Nuclear magnetic resonance (NMR) spectroscopy of paramagnetic molecules provides detailed information about their molecular and electron-spin structure. The paramagnetic NMR spectrum is a very rich source of information about the hyperfine interaction between the atomic nuclei and the unpaired electron density. The Fermi-contact contribution to ligand hyperfine NMR shifts is particularly informative about the nature of the metal-ligand bonding and the structural arrangements of the ligands coordinated to the metal center. In this account, we provide a detailed experimental and theoretical NMR study of compounds of Cr(III) and Cu(II) coordinated with substituted acetylacetonate (acac) ligands in the solid state. For the first time, we report the experimental observation of extremely paramagnetically deshielded 13C NMR resonances for these compounds in the range of 900-1200 ppm. We demonstrate an excellent agreement between the experimental NMR shifts and those calculated using relativistic density-functional theory. Crystal packing is shown to significantly influence the NMR shifts in the solid state, as demonstrated by theoretical calculations of various supramolecular clusters. The resonances are assigned to individual atoms in octahedral Cr(acac)3 and square-planar Cu(acac)2 compounds and interpreted by different electron configurations and magnetizations at the central metal atoms resulting in different spin delocalizations and polarizations of the ligand atoms. Further, effects of substituents on the 13C NMR resonance of the ipso carbon atom reaching almost 700 ppm for Cr(acac)3 compounds are interpreted based on the analysis of Fermi-contact hyperfine contributions.

CEITEC Central European Institute of Technology Masaryk University Kamenice 5 CZ 625 00 Brno Czechia

Department of Chemistry and Biochemistry Faculty of AgriSciences Mendel University Zemědělská 1 CZ 613 00 Brno Czechia

Department of Chemistry Faculty of Science Masaryk University Kamenice 5 CZ 625 00 Brno Czechia

Institute of Inorganic Chemistry Slovak Academy of Sciences Dúbravská cesta 9 SK 84536 Bratislava Slovakia

National Center for Biomolecular Research Faculty of Science Masaryk University Kamenice 5 CZ 625 00 Brno Czechia

National Institute of Chemical Physics and Biophysics Akadeemia tee 23 EE 12618 Tallinn Estonia

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La Mar G. N.; DeW Horrocks W.; Holm R. H.. NMR of Paramagnetic Molecules; Academic Press: New York, 1973.

Bertini I.; Luchinat C.; Parigi G.; Ravera E.. NMR of Paramagnetic Molecules: Applications to Metallobiomolecules and Models; Elsevier: Amsterdam, 2016.

Kaupp M.; Köhler F. H. Combining NMR Spectroscopy and Quantum Chemistry as Tools to Quantify Spin Density Distributions in Molecular Magnetic Compounds. Coord. Chem. Rev. 2009, 253, 2376–2386. 10.1016/j.ccr.2008.12.020. DOI

Pell A. J.; Pintacuda G.; Grey C. P. Paramagnetic NMR in Solution and the Solid State. Prog. Nucl. Magn. Reson. Spectrosc. 2019, 111, 1–271. 10.1016/j.pnmrs.2018.05.001. PubMed DOI

Novotný J.; Sojka M.; Komorovsky S.; Nečas M.; Marek R. Interpreting the Paramagnetic NMR Spectra of Potential Ru(III) Metallodrugs: Synergy between Experiment and Relativistic DFT Calculations. J. Am. Chem. Soc. 2016, 138, 8432–8445. 10.1021/jacs.6b02749. PubMed DOI

Moon S.; Patchkovskii S.. First-Principles Calculations of Paramagnetic NMR Shifts. In Calculation of NMR and EPR Parameters. In Theory and Applications; Kaupp M.; Bühl M.; Malkin V. G., Eds.; Wiley-VCH: Weinheim, 2004; pp 325–328.

