Flexible Disulfoxides as Bridging Ligands for Copper(II) Coordination

Flexible Disulfoxides as Bridging Ligands for Copper(II) Coordination Architectures: Fine Tuning the Complex Structures by Ligand Modifications Jian-Rong Li,† Xian-He Bu,*,† Ruo-Hua Zhang,† and Joan Ribas‡

CRYSTAL GROWTH & DESIGN 2005 VOL. 5, NO. 5 1919-1932

Department of Chemistry, Nankai University, Tianjin 300071, People’s Republic of China, and Departament de Quı´mica Inorga` nica, Universitat de Barcelona, Diagonal, 647, 08028-Barcelona, Spain Received April 26, 2005

ABSTRACT: Ten disulfoxide-CuII coordination architectures, {[Cu(meso-Lb1)2(ClO4)](ClO4)}n (1B), [Cu(meso-Lb2)2(ClO4)2]n (2B), [Cu(rac-Lb3)2(ClO4)2]n (3B), {[Cu(meso-Lb3)3](ClO4)2}n (3B′), [Cu(meso-Lc1)2(ClO4)2]n (1C), [Cu(mesoLc2)2(ClO4)]2(ClO4)2(CHCl3)2 (2C), {[Cu(meso-Lc3)2(ClO4)](ClO4)}n (3C), [Cu(meso-Ld1)2(ClO4)2]n (1D), {[Cu2(racLd2)4(ClO4)2](ClO4)2(CHCl3)}n (2D), and [Cu(rac-Ld3)2(ClO4)2]n (3D), were obtained by the reaction of Cu(ClO4)2 with nine structurally related flexible disulfoxide ligands, RS(O)(CH2)nS(O)R (n ) 2-4; R ) -CH2CH3, -CH2CH2CH3, -CH2CH2CH2CH3 for Lbn-1, Lcn-1, and Ldn-1, respectively) in the presence of dehydrating reagent (diethoxyethane) in acetone/chloroform. The X-ray crystal structural analyses of the complexes revealed that all of them display a 2-D network structure, except for 2B and 2C, which display a one-dimensional and a dinuclear cage structure, respectively. All 2-D systems have a (4,4) topological arrangement with different conformations, except for 3B′, which has a (3,6) structure. It is noteworthy that complexes 3B and 3B′, with different structures, are obtained in the same reaction system, being a relatively rare case. In all of the complexes the ligands react in the bis-monodentate coordination mode, acting as linkage bridges: this feature is important for the assembly of the polymeric complexes. In addition, the configuration inversion of some disulfoxide ligands has been observed when reacting with CuII ions. In combination with other reported disulfoxide-CuII complexes, a systematic structural comparison was performed so as to summarize some general relationships among the spacer lengths, terminal groups of related ligands, and structures of the complexes. The magnetic behavior of three complexes, 1B-3B, as examples, was investigated. Introduction In recent years, much effort has been focused on the crystal engineering of metal-organic coordination architectures, due to their intriguing structural topologies and potential applications.1 The combination of organic “spacer” ligands and metal ion “nodes” has been one of the most common synthetic approaches to produce such coordination polymers.2 The advantage of the metalorganic framework approach is to allow a wide choice of different parameters, including electronic properties and coordination geometry of the metal ions, as well as versatile functions and topologies of organic ligands. This is also the aspiration for achieving one of the ultimate aims of crystal engineering, i.e., gaining control of the topology and geometry of the networks formed through judicious choice of ligand and metal precursor geometry.3 In a sense, supramolecular chemistry has advanced to a stage by this time, at which it is possible to select molecular building blocks to assemble into structures with specific and desired network topologies: namely, a rational design of molecular solids with potentially interesting properties becomes possible.1m,4 So far, however, there is still very limited understanding concerning the factors that determine their synthesis and the resulting structure, and the attainment of rational control over desired topologies and specific properties still remains a great challenge. In other * To whom correspondence should be addressed. Fax: +86-2223502458. E-mail: [email protected]. † Nankai University. ‡ Universitat de Barcelona.

words, no general method can give consistently reliable predictions for the engineering, as recently stated by Dunitz,5 because the supramolecular assembly is highly affected by several factors such as the ligand’s nature, solvents, templates (or guests), counteranions, and so on.6 Therefore, an investigation for the understanding of the relationships between the structures of complexes and the nature of ligands, as well as other factors, is still important. In this field, bridging ligands have been extensively utilized to construct supramolecular coordination species and frameworks, such as rigid cyanide and 4,4bipyridine, which connect to each metal center by a single donor atom. Rigid bridging ligands are anticipated to retain their geometry, and numerous target supramolecular entities based on fixed geometry have been designed and synthesized.7 In comparison to those, flexible bridging ligands with conformational freedom have a higher possibility for obtaining unexpected and interesting products.8 With this idea in mind, in recent years our group has focused on the synthesis and structural exploration of novel coordination polymers with flexible multifunctional ligands, disulfoxides,9 which are types of ditopic bridging ligands having many intriguing features, such as the inherent chiral property of the S atom and the diastereomeric meso and rac forms. They can coordinate to metal ions via either O or S donors, according to electronic and steric factors. In addition, the configuration inversion of S atoms in the disulfoxide molecules can take place when reacting with metal ions,9j which probably leads to the formation of complexes with unpredictable structures.

10.1021/cg050181m CCC: $30.25 © 2005 American Chemical Society Published on Web 07/21/2005

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Crystal Growth & Design, Vol. 5, No. 5, 2005 Chart 1

On the other hand, CuII is a favorable connecting node for the construction of coordination polymers, due to its intriguing stereochemistry and the potential for studying their magnetic properties.10 Therefore, the investigation of CuII complexes with flexible ligands is of significance not only for the structural aspects but also for their properties. In our previous communication,9c three disulfoxide-CuII complexes, [Cu(meso-Le1)2(ClO4)2]n (1E), {[Cu(rac-Le2)3](ClO4)2}n (2E), and {[Cu(meso-Le3)3](ClO4)2}n (3E) (Le1 ) 1,2-bis(phenylsulfinyl)ethane, Le2 ) 1,3-bis(phenylsulfinyl)propane, and Le3 ) 1,4-bis(phenylsulfinyl)butane (Chart 1)), have been reported,9c from which we discovered that such ligands could link CuII ions to form diverse extended structures, which can be influenced and controlled by varying the length of the spacer units. In addition to these three complexes, Calligaris et al. reported four related complexes, [Cu(meso-La1)2](ClO4)2}n (1A),11b [Cu(rac-La1)2(ClO4)2]n (1A′),11b [Cu(rac-Lc2)2(ClO4)2]n (2C′),11a and {[Cu(mesoLc2)2(H2O)2](ClO4)2}n (2C′)11b (La1 ) 1,2-bis(methylsulfinyl)ethane and Lc2 ) 1,3-bis(propylsulfinyl)propane (Chart 1)). Such complexes have different structural features, due to the differences in the disulfoxide ligands used. As an in-depth and systematic investigation, herein we report ten new disulfoxide-CuII coordination architectures, {[Cu(meso-Lb1)2(ClO4)](ClO4)}n (1B), [Cu(meso-Lb2)2(ClO4)2]n (2B), [Cu(rac-Lb3)2(ClO4)2]n (3B), {[Cu(meso-Lb3)3](ClO4)2}n (3B′), [Cu(meso-Lc1)2(ClO4)2]n (1C), [Cu(meso-Lc2)2(ClO4)]2(ClO4)2(CHCl3)2 (2C), {[Cu(meso-Lc3)2(ClO4)](ClO4)}n (3C), [Cu(meso-Ld1)2(ClO4)2]n (1D), {[Cu2(rac-Ld2)4(ClO4)2](ClO4)2(CHCl3)}n (2D), and [Cu(rac-Ld3)2-(ClO4)2]n (3D), obtained by the assembly of Cu(ClO4)2 and nine structurally related disulfoxide ligands, RS(O)(CH2)nS(O)R (n ) 2-4; R ) -CH2CH3, -CH2CH2CH3, -CH2CH2CH2CH3 for Lbn-1, Lcn-1, and Ldn-1, respectively; see Chart 1). The relationship between the nature of the ligands and the structure of their complexes is also discussed. In addition, as three typical examples, the magnetic properties of 1B-3B have also been investigated. Experimental Section General Methods and Physical Measurements. All chemicals were commercially available and used as received. Elemental analyses were performed on a Perkin-Elmer 240C analyzer. 1H NMR spectra were measured on a Bruker AC-P500 spectrometer (300 MHz) at 25 °C with tetramethylsilane as the internal reference. IR spectra (KBr pellets) were taken on a FT-IR 170SX (Nicolet) spectrometer. Melting point measurements were taken on an X-4 melting point meter. Thermal analyses were performed in the temperature range of 25-500 °C on a Rigaku standard TG-DTA analyzer. Electrospray mass spectrum (ES-MS) measurement for 2C was carried out on an LCQ system by using methanol as the mobile phase. Magnetic data were collected on a powdered sample, for the compounds 1B-3B, with a superconducting quantum interference device (SQUID) magnetometer. Susceptibility measurements were made in a field of 1000 G, and magnetiza-

