CRYSTAL GROWTH & DESIGN
Construction of a Three-fold Parallel Interpenetration Network and Bilayer Structure Based on Copper(II) and Trimesic Acid
2007 VOL. 7, NO. 6 1171-1175
Wen-Xian Chen, Shu-Ting Wu, La-Sheng Long,* Rong-Bin Huang, and Lan-Sun Zheng State Key Laboratory of Physical Chemistry of Solid Surface and Department of Chemistry, College of Chemistry and Chemical Engineering, Xiamen UniVersity, Xiamen 361005, China ReceiVed February 2, 2007; ReVised Manuscript ReceiVed March 31, 2007
ABSTRACT: Solvothermal reactions of Cu(NO3)2‚3H2O with trimesic acid (H3BTC) at different pH conditions yield two coordination polymers of [Cu3(BTC)2(H2O)3(NH3)4]n‚2nH2O (1) and [Cu4(BTC)2(OH)2(H2O)2(NH3)4]n (2). Crystal structural analysis reveals that complex 1 exhibits a three-fold parallel interpenetration network and complex 2 shows a two-dimensional bilayer structure. Crystal data are orthorhombic, space group Pbcn, a ) 11.242(3) Å, b ) 16.963(4) Å, c ) 13.898(4) Å, Z ) 4 for 1 and monoclinic, space group C2/c, a ) 18.887(4) Å, b ) 10.761(2) Å, c ) 14.488(3) Å, β ) 126.100(3)°, Z ) 4 for 2. Introduction The design and assembly of metal-involved supramolecular architectures based on crystal engineering are currently of great interest in the field of supramelocular chemistry and material science because they can provide intriguing architectures and functional materials.1,2 Polycarboxylate aromatic ligands, such as 1,4-benzendicarboxylic acid (H2BDC), trimesic acid (H3BTC), and 1,2,4,5-benzeneteracarvoxylic acid (H4BTEC), represent an important kind of functional molecular building unit in the assembly of supramoleular architectures.3-5 The versatile coordination modes of the carboxylates as well as the chemical robustness of these kinds of ligands not only leads to the assembled framework exhibiting structural diversity6 but also benefits the thermal stability of the framework.7 Owing to the relatively weak coordination bonding in coordination complexes (as compared with the strong covalent bonds in organic compounds),8 however, the coordination modes of polycarboxylate aromatic ligands are markedly sensitive to external physical or chemical stimuli.9 Thus, investigation of the influence of each individual factor on coordination modes of these ligands is valuable to expand the structure while preserving the framework topology by increasing the ligand length to generate “isoreticular” materials.9 Although a large number of polycarboxylates-based coordination polymers have been synthesized,3-5,10 investigation of external physical or chemical stimuli effects on the structures of polycarboxylate-based coordination polymers remains rare.9,11 Here we report the syntheses of two copper(II)/BTC coordination polymers, i.e., a three-fold parallel interpenetration network of [Cu3(BTC)2(H2O)3(NH3)4]n‚2nH2O (1) and a bilayer structure of [Cu4(BTC)2(OH)2(H2O)2(NH3)4]n (2), under different pH conditions. Their structural difference clearly shows a structural response to the pH value of the reaction. Experimental Procedures Materials and Methods. All chemicals and solvents used in the syntheses were analytical grade and used without further purification. Infrared spectra were recorded with a Nicolet AVATAR FT-IR360 spectrometer using the KBr pellet technique. Elemental analysis was carried out on a CE instruments EA 1110 elemental analyzer. An X-ray powder diffractometry (XRPD) study of complex 2 was performed on Panalytical X-Pert pro diffractometer with Cu-KR radiation. Magnetic * Author to whom correspondence should be addressed. E-mail: lslong@ xmu.edu.cn. Fax: 86-592-2183047.
