Ag(I) Complexes Containing Flexible - American Chemical Society

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Ag(I) Complexes Containing Flexible N,N′-Di(2-pyridyl)adipoamide Ligands: Syntheses, Structures, and Ligand Conformations Chen,†

Hu,‡

Chan,†

Huan-Ching Hui-Ling Zhi-Kai Chun-Wei Chi-Phi Wu,† Jhy-Der Chen,*,† and Ju-Chun Wang#

Yeh,†

Hsi-Wei

Jia,†

CRYSTAL GROWTH & DESIGN 2007 VOL. 7, NO. 4 698-704

Department of Chemistry, Chung-Yuan Christian UniVersity, Chung-Li, Taiwan, R.O.C., Department of Chemical and Materials Engineering, Nanya Institute of Technology, Chung-Li, Taiwan, R.O.C., and Department of Chemistry, Soochow UniVersity, Taipei, Taiwan, R.O.C. ReceiVed September 16, 2006; ReVised Manuscript ReceiVed December 29, 2006

ABSTRACT: A new flexible ligand N,N′-di(2-pyridyl)adipoamide), LCDCl3 (1), and L‚2H2O (2), and a series of polymeric complexes of the types [AgLNO3]∞, (3); [AgLPF6]∞, (4); [AgLBF4CH3CN(H2O)0.5]∞, (5); [AgLClO4CH3CN]∞, (6); [AgLClO4(H2O)0.67]∞, (7), and [Ag2L2.5SO4]∞, (8), are reported. All the complexes have been structurally characterized by X-ray crystallography, confirming that complexes 3-8 are coordination polymers. The cations of 3-6 form zigzag chains, while those of 7 are helical. Complex 8 forms sinusoidal chains, which demonstrates an unusual coexistence of three ligand conformers in a coordination polymer. While L’s in 1 and 2 adopt GAG trans and AAA trans conformations, respectively, all the ligands in 3-7 adopt the AAA trans conformation, and the three independent L’s in 8 adopt GGG cis, AAA trans, and AGA cis conformations, respectively. These conformations also differ in the dihedral angle between the two pyridyl rings. Introduction Considerable effort has been devoted to understanding the self-assembly of organic and inorganic molecules in the past decade because it extends the range of new solids that can be designed to have particular physical and chemical properties.1,2 The range and variety of self-assembling inorganic structures that can be constructed relies on the presence of suitable metalligand interactions and supramolecular contacts, i.e., hydrogen bondings and other weak interactions.3 Many topologically promising Ag(I)-containing architectures have been constructed with bidentate building blocks containing nitrogen donors.4 The coordination polymers that have been reported include one-, two-, and three-dimensional (1-D, 2-D, and 3-D) network structures.4b Recently, we have reported a series of 1-D Ag(I) coordination polymers containing the bidentate ligand N,N′-di(2-pyridyl)oxamide.5 These complexes were capable of selfassembling into 2-D molecular structures through a series of Ag---O interactions and self-complementary double N-H---O hydrogen bonds.5 Many of the structures reported to date are based upon rigid, linear ligands, with only recent efforts being focused on the use of ligands showing conformational flexibility.6-9 The coordination networks of metal complexes containing flexible bidentate ligands are less predictable due to the possible occurrence of supramolecular isomerism involving the adoption of different ligand conformations. It is well-known that the ligand 1,2-bis(4-pyridyl)ethane can adopt either gauche or anti geometry, whereas the flexible ligand 1,3-bis(4-pyridyl)propane can exist in anti-anti, gauche-anti and gauche-gauche conformations. Moreover, the structural types of the resulting coordination polymers are also affected by factors such as counterion,10 metal-to-ligand ratio,11 and solvent.12 To investigate the possibility that increasing the numbers of the backbone carbon atoms of the bidentate ligand would form a more flexible coordination framework, and the influence of * To whom correspondence should be addressed. † Chung-Yuan Christian University. ‡ Nanya Institute of Technology. # Soochow University.

ligand conformations on crystal structure, we synthesized and studied the bidentate ligand N,N′-di(2-pyridyl)adipoamide, L.

