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Nagelski AL, Ozerov M, Fataftah MS, Krzystek J, Greer SM, Holland PL, Telser J. Electronic Structure of Three-Coordinate Fe II and Co II β-Diketiminate Complexes. Inorg Chem 2024; 63:4511-4526. [PMID: 38408452 DOI: 10.1021/acs.inorgchem.3c03388] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/28/2024]
Abstract
The β-diketiminate supporting group, [ArNCRCHCRNAr]-, stabilizes low coordination number complexes. Four such complexes, where R = tert-butyl, Ar = 2,6-diisopropylphenyl, are studied: (nacnactBu)ML, where M = FeII, CoII and L = Cl, CH3. These are denoted FeCl, FeCH3, CoCl, and CoCH3 and have been previously reported and structurally characterized. The two FeII complexes (S = 2) have also been previously characterized by Mössbauer spectroscopy, but only indirect assessment of the ligand-field splitting and zero-field splitting (zfs) parameters was available. Here, EPR spectroscopy is used, both conventional field-domain for the CoII complexes (with S = 3/2) and frequency-domain, far-infrared magnetic resonance spectroscopy (FIRMS) for all four complexes. The CoII complexes were also studied by magnetometry. These studies allow accurate determination of the zfs parameters. The two FeII complexes are similar with nearly axial zfs and large magnitude zfs given by D = -37 ± 1 cm-1 for both. The two CoII complexes likewise exhibit large and nearly axial zfs, but surprisingly, CoCl has positive D = +55 cm-1 while CoCH3 has negative D = -49 cm-1. Theoretical methods were used to probe the electronic structures of the four complexes, which explain the experimental spectra and the zfs parameters.
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Affiliation(s)
- Alexandra L Nagelski
- Department of Chemistry, Yale University, New Haven, Connecticut 06511, United States
| | - Mykhaylo Ozerov
- National High Magnetic Field Laboratory, Florida State University, Tallahassee, Florida 32310, United States
| | - Majed S Fataftah
- Department of Chemistry, Yale University, New Haven, Connecticut 06511, United States
| | - J Krzystek
- National High Magnetic Field Laboratory, Florida State University, Tallahassee, Florida 32310, United States
| | - Samuel M Greer
- Los Alamos National Laboratory, Los Alamos, New Mexico 87545, United States
| | - Patrick L Holland
- Department of Chemistry, Yale University, New Haven, Connecticut 06511, United States
| | - Joshua Telser
- Department of Biological, Chemical and Physical Sciences, Roosevelt University, Chicago, Illinois 60605, United States
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Kumarage ND, Marts AR, Grindle MP, Kaine JC, Crandall LA, Chen WY, Ziegler CJ, Tierney DL. Field- and Temperature-Dependent Paramagnetic Relaxation Enhancements in Co(II) Trispyrazolylmethanes. Inorg Chem 2023; 62:15952-15962. [PMID: 37725578 DOI: 10.1021/acs.inorgchem.3c02028] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 09/21/2023]
Abstract
A comprehensive field- and temperature-dependent examination of nuclear magnetic resonance paramagnetic relaxation enhancements (PREs) for the constitutive protons of [Co(Tpm)2][BF4]2 is presented. Data for an apically substituted derivative clearly establish that bis-Tpm complexes of Co(II) undergo Jahn-Teller dynamics about the molecular threefold axis. PREs from the parent Tpm complex were used to numerically extract the electron relaxation times (T1e). The Tpm complex showed field-dependent behavior, with an approximately 40% higher activation barrier than the related trispyrazolylborate (Tp) complex, based on fits to the T1e vs T, B0 data. Analysis of the field-dependent line widths revealed a surprisingly large contribution from susceptibility (Curie) relaxation (20-35% at the highest field), and a molecular radius (9.5 Å) that is consistent with a tightly associated counterion slowing rotation in solution. Density functional theory showed a shared vibration that is consistent with the Jahn-Teller and appears proportionately higher in energy in [Co(Tpm)2]2+. Complete active-space self-consistent field calculations support ascribing electron relaxation to enhanced mixing of the two Eg orbital sets that accompanies the tetragonal distortion and the differences in electron correlation times to the higher Jahn-Teller activation barrier in [Co(Tpm)2]2+.