Li et al. tions were made at 2-300 K. All data were corrected for diamagnetism estimated from Pascal’s constants. Polycrystalline power EPR spectra for 1B-3B were recorded at X-band frequency (9.23 GHz) on a Varian ESR9 spectrometer equipped with a continuous-flow 4He cryostat. Safety Note. Although we experienced no problems in this work, perchlorate salts of metal complexes with organic ligands are often explosive and should be handled with great caution. Synthesis. The disulfoxide ligands 1,2-bis(ethylsulfinyl)ethane (Lb1), 1,3-bis(ethylsulfinyl)propane (Lb2), 1,4-bis(ethylsulfinyl)butane (Lb3), 1,2-bis(propylsulfinyl)ethane (Lc1), 1,3bis(propylsulfinyl)propane (Lc2), 1,4-bis(propylsulfinyl)butane (Lc3), 1,2-bis(butylsulfinyl)ethane (Ld1), 1,3-bis(butylsulfinyl)propane (Ld2), and 1,4-bis(butylsulfinyl)butane (Ld3) were synthesized similarly according to a method reported previously,12 and the corresponding high-melting-point isomer was separated from the mixture of products by fractional crystallization from acetone. Lb1. Yield: ∼40%. Mp: 141-143 °C. Anal. Calcd for C6H14O2S2 (182.30): C, 39.53; H, 7.74. Found: C, 39.31; H, 7.91. 1H NMR (CDCl3): δ 1.39 (t, 6H, CH3-), 2.83 (q, 4H, CH3CH2S-), 2.983.22 (m, 4H, -SCH2CH2S-). IR (cm-1): 2962 m, 2937 m, 2919 w, 2875 w, 1460 m, 1447 w, 1432 m, 1421 m, 1374 w, 1317 m, 1269 m, 1245 w, 1137 m, 1125 m, 1043 m, 1017 s, 972 m, 797 m, 742 w, 682 m, 650 m, 407 m. Lb2. Yield: ∼45%. Mp: 101-103 °C. Anal. Calcd for C7H16O2S2 (196.32): C, 42.83; H, 8.21. Found: C, 42.45; H, 8.46. 1H NMR (CDCl3): δ 1.37 (t, 6H, CH3-), 2.39 (t, 2H, CCH2C), 2.82 (q, 4H, CH3CH2S-), 2.93 (t, 4H, CH2CH2S-). IR (cm-1): 2963 m, 2940 m, 2922 m, 2908 m, 2877 w, 1473 w, 1455 m, 1429 m, 1374 m, 1256 w, 1187 w, 1133 w, 1047 s, 1019 s, 976 m, 785 m, 741 w, 681 m, 657 m, 426w. Lb3. Yield: ∼40%. Mp: 88-89 °C. Anal. Calcd for C8H18O2S2 (210.35): C, 45.68; H, 8.63. Found: C, 45.35; H, 8.91. 1H NMR (CDCl3): δ 1.35 (t, 6H, CH3-), 2.00 (t, 4H, CCH2CH2C), 2.64∼2.78 (m, 8H, -CH2SCH2-). IR (cm-1): 2972 m, 2955 m, 2932 m, 2907 m, 2877 m, 1464 m, 1417 w, 1373 m, 1263 w, 1192 w, 1098s, 1040 s, 1014 s, 971 s, 882 m, 783 m, 740 m, 717 m, 657 m, 446 m. Lc1. Yield: ∼45%. Mp: 161-163 °C. Anal. Calcd for C8H18O2S2 (210.35): C, 45.68; H, 8.63. Found: C, 45.77; H, 8.89. 1H NMR (CDCl3): δ 1.11 (t, 6H, CH3-), 1.85 (h, 4H, CH3CH2-), 2.66∼2.89 ( m, 4H, CCH2CH2S-), 3.01-3.20 (m, 4H, -SCH2CH2S-). IR (cm-1): 2959 m, 2873 m, 2028 w, 1635 w, 1443 m, 1425 w, 1384 m, 1243 w, 1112 w, 1062 m, 1011 s, 949 w, 860 w, 774 w, 744 w, 687 w, 480 w. Lc2. Yield: ∼45%. Mp: 137-139 °C. Anal. Calcd for C9H20O2S2 (224.38): C, 48.18; H, 8.98. Found: C, 47.99; H, 9.11. 1H NMR (CDCl3): δ 1.10 (t, 6H, CH3-), 1.83 (h, 4H, CH3CH2-), 2.43 (t, 2H, -CH2CH2CH2-), 2.62-2.69 (m, 4H, CH3CH2CH2S), 2.73-2.92 (m, 4H, -SCH2CH2CH2-). IR (cm-1): 2958 s, 2930 m, 2872 m, 2014 w, 1459 m, 1412 m, 1374 w, 1299 w, 1241 w, 1108 w, 1072 m, 1022 s, 995 s, 892 w, 864 w, 822 w, 751 m, 678 w, 647 w, 449 w. Lc3. Yield: ∼40%. Mp: 124-126 °C. Anal. Calcd for C10H22O2S2 (238.40): C, 50.38; H, 9.30. Found: C, 50.01; H, 9.14. 1H NMR (CDCl3): δ 1.08 (t, 6H, CH3-), 1.83 (h, 4H, CH3CH2-), 2.21 (t, 4H, -CH2CH2CH2CH2-), 2.52∼2.58 (m, 4H, CH3CH2CH2-), 2.60∼2.81 (m, 4H, SCH2CH2CH2-). IR (cm-1): 2959 m, 2925 m, 2872 m, 2015 w, 1635 w, 1467 m, 1455 m, 1414 w, 1379 w, 1298 w, 1238 w, 1100 m, 1059 m, 1013 s, 883 w, 856 w, 817 w, 749 w, 700 w, 642 w, 465 w. Ld1. Yield: ∼50%. Mp: 167-169 °C. Anal. Calcd for C10H22O2S2 (238.40): C, 50.38; H, 9.30. Found: C, 50.09; H, 9.52. 1H NMR (CDCl3): δ 0.98 (t, 6H, CH3-), 1.51 (h, 4H, -CH2CH3), 1.78 (t, 4H, -SCH2CH2CH2CH3), 2.81-3.01 (m, 4H, SCH2CH2CH2-), 3.18-3.22 (m, 4H, -SCH2CH2S-). IR (cm-1): 2959 m, 2928 m, 2872 m, 2861 w, 2036 w, 1465 w, 1427 m, 1379 w, 1295 w, 1123 w, 1052 w, 1015 s, 974 w, 915 w, 778 w, 687 w, 645 w, 450 w. Ld2. Yield: ∼45%. Mp: 144-146 °C. Anal. Calcd for C11H24O2S2 (252.43): C, 52.34; H, 9.58. Found: C, 52.11; H, 9.82. 1H NMR (CDCl3): δ 0.97 (t, 6H, CH3-), 1.45-1.54 (h, 4H, -CH2CH3), 1.79 (t, 4H, -SCH2CH2CH2CH3), 2.40 (t, 2H,

