Four Novel Solid-State Supramolecular Assemblies Constructed from Decavanadate Salts and Decamethylcucurbit[5]uril Noriko Chikaraishi Kasuga,* Mitsuru Umeda, Hajime Kidokoro, Kazuhiko Ueda, Kenji Hattori, and Kazuo Yamaguchi
CRYSTAL GROWTH & DESIGN 2009 VOL. 9, NO. 3 1494–1498
Department of Materials Science, Faculty of Science, Kanagawa UniVersity, Hiratsuka, Kanagawa, 259-1293, Japan ReceiVed September 9, 2008; ReVised Manuscript ReceiVed December 6, 2008
ABSTRACT: The reactions of a barrel-like cyclic host molecule (decamethylcucurbit [5]uril (MeCuc5)) and decavanadate salts (sodium or ammonium decavanadate (M6[V10O28], M ) Na+ or NH4+)) in water at room temperature gave four novel organic-inorganic hybrids, that is, two 2D ladder-like structures, a 1:2 complex, and a one-dimensional infinitely linear chain. Carbonyl oxygen atoms at the portals of the MeCuc5 molecules coordinate to cations (Na+ or NH4+) at the center or corner of the portals, and the resulting cationic organic species and decavanadate anions (HV10O285- and H2V10O284-) interact though electrostatic interaction and hydrogen bonds in the crystals. Introduction Rational design of molecular architectures of various building blocks of organic-organic,1 inorganic-organic materials2 by self-assembly of multiple molecular components is one of the interesting subjects in supramolecular chemistry. Polymeric metal-organic frameworks (MOFs) or metal-organic materials (MOMs) are rapidly growing fields of such hybrid materials due to their wide variety of structures and their potential application as zeolite-like solids for molecular selection, storage, and catalysis.3 Recently, interesting porous organic-inorganic assemblies were reported which were composed of inorganic metal clusters (Keggin polyoxometalate anions, [XW12O40]3- instead of using Werner-type metal complexes) and organic compounds (calix[4]arenes), which exhibited porous threedimensional (3D) structures and guest-sorption abilities.4 Polyoxometalates (POMs), anionic transition metal oxide clusters, are attractive and long-studied inorganic materials because of their discrete structures and acid/base, redox, and photochemical properties.5 Many reports on hydrothermal syntheses and structures of hybrid compounds based on Keggin-type POMs and transition metal coordination compounds have been presented;6 however, there are only several such reports on other types of POMs.7 We are interested in a combination of two bulky components as building blocksscyclic host molecules (cucurbituril homologues) and decavanadate salts. Cucurbit[n]urils are pumpkin-shaped, cyclic oligomers obtained from an acid-catalyzed condensation reaction of glycoluril and formaldehyde.8 They show high affinity toward cations such as alkali metal ions and ammonium cations due to the strong electrostatic interaction between cations and the carbonyl oxygen atoms at the two portals of the cucurbituril molecules. Recently, cucurbiturils have been studied extensively as components of suparamolecular compounds.9 Decamethylcucurbit[5]uril (MeCuc5), shown in Figure 1, is one unique member of a family; its preparation is relatively facile, its water-solubility is high among cucurbiturils without adding salts, and it absorbs gases selectively.10 On the other hand, vanadium polyoxometalate
* To whom correspondence should be addressed. E-mail: nkasuga@ kanagawa-u.ac.jp. Tel.: 81-463-59-4111. Fax: 81-463-58-9684.
