Crystal Engineering of Complexes of Propane-1,2,3-tricarboxylic Acid (H3tca) with Lanthanide(III) Cations† Laura Cañadillas-Delgado,‡ Oscar Fabelo,‡ Jorge Pasán,‡ Fernando S. Delgado,‡,§ Maríadel Déniz,‡ Eliezer Sepúlveda,‡ María-Milagros Laz,4 Miguel Julve,# and Catalina Ruiz-Pérez*,‡
CRYSTAL GROWTH & DESIGN 2008 VOL. 8, NO. 4 1313–1318
Laboratorio de Rayos X y Materiales Moleculares, Departamento de Física Fundamental II, Facultad de Física, UniVersidad de La Laguna, AV. Astrofísico Francisco Sánchez s/n, 38204 La Laguna (Tenerife), Spain, BM16 - LLS European Synchrotron Radiation Facility, 6 Rue Jules Horowitz - BP 220 38043 Grenoble CEDEX 9, France, Laboratorio de Rayos X y Materiales Moleculares, Departamento de Edafología y Geología, Facultad de Biología, UniVersidad de La Laguna, AV. Astrofísico Francisco Sánchez s/n, 38204 La Laguna (Tenerife), Spain, and Instituto de Ciencia Molecular/Departamento de Química Inorgánica, Facultat de Química, UniVersitat de València, Polígono de La Coma s/n, 46980-Paterna (Valencia), Spain ReceiVed NoVember 5, 2007; ReVised Manuscript ReceiVed January 1, 2008
ABSTRACT: The knowledge of the one-synthon based supramolecular network of the propane-1,2,3-tricarboxylic acid (H3tca), commonly referred to as tricarballylic acid (1), induced us to look for new architectures of tricarballylate-containing lanthanide(III) cations having in mind that the structure of the complex [Ce(tca)(H2O)2]n is the only reported example of this type of compounds. Three novel complexes of formulas [Gd(tca)(H2O)3]n · nH2O (2), [Eu(tca)(H2O)3]n · nH2O (3), and [La2(tca)2(H2O)5]n · 4nH2O (4) have been synthesized, and their structures have been determined by X-ray diffraction on single crystals. 2 and 3 are isomorphous compounds. They exhibit a layered structure where the lanthanide atoms are nine-coordinated with three water molecules and six carboxylateoxygen atoms building a monocapped square antiprism surrounding and the tca ligands adopting a tris-bidentate coordination mode. 4 has a three-dimensional structure where two 10-coordinated, crystallographically independent lanthanum atoms [La(1) and La(2)] occur with three/two [La(1)/La(2)] water molecules and seven/eight [La(1)/La(2)] carboxylate-oxygens describing bicapped square antiprism surroundings. Two different tca groups are present in 4 both having in common the tris-bidentate coordination mode but acting in addition as monodentate and bis-monodentate ligands through one and two carboxylate groups, respectively. Introduction Metal-organic framework (MOF) materials have attracted much attention in recent years due to their potential applications in a wide variety of research fields, such as catalysis, ion exchange, and molecular separations.1 Gas storage is one very promising application of these materials, and a lot of attention has been devoted to it.2–5 As a part of our current research work, we are investigating lanthanide-containing MOFs with the goal of harnessing the coordination geometry and properties of these elements.6–10 We are interested in exploring new applications of MOFs, particularly sensing and molecular recognition. The higher coordination numbers associated with lanthanide cations may allow for a more versatile chemistry on the basis of the available coordination sites. The construction of these framework materials typically consists of the assembly of metal centers through multifunctional organic linkers,11–15 and their syntheses become more and complicated depending on the specific properties that one would like to get associated to them. That is why the choice of a suitable ligand is so crucial. In this respect, the knowledge of the pattern that could govern the architecture of our new compounds (crystal engineering) is a very useful tool. † In memoriam Prof. Xavier Solans. The authors have greatly benefited from numerous scientific discussions with Prof. Xavier Solans on X-ray diffraction, and they much enjoyed his enthusiasm, creativity, saVoir faire, and pedagogic virtues. Unfortunately, he passed away recently, but he will remain in our memory forever. * To whom correspondence should be addressed. E-mail:
[email protected]. ‡ Facultad de Física, Universidad de La Laguna. § BM16 - LLS European Synchrotron Radiation Facility. 4 Facultad de Biología, Universidad de La Laguna. # Universitat de València.
