Syntheses and Characterizations of Two Novel Silver(I) Complexes Constructed by Oxydipropionitrile Ligand Jian Zhang, Zhao-Ji Li, Yao Kang, Ye-Yan Qin, Jian-Kai Cheng, and Yuan-Gen Yao* State Key Laboratory of Structural Chemistry, Fujian Institute of Research on the Structure of Matter, The Chinese Academy of Sciences, Fuzhou, Fujian 350002, China
CRYSTAL GROWTH & DESIGN 2005 VOL. 5, NO. 1 73-75
Received April 3, 2004
ABSTRACT: Two novel silver compounds were prepared and characterized by single-crystal X-ray diffraction analysis. They have similar 2D layer networks. The anion effect leads to the overall different 3D crystal packing topological structures. The design of supramolecular assemblies via ligand design, the coordination orientation of metal ions, and the length of spacers have resulted in a variety of novel structural motifs.1 How these motifs are packed into particular crystal structures is of great scientific interest. More subtle effects on the topological configuration such as anion control are receiving renewed attention.2 It was reported that anions can tune the pitch of the selfassembled helical spring that is different in size2a,b and induce transformation of the supramolecular structure in the crystalline state.2c-f The ancillary ligation by the anion may result in a remarkable structural diversity. For example, G. Ciani and co-workers performed a systematic study on the reactions of long-chain dinitriles with silver salts and obtained interesting examples of interpenetrating diamondoids from 4- to 10-fold by changing the counteranions (NO3-, PF6-, AsF6-, and ClO4-).2d,e In addition, long flexible chain bidentate ligands have shown the ability to produce unique interwoven extended structural motifs, such as polycatenanes,3 polyrotaxanes,4 double helices,5 and other uncommon species.6 Here, we present two novel supramolecular solids, [Ag(C6H8N2O)2]BF4 (1) and [Ag(C6H8N2O)2]ClO4 (2), obtained by the self-assembly of AgX (X ) BF4- and ClO4-) with oxydipropionitrile (ODPN, C6H8N2O). They have similar two-dimensional (2D) layer structures. However, their three-dimensional (3D) topological structures are dependent on the effect of anions. Such an unusual phenomenon is, to the best of our knowledge, very rare in the field of coordination chemistry. Compounds 1 and 2 were synthesized by the selfassembly of AgX (X ) BF4- and ClO4-) with ODPN in a mixed solvent MeOH/CH3CN.7 The two compounds were characterized by satisfactory elemental analysis, IR, and X-ray diffraction analysis.8 Compounds 1 and 2 are soluble in acetonitrile and H2O but insoluble in THF. TGA and DSC traces of 1 and 2 indicate that the compounds are thermally stable up to 200 °C. The CtN vibrations of 1 and 2 (2252 cm-1) in the IR spectra show a higher CtN stretching vibration wavenumber value than that of the free ligand (2232 cm-1).9 The two compounds have different crystal appearances: The crystals of 1 are spiculate, and the crystals of 2 are prismatic. Powder diffraction results of the bulk samples confirm that they are the pure phase (see Supporting Information). X-ray single-crystal analysis revealed that the two compounds are composed of the same building unit [Ag(ODPN)4]+ and have similar 2D layer structures as shown in Figure 1b. As each ODPN ligand is bonded to two different AgI ions and each AgI is linked by four ODPN ligands, the whole structure is propagated into a 2D layer * To whom correspondence should be addressed. Fax: +86-591-3714946. E-mail:
[email protected].
Figure 1. (a) Space-filling representation of the cage ring motif. (b) Space-filling representation of the layer, showing the assembly of two kinds of helical chains motif along the ab plane. (c) View of the arrangment of the layers in compound 1 along the a- or b-axis with BF4- anions filled in the channels. (d) View of the arrangement of the layers in compound 2 along the a- or b-axis with ClO4anions filled in the channels.
