Chiral Coordination Polymers with SHG-Active and Luminescence: An

May 1, 2013 - Synopsis. Six coordination polymers based on d-camphorate and V-shaped 4-abpt ligands were synthesized. [Cd(SO4)(4-abpt)(H2O)]n·3nH2O ...
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Chiral Coordination Polymers with SHG-Active and Luminescence: An Unusual Homochiral 3D MOF Constructed from Achiral Components Na Chen,† Ming-Xing Li,*,† Peng Yang,† Xiang He,†,§ Min Shao,‡ and Shou-Rong Zhu*,† †

Department of Chemistry, College of Sciences, Shanghai University, Shanghai 200444, People’s Republic of China Laboratory for Microstructures, Shanghai University, Shanghai 200444, People’s Republic of China § State Key Laboratory of Structural Chemistry, Fujian Institute of Research on the Structure of Matter, Chinese Academy of Sciences, Fuzhou 350002, People’s Republic of China ‡

S Supporting Information *

ABSTRACT: Six new coordination polymers, namely, [Cd(SO4)(4-abpt)(H2O)]n·3nH2O (1), [Cu3(CN)3(4-abpt)2]n (2), [Cd(D-cam)(2-PyBIm)(H2O)]n (3), [Co(D-Hcam)(cptpy)]n (4), [Cd(D-cam)(btmb)]n (5), and [Cd2(D-cam)(L-cam)(btmbb)]n (6) (4-abpt = 4-amino-3,5-bis(4-pyridyl)1,2,4-triazole, D-H2cam = D-camphoric acid, 2-PyBIm = 2-(2pyridyl)benzimidazole, Hcptpy = 4′-(4-carboxyphenyl)-3,2′: 6′,3″-terpyridine, btmb = 1,4-bis(1,2,4-triazol-1-ylmethyl)benzene, btmbb = 4,4′-bis(1,2,4-triazol-1-ylmethyl)-1,1′-biphenyl), have been synthesized under hydro(solvo)thermal conditions. Their structures were determined by single-crystal Xray diffraction analysis and further characterized by elemental analysis, infrared spectra, powder X-ray diffraction, circular dichroism, and thermogravimetric analysis. Complex 1 features a 3D porous metal−organic framework, which is a rare example to obtain a homochiral compound from achiral components. Complex 2 exhibits a 2D polymeric network constructed from μ2cyanide, μ2-4-abpt, and monodentate 4-abpt ligands. Complex 3 is a homochiral 1D helical chain polymer. Complex 4 displays a 1D ladder-like polymeric structure in which cptpy− is tetradentate and D-Hcam− acts as a side arm. Complex 5 displays a homochiral 2D network with (4,4) topology. Complex 6 shows a [Cd2(D-cam)(L-cam)]n (4,4)-connected network with a paddle-wheel Cd2(COO)4 as node, which is further pillared by a btmbb spacer into a 3D metal−organic framework. DCamphoric acid underwent racemization under hydrothermal conditions. Cd(II) complexes 1, 3, and 5 crystallize in chiral space groups, and their circular dichroism spectra exhibit obvious positive or negative Cotton effects. Moreover, 1, 3, and 5 are SHGactive, and the SHG efficiency, respectively, is 0.15, 0.4, and 0.4 times as much as that of KH2PO4. All the complexes exhibit relatively high thermal stability. 1, 3, 5, and 6 emit violet luminescence originating from ligand-centered emission.

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resolution during crystal growth.6 Such a strategy would provide the greatest advantage as it does not use chiral components that often require laborious synthesis. Although numerous cases of such self-resolution of chiral CPs have been made, almost all of these CPs are, in fact, racemic because their bulk samples contain both enantiomorphs (opposite handedness) of CPs. We note that the V-shaped exo-bidentate organic bridging ligand can produce a 1D helical chain coordination polymer and bring out chirality. Using this strategy, we prepared two new CPs, [Cd(SO4)(4-abpt)(H2O)]n·3nH2O (1) and [Cu3(CN)3(4-abpt)2]n (2), by the V-shaped 4-amino-3,5bis(4-pyridyl)-1,2,4-triazole ligand. Interestingly, the complex 1 is SHG-active and crystallizes in chiral space group P212121. By using a circular dichroism spectrum, we convincingly

INTRODUCTION Over the past decade, coordination polymers and metal− organic frameworks (MOFs) have attracted great interest due to their intriguing structural motifs and potential applications as functional materials.1 Much effort has been focused on the rational design and controlled synthesis of coordination polymers using multidentate ligands, such as polycarboxylate and N-heterocyclic ligands.2 Among the numerous metal− organic coordination polymers, the chiral coordination polymers with noncentrosymmetric crystal structures are of special interest owing to their distinctive physical properties, such as second-harmonic generation (SHG), ferroelectricity, piezoelectricity, and pyroelectricity, which are potentially useful in electric-optical devices, information storages, nonlinear optical (NLO) devices, and light modulators.3 Chirality plays important roles in chemical and biological processes.4 To construct chiral coordination polymers (CPs), there are three distinct strategies.5 In the first approach, chiral CPs are prepared from totally achiral components via self© XXXX American Chemical Society

Received: March 22, 2013 Revised: April 26, 2013

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Scheme 1. Coordination Modes of N-Heterocyclic Ligands Involved in Complexes 1−6

