Four Cobaltic Coordination Polymers Based on 5-Iodo-Isophthalic Acid

Article pubs.acs.org/crystal

Four Cobaltic Coordination Polymers Based on 5-Iodo-Isophthalic Acid: Halogen-Related Interaction and Solvent Effect Shuang-Quan Zang,*,† Ming-Ming Dong,† Ya-Juan Fan,† Hong-Wei Hou,† and Thomas C. W. Mak†,‡ †

Department of Chemistry, Zhengzhou University, Zhengzhou 450001, P. R. China Department of Chemistry, The Chinese University of Hong Kong, Shatin, New Territories, Hong Kong SAR, P. R. China

‡

S Supporting Information *

ABSTRACT: A series of four novel cobaltic coordination polymers based on 5-iodo-isophthalic acid (5-iipa) and 1,1′-(1,4-butanediyl)bis(imidazole) (bbi), namely, [Co(5-iipa)(bbi)·3(H2O)]n (1), [Co2(5-iipa)2(bbi)2·3(C2H6O2)]n (2), [Co(5-iipa)(bbi)·DMF]n (3) (DMF = N,N′-dimethylformamide), and [Co2(5-iipa)2(bbi)2·2DMAc]n (4) (DMAc = N,N′-dimethylacetamide) have been solvothermally synthesized by using various solvents. Their thermal analysis, XRD and UV−vis absorption spectra have been investigated as well. Structural analyses exhibit that they all form 2D covalent structures based on the intersection of Co-5-iipa and Co-bbi chains, and adjacent layers are parallel and united together to yield a 3D supramolecular structure through interlayer I···I, I···π, or C−H···O interactions, respectively. More interestingly, channels are detected in the architectures, which are mainly occupied by the guest solvent molecules. Compound 1 features a rare 3-fold interpenetrating 3D supramolecular architecture, while compound 2 exhibits an interesting 3-fold parallel interpenetrated two-dimensional (2D) → three-dimensional (3D) network motifs based on I···I interactions. The adjacent 2D parallel layers in compound 3 deviate from each other with the shift of 3.89 Å along the b or − b axis. Compound 4 shows a double layer structure in which the bbi-Co waving-like ribbon is running along the c-axis. Results demonstrate that both halogen-related interaction and solvent effect play important roles in the assembly of the supramolecular metal−organic networks.

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INTRODUCTION Metallosupramolecular chemistry have received considerable attention because of the creation of various interesting structures and their potential applications in sensor, gas storage, separation, photochemistry, magnetism, and catalysis technologies.1,2 Some characteristics of the supramolecules are related to noncovalent interactions which determine their architectures and properties.3 Classical noncovalent interactions such as hydrogen bonding4 and π···π5 interaction have played important roles in the assembly of the metallosupromolecular systems and have been well analyzed. Recently, halogen-related interactions, including halogen bonding as well as related halogen···halogen and halogen···π intermolecular interactions have been another attractive interactions in crystal engineering.6−8 However, the presence of halogen bonding in metal coordination polymers especially high-dimensional coordination polymers remains largely unexplored and needs more elaborate and systematic studies. Early reports have shown that solvents play a major role in the assembly of metallosupramolecular chemical processes.9 Many interesting systems based on coordination polymers in different solvents have been presented in recent years.10 Du and co-workers11 have demonstrated that the solvent effect on regulating such diversiform metallosupramolecular solids, incorporating their crystal growth/assembly, structural modulation, dynamic transformations, and potential applications, © 2012 American Chemical Society

which may provide new insights into the rational design and construction of such advanced crystalline materials. Considering carboxylate compounds12 are one of the most efficient families in the formation of metal−organic coordination polymers with different structures and halogen groups can be used to create halogen-bonding sites in cross-linked polymers, we make use of the rigid ligand 5-iodo-isophthalic acid (5-iipa) which is the combination of the halogen atom and carboxylate compound to construct metal−organic supramolecular compounds. In our latest works, a series of metallosupromolecular complexes based on 5-iodo-isophthalic acid (5-iipa) and ancillary nitrogen ligands have been synthesized, in which 1D or 2D structures are expanded to 3D supromolecular architectures through I-related and other supromolecular interactions.13 Although we think that 5-iipa is an effective bridging ligand and its tethered iodine atom contributes to the formation of the 3D supramolecular structure by forming halogen bonding, the use of so many different metal ions and different ancillary nitrogen liagnds makes it somewhat not systemic enough to extract such results. To further understand the ability of 5-iipa producing new supramolecular structures based on halogen-related Received: September 24, 2011 Revised: December 27, 2011 Published: January 24, 2012 1239

