Synthesis, Crystal Structure and Magnetic Characterization of a Series

Article pubs.acs.org/crystal

Synthesis, Crystal Structure and Magnetic Characterization of a Series of CuII−LnIII Heterometallic [Ln = La, Ce, Pr, Nd and Sm) Metal− Organic Compounds with an Unusual Single Crystal to Single Crystal Phase Transition Pau Díaz-Gallifa,† Oscar Fabelo,*,‡,§ Laura Cañadillas-Delgado,‡,∥ Jorge Pasán,† Ana Labrador,⊥ Francesc Lloret,# Miguel Julve,# and Catalina Ruiz-Pérez*,† †

Laboratorio de Rayos X y Materiales Moleculares, Departamento de Física Fundamental II, Facultad de Física, Universidad de La Laguna, Avenida Astrofísico Francisco Sánchez s/n, E-38204 La Laguna, Tenerife, Spain ‡ Instituto de Ciencia de Materiales de Aragón, CSIC-Universidad de Zaragoza, Pedro Cerbuna 12, 50009 Zaragoza, Spain § Institut Laue Langevin, B.P. 156, 6 Rue J. Horowitz, 38000, Grenoble, France ∥ Centro Universitario de la Defensa de Zaragoza, Carretera de Huesca s/n, 50090 Zaragoza, Spain ⊥ MAX IV Laboratory, Lund University, P.O. BOX 118, SE 221-00, Lund, Sweden # Instituto de Ciencia Molecular (ICMol), Departament de Química Inorgànica, Universitat de València, c/Catedrático José Beltrán 2, 46980 Paterna, Valencia, Spain S Supporting Information *

ABSTRACT: The synthesis and structural characterization of five Cu(II)− Ln(III) heteronuclear metal−organic frameworks of formula {[Ln4Cu4(H2O)26(bta)5]·mH2O}n and {[Ln4Cu4(H2O)24(bta)5]·pH2O}n [Ln = LaIII (1A/1B), CeIII (2A/2B), PrIII (3A/3B), NdIII (4A/4B) and SmIII (5A/ 5B) with m/p = 20 (1A)/16 (1B), 18 (2A)/16 (2B), 14 (3A)/16 (3B), 22 (4A)/16 (4B) and 21 (5A)/14 (5B); H4bta =1,2,4,5-benzenetetracarboxylic acid (1−5)] have been performed. These compounds present a single-crystal to single-crystal phase transition from expanded A phases toward the B shrinking networks, which is triggered only in the presence of a dry environment. This phase transition is accompanied by a compression of the crystallographic b-axis in the range 2.4 to 2.8 Å with the consequent decrease of the unit cell volume from 9.5% to 12%. The isomorphous crystal structures of 1A−5A can be described as two crystallographically independent [Cu(II)− Ln(III)] heterometallic dinuclear units which are connected through two crystallographically independent bta4− ligands in the acplane, leading to 4,4-rectangular grids. These layers are connected along the crystallographic b-axis, through a pillaring bta4− group. The phase transition implies a change of the coordination mode of the bta4− pillar from bis-monodentate (1A−5A) to tetrakis-monodentate (1B−5B). Magnetic susceptibility measurements of polycrystalline samples of 1A−5A in the temperature range 2.0−300 K have in common the decrease of the χMT product with T which in the case of 1A is due to weak antiferromagnetic interactions between the copper(II) ions through the bta4− skeleton, the LaIII cation being diamagnetic [J = −3.5 cm−1 with the Hamiltonian defined H = −JSCu1·SCu2]. For the 2A−5A compounds, the additional exchange interaction between CuII and the paramagnetic LnIII is masked by the crystal field effects (which partially removes the 2J + 1 degeneracy of the 2S+1LJ free-ion ground state in zero magnetic field) (2A−5A) and the thermal population of excited free-ion states (5A).

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INTRODUCTION

the rational design of systems with external stimulus dependent variable architectures (e.g., pressure, temperature, light, gas or solvent adsorption) is far from being controlled. The design and materialization of systems with dynamic architectures can be achieved through different ways, the most common being the use of flexible ligands (or building blocks) which are linked

The design and construction of metal organic frameworks (MOFs) with well-defined channels/pores has attracted great interest because of the number of applications owing to guest adsorption, host removal, and exchange behaviors in the channels.1,2 A fascinating property of these systems is the ability to modify the framework by the guest molecules.2 This dynamic behavior is not observed in other inorganic compounds, such as zeolites and nano- or mesoporous materials. Although the number of MOFs increases rapidly, © XXXX American Chemical Society

Received: June 8, 2013 Revised: September 11, 2013

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dx.doi.org/10.1021/cg4008679 | Cryst. Growth Des. XXXX, XXX, XXX−XXX

Crystal Growth & Design

Article

shrunk (B) networks. Variable-temperature magnetic studies of the family 1A−5A are also carried out.

via strong coordinative bonds. The dynamic behavior is therefore the response of the flexible ligands to the internal or external stimulus.3 The second option is the use of rigid ligands (or building blocks) which have to be connected via weak interactions, the breaking and formation of new bonds causing the shrinking−expanding effects.1a Another possible choice is the combination of flexible ligands and weak linkages. This last category is the less predictable, because of the difficulty to govern the weak interactions. Nevertheless, the weak interactions between the pore walls and guest molecules can induce important structural changes: the presence/absence of guest molecules modifies the bonding network, producing changes or even bond cleavages.2f This new class of MOFs has been thoroughly investigated by several research teams, and according to the dimensionality of the inorganic network, Férey classified these new porous materials into four different categories.4 The first one consists of a pure inorganic framework (3D inorganic system) (type I). The introduction of organic moieties can induce pillaring between inorganic 2D motifs (type II) or act as linkers between 1D polymers (type III). Inorganic 1D and 2D structures with organic molecules as linkers are usually referred to as hybrid inorganic−organic materials. Finally, organic ligands may arrange around discrete 0D entities which contain one or more metal ions and that are named coordination polymers (type IV). More recently, Kitagawa and Eumura proposed a classification of the different porous coordination polymers into six groups regarding the dimensionality of the inorganic subnetwork and the types of host−guest interactions.5 The first one comprises 1D motifs whose voids are occupied by small sized molecules. The second type consists of 2D motifs stacked on each other with weak interlayer interactions. The third type includes the interdigitated layers which are stacked with interlocked ridges and hollows to form channels. The fourth type involves 3D networks which are built by layers connected through nonrigid spacers. The fifth type covers elongated and shrinking 3D grids, which show spongelike dynamic behavior. The last one relates to the 3D interpenetrated grids. The MOF family which is subject of the present work belongs simultaneously to the IV and V types from Férey and Kitagawa respectively, being 3D compounds that exhibit a spongelike dynamics (expanding and shrinking channels). In this respect, the correct selection of the bridging ligand is of utmost importance. In fact, polycarboxylate-type ligands have been widely used in the design of polynuclear complexes with shrinking/expanding networks, in particular the 1,n-dicarboxylate (n = 4 and 5) and 1,3,5-tricarboxylate ones.1a,c,2b,6 Our approach involves the use of the 1,2,4,5-benzenetetracarboxylic acid (H4bta), whose deprotonated forms have the ability to combine rigidity with a great variety of coordination modes.7 Interestingly, an extraordinary family of MOFs with a shrinking−expanding architecture results from their interaction with heterodinuclear 3d−4f nodes.8 Here we present the synthesis and the structural characterization through synchrotron radiation of five heterometallic 3d−4f complexes of formula {[Ln4Cu4(H2O)26(bta)5]·mH2O}n and {[Ln4Cu4(H2O)24(bta)5]·pH2O}n [Ln = LaIII (1A/1B), CeIII (2A/2B), PrIII (3A/3B), NdIII (4A/4B) and SmIII (5A/ 5B) with m/p = 20 (1A)/16 (1B), 18 (2A)/16 (2B), 14 (3A)/ 16 (3B), 22 (4A)/16 (4B) and 21 (5A)/14 (5B). These compounds present a crystal to crystal phase transition, which is triggered only in a dry environment, from expanded (A) to

