1
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Xu Y, Chen J, Aydt AP, Zhang L, Sergeyev I, Keeler EG, Choi B, He S, Reichman DR, Friesner RA, Nuckolls C, Steigerwald ML, Roy X, McDermott AE. Electron and Spin Delocalization in [Co 6 Se 8 (PEt 3 ) 6 ] 0/+1 Superatoms. Chemphyschem 2024; 25:e202300064. [PMID: 38057144 DOI: 10.1002/cphc.202300064] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2023] [Revised: 11/01/2023] [Indexed: 12/08/2023]
Abstract
Molecular clusters can function as nanoscale atoms/superatoms, assembling into superatomic solids, a new class of solid-state materials with designable properties through modifications on superatoms. To explore possibilities on diversifying building blocks, here we thoroughly studied one representative superatom, Co6 Se8 (PEt3 )6 . We probed its structural, electronic, and magnetic properties and revealed its detailed electronic structure as valence electrons delocalize over inorganic [Co6 Se8 ] core while ligands function as an insulated shell. 59 Co SSNMR measurements on the core and 31 P, 13 C on the ligands show that the neutral Co6 Se8 (PEt3 )6 is diamagnetic and symmetric, with all ligands magnetically equivalent. Quantum computations cross-validate NMR results and reveal degenerate delocalized HOMO orbitals, indicating aromaticity. Ligand substitution keeps the inorganic core nearly intact. After losing one electron, the unpaired electron in [Co6 Se8 (PEt3 )6 ]+1 is delocalized, causing paramagnetism and a delocalized electron spin. Notably, this feature of electron/spin delocalization over a large cluster is attractive for special single-electron devices.
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Affiliation(s)
- Yunyao Xu
- Department of Chemistry, Columbia University New York, New York, 10027, USA
| | - Jia Chen
- Department of Chemistry, Columbia University New York, New York, 10027, USA
| | - Alexander P Aydt
- Department of Chemistry, Columbia University New York, New York, 10027, USA
| | - Lichirui Zhang
- Department of Chemistry, Columbia University New York, New York, 10027, USA
| | - Ivan Sergeyev
- Department of Chemistry, Columbia University New York, New York, 10027, USA
| | - Eric G Keeler
- Department of Chemistry, Columbia University New York, New York, 10027, USA
| | - Bonnie Choi
- Department of Chemistry, Columbia University New York, New York, 10027, USA
| | - Shoushou He
- Department of Chemistry, Columbia University New York, New York, 10027, USA
| | - David R Reichman
- Department of Chemistry, Columbia University New York, New York, 10027, USA
| | - Richard A Friesner
- Department of Chemistry, Columbia University New York, New York, 10027, USA
| | - Colin Nuckolls
- Department of Chemistry, Columbia University New York, New York, 10027, USA
| | | | - Xavier Roy
- Department of Chemistry, Columbia University New York, New York, 10027, USA
| | - Ann E McDermott
- Department of Chemistry, Columbia University New York, New York, 10027, USA
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2
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Kimball JJ, Altenhof AR, Jaroszewicz MJ, Schurko RW. Broadband Cross-Polarization to Half-Integer Quadrupolar Nuclei: Wideline Static NMR Spectroscopy. J Phys Chem A 2023; 127:9621-9634. [PMID: 37922436 DOI: 10.1021/acs.jpca.3c05447] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2023]
Abstract
Cross-polarization (CP) is a technique commonly used for the signal enhancement of NMR spectra; however, applications to quadrupolar nuclei have heretofore been limited due to a number of problems, including poor spin-locking efficiency, inconvenient relaxation times, and reduced CP efficiencies over broad spectral bandwidths─this is unfortunate, since they constitute 73% of NMR-active nuclei in the periodic table. The Broadband Adiabatic Inversion CP (BRAIN-CP) pulse sequence has proven useful for the signal enhancement of wideline and ultra-wideline (i.e., 250 kHz to several MHz in breadth) powder patterns arising from stationary samples; however, a comprehensive investigation of its application to half-integer quadrupolar nuclei (HIQN) is currently lacking. Herein, we present theoretical and experimental considerations for applying BRAIN-CP to acquire central-transition (CT, +1/2 ↔ -1/2) powder patterns of HIQN. Consideration is given to parameters crucial to the success of the experiment, such as the Hartmann-Hahn (HH) matching conditions and the phase modulation of the contact pulse. Modifications to the BRAIN-CP sequence such as flip-back (FB) pulses and ramped contact pulses applied to the 1H spins are used for the reduction of experimental times and increased CP bandwidth capabilities, respectively. Spectra for a series of quadrupolar nuclei with broad CT powder patterns, including 35Cl (S = 3/2), 55Mn (S = 5/2), 59Co (S = 7/2), and 93Nb (S = 9/2), are acquired via direct excitation (CPMG and WCPMG) and indirect excitation (CP/CPMG and BRAIN-CP) methods. We demonstrate that proper implementation of the sequence can enable 1H-S broadband CP over a bandwidth of 1 MHz, which to the best of our knowledge is the largest CP bandwidth reported to date. Finally, we establish the basic principles necessary for simplified optimization and execution of the BRAIN-CP pulse sequence for a wide range of HIQNs.