The syntheses, structures, and ligand conformations of L and Ag(I) complexes of the types [AgLNO3]∞, (3); [AgLPF6]∞, (4); [AgLBF4CH3CN(H2O)0.5]∞, (5); [AgLClO4 CH3CN]∞, (6); [AgLClO4 (H2O)0.67]∞, (7), and [Ag2L2.5SO4]∞, (8), form the subject of this report. Experimental Section General Procedures. All manipulations were carried out under dry, oxygen-free nitrogen by using Schlenk techniques, unless otherwise noted. Solvents were dried and deoxygenated by refluxing over the appropriate reagents before use. Elemental analyses were obtained from a PE 2400 series II CHNS/O analyzer or a HERAEUS VaruoEL analyzer. The IR spectra (KBr disk) were recorded on a Jasco FT/IR460 plus spectrometer. Differential scanning calorimetry (DSC) measurements were carried out on a DuPont DSC Q-10 instrument at a scan rate of 5 °C/min. Materials. The reagents adipoyl chloride, 2-aminopyridine, AgNO3, AgClO4, and Ag2SO4 were purchased from Aldrich Chemical Co. Caution: Perchlorate salts are dangerous (especially if they are dry) and should be handled with care. Synthesis of L. Adipoyl chloride (1.00 g, 5.47 mmol) was added slowly to a DMF solution of 2-aminopyridine (1.03 g, 10.94 mmol), which was stirred for 15 min and triethylamine (1.11 g, 10.94 mmol) was then added. The mixture was refluxed for 6 h, and then the volume was reduced to 10 mL by vacuum evaporation. A brown solid was obtained from the solution after standing at room temperature for 24 h. The solid was filtered off and washed with excess cold water to give a light yellow powder. Yield: 1.11 g (68%). 1H NMR (DMSOd6, ppm) 7.05 (2H, t, H4-py), 7.74 (2H, t, H5-py), 8.08 (2H, d, H6py), 8.28 (2H, d, H3-py), 10.43 (2H, s, NH), 2.40 (4H, t, COCH2), 1.61 (4H, p, COCH2CH2). 13C NMR (DMSO-D6, ppm) 172.14 (CO), 152.15 (C1-py), 147.93 (C3-py), 138.11 (C5-py), 119.23 (C6-py), 113.46 (C4-py), 35.95(COC), 24.69 (COCC). Anal. Calcd for C16H18O2N4

10.1021/cg060619y CCC: $37.00 © 2007 American Chemical Society Published on Web 02/16/2007

Ag(I) and N,N′-Di(2-pyridyl)adipoamide Complexes

Crystal Growth & Design, Vol. 7, No. 4, 2007 699

Table 1. Crystal Data for L and Compounds 1-8 compound

1

2

3

4

formula fw crystal system space group a, Å b, Å c, Å R, ° β, ° γ, ° V, Å3 Z dcalc, g/cm3 cryst size, mm µ (Mo KR), mm-1 temp °C data/restraints/parameters quality-of-fit indicatorc final R indices [I > 2σ(I)]a,b

C17H18Cl3DN4O2 418.72 monoclinic P21/c 9.8917(8) 8.2994(6) 24.1948(18) 90 92.004(6) 90 1985.1(3) 4 1.401 0.6 × 0.2 × 0.1 0.481 25 3452/0/339 1.047 R1 ) 0.0610, wR2 ) 0.1598 R1 ) 0.0840, wR2 ) 0.1781

C16H22N4O4 334.38 monoclinic P21/c 10.909(2) 5.2417(12) 14.816(3) 90 99.742(17) 90 835.0(3) 2 1.330 0.7 × 0.3 × 0.1 0.097 25 1462/0/154 1.083 R1 )0.0474, wR2 ) 0.1146 R1 ) 0.0632, wR2 ) 0.1282

C16H18AgN5O5 468.22 triclinic P1h 8.3486(12) 9.9271(10) 11.5278(11) 99.612(7) 104.505(9) 103.956(10) 870.95(17) 2 1.785 0.8 × 0.4 × 0.1 1.198 25 3045/0/316 1.016 R1 ) 0.0288, wR2 ) 0.0585 R1 ) 0.0313, wR2 ) 0.0598

C16H18AgF6N4O2P 551.18 triclinic P1h 4.9284(8) 10.5139(19) 11.6977(17) 110.359(10) 92.989(11) 93.981(13) 565.01(16) 1 1.620 0.5 × 0.3 × 0.2 1.030 25 1940/0/173 1.032 R1 ) 0.0543, wR2 ) 0.1209 R1 ) 0.0600, wR2 ) 0.1238

R indices (all data) compound

5

6

7

8

formula fw crystal system space group a, Å b, Å c, Å R, ° β, ° γ, ° V, Å3 Z dcalc, g/cm3 cryst size, mm µ (Mo KR), mm-1 temp °C data/restraints/parameters Sc final R indices [I > 2σ(I)]a,b

C18H22AgBF4N5O2.5 543.09 triclinic P1 9.8724(18) 10.2111(11) 11.5477(12) 111.007(8) 93.701(12) 93.778(10) 1079.5(3) 2 1.671 0.4 × 0.3 × 0.2 0.995 25 4402/3/552 1.032 R1 ) 0.0421, wR2 ) 0.0750 R1 ) 0.0639 wR2 ) 0.0846

C18H21AgClN5O6 546.72 triclinic P1 9.8733(19) 10.3078(18) 11.5645(14) 111.169(10) 93.351(13) 93.971(13) 1090.5(3) 2 1.665 0.4 × 0.2 × 0.1 1.091 25 7588/4/559 1.049 R1 ) 0.0370, wR2 ) 0.1057 R1 ) 0.0473, wR2 ) 0.1158

