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Syntheses and characterizations of a series of silver-carboxylate polymers
Inorganica Chimica Acta 357 (2004) 991–1001 www.elsevier.com/locate/ica
Syntheses and characterizations of a series of silver-carboxylate polymers Daofeng Sun, Rong Cao *, Wenhua Bi, Jiabao Weng, Maochun Hong, Yucang Liang State Key Laboratory of Structural Chemistry, Fujian Institute of Research on the Structure of Matter, Chinese Academy of Sciences, Fujian, Fuzhou 350002, China Received 27 May 2003; accepted 4 October 2003
Abstract Self-assembly reaction of H3 btc (1,3,5-benzenetricarboxylic acid), H2 ta (1,4-benzenedicarboxylic acid) or 1,2,4,5-benzenetetracarboxylic dianhydride with Ag(NO3 ) in mixed H2 O/MeOH solution at room temperature gave rise to four novel 3D polymeric silver(I) complexes, [{Ag(H2 btc)}{Ag2 (Hbtc)}]n (1), [Ag(ta)1=2 ]n (2), [Ag2 (btec)1=2 ]n (3) and [{Ag3 (btec)3=4 }{Ag(H2 O)2 (btec)1=4 }]n (4) (H4 btec ¼ 1,2,4,5-benzenetetracarboxylic acid). Complex 1 crystallizes in orthorhombic space group Fddd, with a ¼ 14:877ð5Þ, Z ¼ 32. Complex 2 crystallizes in monoclinic space group P 21 =c, with a ¼ 7:257ð6Þ, b ¼ 8:949ð8Þ, b ¼ 25:926ð1Þ, c ¼ 36:377ð7Þ A, b ¼ 111:654ð3Þ°, Z ¼ 4. Complex 3 crystallizes in orthorhombic space group P 21 =c, with a ¼ 8:333ð8Þ, b ¼ 6:335ð5Þ, c ¼ 6:346ð5Þ A, Z ¼ 4, whereas complex 4 crystallizes in triclinic space group P c ¼ 10:964ð9Þ A, 1, with a ¼ 7:509ð1Þ, b ¼ 9:351ð1Þ, c ¼ 10:307ð7Þ A, a ¼ 69:514ð2Þ, b ¼ 84:521ð2Þ, c ¼ 83:638ð2Þ°, Z ¼ 2. All compounds possess 3D framework and short Ag–Ag contacts are present in 1–4. In 1, the ligand unsupported Ag–Ag interactions play an important role in the formation of the complex, which is constructed by silver chains formed by Ag–Ag interactions and carboxylate spacers. Ó 2003 Elsevier B.V. All rights reserved. Keywords: Self-assembly; Silver(I); Carboxylate; Ag–Ag interactions
1. Introduction The design and synthesis of metal–organic coordination polymers are of great interest due to their special properties and potential applications in sorption, electrical conductivity and catalysis [1–3]. In the past decade, the fascinating properties have prompted the studies on the architectures of metal–organic coordination polymers whose construction, in a large scale, depends on the characters of ligand and metal ion. The recent development of self-assembled supramolecular chemistry has made it possible to rationally design and synthesize metal–organic coordination polymers depending on the ligand geometry and coordination propensity of the metal ion, which has been proved by the
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Corresponding author. Tel.: +86-591-3796710; fax: +86-5913714946. E-mail address: [email protected] (R. Cao). 0020-1693/$ - see front matter Ó 2003 Elsevier B.V. All rights reserved. doi:10.1016/j.ica.2003.10.010
reports of a large number of silver coordination polymers [4]. As known, silver(I) ion principally exhibits linear, trigonal, and tetrahedral coordination and has high affinity for hard donor atoms such as nitrogen or oxygen atoms and soft donor atoms such as sulfur atom, being a favorable and fashionable building block for coordination polymers [5,6]. Furthermore, silver ion is apt to form short Ag–Ag contacts as well as ligand unsupported interaction which has been proved to be two of the most important factors contributing to the formation of such complexes and special properties [7]. For instances, silver cyanurate polymer [Ag2 C3 N3 HO3 ]n comprising silver sheets and organic spacer possesses anisotropic conductivity [8], silver thiolate polymer [Ag(C5 H4 NS)]n having graphite-like Ag6 motifs shows semicoductivity [9]. Previous works [10,11] have proved rigid benzene-multicarboxylic acid, such as 1,4-benzenedicarboxylic acid (H2 ta), 1,3,5-benzenetricarboxylic acid (H3 btc) and 1,2,4,5-benzenetetracarboxylic acid (H4 btec), is a good choice for the construction of
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metal–organic coordination polymers owing to their rich coordination modes. However, although many coordination polymers constructed by benzoic multicarboxylic acid have been reported, most of them focused on the lanthanide(III) and transition metal such as Cu(II), Co(II), Zn(II), and Cd(II), those on silver(I) are very rare, probably because they often appear as insoluble salts that make structural analyses difficult [12,13]. To the best of our knowledge, only a few silver–benzoic multicarboxylic acid complexes have been reported in the literature [14]. Through the self-assembly reaction of H3 btc and AgNO3 , we have successfully isolated an interesting silver(I) complex formed by ligand unsupported Ag–Ag interaction, [{Ag(H2 btc)}{Ag2 (Hbtc)}]n (1) [15]. To extend our work, systematic studies have been carried out by employing different carboxylic acids and changing reaction conditions. In this report, we describe the details of the syntheses and characterizations of four silver-carboxylate coordination polymers, [{Ag(H2 btc)}{Ag2 (Hbtc)}]n (1), [Ag(ta)1=2 ]n (2), [Ag2 (btec)1=2 ]n (3) and [{Ag3 (btec)3=4 }{Ag(H2 O)2 (btec)1=4 }]n (4).
2. Experimental 2.1. Materials and analyses All chemicals used are as purchased without purification. IR spectra were recorded on a Magna 750 FTIR
spectrophotometer as KBr pallets. Elemental analyses were carried out in the elemental analysis group of this institute. 2.2. Preparation of complexes 2.2.1. [{Ag(H2 btc)}{Ag2 (Hbtc)}]n (1) H3 btc (0.053 g, 0.25 mmol) was dissolved in 10 ml of hot water, after cooled the solution was placed in the bottom of a glass tube. Then, a solution of AgNO3 (0.083 g, 0.5 mmol) in MeOH (5 ml) was carefully layered on it, through a 5 ml of mixed MeOH/water (3:2) buffer. The tube was sealed and stored in darkness. Colorless well-formed prism-like crystals were obtained after about one week, collected by filtration and washed with water. Yield: 69%. Anal. Calc. for C18 H9 Ag3 O12 : C, 29.18; H, 1.22. Found: C, 29.20; H, 1.18%. IR(KBr, cm1 ): 3469(vs), 3107(s), 2887(s), 2517(s), 1705(s), 1686(vs), 1610(s), 1564(s), 1275(vs), 931(m), 688(s). 2.2.2. [Ag(ta)1=2 ]n (2) H2 ta (0.02 g, 0.125 mmol) and NaOH (0.008 g, 0.2 mmol) were dissolved in 10 ml of hot water, after cooled the solution was placed in the bottom of a glass tube. Then, a solution of AgNO3 (0.041 g, 0.25 mmol) in MeOH (5 ml) was carefully layered on it, through a 5 ml of mixed MeOH/water (3:2) buffer. The tube was sealed and stored in darkness. After one week, colorless platelike crystals were collected by filtration and washed with water. Yield: 41%. Anal. Calc. for C4 H2 AgO2 : C, 25.30;