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Affiliation(s)
- James J Kimball
- Department of Chemistry & Biochemistry, Florida State University, Tallahassee, Florida 32306, United States
- National High Magnetic Field Laboratory, Tallahassee, Florida 32310, United States
| | - Adam R Altenhof
- Department of Chemistry & Biochemistry, Florida State University, Tallahassee, Florida 32306, United States
- National High Magnetic Field Laboratory, Tallahassee, Florida 32310, United States
| | - Michael J Jaroszewicz
- Department of Chemical & Biological Physics, Weizmann Institute of Science, Rehovot 7610001, Israel
| | - Robert W Schurko
- Department of Chemistry & Biochemistry, Florida State University, Tallahassee, Florida 32306, United States
- National High Magnetic Field Laboratory, Tallahassee, Florida 32310, United States
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3
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Borah BP, Majumder S, Nath PP, Choudhury AK, Bhuyan J. Pyrazine-bridged cobalt porphyrin: characterization, unique crystal structure and computational studies. J Mol Struct 2022. [DOI: 10.1016/j.molstruc.2022.134557] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
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4
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De S, Flambard A, Xu B, Chamoreau L, Gontard G, Lisnard L, Li Y, Boillot M, Lescouëzec R. Molecular Magnetic Materials Based on {Co
III
(Tp*)(CN)
3
}
−
Cyanidometallate: Combined Magnetic, Structural and
59
Co NMR Study. Chemistry 2022; 28:e202200783. [PMID: 35716039 PMCID: PMC9543823 DOI: 10.1002/chem.202200783] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2022] [Indexed: 11/09/2022]
Abstract
The cyanidocobaltate of formula fac‐PPh4[CoIII(Me2Tp)(CN)3] ⋅ CH3CN (1) has been used as a metalloligand to prepare polynuclear magnetic complexes (Me2Tp=hydrotris(3,5‐dimethylpyrazol‐1‐yl)borate). The association of 1 with in situ prepared [FeII(bik)2(MeCN)2](OTf)2 (bik=bis(1‐methylimidazol‐2‐yl)ketone) leads to a molecular square of formula {[CoIII{(Me2Tp)}(CN)3]2[FeII(bik)2]2}(OTf)2 ⋅ 4MeCN ⋅ 2H2O (2), whereas the self‐assembly of 1 with preformed cluster [CoII2(OH2)(piv)4(Hpiv)4] in MeCN leads to the two‐dimensional network of formula {[CoII2(piv)3]2[CoIII(Me2Tp)(CN)3]2 ⋅ 2CH3CN}∞ (3). These compounds were structurally characterized via single crystal X‐ray analysis and their spectroscopic (FTIR, UV‐Vis and 59Co NMR) properties and magnetic behaviours were also investigated. Bulk magnetic susceptibility measurements reveal that 1 is diamagnetic and 3 is paramagnetic throughout the explored temperature range, whereas 2 exhibits sharp spin transition centered at ca. 292 K. Compound 2 also exhibits photomagnetic effects at low temperature, selective light irradiations allowing to promote reversibly and repeatedly low‐spin⇔high‐spin conversion. Besides, the diamagnetic nature of the Co(III) building block allows us studying these compounds by means of 59Co NMR spectroscopy. Herein, a 59Co chemical shift has been used as a magnetic probe to corroborate experimental magnetic data obtained from bulk magnetic susceptibility measurements. An influence of the magnetic state of the neighbouring atoms is observed on the 59Co NMR signals. Moreover, for the very first time, 59Co NMR technique has been successfully introduced to investigate molecular materials with distinct magnetic properties.