C16H19.33AgClN4O6.67 517.67 monoclinic P21/n 17.281(4) 14.731(3) 23.027(5) 90 101.453(4) 90 5745(2) 12 1.795 0.6 × 0.4 × 0.1 1.238 25 10072/0/775 1.060 R1 ) 0.0578, wR2 ) 0.1540 R1 ) 0.0857, wR2 ) 0.1824

C40H45Ag2N10O9S 1057.66 monoclinic C2/c 31.390(5) 14.581(3) 22.107(5) 90 119.167(13) 90 8836(3) 8 1.590 0.8 × 0.2 × 0.1 0.999 25 7781/0/559 1.006 R1 ) 0.0361, wR2 ) 0.0796 R1 ) 0.0640, wR2 ) 0.0906

R indices (all data)

a R ) ∑||F | - |F ||/∑|F |. b wR ) [∑w(F 2 - F 2)2/∑(F 2)2]1/2. w ) 1/[σ2(F 2) + (ap)2 + (bp)], p ) [max(F 2 or 0) + 2(F 2)]/3. a ) 0.0796, b ) 1 o c o 2 o c o o o c 1.4468, 1; a ) 0.0600, b ) 0.2785, 2; a ) 0.0000, b ) 1.4389, 3; a ) 0.0000, b ) 3.0828, 4; a ) 0.0000, b ) 3.6358, 5; a ) 0.0681, b ) 0.7104, 6; a ) 0.0850, b ) 20.1995, 7; a ) 0.0352, b ) 11.6192, 8. c Quality-of-fit ) [∑w(|Fo2| - |Fc2|)2/(Nobserved - Nparameters)]1/2.

(MW ) 298.34): C, 64.41; H, 6.08; N, 18.78%. Found: C, 64.39; H, 6.16; N, 18.53%. IR (cm-1): 3389 (w), 3114 [br, νs(N-H)], 1702 [s, νs(CdO)], 1597 [br, νas(COO-) + ν(CdN)], 1577(s), 1520(s), 1437(s), 1293 [s, νs(COO-)], 1057(w), 789(m), 613(w), 577(w). Synthesis of 3. An ethanol solution of L (0.30 g, 1.00 mmol) was layered on the top of an aqueous solution of AgNO3 (0.17 g, 1.00 mmol), which gave needlelike crystals after 1 month. The crystal were collected, washed by ether, and then dried undera vacuum. Yield: 0.43 g (92%, based on Ag). Anal. Calcd for C16H18AgN5O5 (MW ) 468.22): C, 41.04; H, 3.87; N, 14.96%. Found: C, 41.01; H, 3.75; N, 14.73%. IR (cm-1): 3330(w), 3194 [br, νs(N-H)], 1703 [s, νs(Cd O)], 1679 [s, νs(CdO)], 1599 [br., νas(COO-) + ν(CdN)], 1577(s), 1479(s), 1437(s), 1384(s, NO3-), 1302 [s, νs(COO-)], 775(m), 937(w), 570(w), 487(w). Synthesis of 4. L (0.3 g, 1.00 mmol) was dissolved in a solution containing AgPF6 (0.25 g, 1.00 mmol) in 20 mL of methanol. The mixture was refluxed for 3 h to give a white solid, which was then filtered off and washed with methanol. Colorless crystals were obtained by slow diffusion of diethyl ether into a CH3CN solution of the white solid. The crystal were collected, washed by ether, and then dried under a vacuum. Yield: 0.48 g (81%, based on Ag). Anal. Calcd for C16H18AgPF6N4O2 (MW ) 551.18): C, 34.87; H, 3.29; N, 10.17%. Found: C, 34.52; H, 3.53; N, 10.48%. IR (cm-1): 3251(w), 3113 [br, νs(N-

H)], 1668 [s, νs(CdO)], 1580 [br., νas(COO-) + ν(CdN)], 1531(s), 1435(s), 1300 [s, νs(COO-)], 782(m), 560(w). Synthesis of 5. L (0.3 g, 1.00 mmol) was dissolved in a solution containing AgBF4 (0.19 g, 1.00 mmol) in 20 mL of methanol. The mixture was refluxed for 3 h to give a white solid, which was then filtered off and washed with methanol. By slow diffusion of diethyl ether into a CH3CN solution of the compound, colorless crystals were obtained. The crystals were collected, washed by ether, and then dried under a vacuum. Yield: 0.43 g (81%, based on Ag). Anal. Calcd for C18H22AgBF4N5O2.5 (MW ) 543.08): C, 39.81; H, 4.08; N, 12.90%. Found: C, 39.68; H, 3.97; N, 12.68%. IR (cm-1): 3269(w), [br, νs(N-H)], 1669 [s, νs(CdO)], 1581 [br., νas(COO-) + ν(CdN)], 1528(s), 1435(s), 1301 [s, νs(COO-)], 785(m), 560(w). Synthesis of 6. L (0.30 g, 1.00 mmol) was dissolved in a solution containing AgClO4 (0.20 g, 1.00 mmol) in 20 mL of CH3CN. The mixture was refluxed for 3 h to give a white solid, which was then filtered off and washed with methanol. By slow diffusion of diethyl ether into a CH3CN solution of the compound, colorless crystals were obtained. The crystal were collected, washed by ether, and then dried under a vacuum. Yield: 0.05 g (10%, based on Ag). Anal. Calcd for C18H21AgClN5O6 (MW ) 546.72): C, 39.54; H, 3.87; N, 12.81%. Found: C, 39.61; H, 4.05; N, 12.27%. IR (cm-1): 3255(w), 3113 [br, νs(N-H)], 1702 [s, νs(CdO)], 1596 [br, νas(COO-) + ν(CdN)], 1577-