Scheme 1. (a) Tricarballylic Acid (H3tca) and (b) the Synthon Unit
With these considerations in mind, we have chosen propane1,2,3-tricarboxylic acid (tricarballylic acid, H3tca) as the organic linker.15–19 Two important features concerning this molecule deserve to be outlined: (a) the carboxylic groups adopt a T-shape conformation that would lead to (6,3) type networks with brickwall or herringbone morphologies, and (b) the three carboxylic fragments generated the supramolecular synthon depicted in Scheme 1b, which would promote high-dimensional networks. Indeed, the crystal structure of the H3tca (1) was reported by Barnes and Paton in 1988, but scarce attention was paid in their description to its supramolecular structure, only noting that “the molecules are linked into double sheets by hydrogen bonding”.15 A detailed account of the structure is noteworthy on the basis of such a work. The crystal structure of 1 consists of a one-synthon-based supramolecular network with a (6,3) topology where the T-shape morphology of this ligand leads to a 3-fold interpenetrated herringbone structure. This network is made up of tca units linked via a synthon (Scheme 1b) to form waving layers with rectangular tile-like motifs of dimensions ca. 16 × 7 Å2 disposed on adjacent rows in a herringbone fashion (Figure 1a). These tiles are intertwined in a parallel fashion with two other symmetry-related herringbone sheets (Scheme 2). The 3-fold
10.1021/cg7010925 CCC: $40.75 2008 American Chemical Society Published on Web 03/11/2008
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Figure 2. Space filling view with three intertwined sheets leading to entangled layers stacked along the c axis.
Scheme 3. (a-d) Coordination Modes of the tca Ligand with Lanthanide(III) Cations
Figure 1. A view of the herringbone tiled-pattern along the c direction (a) and the side view of the same layer showing the waving (b).
Scheme 2
interpenetration is allowed by the waving of the layers (Figure 1b), with a periodicity equal to three times the length of the a cell parameter [15.793(2) Å]. These interpenetrated herringbone layers lead to an overall two-dimensional (2D) entangled network of 10 Å width, which is stacked along the c-axis (see Figure 2). Propane-1,2,3-tricarboxylic acid is a very aesthetic T-shaped 3-fold connector, and its synthons only act as linkers (linear nodes). The angles between the three carboxylate carbon atoms (the T-branches) taking the central carbon atom of the propane skeleton as the T-node are 99.99(11), 98.95(10), and 129.13(9)°, and at the same time, and despite the flexibility of the ligand, it adopts a quasi-planar conformation with the maximum
deviation from the mean plane of carbon atoms being 0.677(3) Å. Then, the tca could be envisaged as a 3-fold connector for the construction of metal-organic (6,3) networks. One approach to obtain a desired morphology of the network is to connect adequate metal nodes with linear exobidentate ligands.20 Rather less common is to find the molecule as a node, because the molecule (or tectons) itself rarely adopts the desired geometry.21,22 T-shaped units such as H3tca in 1 combined with suitable metal cations could afford structures with 2D brickwall and herringbone or one-dimensional (1D) ladder morphologies.21 The lanthanide ions with large ionic radii and highcoordination numbers seem to be adequate to promote the chelating conformation for the carboxylate groups and act therefore as nodes of the resulting networks, like the synthons of 1. To the best of our knowledge, only one crystal structure23 has been reported to date based on Ln(III) using tca as bridging ligand, namely [Ce(tca)(H2O)2]n. Single crystals of this compound were obtained by hydrothermal recrystallization of powder samples. Its crystal structure presents a three-dimensional (3D) network where the Ce(III) atoms are nine coordinated and the three-carboxylate groups of the tca ligand exhibit different bridging modes, bidentate, bidentate/monodentate and syn-syn bis-monodentate (Scheme 3d). However, the reliability of the T-shape of the tca ligand remains to be tested since its intrinsic flexibility opens other