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Affiliation(s)
- Siddhartha De
- Institut Parisien de Chimie Moléculaire UMR CNRS 8232 Sorbonne Université, CNRS 75005 Paris France
| | - Alexandrine Flambard
- Institut Parisien de Chimie Moléculaire UMR CNRS 8232 Sorbonne Université, CNRS 75005 Paris France
| | - Buqin Xu
- Institut Parisien de Chimie Moléculaire UMR CNRS 8232 Sorbonne Université, CNRS 75005 Paris France
| | - Lise‐Marie Chamoreau
- Institut Parisien de Chimie Moléculaire UMR CNRS 8232 Sorbonne Université, CNRS 75005 Paris France
| | - Geoffrey Gontard
- Institut Parisien de Chimie Moléculaire UMR CNRS 8232 Sorbonne Université, CNRS 75005 Paris France
| | - Laurent Lisnard
- Institut Parisien de Chimie Moléculaire UMR CNRS 8232 Sorbonne Université, CNRS 75005 Paris France
| | - Yanling Li
- Institut Parisien de Chimie Moléculaire UMR CNRS 8232 Sorbonne Université, CNRS 75005 Paris France
| | - Marie‐Laure Boillot
- Institut Chimie Moléculaire et Matériaux d'Orsay UMR CNRS 8182 Université Paris-Saclay, CNRS 91405 Orsay France
| | - Rodrigue Lescouëzec
- Institut Parisien de Chimie Moléculaire UMR CNRS 8232 Sorbonne Université, CNRS 75005 Paris France
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5
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Altenhof AR, Lindquist AW, Foster LDD, Holmes ST, Schurko RW. On the use of frequency-swept pulses and pulses designed with optimal control theory for the acquisition of ultra-wideline NMR spectra. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2019; 309:106612. [PMID: 31622849 DOI: 10.1016/j.jmr.2019.106612] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/08/2019] [Revised: 09/19/2019] [Accepted: 09/20/2019] [Indexed: 06/10/2023]
Abstract
Frequency-swept (FS) pulses, such as wideband uniform-rate smooth-truncation (WURST) pulses, have found much success for the acquisition of ultra-wideline (UW) solid-state NMR spectra. In this preliminary study, new pulses and pulse sequences are explored in simulation and experimentally for several nuclei exhibiting UWNMR powder patterns under static conditions, including 119Sn (I = 1/2), 195Pt (I = 1/2), 2H (I = 1), and 71Ga (I = 3/2). First, hyperbolic secant (HS) and tanh/tan (THT) pulses are tested and implemented as excitation and refocusing pulses in spin-echo and Carr-Purcell/Meiboom Gill (CPMG)-type sequences, and shown to have comparable performances to analogous WURST pulses. Second, optimal control theory (OCT) is utilized for the design of new Optimal Control Theory Optimized Broadband Excitation and Refocusing (OCTOBER) pulses, using carefully parameterized WURST, THT, and HS pulses as starting points. Some of the new OCTOBER pulses used in spin-echo sequences are capable of efficient broadband excitation and refocusing, in some cases resulting in spectra with increased signal enhancements over those obtained in experiments using conventional FS pulses. Finally, careful consideration of the spin dynamics of several systems, by monitoring of the time evolution of the density matrix via the Liouville-von Neumann equation and analysis of the time-resolved Fourier transforms of the pulses, lends insight into the underlying mechanisms of the FS and OCTOBER pulses. This is crucial for understanding their performance in terms of generating uniformly excited patterns of high signal intensity, and for identifying trends that may offer pathways to generalized parameterization and/or new pulse shapes.
