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Volume 68 
Part 10 
Pages m291-m294  
October 2012  

Received 9 July 2012
Accepted 7 September 2012
Online 18 September 2012

The heterobifunctional ligand 5-[4-(1,2,4-triazol-4-yl)phenyl]-1H-tetrazole and its role in the construction of a CdII metal-organic chain structure

aInorganic Chemistry Department, Taras Shevchenko National University of Kyiv, Volodimirska Street 64, Kyiv 01033, Ukraine
Correspondence e-mail: ab_lysenko@univ.kiev.ua

5-[4-(1,2,4-Triazol-4-yl)phenyl]-1H-tetrazole, C9H7N7, (I), an asymmetric heterobifunctional organic ligand containing triazole (tr) and tetrazole (tz) termini linked directly through a 1,4-phenylene spacer, crystallizes in the polar space group Pc. The heterocyclic functions, serving as single hydrogen-bond donor (tz) or acceptor (tr) units, afford hydrogen-bonded zigzag chains with no crystallographic centre of inversion. In the structure of catena-poly[[diaquacadmium(II)]bis{[mu]2-5-[4-(1,2,4-triazol-4-yl)phenyl]tetrazol-1-ido-[kappa]2N1:N1'}], [Cd(C9H6N7)2(H2O)2]n, (II), the CdII dication resides on a centre of inversion in an octahedral {N4O2} environment. In the equatorial plane, the CdII polyhedron is built up from four N atoms of two kinds, namely of trans-coordinating tr and tz fragments [Cd-N = 2.2926 (17) and 2.3603 (18) Å], and the coordinating aqua ligands occupy the two apical sites. The metal centres are separated at a distance of 11.1006 (7) Å by means of the double-bridging tetrazolate anion, L-, forming a chain structure. The water ligands and tz fragments interact with one another, like a double hydrogen-bond donor-acceptor synthon, leading to a hydrogen-bonded three-dimensional array.

Comment

The ligand-design approach has proved to be a crucial starting point and an attractive design tool for the rapid development of metal-organic frameworks (MOFs), as well as for modulating their properties (Elsevier et al., 2003[Elsevier, C. J., Reedijk, J., Walton, P. H. & Ward, M. D. (2003). Dalton Trans. pp. 1869-1880.]). An interesting perspective may be focused on the screening of heterobitopic ligands consisting of parent azole heterocycles [e.g. 1,2,4-triazole/tetrazole (Aromí et al., 2011[Aromí, G., Barrios, L. A., Roubeau, O. & Gamez, P. (2011). Coord. Chem. Rev. 255, 485-546.]) or their close 1,2,4-triazole/pyrazole analogues etc.], each of which represents a widely known class of organic bridges. The introduction of asymmetry into the bridging-ligand topology may be considered as an interesting supramolecular design tool for engineering acentric and chiral coordination solids (Zhang et al., 2008[Zhang, R.-B., Zhang, J., Li, Z.-J., Qin, Y.-Y., Cheng, J.-K. & Yao, Y.-G. (2008). Chem. Commun. pp. 4159-4161.]). On the other hand, the presence of neutral and acidic heterofunctional donors can also provide specificity towards the preferential coordination of metal ions via the formation of M-[N-N]-M linkages. As mentioned earlier by Colombo et al. (2011[Colombo, V., Galli, S., Choi, H. J., Han, G. D., Maspero, A., Palmisano, G., Masciocchic, N. & Long, J. R. (2011). Chem. Sci. 2, 1311-1319.]), the strength of the resulting M-N bonds correlates well with the pKa values for the deprotonation of the N-H bond in the azole heterocycle. This may be one of the reasons why tetrazolate-based MOFs demonstrate relatively low thermal stability and water sensitivity, which significantly limits their application in hydrogen storage (Dinca et al., 2006[Dinca, M., Dailly, A., Liu, Y., Brown, C. M., Neumann, D. A. & Long, J. R. (2006). J. Am. Chem. Soc. pp. 16876-16883.]) and Lewis acid catalysis (Horike et al., 2008[Horike, S., Dinca, M., Tamaki, K. & Long, J. R. (2008). J. Am. Chem. Soc. pp. 5854-5855.]). Thus, azolate-MOF stability can be optimized and increased through the introduction of heterobifunctional N-donor groups. Recently, Bondar et al. (2008[Bondar, O. A., Lukashuk, L. V., Lysenko, A. B., Krautscheid, H., Rusanov, E. B., Chernega, A. N. & Domasevitch, K. V. (2008). CrystEngComm, 10, 1216-1226.]) described a 1,2,4-triazole/tetrazole ligand linked by a 1,4-phenylene spacer, which shows promise for the production of microporous coordination polymers prepared in aqueous media under hydrothermal conditions. Another interesting example, demonstrating the heterobitopic ligand concept in the construction of porous heterometallic Cd/{Cu6(OH)6} frameworks, was provided by Govor et al. (2011[Govor, E. V., Lysenko, A. B., Quinõnero, D., Rusanov, E. B., Chernega, A. N., Moellmer, J., Staudt, R., Krautscheid, H., Frontera, A. & Domasevitch, K. V. (2011). Chem. Commun. pp. 4159-4161.]). 4-(3,5-Dimethylpyrazol-4-yl)-1,2,4-triazole was utilized in the self-assembly of halide-incorporating nanocluster {Cu6(OH)6} container molecules for halogenated hydrocarbon sorption applications, and their rational integration into polymeric solids was realised using a `step-by-step' approach. These findings have stimulated our interest in heterobitopic ligands. In this paper, we report the crystal structures of the title heterobifunctional ligand, HL, (I)[link], which contains both 1,2,4-triazole (tr) and tetrazole (tz) functions, and its cadmium complex, [CdL2(H2O)2], (II)[link].

