Análisis transversal de los casos

Magnetic measurements: Magnetic measurements of the samples were performed on a

Quantum-Design-MPMSR-XL-SQUID-Magnetometer in a temperature range from 5 to 295 K. The measurements were carried out at two field strengths (0.02 and 0.05 T) in the settle mode. The data were corrected for the magnetisation of the sample holder, and diamagnetic corrections were made by using estimated values according to

χdia≈ −0.5 Mcomplex × 10−6.

X-Ray crystallography: The intensity data of 1 to 5 were collected on a Nonius KappaCCD

diffractometer by using graphite-monochromated MoKα radiation. Data were corrected for

Lorentz and polarisation effects. The structures were solved by direct methods (SIR-97)[13] and refined by full-matrix least-square techniques against F02 (SHELXL-97).[14] The

hydrogen atoms were included at calculated positions with fixed thermal displacement parameters. ORTEP-III was used for structure representation[15] and SCHAKAL-99 was used for the presentation of the packing of the molecules in the crystal.[16] Selected distances and angles are presented in Table 1. Crystallographic data for all complexes are summarised in Supporting Information Table S1.1–2.

Further details on the crystal structures of compounds 1 (CCDC 691145), 2 (691146), 4

(691147) and 5 (691144) can be obtained free of charge on application to Cambridge

Crystallographic Data Centre, 12 Union Road, Cambridge CB2 1EZ, UK (Fax: int.code+(1223)336-033; e-mail [email protected]).

Synthesis: All syntheses were carried out under argon by using Schlenk tube techniques. All

solvents were purified as described in the literature[17] and distilled under argon. The synthesis of the ligands H2L1,[18] H2L2,[18] H4L3,[9a] [FeL1(MeOH)2],[19] [FeL2(MeOH)2][19] and

iron(II)acetate[20] is described in literature. Bis(4-pyridylmethyl)amine was synthesised by using the same procedure as reported for Bis(2-pyridylmethyl)amine but with the educts functionalised at para-position.[21] Anhydrous 4,4′-bipyridine and 1-methylimidazole were

purchased from ACROS, trans-1,2-bis(4-pyridyl)ethylene was purchased from Aldrich and 4-

dimethylaminopyridine was purchased from Fluka. 1-Methylimidazole was distilled under argon; the others were used as received.

[FeL2(4-dpa)] EtOH (1): [FeL2(MeOH)2] (0.46 g, 1.20 mmol) and an ethanol solution of

bis(4-pyridylmethyl)amine (1 M, 6.0 mL, 6.0 mmol) were dissolved in ethanol (50 mL) and

heated to reflux for 4 h. After cooling down to room temperature, a black precipitate was filtered off, washed with ethanol (10 mL) and dried in vacuo (yield: 0.51 g, 73%). MS (DEI-

(+), 70 eV): m/z (%): 382 (100) [FeL2+]; elemental analysis calcd (%) for C32H37FeN5O5

(627.21): C 61.25, H 5.94, N 11.16; found C 61.57, H 5.55, N 11.57.

[FeL2(bipy)] DMF (2): [FeL2(MeOH)2] (0.40 g, 0.90 mmol) and 4,4′-bipyridine (1.40 g,

8.96 mmol) were dissolved in dimethylformamide (40 mL) and heated to reflux for 1 h. After cooling down to room temperature, a black precipitate was filtered off that was washed with methanol (10 mL) and dried in vacuo (yield: 0.28 g, 58%). Elemental analysis calcd (%) for

C31H33FeN5O5 (611.18): C 60.89, H 5.44, N 11.45; found: C 61.10, H 5.24, N 11.05.

[FeL1(bpee)] (3): A suspension of [FeL1(MeOH)2] (0.31 g, 0.61 mmol) and trans-1,2-bis(4-

pyridyl)ethylene (1.12 g, 6.12 mmol) in methanol (35 mL) was heated to reflux for 1 h. After cooling down to room temperature the black precipitate was filtered off, washed with methanol (10 mL) and dried in vacuo (yield: 0.21 g, 55%). MS (FAB-(+)): m/z (%): 442 (31)

[FeL1+]; elemental analysis calcd (%) for C32H32FeN4O6 (624.17): C 61.55, H 5.17, N 8.97;

found: C 61.17, H 5.22, N 8.92.

