15 results on '"Herres-Pawlis, S."'
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2. Understanding the structure-activity relationship and performance of highly active novel ATRP catalysts.
- Author
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Kröckert KW, Garg F, Heinz MV, Lange J, Simões PP, Schmidt R, Bienemann O, Hoffmann A, and Herres-Pawlis S
- Subjects
- Catalysis, Ligands, Structure-Activity Relationship, Copper chemistry, Guanidines
- Abstract
Copper bromide complexes based on a series of substituted guanidine-quinolinyl and -pyridinyl ligands are reported. The ligand systems were chosen based on the large variation with regard to their flexibility in the backbone, different guanidine moieties and influence by electron density donating groups. Relationships between the molecular structures and spectroscopic and electronic properties are described. Beside the expected increase in activity by substituting the 4-position (NMe
2 vs . DMEG moiety, leads to a better stabilsiation of the copper(II) complex. Due to the correlation of the potentials and vs . DMEG moiety, leads to a better stabilsiation of the copper(II) complex. Due to the correlation of the potentials and K py is the most active copper complex for ATRP with a bidentate ligand system. The combination of the strong donating abilities of dimethylamine pyridinyl, the donor properties of the TMG substituent, and the improved flexibility due to the methylene bridging unit leads to high activity. With all NMeATRP values, the catalyst based on the ligand TMGm4NMe2 py is the most active copper complex for ATRP with a bidentate ligand system. The combination of the strong donating abilities of dimethylamine pyridinyl, the donor properties of the TMG substituent, and the improved flexibility due to the methylene bridging unit leads to high activity. With all NMe2 -substituted systems standard ATRP experiments were conducted and with more active NMe2 -substituted pyridinyl systems, ICAR ATRP experiments of styrene were conducted. Low dispersities and ideal molar masses have been achieved.- Published
- 2022
- Full Text
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3. Influence of the amine donor on hybrid guanidine-stabilized Bis(μ-oxido) dicopper(III) complexes and their tyrosinase-like oxygenation activity towards polycyclic aromatic alcohols.
- Author
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Paul M, Teubner M, Grimm-Lebsanft B, Buchenau S, Hoffmann A, Rübhausen M, and Herres-Pawlis S
- Subjects
- Alcohols chemistry, Amines chemistry, Hydroxyquinolines chemistry, Ligands, Magnetic Resonance Spectroscopy methods, Models, Molecular, Molecular Structure, Naphthols chemistry, Spectrum Analysis, Raman methods, Copper chemistry, Guanidine chemistry, Monophenol Monooxygenase metabolism, Organometallic Compounds chemistry, Oxygen chemistry
- Abstract
The tyrosinase-like activity of hybrid guanidine-stabilized bis(μ-oxido) dicopper(III) complexes [Cu
2 (μ-O)2 (L)2 ](X)2 (L = 2-{2-((Diethylamino)methyl)phenyl}-1,1,3,3-tetramethylguanidine (TMGbenzNEt2 , L2) and 2-{2-((Di-isopropylamino)methyl)phenyl}-1,1,3,3-tetramethylguanidine (TMGbenzNiPr2 , L3); X = PF6 - , BF4 - ) is described. New aromatic hybrid guanidine amine ligands were developed with varying amine donor function. Their copper(I) complexes were analyzed towards their ability to activate dioxygen in the presence of different weakly coordinating anions. The resulting bis(μ-oxido) species were characterized at low temperatures by UV/Vis and resonance Raman spectroscopy, cryo-ESI mass spectrometry and density functional theory calculations. Small structural changes in the ligand sphere were found to influence the characteristic ligand-to-metal charge transfer (LMCT) features of the bis(μ-oxido) species, correlating a redshift in the UV/Vis spectrum with weaker N-donor function of the ligand. DFT calculations elucidated the influence of the steric and electronic properties of the bis(μ-oxido) species leading to a higher twist of the Cu3 SO3 - ) is described. New aromatic hybrid guanidine amine ligands were developed with varying amine donor function. Their copper(I) complexes were analyzed towards their ability to activate dioxygen in the presence of different weakly coordinating anions. The resulting bis(μ-oxido) species were characterized at low temperatures by UV/Vis and resonance Raman spectroscopy, cryo-ESI mass spectrometry and density functional theory calculations. Small structural changes in the ligand sphere were found to influence the characteristic ligand-to-metal charge transfer (LMCT) features of the bis(μ-oxido) species, correlating a redshift in the UV/Vis spectrum with weaker N-donor function of the ligand. DFT calculations elucidated the influence of the steric and electronic properties of the bis(μ-oxido) species leading to a higher twist of the Cu2 O2 plane against the CuN2 plane and a stretching of the Cu2 O2 core. Despite their moderate stability at -100 °C, the bis(μ-oxido) complexes exhibited a remarkable activity in catalytic oxygenation reactions of polycyclic aromatic alcohols. Further the selectivity of the catalyst in the hydroxylation reactions of challenging phenolic substrates is not changed despite an increasing shield of the reactive bis(μ-oxido) core. The generated quinones were found to form exclusively bent phenazines, providing a promising strategy to access tailored phenazine derivatives., (Copyright © 2021 Elsevier Inc. All rights reserved.)- Published
- 2021
- Full Text
- View/download PDF
4. Room temperature stable multitalent: highly reactive and versatile copper guanidine complexes in oxygenation reactions.
