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Carella A, Ciuti S, Wiedemann HTA, Kay CWM, van der Est A, Carbonera D, Barbon A, Poddutoori PK, Di Valentin M. The electronic structure and dynamics of the excited triplet state of octaethylaluminum(III)-porphyrin investigated with advanced EPR methods. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2023; 353:107515. [PMID: 37364432 DOI: 10.1016/j.jmr.2023.107515] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/21/2023] [Revised: 06/14/2023] [Accepted: 06/18/2023] [Indexed: 06/28/2023]
Abstract
The photoexcited triplet state of octaethylaluminum(III)-porphyrin (AlOEP) was investigated by time-resolved Electron Paramagnetic Resonance, Electron Nuclear Double Resonance and Electron Spin Echo Envelope Modulation in an organic glass at 10 and 80 K. This main group element porphyrin is unusual because the metal has a small ionic radius and is six-coordinate with axial covalent and coordination bonds. It is not known whether triplet state dynamics influence its magnetic resonance properties as has been observed for some transition metal porphyrins. Together with density functional theory modelling, the magnetic resonance data of AlOEP allow the temperature dependence of the zero-field splitting (ZFS) parameters, D and E, and the proton AZZ hyperfine coupling (hfc) tensor components of the methine protons, in the zero-field splitting frame to be determined. The results provide evidence that the ZFS, hfc and spin-lattice relaxation are indeed influenced by the presence of a dynamic process that is discussed in terms of Jahn-Teller dynamic effects. Thus, these effects should be taken into account when interpreting EPR data from larger complexes containing AlOEP.
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Affiliation(s)
- Angelo Carella
- Department of Chemical Sciences, University of Padova, Via Marzolo 1, 35131 Padova, Italy
| | - Susanna Ciuti
- Department of Chemical Sciences, University of Padova, Via Marzolo 1, 35131 Padova, Italy
| | - Haakon T A Wiedemann
- Department of Chemistry, Saarland University, Campus B 2.2, 66123 Saarbrücken, Germany
| | - Christopher W M Kay
- Department of Chemistry, Saarland University, Campus B 2.2, 66123 Saarbrücken, Germany; London Centre for Nanotechnology, University College London, 17-19 Gordon Street, London WC1H 0AH, UK
| | - Arthur van der Est
- Department of Chemistry, Brock University, 1812 Sir Isaac Brock Way, St. Catharines, Ontario, Canada
| | - Donatella Carbonera
- Department of Chemical Sciences, University of Padova, Via Marzolo 1, 35131 Padova, Italy
| | - Antonio Barbon
- Department of Chemical Sciences, University of Padova, Via Marzolo 1, 35131 Padova, Italy.
| | - Prashanth K Poddutoori
- Department of Chemistry & Biochemistry, University of Minnesota Duluth, 1038 University Drive, Duluth, MN 55812, USA
| | - Marilena Di Valentin
- Department of Chemical Sciences, University of Padova, Via Marzolo 1, 35131 Padova, Italy.
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Mergelsberg ST, Prange M, Song D, Bylaska EJ, Saslow SA, Catalano JG, Ilton ES. Resolving Configurational Disorder for Impurities in a Low-Entropy Phase. J Phys Chem Lett 2021; 12:5689-5694. [PMID: 34115494 DOI: 10.1021/acs.jpclett.1c01218] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
Hematite (α-Fe2O3) exerts a strong control over the transport of minor but critical metals in the environment and is used in multiple industrial applications; the photocatalysis community has explored the properties of hematite nanoparticles over a wide range of transition metal dopants. Nonetheless, simplistic assumptions are used to rationalize the local coordination environment of impurities in hematite. Here, we use ab initio molecular dynamics (AIMD)-guided structural analysis to model the extended X-ray absorption fine structure (EXAFS) of Cu2+- and Zn2+-doped hematite nanoparticles. Specific defect-impurity associations were identified, and the local coordination environments of Cu and Zn both displayed considerable configurational disorder that, in aggregate, approached Jahn-Teller-like distortion for Cu but, in contrast, maintained hematite-like symmetry for Zn. This study highlights the role of defects in accommodating impurities in a nominally low-entropy phase and the limits to traditional shell-by-shell fitting of EXAFS for dopants/impurities in unprecedented bonding environments.