completed on a Netzsch STA 449C thermal analyzer at a heating rate of 10 °C min−1. Luminescence spectra were recorded on a Shimadzu RF-5301 spectrophotometer. The second-order nonlinear optical intensities were estimated by measuring microcrystalline samples relative to KDP (KH2PO4) by a Rigol Oscilloscope 50 MHz DS1052E equipment. Syntheses of 1−6. [Cd(SO4)(4-abpt)(H2O)]n·3nH2O (1). A mixture of CdSO4·4H2O (28 mg, 0.1 mmol), 4-abpt (24 mg, 0.1 mmol), ethanol (4 mL), and H2O (4 mL) was sealed in a 15 mL Teflon-lined reactor. The reactor was heated at 140 °C for 72 h, and then cooled to room temperature at a rate of 10 °C h−1. Colorless crystals of 1 were obtained in 28% yield. Anal. Calcd for C12H18N6O8SCd (%): C, 27.78; H, 3.50; N, 16.20. Found: C, 28.46; H, 3.42; N, 16.65. IR (KBr, cm−1): 3375m, 3301m, 3176m, 1617s, 1458s, 1232s, 1087s, 1041s, 978s, 833s, 734m, 700m, 608s, 511m. [Cu3(CN)3(4-abpt)2]n (2). A mixture of CuCN (27 mg, 0.3 mmol), 4-abpt (72 mg, 0.3 mmol), K3[Fe(CN)6] (66 mg, 0.2 mmol), and H2O (8 mL) was sealed into a 15 mL Teflon-lined reactor. The reactor was heated at 140 °C for 72 h, and then cooled to room temperature at a rate of 10 °C h−1. Light yellow crystals of 2 were obtained with 30% yield based on Cu. Anal. Calcd for C27H20N15Cu3 (%): C, 43.51; H, 2.71; N, 28.20. Found: C, 43.46; H, 2.65; N, 28.06. IR (KBr pellet, cm−1): 3328m, 3170w, 2131m, 1609s, 1456m, 831m, 738m, 699m, 608m. [Cd(D-cam)(2-PyBIm)(H2O)]n (3). A mixture of Cd(NO3)2·4H2O (30 mg, 0.1 mmol), D-H2cam (20 mg, 0.1 mmol), 2-PyBIm (20 mg, 0.1 mmol), triethylamine (25 μL), DMF (4 mL), and H2O (4 mL) was sealed in a 15 mL Teflon-lined reactor. The reactor was heated at 85 °C for 72 h, and then cooled to room temperature at a rate of 10 °C h−1. Colorless crystals of 3 were obtained in 46% yield. Anal. Calcd for C22H25N3O5Cd (%): C, 50.44; H, 4.81; N, 8.02. Found: C, 50.48; H, 4.78; N, 8.06. IR (KBr pellet, cm−1): 3442m, 3176w, 3054w, 2965m, 2875w, 1598w, 1540s, 1456m, 1397s, 792m, 740s. [Co(D-Hcam)(cptpy)]n (4). A mixture of CoSO4·7H2O (28 mg, 0.1 mmol), D-H2cam (20 mg, 0.1 mmol), Hcptpy (18 mg, 0.05 mmol), triethylamine (25 μL), and H2O (8 mL) was sealed in a 15 mL Teflonlined reactor. The reactor was heated at 140 °C for 72 h, and then cooled to room temperature at a rate of 10 °C h−1. Dark red crystals of 4 were obtained in 32% yield based on Co. Anal. Calcd for C32H29N3O6Co (%): C, 62.95; H, 4.79; N, 6.88. Found: C, 62.81; H, 4.82; N, 6.96. IR (KBr pellet, cm−1): 3447m, 3118w, 3088s, 2970m, 2882w, 1707m, 1605s, 1552s, 1418s, 1389m, 783m, 698m. [Cd(D-cam)(btmb)]n (5). A mixture of Cd(NO3)2·4H2O (30 mg, 0.1 mmol), D-H2cam (20 mg, 0.1 mmol), btmb (24 mg, 0.1 mmol), triethylamine (25 μL), MeCN (4 mL), and H2O (4 mL) was sealed in a 15 mL Teflon-lined reactor. The reactor was heated at 120 °C for 72 h, and then cooled to room temperature at a rate of 10 °C h−1. Colorless crystals of 5 were obtained in 48% yield. Anal. Calcd for C22H26N6O4Cd (%): C, 47.97; H, 4.76; N, 15.26. Found: C, 47.92; H, 4.70; N, 14.92. IR (KBr pellet, cm−1): 3107m, 3058w, 2969s, 2883w, 1530s, 1459w, 1402s, 1364s, 1276s, 1125s, 1019s, 808m, 678s. [Cd2(D-cam)(L-cam)(btmbb)]n (6). A mixture of Cd(NO3)2·4H2O (30 mg, 0.1 mmol), D-H2cam (20 mg, 0.1 mmol), btmbb (32 mg, 0.1 mmol), triethylamine (25 μL), MeCN (1 mL), and H2O (7 mL) was

demonstrate the homochiral nature of the bulk crystal product of 1. In the second method, chiral CPs can be synthesized by metal salts and achiral ligands under chiral influence. For example, Rosseinsky et al. utilized enantiopure 1,2-propanediol as a chiral template to synthesize homochiral CPs from 1,3,5benzenetricarboxylate and M(NO3)2 (M = Ni, Co).7 The third method to construct chiral CPs is to use chiral ligands as building blocks. This approach is the most effective strategy and widely adopted. Among chiral ligands, some naturally chiral carboxylic acids, such as D-camphoric acid, L-malic acid, Ltartaric acid, and L-histidine acid, have been widely studied for preparing chiral complexes.8 So far, a number of homochiral CPs have been constructed using D-camphoric acid as a chiral source in combination with N-donor auxiliary ligands, such as pyridine, imidazole, triazole, and tetrazole coligands.9 By using N-heterocyclic auxiliary ligands (Scheme 1), we prepared four new D-camphorate CPs, [Cd(D-cam)(2-PyBIm)(H2O)]n (3), [Co(D-Hcam)(cptpy)]n (4), [Cd(D-cam)(btmb)]n (5), and [Cd2(D-cam)(L-cam)(btmbb)]n (6), in which camphorate displays varied coordination modes (Scheme 2). 3 and 5 are Scheme 2. Coordination Modes of Camphorate Observed in Complexes 3−6

homochiral, whereas 4 and 6 are achiral. Herein, we report their synthesis, crystal structures, thermal stabilities, CD spectra, luminescence, and second-order nonlinear optical properties.

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EXPERIMENTAL SECTION

Materials and Methods. The 4-abpt, 2-PyBIm, Hcptpy, btmb, and btmbb were prepared according to the literature method.10 Other chemicals were of reagent grade and used as received without further purification. C, H, and N analyses were performed on a Vario EL III elemental analyzer. Infrared spectra were recorded with a Nicolet A370 FT-IR spectrometer using KBr pellets in the range of 400−4000 cm−1. Powder X-ray diffractions were measured at a scanning rate of 5° min−1 on a Rigaku DLMAX-2550 diffractometer using Cu−Kα radiation (λ = 1.5418 Å). Circular dichroism (CD) spectra of solid samples were recorded at room temperature with a MOS-450 spectrometer (KBr pellets). Thermogravimetric analyses were B

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Table 1. Crystallographic Data and Structure Refinement for Complexes 1−6 formula fw cryst syst space group a (Å) b (Å) c (Å) α (deg) β (deg) γ (deg) V (Å3) Z Dc (g cm−3) F(000) μ (mm−1) reflns/unique Rint data/restraints/params GOF on F2 R1, wR2 (I > 2σ(I)) R1, wR2 (all data) largest diff. peak and hole (e Å−3)

1

2

3

4

5

6

C12H18N6O8SCd 518.77 orthorhombic P212121 5.703(5) 10.623(10) 29.89(3) 90 90 90 1811(3) 4 1.873 1008 1.377 9129/3203 0.0238 3203/1/274 1.143 0.0258, 0.0689 0.0264, 0.0695 0.619, −0.634

C27H20Cu3N15 745.20 orthorhombic Pna21 17.211(2) 22.975(3) 7.278(1) 90 90 90 2878.1(6) 4 1.720 1496 2.246 14 476/4650 0.0588 4650/1/486 1.024 0.0416, 0.0842 0.0678, 0.0969 0.388, −0.298

