Two Novel Metal−Organic Frameworks (MOFs) with (3,6)-Connected

DOI: 10.1021/cg100104t

Two Novel Metal-Organic Frameworks (MOFs) with (3,6)-Connected Net Topologies: Syntheses, Crystal Structures, Third-Order Nonlinear Optical and Luminescent Properties

2010, Vol. 10 2613–2619

Jian-Ping Zou,*,†,# Qiang Peng,‡ Zhenhai Wen,‡ Gui-Sheng Zeng,‡ Qiu-Ju Xing,‡ and Guo-Cong Guo*,# †

Key Laboratory of Nondestructive Testing, Nanchang Hangkong University, Ministry of Education, Nanchang, Jiangxi 330063, P. R. China, ‡School of Environmental and Chemical Engineering, Nanchang Hangkong University, Nanchang, Jiangxi 330063, P. R. China, and # State Key Laboratory of Structural Chemistry, Fujian Institute of Research on the Structure of Matter, Chinese Academy of Sciences, Fuzhou, Fujian 350002, P. R. China Received January 24, 2010; Revised Manuscript Received April 3, 2010

ABSTRACT: Two novel metal-organic frameworks (MOFs) [Cu3(C7H2NO5)2]n 3 3nH2O (1) and [CuAg2(C7H3NO5)2]n (2) were obtained by the hydrothermal reaction. Complex 1 exhibits a three-dimensional (3,6)-connected anatase topology with the Schl€afli symbol (42.6)2(44.62.88.10), while complex 2 displays a two-dimensional (3,6)-connected TiS2 related net topology with the Schl€afli symbol (43)2(46.66.83). The optical studies show that 1 and 2 both have good third-order nonlinear optical and luminescent properties.

Introduction Metal-organic frameworks (MOFs) represent a new class of metal-ligand coordination compounds, in which the metal centers are interconnected by organic ligands to display a variety of infinite supramolecular networks.1 The crystal engineering of MOFs has attracted enormous interest because of their intriguing structural motifs and potential applications as functional materials.2 Until now, a large number of coordination polymers of MOFs with interesting properties have been prepared and characterized,1,3 among which the coordination polymers with third-order nonlinear optical (NLO) properties are of much interest due to the potential application in the area of modern optical technology, such as all-optical switching, modulating and computing, and so on.4 Network topology is an important and essential aspect of the design and analysis of MOFs and also of inherent interest in understanding the supramolecular assembly. In this approach, complicated frameworks are simplified to simple nodeand-connection reference nets.5 New insights into the development of approaches for the engineering of MOFs are then possible on the basis of topological considerations.1,5 Therefore, new or unusual network topologies are of considerable focus,6 particularly those deliberately constructed from the nodes with connectivity commonly displayed by typical metal ions and organic ligands used in MOFs synthesis. Generally, nodes of 3-, 4-, and 6-connectivity are of the most relevance, and a variety of such uninodal network topologies have been realized so far.5 However, there is an unfavorable lack of systematic investigation on higher dimensional networks with mixed connectivity,5 such as (3,6)-, (4,6)-, and (4,8)-connected frameworks, which are considered to be difficult to achieve.7 Considerable effort has been focused on the rational design and controlled synthesis of coordination polymers using multidentate ligands such as poly carboxylate and N-heterocyclic

ligands.8 Recently, there is a growing interest in the construction of coordination polymers based on pyridine derivates.9 As a multichelating ligand, chelidamic acid (2,6-dicarboxy4-hydroxypyridine) (hereafter HChel) has been of great attraction due to its usage in many areas of science, such as coordinate chemistry, biochemistry, organic chemistry, medical chemistry, and even in HIV investigation.10 However, the coordination polymers with multidimensional structures prepared from chelidamic acid have been rarely reported. Up to now, only the Zn, Mn, Cu, V, Gd, Nd, Dy, Tb, Pr, and Er complexes exhibit two-dimensional (2D) structures with uninodal network topologies,11 and the other known complexes with HChel ligands are discrete or one-dimensional (1D) structures.12 Further studies on MOFs constructed from HChel ligands are of fundamental importance. Therefore, in order to obtain novel MOFs constructed from HChel ligands exhibiting multidimensional structures with mixed connectivity and good NLO properties, we chose Cu(II) and Ag(I) cations to incorporate with this ligand because the metal-HChel complexes may possess spiroconjugated structures to result in a good third-order NLO properties,11a,13 and the Cu and Ag complexes have good physical and chemical properties.14 Herein, by using the hydrothermal method, we have synthesized two novel MOFs, [Cu3(C7H2NO5)2]n 3 3nH2O (1) and [CuAg2(C7H3NO5)2]n (2), which both display good third-order NLO and luminescent properties, as well as (3,6)-connected net topologies with the Schl€ afli symbol (42.6)2(44.62.88.10) and (43)2(46.66.83) for 1 and 2, respectively. To the best of our knowledge, complex 1 is the first example with a three-dimensional (3D) framework among the metal-HChel complexes11,12 and is the fourth example with anatase topology for MOFs and inorganic materials,15 while complex 2 is the second example with TiS2 related net topology for MOFs.16 Experimental Section

*To whom correspondence should be addressed. Tel: þ86 791 3953377; fax: þ86 791 3953373; e-mail: [email protected] (J.-P.Z.), [email protected] (G.-C.G.).