Flexible Disulfoxides as Bridging Ligands -SCH2CH2CH2S-), 2.63-2.91 (m, 8H, -CH2SCH2-). IR (cm-1): 2953 m, 2927 m, 2870 m, 2021 w, 1465 w, 1466 m, 1426 m, 1375 w, 1306 w, 1245 w, 1199 w, 1101 w, 1078 m, 1030 s, 988 s, 913 w, 779 w, 743 w, 679 w, 646 w, 461 w. Ld3. Yield: ∼50%. Mp: 131-133 °C. Anal. Calcd for C12H26O2S2 (266.46): C, 54.09; H, 9.84. Found: C, 54.33; H, 9.02. 1H NMR (CDCl3): δ 0.97 (t, 6H, CH3-), 1.49 (h, 4H, -CH2CH3), 1.78 (t, 4H, -SCH2CH2CH2CH3), 1.97 (t, 4H, -SCH2CH2CH2CH2S-), 2.62-2.78 (m, 8H, CH2SCH2), IR (cm-1): 2953 s, 2925 m, 2871 m, 2017 w, 1640 w, 1469 m, 1417 m, 1379 w, 1318 w, 1291 w, 1222 w, 1201 w, 1100 m, 1076 w, 1064 w, 1014 s, 914 w, 879 w, 730 w, 704 w, 642 w, 462 w. Typically, single crystals suitable for single-crystal X-ray analysis for all the complexes were prepared by diffusion between an acetone solution containing Cu(ClO4)2‚6H2O (75 mg, 0.2 mmol) and an anhydrous chloroform solution of ligand (0.6 mmol) using diethoxyethane as the interlayer and dehydrating reagent in a straight-type glass tube at room temperature. Crystals appeared in the interlayer after several days. All general characterizations were carried out on the basis of the crystal samples. For complexes 3B and 3B′, in the same reaction system, two complexes with different colors (3B, blue; 3B′, colorless) were obtained and were separated manually from each other. {[Cu(meso-Lb1)2(ClO4)](ClO4)}n (1B). Yield: ∼40%. Anal. Calcd for C12H28CuO12S4Cl2 (627.04): C, 22.99; H, 4.50. Found: C, 22.52; H, 5.06. IR (cm-1): 2979 m, 2939 m, 2024 w, 1633 w, 1457 m, 1406 w, 1384 w, 1263 w, 1020 w, 1101 s, 985 m, 943 s, 778 w, 623 s, 510 w. DTA peak position (°C): 201. [Cu(meso-Lb2)2(ClO4)2]n (2B). Yield: ∼45%. Anal. Calcd for C14H32CuO12S4Cl2 (655.09): C, 25.67; H, 4.99. Found: C, 25.84; H, 5.28. IR (cm-1): 2977 m, 2937 m, 2879 w, 2024 w, 1636 w, 1454 m, 1410 w, 1382 w, 1252 w, 1180 m, 1143 s, 1123 s, 1080 s, 1011 m, 982 m, 951 s, 779 w, 625 s, 527 w. DTA peak position (°C): 196. [Cu(rac-Lb3)2(ClO4)2]n (3B). Yield: ∼30%. Anal. Calcd for C16H36CuO12S4Cl2 (683.15): C, 28.13; H, 5.31. Found: C, 28.38; H, 5.21. IR (cm-1): 2976 m, 2939 m, 2878 w, 2022 w, 1637 w, 1457 m, 1409 w, 1379 w, 1266 w, 1145 m, 1115 s, 1091 s, 1022 m, 1003 m, 978 m, 945 s, 774 w, 624 s, 509 w. DTA peak position (°C): 211. {[Cu(meso-Lb3)3](ClO4)2}n (3B′). Yield: ∼10%. Anal. Calcd for C24H54CuO14S6Cl2 (893.50): C, 32.26; H, 6.09. Found: C, 31.95; H, 6.67. IR (cm-1): 2978 m, 2939 m, 2921 w, 2881 w, 2020 w, 1638 w, 1458 m, 1417 w, 1374 w, 1262 w, 1238 w, 1142 m, 1093 s, 1052 m, 1039 w, 1003 m, 983 m, 951 s, 877 w, 775 w, 739 w, 624 s, 509 m. DTA peak position (°C): 204. [Cu(meso-Lc1)2(ClO4)2]n (1C). Yield: ∼35%. Anal. Calcd for C16H36CuO12S4Cl2 (683.15): C, 28.13; H, 5.31. Found: C, 28.58; H, 5.15. IR (cm-1): 2969 m, 2937 m, 2880 w, 2025 w, 1626 w, 1461 m, 1409 m, 1340 w, 1280 w, 1238 w, 1101 s, 1070 s, 981 m, 943 s, 850 w, 757 w, 623 s, 505 m. DTA peak position (°C): 200. [Cu(meso-Lc2)2(ClO4)]2(ClO4)2(CHCl3)2 (2C). Yield: ∼30%. Anal. Calcd for C38H82Cu2O24S8Cl10 (1661.16): C, 27.48; H, 4.98. Found: C, 29.70; H, 5.78. MS: m/z 185.8 (100%), 609.9 (58%). IR (cm-1): 2967 m, 2935 m, 2876 w, 2023 w, 1707 m, 1635 w, 1458 m, 1408 w, 1366 w, 1287 w, 1229 w, 1095 s, 1002 m, 942 s, 756 m, 624 s, 503 m, 405 w. DTA peak positions (°C): 47, 199. {[Cu(meso-Lc3)2(ClO4)](ClO4)}n (3C). Yield: ∼35%. Anal. Calcd for C20H44CuO12S4Cl2 (739.25): C, 32.49; H, 6.00. Found: C, 32.05; H, 6.37. IR (cm-1): 2978 m, 2941 m, 2904 w, 2880 w, 2015 w, 1637 w, 1466 m, 1410 w, 1382 w, 1298 w, 1273 w, 1248 w, 1224 w, 1088 s, 1017 m, 979 m, 953 s, 918 m, 785 m, 728 m, 622 s, 522 m. DTA peak position (°C): 222. [Cu(meso-Ld1)2(ClO4)2]n (1D). Yield: ∼35%. Anal. Calcd for C20H44CuO12S4Cl2 (739.25): C, 32.49; H, 6.00. Found: C, 32.53; H, 5.73. IR (cm-1): 2965 m, 2937 m, 2878 m, 1990 w, 1647 w, 1466 m, 1408 m, 1389 w, 1296 w, 1235 w, 1105 s, 1066 s, 990 m, 957 m, 938 s, 759 m, 623 s, 520 m. DTA peak position (°C): 212. {[Cu2(rac-Ld2)4(ClO4)2](ClO4)2(CHCl3)}n (2D). Yield: ∼35%. Anal. Calcd for C45H97Cu2O24S8Cl7 (1653.99): C, 32.68; H, 5.91. Found: C, 33.74; H, 6.14. IR (cm-1): 2959 m, 2934 m, 2873 m,

Crystal Growth & Design, Vol. 5, No. 5, 2005 1921 2027 w, 1635 w, 1467 m, 1406 m, 1383 w, 1282 w, 1264 m, 1238 w, 1099 s, 999 m, 952 s, 774 w, 733 m, 623 s, 510 m. DTA peak positions (°C): 51 and 221. [Cu(rac-Ld3)2(ClO4)2]n (3D). Yield: ∼30%. Anal. Calcd for C24H52CuO12S4Cl2 (795.36): C, 36.24; H, 6.59. Found: C, 36.05; H, 6.02. IR (cm-1): 2979 m, 2941 w, 2929 m, 2881 m, 2028 w, 1637 w, 1446 m, 1409 m, 1380 w, 1255 w, 1183 w, 1101 s, 1048 m, 981 m, 953 s, 789 w, 756 w, 623 s, 523 m. DTA peak position (°C): 212. X-ray Crystal Structure Determination. Single-crystal X-ray diffraction measurements for 1B-3B, 2C, and 1D were carried out on a Bruker Smart 1000 CCD diffractometer, for 3B′ and 3C on a Siemens Smart CCD diffractometer, for 1C and 3D on a Rigaku RAXIS-RAPID instrument, and for 2D on a Rigaku Mercury CCD area detector. The determination of unit cell parameters and data collections were performed with Mo KR radiation (λ ) 0.710 73 Å). All the structures were solved by direct methods combining successive difference Fourier syntheses using the SHELXS program of the SHELXTL package and refined with SHELXL.13 The final refinement was performed by full-matrix least-squares methods with anisotropic displacement parameters for non-hydrogen atoms on F2, except for those disordered. The hydrogen atoms were added geometrically to carbon and refined with fixed thermal factors, with some in disordered groups not being added. For 3C, the alkyl chain is disordered and was refined in a suitable model with no restraint. It was necessary to use geometrical and displacement restraint in the refinement of 2D to model the disorder in terminal alkyl groups of ligands (the C-C distance is fixed at 1.45 Å with su ) 0.02). Such disordered atoms were refined with isotropic displacement parameters. Thus, the crystallographic data of 2D are not well refined because of the high disorder, and the Uij values are high for some C atoms. Disordered ClO4- groups were also found in some complexes, and a suitable site occupation separation was used for the refinement in each case. Only the major occupancy sites of the disordered atoms are shown in relevant figures in the text. Crystallographic data and experimental details for structural analyses are summarized in Table 1.

Results and Discussion Synthesis and General Characterization. For the construction of such disulfoxide-CuII coordination architectures and a systematic investigation of the relationship between the nature of the ligands and complex structures, our strategy was to use the direct reaction between the disulfoxide ligands with Cu(ClO4)2 under similar conditions, however, changing systematically the spacers and terminal groups of such ligands. The highmelting-point isomer of the ligand is considered as a meso configuration according to the literature.9j,11b Single crystals of complexes were obtained by the reaction of Cu(ClO4)2 with related disulfoxide ligands in a straight-type glass tube at room temperature using diethoxyethane as the interlayer and dehydrating reagent. All single crystals were structurally characterized by X-ray diffraction analyses. The elemental analyses showed that the components of these complexes are consistent with the results of crystal structure analyses, except that of 2C, which may be due to the loss of solvent (CHCl3) during measurement. IR spectra of the complexes are similar and show the characteristic SdO vibration in the range of 978-1002 cm-1, lower than the corresponding vibrations in the respective free ligand, indicating that the O atoms of sulfoxide groups are coordinated to metal ions.14 The existence of ClO4was also confirmed by the IR spectra. The complexes

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Table 1. Crystallographic Data and Structural Refinement Details for 1B-3D formula Mr cryst size (mm) cryst syst space group a (Å) b (Å) c (Å) R (deg) β (deg) γ (deg) V (Å3) Fcalcd (g cm-3) Z T (K) µ (mm-1) F(000) θ range (deg) no. of rflns coll no. of unique rflns Rint no. of obsd rflns no. of params GOF R1 (I >2σ(I)) R1 (all data) wR2 (all data) max/min ∆F (e Å-3)

formula Mr cryst size (mm) cryst syst space group a (Å) b (Å) c (Å) R (deg) β (deg) γ (deg) V (Å3) Fcalcd (g cm-3) Z T (K) µ (mm-1) F(000) θ range (deg) no. of rflns coll no. of unique rflns Rint no. of obsd rflns no. of params GOF R1 (I >2σ(I)) R1 (all data) wR2 (all data) max/min ∆F (e Å-3)