Table 1 The crystallographic data for complexes 1–4 Complex Empirical formula Formula weight Space group T (°C) a (A) b (A) c (A) a (°) b (°) c (°) 3 ) V (A Z qcalcd (g cm3 ) k (A) l (mm1 ) F ð0 0 0Þ Crystal size (mm) h range for data collection (°) Limiting indices
Reflections collected Unique Goodness-of-fit on F 2 R1 wR2
1 C18 H9 Ag3 O12 740.86 Fddd 293 14.877(5) 25.926(1) 36.377(7) 90 90 90 14031.4(2) 32 2.806 0.71073 3.394 11 328 0.40 0.10 0.05 1.67–25.02 17 6 h 6 13, 30 6 k 6 20, 43 6 l 6 33 9447 3094 1.003 0.0433 0.1016
2 C4 H2 AgO2 189.93 P 21 =c 293 7.257(6) 8.949(8) 6.346(6) 90 111.654(3) 90 383.13(11) 4 3.293 0.71073 5.087 356 0.35 0.20 0.08 3.02–25.02 8 6 h 6 8, 10 6 k 6 4, 7 6 l 6 5 1160 663 1.059 0.0499 0.1294
3 C5 HAg2 O4 340.80 P 21 =c 293 8.333(8) 6.335(5) 10.964(9) 90 90 90 578.91(3) 4 3.910 0.71073 6.708 628 0.36 0.32 0.18 2.44–25.01 9 6 h 6 6, 7 6 k 6 5, 7 6 l 6 5 1900 992 1.206 0.0505 0.1213
4 C10 H6 Ag4 O10 717.63 P 1 293 7.509(1) 9.351(1) 10.307(7) 69.514(2) 84.521(2) 83.638(2) 672.57(10) 2 3.544 0.71073 5.794 668 0.38 0.14 0.04 2.11–25.04 7 6 h 6 8, 7 6 k 6 11, 12 6 l 6 12 3432 2320 1.089 0.0638 0.1661
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Table 2 The selected bonds and angles for 1–4 1 Ag(1)–O(4) Ag(1)–O(3)#1 Ag(1)–O(2)#2 Ag(1)–Ag(1)#3 Ag(1)–Ag(1)#1 Ag(1)–Ag(2) Ag(2)–O(8)#4 Ag(2)–O(7)#5 Ag(2)–O(10)#6 Ag(2)–Ag(2)#1
2.209(4) 2.224(4) 2.487(4) 2.9636(11) 2.9748(12) 3.3774(8) 2.226(4) 2.263(4) 2.560(4) 2.9886(12)
Ag(2)–Ag(3) Ag(3)–O(10) Ag(3)–O(10)#6 Ag(3)–Ag(3)#7 Ag(3)–Ag(2)#6 Ag(3)–Ag(4) Ag(4)–O(11)#8 Ag(4)–O(11)#9 Ag(4)–O(9)#6 Ag(4)–O(9)
3.1846(6) 2.108(4) 2.108(4) 3.0913(15) 3.1846(6) 3.2105(11) 2.508(4) 2.508(4) 2.548(4) 2.548(4)
O(4)–Ag(1)–O(3)#1 O(4)–Ag(1)–O(2)#2 O(3)#1–Ag(1)–O(2)#2 O(4)–Ag(1)–Ag(1)#3 O(3)#1–Ag(1)–Ag(1)#3 O(2)#2–Ag(1)–Ag(1)#3 O(4)–Ag(1)–Ag(1)#1 O(3)#1–Ag(1)–Ag(1)#1 O(2)#2–Ag(1)–Ag(1)#1 Ag(1)#3–Ag(1)–Ag(1)#1 O(4)–Ag(1)–Ag(2) O(3)#1–Ag(1)–Ag(2) O(2)#2–Ag(1)–Ag(2) Ag(1)#3–Ag(1)–Ag(2) Ag(1)#1–Ag(1)–Ag(2) O(8)#4–Ag(2)–O(7)#5 O(8)#4–Ag(2)–O(10)#6 O(7)#5–Ag(2)–O(10)#6 O(8)#4–Ag(2)–Ag(2)#1 O(7)#5–Ag(2)–Ag(2)#1 O(10)#6–Ag(2)–Ag(2)#1 O(8)#4–Ag(2)–Ag(3) O(7)#5–Ag(2)–Ag(3) O(10)#6–Ag(2)–Ag(3) Ag(2)#1–Ag(2)–Ag(3) O(8)#4–Ag(2)–Ag(1) O(7)#5–Ag(2)–Ag(1) O(10)#6–Ag(2)–Ag(1)
153.80(17) 123.35(16) 82.68(16) 81.75(12) 106.02(12) 84.27(12) 81.10(12) 74.03(11) 153.46(11) 90.0 117.10(12) 50.58(11) 95.60(12) 156.15(3) 79.478(15) 155.02(16) 91.90(15) 108.48(15) 83.73(12) 75.11(11) 113.33(10) 111.41(12) 77.87(12) 41.29(9) 79.285(15) 109.99(12) 53.51(11) 156.23(10)
Ag(2)#1–Ag(2)–Ag(1) Ag(3)–Ag(2)–Ag(1) O(10)–Ag(3)–O(10)#6 O(10)–Ag(3)–Ag(3)#7 O(10)#6–Ag(3)–Ag(3)#7 O(10)–Ag(3)–Ag(2)#6 O(10)#6–Ag(3)–Ag(2)#6 Ag(3)#7–Ag(3)–Ag(2)#6 O(10)–Ag(3)–Ag(2) O(10)#6–Ag(3)–Ag(2) Ag(3)#7–Ag(3)–Ag(2) Ag(2)#6–Ag(3)–Ag(2) O(10)–Ag(3)–Ag(4) O(10)#6-Ag(3)–Ag(4) Ag(3)#7–Ag(3)–Ag(4) Ag(2)#6-Ag(3)–Ag(4) Ag(2)–Ag(3)–Ag(4) O(11)#8–Ag(4)–O(11)#9 O(11)#8–Ag(4)–O(9)#6 O(11)#9–Ag(4)–O(9)#6 O(11)#8–Ag(4)–O(9) O(11)#9–Ag(4)–O(9) O(9)#6–Ag(4)–O(9) O(11)#8–Ag(4)–Ag(3) O(11)#9–Ag(4)–Ag(3) O(9)#6–Ag(4)–Ag(3) O(9)–Ag(4)–Ag(3)
79.290(15) 130.39(2) 175.2(2) 87.58(12) 87.58(12) 53.27(12) 125.46(12) 77.791(16) 125.46(12) 53.27(12) 77.791(16) 155.58(3) 92.42(12) 92.42(12) 180.0 102.209(16) 102.209(16) 90.5(2) 145.44(15) 82.09(13) 82.09(13) 145.44(15) 121.69(19) 134.74(11) 134.74(11) 60.85(10) 60.85(10)
Symmetry transformations used to generate equivalent atoms: #1 x, y 1=4, z þ 3=4; #2 x þ 1=2, y þ 1=4, z 1=4; #3 x þ 3=4, y, z þ 3=4; #4 x, y 1=4, z 1=4; #5 x, y, z þ 1; #6 x 1=4, y, z þ 3=4; #7 x 1=4, y 1=4, z; #8 x þ 1=4, y þ 1=4, z þ 1 and #9 x 1=2, y þ 1=4, z 1=4 2 Ag–O(2)#1 2.208(5) Ag–O(2)#2 2.511(4) Ag–O(1) 2.230(5) Ag–Ag#1 2.9013(11) O(2)#1–Ag–O(1) O(2)#1–Ag–O(2)#2 O(1)–Ag–O(2)#2
157.9(2) 108.14(17) 89.35(18)
O(2)#1–Ag–Ag#1 O(1)–Ag–Ag#1 O(2)#2–Ag–Ag#1
82.18(12) 79.49(13) 168.56(13)
Symmetry transformations used to generate equivalent atoms: #1 x, y þ 1, z and #2 x, y þ 1=2, z þ 1=2 3 Ag(1)–O(2) 2.236(6) Ag(2)–O(3) 2.277(6) Ag(1)–O(4)#1 2.361(5) Ag(2)–O(1) 2.334(6) Ag(1)–O(3)#2 2.433(6) Ag(2)–O(4) 2.380(6) Ag(1)–Ag(2) 3.0033(9) Ag(2)–O(1)#3 2.440(6) O(2)–Ag(1)–O(4)#1 O(2)–Ag(1)–O(3)#2 O(4)#1–Ag(1)–O(3)#2 O(2)–Ag(1)–Ag(2) O(4)#1–Ag(1)–Ag(2) O(3)#2–Ag(1)–Ag(2) O(3)–Ag(2)–O(1) O(3)–Ag(2)–O(4)
155.9(2) 123.00(19) 79.1(2) 77.05(16) 83.00(15) 121.05(16) 95.9(2) 152.60(19)
O(1)–Ag(2)–O(4) O(3)–Ag(2)–O(1)#3 O(1)–Ag(2)–O(1)#3 O(4)–Ag(2)–O(1)#3 O(3)–Ag(2)–Ag(1) O(1)–Ag(2)–Ag(1) O(4)–Ag(2)–Ag(1) O(1)#3–Ag(2)–Ag(1)
93.2(2) 92.6(2) 129.96(11) 101.10(19) 74.56(16) 161.97(14) 89.13(14) 66.73(14)
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Table 2 (continued) Symmetry transformations used to generate equivalent atoms: #1 x, y þ 1, z; #2 x, y þ 1=2, z 1=2 and #3 x, y 1=2, z þ 1=2 4 Ag(1)–O(4)#1 2.258(8) Ag(3)–O(1) 2.226(9) Ag(1)–O(7)#2 2.348(8) Ag(3)–O(5)#3 2.243(9) Ag(1)–O(7)#3 2.410(9) Ag(3)–Ag(4) 3.0107(15) Ag(1)–Ag(2) 2.8632(15) Ag(4)–O(6)#3 2.293(9) Ag(2)–O(3)#1 2.208(8) Ag(4)–O(9) 2.299(9) Ag(2)–O(8)#2 2.237(8) Ag(4)–O(10) 2.435(11) Ag(2)–O(2) 2.523(9) Ag(4)–O(2)#4 2.456(10) Ag(2)–Ag(3) 3.2057(16) O(4)#1–Ag(1)–O(7)#2 O(4)#1–Ag(1)–O(7)#3 O(7)#2–Ag(1)–O(7)#3 O(4)#1–Ag(1)–Ag(2) O(7)#2–Ag(1)–Ag(2) O(7)#3–Ag(1)–Ag(2) O(3)#1–Ag(2)–O(8)#2 O(3)#1–Ag(2)–O(2) O(1)–Ag(3)–O(5)#3 O(1)–Ag(3)–Ag(4) O(5)#3–Ag(3)–Ag(4) O(1)–Ag(3)–Ag(2) O(5)#3–Ag(3)–Ag(2) Ag(4)–Ag(3)–Ag(2) O(6)#3–Ag(4)–O(9) O(6)#3–Ag(4)–O(10)
151.5(3) 112.5(3) 87.9(3) 82.6(3) 75.2(2) 162.9(2) 156.0(3) 91.7(3) 153.4(3) 80.2(2) 73.7(2) 70.4(3) 111.0(2) 103.56(5) 155.5(4) 88.3(4)
O(8)#2–Ag(2)–O(2) O(3)#1–Ag(2)–Ag(1) O(8)#2–Ag(2)–Ag(1) O(2)–Ag(2)–Ag(1) O(3)#1–Ag(2)–Ag(3) O(8)#2–Ag(2)–Ag(3) O(2)–Ag(2)–Ag(3) Ag(1)–Ag(2)–Ag(3) O(9)–Ag(4)–O(10) O(6)#3–Ag(4)–O(2)#4 O(9)–Ag(4)–O(2)#4 O(10)–Ag(4)–O(2)#4 O(6)#3–Ag(4)–Ag(3) O(9)–Ag(4)–Ag(3) O(10)–Ag(4)–Ag(3) O(2)#4–Ag(4)–Ag(3)
106.2(3) 77.7(2) 78.6(2) 146.9(2) 55.5(3) 115.4(2) 69.9(2) 78.41(4) 92.6(4) 77.6(3) 126.9(3) 87.8(4) 80.0(2) 88.6(3) 153.4(3) 112.5(2)
Symmetry transformations used to generate equivalent atoms: #1 x þ 1, y, z þ 1; #2 x þ 1, y 1, z þ 2; #3 x 1, y þ 1, z and #4 x 1, y, z