General Procedures. All reagents were purchased from commercial sources and used without further purification. Elemental analyses (C, H, and N) were carried out with an Elementar Vario EL.

r 2010 American Chemical Society

Published on Web 04/27/2010

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Table 1. Crystal Data and Structure Refinement Parameters for 1 and 2a chemical formula

C14H10Cu3N2O13 (1)

C14H6Ag2CuN2O10 (2)

fw crystal size (mm3) T (K) λ (Mo KR, A˚) crystal system space group a (A˚) b (A˚) c (A˚) β V (A˚3) Z Dcalcd (g cm-3) μ (mm-1) F(000) θ range (°) measd reflns indep reflns/Rint obs. reflns R1a (I > 2σ(I )) wR2b (all data) GOF on F2 ΔFmax/ΔFmin, e/A˚3

604.86 0.25  0.20  0.13 293(2) 0.71073 orthorhombic Pnna 9.4830(4) 13.8308(7) 12.7221(6)

641.49 0.30  0.20  0.17 293(2) 0.71073 monoclinic C2/c 12.0344 7.6276(8) 17.5964(18) 101.731(3) 1581.5(3) 4 2.694 3.852 1228 2.36 to 25.02 2373 1392/0.0378 1282 0.0665 0.1753 0.985 1.516/-0.987

1668.60(14) 4 2.408 3.876 1196 2.18 to 25.39 4513 1539/0.0621 1510 0.0547 0.1699 1.021 1.064/-0.595

R1 = Fo| - |Fc /|Fo|. b wR2 = [w(Fo2 - Fc2)2]/[w(Fo2)2]1/2.

a

)

And photoluminescent analyses were performed on an Edinburgh FLS920 fluorescence spectrometer. Optical diffuse reflectance spectra were measured on a PE Lambda 900 UV-vis spectrophotometer equipped with an integrating sphere at 293 K, and the BaSO4 plate was used as the reference. The absorption spectra were calculated from reflection spectrum by the Kubelka-Munk function:17 R/S = (1 - R)2/2R, R is the absorption coefficient, S is the scattering coefficient which is practically wavelength independent when the particle size is larger than 5 μm, and R is the reflectance. The energy gap was determined as the intersection point between the energy axis at the absorption offset and the line extrapolated from the linear portion of the absorption edge in the R/S versus E (eV) plot. Synthesis of [Cu3(C7H2NO5)2]n 3 3nH2O (1). A mixture of Cu(CH3COO)2 3 H2O (0.75 mmol), AgNO3 (0.25 mmol), chelidamic acid (0.75 mmol), ethanol (5 mL), and water (10 mL) was loaded into a 25-mL Teflon-lined autoclave, and heated at 433 K for 3 days, after which it was cooled to room temperature over 2 days. Green prismatic crystals of 1 that are stable in air were obtained by filtration of the resulting solution. Yield: 32% (based on HChel ligand). Anal. Calcd. (%) for 1: C, 27.78; H, 1.65; N, 4.63. Found (%): C, 27.83; H, 1.70; N, 4.67. Synthesis of [CuAg2(C7H3NO5)2]n (2). A mixture of Cu(CH3COO)2 3 H2O (0.50 mmol), AgNO3 (0.50 mmol), chelidamic acid (0.50 mmol), ethanol (5 mL), and water (10 mL) was loaded into a 25-mL Teflon-lined autoclave, and heated at 413 K for 3 days, after which it was cooled to room temperature over 2 days. Pale green prismatic crystals of 2 that are stable in air were obtained by filtration of the resulting solution. Yield: 29% (based on HChel ligand). Anal. Calcd. (%) for 2: C, 26.18; H, 0.94; N, 4.36. Found (%): C, 26.22; H, 1.00; N, 4.40. X-ray Crystallography. Single crystals of 1 and 2 were mounted on a glass fiber for the X-ray diffraction analyses, respectively. The measurements were performed on a Siemens SMART CCD diffractometer equipped with a graphite-monochromated Mo KR radiation (λ = 0.71073 A˚) at 293(2) K. Intensities were corrected for LP factors and for empirical absorption using the ω scan technique. Siemens SAINT software was used for data reduction. The structures of 1 and 2 were solved by the direct methods and refined by full-matrix least-squares techniques. Non-hydrogen atoms were located by difference Fourier maps and subjected to anisotropic refinement. All of the calculations were performed by the Siemens SHELXTL version 5 package of crystallographic software.18 The H atoms of coordinated water molecule (O(1W)) and hydroxyl oxygen (O(5)) for 1 and 2, respectively, were placed in calculated positions, with O-H distances of 0.85(3) A˚, and refined in riding mode with Uiso(H) values of 1.5Ueq(O). And the H atoms of O(2W) in 1 were not included. Other H atoms were allowed to ride on their respective parent atoms with C-H distances of 0.93 A˚ and were included in the refinement with isotropic displacement parameters Uiso(H)=1.2Ueq(C). The crystallographic data are listed in Table 1. Selected bond lengths are given in Table 2. The atomic coordinates and thermal parameters are listed in Table S1, Supporting Information. Further details of the crystal structures investigation(s) can be obtained from the Cambridge Crystallographic Data Centre (12, Union Road, Cambridge CB2 1EZ, UK; fax: þ441223/336-033; e-mail: deposit@ ccdc.cam.ac.uk) on quoting the depository numbers CCDC-749204 and CCDC-749205 for 1 and 2, respectively. Powder XRD. The powder XRD patterns were collected with a Rigaku DMAX 2500 diffractometer at 40 kV and 100 mA for CuKR radiation (λ = 1.5406 A˚) with a scan speed of 5 o/min at room temperature. The simulated patterns were produced using the Mercury program and single-crystal reflection data. Figure S1, Supporting Information gives the powder XRD patterns of 1 and 2, which correspond well with the simulated ones, conforming the high purities of the prepared samples. Nonlinear Optical Measurements. The third-order NLO properties of 1 and 2 were investigated by using the Z-scan method.19 A Nd:YAG laser system (Continuum NP70) with pulse duration of 8 ns at a wavelength of 532 nm was employed as the light source. The spatial profiles of the optical pulses were nearly Gaussian contribution. The pulse laser beam was focused onto a sample cell with a 30-cm focal-length lens. The input and output pulses’ energy was measured simultaneously by precision laser detectors (818J-09B, Newport