- Author
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Paul M, Hoffmann A, and Herres-Pawlis S
- Subjects
- Density Functional Theory, Catalysis, Oxidation-Reduction, Molecular Structure, Hydroxylation, Copper chemistry, Guanidine chemistry, Oxygen chemistry, Oxygen metabolism, Temperature, Coordination Complexes chemistry
- Abstract
Inspired by the efficiency of natural enzymes in organic transformation reactions, the development of synthetic catalysts for oxygenation and oxidation reactions under mild conditions still remains challenging. Tyrosinases serve as archetype when it comes to hydroxylation reactions involving molecular oxygen. We herein present new copper(I) guanidine halide complexes, capable of the activation of molecular oxygen at room temperature. The formation of the reactive bis(µ-oxido) dicopper(III) species and the influence of the anion are investigated by UV/Vis spectroscopy, mass spectrometry, and density functional theory. We highlight the catalytic hydroxylation activity towards diverse polycyclic aromatic alcohols under mild reaction conditions. The selective formation of reactive quinones provides a promising tool to design phenazine derivatives for medical applications.
- Published
- 2021
- Full Text
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5. Dual oxidase/oxygenase reactivity and resonance Raman spectra of {Cu 3 O 2 } moiety with perfluoro-t-butoxide ligands.
- Author
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Brazeau SEN, Norwine EE, Hannigan SF, Orth N, Ivanović-Burmazović I, Rukser D, Biebl F, Grimm-Lebsanft B, Praedel G, Teubner M, Rübhausen M, Liebhäuser P, Rösener T, Stanek J, Hoffmann A, Herres-Pawlis S, and Doerrer LH
- Subjects
- Catalysis, Cold Temperature, Kinetics, Ligands, Models, Molecular, Molecular Structure, Oxidation-Reduction, Structure-Activity Relationship, Copper chemistry, Hydrocarbons, Fluorinated chemistry, Monophenol Monooxygenase chemistry
- Abstract
A Cu(i) fully fluorinated O-donor monodentate alkoxide complex, K[Cu(OC4F9)2], was previously shown to form a trinuclear copper-dioxygen species with a {Cu3(μ3-O)2} core, TOC4F9, upon reactivity with O2 at low temperature. Herein is reported a significantly expanded kinetic and mechanistic study of TOC4F9 formation using stopped-flow spectroscopy. The TOC4F9 complex performs catalytic oxidase conversion of hydroquinone (H2Q) to benzoquinone (Q). TOC4F9 also demonstrated hydroxylation of 2,4-di-tert-butylphenolate (DBP) to catecholate, making TOC4F9 the first trinuclear species to perform tyrosinase (both monooxygenase and oxidase) chemistry. Resonance Raman spectra were also obtained for TOC4F9, to our knowledge, the first such spectra for any T species. The mechanism and substrate reactivity of TOC4F9 are compared to those of its bidentate counterpart, TpinF, formed from K[Cu(pinF)(PR3)]. The monodentate derivative has both faster initial formation and more diverse substrate reactivity.