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Affiliation(s)
- Nuwanthika D Kumarage
- Department of Chemistry and Biochemistry, Miami University, Oxford, Ohio 45056, United States
| | - Amy R Marts
- Department of Chemistry and Biochemistry, Miami University, Oxford, Ohio 45056, United States
| | - Matthew P Grindle
- Department of Chemistry and Biochemistry, Miami University, Oxford, Ohio 45056, United States
| | - Joshua C Kaine
- Department of Chemistry and Biochemistry, Miami University, Oxford, Ohio 45056, United States
| | - Laura A Crandall
- Department of Chemistry, University of Akron, Akron, Ohio 44325, United States
| | - Wei-Yuan Chen
- Department of Chemistry, University of Akron, Akron, Ohio 44325, United States
| | | | - David L Tierney
- Department of Chemistry and Biochemistry, Miami University, Oxford, Ohio 45056, United States
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Pyykkönen A, Feher R, Köhler FH, Vaara J. Paramagnetic Pyrazolylborate Complexes Tp 2M and Tp* 2M: 1H, 13C, 11B, and 14N NMR Spectra and First-Principles Studies of Chemical Shifts. Inorg Chem 2020; 59:9294-9307. [PMID: 32558559 DOI: 10.1021/acs.inorgchem.0c01176] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The paramagnetic pyrazolylborates Tp2M and Tp*2M (M = Cu, Ni, Co, Fe, Mn, Cr, V) as well as [Tp2M]+ and [Tp*2M]+ (M = Fe, Cr, V) have been synthesized and their NMR spectra recorded. The 1H signal shift ranges vary from ∼30 ppm (Cu(II) and V(III)) to ∼220 ppm (Co(II)), and the 13C signal shift ranges from ∼180 ppm (Fe(III)) to ∼1150 ppm (Cr(II)). The 11B and 14N shifts are ∼360 and ∼730 ppm, respectively. Both negative and positive shifts have been observed for all nuclei. The narrow NMR signals of the Co(II), Fe(II), Fe(III), and V(III) derivatives provide resolved 13C,1H couplings. All chemical shifts have been calculated from first-principles on a modern version of Kurland-McGarvey theory which includes optimized structures, zero-field splitting, and g tensors, as well as signal shift contributions. Temperature dependence in the Fe(II) spin-crossover complex results from the equilibrium of the ground singlet and the excited quintet. We illustrate both the assignment and analysis capabilities, as well as the shortcomings of the current computational methodology.
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Affiliation(s)
- Ari Pyykkönen
- NMR Research Unit, University of Oulu, P.O. Box 3000, Oulu FI-90014, Finland
| | - Robert Feher
- Department Chemie, Technische Universität München, D-85748 Garching, Germany
| | - Frank H Köhler
- Department Chemie, Technische Universität München, D-85748 Garching, Germany
| | - Juha Vaara
- NMR Research Unit, University of Oulu, P.O. Box 3000, Oulu FI-90014, Finland
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Pavlov AA, Nehrkorn J, Pankratova YA, Ozerov M, Mikhalyova EA, Polezhaev AV, Nelyubina YV, Novikov VV. Detailed electronic structure of a high-spin cobalt(ii) complex determined from NMR and THz-EPR spectroscopy. Phys Chem Chem Phys 2019; 21:8201-8204. [DOI: 10.1039/c9cp01474h] [Citation(s) in RCA: 27] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
Here we report a combined use of THz-EPR and paramagnetic NMR spectroscopy for obtaining a detailed electronic structure of a high-spin cobalt(ii) complex.
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Affiliation(s)
- Alexander A. Pavlov
- A.N.Nesmeyanov Institute of Organoelement Compounds
- Russian Academy of Sciences
- Moscow
- Russia
- Moscow Institute of Physics and Technology
| | - Joscha Nehrkorn
- National High Magnetic Field Laboratory & Florida State University
- 1800 E. Paul Dirac Drive
- Tallahassee
- USA
- Max Planck Institute for Chemical Energy Conversion
| | - Yanina A. Pankratova
- A.N.Nesmeyanov Institute of Organoelement Compounds
- Russian Academy of Sciences
- Moscow
- Russia
- Lomonosov Moscow State University
| | - Mykhaylo Ozerov
- National High Magnetic Field Laboratory & Florida State University
- 1800 E. Paul Dirac Drive
- Tallahassee
- USA
| | - Elena A. Mikhalyova
- L.V.Pisarzhevskii Institute of Physical Chemistry of the National Academy of Sciences of the Ukraine
- Kiev
- Ukraine
| | - Alexander V. Polezhaev
- A.N.Nesmeyanov Institute of Organoelement Compounds