[Scheme 1]

The organic ligand (I)[link], crystallizing in the polar space group Pc, is a dipolar molecule in which two different functions (tr and tz) are separated by a 1,4-phenylene (ph) spacer. Its asymmetric unit contains a whole molecule of 5-[4-(1,2,4-triazol-4-yl)phenyl]-1H-tetrazole (Fig. 1[link]). Similar to simple 5-phenyl-1H-tetrazole (Krygowski & Cyranski, 1996[Krygowski, T. M. & Cyranski, M. (1996). Tetrahedron, 52, 10255-10264.]), in (I)[link] the C1-N4 [1.325 (4) Å] and especially the N2-N3 [1.291 (5) Å] bonds of the tetrazole ring are shorter than the other three (Table 1[link]), suggesting that the compound exists as the 1H-tautomer. It is known that, in solution and in the gas phase, 5-substituted tetrazoles appear in two tautomeric forms, 1H and 2H, while in the solid state, 1H-tetrazole is preferred (Kiselev et al., 2011[Kiselev, V. G., Cheblakov, P. B. & Gritsan, N. P. (2011). J. Phys. Chem. A, pp. 1743-1753.]). This could be the reason for the angular directed intermolecular (tz)NH-N(tr) bonding vectors, leading preferentially to zigzag orientated chains of (I)[link], in which the molecular dipoles interact accurately in the donor-acceptor sequence [N1-H1...N5i; Fig. 2[link] and Table 2[link]]. Additionally, the packing motifs are supported by weaker C-H...N contacts (C3-H3...N4ii and C8-H8...N4iii; Table 2[link]), affording a three-dimensional hydrogen-bonding net (Desiraju & Steiner, 1999[Desiraju, R. G. & Steiner, T. (1999). In The Weak Hydrogen Bond in Structural Chemistry and Biology. New York: Oxford University Press Inc.]). These interactions cause the tz-benzene pair to be even more coplanar than the opposite side of (I)[link] [the C3-N7-C7-C8 and N4-C1-C4-C5 torsion angles are 24.8 (6) and 10.1 (6)°, respectively]. Also, this packing mode eliminates the presence of a crystallographic centre of inversion and the individual molecular dipoles are not cancelled out in the crystal structure.

In the cadmium complex, (II)[link], the asymmetric unit consists of a deprotonated organic ligand, a water molecule and a CdII cation. The cation last lies on an inversion centre and adopts a slightly distorted octahedral {N4O2} environment involving four N atoms of singly coordinated tetrazolate [Cd-N(tz) = 2.3603 (18) Å] and triazole [Cd-N(tr) = 2.2926 (17) Å] donor groups in a 1:1 ratio, and two O atoms of the coordinated water molecules [Cd1-O1 = 2.3960 (15) Å] (Fig. 3[link] and Table 3[link]). These three donors occupy trans dispositions in the coordination environment of the CdII centres. The significant differences observed for the Cd-N distances may indicate a more ionic character of the Cd-N(tz) bond than the Cd-N(tr) bond. The organic ligands, utilizing one N(tr) and one N(tz) atom, act as a bidentate double-bridge between adjacent CdII cations [related by symmetry code (x + 1, y + 1, z + 1)], connecting them at a distance of 11.1006 (7) Å into a linear chain propagating in the [111] direction.