Figure 1. Chemical formula (a) and structure of decamethylcucurbit[5] (MeCuc5) viewed from top (b) and side (c). A representative model of MeCuc5 is shown in (d).
compounds have been studied for their effect on biological systems, plus optical, electronic, and magnetic materials.11 Simple oxovanadate(V), present in aqueous solution, includes species which are mononuclear (H2VO4-, HVO42-, VO43-), dinuclear (H2V2O72-, HV2O73-, V2O72-), tetranuclear (V4O124-), pentanuclear (V5O155-), and decanuclear (H2V10O284-, HV10O285-, V10O286-) but with different protonation states.5,12 The structure of the decavanadate is well established and consists of an arrangement of 10 edge-shared VO6 octahedra with approximate D2h symmetry (Figure 2).13 There are 14 µ2 bridging, 4 µ3 bridging, 2 central and 8 terminal oxygen atoms. Therefore, we expected that a mixture of MeCuc5 and M6V10O28 (M represents a cation) in water would lead to the formation of cationic species, (i.e., M+ · · · MeCuc5 · · · M+) and decavanadate anions (HnV10O28(6-n)-, n ) 0-2), which would self-assemble through electrostatic interaction and hydrogen bonding to form different supramolecular structures depending on the synthetic conditions, such as pH and concentration. Herein, we report the synthesis, characterization, and single-crystal X-ray structural characterization of two structures of
10.1021/cg801007k CCC: $40.75 2009 American Chemical Society Published on Web 01/26/2009
crystal 3 crystal 2
a Several crystals were isolated from the mother liquid and the number of hydrate water molecules was determined by TG/DTA measurements. b Crystals were collected on a membrane filter and dried in vacuo. The number of hydrate water molecules was determined by TG/DTA measurements after drying in vacuo. c The number of hydrate water molecules was determined by complete elemental analysis. d Yield was calculated based on the formula.b
The synthetic conditions and the formula of four types of crystals are summarized in Table 1. They were characterized by complete elemental analysis, TG/DTA, IR, NMR, and singlecrystal X-ray analysis as described in Supporting Information. The lower chemical shift of the carbonyl carbons, compared to MeCuc5 alone in the solid 13C NMR spectra of crystals 1-4, indicated that the carbonyl oxygen atoms of MeCuc5 coordinated to Na+ or NH4+. The formula and number of hydrate water molecules were determined by TG/DTA (before and after drying in vacuum) and complete elemental analysis (after drying in a vacuum). The preparation and characterization details are shown in Supporting Information. Summaries of crystal data and selected distances are given in Tables 2 and 3, respectively. Various molar-ratio reactions of Na6[V10O28] with MeCuc5 (at a range of from 1:3 to 3:1) in water at room temperature gave orange granular crystals (1), yellow block crystals (2), and a white solid (MeCuc5). Three compounds were often codeposited, and isolation of one type of crystal was done only a few times, as shown in Table 1. X-ray analysis revealed that both the orange and yellow crystals are composed of four sodium ions, two protons, one decavanadate anion, two MeCuc5 molecules, and water molecules. In the cavity of MeCuc5 a water molecule is located in both crystals. Both sides of the carbonyl oxygen atoms of MeCuc5 coordinate to Na+ in both crystals, as expected. In the two crystals, the two sodium ions
1.0 0.5 300 8.4 (NH4)5HV10O28 · (MeCuc5)2 · 20H2O (NH4)5HV10O28 · (MeCuc5)2 · 15H2O (NH4)5HV10O28 · (MeCuc5)2 · 20H2O 69
crystal 4
Results and Discussion
0.6 1.3 60 7.5 Na4H2V10O28 · (MeCuc5)2 · 40H2O Na4H2V10O28 · (MeCuc5)2 · 35H2O Na4H2V10O28 · (MeCuc5)2 · 24H2O 52
∞{Na 4H 2[V 10O 28](MeCuc5)}, (NH 4) 5H[V 10O 28] (MeCuc5) 2, and ∞{(NH4)5H[V10O28] (MeCuc5)} (Scheme 1).
crystal 1
2
0.5 1.5 75 8.1 Na4H2V10O28 · (MeCuc5)2 · 30H2O Na4H2V10O28 · (MeCuc5)2 · 13H2O Na4H2V10O28 · (MeCuc5)2 · 24H2O 81
Scheme 1. Preparation and Model Representation of Crystals 1-4
Table 1. Synthetic Conditions, Formula Determined by Thermogravimetric (TG) and Differential Thermal Analysis (DTA), and Yield of Crystals 1-4
Figure 2. Structure of decavanadate anion (V10O28(6-n)-) in (a) ball and stick form and (b) polyhedral model. Atomic numbering of vanadium and oxygen atoms in asymmetry unit is shown.
