Ligand-Isomerism Controlled Structural Diversity of ... - ACS Publications

Article pubs.acs.org/crystal

Ligand-Isomerism Controlled Structural Diversity of Zn(II) and Cd(II) Coordination Polymers from Mixed Dipyridyladipoamide and Benzenedicarboxylate Ligands Pei-Chi Cheng, Po-Ting Kuo, Yu-Hung Liao, Ming-Yuan Xie, Wayne Hsu, and Jhy-Der Chen* Department of Chemistry, Chung-Yuan Christian University, Chung-Li, Taiwan, R.O.C. S Supporting Information *

ABSTRACT: By using isomeric N,N′-di(2-pyridyl)adipoamide (L1), N,N′-di(3-pyridyl)adipoamide (L2) and N,N′-di(4-pyridyl)adipoamide (L3) and isomeric 1,2-benzenedicarboxylic acid (1,2-H2BDC), 1,3-benzenedicarboxylic acid (1,3-H2BDC) and 1,4-benzenedicarboxylic acid (1,4-H2BDC), eight Zn(II) and Cd(II) coordination polymers [Zn(1,2BDC)(L2)]∞, 1; [Zn2(1,3-BDC)2(L2)(H2O)2]∞, 2; [Zn2(1,4BDC)2(L1)(H2O)2]∞, 3; {[Zn2(1,2-BDC)2(L3)(H2O)2]·2H2O}∞, 4; {[Cd(1,2-BDC)(L2)(H2O)]·H2O}∞, 5; [Cd2(1,3-BDC)2(L2)(H2O)4]∞, 6; {[Cd2(1,4-BDC)2(L2)2]·(H2O)3}∞, 7; [Cd2(1,4-BDC)2(L1)(H2O)2]∞, 8, have been synthesized under hydrothermal conditions. Complexes 1, 4, and 5 form 1D double-looped chain, 1D chain with loops and 2D layer with loops, respectively, and complex 6 exhibits a 1D ladder chain. Complex 2 shows rare 3-fold interpenetrated hcb layers, in which each layer interdigitates with other four parallel layers by directing the 1,3-BDC ligands into the windows of the adjacent nets, whereas complexes 3 and 8 forms planar and undulated hcb layers, respectively. Complex 7 shows a 3D selfpenetrating net of {424.5.63}-ilc topology with a unique arrangement for the L2 spacer ligands. The L1 ligands in complexes 3 and 8 adopt the new tetradentate bonding mode involving chelation and bridge through two pyridyl nitrogen atoms and two amide oxygen atoms, whereas the L2 and L3 ligands in other complexes show the bidentate bonding mode through the two pyridyl nitrogen atoms. The various bonding modes and the ligand-isomerism of the spacer ligands BDC2− and L1−L3 as well as the identity of the metal center play important roles in determining the structural diversity.

■

shapes of the dicarboxylates. For complexes with the L3 ligands, those with the linear dicarboxylates form the 3D interpenetrated coordination networks, whereas those with the angular dicarboxylates form coordination networks with less dimensionality, involving a 1D → 2D polycatenane and 2-fold 2D → 2D parallel interpenetration network containing a rotaxane-like motif.7b With this background information, we sought to investigate the influence of the ligand isomerism on the structural diversity of Zn(II) and Cd(II) coordination polymers containing the flexible dipyridyl amide and the rigid dicarboxylate ligands. Reactions of Zn(II) and Cd(II) salts with the isomeric N,N′di(2-pyridyl)adipoamide (L1), N,N′-di(2-pyridyl)adipoamide (L2) and L3, and the isomeric 1,2-benzenedicarboxylic acid (1,2-H2BDC), 1,3-benzenedicarboxylic acid (1,3-H2BDC) and 1,4-H2BDC afforded [Zn(1,2-BDC)(L2)]∞, 1; [Zn2(1,3BDC)2(L2)(H2O)2]∞, 2; [Zn2(1,4-BDC)2(L1)(H2O)2]∞, 3; {[Zn2(1,2-BDC)2(L3)(H2O)2]·2H2O}∞, 4; {[Cd(1,2-BDC)(L2)(H2O)]·H2O}∞, 5; [Cd2(1,3-BDC)2(L2)(H2O)4]∞, 6;

INTRODUCTION The rational design and synthesis of novel coordination polymer is an active topic of investigation, because it expands the range of new complexes with preselected physical and chemical properties.1 The range and variety of the selfassembling structures that can be constructed relies on the presence of suitable metal−ligand interactions and supramolecular contacts, i.e., hydrogen bondings and other weak interactions.2 Additionally, the structural types of the resulting coordination polymers are also affected by factors such as counterion,3 metal-to-ligand ratio,4 and solvent.5 Although many coordination polymers with intriguing topologies and properties have been reported, the control of structural dimensionality remains a great challenge in crystal engineering. The mixed ligand assembly system has been widely adopted for the generation of new coordination networks.6,7 However, due to a great diversity of the resulting structures, the governing principles in this system are less ascertained and remain elusive. Recently, we reported several Cd(II) coordination polymers based on the linear and angular dicarboxylates and the flexible N,N′-di(4-pyridyl)adipoamide (L3) ligand,7 which reveal that the structural types and degree of interpenetration of these Cd(II) coordination networks can be tuned by changing the © XXXX American Chemical Society

Received: September 9, 2012 Revised: October 27, 2012

A

dx.doi.org/10.1021/cg301311m | Cryst. Growth Des. XXXX, XXX, XXX−XXX

Crystal Growth & Design

Article

{[Cd2(1,4-BDC)2(L2)2]·(H2O)3}∞, 7; [Cd2(1,4-BDC)2(L1)(H2O)2]∞, 8, which show 1D, 2D, and 3D structures. The syntheses, structures and thermal and luminescent properties of these complexes form the subject of this report.

