The First Self-Penetrating Topology Based on an Unusual r-Po Net with Double Edges Constructed from a 12-Connected Gd2(µ2-Ocarboxylate)2(µ2-OH2)2(µ3-OH)2Cu2 Core Feng Luo, Yun-xia Che, and Ji-min Zheng* Department of Chemistry, Nankai UniVersity, Tianjin, China
CRYSTAL GROWTH & DESIGN 2006 VOL. 6, NO. 11 2432-2434
ReceiVed June 20, 2006; ReVised Manuscript ReceiVed August 27, 2006
ABSTRACT: Herein, the first self-penetrating topology based on an unusual R-Po net with double edges self-assembled from a 12connected Gd2(µ2-Ocarboxylate)2(µ2-OH2)2(µ3-OH)2Cu2 core was obtained hydrothermally by the reaction of isonicotinic acid (HIN), Gd2O3, and CuCl2 in the presence of HClO4, (NH4)HCOO. Introduction There has been growing interest in recent years in the design and synthesis of 3d-4f polymeric metal systems motivated by their fascinating structural topology and the exploitable applications in magnetism, luminescence materials, molecular adsorption, and bimetallic catalysis.1 So far, most of the work in this area has focused on the assembly of Ln-Cu(II), Ln-Cu(I), Ln-Ag(I), LnZn(II), and Ln-Mn(II) coordination polymers,2 and the selected O/N donor ligands mainly concentrate on both N and O donor pyridine carboxylate ligands, such as pyridine-2,5-dicarboxylic acid (2,5-H2pydc), pyrazine-2,4-dicarboxylic acid (2,4-H2pzdc), pyrazine-2,6-dicarboxylic acid (2,6-H2pzdc), and HIN. However, the hybrid Ln-Cu(II)-Cu(I) coordination polymer is still undeveloped, although there have been a lot of mixed-valence Cu(I,II) coordination compounds created by utilizing a simple kind of ligand containing both a pyridyl group and a carboxylate group through the in situ redox reaction of Cu(II)-pyridyl and the stabilization of Cu(I,II)-carboxylate coordination (usually in the dimeric CuICuII fashion; there are only several examples in the incorporation of discrete single Cu(I) and Cu(II) atoms by organic spacers).3 Fortunately, we isolated the first Ln(III)-Cu(II)-Cu(I) coordination polymer, namely [Gd2Cu(II)2Cu(I)5(IN)10(µ2-Cl)(µ2-OH2)2(µ3-OH)2][(ClO4)2] (1), in which the discrete single Cu(I) and Cu(II) atoms are linked by IN- spacers. We chose HIN as the multifunctional bridging ligand, on the basis of the following considerations: (i) the rigid HIN ligand showing both oxygen and nitrogen donors on opposite sides is one of the judicious choices for obtaining the 3d-4f compounds; (ii) the carboxyl group may induce the lanthanide ions to undergo hydroxo lanthanide cluster aggregations or hydroxo Ln-Cu cluster entities.2 The nitrogen atoms can participate in bonding to Cu(II) ions; in this way, the extended solids containing both hydroxo lanthanide clusters or hydroxo Ln-Cu entities and Cu(II) ions might be obtained; (iii) Mixed-valence Cu(I,II) coordination polymers via hydrothermal synthesis always shows fascinating behavior; however, the mixed-valence CuICuII compounds are of great biological importance and have important electronic properties.4 Polymer 1 was obtained by the reaction of Gd2O3, CuCl2, HIN, (NH4)HCOO, and HClO4 in water via hydrothermal synthesis.5 It is noteworthy that the reagent of (NH4)HCOO is rather important in the formation of polymer 1; if it is removed from this experiment, no product will be obtained. Hence, in our opinion, the formation of polymer 1 may be mainly induced by the common salt of (NH4)HCOO. In order to produce the title compound in high yield, the CuO + NaCl mixture is selected to replace the CuCl2 reagent, and indeed, the yield increases to 75% from the former 62%. In addition, we try to introduce other halide ions (such as F-, Br-, I-) into this system by choosing the corresponding CuO + NaF, CuO + NaBr, * To whom correspondence should be addressed. Fax: 86-22-23502458. Tel: 86-22-23507950. E-mail:
[email protected].