1.0 3.0 150 7.7 (NH4)5HV10O28 · (MeCuc5) · 11H2O (NH4)5HV10O28 · (MeCuc5) · 6H2O (NH4)5HV10O28 · (MeCuc5) · 6H2O 92
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MeCuc5 · nH2O (mmol) M6V10O28 · nH2O (mmol) total volume of H2O (mL) initial pH formulaa formulab formulac yield (%)d
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Table 2. Summary of Crystal Data and Structure Refinement Parameters of Crystals 1-4a
empirical formula formula weight crystal system space group a/Å b/Å c/Å R/o β/° γ/° V/Å3 Dcalcd/g · cm-3 Z µ/mm-1 T/K no. of reflections total unique no. of observations (I > 2σ(I)) Rint R1 wR2 GOF a
crystal 1
crystal 2
crystal 3
crystal 4
C80H162N40O78Na4V10 3645.86 triclinic P1j (No. 2) 11.7281(7) 14.4125(9) 21.0375(13) 96.0720(10) 96.9300(10) 104.0410(10) 3390.7(4) 1.785 1 0.797 90
C80H182N40O88Na4V10 3714.02 monoclinic P21/n (No. 14) 12.169(4) 32.000(9) 18.021(5) 90 90.325(7) 90 7017(4) 1.758 2 0.774 113
C80H161N45O68V10 3350.94 triclinic P1j (No. 2) 14.8274(8) 16.5007(9) 16.5910(9) 63.6040(10) 71.8630(10) 67.3460(10) 3307.0(3) 1.683 1 0.790 130
C40H93N25O49V10 2217.79 monoclinic C2/c (No. 15) 17.5929(8) 14.3354(8) 31.4656(16) 90 91.233(2) 90 7933.8(7) 1.857 4 1.240 130
24779 16445
52217 17341
25120 16266
29613 9918
13965 0.0423 0.0530 0.1488 1.055
17341 0.0553 0.0522 0.1337 1.039
16266 0.0601 0.0583 0.1653 0.986
9918 0.0388 0.0465 0.1475 1.054
R1 ) Σ{|Fo| - |Fc|}/Σ|Fo|, wR2 ) [Σω(|Fo| - |Fc|)2/ΣωFo2]1/2, GOF ) [Σω(|Fo| - |Fc|)2/(m - n)]1/2. m, no. of reflections, n, no. of parameters. Table 3. Selected Distances (Å) of Crystals 1-4a crystal 1 i
Na1-O2 Na1-O10 Na1-O22 Na1-O25 Na1-O26 Na1-O30 Na2-O6 Na2-O7 Na2-O8 Na2-O10 Na2-O26 Na2-O42 O6-O11 O25-O9 O25-O3i O30-O1i O34-O7 O38-O23 O26-O31 O26-O32iv O30-O29 O35-O34
crystal 2 2.381(2) 2.389(2) 2.423(2) 2.371(2) 2.385(2) 2.428(2) 2.411(2) 2.506(2) 2.465(2) 2.528(2) 2.323(2) 2.319(3) 2.666(2) 2.833(2) 2.676(2) 2.677(2) 2.783(2) 2.859(3) 2.829(2) 2.760(2) 2.853(3) 2.855(3)
Na1-O9 Na1-O10 Na1-O15 Na1-O26 Na1-O27 Na1-O28 Na2-O1 Na2-O2 Na2-O3 Na2-O4 Na2-O5 Na2-O25 Na2-O43 O26-O6b O26-O7b O26-O8 O27-O5viii O28-O4viii O27-O13 O27-O18 O25-O26v
crystal 3 2.371(2) 2.290(3) 2.977(2) 2.327(2) 2.339(3) 2.364(3) 2.547(3) 2.604(3) 2.776(3) 2.565(3) 2.470(3) 2.255(3) 2.473(5) 2.937(3) 2.837(3) 2.929(3) 2.840(3) 2.907(4) 2.744(3) 2.946(3) 2.747(4)
N21-O1 N21-O2 N21-O3 N21-O4 N21-O5 N21-O19 N22-O6 N22-O7 N22-O8 N22-O9 N22-O10 O25-O1 O26-O4xi O27-O10xi O29-O11xii O25-O18 O28-O18 O26-O23xii
crystal 4 2.839(5) 2.967(5) 2.787(5) 3.101(5) 2.903(5) 3.010(5) 2.911(5) 2.826(5) 2.904(5) 2.817(5) 2.893(5) 2.847(4) 2.786(5) 2.897(5) 2.711(5) 2.701(4) 2.931(4) 2.815(4)
N21-O1 N21-O2 N21-O3 N21-O4 N21-O5 N21-O23xv O27-O1xviii O26-O11 O28-O12 O29-O20xi O26-O28