■

C16H17N2O7Zn (MW = 414.69): C, 46.34; H, 4.13; N, 6.76%. Found: C, 46.09; H, 4.53; N, 6.80%. IR (KBr disk, cm−1): 3174(br), 1716(m), 1683(s), 1622(m), 1589(s), 1557(s), 1509(s), 1488(m), 1419(s), 1389(s), 1213(w), 1155(m), 843(m), 767(w), 708(m). Synthesis of {[Cd(1,2-BDC)(L2)(H2O)]·H2O}∞, 5. Prepared as described for 1, except that Cd(CH3COO)2·2H2O (0.027 g, 0.10 mmol) was used. Yield: 0.043 g (70%, based on Cd). Anal. Calcd for C24H26CdN4O8 (MW = 610.89): C, 47.19; H, 4.29; N, 9.17%. Found: C, 47.28; H, 4.24; N, 9.13%. IR (KBr disk, cm−1): 3127(br), 1682(s), 1605(m), 1587(m), 1552(s), 1485(s), 1465(w), 1433(s), 1414(s), 1403(s), 1309(w), 1284(m), 752(m), 700(m), 645(w). Synthesis of [Cd2(1,3-BDC)2(L2)(H2O)4]∞, 6. Prepared as described for 1, except that Cd(CH3COO)2 · 2H2O (0.053 g, 0.20 mmol) and 1,3-H2BDC (0.033 g, 0.20 mmol) were used. Yield: 0.077 g (84%, based on Cd). Anal. Calcd for C16H17CdN2O7 (MW = 461.72): C, 41.62; H, 3.71; N, 6.07%. Found: C, 41.70; H, 3.58; N, 6.10%. IR (KBr disk, cm−1): 3121(w), 3068(br), 1677(s), 1607(s), 1584(w), 1548(s), 1480(m), 1427(s), 1369(s), 1330(m), 1314(m), 1284(s), 1172(w), 734(m), 702(w). Synthesis of {[Cd2(1,4-BDC)2(L2)2]·(H2O)3}∞, 7. Prepared as described for 1, except that Cd(CH3COO)2 · 2H2O (0.027 g, 0.10 mmol) and 1,4-H2BDC (0.017 g, 0.10 mmol) were used. Yield: 0.057 g (95%, based on Cd). Anal. Calcd for C48H50Cd2N8O15 (MW = 1203.76): C, 47.89; H, 4.19; N, 9.31%. Found: C, 47.58; H, 3.91; N, 9.16%. IR (KBr disk, cm−1): 3102(br), 1693(s), 1582(s), 1552(s), 1503(m), 1478(m), 1427(s), 1309(s), 1332(m), 1283(s), 837(w), 764(w), 752(m), 700(w). Synthesis of [Cd2(1,4-BDC)2(L1)(H2O)2]∞, 8. Prepared as described for 1, except that Cd(CH3COO)2 · 2H2O (0.053 g, 0.20 mmol), 1,4-H2BDC (0.033 g, 0.20 mmol) and L1 (0.030 g, 0.10 mmol) were used. Yield: 0.062 g (70%, based on Cd). Anal. Calcd for C16H15CdN2O6 (MW = 443.70): C, 43.31; H, 3.41; N, 6.31%. Found: C, 43.34; H, 3.30; N, 6.07%. IR (KBr disk, cm−1): 3103(br), 1673(s), 1623(m), 1586(m), 1557(s), 1540(m), 1507(w), 1479(s), 1400(s), 1378(s), 1353(s), 1336(m), 1283(m), 761(w), 748(w). Thermal Gravimetric Analyses. The samples were heated up in nitrogen gas at a pressure of 1 atm with a heating rate of 10 °C min−1. The TGA curves of complexes 1−8 are shown in Figure S1, Supporting Information. X-ray Crystallography. Single crystal X-ray diffraction data were collected on a Bruker AXS P4 diffractometer (1−3), on a Bruker AXS SMART-1000 diffractometer (4) or on a Bruker AXS SMART APEX II diffractometer (5−8) at 22 °C, which were equipped with a graphite-monochromated Mo Kα (λα = 0.71073 Å) radiation. Data reduction was carried out by using well-established computational procedures.9 The structure factors were obtained after Lorentz and polarization correction. An empirical absorption correction based on a series of ψ-scans was applied to the data for complexes 1−3, while the empirical absorption correction based on “multi-scan” was applied to the data for complexes 4−8. The positions of some of the heavier atoms, including the zinc and cadmium atom, were located by the direct method. The remaining atoms were found in a series of alternating difference Fourier maps and least-squares refinements.10 The hydrogen atoms of the water molecules of complexes 2, 4−6, and 8 were located from the difference Fourier maps, whereas the other hydrogen atoms were added by using the HADD command in SHELXTL 5.10. Basic information pertaining to crystal parameters and structure refinement is summarized in Table 1. Selected bond distances and angles are listed in Table S1.

EXPERIMENTAL SECTION

General Procedures. Elemental analyses were obtained from a HERAEUS VaruoEL analyzer. The IR spectra (KBr disk) were recorded on a Jasco FT/IR-460 plus spectrometer. Thermal gravimetric analyses (TGA) measurements were carried on a TG/ DTA 6200 analyzer. Emission spectra were obtained from a Hitachi F4500 spectrometer. Materials. The reagents Zn(CH 3 COO) 2 ·2H 2 O, Cd(CH3COO)2·2H2O, 1,2-benzenedicarboxylic acid, 1,3-benzenedicarboxylic acid, and 1,4-benzenedicarboxylic acid were purchased from Aldrich Chemical Co. The ligands N,N′-di(2-pyridyl)adipoamide (L1), N,N′-di(3-pyridyl)adipoamide (L 2 ), and N,N′-di(4-pyridyl)adipoamide (L3) were prepared according to published procedures.8 Synthesis of [Zn(1,2-BDC)(L2 )] ∞ , 1. A mixture of Zn(CH3COO)2·2H2O (0.022 g, 0.10 mmol), 1,2-H2BDC (0.017 g, 0.10 mmol), L2 (0.030 g, 0.10 mmol) and H2O (10 mL) were placed in a 23 mL Teflon lined stainless container, which was sealed and heated at 120 °C for 48 h under autogenous pressure and then cooled slowly to room temperature. Colorless block crystals were collected, washed by diethyl ether, and dried under a vacuum. Yield: 0.038 g (72%, based on Zn). Anal. Calcd for C24H22N4O6Zn (MW = 527.83): C, 54.61; H, 4.20; N, 10.61%. Found: C, 54.45; H, 4.22; N, 10.49%. IR (KBr disk, cm−1): 3119(br), 1698(s), 1605(s), 1584(s), 1553(s), 1480(m), 1462(w), 1446(w), 1425(s), 1386(s), 1328(w), 1286(m), 1161(w), 1132(m), 808(m), 703(m). Synthesis of [Zn2(1,3-BDC)2(L2)(H2O)2]∞, 2. Prepared as described for 1, except that Zn(CH3COO)2·2H2O (0.044 g, 0.20 mmol) and 1,3-H2BDC (0.033 g, 0.20 mmol) were used. Yield: 0.059 g (75%, based on Zn). Anal. Calcd for C16H15N2O6Zn (MW = 396.67): C, 48.44; H, 3.81; N, 7.06%. Found: C, 47.69; H, 4.21; N, 7.09%. IR (KBr disk, cm−1): 3119(br), 1684(s), 1644(s), 1612(s), 1584(s), 1557(s), 1484(m), 1429(s), 1375(m), 1347(m), 1327(m), 1291(m), 727(w), 691(w). Synthesis of [Zn2(1,4-BDC)2(L1)(H2O)2]∞, 3. Prepared as described for 1, except that Zn(CH3COO)2·2H2O (0.044 g, 0.20 mmol), 1,4-H2BDC (0.033 g, 0.20 mmol) and L1 (0.030 g, 0.10 mmol) were used. Yield: 0.058 g (73%, based on Zn). Anal. Calcd for C16H15N2O6Zn (MW = 396.67): C, 48.44; H, 3.81; N, 7.06%. Found: C, 48.25; H, 3.61; N, 6.66%. IR (KBr disk, cm−1): 3160(br), 1697(s), 1661(m), 1616(s), 1577(s), 1539(s), 1506(m), 1474(s), 1418(m), 1369(s), 1324(m), 1279(m), 838(w), 787(w), 733(m). Synthesis of {[Zn2(1,2-BDC)2(L3)(H2O)2]·2H2O}∞, 4. Prepared as described for 1, except that Zn(CH3COO)2·2H2O (0.044 g, 0.20 mmol), 1,2-H2BDC (0.033 g, 0.20 mmol) and L3 (0.030 g, 0.10 mmol) were used. Yield: 0.053 g (64%, based on Zn). Anal. Calcd for