Figure 1. (a) Twelve-connected SBU; (b) core of the 12-connected SBU.
and CuO + NaI mixtures as the source of halide ions. On the basis of our experiments, we found that the introduction of the Br- ion from the CuO + NaBr mixture is the only successful result; furthermore, the X-ray diffraction shows that it is a Gd(III)-Cu(I) coordination compound with the bilayer structure linked by INligands. Unfortunately, the crystal data is not good enough that we can report it in detail. The single-crystal X-ray diffraction shows6 that polymer 1 shows an exceptional self-penetrating topology, based on an unusual R-Po nets with double edges constructed from a 12-connected secondary building unit (SBU). The coordination geometries of the different metal centers are listed as follows: Gd1 shows the nine-coordinated tricapped trigonal prism geometry, which is completed by seven oxygen atoms from IN- ligands, one µ3-OH ion (O11), and one µ2-OH2 molecule (O12). The Gd-O bond length spans the range of 2.396-2.704 Å, all of which are comparable to that in other Ln-containing complexes.1,2 Cu1 and Cu2 are two-coordinated by two oxygen or nitrogen atoms from IN- ligands to lead to linear O-Cu-O and N-Cu-N connections with O-Cu1-O and N-Cu2-N angles of 180 and 173.84° (Cu-O, 1.919(8) Å; CuN, 1.928(10) and 1.940(12) Å), respectively. To the best of our knowledge, in Cu(I)-containing coordination polymers, the linear O-Cu-O connection with the 180° angle relative to the linear N-Cu-N connection, is rare. As for Cu4, it adopts a planar trigonal geometry in a CuN2(µ2-Cl) fashion (Cu-N/Cl, 1.951(10), 1.957(10), and 2.592(2) Å; N-Cu-N, 166.0(5)°), whereas for Cu3, it exhibits the six-coordinated CuNOcarboxylate(µ2-OH2)2(µ3-OH)2 mode in an elongated octahedral configuration (Cu-N/O, 2.021(10), 1.996(8), 2.021(8), 2.037(7), 2.529(8), and 2.593(8)Å). On the basis
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Figure 2. (a) R-Po nets with double edges constructed from the 12connected SBUs; (b) schematic description of the R-Po nets with double edges; (c) schematic description of the common R-Po nets.
Figure 3. View of the first self-penetrating topology, based on the R-Po nets; the green is the O1-Cu1-O1′ connectors.
of the above-mentioned coordination surroundings of different Cu centers, we assign Cu1, Cu2, and Cu4 to be monovalent, where Cu3 is considered to be bivalent. And through the calculation of the bond-valence parameter, the above assignments are rational (Cu1 (1.0), Cu2 (0.8), Cu3 (1.7), Cu4 (0.9)).7 In addition, the O11 atom from the OH- ion acts as the tridentate ligand in the µ3-fashion to bridge one Gd and two Cu atoms and shows the typical hydrogen bond (O3‚‚‚H11-O11, 2.838 Å), whereas the O12 atom from the water molecule is ligated to one Gd and one Cu atom in a µ2fashion and also performs typical hydrogen bonds (O3‚‚‚H12-O12, 2.704 Å; O9‚‚‚H12-O12, 2.838 Å). The main original feature of the structure is the unprecedented self-penetration, based on two interpenetrating R-Po nets, and a representation of the beautifully self-entangled network, showing two interwoven R-Po nets cross-linked by linear O-Cu-O connectors, is illustrated in Figure 3. Let us now describe the unusual R-Po net. As shown in Figure 1, Cu3, Gd1, and symmetry-related Cu3′ and Gd1′ are linked together through two µ2-Ocarboxylate atoms, two µ2-OH2 molecules,
Figure 4. (a) χMT vs T plot; (b) M vs H plot.