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Figure 3. Electronic microscope photographs of compound 2 showing the exceptional growing of the crystals [500 (a), 50 (b), and 20 µm (c)]. Table 1. Crystal Data and Details of Structure Determination compound formula M crystal system space group a, Å b, Å c, Å β, (°) V, Å3 Z T (K) index ranges Fcalc (Mg m-3) λ (Mo KR, Å) µ (Mo KR, mm-1) R1, I > 2σ(I) (all) wR2, I > 2σ(I) (all) measurement reflections (Rint) independent reflections (I > 2σ(I)) crystal size (mm)
2
3
4
C6H13GdO10 402.41 monoclinic P21/c 6.7999(6) 21.193(2) 8.5305(4) 105.125(5) 1186.75(16) 4 293(2) -9 e h e 6 -25 e k e 28 -8 e l e 11 2.252 0.71073 5.630 0.0685 (0.1014) 0.1543 (0.1763) 7752 (0.1152) 2949 (2152) 0.02 × 0.06 × 0.08
C6H13EuO10 397.12 monoclinic P21/c 6.8138(6) 21.219(2) 8.5434(10) 105.176(7) 1192.1(2) 4 293(2) -7 e h e 8 -24 e k e 27 -11 e l e 6 2.213 0.71073 5.302 0.0502 (0.0907) 0.0876 (0.0983) 6651 (0.0511) 2642 (1871) 0.02 × 0.02 × 0.02
C12H28La2O21 786.16 monoclinic P21/n 9.5386(6) 14.0679(11) 17.0679(15) 97.466(7) 2270.9(3) 4 293(2) -12 e h e 7 -16 e k e 18 -22 e l e 21 2.299 0.71073 3.811 0.0389 (0.0767) 0.0757 (0.0873) 12444 (0.0426) 5078 (3392) 0.02 × 0.02 × 0.02
possible configurations (for example, the Y one). The present contribution is devoted to clarify this question, and hence, we report the synthesis and the crystal structure of three novel tricarballylate bridged metal-organic hybrid networks having the molecular formulas [Ln(tca)(H2O)3]n · nH2O with Ln ) Gd (2) and Eu (3) and [La2(tca)2(H2O)5]n · 4nH2O (4). Experimental Section Materials. Reagent and solvents used in all the synthesis were purchased from commercial sources and used without further purification. Syntheses of the Complexes. Highly insoluble powder samples of lanthanide-containing tca compounds obtained by precipitation from aqueous solutions at pH 4–5 were investigated previously.24 The fast nucleation and growth of these species preclude the formation of single crystals as observed in the electronic microscopy (EM) images (Figure 3). Therefore, crystal growth techniques are required to prepare single crystals of this series of compounds. The use of the silica gel medium, aiming at decreasing the diffusion rate, allowed us to grow X-ray quality crystals of 2–4 through the techniques described by Henish.25 [Gd(tca)(H2O)3]n · nH2O (2). An aqueous solution of sodium hydroxide was poured into a solution 0.05 M of tricarballylic acid (10 mL) adjusting the pH to 5.20. Then, tetramethoxysilane (1 mL) was added dropwise under continuous 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. Finally, an aqueous solution of gadolinium(III) nitrate hexahydrate 0.1 M (2.5 mL) was carefully placed over the gel, avoiding damages on its surface. The tubes were stored at 30 °C, and X-ray quality colorless prismatic crystals of 2 appeared after a few days. [Eu(tca)(H2O)3]n · nH2O (3). A similar procedure was followed to synthesize compound 3. The pH of a solution 0.02 M (5 mL) of tricarballylic acid was adjusted to 4.40 with an aqueous solution of potassium hydroxide. Tetramethoxysilane (0.5 mL) was added dropwise
