COMMUNICATION pubs.acs.org/crystal
Ferromagnetic Interactions in an Unusual 2D Coordination Polymer Including Di-2-pyridylketone-Methoxilated Anion, (1,1)-Azide, and Rare (1,1,3,3)-Azide Bridging Ligands Noelia De la Pinta,† Zurine Serna,† Gotzon Madariaga,‡ M. Karmele Urtiaga,§ M. Luz Fidalgo,|| and Roberto Cortes*,† Departamento de Química Inorganica, ‡Departamento de Física de la Materia Condensada, and §Departamento de Mineralogía y Petrología, Facultad de Ciencia y Tecnología, Apartado 644, 48080 Bilbao, Spain Departamento de Química Inorganica, Facultad de Farmacia, Apartado 450, 01080 Vitoria-Gasteiz, Spain
)
†
bS Supporting Information ABSTRACT: The compound [Cu4(dpk 3 OCH3)2(N3)6]n [dpk = di-2-pyridylketone] consists of tetranuclear units that repeat in two dimensions. Predominant ferromagnetic interactions are in good agreement with the crystal structure, showing alternating Cu2(1,1)-azide2 and Cu2 (1,1)-azide-oxo bridging units. Rare (1,1,3,3)-azide bridges promote the two-dimensionality and cause the low temperature antiferromagnetism.
T
he preparation of ferromagnetic materials continues to be a challenge for scientists working in the field of molecular magnetism. It is in order to both design new synthesis mechanisms and obtain applicable properties that we have embarked in the search of new ferromagnetic molecular systems. Huge efforts have been made over the past few years not only in the synthesis of new high dimensional coordination polymers on the basis of concepts such as crystal engineering, molecular architecture, etc.1 but also in the synthesis of zero dimensional cluster materials such as single molecule magnets.2 In both cases, one of the desired targets is to obtain ferromagnetism. The right choice of ligands is key in the preparation of these compounds. Pseudohalides have been demonstrated to be not only extremely versatile but also excellent magnetic couplers. The azide3 and cyanate4 groups, in particular, are known to give ferromagnetic interactions in their end-on (1,1) bridging modes. Dpk-derivatives, on the other hand, exhibit a clear trend to form metallic clusters with interesting properties.5 The dpk ligand exhibits three potential donors, being able to chelate in bidentate (N,N or N,O) or tridentate (N,O,N) modes. Moreover, dpk has been observed occasionally to undergo solvolysis, resulting in a derivative product that can coordinate either as a neutral (dpk 3 ROH) or as an anionic (dpk 3 RO) ligand.5m Compounds of higher dimensionality (1D or 2D) are very scarce.5m,6 Following our previous work on dpk-pseudohalide ferromagnetic systems,7 we present in this article the synthesis, infrared spectroscopy, crystal structure, and magnetic characterization of the [Cu4(dpk 3 CH3O)2(N3)6]n (1) complex. This new r 2011 American Chemical Society
compound represents the second6d example of a 2D complex containing dpk 3 CH3O, in this case with only two bridging ligands: dpk 3 CH3O itself and azide. Besides, it shows ferromagnetic interactions through alternating 3 3 3 Cu-[(1,1)azide, oxo]-Cu-[(1,1)azide]2-Cu 3 3 3 bridges. It also contains the rare (1,1,3,3)-azide bridging mode, which gives rise to the twodimensional structure for this complex. The crystal structure8 of 1 (Figure 1) consists of Cu(II) cations linked by alternating double (1,1)-azide and mixed (1,1)-azide-alkoxo bridges. Rare (1,1,3,3)-azide bridges also connect the cations. The structure exhibits two crystallographically independent metallic centers that are distorted octahedrally coordinated (4 þ 2). The Cu2N2 bridging structural motifs are nearly planar (Cu 3 3 3 Cu = 3.284(5) Å; Cu1NCu2 = 94.43(10), 101.73(10)°; torsion angle 176°), while the Cu2NO are not (Cu 3 3 3 Cu = 2.880(6) Å; Cu1O1Cu2 = 96.29(8)°, Cu1N9Cu2 = 91.15(9)°; torsion angle 142.5°). Both structural motifs conform a tetramer, [Cu4(dpk 3 CH3O)2(N3)6] (Figure 2) that repeats along the [010] direction. Pairs of independent copper(II) ions are also connected by (1,1,3,3)-azides to conform a second tetranuclear building block (Figure 3) that spreads in the (100) plane, joined by double (1,1)-azido bridges, to conform the global 2D structure (Figure 4). Received: March 3, 2011 Revised: April 2, 2011 Published: April 04, 2011 1458
dx.doi.org/10.1021/cg200267x | Cryst. Growth Des. 2011, 11, 1458–1461
Crystal Growth & Design
COMMUNICATION
Figure 3. Second tetranuclear building block formed by connection through (1,1,3,3)-azide bridges.