H, 1.06. Found: C, 25.41; H, 1.02%. IR(KBr, cm1 ): 3072(m), 1568(vs), 1497(m), 1439(m), 1389(vs), 1352(w), 1012(m), 823(s), 744(vs), 499(s). 2.2.3. [Ag2 (btec)1=2 ]n (3) 1,2,4,5-Benzenetetracarboxylic dianhydride (0.027 g, 0.125 mmol) was dissolved in 10 ml of hot water, to which 0.25 mmol (0.01 g) NaOH was added. The solution was placed in the bottom of a glass tube after cooled. Then, a solution of AgNO3 (0.083 g, 0.5 mmol) in MeOH (5 ml) was carefully layered on it, through a 5 ml of mixed MeOH/water (3:2) buffer. The tube was sealed and stored in darkness. After two weeks, lightyellow well-formed prism-like crystals were collected by filtration and washed with water. Yield: 55%. Anal. Calc. for C5 HAg2 O4 : C, 17.62; H, 0.30. Found: C, 17.67; H, 0.29%. IR(KBr, cm1 ): 3508(s), 3298(s), 1668(w), 1583(vs), 1566(vs), 1414(s), 1371(vs), 939(w), 814(m), 577(m). 2.2.4. [{Ag3 (btec)3=4 }{Ag(H2 O)2 (btec)1=4 }]n (4) 1,2,4,5-Benzenetetracarboxylic dianhydride (0.027 g, 0.125 mmol) was dissolved in 10 ml of hot water, to which 0.125 mmol Na2 SiO3 was added. After cooled, the solution was placed in the bottom of a glass tube. Then, a solution of AgNO3 (0.02 g, 0.125 mmol) in MeOH (5 ml) was carefully layered on it, through a 5 ml of mixed MeOH/water (3:2) buffer. The tube was sealed and stored in darkness. After two weeks, colorless prism-like crys-
tals were obtained, collected by filtration and washed with water. Yield: 35%. Anal. Calc. for C10 H6 Ag4 O10 : C, 16.74; H, 0.84. Found: C, 16.80; H, 0.82%. IR(KBr, cm1 ): 3370(vs), 3040(m), 1689(w), 1570(vs), 1489(m), 1423(m), 1383(vs), 1327(m), 814(m), 744(m). 2.3. Crystallographic analyses The intensity data of 1–4 were collected on a Siements Smart CCD diffractometer with graphite-monochro radiation at room temmated Mo Ka (k ¼ 0:71073 A) perature. All absorption corrections were performed using the S A D A B S program [16]. The structures were solved by direct methods [17] and refined on F2 by fullmatrix least-squares using the S H E L X T L -97 program package [18] on a legend computer. All non-hydrogen atoms were refined anisotropically. The organic hydro gen atoms were generated geometrically (C–H 0.96 A). The crystallographic data of complexes 1–4 are listed in Table 1, selected bonds and angles in Table 2.
3. Results and discussions 3.1. Synthetic chemistry Our aim is to assemble benzoic multicarboxylic acid with silver(I) salt and study their structure and property. As is well known, the reactions of silver(I) ion with
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multicarboxylates in aqueous solution often result in the formation of insoluble Ôsilver saltsÕ, presumably due to the fast coordination of the carboxylates to silver ion to form polymer. Smith and co-workers [12a] have obtained a series of Ag–benzoic multicarboxylic acid complexes by using ammoniacal conditions to enhance the solubility of the silver carboxylates, Michaelides and co-workers [12b] have reported a novel succinatodisilver(I) complex which was synthesized by gel permeation. Hence, properly lowering the reaction speed may result in the formation of crystalline products. Considering this, we adopt self-assembly reaction of silver(I) ion with multi-carboxylic acids by slow diffusion in the mixture water and organic solution. We first select 1,3,5-benzenetricarboxylic acid (H3 btc) to assemble with silver(I) salt in water/MeOH solution at pH 2.5 and results in the formation of complex 1, which possesses a 3D framework constructed by silver chains formed by ligand unsupported Ag–Ag interactions and organic spacers [15]. The successful isolation of 1 prompted us to extend our study to other benzoic multicarboxylic acid, such as 1,4-benzenedicarboxylic acid (H2 ta) and 1,2,4,5-benzenetetracarboxylic acid(H4 btec). In treatment of H2 ta or 1,2,4,5-benzenetetracarboxylic dianhydride with silver salt, NaOH was added to accelerate the hydrolyzation of 1,2,4,5-benzenetetracarboxylic dianhydride and dissolve 1,4-benzenedicarboxylic acid. As expected, 2 and 3, which possess 3D frameworks, were isolated at pH 6.5 and 9, respectively, as colorless crystals. Since self-assembly reaction is highly influenced by many factors such as the pH value, solvent and the metal– ligand ratio [19], the reactions with different pH value (2–9), solution (DMF and MeCN) were carried out in order to prepare silver polymers with different struc-
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tures. However, same result was obtained for complex 1 in different solution although the yields were different. When pH value is higher than 5, only deposits were obtained. For 1,2,4,5-benzenetetracarboxylic dianhydride, when treated in pH 4 by using Na2 SiO3 as the base, complex 4 that is quite different from complex 3 was successfully isolated, but precipitates were obtained when treated in other solutions. For H2 ta, when treated in other pH value and solvent, only unknown precipitates were obtained, illustrating the solvent and pH value remarkably influence the formations of complex 2, 3 and 4. The carboxylic groups of H3 btc in 1 were partly deprotonated, whereas all of the carboxylic groups were deprotonated in 2, 3 and 4 by NaOH or Na2 SiO3 . X-ray diffraction analyses illustrate the three ligands connected more than one metal ion, especially for btec4 in 3 that acts as a l14 –bridge to link fourteen silver atoms. Scheme 1 shows the coordination modes of the three ligands in complexes 1–4. 3.2. Crystal structure analysis 3.2.1. Crystal structure of complex 1 Complex 1 possesses a 3D network formed by ligandunsupported Ag–Ag interactions. Single-crystal structure analysis shows 1 comprises two independent building units, Ag2 (H2 btc)2 (A) and Ag8 (Hbtc)12=3 (B). The coordination mode of H2 btc in A is illustrated in Scheme 1(b), if neglecting the Ag–Ag contact, the Ag ion (Ag1) is three-coordinate by oxygen atoms from three different ligands with the average Ag–O distances and every two such Ag atoms are being 2.227(4) A bridged by two carboxylate groups with Ag–Ag distance
Scheme 1.
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(a)
(b) Fig. 1. (a) Structure of the linear chain formed by unit A. (b) The 3D open framework generated by ligand-unsupported Ag–Ag interactions in unit A.