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EXPERIMENTAL SECTION

Materials and Methods. Reagents and solvents used in the syntheses were purchased from commercial sources and used without further purification. The preparative methods used to get X-ray quality crystals of compounds 1A−5A are described herein. In the presence of a dry atmosphere, compounds 1A−5A undergo a crystal to crystal phase transition transforming into 1B−5B. Elemental analyses (C, H, N) were performed with an EA 1108 CHNS/0 automatic analyzer. Synthesis o f {[Ln 4 Cu 4 (H 2 O) 2 6 (bta) 5 ]· m H 2 O} n a nd {[Ln4Cu4(H2O)24(bta)5]·pH2O}n [Ln = LaIII (1A/1B), CeIII (2A/2B), III Pr (3A/3B), NdIII (4A/4B) and SmIII (5A/5B) with m/p = 20 (1A)/ 16 (1B), 18 (2A)/16 (2B), 14 (3A)/16 (3B), 22 (4A)/16 (4B) and 21 (5A)/14 (5B). The preparation of 1A−5A is as follows: an aqueous ammonia solution (25% v/v) was poured into an aqueous solution (10 cm3) of H4bta (0.127 g, 0.5 mmol), the pH of the clear solution being 5.0. Tetramethylorthosilicate (0.7 cm3) was added to this solution under vigorous stirring, and the resulting mixture was introduced into test tubes, covered, and stored for one day at room temperature to allow the formation of the gel.9 Once it was set, an aqueous solution (4 cm3) of a mixture of Cu(NO3)2·5(H2O) (0.116 g, 0.5 mmol) and Ln(NO3)2·xH2O [0.032 g, 0.1 mmol (1), 0.043 g, 0.1 mmol (2), 0.043 g, 0.1 mmol (3), 0.043 g, 0.1 mmol (4) and 0.044 g, 0.1 mmol (5) with x = 1 (1) and 6 (2−5)] was layered on the gel, care being taken to avoid any damage of its surface, and the tube was stored at room temperature. Pale blue needles of 1A−5A (see photograph S1 in the Supporting Information) which were suitable for single crystal X-ray diffraction appeared a few days later. They were mechanically separated from other homonuclear phases that cocrystalllize at the same time and washed with a water/ethanol (1:1 v/v) solution [yield ca. 4 (1), 6 (2), 7 (3), 5 (4) and 9 % (5)]. Anal. Calcd for C25H51Cu2O43La2 (1A): C, 20.76; H, 3.53. Found: C, 20.96; H, 3.56 %. Anal. Calcd for C25H49Cu2O42Ce2 (2A): C, 21.04; H, 3.44. Found: C, 21.10; H, 3.41 %. Anal. Calcd for C25H45Cu2O40Pr2 (3A): C, 21.53; H, 3.25. Found: C, 21.64; H, 3.24 %. Anal. Calcd for C25H53Cu2O44Nd2 (4A): C, 20.53; H, 3.62. Found: C, 20.54; H, 3.67 %. Anal. Calcd for C25H52Cu2O43.5Sm2 (5A): C, 20.65; H, 3.58. Found: C, 20.59; H, 3.54 %. The crystals 1A−5A remain stable in a wet atmosphere, and under dry conditions they transform instantaneously into the corresponding 1B−5B phases. This crystal-to-crystal phase transition is reversible, and the crystallinity is kept. Physical Measurements. Magnetic susceptibility measurements on polycrystalline samples of compound 1A−5A were carried out in the temperature range 1.9−300 K with a Quantum Design SQUID magnetometer under applied dc magnetic fields of 100 G (T < 50 K) and 4500 G (over the whole range). Corrections for the diamagnetic contribution of the constituent atoms were applied. The magnetic data were also corrected for the temperature-independent paramagnetism [60 cm3 mol−1 per mol of Cu(II)] as well as for the magnetization of the sample holder previously measured under the same conditions. The thermogravimetric analysis were carried out on a Perkin-Elmer Pyris Diamond TGA/DTA, under a flux of dry nitrogen, which was turned out once the temperature was stable, with a flowing at 100.0 mL min−1. The measurements were done with a heating rate of 5 K min−1 in the temperature range from RT to 593 K and with a rate of 10 K min−1 from 593 to 893 K, using aluminum crucibles. Crystal Structure Determination and Refinement. Because of the low diffraction power of the mechanically isolated needles of compounds 1A−5A in the usual data collection on single crystal X-ray diffractometers, X-ray measurements on 1A−5A and 1B−5B were collected by using the synchrotron radiation [λ = 0.7379 (1A)/ 0.73830 (1B), 0.738 (2A), 0.7383 (3A)/0.7513 (3B), 0.7379 (4A)/ 0.7383 (4B) and 0.7379 (5A)/0.73833 (5B) Å] at the BM16 Spanish beamline of ESRF and [λ = 0.6889 for 2B] at the I19 beamline of DIAMOND facility. The acquisition strategy in the BM16 measurements consists of phi (φ) scans with an oscillation range (Δφ) for each image of one degree, the data collection being carried out on two B



Article

Table 1. Crystal Data Details of the Structure Determination for the Complexes 1A−5A and 1B−5B 1A

2A

3A

4A

5A

1444.54 monoclinic C25H51Cu2O43La2 P21/n 11.006(2) 23.228(5) 19.847(4) 99.91(3) 4998.2(17) 4 2.831 293(2) 1.920 0.73790 −12 ≤ h ≤ 12 −27 ≤ k ≤ 27 −23 ≤ l ≤ 23 34112 8448 (0.0712) 7808 649 1.042 0.0795 0.2065 0.0829 0.2093 1B

1428.95 monoclinic C25H49Cu2O42Ce2 P21/n 10.994(2) 23.098(5) 19.838(4) 99.89(3) 4962.8(17) 4 3.197 293(2) 1.912 0.73800 −14 ≤ h ≤ 14 −29 ≤ k ≤ 29 −25 ≤ l ≤ 25 71163 10754 (0.0640) 10128 650 1.062 0.0692 0.2005 0.0712 0.2037 2B