1B

2B

3B

3B′

1C

C12H28CuO12S4Cl2 627.02 0.25 × 0.20 × 0.15 tetragonal P4/n 11.614(3) 11.614(3) 9.249(5) 90 90 90 1247.6(8) 1.669 2 293(2) 1.476 646 2.20-25.01 4971 1103 0.0499 884 77 1.035 0.0357 0.0496 0.0987 0.516/-0.643

C14H32CuO12S4Cl2 655.08 0.25 × 0.20 × 0.10 monoclinic P21/n 7.784(2) 11.184(4) 15.254(5) 90 96.132(6) 90 1320.4(7) 1.648 2 293(2) 1.399 678 2.26-25.02 5351 2330 0.0463 1555 151 0.962 0.0385 0.0740 0.1009 0.552/-0.332

C16H36CuO12S4Cl2 683.13 0.30 × 0.25 × 0.20 monoclinic P21/c 10.612(4) 13.454(5) 9.890(4) 90 96.943(6) 90 1401.7(9) 1.619 2 293(2) 1.321 710 1.93-26.42 7696 2861 0.0305 2153 162 1.014 0.0319 0.0527 0.0842 0.306/-0.457

C24H54CuO14S6Cl2 893.47 0.28 × 0.26 × 0.24 trigonal R3 hc 10.339(2) 10.339(2) 65.69(1) 90 90 120 6081(2) 1.464 6 293(2) 1.035 2814 2.36-25.03 4545 1200 0.0441 903 72 1.006 0.0577 0.0823 0.1874 0.461/-0.321

C16H36CuO12S4Cl2 683.13 0.28 × 0.26 × 0.26 triclinic P1 h 7.903(2) 8.898(2) 11.495(2) 98.10(3) 96.61(3) 114.66(3) 713.7(2) 1.590 1 293(2) 1.298 355 3.11-26.00 4503 2748 0.0281 2473 160 1.074 0.0488 0.0523 0.1335 0.971/-0.330

2C

3C

1D

2D

3D

C38H82Cu2O24S8Cl10 1661.10 0.32 × 0.30 × 0.30 monoclinic P21/n 13.640(3) 16.355(3) 17.073(3) 90 108.28(3) 90 3617(1) 1.525 2 293(2) 1.253 1716 1.77∼25.50 20218 6656 0.0581 4356 415 1.054 0.0789 0.1232 0.2545 1.364/-1.021

C20H44CuO12S4Cl2 739.23 0.20 × 0.18 × 0.18 tetragonal P4/ncc 14.6317(2) 14.6317(2) 15.8750(6) 90 90 90 3398.6(1) 1.445 4 293(2) 1.096 1548 1.97∼25.03 7506 1491 0.0603 947 130 1.091 0.0598 0.1034 0.1807 0.603/-0.310

C20H44CuO12S4Cl2 739.23 0.24 × 0.20 × 0.20 triclinic P1 h 7.815(3) 8.810(3) 13.419(5) 88.899(6) 78.171(6) 66.659(6) 828.4(6) 1.482 1 293(2) 1.124 387 2.52∼26.42 3866 3077 0.0208 2318 178 1.042 0.0408 0.0626 0.1036 0.494/-0.397

C90H194Cl14Cu4O48S16 3307.87 0.26 × 0.24 × 0.18 triclinic P1 h 11.844(4) 11.924(4) 27.910(9) 94.575(5) 99.754(5) 90.059(5) 3872(2) 1.419 1 183(2) 1.070 1728 1.71∼25.50 16255 13766 0.0789 3744 763 0.719 0.0811 0.2334 0.1572 0.619/-0.551

C24H52CuO12S4Cl2 795.34 0.20 × 0.18 × 0.18 orthorhombic Pbca 12.715(3) 11.765(2) 24.747(5) 90 90 90 3702(1) 1.427 4 293(2) 1.012 1676 3.42∼26.00 6760 3594 0.0364 1431 196 0.866 0.0567 0.1162 0.1296 0.441/-0.224

are all air stable, and the TGA studies showed that almost all complexes decompose near 200 °C. Such complexes are soluble in DMF and DMSO but are almost insoluble in methanol, ethanol, acetone, and water, except for 2C, which is soluble in methanol and ethanol but not in water. The mass spectrum of 2C provided the evidence of the existence of the dinuclear cage cations in its methanol solution. Except for the ion at m/z 185.8 with an abundance of 100%, the most abundant ion in methanol solution is [Cu(Lc2)2ClO4]22+ (m/z 609.9, relative abundance 58%; calculated m/z 610.1). Descriptions of Structures. The structures of the 10 complexes were determined by X-ray crystallography.

The selected bond lengths, bond angles, and torsion angles are given in Tables 2 and 3. Complex 1B, {[Cu(meso-Lb1)2(ClO4)](ClO4)}n. 1B consists of a polymeric 2-D layer structure of (4,4) topology {[Cu(meso-Lb1)2(ClO4)]+}n cations and ClO4-. As shown in Figure 1a, the CuII ion is located on a crystallographic 4-fold axis position equally coordinated to four O donors from four distinct Lb1 ligands and an O atom of a disordered ClO4-, related by the 4-fold axis passing through one Cl-O bond. The coordination geometry of CuII can be described as a square pyramid with four sulfoxide O donors lying in the equatorial plane and one O atom of ClO4- in the apical position. The Cu-O(SdO) and Cu-O(ClO4-) bond lengths are

Flexible Disulfoxides as Bridging Ligands

Crystal Growth & Design, Vol. 5, No. 5, 2005 1923

Table 2. Selected Bond Lengths (Å) and Angles (deg) for 1B-3Da Cu(1)-O(1)

1.943(2)

S(1)-O(1)

Compound 1B 1.531(2) Cu(1)-O(4)*b

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

89.36(2)

S(1)-O(1)-Cu(1)

123.9(1)

1.529(3)

S(2)-O(2)

1.529(3)

121.4(2)

S(2)-O(2)-Cu(1)

127.1(2)

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

2.311(9) 167.9(2)

Cu(1)-O(1) Cu(1)-O(2)

1.936(3) 1.949(3)

Cu(1)-O(3)*

Compound 2B 2.593 S(1)-O(1)

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

180 92.3(1)

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

87.7(1)

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

1.954(2) 1.944(2)

Cu(1)-O(3)*

Compound 3B 2.706 S(1)-O(1)

1.530(2)

S(2)-O(2)

1.543(2)

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

180 91.05(7)

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

88.95(7)

126.6(1)

S(2)-O(2)-Cu(1)#4

122.0(1)

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

2.082(2) 90.3(1)

S(1)-O(1) O(1)-Cu(1)-O(1)#4

Compound 3B′ 1.522(3) 180 O(1)-Cu(1)-O(1)#2

89.7(1)

S(1)-O(1)-Cu(1)

122.0(2)

1.537(2)

S(2)-O(2)

1.531(2)

120.1(1)

S(2)-O(2)-Cu(1)

124.8(1)

1.538(5) 1.541(4)

S(3)-O(3) S(4)-O(4)

1.552(4) 1.553(4)

92.5(4) 97.9(4) 125.3(3)

S(2)-O(2)-Cu(1) S(3)-O(3)-Cu(1) S(4)-O(4)-Cu(1)

123.5(2) 123.8(2) 120.5(2)

S(1)-O(1)-Cu(1)

S(1)-O(1)-Cu(1)

Cu(1)-O(1) Cu(1)-O(2)

1.948(2) 1.931(2)

Cu(1)-O(3)*

Compound 1C 2.572 S(1)-O(1)

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

88.57(9) 180

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

91.43(9)

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

1.938(4) 1.933(4) 1.936(4)

Cu(1)-O(4) Cu(1)-O(5)*

Compound 2C 1.938(4) S(1)-O(1) 2.257(7) S(2)-O(2)

O(1)-Cu(1)-O(2) O(1)-Cu(1)-O(3) O(1)-Cu(1)-O(4) O(1)-Cu(1)-O(5)

88.7(2) 166.3(2) 89.0(2) 100.6(4)

O(2)-Cu(1)-O(3) O(2)-Cu(1)-O(4) O(2)-Cu(1)-O(5) O(3)-Cu(1)-O(4)

89.4(2) 165.7(2) 96.4(4) 89.5(2)

Cu(1)-O(1)

1.932(1)

S(1)-O(1)

Compound 3C 1.537(2) Cu(1)-O(2)*

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

172.3(1)

S(1)-O(1)-Cu(1)

O(3)-Cu(1)-O(5) O(4)-Cu(1)-O(5) S(1)-O(1)-Cu(1)

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

2.395(6)

S(1)-O(1)-Cu(1)

123.58(9)

89.744(8) 1.530(2)

S(2)-O(2)

1.540(2)

125.4(1)

S(2)-O(2)-Cu(1)

119.8(1)

Cu(1)-O(1) Cu(1)-O(2)

1.929(2) 1.941(2)

Cu(1)-O(3)*

Compound 1D 2.642 S(1)-O(1)

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

92.12(8) 180

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

87.88(8)

