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Structural diversity of four novel cadmium coordination polymers constructed by 1,4-bis(imidazol-1-yl)butane and anion ligands
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Journal of Molecular Structure 875 (2008) 527–539 www.elsevier.com/locate/molstruc
Structural diversity of four novel cadmium coordination polymers constructed by 1,4-bis(imidazol-1-yl)butane and anion ligands Yu-Mei Zhang a, Li-Yan Wang a, Bao-Long Li a
a,b,*
, Jian-Hu Yang a, Yong Zhang
a
Key Laboratory of Organic Synthesis of Jiangsu Province, College of Chemistry and Chemical Engineering, Suzhou University, Suzhou 215123, PR China b State Key Laboratory of Coordination Chemistry, Nanjing University, Nanjing 210093, PR China Received 15 March 2007; received in revised form 8 June 2007; accepted 11 June 2007 Available online 21 June 2007
Abstract The reaction of the flexible bis(imidazole) ligand 1,4-bis(imidazol-1-yl)butane (bimb) with corresponding Cd(II) salts (NCS, dicyanamide (dca), N3 , ClO4 ) yields four new coordination polymers, from 1D to 3D networks, namely [Cd(bimb)2(NCS)2]n (1), [Cd(bimb)(dca)2]n (2), [Cd(bimb)(N3)2]n (3) and {[Cd(bimb)3](ClO4)2}n (4). In 1, each Cd(II) atom links two Cd(II) atoms by double bimb ligands and extends to form an one-dimensional chain structure containing the Cd2(bimb)2 22-membered metallocycle. In 2, double l1,5dca bridges connect the Cd(II) atoms to form the zigzag [Cd(dca)2]n chains and extend through bimb long bridges in four different directions alternatively to construct a novel three-dimensional network. In 3, double end-to-end (EE) and double end-on (EO) azide short bridges alternatively link Cd(II) atoms to form the [Cd(N3)2]n chains containing both eight- and four-membered metallocycles which further extend via bimb long bridges in four different directions alternatively to result a three-dimensional network. Compound 4 comprises two equivalent, mutually interpenetrating three-dimensional networks. 2007 Elsevier B.V. All rights reserved. Keywords: Cadmium complex; Bis(imidazol-1-yl)butane; Crystal structure; Coordination polymer; Anion ligand
1. Introduction Recent considerable attention has been paid to the metal coordination polymers for their intriguing structures and potential application as functional materials [1]. Several factors such as the coordination geometry of the central atom, the structural characteristics of the ligand molecule, the solvent system and the counterions can play the key role for the construction of the coordination networks. The selection of the ligand is no doubt very important for the design and construction of the coordination networks. In contrast to the rigid ligands with little or no conformational changes when they interact with the metal ions, the flexible ligands have much more possible coordination modes than the rigid ones
*
Corresponding author. E-mail address: [email protected] (B.-L. Li).
0022-2860/$ - see front matter 2007 Elsevier B.V. All rights reserved. doi:10.1016/j.molstruc.2007.06.006
because the flexible ligands can adopt different conformations according to the geometric needs of the different metal ions [2]. The anion ligands pseudohalide thiocyanate (SCN) [3], azide (N3 Þ [4] and dicyanamide (dca) ([N(CN)2]) [5] are widely used to construct the novel coordination polymers because of their versatile coordination modes and the ability to mediate strong magnetic coupling. In our previous work, we have synthesized a number of novel coordination polymers with the flexible bis(triazole) ligands 1,2-bis(1,2,4-triazol-1-yl)ethane (bte) [6], 1,4bis(1,2,4-triazol-1-yl)butane (btb) [7] and 1,4-bis(1,2,4-triazol-1-methyl)benzene (bbtz) [8]. 1,4-Bis(imidazol-1-yl)butane (bimb) is a very effective bridging ligand for construction of the coordination polymers [9]. The combination of the long flexible ligand bimb and short anion ligands (SCN, N3 and [N(CN)2]) can give rise to novel topologies. In order to extend our work, we synthesized four novel Cd(II) coordination polymers using the flexible
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ligand 1,4-bis(imidazol-1-yl)butane and anion coligands NCS, dicyanamide (dca) and N3 , namely [Cd(bimb)2(NCS)2]n (1), [Cd(bimb)(dca)2]n (2), [Cd(bimb)(N3)2]n (3) and {[Cd(bimb)3](ClO4)2}n (4). We report herein the synthesis and structures of the four Cd(II) coordination polymers.
crystals suitable for X-ray analysis were obtained after one month. Yield: 72%. Anal. calc. for C22H28CdN10S2: C, 43.39; H, 4.63; N, 23.00. Found: C, 43.31; H, 4.52; N, 22.86%. IR data (cm1): 3450w, 3110w, 2068vs, 1613w, 1520m, 1451w, 1389w, 1281w, 1235w, 1088m, 1034w, 934w, 826w, 764w, 656w, 625w, 533w, 471w.
2. Experimental section
2.2.2. [Cd(bimb)(dca)2]n (2) The synthetic procedure was similar to the synthesis of 1, except that Na[N(CN)2] (Na[dca]) was used instead of KNCS. Yield: 76%. Anal. calc. for C14H14CdN10: C, 38.68; H, 3.25; N, 32.23. Found: C, 36.62; H, 3.21; N, 32.16%. IR data (cm1): 3126w, 2292s, 2230m, 2169vs, 1636w, 1520m, 1443w, 1343m, 1281w, 1235w, 1088m, 1042w, 934w, 834w, 749w, 656w, 625w, 525w, 455w.
2.1. General procedures All reagents were of analytical grade and used without further purification. 1,4-Bis(imidazol-1-yl)butane (bimb) was synthesized according to the literature method [9b]. Elemental analyses for C, H and N were performed on a Perkin–Elmer 240C analyser. X-ray power diffractions (XRD) were performed on a D/MAX-3C diffractometer ˚ ) at room temperawith the Cu Ka radiation (k = 1.5406 A ture. IR spectra were obtained for KBr pellets on a Nicolet 170SX FT-IR spectrophotometer in the 4000–400 cm1 region. TG and DSC analysis was measured on a Thermal Analyst 2100 TA Instrument and SDT 2960 Simutaneous TGA-DTA Instrument in flowing dinitrogen at a heating rate 10 C/min.
2.2.3. [Cd(bimb)(N3)2]n (3) The synthetic procedure was similar to the synthesis of 1, except that NaN3 was used instead of KNCS. Yield: 78%. Anal. calc. for C10H14CdN10: C, 31.06; H, 3.65; N, 36.23. Found: C, 31.02; H, 3.63; N, 36.14%. IR data (cm1): 3419w, 2046vs, 1641w, 1517w, 1449w, 1388w, 1336w, 1336w, 1289w, 1232w, 1088m, 1037w, 935w, 826w, 742w, 656m, 618w.