1394.51 monoclinic C25H45Cu2O40Pr2 P21/n 10.953(2) 23.056(5) 19.811(4) 99.88(3) 4929.0(17) 4 2.903 293(2) 1.879 0.73830 −14 ≤ h ≤ 14 −30 ≤ k ≤ 30 −25 ≤ l ≤ 25 90569 11573 (0.0693) 9974 623 1.033 0.0494 0.1544 0.0557 0.1633 3B

1473.23 monoclinic C25H53Cu2O44Nd2 P21/n 10.856(2) 22.799(5) 19.706(4) 99.49(3) 4810.6(17) 4 3.316 293(2) 2.034 0.73790 −14 ≤ h ≤ 14 −29 ≤ k ≤ 29 −25 ≤ l ≤ 25 43378 10967 (0.1029) 8057 659 1.022 0.0713 0.1843 0.0957 0.2081 4B

1476.46 monoclinic C25H52Cu2O43.5Sm2 P21/n 10.923(2) 22.771(5) 19.758(4) 99.64(3) 4845.0(17) 4 3.665 293(2) 1.882 0.73790 −14 ≤ h ≤ 14 −29 ≤ k ≤ 28 −25 ≤ l ≤ 25 39465 10595 (0.0705) 9225 658 1.078 0.0620 0.1730 0.0684 0.1833 5B

C25H45Cu2O40La2 1390.51 monoclinic P21/n 10.985(2) 20.450(4) 19.856(4) 99.73(3) 4396.4(15) 4 3.132 100 2.101 0.73830 −14 ≤ h ≤ 14 −26 ≤ k ≤ 2 6 −25 ≤ l ≤ 25 73169 8749 (0.0587) 9677 623 1.038 0.0587 0.1676 0.0620 0.1729

C25H45Cu2O40Ce2 1392.93 monoclinic P21/n 10.9718(2) 20.2668(3) 19.7821(5) 99.312(2) 4340.84(15) 4 2.743 100 2.131 0.68890 −12 ≤ h ≤ 12 −23≤ k ≤ 23 −23 ≤ l ≤ 20 33514 7298 (0.0512) 6419 622 1.017 0.0462 0.1211 0.0517 0.1263

C25H45Cu2O40Pr2 1394.51 monoclinic P21/n 10.906(2) 20.212(4) 19.769(4) 99.22(3) 4301.4(15) 4 3.327 100 2.156 0.75130 −13 ≤ h ≤ 13 −25 ≤ k ≤ 25 −25 ≤ l ≤ 25 264668 9480 (0.0554) 8857 622 1.093 0.0476 0.1374 0.0500 0.1396

FW FW crystal system formula space group a/Å b/Å c/Å β/deg V/Å Z μ/cm−1 T/K ρcalc/g cm−3 λ/Å index ranges

total reflns indep reflns (Rint) obsd reflns [I > 2σ(I)] parameters goodness-of-fit R [I > 2σ(I)] Rw [I > 2σ(I)] R [all data] Rw [all data] formula FW crystal system space group a/Å b/Å c/Å β/deg V/Å Z μ/cm−1 T/K ρcalc/g cm−3 λ/Å index ranges

total reflections indep reflns (Rint) obsd reflns [I > 2σ(I)] parameters goodness-of-fit R [I > 2σ(I)] Rw [I > 2σ(I)] R [all data] Rw [all data]

different crystal orientations in order to increase the data completeness. The automatic acquisition strategy protocol of CrysAlis Pro software10 was used in the I19 mesurement. Data were indexed, integrated and scaled using HKL2000 and CrysAlis Pro programs.10,11 All compounds were collected at RT and 100 K without and with a cryostream device, respectively.

C25H45Cu2O40Nd2 1401.17 monoclinic P21/n 10.927(2) 20.391(4) 19.807(4) 99.61(3) 4351.4(15) 4 3.624 100 2.111 0.73830 −12 ≤ h ≤ 12 −22 ≤ k ≤ 22 −20 ≤ l ≤ 20 25298 5986 (0.0744) 4238 622 1.071 0.0426 0.1066 0.0715 0.1224

C25H47Cu2O39Sm2 1399.44 monoclinic P21/n 10.899(2) 20.334(4) 19.785(4) 99.48(3) 4324.8(15) 4 3.995 100 2.149 0.73833 0 ≤ h ≤ 13 0≤k≤25 −22 ≤ l ≤ 22 38379 6601(0.0640) 5660 613 1.103 0.0522 0.1502 0.0595 0.1589

The structures were solved by direct methods and subsequent Fourier syntheses using the SHELXS-97,12 and they were refined by the full-matrix least-squares technique against F2 using with the SHELXL-97 program.12 All non-hydrogen atoms were anisotropically refined, with the exception of the O(11w) in compound 2A. The O(11w) water molecule has been refined isotropically because the C



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Cu(1)···O(11w) bond distance becomes anomalously short when the anisotropic displacement parameters of O(11w) are introduced in the refinement. A spurious electron density peak located along the Cu(1)···O(11w) bond at 0.98 Å from O(11w) and 1.22 Å from Cu(1), with no physical meaning, gives rise to this inconsistent bond length shortening. The best refinement model found was achieved maintaining O(11w) with isotropic displacement parameters. The treatment of the hydrogen atoms of the bta4− ligand was constrained for all the complexes whereas the hydrogen atoms from the coordination and crystallization water molecules were neither found nor considered in the refinement. A crystal-to-crystal transition from the shrinking porous {[Ln4Cu4(H2O)26(bta)5]·mH2O}n (1A− 5A) phases to the shrunk {[Ln4Cu4(H2O)24(bta)5]·pH2O}n (1B−5B) ones occurs only in the presence of a dry environment. The number of crystallization water molecules m and p are not univocally determined by means of the X-ray diffraction experiments; nevertheless, the proposed models are the best-refined fits among the different ones which were tested. Moreover, the number of crystallization water molecules obtained from the X-ray measurements correspond with those obtained using thermogravimetric measurements (see Figure S1 in the Supporting Information). The number of crystallization water molecules in compounds 1A−5A is 20, 18, 14, 22, and 21 respectively, while there are 16 in the shrunk complexes except for 5B, which has only 14. For the sake of clarity, we will use m and p to refer to the number of crystallization water molecules in the formulas of the 1A− 5A and 1B−5B compounds, respectively. The final geometrical calculations and the graphical manipulations were carried out with PARST97,13 PLATON,14 and DIAMOND15 programs. The main crystallographic data and some experimental details are shown in Table 1 (1A−5A and 1B−5B). Selected bond lengths and angles for 1A−5A and for 1B−5B are listed in Tables S1a and S1b in the Supporting Information, respectively. Crystallographic data for the structures of 1A−5A and 1B−5B have been deposited at the Cambridge Crystallographic Data Centre with CCDC reference numbers 958829−958833 and 958834−958838, respectively.