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)

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Corp), which were linked to a computer through an RS232 interface. The NLO properties of the samples were manifested by moving the samples along the axis of the incident laser irradiance beam (z-direction) with respect to the focal point and with incident laser irradiance kept constant. An aperture of 2 mm radius was placed in front of the detector to measure the transmitted energy. Computational Procedures. The NLO properties of 1 and 2 were investigated under the time-dependent density functional theory (TDDFT) and the sum-overstates method (SOS) at B3LYP level in GAUSSIAN 03 program.20 The standard basis sets of 3-21G are used for C, H, O, N atoms, and basis sets of Lanl2DZ are used for Cu atoms and Ag and Cu atoms in 1 and 2, respectively. For reasons of economy and computational feasibility, one-fourth of the cell is selected for each of them in the calculated model. The crystallographic data of 1 and 2 determined by X-ray diffraction analyses were used to calculate the electronic band structures. Calculations of the electronic band structures along with density of states (DOS) were carried out with density functional theory (DFT) using one of the three nonlocal gradient corrected exchange-correlation functionals (GGA-PBE) and performed with the CASTEP code,21 which uses a plane wave basis set for the valence electrons and normconserving pseudopotential for the core electrons.22 For 1 and 2, the number of plane waves included in the basis was both determined by a cutoff energy Ec of 550 eV. Pseudoatomic calculations were performed for H-1s1, C-2s22p2, N-2s22p3, O-2s22p4, Cu-3d104s1, and Ag-4d105s1. The parameters used in the calculations and convergence criteria were set by the default values of the CASTEP code.21a

Results and Discussion Single-crystal X-ray diffraction analyses reveal that complex 1 exhibits a 3D framework constructed from Cu(II) ions and HChel ligands, while complex 2 displays a 2D framework constructed from Cu(II) and Ag(I) ions and HChel ligands. The asymmetric unit of 1 consists of one and half Cu(II) ion, one HChel ligand, one coordinated water molecule, and half discrete water molecule (Figure S2a, Supporting Information). As shown in Figure 1a, the Cu1 atom is four-coordinated by O1F, O4D, and O5 atoms from three different HChel ligands (symmetry codes for D: 0.5 þ x, y, 2-z; F: -x, 0.5 þ y, 0.5 þ z), as well as one coordinated water molecule to form a distorted tetrahedron, while the Cu2 atom is coordinated by four O atoms and two N atoms from two chelated HChel ligands to

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Table 2. Selected Bond Distances for 1 and 2 (A˚)a 1 bond

dist

bond

dist

bond

dist

Cu(1)-O(5) Cu(1)-O(1W) Cu(1)-O(4)#1

1.909(3) 1.942(3) 1.975(3)

Cu(1)-O(1)#2 Cu(2)-N(1)#3 Cu(2)-N(1)

1.992(3) 1.924(3) 1.924(3)

Cu(2)-O(1)#3 Cu(2)-O(1) Cu(2)-O(3) Cu(2)-O(3)#3

2.222(3) 2.222(3) 2.225(3) 2.225(3)

bond

dist

bond

dist

bond

dist

Ag(1)-O(4) Ag(1)-O(1)#1 Ag(1)-O(3)#2

2.268(4) 2.346(4) 2.533(4)

Cu(1)-N(1) Cu(1)-N(1)#3 Cu(1)-O(1)

1.934(4) 1.934(4) 2.197(4)

Cu(1)-O(1)#3 Cu(1)-O(3) Cu(1)-O(3)#3

2.197(4) 2.214(4) 2.214(4)

2

a Symmetry codes: for 1: #1 -x, -y þ 1, -z þ 2; #2 x þ 1/2, -y þ 1/2, z þ 1/2; #3 x, -y þ 1/2, -z þ 3/2. For 2: #1 -x þ 1, y - 1, -z þ 3/2; #2 -x þ 1/2, y - 1/2, -z þ 3/2; #3 -x þ 1, y, -z þ 3/2.

