Journal of the American Chemical Society
COMMUNICATION
lowest excited states in 1. Since neither structure contains a
three- or four-fold symmetry axis and the orbital energy levels
in these systems are not degenerate, in-state SOC cannot be
present. Only out-of state SOC can contribute to nonzero ZFS.
The increase of the energies of the two lowest-energy excited
states when going from 1 to 2 should significantly decrease the
out-of-state SOC contribution to the ZFS. Indeed, no ac signal was
observed for 2, even under an applied field, indicating absence of
slow relaxation of the magnetization. This is consistent with
quenched orbital angular momentum and weak out-of-state SOC
in a distorted tetrahedral FeII complex. We can conclude that the
remarkable observation of slow relaxation of the magnetization
of 1 proves that it behaves as a field-induced SMM due to the
large intrinsic magnetic anisotropy arising from out-of-state SOC
in the trigonal planar complex.
The results described herein demonstrate that slow relaxation
of the magnetization in 1 arises from the intrinsic magnetic
anisotropy of the HS FeII ion within a three-coordinate environ-
ment. This gives rise to very low-lying excited states that couple
with the non-degenerate ground state via out-of-state SOC. The
related four-coordinate complex, 2, has a non-degenerate ground
state and excited states with higher energies; thus, it does not
exhibit magnetic anisotropy. We can conclude that out-of-state
spinꢀorbit coupling for systems with low-lying excited states
appear to be an important contributor to the slow magnetic
relaxation of mononuclear complexes. We believe this may provide
new avenues for conceiving polynuclear high-energy-barrier SMMs.
(b) Murugesu, M.; Habrych, M.; Wernsdorfer, W.; Abboud, K. A.;
Christou, G. J. Am. Chem. Soc. 2004, 126, 4766. (c) Larionova, J.; Gross,
M.; Pilkington, M.; Andres, H.; Stoeckli-Evans, H.; Gudel, H.; Decurtins,
S. Angew. Chem., Int. Ed. 2000, 39, 1605.
(4) (a) Long, J.; Habib, F.; Lin, P.-H.; Korobkov, I.; Enright, G.;
Ungur, L.; Wernsdorfer, W.; Chibotaru, L. F.; Murugesu, M. J. Am. Chem.
Soc. 2011, 133, 5319. (b) Ishikawa, N.;Sugita, M.;Ishikawa, T.; Koshihara,
S.; Kaizu, Y. J. Am. Chem. Soc. 2003, 125, 8694. (c) Petit, S.; Pilet, G.;
Luneau, D.; Chibotaru, L. F.; Ungur, L. Dalton Trans. 2007, 4582. (d)
AlDamen, M. A.; Clemente-Juan, J. M.; Coronado, E.; Marti-Gastaldo, C.;
Gaita-Arino, A. J. Am. Chem. Soc. 2008, 130, 8874. (e) Weismann, D.; Sun,
Y.; Lan, Y.; Wolmersh€auser, G.; Powell, A. K.; Sitzman, H. Chem.—Eur. J.
2011, 17, 4700.
(5) (a) Atanasov, M; Ganyushin, D.; Pantazis, D. A.; Sivalingam, K.;
Neese, F. Inorg. Chem. 2011, 50, 7460. (b) Freedman, D. E.; Harman,
W. H.; Harris, T. D.; Long, G. J.; Chang, C. J.; Long, J. R. J. Am. Chem.
Soc. 2010, 132, 1224. (c) Reiff, W. M.; LaPointe, A. M.; Witten, E. H.
J. Am. Chem. Soc. 2004, 126, 10206. (d) Reiff, W. M.; Schulz, C. E.;
Whangbo, M.-H.; Seo, J. I.; Lee, Y. S.; Potratz, G. R.; Spicer, C. W.;
Girolami, G. S. J. Am. Chem. Soc. 2009, 131, 404.
(6) (a) Vela, J.; Smith, J. M.; Lachicotte, R. J.; Holland, P. L. Chem.
Commun. 2002, 2886. (b) Olmstead, M. M.; Power, P. P.; Shoner, S. C.
Inorg. Chem. 1991, 30, 2547. (c) Siemeling, U.; Vorfeld, U.; Neumann,
B.; Stammler, H.-G. Inorg. Chem. 2000, 39, 5159. (d) Chiang, K. P.;
Barrett, P. M.; Ding, F.; Smith, J. M.; Kingsley, S.; Brennessel, W. W.;
Clark, M. M.; Lachicotte, R. J.; Holland, P. L. Inorg. Chem. 2009, 48,
5106. (e) Vela, J.; Stoian, S.; Flaschenriem, C. J.; Munck, E.; Holland,
P. L. J. Am. Chem. Soc. 2004, 126, 4522. (f) Zhang, Y.; Oldfield, E. J. Phys.
Chem. B 2003, 107, 7180. (g) Gregory, E. A.; Lachicotte, R. J.; Holland,
P. L. Organometallics 2005, 24, 1803. (h) Holland, P. L. Acc. Chem. Res.
2008, 41, 905. (i) Fitzsimmons, B. W.; Johnson, C. E. Chem. Phys. Lett.