Figure 1. View along the crystallographic b-axis of a fragment of the layer formed by two independent bta4− ligands (pale green and gray) linked through heterodinuclear Cu(II)−Ln(III) units (blue and purple).

four carboxylate groups of four different bta4− ligands [symmetry code: (b) = −0.5 + x, 0.5 − y, −0.5 + z and (c) = −1.5 + x, 0.5 − y, −0.5 + z ] (see Figure 5) in a distorted monocapped square antiprism with mean values for the bite parameter b of 1.18 (1A and 2A)/1.19 (1B and 2B), 1.17(3A)/ 1.18 (3B), 1.16 (4A)/1.17 (4B) and 1.16 (5A and 5B)].16 Ln(2) is surrounded by five coordination water molecules [O(5w), O(6w), O(7w), O(8w) and O(9w)] and four carboxylate-oxygen atoms [O(3)d, O(4)d, O(16) and O(19) from three different carboxylate groups of three different bta4− ligands [symmetry code: (d) = 1.5 + x, 0.5 − y, 0.5 + z], building also a distorted monocapped square antiprism with mean values for the bite parameter b of 1.18 (1A)/1.17 (1B), 1.17 (2A and 3A)/1.16 (2B and 3B), 1.16 (4A)/1.15 (4B) and 1.15 (5A and 5B). The square-planar base of the polyhedron is defined by the O(1w)O(2w)O(17)cO(18)c/O(3)dO(4)dO(7w)O(9w) set of atoms for Ln(1)/Ln(2), while the upper square-plane is built by O(1)O(5)bO(3w)O(11)/O(6w)O(8w)O(16)O(19) for Ln(1)/Ln(2), the water molecule O(4w)/O(5w) capping the antiprism on Ln(1) and Ln(2), respectively. The values of the Ln−Ocarboxylate bond distance are slightly shorter than those observed for the Ln−Ow, and the mean values of the Ln−Ocarboxylate and Ln−Ow bond lengths for the two families gradually decrease when going from La(III) to Sm(III) as expected due to the contraction of the ionic radii with the increasing atomic number of the 4f ions (see Tables S1a and S1b and Figure S2 in the Supporting Information). Two crystallographically independent copper(II) ions [Cu(1) and Cu(2)] are also present in 1A−5A and 1B−5B. They are both five-coordinate in distorted square pyramidal surroundings. The environment of the Cu(1)/Cu(2) ions in the 1A−5A family is defined by three carboxylate oxygen atoms [O(2)a, O(6) and O(13); symmetry code (a) = 0.5 + x, 0.5 − y, 0.5 + z]/[O(7), O(15) and O(20)b; symmetry code (b) = −0.5 + x, 0.5 − y, −0.5 + z] from three different bta4− ligands plus two water molecules [O(10w) and O(11w)]/[O(12w) and

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RESULTS AND DISCUSSION Structural Description. The structures of the complexes 1A−5A and 1B−5B are made up of neutral 3D motifs of formula [Ln4Cu4(H2O)26(bta)5]n (1A−5A) and [Ln4Cu4(H2O)24(bta)5]n (1B−5B) [Ln = La (1A−1B), Ce (2A−2B), Pr (3A−3B), Nd (4A−4B) and Sm (5A−5B)] and crystallization water molecules [20 (1A)/16 (1B), 18 (2A)/16 (2B), 14 (3A)/16 (3B), 22 (4A)/16 (4B) and 21 (5A)/14 (5B)] which are hosted in the channels of the heterobimetallic networks. Two crystallographically independent Cu(II)−Ln(III) dinuclear units ions having two carboxylate(bta) as bridges in the syn-syn conformation are interlinked along the crystallographic a- and c-axes by means of two crystallographically independent bta4− ligands giving rise to 4,4rectangular layers (see Figure 1). Furthermore, these sheets are connected along the crystallographc b-axis by a third bta4− ligand, following an ABAB sequence (see Figures 2 and 3). This latter interlayer bta4− ligand changes its coordination mode from bis-monodentate in the 1A−5A family to tetrakismonodentate in the 1B−5B series. This bta4− ligand connects two Ln(III) ions from two different heterodinuclear units in 1A−5A, whereas it links two Ln(III) ions and two Cu(II) ions from four different heterodinuclear units in 1B−5B (see Figure 4) Two crystallographically independent lanthanide(III) ions occur in 1A−5A and 1B−5B [Ln(1) and Ln(2)] both being nine-coordinate. Ln(1) is surrounded by four water molecules [O(1w), O(2w), O(3w) and O(4w)] and five carboxylateoxygen atoms [O(1), O(5)b, O(11), O(17)c and O(18)c] from D



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Figure 2. (Left) View along the crystallographic a-axis of the ABAB stacking of the 4,4-rectangular layers which pillared by the remaining bta4− ligand (deep blue) giving rise to the 3D structure of 1A−5A. The coordination and crystallization water molecules, as well as the hydrogen atoms, have been omitted (except for one of the pores), for the sake of clarity. (Right) Topographic representation of the 1A−5A compounds. The 4-fold nodes built up by the bta4− ligands are represented by squares while the 5- and 4-fold metal nodes are represented as purple and blue spheres, respectively.

Figure 3. (Left) View along the crystallographic a-axis of the ABAB stacking of the 4,4-rectangular layers which are pillared by the remaining bta4− ligand (deep blue) giving rise to the 3D structure of 1B−5B; the coordination and crystallization water molecules as well as the hydrogen atoms have been omitted (except for one of the pores), for the sake of clarity. (Right) Topographic representation of the 1B−5B compounds. The 4-fold nodes built up from bta4− ligands are represented by squares while the metal nodes are represented by purple spheres.

Figure 4. Coodination modes of the interlayer bta4− ligand: bis-monodentate in 1A−5A (left) and tetrakis-monodentate in 1B−5B (right). Symmetry code: (e) = −x, −y, 1 − z.

O(13w)] with values for the trigonality parameter τ of 0.12 (1A and 4A), 0.11 (2A and 3A), and 0.08 (5A)/0.15 (1A), 0.14 (2a and 3A), 0.18 (4A) and 0.13 (5A) [the values of τ for the ideal square pyramid and trigonal bipyramid are 0.0 and 1.0, respectively].17 The mean values of the equatorial copper(II) to oxygen bond lengths are 1.979(6) (1A), 1.980(5) (2A), 1.977(4) (3A), 1.982(8) (4A) and 1.979(8) Å (5A). They are all values somewhat shorter than the axial Cu−Ow bond distances [2.248(10) (1A), 2.210(11) (2A), 2.226(7) (3A), 2.225(8) (4A) and 2.232(8) Å (5A)]. The coordination environment of the Cu(1) atom in the 1B−5B family remains almost identical to that observed in the 1A−5A series: a slightly distorted square pyramidal surrounding with τ values equal to 0.12 (1B), 0.11