Table 1. Crystal Data and Details of the Data Collection and Refinement for Complexes 1 and 2 complex formula fw cryst system space group a (Å) b (Å) c (Å) R (°) β (°) γ (°) V (Å3) Z T (K) Dcalcd (g·cm-3) µ (mm-1) indep reflns absd reflns number of parameters R1 [I > 2σ(I)] wR2[I > 2σ(I)] R1 (all data) wR2 (all data)
1 Cu3C18H28N4O17 763.06 orthorhombic Pbcn 11.242(3) 16.963(4) 13.898(4) 90 90 90 2650.2(11) 4 123 1.912 2.475 2188 2017 199 0.0789 0.1854 0.0850 0.1899
2 Cu4C18H24O16N4 806.57 monoclinic C2/c 18.887(4) 10.761(2) 14.488(3) 90 126.100(3) 90 2379.1(8) 4 123 2.252 3.622 2312 2223 214 0.0257 0.0692 0.0268 0.0699
susceptibility was measured by a Quantum Design MPMS superconducting quantum interference device (SQUID). Syntheses. [Cu3(BTC)2(H2O)3(NH3)4]n‚2nH2O (1). To 12 mL of aqua-ethanol (water/ethanol ) 1:1 (v/v)) solution was added Cu(NO3)2‚ 3H2O (0.435 g, 1.8 mmol) and H3BTC (1.0 mmol) while stirring. When the pH value of the mixture was adjusted to ca. 8.3 with NH3‚H2O (1.0 mol‚L-1), the cloudy solution was put into a 25 mL Teflon-lined Parr and heated in an autoclave at 180 °C for 12 h and then cooled to room temperature at a rate of 5 °C‚h-1. Dark blue crystals of 1 were obtained in 27.6% yield based on H3BTC. Anal. Calcd for Cu3C18H28N4O17 (%): C, 28.31; H, 3.67; N, 5.24. Found: C, 27.95; H, 3.69; N, 5.58. FTIR (KBr, cm-1): 3449s, 1616s, 1554s, 1432s, 1359s, 1250m, 1201m, 1099m, 758w, 721w. [Cu4(BTC)2(OH)2(H2O)2(NH3)4]n (2). Complex 2 was prepared in a similar way as illustrated for 1, except that the pH value of the reaction adjusted to 9.2. Prism-like blue crystals of 2 were obtained in 40.2% yield based on Cu(NO3)2‚3H2O. Anal. Calcd for Cu4C18H24O16N4 (%): C, 26.78; H, 2.97; N, 6.94; Found: C, 26.86; H, 2.92; N, 6.88. FTIR (KBr, cm-1): 3449s, 1616s, 1554s, 1432s, 1359s, 1250m, 1201m, 1099m, 758w, 721w. The agreement of experimental X-ray powder diffraction patterns with simulated ones for 2 (Supporting Information, Figure 1) indicates that a single phase of 2 is obtained. X-ray Crystallography. Data collections were performed on a Bruker SMART Apex CCD diffractometer at 123 K for 1 and 2. Absorption corrections were applied by using the multiscan program SADABS.12 The structures were solved by direct methods, and nonhydrogen atoms were refined anisotropically by least-squares on F2
10.1021/cg070119k CCC: $37.00 © 2007 American Chemical Society Published on Web 05/15/2007
1172 Crystal Growth & Design, Vol. 7, No. 6, 2007
Chen et al.
Figure 1. ORTEP plot showing the coordination environment of copper(II) ions in 1. using the SHELXTL program.13 The hydrogen atoms of organic ligands were generated geometrically (C-H, 0.96 Å, N-H, 0.90 Å). Crystal data as well as details of data collection and refinement for the complexes are summarized in Table 1.
Results and Discussion Description of Crystal Structures. Complex 1 crystallizes in the orthorhombic system, space group Pbcn and consists of three copper(II) cations, two BTC ligands, four ammonia, and five water molecules. Single-crystal structure analysis reveals that there are two crystallographically independent copper(II) cations, Cu1 and Cu2, in 1. Cu1 is six-coordinated by two ammonia molecules and two chelate carboxylates from two BTC units in distorted octahedral geometry, and Cu2 is fivecoordinated by three water molecules and two monodentate carboxylates from two different BTC units in distorted squarepyramidal geometry as shown in Figure 1. The bond distances Cu-Ocarboxylate and Cu-N in octahedral geometry are 1.945(5)-2.790(8) and 1.965(7)-1.975(5) Å, respectively. The bond lengths of Cu-Ocarboxylate and Cu-Owater are 1.958(5) and 2.005(6)-2.279(9) Å in square-pyramidal geometry. The bond lengths of Cu-Ocarboxylate and Cu-Owater are comparable to those usually encountered for copper-oxygen coordination.4a,5d Each BTC ligand serves as a three-connected node to coordinate with three copper(II) ions through its two carboxylates in chelate mode and one in monodentate mode, generating a two-dimensional (2D) honeycomb network with 7.4 × 10.2 Å cavities as shown in Figure 2. As is usually found in metal-organic frameworks
Figure 2. ORTEP plot showing the structure of 63 network in 1.
Figure 3. A perspective view of (a) the three-fold parallel interpenetration network of 1 (the three layers are represented in different colors) and (b) side view of (a).
containing large cavities that allow interpenetration,11,14-17 interlocking the 2D network leads to a three-fold parallel interpenetration network as illustrated in Figure 3. It was noted that, although the topology of the 2D network in 1 is similar to the previously reported coordination polymers of Ni3(btc)2(py)9(H2O)318 (py ) pyridine) and [Cu3(Ph2SNH)6(tma)2] (tma ) 1,3,5-benzentricarboxylates),19 there is a significant difference in the structure among the complexes. In the complex of Ni3(btc)2(py)9(H2O)3 and [Cu3(Ph2SNH)6(tma)2], the interpenetration was restricted due to pyridine ligands projecting perpendicularly to the cavities from adjacent layers and the phenyl group of Ph2SNH locating in the cavities of the 2D honeycomb network. The adjacent three interpenetrating networks are further connected through coordinated ammonia molecules from one layer hydrogen-bonded to the carboxylate group from the adjacent layer (N(1)-H(1B)‚‚‚O(2) ) 3.174(10) Å, H(1B)‚‚‚ O(2) ) 2.32 Å,