1974, 24, 422. (j) Cowley, R. E.; DeYonker, N. J.; Eckert, N. A.; Cundari,
T. R.; DeBeer, S.; Bill, E.; Ottenwaelder, X.; Flaschenriem, C.; Holland,
P. L. Inorg. Chem. 2010, 49, 6172. (k) Palii, A. V.; Clemente-Juan, J. M.;
Coronado, E.; Klokishner, S. I.; Ostrovsky, S. M.; Reu, O. S. Inorg. Chem.
2010, 49, 8073.
’ ASSOCIATED CONTENT
S
Supporting Information. Complete experimental and com-
b
putational details (PDF); X-ray crystallographic files (CIF).
This material is available free of charge via the Internet at
(7) Mabbs, F. E.; Machin, D. J. Magnetism and Transition Metal
Complexes; Dover Publications: New York, 2008.
(8) Chirico, R. D.; Carlin, R. L. Inorg. Chem. 1980, 19, 3031.
(9) Davidson, E. R. MAGNET; Indiana University: Bloomington,
IN, 1999.
(10) Perdew, J. P.;Burke, K.;Ernzerhof, M.Phys. Rev. Lett.1997, 78, 1396.
(11) Schafer, A.; Huber, C.; Ahlrichs, R. J. Chem. Phys. 1994, 100,
5829.
’ AUTHOR INFORMATION
Corresponding Author
(12) (a) Becke, A. D. J. Chem. Phys. 1993, 98, 5648. (b) Lee, C.;
Yang, W.; Parr, R. G. Phys. Rev. B 1988, 37, 785.
’ ACKNOWLEDGMENT
(13) Reed, A. E.; Weinstock, R. B.; Weinhold, F. J. Chem. Phys. 1985,
83, 735.
(14) Mayer, I. Int. J. Quantum Chem. 1986, 29, 73.
(15) Gorelsky, S. I.; Basumallick, L.; Vura-Weis, J.; Sarangi, R.;
Hedman, B.; Hodgson, K. O.; Fujisawa, K.; Solomon, E. I. Inorg. Chem.
2005, 44, 4947.
We thank the University of Ottawa (start-up), CCRI, CFI,
FFCR, NSERC (Discovery and RTI grants), ERA, and U.S. DOE
Office of Energy Efficiency and Renewable Energy for their support.
’ REFERENCES
(16) Stratmann, R. E.; Scuseria, G. E.; Frisch, M. J. J. Chem. Phys.
1998, 109, 8218.
(17) Lever, A. B. P. Inorganic Electronic Spectroscopy; Elsevier:
Amsterdam, 1984.
(1) (a) Kahn, O. Molecular Magnetism; VCH-Wiley: New York,
1993. (b) Gatteschi, D.; Sessoli, R.; Villain, J. Molecular Nanomagnets;
Oxford University Press: New York, 2006.
(2) (a) Christou, G.; Gatteschi, D.; Hendrickson, D. N.; Sessoli, R.
MRS Bull. 2000, 25, 66. (b) Thomas, L.; Lionti, L.; Ballou, R.; Gatteschi,
D.; Sessoli, R.; Barbara, B. Nature 1996, 383, 145. (c) Sokol, J. J.; Hee,
A. G.; Long, J. R. J. Am. Chem. Soc. 2002, 124, 7656. (d) Maheswaran, S.;
Chastanet, G.; Teat, S. J.; Mallah, T.; Sessoli, R.; Wernsdorfer, W.;
Winpenny, R. E. P. Angew. Chem., Int. Ed. 2005, 44, 5044. (e) Inglis, R.;
Jones, L. F.; Karotsis, G.; Collins, A.; Parsons, S.; Perleps, S. P.; Wernsdorfer,
W.; Brechin, E. K. Chem. Commun. 2008, 5924. (f) Schelter, E. J.; Karadas,
F.; Avendano, C.; Prosvirin, A. V.; Wernsdorfer, W.; Dunbar, K. R. J. Am.
Chem. Soc. 2007, 129, 8139. (g) Li, D.; Clerac, R.; Parkin, S.; Wang, G.; Yee,
G. T.; Holmes, S. M. Inorg. Chem. 2006, 45, 5251.
(3) (a) Ako, A. M.; Hewitt, I. J.; Mereacre, V.; Clerac, R.; Wernsdorfer,
W.; Anson, C. E.; Powell, A. K. Angew. Chem., Int. Ed. 2006, 45, 4926.
15809
dx.doi.org/10.1021/ja203845x |J. Am. Chem. Soc. 2011, 133, 15806–15809