(2B), 0.13 (3B), 0.11 (4B) and 0.09 (5B). This is not the case for the Cu(2) where the equatorial site of the water molecule O(12w) in the 1A−5A compounds is now occupied by the carboxylate-oxygen atom O(9)e [symmetry code: (e) = −x, −y, 1 − z]: four carboxylate-oxygens [O(7), O(9)e, O(15) and O(20)b] from four different bta4− ligands, and a water molecule [O(13w)] build a somewhat more distorted square pyramidal surrounding at this copper atom [τ = 0.23 (1B), 0.23 (2B), 0.27 (3B), 0.22 (4B) and 0.20 (5b)]. Three different bta4− ligands are present in 1A−5A and 1B− 5B, which are named as bta(1) [set of O(1)−O(8) and C(1)− C(10) atoms (light green colored in Figure 1)], bta(2) [built by the O(13)−O(20) and C(20)−C(29) atoms, (gray colored in Figure 1)] and bta(3) [formed by the O(9)O(10)O(11)E



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Figure 5. Perspective view of the crystallographically independent unit at ORTEP mode (50%) for 1A−5A (top) and 1B−5B (bottom) together with the numbering labels of selected atoms, the atoms in transparence mode are generated by symmetry operations. Crystallization water molecules and hydrogen atoms have been omitted for the sake of clarity.

O(12)C(11)C(12)C(13)C(14)C(15) set of atoms and their symmetry-related ones, dark blue color skeleton in Figure 2]. The bta(1) and bta(2) ligands act simultaneously as bridging pentakis-monodentate [through O(1), O(2), O(5), O(6) and O(7) toward Ln(1), Cu(1)b, Ln(1)a, Cu(1) and Cu(2) respectively (bta(1)), and via O(16), O(15), O(13), O(20) and O(19) toward Ln(2)a, Cu(2), O(13), Cu(1), Cu(2)a and Ln(2) (bta(2))] and chelating bidentate [through O(3) and O(4) toward Ln(2)c (bta(1)) and via O(18) and O(17) toward Ln(1)d (bta(2))] in 1A−5A and 1B−5B. However, the coordination mode of bta(3) ligand changes from bridging bis-monodentate [through O(11) and O(11)e toward Ln(1) and Ln(1)e, respectively] in 1A−5A to tetrakis-monodentate [through O(11), O(9), O(11)e and O(9)e toward Ln(1), Cu(1), Ln(1)e and Cu(1)e, respectively] in (1B−5B) (see Figure 4). In order to allow this change of the coordination of bta(3) in 1B−5B, the interlayer separation is reduced by ca. 1.0 Å and bta(3) slightly rotates over the axis defined by the two

carboxylate groups coordinated to the Ln(III) ions. Therefore, the dihedral angle between the Ln(III)-coordinated carboxylate groups and the benzene ring changes from 7.3(8). 7.3(5), 7.3(5), 9.8(6) and 5.0(5)° (1A−5A) to 16.5(3), 15.7(6), 17.5(3), 16.5(4) and 15.4(5)° (1B−5B). Also, the free carboxylate groups in 1A−5A which are almost perpendicular to the coordinated ones [81.1(4), 83.2(9), 82.7(8), 79.4(9) and 86.3(9)° for 1A−5A, respectively] rotate to coordinate the copper(II) ions [73.0(5), 73.2(8), 71.5(4), 72.5(6) and 71.6(6)° for 1B−5B, respectively]. Considering the Cu(II)−Ln(III) dinuclear units as single nodes, the topological structure of 1A−5A is built up by one 5fold and three 4-fold connectors, giving rise to a [4462]3[446482] (4,5)-binodal network18 (according to the extended Schläfli notation). Once the phase transition takes place, and considering the dinuclear units are single nodes, the topological structure of 1B−5B is constructed by three 4-fold and two 5fold connectors, giving a [4284][4462]4[4664]4 (4,4,5)-threeF



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these problems consists of preparing an isomorphous complex where the paramagnetic 3d metal ion is replaced by the diamagnetic Zn2+ cations. With this procedure, it is possible to calculate the difference between the χMT3d‑Ln and χMTZn−Ln curves. The magnetic behavior of the Zn(II)−Ln(III) complexes must obey that of the magnetically isolated cation. The difference between the magnetic behavior of the isomorphous [Zn(II)−Ln(III)] and [M(II)−Ln(III)] complexes would be a good approach to establish the nature of the weak M(II)−Ln(III) magnetic interaction, if any. Although all our attempts to prepare the isomorphous Ln(III)−Zn(II) compounds of 1A−5A have been unsuccessful, the magnetostructural study of 1A (where the diamagnetic La3+ occurs) that we carried out here, together with previous reports by other authors on the Cu(II)−Ln(III) heterodinuclear units,20 allowed us to analyze the magnetic pathways existing in the threedimensional compounds 1A−5A. Freshly prepared crushed crystals of 1A−5A were used in the magnetic measurements to guarantee the reliability of the data collected. The magnetic properties are shown under the form of a χMT versus T plot where χM is the magnetic susceptibility per either two copper(II) ions (1A) or one Cu(II)−Ln(III) pair (2A−5A) [Figures 6 (1A), 7 (2A−4A) and 8 (5A)].

nodal network. As far as we are aware, the present topologies are only observed in these coordination compounds8 [see Figure 2 (right) and Figure 3 (right)]. The two independent dinuclear Cu(II)−Ln(III) units in both families regularly alternate along the [10̅ 1] direction within each layer, the position of the metal ions above or below the layer being inverted to afford a Ln(III)/Cu(II)Ln(III)/ Cu(II)Cu(II)/Ln(III)Cu(II)/Ln(III) sequence. Due to this alternation and the stacking of the layers, the minimum interlayer M···M distance occurs between Cu(II) and Ln(III) ions, with values slightly longer than the shortest intralayer copper−copper, copper−lanthanide and lanthanide−lanthanide separations (see Table 2). Table 2. Shortest Intralayer Metal−Metal Separations (Å) in 1A−5A and 1B−5Ba compd

Cu(1)···Cu(2)

Cu(1)···Ln(1)

Cu(2)···Ln(2)

Ln(1)···Ln(2)

1A 2A 3A 4A 5A 1B 2B 3B 4B 5B

5.784(2) 5.7795(17) 5.7767(16) 5.765(2) 5.7422(17) 5.6905(16) 5.6792(9) 5.6756(16) 5.675(2) 5.6658(19)

4.1282(15) 4.1075(11) 4.1054(11) 4.0991(13) 4.0694(13) 4.1093(10) 4.1015(7) 4.0992(10) 4.0833(14) 4.0559(13)

4.1374(15) 4.1169(12) 4.1088(11) 4.1010(13) 4.0548(12) 4.1281(10) 4.1241(7) 4.1041(10) 4.1078(14) 4.0840(12)

6.5691(18) 6.5551(17) 6.5224(17) 6.4132(18) 6.5041(17) 6.6694(17) 6.6174(5) 6.5636(17) 6.6366(18) 6.6238(18)

a

Ln = LaIII (1A/1B), CeIII (2A/2B), PrIII (3A/3B), NdIII (4A/4B) and SmIII (5A/5B).