Figure 1. ORTEP view of the asymmetric unit of 1 with 50% thermal ellipsoids, showing the atom-labeling scheme.
Figure 4. Global 2D structure of 1 in the (100) plane. Figure 2. Tetranuclear building block of [Cu4(dpk 3 CH3O)2(N3)6].
The thermal evolution, between 4.2 and 300 K, of the magnetic susceptibility is shown in Figure 5 in the form of the χmT and χm1 vs temperature plots. For temperatures higher than 130 K, a fit to a CurieWeiss law gives values of C and θ of 0.41 cm3 3 K 3 mol1 and þ28 K, respectively, and a calculated g = 2.08. Below 130 K, the experimental data clearly deviate from the CurieWeiss law. The obtained θ value is indicative of significant ferromagnetic exchange. The χmT (4 Cu) product continuously increases upon cooling from 1.78 cm3 3 K 3 mol1 at room temperature (a value larger than that corresponding to four uncoupled CuII ions), up to a maximum of 2.32 cm3 3 K 3 mol1 at 16 K. It approximately represents an enhancement by a 30% factor. Both the positive temperature intercept and the continuous increase of χmT with decreasing temperature until 16 K are in accord with the presence of significant ferromagnetic interactions in this 2D compound. Ferromagnetic coupling must be attributed to the exchange between coppers inside the tetranuclear unit. Furthermore, the 30% enhancement in χmT may indicate that this coupling is primarily between the coppers within each dinuclear unit of the tetramer (a uniform ferromagnetic tetramer will undergo an enhancement of 100%), that further ferromagnetically interact with each other. Interactions take place through the alternating double (1,1)-azido bridges [N3(N4N5), N6(N7N8)] and mixed (1,1)-azido-alkoxo bridges [N9(N10N11), O1]. Below the maximum, the χmT product rapidly decreases, tending to zero. This decrease of the χmT product at low
Figure 5. Thermal dependence of χmT and χm1 (per 4 copper(II) ions). The dashed red curve represents the best fit for the model with negative zJ0 (iii), based upon a 2 J Hamiltonian.
temperatures should be attributed to the antiferromagnetic interactions corresponding to the Cu2N3N4N5Cu2 intermetallic connections. Therefore, the compound would consist of ferromagnetically coupled tetramers with S = 2 that couple antiferromagnetically below 16 K. There is no exact model for the susceptibility of a 2D lattice of heterogeneous exchange S = 1/2 tetramers. Notwithstanding, we 1459
dx.doi.org/10.1021/cg200267x |Cryst. Growth Des. 2011, 11, 1458–1461
Crystal Growth & Design
COMMUNICATION
’ ACKNOWLEDGMENT This work was supported by the Universidad del País Vasco (UPV/EHU) (UPV00169. EHU 2010/14), the Spanish Ministerio de Ciencia y Tecnología (MCYT) (CTQ2005-05778PPQ), and the Basque Government (project IT-282-07). N.D. P. thanks UPV/EHU for financial support from “Convocatoria para la concesion de ayudas de especializacion para investigadores doctores en la UPV/EHU (2008)”. ’ REFERENCES
Figure 6. Magnetization versus applied field at 5 and 10 K (per 4 copper(II) ions).
have tried tentative fittings to (i) a dinuclear model9 (JCu1Cu2 = þ55.3 K, g = 2.20); (ii) to dimers with an interdimer molecular field10 (JCu1Cu2 = þ70.2 K, zJ0 Cu1Cu2 = þ1.53 K, g = 2.16); (iii) and to dimers with the low temperature antiferromagnetic exchange as an interdimer molecular field (JCu1Cu2 = þ43.7 K, zJ0 Cu1Cu1 = 0.7 K, g = 2.23) (see Figure S6 of the Supporting Information). Although neither of them are ideal, the estimated values of J and zJ0 are comparable to others found in the literature for Cu(II)-azide compounds.6a,10 Our system compares partially with the observed tetranuclear units in the [Cu4(dpk 3 CH3O)2(Cl)6]n compound.6a In it, alternating 3 3 3 CuCl2CuClO 3 3 3 units promote ferromagnetic interactions ( 3 3 3 Cu(N3)2Cu(N3)O 3 3 3 in our case) that couple antiferromagnetically at low temperature. In this latter case, the obtained best J values are as follows: J1 = þ71.3 cm1, J2 = þ1.4 cm1, J3 = þ0.1 cm1, zJ0 = 0.55 cm1, and g = 2.1 (fixed). The (1,1,3,3)-azide bridges allow obtainment of the two dimensionality in our case. To corroborate the magnetic susceptibility observations, the magnetization versus applied field curves have been registered at 5 and 10 K (Figure 6). The curve at 5 K indicates that the complex will saturate at 4 B€ohr magnetons from four aligned S = 1/2 moments. These results are consistent with a ferromagnetically coupled high-spin Cu4 system with total S = 2. The field aligns the spins of the tetramers even at temperatures where antiferromagnetic coupling is observed. No electronic spin resonance spectrum is observed for 1 at room temperature, in good agreement with the presence of significant magnetic interactions.