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Affiliation(s)
- Adam R Altenhof
- Department of Chemistry and Biochemistry, Florida State University, Tallahassee, FL 32308, United States
| | - Austin W Lindquist
- Department of Chemistry and Biochemistry, University of Windsor, Windsor, ON N9B 3P4, Canada
| | - Lucas D D Foster
- Department of Chemistry and Biochemistry, University of Windsor, Windsor, ON N9B 3P4, Canada
| | - Sean T Holmes
- Department of Chemistry and Biochemistry, Florida State University, Tallahassee, FL 32308, United States
| | - Robert W Schurko
- Department of Chemistry and Biochemistry, Florida State University, Tallahassee, FL 32308, United States.
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6
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Kohno Y, Yamamoto K, Tsuboyama S, Mori K. Theoretical study of chloro-α,β,γ,δ-tetraphenylporphyrinato cobalt(III) dimer reaction: A reaction path to form π cation radicals. Chem Phys 2019. [DOI: 10.1016/j.chemphys.2019.03.023] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
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7
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Shen J, Terskikh V, Wu G. A Quadrupole-Central-Transition 59
Co NMR Study of Cobalamins in Solution. Chemphyschem 2018; 20:268-275. [DOI: 10.1002/cphc.201800683] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2018] [Indexed: 11/09/2022]
Affiliation(s)
- Jiahui Shen
- Department of Chemistry; Queen's University, 90 Bader Lane, Kingston; Ontario Canada K7L 3N6
| | - Victor Terskikh
- Department of Chemistry; Queen's University, 90 Bader Lane, Kingston; Ontario Canada K7L 3N6
- Department of Chemistry; University of Ottawa, Ottawa; Ontario Canada K1N 6N5
| | - Gang Wu
- Department of Chemistry; Queen's University, 90 Bader Lane, Kingston; Ontario Canada K7L 3N6
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8
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Bakhmutov VI. Strategies for solid-state NMR studies of materials: from diamagnetic to paramagnetic porous solids. Chem Rev 2010; 111:530-62. [PMID: 20843066 DOI: 10.1021/cr100144r] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
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9
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Huang W, Vega AJ, Gullion T, Polenova T. Internuclear (31)P-(51)V distance measurements in polyoxoanionic solids using rotational echo adiabatic passage double resonance NMR spectroscopy. J Am Chem Soc 2007; 129:13027-34. [PMID: 17918932 PMCID: PMC3985602 DOI: 10.1021/ja073170l] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
We report the first results establishing rotational echo adiabatic passage double resonance (REAPDOR) experiments for distance measurements between a spin-1/2 (31P) and spin-7/2 (51V) pair in a series of vanadium-substituted polyoxoanionic solids from the Keggin and Wells-Dawson families. We have quantitatively measured 31P-51V distances in monovanadium substituted K4PVW11O40, 1-K7P2VW17O62, and 4-K7P2VW17O62. Numerical simulations of the experimental data yield very good agreement with the averaged P-W/P-V distances determined from the X-ray diffraction measurements in the same or related compounds. REAPDOR is therefore a very sensitive P-V distance probe anticipated to be especially useful in the absence of long-range order. Our results suggest that REAPDOR spectroscopy could be broadly applicable for interatomic distance measurements in other spin-7/2-spin-1/2 nuclear pairs.