The partially coordinated tetrazolide ligand can be considered as a scaffold with multiple hydrogen-bonded acceptor sites (through peripheral atoms N3 and N4), whereas the bound water molecule is a double hydrogen-bond donor. Two water molecules and two tz fragments interact with one another, leading to a ten-membered {H-O-H-[N-N]-}2 synthon in the ab plane [O1...N4ii = 2.900 (3) Å and O1...N3iii = 2.920 (2) Å; Fig. 4[link] and Table 4[link]]. In terms of graph-set analysis, these cyclic rings can be identified as R44(10) (Etter et al., 1990[Etter, M. C., MacDonald, J. C. & Bernstein, J. (1990). Acta Cryst. B46, 256-262.]). Indeed, the {H-O-H-[N-N]-}2 motifs are very characteristic and essential to controlling the organisation of the extended structures of molecular diaquabis[5-(2-pyridyl)tetrazolato]copper(II) (Mukhopadhyay et al., 2009[Mukhopadhyay, B. G., Mukhopadhyay, S., da Silva, M. F. C. G., Charmier, M. A. J. & Pombeiro, A. J. L. (2009). Dalton Trans. pp. 4778-4785.]) and the related diaquabis[4-(4H-1,2,4-triazol-4-yl)benzoato-[kappa]2O,O']cobalt(II)/cadmium(II)/copper(II) analogues (Lukashuk et al., 2007[Lukashuk, L. V., Lysenko, A. B., Rusanov, E. B., Chernega, A. N. & Domasevitch, K. V. (2007). Acta Cryst. C63, m140-m143.]).

Thus, the [Cd(C9H6N7)2(H2O)2] chains of (I)[link] are tightly packed in a three-dimensional hydrogen-bonded network, which is additionally stabilized by means of numerous weak (tr)C-H-N(tz) interactions (Table 4[link]).

In complex (II)[link], it is interesting to note that the Ntr,Ntz-coordinating ligand possesses an arc-shaped configuration that may be a consequence of the close interligand disposition in the polymeric chain (Fig. 5[link]). A similar deformation effect for a tetradentate ligand was previously observed in the three-dimensional framework structure of [Cu2([mu]4-L)3]Cl·12H2O (Bondar et al., 2008[Bondar, O. A., Lukashuk, L. V., Lysenko, A. B., Krautscheid, H., Rusanov, E. B., Chernega, A. N. & Domasevitch, K. V. (2008). CrystEngComm, 10, 1216-1226.]).

Summarizing, we have shown that 5-[4-(1,2,4-triazol-4-yl)phenyl]-1H-tetrazole is a prospective heterobifunctional asymmetric ligand for the controlled construction of acentric solids and coordination polymers utilizing triazole and tetrazolate donor moieties. The singly coordinated tetrazolide group tends to be involved in the formation of a cyclic hydrogen-bonded {H-O-H-[N-N]-}2 synthon, which may be an important component for the organization of the crystal structures of coordination polymers.

[Figure 1]
Figure 1
The molecule of HL, (I)[link], showing the atom-labelling scheme. Displacement ellipsoids are drawn at the 50% probability level.
[Figure 2]
Figure 2
The hydrogen-bonding motif of (I)[link], showing the zigzag packing of the HL molecules. The ligand dipoles are aligned in a parallel mode, forming layers. [Symmetry codes: (i) x - 1, -y + 1, z + [{1\over 2}]; (ii) x + 1, y + 1, z; (iii) x, y + 1, z.]
[Figure 3]
Figure 3
A fragment of the structure of (II)[link], showing the atom-labelling scheme. Displacement ellipsoids are drawn at the 50% probability level. [Symmetry codes: (i) -x + 1, -y + 1, -z + 1; (ii) x - 1, y - 1, z - 1; (iii) -x, -y, -z; (iv) x + 1, y + 1, z + 1.]
[Figure 4]
Figure 4
Projections of the structure of (II)[link], showing the formation of (a) the cyclic hydrogen-bonded {H-O-H-[N-N]-}2 synthon and (b) the hydrogen-bonded network. Hydrogen bonds are shown as dashed lines. [Symmetry codes: (ii) -x + 1, -y, -z; (iii) x, y + 1, z; (iv) -x + 1, -y, -z + 1.]
[Figure 5]
Figure 5
The packing of (II)[link], showing the O-H...N(tz) interchain interactions that lead to the three-dimensional hydrogen-bonded framework. Hydrogen bonds are represented as dashed lines. [Symmetry code: (ii) -x + 1, -y, -z.]

