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Assembly of anion-controlled cadmium(II) coordination polymers based on flexible bis(imidazole) derivative
Inorganica Chimica Acta 375 (2011) 70–76
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Assembly of anion-controlled cadmium(II) coordination polymers based on flexible bis(imidazole) derivative Xiu-Li Wang ⇑, Song Yang, Guo-Cheng Liu, Jin-Xia Zhang, Hong-Yan Lin, Ai-Xiang Tian Faculty of Chemistry and Chemical Engineering, Bohai University, Jinzhou 121000, PR China
a r t i c l e
i n f o
Article history: Received 23 October 2010 Received in revised form 11 April 2011 Accepted 15 April 2011 Available online 30 April 2011 Keywords: Anion-controlled Hydrothermal syntheses Crystal structure Bis(imidazole) derivative
a b s t r a c t Four Cd(II) metal–organic complexes, namely, [Cd(Cl)2(bbdmbm)] (1), [Cd(NO3)(N3)(bbdmbm)1.5] (2), [Cd(BBA)2(bbdmbm)(H2O)] (3), [Cd(DNBA)2(bbdmbm)] (4), (bbdmbm = 1,1-(1,4-butanediyl)bis(5,6dimethylbenzimidazole), HBBA = 4-bromobenzoic acid, and HDNBA = 3,5-dinitrobenzoic acid) have been obtained from hydrothermal reactions of different Cd(II) salts with the mixed ligands of bbdmbm and five anions (Cl, NO3, N3, BBA and DNBA). Single crystal X-ray diffraction analyses reveal that the four complexes exhibit different structures. Complex 1 possesses a one-dimensional (1D) helical chain, which is finally extended into a two-dimensional (2D) supramolecular structure through p–p stacking interactions. Complex 2 shows a 1D ladderlike chain bridged by bbdmbm ligands with two kinds of coordination conformations. Complex 3 is a 1D coordination polymer and is ultimately extended into a 2D supramolecular network through H-bonding interactions. Complex 4 displays a dinuclear cluster, which is finally packed into a three-dimensional (3D) supramolecular framework through three kinds of p–p stacking interactions. The Cd(II) exhibits four different coordination modes in complexes 1–4, respectively. The results indicate that the anion ligands with different steric hindrance and size play important roles in the coordination modes of Cd(II) and construction of the title complexes, leading to the structural diversity. In addition, the conformations of bbdmbm ligand also show some effect on the final structures. Fluorescence properties of complexes 1–4 are reported in this paper. Ó 2011 Elsevier B.V. All rights reserved.
1. Introduction The design and construction of metal–organic complexes have attracted great interest in recent years, owing to their variety of structures, interesting properties and potential applications in the fields of catalysis, luminescence, gas adsorption, and magnetic materials [1–12]. However, control of the complex structures in hydrothermal reactions is still a challenge, owing to the facts that the assembly of such complexes can be easily influenced by the geometrical and electronic properties of metal ions and ligands, temperature, pH value of the solution, etc. [13–16]. Recent researches indicate that the anions with different sizes, coordination abilities and electronic properties play important roles in the assembly of metal–organic complexes, because the anions not only function as counterions and structure-directing agents, but also function as ligands and secondary building unit (SBU) in the complexes [17–20]. Therefore, predictably using organic/inorganic anions in the assembly of new functional materials has become a rapidly emerging field [21–23].
⇑ Corresponding author. Tel.: +86 416 3400158. E-mail address: [email protected] (X.-L. Wang). 0020-1693/$ - see front matter Ó 2011 Elsevier B.V. All rights reserved. doi:10.1016/j.ica.2011.04.023
Compared with the common rigid N-donor ligands [24–27], flexible bis(imidazole) ligands possess long spacers, which can lead to various conformations in constructing coordination polymers and have been employed in the syntheses of metal–organic complexes [28–34]. Recently, Lang’s group focus on the [CuX]n-based coordination polymers (X = SCN, I) with flexible N-heterocyclic ligands 1,10 -(1,4-butanediyl)bis-1H-benzimidazole (bbbm), 1,10 (1,5-pentanediyl)bis-1H-benzimidazole (pbbm), [(bzim)(CH2)n(bzim)] (bzim = benzimidazolyl, n = 1–6) and a number of interesting complexes have been gained [35,36]. In this work, a bis(imidazole) derivative 1,10 -(1,4-butanediyl)bis(5,6-dimethylbenzimidazole) (bbdmbm) was employed as the main ligand to construct metal– organic complexes at the presence of different secondary anions. Compared with the previous work, the ligand bbdmbm is chosen here to investigate the effect of substituting group of ligand on the structure of complexes. To the best of our knowledge, such ligand used in complexes has not been reported up to now. The Cd(II) atom with d10 configuration exhibits a wide variety of coordination geometries and modes [37–39]. To our knowledge, the anion effect on the coordination mode of Cd(II) atom has rarely been systematically reported. In this work, we selected five inorganic/organic anions as the secondary ligands at the presence of bbdmbm to react with Cd(II) atom and obtained four new Cd(II) complexes, [Cd(Cl)2(bbdmbm)] (1), [Cd(NO3)(N3)(bbdmbm)1.5]
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yellow block crystals of 4 were obtained. Yield: 31% based on Cd(II). Anal. Calc. for C72H64Cd2N16O24: C, 49.03; H, 3.63; N, 12.71. Found: C, 49.10; H, 3.65; N, 12.80%. IR (KBr, cm1): 3103s, 2941m, 1620s, 1571w, 1539s, 1508w, 1458m, 1388s, 1346s, 1215m, 1074m, 842m, 727s.
Scheme 1. The ligands used in this paper.