C22H25N3O5Cd 523.85 orthorhombic P212121 6.849(1) 13.200(2) 23.247(4) 90 90 90 2101.6(6) 4 1.656 1064 1.079 13 222/4809 0.0378 4809/0/296 1.043 0.0313, 0.0611 0.0340, 0.0631 0.463, −0.432

C32H29N3O6Co 610.51 monoclinic P21/c 17.687(3) 12.908(2) 13.411(2) 90 111.402(2) 90 2850.7(8) 4 1.423 1268 0.652 17 062/6548 0.0862 6548/19/348 1.110 0.1071, 0.3241 0.1968, 0.3819 1.600, −0.897

C22H26N6O4Cd 550.89 monoclinic P21 6.639(5) 18.167(13) 9.773(7) 90 96.891(8) 90 1170.2(14) 2 1.563 560 0.974 5815/3889 0.0257 3889/124/289 1.094 0.0480, 0.1162 0.0495, 0.1176 0.646, −0.709

C38H44N6O8Cd2 937.59 monoclinic P21/c 10.511(2) 14.073(2) 13.283(2) 90 97.940(2) 90 1946.0(5) 2 1.600 948 1.151 11 405/4415 0.0387 4415/0/247 0.994 0.0924, 0.1817 0.1383, 0.1992 0.977, −0.926

Table 2. Selected Bond Distances (Å) and Angles (deg) for Complexes 1−6 1 Cd(1)−O(1) Cd(1)−O(2) N(1)−Cd(1)−N(2)

2.328(3) 2.331(3) 173.64(12)

Cu(1)−N(1) Cu(1)−N(13) Cu(1)−C(26) N(13)−Cu(1)−C(26) N(13)−Cu(1)−N(1) N(1)−Cu(1)−C(26)

2.082(4) 1.924(7) 1.856(5) 141.4(2) 113.7(2) 104.6(2)

Cd(1)−O(1) Cd(1)−O(2) O(1)−Cd(1)−O(5W)

2.491(3) 2.277(2) 142.5(1)

Co(1)−O(1) Co(1)−O(2) O(1)−Co(1)−O(4)

2.070(5) 2.273(6) 156.1(2)

Cd(1)−O(1) Cd(1)−O(2) O(2)−Cd(1)−O(3) N(1)−Cd(1)−N(5)

2.359(10) 2.349(9) 144.2(3) 98.5(2)

Cd(1)−O(1) Cd(1)−O(2) O(1)−Cd(1)−O(2)

2.257(7) 2.186(8) 157.4(3)

Cd(1)−O(3) Cd(1)−O(5W) O(5W)−Cd(1)−O(2) 2 Cu(2)−N(7) Cu(2)−N(14) Cu(2)−C(27) N(14)−Cu(2)−N(7) N(14)−Cu(2)−C(27) N(7)−Cu(2)−C(27) 3 Cd(1)−O(4) Cd(1)−O(5W) O(4)−Cd(1)−N(1) 4 Co(1)−O(3) Co(1)−O(4) O(2)−Co(1)−N(3) 5 Cd(1)−O(3) Cd(1)−O(4) N(1)−Cd(1)−O(1) N(1)−Cd(1)−O(2) 6 Cd(1)−O(3) Cd(1)−O(4) O(3)−Cd(1)−O(4)

2.350(3) 2.300(3) 167.02(10)

Cd(1)−N(1) Cd(1)−N(2) O(1)−Cd(1)−O(3)

2.292(4) 2.298(4) 172.13(10)

2.091(5) 1.903(7) 1.829(6) 108.3(2) 106.7(3) 104.0(2)

Cu(3)−N(12) Cu(3)−N(15) Cu(3)−C(25) N(15)−Cu(3)−N(12) C(25)−Cu(3)−N(12) C(25)−Cu(3)−N(15)

2.039(6) 1.929(8) 1.904(5) 128.6(2) 113.9(2) 126.1(1)

2.222(2) 2.301(3) 157.65(9)

Cd(1)−N(1) Cd(1)−N(2) O(2)−Cd(1)−N(2)

2.445(3) 2.282(3) 162.2(1)

2.112(7) 2.221(6) 153.6(2)

Co(1)−N(2) Co(1)−N(3) O(3)−Co(1)−N(2)

2.101(6) 2.122(6) 135.0(3)

2.280(6) 2.356(6) 132.8(3) 85.3(3)

Cd(1)−N(1) Cd(1)−N(5) N(5)−Cd(1)−O(4) N(5)−Cd(1)−O(3)

2.285(11) 2.301(8) 134.0(4) 89.6(3)

2.252(8) 2.348(8) 158.2(3)

Cd(1)−N(1) N(1)−Cd(1)−O(2) N(1)−Cd(1)−O(1)

2.226(9) 110.6(3) 87.7(3)

X-ray Crystallography. The single-crystal X-ray diffraction measurements of 1−6 were carried out on a Bruker Smart Apex-II CCD diffractometer with graphite monochromatic Mo Kα radiation (λ = 0.71073 Å) using both φ- and ω-scan modes at room temperature. Determinations of the crystal system, orientation matrix, and cell dimensions were performed according to the established procedures. Lorentz polarization and absorption correction were applied. The

sealed in a 15 mL Teflon-lined reactor. The reactor was heated at 140 °C for 72 h, and then cooled to room temperature at a rate of 10 °C h−1. Colorless crystals of 6 were obtained in 38% yield based on Cd. Anal. Calcd for C38H44N6O8Cd2 (%): C, 48.68; H, 4.73; N, 8.96. Found: C, 48.60; H, 4.78; N, 9.03. IR (KBr pellet, cm−1): 3127m, 3030w, 2965s, 2879w, 1598s, 1542s, 1461w, 1394s, 1364m, 1281m, 1132m, 800m, 752s, 672s. C

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Figure 1. (a) The coordination structure of 1 (lattice water and H atoms are omitted for clarity). (b) The 2D [Cd(SO4)(H2O)]n polymeric network. (c) The 3D porous MOF pillared by V-shaped 4-abpt spacer.

