Single-molecule magnets display magnetic bistability of molecular origin, which may one day be exploited in magnetic data storage devices. Recently it was realised that increasing the magnetic moment of polynuclear molecules does not automatically lead to a substantial increase in magnetic bistability. Attention has thus increasingly focussed on ions with large magnetic anisotropies, especially lanthanides. In spite of large effective energy barriers towards relaxation of the magnetic moment, this has so far not led to a big increase in magnetic bistability. Here we present a comprehensive study of a mononuclear, tetrahedrally coordinated cobalt(II) single-molecule magnet, which has a very high effective energy barrier and displays pronounced magnetic bistability. The combined experimental-theoretical approach enables an in-depth understanding of the origin of these favourable properties, which are shown to arise from a strong ligand field in combination with axial distortion. Our findings allow formulation of clear design principles for improved materials.

Institut für Chemie und Biochemie Anorganische Chemie Freie Universität Berlin Fabeckstraße 34 36 Berlin D 14195 Germany

Institut für Physikalische Chemie Universität Stuttgart Pfaffenwaldring 55 Stuttgart D 70569 Germany

Institute of General and Inorganic Chemistry Bulgarian Academy of Sciences Sofia 1113 Bulgaria

Institute of Physics Charles University Prague Prague CZ 12116 Czech Republic

Laboratoire national des champs magnétiques intenses CNRS UJF UPS INS Grenoble F 38042 France

Max Planck Institute for Chemical Energy Conversion Stiftstraße 34 36 Mülheim an der Ruhr D 45470 Germany

Zobrazit více v PubMed

Gatteschi D. & Sessoli R. Quantum tunneling of magnetization and related phenomena in molecular materials. Angew. Chem. Int. Ed. 42, 268–297 (2003) . PubMed

Gatteschi D., Sessoli R. & Villain J. Molecular Nanomagnets Oxford Univ. Press (2006) .

Ako A. M. et al.. A ferromagnetically coupled Mn-19 aggregate with a record S=83/2 ground spin state. Angew. Chem. Int. Ed. 45, 4926–4929 (2006) . PubMed

Sessoli R., Gatteschi D., Caneschi A. & Novak M. A. Magnetic bistability in a metal-ion cluster. Nature 365, 141–143 (1993) .

Milios C. J. et al.. A record anisotropy barrier for a single-molecule magnet. J. Am. Chem. Soc. 129, 2754–2755 (2007) . PubMed

Bencini A. & Gatteschi D. EPR of Exchange Coupled Systems Springer-Verlag (1990) .

Waldmann O. A criterion for the anisotropy barrier in single-molecule magnets. Inorg. Chem. 46, 10035–10037 (2007) . PubMed

Sessoli R. Molecular nanomagnetism in Florence: advancements and perspectives. Inorg. Chim. Acta 361, 3356–3364 (2008) .

Woodruff D. N., Winpenny R. E. P. & Layfield R. A. Lanthanide single-molecule magnets. Chem. Rev. 113, 5110–5148 (2013) . PubMed

Blagg R. J. et al.. Magnetic relaxation pathways in lanthanide single-molecule magnets. Nat. Chem. 5, 673–678 (2013) . PubMed

Demir S., Jeon I.-R., Long J. R. & Harris T. D. Radical ligand-containing single-molecule magnets. Coord. Chem. Rev. 289–290, 149–176 (2015) .

Rinehart J. D., Fang M., Evans W. J. & Long J. R. Strong exchange and magnetic blocking in N23−-radical-bridged lanthanide complexes. Nat. Chem. 3, 538–542 (2011) . PubMed

Demir S., Zadrozny J. M., Nippe M. & Long J. R. Exchange coupling and magnetic blocking in bipyrimidyl radical-bridged dilanthanide complexes. J. Am. Chem. Soc. 134, 18546–18549 (2012) . PubMed

Craig G. A. & Murrie M. 3d single-ion magnets. Chem. Soc. Rev. 44, 2135–2147 (2015) . PubMed

Gómez-Coca S., Aravena D., Morales R. & Ruiz E. Large magnetic anisotropy in mononuclear metal complexes. Coord. Chem. Rev. 289–290, 379–392 (2015) .