700 Crystal Growth & Design, Vol. 7, No. 4, 2007 (s), 1521(s), 1437(s), 1293 [s, νs(COO-)], 1149(s, ClO4-), 791(m), 728(w), 547(w), 491(w). Synthesis of 7. An ethanol solution of L (0.30 g, 1.00 mmol) was layered on the top of an aqueous solution of AgClO4 (0.21 g, 1.00 mmol). After 1 month, needlelike crystals were found at the interface. The crystal were collected, washed by ether, and then dried under vacuum. Yield: 0.31 g (62%, based on Ag). Anal. Calcd for C16H19.33AgN4O6.67Cl (MW ) 517.67): C, 37.12; H, 3.76; N, 10.82%. Found: C, 37.61; H, 4.05; N, 10.27%. IR (cm-1): 3255(w), 3114 [br, νs(NH)], 1702 [s, νs(CdO)], 1597 [br, νas(COO-) + ν(CdN)], 1577(s), 1521(s), 1437(s), 1293 [s, νs(COO-)], 1149(s, ClO4-), 791(m), 728(w), 525(w), 414(w). Synthesis of 8. An acetone solution of L (0.37 g, 1.25 mmol) was layered on the top of an aqueous solution of Ag2SO4 (0.31 g, 1.00 mmol), which gave colorless crystals after three weeks. The crystals were collected, washed by ether, and then dried under vacuum. Several different M to L ratios have been tried to grow crystals for 8, which afforded the same structure, indicating that the stoichiometry of 8 is independent of the metal-to-ligand ratio. Yield: 0.54 g (51%, based on Ag). Anal. Calcd for C40H45Ag2N10O9S (MW ) 1057.65): C, 45.80; H, 3.92; N, 12.97%. Found: C, 45.49; H, 4.30; N, 13.27%. IR (cm-1): 3420(w), 3287 [br, νs(N-H)], 1703 [s, νs(CdO)], 1666 [s, νs(CdO)], 1605 [br, νas(COO-) + ν(CdN)], 1577(s), 1470(s), 1437(s), 1319 [s, νs(COO-)], 783(m), 625(w), 566(w), 517(w). X-ray Crystallography. The diffraction data of 1-6 were collected on a Bruker AXS diffractometer, while those for 7 and 8 were collected on a Siemens CCD diffractometer, which was equipped with a graphitemonochromated Mo KR (λKR ) 0.71073 Å) radiation. Data reduction was carried out by standard methods with use of well-established computational procedures.13 The structure factors were obtained after Lorentz and polarization corrections. The positions of the heavy atoms, including the silver atoms, were located by the direct method. The remaining atoms, including the hydrogen atoms in 1-3, were found in a series of alternating difference Fourier maps and least-square refinements,14 while the hydrogen atoms in 4-8 were added by using the HADD program and refined using a riding model. The CDCl3 molecule in 1 is disordered such that two sets of Cl atoms, each with 0.5 occupancy, can be found. Space group Pıj has been tested for compounds 5 and 6. However, unresolved disordered problems for BF4and ClO4- anions and cocrystallized solvent molecules were resulted, and relative high R values (R1 higher than 10%) were obtained. Therefore, space group P1 was reported for these two structures. Basic information pertaining to crystal parameters and structure refinement is summarized in Table 1. Selected bond lengths and angles are listed in Table 2.

Results and Discussions Structures of 1 and 2. Two different solid-state structures were found for the ligand L. Both structures were solved in the space group P21/c with four and two molecules in a unit cell for 1 and 2, respectively. The structure of 1 is twisted, while that of 2 is planar, and the dihedral angles between the two pyridyl rings are 56.1 and 0°, respectively. Figure 1a,b shows the molecular structures and packing diagrams for 1 and 2, respectively. It is seen from Figure 1 that the molecules of both 1 and 2 are linked by the self-complementary donor (D)acceptor (A) double hydrogen bonds involving two N-H---N interactions (N---N ) 3.037(2) Å and 3.076(4) Å for 1; 3.236(4) Å for the two symmetry-related interactions in 2). The L molecules in 2 are bridged extensively by the water molecules through O(water)-H---O(L) interactions (O(water)---O(L) ) 2.94(2) Å), while the CDCl3 in 1 are only interacted with the L molecules through C-D---O interactions (C---O ) 3.122(3) Å). Noticeably, the water molecules in 2 are interacted to each other in a linear way, which is approximately perpendicular to the interlinked L molecules, through O-H---O interactions (O(water)---O(water) ) 2.907(4) Å), Figure 1c. The planar structure of L in 2 is most probably due to the strains imposed by the water molecules. Structures of 3 and 4. The structures of complexes 3 and 4 are similar, and their crystals suitable for X-ray crystallography

