DALTON COMMUNICATION J. Chem. Soc., Dalton Trans., 1998, Pages 5–6 5 A novel two-dimensional rectangular network. Synthesis and structure of {[Cu(4,49-bpy)(pyz)(H2O)2][PF6]2}n (4,49-bpy 5 4,49-bipyridine, pyz 5 pyrazine) Ming-Liang Tong,a Xiao-Ming Chen,*,a Xiao-Lan Yu a,b and Thomas C. W. Makb a Department of Chemistry, Zhongshan University, Guangzhou 510275, China b Department of Chemistry, The Chinese University of Hong Kong, Shatin, New Territories, Hong Kong The complex {[Cu(4,49-bpy)(pyz)(H2O)2][PF6]2}n comprising two-dimensional rectangular grids with each cavity enclosed by two 4,49-bipyridine (4,49-bipy) and two pyrazine (pyz) ligands, which superpose in an off-set fashion to give smaller rectangular channels, has been prepared and characterized by single-crystal X-ray structural analysis.Considerable research effort has been focused on the crystal engineering of supramolecular architectures organized by coordinate covalent or hydrogen bonding.1,2 So far a number of one-, two- and three-dimensional infinite frameworks have already been generated with linear N,N9 bidentate spacers.3–9 However, the above-mentioned frameworks are virtually all formed by only one type of bridging ligand; only three infinite frameworks containing two different types of ligand as edges have been reported,9,10 and two of them are triply interpenetrating frameworks.We have initiated a synthetic strategy for the preparation of non-interpenetrating open-frameworks with variable cavities or channels, in which the rod-like rigid spacers such as 4,49-bipyridine (4,49-bpy), pyrazine (pyz) and related species are chosen as building blocks.11 In the present work, we report the preparation and crystal structure of a novel twodimensional rectangular grid constructed simultaneously by 4,49-bpy and pyz ligands, namely {[Cu(4,49-bpy)(pyz)(H2O)2]- [PF6]2}n 1.Complex 1 was synthesized by self-assembly of CuII ions with 4,49-bpy and pyz ligands, as shown in Scheme 1.An alcoholic solution (10 cm3) of pyz (0.080 g, 1.0 mmol) was added dropwise to a stirring aqueous solution (5 cm3) of Cu(NO3)2?6H2O (0.296 g, 1.0 mmol) at 50 8C for 15 min. An alcoholic solution (10 cm3) of 4,49-bpy (0.156 g, 1.0 mmol) was then added and followed by NaPF6 (0.336 g, 2.0 mmol). The resulting blue solution was allowed to stand in air at room temperature for 5 d, yielding deep blue block crystals (65% yield). The elemental Scheme 1 N N Cu Cu N N N N Cu Cu N N N N CuII + + N N EtOH–H2O (the aqua ligands are omitted) * E-Mail: cedc03@zsu.edu.cn analysis and IR spectrum confirmed the formula of 1.† It is noteworthy that no product of square grids based on Cu(4,49- bpy)2 or Cu(pyz)2 has been observed, which could in principle be produced in the reaction.X-ray crystallography ‡ has established that complex 1 is made up of a two-dimensional rectangular network and PF6 2 anions. As illustrated in Fig. 1, each layer consists of perfectly ideal planar rectangles with a CuII ion, a 4,49-bpy and a pyz at each corner and side, respectively, two pyridyl rings of each 4,49-bpy ligand are twisted by 66.5(1)8. The inner rectangular cavity is hydrophobic and has dimensions of 6.83 × 11.15 Å, which are comparable to those of related compounds.4b,10 The CuII ion has an elongated octahedral geometry with two pyridyl [Cu]N 2.045(3) Å] and two pyz groups [Cu]N 2.036(3) Å] at the equatorial positions and two water molecules [Cu]O 2.445(3) Å] at the axial positions (Fig. 1). The off-set superposition of each pair of adjacent layers by half of the longer