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Affiliation(s)
- Wenlin Huang
- Department of Chemistry and Biochemistry, University of Delaware, Newark, DE 19716
| | - Alexander J. Vega
- Department of Chemistry and Biochemistry, University of Delaware, Newark, DE 19716
| | - Terry Gullion
- Department of Chemistry, West Virginia University, Morgantown, WV 26506
| | - Tatyana Polenova
- Department of Chemistry and Biochemistry, University of Delaware, Newark, DE 19716
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10
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Ooms KJ, Wasylishen RE. Solid-State Ru-99 NMR Spectroscopy: A Useful Tool for Characterizing Prototypal Diamagnetic Ruthenium Compounds. J Am Chem Soc 2004; 126:10972-80. [PMID: 15339183 DOI: 10.1021/ja0400887] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The feasibility of (99)Ru NMR spectroscopy as a tool to characterize solid compounds is demonstrated. Results of the first solid-state (99)Ru NMR investigation of diamagnetic compounds are presented for Ru(NH(3))(6)Cl(2), K(4)Ru(CN)(6). xH(2)O (x = 0, 3), LaKRu(CN)(6), and Ru(3)(CO)(12). The sensitivity of the ruthenium magnetic shielding tensor to subtle changes in the local structure about the ruthenium nucleus is highlighted by comparing the (99)Ru isotropic chemical shift of Ru(NH(3))(6)Cl(2) in aqueous solutions and in the solid state. The narrow isotropic (99)Ru NMR peak observed for solid Ru(NH(3))(6)Cl(2) indicates that this compound is an ideal secondary reference sample for solid-state (99)Ru NMR studies. The isotropic (99)Ru chemical shift, (99)Ru nuclear quadrupolar coupling constant, C(Q), and quadrupolar asymmetry parameter of K(4)Ru(CN)(6). xH(2)O (x = 0, 3) are shown to be sensitive to x. For Ru(3)(CO)(12), the magnetic shielding tensors of each of the three nonequivalent Ru nuclei have spans of 1300-1400 ppm, and the (99)Ru C(Q) values are also similar, 1.36-1.85 MHz, and are surprisingly small given that (99)Ru has a moderate nuclear quadrupole moment. Information about the relative orientation of the Ru magnetic shielding and electric field gradient tensors has been determined for Ru(3)(CO)(12) from experimental (99)Ru NMR spectra as well as quantum chemical calculations.
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Affiliation(s)
- Kristopher J Ooms
- Contribution from the Department of Chemistry, University of Alberta, Edmonton, Alberta T6G 2G2, Canada
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11
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Rovnyak D, Filip C, Itin B, Stern AS, Wagner G, Griffin RG, Hoch JC. Multiple-quantum magic-angle spinning spectroscopy using nonlinear sampling. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2003; 161:43-55. [PMID: 12660110 DOI: 10.1016/s1090-7807(02)00189-1] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
NMR spectroscopy is a relatively insensitive technique and many biomolecular applications operate near the limits of sensitivity and resolution. A particularly challenging example is detection of the quadrupolar nucleus 17O, due to its low natural abundance, large quadrupole couplings, and low gyromagnetic ratio. Yet the chemical shift of 17O spans almost 1000 ppm in organic molecules and it serves as a potentially unique reporter of hydrogen bonding in peptides, nucleic acids, and water, and as a valuable complement to 13C and 15N NMR. Recent developments including the multiple-quantum magic-angle spinning (MQMAS) experiment have enabled the detection of 17O in biological solids, but very long data acquisitions are required to achieve sufficient sensitivity and resolution. Here, we perform nonlinear sampling in the indirect dimension of MQMAS experiments to substantially reduce the total acquisition time and improve sensitivity and resolution. Nonlinear sampling prevents the use of the discrete Fourier transform; instead, we employ maximum entropy (MaxEnt) reconstruction. Nonlinearly sampled MQMAS spectra are shown to provide high resolution and sensitivity in several systems, including lithium sulfate monohydrate (LiSO(4)-H(2)17O) and L-asparagine monohydrate (H(2)17O). The combination of nonlinear sampling and MaxEnt reconstruction promises to make the application of 17O MQMAS practical in a wider range of biological systems.