Experimental

All materials were of reagent grade and were used as received. The organic ligand, 5-[4-(1,2,4-triazol-4-yl)phenyl]-1H-tetrazole (HL), (I)[link], was prepared according to a previously described procedure (Bondar et al., 2008[Bondar, O. A., Lukashuk, L. V., Lysenko, A. B., Krautscheid, H., Rusanov, E. B., Chernega, A. N. & Domasevitch, K. V. (2008). CrystEngComm, 10, 1216-1226.]). Colourless prismatic monocrystals of HL suitable for X-ray analysis were grown by recrystallization from a hot aqueous solution.

For the synthesis of [CdL2(H2O)2], (II)[link], HL (10.6 mg, 49.7 µmol) was placed in a 50 ml test tube and dissolved in hot water (25 ml). To this solution was added Cd(NO3)2·4H2O (0.0308 mg, 99.8 µmol) in water (5 ml). The test tube was closed, placed in a 2 l Dewar flask filled with hot water and allowed to cool slowly to ambient temperature over a period of 48 h. The pale-yellow prisms of (II)[link] which formed were collected and dried at room temperature (yield 8.1 mg, 56%).

Compound (I)[link]

Crystal data
  • C9H7N7

  • Mr = 213.22

  • Monoclinic, P c

  • a = 3.7413 (7) Å

  • b = 7.8684 (9) Å

  • c = 15.4092 (13) Å

  • [beta] = 91.54 (3)°

  • V = 453.39 (11) Å3

  • Z = 2

  • Mo K[alpha] radiation

  • [mu] = 0.11 mm-1

  • T = 153 K

  • 0.28 × 0.25 × 0.25 mm

Data collection
  • Bruker APEXII area-detector diffractometer

  • Absorption correction: empirical (using intensity measurements) (SADABS; Sheldrick, 1996[Sheldrick, G. M. (1996). SADABS. University of Göttingen, Germany.]) Tmin = 0.970, Tmax = 0.974

  • 2647 measured reflections

  • 1317 independent reflections

  • 956 reflections with I > 2[sigma](I)

  • Rint = 0.052

Refinement
  • R[F2 > 2[sigma](F2)] = 0.049

  • wR(F2) = 0.104

  • S = 0.99

  • 1317 reflections

  • 146 parameters

  • 2 restraints

  • H-atom parameters constrained

  • [Delta][rho]max = 0.20 e Å-3

  • [Delta][rho]min = -0.19 e Å-3

Table 1
Selected bond lengths (Å) for (I)[link]

N1-C1 1.333 (5)
N1-N2 1.342 (4)
N2-N3 1.291 (5)
N3-N4 1.364 (5)
N4-C1 1.325 (4)
N5-C2 1.310 (5)
N5-N6 1.389 (6)
N6-C3 1.303 (5)
N7-C2 1.337 (5)
N7-C3 1.363 (5)

Table 2
Hydrogen-bond geometry (Å, °) for (I)[link]

D-H...A D-H H...A D...A D-H...A
N1-H1...N5i 0.88 2.01 2.875 (6) 170
C3-H3...N4ii 0.95 2.52 3.353 (6) 147
C8-H8...N4iii 0.95 2.50 3.414 (5) 162
Symmetry codes: (i) [x-1, -y+1, z+{\script{1\over 2}}]; (ii) x+1, y+1, z; (iii) x, y+1, z.