Each two A units are linked together of 2.976(3) A. through weak Ag–Ocarbonyl bonding with Ag–O distance completing the distorted trigonal cobeing 2.487(4) A, ordination geometry of Ag and yielding a 1D chain structure (Fig. 1(a)). Each two adjacent chains that are aligned in different directions are combined via ligand unsupported Ag–Ag interactions (Ag–Ag, 2.962(7) A), forming a 3D open framework structure (Fig. 1(b)). Unit B is composed of four Ag2 subunits, each of them is connected by two carboxylate groups. Two Ag3–Ag4 are joined by ligandsubunits (Ag3–Ag4, 3.210(5) A) unsupported Ag–Ag interaction (Ag3–Ag3, 3.092(4) A), generating a linear Ag4 chain, which connects two Ag2– subunits through weak Ag–O bonding Ag2 (2.989(5) A) and ligand-unsupported Ag–Ag interactions (Ag2–Ag3, (Fig. 2(a)). There are three kinds of Ag in B: 3.184(9) A) Ag2, Ag3 and Ag4 are in O3 distorted trigonal, O2 linear and O4 distorted tetragonal geometry, respectively. Interestingly, all Ag4–O bonding is very weak (Ag4–O, e.g. Ag4 may be viewed as ‘‘loose’’ 2.505(5)–2.547(5) A),
atom dotted in B through Ag–Ag and Ag–O interactions. Hbtc2 ligand acts as a l6 -bridge (Scheme 1(c)) to link three B units, generating another 3D open framework structure (Fig. 2(b)). Owing to the ligand unsup interactions ported Ag–Ag (Ag1–Ag2, 3.278(3) A) between the two kinds of 3D open framework structures, they are penetrating into each other, producing linear distorted ladder-like Ag chains (Fig. 3(a)) and the final condensed 3D structure. Thus the whole structure can also be regarded as parallel Ag chains linking by H2 btc and Hbtc2 spacers (Fig. 3(b)). The importance of ligand unsupported Ag–Ag interactions in the formation of polymeric structure has been documented [19]. In 1, such interaction also play an important role in the formation of the complex: they induce the formations of the 3D structure formed by unit A, unit B itself and the Ag chains in the whole structure. All of Ag–Ag distances (2.962(7)–3.378(3) A) are shorter than the van der Waals contact distance for [20], and the shortest one (2.962(7) A) is Ag–Ag (3.40 A)
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997
(a)
(b) Fig. 2. (a) Structure of unit B. (b) The 3D open framework in unit B.
only slightly longer than that found in metallic silver To our best knowledge, complex 1, which (2.89 A). contains silver chains formed by ligand unsupported Ag–Ag interactions, is the first example found in Ag– multicarboxylate systems. 3.2.2. Crystal structure of complex 2 The structure determination of complex 2 reveals a 3D framework with short Ag–Ag contacts. As shown in Fig. 4, the silver ion is coordinated by three oxygen atoms from three different ta2 ligands with the Ag–O
and forms bonds ranging from 2.208(5) to 2.511(4) A, with adjacent silver short Ag–Ag contact (2.901(4) A) (AgA) through the bridging carboxylate group. The Ag– Ag distance is slightly shorter than those found in other Ag–Ag contact complexes, such as catena-bis(4-aminobenzoato)disilver(I) [7a], [Ag{CH(COOC2 H5 )2 }PPh2 ]2 [21a], [AgCH2 P(S)Ph2 ]2 (2.990(2) A) [21b], (2.953(1) A) and Ag2 (H2 L)3 ]n (ClO4 )2n (H2 L ¼ N,N 0 -bis(salicylidene) [19]. If neglecting the 1,4-diaminobutane) (2.946 A) Ag–Ag bond, each silver ion is three-coordinate in a ‘‘T-shape’’ geometry. Every ta2 ligand acts as a
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(a)
(b) Fig. 3. (a) The structure of silver chain formed by ligand unsupported Ag–Ag interactions in 1. (b) The packing structure along the a axis of 1, the organic spacers are omitted for clarity.
bonds of one carboxylate l2 –O of ta2 with distance to generate a 2D wave-like layer being 2.511(4) A, (Fig. 5(a)). The layers are spliced each other by the Ag– O bonds of the other carboxylate l2 –O of ta2 to result in a 3D framework. As shown in Fig. 5(b), the structure can also be regarded as inorganic silver layers linked by organic ta2 spacers, the distance between two silver layers is 11.267 A.
Fig. 4. Local coordination environment of Ag(I) in 2.
l6 -bridge to link six silver atoms (Scheme 1(a)). The binuclear [Ag2 (ta)2 ] species, which is formed by two silver ions linked by two bridging carboxylate groups from two ta2 , may be viewed as the building unit of the whole structure. Such binuclear units are linked head-totail through sharing ta2 ligands to form a 1D chain. The 1D chains are connected each other by weak Ag–O
3.2.3. Crystal structure of complex 3 Complex 3 has a 3D structure. As shown in Fig. 6, two coordination environments of silver(I) ions are found in complex 3: Ag(1) is three-coordinate by three oxygen atoms from different btec4 ligands with Ag(1)– Ag(2) O distances ranging from 2.236(6) to 2.433(6) A; is coordinated by four oxygen atoms from four ligands with Ag(2)–O distances ranging from 2.277(6) to The distance of Ag(1)–Ag(2) (3.003(4) A) is 2.440(6) A. significantly shorter than the van der Waals contact [20], illustrating the existing of weak distance 3.40 A metal–metal interaction between Ag(1) and Ag(2). The distance is slightly longer than that found in silver [3], but between benzenesulfonate complex (2.915 A) those in the succinatodisilver complex (2.938 and 3.104 [12b]. Each btec4 ligand acts as a l14 -bridge, linking A) 14 silver atoms (Scheme 1(d)). Thus, Ag(1) and Ag(2)
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999
(a)
(b)
Fig. 7. (a) The layer structure in 3. (b) The 3D framework of 3.
Fig. 5. (a) The 2D layer in 2. (b) Packing structure along the c axis of 2.
(Fig. 7(b)). Complex 3 is quite different from previous reported complex [Ag2 (H2 btec)]n [14a], in which two carboxyl groups are protonated and every H2 btec2 acts as a l10 -bridge to link ten silver atoms to form the 3D framework.
Fig. 6. Local coordination environment of Ag(I) in 3.
are bridged by two carboxylate groups to form an Ag2 unit. Each Ag2 unit is connected by four btec4 ligands and every btec4 ligand attaches four Ag2 units to form a 2D layer structure (Fig. 7(a)). The layers are further linked by Ag–O bonds through the l2 -O atoms of carboxylate groups to generate the final 3D framework
3.2.4. Crystal structure of complex 4 Although the original materials for 4 are similar to those for 3 except the base used in the reaction, the structures of the two complexes are quite different. Complex 4 is a 3D coordination polymer with [{Ag3 (btec)3=4 }{Ag(H2 O)2 (btec)1=4 }] formula. As shown in Fig. 8, different from complex 3, there are four crystallographically distinct silver centers. Ag(1), Ag(2) and Ag(3) are coordinated by three oxygen atoms from different btec4 ligands with the Ag–O distances ranging which is slightly longer than from 2.208(8) to 2.523(9) A, those found in complex 3, whereas Ag(4) is coordinated by four oxygen atoms, two from two different btec4 ligands and the other two from coordinated water molecules with average Ag–O distance being 2.353(11) As found in other silver complexes, short Ag–Ag A. contacts are present among Ag(1)–Ag(2), Ag(2)–Ag(3) and Ag(3)–Ag(4) with average Ag–Ag distance being The shortest one (Ag(1)–Ag(2): 2.863(3) A) 3.026(6) A. is shorter than that found in metallic silver (2.89 A), illustrating the existence of strong Ag–Ag interaction between Ag(1) and Ag(2), similar to those observed in some previous reported complexes such as [Ag(p [22a], CH3 C6 H4 NCHNC6 H4 -p-CH3 )]2 (2.705(1) A) [22b]. All carboxyl groups [Ag(PhN3 Ph)]2 (2.669(1) A)
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are bridged by another carboxylate group with Ag(1)– Ag(2)–Ag(3) angle being 78.41(4)°, to form the subunit Ag3 (btec)3=4 . Every two Ag3 units are linked by btec4 ligands to form a 2D layer (Fig. 9(a)), in which each btec4 links four Ag3 units and each Ag3 unit attaches to four btec4 ligands. The layers were further connected by Ag(H2 O)2 (btec)1=4 unit through Ag4–Obtec as well as Ag3–Ag4 contact to form the finally 3D framework (Fig. 9(b)).
4. Conclusion
Fig. 8. Local coordination environment of Ag(I) in 4.
We have successfully synthesized four novel silvercarboxylate polymeric complexes by self-assembly reaction of rigid benzoic multicarboxylic acid with AgNO3 at room temperature. In 1–4, the short Ag–Ag contacts or ligand unsupported Ag–Ag interactions play important roles in the formation of these complexes as well as their properties, especially in complex 1. Meanwhile, complex 1 is the first silver-benzoic multicarboxylate polymer containing ligand unsupported Ag–Ag interactions. During the preparations of 3 and 4, 1,2,4,5benzenetetracarboxylic dianhydride was hydrolyzed to 1,2,4,5-benzenetetracarboxylic acid and deprotonated by NaOH or Na2 SiO3; similar to our previous reported under the hydrothermal condition [10b,10c]. It is interesting to note that complexes 3 and 4 are obtained under different pH value, which proves that some factors, such as pH value, solvent, are crucial in self-assembly system and also indicate that different metal coordination polymers can be constructed by subtly altering any of these factors.
5. Supplementary data Atomic coordinates, thermal parameters and bond lengths and angles for complexes 1–4 have been deposited at the Cambridge Crystallographic Center (CCDC). Any request to the CCDC for this material should quote the full literature citation and the reference numbers CCDC 166791 for 1, 198096–198098 for 2–4. Copies of this information may be obtained free of charge from The Director, CCDC, 12 Union Road. Cambridge. CB2 1EZ. UK. (Fax: +441223-336033; email: deposit@ccdc. cam.ac.uk or http://www.ccdc.cam.ac.uk/). Fig. 9. (a) The layer structure in 4. (b) Packing structure of 4 along the c-axis.
Acknowledgements
of btec4 are deprotonated by Na2 SiO3 during the selfassembly reaction and each btec4 acts as a l10 -bridge to link ten silver atoms (Scheme 1(e)). Ag(1) and Ag(2) are bridged by two carboxylate groups and Ag(2) and Ag(3)
The authors are grateful to the financial support from NNSF of China (90206040, 29901005), NSF of Fujian Province and the key and the ‘‘One Hundred Talent’’ projects from CAS.