The two families show channels along the crystallographic aaxis, where several crystallization water molecules are hosted. Their number remains undetermined because of the high mobility that they exhibit within the channels. These water molecules occupy a volume of about 1462.7/909 (1A/1B), 1452/948 (2A/2B), 1373/843 (3A/3B), 1327/896 (4A/4B) and 1358/894 Å3 (5A/5B) per unit cell, values which account for percentages of 29.3/20.7 (1A/1B), 29.3/21.6 (2A/2B), 28.2/19.6 (3A/3B), 27.6/20.6 (4A/4B) and 28.0/20.7 % (5A/ 5B) of the total volume. The difference between the open and closed forms is striking: the bonding structure of the framework is slightly changed, involving the torsion of the interlayer bta4− ligand to coordinate to two extra metal ions. This results in the compression of the crystallographic b-axis by more than 2.0 Å, and the consequent decrease of the unit cell volume by over 12 (1B), 11.5 (2B and 3B), 9.5 (4B) and 10.7 % (5B). Magnetic Properties of 1A−5A. During the past years the nature and the magnitude of the factors that govern the magnetic properties of the mixed 3d−4f complexes have been thoroughly investigated.19 In general, the magnetic behavior even for the simplest 3d−4f heterodinuclear units is determined by different phenomena: (i) the first-order angular momentum of the trivalent lanthanide ion (with the exception of the Gd3+ and the diamagnetic La3+ and Lu3+ ions) which prevents the use of the spin-only formalism; (ii) the value of the crystal field splitting of the rare-earth element which is usually on the order of kT at room temperature, so that the thermal population of the Stark levels has to be implicitly taken into account; (iii) the weak exchange interaction between the paramagnetic 3d and 4f metal ions whose nature and magnitude can be masked by the orbital contribution, crystal field effects and intermolecular interactions. One of the most common procedures to overcome

Figure 6. Temperature dependence of the χMT plot for 1A: (○) experimental data; () best-fit curve through eq 1 (see text). The inset shows the χM versus T plot in the low temperature region.

Let us start with compound 1A where the presence of the diamagnetic La(III) cation simplifies the treatment and discussion of its magnetic behavior. At room temperature, χMT for 1A is equal to 0.82 cm3 mol−1, a value which is as expected for two magnetically isolated spin doublets (SCu = 1/2 with gCu = 2.1). This value remains practically constant when cooling until 30 K and it further decreases to ca. 0.40 cm3 mol−1 K at 2.0 K (Figure 6). A maximum on the magnetic susceptibility is observed at 3.1 K. These features are typical of a weak antiferromagnetic coupling between the copper(II) ions. An inspection of the structure shows that the exchange pathway responsible for this coupling would be the two arms linking Cu(1) and Cu(2) which are defined by O(6)C(9)C(4)C(5)C(10)O(7) and O(13)C(26)C(20)C(21)C(27)O(15) (see Figure 5). Consequently, the magnetic data of 1A were treated by means of a simple Bleaney−Bowers expression for two spin doublets derived through the Hamiltonian H = −JSCu1·SCu2 (eq 1) G



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Figure 7. Plots of χMT versus T for compounds 2−4 from a to c, respectively. The insets show the χM−1 against T plots: (○) experimental data; () best-fit curve through Curie−Weiss law (see text).

4H2O with terpy = 2,2′:6′,2″-terpyridine and H2phta = phthalic acid (J = −0.28 cm−1).22 The fact that only one of two dicarboxylate arms connects equatorial sites of the two copper(II) ions in this dinuclear species instead of two of these arms in 1A accounts for the weaker magnetic coupling in the terpy-containing complex. As far as for the magnetic properties of 2A−4A are concerned, it deserves to be noted that the ground state of Ln(III) ion in this series is well separated in energy from the first excited state (see Table 3), and their contribution at high Table 3. Electronic Configuration, Ground State, χMT Value in the Free-Ion Approximation and Energy Gap between the Ground State and the First Excited One for the Trivalent Rare-Earth Cations in 1A−5A Figure 8. Dependence with the temperature of the χMT for compound 5A. 2

−1

χM = (2Nβg /kT )[3 + exp( −J /kT )]

(1)

where J is the magnetic coupling and N, β, g and k have their usual meaning. Least-squares best fit parameters are J = −3.5 cm−1 and g = 2.09. This weak magnetic coupling can be understood by simple orbital symmetry considerations. The molecular orbital which defines the unpaired electron at each copper(II) ion [Cu(1) and Cu(2) atoms], the so-called magnetic orbital, is of the d(x2−y2) type with the x and y axes corresponding roughly to the equatorial Cu−Ocarboxylate bonds]. The σ-overlap between these equatorially located magnetic orbitals through the two −OCCCCO− multiatom bridges [Cu(1)···Cu(2) = 5.784(2) Å] is predicted to be very poor. As the antiferromagnetic coupling in a dicopper(II) unit is proportional to the square of the overlap integral,21 a weak magnetic coupling is predicted for 1A, as observed. The value of J obtained by fit for 1A is of the same nature but somewhat greater than the one reported by some of us for the dicopper(II) complex of formula [Cu2(terpy)2Cl2(μ-phta)]·

Ln(III)

electronic configuration

La(III) Ce(III) Pr(III) Nd(III) Sm(III)

4f0 4f1 4f2 4f3 4f5

ground state

χMTcalc/cm3 mol−1 K

ΔE /cm−1

0.80 1.60 1.64 0.09

2200 2100 1900 700

1

S0 F5/2 3 H4 4 I9/2 6 H5/2 2

temperature should follow the free ion approximation.21c At 300 K, the values of χMT are equal to 1.24 (2A), 2.03 (3A) and 1.92 cm3 mol−1 K (4A), which correspond to the expected ones for a magnetically non-interacting CuII−LnIII pair through eq 2, χM T = (Nβ 2gCu 2 /3k)[SCu(SCu + 1)] + (Nβ 2gLn 2 /3k) [JLn (JLn + 1)]

(2)

with SCu = 1/2, gCu = 2.1, gLn = 6/7 (Ce), 4/5 (Pr) and 8/11 (Nd), and JLn = 5/2 (Ce), 4 (Pr) and 9/2 (Nd). Upon cooling down, χMT monotonically decreases, first smoothly from room temperature to ca. 100 K and further sharply to reach minimum values of 0.48 (2A), 0.19 (3A) and 0.71 cm3 mol−1 K (4A) at 2.0 K. In the temperature range from 35 to 300 K, the plot of H