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Affiliation(s)
- David Rovnyak
- MIT/Harvard Center for Magnetic Resonance, Massachusetts Institute of Technology, 150 Albany Street, Cambridge, MA 02139, USA
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12
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Geller JM, Wosnick JH, Butler IS, Gilson DFR, Morin FG, Bélanger-Gariépy F. X-ray diffraction, Raman spectroscopic, and solid-state NMR studies of the group 14 metal-(tetracarbonyl)cobalt complexes Ph3MCo(CO)4 (M = Si, Sn, Pb). CAN J CHEM 2002. [DOI: 10.1139/v02-110] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Single-crystal X-ray diffraction studies illustrate that the three title compounds are isomorphous, belonging to the triclinic space group P[Formula: see text], with slightly distorted trigonal bipyramidal geometry about cobalt. The solid-state 29Si, 119Sn, and 207Pb cross-polarization magic angle spinning (CP MAS) NMR spectra are presented. The indirect spinspin coupling constant (J), quadrupolardipolar shift (d), direct dipolar coupling constant (D' ), anisotropy in spinspin coupling (ΔJ), and the chemical shift tensor were extracted. A plot of the reduced coupling constant vs. s-electron densities at the nucleus indicates that the Fermi contact term may be dominant for the tin and lead complexes; however, the large ΔJ for all complexes indicate that there are also significant anisotropic terms. Trends in the Raman scattering spectra are also discussed.Key words: 29Si, 119Sn, and 207Pb CP MAS NMR, tetracarbonyl cobalt, spinspin coupling, chemical shift tensor, quadrupole coupling, Fermi contact, cobaltgroup 14.
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13
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Munro OQ, Shabalala SC, Brown NJ. Structural, computational, and (59)Co NMR studies of primary and secondary amine complexes of Co(III) porphyrins. Inorg Chem 2001; 40:3303-17. [PMID: 11421673 DOI: 10.1021/ic000976c] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Four novel low-spin bis(amine) Co(III) porphyrins [Co(TPP)(BzNH(2))(2)](SbF(6)), 1, [Co(TPP)(1-BuNH(2))(2)](SbF(6)), 2, [Co(TPP)(PhCH(2)CH(2)NH(2))(2)](SbF(6)), 3, and [Co(TPP)(1-MePipz)(2)](SbF(6)), 4, have been synthesized and characterized by low-temperature X-ray crystallography, IR, electronic, and NMR ((1)H, (13)C, and (59)Co) spectroscopy. The mean Co-N(p) distance for the four structures is 1.986(1) A. The Co-N(ax) distances for the 1 degrees amine derivatives average to 1.980(5) A; the axial bonds of the 2 degrees amine derivative are significantly longer, averaging 2.040(1) A. The porphyrin core conformation of 4 is significantly nonplanar (mixture of S(4)-ruf and D(2d)-sad distortions) due to a staggered arrangement of the axial ligands over the porphyrin core and meso-phenyl group orientations < 90 degrees. The X-ray structures have been used with the coordinates for [Co(TPP)(Pip)(2)](NO(3)) (Scheidt et al. J. Am. Chem. Soc. 1973, 95, 8289-8294.) to parametrize a molecular mechanics (MM) force field for bis(amine) complexes of Co(III) porphyrins. The calculations show that two types of crystal packing interactions (van der Waals and hydrogen bonding) largely control the crystallographically observed conformations. Gas phase conformational energy surfaces have been computed for these complexes by dihedral angle driving methods and augmented with population distributions calculated by MD simulations at 298 K; the calculations demonstrate that the bis(1 degrees amine) complexes are significantly more flexible than the bis(2 degrees amine) analogues. (59)Co NMR spectra have been acquired for a range of [Co(TPP)(amine)(2)]Cl derivatives as a function of temperature. The (59)Co chemical shifts increase linearly with increasing temperature due to population of thermally excited vibrational levels of the (1)A(1) ground state. Activation energies for molecular reorientation (tumbling) have been determined from an analysis of the (59)Co NMR line widths as a function of 1/T; lower barriers exist for the conformationally rigid 2 degrees amine derivatives (2.6-3.8 kJ mol(-1)). The (59)Co chemical shifts vary linearly with the DFT-calculated radial expectation values <r(-3)>(3d) for the Co(III) ion. The correlation leads to the following order for the sigma-donor strengths of the axial ligands: BzNH(2) > or = Cl(-) > 1-BuNH(2) > PhCH(2)CH(2)NH(2) > 1-Bu(2)NH > Et(2)NH. The (59)Co NMR line widths are proportional to the square of the DFT-calculated valence electric field gradient at the Co nucleus. Importantly, this is the first computational rationalization of the (59)Co NMR spectra of Co(III) porphyrins.
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Affiliation(s)
- O Q Munro
- School of Chemical and Physical Sciences, University of Natal, Pietermaritzburg, Private Bag X01, Scottsville, 3209, South Africa.