Freedman D. E. et al.. Slow magnetic relaxation in a high-spin iron(II) complex. J. Am. Chem. Soc. 132, 1224–1225 (2010) . PubMed

Harman W. H. et al.. Slow magnetic relaxation in a family of trigonal pyramidal iron(II) pyrrolide complexes. J. Am. Chem. Soc. 132, 18115–18126 (2010) . PubMed

Zadrozny J. M. et al.. Magnetic blocking in a linear iron(I) complex. Nat. Chem. 5, 577–581 (2013) . PubMed

Fataftah M. S., Zadrozny J. M., Rogers D. M. & Freedman D. E. A mononuclear transition metal single-molecule magnet in a nuclear spin-free ligand environment. Inorg. Chem. 53, 10716–10721 (2014) . PubMed

Zadrozny J. M., Telser J. & Long J. R. Slow magnetic relaxation in the tetrahedral cobalt(II) complexes Co(EPh)42− (E=O, S, Se). Polyhedron 64, 209–217 (2013) .

Saber M. R. & Dunbar K. R. Ligands effects on the magnetic anisotropy of tetrahedral cobalt complexes. Chem. Commun. 50, 12266–12269 (2014) . PubMed

Šebová M., Jorík V., Moncoľ J., Kožíšek J. & Boča R. Structure and magnetism of Co(II) complexes with bidentate heterocyclic ligand Hsalbim derived from benzimidazole. Polyhedron 30, 1163–1170 (2011) .

Gómez-Coca S. et al.. Origin of slow magnetic relaxation in Kramers ions with non-uniaxial anisotropy. Nat. Commun. 5, 4300 (2014) . PubMed

Carl E., Demeshko S., Meyer F. & Stalke D. Triimidosulfonates as acute bite-angle chelates: slow relaxation of the magnetization in zero field and hysteresis loop of a COII complex. Chem. Eur. J. 21, 10109–10115 (2015) . PubMed

Bhattacharya S., Gupta P., Basuli F. & Pierpont C. G. Structural systematics for o-C6H4XY ligands with X,Y= O, NH, and S donor atoms. o-Iminoquinone and o-Iminothioquinone complexes of ruthenium and osmium. Inorg. Chem. 41, 5810–5816 (2002) . PubMed

Bill E. et al.. Molecular and electronic structure of four- and five-coordinate cobalt complexes containing two o-phenylenediamine- or two o-aminophenol-type ligands at various oxidation levels: an experimental, density functional, and correlated ab initio study. Chem. Eur. J. 11, 204–224 (2005) . PubMed

Zadrozny J. M. & Long J. R. Slow magnetic relaxation at zero field in the tetrahedral complex Co(SPh)42−. J. Am. Chem. Soc. 133, 20732–20734 (2011) . PubMed

Buchholz A., Eseola A. O. & Plass W. Slow magnetic relaxation in mononuclear tetrahedral cobalt(II) complexes with 2-(1H-imidazol-2-yl)phenol based ligands. C. R. Chim. 15, 929–936 (2012) .

Novikov V. V. et al.. A trigonal prismatic mononuclear cobalt(II) complex showing single-molecule magnet behavior. J. Am. Chem. Soc. 137, 9792–9795 (2015) . PubMed

Abragam A. & Bleany B. Electron Paramagnetic Resonance of Transition Ions Dover Publications, Inc. (1986) .

Liddle S. T. & van Slageren J. Improving f element single molecule magnets. Chem. Soc. Rev. 44, 6655–6669 (2015) . PubMed

Zhu Y.-Y. et al.. A family of CoIICoIII3 single-ion magnets with zero-field slow magnetic relaxation: fine tuning of energy barrier by remote substituent and counter cation. Inorg. Chem. 54, 5475–5486 (2015) . PubMed

Zhu Y.-Y. et al.. Zero-field slow magnetic relaxation from single Co(II) ion: a transition metal single-molecule magnet with high anisotropy barrier. Chem. Sci. 4, 1802–1806 (2013) .

Jiang S.-D., Wang B.-W., Sun H.-L., Wang Z.-M. & Gao S. An organometallic single-ion magnet. J. Am. Chem. Soc. 133, 4730–4733 (2011) . PubMed

Ungur L., Le Roy J. J., Korobkov I., Murugesu M. & Chibotaru L. F. Fine-tuning the local symmetry to attain record blocking temperature and magnetic remanence in a single-ion magnet. Angew. Chem. Int. Ed. 53, 4413–4417 (2014) . PubMed

Pedersen K. S. et al.. Design of single-molecule magnets: insufficiency of the anisotropy barrier as the sole criterion. Inorg. Chem. 54, 7600–7606 (2015) . PubMed

Boulon M. E. et al.. Magnetic anisotropy and spin-parity effect along the series of lanthanide complexes with DOTA. Angew. Chem. Int. Ed. 52, 350–354 (2013) . PubMed

Zadrozny J. M. et al.. Slow magnetization dynamics in a series of two-coordinate iron(II) complexes. Chem. Sci. 4, 125–138 (2013) .