Figure 1. (a) View of the molecular structure of 1. Symmetry codes for A: 0.5 þ x, 1.5 - y, -0.5 þ z; B: 1 - x, 1 - y, 2 - z; C: 0.5 - x, 0.5 þ y, 1.5 - z; D: 0.5 þ x, y, 2 - z; E: 1 - x, 0.5 þ y, -0.5 þ z; F: -x, 0.5 þ y, 0.5 þ z. (b) View of the 3D (3,6)-connected anatase net topology of 1. The light blue and rosy spheres represent the Cu1 atoms centers and the nodes reduced by CuL2 (L = HChel ligand) units, respectively.

form a distorted octahedron. It is noted that the two chelated HChel ligands connected by the Cu2 atom are almost vertical, and the dihedral angle is about 87.9°. The Cu2 atom and two chelated HChel ligands form a CuL2 (L = HChel ligand) unit that is linked by six different Cu1 atoms. Therefore, the Cu1

atom can be considered as a three-connected node, while the CuL2 unit can be considered as a six-connected node in the structure of 1 (Figure 1a). As a result, the CuL2 units are interconnected through Cu1 atoms to generate a 3D architecture, which is the first example with a 3D framework for the HChel ligands. The Cu-O bond distances in 1 range from 1.909(3) ˚ and the Cu-N bond distance is 1.924(3) A ˚ to 2.225(3) A (Table 2), which all lie in the normal range of those reported for the copper complexes with HChel ligand.23 A better insight into the 3D network of 1 can be achieved by application of a topological approach. As mentioned above, the architecture of 1 can be reduced to a binodal structure with sixconnected (CuL2 units) and three-connected (Cu1 atoms) nodes, adopting a 3D anatase topology with the Schl€ afli symbol (42.6)2(44.62.88.10) (Figure 1b), which is the first symbol for the HChel ligands.11,12 Noteworthily, unlike the known metal-HChel complexes,11,12 in which the HChel acts as a mono- or bidentate ligand to form 0D, 1D, or 2D structures, the HChel ligand in 1 acts as a μ4-bridge to link copper atoms into a 3D structure for the first time (Figure 1). To our knowledge, only two complexes (Gd and Cu)11c,d have the hydroxyl O coordinating with metal atoms for the HChel ligand reported in the literature, and complex 1 is the third case. To the best of our knowledge, only 17 3D (3,6)-connected topologies for MOFs plus a further four for inorganic materials have been documented so far.15,24 Furthermore, it should be noted that among these topologies, only three examples are observed with anatase topology, and 1 is the fourth example.15,24 As for 2, the asymmetric unit consists of half Cu(II) ion, one Ag(I) ion, and one HChel ligand (Figure S2b, Supporting Information). As shown in Figure 2a, the Cu1 atom is coordinated by four O atoms and two N atoms from two chelated HChel ligands to form a distorted octahedron, while the Ag1 atom is coordinated by O1G, O3F, and O4 atoms from three different HChel ligands to form a distorted trigonal planar (symmetry codes for F: 0.5 - x, -0.5 þ y, 1.5 - z; G: 1 - x, -1 þ y, 1.5 - z). It is noted that the two chelated HChel ligands connected by the Cu1 atom are almost vertical, and the dihedral angle is about 75.9°. The Cu1 atom and two chelated HChel ligands form a CuL2 (L = HChel ligand) unit that is linked by six different Ag1 atoms. Therefore, this CuL2 unit can be considered as a six-connected node, and the Ag1 atom can be considered as a three-connected node in the structure of 2 (Figure 2a). Unlike the 3D framework of 1, in 2, the CuL2 units are interconnected through Ag1 atoms to generate a 2D architecture. The Cu-O bond distances in 2 range from

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Figure 3. (a) Convergence behavior of static γxxyy with number of excited states for 1 in the static case based on SOS//TDB3LYP/ 3-21GþLanl2DZ level. (b) Convergence behavior of static γzzzz with the number of excited states for 2 in the static case based on the SOS//TDB3LYP/3-21GþLanl2DZ level. Figure 2. (a) View of the molecular structure of 2. Symmetry codes for A: 1 - x, y, 1.5 - z; B: 0.5 - x, 0.5 þ y, 1.5 - z; C: 0.5 þ x, 0.5 þ y, z; D: x, 1 þ y, z; E: 1 - x, 1 þ y, 1.5 - z; F: 0.5 - x, -0.5 þ y, 1.5 - z; G: 1 - x, -1 þ y, 1.5 - z. (b) View of the 2D (3,6)-connected TiS2 related net topology of 2. The rosy and light blue spheres represent the Ag atoms centers and the nodes reduced by CuL2 (L = HChel ligand) units, respectively.

˚ and the Cu-N bond distance is 1.934(4) A ˚ 2.197(4) to 2.214(4) A (Table 2), which all lie in the normal range of those reported for the copper complexes with HChel ligand.23 The Ag-O ˚ (Table 2), bond distances in 2 range from 2.268(4) to 2.533(4) A which are comparable to those reported for the Ag complexes with HChel ligand.11c A better insight into the 2D network of 2 can be also achieved by application of a topological approach. As mentioned above, the architecture of 2 can be reduced to a binodal structure with six-connected (CuL2 units) and three-connected (Ag1 atoms) nodes, adopting an unusual (43)2(46.66.83) topology (Figure 2b), which is the first symbol for the HChel ligands.11,12 This structure is closely related to the intercalated TiS2 structure.25 To the best of our knowledge, this is the second observation of TiS2 related topology in MOF structures.16 Furthermore, it is noted that 1 and 2 are the first two examples with mixed-connected network topology for the metal-HChel complexes.11,12 Noteworthily, all of the known complexes with HChel ligands contain only one kind of metal ion except for the seven complexes composed of Dy and Mn, V and Na, Cu and Ag, Er and Zn, Er and Mn, Ho and Zn, as well as Ho and Mn, respectively.11 Complex 2 is the eighth example of heterometalorganic coordination polymers with HChel ligands. Furthermore, dissimilar to 1, the HChel ligand in 2, chelating one Cu atom and linking three Ag atoms, acts as a μ4-bridge to link Cu and Ag atoms into a 2D but not 3D structure (Figure 1a),

