1524 Inorg. Chem. 2010, 49, 1524–1534 DOI: 10.1021/ic901903f
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Anomalous Non-Prussian Blue Structures and Magnetic Ordering of K2MnII[MnII(CN)6] and Rb2MnII[MnII(CN)6] Jae-Hyuk Her,‡,§ Peter W. Stephens,*,‡ Christopher M. Kareis,† Joshua G. Moore,† Kil Sik Min,†, Jong-Won Park,† Garima Bali,† Bretni S. Kennon,† and Joel S. Miller*,† †
Department of Chemistry, 315 S. 1400 E. RM 2124, University of Utah, Salt Lake City, Utah 84112-0850 and Department of Physics & Astronomy, Stony Brook University, Stony Brook, New York 11794-3800. § Current address: GE Global Research, 1 Research Circle, Niskayuna, NY 12309. Current address: Department of Chemistry Education, Kyungpook National University, Daegu, South Korea. )
‡
Received September 29, 2009
The reaction of MnII and KCN in aqueous and non-aqueous media leads to the isolation of three-dimensional (3-D) Prussian blue analogues, K2Mn[Mn(CN)6] (1a-d, 1e, respectively). Use of RbCN forms Rb2Mn[Mn(CN)6] (2). 1 and 2 are isomorphic {monoclinic, P21/n: 1 [a = 10.1786(1) A˚, b = 7.4124(1) A˚, c = 6.9758(1) A˚, β = 90.206(1)o]; 2 [a = 10.4101(1) A˚, b = 7.4492(1) A˚, c = 7.2132(1) A˚, β = 90.072(1)o]}, with a small monoclinic distortion from the face centered cubic (fcc) structure that is typical of Prussian blue structured materials that was previously reported for K2Mn[Mn(CN)6]. Most notably the average Mn-N-C angles are 148.8° and 153.3° for 1 and 2, respectively, which are significantly reduced from linearity. This is attributed to the ionic nature of high spin MnII accommodating a reduced M-CN-M0 angle and minimizing void space. Compounds 1a,b have a sharp, strong νOH band at 3628 cm-1, while 1e lacks a νOH absorption. The νOH absorption in 1a,b is attributed to surface water, as use of D2O shifts the νOH absorption to 2677 cm-1, and that 1a-e are isostructural. Also, fcc Prussian blue-structured Cs2Mn[Mn(CN)6] (3) has been structurally [Fm3hm: a = 10.6061(1) A˚] and magnetically characterized. The magnetic ordering temperature, Tc, increases as Kþ (41 K) > Rbþ (34.6 K) > Csþ (21 K) for A2Mn[Mn(CN)6] in accord with the increasing deviation for linearity of the Mn-N-C linkages [148.8 (Kþ) > 153.3 (Rbþ) > 180° (Csþ)], decreasing Mn(II) 3 3 3 Mn(II) separations [5.09 (Kþ) < 5.19 (Rbþ) < 5.30 A˚ (Csþ)], and decreasing size of the cation (increasing electrostatic interactions). Hence, the bent cyanide bridges play a crucial role in the superexchange mechanism by increasing the coupling via shorter Mn(II) 3 3 3 Mn(II) separations, and perhaps enhanced overlap. In addition, the temperature dependent magnetic behavior of K4[MnII(CN)6] 3 3H2O is reported.