- Published
- 2019
- Full Text
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6. Transferring the entatic-state principle to copper photochemistry.
- Author
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Dicke B, Hoffmann A, Stanek J, Rampp MS, Grimm-Lebsanft B, Biebl F, Rukser D, Maerz B, Göries D, Naumova M, Biednov M, Neuber G, Wetzel A, Hofmann SM, Roedig P, Meents A, Bielecki J, Andreasson J, Beyerlein KR, Chapman HN, Bressler C, Zinth W, Rübhausen M, and Herres-Pawlis S
- Subjects
- Density Functional Theory, Electron Transport, Molecular Structure, Coordination Complexes chemistry, Copper chemistry, Photochemical Processes
- Abstract
The entatic state denotes a distorted coordination geometry of a complex from its typical arrangement that generates an improvement to its function. The entatic-state principle has been observed to apply to copper electron-transfer proteins and it results in a lowering of the reorganization energy of the electron-transfer process. It is thus crucial for a multitude of biochemical processes, but its importance to photoactive complexes is unexplored. Here we study a copper complex-with a specifically designed constraining ligand geometry-that exhibits metal-to-ligand charge-transfer state lifetimes that are very short. The guanidine-quinoline ligand used here acts on the bis(chelated) copper(I) centre, allowing only small structural changes after photoexcitation that result in very fast structural dynamics. The data were collected using a multimethod approach that featured time-resolved ultraviolet-visible, infrared and X-ray absorption and optical emission spectroscopy. Through supporting density functional calculations, we deliver a detailed picture of the structural dynamics in the picosecond-to-nanosecond time range.
- Published
- 2018
- Full Text
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7. Copper Guanidinoquinoline Complexes as Entatic State Models of Electron-Transfer Proteins.
- Author
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Stanek J, Sackers N, Fink F, Paul M, Peters L, Grunzke R, Hoffmann A, and Herres-Pawlis S
- Subjects
- Electron Transport, Kinetics, Ligands, Nitriles chemistry, Oxidation-Reduction, Solvents chemistry, Spectrophotometry, Thermodynamics, Coordination Complexes chemistry, Copper chemistry, Models, Molecular, Quinolines chemistry
- Abstract
The electron-transfer abilities of the copper guanidinoquinoline (GUAqu) complexes [Cu(TMGqu)
2 ]+/2+ and [Cu(DMEGqu)2 ]+/2+ (TMGqu=tetramethylguanidinoquinoline, DMEGqu=dimethylethylguanidinoquinoline) were examined in different solvents. The determination of the electron self-exchange rate based on the Marcus theory reveals the highest electron-transfer rate of copper complexes with pure N-donor ligands (k11 =1.2×104 s-1 m-1 in propionitrile). This is supported by an examination of the reorganisation energy of the complexes by using Eyring theory and DFT calculations. The low reorganisation energies in nitrile solvents correspond with the high electron-transfer rates of the complexes. Therefore, the [Cu(GUAqu)2 ]+/2+ complexes act as good entatic states model of copper enzymes. The structural influence of the complexes on the kinetic parameters shows that the TMGqu system possesses a higher electron-transfer rate than DMEGqu. Supporting DFT calculations give a closer insight into the kinetics and thermodynamics (Nelsen's four-point method and isodesmic reactions) of the electron transfer., (© 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)- Published
- 2017
- Full Text
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8. On the Way to a Trisanionic {Cu 3 O 2 } Core for Oxidase Catalysis: Evidence of an Asymmetric Trinuclear Precursor Stabilized by Perfluoropinacolate Ligands.