- Russian Academy of Sciences
- Moscow
- Russia
- Bauman Moscow State Technical University
| | - Yulia V. Nelyubina
- A.N.Nesmeyanov Institute of Organoelement Compounds
- Russian Academy of Sciences
- Moscow
- Russia
- Moscow Institute of Physics and Technology
| | - Valentin V. Novikov
- A.N.Nesmeyanov Institute of Organoelement Compounds
- Russian Academy of Sciences
- Moscow
- Russia
- Moscow Institute of Physics and Technology
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Temperature-Dependant Assemblies of Cu(II) Coordination Polymers and In Situ Ligand Reaction Based on 2,2′-Bipyridine-3,3′,6,6′-Tetracarboxylic acid. J Inorg Organomet Polym Mater 2017. [DOI: 10.1007/s10904-017-0556-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
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Marts AR, Kaine JC, Baum RR, Clayton VL, Bennett JR, Cordonnier LJ, McCarrick R, Hasheminasab A, Crandall LA, Ziegler CJ, Tierney DL. Paramagnetic Resonance of Cobalt(II) Trispyrazolylmethanes and Counterion Association. Inorg Chem 2016; 56:618-626. [PMID: 27977149 DOI: 10.1021/acs.inorgchem.6b02520] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Paramagnetic resonance studies (EPR, ESEEM, ENDOR, and NMR) of a series of cobalt(II) bis-trispyrazolylmethane tetrafluoroborates are presented. The complexes studied include the parent, unsubstituted ligand (Tpm), two pyrazole-substituted derivatives (4Me and 3,5-diMe), and tris(1-pyrazolyl)ethane (Tpe), which includes a methyl group on the apical carbon atom. NMR and ENDOR establish the magnitude of 1H hyperfine couplings, while ESEEM provides information on the coordinated 14N. The data show that the pyrazole 3-position is more electron rich in the Tpm analogues, that the geometry about the apical atom influences the magnetic resonance, and that apical atom geometry appears more fixed in Tpm than in Tp. NMR and ENDOR establish that the BF4- counterion remains associated in fluid solution. In the case of the Tpm3,5Me complex, it appears to associate in solution, in the same position it occupies in the X-ray structure.
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Affiliation(s)
- Amy R Marts
- Department of Chemistry and Biochemistry, Miami University , Oxford, Ohio 45056, United States
| | - Joshua C Kaine
- Department of Chemistry and Biochemistry, Miami University , Oxford, Ohio 45056, United States
| | - Robert R Baum
- Department of Chemistry and Biochemistry, Miami University , Oxford, Ohio 45056, United States
| | - Vivien L Clayton
- Department of Chemistry and Biochemistry, Miami University , Oxford, Ohio 45056, United States
| | - Jami R Bennett
- Department of Chemistry and Biochemistry, Miami University , Oxford, Ohio 45056, United States
| | - Laura J Cordonnier
- Department of Chemistry and Biochemistry, Miami University , Oxford, Ohio 45056, United States
| | - Robert McCarrick
- Department of Chemistry and Biochemistry, Miami University , Oxford, Ohio 45056, United States
| | - Abed Hasheminasab
- Department of Chemistry, University of Akron , Akron, Ohio 44325, United States
| | - Laura A Crandall
- Department of Chemistry, University of Akron , Akron, Ohio 44325, United States
| | | | - David L Tierney
- Department of Chemistry and Biochemistry, Miami University , Oxford, Ohio 45056, United States
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Soncini A, Calvello S. Room Temperature Chiral Discrimination in Paramagnetic NMR Spectroscopy. PHYSICAL REVIEW LETTERS 2016; 116:163001. [PMID: 27152797 DOI: 10.1103/physrevlett.116.163001] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/08/2015] [Indexed: 05/13/2023]
Abstract
A recently proposed theory of chiral discrimination in NMR spectroscopy based on the detection of a molecular electric polarization P rotating in a plane perpendicular to the NMR magnetic field [A. D. Buckingham, J. Chem. Phys. 140, 011103 (2014)] is generalized here to paramagnetic systems. Our theory predicts new contributions to P, varying as the square of the inverse temperature. Ab initio calculations for ten Dy^{3+} complexes, at 293 K, show that, in strongly anisotropic paramagnetic molecules, P can be more than 1000 times larger than in diamagnetic molecules, making paramagnetic NMR chiral discrimination amenable to room temperature detection.