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Affiliation(s)
| | - Micah Prange
- Pacific Northwest National Laboratory, Richland, Washington 99354, United States
| | - Duo Song
- Pacific Northwest National Laboratory, Richland, Washington 99354, United States
| | - Eric J Bylaska
- Pacific Northwest National Laboratory, Richland, Washington 99354, United States
| | - Sarah A Saslow
- Pacific Northwest National Laboratory, Richland, Washington 99354, United States
| | - Jeffrey G Catalano
- Department of Earth and Planetary Sciences, Washington University, St. Louis, Missouri 63130, United States
| | - Eugene S Ilton
- Pacific Northwest National Laboratory, Richland, Washington 99354, United States
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Colaneri MJ, Vitali J. Effect of the Lattice Field on the Electronic Structure and Dynamics of Copper-Hexahydrate in Tutton Salts. J Phys Chem A 2021; 125:3268-3278. [PMID: 33861605 DOI: 10.1021/acs.jpca.1c00074] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Previous structural and electron paramagnetic resonance (EPR) results are combined with new theoretical chemistry calculations on a series of copper-containing Tutton salts to investigate the influence of the host crystal electric field on the copper unpaired wave function and dynamics. Density functional theory (DFT) computations were performed on clusters centered on the host structure metal-hexahydrate complex to provide a model of atomic charges, which in turn were used to determine the electric fields and potentials at points along coordinate bonds of the complex. A significantly higher electric potential at the metal-water bonds is found for those Tutton salt systems having a greater copper EPR temperature dependency. Such a dependency has long been interpreted to arise from the averaging of tensor coupling parameters of the copper-hexahydrate complex due to a dynamic Jahn-Teller effect. However, the correlation found here reinforces a recent view that the coupling of the copper complex to the surrounding crystal lattice is the major determinant of these dynamics. The lattice potentials lack any significant temperature dependency and thus do not appear to be responsible for changes in the EPR patterns. A trend also appears between unbalanced spin in the compressed d-orbital lobe of the unpaired wave function and the magnitude of the potential. Hence, the lattice field is an important factor in defining both the electronic and dynamic characteristics of the copper-hexahydrate complex in these systems.
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Affiliation(s)
- Michael J Colaneri
- Department of Chemistry and Physics, State University of New York at Old Westbury, Old Westbury, New York 11568, United States
| | - Jacqueline Vitali
- Department of Physics and Department of Biological, Geological and Environmental Sciences, Cleveland State University, Cleveland, Ohio 44115, United States
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K A, Kathirvelu V. Electron spin relaxation time of Ni(II) ion in hexapyrazole zinc(II) dinitrate at 300 K. MAGNETIC RESONANCE IN CHEMISTRY : MRC 2020; 58:329-333. [PMID: 32017195 DOI: 10.1002/mrc.5007] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/17/2019] [Revised: 01/27/2020] [Accepted: 02/01/2020] [Indexed: 06/10/2023]
Abstract
Understanding the electron spin relaxation properties of paramagnetic species is a fundamental requirement to use them as a probe to measure distances between sites in biomolecules by electron paramagnetic resonance (EPR) spectroscopy. Even though Ni(II) ion is an essential trace element for many species, relaxation properties are not well understood. Herein, the polycrystalline sample of Ni(II) ion magnetically diluted in Zn(Pyrazole)6 (NO3 )2 (Ni/ZPN) has been studied in detail by EPR spectroscopy to explore the electron spin relaxation time. Progressive continuous-wave (CW) EPR power saturation study on Ni/ZPN at 300 K yielded 907 mW as the P1/2 value. The cavity constant (KQ ) has been calculated using tempol in PVA-BA glass matrix and the product of electron spin-lattice relaxation time (T1 ) and spin-spin relaxation time (T2 ) for Ni/ZPN at 300 K has been reported for the first time.