1551 and 1418 cm−1 for 4, 1530 and 1402 cm−1 for 5, and 1542 and 1394 cm−1 for 6. However, complex 4 has a vas(COOH) vibration absorption at 1707 cm−1, which indicates that one carboxyl group of camphoric acid keeps protonation.13 In addition, the characteristic C−H stretching vibration of camphorate occurs at about 2965 cm−1. The ν(C−H) stretching vibration and δ(C−H) bending vibration of Nheterocyclic ligands appear at about 3100 and the 850−600 cm−1 range, respectively. These IR spectra are in good agreement with the results of elemental analysis and X-ray diffraction analysis. Description of Crystal Structures. Structure of [Cd(4abpt)(SO4)(H2O)]n·3nH2O (1). The X-ray structural analysis reveals that complex 1 crystallizes in the orthorhombic chiral space group P212121 with an absolute structural Flack factor of 0.00(3), which is a chiral three-dimensional (3D) porous metal−organic framework constructed from achiral 4-abpt and sulfate ligands. As shown in Figure 1a, the asymmetry unit is made up of one Cd(II) atom, one 4-abpt ligand, one sulfate ligand, and one coordinated water together with three lattice water molecules. The Cd(II) atom is six-coordinated by two pyridyl nitrogen atoms, three sulfate oxygen atoms, and water O5W, forming a trans-octahedral geometry. The equatorial plane is formed by the coordination of four oxygen atoms. The Cd−O bond distances vary from 2.300(3) to 2.350(3) Å. The O1−Cd1−O3 and O5W−Cd1−O2 bond angles are 172.13(10)° and 167.02(10)°, respectively. Two pyridyl nitrogen atoms occupy the axial positions with an average Cd−N bond distance of 2.295(4) Å. The N1−Cd1−N2 bond angle is 173.64(12)°. Other bond distances and angles are normal as reported for 4-abpt complexes.14 Each SO42− anion adopts a μ3-η1,η1,η1 tridentate coordination mode, bridging three Cd(II) atoms to form a 2D [Cd(SO4)(H2O)]n polymeric network (Figure 1b). Three Cd−O bond distances are a little different. The sulfate O4 atom is uncoordinated. Sulfate often acts as a charge-balance dianion in many compounds, whereas sulfate-coordinated complexes are rarely observed.15 The 2D [Cd(SO4)(H2O)]n

structures were solved by direct methods and refined on F2 by fullmatrix least-squares techniques with the SHELXTL program.11 All non-hydrogen atoms were refined anisotropically, and hydrogen atoms were located and included at their calculated position. The crystallographic data and structural refinement results are summarized in Table 1. The selected bond distances and angles are listed in Table 2.

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RESULTS AND DISCUSSION Synthesis and Infrared Spectra. Complexes 1−6 were successfully prepared by hydro(solvo)thermal reactions. The molar ratio of CdSO4 or CuCN with the 4-abpt ligand was kept in 1:1 for preparing 1 and 2. It is unexpected that complex 1 is a homochiral compound originating from achiral 4-abpt and sulfate ligands. K3[Fe(CN)6] acts as an additional cyanide source in the reaction of 2; however, trying to prepare 2 without K3[Fe(CN)6] failed.12 The complexes 3−6 are all camphorate coordination polymers. The molar ratios of metal salts with D-camphoric acid and N-heterocyclic coligands were kept in 1:1:1 for the preparation of 3, 5, and 6, except 2:2:1 for 4. Triethylamine was used as an organic base. The moles of 25 μL triethylamine is equal to ca. 0.18 mmol. It should be noticed that partial D-camphorate changed to L-camphorate in the preparation of 6 under hydrothermal conditions. The infrared spectra of 1−6 are all consistent with their structural characteristics as determined by single-crystal X-ray diffraction. Complex 1 displays characteristic strong peaks of sulfate at 1087 and 1041 cm−1. The bands at 3301, 3176, 1617, and 1458 cm−1 are, respectively, assigned to the stretching vibrations of N−H, C−H, CC, and CN bonds of 4-abpt. The bands at 833, 734, 700, and 608 cm−1 are assigned to the C−H out-of-plane bending vibration of the pyridyl group. For 2, the characteristic vibration absorption of cyanide appears at 2131 cm−1. Similar to 1, the absorption bands of 4-abpt also occur in the IR spectrum of 2. The IR spectra of 3−6 exhibit characteristic bands of camphorate. The asymmetric and symmetric stretching vibrations of carboxylate occur at 1540 and 1397 cm−1 for 3, D

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Figure 2. Coordination structure and 2D polymeric network of 2.

Figure 3. (a) The coordination structure of 3. (b) 1D left-handed helical chain along the b axis. (c) 3D supramolecular framework with π−π stacking interaction.

polymeric layers are parallelly arranged along the c axis, which are further pillared by a 4-abpt spacer to form a 3D porous metal−organic framework (Figure 1c). The neutral 4-abpt ligand coordinates to two Cd(II) atoms via two terminal pyridyl groups. Both pyridyl groups are coplanar with the central triazolyl group. Cd(II) atoms are connected together by the Vshaped 4-abpt linkers in a continuous fashion along the c axis,

forming a 1D waved infinite chain with a Cd···Cd separation of 14.97(2) Å. Interestingly, complex 1 crystallizes in the chiral space group P212121, which indicates that complex 1 is a chiral complex. The CD spectrum exhibits an obvious negative Cotton effect, which further confirms the homochiral nature of the bulk crystal product. Complex 1 is a rare example of a homochiral compound assembled from achiral components. Though E

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Figure 4. (a) The asymmetric unit of 4. (b) The 1D ladder-like chain. (c) D-Hcam− binds to the ladder-like chain as a side arm. (d) 2D supramolecular network containing left-handed (blue) and right-handed (red) helical chains.

Structure of [Cu3(CN)3(4-abpt)2]n (2). Complex 2 is a 2D copper(I) coordination polymer constructed from μ2-cyanide, μ2-4-abpt, and monodentate 4-abpt ligands. As shown in Figure 2, the asymmetric unit contains three crystallographically independent Cu(I) atoms, three cyanide groups, and two 4abpt ligands. Three distinct Cu(I) atoms are all threecoordinated by two cyanides and one pyridyl nitrogen donor and keep a trigonal geometry. All of the cyanide groups act as a μ2-bridge to link Cu1, Cu2, and Cu3 into an S-shaped 1D infinite chain. The CN−Cu−CN bond angles around Cu1, Cu2, and Cu3 are 141.4(2), 146.7(3), and 126.1(3)°, respectively. Two 4-abpt ligands exhibit different coordination modes. One 4-abpt is monodentate and binds to Cu1 through one terminal pyridyl group. Another 4-abpt acts as a bidentate bridge to link Cu2 and Cu3 through two terminal pyridyl groups. Three Cu(I)−Npy bond distances are in the range of 2.039(6)−2.091(5) Å. Adjacent copper(I)-cyanide 1D chains are connected by a bidentate 4-abpt linker to form a 2D coordination polymer (Figure 2). Originating from the Sshaped Cu(I)-cyanide 1D chain, the V-shaped exo-bidentate 4abpt ligand, and the monodentate 4-abpt ligand, the complex 2 is noncentrosymmetric and crystallizes in the orthorhombic acentric space group Pna21. Structure of [Cd(D-cam)(2-PyBIm)(H2O)]n (3). Complex 3 crystallizes in the orthorhombic chiral space group P212121 with a Flack factor of 0.03(2). The asymmetric unit contains one Cd(II) atom, one D-cam2− ligand, one 2-PyBIm ligand, and one coordinated water molecule (Figure 3a). Cd1 adopts a distorted cis-octahedral geometry, coordinated by three carboxyl oxygen atoms, two 2-PyBIm nitrogen atoms, and water O5W. The equatorial plane is completed by the coordination of N1, N2, O2, and O4 atoms. The axial positions