Chen et al. Table 2. Selected Bond Distances (Å) and Angles (°) for Compounds 1-8 O(1)-C(6) N(1)-C(4) N(2)-C(6) N(3)-C(11) N(4)-C(12) C(1)-C(2) C(2)-C(3) C(6)-C(7) C(8)-C(9) C(10)-C(11) C(13)-C(14) C(15)-C(16) C(4)-N(1)-C(5) C(11)-N(3)-C(12) C(2)-C(1)-C(5) C(4)-C(3)-C(2) N(1)-C(5)-C(1) C(1)-C(5)-N(2) O(1)-C(6)-C(7) C(6)-C(7)-C(8) C(8)-C(9)-C(10) O(2)-C(11)-N(3) N(3)-C(11)-C(10) N(4)-C(12)-N(3) C(14)-C(13)-C(12) C(16)-C(15)-C(14)

Compound 1 1.225(3) O(2)-C(11) 1.337(4) N(1)-C(5) 1.359(4) N(2)-C(5) 1.357(4) N(3)-C(12) 1.334(4) N(4)-C(16) 1.374(5) C(1)-C(5) 1.380(5) C(3)-C(4) 1.504(5) C(7)-C(8) 1.512(5) C(9)-C(10) 1.508(4) C(12)-C(13) 1.374(5) C(14)-C(15) 1.362(5) 117.3(3) C(6)-N(2)-C(5) 129.0(3) C(12)-N(4)-C(16) 118.2(3) C(1)-C(2)-C(3) 117.6(4) N(1)-C(4)-C(3) 122.8(3) N(1)-C(5)-N(2) 125.0(3) O(1)-C(6)-N(2) 121.3(3) N(2)-C(6)-C(7) 110.8(3) C(9)-C(8)-C(7) 114.4(3) C(11)-C(10)-C(9) 123.0(3) O(2)-C(11)-C(10) 113.9(3) N(4)-C(12)-C(13) 113.1(2) C(13)-C(12)-N(3) 118.1(3) C(15)-C(14)-C(13) 118.3(3) N(4)-C(16)-C(15)

128.1(3) 117.4(3) 120.1(3) 124.0(3) 112.2(2) 122.8(3) 115.9(3) 112.7(3) 114.4(3) 123.1(3) 122.7(3) 124.3(3) 119.8(3) 123.6(3)

O(1)-C(6) N(1)-C(1) N(2)-C(5) C(2)-C(3) C(4)-C(5) C(7)-C(8) C(6)-N(2)-C(5) C(1)-C(2)-C(3) C(3)-C(4)--C(5) N(1)-C(5)--N(2) O(1)-C(6)-N(2) N(2)-C(6)-C(7) C(7)-C(8)-C(8A)

Compound 2a 1.226(2) N(1)-C(5) 1.338(3) N(2)-C(6) 1.400(2) C(1)-C(2) 1.373(3) C(3)-C(4) 1.386(3) C(6)-C(7) 1.499(3) C(8)-C(8A) 128.16(18) C(5)-N(1)-C(1) 117.8(2) N(1)-C(1)-C(2) 118.28(19) C(2)-C(3)-C(4) 113.57(17) N(1)-C(5)-C(4) 123.05(19) C(4)-C(5)-N(2) 113.37(18) O(1)-C(6)-C(7) 112.2(2) C(8)-C(7)-C(6)

1.333(3) 1.362(2) 1.365(3) 1.374(3) 1.504(3) 1.508(5) 116.75(18) 124.4(2) 119.7(2) 122.94(18) 123.49(18) 123.57(18) 115.04(19)

1.216(4) 1.339(4) 1.399(4) 1.397(4) 1.342(4) 1.378(4) 1.365(5) 1.529(4) 1.523(4) 1.387(4) 1.373(5)

Ag(1)-N(1) N(1)-Ag(1)-N(4A)

Compound 3b 2.222(2) Ag(1)-N(4A) 175.52(9)

2.230(2)

Ag(1)-N(1) N(1)-Ag(1)-N(4A)

Compound 4c 2.128(5) Ag(1)-N(4A) 177.5(7)

2.091(13)

Ag(1)-N(8) Ag(2)-N(4) N(8)-Ag(1)-N(1)

Compound 5 2.154(15) Ag(1)-N(1) 2.077(16) Ag(2)-N(5) 178.6(7) N(4)-Ag(2)-N(5)

2.160(13) 2.118(16) 179.2(7)

Ag(1)-N(8) Ag(2)-N(4) N(8)-Ag(1)-N(1)