- Author
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Hannigan SF, Arnoff AI, Neville SE, Lum JS, Golen JA, Rheingold AL, Orth N, Ivanović-Burmazović I, Liebhäuser P, Rösener T, Stanek J, Hoffmann A, Herres-Pawlis S, and Doerrer LH
- Subjects
- Caprylates metabolism, Catalysis, Drug Stability, Fluorocarbons metabolism, Ligands, Oxidoreductases chemistry, Caprylates chemistry, Copper chemistry, Fluorocarbons chemistry, Glycols chemistry, Oxidoreductases metabolism, Oxygen chemistry
- Abstract
Cu
I complexes of the form K[(R3 P)Cu(pinF )], in which (pinF )2- is the bidentate, oxygen-donating ligand perfluoropinacolate, were synthesized and characterized. Low-temperature oxygenation of the K[(R3 P)Cu(pinF )(PR3 )] species resulted in a trisanionic bis(μ3 -oxo) trinuclear copper(II,II,III) core characterized by UV/Vis spectroscopy (λmax [nm] = 330, 535, 630), cryospray-ionization mass spectrometry, and X-band electron paramagnetic resonance spectroscopy (derivative resonance at 3300 G, Δms =2 at 1500 G). The kinetic behavior of the trimeric {Cu3 O2 } species was quantified by stopped-flow spectroscopy and the associated electronic structures were investigated by DFT calculations. An asymmetric {Cu3 O2 } species,As TpinF , which bears a structure similar to multicopper oxidases, forms prior to full formation of the symmetric trinuclear core,Sy TpinF . The trimer catalytically oxidizes para-hydroquinone to benzoquinone (a form of oxidase chemistry)., (© 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)- Published
- 2017
- Full Text
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9. Efficient Biomimetic Hydroxylation Catalysis with a Bis(pyrazolyl)imidazolylmethane Copper Peroxide Complex.
- Author
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Wilfer C, Liebhäuser P, Hoffmann A, Erdmann H, Grossmann O, Runtsch L, Paffenholz E, Schepper R, Dick R, Bauer M, Dürr M, Ivanović-Burmazović I, and Herres-Pawlis S
- Subjects
- Biological Phenomena, Biomimetics, Catalysis, Hydroxylation, Kinetics, Ligands, Molecular Structure, Monophenol Monooxygenase metabolism, Photoelectron Spectroscopy, Copper chemistry, Imidazoles chemistry, Monophenol Monooxygenase chemistry, Oxyquinoline chemistry, Pyrazoles chemistry
- Abstract
Bis(pyrazolyl)methane ligands are excellent components of model complexes used to investigate the activity of the enzyme tyrosinase. Combining the N donors 3-tert-butylpyrazole and 1-methylimidazole results in a ligand that is capable of stabilising a (μ-η(2) :η(2) )-dicopper(II) core that resembles the active centre of tyrosinase. UV/Vis spectroscopy shows blueshifted UV bands in comparison to other known peroxo complexes, due to donor competition from different ligand substituents. This effect was investigated with the help of theoretical calculations, including DFT and natural transition orbital analysis. The peroxo complex acts as a catalyst capable of hydroxylating a variety of phenols by using oxygen. Catalytic conversion with the non-biological phenolic substrate 8-hydroxyquinoline resulted in remarkable turnover numbers. In stoichiometric reactions, substrate-binding kinetics was observed and the intrinsic hydroxylation constant, kox , was determined for five phenolates. It was found to be the fastest hydroxylation model system determined so far, reaching almost biological activity. Furthermore, Hammett analysis proved the electrophilic character of the reaction. This sheds light on the subtle role of donor strength and its influence on hydroxylation activity., (© 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)
- Published
- 2015
- Full Text
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10. The Cu2O2 torture track for a real-life system: [Cu2(btmgp)2O2](2+) oxo and peroxo species in density functional calculations.
- Author
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Rohrmüller M, Hoffmann A, Thierfelder C, Herres-Pawlis S, and Schmidt WG
- Subjects
- Electrons, Models, Molecular, Quantum Theory, Copper chemistry, Oxygen chemistry, Peroxides chemistry
- Abstract
Density functional theory (DFT) calculations of the equilibrium geometry, vibrational modes, ionization energies, electron affinities, and optical response of [Cu2(btmgp)2(μ-O)2](2+) (oxo) and [Cu2(btmgp)2(μ-η(2):η(2)-O2)](2+) (peroxo) are presented. Comprehensive benchmarking shows that the description of the oxo-peroxo energetics is still a torture track for DFT, but finds the molecular geometry to be comparatively robust with respect to changes in the exchange-correlation functionals and basis sets. Pure functionals favor the oxo core found experimentally, whereas hybrid functionals shift the bias toward the peroxo core. Further stabilization of peroxo core results from relaxing the spin degrees of freedom using the broken-symmetry (BS) approach. Dispersion effects, conversely, tend to favor the oxo configuration. Triple-zeta basis sets are found to represent a sensible compromise between numerical accuracy and computational effort. Particular attention is paid to the modification of the electronic structure, optical transitions, and excited-state energies along the transition path between the oxo and peroxo species. The excited-state potential energy surface calculations indicate that two triplet states are involved in the transition that stabilize the BS solution. Charge decomposition and natural transition orbital analyses are used for obtaining microscopic insight into the molecular orbital interactions. Here, the crucial role of guanidine π-interactions is highlighted for the stabilization of the Cu2O2 core., (© 2015 Wiley Periodicals, Inc.)