Komorovsky S.; Repisky M.; Ruud K.; Malkina O. L.; Malkin V. G. Four-Component Relativistic Density Functional Theory Calculations of NMR Shielding Tensors for Paramagnetic Systems. J. Phys. Chem. A 2013, 117, 14209–14219. 10.1021/jp408389h. PubMed DOI

Van den Heuvel W.; Soncini A. NMR Chemical Shift in an Electronic State with Arbitrary Degeneracy. Phys. Rev. Lett. 2012, 109, 07300110.1103/PhysRevLett.109.073001. PubMed DOI

Van den Heuvel W.; Soncini A. NMR Chemical Shift as Analytical Derivative of the Helmholtz Free Energy. J. Chem. Phys. 2013, 138, 05411310.1063/1.4789398. PubMed DOI

Hrobárik P.; Reviakine R.; Arbuznikov A. V.; Malkina O. L.; Malkin V. G.; Köhler F. H.; Kaupp M. Density Functional Calculations of NMR Shielding Tensors for Paramagnetic Systems with Arbitrary Spin Multiplicity: Validation on 3d Metallocenes. J. Chem. Phys. 2007, 126, 02410710.1063/1.2423003. PubMed DOI

Gendron F.; Sharkas K.; Autschbach J. Calculating NMR Chemical Shifts for Paramagnetic Metal Complexes from First-Principles. J. Phys. Chem. Lett. 2015, 6, 2183–2188. 10.1021/acs.jpclett.5b00932. PubMed DOI

Rouf S. A.; Mareš J.; Vaara J. 1H Chemical Shifts in Paramagnetic Co(II) Pyrazolylborate Complexes: A First-Principles Study. J. Chem. Theory Comput. 2015, 11, 1683–1691. 10.1021/acs.jctc.5b00193. PubMed DOI

Vaara J.; Rouf S. A.; Mareš J. Magnetic Couplings in the Chemical Shift of Paramagnetic NMR. J. Chem. Theory Comput. 2015, 11, 4840–4849. 10.1021/acs.jctc.5b00656. PubMed DOI

Vaara J.Chemical Shift in Paramagnetic Systems. In High Resolution NMR Spectroscopy: Understanding Molecules and Their Electronic Structures. In Science and Technology of Atomic Molecular Condensed Matter and Biological Systems; Contreras R. H.; Contreras R. H., Eds.; Elsevier, 2013; pp 41–67.

Autschbach J.NMR Calculations for Paramagnetic Molecules and Metal Complexes. In Annual Reports in Computational Chemistry; Dixon D. A., Ed.; Elsevier, 2015; Chapter 1, Vol. 11, pp 3–36.

Novotný J.; Přichystal D.; Sojka M.; Komorovsky S.; Nečas M.; Marek R. Hyperfine Effects in Ligand NMR: Paramagnetic Ru(III) Complexes with 3-Substituted Pyridines. Inorg. Chem. 2018, 57, 641–652. 10.1021/acs.inorgchem.7b02440. PubMed DOI

Chyba J.; Novák M.; Munzarová P.; Novotný J.; Marek R. Through-Space Paramagnetic NMR Effects in Host–Guest Complexes: Potential Ruthenium(III) Metallodrugs with Macrocyclic Carriers. Inorg. Chem. 2018, 57, 8735–8747. 10.1021/acs.inorgchem.7b03233. PubMed DOI

Bora P. L.; Novotný J.; Ruud K.; Komorovsky S.; Marek R. Electron-Spin Structure and Metal–Ligand Bonding in Open-Shell Systems from Relativistic EPR and NMR: A Case Study of Square-Planar Iridium Catalysts. J. Chem. Theory Comput. 2019, 15, 201–214. 10.1021/acs.jctc.8b00914. PubMed DOI

Mabbs F. E.; Collison D.. Electron Paramagnetic Resonance of d Transition Metal Compounds; Elsevier Science: Amsterdam, 1992; Vol. 16, pp 338–441.

Abragam A.; Bleaney B.. Electron Paramagnetic Resonance of Transition Ions; Oxford Classic Texts in the Physical Sciences; Oxford University Press: Oxford, New York, 2012.