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Syntheses and characterizations of a series of silver-carboxylate polymers Daofeng Sun, Rong Cao *, Wenhua Bi, Jiabao Weng, Maochun Hong, Yucang Liang State Key Laboratory of Structural Chemistry, Fujian Institute of Research on the Structure of Matter, Chinese Academy of Sciences, Fujian, Fuzhou 350002, China Received 27 May 2003; accepted 4 October 2003
Abstract Self-assembly reaction of H3 btc (1,3,5-benzenetricarboxylic acid), H2 ta (1,4-benzenedicarboxylic acid) or 1,2,4,5-benzenetetracarboxylic dianhydride with Ag(NO3 ) in mixed H2 O/MeOH solution at room temperature gave rise to four novel 3D polymeric silver(I) complexes, [{Ag(H2 btc)}{Ag2 (Hbtc)}]n (1), [Ag(ta)1=2 ]n (2), [Ag2 (btec)1=2 ]n (3) and [{Ag3 (btec)3=4 }{Ag(H2 O)2 (btec)1=4 }]n (4) (H4 btec ¼ 1,2,4,5-benzenetetracarboxylic acid). Complex 1 crystallizes in orthorhombic space group Fddd, with a ¼ 14:877ð5Þ, Z ¼ 32. Complex 2 crystallizes in monoclinic space group P 21 =c, with a ¼ 7:257ð6Þ, b ¼ 8:949ð8Þ, b ¼ 25:926ð1Þ, c ¼ 36:377ð7Þ A, b ¼ 111:654ð3Þ°, Z ¼ 4. Complex 3 crystallizes in orthorhombic space group P 21 =c, with a ¼ 8:333ð8Þ, b ¼ 6:335ð5Þ, c ¼ 6:346ð5Þ A, Z ¼ 4, whereas complex 4 crystallizes in triclinic space group P c ¼ 10:964ð9Þ A, 1, with a ¼ 7:509ð1Þ, b ¼ 9:351ð1Þ, c ¼ 10:307ð7Þ A, a ¼ 69:514ð2Þ, b ¼ 84:521ð2Þ, c ¼ 83:638ð2Þ°, Z ¼ 2. All compounds possess 3D framework and short Ag–Ag contacts are present in 1–4. In 1, the ligand unsupported Ag–Ag interactions play an important role in the formation of the complex, which is constructed by silver chains formed by Ag–Ag interactions and carboxylate spacers. Ó 2003 Elsevier B.V. All rights reserved. Keywords: Self-assembly; Silver(I); Carboxylate; Ag–Ag interactions
1. Introduction The design and synthesis of metal–organic coordination polymers are of great interest due to their special properties and potential applications in sorption, electrical conductivity and catalysis [1–3]. In the past decade, the fascinating properties have prompted the studies on the architectures of metal–organic coordination polymers whose construction, in a large scale, depends on the characters of ligand and metal ion. The recent development of self-assembled supramolecular chemistry has made it possible to rationally design and synthesize metal–organic coordination polymers depending on the ligand geometry and coordination propensity of the metal ion, which has been proved by the
*
Corresponding author. Tel.: +86-591-3796710; fax: +86-5913714946. E-mail address: [email protected] (R. Cao). 0020-1693/$ - see front matter Ó 2003 Elsevier B.V. All rights reserved. doi:10.1016/j.ica.2003.10.010
reports of a large number of silver coordination polymers [4]. As known, silver(I) ion principally exhibits linear, trigonal, and tetrahedral coordination and has high affinity for hard donor atoms such as nitrogen or oxygen atoms and soft donor atoms such as sulfur atom, being a favorable and fashionable building block for coordination polymers [5,6]. Furthermore, silver ion is apt to form short Ag–Ag contacts as well as ligand unsupported interaction which has been proved to be two of the most important factors contributing to the formation of such complexes and special properties [7]. For instances, silver cyanurate polymer [Ag2 C3 N3 HO3 ]n comprising silver sheets and organic spacer possesses anisotropic conductivity [8], silver thiolate polymer [Ag(C5 H4 NS)]n having graphite-like Ag6 motifs shows semicoductivity [9]. Previous works [10,11] have proved rigid benzene-multicarboxylic acid, such as 1,4-benzenedicarboxylic acid (H2 ta), 1,3,5-benzenetricarboxylic acid (H3 btc) and 1,2,4,5-benzenetetracarboxylic acid (H4 btec), is a good choice for the construction of
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metal–organic coordination polymers owing to their rich coordination modes. However, although many coordination polymers constructed by benzoic multicarboxylic acid have been reported, most of them focused on the lanthanide(III) and transition metal such as Cu(II), Co(II), Zn(II), and Cd(II), those on silver(I) are very rare, probably because they often appear as insoluble salts that make structural analyses difficult [12,13]. To the best of our knowledge, only a few silver–benzoic multicarboxylic acid complexes have been reported in the literature [14]. Through the self-assembly reaction of H3 btc and AgNO3 , we have successfully isolated an interesting silver(I) complex formed by ligand unsupported Ag–Ag interaction, [{Ag(H2 btc)}{Ag2 (Hbtc)}]n (1) [15]. To extend our work, systematic studies have been carried out by employing different carboxylic acids and changing reaction conditions. In this report, we describe the details of the syntheses and characterizations of four silver-carboxylate coordination polymers, [{Ag(H2 btc)}{Ag2 (Hbtc)}]n (1), [Ag(ta)1=2 ]n (2), [Ag2 (btec)1=2 ]n (3) and [{Ag3 (btec)3=4 }{Ag(H2 O)2 (btec)1=4 }]n (4).
2. Experimental 2.1. Materials and analyses All chemicals used are as purchased without purification. IR spectra were recorded on a Magna 750 FTIR
spectrophotometer as KBr pallets. Elemental analyses were carried out in the elemental analysis group of this institute. 2.2. Preparation of complexes 2.2.1. [{Ag(H2 btc)}{Ag2 (Hbtc)}]n (1) H3 btc (0.053 g, 0.25 mmol) was dissolved in 10 ml of hot water, after cooled the solution was placed in the bottom of a glass tube. Then, a solution of AgNO3 (0.083 g, 0.5 mmol) in MeOH (5 ml) was carefully layered on it, through a 5 ml of mixed MeOH/water (3:2) buffer. The tube was sealed and stored in darkness. Colorless well-formed prism-like crystals were obtained after about one week, collected by filtration and washed with water. Yield: 69%. Anal. Calc. for C18 H9 Ag3 O12 : C, 29.18; H, 1.22. Found: C, 29.20; H, 1.18%. IR(KBr, cm1 ): 3469(vs), 3107(s), 2887(s), 2517(s), 1705(s), 1686(vs), 1610(s), 1564(s), 1275(vs), 931(m), 688(s). 2.2.2. [Ag(ta)1=2 ]n (2) H2 ta (0.02 g, 0.125 mmol) and NaOH (0.008 g, 0.2 mmol) were dissolved in 10 ml of hot water, after cooled the solution was placed in the bottom of a glass tube. Then, a solution of AgNO3 (0.041 g, 0.25 mmol) in MeOH (5 ml) was carefully layered on it, through a 5 ml of mixed MeOH/water (3:2) buffer. The tube was sealed and stored in darkness. After one week, colorless platelike crystals were collected by filtration and washed with water. Yield: 41%. Anal. Calc. for C4 H2 AgO2 : C, 25.30;