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14
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Kirby CW, Power WP. Cobalt-59 chemical shift and quadrupolar tensors of simple octahedral cobalt(III) complexes. CAN J CHEM 2001. [DOI: 10.1139/v01-025] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Analysis of the solid-state powder 59Co NMR spectra of ten simple inorganic cobalt(III) complexes at 11.75, and in most cases, 4.7 T have permitted the assignment of specific ligand planes to ranges of values of the observed chemical shift principal components. The relevant chemical shift components were determined from the simulations of the powder line shapes. These simulations also provided the relative orientations of the chemical shift (CS) and electric field gradient (efg) tensors, as well as magnitude and asymmetry of the 59Co quadrupolar coupling. Using symmetry arguments and ab initio calculations, as appropriate or necessary, the orientations of the efg tensors in the molecular frame were deduced. This allowed the determination of the CS tensors in the molecular frame and thus assignment of the ligand planes responsible for the observed values of chemical shifts.Key words: cobalt, chemical shift, quadrupolar coupling, solid state NMR.
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15
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Rovnyak D, Baldus M, Wu G, Hud NV, Feigon J, Griffin RG. Localization of 23Na+ in a DNA Quadruplex by High-Field Solid-State NMR. J Am Chem Soc 2000. [DOI: 10.1021/ja001022o] [Citation(s) in RCA: 55] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- David Rovnyak
- Contribution from the MIT/Harvard Center for Magnetic Resonance, Francis Bitter Magnet Laboratory and Department of Chemistry, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139, Department of Chemistry, Queen's University, Kingston, Ontario K7L 3N6, Canada, and Department of Chemistry and Biochemistry and the Molecular Biology Institute, University of California, Los Angeles, 405 Hilgard Avenue, Los Angeles, California 90095-1569
| | - Marc Baldus
- Contribution from the MIT/Harvard Center for Magnetic Resonance, Francis Bitter Magnet Laboratory and Department of Chemistry, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139, Department of Chemistry, Queen's University, Kingston, Ontario K7L 3N6, Canada, and Department of Chemistry and Biochemistry and the Molecular Biology Institute, University of California, Los Angeles, 405 Hilgard Avenue, Los Angeles, California 90095-1569
| | - Gang Wu
- Contribution from the MIT/Harvard Center for Magnetic Resonance, Francis Bitter Magnet Laboratory and Department of Chemistry, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139, Department of Chemistry, Queen's University, Kingston, Ontario K7L 3N6, Canada, and Department of Chemistry and Biochemistry and the Molecular Biology Institute, University of California, Los Angeles, 405 Hilgard Avenue, Los Angeles, California 90095-1569
| | - Nicholas V. Hud
- Contribution from the MIT/Harvard Center for Magnetic Resonance, Francis Bitter Magnet Laboratory and Department of Chemistry, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139, Department of Chemistry, Queen's University, Kingston, Ontario K7L 3N6, Canada, and Department of Chemistry and Biochemistry and the Molecular Biology Institute, University of California, Los Angeles, 405 Hilgard Avenue, Los Angeles, California 90095-1569
| | - Juli Feigon
- Contribution from the MIT/Harvard Center for Magnetic Resonance, Francis Bitter Magnet Laboratory and Department of Chemistry, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139, Department of Chemistry, Queen's University, Kingston, Ontario K7L 3N6, Canada, and Department of Chemistry and Biochemistry and the Molecular Biology Institute, University of California, Los Angeles, 405 Hilgard Avenue, Los Angeles, California 90095-1569
| | - Robert G. Griffin
- Contribution from the MIT/Harvard Center for Magnetic Resonance, Francis Bitter Magnet Laboratory and Department of Chemistry, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139, Department of Chemistry, Queen's University, Kingston, Ontario K7L 3N6, Canada, and Department of Chemistry and Biochemistry and the Molecular Biology Institute, University of California, Los Angeles, 405 Hilgard Avenue, Los Angeles, California 90095-1569
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Xu XP, Au-Yeung SCF. A DFT and 59Co Solid-State NMR Study of the Chemical Shielding Property and Electronic Interaction in the Metalloporphyrin System. J Am Chem Soc 2000. [DOI: 10.1021/ja9911723] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Xiao-Ping Xu