[Fe2L3(1-meim)4] 4 1-meim (4): A solution of H4L3 (0.60 g, 0.85 mmol), iron(II)acetate

(0.38 g, 2.18 mmol) and 1-methylimidazole (1.24 g, 15.2 mmol) in methanol (20 mL) was heated to reflux for 1 h. After cooling down to room temperature the brown precipitate was filtered off, washed with methanol (10 mL) and dried in vacuo (yield: 0.15 g, 18%). MS

(FAB-(+)): m/z (%): 805 (85) [Fe2L3+]; elemental analysis calcd (%) for C66H86Fe2N20O12

(1462.54): C 54.18, H 5.92, N 19.15; found: C 53.54, H 5.81, N 19.42.

[FeL1(DMAP)2] (5): [FeL1(MeOH)2] (0.85 g, 1.68 mmol) and 4-dimethylaminopyridine

(10.5 g, 0.086 mol) were dissolved in methanol (30 mL) and heated to reflux for 0.5 h. After cooling, the solution was left in the refrigerator (4 °C) to form black crystals that were collected, washed with a little methanol and dried in vacuo (yield: 0.8 g, 69%). IR (KBr):

ν = 1683(s) cm−1 (CO); MS (DEI-(+), 70 eV): m/z (%): 442 (10) [FeL1+], 121 (100)

[DMAP+]; elemental analysis calcd (%) for C34H42FeN6O6Fe (686.25): C 59.47, H 6.17,

N 12.24; found: C 59.64, H 6.12, N 12.44; DTG: up to 270°C: −39.5% = loss of 2 DMAP (theory: 35%); at 280°C: decomposition

Supplementary material: Supplementary data associated with this article can be found in the

online version at doi: 10.1016/j.ica.2008.10.018.

Acknowledgements

This work has been supported financially by the Deutsche Forschungsgemeinschaft (SPP 1137) the Fonds der Chemischen Industrie and the Center for Integrated Protein Science Munich (CIPSM). The Authors would like to thank E. Kaps and A. Glas for the preparation of some of the complexes and P. Mayer, S. Albrecht and M. Reichvilser for the acquisition of the crystallographic data.

5.5

References

[1] a) H.A. Goodwin, Coord. Chem. Rev. 1976, 18, 293; b) P. Gütlich, Struct. Bonding (Berlin) 1981, 44, 83; c) E. König, Prog. Inorg. Chem. 1987, 35, 527; d) P. Gütlich, A.

Hauser, Coord. Chem. Rev.1990, 97, 1; e) E. König, Struct. Bonding (Berlin)1991, 76,

51; f) P. Gütlich, A. Hauser, H. Spiering, Angew. Chem. Int. Ed. Engl. 1994,33, 2024,

and references therein; Angew. Chem. 1994, 106, 2109; g) P. Gütlich, J. Jung, H.A.

Goodwin, Molecular Magnetism: From Molecular Assemblies to the Devices (Eds.: E.

Coronado et al.), NATO ASI Series E: Applied Sciences, Vol. 321, Kluwer, Dordrecht, 1996, 327; h) P. Gütlich, H.A. Goodwin (Eds.), Spin Crossover in Transition Metal Compounds I–III, Topics in Current Chemistry, Springer, Berlin, Heidelberg, New York 2004; i) J.A. Real, A.B. Gaspar, M.C. Munoz, Dalton Trans. 2005, 2062, j) O. Sato, J.

Tao, Y.-Z. Zhang, Angew. Chem. 2007, 119, 2200; Angew. Chem. Int. Ed. 2007, 46,

2152.

[2] a) O. Kahn, C. Jay Martinez, Science 1998, 279, 44; b) O. Kahn, C. Jay, J. Kröber, R.