2.2. Preparation of the complexes 2.2.1. [Cd(bimb)2(NCS)2]n (1) An aqueous (20 mL) solution of Cd(NO3)2 4H2O (0.154 g, 0.5 mmol) and KSCN (0.097 g, 1.0 mmol) was added to one side of a ‘‘H-shape’’ tube, and a methanolic solution (20 mL) of bimb (0.190 g, 1.0 mmol) was added to the another side of the ‘‘H-shape’’ tube. The colorless
2.2.4. {[Cd(bimb)3](ClO4)2}n (4) The synthetic procedure was similar to the synthesis of 1, except that Cd(ClO4)2 6H2O was used instead of Cd(NO3)2Æ4H2O and KSCN. Yield: 64%. Anal. calc. for C30H42CdCl2N12O8: C, 40.85; H, 4.80; N, 19.06. Found: C, 40.57; H, 4.61; N, 18.91. IR data (cm1): 3126w, 1621w, 1520m, 1466w, 1382w, 1281w, 1234w, 1096vs,
Table 1 Crystallographic data for 1–4
Formula Fw Crystal system Space group Temp (K) ˚) a (A ˚) b (A ˚) c (A a () b () c () V (A˚3) Z qcalc(g/cm3) l (mm1) F(0 0 0) Reflections collected Unique reflections Parameters Goodness of fit R1 [I > 2r(I)] wR2 (all data)
1
2
3
4
C22H28CdN10S2 609.06 Monoclinic P21/c 153 (2) 9.0805 (13) 9.6021 (14) 14.556 (2) 90 90.301 (3) 90 1269.1 (3) 2 1.594 1.057 620 12000 2311 [R(int) = 0.0260] 161 1.028 0.0234 0.0575
C14H14CdN10 434.75 Triclinic P1 173 (2) 8.8884 (14) 9.9069 (16) 11.4065 (18) 103.168 (2) 104.716 (2) 110.765 (2) 850.4 (2) 2 1.698 1.304 432 8200 3074 [R(int) = 0.0332] 227 1.074 0.0443 0.1451
C10H14CdN10 386.71 Monoclinic P21/c 153 (2) 8.6373 (7) 19.7418 (14) 8.6117 (7) 90 101.893 (2) 90 1436.91 (19) 4 1.788 1.531 768 15595 3265 [R(int) = 0.0312] 191 1.058 0.0279 0.0607
C30H42CdCl2N12O8 882.39 Triclinic P1 153 (2) 9.9577 (7) 22.6327 (13) 27.1552 (17) 72.219 (3) 89.388 (4) 85.908 (4) 5812.4 (6) 6 1.512 0.764 2712 56706 21070 [R(int) = 0.0288] 1436 1.097 0.0405 0.0983
Y.-M. Zhang et al. / Journal of Molecular Structure 875 (2008) 527–539 Table 2 ˚ ) and angles (o) for1–4 Selected bond lengths (A
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Table 2 (continued)
1 Cd1AN2 Cd1AN5 N2ACd1AN4C N4CACd1AN5 Cd1AN5AC11
2.3108(17) 2.343(2) 89.51(6) 89.01(7) 151.84(18)
Cd1AN4C N2ACd1AN5 N5AC11AS1
89.37(7) 179.3(2)
2 Cd1AN2 Cd1AN6 Cd1AN9 N5AC11 N6AC11 N8AC14 N9AC13 N2ACd1AN4 N2ACd1AN7C N2ACd1AN10D N4ACd1AN7C N4ACd1AN10D N6ACd1AN9 N7CACd1AN9 N9ACd1AN10D C14AN8AC13 N5AC12AN7 N8AC14AN10
2.279(4) 2.379(5) 2.332(5) 1.298(7) 1.164(7) 1.285(7) 1.147(7) 87.83(15) 90.27(16) 91.02(16) 92.20(17) 90.52(15) 84.40(17) 93.53(17) 85.16(17) 123.3(5) 173.4(5) 171.7(5)
Cd1AN4 Cd1AN7C Cd1AN10D N5AC12 N7AC12 N8AC13 N10AC14 N2ACd1AN6 N2ACd1AN9 N4ACd1AN6 N4ACd1AN9 N6ACd1AN7C N6ACd1AN10D N7CACd1AN10D C11AN5AC12 N5AC11AN6 N8AC13AN9
2.317(4) 2.341(5) 2.354(4) 1.304(7) 1.157(7) 1.310(7) 1.154(7) 95.26(16) 176.17(13) 176.89(14) 92.55(16) 87.40(17) 89.82(16) 177.03(13) 121.8(5) 172.5(6) 173.0(5)
3 Cd1AN2 Cd1AN5 Cd1AN8 N2ACdAN4A N2ACd1AN7B N2ACd1AN8C N4AACd1AN7B N4AACd1AN8C N5ACd1AN8 N7BACd1AN8 N8ACd1AN8C N8AN9AN10 Cd1AN8AN9
2.296(2) 2.362(2) 2.284(2) 96.74(8) 167.55(8) 89.55(7) 88.94(8) 84.33(7) 100.41(9) 84.72(8) 74.85(8) 178.3(3) 115.82(17)
Cd1AN4A Cd1AN7B Cd1AN8C N2ACd1AN5 N2ACd1AN8 N4AACd1AN5 N4AACd1AN8 N5ACd1AN7B N5ACd1AN8C N7BACd1AN8C N5AN6AN7 Cd1AN5AN6
2.270(2) 2.449(2) 2.505(2) 86.12(8) 94.15(8) 101.18(9) 156.39(8) 81.90(8) 173.34(8) 102.07(7) 177.0(3) 117.05(18)
4 Cd1AN2 Cd1AN10 Cd1AN14 Cd2AN4 Cd2AN22 Cd3AN24 Cd3AN30 Cd3AN34 Cd4AN26 N2ACd1AN6 N2ACd1AN12 N2ACd1AN16 N6ACd1AN12 N6ACd1AN16 N10ACd1AN14 N12ACd1AN14 N14ACd1AN16 N4ACd2AN22 N20ACd3AN24 N20ACd3AN30 N20ACd3AN34 N24ACd3AN30 N24ACd3AN34 N28ACd3AN32
2.344(2) 2.371(2) 2.367(2) 2.351(2) 2.363(2) 2.370(2) 2.360(2) 2.356(2) 2.367(2) 91.76(8) 176.82(9) 92.05(8) 89.08(8) 89.28(8) 92.21(8) 88.71(8) 88.75(8) 92.09(8) 88.72(8) 91.78(8) 89.09(8) 88.35(8) 89.87(8) 92.34(8)
Cd1AN6 Cd1AN12 Cd1AN16 Cd2AN18 Cd3AN20 Cd3AN28 Cd3AN32 Cd4AN8 Cd4AN36 N2ACd1AN10 N2ACd1AN14 N6ACd1AN10 N6ACd1AN14 N10ACd1AN12 N10ACd1AN16 N12ACd1AN16 N4ACd2AN18 N18ACd2AN22 N20ACd3AN28 N20ACd3AN32 N24ACd3AN28 N24ACd3AN32 N28ACd3AN30 N28ACd3AN34
2.3615(17)
N30ACd3AN32 N32ACd3AN34 N8ACd4AN36
89.25(8) 89.79(8) 90.29(8)
N30ACd3AN34 N8ACd4AN26 N26ACd4AN36
178.01(8) 90.21(8) 89.75(8)
Symmetry codes: 1 A x + 1, y + 1, z + 1 B x 1, y, z C x + 2, y + 1, z + 1; 2 A x 1, y, z 1 C x, y + 1, z D x + 1, y + 1, z + 1; 3 A x + 1, y + 1/2, z 1/2 B x + 1, y + 1, z C x, y + 1, z; 4 A x + 1, y, z + 1 B x + 3, y + 2, z.