Herchel R., Váhovská L., Potočňák I. & Trávníček Z. Slow magnetic relaxation in octahedral cobalt(II) Field-induced single-ion magnet with positive axial and large rhombic anisotropy. Inorg. Chem. 53, 5896–5898 (2014) . PubMed

Eaton S. S. & Eaton G. R. Relaxation times of organic radicals and transition metal ions. Biol. Magn. Reson. 19, 29–154 (2000) .

Shrivastava K. N. Theory of spin–lattice relaxation. Phys. Stat. Solidi B 117, 437–458 (1983) .

Ungur L., Thewissen M., Costes J. P., Wernsdorfer W. & Chibotaru L. F. Interplay of strongly anisotropic metal ions in magnetic blocking of complexes. Inorg. Chem. 52, 6328–6337 (2013) . PubMed

van Slageren J., Piligkos S. & Neese F. Magnetic circular dichroism spectroscopy on the Cr8 antiferromagnetic ring. Dalton Trans. 39, 4999–5004 (2010) . PubMed

Lever A. B. P. Inorganic Electronic Spectroscopy Elsevier (1984) .

Neese F. & Solomon E. I. MCD C-term signs, saturation behavior, and determination of band polarizations in randomly oriented systems with spin S ⩾1/2. Applications to S=1/2 and S=5/2. Inorg. Chem. 38, 1847–1865 (1999) . PubMed

Ruamps R. et al.. Ising-type magnetic anisotropy and single molecule magnet behaviour in mononuclear trigonal bipyramidal Co(II) complexes. Chem. Sci. 5, 3418–3424 (2014) .

Guo Y. N. et al.. Strong axiality and ising exchange interaction suppress zero-field tunneling of magnetization of an asymmetric Dy2 single-molecule magnet. J. Am. Chem. Soc. 133, 11948–11951 (2011) . PubMed

Boča R. Zero-field splitting in metal complexes. Coord. Chem. Rev. 248, 757–815 (2004) .

Sheldrick, G.M. SHELX-97, Program for Crystal Structure Refinement (Univ. Göttingen, 1997) .

Stoll S. & Schweiger A. EasySpin, a comprehensive software package for spectral simulation and analysis in EPR. J. Magn. Reson. 178, 42–55 (2006) . PubMed

Adamsky, H. AOMX: A FORTRAN Program for the Calculation of dn terms within the Angular Overlap Model with Interelectronic Repulsion and Spin-Orbit Coupling (Institute of Theoretical Chemistry, Heinrich-Heine-Univ., 1995) .

Neese F. The ORCA program system. Wiley Interdiscip. Rev. Comp. Mol. Sci. 2, 73–78 (2012) .

Neese, F., et al.., ORCA: An ab Initio, DFT, and Semiempirical SCF-MO Package, version 3.0 (MPI fur Chemische Energiekonversion, Mulheim an der Ruhr, 2012) .

Schweinfurth D. et al.. The ligand field of the azido ligand: insights into bonding parameters and magnetic anisotropy in a Co(II)–Azido complex. J. Am. Chem. Soc. 137, 1993–2005 (2015) . PubMed

Atanasov M., Ganyushin D., Sivalingam K. & Neese F. Molecular Electronic Structures of Transition Metal Complexes II Vol 143 (eds Mingos D. M. P., Day P., Dahl J. P. 149-220, Springer (2012) .

Atanasov M., Zadrozny J. M., Long J. R. & Neese F. A theoretical analysis of chemical bonding, vibronic coupling, and magnetic anisotropy in linear iron(II) complexes with single-molecule magnet behavior. Chem. Sci. 4, 139–156 (2013) .

Probing spin-electric transitions in a molecular exchange qubit

Tetracoordinate Co(II) complexes with semi-coordination as stable single-ion magnets for deposition on graphene

Co(II) single-ion magnets: synthesis, structure, and magnetic properties

Trigonally Distorted Hexacoordinate Co(II) Single-Ion Magnets

Determination of the electronic structure of a dinuclear dysprosium single molecule magnet without symmetry idealization

Magnetic Anisotropy and Field-induced Slow Relaxation of Magnetization in Tetracoordinate CoII Compound [Co(CH₃-im)₂Cl₂]