Andersen A. B. A.; Pyykkönen A.; Jensen H. J. A.; McKee V.; Vaara J.; Nielsen U. G. Remarkable Reversal of 13C-NMR Assignment in D1, D2 Compared to D8, D9 Acetylacetonate Complexes: Analysis and Explanation Based on Solid-State MAS NMR and Computations. Phys. Chem. Chem. Phys. 2020, 22, 8048–8059. 10.1039/D0CP00980F. PubMed DOI

Pritchard B.; Autschbach J. Theoretical Investigation of Paramagnetic NMR Shifts in Transition Metal Acetylacetonato Complexes: Analysis of Signs, Magnitudes, and the Role of the Covalency of Ligand–Metal Bonding. Inorg. Chem. 2012, 51, 8340–8351. 10.1021/ic300868v. PubMed DOI

Rastrelli F.; Bagno A. Predicting the NMR Spectra of Paramagnetic Molecules by DFT: Application to Organic Free Radicals and Transition-Metal Complexes. Chem. - Eur. J. 2009, 15, 7990–8004. 10.1002/chem.200802443. PubMed DOI

Jeremias L.; Novotný J.; Repisky M.; Komorovsky S.; Marek R. Interplay of Through-Bond Hyperfine and Substituent Effects on the NMR Chemical Shifts in Ru(III) Complexes. Inorg. Chem. 2018, 57, 8748–8759. 10.1021/acs.inorgchem.8b00073. PubMed DOI

Lennartson A.; Christensen L. U.; McKenzie C. J.; Nielsen U. G. Solid State 13C and 2H NMR Investigations of Paramagnetic [Ni(II)(Acac)2L2] Complexes. Inorg. Chem. 2014, 53, 399–408. 10.1021/ic402354r. PubMed DOI

Rouf S. A.; Jakobsen V. B.; Mareš J.; Jensen N. D.; McKenzie C. J.; Vaara J.; Nielsen U. G. Assignment of Solid-State 13C and 1H NMR Spectra of Paramagnetic Ni(II) Acetylacetonate Complexes Aided by First-Principles Computations. Solid State Nucl. Magn. Reson. 2017, 87, 29–37. 10.1016/j.ssnmr.2017.07.003. PubMed DOI

Kaupp M.; Bühl M.; Malkin V. G.. Calculation of NMR and EPR Parameters: Theory and Applications; Wiley-VCH: Weinheim, 2004.

Singer L. S. Paramagnetic Resonance Absorption in Some Cr +3 Complexes. J. Chem. Phys. 1955, 23, 379–388. 10.1063/1.1741973. DOI

Sugisaki K.; Toyota K.; Sato K.; Shiomi D.; Takui T. Behaviour of DFT-Based Approaches to the Spin–Orbit Term of Zero-Field Splitting Tensors: A Case Study of Metallocomplexes, M III (Acac) 3 (M = V, Cr, Mn, Fe and Mo). Phys. Chem. Chem. Phys. 2017, 19, 30128–30138. 10.1039/C7CP05533A. PubMed DOI

Repisky M.; Komorovsky S.; Kadek M.; Konecny L.; Ekström U.; Malkin E.; Kaupp M.; Ruud K.; Malkina O. L.; Malkin V. G. ReSpect: Relativistic Spectroscopy DFT Program Package. J. Chem. Phys. 2020, 152, 18410110.1063/5.0005094. PubMed DOI

Dolomanov O. V.; Bourhis L. J.; Gildea R. J.; Howard J. aK.; Puschmann H. OLEX2: A Complete Structure Solution, Refinement and Analysis Program. J. Appl. Crystallogr. 2009, 42, 339–341. 10.1107/S0021889808042726. DOI

Maliňáková K.; Novosadová L.; Lahtinen M.; Kolehmainen E.; Brus J.; Marek R. 13C Chemical Shift Tensors in Hypoxanthine and 6-Mercaptopurine: Effects of Substitution, Tautomerism, and Intermolecular Interactions. J. Phys. Chem. A 2010, 114, 1985–1995. 10.1021/jp9100619. PubMed DOI

Babinský M.; Bouzková K.; Pipíška M.; Novosadová L.; Marek R. Interpretation of Crystal Effects on NMR Chemical Shift Tensors: Electron and Shielding Deformation Densities. J. Phys. Chem. A 2013, 117, 497–503. 10.1021/jp310967b. PubMed DOI

Bouzková K.; Babinský M.; Novosadová L.; Marek R. Intermolecular Interactions in Crystalline Theobromine as Reflected in Electron Deformation Density and 13 C NMR Chemical Shift Tensors. J. Chem. Theory Comput. 2013, 9, 2629–2638. 10.1021/ct400209b. PubMed DOI

Golchoubian H. Redetermination of Crystal Structure of Bis(2,4-Pentanedionato)Copper(II). Asian J. Chem. 2008, 20, 5834–5838.