Claude, F. Grolière, Patent EP0666561 1995; c) J.-F. Létard, O. Nguyen, N. Daro, Patent FR0512476 2005; d) J.-F. Létard, P. Guionneau, L. Goux-Capes, Topics in Current Chemistry, Vol. 235 (Eds.: P. Gütlich, H.A. Goodwin), Springer, Wien,

NewYork, 2004, 221; e) A. Galet, A.B. Gaspar, M.C. Munoz, G.V. Bukin, G.

Levchenko, J.A. Real, Adv. Mater.2005,17, 2949.

[3] A.B. Gaspar, V. Ksenofontov, J.A. Real, P. Gütlich, Chem. Phys. Lett. 2003,373, 385.

[4] V. Ksenofontov, A.B. Gaspar, V. Niel, S. Reiman, J.A. Real, P. Gütlich, Chem. Eur. J. 2004,10, 1291.

[5] a) S. Zein, S.A. Borshch, J. Am. Chem. Soc. 2005, 127, 16197; b) K. Nakano, S.

Kawata, K. Yoneda, A. Fuyuhiro, T. Yagi, S. Nasu, S. Morimoto, S. Kaizaki, Chem. Commun.2004, 2892.

[6] N. Ortega-Villar, A.L. Thompson, M.C. Munoz, V.M. Ugalde-Sadivar, A.E. Goeta, R. Moreno-Esparza, J.A. Real, Chem. Eur. J.2005,11, 5721.

[7] a) B. Weber, R. Tandon, D. Himsl, Z. Anorg. Allg. Chem.2007,633, 1159; b) B. Weber,

E.S. Kaps, C. Desplanches, J.-F. Létard, Eur. J. Inorg. Chem.2008, 1589.

[8] a) B. Weber, E. Kaps, J. Weigand, C. Carbonera, J.-F. Létard, K. Achterhold, F.-G. Parak, Inorg. Chem. 2008, 47, 487; b) B. Weber, E.S. Kaps, J. Obel, W. Bauer, Z. Anorg. Allg. Chem. 2008, 1421; c) B. Weber, C. Carbonera, C. Desplanches, J.-F.

Létard, Eur. J. Inorg. Chem.2008,1589.

[9] a) B. Weber, E. Kaps, Heteroatom Chem. 2005, 16, 391; b) B. Weber, F.-A. Walker, Inorg. Chem.2007,46, 6794.

[10] B. Weber, W. Bauer, J. Obel, Angew. Chem. 2008, 120, 10252; Angew. Chem., Int. Ed. 2008, 47, 10098;

[11] G.A. Jeffrey, H. Maluszynska, J. Mitra, Int. J. Biol. Macromol.1985,7, 336.

[12] A. Real, J. Zarembowitch, O. Kahn, X. Solans, Inorg. Chem. 1987,26, 2939.

[13] A. Altomare, M.C. Burla, G.M. Camalli, G. Cascarano, C. Giacovazzo, A. Guagliardi, A.G.G. Moliterni, G. Polidori, R. Spagna, SIR-97, University of Bari, Bari (Italy), 1997; J. Appl. Crystallogr.1999,32, 115.

[14] G.M. Sheldrick, SHELXL-97, University of Göttingen, Göttingen (Germany), 1997.

[15] C.K. Johnson, M.N. Burnett, ORTEP-III, Oak-Ridge National Laboratory, Oak-Ridge TN (USA) 1996; L.J. Farrugia, J. Appl. Crystallogr.1997,30, 565.

[16] E. Keller, SCHAKAL-99, University of Freiburg, Freiburg (Germany), 1999.

[17] Team of authors: Organikum, Johann Ambrosius Barth Leipzig, Berlin, Heidelberg, 1993.

[18] L. Wolf, E.-G. Jäger, Z. anorg. allg. Chem.1966,346, 76.

[19] E.-G. Jäger, E. Häussler, M. Rudolph, M. Rost, Z. Anorg. Allg. Chem.1985,525, 67.

[20] B. Heyn, B. Hipler, G. Kreisel, H. Schreer, D. Walter, Anorganische Synthesechemie, 2.

edition, Springer, Heidelberg, 1986.