complex 1 is definitely a homochiral complex, we need to understand which asymmetric element gives rise to the chirality. It is well-known that a chiral organic compound often contains a tetrahedral chiral carbon atom, a BINOLderivate contains a chiral axis, and a 1D chiral helical complex contains a helical axis. However, the molecular structure of complex 1 shows the obvious absence of a chiral carbon atom and a chiral axis. Though space group P212121 indicates that the crystal structure of 1 only has a 21 helical axis, however, it is difficult to find a 21 helical axis in the polymeric structure of 1. The probable reasons why complex 1 is homochiral are as follows. On the one hand, it is well-known that helical chains often produce chirality. The V-shaped exo-bidentate bridging ligand can improve the helicity of the 1D polymeric chains.16 Wang et al. reported two homochiral Cd(II) complexes involving a V-shaped achiral ligand 2-[5-(pyridin-4-yl)-1,3,4oxadiazol-2-yl]pyridine that is similar to the 4-abpt ligand.17 As depicted in Figure S1 (Supporting Information), we suspect that Cd(II) atoms are connected together by the V-shaped 4abpt to form a flexuous chain along the c axis, which probably produces the chirality of complex 1. The dihedral angle between two Cd-combined pyridyl groups is 4.02°. On the other hand, we further observe the 2D [Cd(SO4)(H2O)]n polymeric network. It consists of asymmetric tetrahedral SO42− bridging ligands (four different S−O bonds and one uncoordinated O4 atom) and asymmetric planar CdO4 units (three different Cd−O coordination bonds and one terminal O5W atom). We find that this 2D [Cd(SO4)(H2O)]n network lacks a symmetric center, symmetric plane, and symmetric axis (Figure 1b and Figure S1, Supporting Information). Therefore, we also guess that the asymmetric 2D [Cd(SO4)(H2O)]n network may give rise to the chirality of complex 1. F

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Figure 5. (a) The coordination structure of 5. (b) 2D waved polymeric network. (c) 2D (4,4) topologic network. (d) The right-handed helical chains along the b axis.

consists of one independent Co(II) atom, one D-Hcam− ligand, and one cptpy− ligand (Figure 4a). Co1 adopts a distorted cis-octahedral geometry, coordinated by four carboxyl oxygen and two pyridyl nitrogen atoms. The equatorial plane is completed by the coordination of O1A, O3, O4, and N2A atoms. N3 and O2A atoms from cptpy− occupy the axial positions with a N3−Co1−O2A bond angle of 153.6(2)°. The carboxyl group of Hcptpy is deprotonated. The cptpy− anion is a tetradentate ligand and coordinates to three Co(II) atoms through a chelating carboxyl group and two outer pyridyl groups. The inner pyridyl group is free. Three pyridyl groups and a phenyl group are essentially coplanar. The cptpy− ligands link Co(II) atoms to form a 1D ladder-like infinite chain, as shown in Figure 4b. One carboxyl group of D-H2cam keeps protonated, and the other carboxyl group is deprotonated and chelates to the Co(II) atom (mode IV, Scheme 2). The DHcam− ligands bind to both sides of the 1D ladder-like chain as side-arms (Figure 4c). As shown in Figure 4d, the 1D ladder-like chains are parallelly arranged, which are further extended into a 2D supramolecular network by a strong hydrogen bond [O(5)− H(5WA)···O(4A) = 2.658(7) Å] between the carboxyl group

are occupied by O1 and O5W atoms with a O1−Cd1−O5W bond angle of 142.53(10)°. The Cd−O bond distances vary from 2.222(2) to 2.491(3) Å, and the average Cd−N bond distance is 2.364 Å. The neutral 2-PyBIm ligand is bidentate and chelates to the Cd(II) center. D-H2cam is completely deprotonated. The Dcam2− ligand coordinates to Cd1 and Cd1A via a chelating carboxyl group and a monodentate carboxyl group (mode III, Scheme 2). This connection results in the formation of a 1D left-handed helical chain with a pitch of 13.200 Å (Figure 3b). The 1D chains are parallelly stacked closely (Figure 3c). Each 1D chain interacts with neighboring chains via π−π interactions between aromatic rings of parallel 2-PyBIm ligands with an average centroid−centroid separation of 3.730 Å. There exist two strong hydrogen bonds that link carboxyl O3 with coordinated water and the imino group of 2-PyBIm. The O5W−H5B···O3#3 and N3−H3···O3#4 hydrogen bond distances are 2.790(4) and 2.787(4) Å, respectively. These π−π stacking and H-bonding interactions further extend the 1D helical chains into a 3D supramolecular framework. Structure of [Co(D-Hcam)(cptpy)]n (4). The complex 4 is a 1D ladder-like coordination polymer. The asymmetric unit G

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Figure 6. (a) The coordination structure of 6. (b) Cd-camphorate 2D (4,4) network. (c) 3D MOF pillared by a btmbb spacer. (d) Paddle-wheel Cd2 dimer surrounded by D-cam2− and L-cam2− ligands.

(COOH) and the coordinated carboxylate (COO−) of DHcam− in the neighboring 1D chain. Further research finds that there exist left-/right-handed helical chains L/R-[Co(DHcam)(3-cptpy)]n in the 2D supramolecular network linking by hydrogen-bonding interaction. D-Hcam− and 3-cptpy appear alternately in the helical chain (Figure 4d). Although chiral D-camphorate is used, the complex 4 is achiral due to the left-/right-handed helical chains that occur in an equal ratio. It can explain why the complex 4 is a racemic compound and crystallizes in achiral space group P21/c. Structure of [Cd(D-cam)(btmb)]n (5). Complex 5 crystallizes in the monoclinic chiral space group P21 with a Flack factor of 0.00. The asymmetry unit contains one independent Cd(II) atom, one D-cam2− ligand, and one btmb ligand (Figure 5a). Cd1 is six-coordinated by four carboxyl oxygen atoms and two btmb nitrogen atoms, forming a distorted cis-octahedral geometry. The equatorial plane is completed by N1, O1, O2, and O3 atoms. The axial positions are occupied by N5 and O4 atoms. The N5−Cd1−N1 and N5−Cd1−O4 bond angles are 98.5(2) and 134.0(4)°, respectively. The Cd−O bond distances vary from 2.280(6) to 2.359(10) Å, and the average Cd−N bond distance is 2.293 Å. The neutral btmb ligand is bidentate and adopts a transconformation. The dihedral angles between the central phenyl ring and each terminal triazolyl ring are 78.2 and 82.4°, respectively. D-camphoric acid is completely deprotonated.