■

RESULTS AND DISCUSSION Structure of 1. Figure 1a depicts a structure showing the coordination environment about the Zn(II) ion, which is coordinated by two pyridyl nitrogen atoms of two L2 ligands [Zn−N = 2.047(2) and 2.070(2) Å] and two oxygen atoms of two μ2-η1,η0,η1,η0-1,2-BDC2− ligands [Zn−O = 1.935 (2) and 1.937(2) Å], resulting in a distorted tetrahedral geometry. Figure 1b shows that the Zn(II) ions are bridged by two 1,2BDC2− ligands to form dinuclear units with the metal B


C

C16H15N2O6Zn 396.67 monoclinic P21/n 12.6631(13) 9.8425(11) 13.623(3) 90 97.364(14) 90 1684.0(4) 4 1.565 812 1.493 4.14 ≤ 2θ ≤ 50.00 2932 [R(int) = 0.0557] 2932/0/232 1.028 R1 = 0.0531, wR2 = 0.1108 R1 = 0.0890, wR2 = 0.1260

4080 [R(int) = 0.0275] 4080/0/316 1.033 R1 = 0.0353, wR2 = 0.0793 R1 = 0.0481, wR2 = 0.0853

2

C24H22N4O6Zn 527.83 triclinic P1̅ 10.8955(16) 11.1843(15) 11.4108(17) 109.354(10) 91.874(11) 112.591(11) 1190.7(3) 2 1.472 544 1.079 3.84 ≤ 2θ ≤ 50.00

1

2733 [R(int) = 0.0416] 2733/0/223 1.034 R1 = 0.0499, wR2 = 0.1027 R1 = 0.0800, wR2 = 0.1156


3

3383 [R(int) = 0.0539] 3383/0/247 1.004 R1 = 0.0519, wR2 = 0.0818 R1 = 0.0982, wR2 = 0.923


4

6031 [R(int) = 0.0276] 6031/0/368 1.014 R1 = 0.0305, wR2 = 0.0645 R1 = 0.0415, wR2 = 0.0687

C24H26CdN4O8 610.89 triclinic P1̅ 10.8608(1) 11.7607(2) 12.1209(2) 116.788(1) 90.086(1) 114.488(1) 1223.48(3) 2 1.658 620 0.950 3.86 ≤ 2θ ≤ 56.66

5

4134 [R(int) = 0.0179] 4134/0/241 1.031 R1 = 0.0207, wR2 = 0.0482 R1 = 0.0259, wR2 = 0.0504

C16H17CdN2O7 461.72 monoclinic P21/c 10.2984(1) 22.2132(2) 7.4487(1) 90 103.267(1) 90 1658.49(3) 4 1.849 924 1.361 3.66 ≤ 2θ ≤ 56.84

6

12119 [R(int) = 0.0242] 12119/0/658 1.020 R1 = 0.0247, wR2 = 0.0580 R1 = 0.0322, wR2 = 0.0615

C48H50Cd2N8O15 1203.76 triclinic P1̅ 9.9158(1) 16.0847(2) 16.8007(2) 64.814(0) 87.051(1) 88.193(1) 2421.49(5) 2 1.651 1220 0.957 4.12 ≤ 2θ ≤ 56.88

7

4009 [R(int) = 0.0176] 4009/0/243 1.062 R1 = 0.0175, wR2 = 0.0439 R1 = 0.0197, wR2 = 0.0447

C16H15CdN2O6 443.70 triclinic P1̅ 9.6183(2) 9.6505(1) 10.6636(1) 116.736(0) 102.468(1) 102.090(1) 808.04(2) 2 1.824 442 1.388 4.58 ≤ 2θ ≤ 56.70

8

a R1 = Σ||Fo| − |Fc||/Σ|Fo|. bwR2 = [Σw(Fo2 − Fc2)2/Σw(Fo2)2]1/2. w = 1/[σ2(Fo2) + (ap)2 + (bp)], p = [max(Fo2 or 0) + 2(Fc2)]/3. a = 0.0317, b = 0.7322, 1; a = 0.0611, b = 0.9946, 2; a = 0.0466, b = 0.9059, 3; a = 0.0166, b = 0.0000, 4; a = 0.0332, b = 0.2423, 5; a = 0.0234, b = 0.7382, 6; a = 0.0302, b = 1.1276, 7; a = 0.0232, b = 0.2288, 8. cQuality-of-fit = [Σw(|Fo2| − |Fc2|)2/Nobserved − Nparameters)]1/2.