Crystal Growth & Design, Vol. 6, No. 11, 2006 2433 and two µ3-OH- ions to give rise to the tetramer fragment, in which the Gd-Cu distance and Gd-O-Cu angle are 3.718 Å for Gd1Cu3, 3.889 Å for Gd1-Cu3′, 93.85° for Gd1-O12-Cu3, 97.45° for Gd1-O10-Cu3′, 108.45° for Gd1-O11-Cu3, 115.69° for Gd1-O11-Cu3′, and the Cu3-Cu3′ distance and Cu3-O11-Cu3′ angle are 3.051 Å and 97.51°. In addition, the special tetramer core is arranged to join with four IN- anions and four linear Cu(IN)2 fragments, as well as two H-shaped Cu2(µ2-Cl)(IN)4 fragments to furnish the final 12-connected SBU. In this way, if we take the tetramer core as being a single node, this SBU can be viewed as a 12-connected node. As we know, it is usually believed that the 6-, 8-, and 12-connectivities would like to fall into the pcc (primitivecentered cubic), bcc (body-center cubic), and fcc (face-center cubic) type nets, respectively. Herein, the high connectivity (12-connectivity) would like to give rise to the pcc-related type, rather than the fcc type, as the 12 links orient in only six different directions and each pair of them chelates to another SBU. Comparing with the common pcc type nets showing the self-dual structure and 1111 transitivity with the 41263 topology, this special pcc type net is obviously characterized by the double-edge-containing configuration. In addition, we carefully checked the structure of 1, and there only two analogous pcc type nets with double edges, one set (Zn8(SiO4)(tpht)6) featuring the 2-fold interpenetration,8 another set (Cd4(ip)4(bpp)2) characterized by the first non-interpenetration,9 hence, it should be highlighted here that this special net with double edges is the first R-Po net containing 3d-4f building block and mixedvalence Cu(I,II) atoms. However, if we ignore the O-Cu-O connectors, then the structure can be simply viewed as the interpenetrating R-Po network (Figure 2), but in fact, when we take into account the O-Cu-O connectors, it then becomes a single net with more complicated topology. Furthermore, the self-penetrating network retains some free volume (126.2 Å3 in a unit cell, equivalently, 7.0% of the cell volume),10 which is fully populated by counterions of ClO4- that are partly stabilized by hydrogen bonds (O15‚‚‚H21-C21, 3.433 Å; O15‚‚‚H3-C3, 3.408 Å; O14‚‚‚H7-C7, 3.169 Å; O13‚‚‚H3C3, 3.200 Å; O16‚‚‚H20-C20, 3.219 Å; O16‚‚‚H26-C26, 3.352 Å).7 The magnetic properties of 1 were investigated over the temperature range 2-300 K in a field of 1000 Oe. In the χMT versus T plot, the χMT value (16.4 cm3 mol-1 K) at room temperature is approximately equal to the sum of the expected value (16.5 cm3 mol-1 K, g ) 2.0) of two isolated Gd(III) ions with S ) 7/2 spin and two isolated Cu(II) ions with S ) 1/2 spin; upon temperate cooling, the χMT values laggardly increase to 17.09 cm3 mol-1 K at 50 K, suggesting the occurrence of ferromagnetic correlation, and it then sharply decrease to 14.3 cm3 mol-1 K until 2 K, because
2434 Crystal Growth & Design, Vol. 6, No. 11, 2006 of the dipolar-dipolar and/or antiferromagnetic interaction. The observed susceptibility data (2-300 K) were well-fitted to the Curie-Weiss law (χM ) C/(T - θ)) with θ ) +0.9 K, indicating the weak ferromagnetic behavior in polymer 1. Furthermore, at 2 K, the magnetization versus field plot shows that at 0-15000 Oe, the M values rapidly increase, and then above 25000 Oe, the increase of magnetization slows down and tends to reach saturation (10.8 Nβ), which is largely smaller than the value(16 Nβ) of the sum of Gd2Cu2. Seen from the above descriptions, at low temperature, polymer 1 is estimated to own the ground state S ) 5 or less (at present, we do not have a suitable model to simulate the experimental data), on the basis of the plots of χMT versus T and M versus H11 (see Figure 4). However, polymer 1 may possess the potential function as molecular-based magnetic materials.12 Seem from the TG plot (see the Supporting Information, Figure S1), we can deduce some useful information: the two coordinated water molecules lost about 260 °C (calcd, -1.3%; found, -1.1%); before the process of chemical decomposition at about 295 °C, the counterions of ClO4- were not removed; and the final product after heating to 600 °C may be a mixture of Gd2O3, 2.5(Cu2O), and 2(CuO) (calcd, -69.8%; found, -70.9%). In this communication, the first self-penetrating topology based on unusual R-Po nets with double edges and self-assembled from a 12-connected SBU, was obtained by the reaction of Gd2O3, CuCl2, HIN, (NH4)HCOO, and HClO4 in water via hydrothermal synthesis. In 1, some unique characters, such as linear Cu-O-Cu connection with a 180° angle and discrete Cu(I,II) incorporation, are also attractive. In addition, polymer 1 can be viewed to be a high-spin molecule (S ) 5 or less) at low temperature, which is rather important in the preparation of molecular-based magnetic materials. Acknowledgment. This work was supported by the National Natural Science Foundation of China (50572040). Supporting Information Available: Crystal data in CIF format and TG plot. This material is available free of charge via the Internet at http:// pubs.acs.org.