2.920(3) 2.856(3) 2.931(3) 2.850(3) 2.907(3) 2.971(3) 2.846(4) 2.614(4) 2.723(4) 2.765(4) 2.799(6)
a Oxygen atoms having an atomic number of less than 10 are belong to MeCuc5 and those of 11-24 are contained in decavanadate anions. Oxygen atoms having an atomic number of more than 25 are those of water molecules. Symmetry operations i ) -1 + x, y, z; iv ) -1 + x, 1 - y, 1 - z; v ) 1 + x, y, z; viii ) -1 + x, y, z; xi ) 1 - x, 1 - y, 1 - z; xii ) x, y, 1 + z; xv ) -0.5 + x, 0.5 + y, z; xviii ) x, -1 + y, z. b Three atoms (O26-H26 · · · O6 nor O26-H26 · · · O7) are not in line, but the orientation of two atoms (O26-H26) directs middle of O6 and O7.
are coordinated by the two portals of MeCuc5 asymmetrically; one cation is located at the pseudocenter of the five oxygen atoms and the other one is at the corner. Polymeric ladder structures constructed of hydrated Na+ · · · MeCuc5 · · · Na+ and decavanadate anions are formed in crystals 1 and 2, as shown in Figures 3 and 4, respectively. The inside and outside cavities of the two crystals are occupied by water molecules. The number of hydrate molecules and the manner of connecting hydrated Na+ · · · MeCuc5 · · · Na+ and decavanadate anions are different in crystals 1 and 2. In crystal 1, the Na1 ions bridge the oxygen atoms of MeCuc5 and the decavanadate anions to make a ladder structure. Judging from van der Waals radii and the ionic radii of oxygen atoms and sodium ions,14,15 terminal oxygen atom of decavanadate (O22) coordinates to Na1. Na1 coordinates to O2i (symmetry
operation i ) -1 + x, y, z) on one side of MeCuc5, as shown in Figure 3. Four other oxygen atoms of the portal (O1i, O3i, O4i, and O5i) do not coordinate to Na1. In contrast, four oxygen atoms (O6i, O7i, O8i, and O10i) on the other side of the portal of MeCuc5 coordinate to Na2i. Two sodium ions (Na1 and Na2) are bridged by O10 of MeCuc5 and O26 of hydrate water. Each sodium ion is coordinated by six oxygen atoms. However, coordination environment of two sodium ions is different, which is in contrast to the symmetric structure of [Na(µ-H2O)(H2O)5]2 having an inversion center in the report of (NH4)4Na2[V10O28] · 10H2O.16 Complex intermolecular hydrogen bond networks are formed through hydrate water molecules, the carbonyl oxygen atoms of MeCuc5 and decavanadate anions. Among three hydrate water molecules (O25, O26, and O30) coordinating to Na1, one water molecule (O25) forms inter-
Decavanadate Salts and Organic Host Molecule
Figure 3. Ladder-like polymeric fragment in the crystal structure of 1. Methyl groups, partial water molecules, and hydrogen atoms are omitted for clarity. Symmetry operations; i ) -1 + x, y, z; ii ) 2 - x, 2 - y, 1 - z; iii ) 1 - x, 2 - y, 1 - z.