network along the ab plane. All of the AgI ions are coplanar. The AgI center is bonded by four nitrogen donors from four individual but symmetry equivalent ODPN ligands and situates in the center of a tetrahedral coordination sphere. Each ODPN ligand links two AgI centers through its two cyano groups. The Ag-N bond length in 1 [2.277(8) Å] is slightly longer than that in 2 [2.265(5) Å]. As illustrated in Figure 1a, a basic motif of the 2D cationic layer is the cage ring consisting of 40 atoms including four AgI ions. Within the cage ring, four AgI ions occupy the four corners of a squareplane with a crystallographic S4 symmetry axis passing through the cage center. The closest Ag‚‚‚Ag distance is 9.006 Å in 1 and 9.170 Å in 2, respectively. The anion (BF4- or ClO4- in gray color as shown in Figure 1a) is partially encapsulated inside the cavity of [Ag4(ODPN)4]. Another structural motif of the 2D cationic layer is the helical chain. As shown in Figure 1b, two kinds of helices are vertically interwoven to each other with Ag atoms functioning as hinges. These [AgODPN] helical tubes are driven by sp3 configurations of C and the O(CH2CH2-)2 spacer, so the helical chains are arranged nonlinearly into the twisty {C-O-C [111.0(10)°] and O-C-C [108.0(8)°]} helical conformation. These two compounds crystallize in asymmetric space groups P4 h (1) and P4 h 21c (2), respectively.10 Both of them belong to
10.1021/cg0498756 CCC: $30.25 © 2005 American Chemical Society Published on Web 08/05/2004
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Crystal Growth & Design, Vol. 5, No. 1, 2005 Scheme 1. Silver Atom Arrangement in Two Adjacent Layers: (1) for Complex 1 and (2) for Complex 2
noncentric space groups containing -4 inversion axes, and each crystal structure contains both left- and right-handed helical chains. Although there are various examples of structural motifs, this type of helix-assembled motif is, to our best knowledge, unprecedented. Even BF4- and ClO4- have similar shapes and dimensions, and they play surprisingly different roles to orientating the crystal packing. A striking structural feature of the two compounds is the different assembly of the layer networks. In compound 1, the layers are stacked in a faceto-back manner (Figure 1c). As a contrast, in compound 2, the layers are stacked in a face-to-face manner (Figure 1d). The two compounds display an obvious different Ag arrangement between the adjacent layers. In compound 1 (Scheme 1), the silver atoms in two adjacent layers are arranged perpendicularly, the adjacent planes are separated by 5.663 Å, and the closest atomic separation between the adjacent layers is 4.142 Å. As a contrast, in compound 2, the silver atoms in two adjacent layers are arranged staggered, the two adjacent planes are separated by 4.585 Å, and the closest atomic separation between the adjacent layers is 4.056 Å, which means that the stacking of compound 2 is more effective. As shown in Scheme 2, the dimension of the anion cavities in 2 (9.170 Å × 9.170 Å) is slightly larger than in 1 (9.002 Å × 9.002 Å). It is speculated that the very slightly larger ClO4 anion [Cl-O 1.316(9) Å] is better to template the crystal packing as compared to the smaller BF4 anion [B-F 1.248(10) Å].11 In each cavity, the anion occupies the central position of the squareplane defined by four AgI ions, and they are oriented in such a way that four F atoms (or O atoms) are directed toward Ag centers in the same layer with the shortest Ag-F (or Ag-O) distance (Ag-F, 5.435 Å; Ag-O, 5.438 Å). We also noticed that in compound 2, the shortest Ag-O distance between ClO4- and AgI center from the neighboring layer is 4.949 Å, which is significantly shorter than the Ag-O distance in the same layer. In 1, one BF4- anion was surrounded by six BF4- anions, while in 2, one ClO4- anion was surrounded by eight ClO4anions. The shortest distances between two adjacent anions are 5.663 Å in 1 and 8.505 Å in 2, respectively. The closest atomic separations between anion and the adjacent layer are 2.731 Å (F-H distance) in 1 and 2.654 Å (O-H distance) in 2, respectively. The other interesting characteristics of the two compounds are their blue-green fluorescent properties (see Supporting Information). Excitation of solid samples of 1 at λ ) 335 nm produces an intense luminescence with the peak maximum at 450 nm; excitation of solid samples of 2 at λ ) 250 and 324 nm produces an intense and a weak luminescence with the peak maximums at 397 and 324 nm,
Communications Scheme 2.