’ ASSOCIATED CONTENT
bS
Supporting Information. Detailed experimental procedures, figures depicting the structure, and IR data. An X-ray crystallographic file, in CIF format. This material is available free of charge via the Internet at http://pubs.acs.org.
’ AUTHOR INFORMATION Corresponding Author
*E-mail:
[email protected]. Fax: þ34-946013500.
(1) (a) Real, J. A.; Andres, E.; Mu~ noz, M. C.; Julve, M.; Granier, T.; Bousseksou, A.; Varret, F. Science 1995, 268, 265. (b) Cortes, R.; Lezama, L.; Ruiz de Larramendi, J. I.; Madariaga., G.; Mesa, J. L.; Zu~ niga, F. J.; Rojo, T. Inorg. Chem. 1995, 34, 778. (c) Mukherjee, P. S.; Konar, S.; Zangrando, E.; Mallah, T.; Ribas, J.; Chaudhuri, N. R. Inorg. Chem. 2003, 42, 2695–2703. (d) Kitagawa, S.; Noro, S.-I.; Nakamura, T. Chem. Commun. 2006, 701–707. (e) Sorai, M.; Nakano, M.; Miyazaki, I. Chem. Rev. 2006, 106, 976–1031. (f) Chesman, A. S. R.; Turner, D. R.; Deacon, G. B.; Batten, S. R. Chem. Commun. 2010, 46, 4899–4901. (g) Ren, C.; Hou, L.; Liu, B.; Yang, G.-P.; Wang, Y.-Y.; Shi, Q.-Z. Dalton Trans. 2011, 40, 793–804. (2) (a) Sessoli, R.; Tsai, H.-L.; Schake, A. R.; Wang, S.; Vincent, J. B.; Folting, K.; Gatteschi, D.; Christou, G.; Hendrickson, D. N. J. Am. Chem. Soc. 1993, 115, 1804–1816. (b) Gatteschi, D.; Sessoli, R.; Cornia, A. Chem. Commun. 2000, 725–727. (c) Aromi, G.; Brechin, E. K. Struct. Bonding (Berlin) 2006, 122, 1and references cited therein. (d) Bagai, R.; Christou, G. Chem. Soc. Rev. 2009, 38, 1011and references therein. (e) Moushi, E. E.; Stamatatos, T. C.; Wernsdorfer, W.; Nastopoulos, V.; Christou, G.; Tasiopoulos, A. J. Inorg. Chem. 2009, 48, 5049–5051. (3) (a) Commarmond, J.; Plumere, P.; Lehn, J. M.; Agnus, Y.; Louis, R.; Weiss, R.; Kahn, O.; Morgenstern-Badarau, I. J. Am. Chem. Soc. 1982, 104, 6330–6340. (b) Ruiz, E.; Cano, J.; Alvarez, S.; Alemany, P. J. Am. Chem. Soc. 1998, 120, 11122–11129. (c) Ribas, J.; Escuer, A.; Monfort, M.; Vicente, R.; Cortes, R.; Lezama, L.; Rojo, T. Coord. Chem. Rev. 1999, 195, 1027–1068and references therein. (d) Monfort, M.; Resino, I.; Ribas, J.; Stoeckli-Evans, H. Angew. Chem., Int. Ed. 2000, 39, 191–193. (e) Serna, Z.; Lezama, L.; Urtiaga, M. K.; Arriortua, M. I.; Barandika, M. G.; Cortes, R.; Rojo, T. Angew. Chem., Int. Ed. 2000, 39, 344–347. (f) Karmakar, T. K.; Kandra, S. K.; Ribas, J.; Mostafa, G.; Lu, T. H.; Gosh, B. K. Chem. Commun. 2002, 2364–2365. (g) Demeshko, S.; Leibeling, G.; Maringgele, W.; Meyder, F.; Mennerich, C.; Klauss, H.-H.; Pritzkow, H. Inorg. Chem. 2005, 44, 519–528. (h) Escuer, A.; Aromí, G. Eur. J. Inorg. Chem. 2006, 4721–4736and references therein. (i) Mandal, D.; Bertolasi, V.; Ribas-Ari~ no, J.; Aromí, G.; Ray, D. Inorg. Chem. 2008, 47, 3465–3467. (j) Zhao, J.