which may be caused by the hydroxyl O not coordinating with metal atoms. Since Simmons and Hoffmann et al. reported that the spiroconjugation of the molecular structure demonstrated excellent NLO properties in 1967,13 many investigations show the thirdorder polarizability came from the delocalization of π electrons in the molecular plane. In fact, when two π systems (as chelidamic acid) share a metal ion, a spiroconjugated π bond may be formed between them if the molecular orbital is under vertical or parallel situation. According to the structural analysis of 1 and 2, the central Cu ions in 1 and 2 link to two chelated HChel ligands, and their d orbitals can act as electron bridges for charge transfer. This structure will lead to an expansion of the delocalization, generating the phenomenon of spiroconjugation. All of these may eventually enhance the NLO polarizabilities of the molecule. Therefore, we investigated the optical properties of 1 and 2 by experimental and computational methods. The NLO properties of 1 and 2 are calculated by GAUSSIAN 03 program. The results show that the static (input photon energy = 0) hyperpolarizabilities of 1 and 2 both present strong anisotropy. The largest components are γxxyy and γzzzz for 1 and 2, respectively. As shown in Figure 3, the convergent behavior of the static third-order polarizabilities is stable after the summation of 50 states for each of them, and the convergence values are 1.67  10-33 and 1.52  10-30 esu for 1 and 2, respectively. The value of 1 is close to those calculated for the metal-HChel complexes, [AgCu2(C7H2NO5)(C7H3NO5)]n 3 2nH2O (2.79 10-33 esu)11d and Zn(C7H3O5N) 3 H2O (0.97  10-33 esu),11a while the value of 2 is larger than those of them. The theoretical calculations reveal that the present complexes have a good effect of third-order nonlinear optics.

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Figure 5. Solid-state emission spectra of 1 (λex = 333 nm), 2 (λex = 358 nm), and HChel ligand (λex =365 nm) recorded at room temperature.

Figure 4. Z-scan data for 1 and 2 in 2.0  10-4 mol 3 dm-3 DMF solution, obtained by dividing the normalized Z-scan data obtained under the closed-aperture configuration by the normalized Z-scan data obtained under the open-aperture configuration. The black dots are the experimental data, and the solids curve is the theoretical fit (a and b for 1 and 2, respectively).

The third-order NLO refractive properties of 1 and 2 in DMF were measured by the Z-scan method with 8 ns pulses at a wavelength of 532 nm generated from a Nd:YAG laser. The nonlinear refractive components were assessed by dividing the normalized Z-scan data obtained under the closed aperture configuration by the normalized Z-scan data obtained under the open aperture configuration. As shown in Figure 4, the typical NLO refractive data for 1 and 2 show that the present complexes both have a positive sign for the nonlinear refraction and exhibit strong self-focusing behavior. A reasonably good fit between the experimental data (black dot) and the theoretical curves (solids curves) based on Sheik-Bahae’s report was obtained for each of them.4c The effective third-order refractive indexes n2 of 1 and 2 are calculated to be 3.63  10-11 and 4.15  10-11 esu, respectively. The third-order polarizabilities of 1 and 2 are 0.9210-12 and 1.05  10-12 esu, respectively, which are both comparable to the values reported for [AgCu2(C7H2NO5)(C7H3NO5)]n 3 2nH2O (5.44  10-12 esu),11d Zn(C7H3O5N) 3 H2O (1.05  10-12 esu),11a and the metal phthalocyanines (0.68-10.01 10-12 esu).4c,26 Those indicate that complexes 1 and 2 will be promising candidates for third-order NLO materials. The solid-state electronic emission spectra of 1, 2 and the free HChel ligand show luminescent features as given in

Figure 5. Complex 1 exhibits blue fluorescence with the maximum emission at 398 and 478 nm upon excitation at 333 nm, while complex 2 and the free HChel ligand both display green fluorescence with the maximum emission at 515 and 526 nm upon excitation at 358 and 365 nm, respectively. Compared to the free HChel ligand, complex 1 results in much higher emission energy and two large blue shift of 59 and 48 nm, respectively, while complex 2 results in much higher emission energy and a little blue shift of 11 nm. This indicates that the emission of 1 may be originated from charge transition between the ligand and the metal ions, while the emission of 2 may be originated from π-π* transition of the ligand.12c,d,27 The good luminescence efficiencies indicate 1 and 2 may be good candidates for luminescent materials. The diffuse reflectance spectra of 1 and 2 reveal the presence of an optical gap of 3.59 and 3.22 eV for 1 and 2, respectively (Figure S3, Supporting Information). The calculated band structures of 1 and 2 along high symmetry points of the first Brillouin zone are plotted in Figures S4 and S5 for 1 and 2, respectively. It is found that the top of valence bands (VBs) and the bottom of conduction bands (CBs) are both relatively flat. The highest energy (0.00 eV) of VBs and the lowest energy (2.94 eV) of CBs in 1 are localized at the X and G points, respectively, while the highest energy (0.00 eV) of VBs and the lowest energy (2.72 eV) of CBs in 2 are localized at the A and G points, respectively. According to our calculations, the solid-state complexes 1 and 2 thus both pose an indirect energy band gap of 2.94 and 2.72 eV, respectively, which are comparable to their experimental values (3.59 and 3.22 eV for 1 and 2, respectively). The bands can be assigned according to total and partial densities of states (DOS), as plotted in Figures S6 and S7 for 1 and 2, respectively. In 1, the VBs between energy -35.0 and -5.0 eV are mostly formed by the O-2s, O-2p, and C-2s, C-2p states, mixing with small Cu-3d, N-2s, and N-2p states. And the VBs between energy -5.0 eV and the Fermi level (0.0 eV) are the main contributions from the O-2p and Cu-3d states mixing with a small amount of C-2p and N-2p states, while the CBs between 2.9 and 9.0 eV are almost a contribution from the C-2p and O-2p states mixing with a small amount of N-2p and Cu-3d states. In 2, the O-2s, O-2p, and C-2s, C-2p states, mixing with small N-2s and N-2p states create the VBs localized at about -25.0 and -5.0 eV. And the VBs between