Compound 6 2.101(6) Ag(1)-N(1) 2.084(6) Ag(2)-N(5) 178.5(2) N(4)-Ag(2)-N(5)

2.170(5) 2.154(6) 178.8(2)

Ag(1)-N(3) Ag(2)-N(7) Ag(3)-N(9) N(3)-Ag(1)-N(1) N(9)-Ag(3)-N(11)

Compound 7 2.138(5) Ag(1)-N(1) 2.153(5) Ag(2)-N(5) 2.154(5) Ag(3)-N(11) 169.01(19) N(7)-Ag(2)-N(5) 169.86(18)

Ag(1)-N(10) Ag(1)-O(6) Ag(2)-N(4) Ag(2)-O(7) N(10)-Ag(1)-O(6) N(7)-Ag(2)-N(4) N(4)-Ag(2)-N(5) N(4)-Ag(2)-O(7)

Compound 8 2.238(8) Ag(1)-N(1) 2.460(2) Ag(2)-N(7) 2.283(3) Ag(2)-N(5) 2.536(2) N(10)-Ag(1)-N(1) 100.26(10) N(1)-Ag(1)-O(6) 123.80(11) N(7)-Ag(2)-N(5) 111.63(12) N(7)-Ag(2)-O(7) 94.05(9) N(5)-Ag(2)-O(7)

2.149(5) 2.160(5) 2.177(5) 177.52(18)

2.243(3) 2.291(3) 2.382(4) 152.69(11) 94.93(10) 110.47(13) 102.83(10) 112.09(10)

a Symmetry transformations used to generate equivalent atoms: (A): -x + 2, -y + 1, -z + 2. b Symmetry transformations used to generate equivalent atoms: (A): x - 1, y, z + 1. c Symmetry transformations used to generate equivalent atoms: (A): x - 1, y, z + 1.

Ag(I) and N,N′-Di(2-pyridyl)adipoamide Complexes

Crystal Growth & Design, Vol. 7, No. 4, 2007 701

Figure 2. (a) An ORTEP diagram for the asymmetric unit of 3. The asymmetric unit of 4 is similar to that of 3, except that the anion is PF6-. Thermal ellipsoids are shown at the 20% probability level. (b) A representative ORTEP diagram showing the interactions between the zigzag chains. The anions are not shown for clarity.

Figure 1. (a) ORTEP drawings showing the molecular structure of 1 and the interactions among the molecules. Thermal ellipsoids are shown at 20% probability level for the molecular structure. (b) ORTEP drawings showing the molecular structure of 2 and the interactions among the molecules. Thermal ellipsoids are shown at the 20% probability level for the molecular structure. (c) The water molecules in 2 are linked to each other in a linear way through O-H---O hydrogen bonding.

conform to the space group P1h; a representative ORTEP diagram of the cation is shown in Figure 2a. The silver atom is bound to the nitrogen atoms of two symmetry-related L ligands in a linear geometry [N-Ag-N ) 175.52(9) for 3 and 180o for 4], Figure 2b. The Ag-N distances are similar and are 2.222(2) and 2.230(2) Å for 1 and 2.128(5) Å for 3, respectively. Complexes 3 and 4 form zigzag chains, which are interlinked through Ag---O (2.946(10) Å for 3 and 3.032(19) Å for 4) interactions and N-H---O (N---O ) 3.027(9) Å for 3; 2.824(8) and 3.056(7) Å for 4) hydrogen bonds. The Ag---Ag distances between two silver atoms of two adjacent zigzag chains are 3.842(13) and 4.928(1) Å for 3 and 4, respectively, which are significantly longer than their van der Waals contact of 3.44 Å (van der Waals radius for Ag ) 1.72 Å), indicating no Ag---Ag interaction. The nitrate ions bridge adjacent chains through all three oxygen atoms and link the cations through a series of Ag---O (2.6716(25) and 3.3998(42) Å) interactions, and C-H---O (C---O ) 3.139(21)-3.353(17) Å) and N-H---O (N---O ) 2.909(10) Å) hydrogen bonds. In complex 4, the PF6ions bridge adjacent chains through a series of C-H---F hydrogen bonds (C---F ) 3.239(18)-3.698(28) Å).

Figure 3. (a) A representative ORTEP diagram for cations of 5 and 6. Thermal ellipsoids are shown at the 20% probability level. (b) A representative ORTEP diagram showing the interactions between the cations. The anions are not shown for clarity.