-P.; Hu, B.-W.; Sa~ nudo, E. C.; Yang, Q.; Zeng, Y.-F.; Bu, X.-H. Inorg. Chem. 2009, 48, 2482–2489. (k) Yoon, J. H.; Ryu, D. W.; Kim, H. C.; Yoon, S. W.; Suh, B. J.; Hong, C. S. Chem.—Eur. J. 2009, 15, 3661. (l) Stamatatos, T. C.; Abboud, K. A.; Wernsdorfer, W.; Christou, G. Inorg. Chem. 2009, 48, 807–809. (m) Zeng, M.-H.; Zhou, Y.-L.; Zhang, W.-X.; Du, M.; Sun, H.-L. Cryst. Growth Des. 2010, 10, 20–24. (n) Hu, B.-W.; Zhao, J.-P.; Tao, J.; Sun, X.-J.; Yang, Q.; Zhang, X.-F.; Bu, X.-H Cryst. Growth Des. 2010, 10, 2829–2831. (4) (a) Bursmeister, J. L. Coord. Chem. Rev. 1968, 3, 225–245. (b) Norbury, A. H. Adv. Inorg. Chem. Radiochem. 1975, 17, 232–236. (c) Kohout, J.; Havastijova, M.; Gazo, J. Coord. Chem. Rev. 1987, 27, 141–172. (d) Arriortua, M. I.; Cortes, R.; Mesa, J. L.; Lezama, L.; Rojo, T.; Villeneuve, G. Transition Met. Chem. 1988, 13, 371–375. (e) Dey, S. K.; Mondal, N.; Salah El Fallah, M.; Vicente, R.; Escuer, A.; Solans, X.; Font-Bardía, M.; Matsushita, T.; Gramlich, V.; Mitra, S. Inorg. Chem. 2004, 43, 2427–2434. (f) Habib, M.; Karmakar, T. K.; Aromí, G.; Ribas-Ari~ no, J.; Fun, H.-K.; Chantrapromma, S.; Chandra, S. K. Inorg. Chem. 2008, 47, 4109–4117. (g) Feng, P. L.; Stephenson, C. J.; Amjad, A.; Ogawa, G.; del Barco, E.; Hendrickson, D. N. Inorg. Chem. 2010, 49, 1304–1306. (5) (a) Feller, M. C.; Robson, R. Aust. J. Chem. 1968, 21, 2919. (b) Basu, A.; Saple, A. R.; Sapre, N. Y. J. Chem. Soc., Dalton Trans. 1460
dx.doi.org/10.1021/cg200267x |Cryst. Growth Des. 2011, 11, 1458–1461
Crystal Growth & Design
COMMUNICATION
1987, 1797–1799. (c) Sommerer, O. S.; Baker, J. D.; Jensen, W. P.; Hamzan, A.; Jacobson, R. A. Inorg. Chim. Acta 1993, 210, 173–176. (d) Sommerer, O. S.; Jensen, W. P.; Jacobson, R. A. Inorg. Chim. Acta 1990, 172, 3–11. (e) Alonzo, G.; Bertazzi, N.; Maggio, F.; Benetollo, F.; Bombieri, G. Polyhedron 1996, 15, 4269–4273. (f) Tangoulis, V.; Raptopoulou, C. P.; Terzis, A.; Paschalidou, S.; Perlepes, S. P.; Bakalbassis, E. G. Inorg. Chem. 1997, 36, 3996. (g) Tsohos, A. E.; Dyonyssopoulou, S.; Raptopoulou, C. P.; Terzis, A.; Bakalbassis, E. G.; Perlepes, S. P. Angew. Chem., Int. Ed. 1999, 38, 983. (h) Papaefstathiou, G. S.; Escuer, A.; Raptopoulou, C. P.; Terzis, A.; Perlepes, S. P.; Vicente, R. Eur. J. Inorg. Chem. 2001, 1567–1574. (i) Papaefstathiou, G. S.; Escuer, A.; Mautner, F. A.; Raptopoulou, C. P.; Terzis, A.; Perlepes, S. P.; Vicente, R. Eur. J. Inorg. Chem. 2005, 879–893. (j) Efthymiou, C. G.; Raptopoulou, C. P.; Terzis, A.; Boca, R.; Korabic, M.; Mrozinski, J.; Perlepes, S. P.; Bakalbassis, E. G. Eur. J. Inorg. Chem. 2006, 2236–2252. (k) Stamatatos, T. C.; Efthymiou, C. G.; Stoumpos, C. C.; Perlepes, S. P. Eur. J. Inorg. Chem. 2009, 3361–3391and references therein. (l) Efthymiou, C. G.; Georgopoulou, A. N.; Papatriantafyllopoulou, C.; Terzis, A.; Raptopoulou, C. P.; Escuer, A.; Perlepes, S. P. Dalton Trans. 