Supplementary Information Single chain magnets based on the oxalate ligand Eugenio Coronado*, José R. Galán-Mascarós and Carlos Martí-Gastaldo
Table of Contents SUPPLEMENTARY INFORMATION .................................................................................................. 1 EXPERIMENTAL DETAILS..................................................................................................................................... 2 SI 1. TEMPERATURE DEPENDENCE OF χM (UP) AND χMT (DOWN) IN THE LOW TEMPERATURE REGIME MEASURED UNDER A 1000 G APPLIED FIELD. SOLID LINE IS ONLY A GUIDE TO THE EYE........................ 3 SI 2. FITTING OF THE MAGNETIC DATA IN THE HIGH TEMPERATURE REGIME (50-300 K) TO THE CURIE-WEISS LAW (RED LINE).......................................................................................................................... 4 SI 3. FIELD-COOLED (FC) AND ZERO FIELD-COOLED (ZFC) MAGNETIZATIONS UNDER AN EXTERNAL APPLIED FIELD OF 25 OE. ................................................................................................................................... 5 SI 4. FIELD DEPENDENCE OF THE MAGNETIZATION AT 2K. SOLID LINE IS ONLY A GUIDE TO THE EYE. 6 SI 5. HYSTERESIS LOOP FOR COMPOUND 1 AT 2K (UP). ENLARGEMENT OF THE LOW-FIELD AREA DEPICTING THE COERCIVE FIELD (DOWN)........................................................................................................ 7 SI 6. PLOT OF LN(χM´T) VS. 1/T FOR 1. SOLID LINE REPRESENTS THE BEST FITTING TO A LINEAR REGIME. AC DATA WERE MEASURED AT 1 HZ FREQUENCY, 3.95 OE OSCILLATING FIELD AND ZERO EXTERNAL FIELD................................................................................................................................................... 8 SI 7. COLE-COLE DIAGRAM AT 2.4 (BLACK), 2.3 (RED) AND 2.2 K (BLUE). SOLID LINES REPRESENT THE BEST FITTING OF THE DATA TO A DEBYE MODEL (OBTAINED α VALUES RANGE IN THE 0.18-0.23 INTERVAL). ............................................................................................................................................................ 9 SI 8. THERMAL TREATMENT EFFECT ON THE MAGNETIC PROPERTIES OF 1. IN-PHASE (LEFT) AND OUT-OF-PHASE (RIGHT) DYNAMIC SUSCEPTIBILITY OF 1 AT 1 (BLACK) AND 110 HZ (BLUE) AFTER GENTLY HEATING UP TO 350 K........................................................................................................................10
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Experimental details. All reagents and solvents used were of commercially available grade and were used without any previous purification. K3[Cr(ox)3] salt was prepared following a previously described method. The Ag3[Cr(ox)3] derivative was obtained by metathesis of the potassium salt and protected from light to avoid further reduction. The 4fluoroanilinium complex was prepared as follows: p-toluidine was dissolved in HCl 4M by mechanical stirring and the resulting solution was left to stand at room temperature. Colourless prismatic crystals of [FPh(NH3)]Cl were filtrated and dried under vacuum. Single crystals of 1, suitable for X-ray diffraction, were prepared by slow diffusion of its components. Ag3[Cr(ox)3] (698 mg; 1 mmol) and [FPh(NH3)]Cl (443 mg; 3mmol) were suspended in 15 mL of methanol and mechanically stirred for 20 min. The resulting mixture was left to stand at room temperature and the AgCl white precipitate was filtered off under vacuum. Afterwards, solid CoCl26H2O (238 mg; 1mmol) was added to the filtrated solution. The resulting mixture was layered onto a 10 mL aqueous solution of 18-crown-6 (0.793 mg; 3mmol) previously poured in a glass tube and left to stand protected from the light. After 4 days, formation of prismatic purple crystals of [C12H24O6K][(C12H24O6)(FC6H4NH3)][Co(H2O)2Cr(ox)3]2 was observed. They were hand-collected from their mother-liquor, washed thoroughly with methanol and dried in air. Yield: 40 %. Anal calcd for H55C42Cr2KCo2FNO40 (Mw = 1493.83): C, 33.77 ; H, 3.71. Found: C, 33.98; H, 3.84.