Figure 4. Ladder-like polymeric fragment in the crystal structure of 2. Methyl groups, partial water molecules, and hydrogen atoms are omitted for clarity. Symmetry operations; v ) 1 + x, y, z; vi ) 1 - x, 2 - y, 1 - z; vii ) -x, 2 - y, 1 - z; viii ) -1 + x, y, z; ix ) 2 - x, 2 y, 1 - z.
Figure 5. Structure of 1:2 complex in 3. Methyl groups, partial water molecules, and hydrogen atoms are omitted for clarity. Symmetry operation: x ) 1 - x, 1 - y, -z.
molecular hydrogen bonds with two MeCuc5 (O25-O9 2.833(2) Å and O25-O3i 2.676(2) Å). Another oxygen atom (O26) forms intermolecular hydrogen bonds with other water molecules (O31 and O32iv, symmetry operation iv ) -1 + x, 1 - y, 1 - z) and the other oxygen atom (O30) forms an intermolecular hydrogen
Crystal Growth & Design, Vol. 9, No. 3, 2009 1497
bonds with another hydrate water molecule (O29) and MeCuc5 (O1i). Other hydrate water molecules (O34, O35, and O38) which do not coordinate to sodium ions form intermolecular hydrogen bonds with MeCuc5, vanadate anions, and hydrate water molecules. Figure 4 shows the connecting moiety between MeCuc5 and decavanadate in crystal 2. The location and orientation of decavanadate relating to MeCuc5 are different from those of crystal 1. In crystal 2 a bridging oxygen atom (O15), not a terminal oxygen as seen in crystal 1, coordinates to Na1. Na1 is coordinated by two carbonyl oxygen atoms (O9 and O10) on one side of MeCuc5 and three water molecules (O26, O27, and O28). On the other side of the portal of MeCuc5, four carbonyl oxygen atoms (O1, O2, O4, and O5), and two water molecules (O25 and O43) coordinate to Na2. In crystal 2, Na1 and Na2 are not bridged by oxygen atoms. Instead, hydrated Na+ · · · MeCuc5 · · · Na+ and decavanadate anions are connected by several intermolecular hydrogen bonds (O28-O4viii 2.907(4) Å, O27-O5viii 2.840(3) Å and O25-O26v 2.747(4) Å, symmetry operations v ) 1 + x, y, z; viii ) -1 + x, y, z). The water molecule (O27) also forms hydrogen bonds with a decavanadate anion (O27-O13 2.744(3) Å and O27-O18 2.946(3) Å). Reactions of (NH4)6[V10O28] with MeCuc5 in water at room temperature gave orange prisms, crystals 3 and 4. When (NH4)6[V10O28] and MeCuc5 were stirred in water at a 1:2 molar-ratio crystal 3 was formed in high yield, the formula of which is represented by one proton, five ammonium cations, one decavanadate anion, two MeCuc5 molecules, and water molecules. Several water molecules were highly disordered. Two ammonium cations were located at the pseudocenter of both sides of the portals. Two units of NH4+ · · · MeCuc5 · · · NH4+ hold a decavanadate anion through hydrogen bonding and electrostatic interaction, as shown in Figure 5. The nearest oxygen atom of the decavanadate to the cation is bridging oxygen atom O19. MeCuc5 and decavanadates form complex hydrogen bonds with hydrate water molecules: three kinds of hydrogen bonds between water molecules (O25, O26, and O27) and MeCuc5; five kinds of hydrogen bonds between water molecules (O25, O26, O28, and O29) and a decavanadate anion. When (NH4)6[V10O28] and MeCuc5 were stirred in water at a 3:1 molar-ratio, crystal 4 (which contained one proton, one decavanadate anion, five ammonium cations, one MeCuc5 molecule and water molecules) was obtained in high yield. Two ammonium cations were also located at the pseudocenter of both sides of the portals, as seen in crystal 3. However, the unit consisting of NH4+ · · · MeCuc5 · · · NH4+ and a decavanadate anion stand in a line alternately, as shown in Figure 6. The nearest oxygen atom of the