edges divides the voids into smaller rectangular channels (ca. 5.6 × 6.8 Å) as Fig. 1 An ORTEP14 drawing (at 35% probability level) of the rectangular units in complex 1 † (Found: C, 27.10; H, 2.45; N, 9.15. Calc. for C14H16CuF12N4O2P2 1: C, 26.88; H, 2.58; N, 8.96%). IR data (n& /cm21): 3620s, 3557m, 3423m (br), 3135w, 3071w, 1644s, 1609vs, 1539w, 1496w, 1426s, 1222s, 1173w, 1124m, 1075s, 1018w, 835vs (br), 646m, 561vs, 477m. ‡ Crystal data for complex 1: C14H16CuF12N4O2P2, M = 625.79, orthorhombic, space group Ibam (no. 72), a = 14.756(3), b = 11.149(2), c = 13.656(3) Å, U = 2246.6(8) Å3, Z = 4, Dc = 1.850 g cm23, m = 1.234 cm21. Data collection (2.88 < q<26.78) was performed at 293 K on a Siemens P4 diffractometer (Mo-Ka, l = 0.710 73 Å). The structure was solved with direct methods (SHELXTL-PC)12 and refined with fullmatrix least-squares technique (SHELXL 93)13 to final R1 value of 0.0469 for 87 parameters and 1164 unique reflections with I > 2s(I) and wR2 of 0.1495 for all 1184 reflections.CCDC reference number 186/800.6 J. Chem. Soc., Dalton Trans., 1998, Pages 5–6 shown in Fig. 2, which are similar to those found in A-zeolites and Pentasil zeolites.15 The PF6 2 anions are located in these channels, and each PF6 2 anion forms two accepter hydrogen bonds with two adjacent aqua ligands [O? ? ? F 2.848(4) Å].It is noteworthy that complex 1 is to our knowledge the first example of a two-dimensional framework that is sustained by the self-assembly of two different types of linear bidentate N,N9-donor ligands. Although the porous structures with designable pore sizes are in principle achievable via crystal engineering, interpenetration or self-inclusion commonly occur in these frameworks with voids of large volume, thereby reducing the pore size.4a,5,8a,9 The self-assembly of these frameworks is also highly influenced by factors such as the solvent system,1a template 8c,11,16 and steric requirement of the counter ion;17 the failure to prepare molecular rectangles containing 4,49-bpy and pyz edges is thus not surprising.3 In this sense, the exploration of the synthetic strategies and routes is therefore a long-term challenge.Much work is required to extend the knowledge of the relevant structural types and establish proper synthetic strategies leading to the desired species.The isolation of complex 1 suggests the possibility of constructing similar rectangular frameworks with divalent metal salts and two types of ligand under the appropriate conditions. Acknowledgements This work was supported by the National Natural Science Fig. 2 Top view showing the rectangular channels in complex 1. Carbon and hydrogen atoms are omitted for clarity, the 4,49-bpy and pyz molecular rods are shown as single bold lines Foundation of China (No. 29625102) and a Hong Kong Research Grants Council Earmarked Grant No. CUHK 89/ 93E. References 1 (a) R. Robin, B. F. Abrahams, S. R. Batten, R, W. Gable, B. F. Huskiness and J. Lieu, Supramolecular Architecture, ACS publications, Washington, DC, 1992, p. 256; (b) J. M. Lehn, Supramolecular Chemistry, VCH, Weinheim, 1995, ch. 9. 2 C. B. Aakeroy and K. R. Seddon, Chem. Soc. Rev., 1993, 397. 3 R. V. Slone, J. T. Hupp, C.L. Stern and T. E. Albrecht-Schmitt, Inorg. Chem., 1996, 35, 4096. 4 (a) L. Carlucci, G. Ciani, D. M. Proserpio and A. Sironi, J. Chem. Soc., Chem. Commun., 1994, 2755; (b) O. M. Yaghi and H. Li, J. Am. Chem. Soc., 1995, 117, 10 401. 5 G. B. Gardner, D. Venkataraman, J. S. Moore and S. 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