934w, 834w, 772w, 741w, 664w, 625w, 548w, 509w, 425w. 2.3. X-ray crystallography Suitable single crystals of 1–4 were carefully selected under an optical microscope and glued to thin glass fibers. The diffraction data were collected on a Rigaku Mercury CCD diffractometer with graphite monochro˚ ). Intensities were mated Mo Ka radiation (k = 0.71073 A collected by the x scan technique. The structures were solved by direct methods and refined with full-matrix least-squares technique (SHELXTL-97) [10]. The positions of hydrogen atoms were determined with theoretical calculation. The residual peaks of 2 are high. The largest five residual peaks of 2 are 3.40, 3.01, 2.87, ˚ 3, which are located at (0.0734 2.50 and 2.50 e/A 0.1963 0.2459), (0.1549 0.1170 0.2472), (0.1166 0.3869 0.2525), (0.1992 0.4670 0.2512) and (0.2492 0.0228 0.2415), respectively. The parameters of the crystal data collection and refinement of 1–4 are given in Table 1. Selected bond lengths and bond angles are listed in Table 2. 3. Results and discussion 3.1. Crystal structures
2.347(2) 2.364(2) 2.363(2) 2.368(2) 2.360(2) 2.343(2) 2.364(2) 2.339(2) 2.364(2) 90.55(8) 90.56(8) 89.66(8) 177.01(8) 86.39(8) 177.22(8) 91.02(8) 90.06(8) 91.24(8) 90.86(8) 176.63(8) 179.07(9) 88.10(8) 90.83(8) 90.95(8)
3.1.1. [Cd(bimb)2(NCS)2]n (1) Compound 1 has the one-dimensional chain structure containing double bridges of bimb ligands (Fig. 1) [3c,6b,6c]. Each Cd(II) center in 1 is coordinated to four imidazole nitrogen atoms from four different bimb ˚, ligands in the equatorial plane [Cd1AN2 2.3108(17) A ˚ Cd1AN4C 2.3615(17) A], and two nitrogen atoms from ˚ ] in the apial two thiocyanate ions [Cd1AN5 2.343(2) A positions. Each Cd(II) atom connects to other Cd(II) atoms by two bimb ligands, resulting the Cd2(bimb)2 22-membered metallocycle. Two stranded of bimb ligands are wrapped around each other and are held together by Cd(II) atoms, forming a double chain structure. The bimb ligands exhibit the gauche–anti-gauche conformation. The plane of N(CH2)4N chain steeply inclined, by 96.9 and 76.8, to the two imidazole ring planes. The torsion angle of the butane chain is 83.198(8). The Cd Cd distances separated via the bridging bimb ˚. is 9.081 A
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Fig. 1. The one-dimensional double chain structure along the a direction in 1 (A 1 x, 1 y, 1 z; B 1 + x, y, z; C 2 x, 1 y, 1 z; D 1 + x, y, z).
3.1.2. [Cd(bimb)(dca)2]n (2) and [Cd(bimb)(N3)2]n (3) As can be seen from Fig. 2(a), every Cd(II) atom in 2 is coordinated by six nitrogen atoms, two from two bimb ˚; ligands in the cis-positions (Cd1AN2 2.279(4) A ˚ ) and the others from four dicyanaCd1AN4 2.317(4) A ˚; mide ligands (Cd1AN6 2.379(5) A Cd1AN7C ˚; ˚; 2.341(5) A Cd1AN9 2.332(5) A Cd1AN10D ˚ ), in the distorted octahedral geometry. The 2.354(4) A CdAN bond lengths are similar to those in 1. The NACdAN bond angles are in the range of 84.40(17)– 95.60(17). There are two symmetry independent dicyanamide ligands (N6AC11AN5AC12AN7 and N9AC13AN8AC14AN10) and they both act as bismonodentate bridges. The double dicyanamide ligands link the Cd(II) atoms to form Cd2(dca)2 12-membered metallacycle and further extend to result a one-dimensional zigzag [Cd(dca)2]n chain (Fig. 2b). The Cd1 Cd1C and Cd1 Cd1D separations via the ˚, dicyamamide ligands are 7.7316(9) and 7.8586(10) A respectively (Fig. 2a). The Cd1 Cd1A and Cd1 Cd1B separations via the bimb ligands are ˚ , respectively. There are 12.5282(13) and 13.9266(21) A also two symmetry independent bimb ligands (N1/N2/ C1–C5 and N3/N4/C6–C10) and they both have the center symmetry. The N1/N2/C1–C5 bimb ligand exhibits the gauche–anti-gauche conformation with the torsion angle C1AAC1AC2AN1 58.821(14) and the plane of N(CH2)4N chain steeply inclined, by 80.7, to the imidazole ring planes. While the N3/N4/C6–C10 bimb ligand exhibits the completely anti (anti-anti-anti) conformation with the torsion angle C6BAC6AC7AN3A171.776(10) and the plane of N(CH2)4N chain steeply inclined, by 102.6, to the imidazole ring planes. Along the [Cd(dca)2]n chain, the bimb lignads point in four different directions alternatively (Fig. 2c). So each [Cd(dca)2]n chain links four adjacent [Cd(dca)2]n chains through the bimb bridges, leading to the novel threedimensional network with the one-dimensional channel ˚ · 13.9 A ˚ (Fig. 2d). The similar 1,2-bis(imica. 18.6 A
dazol-1-yl)ethane complex [Cd(1,2-bis(imidazol-1-yl)ethane)(dca)2] has an one-dimensional triple chain structure [11]. The structure of 3 has the part of similar properties as that of 2. As can be seen from Fig. 3a, every Cd(II) atom in 3 is coordinated by six nitrogen atoms, two from two bimb ligands in the cis-positions (Cd1AN2 ˚ ; Cd1AN4A 2.270(2) A ˚ ) and the others from 2.296(2) A ˚ ; Cd1AN7B four azide ligands (Cd1AN5 2.362(2) A ˚ ; Cd1AN8 2.284(2) A ˚ ; Cd1AN8C 2.505(2) A ˚ ), 2.449(2) A in the distorted octahedral coordination environment. The bond lengths Cd1AN7B and Cd1AN8C are obviously longer these in 1 and 2. The bond angle N8ACd1AN8C is 74.85(8), is obviously deviated from 90. The azide ligands exhibit two kinds of coordination modes. One is end-to-end (EE) coordination mode. The other is end-on (EO) coordination mode. The double EEazide ligands and double EO-azide ligands alternatively link the Cd(II) atoms to form a one-dimensional zigzag [Cd(N3)2]n chain (Fig. 3b). The Cd1 Cd1B and Cd1 Cd1C separations via the EE-azide and EO-azide ˚ , respectively. There ligands are 5.5774(4) and 3.8056(3) A is one symmetry independent bimb ligand in 3. The Cd Cd1 separations via the bimb ligands are ˚ . The bimb ligand exhibits the completely anti 13.3973(7) A (anti-anti-anti) conformation with the torsion angle C1AC2AC3AC4 178.5(2) and the plane of N(CH2)4N chain steeply inclined, by 14.0 and 100.5, to the two imidazole ring planes. The dihedral angle between two imidazole ring planes is 88.4. Along the [Cd(N3)2]n chain, the bimb lignads point in four different directions alternatively (Fig. 3c). So each [Cd(dca)2]n chain links four adjacent [Cd(N3)2]n chains through the bimb bridges, leading the novel three-dimensional network with the one-dimensional channel ca. ˚ · 13.9A ˚ (Fig. 3d). 18.6 A Previously we reported a similar coordination polymer [Mn(bim)(N3)2]n (bim = 1,2-bis(imidazole-1-yl)ethane)
Y.-M. Zhang et al. / Journal of Molecular Structure 875 (2008) 527–539
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Fig. 2. (a) Coordination environment of Cd1 in 2 (Symmetry codes: A 1 x, y, 1 z; B 1 x, 1 y, z; C x, 1 y, z; D 1 x, 1 y, 1 z). (b) One-dimensional chain structure bridged by bis-monodentate dicyanamide ligands in 2. (c) Connections between the adjacent chains in 2. (d) The three-dimensional topology of 2. The long sticks represent the bimb ligands and the short ones double dicyanamide ligands in 2.