Representation of the Silver Polyhedron with Encapsulated Anions
respectively. The differences of the emissions for 1 and 2 and the origins of these emissions are still under investigation in our laboratory. In summary, different shape/size selectivity, electrostatic repulsion, anion arrangement, anion-metal and anionanion/anion-ligand interactions result in a considerably different structure appearance. The two novel compounds exhibit a fascinating self-assembled 3D architecture. The structures differ in the identity of the counteranions (BF4vs ClO4-) and the packing of discrete Ag-ligand layers. Such structural types may provide greater insight into the basic structural level. On the basis of this work, further syntheses, structural diffraction studies, physical characterizations of the complexes assembled from other AgX (X ) NO3-, PF6-, CF3SO4-), and anion exchange properties are being studied. Acknowledgment. This work was supported by the National Natural Science Foundation of China under Project 20173063, the State Key Basic Research and Development Plan of China (001CB108906), and the NSF of Fujian Province (E0020001). Supporting Information Available: TGA analysis, luminescence emission spectra, XPRD patterns of the two complexes, and crystallographic data in CIF. This material is available free of charge via the Internet at http://pubs.acs.org.
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(8)
(9) (10)
(11)
ClO4-) (1.0 mmol) and ODPN (0.25 g, 2.0 mmol) in a 1:2 ratio were mixed and stirred in MeOH (10 mL)/CH3CN (2 mL) at room temperature for 1 h. After filtration, the mixtures were left for 2-3 days in the dark and then allowed to concentrate by slow evaporation in air. The crystals of the two products were recovered in good yield by filtration. Elemental analyses calcd for [Ag(C6H8N2O) 2]BF4 (1): C, 32.54; H, 3.64; N, 12.65. Found: C, 33.06; H, 3.56; N, 12.63%. Calcd for [Ag(C6H8N2O) 2]ClO4 (2): C, 31.64; H, 3.54; N, 12.30. Found: C, 31.80; H, 3.35; N, 12.28%. IR for 1 (KBr, cm-1): 2889(m), 2252(s), 1417(s), 1365(m), 1120(vs), 1035(vs), 534(m), 522(m). IR for 2 (KBr, cm-1): 2889(m), 2252(s), 1415(s), 1365(m), 1146(vs), 1115(vs), 1088(vs), 627(s). Crystal data for 1: C12H16AgBF4N4O2, Fw ) 442.97, tetragonal, P4 h ; a ) b ) 9.006(2) Å, c ) 5.663(2) Å, R ) β ) γ ) 90.00°, V ) 459.3(2) Å3, Z ) 1, Dc ) 1.601 g/cm3, F(000) ) 220, crystal size ) 0.80 mm × 0.32 mm × 0.32 mm. The structure was solved by direct methods and refined by full matrix least-squares techniques. The final R ) 0.0506, wR2 ) 0.1412, and S ) 1.082 for 699 observed reflections with I > 2.0σ(I). Crystal data for 2: C12H16AgClN4O6, Fw ) 455.61, tetragonal, P4 h 2(1)c; a ) b ) 9.1699(10) Å, c ) 11.0088(17) Å, R ) β ) γ ) 90.00°, V ) 925.7(2) Å3, Z ) 2, Dc ) 1.635 g/cm3, F(000) ) 456, crystal size ) 0.74 mm × 0.60 mm × 0.42 mm. The structure was solved by direct methods and refined by full matrix least-squares techniques. The final R ) 0.0371, wR2 ) 0.1010, and S ) 1.048 for 746 observed reflections with I > 2.0σ(I). Nakamoto, K. Infrared and Raman Spectra of Inorganic and Coordination Compounds, 5th ed.; John Wiley & Sons: New York, 1997; Part B, p 105. (a) Han, L.; Hong, M. C.; Wang, R. H.; Luo, Z. H.; Lin, Z. Z.; Yuan, D. Q. Chem. Commun. 2003, 2580. (b) Kondo, M.; Miyazawa, M.; Irie, Y.; Shinagawa, R.; Horiba, T.; Nakamura, A.; Naito, T.; Maeda, K.; Utsuno, S.; Uchida, F. Chem. Commun. 2002, 2156. The calculated molecular volumes of the anions BF4 and ClO4 are 38 and 47 Å3, respectively. Mingos, D. M. P.; Rohl, A. L. Inorg. Chem. 1991, 30, 3769.
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