data/restraints/parameters quality−of−fit indicatorc final R indices [I > 2σ(I)]a,b R indices (all data)

formula fw crystal system space group a, Å b, Å c, Å α, ° β, ° γ, ° V, Ǻ 3 Z Dcalc, g/cm3 F(000) μ(Mo Kα), mm−1 range (2θ) for data collection, deg independent reflections

compound

Table 1. Crystal Data for Complexes 1−8

Crystal Growth & Design Article



Article

structure, Figure 2d. The peculiar feature is that only two hcb from each set of the 3-fold layers “above” and “below” interdigitate with any given hcb and not with all three. This is due to the undulation of the layers. Such a rare feature is in marked contrast to the parallel polycatenation of 2-fold interpenetrated hcb layer found in [Ag(L)(CF3SO3)]·0.5H2O (L = 1,3,5-tris(4-cyano-phenoxymethyl)-2,4,6-trimethylbenzene),11 and the 3D entanglement from parallel polycatenation of 3-fold interpenetrated square layers observed for [Cd(L3)2(ClO4)2(CH3CH2OH)2]∞.8a The different nets that are interdigitating to each other are interlinked by the π−π [3.80(1) Å] interactions and N−H---O hydrogen bondings between the N−H groups of L2 ligands and carboxylate oxygen atoms of 1,3-BDC2− ligands [N---O = 2.773(5) Å, ∠N−H---O = 157.0(3)°], Figure S3, Supporting Information. Such nets are also linked by the water molecules through O−H---O hydrogen bonds to the amide oxygen atoms [O---O = 2.757(6) Å, ∠O−H---O = 157.5(5)o] and to the carboxylate oxygen atoms [O---O = 2.637(5) Å, ∠O−H---O = 176.5(6)°]. Structure of 3. Figure 3a depicts a structure showing the coordination environment of Zn(II) ion, which is coordinated by one pyridyl nitrogen atoms and one amide oxygen atoms of L1 ligand [Zn−N = 2.168(4), Zn−O = 2.006(3) Å], two oxygen atoms of two μ2-η1,η0,η1,η0-1,4-BDC2− ligands [Zn−O = 1.984(3) and 2.022(3) Å] and one oxygen atom of the coordinated water molecule [Zn−O = 2.156(5) Å], resulting in a distorted square pyramidal geometry (τ = 0.4).12 The Zn(II) ions are bridged by the L1 and 1,4-BDC2− ligands to form planar 2D hexagonal nets (hcb), Figure 3b. The 54-membered ring involving {Zn6O12C36} has the approximate ring size of 17.54 × 26.09 Å2 and the Zn−Zn distances are 10.99 (through 1,4-BDC2‑), 11.20 (through 1,4-BDC2−), and 10.28 (through L1), respectively. The 2D nets are also interlinked by the N− H---O hydrogen bonds between the N−H groups of L1 ligands and carboxylate oxygen of 1,4-BDC2− ligands [N---O = 2.821(4) Å, ∠N−H---O = 173.7(3)°], Figure S4, Supporting Information. Structure of 4. Figure 4a depicts a structure showing the coordination environment of Zn(II) ion, which is coordinated by one pyridyl nitrogen atoms of L3 ligands [Zn−N = 2.000(3) Å], two oxygen atoms of two μ2-η1,η0,η1,η0-1,2-BDC2− ligands [Zn−O = 1.940(3) and 1.934(3) Å] and one oxygen atom of the coordinated water molecule [Zn−O = 2.012(4) Å], forming a distorted tetrahedral geometry. The Zn(II) atoms are bridged by two 1,2-BDC2− ligands to form dinuclear units, which are linked to each other by the L3 ligands through the pyridyl nitrogen atoms to form chains with loops, Figure 4b,c. The 14membered ring involving {Zn2O4C8} has the approximate ring size of 5.19 × 9.69 Å2, and the Zn−Zn distances are 5.19 (through 1,2-BDC2−) and 20.55 (through L3) Å, respectively. For two adjacent chains, there are π−π [3.782(1) Å] interactions between the pyridyl ring of L3 ligands and benzene ring of 1,2-BDC2− ligands, Figure S5, Supporting Information. Structure of 5. Figure 5a depicts a structure showing the coordination environment of Cd(II) ion, which is coordinated by two pyridyl nitrogen atoms of two L2 ligands [Cd−N = 2.305(2) and 2.377(2) Å], four oxygen atoms of two μ2η1,η1,η1,η1-1,2-BDC2− ligands [Cd−O = 2.381(2)−2.510(2) Å] and one oxygen atom of the coordinated water molecule [Cd− O = 2.349(2) Å], resulting in a distorted pentagonal bipyramidal geometry. Four oxygen atoms of the two chelating 1,2-BDC2− ligands and one pyridyl nitrogen atoms of the L2

Figure 1. (a) Coordination environment of Zn(II) ion in 1. Symmetry transformations used to generate equivalent atoms: (A) −x + 2, −y + 2, −z; (B) x, y + 1, z. (b) A drawing showing the 1D double-looped chain. (c) A schematic drawing of the 1D double-looped chain.

separation of 5.25 Å and Figure 1c depicts a schematic drawing. The Zn2 units are linked to each other through the pyridyl nitrogen atoms of the L2 ligands with the metal separation of 11.185 Å to form a 1D double-looped chain with alternating 14- and 56-menbered metallocycles. The 14-membered ring involving {Zn2O4 C8} and 56-membered ring involving {Zn4N8O4C40} have the approximate ring sizes of 5.3 × 9.7 and 14.1 × 17.5 Å2, respectively. The adjacent chains are linked by N−H---O [N---O = 2.855(3)−2.870(3) Å, ∠N−H---O = 163.5(2)−164.5(2)°] hydrogen bonds originating from the N− H groups of L2 ligands and carboxylate oxygen of 1,2-BDC2− ligands, Figure S2, Supporting Information. Structure of 2. Figure 2a depicts a structure showing the coordination environment about the Zn(II) atom, which is coordinated by one pyridyl nitrogen atom of L2 ligands [Zn−N = 2.043(4) Å], two oxygen atoms of two μ2-η1,η0,η1,η0-1,3BDC2− ligands [Zn−O = 1.915(3) and 1.926(3) Å] and one oxygen atom of the coordinated water molecule [Zn−O = 2.035(4) Å], resulting in a distorted tetrahedral geometry. The Zn(II) ions are bridged by the L1 and 1,3-BDC2− ligands to form highly undulated 2D hexagonal (hcb) layers, which are equivalent and are composed of 62-membered metallocycles with an approximate size of 20.38 × 26.34 Å2, Figure 2b. Three hcb interpenetrate parallelly (i.e., with the same average plane), forming a 2D layer with a thickness of approximately 15.9 Å (2D → 2D interpenetration), Figure 2c. In addition, each layer of the 3-fold parallel interpenetration sheets interdigitate with other four parallel hcb layers by directing the 1,3-BDC ligands into the windows of the adjacent nets, giving the final 3D D