(2), [Cd(BBA)2(bbdmbm)(H2O)] (3), and [Cd(DNBA)2(bbdmbm)] (4), (HBBA = 4-bromobenzoic acid, HDNBA = 3,5-dinitrobenzoic acid) (Scheme 1). Complex 1 is a one-dimensional (1D) helical chain. Complex 2 shows a 1D ladderlike chain bridged by bbdmbm ligands. Complex 3 is a 1D linear coordination polymer. Complex 4 exhibits a dinuclear cluster. The effects of anions and conformations of bbdmbm ligand on the coordination modes of Cd(II) and structures of the title complexes have been investigated. 2. Experimental 2.1. Materials and measurements All chemicals were used as supplied from commercial sources without further purification. The bbdmbm ligand was synthesized by the method of literature [36] and characterized by FT-IR spectra. FT-IR spectra (KBr pellets) were taken on a Magna FT-IR 560 spectrometer. Elemental analyses were performed on a Perkin–Elmer 240CHN analyzer. The luminescence spectra for the samples were measured on a HITACHI F-4500 Fluorescence Spectrophotometer. 2.2. Preparation of the complexes 1–4 2.2.1. [Cd(Cl)2(bbdmbm)] (1) A mixture of CdCl22.5H2O (0.023 g, 0.1 mmol), bbdmbm (0.035 g, 0.1 mmol), H2O (10 mL) was sealed in a 25 mL Teflon reactor at 150 °C for 3 days. After slow cooling to room temperature, yellow block crystals of 1 were obtained. Yield: 35% based on Cd(II). Anal. Calc. for C22H26CdCl2N4: C, 49.83; H, 4.91; N, 10.57. Found: C, 49.91; H, 4.96; N, 10.62%. IR (KBr, cm1): 2954w, 2918w, 1510s, 1452m, 1205m, 842m. 2.2.2. [Cd(NO3)(N3)(bbdmbm)1.5] (2) A mixture of Cd(NO3)24H2O (0.031 g, 0.1 mmol), bbdmbm (0.035 g, 0.1 mmol), NaN3 (0.0065 g, 0.1 mmol) and H2O (10 mL) was sealed in a 25 mL Teflon reactor at 150 °C for 3 days. After slow cooling to room temperature, yellow block crystals of 2 were obtained. Yield: 12% based on Cd(II). Anal. Calc. for C33H39CdN10O3: C, 53.79; H, 5.30; N, 19.02. Found: C, 53.82; H, 5.39; N, 19.11%. IR (KBr, cm1): 3109w, 2937m, 2052s, 1504s, 1427m, 1336s, 848s. 2.2.3. [Cd(BBA)2(bbdmbm)(H2O)] (3) A mixture of CdSO48/3H2O (0.026 g, 0.1 mmol), bbdmbm (0.035 g, 0.1 mmol), HBBA (0.04 g, 0.2 mmol), NaOH (0.2 mL, 0.1 mol/L) and H2O (10 mL) was sealed in a 25 mL Teflon reactor at 150 °C for 3 days. After slow cooling to room temperature, yellow block crystals of 3 were obtained. Yield: 30% based on Cd(II). Anal. Calc. for C36H36CdBr2N4O5: C, 49.33; H, 4.11; N, 6.41. Found: C, 50.31; H, 4.12; N, 6.70%. IR (KBr, cm1): 3359m, 3103w, 2931m, 1589s, 1544s, 1504m, 1467m, 1215m, 848s, 769s. 2.2.4. [Cd(DNBA)2(bbdmbm)] (4) A mixture of CdSO48/3H2O (0.026 g, 0.1 mmol), bbdmbm (0.035 g, 0.1 mmol), HDNBA (0.042 g, 0.2 mmol), NaOH (0.2 mL, 0.1 mol/L) and H2O (10 mL) was sealed in a 25 mL Teflon reactor at 150 °C for 3 days. After slow cooling to room temperature,
2.3. X-ray crystallographic study Diffraction data for complexes 1–4 were collected on a Bruker Smart 1000 CCD area detector diffractometer (Mo-Ka radiation, graphite monochromator, k = 0.71069 Å for 1, 2 and k = 0.71073 Å for 3, 4). The crystal structures of 1–4 were solved by the direct method and refined on F2 by full-matrix least-squares technique with the SHELXL-97 software package [40,41]. All non-hydrogen atoms were refined anisotropically, and hydrogen atoms of ligand were placed in geometrically idealized positions and refined isotropically. In the complex 2, part of the bbdmbm ligands and the water molecules are disordered and the C32, C33, N4, O2, O3 positions were refined with half-occupancy atoms. The details of crystallographic information for complexes 1–4 are summarized in Table 1. Selected bond lengths and angles of complexes 1–4 are listed in Table S1.
3. Results and discussion 3.1. Description of crystal structures 3.1.1. [Cd(Cl)2(bbdmbm)] (1) The crystal structure analysis shows that complex 1 is a 1D helical chainlike coordination polymer constructed from chloridion and bbdmbm ligands. The coordination environment of Cd(II) is shown in Fig. 1. Each Cd(II) atom is tetra-coordinated by two chloridions and two nitrogen atoms (N1, N4) from two separated bbdmbm ligands, showing a distorted tetrahedral geometry (CdCl2N2). The bond distances of Cd–Cl(1), Cd–Cl(2), Cd–N(1), and Cd–N(4) are 2.4024(8), 2.4331(10), 2.2452(17), and 2.2430(15) Å, respectively. The bond angles of N–Cd–Cl are in the range of 102.44(6)–117.51(3)°. The bond angles of N–Cd–N and Cl–Cd–Cl are 105.33(6)° and 117.51(3)°, respectively. In complex 1, the bbdmbm ligand acts as a bridging bis(monodentate) ligand adopting a cis–trans–cis conformation and connects with two adjacent CdCl2N2 tetrahedron forming a 1D helical chain, as shown in Fig. 2. The distance between two Cd(II) atoms is 12.5691(48) Å (Fig. S1). Furthermore, the bbdmbm ligands from two adjacent chains are nearly parallel to each other with the dihedral angle of 2.17°, resulting in the formation of p–p stacking interactions between the N-rings and the C-rings of bbdmbm ligands from different 1D helical chains. Thus, the helical chains are expanded to 2D supramolecular network by the p–p stacking interactions, and the face-to-face distance between the N-rings and the C-rings of bbdmbm ligands is 3.770(2) Å. 3.1.2. [Cd(NO3)(N3)(bbdmbm)1.5] (2) X-ray diffraction analysis indicates that complex 2 is a 1D ladderlike coordination polymer and the asymmetric unit contains one Cd(II) atom, one NO3 anion, one N3 anion and one and a half bbdmbm ligands. The coordination environment of Cd(II) atom is depicted in Fig. 3. Different from that in complex 1, the Cd(II) atom is coordinated by three nitrogen atoms (N1, N3, N5) from three separated bbdmbm ligands, two oxygen atoms (O1, O2) from two nitrate anions and another nitrogen atom (N7) from N3 anion to complete a six-coordinated environment, showing a distorted octahedral geometry (CdO2N4). The lengths of Cd–N and Cd–O are 2.225(3)–2.4331(10) Å and 2.396(5)–2.449(3) Å, respectively.
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Table 1 Crystal data and structure refinement details for complexes 1–4.
a b
Complex
1
2
3
4
Formula Formula weight Crystal system Space group a (Å) b (Å) c (Å) a (°) b (°) c (°) V (Å3) Z Dcalc (g cm3) l (mm1) F(0 0 0) hmax (°) Total data collected Unique data reflections Rint R1a [I > 2r(I)] wR2b (all data) Goodness-of-fit (GOF) Dqmax (e Å3) Dqmin (e Å3)
C22H26CdCl2N4 529.77 monoclinic P21/n 9.174(5) 14.072(5) 17.537(5) 90 96.689(5) 90 2248.6(16) 4 1.565 1.225 1072 25.50 17618 4426 0.0151 0.0195 0.0568 1.03 0.286 0.307
C33H39CdN10O3 736.14 triclinic P1
C36H36CdBr2N4O5 842.61 triclinic P1 6.2705(9) 11.9708(16) 12.8551(17) 109.291(2) 101.464(2) 96.621(2) 875.3(2) 1 1.595 2.951 402 25.00 4471 3709 0.0187 0.0456 0.1253 1.042 0.639 0.642
C72H64Cd2N16O24 1762.21 triclinic P1
10.870(5) 12.164(5) 14.439(5) 109.434(5) 103.844(5) 101.199(5) 1668.1(12) 2 1.466 0.705 758 25.10 10167 5880 0.0136 0.0319 0.0939 1.08 1.107 0.949
10.4046(10) 12.9086(12) 14.3666(13) 80.6440(10) 80.7020(10) 79.5630(10) 1855.0(3) 1 1.578 0.664 896 25.00 9506 6459 0.0279 0.0409 0.0886 1.017 0.364 0.397
R1 = Rh(||Fo| |Fc||)/R|Fo|. i wR2 = ðwðjF o j2 jF c j2 Þ2 =ðwjF o j2 Þ2 1/2.