Cu(1)-O(1) Cu(1)-O(2) Cu(1)-O(3) Cu(1)-O(4) Cu(1)-O(9)*

1.916(5) 1.943(5) 1.926(5) 1.955(5) 2.637

Cu(2)-O(5) Cu(2)-O(6) Cu(2)-O(7) Cu(2)-O(8) Cu(2)-O(13)*

Compound 2D 1.968(6) S(1)-O(1) 1.920(5) S(2)-O(2) 1.954(5) S(3)-O(3) 1.960(6) S(4)-O(4) 2.39(1)

1.555(5) 1.544(6) 1.584(5) 1.546(5)

S(5)-O(5) S(6)-O(6) S(7)-O(7) S(8)-O(8)

1.565(5) 1.560 (6) 1.554(6) 1.511(5)

O(1)-Cu(1)-O(2) O(1)-Cu(1)-O(3) O(1)-Cu(1)-O(4) O(2)-Cu(1)-O(3) O(2)-Cu(1)-O(4) O(3)-Cu(1)-O(4)

90.2(2) 171.5(3) 88.7(2) 90.7(2) 168.3(3) 88.8(2)

O(5)-Cu(2)-O(6) O(5)-Cu(2)-O(7) O(5)-Cu(2)-O(8) O(5)-Cu(2)-O(13) O(6)-Cu(2)-O(7) O(6)-Cu(2)-O(8)

90.2(2) 173.9(3) 88.6(2) 97.2(3) 90.1(2) 174.5(3)

100.2(4) 90.5(2) 88.7(3) 85.3(4) 125.0(3) 124.3(3)

S(3)-O(3)-Cu(1) S(4)-O(4)-Cu(1) S(5)-O(5)-Cu(2) S(6)-O(6)-Cu(2) S(7)-O(7)-Cu(2) S(8)-O(8)-Cu(2)

123.6(3) 124.4(3) 118.4(4) 122.5(3) 119.6(3) 119.5(3)

Cu(1)-O(1) Cu(1)-O(2)

1.948(3) 1.923(3)

Cu(1)-O(3)*

Compound 3D 2.683 S(1)-O(1)

1.540(3)

S(2)-O(2)

1.504(3)

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

90.2(1) 180

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

89.8(1)

123.3(2)

S(2)-O(2)-Cu(1)

129.6(2)

S(1)-O(1)-Cu(1)

O(6)-Cu(2)-O(13) O(7)-Cu(2)-O(8) O(7)-Cu(2)-O(13) O(8)-Cu(2)-O(13) S(1)-O(1)-Cu(1) S(2)-O(2)-Cu(1)

S(1)-O(1)-Cu(1)

a Symmetry codes are as follows. 1B: (#1) y, 3/ - x, z; (#2) 3/ - x, 3/ - y, z. 2B: (#1) -x, -y, -z. 3B: (#1) 1 - x, y - 1/ , 3/ - z; (#2) 2 2 2 2 2 x, -y + 1/2, z + 1/2; (#3) 1 - x, -y, 2 - z; (#4) 1 - x, y + 1/2, 3/2 - z. 3B′: (#1) y, y - x, -z; (#2) y - x, -x, z; (#4) -x, -y, -z. 1C: (#1) 1 1 1 1 b - x, -y, 1 - z. 3C: (#1) /2 - x, /2 - y, z; (#2) y, /2 - x, z. 1D: (#1) -x, -y, -z. 3D: (#1) 1 - x, -y, 1 - z. Asterisks denote the O atoms of ClO4-.

1.943(2) and 2.311(9) Å, respectively, and the cis O-Cu-O angle in the equatorial plane is almost 90° (89.36(2)°). The CuII center slightly deviates from the mean equatorial plane of the square pyramid by 0.164 Å toward the apical O (O4) of ClO4-, due to its axial coordination. In 1B each ligand links two CuII ions through the O atoms of the sulfoxide groups, and each

CuII center is bridged to four neighboring CuII ions by Lb1 ligands to form a centrosymmetric 28-membered [Cu4(Lb1)4] square metallamacrocyclic grid unit (Figure 1b). In the square the distance between adjacent CuII ions is 8.792 Å and that of the diagonal is 11.614 Å. The metallamacrocyclic unit extends out along the a and b directions to form a 2-D (4,4) net containing square

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Table 3. Selected Torsion Angles (deg) for 1B-3Da

a

Compound 1B C(2)-S(1)-O(1)-Cu(1) C(3)-S(1)-O(1)-Cu(1)

241.8(2) 140.4(2)

Compound 2B C(2)-S(1)-O(1)-Cu(1) C(3)-S(1)-O(1)-Cu(1) C(5)-S(2)-O(2)-Cu(1) C(6)-S(2)-O(2)-Cu(1)

250.7(2) 145.4(2) 131.2(2) 235.7(2)

Compound 3B C(2)-S(1)-O(1)-Cu(1) C(3)-S(1)-O(1)-Cu(1) C(6)-S(2)-O(2)-Cu(1)#4 C(7)-S(2)-O(2)-Cu(1)#4

104.3(2) 207.1(1) 241.4(1) 138.2(1)

Compound 3B′ C(2)-S(1)-O(1)-Cu(1) C(3)-S(1)-O(1)-Cu(1)

235.1(2) 131.1(2)

Compound 1C C(3)-S(1)-O(1)-Cu(1) C(4)-S(1)-O(1)-Cu(1) C(5)-S(2)-O(2)-Cu(1) C(6)-S(2)-O(2)-Cu(1)

256.6(2) 150.7(2) 105.4(2) 208.8(2)

Compound 2C C(3)-S(1)-O(1)-Cu(1) C(4)-S(1)-O(1)-Cu(1) C(7)-S(2)-O(2)-Cu(1) C(8)-S(2)-O(2)-Cu(1) C(11)-S(3)-O(3)-Cu(1) C(12)-S(3)-O(3)-Cu(1) C(16)-S(4)-O(4)-Cu(1) C(17)-S(4)-O(4)-Cu(1)

158.6(4) 264.1(4) 160.3(4) 264.9(3) 160.4(4) 265.9(4) 154.2(3) 260.8(3)

Compound 3C C(3)-S(1)-O(1)-Cu(1) C(4)-S(1)-O(1)-Cu(1)

127.6(2) 236.7(2)

Compound 1D C(4)-S(1)-O(1)-Cu(1) C(5)-S(1)-O(1)-Cu(1) C(9)-S(2)-O(2)-Cu(1) C(10)-S(2)-O(2)-Cu(1)

155.9(2) 258.1(2) 253.3(2) 150.3(2)

Compound 2D C(4)-S(1)-O(1)-Cu(1) C(5)-S(1)-O(1)-Cu(1) C(10)-S(2)-O(2)-Cu(1) C(11)-S(2)-O(2)-Cu(1) C(16)-S(3)-O(3)-Cu(1) C(17)-S(3)-O(3)-Cu(1) C(21)-S(4)-O(4)-Cu(1) C(22)-S(4)-O(4)-Cu(1) C(24)-S(5)-O(5)-Cu(2) C(25)-S(5)-O(5)-Cu(2) C(32)-S(6)-O(6)-Cu(2) C(33)-S(6)-O(6)-Cu(2) C(37)-S(7)-O(7)-Cu(2) C(38)-S(7)-O(7)-Cu(2) C(42)-S(8)-O(8)-Cu(2) C(43)-S(8)-O(8)-Cu(2)

240.8(5) 136.7(5) 229.5(4) 129.5(4) 230.8(5) 129.1(4) 230.2(5) 126.5(5) 131.9(4) 235.5(6) 235.4(5) 130.0(4) 232.1(5) 128.7(4) 230.3(5) 127.5(4)

Compound 3D C(4)-S(1)-O(1)-Cu(1) C(5)-S(1)-O(1)-Cu(1) C(8)-S(2)-O(2)-Cu(1) C(9)-S(2)-O(2)-Cu(1)

239.5(3) 135.9(3) 225.1(3) 130.3(4)

Symmetry code: (#4) 1 - x, y + 1/2, 3/2 - z.

grids (Figure 1b), in which the CuII ions are located on two different planes, up and down alternately. It is interesting to point out that the uncoordinated ClO4anions are fixed in the square cavities and weakly interact with the S atoms of ligands, with S‚‚‚O distances of 3.222 Å, probably acting as a template for the formation of the network and keeping the structure stable. It should be emphasized that in the 2-D layer the four bridging ligands around a CuII center arrange

Figure 1. (a) Coordination modes of CuII and the ligand in 1B and (b) 2-D (4,4) network of 1B with ClO4- located in the cavities (hydrogen atoms omitted for clarity).

themselves in the same direction based on the CuO4 coordination plane and those around the adjacent CuII centers in an opposite direction, so as to form nests, in which the coordinated ClO4- anions are accommodated. Furthermore, four ethyl groups of the ligand around each CuII are located on the same side of each coordination plane but on the opposite side of the coordinated ClO4-, which may help to reduce the steric hindrance. In addition, such 2-D layers stack in the c direction without any offset and turn with each other, to leave micro channels in the stacking direction, which are occupied by uncoordinated ClO4- anions as mentioned above. In 1B, Lb1 adopts an R,S configuration with the quasi-torsion angle between two SdO groups of the ligand being 180°, and the O coordination adopts a trans,trans arrangement, as estimated by the torsion angles of C-S-O-Cu lying in the range of 90-270°, as shown in Table 3.15 Complex 2B, [Cu(meso-Lb2)2(ClO4)2]n. As shown in Figure 2, 2B has a 1-D structure similar to that of 2C′′ in ref 11b, in which the CuII ion is located at a crystallographic inversion center and in an elongatedoctahedral environment formed by six O atoms from four distinct Lb2 ligands and two ClO4- groups. Four



Figure 2. 1-D chain of 2B showing the coordination environment of CuII with hydrogen atoms omitted for clarity.