to the previous solution under continuous stirring, and the resultant mixture was transferred into test tubes. Once the gel was formed, an aqueous solution 0.033 M (1.5 mL) of europium(III) nitrate hexahydrate was carefully layered over the gel. X-ray suitable colorless prisms of 3 were grown after a few days. [La2(tca)2(H2O)5]n · 4nH2O (4). Compound 4 was obtained by a procedure similar to that of 3, but fixing the pH to 3.50. An aqueous solution of 0.067 M lanthanum(III) nitrate hexahydrate (3 mL) was added over the gel. X-ray quality colorless prisms of 4 were formed after a few days. Crystallographic Data Collection and Structural Determination. Single crystals of 2–4 were mounted on a Nonius Kappa CCD diffractometer.26 Diffraction data were collected at 293(2) K using graphite-monochromated Mo KR radiation (λ ) 0.71073 Å). A summary of the crystallographic data and structure refinement is given in Table 1. The structures were solved by direct methods and refined with full-matrix least-squares technique on F2 using the SHELXS-97 and SHEXL-97 programs27 included in the WINGX software package.28 All non-hydrogen atoms were refined anisotropically. The hydrogen atoms of the tca ligand were set in calculated positions for 2 and 3, whereas they where located from difference maps in 4. All hydrogen atoms were refined isotropically. The final geometrical calculations and the graphical manipulations were carried out with PARST95,29 PLATON,30 and DIAMOND31 programs. Selected bond lengths and angles as well as hydrogen bonds of compounds 2–4 are listed in Tables 2 (2 and 3) and 3 (4). Description of the Structures. [Gd(tca)(H2O)3]n · nH2O (2) and [Eu(tca)(H2O)3]n · nH2O (3). The complexes 2 and 3 are isostructural. Their structure consists of 2D (6,3) brick-wall networks parallel to the (101) plane where the [Ln(H2O)3]3+ units and the (tca)3- groups act as 3-fold nodes and 3-fold connectors, respectively (see Figure 4a). The rectangular tiles are of approximate dimensions 9 × 5 Å2. The layers are stacked along the b axis following the ABCDABCD sequence (Figure 4b), A and B being related by an inversion center while the AB and CD pairs do it by a c-glide plane. The interlayer separation between
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Table 2. (a) Selected Bond Lengths (Å) and Angles (°) and (b) Intermolecular Contacts of 2 and 3 2
3
(a) Selected Bond Lengths (Å) and Angles (°) of 4a
(a) Selected Bond Lengths (Å) and Angles (°)a Gd(1)-O(1) 2.433(8) Eu(1)-O(1) Gd(1)-O(2) 2.503(9) Eu(1)-O(2) Gd(1)-O(3a1) 2.521(8) Eu(1)-O(3a1) Gd(1)-O(4a1) 2.473(8) Eu(1)-O(4a1) Gd(1)-O(5b1) 2.527(9) Eu(1)-O(5b1) Gd(1)-O(6b1) 2.439(8) Eu(1)-O(6b1) Gd(1)-O(1w) 2.383(9) Eu(1)-O(1w) Gd(1)-O(2w) 2.397(9) Eu(1)-O(2w) Gd(1)-O(3w) 2.425(8) Eu(1)-O(3w) O(1)-Gd(1)-O(2) O(3a1)-Gd(1)-O(4a1) O(5b1)-Gd(1)-O(6b1)
52.2(3) 52.2(3) 52.0(3)
O(1)-Eu(1)-O(2) O(3a1)-Eu(1)-O(4a1) O(5b1)-Eu(1)-O(6b1)
2.443(6) 2.511(6) 2.524(6) 2.485(6) 2.534(6) 2.442(6) 2.378(6) 2.400(6) 2.436(6) 52.2(2) 51.6(2) 52.1(2)
D · · · A/ Å D· · ·A
2
Table 3. (a) Selected Bond Lengths (Å) and Angles (°) and (b) Intermolecular Contacts of 4b
3
(b) Intermolecular Contacts of 2 and 3b 2.687(13) 2.714 (10) O(1w) · · · O(3d1) O(1w) · · · O(6d1) 2.768(11) 2.758(9) 1 O(2w) · · · O(5e ) 2.751(13) 2.761(9) O(2w) · · · O(4we1) 2.667(15) 2.676(11) O(3w) · · · O(4f1) 2.823(13) 2.838(10) O(3w) · · · O(2c1) 2.784(13) 2.775(9) O(4w) · · · O(1) 2.756(13) 2.768(9) O(4w) · · · O(4g1) 2.816(14) 2.809(10) a Symmetry code: a1 ) x - 1, y, z - 1; b1 ) x - 1, y, z. Symmetry code: c1 ) x, -y + 3/2, z - 1/2; d1 ) x - 1, -y + 3/2, z - 1/2; e1 ) -x + 1, -y + 1, -z + 1; f1 ) x, y, z - 1; g1 ) -x + 1, -y + 1, -z + 2. b
La(1)-O(1) La(1)-O(1a2) La(1)-O(2) La(1)-O(3b2) La(1)-O(4b2) La(1)-O(7) La(1)-O(9c2) La(1)-O(10c2) La(1)-O(1w) La(1)-O(2w)
2.732(4) 2.501(4) 2.562(4) 2.709(4) 2.576(4) 2.514(4) 2.608(4) 2.579(4) 2.571(4) 2.696(4)
La(2)-O(3b2) La(2)-O(5d2) La(2)-O(6d2) La(2)-O(7) La(2)-O(8) La(2)-O(11b2) La(2)-O(12b2) La(2)-O(3w) La(2)-O(4w) La(2)-O(5w)
2.506(4) 2.547(4) 2.606(4) 2.724(4) 2.610(4) 2.651(4) 2.580(4) 2.619(4) 2.591(4) 2.709(4)