Fig. 1. The coordination environment of Cd(II) in complex 1, showing a distorted tetrahedral geometry. The hydrogen atoms were omitted for clarity.
The bond angles of N–Cd–N and N–Cd–O are in the range of 84.11(10)–176.12(8)° and 51.98(14)–150.94(15)°, respectively. It should be noted that the bbdmbm ligands show two kinds of coordination conformations in complex 2 with the NN distances 10.30 Å and 9.17 Å, respectively (Fig. S2). One kind of bbdmbm ligand adopts trans–trans–trans conformation, connecting two neighboring CdO2N4 geometry into a 1D linear chain. Another kind of bbdmbm ligand exhibits a cis–trans–cis conformation, which is shorter in length, and links two neighboring 1D chain to a ladderlike structure. The distances between Cd(II) atoms linked by two kinds of bbdmbm ligands are 14.439(5) Å and 13.563(4) Å, respectively (see Fig. 4).
Fig. 2. 2D supramolecular network constructed from 1D helical chain through p–p stacking interactions in complex 1.
3.1.3. [Cd(BBA)2(bbdmbm)(H2O)] (3) X-ray structural determination reveals that complex 3 is a 1D chain constructed from a Cd(II) atom, two BBA anions, one
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In complex 3, the adjacent CdO5N2 geometry is linked into a 1D chain by bbdmbm ligands, which adopts cis–cis–cis conformations (see Fig. S3). Each bbdmbm ligand links two CdO5N2 polyhedron with the distance of 14.383(2) Å between the adjacent Cd(II). Moreover, in the adjacent 1D chains, H-bonding interactions are found among the carboxylic oxygen atoms from BBA anions and the coordination water molecules [O(5)–H(5A)O(3): 2.706 Å, O(5)–H(5B)O(2): 2.744 Å]. Thus, a 2D supramolecular network was obtained through H-bonding interactions, as shown in Fig. 6.
Fig. 3. The coordination environment of Cd(II) in complex 2, showing a distorted octahedral geometry. The hydrogen atoms were omitted for clarity.
Fig. 4. 1D ladderlike chain connected by bbdmbm ligand in complex 2.
coordination water molecule and one bbdmbm ligand. The coordination environment of Cd(II) atom is shown in Fig. 5. Different from those in complexes 1 and 2, the Cd(II) atom is seven-coordinated by four oxygen atoms from two chelating carboxylic groups of two BBA anions [Cd–O 2.400(9)–2.451(10) Å], two nitrogen atoms belonging to two bbdmbm ligands [Cd–N 2.287(10), 2.336(9) Å] and one oxygen atom from a coordination water molecule [Cd–O 2.327(6) Å], showing a pentagonal bipyramid geometry (CdO5N2). The bond angles of N–Cd–O and O–Cd–O are in the range of 86.0(3)–91.8(3)° and 53.7(2)–167.8(2)°, respectively.
Fig. 5. The coordination environment of Cd(II) in complex 3, showing a pentagonal bipyramid geometry. The hydrogen atoms were omitted for clarity.
3.1.4. [Cd(DNBA)2(bbdmbm)] (4) Compared with the 1D coordination polymers of complexes 1– 3, complex 4 exhibits a dinuclear structure. The asymmetric unit of 4 contains one Cd(II) atom, two DNBA and one bbdmbm ligand. The coordination environment of Cd(II) atom is shown in Fig. 7. Each Cd(II) atom is pent-coordinated by two nitrogen atoms from two bbdmbm ligands [Cd–N 2.185(3), 2.278(3) Å], two oxygen atoms from a chelating carboxylic group of DNBA anion [Cd–O 2.219(3) Å, 2.682(3) Å], and one oxygen atom from a monodentate carboxylic group of DNBA anion [Cd–O 2.240(3) Å], showing a distorted trigonal bipyramid geometry (CdO3N2). The adjacent CdO3N2 geometries are bridged by bbdmbm ligands to form a dinuclear cluster, with the distance of 8.0881(6) Å between Cd(II) atoms. The bond angles of N–Cd–O and O–Cd–O are in the range of 88.63(11)–128.51(11)° and 52.46(10)–142.82(10)°, respectively. DNBA anion adopts two kinds of coordination modes in complex 4, which is monodentate mode [Cd–O 2.240(3) Å] and chelating mode [Cd–O 2.219(3) Å, 2.682(3) Å], respectively. The bbdmbm ligand links CdO3N2 geometries in cis–trans–trans conformations. Unlike complex 1, three different kinds of p–p stacking interactions exist in complex 4: p–p stacking interactions between the aromatic rings from two parallel monodentate DNBAa with the face-to-face distance of 3.565 Å (Fig. S4a), two parallel chelating DNBAb with the face-to-face distance of 3.751 Å (Fig. S4b), and the p–p stacking interactions between the aromatic rings from two paired bbdmbm ligands with the face-to-face distance of 3.653 Å (Fig. S4c). Thus, the neighboring dinuclear units are further extended into a 3D supramolecular framework through these p–p stacking interactions, as shown in Fig. 8. 3.2. Effect of anions and conformation of bbdmbm on complexes 1–4 In complexes 1–4, Cd(II) atoms show different coordination modes at the presence of bbdmbm ligand and different secondary anion ligands, as shown in Fig. 9. In 1, Cd(II) atom adopts tetracoordinated tetrahedral geometry at the presence of Cl anion. In 2, we choose NO3 and N3 as secondary anion ligands and Cd(II) atom exhibits six-coordinated octahedral geometry. In 3, Cd(II) atom shows seven-coordinated mode when BBA was used as secondary anion. In 4, Cd(II) atom shows five-coordinated distorted trigonal bipyramid geometry at the presence of DNBA anion. The results indicate that the anion shows great influence on the coordination mode of Cd(II). On the other hand, the size of anion ligands plays an important role in constructing the title complexes. In complex 1, a small sphere inorganic anion Cl is used and a 1D helical chain is obtained. In complex 2, Cd(II) is coordinated by N3 and NO3 simultaneously and then a 1D ladderlike coordination polymer is synthesized. In complexes 3 and 4, we select the larger aromatic carboxylate anions BBA and DNBA, a 1D linear and a dinuclear complex are prepared. It is noticed that H-bonding and p–p stacking interactions between the inorganic and organic ligands show significant effect on constructing high-dimensional supramolecular frameworks. Compared with the complexes reported by Lang’s group, the title complexes show low dimensional structures, which
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Fig. 6. 2D supramolecular network constructed from 1D chain through hydrogen bonds in complex 3.
Fig. 7. The coordination environment of Cd(II) in complex 4, showing a distorted trigonal bipyramid geometry. The hydrogen atoms were omitted for clarity.