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Y.-M. Zhang et al. / Journal of Molecular Structure 875 (2008) 527–539
Fig. 2 (continued)
which has a similar three-dimensional network constructed through one-dimensional double end-on azidebridged Mn(II) chains and extended through the antibim ligands [6a]. The difference is that the azide ligands has one coordination mode (end-on) in [Mn(bim)(N3)2]n but two different coordination modes (end-to-end and end-on) in 3. If a dimer Mn(II) bridged by azide is considered as one node, the structure of [Mn(bim)(N3)2]n can be viewed as a simple cubic topology. If a dimer Cd(II) bridged by azide or dicyanamide is also considered as one node, the structure of 3 and 2 can be also viewed as a simple cubic topology. 3.1.3. {[Cd(bimb)3](ClO4)2}n (4) The structure of 4 is similar to [Mn(bimb)3](BF4)2 [9a], [Mn(bimb)3](ClO4)2 and the analogous compounds containing combinations of ClO4 =PF6 or ClO4 =AsF6 [9b], and comprises two equivalent, mutually interpenetrating three-dimensional networks. As shown in Fig. 4a, there are four independent Cd(II) atoms and each of them is coordinated by six nitrogen atoms from six bimb ligands. There are ten independent bimb ligands. All bimb ligands exhibit the completely anti conformation. The torsion angles of the butane chains of ten independent bimb ligands are in the range of 175.443(10)–180.00(1). The planes of N(CH2)4N chains steeply inclined, by in the range of 56.1–118.4, to the imidazole ring planes. The CdAN bond lengths are sim-
˚ and the ilar in the ranges of 2.339(2)–2.371(2) A NACdAN bond angles are in the range of 86.39(8)– 93.71(8). Each bimb ligand bridges two Cd(II) atoms and each Cd(II) atom links six Cd(II) atoms via six bimb ligands along six directions, resulting the three-dimensional network (Fig. 4b and c). The Cd Cd separa˚ . Two tions are in the range of 14.1666(8)–14.6212(9) A equivalent three-dimensional networks interpenetrate each other to form interpenetrating three-dimensional network (Fig. 4d). 3.2. Syntheses, XRD, IR and thermal properties of the complexes As pseudohalide thiocyanate (SCN), azide ðN3 Þ and dicyanamide (dca) ([N(CN)2]) not only can act as counter anions to sustain charge neutral but also have various coordination modes, they can provide the suitable building block for assembling novel coordination polymers. We want to introduce these anionic ligands into the Cd/bimb reaction mixture as co-ligands in order to prepare the novel complexes. Our combinations of bimb, pseudohalide thiocyanate (SCN), azide ðN3 Þ and dicyanamide (dca) ([N(CN)2]) with Cd(II) salts have synthesized four new coordination polymers. The anions play an key role in the construction of motifs. Each motif is efficiently constructed irrespective of the stoichiometry and the concentration. The Cd(II) complexes 1–4
Y.-M. Zhang et al. / Journal of Molecular Structure 875 (2008) 527–539
were synthesized by the diffuse methods because the synthesis of Cd(II) complexes was unsuccessful by the direct reactions.
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The experimental power diffraction patterns of 1–4 (Figs. 5–8) are in agreement with that calculated for the four coordination polymers.
Fig. 3. (a) Coordination environment of Cd1 in 3 (Symmetry codes: A 1 + x, 0.5 y, 0.5 + z; B 1 x, 1 y, z; C x, 1 y, z). (b) The onedimensional chain structure bridged by the alternative EE-azide and EO-azide ligands along the a direction in 3. (c) Connections between adjacent chains in 3. (d) Three-dimensional topology of 3. The long sticks represent the bimb ligands and the short ones azide lignads.
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Fig. 3 (continued )
The IR spectrum determination shows that the imidazole ring vibrations in complexes 1–4 are at 1520 and 1281, 1520 and 1281, 1517 and 1289, 1520 and 1281 cm1, respectively [3c]. The strong absorptions at 2068 cm1 for 1 indicate the C@N stretching vibration of the thiocyanate group, which is consistent with the occurrence of thiocyanate-N coordination [3]. The strong absorptions of at 2292, 2230 and 2169 cm1 for 2 are assigned to the C„N symmetric stretch band (msym), the asymmetric stretch band (masym) and the combination band of msym and masym of dca [3c,4]. The bigger shift (2292 cm1) for 2 towards high frequencies, confirmed that dca bis-monodentate coordinated to metal center. Two absorptions at 2046 and 2059 cm1 for 3 show two different coordination modes of azide anions and which is confirmed by X-ray diffraction. The strong absorption band at 1096 cm1 for 4 is assigned to ClO4 anions. The TGA studies showed that 1–4 are stable under 200 C, and decomposition begins at 268, 227, 239 and 272 C, respectively. 4. Conclusion The reaction of the flexible bis(imidazole) ligand 1,4bis(imidazol-1-yl)butane (bimb) with Cd(II) salts (NCS, dicyanamide (dca), N3 , ClO4 Þ yields four new organic-inorganic hybrid frameworks. [Cd(bimb)2 (NCS)2]n (1) is one-dimensional chain structure contain-
ing double bridges of bimb ligands. [Cd(bimb)(dca)2]n (2) is a novel three-dimensional network, in which double l1,5-dca bridges connect the Cd(II) atoms to form the zigzag [Cd(dca)2]n chains and extend through bimb long bridges in four different directions alternatively to construct a novel three-dimensional network. [Cd(bimb) (N3)2]n (3) is also a three-dimensional network contains double end-to-end (EE) and double end-on (EO) azide short bridges. {[Cd(bimb)3](ClO4)2}n (4) comprises two equivalent, mutually interpenetrating three-dimensional networks. The Cd–bimb complex {[Cd(bimb)1.5(H2O)2(SO4)]4H2O}n (5) previous reported by Ma and co-workers is composed of a two-dimensional (6,3) network with the hexagonal smallest circuit containing six Cd(II) atoms and six bimb ligands [9c]. [Cd(bimb)2Cl2]n (6) is a two-dimensional (4,4) network [9f]. The six Cd–bimb complexes illustrate the diversity of structures that can be obtained by using bimb ligand and anion ligands. The combination of long flexible ligand and short anion ligand seems to be a successful way to assemble novel coordination frameworks. The anions play an key role in structural assembly of Cd–bimb complexes (1: 1D chain for NCS; 2: 3D network for [N(CN)2] (dca); 3: 3D network for N3 ; 4: interpenetrating 3D network for ClO4 ; 5: 2D (6,3) network for SO4 2- ; 6: 2D (4,4) network for Cl). However, it is still a great challenge to design and assemble the programmed coordination frameworks by coordination bonds and more work is still need to extend this
Y.-M. Zhang et al. / Journal of Molecular Structure 875 (2008) 527–539
knowledge. In summary, this work is expected to provide new information for understanding and developing of the crystal engineering of coordination frameworks.
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Further designation and synthesis of new motifs with bimb and different metal salts, are under way in our lab.
Fig. 4. (a) The coordination environment of the four independent Cd(II) atoms in 4 (Symmetry codes: A 1 x, y, 1 z; B 3 x, 2 y, z). (b) The distorted cubic network in 4, the ClO4 anions are omitted. (c) The distorted cubic topology in 4. (d) The two interpenetrating distorted cubic topology in 4.
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Fig. 4 (continued )
Y.-M. Zhang et al. / Journal of Molecular Structure 875 (2008) 527–539
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2θ ( ) Fig. 6. Observed (a) and calculated (b) X-ray power diffraction patterns of 2.
Acknowledgments
Appendix A. Supplementary data
This work was supported by the Natural Science Foundation of China (No. 20671066), the Jiangsu Province (No. BK2006049), the Funds of Key Laboratory of Organic Synthesis of Jiangsu Province (No. KJS0612) and State Key Laboratory of Coordination Chemistry.
Crystallographic data for the structural analyses have been deposited with the Cambridge Crystallographic Data Centre, with CCDC refere7nce numbers CCDC-612540 for 1, CCDC-612541 for 2, CCDC-612542 for 3, CCDC612543 for 4. Supplementary data associated with this
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2θ ( ) Fig. 7. Observed (a) and calculated (b) X-ray power diffraction patterns of 3.
