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Structure determination of a novel metal-organic compound synthesized from aluminum and 2,5-pyridinedicarboxylic acid

Published online by Cambridge University Press:  06 March 2012

Kenny Ståhl ,
Bastian Brink  and
Jonas Andersen
Kenny Ståhl*
Affiliation:
Department of Chemistry, Building 207, Technical University of Denmark, DK-2800 Kgs. Lyngby, Denmark
Bastian Brink
Affiliation:
Department of Chemistry, Building 207, Technical University of Denmark, DK-2800 Kgs. Lyngby, Denmark
Jonas Andersen
Affiliation:
Department of Chemistry, Building 207, Technical University of Denmark, DK-2800 Kgs. Lyngby, Denmark
*
a)Author to whom correspondence should be addressed. Electronic mail: kenny@kemi.dtu.dk
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Abstract

The structure of [Al2(pydc)2(μ2-OH)2(H2O)2]n(pydc = 2,5-pyridinedicarboxylate) was successfully determined from powder X-ray diffraction data. The compound crystallizes in the triclinic system (space group P -1) with a = 6.7813(1) Å, b = 7.4944(1) Å, c = 8.5013(1) Å, α = 95.256(1)°, β = 102.478(1)°, γ = 108.979(1)°. The structure consists of aluminum ions coordinating N and O in distorted octahedra, sharing an edge through two hydroxide ions. These dinuclear complexes are connected by pydc ions, which at one end coordinate by nitrogen and oxygen and only by oxygen at the other end. The pydc orientation is reversed in the neighboring pydc, forming double stranded chains interconnected by the aluminum dinuclear complexes in a ladder-like arrangement along [001].

Keywords

aluminum2,5-pyridinedicarboxylic acidhydrothermal synthesismetal-organic frameworkXRPD
Type
Technical Articles
Information
Powder Diffraction , Volume 26 , Supplement S1 , December 2011 , pp. S44 - S46
Copyright
Copyright © Cambridge University Press 2011

INTRODUCTION

Studies of dicarboxylic acids and their reactions with various metals have led to novel materials, the so-called metal organic frameworks (MOFs). These compounds can form layered materials as well as microporous and macroporous three-dimensional structures. Increasing interest in MOF is connected with the possible applications in, e.g., gas storage, gas separation, drug delivery, ion exchange, and catalysis (Férey, Reference Férey2008). In the investigation of functionalized materials based on the well-known MOFs, MIL-53 (Loiseau et al., Reference Loiseau, Serre, Huguenard, Fink, Taulelle, Henry, Bataille and Férey2004) and MOF-5 (Li et al., Reference Li, Eddaoudi, O’Keeffe and Yaghi1999) with benzene-1,4-dicarboxylate linkers, a new material was synthesized from 2,5-pyridinedicarboxylic acid (H2pydc) and aluminum nitrate. This paper presents the synthesis and structure determination and refinement from X-ray powder diffraction data for a new aluminum 2,5-pyridinedicarboxylate compound, [Al2(pydc)2(μ2-OH)2(H2O)2]n.

EXPERIMENTAL

Synthesis

The synthesis of aluminum 2,5-pyridinedicarboxylate hydroxide dehydrate is carried out with 5.5 g aluminum nitrate nonahydrate (Sigma-Aldrich 98+ % ACS), 2.95 g 2,5-pyridinedicarboxylic acid (Aldrich, 98%) and 0.7 g sodium hydroxide (Fluka ≥ 97.0%) dissolved in 150 ml of water. The solution is transferred to a Teflon lined stainless steel autoclave and heated to 150 °C for 24 h. The solution is cooled and the crystals are separated by centrifugation and washed with water to neutral pH. The white crystals are finally dried in air at 102 °C.

Data collection

The powder diffraction data were collected using a Huber G670 Guinier imaging plate camera, using Cu Kα1 radiation. The samples were placed in a thin layer on scotch tape and rotated during data collection. Data were collected in transmission mode for 2 h in the range of 3 to 100° in steps of 0.005° in 2θ.

Structure determination and refinements

The pattern was indexed using the program ITO (Visser, Reference Visser1969) and the crystal structure subsequently solved by EXPO (Altomare et al., Reference Altomare, Cascarano, Giacovazzo, Burla, Polodori and Camalli1994; Altomare et al., Reference Altomare, Burla, Cascarano, Giacovazzo, Guagliardi, Moliterni and Polodori1995). The structure was refined by WINPOW (a local variation of LHMP, Howard et al., Reference Howard and Hill1986). The Rietveld refinement was carried out by refining 80 parameters in a 2θ interval from 7° to 99° in steps of 0.005° in 2θ. A split pseudo-Voigt profile function was applied together with a Chebyshev background polynomial. All nonhydrogen

TABLE I. Crystallographic data and refinement summary of [Al2(pydc)2(μ2-OH)2(H2O)2]∞.

TABLE II. Fractional coordinates and thermal parameters of [Al2(pydc)2(μ2-OH)2(H2O)2]∞.

coordinates were refined with thermal parameters coupled for the pydc and for the hydroxyl and water oxygens. The expected bond lengths of the pydc (Liang et al., Reference Liang, Hong, Cao and Weng2001) were used as restrains. Hydrogens of the pydc were added in calculated positions and allowed to ride on the corresponding carbon atom. The hydroxyl and water hydrogens could not be located. Some crystallographic data and a refinement summary are given in Table I, the resulting atomic parameters in Table II and the refinement profiles

Figure 1. Rietveld refinement profile for [Al2(pydc)2(μ2-OH)2(H2O)2]n. The top pattern illustrates observed intensities, while the lower curve shows the difference from calculated intensities. Bragg positions are illustrated by short vertical bars.