Table 1 The crystallographic data for complexes 1–4 Complex Empirical formula Formula weight Space group T (°C) a (A) b (A) c (A) a (°) b (°) c (°) 3 ) V (A Z qcalcd (g cm3 ) k (A) l (mm1 ) F ð0 0 0Þ Crystal size (mm) h range for data collection (°) Limiting indices
Reflections collected Unique Goodness-of-fit on F 2 R1 wR2
1 C18 H9 Ag3 O12 740.86 Fddd 293 14.877(5) 25.926(1) 36.377(7) 90 90 90 14031.4(2) 32 2.806 0.71073 3.394 11 328 0.40 0.10 0.05 1.67–25.02 17 6 h 6 13, 30 6 k 6 20, 43 6 l 6 33 9447 3094 1.003 0.0433 0.1016
2 C4 H2 AgO2 189.93 P 21 =c 293 7.257(6) 8.949(8) 6.346(6) 90 111.654(3) 90 383.13(11) 4 3.293 0.71073 5.087 356 0.35 0.20 0.08 3.02–25.02 8 6 h 6 8, 10 6 k 6 4, 7 6 l 6 5 1160 663 1.059 0.0499 0.1294
3 C5 HAg2 O4 340.80 P 21 =c 293 8.333(8) 6.335(5) 10.964(9) 90 90 90 578.91(3) 4 3.910 0.71073 6.708 628 0.36 0.32 0.18 2.44–25.01 9 6 h 6 6, 7 6 k 6 5, 7 6 l 6 5 1900 992 1.206 0.0505 0.1213
4 C10 H6 Ag4 O10 717.63 P 1 293 7.509(1) 9.351(1) 10.307(7) 69.514(2) 84.521(2) 83.638(2) 672.57(10) 2 3.544 0.71073 5.794 668 0.38 0.14 0.04 2.11–25.04 7 6 h 6 8, 7 6 k 6 11, 12 6 l 6 12 3432 2320 1.089 0.0638 0.1661
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Table 2 The selected bonds and angles for 1–4 1 Ag(1)–O(4) Ag(1)–O(3)#1 Ag(1)–O(2)#2 Ag(1)–Ag(1)#3 Ag(1)–Ag(1)#1 Ag(1)–Ag(2) Ag(2)–O(8)#4 Ag(2)–O(7)#5 Ag(2)–O(10)#6 Ag(2)–Ag(2)#1
2.209(4) 2.224(4) 2.487(4) 2.9636(11) 2.9748(12) 3.3774(8) 2.226(4) 2.263(4) 2.560(4) 2.9886(12)
Ag(2)–Ag(3) Ag(3)–O(10) Ag(3)–O(10)#6 Ag(3)–Ag(3)#7 Ag(3)–Ag(2)#6 Ag(3)–Ag(4) Ag(4)–O(11)#8 Ag(4)–O(11)#9 Ag(4)–O(9)#6 Ag(4)–O(9)
3.1846(6) 2.108(4) 2.108(4) 3.0913(15) 3.1846(6) 3.2105(11) 2.508(4) 2.508(4) 2.548(4) 2.548(4)
O(4)–Ag(1)–O(3)#1 O(4)–Ag(1)–O(2)#2 O(3)#1–Ag(1)–O(2)#2 O(4)–Ag(1)–Ag(1)#3 O(3)#1–Ag(1)–Ag(1)#3 O(2)#2–Ag(1)–Ag(1)#3 O(4)–Ag(1)–Ag(1)#1 O(3)#1–Ag(1)–Ag(1)#1 O(2)#2–Ag(1)–Ag(1)#1 Ag(1)#3–Ag(1)–Ag(1)#1 O(4)–Ag(1)–Ag(2) O(3)#1–Ag(1)–Ag(2) O(2)#2–Ag(1)–Ag(2) Ag(1)#3–Ag(1)–Ag(2) Ag(1)#1–Ag(1)–Ag(2) O(8)#4–Ag(2)–O(7)#5 O(8)#4–Ag(2)–O(10)#6 O(7)#5–Ag(2)–O(10)#6 O(8)#4–Ag(2)–Ag(2)#1 O(7)#5–Ag(2)–Ag(2)#1 O(10)#6–Ag(2)–Ag(2)#1 O(8)#4–Ag(2)–Ag(3) O(7)#5–Ag(2)–Ag(3) O(10)#6–Ag(2)–Ag(3) Ag(2)#1–Ag(2)–Ag(3) O(8)#4–Ag(2)–Ag(1) O(7)#5–Ag(2)–Ag(1) O(10)#6–Ag(2)–Ag(1)
153.80(17) 123.35(16) 82.68(16) 81.75(12) 106.02(12) 84.27(12) 81.10(12) 74.03(11) 153.46(11) 90.0 117.10(12) 50.58(11) 95.60(12) 156.15(3) 79.478(15) 155.02(16) 91.90(15) 108.48(15) 83.73(12) 75.11(11) 113.33(10) 111.41(12) 77.87(12) 41.29(9) 79.285(15) 109.99(12) 53.51(11) 156.23(10)
Ag(2)#1–Ag(2)–Ag(1) Ag(3)–Ag(2)–Ag(1) O(10)–Ag(3)–O(10)#6 O(10)–Ag(3)–Ag(3)#7 O(10)#6–Ag(3)–Ag(3)#7 O(10)–Ag(3)–Ag(2)#6 O(10)#6–Ag(3)–Ag(2)#6 Ag(3)#7–Ag(3)–Ag(2)#6 O(10)–Ag(3)–Ag(2) O(10)#6–Ag(3)–Ag(2) Ag(3)#7–Ag(3)–Ag(2) Ag(2)#6–Ag(3)–Ag(2) O(10)–Ag(3)–Ag(4) O(10)#6-Ag(3)–Ag(4) Ag(3)#7–Ag(3)–Ag(4) Ag(2)#6-Ag(3)–Ag(4) Ag(2)–Ag(3)–Ag(4) O(11)#8–Ag(4)–O(11)#9 O(11)#8–Ag(4)–O(9)#6 O(11)#9–Ag(4)–O(9)#6 O(11)#8–Ag(4)–O(9) O(11)#9–Ag(4)–O(9) O(9)#6–Ag(4)–O(9) O(11)#8–Ag(4)–Ag(3) O(11)#9–Ag(4)–Ag(3) O(9)#6–Ag(4)–Ag(3) O(9)–Ag(4)–Ag(3)
79.290(15) 130.39(2) 175.2(2) 87.58(12) 87.58(12) 53.27(12) 125.46(12) 77.791(16) 125.46(12) 53.27(12) 77.791(16) 155.58(3) 92.42(12) 92.42(12) 180.0 102.209(16) 102.209(16) 90.5(2) 145.44(15) 82.09(13) 82.09(13) 145.44(15) 121.69(19) 134.74(11) 134.74(11) 60.85(10) 60.85(10)
Symmetry transformations used to generate equivalent atoms: #1 x, y 1=4, z þ 3=4; #2 x þ 1=2, y þ 1=4, z 1=4; #3 x þ 3=4, y, z þ 3=4; #4 x, y 1=4, z 1=4; #5 x, y, z þ 1; #6 x 1=4, y, z þ 3=4; #7 x 1=4, y 1=4, z; #8 x þ 1=4, y þ 1=4, z þ 1 and #9 x 1=2, y þ 1=4, z 1=4 2 Ag–O(2)#1 2.208(5) Ag–O(2)#2 2.511(4) Ag–O(1) 2.230(5) Ag–Ag#1 2.9013(11) O(2)#1–Ag–O(1) O(2)#1–Ag–O(2)#2 O(1)–Ag–O(2)#2
157.9(2) 108.14(17) 89.35(18)
O(2)#1–Ag–Ag#1 O(1)–Ag–Ag#1 O(2)#2–Ag–Ag#1
82.18(12) 79.49(13) 168.56(13)
Symmetry transformations used to generate equivalent atoms: #1 x, y þ 1, z and #2 x, y þ 1=2, z þ 1=2 3 Ag(1)–O(2) 2.236(6) Ag(2)–O(3) 2.277(6) Ag(1)–O(4)#1 2.361(5) Ag(2)–O(1) 2.334(6) Ag(1)–O(3)#2 2.433(6) Ag(2)–O(4) 2.380(6) Ag(1)–Ag(2) 3.0033(9) Ag(2)–O(1)#3 2.440(6) O(2)–Ag(1)–O(4)#1 O(2)–Ag(1)–O(3)#2 O(4)#1–Ag(1)–O(3)#2 O(2)–Ag(1)–Ag(2) O(4)#1–Ag(1)–Ag(2) O(3)#2–Ag(1)–Ag(2) O(3)–Ag(2)–O(1) O(3)–Ag(2)–O(4)
155.9(2) 123.00(19) 79.1(2) 77.05(16) 83.00(15) 121.05(16) 95.9(2) 152.60(19)
O(1)–Ag(2)–O(4) O(3)–Ag(2)–O(1)#3 O(1)–Ag(2)–O(1)#3 O(4)–Ag(2)–O(1)#3 O(3)–Ag(2)–Ag(1) O(1)–Ag(2)–Ag(1) O(4)–Ag(2)–Ag(1) O(1)#3–Ag(2)–Ag(1)
93.2(2) 92.6(2) 129.96(11) 101.10(19) 74.56(16) 161.97(14) 89.13(14) 66.73(14)
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Table 2 (continued) Symmetry transformations used to generate equivalent atoms: #1 x, y þ 1, z; #2 x, y þ 1=2, z 1=2 and #3 x, y 1=2, z þ 1=2 4 Ag(1)–O(4)#1 2.258(8) Ag(3)–O(1) 2.226(9) Ag(1)–O(7)#2 2.348(8) Ag(3)–O(5)#3 2.243(9) Ag(1)–O(7)#3 2.410(9) Ag(3)–Ag(4) 3.0107(15) Ag(1)–Ag(2) 2.8632(15) Ag(4)–O(6)#3 2.293(9) Ag(2)–O(3)#1 2.208(8) Ag(4)–O(9) 2.299(9) Ag(2)–O(8)#2 2.237(8) Ag(4)–O(10) 2.435(11) Ag(2)–O(2) 2.523(9) Ag(4)–O(2)#4 2.456(10) Ag(2)–Ag(3) 3.2057(16) O(4)#1–Ag(1)–O(7)#2 O(4)#1–Ag(1)–O(7)#3 O(7)#2–Ag(1)–O(7)#3 O(4)#1–Ag(1)–Ag(2) O(7)#2–Ag(1)–Ag(2) O(7)#3–Ag(1)–Ag(2) O(3)#1–Ag(2)–O(8)#2 O(3)#1–Ag(2)–O(2) O(1)–Ag(3)–O(5)#3 O(1)–Ag(3)–Ag(4) O(5)#3–Ag(3)–Ag(4) O(1)–Ag(3)–Ag(2) O(5)#3–Ag(3)–Ag(2) Ag(4)–Ag(3)–Ag(2) O(6)#3–Ag(4)–O(9) O(6)#3–Ag(4)–O(10)
151.5(3) 112.5(3) 87.9(3) 82.6(3) 75.2(2) 162.9(2) 156.0(3) 91.7(3) 153.4(3) 80.2(2) 73.7(2) 70.4(3) 111.0(2) 103.56(5) 155.5(4) 88.3(4)
O(8)#2–Ag(2)–O(2) O(3)#1–Ag(2)–Ag(1) O(8)#2–Ag(2)–Ag(1) O(2)–Ag(2)–Ag(1) O(3)#1–Ag(2)–Ag(3) O(8)#2–Ag(2)–Ag(3) O(2)–Ag(2)–Ag(3) Ag(1)–Ag(2)–Ag(3) O(9)–Ag(4)–O(10) O(6)#3–Ag(4)–O(2)#4 O(9)–Ag(4)–O(2)#4 O(10)–Ag(4)–O(2)#4 O(6)#3–Ag(4)–Ag(3) O(9)–Ag(4)–Ag(3) O(10)–Ag(4)–Ag(3) O(2)#4–Ag(4)–Ag(3)
106.2(3) 77.7(2) 78.6(2) 146.9(2) 55.5(3) 115.4(2) 69.9(2) 78.41(4) 92.6(4) 77.6(3) 126.9(3) 87.8(4) 80.0(2) 88.6(3) 153.4(3) 112.5(2)
Symmetry transformations used to generate equivalent atoms: #1 x þ 1, y, z þ 1; #2 x þ 1, y 1, z þ 2; #3 x 1, y þ 1, z and #4 x 1, y, z