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χM−1 vs T was fitted following a Curie−Weiss law (see inset Figures 7a−c), being C = 1.59 (2), 2.22 (3) and 4.47 cm3 mol−1 K (4) and θ = −25.93 (2), −42.01 (3) and −34.56 K (4) the best-fit parameters in this temperature range. The decrease of χMT in the high temperature domain is mainly due to the splitting of the 6- (Ce), 9- (Pr) and 10-fold (Nd) degenerate 2 F5/2 (Ce), 3H4 (Pr) and 4I9/2 (Nd) ground states into Stark levels by the crystal-field effects and the progressive depopulation of the higher energy levels when the temperature is lowered. The antiferromagnetic interaction between the copper(II) ions observed in 1A, which also occurs in 2A−4A, contributes to the abrupt decrease of χMT in the low temperature region. In addition to this exchange pathway, the magnetic coupling within the CuII−LnIII pair and that through the benzene ring of the bta4− ligand could be also involved. In fact, this last one has to be discarded in the light of previous magnetostructural studies on bta-bridged systems.23 Focusing on the efficiency of the double-carboxylate-bridged CuII−LnIII pair, one can see that the value of χMT at 2.0 K for 3A (0.19 cm3 mol−1 K) is practically identical to that observed in 1A [0.22 cm3 mol−1 K per one copper(II) ion]. So, the magnetic interaction, if any, between CuII and PrIII is practically nonexistent. This conclusion is consistent with the fact that the ground term 3H4 of the praseodymium(III) cation can give rise to a singlet ground Stark level. However, the values of χMT for 2A and 4A at 2.0 K which are well above that observed for 1A [per mol of copper(II) ion] do not allow one to ascertain the nature of the magnetic interaction within the CuII−CeIII and CuII−NdIII couples. Anyway, previous magnetostructural studies on diphenoxo-20a,b or oxamato-bridged24 CuII−LnIII pair (Ln = Ce, Pr and Nd) cations have revealed the occurrence of very weak antiferromagnetic interactions whose magnitude remains undetermined. The magnetic behavior of compound 5A is more complicated. The 6H ground term of Sm(III) ion is split into six levels as a consequence of the spin−orbit coupling, increasing its energy from 6H5/2 to 6H15/2. Since the spin− orbit parameter is small enough (λ ca. 200 cm−1), the first and even higher excited states are not far from the ground state, and therefore, they can be populated at room temperature.21c In this case, the magnetic susceptibility deviates from free ion approximation as a result of the population at relatively high temperatures of exited states. The theoretical χMT value for the Sm(III) ion would be ca. 0.1 cm3 mol−1 K if the ground multiplet were the only state populated (see Table 3). However, as the higher excited states are populated in a large range of temperatures, the experimental values of χMT per one samarium(III) ion at room temperature vary in the range to 0.3−0.4 cm3 mol−1.21c,25 The χMT vs T plot for 5A (see Figure 8) decreases almost linearly from 0.65 cm3 mol−1 K at 300 K to 0.38 cm3 mol−1 K at 30 K, this decrease being mainly due to the effect of spin−orbit coupling of the Sm(III) ions. Below 30 K, a sharp decrease is observed, reaching a value of 0.14 cm3 mol−1 K at 2.0 K. The fact that this value is somewhat below that observed in 1A [per one copper(II) ion] may indicate the occurrence of an antiferromagnetic interaction between the CuII and the SmIII cations in 5A. This is in good agreement with other metal− organic systems containing Cu(II)−Sm(III) units.20b−d,24 On the Structural Transformation. A literature survey shows that different structural transformations in guestresponsive metal−organic frameworks have been extensively studied, mainly those involving a single crystal to amorphous

phase or the less common single crystal to single crystal transformations.26 Nevertheless the number of MOF compounds that present a phase transition induced to external stimulus are still scarce.2 The low dimensional compounds have a structural freedom which allows the recombination of the coordination bonds, giving rise to the new topologies and therefore new phases.27 Nevertheless, this ability is not common in 3D frameworks, where the metal−organic frameworks are much more rigid. The present complexes have the extraordinary ability to change the coordination mode of the pillared organic ligand as a consequence of the change in the coordination environment of the copper(II) ions. This dynamic effect is closely related with the Jahn−Teller character of the copper(II) ions that allow a carboxylate-assisted water migration, the apical position at the copper(II) ion being filled by a weakly coordinated water molecule in the 1A−5A phases. Nevertheless, once the crystal is in a dry atmosphere (1B−5B phases), these coordination water molecules are not anchored anymore at the copper environment, and this position is occupied by a neighboring carboxylate-oxygen atom. At this point, the crystal-to-crystal phase transition is reversible and the crystallinity is kept. However, we wonder if the crystal structure will remain unaltered after a full dehydration process. It was tested in two different ways: in the first one, the crystal was warmed under a dry-nitrogen atmosphere (ca. 80 °C), whereas in the second one, the crystals were kept in a dry atmosphere for a long time (over 24 hours). In both cases, the final result was the same, the color and the crystal shape was unaltered but the crystallinity was lost, and after this point a rehydration process is not enough to recover the sample crystallinity.

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CONCLUSIONS In summary, we have prepared and structurally characterized five heterometallic 3d−4f polymeric architectures, which present a remarkable ability to transform from expanded to shrinking phases only in a dry atmosphere. This phase change involves a compression along the crystallographic b-axis greater than 2 Å, and a consequent modification in the unit cell volume ranged from 9.5 to 12%. The structural phase transition between 1A−5A toward 1B−5B involves mainly the change in the coordination mode of the pillared bta4− ligand, which produces a remarkable modification in the system topology, the basic metal−organic frameworks remaining almost unchanged after the phase transition. The [Cu(II)−Ln(III)] dinuclear units are formed through a double anti-syn carboxylate bridge, an unprecented structural feature in 3d−4f dinuclear units. Complexes 1−5 are isomorphous, having a covalent bonded 3D polymeric network with rectangular cavities partially occupied by crystallization water molecules. A clear decrease in the Ln−Ocarboxylate and Ln−Ow bond distances has been observed with increase of the atomic number of the lanthanide ion (from lanthanum to samarium), and this effect is closely related to the lanthanide contraction effect. The low temperature magnetic study in 1A shows the occurrence of weak antiferromagnetic interactions; this behavior has been interpreted as a weak interdinuclear interaction, between the copper(II) ions through the two −OCCCCO− multiatom bridges, the metal−metal separation being 5.784(2) Å. This exchange pathway coexists in 2A−5A together with that concerning the double anti-syn carboxylatebridged Cu(II)−Ln(III) pair. Although our magnetic data clearly support the occurrence of a weak antiferromagnetic I