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Affiliation(s)
- Amrutha K
- Department of Applied Sciences, National Institute of Technology Goa, Ponda, India
| | - Velavan Kathirvelu
- Department of Applied Sciences, National Institute of Technology Goa, Ponda, India
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Colaneri MJ, Teat SJ, Vitali J. Electron Paramagnetic Resonance Characteristics and Crystal Structure of a Tutton Salt Analogue: Copper-Doped Cadmium Creatininium Sulfate. J Phys Chem A 2020; 124:2242-2252. [PMID: 32078331 DOI: 10.1021/acs.jpca.0c00004] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Electron paramagnetic resonance and crystallographic studies on copper-doped cadmium creatininium sulfate (CdCrnS) were undertaken to study the characteristics of a copper-hexahydrate complex in an organic analogue of Tutton's salt. X-ray diffraction experiments determined the crystal structure of CdCrnS at both 100 and 298 K. CdCrnS, like Tutton salt, crystallizes in the monoclinic space group P21/n. The unit cell contains two cadmium hexahydrate complexes, four creatininium ions, four sulfates, and four additional solvation waters. Both crystallography and EPR find that the doped copper replaces the cadmium in the structure. Single-crystal EPR measurements at room temperature determined the g and copper hyperfine (ACu) tensors (principal values: g = 2.437, 2.134, and 2.080 and ACu = -327, -84.8, and 7.33 MHz). EPR spectra of the powder at room temperature gave g = 2.448, 2.125, and 2.085 and ACu = -315, -75.0, and 35.0 MHz and at 110 K gave g = 2.462, 2.116, and 2.077 and ACu = -340, -30.0, and 35.0 MHz. The room-temperature tensors are close to the "rigid lattice limit" values found in copper-doped Tutton salts but with a higher gmin and weaker ACux coupling than average. A small but measurable temperature dependency of the tensors indicated the presence of a dynamic Jahn-Teller (JT) effect. In addition, the EPR line width changed dramatically with temperature, which is like that found in all copper-doped Tutton crystals. Utilizing the model of Silver-Getz for the g-value variation gave an estimate for the energy difference (δ12 = 640 cm-1) between the ground and next highest JT configurations. An empirical correlation appears to exist between δ12 and gmin and ACux for the copper hexahydrates studied in similar crystals. This suggests a relationship between the amount of unpaired spins in the copper d-orbital x lobe and the gap between wells of the adiabatic potential surface.
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Affiliation(s)
- Michael J Colaneri
- Department of Chemistry and Physics, State University of New York at Old Westbury, Old Westbury, New York 11568, United States
| | - Simon J Teat
- Lawrence Berkeley National Laboratory, 1 Cyclotron Road MS 15RO317, Berkeley, California 94720, United States
| | - Jacqueline Vitali
- Department of Physics and Department of Biological, Geological and Environmental Sciences, Cleveland State University, Cleveland, Ohio 44115, United States
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Colaneri MJ, Vitali J, Kirschbaum K. Electron paramagnetic resonance spectroscopic study of copper hopping in doped bis(L-histidinato)cadmium dihydrate. J Phys Chem A 2013; 117:3414-27. [PMID: 23530765 DOI: 10.1021/jp401477m] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Electron paramagnetic resonance (EPR) spectroscopy was used to study Cu(II) dynamic behavior in a doped biological model crystal, bis(L-histidinato)cadmium dihydrate, in order to gain better insight into copper site stability in metalloproteins. Temperature-dependent changes in the low temperature X-band EPR spectra became visible around 100 K and continued up to room temperature. The measured 298 K g-tensor (principal values: 2.17, 2.16, 2.07) and copper hyperfine coupling tensor (principal values: -260, -190, -37 MHz) were similar to the average of the 77 K tensor values pertaining to two neighboring histidine binding sites. The observed temperature dependence was interpreted using Anderson's theory of motional narrowing, where the magnetic parameters for the different states are averaged as the copper rapidly hops between sites. The EPR pattern was also found to undergo a sharp sigmoidal-shaped, temperature-dependent conversion between two species with a critical temperature T(c) ≈ 160 K. The species below T(c) hops between the two low temperature site patterns, and the one above T(c) represents an average of the molecular spin Hamiltonian coupling tensors of the two 77 K sites. In addition, the low and high temperature species hop between one another, contributing to the dynamic averaging. Spectral simulations using this 4-state model determined a hop rate between the two low temperature sites ν(h4) = 4.5 × 10(8) s(-1) and between the low and high temperature states ν(h2) = 1.7 × 10(8) s(-1) at 160 K. An Arrhenius relationship of hop rate and temperature gave energy barriers of ΔE4 = 389 cm(-1) and ΔE2 = 656 cm(-1) between the two low temperature sites and between the low and high temperature states, respectively.