- Published
- 2015
- Full Text
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11. Geometrical and optical benchmarking of copper(II) guanidine-quinoline complexes: insights from TD-DFT and many-body perturbation theory (part II).
- Author
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Hoffmann A, Rohrmüller M, Jesser A, dos Santos Vieira I, Schmidt WG, and Herres-Pawlis S
- Subjects
- Molecular Structure, Coordination Complexes chemistry, Copper chemistry, Guanidine chemistry, Quantum Theory, Quinolines chemistry
- Abstract
Ground- and excited-state properties of copper(II) charge-transfer systems have been investigated starting from density-functional calculations with particular emphasis on the role of (i) the exchange and correlation functional, (ii) the basis set, (iii) solvent effects, and (iv) the treatment of dispersive interactions. Furthermore (v), the applicability of TD-DFT to excitations of copper(II) bis(chelate) charge-transfer systems is explored by performing many-body perturbation theory (GW + BSE), independent-particle approximation and ΔSCF calculations for a small model system that contains simple guanidine and imine groups. These results show that DFT and TD-DFT in particular in combination with hybrid functionals are well suited for the description of the structural and optical properties, respectively, of copper(II) bis(chelate) complexes. Furthermore, it is found an accurate theoretical geometrical description requires the use of dispersion correction with Becke-Johnson damping and triple-zeta basis sets while solvent effects are small. The hybrid functionals B3LYP and TPSSh yielded best performance. The optical description is best with B3LYP, whereby heavily mixed molecular transitions of MLCT and LLCT character are obtained which can be more easily understood using natural transition orbitals. An natural bond orbital analysis sheds light on the donor properties of the different donor functions and the intraguanidine stabilization during coordination to copper(I) and (II)., (Copyright © 2014 Wiley Periodicals, Inc.)
- Published
- 2014
- Full Text
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12. Geometrical and optical benchmarking of copper guanidine-quinoline complexes: insights from TD-DFT and many-body perturbation theory.
- Author
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Jesser A, Rohrmüller M, Schmidt WG, and Herres-Pawlis S
- Subjects
- Models, Molecular, Optical Phenomena, Copper chemistry, Guanidine chemistry, Organometallic Compounds chemistry, Quantum Theory, Quinolines chemistry
- Abstract
We report a comprehensive computational benchmarking of the structural and optical properties of a bis(chelate) copper(I) guanidine-quinoline complex. Using various (TD-)DFT flavors a strong influence of the basis set is found. Moreover, the amount of exact exchange shifts metal-to-ligand bands by 1 eV through the absorption spectrum. The BP86/6-311G(d) and B3LYP/def2-TZVP functional/basis set combinations were found to yield results in best agreement with the experimental data. In order to probe the general applicability of TD-DFT to excitations of copper bis(chelate) charge-transfer (CT) systems, we studied a small model system that on the one hand is accessible to methods of many-body perturbation theory (MBPT) but still contains simple guanidine and imine groups. These calculations show that large quasiparticle energies of the order of several electronvolts are largely offset by exciton binding energies for optical excitations and that TD-DFT excitation energies deviate from MBPT results by at most 0.5 eV, further corroborating the reliability of our TD-DFT results. The latter result in a multitude of MLCT bands ranging from the visible region at 3.4 eV into the UV at 5.5 eV for the bis(chelate) complex. Molecular orbital analysis provided insight into the CT within these systems but gave mixed transitions. A meaningful transition assignment is possible, however, by using natural transition orbitals. Additionally, we performed a thorough conformational analysis as the correct description of the copper coordination is crucial for the prediction of optical spectra. We found that DFT identifies the correct conformational minimum and that the MLCTs are strongly dependent on the torsion of the chelate angles at the copper center. From the results, it is concluded that extensive benchmarking allows for the quantitative analyses of the CT behavior of copper bis(chelate) complexes within TD-DFT., (Copyright © 2013 Wiley Periodicals, Inc.)