O(1)-La(1)-O(2) 48.63(12) O(5d2)-La(2)-O(6d2) 50.67(13) O(3b2)-La(1)-O(4b2) 48.73(12) O(7)-La(2)-O(8) 48.57(12) 2 2 O(9d)-La(1)-O(10d) 50.02(13) O(11b )-La(2)-O(12b ) 49.39(13) (b) Intermolecular Contacts of 4b D· · ·A O(1w) · · · O(5a2) O(1w) · · · O(6d2) O(1w) · · · O(4wi2) O(2w) · · · O(10e2) O(3w) · · · O(3wf2) O(8w) · · · O(3wd2) O(4w) · · · O(6wg2) O(4w) · · · O(8wh2) O(5w) · · · O(7wg2) O(7w) · · · O(5wd2) O(6w) · · · O(12b2) O(6w) · · · O(7w) O(6w) · · · O(8i2) O(7w) · · · O(2d2) O(7w) · · · O(9b2) O(8w) · · · O(9b2) O(8w) · · · O(11i2) O(9w) · · · O(4b2) O(9w) · · · O(8j2) O(9w) · · · O(6wk2)
D · · · A/ Å 2.718(6) 2.937(6) 3.108(6) 2.785(6) 2.990(6) 2.759(7) 2.836(7) 2.910(6) 2.794(7) 2.920(7) 2.779(7) 2.795(7) 3.106(7) 2.900(6) 3.087(7) 2.736(6) 2.670(6) 2.861(7) 2.884(7) 2.684(8)
a Symmetry code: a2 ) -x, -y, -z + 1; b2 ) x + 1, y, z; c2 ) x + 1/2, -y + 1/2, z + 1/2; d2 ) x + 1/2, -y + 1/2, z - 1/2. b Symmetry code: e2 ) -x - 1/2, y - 1/2, -z + 1/2; f2 ) -x + 1, -y + 1, -z + 1; g2 ) -x + 1/2, y + 1/2, -z + 1/2; h2 ) -x + 3/2, y + 1/2, -z + 1/2; i2 ) -x + 1/2, y - 1/2, -z + 1/2; j2 ) x + 1/2, -y + 1/2, z + 1/ 2; k2 ) -x + 1, -y, -z + 1.
Figure 4. View of the crystal structure of compounds 2 and 3: (a) a view along the b axis showing the layers constructed by the lanthanide atoms as 3-fold nodes and tca ligands as 3-fold connectors; (b) crystal packing exhibiting the ABCDABCD sequence. the A-B and C-D layers, where the crystallization water molecules are located, is 6.317(2) Å (distance between mean planes). The gliding between the B and C, and the D and A layers reduces the interlayer separation [distance between mean planes of 4.286(4) Å] and avoids the formation of large pores in the structure. The available space for the coordinated and uncoordinated water molecules in these compounds accounts for the ca. 14.0 and 12.8% of the total volume for 2 and 3, respectively.30 These layers are connected through weak hydrogen bonds involving the crystallization [O(4w)] and coordinated [O(1w), O(2w) and O(3w)] water molecules and the carboxylate-oxygen atoms from the tca ligand (see Table 2) to afford a 3D supramolecular network. The lanthanide ion in 2 and 3 is surrounded by six oxygen atoms from three different tca ligands [O(1), O(2), O(3a1), O(4a1), O(5b1), and O(6b1); a1 ) x - 1, y, z - 1 and b1 ) x - 1, y, z], and three coordination water molecules [O(1w), O(2w), and O(3w)] (see Figure 5). These nine atoms build a monocapped square antiprism that wraps the ion. The O(1), O(2), O(5b1), and O(6b1) set of atoms form the base of the polyhedron, while O(4a1), O(1w), O(2w), and O(3w) build the upper plane that is capped by O(3a1). The dihedral angle between the two square faces is 0.92° and 0.84° in compounds 2 and 3, respectively. The average Ln-O bond distances are 2.456(9) Å (2)
Figure 5. A view of a fragment of the complex [Ln(tca)(H2O)3] · H2O [Ln ) Gd (2) and Eu (3)] along with the numbering scheme. and 2.461(6) Å (3), values that are shorter than that reported for the nine coordinated Ce(III) in the Ce-tca structure (2.542 Å).23 The tca ligand in 2 and 3 adopts a quasi-planar T-shaped configuration that allows the formation of (6,3) sheets with all the lanthanide ions belonging to the same plane. The maximum deviation of a carbon
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Figure 6. Crystal structure of 4: (a) schematic and structural views of the ladder-like chains growing along the a axis (the T-shaped tca ligand links 3-fold La(III) nodes); (b) a view of the structure along the a axis showing the channels where the crystallization water molecules are located (the ladder-like chains are noted in red and blue colors); (c) a perspective view of the 3D structure along the a axis (the water molecules have been removed for clarity). atom from the mean tca plane is 0.46(1) Å for 2, and 0.43(1) Å for 3, whereas the angles between the three carboxylate carbon atoms of the tca ligand (taking the central one as a node) are 141.6(8), 96.4(7) and 120.6(5)° in complex 2, and 141.2(7), 96.7(7) and 120.6(7)° in complex 3. This is a more planar configuration than that of