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Affiliation(s)
- Michael J Colaneri
- Department of Chemistry and Physics, State University of New York at Old Westbury, Old Westbury, New York 11568, USA.
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Hoffmann SK, Goslar J, Lijewski S. Suppression of Raman electron spin relaxation of radicals in crystals. Comparison of Cu2+ and free radical relaxation in triglycine sulfate and Tutton salt single crystals. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2011; 23:345403. [PMID: 21841228 DOI: 10.1088/0953-8984/23/34/345403] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
Electron spin-lattice relaxation was measured by the electron spin echo method in a broad temperature range above 4.2 K for Cu(2+) ions and free radicals produced by ionizing radiation in triglycine sulfate (TGS) and Tutton salt (NH4)(2)Zn(SO4)2 ⋅ 6H2O crystals. Localization of the paramagnetic centres in the crystal unit cells was determined from continuous wave electron paramagnetic resonance spectra. Various spin relaxation processes and mechanisms are outlined. Cu(2+) ions relax fast via two-phonon Raman processes in both crystals involving the whole phonon spectrum of the host lattice. This relaxation is slightly slower for TGS where Cu(2+) ions are in the interstitial position. The ordinary Raman processes do not contribute to the radical relaxation which relaxes via the local phonon mode. The local mode lies within the acoustic phonon band for radicals in TGS but within the optical phonon range in (NH4)(2)Zn(SO4)2 ⋅ 6H2O. In the latter the cross-relaxation was considered. A lack of phonons around the radical molecules suggested a local crystal amorphisation produced by x- or γ-rays.
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Affiliation(s)
- S K Hoffmann
- Institute of Molecular Physics, Polish Academy of Sciences, Smoluchowskiego 17, PL-60179 Poznan, Poland
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Hoffmann SK, Goslar J, Tadyszak K. Electronic structure and dynamics of low symmetry Cu2+ complexes in kainite-type crystal KZnClSO4.3H2O: EPR and ESE studies. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2010; 205:293-303. [PMID: 20638996 DOI: 10.1016/j.jmr.2010.05.014] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/23/2010] [Revised: 05/19/2010] [Accepted: 05/21/2010] [Indexed: 05/29/2023]
Abstract
EPR measurements at X-band were performed in the temperature range 4.2-300 K with angular dependence measurements at 77 K for Cu(2+) in KZnClSO(4).3H(2)O. Rigid lattice spin-Hamiltonian parameters are: g(z) = 2.4247, g(y) = 2.0331, g(x) = 2.1535, A(z) = -103 x 10(-4) cm(-1), 63 x 10(-4) cm(-1), and -31 x 10(-4) cm(-1). The parameters were analyzed using MO-theory with the d(x(2)-y(2)) ground state containing admixture of the d(z(2))-state in the rhombic symmetry D(2h). The analysis consistently explained unusual g-factor sequence and relatively small hyperfine splitting anisotropy as the consequence of the mixing and spin density delocalization via excited orbital states. We assigned that Cu(2+) ions substituting host Zn(2+) prefer one of the four structurally different zinc sites where they are coordinated by four water molecules and two SO(4) groups in an distorted octahedron elongated along SO(4)-Cu-SO(4) direction. The distortion is due to the Jahn-Teller effect which is static at low temperatures but becomes dynamic above 20 K with jumps of the Cu(2+) complex between two lowest potential wells. The jumps produce continuous g-factor and hyperfine splitting averaging when temperature increases. This process is discussed in terms of two motional averaging theories: classical theory based on generalized Bloch equations and Silver-Getz model. Their limitations are discussed. Importance of the difference in the g-factors of the averaged line is explained and a new expression for calculation of jump frequency from the line shift is proposed. The jumps are described as phonon induced tunneling via excited vibrational level of energy 76 (+/-6) cm(-1). This process is not effective enough at low temperatures and Boltzmann population of the two lowest energy potential wells is reached above 110 K. From electron spin-lattice relaxation measurements by electron spin echo methods the Debye temperature was determined as Theta(D) = 172 K. Fourier Transform of strongly modulated spin echo decay gives pseudo-ENDOR spectrum with peaks from (1)H and (35)Cl nuclei. From splitting of the peaks into doublets we determined the distance to the modulating nuclei and confirmed the position of the site where Cu(2+) ion is located.