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2θ ( ) Fig. 8. Observed (a) and calculated (b) X-ray power diffraction patterns of 4.
article can be found, in the online version, at doi:10.1016/ j.molstruc.2007.06.006. References [1] (a) S.R. Batten, R. Robson, Angew. Chem. Int. Ed. 37 (1998) 1460; (b) P.J. Hagrman, D. Hagrmam, J. Zubieta, Angew. Chem. Int. Ed. 38 (1999) 2638; (c) S. Leininger, B. Olenyuk, P.J. Stang, Chem. Rev. 100 (2000) 853;
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Journal of Molecular Structure 875 (2008) 527–539 www.elsevier.com/locate/molstruc
Structural diversity of four novel cadmium coordination polymers constructed by 1,4-bis(imidazol-1-yl)butane and anion ligands Yu-Mei Zhang a, Li-Yan Wang a, Bao-Long Li a
a,b,*
, Jian-Hu Yang a, Yong Zhang
a
Key Laboratory of Organic Synthesis of Jiangsu Province, College of Chemistry and Chemical Engineering, Suzhou University, Suzhou 215123, PR China b State Key Laboratory of Coordination Chemistry, Nanjing University, Nanjing 210093, PR China Received 15 March 2007; received in revised form 8 June 2007; accepted 11 June 2007 Available online 21 June 2007
Abstract The reaction of the flexible bis(imidazole) ligand 1,4-bis(imidazol-1-yl)butane (bimb) with corresponding Cd(II) salts (NCS, dicyanamide (dca), N3 , ClO4 ) yields four new coordination polymers, from 1D to 3D networks, namely [Cd(bimb)2(NCS)2]n (1), [Cd(bimb)(dca)2]n (2), [Cd(bimb)(N3)2]n (3) and {[Cd(bimb)3](ClO4)2}n (4). In 1, each Cd(II) atom links two Cd(II) atoms by double bimb ligands and extends to form an one-dimensional chain structure containing the Cd2(bimb)2 22-membered metallocycle. In 2, double l1,5dca bridges connect the Cd(II) atoms to form the zigzag [Cd(dca)2]n chains and extend through bimb long bridges in four different directions alternatively to construct a novel three-dimensional network. In 3, double end-to-end (EE) and double end-on (EO) azide short bridges alternatively link Cd(II) atoms to form the [Cd(N3)2]n chains containing both eight- and four-membered metallocycles which further extend via bimb long bridges in four different directions alternatively to result a three-dimensional network. Compound 4 comprises two equivalent, mutually interpenetrating three-dimensional networks. 2007 Elsevier B.V. All rights reserved. Keywords: Cadmium complex; Bis(imidazol-1-yl)butane; Crystal structure; Coordination polymer; Anion ligand
1. Introduction Recent considerable attention has been paid to the metal coordination polymers for their intriguing structures and potential application as functional materials [1]. Several factors such as the coordination geometry of the central atom, the structural characteristics of the ligand molecule, the solvent system and the counterions can play the key role for the construction of the coordination networks. The selection of the ligand is no doubt very important for the design and construction of the coordination networks. In contrast to the rigid ligands with little or no conformational changes when they interact with the metal ions, the flexible ligands have much more possible coordination modes than the rigid ones
*
Corresponding author. E-mail address: [email protected] (B.-L. Li).
0022-2860/$ - see front matter 2007 Elsevier B.V. All rights reserved. doi:10.1016/j.molstruc.2007.06.006
because the flexible ligands can adopt different conformations according to the geometric needs of the different metal ions [2]. The anion ligands pseudohalide thiocyanate (SCN) [3], azide (N3 Þ [4] and dicyanamide (dca) ([N(CN)2]) [5] are widely used to construct the novel coordination polymers because of their versatile coordination modes and the ability to mediate strong magnetic coupling. In our previous work, we have synthesized a number of novel coordination polymers with the flexible bis(triazole) ligands 1,2-bis(1,2,4-triazol-1-yl)ethane (bte) [6], 1,4bis(1,2,4-triazol-1-yl)butane (btb) [7] and 1,4-bis(1,2,4-triazol-1-methyl)benzene (bbtz) [8]. 1,4-Bis(imidazol-1-yl)butane (bimb) is a very effective bridging ligand for construction of the coordination polymers [9]. The combination of the long flexible ligand bimb and short anion ligands (SCN, N3 and [N(CN)2]) can give rise to novel topologies. In order to extend our work, we synthesized four novel Cd(II) coordination polymers using the flexible
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ligand 1,4-bis(imidazol-1-yl)butane and anion coligands NCS, dicyanamide (dca) and N3 , namely [Cd(bimb)2(NCS)2]n (1), [Cd(bimb)(dca)2]n (2), [Cd(bimb)(N3)2]n (3) and {[Cd(bimb)3](ClO4)2}n (4). We report herein the synthesis and structures of the four Cd(II) coordination polymers.
crystals suitable for X-ray analysis were obtained after one month. Yield: 72%. Anal. calc. for C22H28CdN10S2: C, 43.39; H, 4.63; N, 23.00. Found: C, 43.31; H, 4.52; N, 22.86%. IR data (cm1): 3450w, 3110w, 2068vs, 1613w, 1520m, 1451w, 1389w, 1281w, 1235w, 1088m, 1034w, 934w, 826w, 764w, 656w, 625w, 533w, 471w.
2. Experimental section
2.2.2. [Cd(bimb)(dca)2]n (2) The synthetic procedure was similar to the synthesis of 1, except that Na[N(CN)2] (Na[dca]) was used instead of KNCS. Yield: 76%. Anal. calc. for C14H14CdN10: C, 38.68; H, 3.25; N, 32.23. Found: C, 36.62; H, 3.21; N, 32.16%. IR data (cm1): 3126w, 2292s, 2230m, 2169vs, 1636w, 1520m, 1443w, 1343m, 1281w, 1235w, 1088m, 1042w, 934w, 834w, 749w, 656w, 625w, 525w, 455w.
2.1. General procedures All reagents were of analytical grade and used without further purification. 1,4-Bis(imidazol-1-yl)butane (bimb) was synthesized according to the literature method [9b]. Elemental analyses for C, H and N were performed on a Perkin–Elmer 240C analyser. X-ray power diffractions (XRD) were performed on a D/MAX-3C diffractometer ˚ ) at room temperawith the Cu Ka radiation (k = 1.5406 A ture. IR spectra were obtained for KBr pellets on a Nicolet 170SX FT-IR spectrophotometer in the 4000–400 cm1 region. TG and DSC analysis was measured on a Thermal Analyst 2100 TA Instrument and SDT 2960 Simutaneous TGA-DTA Instrument in flowing dinitrogen at a heating rate 10 C/min.
2.2.3. [Cd(bimb)(N3)2]n (3) The synthetic procedure was similar to the synthesis of 1, except that NaN3 was used instead of KNCS. Yield: 78%. Anal. calc. for C10H14CdN10: C, 31.06; H, 3.65; N, 36.23. Found: C, 31.02; H, 3.63; N, 36.14%. IR data (cm1): 3419w, 2046vs, 1641w, 1517w, 1449w, 1388w, 1336w, 1336w, 1289w, 1232w, 1088m, 1037w, 935w, 826w, 742w, 656m, 618w.