References (1) (a) Kagan, H. B. Chem. ReV. 2002, 102, 1805. (b) Plecnik, C. E.; Liu, S.; Shore, S. G. Acc. Chem. Res. 2003, 36, 499.
Communications (2) (a) Zhou, Y. F.; Hong, M. C.; Wu, X. T. Chem. Commun. 2006, 135. (b) Cheng, J. W.; Zhang, J.; Zheng, S. T.; Zhang, M. B.; Yang, G. Y. Angew. Chem., Int. Ed. 2006, 45, 73. (c) Zhang, M. B.; Zhang, J.; Zheng, S. T.; Yang, G. Y. Angew. Chem., Int. Ed. 2006, 44, 1385. (d) Zhao, B.; Chen, X. Y.; Cheng, P.; Liao, D. Z.; Yan, S. P.; Jiang, Z. H. J. Am. Chem. Soc. 2004, 126, 15394. (3) Tong, M. L.; Li, L.; Mochizuki, J. K.; Chang, H. C.; Chen, X. M.; Li, Y.; Kitagawa, S. Chem. Commun. 2003, 428. (4) (a) Dunaj-Jurco, M.; Ondrejovic, G.; Melnik, M.; Garaj, J. Coord. Chem. ReV. 1988, 83, 1. (b) Houser, R. P.; Young, V. G.; Tolman, W. B. J. Am. Chem. Soc. 1996, 118, 2101. (c) Luo, F.; Che, Y. X.; Zheng, J. M. Inorg. Chem. Commun. 2006, 9, 848. (5) Elemental anal. Calcd for 1 (C60H46Cl3Cu7Gd2N10O32): C, 31.54; N, 6.13; H, 2.03. Found: C, 31.98; N, 6.23; H, 2.73. (6) Crystal data for 1: triclinic, space group P1h, a ) 9.1130(18) Å, b ) 11.681(2) Å, c ) 17.354(4) Å, R ) 86.93(3)°, β ) 80.89(3)°, γ ) 84.54(3)°, V ) 1814.4(6) Å3, Z ) 1, Dc ) 2.085 g cm-3, final R1 ) 0.0749, wR2 ) 0.1704. Data collections of 1 were performed with MoKR radiation (0.71073Å) on a Bruker SMART Apex CCD diffractometer. The structures were solved by direct methods and all non-hydrogen atoms were subjected to anisotropic refinement by full matrix least-squares on F2 using the SHELXTL program; all hydrogen atoms were added by calculation.13 Seen from the 060310bm.cif file, the remaining peaks around the heavy metal atoms of about 0.9 Å were more than 2.0 e Å-3, resulting in the high R1 and wR2. We tried other absorption correction methods, but the results were not satisfactory; however, this phenomenon is common. CCDC 605606 (1). (7) Brese, N. E.; O’Keeffe, M. Acta Crystallogr., Sect. B 1991, 47, 192. (8) (a) Blatov, V. A.; Carlucci, L.; Ciani, G.; Proserpio, D. M. CrystEngComm 2004, 6, 377. (b) Yang, S. Y.; Long, L. S.; Jiang, Y. B.; Huang, R. B.; Zheng, L. S. Chem. Mater. 2002, 14, 3229. (9) Wen, Y. H.; Zhang, J.; Wang, X. Q.; Feng, Y. L.; Cheng, J. K.; Lia, Z. J.; Yao, Y. G. New. J. Chem. 2005, 29, 995. (10) Spek, A. L. PLATON; Utrecht University: Utrecht, The Netherlands, 1999. (11) Kahn, O. Molecular Magnetism; Wiley-VCH: New York, 1993. (12) Eppley, H. J.; Tsai, H. L.; Vries, N. D.; Felting, K.; Christou, G.; Hendrickson, D. N. J. Am. Chem. Soc. 1995, 117, 301. (13) (a) Sheldrick, G.M. SHELXS97, Program for Crystal Structure Determination; University of Go¨ttingen: Go¨ttingen, Germany, 1997. (b) Sheldrick, G.M. SHELXL-97-2, Program for Crystal Structure Refinement; University of Go¨ttingen: Go¨ttingen, Germany, 1997.
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