the H3tca molecule (1) and, at the same time, with a less distorted T-shape which together with the presence of the bulky Ln(III) ions preclude the interpenetration. The tca exhibits a tris-bidentate conformation, each carboxylate group chelating the lanthanide atom. Hence, the tca ligand acts as a 3-fold connector, whereas each lanthanide atom is linked to three different ligands, as a 3-fold node, building the neutral layers. The three lanthanide atoms connected by each tca ligand form a triangle (see Scheme 3a) whose shorter edge amounts 6.7999(9) Å (2) and 6.8138(6) Å (3). These values are greater than the shortest separation between lanthanide atoms from different layers [6.0437(9) (2) and 6.0541(5) Å (3) for B-C and 6.5747(11) (2) and 6.5790(6) Å (3) for A-B]. The brick-wall sheets formed in the structures of 2 and 3 are different from the herringbone ones in 1, both being (6,3) networks with the tca acting as a 3-fold connector, which confirms the trend of the tricarballylate ligand to exhibit the T-shape conformation. The bulky lanthanide atoms introduce subtle changes in the structure, and they preclude the formation of intertwinned structures. [La2(tca)2(H2O)5]n · 4nH2O (4). The structure of 4 consists of ladderlike tapes of [La(2)(H2O)2]3+ on one side and [La(1)(H2O)3]3+ on the other, acting as 3-fold nodes, linked through (tca)3- ligands as 3-fold connectors. The ladders are ca. 6.6 Å width and run along the a axis (Figure 6a). Each ladder is linked to other three through µ-oxo bridges involving carboxylate-oxygen atoms of the tca ligands (Figure 6b) [the La(1) edge connected to two other ladders, whereas the La(2) side connected to only one]. The resulting 3D structure presents channels
running in the direction of the ladders (the a axis) where the crystallization water molecules are located (Figure 6c). These channels are irregularly shaped, and they account for the ca. 16% of the accessible volume per unit cell. The available space without coordinated and crystallization water molecules is ca. 28%, a larger value than that found for 2 and 3. Extensive hydrogen bonds involving carboxylate groups, coordinated and free water molecules contribute to the stabilization of the crystal structure (see Table 3). Two crystallographically independent lanthanum atoms [La(1) and La(2)] occur in 4. Both of them are ten coordinated and their environments are best described as bicapped square antiprisms [b ) 0.83 and 0.84 for La(1) and La(2), respectively].32 La(1) is surrounded by eight carboxylate oxygens belonging to five different tca ligands [O(1), O(1a2), O(2), O(3b2), O(4b2), O(7), O(9c2), and O(10c2); a2 ) -x, -y, -z+1; b2 ) x + 1, y, z; and c2 ) x + 1/2, -y + 1/2, z + 1/2] and two coordination water molecules [O(1w) and O(2w)]. The coordination polyhedron of La(2) is formed by seven carboxylateoxygens from four different tca ligands [O(3b2), O(5d2), O(6d2), O(7), O(8), O(11b2), and O(12b2); d2 ) x + 1/2, -y + 1/2, z - 1/2 ] and three coordinated water molecules [O(3w), O(4w), and O(5w)]. The mean La(1)-O and La(2)-O bond distances are 2.605(4) and 2.614(4) Å, respectively, values that are larger than those observed for the Gd(III) (2) and Eu(III) (3) complexes. Two crystallographically independent tca ligands are present in 4. They have in common the tris-bidentate T-shaped configuration observed in 2 and 3, but in addition, one of them [tca(1)] also acts as a monodentate ligand [C(1)C(2)C(3)C(4)C(5)C(6), Scheme 3b], and theother[tca(2)]adoptsabis-monodentate[C(7)C(8)C(9)C(10)C(11)C(12), Scheme 3c]. The maximum deviation of the mean plane formed by the carbon atoms of the tricarballylate ligands corresponds to C(5) and
1318 Crystal Growth & Design, Vol. 8, No. 4, 2008
Cañadillas-Delgado et al. Supporting Information Available: Crystallographic information files are available free of charge via the Internet at http://pubs.acs.org.