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SI 1. Temperature dependence of χM (up) and χMT (down) in the low temperature regime measured under a 1000 G applied field. Solid line is only a guide to the eye.
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SI 2. Fitting of the magnetic data in the high temperature regime (50-300 K) to the Curie-Weiss law (red line).
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SI 3. Field-cooled (FC) and zero field-cooled (ZFC) magnetizations under an external applied field of 25 Oe.
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SI 4. Field dependence of the magnetization at 2K. Solid line is only a guide to the eye.
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SI 5. Hysteresis loop for compound 1 at 2K (up). Enlargement of the lowfield area depicting the coercive field (down).
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SI 6. Plot of Ln(χM´T) vs. 1/T for 1. Solid line represents the best fitting to a linear regime. AC data were measured at 1 Hz frequency, 3.95 Oe oscillating field and zero external field. The linear behavior exhibited by the Ln (χM´T) vs. 1/T plot in the 5.4-7.7 K regime is indicative of the strong Ising-like anisotropy of 1 (∆ζ/kB = 32 K; R=0.997%).1 The high and low temperature divergences from the exponential behavior must be ascribed to the population of excited states of the Co2+ ion and the geometrical limitation of the correlation length induced by the presence of structural defects respectively.2
1
a) Coulon, C.; Clérac, R.; Lecren, L.; Wernsdorfer, W.; Miyasaka, H. Phys. Rev. B 2004, 69, 132408. b) Bogani, L; Sessoli, R; Pini, M. G.; Rettori, A.; Novak, M. A.; Rosa, P.; Massi, M.; Fedi, M. E.; Giuntini, L.; Caneschi, A.; Gatteschi, D. Phys. Rev. B 2005, 72, 064406. 2 Li, X. J.; Wang, X. Y.; Gao, S.; Cao, R. Inorg. Chem. 2006, 45, 1508-1516.
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SI 7. Cole-Cole diagram at 2.4 (black), 2.3 (red) and 2.2 K (blue). Solid lines represent the best fitting of the data to a Debye model (obtained α values range in the 0.18-0.23 interval).
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SI 8. Thermal treatment effect on the magnetic properties of 1. In-phase (left) and out-of-phase (right) dynamic susceptibility of 1 at 1 (black) and 110 Hz (blue) after gently heating up to 350 K. In view of the SCM-like behavior described along the text, even though hydrogen bonding interactions are known to offer an effective pathway for the transmission of magnetic interactions,i the effective inter-chain interaction in this particular case is not strong enough to promote the onset of long-range bulk magnetic ordering. To ascertain the effect that the approaching of the interacting ferromagnetic chains might have in the overall magnetic behavior, we subjected a polycrystalline sample of 1 to gently heating prior to its magnetic characterization. AC measurements performed on the resulting compound show an additional out-of-phase signal at 7.5 K along with that previously observed around 4.5 K (see below). While the high-temperature signal shows no frequency-dependence the latter exhibits approximately the same dependence than prior to thermal treatment. In our opinion this fact must be ascribed to the formation of a secondary 2D phase resulting from the collapse of the 1D chains after thermal removal of the coordinating water molecules.
i
a) Veciana, J.; Cirujeda, J.; Rovira, C.; Vidal-Gancedo, J. Adv. Mater. 1995, 7, 221-225. b) Cirujeda, J.; Mas, M.; Molins, E.; Lanfranc de Panthou, F.; Laugier, J.; Park, J. G.; Paulsen, C.; Rey, P.; Rovira, C.; Veciana, J. J. Chem. Soc. Chemm. Commun. 1995, 709-710. c) Romero, F. M.; Ziessel, R.; Bonnet, M.; Pontillon, Y.; Ressouche, E.; Schweizer, J.; Delley, B.; Grand, A.; Paulsen, C. J. Am. Chem. Soc. 2000, 122, 1298. d) Coronado, E.; Galán-Mascarós, J. R.; Martí-Gastaldo, C., Inorg. Chim. Acta, 2008, 361, 4017-4023.
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