- Contribution from the Department of Chemistry, The Chinese University of Hong Kong, Shatin, New Territories, Hong Kong
| | - Steve C. F. Au-Yeung
- Contribution from the Department of Chemistry, The Chinese University of Hong Kong, Shatin, New Territories, Hong Kong
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17
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Medek A, Frydman L. A Multinuclear Solid-State NMR Analysis of Vitamin B12 in Its Different Polymorphic Forms. J Am Chem Soc 2000. [DOI: 10.1021/ja992939u] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Ales Medek
- Contribution from the Department of Chemistry (M/C 111), University of Illinois at Chicago, 845 West Taylor Street, Chicago, Illinois 60607-7061
| | - Lucio Frydman
- Contribution from the Department of Chemistry (M/C 111), University of Illinois at Chicago, 845 West Taylor Street, Chicago, Illinois 60607-7061
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18
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Medek A, Frydman V, Frydman L. Central Transition Nuclear Magnetic Resonance in the Presence of Large Quadrupole Couplings: Cobalt-59 Nuclear Magnetic Resonance of Cobaltophthalocyanines. J Phys Chem A 1999. [DOI: 10.1021/jp990410d] [Citation(s) in RCA: 91] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Ales Medek
- Department of Chemistry, M/C 111, University of Illinois at Chicago, 845 West Taylor Street, Chicago, Illinois 60607-7061
| | - Veronica Frydman
- Department of Chemistry, M/C 111, University of Illinois at Chicago, 845 West Taylor Street, Chicago, Illinois 60607-7061
| | - Lucio Frydman
- Department of Chemistry, M/C 111, University of Illinois at Chicago, 845 West Taylor Street, Chicago, Illinois 60607-7061
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19
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Affiliation(s)
- William P. Power
- Contribution from the Guelph-Waterloo Center for Graduate Work in Chemistry, Department of Chemistry, University of Waterloo, Waterloo, Ontario N2L 3G1, Canada
| | - Christopher W. Kirby
- Contribution from the Guelph-Waterloo Center for Graduate Work in Chemistry, Department of Chemistry, University of Waterloo, Waterloo, Ontario N2L 3G1, Canada
| | - Nicholas J. Taylor
- Contribution from the Guelph-Waterloo Center for Graduate Work in Chemistry, Department of Chemistry, University of Waterloo, Waterloo, Ontario N2L 3G1, Canada
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20
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Medek A, Frydman V, Frydman L. Solid and liquid phase 59Co NMR studies of cobalamins and their derivatives. Proc Natl Acad Sci U S A 1997; 94:14237-42. [PMID: 9405596 PMCID: PMC24922 DOI: 10.1073/pnas.94.26.14237] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
We describe the application of 59Co NMR to the study of naturally occurring cobalamins. Targets of these investigations included vitamin B12, the B12 coenzyme, methylcobalamin, and dicyanocobyrinic acid heptamethylester. These measurements were carried out on solutions and powders of different origins, and repeated at a variety of magnetic field strengths. Particularly informative were the solid-state central transition NMR spectra, which when combined with numerical line shape analyses provided a clear description of the cobalt coupling parameters. These parameters showed a high sensitivity to the type of ligands attached to the metal and to the crystallization history of the sample. 59Co NMR determinations also were carried out on synthetic cobaloximes possessing alkyl, cyanide, aquo, and nitrogenated axial groups, substituents that paralleled the coordination of the natural compounds. These analogs displayed coupling anisotropies comparable to those of the cobalamins, as well as systematic up-field shifts that can be rationalized in terms of their stronger binding affinity to the cobalt atom. Cobaloximes also displayed a higher regularity in the relative orientations of their quadrupole and shielding coupling tensors, reflecting a higher symmetry in their in-plane coordination. For the cobalamines, poor correlations were observed between the values measured for the quadrupole couplings in the solid and the line widths observed in the corresponding solution 59Co NMR resonances.
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Affiliation(s)
- A Medek
- Department of Chemistry, University of Illinois, Chicago, IL 60607, USA
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