Bühl M.; Ashbrook S. E.; Dawson D. M.; Doyle R. A.; Hrobárik P.; Kaupp M.; Smellie I. A. Paramagnetic NMR of Phenolic Oxime Copper Complexes: A Joint Experimental and Density Functional Study. Chem. - Eur. J. 2016, 22, 15328–15339. 10.1002/chem.201602567. PubMed DOI

Mali G.; Mazaj M. Hyperfine Coupling Constants in Cu-Based Crystalline Compounds: Solid-State NMR Spectroscopy and First-Principles Calculations with Isolated-Cluster and Extended Periodic-Lattice Models. J. Phys. Chem. C 2021, 125, 4655–4664. 10.1021/acs.jpcc.0c09651. DOI

Hrobárik P.; Repiský M.; Komorovský S.; Hrobáriková V.; Kaupp M. Assessment of Higher-Order Spin–Orbit Effects on Electronic g-Tensors of D1 Transition-Metal Complexes by Relativistic Two- and Four-Component Methods. Theor. Chem. Acc. 2011, 129, 715–725. 10.1007/s00214-011-0951-7. DOI

Martin B.; Autschbach J. Kohn-Sham Calculations of NMR Shifts for Paramagnetic 3d Metal Complexes: Protocols, Delocalization Error, and the Curious Amide Proton Shifts of a High-Spin Iron(II) Macrocycle Complex. Phys. Chem. Chem. Phys. 2016, 18, 21051–21068. 10.1039/C5CP07667F. PubMed DOI

Adato I.; Eliezer I. Effect of the Solvent on the ESR Parameters of Copper Acetylacetonate. J. Chem. Phys. 1971, 54, 1472–1476. 10.1063/1.1675040. DOI

Symons M. C. R.Chemical and Biochemical Aspects of Electron Spin Resonance Spectroscopy; Van Nostrand Reinhold Inc: New York, US, 1978.

Lintvedt R. L.; Fatta N. M. Nephelauxetic and Spectrochemical Series for 1,3-Diketonates. Ligand Field Spectra of Some Tris(1,3-Diketonato)Chromium(III) Chelates. Inorg. Chem. 1971, 10, 478–481. 10.1021/ic50097a008. DOI

Guan X.; Stark R. E. A General Protocol for Temperature Calibration of MAS NMR Probes at Arbitrary Spinning Speeds. Solid State Nucl. Magn. Reson. 2010, 38, 74–76. 10.1016/j.ssnmr.2010.10.001. PubMed DOI PMC

Adamo C.; Barone V. Toward Reliable Density Functional Methods without Adjustable Parameters: The PBE0 Model. J. Chem. Phys. 1999, 110, 6158–6170. 10.1063/1.478522. DOI

Adamo C.; Scuseria G. E.; Barone V. Accurate Excitation Energies from Time-Dependent Density Functional Theory: Assessing the PBE0 Model. J. Chem. Phys. 1999, 111, 2889–2899. 10.1063/1.479571. DOI

Schäfer A.; Huber C.; Ahlrichs R. Fully Optimized Contracted Gaussian Basis Sets of Triple Zeta Valence Quality for Atoms Li to Kr. J. Chem. Phys. 1994, 100, 5829–5835. 10.1063/1.467146. DOI

TURBOMOLE V7.0 2015; TURBOMOLE GmbH. http://www.turbomole.com, 2007.

Vícha J.; Patzschke M.; Marek R. A Relativistic DFT Methodology for Calculating the Structures and NMR Chemical Shifts of Octahedral Platinum and Iridium Complexes. Phys. Chem. Chem. Phys. 2013, 15, 7740–7754. 10.1039/c3cp44440f. PubMed DOI

Vícha J.; Novotný J.; Straka M.; Repisky M.; Ruud K.; Komorovsky S.; Marek R. Structure, Solvent, and Relativistic Effects on the NMR Chemical Shifts in Square-Planar Transition-Metal Complexes: Assessment of DFT Approaches. Phys. Chem. Chem. Phys. 2015, 17, 24944–24955. 10.1039/C5CP04214C. PubMed DOI