Introduction Ferri- and to a lesser extent ferromagnetic ordering has been reported for several hexacyanometalates possessing the *To whom correspondence should be addressed. E-mail: jsmiller@ chem.utah.edu (J.S.M.),
[email protected] (P.W.S.). (1) Verdaguer, M.; Girolami, G. S. In Magnetism - Molecules to Materials; Miller, J. S., Drillon, M., Eds.; Wiley-VCH: Weinheim, 2005, Vol. 5, p 283. Hashimoto, K.; Ohkoshi, S. Phil. Trans. R. Soc. Lond. A 1999, 357, 2977. Verdaguer, M.; Bleuzen, A.; Marvaud, V.; Vaissermann, J.; Seuleiman, M.; Desplanches, C.; Scuiller, A.; Train, C.; Garde, R.; Gelly, G.; Lomenech, C.; Rosenman, I.; Veillet, P.; Cartier, C.; Villain, F. Coord. Chem. Rev. 1999, 190-192, 1023. (2) (a) Ferlay, S.; Mallah, T.; Ouahes, R.; Veillet, P.; Verdaguer, M. Nature 1995, 378, 701. (b) Dujardin, E.; Ferlay, S.; Phan, X.; Desplanches, C.; Moulin, C. C. D.; Sainctavit, P.; Baudelet, F.; Dartyge, E.; Veillet, P.; Verdaguer, M. J. Am. Chem. Soc. 1998, 120, 11347. (c) Ferlay, S.; Mallah, T.; Ouahes, R.; Veillet, P.; Verdaguer, M. Inorg. Chem. 1999, 38, 229. (d) Verdaguer, M.; Bleuzen, A.; Train, C.; Garde, R.; Fabrizi de Biani, F.; Desplanches, C. Phil. Trans. R. Soc. Lond. A 1999, 357, 2959. (3) (a) Holmes, S. M.; Girolami, G. S. J. Am. Chem. Soc. 1999, 121, 5593. (b) Hatlevik, Oe.; Buschmann, W. E.; Zhang, J.; Manson, J. L.; Miller, J. S. Adv. Mater. 1999, 11, 914.
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Prussian blue structure.1-3 Critical temperatures, Tc, as great as ∼100 °C have been reported for KVII[CrIII(CN)6] 3 2H2O 3 0.1(KO3SCF3)3a and K0.058VII0.57VIII0.43[CrIII(CN)6]0.79 3 (SO4)0.058 3 0.93H2O3b with the anticipation that they may find applications in areas such as magnetic shielding4 and spintronic memory storage devices.5 Magnetic ordering occurs in these materials because of the strong spin coupling between adjacent metal sites via the superexchange interaction6 of the cyanide ligand. This family includes MnIII[MnIII(CN)6] (Tc = 31 K),7 MnIII3[MnII(CN)6]2 3 zH2O (4) (a) Morin, B. G.; Hahm, C.; Epstein, A. J.; Miller, J. S. J. Appl. Phys. 1994, 75, 5782. (b) Miller, J. S. Adv. Mater. 1994, 6, 322. (c) Landee, C. P.; Melville, D.; Miller, J. S. In NATO ARW Molecular Magnetic Materials; Kahn, O., Gatteschi, D., Miller, J. S., Palacio, F., Eds.; Kluwer Academic Publishers: London, 1991, Vol. E198, p 395. (5) Prigodin, V. N.; Raju, N. P.; Pokhodnya, K. I.; Miller, J. S.; Epstein, A. J. Adv. Mater. 2002, 14, 1230. (6) (a) Anderson, P. W. Phys. Rev. 1950, 79, 350. (b) Goodenough, J. B. J. Phys. Chem. Solids 1958, 6, 287. (c) Kanamori, J. J. Phys. Chem. Solids 1959, 10, 87. (7) Buschmann, W. E.; Miller, J. S. Inorg. Chem. 2000, 39, 2411.
r 2010 American Chemical Society
Article
(12 e z e 16; Tc = 35.5 K),8,9 CsMnII[MnIII(CN)6] 3 1/ 2(H2O) (Tc = 31 K),8 and MnII[MnIV(CN)6] 3 1.14H2O (Tc = 49 K).7,10 In the case of MnII3[MnIII(CN)6]2 3 12H2O, the C-bound low spin (ls) MnIII (t2g4, S = 1) interacts with the N-bound high spin (hs) MnII (t2g3eg2, S = 5/2) ferrimagnetically.8,9 Additionally, face-centered cubic (fcc) K2MnII[MnII(CN)6]8,11a and NaMn[Cr(CN)6]12 were reported to be ferrimagnets with Tcs of 41 and 60 K, respectively. Recently, MII[MnIV(CN)6] (M = Co, Ni) and MIII[MnIII(CN)6] (M = V, Cr, Mn) made in non-aqueous media showed unexpected magnetic behaviors.7 The formation of the waterfree lattice led to spin-glass behavior that is atypical of Prussian blue analogues (PBAs).1-3 Also, the study of anhydrous Fe[Mn(CN)6] and its hydrate revealed