Fig. 8. 3D supramolecular framework constructed from the dinuclear cluster through p–p stacking interactions in complex 4.
conformation with the distance between two adjacent Cd(II) atoms of 12.5691(48) Å. Two kinds of conformations of bbdmbm ligands exist in 2 with distances between two adjacent Cd(II) atoms of 14.439(5) Å and 13.563(4) Å, respectively. In 3, bbdmbm ligands adopt cis–cis–cis conformation with the distance between two adjacent Cd(II) atoms of 14.383(2) Å. Different from 1–3, bbdmbm ligands adopt cis–trans–trans conformation and the distance between two adjacent Cd(II) atoms is much shorter in 4, which may lead to the formation of dinuclear structure of complex 4. Fig. 9. The coordination modes of Cd(II) in complexes 1–4.
3.3. Properties might be attributed to the steric hindrance of –CH3 substituting group of bbdmbm. Bbdmbm ligands adopt five kinds of conformations in complexes 1–4 (see Fig. 10). In complex 1, bbdmbm ligands adopt cis–trans–cis
3.3.1. IR spectroscopy In complex 1, the bands at 842 cm1, 1452 cm1, 1510 cm1 (848 cm1, 1427 cm1, 1504 cm1 for 2; 848 cm1, 1467 cm1,
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Fig. 10. Five kinds of conformations of bbdmbm in the complexes 1–4 with CdCd distances 12.57 Å, 13.56 Å, 14.44 Å, 14.38 Å, 8.09 Å, respectively.
the crystal structures and fluorescent emission of the Cd(II) coordination polymers. 4. Conclusion Four new Cd(II) complexes were obtained under hydrothermal conditions by using bbdmbm ligand and different organic/inorganic anions. Complexes 1–4 show diverse crystal architectures. This work reflects that organic/inorganic anions, acting as ligands, show great effect on the coordination geometry of center Cd(II) atom and conformations of bbdmbm ligand, thus leading to structural diversification and different luminescence properties of title complexes. Acknowledgments
Fig. 11. Emission spectra of bbdmbm and complexes 1–4 in the solid state at room temperature.
This work was supported by the NCET-09-0853, the National Natural Science Foundation of China (No. 20871022) and the Foundation of Liaoning Province (No. 2009R03 and 2009A028). Appendix A. Supplementary material
1504 cm1 for 3; 842 cm1, 1458 cm1, 1508 cm1 for 4) can be attributed to mC–N of N-heterocyclic rings of bbdmbm ligands. The presence of band at 2918 cm1 and 2954 cm1 (2937 cm1, 3109 cm1, for 2; 2931 cm1, 3105 cm1 for 3; 2941 cm1, 3103 cm1 for 4) can be considered as mC–C of –CH3 and –CH2– of bbdmbm. In 2, the IR bands at 2052 cm1 and 1336 cm1 are attributed to the m(N3) and m(–NO2). In 3, the IR bands at 3359 cm1 and 1589 cm1 are attributed to the m(H2O) and m(–COO) of BBA. In 4, strong bands at 1346 cm1 to 1620 cm1 can be attributed to the m(–NO2) (1539 cm1 and 1346 cm1) and m(–COO) (1388 cm1 and 1620 cm1) of DNBA [42]. 3.3.2. Fluorescence properties of complexes 1–4 The photoluminescent properties of complexes 1–4, together with the ligand bbdmbm, were studied in solid state at room temperature. The emission spectra of the complexes and the bbdmbm ligand are shown in Fig. 11. Emission bands can be observed at 421 nm (kex = 350 nm) for 1, 420 nm (kex = 370 nm) for 2, 410 nm (kex = 360 nm) for 3, 470 nm (kex = 330 nm) for 4, which is different from that of the bbdmbm ligand 533 nm (kex = 300 nm). The main emission bands may be attributed to the ligand–metal charge transfer (LMCT) as reported in other Cd(II) complexes with N-donor ligands [43,44]. The obvious blue-shift of ca. 60–120 nm occurred in the title complexes compared with the bbdmbm ligand. In addition, compared with complexes 1–3, complex 4 has less significant change of ca. 60 nm, which is probably rationalized by the different crystal architectures [45,46]. The photoluminescent property shows that the coordination anions make great contribution to
CCDC 778432, 778433, 778434, and 778435 contain the supplementary crystallographic data for complexes 1–4, respectively. These data can be obtained free of charge from The Cambridge Crystallographic Data Centre via www.ccdc.cam.ac.uk/data_request/cif. Supplementary data associated with this article can be found, in the online version, at doi:10.1016/j.ica.2011.04.023. References [1] R. Matsuda, R. Kitaura, S. Kitagawa, Y. Kubota, R.V. Belosludov, T.C. Kobayashi, H. Sakamoto, T. Chiba, M. Takata, Y. Kawazoe, Nature 436 (2005) 238. [2] R.E. Morris, P.S. Wheatley, Angew. Chem., Int. Ed. 47 (2008) 4966. [3] J.R. Li, X.H. Bu, R.H. Zhang, Inorg. Chem. 43 (2004) 237. [4] A.R. Millward, O.M. Yaghi, J. Am. Chem. Soc. 127 (2005) 17998. [5] H. Furukawa, M.A. Miller, O.M. Yaghi, J. Mater. Chem. 17 (2007) 3197. [6] H. Chun, H. Jung, J. Seo, Inorg. Chem. 48 (2009) 2043. [7] G. Yang, R.G. Raptis, P. Šafár, Cryst. Growth Des. 8 (2008) 981. [8] D.L. Long, A.J. Blake, N.R. Champness, C. Wilson, M. Schröder, J. Am. Chem. Soc. 123 (2001) 3401. [9] A.Ö. Yazaydin, R.Q. Snurr, T.H. Park, K. Koh, J. Liu, M.D. LeVan, A.I. Benin, P. Jakubczak, M. Lanuza, D.B. Galloway, J.J. Low, R.R. Willis, J. Am. Chem. Soc. 131 (2009) 18198. [10] C. Qin, X.L. Wang, E.B. Wang, Z.M. Su, Inorg. Chem. 44 (2005) 7122. [11] K.Z. Shao, Y.H. Zhao, X.L. Wang, Y.Q. Lan, D.J. Wang, Z.M. Su, R.S. Wang, Inorg. Chem. 48 (2009) 10. [12] W.Q. Zou, M.S. Wang, Y. Li, A.Q. Wu, F.K. Zheng, Q.Y. Chen, G.C. Guo, J.S. Huang, Inorg. Chem. 46 (2007) 6852. [13] D. Venkataraman, S. Lee, J.S. Moore, P. Zhang, K.A. Hirsch, G.B. Gardner, A.C. Covey, C.L. Prentice, Chem. Mater. 8 (1996) 2030. [14] B. Moulton, M.J. Zaworotko, Chem. Rev. 101 (2001) 1629. [15] L. Carlucci, G. Ciani, P. Macchi, D.M. Proserpio, S. Rizzato, Chem. Eur. J. 5 (1999) 237. [16] O.S. Jung, S.H. Park, K.M. Kim, H.G. Jang, Inorg. Chem. 37 (1998) 5781.
