsorption (Stark spectroscopy) measurements reveal small dipole moment changes associated with interValence excitation (|Δμ12| = 0.30 ± 0.02 eA for 1- and 0.48 ± 0.02 eA for 2-), as well as noncollinear transition dipole moment (μ12) and dipole moment change vectors (ζ ≈ 45°). DFT electronic structure calculations support this unusual result, ...
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delocalization in platinum alkynyl systems a metal bridged organic Mixed Valence compound
Journal of the American Chemical Society, 2004Co-Authors: Simon C Jones, Veaceslav Coropceanu, Stephen Barlow, Jeanluc Bredas, Tiffany L Kinnibrugh, Tatiana V Timofeeva, Seth R MarderAbstract:A complex featuring two triarylamine redox centers bridged by Pt, trans-bis(triethylphosphine)-bis{4-[bis(4-methoxyphenyl)amino]phenylethynyl} platinum(II), has been synthesized as a model system for pi-conjugated Pt-containing polymers. Analysis of the interValence charge-transfer band displayed by its Mixed-Valence monocation affords a quantitative assessment of electronic delocalization through the Pt bridge; this is found to be only slightly smaller than that determined for a benzene-bridged analogue. These results are supported by density functional theory calculations, which show that the active orbitals involved in the electron-transfer process in both cases have similar delocalization through the bridging unit.
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electronic couplings in organic Mixed Valence compounds the contribution of photoelectron spectroscopy
Journal of the American Chemical Society, 2004Co-Authors: Veaceslav Coropceanu, Christoph Lambert, Nadine E Gruhn, Stephen Barlow, Jason C Durivage, Tonja G Bill, Gilbert Noll, Seth R Marder, Jeanluc BredasAbstract:We show that the electronic coupling in strongly coupled organic Mixed-Valence systems can be effectively probed by means of gas-phase ultraviolet photoelectron spectroscopy (UPS). Taking six diamines as examples, the UPS estimates for the electronic couplings Hab are compared with the corresponding values determined from the interValence charge-transfer absorption bands and from electronic structure calculations. Similar trends are observed for the Hab values estimated from UPS and optical spectra; this provides support for the applicability of Hush theory to strongly coupled organic Mixed-Valence systems. The UPS electronic couplings are found to be somewhat smaller than those from optical spectroscopy, which is attributed to the role of vibronic coupling to symmetrical modes; when corrected for this vibronic coupling, the UPS Hab estimates confirm that triarylamine-based Mixed-Valence systems are close to the class-II/class-III borderline.
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an anionic organic Mixed Valence system with a remarkably well resolved vibrational structure in its interValence band
Chemical Communications, 2003Co-Authors: Chad Risko, Veaceslav Coropceanu, Stephen Barlow, Jeanluc Bredas, Marcus Halik, Seth R MarderAbstract:The reduction of a phenylene-bridged bis(dioxaborine) affords a strongly delocalised organic Mixed-Valence system; for the first time details of the vibrations coupled to the electron transfer have been extracted from the interValence band.
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charge transfer transitions in triarylamine Mixed Valence systems a joint density functional theory and vibronic coupling study
Journal of the American Chemical Society, 2002Co-Authors: Veaceslav Coropceanu, Massimo Malagoli, Jeanmarie Andre, Jeanluc BredasAbstract:A theoretical model is developed to describe the intramolecular transfer in organic Mixed-Valence systems. It is applied to rationalize the interValence charge-transfer transitions in triarylamine Mixed-Valence compounds. The electronic coupling parameter is evaluated at the density functional theory (DFT) and time-dependent density functional theory (TD-DFT) levels. The shapes of the charge-transfer absorption bands are analyzed in the framework of a dynamic vibronic model. The influence on the optical properties of diagonal and nondiagonal vibronic couplings is discussed. Our results are compared to recent experimental data.
Veaceslav Coropceanu - One of the best experts on this subject based on the ideXlab platform.