Figure 2. (Color) The molecular structure and atomic positions of [Al2(pydc)2(μ2-OH)2(H2O)2]n. Red: oxygen, blue: nitrogen, green: aluminum, grey: carbon, white: calculated hydrogen positions.

are shown in Figure 1. In addition, a CIF file is provided as supplemental data.

RESULTS AND DISCUSSION

Aluminum ions coordinate N and O in distorted octahedra sharing an edge through two hydroxide ions, as seen in Figure 2. These dinuclear complexes (Al-Al = 2.844(6) Å, Table III) are connected by pydc ions, that at one end is coordinating through N1 and O4 and at the other by O2. The pydc orientation is reversed in the neighboring pydc, forming double stranded chains interconnected by the aluminum dinuclear complexes in a ladder-like arrangement along [001], as seen

TABLE III. Selected interatomic and tentative hydrogen bond distances in [Al2(pydc)2(μ2-OH)2(H2O)2]n.

a Symmetry code: 1−x, y, 1−z.

b Symmetry code: x, y, z−1.

c Symmetry code: x−1, y, z.

d Symmetry code: 1−x, y, 2−z.

e Symmetry code: 1−x, 1−y, 1−z.

in Figure 3. The ladders are tentatively connected by hydrogen bonds. Although the hydroxyl and water hydrogen positions could not be located in this study the O5 and O6 distances to the uncoordinated carboxylate O1 and O3 in the range 2.539(5) to 2.542(5) Å suggest reasonably strong hydrogen bonding (Table III). The crystal structure of [Al2(pydc)2(μ2-OH)2(H2O)2]n is surprisingly similar to the structures of [Ni2(Hdcp)2(μ2-H2O)2(H2O)2]n (King et al., Reference King, Clérac, Anson and Powell2004) and [Cu2(Hdcp)2(μ2-H2O)2(H2O)2]n (Hdpc = pyrazole-3,5-dicarboxylate) (Han and Ma, Reference Han and Ma2006) despite the difference in ring system of the organic linker and in cation charge. The charge difference is compensated for by exchanging one water by one hydroxyl ion per aluminum. The hydroxyl O5 thus shows a significantly shorter Al coordination distance than the water O6, 1.825(5) Å as compared with 2.005(4) Å, as also observed in MIL-53 (Loiseau et al., Reference Loiseau, Serre, Huguenard, Fink, Taulelle, Henry, Bataille and Férey2004). Also the hydrogen bonding schemes will be different in that the additional water H and the protonated pyrazole N allow for more hydrogen bonds (King et al., Reference King, Clérac, Anson and Powell2004; Han and Ma, Reference Han and Ma2006).

CONCLUSION

The crystal structure of [Al2(pydc)2(μ2-OH)2(H2O)2]∞ was successfully determined from X-ray powder diffraction data. The structure can be described as a parallel stacking of ladders, with ladder steps consisting of two edge-sharing aluminum octahedra connected by organic 2,5-pyridinedicarboxylate linkers forming a one-dimensional metal-organic network structure.

Figure 3. (Color) Packing of the unit cell of [Al2(pydc)2(μ2-OH)2(H2O)2]n seen along the a axis. Red: oxygen, blue: nitrogen, green: aluminum, grey: carbon. Hydrogens are omitted for clarity.

References

Altomare, A., Burla, M. C., Cascarano, G., Giacovazzo, C., Guagliardi, A., Moliterni, A. G. G., and Polodori, G. (1995). “EXTRA: A program for extracting structure-factor amplitudes from powder diffraction data,” J. Appl. Crystallogr. 28, 842–846.10.1107/S0021889895005619CrossRefGoogle Scholar
Altomare, A., Cascarano, G., Giacovazzo, C., Burla, M. C., Polodori, G., and Camalli, G. (1994). “SIR92—A program for automatic solution of crystal structures by direct methods,” J. Appl. Crystallogr. 27, 435–436.10.1107/S002188989400021XGoogle Scholar
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Han, Z. and Ma, Y. (2006). “Poly[di-μ2-aqua-μ-pyrazole-3,5-dicarboxylato-copper(II)],” Acta. Crystallogr. E 62, m2236–m2237.10.1107/S1600536806031795CrossRefGoogle Scholar
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Figure 0

TABLE I. Crystallographic data and refinement summary of [Al2(pydc)2(μ2-OH)2(H2O)2]∞.

Figure 1

TABLE II. Fractional coordinates and thermal parameters of [Al2(pydc)2(μ2-OH)2(H2O)2]∞.

Figure 2

Figure 1. Rietveld refinement profile for [Al2(pydc)2(μ2-OH)2(H2O)2]n. The top pattern illustrates observed intensities, while the lower curve shows the difference from calculated intensities. Bragg positions are illustrated by short vertical bars.

Figure 3

Figure 2. (Color) The molecular structure and atomic positions of [Al2(pydc)2(μ2-OH)2(H2O)2]n. Red: oxygen, blue: nitrogen, green: aluminum, grey: carbon, white: calculated hydrogen positions.

Figure 4

TABLE III. Selected interatomic and tentative hydrogen bond distances in [Al2(pydc)2(μ2-OH)2(H2O)2]n.

Figure 5

Figure 3. (Color) Packing of the unit cell of [Al2(pydc)2(μ2-OH)2(H2O)2]n seen along the a axis. Red: oxygen, blue: nitrogen, green: aluminum, grey: carbon. Hydrogens are omitted for clarity.

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