2010, 39, 8603–8605. (m) Mautner, F. A.; Salah El Fallah, M.; Speed, S.; Vicente, R. Dalton Trans. 2010, 39, 4070–4079. (6) For 1D see:(a) Papadopoulou, A. N.; Tangoulis, V.; Raptopoulou, C. P.; Terzis, A.; Kessissoglou, D. P. Inorg. Chem. 1996, 35, 559–565. (b) Serna, Z. E.; Cortes, R.; Urtiaga, M. K.; Barandika, M. G.; Lezama, L.; Arriortua, M. I.; Rojo, T. Eur. J. Inorg. Chem. 2001, 865–872. (c) Li, C.-M.; Zhang, D.-Q.; Zhu, D.-B. Inorg. Chim. Acta 2009, 362, 1383–1386. For 2D see:(d) Stamatatos, T. C.; Tangoulis, V.; Raptopoulou, C. P.; Terzis, A.; Papaefstathiou, G. S.; Perlepes, S. P. Inorg. Chem. 2008, 49, 7969–7971. (7) (a) Serna, Z. E.; Barandika, M. G.; Cortes, R.; Urtiaga, M. K.; Arriortua, M. I. Polyhedron 1999, 18, 249–255. (b) Serna, Z. E.; Lezama, L.; Urtiaga, M. K.; Arriortua, M. I.; Barandika, M. G.; Cortes, R.; Rojo, T. Angew. Chem., Int. Ed. 2000, 39, 344–347. (c) Serna, Z. E.; Barandika, M. G.; Cortes, R.; Urtiaga, M. K.; Barberis, G. E.; Rojo, T. J. Chem. Soc., Dalton Trans. 2000, 29–34.(d) Serna, Z. E. Ph.D. Thesis, UPV/EHU, 2001. (e) Barandika, M. G.; Serna, Z. E.; Cortes, R.; Lezama, L.; Urtiaga, M. K.; Arriortua, M. I.; Rojo, T. Chem. Commun. 2001, 45–46. (f) Serna, Z. E.; Urtiaga, M. K.; Barandika, M. G.; Cortes, R.; Martin, S.; Lezama, L.; Arriortua, M. I.; Rojo, T. Inorg. Chem. 2001, 40, 4550–4555. (g) Serna, Z. E.; De la Pinta, N.; Urtiaga, M. K.; Lezama, L.; Madariaga, G.; Clemente-Juan, J.-M.; Coronado, E.; Cortes, R. Inorg. Chem. 2010, 49, 11541–11549. (8) Crystal data for 1: Crystal dimensions, 0.13 0.11 0.09 mm; monoclinic, P21/c; a = 10.832(2) Å, b = 11.363(4) Å, c = 13.731(4) Å, β = 94.53(2)°, V = 1684.8(8)Å3, Z = 4, Fcalc = 1.847 g 3 cm3, θmax = 29.98°, θmin = 1.89°, Enraf Nonius CAD4 diffractometer, T = 100(2) K, λ(Mo KR) = 0.71073 Å, μ = 2.561 mm1, 5298 reflections, 4899 unique reflections, 245 parameters, R1 = 0.0462 [I > 2σ(I)], wR2 = 0.1285, maximum residual electron density 0.72 e 3 Å3. (9) Bleaney, B.; Bowers, K. D. Proc. R. Soc. London, Ser. A 1952, 214, 451–465. (10) (a) Shen, Z.; Zuo, J.-L.; Yu, Z.; Zhang, Y.; Bai, J.-F.; Che, C.-M.; Fun, H.-K.; Vittal, J. J.; You, X.-Z. J. Chem. Soc., Dalton Trans. 1999, 3393–3398. (b) Shen, Z.; Zuo, J.-L.; Gao, S.; Song, Y.; Che, C.-M.; Fun, H.-K.; You, X.-Z. Angew. Chem., Int. Ed. 2000, 39, 3633–3635.
1461
dx.doi.org/10.1021/cg200267x |Cryst. Growth Des. 2011, 11, 1458–1461