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a new class of Mixed Valence systems with orbitally degenerate organic redox centers examples based on hexa rhenium molecular prisms
Journal of the American Chemical Society, 2006Co-Authors: Peter H Dinolfo, Veaceslav Coropceanu, Jeanluc Bredas, Joseph T HuppAbstract:The ligand-centered Mixed-Valence (LCMV) properties of two supramolecular complexes are reported: triangular prisms of the form ([Re(CO)3]2X)3-μ,μ‘,μ‘ ‘-[tPyTz]2, where X is 2,2‘-bisbenzimidazolate (1) or a pair of benzylthiols (2), and tPyTz is tri-(4-pyridyl)-1,3,5-triazine. Cyclic voltammetry demonstrates that the redox-accessible bridging ligands, tPyTz, are reduced in sequential, one-electron reactions. The singly reduced prisms, which represent an unusual type of Mixed-Valence compound in which the tPyTz ligands themselves are the redox centers, show intense, broad intervalance transfer (IT) bands in the NIR, consistent with highly coupled MV species. Electroabsorption (Stark spectroscopy) measurements reveal small dipole moment changes associated with interValence excitation (|Δμ12| = 0.30 ± 0.02 eA for 1- and 0.48 ± 0.02 eA for 2-), as well as noncollinear transition dipole moment (μ12) and dipole moment change vectors (ζ ≈ 45°). DFT electronic structure calculations support this unusual result, ...
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delocalization in platinum alkynyl systems a metal bridged organic Mixed Valence compound
Journal of the American Chemical Society, 2004Co-Authors: Simon C Jones, Veaceslav Coropceanu, Stephen Barlow, Jeanluc Bredas, Tiffany L Kinnibrugh, Tatiana V Timofeeva, Seth R MarderAbstract:A complex featuring two triarylamine redox centers bridged by Pt, trans-bis(triethylphosphine)-bis{4-[bis(4-methoxyphenyl)amino]phenylethynyl} platinum(II), has been synthesized as a model system for pi-conjugated Pt-containing polymers. Analysis of the interValence charge-transfer band displayed by its Mixed-Valence monocation affords a quantitative assessment of electronic delocalization through the Pt bridge; this is found to be only slightly smaller than that determined for a benzene-bridged analogue. These results are supported by density functional theory calculations, which show that the active orbitals involved in the electron-transfer process in both cases have similar delocalization through the bridging unit.
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electronic couplings in organic Mixed Valence compounds the contribution of photoelectron spectroscopy
Journal of the American Chemical Society, 2004Co-Authors: Veaceslav Coropceanu, Christoph Lambert, Nadine E Gruhn, Stephen Barlow, Jason C Durivage, Tonja G Bill, Gilbert Noll, Seth R Marder, Jeanluc BredasAbstract:We show that the electronic coupling in strongly coupled organic Mixed-Valence systems can be effectively probed by means of gas-phase ultraviolet photoelectron spectroscopy (UPS). Taking six diamines as examples, the UPS estimates for the electronic couplings Hab are compared with the corresponding values determined from the interValence charge-transfer absorption bands and from electronic structure calculations. Similar trends are observed for the Hab values estimated from UPS and optical spectra; this provides support for the applicability of Hush theory to strongly coupled organic Mixed-Valence systems. The UPS electronic couplings are found to be somewhat smaller than those from optical spectroscopy, which is attributed to the role of vibronic coupling to symmetrical modes; when corrected for this vibronic coupling, the UPS Hab estimates confirm that triarylamine-based Mixed-Valence systems are close to the class-II/class-III borderline.
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an anionic organic Mixed Valence system with a remarkably well resolved vibrational structure in its interValence band
Chemical Communications, 2003Co-Authors: Chad Risko, Veaceslav Coropceanu, Stephen Barlow, Jeanluc Bredas, Marcus Halik, Seth R MarderAbstract:The reduction of a phenylene-bridged bis(dioxaborine) affords a strongly delocalised organic Mixed-Valence system; for the first time details of the vibrations coupled to the electron transfer have been extracted from the interValence band.
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charge transfer transitions in triarylamine Mixed Valence systems a joint density functional theory and vibronic coupling study
Journal of the American Chemical Society, 2002Co-Authors: Veaceslav Coropceanu, Massimo Malagoli, Jeanmarie Andre, Jeanluc BredasAbstract:A theoretical model is developed to describe the intramolecular transfer in organic Mixed-Valence systems. It is applied to rationalize the interValence charge-transfer transitions in triarylamine Mixed-Valence compounds. The electronic coupling parameter is evaluated at the density functional theory (DFT) and time-dependent density functional theory (TD-DFT) levels. The shapes of the charge-transfer absorption bands are analyzed in the framework of a dynamic vibronic model. The influence on the optical properties of diagonal and nondiagonal vibronic couplings is discussed. Our results are compared to recent experimental data.
Kosmas Prassides - One of the best experts on this subject based on the ideXlab platform.