Article

Figure 2. (a) Coordination environment of Zn(II) ion in 2. Symmetry transformations used to generate equivalent atoms: (A) x + 1/2, −y + 3/2, z + 1/2. (b) A drawing showing the 2D hexagonal nets. (c) A drawing showing the 3-fold interpenetrated hcb nets looking down the c axis. (d) A drawing the 3-fold interpenetration and interdigitation.

ladder chains, Figure 6b. The 38-membered ring involving {Cd4O4C30} has the approximate ring size of 10.30 × 17.03 Å2, which is defined by measuring the Cd−Cd distance which is linked by the 1,3-BDC2− ligands and L2 ligands, respectively. For two adjacent ladder chains, there are π−π [3.405(1) Å] interactions between the pyridyl rings of L2 ligands and N−H--O hydrogen bonds between the N−H groups of L2 ligands and carboxylate oxygen of 1,3-BDC2− ligands [N---O = 2.871(2) Å, ∠N−H---O = 143.7(1)°], Figure S7, Supporting Information. Structure of 7. Figure 7a depicts a structure showing the environments about the two independent Cd(II) ions. Each of the Cd(II) ions is coordinated by two pyridyl nitrogen atoms of the L2 ligands [Cd(1)−N = 2.326(1) and 2.332(1) Å, Cd(2)− N = 2.316(2) and 2.329 (2) Å] and four oxygen atoms of three 1,4-BDC2− ligands [Cd(1)−O = 2.246(1)−2.458(1) Å, Cd(2)−O = 2.229(1)−2.516(1) Å], resulting in a distorted octahedral geometry. The Cd(II) ions are bridged by 1,4BDC2− ligands to form 2D nets, Figure 7b, which are also linked to each other through the pyridyl nitrogen atoms of L2 ligands to form a 3D coordination network, Figure 7c. The Cd(II) ions form the binuclear secondary building unit (SBU) via the μ2-η1,η1,η1,η1 and μ4-η1,η1,η1,η1-1,4-BDC2− bridging ligands, with metal separation of 4.46 and 4.67 Å for the Cd2 unit involving Cd(1) and Cd(2), respectively. Each Cd2 unit is connected to eight neighboring ones through four L2 and four

ligands are located in the equatorial plane [∠O(3)−Cd−O(4) + ∠O(4)−Cd−O(5A) + ∠O(5A)−Cd−O(6A) + ∠O(6A)− Cd−N(3) + ∠N(3)−Cd−O(3) = 359.10°], with the Cd(II) center deviating from the plane by 0.30 Å, while one pyridyl nitrogen atom of L2 ligand and one water molecule occupy the axial positions. The Cd(II) ions are bridged by the L2 and the 1,2-BDC2− to form 2D pleated layer with loops, Figure 5b,c. The 74-membered ring involving {Cd6N16O4C48} and 14membered ring involving {Cd2O4C8} have the approximate ring sizes of 16.29 × 37.83 and 5.25 × 9.98 Å2, and the Cd−Cd distances are 5.25 (through 1,2-BDC2−), 18.06 (through L2) and 19.35 (through L2) Å, respectively. The 2-D nets are also interlinked by the N−H---O hydrogen bonds between the N− H groups of L2 ligands and carboxyl oxygen of 1,2-BDC2− ligands [N---O = 3.032(4) Å, ∠N−H---O = 157.9(3)°], Figure S6, Supporting Information. Structure of 6. Figure 6a depicts a structure showing the coordination environment of the Cd(II) ion, which is coordinated by one pyridyl nitrogen atoms of L2 ligands [Cd−N = 2.288(1) Å], three oxygen atoms of two μ2η1,η1,η1,η0-1,3-BDC2− ligands [Cd−O = 2.194(1)−2.420(1) Å] and two oxygen atoms of two coordinated water molecules [Cd−O = 2.327(2)−2.354(2) Å] to form a distorted octahedral geometry. The Cd(II) ions are bridged by the 1,3-BDC2− ligands and the pyridyl nitrogen atoms of L2 ligands to form E



Article

Figure 3. (a) Coordination environment of Zn(II) ion in 3. (b) A drawing showing the 2D hexagonal nets.

Figure 5. (a) Coordination environment of Cd(II) atom in 5. Symmetry transformations used to generate equivalent atoms: (A) −x + 2, −y + 2, −z + 2. (b) A drawing showing the pleated 2D net. (c) A schematic drawing of the pleated 2D net.

Figure 4. (a) Coordination environment of Zn(II) ion in 4. Symmetry transformations used to generate equivalent atoms: (A) −x + 1, −y + 2, −z + 2. (b) A drawing showing the 1D chain with loops. (c) A schematic drawing of the 1D chain with loops.

1,4-BDC2− ligands, and thus can be considered as a 8connected node. The Cd2 adjoining nodes are separated by distances that are 20.41 (dark green), 20.06 (green), 19.94 (purple), and 19.06 (red) Å (through L2) and 9.92 and 15.83 (through 1,4-BDC2−) Ǻ , Figure 7d. Topological analysis reveals that complex 7 forms a uninodal 8-connected self-penetrating net of {424.5.63}-ilc topology, determined using TOPOS.13 Noticeably, the parallel (4,4) nets (yellow) of 7 are cross-linked by the spacer ligands with four different connection modes, as

Figure 6. (a) Coordination environment of Cd(II) ion in 6. Symmetry transformations used to generate equivalent atoms: (A) x + 1, y, z. (b) A drawing showing the 1D ladder chains.

F



Article

1,4-benzenedicarboxylic acid, phen = 1,10-phenanthroline),14a in which only two types of connection modes, A → A and A → B, are observed. Figure 8 shows several views for 7 and [Zn 5 (μ 3 OH)2(bdc)4(phen)2]. In the first ilc net observed for

Figure 8. (a) Several views of the ilc nets of 1. (b) Views redrawn for [Zn5(μ3-OH)2(bdc)4(phen)2]. Side view: looking down the axis parallel to the (4,4) planes. Top view: looking down the axis perpendicular to the (4,4) planes.