- Published
- 2014
- Full Text
- View/download PDF
13. Catching an entatic state--a pair of copper complexes.
- Author
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Hoffmann A, Binder S, Jesser A, Haase R, Flörke U, Gnida M, Salomone Stagni M, Meyer-Klaucke W, Lebsanft B, Grünig LE, Schneider S, Hashemi M, Goos A, Wetzel A, Rübhausen M, and Herres-Pawlis S
- Subjects
- Electrochemistry, Models, Molecular, Molecular Structure, Oxidation-Reduction, X-Ray Diffraction, Copper chemistry, Electron Spin Resonance Spectroscopy methods
- Abstract
The structures of two types of guanidine-quinoline copper complexes have been investigated by single-crystal X-ray crystallography, K-edge X-ray absorption spectroscopy (XAS), resonance Raman and UV/Vis spectroscopy, cyclic voltammetry, and density functional theory (DFT). Independent of the oxidation state, the two structures, which are virtually identical for solids and complexes in solution, resemble each other strongly and are connected by a reversible electron transfer at 0.33 V. By resonant excitation of the two entatic copper complexes, the transition state of the electron transfer is accessible through vibrational modes, which are coupled to metal-ligand charge transfer (MLCT) and ligand-metal charge transfer (LMCT) states., (Copyright © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)
- Published
- 2014
- Full Text
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14. Bis-μ-oxo and μ-η2:η2-peroxo dicopper complexes studied within (time-dependent) density-functional and many-body perturbation theory.
- Author
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Rohrmüller M, Herres-Pawlis S, Witte M, and Schmidt WG
- Subjects
- Models, Molecular, Molecular Structure, Coordination Complexes chemistry, Copper chemistry, Oxygen chemistry, Quantum Theory
- Abstract
Based on the equilibrium geometries of [Cu2(dbdmed)2O2](2+) and [Cu2(en)2O2](2+) obtained within density-functional theory, we investigate their molecular electronic structure and optical response. Thereby results from occupation-constrained as well as time-dependent DFT (ΔSCF and TDDFT) are compared with Green's function-based approaches within many-body perturbation theory such as the GW approximation (GWA) to the quasiparticle energies and the Bethe-Salpeter equation (BSE) approach to the optical absorption. Concerning the ground-state energies and geometries, no clear trend with respect to the amount of exact exchange in the DFT calculations is found, and a strong dependence on the basis sets is to be noted. They affect the energy difference between bis-μ-oxo and μ-η(2):η(2)-peroxo complexes by as much as 0.8 eV (18 kcal/mol). Even stronger, up to 5 eV is the influence of the exchange-correlation functional on the gap values obtained from the Kohn-Sham eigenvalues. Not only the value itself but also the trends observed upon the bis-μ-oxo to μ-η(2):η(2)-peroxo transition are affected. In contrast, excitation energies obtained from ΔSCF and TDDFT are comparatively robust with respect to the details of the calculations. Noteworthy, in particular, is the near quantitative agreement between TDDFT and GWA+BSE for the optical spectra of [Cu2(en)2O2](2+)., (Copyright © 2013 Wiley Periodicals, Inc.)
- Published
- 2013
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15. Stabilisation of a highly reactive bis(mu-oxo)dicopper(III) species at room temperature by electronic and steric constraint of an unconventional nitrogen donor ligand.
- Author
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Herres-Pawlis S, Binder S, Eich A, Haase R, Schulz B, Wellenreuther G, Henkel G, Rübhausen M, and Meyer-Klaucke W
- Subjects
- Ligands, Molecular Structure, Spectrum Analysis, Raman, Copper chemistry, Nitrogen chemistry, Organometallic Compounds chemistry, Oxygen chemistry
- Published
- 2009
- Full Text
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