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Assembly of anion-controlled cadmium(II) coordination polymers based on flexible bis(imidazole) derivative Xiu-Li Wang ⇑, Song Yang, Guo-Cheng Liu, Jin-Xia Zhang, Hong-Yan Lin, Ai-Xiang Tian Faculty of Chemistry and Chemical Engineering, Bohai University, Jinzhou 121000, PR China
a r t i c l e
i n f o
Article history: Received 23 October 2010 Received in revised form 11 April 2011 Accepted 15 April 2011 Available online 30 April 2011 Keywords: Anion-controlled Hydrothermal syntheses Crystal structure Bis(imidazole) derivative
a b s t r a c t Four Cd(II) metal–organic complexes, namely, [Cd(Cl)2(bbdmbm)] (1), [Cd(NO3)(N3)(bbdmbm)1.5] (2), [Cd(BBA)2(bbdmbm)(H2O)] (3), [Cd(DNBA)2(bbdmbm)] (4), (bbdmbm = 1,1-(1,4-butanediyl)bis(5,6dimethylbenzimidazole), HBBA = 4-bromobenzoic acid, and HDNBA = 3,5-dinitrobenzoic acid) have been obtained from hydrothermal reactions of different Cd(II) salts with the mixed ligands of bbdmbm and five anions (Cl, NO3, N3, BBA and DNBA). Single crystal X-ray diffraction analyses reveal that the four complexes exhibit different structures. Complex 1 possesses a one-dimensional (1D) helical chain, which is finally extended into a two-dimensional (2D) supramolecular structure through p–p stacking interactions. Complex 2 shows a 1D ladderlike chain bridged by bbdmbm ligands with two kinds of coordination conformations. Complex 3 is a 1D coordination polymer and is ultimately extended into a 2D supramolecular network through H-bonding interactions. Complex 4 displays a dinuclear cluster, which is finally packed into a three-dimensional (3D) supramolecular framework through three kinds of p–p stacking interactions. The Cd(II) exhibits four different coordination modes in complexes 1–4, respectively. The results indicate that the anion ligands with different steric hindrance and size play important roles in the coordination modes of Cd(II) and construction of the title complexes, leading to the structural diversity. In addition, the conformations of bbdmbm ligand also show some effect on the final structures. Fluorescence properties of complexes 1–4 are reported in this paper. Ó 2011 Elsevier B.V. All rights reserved.
1. Introduction The design and construction of metal–organic complexes have attracted great interest in recent years, owing to their variety of structures, interesting properties and potential applications in the fields of catalysis, luminescence, gas adsorption, and magnetic materials [1–12]. However, control of the complex structures in hydrothermal reactions is still a challenge, owing to the facts that the assembly of such complexes can be easily influenced by the geometrical and electronic properties of metal ions and ligands, temperature, pH value of the solution, etc. [13–16]. Recent researches indicate that the anions with different sizes, coordination abilities and electronic properties play important roles in the assembly of metal–organic complexes, because the anions not only function as counterions and structure-directing agents, but also function as ligands and secondary building unit (SBU) in the complexes [17–20]. Therefore, predictably using organic/inorganic anions in the assembly of new functional materials has become a rapidly emerging field [21–23].
⇑ Corresponding author. Tel.: +86 416 3400158. E-mail address: [email protected] (X.-L. Wang). 0020-1693/$ - see front matter Ó 2011 Elsevier B.V. All rights reserved. doi:10.1016/j.ica.2011.04.023
Compared with the common rigid N-donor ligands [24–27], flexible bis(imidazole) ligands possess long spacers, which can lead to various conformations in constructing coordination polymers and have been employed in the syntheses of metal–organic complexes [28–34]. Recently, Lang’s group focus on the [CuX]n-based coordination polymers (X = SCN, I) with flexible N-heterocyclic ligands 1,10 -(1,4-butanediyl)bis-1H-benzimidazole (bbbm), 1,10 (1,5-pentanediyl)bis-1H-benzimidazole (pbbm), [(bzim)(CH2)n(bzim)] (bzim = benzimidazolyl, n = 1–6) and a number of interesting complexes have been gained [35,36]. In this work, a bis(imidazole) derivative 1,10 -(1,4-butanediyl)bis(5,6-dimethylbenzimidazole) (bbdmbm) was employed as the main ligand to construct metal– organic complexes at the presence of different secondary anions. Compared with the previous work, the ligand bbdmbm is chosen here to investigate the effect of substituting group of ligand on the structure of complexes. To the best of our knowledge, such ligand used in complexes has not been reported up to now. The Cd(II) atom with d10 configuration exhibits a wide variety of coordination geometries and modes [37–39]. To our knowledge, the anion effect on the coordination mode of Cd(II) atom has rarely been systematically reported. In this work, we selected five inorganic/organic anions as the secondary ligands at the presence of bbdmbm to react with Cd(II) atom and obtained four new Cd(II) complexes, [Cd(Cl)2(bbdmbm)] (1), [Cd(NO3)(N3)(bbdmbm)1.5]
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yellow block crystals of 4 were obtained. Yield: 31% based on Cd(II). Anal. Calc. for C72H64Cd2N16O24: C, 49.03; H, 3.63; N, 12.71. Found: C, 49.10; H, 3.65; N, 12.80%. IR (KBr, cm1): 3103s, 2941m, 1620s, 1571w, 1539s, 1508w, 1458m, 1388s, 1346s, 1215m, 1074m, 842m, 727s.
Scheme 1. The ligands used in this paper.