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Affiliation(s)
- Stanisław K Hoffmann
- Institute of Molecular Physics, Polish Academy of Sciences, PL-60179 Poznań, Poland.
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9
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Wesełucha-Birczyńska A, Oleksyn B, Śliwiński J, Goslar J, Hilczer W, Hoffmann S. Crystal structure and EPR studies of (cinchonineH2)2(CdCl4)(Cd/CuCl4) crystals with thermochromic and Jahn–Teller effect. J Mol Struct 2005. [DOI: 10.1016/j.molstruc.2005.05.004] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
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Burda JV, Pavelka M, Šimánek M. Theoretical model of copper Cu(I)/Cu(II) hydration. DFT and ab initio quantum chemical study. ACTA ACUST UNITED AC 2004. [DOI: 10.1016/j.theochem.2004.06.013] [Citation(s) in RCA: 60] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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Kiczka S, Hoffmann SK, Goslar J, Szczepanska L. Electronic structure, Jahn–Teller dynamics and electron spin relaxation of two types of octahedral Cu(ii) complexes in cadmium formate dihydrate Cd(HCOO)2·2H2O. EPR and ESE studies. Phys Chem Chem Phys 2004. [DOI: 10.1039/b311063j] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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12
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Harbridge JR, Eaton SS, Eaton GR. Comparison of electron spin relaxation times measured by Carr-Purcell-Meiboom-Gill and two-pulse spin-echo sequences. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2003; 164:44-53. [PMID: 12932454 DOI: 10.1016/s1090-7807(03)00182-4] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
Electron spin relaxation times obtained by two-pulse spin-echo and Carr-Purcell-Meiboom-Gill (CPMG) experiments were compared for samples with: (i) low concentrations of nuclear spins, (ii) higher concentrations of nuclear spins and low concentrations of unpaired electrons, (iii) higher concentrations of nuclear spins and of electron spins, and (iv) dynamic averaging of inequivalent hyperfine couplings on the EPR timescale. In each case, the CPMG time constant decreased as the time between the refocusing pulses increased. For the samples with low concentrations of nuclear spins (the E' center in irradiated amorphous SiO2) the limiting value of the CPMG time constant at short interpulse spacings was similar to the Tm obtained by two-pulse spin echo at small turning angle. For the other samples, the time constants obtained by CPMG at short interpulse spacings were systematically longer than Tm obtained by two-pulse spin echo. For most of the samples, the CPMG time constant decreased with increasing electron spin concentration, which is consistent with the expectation that the CPMG sequence does not refocus dephasing due to electron-electron dipolar interaction between resonant spins. Dynamic processes that average inequivalent hyperfine couplings contributed less to the CPMG time constant than to the spin-echo decay time constant. The impact of nuclear echo envelope modulation on CPMG time constants also was examined. For a Nycomed trityl radical in glassy D2O:glycerol-d8 solution, the CPMG time constant was up to 20 times longer when the time between pulses was approximately equal to integer multiples of the reciprocal of the deuterium Larmor frequency than when the time between pulses was an odd multiple of half the reciprocal of the deuterium Larmor frequency.