Compound (II)[link]

Crystal data
  • [Cd(C9H6N7)2(H2O)2]

  • Mr = 572.85

  • Triclinic, [P \overline 1]

  • a = 7.6554 (5) Å

  • b = 7.8589 (7) Å

  • c = 9.0762 (8) Å

  • [alpha] = 98.926 (2)°

  • [beta] = 98.066 (3)°

  • [gamma] = 108.354 (2)°

  • V = 501.47 (7) Å3

  • Z = 1

  • Mo K[alpha] radiation

  • [mu] = 1.14 mm-1

  • T = 296 K

  • 0.24 × 0.23 × 0.20 mm

Data collection
  • Bruker APEXII area-detector diffractometer

  • Absorption correction: empirical (using intensity measurements) (SADABS; Sheldrick, 1996[Sheldrick, G. M. (1996). SADABS. University of Göttingen, Germany.]) Tmin = 0.771, Tmax = 0.804

  • 5552 measured reflections

  • 2037 independent reflections

  • 1968 reflections with I > 2[sigma](I)

  • Rint = 0.026

Refinement
  • R[F2 > 2[sigma](F2)] = 0.024

  • wR(F2) = 0.050

  • S = 1.10

  • 2037 reflections

  • 160 parameters

  • H-atom parameters constrained

  • [Delta][rho]max = 0.32 e Å-3

  • [Delta][rho]min = -0.35 e Å-3

Table 3
Selected bond lengths (Å) for (II)[link]

Cd1-N5i 2.2926 (17)
Cd1-N1 2.3603 (18)
Cd1-O1 2.3960 (15)
N1-C1 1.341 (3)
N1-N2 1.349 (2)
N2-N3 1.303 (3)
N3-N4 1.356 (2)
N4-C1 1.336 (3)
N5-C2 1.304 (3)
N6-C3 1.296 (3)
N7-C2 1.353 (3)
N7-C3 1.361 (3)
Symmetry code: (i) -x+1, -y+1, -z+1.

Table 4
Hydrogen-bond geometry (Å, °) for (II)[link]

D-H...A D-H H...A D...A D-H...A
O1-H1W...N4ii 0.85 2.06 2.900 (3) 172
O1-H2W...N3iii 0.85 2.08 2.920 (2) 169
C2-H2...N3iv 0.93 2.56 3.386 (3) 149
Symmetry codes: (ii) -x+1, -y, -z; (iii) x, y+1, z; (iv) -x+1, -y, -z+1.

All H atoms were located in difference maps and then refined as riding, with O-H = 0.85 Å, N-H = 0.88 Å or C-H = 0.95 Å for (I) and 0.93 Å for (II), and with Uiso(H) = 1.2Ueq(C) or 1.5Ueq(N,O).

For both compounds, data collection: SMART-NT (Bruker, 1998[Bruker (1998). SMART-NT. Bruker AXS Inc., Madison, Wisconsin, USA.]); cell refinement: SAINT-NT (Bruker, 1999[Bruker (1999). SAINT-NT and SADABS. Bruker AXS Inc., Madison, Wisconsin, USA.]); data reduction: SAINT-NT; program(s) used to solve structure: SHELXS97 (Sheldrick, 2008[Sheldrick, G. M. (2008). Acta Cryst. A64, 112-122.]); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008[Sheldrick, G. M. (2008). Acta Cryst. A64, 112-122.]); molecular graphics: DIAMOND (Brandenburg, 1999[Brandenburg, K. (1999). DIAMOND. Crystal Impact GbR, Bonn, Germany.]); software used to prepare material for publication: WinGX (Farrugia, 1999[Farrugia, L. J. (1999). J. Appl. Cryst. 32, 837-838.]).


Supplementary data for this paper are available from the IUCr electronic archives (Reference: FG3264 ). Services for accessing these data are described at the back of the journal.


Acknowledgements

The author thanks Dr Konstantin Domasevitch for his help in preparing the paper.

References

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Horike, S., Dinca, M., Tamaki, K. & Long, J. R. (2008). J. Am. Chem. Soc. pp. 5854-5855.
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Mukhopadhyay, B. G., Mukhopadhyay, S., da Silva, M. F. C. G., Charmier, M. A. J. & Pombeiro, A. J. L. (2009). Dalton Trans. pp. 4778-4785.
Sheldrick, G. M. (1996). SADABS. University of Göttingen, Germany.
Sheldrick, G. M. (2008). Acta Cryst. A64, 112-122.  [CrossRef] [details]
Zhang, R.-B., Zhang, J., Li, Z.-J., Qin, Y.-Y., Cheng, J.-K. & Yao, Y.-G. (2008). Chem. Commun. pp. 4159-4161.


Acta Cryst (2012). C68, m291-m294   [ doi:10.1107/S0108270112038498 ]