(2), [Cd(BBA)2(bbdmbm)(H2O)] (3), and [Cd(DNBA)2(bbdmbm)] (4), (HBBA = 4-bromobenzoic acid, HDNBA = 3,5-dinitrobenzoic acid) (Scheme 1). Complex 1 is a one-dimensional (1D) helical chain. Complex 2 shows a 1D ladderlike chain bridged by bbdmbm ligands. Complex 3 is a 1D linear coordination polymer. Complex 4 exhibits a dinuclear cluster. The effects of anions and conformations of bbdmbm ligand on the coordination modes of Cd(II) and structures of the title complexes have been investigated. 2. Experimental 2.1. Materials and measurements All chemicals were used as supplied from commercial sources without further purification. The bbdmbm ligand was synthesized by the method of literature [36] and characterized by FT-IR spectra. FT-IR spectra (KBr pellets) were taken on a Magna FT-IR 560 spectrometer. Elemental analyses were performed on a Perkin–Elmer 240CHN analyzer. The luminescence spectra for the samples were measured on a HITACHI F-4500 Fluorescence Spectrophotometer. 2.2. Preparation of the complexes 1–4 2.2.1. [Cd(Cl)2(bbdmbm)] (1) A mixture of CdCl22.5H2O (0.023 g, 0.1 mmol), bbdmbm (0.035 g, 0.1 mmol), H2O (10 mL) was sealed in a 25 mL Teflon reactor at 150 °C for 3 days. After slow cooling to room temperature, yellow block crystals of 1 were obtained. Yield: 35% based on Cd(II). Anal. Calc. for C22H26CdCl2N4: C, 49.83; H, 4.91; N, 10.57. Found: C, 49.91; H, 4.96; N, 10.62%. IR (KBr, cm1): 2954w, 2918w, 1510s, 1452m, 1205m, 842m. 2.2.2. [Cd(NO3)(N3)(bbdmbm)1.5] (2) A mixture of Cd(NO3)24H2O (0.031 g, 0.1 mmol), bbdmbm (0.035 g, 0.1 mmol), NaN3 (0.0065 g, 0.1 mmol) and H2O (10 mL) was sealed in a 25 mL Teflon reactor at 150 °C for 3 days. After slow cooling to room temperature, yellow block crystals of 2 were obtained. Yield: 12% based on Cd(II). Anal. Calc. for C33H39CdN10O3: C, 53.79; H, 5.30; N, 19.02. Found: C, 53.82; H, 5.39; N, 19.11%. IR (KBr, cm1): 3109w, 2937m, 2052s, 1504s, 1427m, 1336s, 848s. 2.2.3. [Cd(BBA)2(bbdmbm)(H2O)] (3) A mixture of CdSO48/3H2O (0.026 g, 0.1 mmol), bbdmbm (0.035 g, 0.1 mmol), HBBA (0.04 g, 0.2 mmol), NaOH (0.2 mL, 0.1 mol/L) and H2O (10 mL) was sealed in a 25 mL Teflon reactor at 150 °C for 3 days. After slow cooling to room temperature, yellow block crystals of 3 were obtained. Yield: 30% based on Cd(II). Anal. Calc. for C36H36CdBr2N4O5: C, 49.33; H, 4.11; N, 6.41. Found: C, 50.31; H, 4.12; N, 6.70%. IR (KBr, cm1): 3359m, 3103w, 2931m, 1589s, 1544s, 1504m, 1467m, 1215m, 848s, 769s. 2.2.4. [Cd(DNBA)2(bbdmbm)] (4) A mixture of CdSO48/3H2O (0.026 g, 0.1 mmol), bbdmbm (0.035 g, 0.1 mmol), HDNBA (0.042 g, 0.2 mmol), NaOH (0.2 mL, 0.1 mol/L) and H2O (10 mL) was sealed in a 25 mL Teflon reactor at 150 °C for 3 days. After slow cooling to room temperature,
2.3. X-ray crystallographic study Diffraction data for complexes 1–4 were collected on a Bruker Smart 1000 CCD area detector diffractometer (Mo-Ka radiation, graphite monochromator, k = 0.71069 Å for 1, 2 and k = 0.71073 Å for 3, 4). The crystal structures of 1–4 were solved by the direct method and refined on F2 by full-matrix least-squares technique with the SHELXL-97 software package [40,41]. All non-hydrogen atoms were refined anisotropically, and hydrogen atoms of ligand were placed in geometrically idealized positions and refined isotropically. In the complex 2, part of the bbdmbm ligands and the water molecules are disordered and the C32, C33, N4, O2, O3 positions were refined with half-occupancy atoms. The details of crystallographic information for complexes 1–4 are summarized in Table 1. Selected bond lengths and angles of complexes 1–4 are listed in Table S1.
3. Results and discussion 3.1. Description of crystal structures 3.1.1. [Cd(Cl)2(bbdmbm)] (1) The crystal structure analysis shows that complex 1 is a 1D helical chainlike coordination polymer constructed from chloridion and bbdmbm ligands. The coordination environment of Cd(II) is shown in Fig. 1. Each Cd(II) atom is tetra-coordinated by two chloridions and two nitrogen atoms (N1, N4) from two separated bbdmbm ligands, showing a distorted tetrahedral geometry (CdCl2N2). The bond distances of Cd–Cl(1), Cd–Cl(2), Cd–N(1), and Cd–N(4) are 2.4024(8), 2.4331(10), 2.2452(17), and 2.2430(15) Å, respectively. The bond angles of N–Cd–Cl are in the range of 102.44(6)–117.51(3)°. The bond angles of N–Cd–N and Cl–Cd–Cl are 105.33(6)° and 117.51(3)°, respectively. In complex 1, the bbdmbm ligand acts as a bridging bis(monodentate) ligand adopting a cis–trans–cis conformation and connects with two adjacent CdCl2N2 tetrahedron forming a 1D helical chain, as shown in Fig. 2. The distance between two Cd(II) atoms is 12.5691(48) Å (Fig. S1). Furthermore, the bbdmbm ligands from two adjacent chains are nearly parallel to each other with the dihedral angle of 2.17°, resulting in the formation of p–p stacking interactions between the N-rings and the C-rings of bbdmbm ligands from different 1D helical chains. Thus, the helical chains are expanded to 2D supramolecular network by the p–p stacking interactions, and the face-to-face distance between the N-rings and the C-rings of bbdmbm ligands is 3.770(2) Å. 3.1.2. [Cd(NO3)(N3)(bbdmbm)1.5] (2) X-ray diffraction analysis indicates that complex 2 is a 1D ladderlike coordination polymer and the asymmetric unit contains one Cd(II) atom, one NO3 anion, one N3 anion and one and a half bbdmbm ligands. The coordination environment of Cd(II) atom is depicted in Fig. 3. Different from that in complex 1, the Cd(II) atom is coordinated by three nitrogen atoms (N1, N3, N5) from three separated bbdmbm ligands, two oxygen atoms (O1, O2) from two nitrate anions and another nitrogen atom (N7) from N3 anion to complete a six-coordinated environment, showing a distorted octahedral geometry (CdO2N4). The lengths of Cd–N and Cd–O are 2.225(3)–2.4331(10) Å and 2.396(5)–2.449(3) Å, respectively.
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Table 1 Crystal data and structure refinement details for complexes 1–4.
a b
Complex
1
2
3
4
Formula Formula weight Crystal system Space group a (Å) b (Å) c (Å) a (°) b (°) c (°) V (Å3) Z Dcalc (g cm3) l (mm1) F(0 0 0) hmax (°) Total data collected Unique data reflections Rint R1a [I > 2r(I)] wR2b (all data) Goodness-of-fit (GOF) Dqmax (e Å3) Dqmin (e Å3)
C22H26CdCl2N4 529.77 monoclinic P21/n 9.174(5) 14.072(5) 17.537(5) 90 96.689(5) 90 2248.6(16) 4 1.565 1.225 1072 25.50 17618 4426 0.0151 0.0195 0.0568 1.03 0.286 0.307
C33H39CdN10O3 736.14 triclinic P1
C36H36CdBr2N4O5 842.61 triclinic P1 6.2705(9) 11.9708(16) 12.8551(17) 109.291(2) 101.464(2) 96.621(2) 875.3(2) 1 1.595 2.951 402 25.00 4471 3709 0.0187 0.0456 0.1253 1.042 0.639 0.642
C72H64Cd2N16O24 1762.21 triclinic P1
10.870(5) 12.164(5) 14.439(5) 109.434(5) 103.844(5) 101.199(5) 1668.1(12) 2 1.466 0.705 758 25.10 10167 5880 0.0136 0.0319 0.0939 1.08 1.107 0.949
10.4046(10) 12.9086(12) 14.3666(13) 80.6440(10) 80.7020(10) 79.5630(10) 1855.0(3) 1 1.578 0.664 896 25.00 9506 6459 0.0279 0.0409 0.0886 1.017 0.364 0.397
R1 = Rh(||Fo| |Fc||)/R|Fo|. i wR2 = ðwðjF o j2 jF c j2 Þ2 =ðwjF o j2 Þ2 1/2.