2.2. Preparation of the complexes 2.2.1. [Cd(bimb)2(NCS)2]n (1) An aqueous (20 mL) solution of Cd(NO3)2 4H2O (0.154 g, 0.5 mmol) and KSCN (0.097 g, 1.0 mmol) was added to one side of a ‘‘H-shape’’ tube, and a methanolic solution (20 mL) of bimb (0.190 g, 1.0 mmol) was added to the another side of the ‘‘H-shape’’ tube. The colorless
2.2.4. {[Cd(bimb)3](ClO4)2}n (4) The synthetic procedure was similar to the synthesis of 1, except that Cd(ClO4)2 6H2O was used instead of Cd(NO3)2Æ4H2O and KSCN. Yield: 64%. Anal. calc. for C30H42CdCl2N12O8: C, 40.85; H, 4.80; N, 19.06. Found: C, 40.57; H, 4.61; N, 18.91. IR data (cm1): 3126w, 1621w, 1520m, 1466w, 1382w, 1281w, 1234w, 1096vs,
Table 1 Crystallographic data for 1–4
Formula Fw Crystal system Space group Temp (K) ˚) a (A ˚) b (A ˚) c (A a () b () c () V (A˚3) Z qcalc(g/cm3) l (mm1) F(0 0 0) Reflections collected Unique reflections Parameters Goodness of fit R1 [I > 2r(I)] wR2 (all data)
1
2
3
4
C22H28CdN10S2 609.06 Monoclinic P21/c 153 (2) 9.0805 (13) 9.6021 (14) 14.556 (2) 90 90.301 (3) 90 1269.1 (3) 2 1.594 1.057 620 12000 2311 [R(int) = 0.0260] 161 1.028 0.0234 0.0575
C14H14CdN10 434.75 Triclinic P1 173 (2) 8.8884 (14) 9.9069 (16) 11.4065 (18) 103.168 (2) 104.716 (2) 110.765 (2) 850.4 (2) 2 1.698 1.304 432 8200 3074 [R(int) = 0.0332] 227 1.074 0.0443 0.1451
C10H14CdN10 386.71 Monoclinic P21/c 153 (2) 8.6373 (7) 19.7418 (14) 8.6117 (7) 90 101.893 (2) 90 1436.91 (19) 4 1.788 1.531 768 15595 3265 [R(int) = 0.0312] 191 1.058 0.0279 0.0607
C30H42CdCl2N12O8 882.39 Triclinic P1 153 (2) 9.9577 (7) 22.6327 (13) 27.1552 (17) 72.219 (3) 89.388 (4) 85.908 (4) 5812.4 (6) 6 1.512 0.764 2712 56706 21070 [R(int) = 0.0288] 1436 1.097 0.0405 0.0983
Y.-M. Zhang et al. / Journal of Molecular Structure 875 (2008) 527–539 Table 2 ˚ ) and angles (o) for1–4 Selected bond lengths (A
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Table 2 (continued)
1 Cd1AN2 Cd1AN5 N2ACd1AN4C N4CACd1AN5 Cd1AN5AC11
2.3108(17) 2.343(2) 89.51(6) 89.01(7) 151.84(18)
Cd1AN4C N2ACd1AN5 N5AC11AS1
89.37(7) 179.3(2)
2 Cd1AN2 Cd1AN6 Cd1AN9 N5AC11 N6AC11 N8AC14 N9AC13 N2ACd1AN4 N2ACd1AN7C N2ACd1AN10D N4ACd1AN7C N4ACd1AN10D N6ACd1AN9 N7CACd1AN9 N9ACd1AN10D C14AN8AC13 N5AC12AN7 N8AC14AN10
2.279(4) 2.379(5) 2.332(5) 1.298(7) 1.164(7) 1.285(7) 1.147(7) 87.83(15) 90.27(16) 91.02(16) 92.20(17) 90.52(15) 84.40(17) 93.53(17) 85.16(17) 123.3(5) 173.4(5) 171.7(5)
Cd1AN4 Cd1AN7C Cd1AN10D N5AC12 N7AC12 N8AC13 N10AC14 N2ACd1AN6 N2ACd1AN9 N4ACd1AN6 N4ACd1AN9 N6ACd1AN7C N6ACd1AN10D N7CACd1AN10D C11AN5AC12 N5AC11AN6 N8AC13AN9
2.317(4) 2.341(5) 2.354(4) 1.304(7) 1.157(7) 1.310(7) 1.154(7) 95.26(16) 176.17(13) 176.89(14) 92.55(16) 87.40(17) 89.82(16) 177.03(13) 121.8(5) 172.5(6) 173.0(5)
3 Cd1AN2 Cd1AN5 Cd1AN8 N2ACdAN4A N2ACd1AN7B N2ACd1AN8C N4AACd1AN7B N4AACd1AN8C N5ACd1AN8 N7BACd1AN8 N8ACd1AN8C N8AN9AN10 Cd1AN8AN9
2.296(2) 2.362(2) 2.284(2) 96.74(8) 167.55(8) 89.55(7) 88.94(8) 84.33(7) 100.41(9) 84.72(8) 74.85(8) 178.3(3) 115.82(17)
Cd1AN4A Cd1AN7B Cd1AN8C N2ACd1AN5 N2ACd1AN8 N4AACd1AN5 N4AACd1AN8 N5ACd1AN7B N5ACd1AN8C N7BACd1AN8C N5AN6AN7 Cd1AN5AN6
2.270(2) 2.449(2) 2.505(2) 86.12(8) 94.15(8) 101.18(9) 156.39(8) 81.90(8) 173.34(8) 102.07(7) 177.0(3) 117.05(18)
4 Cd1AN2 Cd1AN10 Cd1AN14 Cd2AN4 Cd2AN22 Cd3AN24 Cd3AN30 Cd3AN34 Cd4AN26 N2ACd1AN6 N2ACd1AN12 N2ACd1AN16 N6ACd1AN12 N6ACd1AN16 N10ACd1AN14 N12ACd1AN14 N14ACd1AN16 N4ACd2AN22 N20ACd3AN24 N20ACd3AN30 N20ACd3AN34 N24ACd3AN30 N24ACd3AN34 N28ACd3AN32
2.344(2) 2.371(2) 2.367(2) 2.351(2) 2.363(2) 2.370(2) 2.360(2) 2.356(2) 2.367(2) 91.76(8) 176.82(9) 92.05(8) 89.08(8) 89.28(8) 92.21(8) 88.71(8) 88.75(8) 92.09(8) 88.72(8) 91.78(8) 89.09(8) 88.35(8) 89.87(8) 92.34(8)
Cd1AN6 Cd1AN12 Cd1AN16 Cd2AN18 Cd3AN20 Cd3AN28 Cd3AN32 Cd4AN8 Cd4AN36 N2ACd1AN10 N2ACd1AN14 N6ACd1AN10 N6ACd1AN14 N10ACd1AN12 N10ACd1AN16 N12ACd1AN16 N4ACd2AN18 N18ACd2AN22 N20ACd3AN28 N20ACd3AN32 N24ACd3AN28 N24ACd3AN32 N28ACd3AN30 N28ACd3AN34
2.3615(17)
N30ACd3AN32 N32ACd3AN34 N8ACd4AN36
89.25(8) 89.79(8) 90.29(8)
N30ACd3AN34 N8ACd4AN26 N26ACd4AN36
178.01(8) 90.21(8) 89.75(8)
Symmetry codes: 1 A x + 1, y + 1, z + 1 B x 1, y, z C x + 2, y + 1, z + 1; 2 A x 1, y, z 1 C x, y + 1, z D x + 1, y + 1, z + 1; 3 A x + 1, y + 1/2, z 1/2 B x + 1, y + 1, z C x, y + 1, z; 4 A x + 1, y, z + 1 B x + 3, y + 2, z.