References
Figure 7. View of a fragment of the structure of complex 4 with the numbering scheme. C(10) [deviations of 0.401(7) and 0.389(7) Å, respectively]. The angles between the three carboxylate carbon atoms, (the T-branches), taking the central carbon atom of the propane skeleton as the T-node, are 139.5(4), 99.1(3), and 118.5(2)° for tca(1) and 139.8(4), 98.8(3), and 118.2(3)° for tca(2). These values are similar to the corresponding ones in 2 and 3, but they are less distorted than those of 1. The larger branches of the tca(1) and tca(2) ligands [La(1) · · · La(1) and La(2) · · · La(2), respectively, with a separation of 9.5386(7) Å] correspond to the edges of the ladders. Other structural parameters of the tca ligands can be found in Scheme 3. The shortest separation between the lanthanide atoms inside the ladders is 7.5482(8) Å [La(1) · · · La(2)], a value that is greater than the separation through the µ-oxo bridge that links them [4.4485(6) Å]. The higher coordination number of the lanthanum atom in 4 with respect to that of the gadolinium (2) and europium (3) accounts for the greater diversity of the coordination modes of the tricarballylate in this compound, which apart from its tris-bidentate character acts as a monodentate in one case and as bis-monodentate in the other. This situation results in the presence of µ-oxo bridges in the structure and the formation of a complex 3D network in 4. However, it is worthy of note that the T-configuration of the tca ligand is preserved in 4 with structural parameters similar to those of 2 and 3.
Conclusions This structural work has shown the trend of the tricarballylate ligand to adopt a T-shaped tris-bidentate configuration in its complexes with the lanthanide(III) cations. The tca ligand in 2–4 acts as a 3-fold connector of (6,3) brick-wall sheets (2 and 3) and ladder-like tapes (4), whereas the lanthanide atoms act as 3-fold nodes. The complexity of the structure of complex 4 arises from the higher coordination number of the La(III); the channels, resulting from the connection of the ladders, can be envisaged as porous for absorption of gases, but further investigations are needed to clarify this point. Although the influence of the metal ion cannot be left out, the tca could be a good scaffold for the crystal engineering of (6,3) brick-wall, herringbone, or ladder-like structures based on T-shaped connectors. Acknowledgment. Funding for this work is provided by the Ministerio Español de Educación y Ciencia through projects MAT2004-03112, MAT2007-60660 and “Factoría de Cristalización” (Consolider-Ingenio2010, CSD2006-00015). Postdoctoral (F.S.D.) and predoctoral (O.F.) fellowships from Ministerio Español de Educación y Ciencia and a predoctoral fellowship from the Gobierno Autónomo de Canarias (L.C.-D.) are acknowledged. J.P. also thanks the CSD2006-00015 for a postdoctoral contract.
(1) Janiak, C. J. Chem. Soc., Dalton Trans. 2003, 2781. (2) Zhao, X.; Xiao, B.; Fletcher, A. J.; Thomas, K. M.; Bradshaw, D.; Rosseinsky, M. J. Science 2004, 306, 1012. (3) Rowsell, J. L. C.; Millward, A. R.; Park, K. S.; Yaghi, O. M. J. Am. Chem. Soc. 2004, 126, 5666. (4) Pan, L.; Adams, K. M.; Hernandez, H. E.; Wang, X.; Zheng, C.; Hattori, Y.; Kaneko, K. J. Am. Chem. Soc. 2003, 125, 3062. (5) Li, H.; Eddaoudi, M.; Groy, T. L.; Yaghi, O. M. J. Am. Chem. Soc. 1998, 120, 8571. (6) Hernández-Molina, M.; Lorenzo-Luis, P. A.; López, T.; Ruiz-Pérez, C.; Lloret, F.; Julve, M. CrystEngComm 2000, 2, 169. (7) Hernández-Molina, M.; Lorenzo-Luis, P. A.; Ruiz-Pérez, C.; López, T.; Martín, I. R.; Anderson, K. M.; Orpen, A. G.; Bocanegra, E. H.; Lloret, F.; Julve, M. J. Chem, Soc., Dalton Trans. 