Fig. 1. The coordination environment of Cd(II) in complex 1, showing a distorted tetrahedral geometry. The hydrogen atoms were omitted for clarity.
The bond angles of N–Cd–N and N–Cd–O are in the range of 84.11(10)–176.12(8)° and 51.98(14)–150.94(15)°, respectively. It should be noted that the bbdmbm ligands show two kinds of coordination conformations in complex 2 with the NN distances 10.30 Å and 9.17 Å, respectively (Fig. S2). One kind of bbdmbm ligand adopts trans–trans–trans conformation, connecting two neighboring CdO2N4 geometry into a 1D linear chain. Another kind of bbdmbm ligand exhibits a cis–trans–cis conformation, which is shorter in length, and links two neighboring 1D chain to a ladderlike structure. The distances between Cd(II) atoms linked by two kinds of bbdmbm ligands are 14.439(5) Å and 13.563(4) Å, respectively (see Fig. 4).
Fig. 2. 2D supramolecular network constructed from 1D helical chain through p–p stacking interactions in complex 1.
3.1.3. [Cd(BBA)2(bbdmbm)(H2O)] (3) X-ray structural determination reveals that complex 3 is a 1D chain constructed from a Cd(II) atom, two BBA anions, one
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In complex 3, the adjacent CdO5N2 geometry is linked into a 1D chain by bbdmbm ligands, which adopts cis–cis–cis conformations (see Fig. S3). Each bbdmbm ligand links two CdO5N2 polyhedron with the distance of 14.383(2) Å between the adjacent Cd(II). Moreover, in the adjacent 1D chains, H-bonding interactions are found among the carboxylic oxygen atoms from BBA anions and the coordination water molecules [O(5)–H(5A)O(3): 2.706 Å, O(5)–H(5B)O(2): 2.744 Å]. Thus, a 2D supramolecular network was obtained through H-bonding interactions, as shown in Fig. 6.
Fig. 3. The coordination environment of Cd(II) in complex 2, showing a distorted octahedral geometry. The hydrogen atoms were omitted for clarity.
Fig. 4. 1D ladderlike chain connected by bbdmbm ligand in complex 2.
coordination water molecule and one bbdmbm ligand. The coordination environment of Cd(II) atom is shown in Fig. 5. Different from those in complexes 1 and 2, the Cd(II) atom is seven-coordinated by four oxygen atoms from two chelating carboxylic groups of two BBA anions [Cd–O 2.400(9)–2.451(10) Å], two nitrogen atoms belonging to two bbdmbm ligands [Cd–N 2.287(10), 2.336(9) Å] and one oxygen atom from a coordination water molecule [Cd–O 2.327(6) Å], showing a pentagonal bipyramid geometry (CdO5N2). The bond angles of N–Cd–O and O–Cd–O are in the range of 86.0(3)–91.8(3)° and 53.7(2)–167.8(2)°, respectively.
Fig. 5. The coordination environment of Cd(II) in complex 3, showing a pentagonal bipyramid geometry. The hydrogen atoms were omitted for clarity.
3.1.4. [Cd(DNBA)2(bbdmbm)] (4) Compared with the 1D coordination polymers of complexes 1– 3, complex 4 exhibits a dinuclear structure. The asymmetric unit of 4 contains one Cd(II) atom, two DNBA and one bbdmbm ligand. The coordination environment of Cd(II) atom is shown in Fig. 7. Each Cd(II) atom is pent-coordinated by two nitrogen atoms from two bbdmbm ligands [Cd–N 2.185(3), 2.278(3) Å], two oxygen atoms from a chelating carboxylic group of DNBA anion [Cd–O 2.219(3) Å, 2.682(3) Å], and one oxygen atom from a monodentate carboxylic group of DNBA anion [Cd–O 2.240(3) Å], showing a distorted trigonal bipyramid geometry (CdO3N2). The adjacent CdO3N2 geometries are bridged by bbdmbm ligands to form a dinuclear cluster, with the distance of 8.0881(6) Å between Cd(II) atoms. The bond angles of N–Cd–O and O–Cd–O are in the range of 88.63(11)–128.51(11)° and 52.46(10)–142.82(10)°, respectively. DNBA anion adopts two kinds of coordination modes in complex 4, which is monodentate mode [Cd–O 2.240(3) Å] and chelating mode [Cd–O 2.219(3) Å, 2.682(3) Å], respectively. The bbdmbm ligand links CdO3N2 geometries in cis–trans–trans conformations. Unlike complex 1, three different kinds of p–p stacking interactions exist in complex 4: p–p stacking interactions between the aromatic rings from two parallel monodentate DNBAa with the face-to-face distance of 3.565 Å (Fig. S4a), two parallel chelating DNBAb with the face-to-face distance of 3.751 Å (Fig. S4b), and the p–p stacking interactions between the aromatic rings from two paired bbdmbm ligands with the face-to-face distance of 3.653 Å (Fig. S4c). Thus, the neighboring dinuclear units are further extended into a 3D supramolecular framework through these p–p stacking interactions, as shown in Fig. 8. 3.2. Effect of anions and conformation of bbdmbm on complexes 1–4 In complexes 1–4, Cd(II) atoms show different coordination modes at the presence of bbdmbm ligand and different secondary anion ligands, as shown in Fig. 9. In 1, Cd(II) atom adopts tetracoordinated tetrahedral geometry at the presence of Cl anion. In 2, we choose NO3 and N3 as secondary anion ligands and Cd(II) atom exhibits six-coordinated octahedral geometry. In 3, Cd(II) atom shows seven-coordinated mode when BBA was used as secondary anion. In 4, Cd(II) atom shows five-coordinated distorted trigonal bipyramid geometry at the presence of DNBA anion. The results indicate that the anion shows great influence on the coordination mode of Cd(II). On the other hand, the size of anion ligands plays an important role in constructing the title complexes. In complex 1, a small sphere inorganic anion Cl is used and a 1D helical chain is obtained. In complex 2, Cd(II) is coordinated by N3 and NO3 simultaneously and then a 1D ladderlike coordination polymer is synthesized. In complexes 3 and 4, we select the larger aromatic carboxylate anions BBA and DNBA, a 1D linear and a dinuclear complex are prepared. It is noticed that H-bonding and p–p stacking interactions between the inorganic and organic ligands show significant effect on constructing high-dimensional supramolecular frameworks. Compared with the complexes reported by Lang’s group, the title complexes show low dimensional structures, which
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Fig. 6. 2D supramolecular network constructed from 1D chain through hydrogen bonds in complex 3.
Fig. 7. The coordination environment of Cd(II) in complex 4, showing a distorted trigonal bipyramid geometry. The hydrogen atoms were omitted for clarity.