Both carboxyl groups of D-cam2− display a chelating coordination mode (mode I, Scheme 2). Each D-cam2− ligand connects two Cd(II) atoms to form a 1D [Cd(D-cam)]n linear chain. These 1D chains are further linked by bidentate btmb spacers to afford a 2D waved polymeric network (Figure 5b). The Cd···Cd distances spanned by D-cam2− and btmb ligands are 9.77(1) and 14.42(6) Å, respectively. Taking D-cam2− and btmb ligands as linkers and Cd(II) atoms as nodes, the 2D polymeric layer can be simplified to a (4,4) topologic network (Figure 5c). Liang et al. reported a 2D (4,4) network [Zn(1,4bimb)(D-cam)]n, in which Zn(II) is four-coordinated, and 1,4bimb is 1,4-bis(imidazol-1-ylmethyl)benzene.18 From a chiral viewpoint, the btmb ligand and chiral D-cam2− ligand connect Cd(II) atoms alternately to form a 1D helical chain with a pitch of 18.167 Å, as shown in Figure 5d. All the helical chains exhibit the same right-handedness. As a result, these right-handed helical chains via sharing the metal sites form the homochiral 2D coordination polymer 5. Structure of [Cd2(D-cam)(L-cam)(btmbb)]n (6). Complex 6 crystallizes in the monoclinic achiral space group P21/c. The asymmetric unit contains one independent Cd(II) atom, half D-cam2− ligand, half L-cam2− ligand, and half btmbb ligand. Cd1 is five-coordinated by four oxygen atoms from four camphorates and one btmbb nitrogen atom, forming a slightly distorted tetragon-pyramidal geometry (Figure 6a). The basal plane is completed by four carboxyl oxygen atoms with Cd−O H

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bond distances varying from 2.186(8) to 2.348(8) Å. The apical site is occupied by N1 with a Cd−N bond distance of 2.226(9) Å. Similar as the btmb ligand in 5, the neutral btmbb ligand is bidentate and adopts a trans-conformation. Both central phenyl rings are coplanar. The dihedral angles between the central phenyl groups and two terminal triazolyl groups are both 78.5°. The btmbb ligand coordinates to two Cd(II) atoms via two terminal triazolyl nitrogen donors. The Cd···Cd distance spanned by btmbb is 16.80(2) Å. Camphoric acid is completely deprotonated. Both carboxyl groups of camphorate adopt a bidentate-bridging coordination mode (mode II, Scheme 2), which is obviously different with the D-cam2− coordination mode in 5. Cd1 and Cd1A are bridged by four carboxyl groups to form a paddle-wheel Cd2(COO)4 dimer. Such dimers are connected by D-camphorate and L-camphorate to afford a 2D (4,4) polymeric network (Figure 6b). The Cd···Cd distance spanned by each camphorate is 9.773(7) Å. Such 2D [Cd2(Dcam)(L-cam)]n polymeric layers are parallelly arranged along the a axis, which are further pillared by a btmbb spacer to form a 3D metal−organic framework (Figure 6c). Interestingly, the paddle-wheel Cd2(COO)4 dimer is surrounded by two D-cam2− ligands and two L-cam2− ligands (Figure 6d). It indicates that the chiral source D-camphoric acid of 6 undergoes the racemization under hydrothermal conditions, leading to the structure of 6 composed of both Dand L-camphorate with an equal ratio. This structural variation can be clearly observed through contrasting the position changes of four different atoms around chiral C*(11) or C*(14) atoms. The similar racemization phenomena were also observed in other work.19 PXRD and Circular Dichroism (CD). To check the phase purity of the products, powder X-ray diffraction (PXRD) experiments have been carried out for these complexes (Figure S3, Supporting Information). The peak positions of the experimental and simulated PXRD patterns are in good agreement with each other, indicating that the crystal structures are truly representative of the bulk crystal products. The differences in intensity may be owing to the preferred orientation of the crystal samples. Interestingly, the complex 1 crystallizes in the chiral space group P212121, which indicates that complex 1 is a chiral complex. The solid-state circular dichroism spectrum of 1 is recorded on the bulk crystal product with a KBr pellet between 200 and 800 nm (Figure 7). The CD spectrum exhibits an obvious negative Cotton effect with peaks around 219 and 509 nm, confirming that the entire crystal product of 1 is homochiral. The CD spectrum of complex 3 exhibits a positive Cotton effect with peaks at 245 and 309 nm, and a negative Cotton effect around 688 nm (Figure S4, Supporting Information). The CD spectrum of complex 5 shows a negative Cotton effect with peaks around 336 and 513 nm. These CD spectra confirm the enantiopure nature of complexes 1, 3, and 5. Thermogravimetric Analysis (TGA). The thermal stabilities of coordination polymers 1−6 were determined in the temperature range of 20−800 °C (Figure S5, Supporting Information). The thermogravimetric curve displays that the complex 1 released three lattice water molecules and one coordinated water molecule in the 50−110 °C range (found, 11.36%; calcd, 13.88%). The anhydrous framework of [Cd(4abpt)(SO4)]n is thermal stable up to 370 °C. Two weight-loss processes appearing in 370−420 and 500−570 °C ranges

Figure 7. CD spectrum of complex 1.

indicate that the complex completely decomposed. Complex 2 is thermal stable under 330 °C without any weight loss. An exothermic maximum at 290.8 °C without weight loss indicates that a phase transfer process happened. The polymeric framework then successively decomposes to 800 °C without stopping. Complex 3 loses one coordinated water molecule in 160−200 °C with a weight loss of 3.1% (calcd 3.4%). The anhydrous compound is thermally stable until 350 °C. The successive weight-loss process then corresponds to the decomposition of 2-PyBIm and D-cam2− ligands. Complex 4 is thermal stable under 355 °C, and then releases D-Hcam− and cptpy− ligands continuously to afford the CoCO3 residue at 600 °C (found, 18.54%; calcd, 19.50%). The thermogravimetric curves of 5 and 6 are similar. The networks remain intact until heated to 290 and 320 °C, respectively, and then both complexes begin to collapse. Photoluminescence. It is well-known that d10 transitionmetal complexes possess varied luminescent properties. Organic ligands and their coordination modes obviously affect the emission wavelength and luminescent mechanism.20 The luminescent behaviors of four Cd(II) complexes and their corresponding N-heterocyclic ligands were investigated (Figure 8, and Figure S6, Supporting Information). When excited with 300 nm light, the free 4-abpt ligand exhibits a strong emission