934w, 834w, 772w, 741w, 664w, 625w, 548w, 509w, 425w. 2.3. X-ray crystallography Suitable single crystals of 1–4 were carefully selected under an optical microscope and glued to thin glass fibers. The diffraction data were collected on a Rigaku Mercury CCD diffractometer with graphite monochro˚ ). Intensities were mated Mo Ka radiation (k = 0.71073 A collected by the x scan technique. The structures were solved by direct methods and refined with full-matrix least-squares technique (SHELXTL-97) [10]. The positions of hydrogen atoms were determined with theoretical calculation. The residual peaks of 2 are high. The largest five residual peaks of 2 are 3.40, 3.01, 2.87, ˚ 3, which are located at (0.0734 2.50 and 2.50 e/A 0.1963 0.2459), (0.1549 0.1170 0.2472), (0.1166 0.3869 0.2525), (0.1992 0.4670 0.2512) and (0.2492 0.0228 0.2415), respectively. The parameters of the crystal data collection and refinement of 1–4 are given in Table 1. Selected bond lengths and bond angles are listed in Table 2. 3. Results and discussion 3.1. Crystal structures
2.347(2) 2.364(2) 2.363(2) 2.368(2) 2.360(2) 2.343(2) 2.364(2) 2.339(2) 2.364(2) 90.55(8) 90.56(8) 89.66(8) 177.01(8) 86.39(8) 177.22(8) 91.02(8) 90.06(8) 91.24(8) 90.86(8) 176.63(8) 179.07(9) 88.10(8) 90.83(8) 90.95(8)
3.1.1. [Cd(bimb)2(NCS)2]n (1) Compound 1 has the one-dimensional chain structure containing double bridges of bimb ligands (Fig. 1) [3c,6b,6c]. Each Cd(II) center in 1 is coordinated to four imidazole nitrogen atoms from four different bimb ˚, ligands in the equatorial plane [Cd1AN2 2.3108(17) A ˚ Cd1AN4C 2.3615(17) A], and two nitrogen atoms from ˚ ] in the apial two thiocyanate ions [Cd1AN5 2.343(2) A positions. Each Cd(II) atom connects to other Cd(II) atoms by two bimb ligands, resulting the Cd2(bimb)2 22-membered metallocycle. Two stranded of bimb ligands are wrapped around each other and are held together by Cd(II) atoms, forming a double chain structure. The bimb ligands exhibit the gauche–anti-gauche conformation. The plane of N(CH2)4N chain steeply inclined, by 96.9 and 76.8, to the two imidazole ring planes. The torsion angle of the butane chain is 83.198(8). The Cd Cd distances separated via the bridging bimb ˚. is 9.081 A
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Fig. 1. The one-dimensional double chain structure along the a direction in 1 (A 1 x, 1 y, 1 z; B 1 + x, y, z; C 2 x, 1 y, 1 z; D 1 + x, y, z).
3.1.2. [Cd(bimb)(dca)2]n (2) and [Cd(bimb)(N3)2]n (3) As can be seen from Fig. 2(a), every Cd(II) atom in 2 is coordinated by six nitrogen atoms, two from two bimb ˚; ligands in the cis-positions (Cd1AN2 2.279(4) A ˚ ) and the others from four dicyanaCd1AN4 2.317(4) A ˚; mide ligands (Cd1AN6 2.379(5) A Cd1AN7C ˚; ˚; 2.341(5) A Cd1AN9 2.332(5) A Cd1AN10D ˚ ), in the distorted octahedral geometry. The 2.354(4) A CdAN bond lengths are similar to those in 1. The NACdAN bond angles are in the range of 84.40(17)– 95.60(17). There are two symmetry independent dicyanamide ligands (N6AC11AN5AC12AN7 and N9AC13AN8AC14AN10) and they both act as bismonodentate bridges. The double dicyanamide ligands link the Cd(II) atoms to form Cd2(dca)2 12-membered metallacycle and further extend to result a one-dimensional zigzag [Cd(dca)2]n chain (Fig. 2b). The Cd1 Cd1C and Cd1 Cd1D separations via the ˚, dicyamamide ligands are 7.7316(9) and 7.8586(10) A respectively (Fig. 2a). The Cd1 Cd1A and Cd1 Cd1B separations via the bimb ligands are ˚ , respectively. There are 12.5282(13) and 13.9266(21) A also two symmetry independent bimb ligands (N1/N2/ C1–C5 and N3/N4/C6–C10) and they both have the center symmetry. The N1/N2/C1–C5 bimb ligand exhibits the gauche–anti-gauche conformation with the torsion angle C1AAC1AC2AN1 58.821(14) and the plane of N(CH2)4N chain steeply inclined, by 80.7, to the imidazole ring planes. While the N3/N4/C6–C10 bimb ligand exhibits the completely anti (anti-anti-anti) conformation with the torsion angle C6BAC6AC7AN3A171.776(10) and the plane of N(CH2)4N chain steeply inclined, by 102.6, to the imidazole ring planes. Along the [Cd(dca)2]n chain, the bimb lignads point in four different directions alternatively (Fig. 2c). So each [Cd(dca)2]n chain links four adjacent [Cd(dca)2]n chains through the bimb bridges, leading to the novel threedimensional network with the one-dimensional channel ˚ · 13.9 A ˚ (Fig. 2d). The similar 1,2-bis(imica. 18.6 A
dazol-1-yl)ethane complex [Cd(1,2-bis(imidazol-1-yl)ethane)(dca)2] has an one-dimensional triple chain structure [11]. The structure of 3 has the part of similar properties as that of 2. As can be seen from Fig. 3a, every Cd(II) atom in 3 is coordinated by six nitrogen atoms, two from two bimb ligands in the cis-positions (Cd1AN2 ˚ ; Cd1AN4A 2.270(2) A ˚ ) and the others from 2.296(2) A ˚ ; Cd1AN7B four azide ligands (Cd1AN5 2.362(2) A ˚ ; Cd1AN8 2.284(2) A ˚ ; Cd1AN8C 2.505(2) A ˚ ), 2.449(2) A in the distorted octahedral coordination environment. The bond lengths Cd1AN7B and Cd1AN8C are obviously longer these in 1 and 2. The bond angle N8ACd1AN8C is 74.85(8), is obviously deviated from 90. The azide ligands exhibit two kinds of coordination modes. One is end-to-end (EE) coordination mode. The other is end-on (EO) coordination mode. The double EEazide ligands and double EO-azide ligands alternatively link the Cd(II) atoms to form a one-dimensional zigzag [Cd(N3)2]n chain (Fig. 3b). The Cd1 Cd1B and Cd1 Cd1C separations via the EE-azide and EO-azide ˚ , respectively. There ligands are 5.5774(4) and 3.8056(3) A is one symmetry independent bimb ligand in 3. The Cd Cd1 separations via the bimb ligands are ˚ . The bimb ligand exhibits the completely anti 13.3973(7) A (anti-anti-anti) conformation with the torsion angle C1AC2AC3AC4 178.5(2) and the plane of N(CH2)4N chain steeply inclined, by 14.0 and 100.5, to the two imidazole ring planes. The dihedral angle between two imidazole ring planes is 88.4. Along the [Cd(N3)2]n chain, the bimb lignads point in four different directions alternatively (Fig. 3c). So each [Cd(dca)2]n chain links four adjacent [Cd(N3)2]n chains through the bimb bridges, leading the novel three-dimensional network with the one-dimensional channel ca. ˚ · 13.9A ˚ (Fig. 3d). 18.6 A Previously we reported a similar coordination polymer [Mn(bim)(N3)2]n (bim = 1,2-bis(imidazole-1-yl)ethane)
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Fig. 2. (a) Coordination environment of Cd1 in 2 (Symmetry codes: A 1 x, y, 1 z; B 1 x, 1 y, z; C x, 1 y, z; D 1 x, 1 y, 1 z). (b) One-dimensional chain structure bridged by bis-monodentate dicyanamide ligands in 2. (c) Connections between the adjacent chains in 2. (d) The three-dimensional topology of 2. The long sticks represent the bimb ligands and the short ones double dicyanamide ligands in 2.