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Affiliation(s)
- Alessandro Soncini
- School of Chemistry, University of Melbourne, Parkville, Victoria 3010, Australia
| | - Simone Calvello
- School of Chemistry, University of Melbourne, Parkville, Victoria 3010, Australia
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Baum RR, Myers WK, Greer SM, Breece RM, Tierney DL. The Original CoII Heteroscorpionates Revisited: On the EPR of Pseudotetrahedral CoII. Eur J Inorg Chem 2016. [DOI: 10.1002/ejic.201501356] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Affiliation(s)
- Robert R. Baum
- Department of Chemistry and BiochemistryMiami University45056OxfordOHUSA
| | - William K. Myers
- Department of Chemistry and BiochemistryMiami University45056OxfordOHUSA
| | - Samuel M. Greer
- Department of Chemistry and BiochemistryMiami University45056OxfordOHUSA
| | - Robert M. Breece
- Department of Chemistry and BiochemistryMiami University45056OxfordOHUSA
| | - David L. Tierney
- Department of Chemistry and BiochemistryMiami University45056OxfordOHUSA
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Tsitovich PB, Cox JM, Benedict JB, Morrow JR. Six-coordinate Iron(II) and Cobalt(II) paraSHIFT Agents for Measuring Temperature by Magnetic Resonance Spectroscopy. Inorg Chem 2016; 55:700-16. [PMID: 26716610 PMCID: PMC5555598 DOI: 10.1021/acs.inorgchem.5b02144] [Citation(s) in RCA: 54] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
Paramagnetic Fe(II) and Co(II) complexes are utilized as the first transition metal examples of (1)H NMR shift agents (paraSHIFT) for thermometry applications using Magnetic Resonance Spectroscopy (MRS). The coordinating ligands consist of TACN (1,4,7-triazacyclononane) and CYCLEN (1,4,7,10-tetraazacyclododecane) azamacrocycles appended with 6-methyl-2-picolyl groups, denoted as MPT and TMPC, respectively. (1)H NMR spectra of the MPT- and TMPC-based Fe(II) and Co(II) complexes demonstrate narrow and highly shifted resonances that are dispersed as broadly as 440 ppm. The six-coordinate complex cations, [M(MPT)](2+) and [M(TMPC)](2+), vary from distorted octahedral to distorted trigonal prismatic geometries, respectively, and also demonstrate that 6-methyl-2-picolyl pendents control the rigidity of these complexes. Analyses of the (1)H NMR chemical shifts, integrated intensities, line widths, the distances obtained from X-ray diffraction measurements, and longitudinal relaxation time (T1) values allow for the partial assignment of proton resonances of the [M(MPT)](2+) complexes. Nine and six equivalent methyl protons of [M(MPT)](2+) and [M(TMPC)](2+), respectively, produce 3-fold higher (1)H NMR intensities compared to other paramagnetically shifted proton resonances. Among all four complexes, the methyl proton resonances of [Fe(TMPC)](2+) and [Co(TMPC)](2+) at -49.3 ppm and -113.7 ppm (37 °C) demonstrate the greatest temperature dependent coefficients (CT) of 0.23 ppm/°C and 0.52 ppm/°C, respectively. The methyl groups of these two complexes both produce normalized values of |CT|/fwhm = 0.30 °C(-1), where fwhm is full width at half-maximum (Hz) of proton resonances. The T1 values of the highly shifted methyl protons are in the range of 0.37-2.4 ms, allowing rapid acquisition of spectroscopic data. These complexes are kinetically inert over a wide range of pH values (5.6-8.6), as well as in the presence of serum albumin and biologically relevant cations and anions. The combination of large hyperfine shifts, large temperature sensitivity, increased signal-to-noise ratio, and short T1 values suggests that these complexes, in particular the TMPC-based complexes, show promise as paraSHIFT agents for thermometry.
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Affiliation(s)
- Pavel B. Tsitovich
- Department of Chemistry, University at Buffalo, State University of New York, Buffalo, NY 14260
| | - Jordan M. Cox
- Department of Chemistry, University at Buffalo, State University of New York, Buffalo, NY 14260
| | - Jason B. Benedict
- Department of Chemistry, University at Buffalo, State University of New York, Buffalo, NY 14260
| | - Janet R. Morrow
- Department of Chemistry, University at Buffalo, State University of New York, Buffalo, NY 14260
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Kadel LR, Bullinger JR, Baum RR, Moore CE, Tierney DL, Eichhorn DM. Cyanoscorpionate Ligands: Agostic Interactions in a Series of Metal Complexes Containing the Tris(4‐cyano‐3‐phenylpyrazolyl)borate and Bis(4‐cyano‐3‐phenylpyrazolyl)borate Ligands. Eur J Inorg Chem 2016. [DOI: 10.1002/ejic.201501268] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Affiliation(s)
- Lava R. Kadel
- Department of ChemistryWichita State University67260WichitaKSUSA
| | | | - Robert R. Baum
- Department of Chemistry and BiochemistryMiami University45056SAOxfordOHUSA
| | - Curtis E. Moore
- Department of Chemistry and BiochemistryUniversity of CaliforniaSan DiegoCAUSA
| | - David L. Tierney
- Department of Chemistry and BiochemistryMiami University45056SAOxfordOHUSA
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Li QQ, Kang YF, Ren CY, Yang GP, Liu QLP, Wang YY. Reaction-controlled assemblies and structural diversities of seven Co(ii)/Cu(ii) complexes based on a bipyridine-dicarboxylate N-oxide ligand. CrystEngComm 2015. [DOI: 10.1039/c4ce02008a] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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12
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Gruden-Pavlović M, Stepanović S, Perić M, Güell M, Swart M. A density functional study of the spin state energetics of polypyrazolylborato complexes of first-row transition metals. Phys Chem Chem Phys 2014; 16:14514-22. [DOI: 10.1039/c3cp55488k] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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