Figure 8. Emission spectra of Cd(II) complexes 1, 3, 5, and 6. I

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Table 3. SHG-Active 3D MOFs Constructed by Achiral Ligands MOFs

chemical formula

space group

SHG

ref

1 2 3 4 5

[Cd(4-abpt)(SO4)(H2O)]n·3nH2O Zn4(tcsm)2(H2O)3(DMA)3·2H2O Nd(Hhnic)2(CH3COO) [Zn2(dpp)2(bza)2]2 2H2O Tb(tdea)(NO3)3

P212121 (chiral) Cc (acentric) Cmc2 (acentric) P21 (acentric) P3c1 (acentric)

0.15 × KDP 0.6 × KDP 0.2 × KDP active active

this paper 23 24 25 26

Table 4. SHG-Active Chiral Coordination Polymers Built from D-Camphorate Ligand CPs

chemical formula

dimension

space group

1 2 3 4 5 6 7 8 9 10 11

[Cd(D-cam)(btmb)]n [Cd(D-cam)(2-PyBim)(H2O)]n Zn2(TPOM)(D-Cam)2(H2O)2 Cd2(TPOM)(D-Cam)2(H2O)2 [Zn(1,3-bimb)(D-ca)]n [Cd(1,3-bimb)(D-ca)]n [Zn(1,4-bimb)(D-ca)]n {[Cd2(dpys)(D-ca)2(H2O)2](H2O)3}n [Cd2(D-cam)2(La)2](H2O)6 [Cd2(D-cam)2(La)(H2O)] [Zn2(D-cam)2(Lb)2](H2O)5

2D 1D 3D 3D 1D 1D 2D 2D 3D 3D 3D

P21 P212121 P21212 P21212 Pna21 Pna21 P21 Cmc21 P212121 P21 P21

SHG 0.4 0.4 0.8 0.9 0.3 0.1 0.3 0.8 0.5 0.5 0.2

× × × × × × × × × × ×

KDP KDP urea urea urea urea urea urea urea urea urea

ref this paper this paper 27 27 18 18 18 18 28 28 28

SHG efficiency of 1 is approximately 0.15 times as much as that of KDP, which is consistent with its homochiral framework. Several reported 3D MOFs synthesized by achiral ligands were also found to crystallize in acentric space groups and gave rise to SHG activity, as shown in Table 3. The D-camphorate complexes 3 and 5 are homochiral 1D helical chain and 2D layered coordination polymers that crystallize in the chiral space groups P212121 and P21, respectively. Preliminary SHG optical experimental results indicate that both complexes are SHG-active and the SHG efficiency is approximately 0.4 times as much as that of KDP. A number of homochiral coordination polymers have been constructed using D-camphoric acid as a chiral source. Table 4 exhibits all SHG-active chiral coordination polymers involving the D-camphorate ligand.

peak at 369 and two weak peaks at 420 and 466 nm. Under the same excitation condition, complex 1 displays similar luminescent behavior with a strong emission peak at 367 and two weak peaks at 420 and 465 nm. The similar luminescent behaviors indicate that the luminescence of 1 originates from ligand-centered emission. When excited with 336 nm light, complex 3 shows a violet luminescence with an emission maximum at 426 nm. The free 2-PyBIm ligand shows an emission peak at ca. 425 nm.21 The btmb and btmbb ligands contain conjugated phenyl and triazolyl groups, which show two weak emission peaks at 366/ 410 and 378/421 nm, respectively (excited at 320 nm). The btmb complex 5 and btmbb complex 6 exhibit two intense emission peaks at 380/416 and 385/423 nm. The similar luminescent energy between Cd(II) complexes and their Nheterocyclic ligands indicates that the luminescent mechanism of 3, 5, and 6 originates also from ligand-centered emission. Second-Harmonic Generation Efficiency. Considering that the homochiral Cd(II) complexes 1, 3, and 5 are colorless, transparent crystals and crystallize in the noncentrosymmetric chiral space groups, their nonlinear optical properties are investigated. According to the method proposed by Kurtz and Perry,22 the second-harmonic generation (SHG) efficiency can be measured by using a powder technique. The SHG efficiency is compared with a standard material, such as α-quartz, KH2PO4 (KDP), or urea. KDP has an efficiency of 16 × αquartz, whereas urea has an efficiency of 400 × α-quartz. The technologically important LiNbO3 is 600 × α-quartz. In this work, the SHG efficiency of 1, 3, and 5 is measured by using pure microcrystalline samples, and the result is in contrast with KDP. Complex 1 is a homochiral 3D metal−organic framework originating from an achiral V-shaped 4-abpt ligand. It crystallizes in chiral space group P212121, and exhibits an obvious negative Cotton effect. The second-harmonic generation (SHG) is measured using a pulsed laser at a wavelength of 1064 nm. Upon irradiation, the microcrystalline sample of 1 emits green light at a wavelength of 532 nm. The SHG optical experimental result indicates that complex 1 is SHG-active. The

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CONCLUSIONS In conclusion, six 1D, 2D, and 3D coordination polymers, including three homochiral Cd(II) complexes, have been successfully synthesized and structurally characterized. The Dcamphorate and N-heterocyclic ligands exhibit various coordination modes and conformations. Complex 1 features a 3D porous metal−organic framework, which is a rare example to obtain a homochiral compound from achiral components. Complex 6 possesses a [Cd2(D-cam)(L-cam)]n (4,4)-network with a paddle-wheel Cd2(COO)4 dimer as node, which is further pillared by a btmbb spacer into a 3D MOF. The chiral source D-camphoric acid undergoes racemization under hydrothermal conditions. All the complexes exhibit relatively high thermal stabilities. Four Cd(II) complexes emit violet luminescence. The homochiral Cd(II) complexes 1, 3, and 5 exhibit obvious positive or negative Cotton effects, which are SHG-active, and the SHG efficiency is, respectively, 0.15, 0.4, and 0.4 times as much as that of KDP. This work indicates that building chiral MOFs with enantiopure ligands appears to be the most straightforward strategy to design SHG-active materials. Meanwhile, an achiral V-shaped ligand is worthy of consideration, which may generate a homochiral coordination J