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elusive Valence transition in Mixed Valence sesquioxide cs4o6
Inorganic Chemistry, 2019Co-Authors: R H Colman, Esma H Okur, W Kockelmann, Craig M Brown, Annette Sans, Claudia Felser, Martin Jansen, Kosmas PrassidesAbstract:Cs4O6 is a Mixed-Valence molecular oxide with a cubic structure, comprising valency-delocalized O24/3– units and with properties highly sensitive to cooling protocols. Here we use neutron powder di...
Don T Tilley - One of the best experts on this subject based on the ideXlab platform.
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aryl group transfer from tetraarylborato anions to an electrophilic dicopper i center and Mixed Valence μ aryl dicopper i ii complexes
Journal of the American Chemical Society, 2016Co-Authors: Micah S Ziegler, K. V. Lakshmi, Daniel S. Levine, Don T TilleyAbstract:The synthesis of discrete, cationic binuclear μ-aryl dicopper complexes [Cu2(μ-η1:η1-Ar)DPFN]X (Ar = C6H5, 3,5-(CF3)2C6H3, and C6F5; DPFN = 2,7-bis(fluoro-di(2-pyridyl)methyl)-1,8-naphthyridine; X = BAr4– and NTf2–; Tf = SO2CF3) was achieved by treatment of a dicopper complex [Cu2(μ-η1:η1-NCCH3)DPFN]X2 (X = PF6– and NTf2–) with tetraarylborates. Structural characterization revealed symmetrically bridging aryl groups, and 1H NMR spectroscopy evidenced the same structure in solution at 24 °C. Electrochemical investigation of the resulting arylcopper complexes uncovered reversible redox events that led to the synthesis and isolation of a rare Mixed-Valence organocopper complex [Cu2(μ-η1:η1-Ph)DPFN](NTf2)2 in high yield. The solid-state structure of the Mixed-Valence μ-phenyl complex exhibits inequivalent copper centers, despite a short Cu···Cu distance. Electronic and variable-temperature electron paramagnetic resonance spectroscopy of the Mixed-Valence μ-phenyl complex suggest that the degree of spin locali...
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aryl group transfer from tetraarylborato anions to an electrophilic dicopper i center and Mixed Valence μ aryl dicopper i ii complexes
Journal of the American Chemical Society, 2016Co-Authors: Micah S Ziegler, K. V. Lakshmi, Daniel S. Levine, Don T TilleyAbstract:The synthesis of discrete, cationic binuclear μ-aryl dicopper complexes [Cu2(μ-η1:η1-Ar)DPFN]X (Ar = C6H5, 3,5-(CF3)2C6H3, and C6F5; DPFN = 2,7-bis(fluoro-di(2-pyridyl)methyl)-1,8-naphthyridine; X = BAr4– and NTf2–; Tf = SO2CF3) was achieved by treatment of a dicopper complex [Cu2(μ-η1:η1-NCCH3)DPFN]X2 (X = PF6– and NTf2–) with tetraarylborates. Structural characterization revealed symmetrically bridging aryl groups, and 1H NMR spectroscopy evidenced the same structure in solution at 24 °C. Electrochemical investigation of the resulting arylcopper complexes uncovered reversible redox events that led to the synthesis and isolation of a rare Mixed-Valence organocopper complex [Cu2(μ-η1:η1-Ph)DPFN](NTf2)2 in high yield. The solid-state structure of the Mixed-Valence μ-phenyl complex exhibits inequivalent copper centers, despite a short Cu···Cu distance. Electronic and variable-temperature electron paramagnetic resonance spectroscopy of the Mixed-Valence μ-phenyl complex suggest that the degree of spin locali...
Luis Seijo - One of the best experts on this subject based on the ideXlab platform.
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Mixed Valence lanthanide activated phosphors invariance of the interValence charge transfer ivct absorption onset across the series
The Journal of Physical Chemistry, 2020Co-Authors: Ivo Neefjes, Jonas Joos, Zoila Barandiaran, Luis SeijoAbstract:Recently, direct evidence was given for the existence of interValence charge transfer (IVCT) states of Eu²⁺/Eu³⁺ pairs in Eu-doped fluorite hosts and their signature in absorption spectra was characterized [J. Phys. Chem. Lett.2019, 10, 1851]. Here we show, by means of multiconfigurational ab initio calculations, that the IVCT absorptions of all 2+/3+ Mixed Valence lanthanides doped in CaF₂ start basically at the same energy. This is rationalized with a simplified model of IVCT absorptions. Emissions above that energy are expected to be partly or totally quenched when 2+/3+ pairs are formed. On the basis of this finding and existing calculations, we report expected IVCT absorptions of Mixed Valence lanthanides doped in several fluoride, oxide, and sulfide hosts.