Fig. 8. 3D supramolecular framework constructed from the dinuclear cluster through p–p stacking interactions in complex 4.
conformation with the distance between two adjacent Cd(II) atoms of 12.5691(48) Å. Two kinds of conformations of bbdmbm ligands exist in 2 with distances between two adjacent Cd(II) atoms of 14.439(5) Å and 13.563(4) Å, respectively. In 3, bbdmbm ligands adopt cis–cis–cis conformation with the distance between two adjacent Cd(II) atoms of 14.383(2) Å. Different from 1–3, bbdmbm ligands adopt cis–trans–trans conformation and the distance between two adjacent Cd(II) atoms is much shorter in 4, which may lead to the formation of dinuclear structure of complex 4. Fig. 9. The coordination modes of Cd(II) in complexes 1–4.
3.3. Properties might be attributed to the steric hindrance of –CH3 substituting group of bbdmbm. Bbdmbm ligands adopt five kinds of conformations in complexes 1–4 (see Fig. 10). In complex 1, bbdmbm ligands adopt cis–trans–cis
3.3.1. IR spectroscopy In complex 1, the bands at 842 cm1, 1452 cm1, 1510 cm1 (848 cm1, 1427 cm1, 1504 cm1 for 2; 848 cm1, 1467 cm1,
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Fig. 10. Five kinds of conformations of bbdmbm in the complexes 1–4 with CdCd distances 12.57 Å, 13.56 Å, 14.44 Å, 14.38 Å, 8.09 Å, respectively.
the crystal structures and fluorescent emission of the Cd(II) coordination polymers. 4. Conclusion Four new Cd(II) complexes were obtained under hydrothermal conditions by using bbdmbm ligand and different organic/inorganic anions. Complexes 1–4 show diverse crystal architectures. This work reflects that organic/inorganic anions, acting as ligands, show great effect on the coordination geometry of center Cd(II) atom and conformations of bbdmbm ligand, thus leading to structural diversification and different luminescence properties of title complexes. Acknowledgments
Fig. 11. Emission spectra of bbdmbm and complexes 1–4 in the solid state at room temperature.
This work was supported by the NCET-09-0853, the National Natural Science Foundation of China (No. 20871022) and the Foundation of Liaoning Province (No. 2009R03 and 2009A028). Appendix A. Supplementary material
1504 cm1 for 3; 842 cm1, 1458 cm1, 1508 cm1 for 4) can be attributed to mC–N of N-heterocyclic rings of bbdmbm ligands. The presence of band at 2918 cm1 and 2954 cm1 (2937 cm1, 3109 cm1, for 2; 2931 cm1, 3105 cm1 for 3; 2941 cm1, 3103 cm1 for 4) can be considered as mC–C of –CH3 and –CH2– of bbdmbm. In 2, the IR bands at 2052 cm1 and 1336 cm1 are attributed to the m(N3) and m(–NO2). In 3, the IR bands at 3359 cm1 and 1589 cm1 are attributed to the m(H2O) and m(–COO) of BBA. In 4, strong bands at 1346 cm1 to 1620 cm1 can be attributed to the m(–NO2) (1539 cm1 and 1346 cm1) and m(–COO) (1388 cm1 and 1620 cm1) of DNBA [42]. 3.3.2. Fluorescence properties of complexes 1–4 The photoluminescent properties of complexes 1–4, together with the ligand bbdmbm, were studied in solid state at room temperature. The emission spectra of the complexes and the bbdmbm ligand are shown in Fig. 11. Emission bands can be observed at 421 nm (kex = 350 nm) for 1, 420 nm (kex = 370 nm) for 2, 410 nm (kex = 360 nm) for 3, 470 nm (kex = 330 nm) for 4, which is different from that of the bbdmbm ligand 533 nm (kex = 300 nm). The main emission bands may be attributed to the ligand–metal charge transfer (LMCT) as reported in other Cd(II) complexes with N-donor ligands [43,44]. The obvious blue-shift of ca. 60–120 nm occurred in the title complexes compared with the bbdmbm ligand. In addition, compared with complexes 1–3, complex 4 has less significant change of ca. 60 nm, which is probably rationalized by the different crystal architectures [45,46]. The photoluminescent property shows that the coordination anions make great contribution to
CCDC 778432, 778433, 778434, and 778435 contain the supplementary crystallographic data for complexes 1–4, respectively. These data can be obtained free of charge from The Cambridge Crystallographic Data Centre via www.ccdc.cam.ac.uk/data_request/cif. Supplementary data associated with this article can be found, in the online version, at doi:10.1016/j.ica.2011.04.023. References [1] R. Matsuda, R. Kitaura, S. Kitagawa, Y. Kubota, R.V. Belosludov, T.C. Kobayashi, H. Sakamoto, T. Chiba, M. Takata, Y. Kawazoe, Nature 436 (2005) 238. [2] R.E. Morris, P.S. Wheatley, Angew. Chem., Int. Ed. 47 (2008) 4966. [3] J.R. Li, X.H. Bu, R.H. Zhang, Inorg. Chem. 43 (2004) 237. [4] A.R. Millward, O.M. Yaghi, J. Am. Chem. Soc. 127 (2005) 17998. [5] H. Furukawa, M.A. Miller, O.M. Yaghi, J. Mater. Chem. 17 (2007) 3197. [6] H. Chun, H. Jung, J. Seo, Inorg. Chem. 48 (2009) 2043. [7] G. Yang, R.G. Raptis, P. Šafár, Cryst. Growth Des. 8 (2008) 981. [8] D.L. Long, A.J. Blake, N.R. Champness, C. Wilson, M. Schröder, J. Am. Chem. Soc. 123 (2001) 3401. [9] A.Ö. Yazaydin, R.Q. Snurr, T.H. Park, K. Koh, J. Liu, M.D. LeVan, A.I. Benin, P. Jakubczak, M. Lanuza, D.B. Galloway, J.J. Low, R.R. Willis, J. Am. Chem. Soc. 131 (2009) 18198. [10] C. Qin, X.L. Wang, E.B. Wang, Z.M. Su, Inorg. Chem. 44 (2005) 7122. [11] K.Z. Shao, Y.H. Zhao, X.L. Wang, Y.Q. Lan, D.J. Wang, Z.M. Su, R.S. Wang, Inorg. Chem. 48 (2009) 10. [12] W.Q. Zou, M.S. Wang, Y. Li, A.Q. Wu, F.K. Zheng, Q.Y. Chen, G.C. Guo, J.S. Huang, Inorg. Chem. 46 (2007) 6852. [13] D. Venkataraman, S. Lee, J.S. Moore, P. Zhang, K.A. Hirsch, G.B. Gardner, A.C. Covey, C.L. Prentice, Chem. Mater. 8 (1996) 2030. [14] B. Moulton, M.J. Zaworotko, Chem. Rev. 101 (2001) 1629. [15] L. Carlucci, G. Ciani, P. Macchi, D.M. Proserpio, S. Rizzato, Chem. Eur. J. 5 (1999) 237. [16] O.S. Jung, S.H. Park, K.M. Kim, H.G. Jang, Inorg. Chem. 37 (1998) 5781.
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