H, 1.06. Found: C, 25.41; H, 1.02%. IR(KBr, cm1 ): 3072(m), 1568(vs), 1497(m), 1439(m), 1389(vs), 1352(w), 1012(m), 823(s), 744(vs), 499(s). 2.2.3. [Ag2 (btec)1=2 ]n (3) 1,2,4,5-Benzenetetracarboxylic dianhydride (0.027 g, 0.125 mmol) was dissolved in 10 ml of hot water, to which 0.25 mmol (0.01 g) NaOH was added. The solution was placed in the bottom of a glass tube after cooled. Then, a solution of AgNO3 (0.083 g, 0.5 mmol) in MeOH (5 ml) was carefully layered on it, through a 5 ml of mixed MeOH/water (3:2) buffer. The tube was sealed and stored in darkness. After two weeks, lightyellow well-formed prism-like crystals were collected by filtration and washed with water. Yield: 55%. Anal. Calc. for C5 HAg2 O4 : C, 17.62; H, 0.30. Found: C, 17.67; H, 0.29%. IR(KBr, cm1 ): 3508(s), 3298(s), 1668(w), 1583(vs), 1566(vs), 1414(s), 1371(vs), 939(w), 814(m), 577(m). 2.2.4. [{Ag3 (btec)3=4 }{Ag(H2 O)2 (btec)1=4 }]n (4) 1,2,4,5-Benzenetetracarboxylic dianhydride (0.027 g, 0.125 mmol) was dissolved in 10 ml of hot water, to which 0.125 mmol Na2 SiO3 was added. After cooled, the solution was placed in the bottom of a glass tube. Then, a solution of AgNO3 (0.02 g, 0.125 mmol) in MeOH (5 ml) was carefully layered on it, through a 5 ml of mixed MeOH/water (3:2) buffer. The tube was sealed and stored in darkness. After two weeks, colorless prism-like crys-
tals were obtained, collected by filtration and washed with water. Yield: 35%. Anal. Calc. for C10 H6 Ag4 O10 : C, 16.74; H, 0.84. Found: C, 16.80; H, 0.82%. IR(KBr, cm1 ): 3370(vs), 3040(m), 1689(w), 1570(vs), 1489(m), 1423(m), 1383(vs), 1327(m), 814(m), 744(m). 2.3. Crystallographic analyses The intensity data of 1–4 were collected on a Siements Smart CCD diffractometer with graphite-monochro radiation at room temmated Mo Ka (k ¼ 0:71073 A) perature. All absorption corrections were performed using the S A D A B S program [16]. The structures were solved by direct methods [17] and refined on F2 by fullmatrix least-squares using the S H E L X T L -97 program package [18] on a legend computer. All non-hydrogen atoms were refined anisotropically. The organic hydro gen atoms were generated geometrically (C–H 0.96 A). The crystallographic data of complexes 1–4 are listed in Table 1, selected bonds and angles in Table 2.
3. Results and discussions 3.1. Synthetic chemistry Our aim is to assemble benzoic multicarboxylic acid with silver(I) salt and study their structure and property. As is well known, the reactions of silver(I) ion with
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multicarboxylates in aqueous solution often result in the formation of insoluble Ôsilver saltsÕ, presumably due to the fast coordination of the carboxylates to silver ion to form polymer. Smith and co-workers [12a] have obtained a series of Ag–benzoic multicarboxylic acid complexes by using ammoniacal conditions to enhance the solubility of the silver carboxylates, Michaelides and co-workers [12b] have reported a novel succinatodisilver(I) complex which was synthesized by gel permeation. Hence, properly lowering the reaction speed may result in the formation of crystalline products. Considering this, we adopt self-assembly reaction of silver(I) ion with multi-carboxylic acids by slow diffusion in the mixture water and organic solution. We first select 1,3,5-benzenetricarboxylic acid (H3 btc) to assemble with silver(I) salt in water/MeOH solution at pH 2.5 and results in the formation of complex 1, which possesses a 3D framework constructed by silver chains formed by ligand unsupported Ag–Ag interactions and organic spacers [15]. The successful isolation of 1 prompted us to extend our study to other benzoic multicarboxylic acid, such as 1,4-benzenedicarboxylic acid (H2 ta) and 1,2,4,5-benzenetetracarboxylic acid(H4 btec). In treatment of H2 ta or 1,2,4,5-benzenetetracarboxylic dianhydride with silver salt, NaOH was added to accelerate the hydrolyzation of 1,2,4,5-benzenetetracarboxylic dianhydride and dissolve 1,4-benzenedicarboxylic acid. As expected, 2 and 3, which possess 3D frameworks, were isolated at pH 6.5 and 9, respectively, as colorless crystals. Since self-assembly reaction is highly influenced by many factors such as the pH value, solvent and the metal– ligand ratio [19], the reactions with different pH value (2–9), solution (DMF and MeCN) were carried out in order to prepare silver polymers with different struc-
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tures. However, same result was obtained for complex 1 in different solution although the yields were different. When pH value is higher than 5, only deposits were obtained. For 1,2,4,5-benzenetetracarboxylic dianhydride, when treated in pH 4 by using Na2 SiO3 as the base, complex 4 that is quite different from complex 3 was successfully isolated, but precipitates were obtained when treated in other solutions. For H2 ta, when treated in other pH value and solvent, only unknown precipitates were obtained, illustrating the solvent and pH value remarkably influence the formations of complex 2, 3 and 4. The carboxylic groups of H3 btc in 1 were partly deprotonated, whereas all of the carboxylic groups were deprotonated in 2, 3 and 4 by NaOH or Na2 SiO3 . X-ray diffraction analyses illustrate the three ligands connected more than one metal ion, especially for btec4 in 3 that acts as a l14 –bridge to link fourteen silver atoms. Scheme 1 shows the coordination modes of the three ligands in complexes 1–4. 3.2. Crystal structure analysis 3.2.1. Crystal structure of complex 1 Complex 1 possesses a 3D network formed by ligandunsupported Ag–Ag interactions. Single-crystal structure analysis shows 1 comprises two independent building units, Ag2 (H2 btc)2 (A) and Ag8 (Hbtc)12=3 (B). The coordination mode of H2 btc in A is illustrated in Scheme 1(b), if neglecting the Ag–Ag contact, the Ag ion (Ag1) is three-coordinate by oxygen atoms from three different ligands with the average Ag–O distances and every two such Ag atoms are being 2.227(4) A bridged by two carboxylate groups with Ag–Ag distance
Scheme 1.
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(a)
(b) Fig. 1. (a) Structure of the linear chain formed by unit A. (b) The 3D open framework generated by ligand-unsupported Ag–Ag interactions in unit A.