Cu-O(SdO) bond distances are almost equivalent with an average value of 1.943 Å, and the CuII ion lies on a plane defined by the four O atoms with cis O-Cu-O angles of 92.3(1) and 87.7(1)°, respectively. The O atoms of ClO4- anions are weakly coordinated to the CuII ions at the apical position with a Cu1-O3 distance of 2.593 Å. In 2B, the ligand Lb2 displays a bis-monodentate mode to bridge adjacent CuII ions, resulting in a doublebridging chain containing 16-membered rings, in which the Cu‚‚‚Cu distance is 7.784 Å. As in 1B, Lb2 ligands also have an R,S configuration, but the quasi-torsion angle between two SdO groups of the ligand is 87.4°. The O coordination of the sulfoxide group is a trans,trans arrangement,15 with the torsion angles C-S-O-Cu being 131.2(2)-250.7(2)° (Table 3). In addition, in the crystal of 2B all the chains are arranged in the same direction along the crystallographic a axis and also are parallel with each other, on the basis of the CuO4 planes. Complex 3B, [Cu(rac-Lb3)2(ClO4)2]n. 3B also has a 2-D layer structure, in which each CuII ion, lying in a crystallographic inversion center, is coordinated to four O donors from four distinct Lb3 ligands and weakly coordinated to two O atoms of ClO4- to give an elongatedoctahedral coordination geometry (Figure 3a). The Cu-O(SdO) bond lengths of 1.954(2) and 1.944(2) Å are almost equal and comparable with those of other disulfoxide-CuII complexes reported herein, the cis angles of O-Cu-O are 91.05(7) and 88.95(7)°, and the CuII center is coplanar with the four coordinated sulfoxide O atoms. In 3B each CuII is bridged to four neighboring CuII atoms by four Lb3 ligands to form a 36-membered [Cu4(Lb3)4] rhombus grid unit. In the grid the distance between adjacent CuII ions is 8.349 Å and the diagonal distance is 9.890 Å. The metallamacrocyclic unit extends out along the bc plane to form a 2-D (4,4) net (Figure 3b), in which all CuII ions are coplanar, being different from those in 1B. It is interesting that in each grid two ClO4- anions are fixed in one of the diagonal corners and are weakly coordinated to the CuII ions with a Cu-O distance of 2.706 Å, and simultaneously another O atom of each ClO4- weakly interacts with an S atom of the ligand with an S‚‚‚O distance of 3.176 Å. The ClO4- anions act, thus, as a template. Different from those in 1B, the four bridging ligands around each CuII extend in two directions on the basis of the coordination plane, with the two adjacent ligands being analogous. In addition, as those in 1B, these 2-D layers stack with no offset and turn with each other, to leave microchannels in the stacking direction, which are occupied by ClO4- as mentioned above. It is noteworthy that the starting ligand is the high-melting-point isomer, which is considered as a meso configuration.9j,11b In 3B the

Figure 3. (a) Coordination modes of CuII and the ligand in 3B and (b) 2-D framework structure (all hydrogen atoms omitted for clarity).

ligands adopt the rac (S,S or R,R) isomer form, indicating a configuration change of Lb3 during the formation process of the complex. The ligands around the CuII center at the diagonal positions adopt S,S and R,R forms. Thus, as a whole, 3B has no chiral characteristics. In addition, all these rac ligands also have a trans,trans arrangement (Table 3) for the O coordination,15 and the quasi-torsion angle between two SdO groups of the ligand is 155.1°. Complex 3B′, {[Cu(meso-Lb3)3](ClO4)2}n. In the same reacting system, together with the formation of the blue crystals of 3B, colorless crystals of 3B′ were obtained. X-ray crystal structure analyses revealed that 3B′ is a 2-D (3,6) network (Figure 4), in which each CuII center is coordinated by six sulfoxide O donors from six independent ligands in an ideal octahedral coordination geometry, with a crystallographic symmetry center passing through it. The six Cu-O bond lengths are

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Figure 4. (3,6) network of 3B′ with ClO4- in the cavities (all hydrogen atoms omitted for clarity).

equal (2.082(2) Å), which is longer than those in the four- or five-coordinated disulfoxide-CuII complexes discussed here, and the cis O-Cu-O angles around CuII center are 90.3(1) and 89.7(1)°, being very close to 90°. It should be pointed out that although the octahedral six-coordinated CuII complexes are common, those with a regular ideal octahedron are extremely rare. In 3B′, each CuII ion is linked to six adjacent CuII ions by Lb3 ligands to generate a unique six-connected 2-D (3,6) topology network containing 27-membered trigonal grids formed by three metal centers and three ligands. In such trigonal grids, the Cu‚‚‚Cu distances are equal (10.636 Å) and leave about 100 Å2 cavities, in which ClO4- anions are incorporated with up-and-down arrangements alternately, which may also be regarded as a template (Figure 4). It is also noteworthy that although (6,3) topology is very common in coordination polymers, the (3,6) topology is still rare.9i,16 In 3B′ all ligands adopt a meso configuration and the quasi-torsion angle between two SdO groups of the ligand is 180°, different, thus, from the case in 3B. Furthermore, O atoms of the ligands are also in a trans,trans arrangement15 when coordinating to the metal center (Table 3). The Lb3 ligands are stretched out up and down to generate such a layer structure, and the high symmetry with such a close arrangement of molecules may help to prevent interpenetration. In addition, the face-to-face stacking of such lamellar layers does not afford any substantial channel in the crystals, because adjacent layers move each other 1/2 triangular unit in the a or b direction sequentially. Complex 1C, [Cu(meso-Lc1)2(ClO4)2]n. As shown in Figure 5, 1C has a 2-D (4,4) structure, in which each CuII ion located on an inversion center and is coordinated to four O donors from four distinct Lc1 ligands in the equatorial plane and to two O atoms of ClO4- in the axis position (Figure 5a). The Cu-O(SdO) distances are 1.948(2) and 1.931(2) Å, which compare well with those for other related complexes reported in this work, and the cis angles of O-Cu-O in the equatorial plane are almost 90° (88.57(9) and 91.43(9)°). The

Figure 5. (a) Coordination modes of CuII and the ligand in 1C and (b) 2-D framework structure (hydrogen atoms and ClO4- omitted for clarity).

Cu-O(ClO4-) bond distance is 2.572 Å. The CuII center is coplanar with the coordinated disulfoxide O atoms. In 1C each CuII center is bridged to four neighboring CuII ions by Lc1 ligands to form a centrosymmetric 28membered [Cu4(Lc1)4] metallamacrocyclic unit, in which the distances of adjacent CuII ions are 7.903 and 8.898 Å. The metallamacrocyclic unit extends out along the a and b directions to form a 2-D (4,4) net containing rectangular grids (Figure 5b), in which all the CuII ions are located in one plane. It should also be pointed out that the ClO4- anions not only coordinate to the CuII ion as mentioned above but also form weak interactions with the S atoms of ligands with S‚‚‚O distances of 3.201 Å. As for those in 3B, the four bridging ligands around each CuII center extend in two directions on the basis of the coordination plane, with the adjacent ones being analogous. In addition, such 2-D layers stack in the c direction without any offset and turn with each other to leave micro channels, which are partially occupied by ClO4- anions. In 1C, Lc1 adopts an R,S configuration with the quasi-torsion angle between two SdO groups of the ligand being 180°, and the O coordination adopts a trans,trans arrangement (Table 3).15 Complex 2C, [Cu(meso-Lc2)2(ClO4)]2(ClO4)2(CHCl3)2. Different from other disulfoxide-CuII complexes in this and previous reports, 2C has an unexpected discrete dinuclear cage-like cationic structure, [Cu2(Lc2)4(ClO4)2]2+ (Figure 6), combining ClO4- anions and solvent CHCl3 molecules. The binuclear unit is related by a crystallographic inversion center. The CuII center is coordinated by four O atoms from four distinct


Figure 6. Cage structure of 2C showing the coordination modes of CuII and the ligand with hydrogen atoms (noncoordinated ClO4- and CHCl3 molecules omitted for clarity): (a) side view; (b) top view.