Structures of Isomorphous 5 and 6. Crystals of complexes 5 and 6 conform to the space group P1. A representative ORTEP diagram of the cation, Figure 3a, shows that the silver atoms are bonded to the nitrogen atoms of two L ligands [Ag-N ) 2.076(16)-2.159(13) Å for 5; 2.094(6)-2.170(5) Å for 6] in an approximately linear geometry [N(8)-Ag(1)-N(1) ) 178.6(7), N(4)-Ag(2)-N(5) ) 179.3(7)° for 5; N(8)-Ag(1)-N(1) ) 178.5(2), N(4)-Ag(2)-N(5) ) 178.8(2)° for 6]. Complexes 5 and 6 form zigzag chains that are interlinked through a series of Ag---O (2.923(16)-3.078(20) Å for 5; 2.923-3.057 Å for 6) interactions and N-H---O (N---O ) 2.128(9)-3.034(8) Å for 5; 2.876(9) and 3.043(9) Å for 6) hydrogen bonds, Figure 3b. The BF4- and ClO4- anions in 5 and 6 interact with the

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Figure 4. (a) An ORTEP diagram showing the three independent cations of 7. Thermal ellipsoids are shown at the 20% probability level. Symmetry transformations used to generate equivalent atoms: (A): x + 1/2, -y + 3/2, z + 1/2, (B): x - 1/2, -y + 3/2, z - 1/2. (b) Disposition of the molecules about the axis passing through the Ag atoms. (c) A view of the helical chain looking down the Ag atoms. (d) The interactions among the helical chains. The H2O molecules and the anions are not shown for clarity.

hydrogen atoms of the CH3CN molecules and the methylene and pyridyl hydrogen atoms of the L ligands through C-H---F (C---F ) 3.13(3)-3.298(32) Å) and C-H---O (C---O ) 3.168(27)-3.195(27) Å) hydrogen bonds, respectively. Structure of 7. The structure of complex 7 was solved in the space group P21/n, and each asymmetric unit contains three independent molecules, Figure 4a. All the cations of the three independent molecules form helical chains rotating about the axes linking the Ag atoms, and the lengths of the repeating units of the three helical chains are the same, 25.90(6) Å. Figure 4b shows a representative ORTEP diagram of the helical chains, and Figure 4c shows a view looking down the Ag atoms. The two L ligands coordinate to the metal centers in an approximately linear geometry [N(3)-Ag(1)-N(1) ) 169.01(19), N(7)-Ag(2)-N(5) ) 177.52(18), N(9)-Ag(3)-N(11) ) 169.86 (18)o]. Each polymeric chain is linked to the other through series of N-H---O (N---O ) 3.001(3) and 3.073(3) Å) hydrogen bonds and Ag---H (3.041(1)-3.194(1) Å) and Ag---O interactions (2.800(1)-3.340(2) Å), Figure 4d. The ClO4- anions form bridges between adjacent chains through C-H---O (C---O ) 3.167(2)-3.394(1) Å) hydrogen bonds. It is noted that in the helical complex 7, the dihedral angles between the two pyridyl rings of the L ligands are 52.2, 58.1, and 58.4°, respectively, for the three independent coordination polymers, which are in marked contrast to those in the zigzag complexes 3-6, which are in the range from 1.0 to 9.0°, Table 3. Structure of 8. The crystal structure of 8 was solved in the space group C2/c. An ORTEP diagram showing the asymmetric unit for 8 is depicted in Figure 5a, while Figure 5b shows its infinite structure. Two types of coordination geometries are

observed for the metal centers. The Ag(1) ion, which is coordinated by two nitrogen atoms of the pyridyl rings and one oxygen atom of the SO42- anion, has a distorted T-shaped geometry, with the N(1)-Ag(1)-N(10A), O(6)-Ag(1)-N(1) and O(6)-Ag(1)-N(10A) angles being 152.8 (3), 94.6 (3), and 100.3(3)°, respectively, whereas the Ag(2) atom, which is coordinated by three nitrogen atoms of the pyridyl rings and one oxygen atom of the SO42- anion, has a distorted tetrahedral geometry. The largest N(7)-Ag(2)-N(4) angle opened up to 123.8(3)° from the ideal tetrahedral angle, while the remaining angles are in the range from 94.1(2) to 112.3(3)°. Figure 5b shows that complex 8 is a coordination polymer forming sinusoidal chains. Each peak or valley is composed of four Ag(I), three L’s, and two SO42-, Figure 5c, which are interlinked by two L’s to form the infinite structure. These wavy chains are interlinked to each other through extensive C-H---O (C---O ) 3.400(2) and 3.185(12) Å) hydrogen bonds. Three different types of conformations can be observed for the ligands, and the dihedral angles between the two pyridyl angles are 12.1, 39.7, and 81.8°, respectively (vide infra). It is worthwhile to note here that in comparison with the structures of Ag(I) complexes containing N,N′-di(2-pyridyl)oxamide we reported earlier,5a increasing the backbone carbon atoms, as shown in L ligands of 3-8, resulted in the disappearance of the self-complementary double N-H---O hydrogen bonds, which were important in self-assembling the 1-D polymers into 2-D molecular structures.5a Conformations of the Ligands. The structures of 1-8 provide an opportunity to investigate the conformation of a flexible ligand containing six backbone carbon atoms in the solid