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energy -5.0 eV and the Fermi level (0.0 eV) are mainly a contribution from the O-2p, C-2p, and Ag-4d states mixing with a small amount of Cu-3d and N-2p states, while the CBs between 2.7 and 9.0 eV are almost a contribution from the C-2p and O-2p states mixing with a small amount of N-2p and Ag-5s states. Therefore, the origin of the emission band of 1 may be mainly ascribed to metal-to-ligand charge transfer (MLCT) where the electrons are transferred from the Cu-3d to O-2p and N-2p states,12c,28 while the origin of the emission band of 2 may be mainly ascribed to intraligand charge transfer (ILCT) where the electrons are transferred from the O-2p to C-2p states.12d,29 The analyses are also consistent with the above experimental results. Conclusions Two novel metal-organic frameworks (MOFs), [Cu3(C7H2NO5)2]n 3 3nH2O (1) and [CuAg2(C7H3NO5)2]n (2), were prepared by the hydrothermal method. Complex 1 exhibits a (3,6)-connected net topology with the Schl€ afli symbol (42.6)24 2 8 (4 .6 .8 .10), which is the first example with a 3D framework among those containing chelidamic acid ligands and is the fourth example with anatase topology for MOFs and inorganic materials. Complex 2 displays a 2D (3,6)-connected net topology with the Schl€ afli symbol (43)2(46.66.83), which is the second example with TiS2 related net topology for MOFs. Furthermore, 1 and 2 are the first two examples with mixedconnected network topology for the metal-HChel complexes. Their good third-order NLO and luminescent properties indicate they may be good candidates for NLO and luminescent materials. Acknowledgment. We gratefully acknowledge the financial support of the NSF of China (20801026), the NSF for Distinguished Young Scientist of China (20425104), 973 program (2009CB939801), the NSF of Jiangxi Province (2008GQC0036), the Aviation Science Foundation of China (2008ZF56012), and Open Fund of the Key Laboratory of Nondestructive Testing, Ministry of Education, Nanchang Hangkong University (ZD200929007). Supporting Information Available: X-ray crystallographic files in CIF format, molecular structure figures, the diffuse reflectance spectra, as well as calculated energy band structures and total and partial DOS of 1 and 2. This material is available free of charge via the Internet at http://pubs.acs.org/.

References (1) (a) Hoskins, B. F.; Robson, R. J. Am. Chem. Soc. 1990, 112, 1546. (b) Batten, S. R.; Robson, R. Angew. Chem., Int. Ed. 1998, 37, 1460. (c) Moulton, B.; Zaworotko, M. J. Chem. Rev. 2001, 101, 1629. (2) (a) Ferey, G. Chem. Soc. Rev. 2008, 37, 191. (b) Rosi, N. L.; Eckert, J.; Eddaoudi, M.; Vodak, D. T.; Kim, J.; O'Keeffe, M.; Yaghi, O. M. Science 2003, 300, 1127. (c) Fujita, M.; Tominaga, M.; Hori, A.; Therrien, B. Acc. Chem. Res. 2005, 38, 371. (3) (a) Eddaoudi, M.; Moler, D. B.; Li, H. L.; Chen, B. L.; Reineke, T. M.; O’Keeffe, M.; O. Yaghi, M. Acc. Chem. Res. 2001, 34, 319. (b) Chae, H. K.; Siberio-Perez, D. Y.; Kim, J.; Go, Y. B.; Eddaoudi, M.; Matzger, A. J.; O'Keeffe, M.; Yaghi, O. M. Nature 2004, 427, 523. (4) (a) Zhang, J.; Song, Y.; Yang, J.; Humphrey, M. G.; Zhang, C. Cryst. Growth Des. 2008, 8, 387. (b) Cheng, W.-D.; Wu, D.-S.; Zhang, H.; Chen, J.-T. Phys. Rev. B. 2001, 64, 125109. (c) Coronado, E.; Gatteschi, D. J. Mater. Chem. 2006, 16, 2513. (d) Maspoch, D.; RuizMolina, D.; Veciana, J. Chem. Soc. Rev. 2007, 36, 770. (e) Tao, S.; Miyagoe, T.; Maeda, A.; Matsuzaki, H.; Ohtsu, H.; Hasegawa, M.; Takaishi, S.; Yamashita, M.; Okamoto, H. Adv. Mater. 2007, 19, 2707.