Lc2 ligands and an O atom of a disordered ClO4- anion. The coordination geometry can be described as a slightly distorted square pyramid with four sulfoxide O atoms located in the basal plane and a perchlorate O in the axial position. The Cu-O(SdO) bond lengths are different but lie in the narrow range of 1.933(4)-1.938(4) Å with an average value of 1.936 Å, being comparable with other related complexes reported in this work. The Cu-O(ClO4-) bond length of 2.247(8) Å is normal for the CuII complexes. The cis angles of O-Cu-O in the equatorial plane lie in the range of 88.7(2)-97.9(4)°. In 2C the two CuII centers are linked by four Lc2 bridging ligands to form a cage structure, in which the Cu‚‚‚Cu distance is 5.219 Å, which is rather shorter than those observed in other CuII complexes in this work. In addition, other ClO4- anions and solvent CHCl3 molecules are packed in the crystal. The Lc2 ligands in 2C also have an R,S configuration with the quasi-torsion angles between two SdO groups of the ligand being 1.8 and 2.0°, and O coordination is a trans,trans arrangement (Table 3).15


Figure 7. (a) Coordination modes of CuII and the ligand in 3C and (b) 2-D network structure (all hydrogen atoms and ClO4- omitted for clarity).

The Lc2 ligand is very fascinating, because under different synthetic conditions the three complexes 2C (this work), [Cu(rac-Lc2)2(ClO4)2]n11a (2C′), and {[Cu(meso-Lc2)2(H2O)2](ClO4)2}n (2C′′),11b with different structures, may be obtained. 2C′ has a 2-D (4,4) structure, while 2C′′ has a chain structure. Complex 3C, {[Cu(meso-Lc3)2(ClO4)](ClO4)}n. As shown in Figure 7, 3C has structural features similar to those found for 1B. The Cu-O(SdO) and Cu-O(ClO4-) bond lengths are 1.932(1) and 2.395(6) Å, respectively, and the cis angle of O1-Cu1-O1A in the equatorial plane is 89.744(8)°. The CuII center slightly deviates from the mean equatorial plane of the square pyramid by 0.1292 Å, due to the axial coordination of disordered ClO4-. In 3C each ligand links two CuII ions and each CuII center is bridged to four neighboring CuII ions by Lc3 ligands to form a centrosymmetric 36membered square grid unit (Figure 7b). In the square grid the distance of adjacent CuII ions is 10.878 Å. The metallamacrocyclic unit extends out along the ab plane to form a 2-D (4,4) net, in which the CuII ions are located at two different planes, up and down alternately. The

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Figure 8. (a) Coordination modes of CuII and the ligand in 1D and (b) 2-D framework structure (all hydrogen atoms and ClO4- omitted for clarity).

uncoordinated ClO4- anions are located in the square cavities. In the 2-D layer the four bridging ligands around each CuII center extend themselves in the same direction and those around the adjacent CuII centers in an opposite direction, to form nests, where the coordinated ClO4- is located. Four propyl groups of the ligand around each CuII are located on the same side of each CuII coordination plane, which may help to reduce the steric hindrance. Different from those in 1B, in the 3C the 2-D layers stack in the c direction, although without any offset, but turn 45° around the 4-fold axis with each other, to leave micro channels in the stacking direction, which are occupied by ClO4- anions as mentioned above. In 3C, Lc3 adopts an R,S configuration with the quasitorsion angle between two SdO groups of the ligand being 180° and with a trans,trans arrangement for the O coordination (Table 3).15 Complex 1D, [Cu(meso-Ld1)2(ClO4)2]n. The structure of 1D is similar to that of 1C, having a 2-D (4,4) structure (Figure 8). The distances of Cu-O(SdO) are 1.929(2) and 1.941(2) Å, and the cis angles of O-Cu-O in the equatorial plane are 92.12(8) and 87.88(8)°. The Cu-O(ClO4-) bond length is 2.624(3) Å, being longer than that in 1C. In 1D each CuII center is bridged to four neighboring CuII ions by Ld1 ligands to form a centrosymmetric 28-membered rectangular metallamacrocyclic unit (Figure 8b), in which the distances between adjacent CuII ions are 7.815 and 8.810 Å. The metallamacrocyclic unit extends out along the a and b directions to form a 2-D (4,4) net, in which all the CuII ions are located on the same plane. The ClO4- anions partially fit into the rectangular cavities and form weak

Figure 9. (a) Coordination environment of CuII and ligand linkage modes in 2D and (b) 2-D framework structure (all hydrogen atoms and ClO4- omitted for clarity).

interactions with S atoms (the S‚‚‚O distance is 3.211 Å). As in 1C, the 2-D layers stack in the c direction without any offset and turn with each other, to leave micro channels in the stacking direction, which are partially occupied by ClO4- anions as mentioned above. In 1D, Ld1 adopts an R,S configuration with the quasitorsion angle between two sulfoxide groups of the ligand being 180° and has a trans,trans arrangement for the O coordination (Table 3).15 Complex 2D, {[Cu2(rac-Ld2)4(ClO4)2](ClO4)2(CHCl3)}n. 2D has also a 2-D (4,4) network structure and consists of {[Cu2(Ld2)4(ClO4)2]3+}n cations, ClO4anions, and CHCl3 molecules (Figure 9). In the structure of 2D there are two kinds of coordination geometries of CuII ions. This is also a rare example for disulfoxideCuII complexes in which a binuclear unit acts as a fundamental building block in the infinite network structure. As shown in Figure 9a, in the asymmetric unit two CuII centers are linked by a bis-monodentate ligand (Ld2), with a Cu‚‚‚Cu separation of 9.866 Å. The differences between both CuII centers are that Cu2 is coordinated by an O atom of ClO4- at the apical position with a Cu2-O13 bond distance of 2.39(1) Å, while Cu1 is weakly coordinated (Cu2-O9 ) 2.637 Å). The Cu1-


O(SdO) bond lengths range from 1.916(5) to 1.955(5) Å, with an average of 1.935 Å, and the cis angles of O-Cu1-O are in the range 88.7(2)-90.5(2)°. The Cu1 atom slightly deviates from the mean equatorial plane by 0.0696 Å. For Cu2, the corresponding values are 1.920(5)-1.968(6) Å, 1.951 Å, 88.6(2)-90.5(2)°, and 0.1361 Å, respectively. The binuclear cationic units are linked by ligands Ld2 to form a 2-D (4,4) network with 32-membered metallamacrocyclic units (Figure 9b). In the structural unit [CuLd2]4, the diagonal CuII centers have the same coordination environment, while the adjacent ones are different. In the 2-D structure, the two kinds of CuII centers alternate, having different adjacent bridging ligands. The CuII ions thus lie alternately in two parallel planes. In addition, in 2D such 2-D layers stack in the c direction without any offset and movement, to leave micro channels, in which the noncoordinated ClO4- is located. The CHCl3 molecules are located between layers. Another interesting feature is that in 2D the disulfoxide ligands adopt a rac configuration (the quasitorsion angles of sulfoxide groups range from 45.0 to 52.8°). In each layer the configurations of all the ligands are the same S,S (or R,R) form, but in adjacent layers, the ligands adopt the different configuration R,R (or S,S). Thus, each 2-D layer is chiral, but the whole crystal is nonchiral. This feature is different from that found in 3B, 2E, and 3D (vide infra) and is also the first example for disulfoxide-metal complexes. This result indicates that the configuration of the ligand Ld2 changes when reacted with Cu(ClO4)2 as in the formation of 3B. As for the other complexes reported in this work, the O coordination of the ligands adopts a trans,trans arrangement (Table 3).15 Complex 3D, [rac-Cu(Ld3)2(ClO4)2]n. As shown in Figure 10, 3D has also a 2-D (4,4) structure similar to that of 3B, consisting of rhombic 36-membered rings, [CuLd3]4 units, with a CuII ion at each corner and an Ld3 molecule at each edge. The Cu-O(SdO) bond lengths are 1.923(3) and 1.948(3) Å, perfectly comparable with those of other disulfoxide-CuII complexes reported here. The cis O-Cu-O angles are 89.8(1) and 90.2(1)°. The CuII center is coplanar with the coordinated O atoms. In 3D, each CuII center is linked by four ligands to form the repeating units of a square 36membered ring with a Cu‚‚‚Cu separation of 8.661 Å. The repeating unit extends along the ab plane to form a 2-D sheet, as shown in Figure 10b. ClO4- anions occupy the cavities and weakly interact with the CuII center (the Cu-O distance is 2.683 Å). It is noteworthy that in 3D the ligand is also in a rac configuration (R,R and S,S), indicating the configurational change of the ligand during the reaction process. Two S atoms in trans positions with respect to the CuII atom have different configurations and the adjacent two S atoms have the same configuration. Thus, the 3D network as a whole is also mesomeric. The quasi-torsion angle between two sulfoxide groups of the ligand is 155.6°, and the O coordination of the sulfoxide group adopts a trans,trans arrangement (Table 3).15 Comparison of the Structures and Networks: Possible Generalizations. (1) 1A,11b 1B, 1C, 1D, and 1E9c show the same molar ratio of M:L ) 1:2 and similar structural features (2-D (4,4) framework), except for 1A


Figure 10. (a) Coordination environment of the center CuII ion and the ligand linkage modes in 3D and (b) 2-D framework structure (all hydrogen atoms and ClO4- omitted for clarity).