Chrzanowski L. S.; von Lutz M.; Spek A. L. α-Tris(2,4-Pentanedionato-κ 2 O, O ′)Cobalt(III) at 240, 210, 180, 150 and 110 K. Acta Crystallogr., Sect. C: Cryst. Struct. Commun. 2007, 63, m283–m288. 10.1107/S0108270107022950. PubMed DOI

Andrae D.; Häußermann U.; Dolg M.; Stoll H.; Preuß H. Energy-Adjusted Ab Initio Pseudopotentials for the Second and Third Row Transition Elements. Theor. Chim. Acta 1990, 77, 123–141. 10.1007/BF01114537. DOI

Grimme S.; Antony J.; Ehrlich S.; Krieg H. A Consistent and Accurate Ab Initio Parametrization of Density Functional Dispersion Correction (DFT-D) for the 94 Elements H-Pu. J. Chem. Phys. 2010, 132, 15410410.1063/1.3382344. PubMed DOI

Grimme S.; Ehrlich S.; Goerigk L. Effect of the Damping Function in Dispersion Corrected Density Functional Theory. J. Comput. Chem. 2011, 32, 1456–1465. 10.1002/jcc.21759. PubMed DOI

van Lenthe E.; Snijders J. G.; Baerends E. J. The Zero-order Regular Approximation for Relativistic Effects: The Effect of Spin–Orbit Coupling in Closed Shell Molecules. J. Chem. Phys. 1996, 105, 6505–6516. 10.1063/1.472460. DOI

Saue T. Relativistic Hamiltonians for Chemistry: A Primer. ChemPhysChem 2011, 12, 3077–3094. 10.1002/cphc.201100682. PubMed DOI

te Velde G.; Bickelhaupt F. M.; Baerends E. J.; Fonseca Guerra C.; van Gisbergen S. J. A.; Snijders J. G.; Ziegler T. Chemistry with ADF. J. Comput. Chem. 2001, 22, 931–967. 10.1002/jcc.1056. DOI

Guerra C. F.; Snijders J. G.; Velde G.; te Baerends E. J. Towards an Order-N DFT Method. Theor. Chem. Acc. 1998, 99, 391–403. 10.1007/s002140050353. DOI

Baerends E. J.; Ziegler T.; Atkins A. J.; Autschbach J.; Baseggio O.; Bashford D.; Bérces A.; Bickelhaupt F. M.; Bo C.; Boerrigter P. M.; Cavallo L.; Daul C.; Chong D. P.; Chulhai D. V.; Deng L.; Dickson R. M.; Dieterich J. M.; Ellis D. E.; van Faassen M.; Fan L.. ADF2019, SCM, Theoretical Chemistry; Vrije Universiteit: Amsterdam: The Netherlands, 2019.

Güell M.; Luis J. M.; Solà M.; Swart M. Importance of the Basis Set for the Spin-State Energetics of Iron Complexes. J. Phys. Chem. A 2008, 112, 6384–6391. 10.1021/jp803441m. PubMed DOI

Autschbach J.; Patchkovskii S.; Pritchard B. Calculation of Hyperfine Tensors and Paramagnetic NMR Shifts Using the Relativistic Zeroth-Order Regular Approximation and Density Functional Theory. J. Chem. Theory Comput. 2011, 7, 2175–2188. 10.1021/ct200143w. PubMed DOI

Martin B.; Autschbach J. Temperature Dependence of Contact and Dipolar NMR Chemical Shifts in Paramagnetic Molecules. J. Chem. Phys. 2015, 142, 05410810.1063/1.4906318. PubMed DOI

Mulliken R. S. Electronic Population Analysis on LCAO–MO Molecular Wave Functions, I. J. Chem. Phys. 1955, 23, 1833–1840. 10.1063/1.1740588. DOI

Haase P. A. B.; Repisky M.; Komorovsky S.; Bendix J.; Sauer S. P. A. Relativistic DFT Calculations of Hyperfine Coupling Constants in 5d Hexafluorido Complexes: [ReF6]2– and [IrF6]2–. Chem. - Eur. J. 2018, 24, 5124–5133. 10.1002/chem.201704653. PubMed DOI PMC

Paramagnetic Effects in NMR Spectroscopy of Transition-Metal Complexes: Principles and Chemical Concepts

Nature of NMR Shifts in Paramagnetic Octahedral Ru(III) Complexes with Axial Pyridine-Based Ligands