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Affiliation(s)
- James R Harbridge
- Department of Chemistry and Biochemistry, University of Denver, Denver, CO 80208-2436, USA
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Dobe C, Andres HP, Tregenna-Piggott PL, Mossin S, Weihe H, Janssen S. Variable temperature inelastic neutron scattering study of chromium(II) Tutton salt: manifestation of the 5E⊗e Jahn–Teller effect. Chem Phys Lett 2002. [DOI: 10.1016/s0009-2614(02)01131-4] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
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BIETSCH W, MIREA A, KAMLEITER T, WEISS M, SCHUBERT US, WEIDL CH, ESCHBAUMER C, OVCHINNIKOV I, DOMRACHEVA N. Exchange interaction and Jahn—Teller correlations in novel tetranuclear supramolecular Cu(II) grid complexes: an ESR study. Mol Phys 2002. [DOI: 10.1080/00268970210127979] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/14/2022]
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Eaton SS, Eaton GR. Relaxation Times of Organic Radicals and Transition Metal Ions. DISTANCE MEASUREMENTS IN BIOLOGICAL SYSTEMS BY EPR 2002. [DOI: 10.1007/0-306-47109-4_2] [Citation(s) in RCA: 95] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
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Hoffmann SK, Goslar J, Hilczer W, Augustyniak-Jablokow MA, Kiczka S. Dephasing relaxation of the electron spin echo of the vibronic Cu(H(2)O)(6) complexes in Tutton salt crystals at low temperatures. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2001; 153:56-68. [PMID: 11700081 DOI: 10.1006/jmre.2001.2426] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
Two-pulse electron spin echo (ESE) measurements of the phase relaxation (phase memory time T(M)) were performed in a series of Tutton salt crystals M(I)(2)M(II)(SO(4))(2).6X(2)O (M(I)=NH(4), K, Cs; M(II)=Zn, Mg; X=H, D) weakly doped with Cu(2+) ions (c approximately equal to 10(18) ions/cm(3)) in temperature range 4-60 K where ESE signals were detectable. The ESE decay was strongly modulated with proton (or deuteron) frequencies and described by the decay function V(2tau)=V(0)exp(-btau-mtau(2)) with the mtau(2) term being temperature independent and negligible above 20 K. Various mechanisms leading to the tau- or tau(2)-type ESE decay are reviewed. The m and b coefficients for nuclear spectral diffusion (NSD), electron spectral diffusion (SD), and instantaneous diffusion (ID) were calculated in terms of existing theories and the resulting rigid lattice T(0)(M) times were found to be close one to another within the crystal family with average values: 17.5 micros (NSD protons), 200 micros (NSD deuterons), 8 micros (SD), and 5 micros (ID). The ID dominates but the calculated effective T(M)(0) is longer than the experimental T(M)(0)=2 micros. This is due to a nonuniform distribution of the Cu(2+) ions with a various degree of the disorder in the studied crystals. The acceleration of the dephasing rate 1/T(M) with temperature is due to the mechanisms producing exp(-btau) decay. They are reviewed and two of them were found to be operative in Tutton salt crystals: (a) Excitations to the vibronic levels of energy Delta leading to the temperature dependence 1/T(M)=B exp(-Delta/kT), with the vibronic levels produced by strong Jahn-Teller effect, and (b) spin-lattice relaxation processes being effective above 50 K. Based on the Delta values being on the order of 100 cm(-1), the scheme of vibronic levels in the Tutton salts is presented, and the independence of the Delta on temperature proves that the adiabatic potential surface shape of Jahn-Teller active Cu(H(2)O)(6) complexes is not affected by temperature below 65 K.
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Affiliation(s)
- S K Hoffmann
- Institute of Molecular Physics, Polish Academy of Sciences, Smoluchowskiego 17, PL-60179 Poznan, Poland.