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(7) (a) Bradshaw, D.; Timothy, J.; Cussen, E. J.; Claridge, J. B.; Rosseinsky, M. J. J. Am. Chem. Soc. 2004, 126, 6106. (b) Kepert, C.; Prior, T.; Rosseinsky, M. J. Am. Chem. Soc. 2000, 122, 5158. (8) (a) Zhang, J.; Chen, S.; Valle, H.; Wong, M.; Austria, C.; Cruz, M.; Bu, X. J. Am. Chem. Soc. 2007, 129, 14168. (b) Zhang, J.; Chen, S.; Zingiryan, A.; Bu, X. J. Am. Chem. Soc. 2008, 130, 17246. (c) Zhang, J.; Bu, X. Angew. Chem., Int. Ed. 2007, 46, 6115. (9) (a) Liang, X. Q.; Li, D. P.; Zhou, X. H.; Sui, Y.; Li, Y. Z.; Zuo, J. L.; You, X. Z. Cryst. Growth Des. 2009, 9, 4872. (b) Yang, P.; He, X.; Li, M. X.; Ye, Q.; Ge, J. Z.; Wang, Z. X.; Zhu, S. R.; Shao, M.; Cai, H. L. J. Mater. Chem. 2012, 22, 2398. (c) Klingele, M. Coord. Chem. Rev. 2003, 241, 119. (10) (a) Cheng, L.; Zhang, W. X.; Ye, B. H.; Lin, J. B.; Chen, X. M. Inorg. Chem. 2007, 46, 1135. (b) Meng, X.; Song, Y.; Hou, H.; Han, H.; Xiao, B.; Fan, Y.; Zhu, Y. Inorg. Chem. 2004, 43, 3528. (c) Li, N.; Zhu, Q. E.; Hu, H. M.; Guo, H. L.; Xie, J.; Wang, F.; Dong, F. X.; Yang, M. L.; Xue, G. L. Polyhedron 2013, 49, 207. (d) Schiffmann, R.; Neugebauer, A.; Klein, C. D. J. Med. Chem. 2006, 49, 511. (11) Sheldrick, G. M. SHELXTL, V6.1 Software Reference Manual; Bruker AXS Inc.: Madison, WI, 2000. (12) (a) He, X.; Lu, C. Z.; Wu, C. D.; Chen, L. J. Eur. J. Inorg. Chem. 2006, 2491. (b) Liang, S. W.; Li, M. X.; Shao, M.; Miao, Z. X. Inorg. Chem. Commun. 2006, 9, 1312. (13) Deacon, G. B.; Phillips, R. J. Coord. Chem. Rev. 1980, 33, 227. (14) (a) Meng, Z. S.; Yun, L.; Zhang, W. X.; Hong, C. G.; Herchel, R.; Ou, Y. C.; Leng, J. D.; Peng, M. X.; Lin, Z. J.; Tong, M. L. Dalton Trans. 2009, 10284. (b) Dupouy, G.; Marchivie, M.; Triki, S.; SalaPala, J.; Salaun, J. Y.; Gomez-Garcia, C. J.; Guionneau, P. Inorg. Chem. 2008, 47, 8921. (c) Guo, H. M.; He, X.; Liu, J. J.; Han, J.; Li, M. X. Polyhedron 2011, 30, 1982. (15) (a) Xu, Z.; Wang, Q.; Li, H.; Meng, W.; Han, Y.; Hou, H.; Fan, Y. Chem. Commun. 2012, 48, 5736. (b) Xu, J.; Su, W.; Hong, M. CrystEngComm 2011, 13, 3998. (c) Li, M. X.; Miao, Z. X.; Shao, M.; Liang, S. W.; Zhu, S. R. Inorg. Chem. 2008, 47, 4481. (16) (a) Chen, X. M.; Liu, G. F. Chem.Eur. J. 2002, 8, 4811. (b) Moulton, B.; Zaworotko, M. J. Chem. Rev. 2001, 101, 1629. (17) Wang, Y. T.; Tong, M. L.; Fan, H. H.; Wang, H. Z.; Chen, X. M. Dalton Trans. 2005, 424. (18) Liang, X. Q.; Li, D. P.; Li, C. H.; Zhou, X. H.; Li, Y. Z.; Zuo, J. L.; You, X. Z. Cryst. Growth Des. 2010, 10, 2596. (19) (a) Luo, F.; Ning, Y.; Luo, M.; Huang, G. CrystEngComm 2010, 12, 2769. (b) Zhang, J.; Yao, Y. G.; Bu, X. Chem. Mater. 2007, 19, 5083. (20) (a) Colacio, E.; Kivekas, R.; Lloret, F.; Sunberg, M.; SuarezVarela, J.; Bardaji, M.; Laguna, A. Inorg. Chem. 2002, 41, 5141. (b) Phillips, D. L.; Che, C. M.; Leung, K. H.; Mao, Z.; Tse, M. C. Coord. Chem. Rev. 2005, 249, 1476. (21) Li, M. X.; Wang, H.; Liang, S. W.; Shao, M.; He, X.; Wang, Z. X.; Zhu, S. R. Cryst. Growth Des. 2009, 9, 4626. (22) Kurtz, S. K.; Perry, T. T. J. Appl. Phys. 1968, 39, 3798. (23) Liang, L. L.; Ren, S. B.; Zhang, J.; Li, Y. Z.; Du, H. B.; You, X. Z. Dalton Trans. 2010, 39, 7723. (24) Liu, C. M.; Zuo, J. L.; Zhang, D. Q.; Zhu, D. B. CrystEngComm 2008, 10, 1674. (25) Zheng, Y. Q.; Zhang, J.; Liu, J. Y. CrystEngComm 2010, 12, 2740. (26) Wong, K. L.; Law, G. L.; Kwok, W. M.; Wong, W. T.; Phillips, D. L. Angew. Chem., Int. Ed. 2005, 44, 3436. (27) Liang, L. L.; Ren, S. B.; Zhang, J.; Li, Y. Z.; Du, H. B.; You, X. Z. Cryst. Growth Des. 2010, 10, 1307. (28) Wang, L.; You, W.; Huang, W.; Wang, C.; You, X. Z. Inorg. Chem. 2009, 48, 4295.

polymer that has an SHG efficiency with other functional properties.

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ASSOCIATED CONTENT

S Supporting Information *

Views of 2D network and 1D waved chain, FT-IR spectra, PXRD patterns, CD spectra, TG curves, and emission spectra. This material is available free of charge via the Internet at http://pubs.acs.org. Crystallographic data have been deposited at the Cambridge Crystallographic Data Center, CCDC− 920417 for 1, −645362 for 2, −920420 for 3, −923427 for 4, −920418 for 5, and −920419 for 6. These data can be obtained from the Cambridge Crystallographic Data Center, 12, Union Road, Cambridge CB21EZ, U.K.

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AUTHOR INFORMATION

Corresponding Author

*E-mail: [email protected] (M.-X.L.), shourongzhu@shu. edu.cn (S.-R.Z.). Fax: +86-21-66134594 (M.-X.L.). Notes

The authors declare no competing financial interest.

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ACKNOWLEDGMENTS Financially supported by the National Natural Science Foundation of China (21171115, 21203117), the Innovation Program (12ZZ089) of Shanghai Municipal Education Commission, and the Natural Science Foundation of Shanghai (10ZR1411100).

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REFERENCES

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dx.doi.org/10.1021/cg400426m | Cryst. Growth Des. XXXX, XXX, XXX−XXX