decavanadate to the cation is terminal oxygen atom O23xv. The 1D polymer chains are piled up through crystal 4. An intermolecular hydrogen bond is seen between MeCuc5 and water molecule (O27). Several hydrate water molecules (O26, O28, and O29) form hydrogen bonds with vanadate anions. Intermolecular hydrogen bonds between water molecules (O26 and O28) also exist in crystal 4. In crystals 3 and 4 remaining disordered ammonium cations locate to neutralize charge and also participate in intermolecular hydrogen bonds with water molecules. Hydrate sodium ions can coordinate more freely to MeCuc5 than ammonium cations can do, comparing four structures. They can interact with decavanadate anions electrostatically through terminal and bridging oxygen atoms. They can be also coordinated by a few to four oxygen atoms of MeCuc5. In addition, hydrated sodium ions have at least two choices:
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Figure 6. Fragment of linear polymeric chain in the structure of 4. Methyl groups, partial water molecules, and hydrogen atoms are omitted for clarity. Symmetry operations: xiii ) 1 - x, y, 0.5 - z; xiv ) 1.5 - x, 0.5 + y, 0.5 - z; xv ) -0.5 + x, 0.5 + y, z; xvi ) 0.5 + x, 1.5 - y, 0.5 + z; xvii ) 0.5 - x, 1.5 - y, -z.
bridging by hydrate water molecules or forming several intermolecular hydrogen bonds. Accordingly, two ladder structures of crystals 1 and 2 were grown. In contrast, each ammonium cation locates at almost the center of the portals of MeCuc5 through electrostatic interaction as well as hydrogen bonds. Different molar-ratio reactions of MeCuc5 and (NH4)6V10O28 gave monomer and polymeric structures. The protonation number of decavanadate differs depending on the choice of the cation. Conclusions Comparing the crystal structures of 1-4, the effect of cation on the arrangement of M+ · · · MeCuc5 · · · M+ and decavanadate anions is clearly shown. The protonation number of decavanadate depends on the nature of the cation. Both cations (Na+ and NH4+) can interact with decavanadate anions either through terminal or µ2-bridging oxygen atoms. However, the coordination manner of the two cations to MeCuc5 is different. The location of hydrated Na+ is either at the pseudocenter or corner of the portals. Hydrated sodium ions are coordinated by carbonyl oxygen atoms of MeCuc5 more freely than NH4+ to form two types of ladder structures. The reaction of MeCuc5 and (NH4)6V10O28 provided two different complexes, depending on the molar ratios. The ammonium ion has four hydrogen atoms as well as one plus charge, and it interacts with decavanadate through electrostatic interaction and hydrogen bonding. Each ammonium cation is located at the center of both portals of MeCuc5. Four ionic complexes are highly hydrated by a number of water molecules. By selecting the cation of decavanadate and the reaction conditions, such as the molar ratio of the starting materials, several novel supramolecular hybrids were obtained as described above under mild conditions. Acknowledgment. This work was supported by a High-tech Research Center Project from the Ministry of Education, Culture, Sports, Science and Technology, Japan. We thank Dr. H. Ijuin for her advice and discussion in regard to the characterization of this article. Supporting Information Available: Preparation and characterization data (SI-1) and crystallographic information files (CIF format) of crystals 1-4 are available free of charge via the Internet at http:// pubs.acs.org.
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CG801007K