Each two A units are linked together of 2.976(3) A. through weak Ag–Ocarbonyl bonding with Ag–O distance completing the distorted trigonal cobeing 2.487(4) A, ordination geometry of Ag and yielding a 1D chain structure (Fig. 1(a)). Each two adjacent chains that are aligned in different directions are combined via ligand unsupported Ag–Ag interactions (Ag–Ag, 2.962(7) A), forming a 3D open framework structure (Fig. 1(b)). Unit B is composed of four Ag2 subunits, each of them is connected by two carboxylate groups. Two Ag3–Ag4 are joined by ligandsubunits (Ag3–Ag4, 3.210(5) A) unsupported Ag–Ag interaction (Ag3–Ag3, 3.092(4) A), generating a linear Ag4 chain, which connects two Ag2– subunits through weak Ag–O bonding Ag2 (2.989(5) A) and ligand-unsupported Ag–Ag interactions (Ag2–Ag3, (Fig. 2(a)). There are three kinds of Ag in B: 3.184(9) A) Ag2, Ag3 and Ag4 are in O3 distorted trigonal, O2 linear and O4 distorted tetragonal geometry, respectively. Interestingly, all Ag4–O bonding is very weak (Ag4–O, e.g. Ag4 may be viewed as ‘‘loose’’ 2.505(5)–2.547(5) A),
atom dotted in B through Ag–Ag and Ag–O interactions. Hbtc2 ligand acts as a l6 -bridge (Scheme 1(c)) to link three B units, generating another 3D open framework structure (Fig. 2(b)). Owing to the ligand unsup interactions ported Ag–Ag (Ag1–Ag2, 3.278(3) A) between the two kinds of 3D open framework structures, they are penetrating into each other, producing linear distorted ladder-like Ag chains (Fig. 3(a)) and the final condensed 3D structure. Thus the whole structure can also be regarded as parallel Ag chains linking by H2 btc and Hbtc2 spacers (Fig. 3(b)). The importance of ligand unsupported Ag–Ag interactions in the formation of polymeric structure has been documented [19]. In 1, such interaction also play an important role in the formation of the complex: they induce the formations of the 3D structure formed by unit A, unit B itself and the Ag chains in the whole structure. All of Ag–Ag distances (2.962(7)–3.378(3) A) are shorter than the van der Waals contact distance for [20], and the shortest one (2.962(7) A) is Ag–Ag (3.40 A)
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(a)
(b) Fig. 2. (a) Structure of unit B. (b) The 3D open framework in unit B.
only slightly longer than that found in metallic silver To our best knowledge, complex 1, which (2.89 A). contains silver chains formed by ligand unsupported Ag–Ag interactions, is the first example found in Ag– multicarboxylate systems. 3.2.2. Crystal structure of complex 2 The structure determination of complex 2 reveals a 3D framework with short Ag–Ag contacts. As shown in Fig. 4, the silver ion is coordinated by three oxygen atoms from three different ta2 ligands with the Ag–O
and forms bonds ranging from 2.208(5) to 2.511(4) A, with adjacent silver short Ag–Ag contact (2.901(4) A) (AgA) through the bridging carboxylate group. The Ag– Ag distance is slightly shorter than those found in other Ag–Ag contact complexes, such as catena-bis(4-aminobenzoato)disilver(I) [7a], [Ag{CH(COOC2 H5 )2 }PPh2 ]2 [21a], [AgCH2 P(S)Ph2 ]2 (2.990(2) A) [21b], (2.953(1) A) and Ag2 (H2 L)3 ]n (ClO4 )2n (H2 L ¼ N,N 0 -bis(salicylidene) [19]. If neglecting the 1,4-diaminobutane) (2.946 A) Ag–Ag bond, each silver ion is three-coordinate in a ‘‘T-shape’’ geometry. Every ta2 ligand acts as a
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(a)
(b) Fig. 3. (a) The structure of silver chain formed by ligand unsupported Ag–Ag interactions in 1. (b) The packing structure along the a axis of 1, the organic spacers are omitted for clarity.
bonds of one carboxylate l2 –O of ta2 with distance to generate a 2D wave-like layer being 2.511(4) A, (Fig. 5(a)). The layers are spliced each other by the Ag– O bonds of the other carboxylate l2 –O of ta2 to result in a 3D framework. As shown in Fig. 5(b), the structure can also be regarded as inorganic silver layers linked by organic ta2 spacers, the distance between two silver layers is 11.267 A.
Fig. 4. Local coordination environment of Ag(I) in 2.
l6 -bridge to link six silver atoms (Scheme 1(a)). The binuclear [Ag2 (ta)2 ] species, which is formed by two silver ions linked by two bridging carboxylate groups from two ta2 , may be viewed as the building unit of the whole structure. Such binuclear units are linked head-totail through sharing ta2 ligands to form a 1D chain. The 1D chains are connected each other by weak Ag–O
3.2.3. Crystal structure of complex 3 Complex 3 has a 3D structure. As shown in Fig. 6, two coordination environments of silver(I) ions are found in complex 3: Ag(1) is three-coordinate by three oxygen atoms from different btec4 ligands with Ag(1)– Ag(2) O distances ranging from 2.236(6) to 2.433(6) A; is coordinated by four oxygen atoms from four ligands with Ag(2)–O distances ranging from 2.277(6) to The distance of Ag(1)–Ag(2) (3.003(4) A) is 2.440(6) A. significantly shorter than the van der Waals contact [20], illustrating the existing of weak distance 3.40 A metal–metal interaction between Ag(1) and Ag(2). The distance is slightly longer than that found in silver [3], but between benzenesulfonate complex (2.915 A) those in the succinatodisilver complex (2.938 and 3.104 [12b]. Each btec4 ligand acts as a l14 -bridge, linking A) 14 silver atoms (Scheme 1(d)). Thus, Ag(1) and Ag(2)
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(a)
(b)
Fig. 7. (a) The layer structure in 3. (b) The 3D framework of 3.
Fig. 5. (a) The 2D layer in 2. (b) Packing structure along the c axis of 2.
(Fig. 7(b)). Complex 3 is quite different from previous reported complex [Ag2 (H2 btec)]n [14a], in which two carboxyl groups are protonated and every H2 btec2 acts as a l10 -bridge to link ten silver atoms to form the 3D framework.
Fig. 6. Local coordination environment of Ag(I) in 3.
are bridged by two carboxylate groups to form an Ag2 unit. Each Ag2 unit is connected by four btec4 ligands and every btec4 ligand attaches four Ag2 units to form a 2D layer structure (Fig. 7(a)). The layers are further linked by Ag–O bonds through the l2 -O atoms of carboxylate groups to generate the final 3D framework
3.2.4. Crystal structure of complex 4 Although the original materials for 4 are similar to those for 3 except the base used in the reaction, the structures of the two complexes are quite different. Complex 4 is a 3D coordination polymer with [{Ag3 (btec)3=4 }{Ag(H2 O)2 (btec)1=4 }] formula. As shown in Fig. 8, different from complex 3, there are four crystallographically distinct silver centers. Ag(1), Ag(2) and Ag(3) are coordinated by three oxygen atoms from different btec4 ligands with the Ag–O distances ranging which is slightly longer than from 2.208(8) to 2.523(9) A, those found in complex 3, whereas Ag(4) is coordinated by four oxygen atoms, two from two different btec4 ligands and the other two from coordinated water molecules with average Ag–O distance being 2.353(11) As found in other silver complexes, short Ag–Ag A. contacts are present among Ag(1)–Ag(2), Ag(2)–Ag(3) and Ag(3)–Ag(4) with average Ag–Ag distance being The shortest one (Ag(1)–Ag(2): 2.863(3) A) 3.026(6) A. is shorter than that found in metallic silver (2.89 A), illustrating the existence of strong Ag–Ag interaction between Ag(1) and Ag(2), similar to those observed in some previous reported complexes such as [Ag(p [22a], CH3 C6 H4 NCHNC6 H4 -p-CH3 )]2 (2.705(1) A) [22b]. All carboxyl groups [Ag(PhN3 Ph)]2 (2.669(1) A)
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are bridged by another carboxylate group with Ag(1)– Ag(2)–Ag(3) angle being 78.41(4)°, to form the subunit Ag3 (btec)3=4 . Every two Ag3 units are linked by btec4 ligands to form a 2D layer (Fig. 9(a)), in which each btec4 links four Ag3 units and each Ag3 unit attaches to four btec4 ligands. The layers were further connected by Ag(H2 O)2 (btec)1=4 unit through Ag4–Obtec as well as Ag3–Ag4 contact to form the finally 3D framework (Fig. 9(b)).
4. Conclusion
Fig. 8. Local coordination environment of Ag(I) in 4.
We have successfully synthesized four novel silvercarboxylate polymeric complexes by self-assembly reaction of rigid benzoic multicarboxylic acid with AgNO3 at room temperature. In 1–4, the short Ag–Ag contacts or ligand unsupported Ag–Ag interactions play important roles in the formation of these complexes as well as their properties, especially in complex 1. Meanwhile, complex 1 is the first silver-benzoic multicarboxylate polymer containing ligand unsupported Ag–Ag interactions. During the preparations of 3 and 4, 1,2,4,5benzenetetracarboxylic dianhydride was hydrolyzed to 1,2,4,5-benzenetetracarboxylic acid and deprotonated by NaOH or Na2 SiO3; similar to our previous reported under the hydrothermal condition [10b,10c]. It is interesting to note that complexes 3 and 4 are obtained under different pH value, which proves that some factors, such as pH value, solvent, are crucial in self-assembly system and also indicate that different metal coordination polymers can be constructed by subtly altering any of these factors.
5. Supplementary data Atomic coordinates, thermal parameters and bond lengths and angles for complexes 1–4 have been deposited at the Cambridge Crystallographic Center (CCDC). Any request to the CCDC for this material should quote the full literature citation and the reference numbers CCDC 166791 for 1, 198096–198098 for 2–4. Copies of this information may be obtained free of charge from The Director, CCDC, 12 Union Road. Cambridge. CB2 1EZ. UK. (Fax: +441223-336033; email: deposit@ccdc. cam.ac.uk or http://www.ccdc.cam.ac.uk/). Fig. 9. (a) The layer structure in 4. (b) Packing structure of 4 along the c-axis.
Acknowledgements
of btec4 are deprotonated by Na2 SiO3 during the selfassembly reaction and each btec4 acts as a l10 -bridge to link ten silver atoms (Scheme 1(e)). Ag(1) and Ag(2) are bridged by two carboxylate groups and Ag(2) and Ag(3)
The authors are grateful to the financial support from NNSF of China (90206040, 29901005), NSF of Fujian Province and the key and the ‘‘One Hundred Talent’’ projects from CAS.
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