[Zn5(μ3-OH)2(bdc)4(phen)2], the parallel (4,4) nets are cross-linked by the spacer ligands pointing two orientations, whereas four orientations of the spacer ligands are observed for 7, Figure 8, side view. Upon looking down the (4,4) nets, Figure 8, top view, it can be seen that the spacer ligands of [Zn5(μ3-OH)2(bdc)4(phen)2] that bridge the (4,4) nets either lie on the edges of the windows (A → A) or pass through the diagonal of single window of the (4,4) net (A → B), whereas spacer ligands that pass through the diagonal of two adjacent windows (A → C), as well as those that through a single window with different orientations (A → B and B → A) and those that lie on the edges of the windows (A → A) are observed for 7. Complex 7 and [Zn5(μ3-OH)2(bdc)4(phen)2] are thus topologically identical but geometrically different.15 Noticeably, while the most common strategy to prepare such higher 8-connected connected networks is to use the polynuclear cluster as decorated nodes,14b the adjoining nodes of the ilc net of 7 are composed of the dinuclear Cd2 units. Inside the ilc net of 7, the water molecules form (H2O)3 trimers through the O−H---O [O---O = 2.820(3)−2.920(4) Å, ∠N−H---O = 112.4(2)−142.6(2)°] hydrogen bonds to the other water molecules, which are supported by the N−H---O [N---O = 2.784(3) Å, ∠N−H---O = 155.9(1)°] hydrogen bonds and O−H---O hydrogen bonds to the carboxylate oxygen atoms [O---O = 2.974(3) and 3.056(3) Å, ∠O−H---O = 161.0(2) and 124.1(2)°] and the amide oxygen atoms [O---O = 2.857(3)−3.049(4) Å, ∠O−H---O = 112.2(2)−173.5(2)°]. The net is also stabilized by the N−H---O [N---O = 2.909(2) and 3.011(2) Å, ∠N−H---O = 169.3(1) and 163.6(1)°] hydrogen bonds originating from the amide hydrogen atoms of the L2 ligands to the carboxylate oxygen atoms, Figure S8, Supporting Information. Structure of 8. Figure 9a depicts a structure showing the coordination environment of the Cd(II) ion, which is coordinated by one pyridyl nitrogen atoms and one amide oxygen atoms of L1 ligands [Cd−N = 2.338(1), Cd−O = 2.327(1) Å], three oxygen atoms of two μ2-η1,η1,η1,η1- and μ2η1,η0,η1,η0-1,4-BDC2− ligands [Cd−O = 2.236(1)−2.412(5) Å] and one oxygen atom of the coordinated water molecule [Cd− O = 2.306(1) Å], resulting in a distorted octahedral geometry. The Cd(II) ions are bridged by the L1 and 1,4-BDC2− ligands

Figure 7. (a) Coordination environments of Cd(II) ions in 7. Two L2 ligands are represented by N(1) and N(7) atoms for clarity. Symmetry transformations used to generate equivalent atoms: (A) −x + 2, −y + 2, −z; (B) −x + 1, −y + 1, −z + 2. (b) A drawing showing the 2D layer formed by Cd(II) ions and 1,4-BDC2− ligands. (c) A drawing showing the 3D framework. (d) A drawing showing the selfpenetrating net of ilc topology.

denoted by the different colors (green: A → A, dark green: A → C, purple: B → A and red: A → B). The nodes on the (4,4) net are arranged in alphabetical order and the arrow denotes the direction from upper to lower layer. Such arrangement for the spacer ligands is in marked contrast to that found in the first ilc net observed for [Zn5(μ3-OH)2(bdc)4(phen)2] (H2bdc = G



Article

Accordingly, the conformations adopted by the L1−L3 ligands in complexes 1−8 are shown in Table 2. It is noticeable that Table 2. Ligand Conformations and Corresponding Angles for Complexes 1−8

one of the four independent L2 ligands in complex 7 adopts the GAG trans syn-syn and the other three the AAA trans syn-syn, giving a 3D self-penetrating net of ilc topology with four different connection modes for the L2 spacer ligands. Apparently, L1−L3 are sufficiently flexible to adjust to the stereochemical requirements for the formation of the complexes 1−8, which adopt the conformations that maximize their intra- and intermolecular forces. The L1 ligands in complexes 3 and 8 adopt the unique tetradentate bonding modes involving chelation and bridge through two pyridyl nitrogen atoms and two amide oxygen atoms, whereas the L2 and L3 ligands of the other complexes adopt the bidentate bonding mode through the two pyridyl nitrogen atoms. The tetradentate bonding mode of the L1 ligands in 3 and 8 that results in 2D hcb layers is in marked contrast to the bidentate bonding mode found in the 1D Ag(I) coordination polymers containing the L1 ligands.16 Figure 10 shows the bonding mode observed for the BDC2− ligands in 1− 8. The 1,2-BDC2− ligands in complexes 1 and 4, Figure 10a, the 1,3-BDC2− ligands in complex 2, Figure 10b, and the 1,4BDC2− ligands in complex 3, Figure 10c, adopt the bidentate μ2-η1,η0,η1,η0 bonding mode, whereas the 1,2-BDC2− ligands in complex 5 show the chelating μ2-η1,η1,η1,η1 mode, Figure 10d, and the 1,3-BDC2− ligands in complex 6 adopt the bidentate μ2-η1,η1,η1,η0 bonding mode, Figure 10e. In complex 8, the 1,4BDC2− ligands show both the bidentate μ2-η1,η0,η1,η0 bonding mode, Figure 10c, and the chelating μ2-η1,η1,η1,η1 bonding mode, Figure 10f, whereas those in 7 show both the bidentate μ2-η1,η1,η1,η1 and the tetradentate μ4-η1,η1,η1,η1 bonding modes, Figure 10g. Thermal and Luminescent Properties. Thermal gravimetric analyses were carried out to examine the thermal stabilities of complexes 1−8, Table 3. The results show that complexes 2−8 are stable up to 80−130 °C and the first weight losses that are due to the removal of cocrystallized and/or bonded water molecules occurred in 80−240 °C. Complex 1, which does not contain water molecule, is stable up to 290 °C,

Figure 9. (a) Coordination environment of Cd(II) ion in 8. (b) A drawing showing the pleated 2D hexagonal net. (c) The side views of 3, top and 8, bottom.