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Hoffmann SK, Hilczer W, Goslar J, Massa MM, Calvo R. Electron spin relaxation in pseudo-Jahn-Teller low-symmetry Cu(II) complexes in diaqua(L-aspartate)Zn(II).H(2)O crystals. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2001; 153:92-102. [PMID: 11700085 DOI: 10.1006/jmre.2001.2434] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
Low-temperature (4-55 K) pulsed EPR measurements were performed with the magnetic field directed along the z-axis of the g-factor of the low-symmetry octahedral complex [(63)Cu(L-aspartate)(2)(H2O)2] undergoing dynamic Jahn-Teller effect in diaqua(L-aspartate)Zn(II) hydrate single crystals. Spin-lattice relaxation time T(1) and phase memory time T(M) were determined by the electron spin echo (ESE) method. The relaxation rate 1/T(1) increases strongly over 5 decades in the temperature range 4-55 K. Various processes and mechanisms of T(1)-relaxation are discussed, and it is shown that the relaxation is governed mainly by Raman relaxation processes with the Debye temperature Theta(D)=204 K, with a detectable contribution from disorder in the doped Cu(2+) ions system below 12 K. An analytical approximation of the transport integral I(8) is given in temperature range T=0.025-10Theta(D) and applied for computer fitting procedures. Since the Jahn-Teller distorted configurations differ strongly in energy (delta(12)=240 cm(-1)), there is no influence of the classical vibronic dynamics mechanism on T(1). Dephasing of the ESE (phase relaxation) is governed by instantaneous diffusion and spectral diffusion below 20 K with resulting rigid lattice value 1/T(0)(M)=1.88 MHz. Above this temperature the relaxation rate 1/T(M) increases upon heating due to two mechanisms. The first is the phonon-controlled excitation to the first excited vibronic level of energy Delta=243 cm(-1), with subsequent tunneling to the neighbor potential well. This vibronic-type dynamics also produces a temperature-dependent broadening of lines in the ESEEM spectra. The second mechanism is produced by the spin-lattice relaxation. The increase in T(M) is described in terms of the spin packets forming inhomogeneously broadened EPR lines.
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Affiliation(s)
- S K Hoffmann
- Institute of Molecular Physics, Polish Academy of Sciences, Smoluchowskiego 17, PL-60179 Poznan, Poland
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Neto JA, Vugman NV. Electron spin relaxation via vibronic level of rhodium(II) hexacyanide complex in KCl crystal. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2001; 150:105-109. [PMID: 11384167 DOI: 10.1006/jmre.2001.2330] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
Electron spin-lattice relaxation rates for the low-spin [Rh(CN)(6)](4-) complex in KCl were measured by the inversion recovery and saturation recovery techniques, in the range of 5 to 30 K. Angular variation experiments indicate that electron spin-lattice relaxation times present axial symmetry. The data fit very well to a relaxation process involving localized anharmonic vibration modes, also responsible for the g tensor temperature dependence.