Zou et al. (5) Ockwig, N. W.; Delgado-Friedrichs, O.; O’Keeffe, M.; Yaghi, O. M. Acc. Chem. Res. 2005, 38, 176. (6) (a) Long, D. L.; Blake, A. J.; Champness, N. R.; Wilson, C.; Schr€ oder, M. J. Am. Chem. Soc. 2001, 123, 3401. (b) Moulton, B.; Lu, J. J.; Zaworotko, M. J. J. Am. Chem. Soc. 2001, 123, 9224. (c) Tong, M.-L.; Chen, X.-M.; Batten, S. R. J. Am. Chem. Soc. 2003, 125, 16170. (d) Wang, X.-L.; Qin, C.; Wang, E.-B.; Su, Z.-M. Chem.; Eur. J. 2006, 12, 2680. (7) (a) Chun, H.; Kim, D.; Dybtsev, D. N.; Kim, K. Angew. Chem., Int. Ed. 2004, 43, 971. (b) Natarajan, R.; Savitha, G.; Dominiak, P.; Wozniak, K.; Moorthy, J. N. Angew. Chem., Int. Ed. 2005, 44, 2115. (c) Du, M.; Zhang, Z.-H.; Zhao, X.-J.; Xu, Q. Inorg. Chem. 2006, 45, 5785. (8) (a) Furukawa, H.; Kim, J.; Ockwig, N. W.; O’Keeffe, M.; Yaghi, O. M. J. Am. Chem. Soc. 2008, 130, 11650. (b) Seidel, S. R.; Stang, P. J. Acc. Chem. Res. 2002, 35, 972. (c) Hong, M. C. Cryst. Growth Des. 2007, 7, 10. (d) Li, M. X.; Miao, Z. X.; Shao, M.; Liang, S. W.; Zhu, S. R. Inorg. Chem. 2008, 47, 4481. (e) Ye, B.-H.; Tong, M.-L.; Chen, X.-M. Coord. Chem. Rev. 2005, 249, 545. (9) (a) Niu, C. Y.; Wu, B. L.; Zheng, X. F.; Zhang, H. Y.; Hou, H. W.; Niu, Y. Y.; Li, Z. J. Cryst. Growth Des. 2008, 8, 1566. (b) Wang, X. W.; Chen, J. Z.; Liu, J. H. Cryst. Growth Des. 2007, 7, 1227. (c) Zhou, L. J.; Wang, Y. Y.; Zhou, C. H.; Wang, C. J.; Shi, Q. Z.; Peng, S. M. Cryst. Growth Des. 2007, 7, 300. (10) (a) Boger, D. L.; Hong, J.; Hikota, M.; Ishida, M. J. Am. Chem. Soc. 1999, 121, 2471. (b) Fessmann, T.; Kilburn, J. D. Angew. Chem., Int. Ed. 1999, 38, 1993. (c) Searcey, M.; MeClean, S.; Madden, B.; McGown, A. T.; Wakelin, L. P. G. Anti-Cancer Drug Des. 1998, 13, 837. (11) (a) Zhou, G.-W.; Lan, Y.-Z.; Zheng, F.-K.; Zhang, X.; Lin, M.-H.; Guo, G.-C.; Huang, J.-S. Chem. Phys. Lett. 2006, 426, 341. (b) Ghosh, S. K.; Ribas, J.; El Fallah, M. S.; Bharadwaj, P. K. Inorg. Chem. 2005, 44, 3856. (c) Gao, H.-L.; Yi, L.; Zhao, B.; Zhao, X.-Q.; Cheng, P.; Liao, D.-Z.; Yan, S.-P. Inorg. Chem. 2006, 45, 5980. (d) Zou, J.-P.; Zhou, G.-W.; Zhang, X.; Wang, M.-S.; Lu, Y.-B.; Zhou, W.-W.; Zhang, Z.-J.; Guo, G.-C.; Huang, J.-S. CrystEngComm 2009, 11, 972. (e) Zhao, B.; Gao, H.-L.; Chen, X.-Y.; Cheng, P.; Shi, W.; Liao, D.-Z.; Yan, S.-P.; Jiang, Z.-H. Chem.;Eur. J. 2006, 12, 149. (f) Yang, L.; Cour, A.; Anderson, O. P.; Crans, D. C. Inorg. Chem. 2002, 41, 6322. (g) Gao, H.-L.; Zhao, B.; Zhao, X.-Q.; Song, Y.; Cheng, P.; Liao, D.-Z.; Yan, S.-P. Inorg. Chem. 2008, 47, 11057. (h) Chen, Z.; Fang, M.; Ren, P.; Li, X.-H.; Zhao, B.; Wei, S.; Cheng, P. Z. Anorg. Allg. Chem. 2008, 634, 382. (12) (a) Devereux, M.; McCann, M.; Leon, V.; McKee, V.; Ball, R. J. Polyhedron 2002, 21, 1063. (b) Zou, J.-P.; Peng, Q.; Zeng, G.-S.; Wen, Z.-H.; Xing, Q.-J.; Chen, M.-H.; Guo, G.-C.; Huang, J.-S. J. Mol. Struct. 2009, 921, 323. (c) Zou, J.-P.; Zeng, G.-S.; Wen, Z.-H.; Peng, Q.; Xing, Q.-J.; Chen, M.-H.; Guo, G.-C.; Huang, J.-S. Inorg. Chim. Acta 2009, 362, 4843. (d) Zou, J.-P.; Wen, Z.-H.; Peng, Q.; Zeng, G.-S.; Xing, Q.-J.; Chen, M.-H. J. Coord. Chem. 2009, 62, 3324. (13) (a) Hoffmann, R.; Imamura, A.; Zeiss, G. D. J. Am. Chem. Soc. 1967, 89, 5215. (b) Simmons, H. E.; Fukunaga, T. J. Am. Chem. Soc. 1967, 89, 5208. (c) Bredas, J. L. Science 1994, 263, 487. (d) Bredas, J. L.; Adant, C.; Tackx, P.; Persoons, A. Chem. Rev. 1994, 94, 243. (14) (a) Guo, D.; Pang, K.-L.; Duan, C.-Y.; Zhao, Y.-G.; Meng, Q.-J. Chem. Lett. 2002, 31, 1014. (b) Komuro, T.; Matsuo, T.; Kawaguchi, H.; Tatsumi, K. Inorg. Chem. 2003, 42, 5340. (c) Barclay, T. M.; Hicks, R. G.; Lemaire, M. T.; Thompson, L. K. Inorg. Chem. 2001, 40, 6521. (15) (a) Caskey, S. R.; Wong-Foy, A. G.; Matzger, A. J. Inorg. Chem. 2008, 47, 7751. (b) Verduzco, J. M.; Chung, H.; Hu, C.; Choe, W. Inorg. Chem. 2009, 48, 9060. (c) Xiang, S.; Wu, X.; Zhang, J.; Fu, R.; Hu, S.; Zhang, X. J. Am. Chem. Soc. 2005, 127, 16352. (16) Mahata, P.; Natarajan, S. CrystEngComm 2009, 11, 560. (17) (a) Wendlandt, W. W.; Hecht, H. G. Reflectance Spectroscopy; Interscience Publishers: New York, 1966. (b) Kort€um, G. Reflectance Spectroscopy; Springer-Verlag: New York, 1969. (18) SHELXTL Reference Manual, version 5; Siemens Energy & Automation Inc.: Madison, WI, 1994. (19) Sheik-Bahae, M.; Said, A. A.; Wei, T. H.; Hagan, D. J.; Stryland, E. W. V. IEEE J. Quantum Electron. 1990, 26, 760. (20) (a) Frisch, M. J.; Trucks, G. W.; Schlegel, H. B.; Scuseria, G. E.; Robb, M. A. GAUSSIAN 03; GAUSSIAN Inc.: Pittsburgh, PA, 2003. (b) Orr, B. J.; Ward, J. F. Mol. Phys. 1971, 20, 513. (c) Pierce, B. M. J. Chem. Phys. 1989, 91, 791. (21) (a) Segall, M.; Linda, P.; Probert, M.; Pickard, C.; Hasnip, P.; Clark, S.; Payne, M. Materials Studio CASTEP, version 2.2; Accelrys: San Diego, CA, 2002. (b) Segall, M.; Linda, P.; Probert, M.; Pickard, C.; Hasnip, P.; Clark, S.; Payne, M. J. Phys.: Condens. Matter 2002, 14, 2717.