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Fig. 2 (continued)
which has a similar three-dimensional network constructed through one-dimensional double end-on azidebridged Mn(II) chains and extended through the antibim ligands [6a]. The difference is that the azide ligands has one coordination mode (end-on) in [Mn(bim)(N3)2]n but two different coordination modes (end-to-end and end-on) in 3. If a dimer Mn(II) bridged by azide is considered as one node, the structure of [Mn(bim)(N3)2]n can be viewed as a simple cubic topology. If a dimer Cd(II) bridged by azide or dicyanamide is also considered as one node, the structure of 3 and 2 can be also viewed as a simple cubic topology. 3.1.3. {[Cd(bimb)3](ClO4)2}n (4) The structure of 4 is similar to [Mn(bimb)3](BF4)2 [9a], [Mn(bimb)3](ClO4)2 and the analogous compounds containing combinations of ClO4 =PF6 or ClO4 =AsF6 [9b], and comprises two equivalent, mutually interpenetrating three-dimensional networks. As shown in Fig. 4a, there are four independent Cd(II) atoms and each of them is coordinated by six nitrogen atoms from six bimb ligands. There are ten independent bimb ligands. All bimb ligands exhibit the completely anti conformation. The torsion angles of the butane chains of ten independent bimb ligands are in the range of 175.443(10)–180.00(1). The planes of N(CH2)4N chains steeply inclined, by in the range of 56.1–118.4, to the imidazole ring planes. The CdAN bond lengths are sim-
˚ and the ilar in the ranges of 2.339(2)–2.371(2) A NACdAN bond angles are in the range of 86.39(8)– 93.71(8). Each bimb ligand bridges two Cd(II) atoms and each Cd(II) atom links six Cd(II) atoms via six bimb ligands along six directions, resulting the three-dimensional network (Fig. 4b and c). The Cd Cd separa˚ . Two tions are in the range of 14.1666(8)–14.6212(9) A equivalent three-dimensional networks interpenetrate each other to form interpenetrating three-dimensional network (Fig. 4d). 3.2. Syntheses, XRD, IR and thermal properties of the complexes As pseudohalide thiocyanate (SCN), azide ðN3 Þ and dicyanamide (dca) ([N(CN)2]) not only can act as counter anions to sustain charge neutral but also have various coordination modes, they can provide the suitable building block for assembling novel coordination polymers. We want to introduce these anionic ligands into the Cd/bimb reaction mixture as co-ligands in order to prepare the novel complexes. Our combinations of bimb, pseudohalide thiocyanate (SCN), azide ðN3 Þ and dicyanamide (dca) ([N(CN)2]) with Cd(II) salts have synthesized four new coordination polymers. The anions play an key role in the construction of motifs. Each motif is efficiently constructed irrespective of the stoichiometry and the concentration. The Cd(II) complexes 1–4
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were synthesized by the diffuse methods because the synthesis of Cd(II) complexes was unsuccessful by the direct reactions.
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The experimental power diffraction patterns of 1–4 (Figs. 5–8) are in agreement with that calculated for the four coordination polymers.
Fig. 3. (a) Coordination environment of Cd1 in 3 (Symmetry codes: A 1 + x, 0.5 y, 0.5 + z; B 1 x, 1 y, z; C x, 1 y, z). (b) The onedimensional chain structure bridged by the alternative EE-azide and EO-azide ligands along the a direction in 3. (c) Connections between adjacent chains in 3. (d) Three-dimensional topology of 3. The long sticks represent the bimb ligands and the short ones azide lignads.
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Fig. 3 (continued )
The IR spectrum determination shows that the imidazole ring vibrations in complexes 1–4 are at 1520 and 1281, 1520 and 1281, 1517 and 1289, 1520 and 1281 cm1, respectively [3c]. The strong absorptions at 2068 cm1 for 1 indicate the C@N stretching vibration of the thiocyanate group, which is consistent with the occurrence of thiocyanate-N coordination [3]. The strong absorptions of at 2292, 2230 and 2169 cm1 for 2 are assigned to the C„N symmetric stretch band (msym), the asymmetric stretch band (masym) and the combination band of msym and masym of dca [3c,4]. The bigger shift (2292 cm1) for 2 towards high frequencies, confirmed that dca bis-monodentate coordinated to metal center. Two absorptions at 2046 and 2059 cm1 for 3 show two different coordination modes of azide anions and which is confirmed by X-ray diffraction. The strong absorption band at 1096 cm1 for 4 is assigned to ClO4 anions. The TGA studies showed that 1–4 are stable under 200 C, and decomposition begins at 268, 227, 239 and 272 C, respectively. 4. Conclusion The reaction of the flexible bis(imidazole) ligand 1,4bis(imidazol-1-yl)butane (bimb) with Cd(II) salts (NCS, dicyanamide (dca), N3 , ClO4 Þ yields four new organic-inorganic hybrid frameworks. [Cd(bimb)2 (NCS)2]n (1) is one-dimensional chain structure contain-
ing double bridges of bimb ligands. [Cd(bimb)(dca)2]n (2) is a novel three-dimensional network, in which double l1,5-dca bridges connect the Cd(II) atoms to form the zigzag [Cd(dca)2]n chains and extend through bimb long bridges in four different directions alternatively to construct a novel three-dimensional network. [Cd(bimb) (N3)2]n (3) is also a three-dimensional network contains double end-to-end (EE) and double end-on (EO) azide short bridges. {[Cd(bimb)3](ClO4)2}n (4) comprises two equivalent, mutually interpenetrating three-dimensional networks. The Cd–bimb complex {[Cd(bimb)1.5(H2O)2(SO4)]4H2O}n (5) previous reported by Ma and co-workers is composed of a two-dimensional (6,3) network with the hexagonal smallest circuit containing six Cd(II) atoms and six bimb ligands [9c]. [Cd(bimb)2Cl2]n (6) is a two-dimensional (4,4) network [9f]. The six Cd–bimb complexes illustrate the diversity of structures that can be obtained by using bimb ligand and anion ligands. The combination of long flexible ligand and short anion ligand seems to be a successful way to assemble novel coordination frameworks. The anions play an key role in structural assembly of Cd–bimb complexes (1: 1D chain for NCS; 2: 3D network for [N(CN)2] (dca); 3: 3D network for N3 ; 4: interpenetrating 3D network for ClO4 ; 5: 2D (6,3) network for SO4 2- ; 6: 2D (4,4) network for Cl). However, it is still a great challenge to design and assemble the programmed coordination frameworks by coordination bonds and more work is still need to extend this
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knowledge. In summary, this work is expected to provide new information for understanding and developing of the crystal engineering of coordination frameworks.
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Further designation and synthesis of new motifs with bimb and different metal salts, are under way in our lab.
Fig. 4. (a) The coordination environment of the four independent Cd(II) atoms in 4 (Symmetry codes: A 1 x, y, 1 z; B 3 x, 2 y, z). (b) The distorted cubic network in 4, the ClO4 anions are omitted. (c) The distorted cubic topology in 4. (d) The two interpenetrating distorted cubic topology in 4.
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Fig. 4 (continued )
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2θ( ) Fig. 5. Observed (a) and calculated (b) X-ray power diffraction patterns of 1.
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2θ ( ) Fig. 6. Observed (a) and calculated (b) X-ray power diffraction patterns of 2.
Acknowledgments
Appendix A. Supplementary data
This work was supported by the Natural Science Foundation of China (No. 20671066), the Jiangsu Province (No. BK2006049), the Funds of Key Laboratory of Organic Synthesis of Jiangsu Province (No. KJS0612) and State Key Laboratory of Coordination Chemistry.
Crystallographic data for the structural analyses have been deposited with the Cambridge Crystallographic Data Centre, with CCDC refere7nce numbers CCDC-612540 for 1, CCDC-612541 for 2, CCDC-612542 for 3, CCDC612543 for 4. Supplementary data associated with this
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2θ ( ) Fig. 7. Observed (a) and calculated (b) X-ray power diffraction patterns of 3.
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2θ ( ) Fig. 8. Observed (a) and calculated (b) X-ray power diffraction patterns of 4.
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