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(7) Fabelo, O.; Pasán, J.; Lloret, F.; Julve, M.; Ruiz-Pérez, C. CrystEngComm 2007, 9, 815−827. (8) Fabelo, O.; Canadillas-Delgado, L.; Pasan, J.; Diaz-Gallifa, P.; Labrador, A.; Ruiz-Perez, C. CrysEngComm 2012, 14 (3), 765−767. (9) Henisch, H. K. Crystal Growth in Gels; The Pennsylvania State Univ. Press: Pittsburgh, 1970. (10) Agilent, CrysAlis PRO; Agilent Technologies: Yarnton, Oxfordshire, England, 2012. (11) HKL-2000: Otwinowski, Z.; Minor, W. Processing of X-ray Diffraction Data Collected in Oscillation Mode. In Methods in Enzymology, Volume 276: Macromolecular Crystallography, Part A; Academic Press: New York, 1997; pp 307−326. (12) Sheldrick, G. M. Acta Crystallogr., A 2008, 64, 112−122. (13) Nardelli, M. J. Appl. Crystallogr. 1995, 28, 659. (14) Spek, A. L. J. Appl. Crystallogr. 2003, 36, 7−13. (15) DIAMOND 2.1d, Crystal Impact GbR, CRYSTAL IMPACT, K. Brandenburg & H. Putz GbR, Postfach 1251, D-53002 Bonn, Germany, 2000. ́ (16) Ribas Gispert, J. Quimica de Coordinacion; Ediciones Omega, S.A., 2000. (17) Addison, A. W.; Rao, T. N.; Reedijk, J.; Van Rijn, J.; Verschoor, G. C. J. Chem. Soc., Dalton Trans. 1984, 1349−1356. (18) Blatov, V. A. IUCr CompComm Newsl. 2006, 7, 4−38. (19) (a) Figuerola, A.; Diaz, C.; Ribas, J.; Tangoulis, V.; Granell, J.; Lloret, F.; Mahia, J.; Maestro, M. Inorg. Chem. 2003, 42, 641−649. (b) Stoian, S. A.; Paraschiv, C.; Kiritsakas, N.; Lloret, F.; Munck, E.; Bominaar, E. L.; Andruh, M. Inorg. Chem. 2010, 49, 3387−3401. (c) Sarwar, M.; Madalan, A. M.; Lloret, F.; Julve, M.; Andruh, M. Polyhedron 2011, 30, 2414−2420. (d) Liu, F.-C.; Zeng, Y.-F.; Jiao, J.; Li, J.-R.; Bu, X.-H.; Ribas, J.; Batten, S. R. Inorg. Chem. 2006, 45, 6129−6131. (20) (a) Jana, A.; Majumder, S.; Carrella, L.; Nayak, M.; Weyhermueller, T.; Dutta, S.; Schollmeyer, D.; Rentschler, E.; Koner, R.; Mohanta, S. Inorg. Chem. 2010, 49, 9012−9025. (b) Costes, J. P.; Dahan, F.; Dupuis, A.; Laurent, J. P. Chem.Eur. J. 1998, 4, 1616−1620. (c) Gheorghe, R.; Cucos, P.; Andruh, M.; Costes, J. P.; Donnadieu, B.; Shova, S. Chem.Eur. J. 2006, 12, 187−203. (d) He, F.; Tong, M. L.; Yu, X. L.; Chen, X. M. Inorg. Chem. 2005, 44, 559− 565. (e) Wojciechowski, W.; Legendziewicz, J.; Puchalska, M.; Ciunik, Z. J. Alloys Compd. 2004, 380, 285−295. (f) Sanz, J. L.; Ruiz, R.; Gleizes, A.; Lloret, F.; Faus, J.; Julve, M.; BorrasAlmenar, J. J.; Journaux, Y. Inorg. Chem. 1996, 35, 7384−7393. (g) Alexandru, M. G.; Visinescu, D.; Madalan, A. M.; Lloret, F.; Julve, M.; Andruh, M. Inorg. Chem. 2012, 51, 4906−4908. (21) (a) Girerd, J. J.; Charlot, M. F.; Kahn, O. Mol. Phys. 1977, 34, 1063−1076. (b) Kahn, O.; Charlot, M. F. New J. Chem. 1980, 4, 567. (c) Kahn, O. Molecular Magnetism; VCH: New York, 1993. (22) Cano, J.; De Munno, G.; Sanz, J. L.; Lloret, F.; Faus, J.; Julve, M. ́ Int. Ed. 1997, 93, 174−181. An. Quim. (23) Fabelo, O.; Pasán, J.; Cañadillas-Delgado, L.; Delgado, F. S.; Labrador, A.; Lloret, F.; Julve, M.; Ruiz-Pérez, C. Cryst. Growth Des. 2008, 8 (11), 3984−3992. (24) Kahn, M. L.; Mathonière, C.; Kahn, O. Inorg. Chem. 1999, 38, 3692−3697. (25) Casey, A. T., Mitra, S., Boudreaux, E. A., Mulay, L. N., Eds. Theory and Applications of Molecular Paramagnetism; Wiley: New York, 1976; p 271. (26) (a) Maji, T. K.; Mostafa, G.; Matsuda, R.; Kitagawa, S. J. Am. Chem. Soc. 2005, 127, 17152−17153. (b) Zhang, J.-P.; Lin, Y.-Y.; Zhang, W.-X.; Chen, X.-M. J. Am. Chem. Soc. 2005, 127, 14162− 14163. (c) Myunghyun, P. S.; Jung, W. K.; Hye, J. C. J. Am. Chem. Soc. 2002, 124, 10976−10977. (d) Cussen, E. J.; Claridge, J. B.; Rosseinsky, M. J.; Kepert, C. J. J. Am. Chem. Soc. 2002, 124, 9574− 9581. (e) Armentano, D.; De Munno, G.; Mastropietro, T. F.; Julve, M.; Lloret, F. J. Am. Chem. Soc. 2005, 127, 10778−10779. (f) Armentano, D.; Mastropietro, T. F.; De Munno, G.; Rossi, P.; Lloret, F.; Julve, M. Inorg. Chem. 2008, 47, 3772−3786.

coupling for this pair only in the case of 5A, weak antiferromagnetic interactions have been stated for this pair of cations with the 4f1-4f6 electronic configurations of the LnIII cation according to the Kahn et al. model.24,28

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ASSOCIATED CONTENT

S Supporting Information *

Photography with the crystal morphology for 1A−5A, the TG and DTG plots for 1A−5A, the curve of the variation of the average values of the Ln−Ocarboxylate and Ln−Ow bond lengths as a function of the atomic number for 1A−5A and 1B−5B, Xray crystallographic data in CIF format and selected bond lengths and angles for 1A−5A (Table S1a) and for 1B−5B (Table S1b) and the powder diffraction pattern of 1A−5A. This material is available free of charge via the Internet at http:// pubs.acs.org.

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AUTHOR INFORMATION

Corresponding Authors

*Fax: 33 (0)476207648. Tel: 33 (0)476207629. E-mail: [email protected]. *Fax: 34 922318320. Tel: 34 922318236. E-mail: [email protected]. Notes

The authors declare no competing financial interest.

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ACKNOWLEDGMENTS Funding for this work was partially provided Ministerio Español de Economia y Competitividad through Projects MAT201016981, MAT2011-27233-C0-02, DPI2010-21103-C04-03, CTQ2010-15364 and “Factoriá de Cristalización” (Consolider-Ingenio2010, CSD2006-00015), the Gobierno de Canarias through projects PIL2070901 and structuring NANOMAC and the Generalitat Valenciana (PROMETEO2009/108 and ISIC/ 2012/002). P.D-G. and J.P. also thank Ministerio Español de Economia y Competitividad through FPI program and the NANOMAC project for predoctoral and postdoctoral contracts, respectively.

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REFERENCES

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