to form pleated 2D hexagonal nets (hcb), Figure 9b. The 54membered ring involving {Cd6O12C36} has the approximate ring size of 17.46 × 23.36 Å2 and the Cd−Cd distances are 11.17 (through 1,4-BDC2−), 11.45 (through 1,4-BDC2−) and 11.63 (through L1) Å, respectively. The 2D nets are also interlinked by the N−H---O hydrogen bonding interactions between the N−H groups of L1 ligands and carboxyl oxygen of 1,4-BDC2− ligands [N---O = 2.862(2) Å, ∠N−H---O = 170.5(1)°], Figure S9, Supporting Information. A comparison of the structures of 3 and 8 shows that the Zn(II) ions of 3 locate almost on a plane, whereas the Cd(II) ions of 8 show undulation, Figure 9c, indicating that these two complexes are topologically identical but geometrically different. This observation verifies the influence of the size and thus the geometry of the metal ion on the geometry of the hcb layer. The structures of 7 and 8 are in marked contrast to the 9-fold interpenetrating dia net of {[Cd(1,4-BDC)(L3)]·2H2O}∞,7a which demonstrate the effect of the ligand isomerism of the dipyridyladipoamide ligands on the structural diversity. Ligand Conformations and Bonding Modes of the Ligands. It has been shown that L3 ligand can be arranged in anti-anti-anti (AAA), anti-anti-gauche (AAG), anti-gauche-anti (AGA), anti-gauche-gauche (AGG), gauche-anti-gauche (GAG), and gauche-gauche-gauche (GGG) conformations, and based on the relative orientation of the CO (or N−H) groups, each conformation can adopts cis or trans arrangement.8b Because of the differences in the orientations of the pyridyl nitrogen atom and amide oxygen atom, three more orientations, anti-anti, synanti and syn-syn, are also possible for the L1 and L2 ligands.7a H



Article

be oxidized or reduced, these emissions may be attributed mainly to ligand-to-ligand charge transfer (LLCT), which is mixed with metal-to-ligand charge transfer (MLCT) and metalto-ligand charge transfer (MCLT).17

■

CONCLUSION Eight new Zn(II) and Cd(II) coordination polymers have been synthesized under hydrothermal conditions, which show 1D, 2D and 3D structures. Complexes 3 and 8 and complex 7 and [Zn5(μ3-OH)2(bdc)4(phen)2] form two pairs of coordination polymers that are topologically identical but geometrically different. Various bonding modes of BDC2− ligands and ligand conformations of L1−L3 are observed in these complexes, whereas the L1 ligands in 3 and 8 adopt the unique tetradentate bonding mode. The structures of complexes 5−7, which contain Cd(II) ions and L2 ligands, are directed by the isomeric 1,2-, 1,3-, and 1,4-BDC2− ligands, resulting in 2D, 1D, and 3D structures, respectively. The effect of the ligand-isomerism of the dipyridyl amide ligands on the structural diversity is observed in complexes 1 and 4 as well as in 7, 8 and {[Cd(1,4BDC)(L3)]·2H2O}∞. Structural comparisons between 1 and 5, 2 and 6, and 3 and 8 reveal that the identity of the metal center is also important in determining the structural diversity. The structural types of these Zn(II) and Cd(II) coordination polymers are thus subjected to the changes of the donor atom positions of the dicarboxylate and dipyridyl amide ligands and the nature of the metal atoms.

Figure 10. (a−g) The various bonding modes adopted by the benzenedicarboxylate ligands.

Table 3. Thermal Properties of Complexes 1−8 complex

weight loss of H2O, T, °C (found/calc), %

1 2 3

100−200 (4.3/4.5) 80−130 (4.0/4.5)

4

80−150 (9.2/8.7)

5

100−160 (6.2/5.9)

6 7 8

130−240 (7.3/7.8) 100−200 (4.3/4.5) 130−200 (3.8/4.1)

weight loss of L, T, °C (found/calc), % 290−350 (56.8/56.5) 200−900 130−370 (37.1/37.6) 150−340 (36.5/36.0) 160−330 (49.0/48.8) 240−900 200−900 200−360 (33.1/33.6)

weight loss of carboxylate, T, °C (found/calc), % 350 - 900 (30.6/31.1) (78.5/79.0) 370−900 (40.9/41.4)

■

340−900 (39.1/39.6) 330−900 (26.4/26.9)

Selected bond distances and angles (Table S1). TGA curves for (a) 1−4 and (b) 5−8 (Figure S1). Packing diagrams (Figures S2−S9). Emission spectra (Figure S10). This material is available free of charge via the Internet at http://pubs.acs.org. In addition, crystallographic data (CIF files, excluding structure factors) for complexes 1−8 have been deposited with the Cambridge Crystallographic Data Centre, CCDC Nos. 899983−899990.

(67.4/67.9) (76.3/76.8) 360 - 900 (36.5/37.0)

probably indicating the better thermal stability of the doublelooped chain structure of complex 1. The luminescent properties of 1−8 as well as L1−L3 and the corresponding dicarboxylic acids were thus investigated in the solid state at room temperature, Figure S10 and Table 4. The

■

compound

λex/λem (nm)

compound

λex/λem (nm)

298/398 376/415 359/397 351/387 351/388 333/386 310/386

2 3 4 5 6 7 8

339/398 340/392 345/397 328/414 356/415 325/385 335/387

AUTHOR INFORMATION

Corresponding Author

*E-mail: [email protected].

Table 4. Luminescent Properties of L1, L2, L3, Dicarboxylic Acids and 1−8 in the Solid State L1 L2 L3 1,2-H2BDC 1,3-H2BDC 1,4-H2BDC 1

ASSOCIATED CONTENT

S Supporting Information *

Notes

The authors declare no competing financial interest.