Article (22) Hamann, D. R.; Schluter, M.; Chiang, C. Phys. Rev. Lett. 1979, 43, 1494. (23) (a) Ghosh, S. K.; Neogi, S.; Sa~ nudo, E. C.; Bharadwaj, P. K. Inorg. Chim. Acta 2008, 361, 56. (b) Zhou, G.-W.; Guo, G.-C.; Cai, L.-Z.; Liu, B.; Huang, J.-S. Chin. J. Struct. Chem. 2006, 25, 59. (c) Gao, H.-L.; Cui, J.-Z. Chin. J. Inorg. Chem. 2007, 23, 1072. (24) (a) Du, M.; Zhang, Z.-H.; Tang, L.-F.; Wang, X.-G.; Zhao, X.-J.; Batten, S. R. Chem.;Eur. J. 2007, 13, 2578. (b) Zhou, W.-W.; Chen, J.-T.; Xu, G.; Wang, M.-S.; Zou, J.-P.; Long, X.-F.; Wang, G.-J.; Guo, G.-C.; Huang, J.-S. Chem. Commun. 2008, 2762. (25) Gopalakrishnan, J.; Rao, C. N. R. New Directions in Solid State Chemistry; Cambridge University Press: UK, 1995.

Crystal Growth & Design, Vol. 10, No. 6, 2010

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(26) Sanghadasa, M.; Wu, B.; Clark, R. D.; Guo, H.; Penn, B. G. Proc. SPIE 1997, 3147, 185. (27) (a) Zhang, J.-P.; Lin, Y.-Y.; Huang, X.-C.; Chen, X.-M. J. Am. Chem. Soc. 2005, 127, 5495. (b) Liu, B.; Xu, L.; Guo, G.-C.; Huang, J.-S. Inorg. Chem. Commun. 2006, 9, 687. (28) (a) Yue, C.; Jiang, F.; Xu, Y.; Yuan, D.; Chen, L.; Yan, C.; Hong, M. Cryst. Growth Des. 2008, 8, 2725. (b) Liu, X.; Guo, G.-C.; Wu, A.-Q.; Cai, L.-Z.; Huang, J.-S. Inorg. Chem. 2005, 44, 4282. (29) (a) Zhang, R.-B.; Li, Z.-J.; Qin, Y.-Y.; Cheng, J.-K.; Zhang, J.; Yao, Y.-G. Inorg. Chem. 2008, 47, 4861. (b) Yi, F.-Y.; Zhao, N.; Wu, W.; Mao, J.-G. Inorg. Chem. 2009, 48, 628.