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Affiliation(s)
- J A Neto
- Instituto de Física, Universidade Federal do Rio de Janeiro, Rio de Janeiro 21910-240, RJ, Brazil
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Dalosto SD, Calvo R, Pizarro JL, Arriortua MI. Structure, Disorder, and Molecular Dynamics in Zn(d,l-histidine)2: EPR of Copper Ion Dopants, X-ray Diffraction, and Calorimetric Studies. J Phys Chem A 2001. [DOI: 10.1021/jp003167n] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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Massa MB, Dalosto SD, Ferreyra MG, Labadie G, Calvo R. Vibronic Behavior and Single-Crystal EPR Spectra of Cu(II) in Copper-Doped Diaqua(l-aspartato)zinc(II) Hydrate. J Phys Chem A 1999. [DOI: 10.1021/jp984432w] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Marta B. Massa
- Facultad de Ciencias Exactas, Ingeniería y Agrimensura, Universidad Nacional de Rosario, Avda. Pellegrini 250, 2000 Rosario, Argentina, Facultad de Bioquímica y Ciencias Biológicas, Universidad Nacional del Litoral, Casilla 530, 3000 Santa Fe, Argentina, INTEC (CONICET, UNL), Güemes 3450, 3000 Santa Fe, Argentina, and Facultad de Ciencias Bioquímicas y Farmacéuticas, Universidad Nacional de Rosario, Suipacha 570, 2000 Rosario, Argentina
| | - Sergio D. Dalosto
- Facultad de Ciencias Exactas, Ingeniería y Agrimensura, Universidad Nacional de Rosario, Avda. Pellegrini 250, 2000 Rosario, Argentina, Facultad de Bioquímica y Ciencias Biológicas, Universidad Nacional del Litoral, Casilla 530, 3000 Santa Fe, Argentina, INTEC (CONICET, UNL), Güemes 3450, 3000 Santa Fe, Argentina, and Facultad de Ciencias Bioquímicas y Farmacéuticas, Universidad Nacional de Rosario, Suipacha 570, 2000 Rosario, Argentina
| | - M. Graciela Ferreyra
- Facultad de Ciencias Exactas, Ingeniería y Agrimensura, Universidad Nacional de Rosario, Avda. Pellegrini 250, 2000 Rosario, Argentina, Facultad de Bioquímica y Ciencias Biológicas, Universidad Nacional del Litoral, Casilla 530, 3000 Santa Fe, Argentina, INTEC (CONICET, UNL), Güemes 3450, 3000 Santa Fe, Argentina, and Facultad de Ciencias Bioquímicas y Farmacéuticas, Universidad Nacional de Rosario, Suipacha 570, 2000 Rosario, Argentina
| | - Guillermo Labadie
- Facultad de Ciencias Exactas, Ingeniería y Agrimensura, Universidad Nacional de Rosario, Avda. Pellegrini 250, 2000 Rosario, Argentina, Facultad de Bioquímica y Ciencias Biológicas, Universidad Nacional del Litoral, Casilla 530, 3000 Santa Fe, Argentina, INTEC (CONICET, UNL), Güemes 3450, 3000 Santa Fe, Argentina, and Facultad de Ciencias Bioquímicas y Farmacéuticas, Universidad Nacional de Rosario, Suipacha 570, 2000 Rosario, Argentina
| | - Rafael Calvo
- Facultad de Ciencias Exactas, Ingeniería y Agrimensura, Universidad Nacional de Rosario, Avda. Pellegrini 250, 2000 Rosario, Argentina, Facultad de Bioquímica y Ciencias Biológicas, Universidad Nacional del Litoral, Casilla 530, 3000 Santa Fe, Argentina, INTEC (CONICET, UNL), Güemes 3450, 3000 Santa Fe, Argentina, and Facultad de Ciencias Bioquímicas y Farmacéuticas, Universidad Nacional de Rosario, Suipacha 570, 2000 Rosario, Argentina
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HOFFMANN SK, AUGUSTYNIAK MA, GOSLAR J, HILCZER W. Does the Jahn-Teller effect influence electron spin relaxation? Electron paramagnetic resonance and electron spin echo studies of the Mn2+doped (NH4)2Mg(SO4) · 6H2O single crystal and comparison with Cu2+data. Mol Phys 1998. [DOI: 10.1080/00268979809483257] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
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Goslar J, Hilczer W, Hoffmann SK. Vibronic Averaging Effect in ESEEM Spectra of (NH4)2Mg(SO4)2·6H2O Single Crystal Doped with Jahn−Teller Active Cu(H2O)6 Complexes. Inorg Chem 1998. [DOI: 10.1021/ic9805675] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Janina Goslar
- Institute of Molecular Physics, Polish Academy of Sciences, Smoluchowskiego 17, PL-60179 Poznań, Poland
| | - Wojciech Hilczer
- Institute of Molecular Physics, Polish Academy of Sciences, Smoluchowskiego 17, PL-60179 Poznań, Poland
| | - Stanisław K. Hoffmann
- Institute of Molecular Physics, Polish Academy of Sciences, Smoluchowskiego 17, PL-60179 Poznań, Poland
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