that they have uncommon mixed valency and magnetic properties.13 Keggin and Miles originally reported the structure of AnFe[Fe(CN)6] (A = alkali cation) as being fcc, and this has been recognized as the general structure for AnM[M0 (CN)6] 3 zH2O PBAs.14 PBAs have two distinct metal sites consisting of C bonded to strong field metal sites, M0 C6, and N bonded to weak field metal sites, MN6, and charge balancing cations and/or water molecules are located within the void spaces of each lattice. Often PBAs have incomplete lattices with water coordinated to M rather than nitrogen.15,16 Herein, we investigate the magnetic properties of K2MnII[MnII(CN)6] (1a-e) and Rb2MnII[MnII(CN)6] (2), and report the first non-face centered cubic structure of A2Mn[Mn(CN)6] (A = K, Rb) composition with bent Mn-CN-Mn linkages. For comparison the magnetic behavior of K4[MnII(CN)6] is revisited.17 We also extend the fcc Prussian blue structure type with the preparation and structural and magnetic characterization of Cs2MnII[MnII(CN)6] (3). The genesis of this study was to identify a route to make [NEt4]2[MnII(CN)4],18 as well as to prepare [NEt4]4[MnII(CN)6], and these results will be reported later.19 Experimental Section KCN, Mn(O2CMe)2 3 4H2O, and MnCl2 3 4H2O were used as purchased. Mn(O2CMe)2 3 4H2O was dehydrated by heating in a vacuum oven at 100 °C over P2O5 for 24 h, and after putting Mn(O2CMe)2 3 xH2O into the DryBox, x was determined to be 2 from a thermogravimetric analysis (TGA). RbCN was obtained as a gift from M. C. DeLong, and used as (8) (a) Entley, W. R.; Girolami, S. G. Inorg. Chem. 1994, 33, 5165. (b) Entley, W. R.; Girolami, S. G. Inorg. Chem. 1995, 34, 2262. (9) Franz, P.; Ambrus, C.; Hauser, A.; Chernyshov, D.; Hostettler, M.; Hauser, J.; Keller, L.; Kr€amer, K.; Stoeckli-Evans, H.; Pattison, P.; B€urgi, H.-B.; Decurtins, S. J. Am. Chem. Soc. 2004, 126, 16472. (10) Klenze, R.; Kanellakopoulos, B.; Trageser, G.; Eysel, H. H. J. Chem. Phys. 1980, 72, 5819. (11) Qureshi, A. M.; Sharpe, A. G. J. Inorg. Nucl. Chem. 1968, 30, 2269. (12) Dong, W.; Zhu, L.-N.; Song, H.-B.; Liao, D.-Z.; Jiang, Z.-H.; Yan, S.-P.; Cheng, P.; Gao, S. Inorg. Chem. 2004, 43, 2465. (13) Buschmann, W. E.; Ensling, J.; G€utlich, P.; Miller, J. S. Chem.;Eur. J. 1999, 5, 3019. (14) (a) Keggin, J. F.; Miles, F. D. Nature 1936, 137, 577. (b) Itaya, K.; Uchida, I.; Neff, V. D. Acc. Chem. Res. 1986, 19, 162. (15) Beall, G. W.; Milligan, W. O.; Korp, J.; Bernal, I. Inorg. Chem. 1977, 16, 2715. Mullica, D. F.; Zielke, J. T.; Sappenfield, E. L. J. Sol. State. Chem. 1994, 112, 92. (16) Herren, F.; Fisher, P.; Ludi, A.; H€alg, W. Inorg. Chem. 1980, 19, 956. (17) Kotani, M. J. Phys. Soc. Jpn. 1949, 4, 293. (18) Buschmann, W. E.; Arif, A. M.; Miller, J. S. Angew. Chem., Int. Ed. 1998, 37, 781. Angew. Chem. 1998, 110, 813. (19) Her, J.-H.; Stephens. P. W.; Kareis, C. M.; Moore, J. G.; Min, K. S.; Park, J.-W.; Miller, J. S., in preparation. (20) DeLong, M. C.; Rosenberger, F. J. Cryst. Growth 1986, 75, 164.
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received.20 K4[Mn(CN)6]21a and CsCN21b were prepared via literature routes. Diethyl ether was purified through an activated alumina dual-column purification system under a positive pressure of N2, while H2O was purified through a Barnstead “E-pure” water purification system and deoxygenated through distillation under N2. All other solvents were distilled from the appropriate drying agents under nitrogen before use. All syntheses were performed in an oxygen-free (