■ ■

ACKNOWLEDGMENTS We are grateful to the National Science Council of the Republic of China for support. REFERENCES

(1) (a) Tiekink, E. R. T.; Vittal, J. J. Frontiers in Crystal Engineering; John Wiley & Sons, Ltd: England, 2006. (b) Robson, R.; Abrahams, B. E.; Batten, S. R.; Gable, R. W.; Hoskins, B. F.; Lieu, J. Supramolecular Architecture; ACS Publications: Washington, DC, 1992. (c) Yaghi, O. M.; Li, H.; Davis, C.; Richardson, D.; Groy, T. L. Acc. Chem. Res. 1998, 31, 474. (d) Fujita, M.; Ogura, K. Coord. Chem. Rev. 1996, 148, 249. (e) Leong, W. L.; Vittal, J. J. Chem. Rev. 2011, 111, 688. (2) (a) Sherrington, D. C.; Taskinen, K. A. Chem. Soc. Rev. 2001, 30, 83. (b) Lawrence, D. S.; Jiang, T.; Levett, M. Chem. Rev. 1995, 95, 2229. (3) (a) Li, H.-H.; Chen, Z.-R.; Li, J.-Q.; Huang, C.-C.; Zhang, Y. F.; Jia, G.-X. Cryst. Growth Des. 2006, 6, 1813. (b) Awaleh, M. O.; Badia, A.; Brisse, F. Cryst. Growth Des. 2006, 6, 2674. (c) Noro, S.; Kitaura,

organic ligands L1−L3, 1,2-H2BDC, 1,3-H2BDC, and 1,4H2BDC show the emissions in the range 386−415 nm, which may be tentatively ascribed to the intraligand (IL) n → π* or π → π* transitions. The red and blue shifts observed for the emissions of complexes 1−8 are most probably due to the different ligand conformations and coordination modes adopted by the organic ligands and the formation of different structural types. Since the Zn(II) and Cd(II) ions are hardly to I



Article

R.; Kondo, M.; Kitagawa, S.; Ishii, T.; Matsuzaka, H.; Yamashita, M. J. Am. Chem. Soc. 2002, 124, 2568. (d) Wang, Y.-H.; Chu, K.-L.; Chen, H.-C.; Yeh, C.-W.; Chan, Z.-K.; Suen, M.-C.; Chen, J.-D. CrystEngComm 2006, 8, 84. (e) Lin, C.-Y.; Chan, Z.-K.; Yeh, C.-W.; Wu, C.-J.; Chen, J.-D.; Wang, J.-C. CrystEngComm 2006, 8, 841. (4) Bu, X. H.; Chen, W.; Hou, W. F.; Zhang, R. H.; Brisse, F. Inorg. Chem. 2002, 41, 3477. (5) Blake, A. J.; Champness, N. R.; Cooke, P. A.; Nicolson, J. E. B.; Wilson, C. J. J. Chem. Soc., Dalton Trans. 2000, 3811. (6) (a) Du, M.; Jiang, X.-J.; Zhao, X.-J. Chem. Commun. 2005, 5521. (b) Du, M.; Zhang, Z.-H.; Wang, X.-G.; Tang, L.-F.; Zhao, X.-J. CrystEngComm 2008, 10, 1855. (c) Du, M.; Jiang, X.-J.; Zhao, X.-J. Inorg. Chem. 2007, 46, 3984. (d) Yang, J.; Ma, J.-F.; Liu, Y.-Y.; Ma, J.C.; Batten, S. R. Cryst. Growth Des. 2009, 9, 1894. (7) (a) Cheng, J.-J.; Chang, Y.-T.; Wu, C.-J.; Hsu, Y.-F.; Lin, C.-H.; Proserpio, D. M.; Chen, J.-D. CrystEngComm 2012, 14, 537. (b) Sie, M.-J.; Chang, Y.-J.; Cheng, P.-W.; Kuo, P.-T.; Yeh, C.-W.; Cheng, C.F.; Chen, J.-D.; Wang, J.-C. CrystEngComm 2012, 14, 5505. (8) (a) Rajput, L.; Singha, S.; Biradha, K. Cryst. Growth Des. 2007, 7, 2788. (b) Hsu, Y.-F.; Hu, H.-L.; Wu, C.-J.; Yeh, C.-W.; Proserpio, D. M.; Chen, J.-D. CrystEngcComm 2009, 11, 168. (c) Hsu, Y.-F.; Hsu, W.; Wu, C.-J; Cheng, P.-C.; Yeh, C.-W.; Chang, W.-J.; Chen, J.-D.; Wang, J.-C. CrystEngComm 2010, 12, 702. (d) Cheng, P.-C.; Yeh, C.W.; Hsu, W.; Chen, T.-R.; Wang, H.-W.; Chen, J.-D.; Wang, J.-C. Cryst. Growth Des. 2012, 12, 943. (9) (a) XSCANS, Release, 2.1; Siemens Energy & Automation, Inc: Madison, Wisconsin, USA, 1995. (b) SMART/SAINT/ASTRO, Release 4.03; Siemens Energy & Automation, Inc.: Madison, Wisconsin, USA, 1995. (c) Bruker AXS, APEX2, V2008.6; SAD ABS V2008/1; SAINT+ V7.60A; SHELXTL V6.14; Bruker AXS Inc.: Madison, Wisconsin, USA, 2008. (10) Sheldrick, G. M. Acta Crystallogr. 2008, A64, 112. (11) Banfi, S.; Carlucci, L.; Caruso, E.; Ciani, G.; Proserpio, D. M. Cryst. Growth Des. 2004, 4, 29. (12) Addison, A. W.; Rao, T. N.; Reedijik, J.; Rijn, J. V.; Verschoor, G .C. J. Chem. Soc., Dalton Trans. 1984, 1349. (13) http://www.topos.ssu.samara.ru; Blatov, V. A. IUCr CompComm Newsl. 2006, 7, 4. (14) (a) Wang, X.-L.; Qin, C.; Wang, E.-B.; Su, Z.-M.; Xu, L.; Batten, S. R. Chem. Commun. 2005, 4789. (b) Ke, X.-J.; Li, D.-S.; Du, M. Inorg. Chem. Commun. 2011, 14, 788. (15) Batten, S. R.; Neville, S. M.; Turner, D. R. Coordination Polymers. Design, Analysis and Application; The Royal Society of Chemistry: Cambridge, 2008. (16) Chen, H.-C.; Hu, H.-L.; Chan, Z.-K.; Yeh, C.-W.; Jia, H.-W.; Wu, C.-P.; Chen, J.-D.; Wang, J.-C. Cryst. Growth Des. 2007, 7, 698. (17) (a) Ma, L.-F.; Wang, L.-Y.; Hu, J.-L.; Wang, Y.-Y.; Yang, G.-P. Cryst. Growth Des. 2009, 9, 5334. (b) Gong, Y.; Li, J.; Qin, J.; Wu, T.; Cao, R.; Li, J. Cryst. Growth Des. 2011, 11, 1662.

J


Ligand-Isomerism Controlled Structural Diversity of ... - ACS Publications

Recommend Documents