(1-D chain). However, there are two different important points. First, the CuII coordination environment in 1C and 1E is six-coordinated with octahedral geometry with two coordinated ClO4-anions, in 1B the CuII center is five-coordinated with a square-pyramidal coordination geometry and with only one coordinated ClO4- anion, and in 1A and 1D the CuII center exhibits fourcoordination with a square-planar geometry. Second, in 1B-E compounds the networks are different: CuII centers lie in two parallel planes and adjacent Cu‚‚‚Cu distances in metallamacrocyclic units are equal in 1B, while in 1C-E the CuII centers are coplanar and the Cu‚‚‚Cu distances are different. These peculiarities must be attributed to the differences of the terminal groups of the ligands, because the central parts are the same. (2) 2B-E have the same central part, -CH2CH2CH2-. Thus, their structural differences are due to the different terminal-ligand groups, such as the case in the series 1B-D. In addition, different coordination geometries of the CuII ion are also observed in this series of complexes. (3) Comparing the structures of 3B-E, we realize, again, that similar disulfoxide ligands containing the same spacer but different terminal groups form different structural complexes, and the coordination geometries of the CuII ion are also different. (4) On comparison of series with different spacers, the greater flexibilities of the longer ligands can allow by

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Scheme 1. Coordination Architectures and Structural Types of the Disulfoxide-CuII Complexes

themselves the adoption of different arrangements in the complex formation process, due to steric and electronic requirements. The highly flexible -(CH2)4backbone of the ligands allows the suitable rearrangement of the ligands so as to minimize steric interactions in the coordinated forms, thus creating different structures. As a paradigmatic example, two complexes, 3B and 3B′, with different compositions and structures are simultaneously obtained with the same reacting system. Each one contains a different ligand configuration (meso or rac). The phenomenon is rare in metal-organic complexes and is the first example in disulfoxide-metal complexes. The structural differences found in the above four B series complexes reveal that the different spacer lengths in the bridging ligands may lead to different structural networks. The results also indicate that the ligand with the long spacer (Lb3) is highly flexible: it easily changes linkage conformations to form two different fascinating structures. (5) Finally, to sum up all these results, together with those previously reported by us and others,9c,11 different series of structurally related flexible disulfoxide ligands were designed and used to assemble CuII complexes (Chart 1 and Scheme 1). Four important features of the overall structures of these complexes can be concluded. (i) Under the same synthetic conditions most of the CuII complexes with La-Le have the same Cu:L ratio (1:2) in the solid state, except for complexes 3B′, 2E, and 3E, which have 1:3 ratios of Cu:L. This result indicates that the complexes having 1:2 ratios of Cu:L are more suitable, due to the inherent coordination nature of the CuII ion and the steric hindrance of the coordination phase of the ligands. However, when the spacers of the ligand are lengthened, the hindrance among ligands decreases, and so a higher Cu:L ratio is possible. (ii) In all complexes the ligands adopt a bis-monodentate bridging mode and coordinate to the CuII center by the O atoms of sulfoxide moieties. For complexes with a 1:2 ratio of Cu to L, the coordinated donors of the ligands locate preferably in the equatorial plane of CuII coordi-

Li et al.

nation sites, with the remaining coordination sites being occupied by ClO4- anions in different coordination degrees. Furthermore, when the apical positions are occupied by the donors of the ligands, complexes with 2-D (3,6) (3B′), 2-D (4,4) (2E), and 3-D (3E) frameworks are formed. (iii) In each one of the four series of the complexes (1B-3E), in which the ligands contain the same terminal groups but different spacers with two, three, or four carbon atoms, the structural differences of the complexes may be attributed to the influence of the spacer: the longer spacers allow the ligand to enjoy more freedom in arranging itself around the metal center, which promotes the formation of various structures. For example, in the complexes with RS(O)(CH2)2S(O)R sulfoxides, the structures of the complexes are basically similar, having a 2-D (4,4) network, while in the series of the complexes with the RS(O)(CH2)4S(O)R ligands, completely different structures, previously reported, were formed. (iv) There are also many differences in the structures of complexes with ligands having the same spacer but different terminal groups. These differences are more difficult to tune. (v) In all complexes the ligands take three kinds of configurations: meso-(R,S), R,R, and S,S forms. Although disulfoxides are configurationally inert, meso forms (high melting point) are easily separated from racemates. In this work, however, when meso ligands react with CuII ions at room temperature to form complexes, the disulfoxide ligands in the complexes 3B, 2D, and 3D have a rac configuration, indicating that the change of the configuration occurs from a meso to a rac form in the reacting process. In some earlier investigations,9j,17 the configurational change of the sulfoxide entities seemed to occur at higher temperature (ca. 70∼80 °C). However, in this work, the change happens at room temperature. This result indicates that a metal-assisted configurational change of the disulfoxide compound may occur even at room temperature. Simultaneously, it is also reported in the literature that the configurational inversion of disulfoxides occurs, more frequently, not from meso to rac but from rac to meso in bis(phenylsulfinyl)alkane complexes,17b This result may be attributed to the difference in stability of the two forms (meso and rac), due to the different kinds of disulfoxide ligands. (vi) Finally, all these complexes with O coordination adopt a trans,trans arrangement with the M-O-S-C angle being in the range of 90-270° (see Table 3). This feature is consistent with that reported for other transitionmetal complexes with disulfoxide ligands. Magnetic Properties. Owing to the presence of long bridging ligands in all the complexes reported in this work, one might expect the lack of any noticeable magnetic coupling between CuII ions. To corroborates or modifysthis idea, the magnetic behavior of three of them, 1B-3B, was studied. Figure 11 shows the temperature dependence of χmT. With a decrease in temperature, the observed χmT values of 1B are constant up to 50 K, approximately (0.4375 cm3 mol-1 K, typical for an isolated CuII ion). From 50 to 2 K χmT slightly decreases, giving a value of 0.4367 cm3 mol-1 K at 2 K. This difference is not at all significant, and thus, the behavior is simply a Curie law. On calculation of the theoretical Weiss constant with these χmT values, Θ would be -3.6 × 10-3 K (almost zero). The calculated g



2B, and four for complex 3B). Indeed, from a structural point of view, the Cu‚‚‚Cu distances do not follow this number of C atoms either: 8.792 Å for complex 1B, 7.784 Å for the complex 2B, and 8.349 Å for complex 3B. The shapes of the EPR spectra (see the Supporting Information) do not vary with temperature. The CuII ions in the three complexes show square-planar coordination with one or two ClO4- anions at a longer distance (2.311 Å for 1B, 2.593 Å for 2B, and 2.706 Å for 3B). Thus, complexes 1B and 2B show the typical pattern for CuII having square-pyramidal (1B) and elongated-octahedral (2B) coordination geometries. The magnetic orbital will be in the x2 - y2 orbital in the three cases, and thus, g| > g⊥ > 2.00. For 1B this pattern is g| ) 2.33 and g⊥ > 2.07 (gav ) 2.16, in perfect agreement with the g value calculated from susceptibility measurements). For 2B this pattern is g| ) 2.35 and g⊥ > 2.07 (gav ) 2.16, in perfect agreement with the g value calculated from susceptibility measurements). For 3B, the pattern is somewhat different, with two g values of the same intensity at 2.24 and 2.05, which may indicate some influence of the crystal packing or sample impurity. Conclusion

Figure 11. Temperature dependence of χmT for (a) 1B, (b) 2B, and (c) 3B.

value from χmT at room temperature is 2.16 cm3 mol-1 K. 2B and 3B also exhibit similar behavior. For 2B χmT values start at 0.4375 cm3 mol-1 K at 300 K and finish at 0.4302 cm3 mol-1 K at 2 K. This small variation is indicative of Curie-Weiss law with the Weiss constant Θ ) -0.033 K. The calculated g value from the χmT at room temperature is 2.16. For 3B χmT values start at 0.4294 cm3 mol-1 K at 300 K and finish at 0.42101 cm3 mol-1 K at 2 K. This small variation is indicative of Curie-Weiss law with the Weiss constant Θ ) -0.041 K. The g value calculated from χmT at room temperature is 2.14. Thus, in fact, the susceptibility data indicate that the CuII ions are not coupled in the three complexes. The small decreases in χmT at very low temperatures could indicate a very small antiferromagnetic coupling, with J values very close to 0 cm-1. The calculation of these J values would be without any chemical sense. It can be pointed out that the calculated Weiss (Θ) parameters do not follow the number of C atoms in the bridged chain (two for complex 1B, three for complex

The coordination chemistry of CuII with flexible disulfoxide ligands has been systematically studied. Ten CuII coordination architectures showing diverse structural types with three series of flexible disulfoxide ligands, along with a comparison with other similar complexes already published, have been reported. Three different kinds of ligand configurations were found in the complexes: meso (R,S) and rac (R,R and S,S), despite the fact that meso ligands were always used as starting reagents, thus showing a configuration inversion in the process of complex formation at room temperature. The structural differences between such complexes reveal that the spacer lengths and terminal groups of the ligands have great influence on the complex structures. This approach may be useful for synthesizing other complexes with high-dimensional structures. Acknowledgment. This work was supported by the National Science Funds for Distinguished Young Scholars of China (No. 20225101) and the NSFC (No. 20373028). Supporting Information Available: EPR spectra for 1B-3B and crystallographic data in CIF format for all complexes. This material is available free of charge via the Internet at http://pubs.acs.org.

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