Ag(I) and N,N′-Di(2-pyridyl)adipoamide Complexes

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Table 3. Ligand Conformations and Corresponding Angles for Compounds 1-8

state. The ligand L can be arranged in anti-anti-anti (AAA), anti-anti-gauche (AAG), anti-gauche-anti (AGA), antigauche-gauche (AGG), gauche-anti-gauche (GAG) and gauche-gauche-gauche (GGG) conformations, and based on the relative orientation of the CdO (or N-H) groups, each conformation can adopt a cis or trans arrangement. The A and G conformations are given when the C-C-C-C torsion angle (θ) is 180 g θ > 90o and 0 E θ E 90o, respectively.15 Thus, the ligand L can possibly show 12 conformations in the solid state. Table 3 lists the ligand conformations found for the free ligand and complexes 1-8. These ligand conformations also differ in the dihedral angle (0-81.8o) between the two pyridyl ring, i.e., the two rings are coplanar or twisted about the C-N bonds. It is seen from Table 3 that although both structures of the free ligands, 1 and 2, were solved in the same space group, their conformations are different, which are GAG trans and AAA trans, respectively. This indicates that the nature of the hydrogen bonding between L and the solvent molecule can drastically change the conformation of L. However, regardless of the types of anions and solvents, all the ligands in complexes 3-7 adopt the AAA trans conformation. Most interestingly, in marked contrast to complexes 3-7, the three L’s in 8 adopt different conformations, which are GGG cis, AAA trans and AGA cis, respectively. The different ligand conformations and coordination numbers about Ag(I) in 8 are presumably due to the better coordination ability of the SO42- anions. To our best knowledge, L is the first ligand that shows three different conformations in a coordination polymer. Complexes 3-8 also make interesting comparisons with the Ag(I) complexes containing the flexible ligand N,N′-bis(3pyridinecarboxamide)-1,6-hexane (L′).4b In the complex [AgL′][ClO4], the ligands L′ coordinated to Ag cations to adopt two different conformations A and B, which differ in the dihedral angle of the two pyridyl rings and the orientations of the nitrogen

atoms of the pyridine rings. In the A conformation, the two rings are nearly coplanar and the two nitrogen atoms of the two pyridine rings show an anti-orientation, while in the B conformation, the two rings show a dihedral angle of 83.3° and the two nitrogen atoms of the two pyridine rings lies at the same side.4b Thermal Properties. To investigate the thermal stability of the ligand and complexes 3-8, we have measured their Tm values by using differential scanning calorimetry (DSC). These Tm values, which correspond to the breakdown of their supramolecular framework, are 188.2 (L), 253.1 (3), 249.8 (4), 251.7 (5), 256.7 (6), 257.0 (7), and 282.4 °C (8), respectively. It is noted that the Tm values of 6 and 7 are almost the same, indicating that the Tm value of the 1-D Ag(I) coordination polymer is independent of their structural type. The results also show that 8, where the SO42- anions are coordinated to Ag(I) centers, has a better thermal stability. This is in marked contrast to the other complexes in which their counteranions interact weakly with cations. Concluding Remarks In this study, the coordination chemistry of a new flexible ligand N,N′-di(2-pyridyl)adipoamide (L) with Ag(I) salts was investigated. Complexes 3-6 form zigzag chains and the pyridyl rings of the ligand are nearly coplanar, while complex 7 forms helical chains and the pyridyl rings of the ligand are twisted about the C-N bonds. The conformations of the free ligands 1 and 2 are susceptible to the change in the solvent type. While the 1-D chains of the cations in 3-7 are interlinked through Ag---O interactions and N-H---O hydrogen bonds, their counteranions interact weakly with the cations through C-H---F or C-H---O hydrogen bonds. Only one type of ligand conformation was observed for 3-7. Because of the better coordination

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References

Figure 5. (a) An ORTEP diagram showing the asymmetric unit of 8. Thermal ellipsoids are shown at the 20% probability level. (b) The infinite structure of 8, showing the three different conformations of the L ligands in different colors. (c) An expanded ORTEP diagram inside each peak or valley in (b). The three ligands are drawn in red, green, and yellow, while the anions are in blue.

ability of the SO42- anions to the Ag(I) ions, complex 8 forms sinusoidal chains, resulting in three types of ligand conformations. Although only four different ligand conformations for 1-8 were found, those with the same conformations show significant differences in torsion angles and dihedral angles. Obviously, the ligand L is sufficiently flexible to adjust to the stereochemical requirements for the formation of the complexes 3-8. The flexibility of the spacer ligand as well as the coordination ability of the counterion and solvent are essential in determining the structural type, and the spacer ligand adopts the conformation that maximizes the intra- and intermolecular forces. Acknowledgment. We are grateful to the National Science Council of the Republic of China for support. Supporting Information Available: Crystallographic data (CIF files, excluding structure factors) for 1-8. These files also have been deposited with the Cambridge Crystallographic Data Centre, CCDC Nos. 266170 (1), 266171 (2), 266172 (3), 611328 (4), 611329 (5), 266173 (6), 266174 (7), 266175 (8). This material is available free of charge via the Internet at http://pubs.acs.org.

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