2002, 3462. (8) Hernández-Molina, M.; Ruiz-Pérez, C.; López, T.; Lloret, F.; Julve, M. Inorg. Chem. 2003, 42, 5456. (9) Cañadillas-Delgado, L.; Pasán, J.; Fabelo, O.; Hernández-Molina, M.; Lloret, F.; Julve, M.; Ruiz-Pérez, C. Inorg. Chem. 2006, 45, 10585. (10) Cañadillas-Delgado, L.; Fabelo, O.; Ruiz-Pérez, C.; Delgado, F. S.; Julve, M.; Hernández-Molina, M.; Laz, M. M.; Lorenzo-Luis, P. Cryst. Growth Des. 2006, 6, 87. (11) James, S. L. Chem. Soc. ReV. 2003, 32, 276. (12) Wuest, J. D. Chem. Commun. 2005, 5830. (13) Ockwig, N. W.; Delgado-Friedrichs, O.; O’Keeffe, M.; Yaghi, O. M. Acc. Chem. Res. 2005, 38, 176. (14) Kim, J.; Chen, B.; Reineke, T. M.; Li, H.; Eddaoudi, M.; Moler, D. B.; O’Keeffe, M.; Yaghi, O. M. J. Am. Chem. Soc. 2001, 123, 8239. (15) (a) Barnes, J. C.; Paton, J. D. Acta Crystallogr., Sect. C 1988, 44, 758. (b) Barnes, J. C. PriVate Communication CCDC 2004, 233347. (16) Shan, N.; Jones, W. Tetrahedron Lett. 2003, 44, 3687. (17) Metzger, A.; Lynch, V. M.; Anslyn, E. V. Angew. Chem., Int. Ed. 1997, 36, 862. (18) Shan, N.; Bond, A. D.; Jones, W. Cryst. Eng. 2002, 5, 9. (19) Barnes, J. C.; Barnes, H. A. Acta Crystallogr., Sect. C 1996, 52, 731. (20) (a) Fujita, M.; Kwon, Y. J.; Sasaki, O.; Yamaguchi, K.; Ogura, K. J. Am. Chem. Soc. 1995, 117, 7287. (b) Carlucci, L.; Ciani, G.; Proserpio, D. M. J. Chem. Soc., Dalton Trans. 1999, 1799. (c) Dong, Y.-B.; Layland, R. C.; Pschirer, N. G.; Smith, M. D.; Bunz, U. H. F.; zur Loye, H.-C. Chem. Mater. 1999, 11, 1413. (d) Withersby, M. A.; Blake, A. J.; Champness, N. R.; Cooke, P. A.; Hubberstey, P.; Schröder, M. New J. Chem. 1999, 23, 573. (e) Withersby, M. A.; Blake, A. J.; Champness, N. R.; Cooke, P. A.; Hubberstey, P.; Realf, A. L.; Teat, S. J.; Schröder, M. J. Chem. Soc., Dalton Trans. 2000, 3261. (f) Plater, M. J.; Foreman, M. R. St, J.; Gelbrich, T.; Coles, S. J.; Hursthouse, M. B. J. Chem. Soc., Dalton Trans. 2000, 3065. (g) Kondo, M.; Shimamura, M.; Noro, S.; Minakoshi, S.; Asami, A.; Seki, K.; Kitagawa, S. Chem. Mater. 2000, 12, 1288. (21) Kumar, V. S. S.; Nangia, A.; Kirchner, M. T.; Boese, R. New J. Chem. 2003, 27, 224. (22) Vishweshwar, P.; Nangia, A.; Lynch, V. M. J. Org. Chem. 2002, 67, 556. (23) Armstrong, J. A.; Barnes, J. C. Acta Crystallogr., Sect. E 2004, E60, m791. (24) (a) Gupta, A. K.; Powel, J. E. USAEC Rep. IS 1963, 657. (b) Gupta, A. K.; Powel, J. E. USAEC Rep. IS 1964, 825. (25) Henish, H. K. Crystal Growth in Gels; The Pennsylvania State University Press: Pittsburgh, PA, 1970. (26) SADABS, Program for Empirical AbsorptionCorrection of Area Detector Data; University of Göttingen: Göttingen, Germany, 1996. (27) Sheldrick, G. M. SHELXTL-97, Program for Crystal Structure Solution and Refinement; University of Göttingen: Göttingen, Germany, 1997. (28) Farrugia, L. J. J. Appl. Crystallogr. 1999, 32, 837. (29) Nardelli, M. J. Appl. Crystallogr. 1995, 28, 659. (30) Speck, A. L. Acta Crystallogr., Sect. A 1990, 46, C34. (31) Brandenburg, K.; Putz H. DIAMOND 2.1d, Crystal Impact GbR, CRYSTAL IMPACT; GbR: Bonn, Germany, 2000. (32) Ribas-Gispert, J. Química de Coordinación; Edicions de la Universitat de Barcelona: Barcelona, Spain, 2000.
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