dx.doi.org/10.1021/cg201257j | Cryst. Growth Des. 2012, 12, 1239−1246

Crystal Growth & Design

Article

[Co2(5-iipa)2(bbi)2·3(C2H6O2)]n (2). Complex 2 was synthesized by a solvothermal procedure similar to that described for 1 except using glycol instead of distilled water. Purple rectangular crystals of 1 were obtained in 65% yield based on cobalt. Anal. Calcd for (C42H52Co2I2N8O10): C, 38.89; H, 4.14; N, 8.86%. Found: C, 38.96; H, 4.08; N, 8.79%. IR/cm−1 (KBr): 3423(s), 3129(m), 2928(w), 1616(vs), 1542(m), 1342(vs), 1231(w), 1107(m), 1089(m), 773(m), 718(s), 656(m). [Co(5-iipa)(bbi)·DMF]n (3). A mixture of 5-iodo-isophthalic acid (0.0146 g, 0.05 mmol), 1,1′-(1,4-butanediyl)bis(imidazole) (bbi) (0.0095 g, 0.05 mmol) and CoCl2·6H2O (0.0119 g, 0.05 mmol) in DMF (7 mL) was placed in a Teflon-lined stainless steel container, heated to 120 °C for 3 days, and then cooled to room temperature. Purple block crystals of 3 were obtained in 69% yield based on cobalt. Anal. Calcd for (C21H24CoIN5O5): C, 41.19; H, 3.95; N, 11.44%. Found: C, 41.11; H, 3.89; N, 11.50%. IR/cm−1 (KBr): 3419(w), 3128(s), 2927(w), 1667(m), 1615(s), 1526(m), 1231(w), 1342(vs), 1107(s), 1089(s), 772(s), 718(s), 654(m). [Co2(5-iipa)2(bbi)2·2DMAc]n (4). Complex 4 was synthesized by a solvothermal procedure similar to that described for 3 except using DMAc instead of DMF and Co(NO3)2·6H2O (0.0146 g, 0.05 mmol) instead of CoCl2·6H2O. Purple needle crystals of 4 were obtained in 82% yield based on cobalt. Anal. Calcd for (C44H52Co2I2N10O10): C, 42.19; H, 4.18; N, 11.18%. Found: C, 42.26; H, 4.10; N, 11.27%. IR/ cm−1 (KBr): 3424(s), 3128(m), 2938(w), 1619(vs), 1548(m), 1422(w), 1367(vs), 1235(w), 1110(m), 1092(m), 774(m), 724(s), 658(m). X-ray Crystallography. Single crystals suitable for X-ray analyses were used for intensity data collection on a Bruker SMART APEX CCD diffractometer17 using graphite-monochromatized Cu Kα radiation (λ = 1.54178 Å) at low temperature for 1 and Mo Kα radiation (λ = 0.71073 Å) at room temperature for others using the ω-scan technique. Lorentz polarization and absorption corrections were applied. The structures were solved by direct methods with SHELXS9718 and refined with the full-matrix least-squares technique using the SHELXL-9719 program. Anisotropic thermal parameters were assigned to all non-hydrogen atoms. The hydrogen atoms of the coordination water molecules and ligands were included in the structure factor calculation at idealized positions by using a riding model and refined isotropically. The hydrogen atoms of the solvent water molecules were located from the different Fourier maps, then restrained at fixed positions and refined isotropically. Analytical expressions of neutral atom scattering factors were employed, and anomalous dispersion corrections were incorporated. The crystallographic data and selected bond lengths and bond angles for 1−4 are listed in Tables 1 and 2.

interaction, the synthetic strategy utilized in our continuate study is using same metal center and ligand, and studying the influence of solvent molecules to tune the halogen bonding in supramolecular architectures. The use of the “mix-ligand” synthetic strategies is an effective method for the construction of coordination polymers.14 In our latest investigation of the coordination chemistry of 5-iodoisophthalic acid, we have selected four nitrogen heterocyclic ligands as ancillaries, namely, phen, bpe, p-bix, and m-bix (phen = 1,10-phenanthroline, bpe = 1,2-bis(4-pyridyl)ethene, p-bix = 1,4-bis(imidazol-1-ylmethyl)-benzene, m-bix = 1,3bis(imidazol-1-ylmethyl)-benzene,). In this study, we have selected a different 1,1′-(1,4-butanediyl)bis(imidazole) (bbi) as ancillary ligand because its longer and more flexible −(CH2)4− spacers may lead to structures with novel topologies.15 Presented here is a series of four novel cobaltic coordination polymers based on 5-iodo-isophthalic acid (5-iipa) and ancillary ligand 1,1′-(1,4-butanediyl)bis(imidazole) (bbi), namely, [Co(5-iipa)(bbi)·3(H 2 O)] n (1), [Co 2 (5-iipa) 2 (bbi) 2·3 (C2H6O2)]n (2), [Co(5-iipa)(bbi)·DMF]n (3) (DMF = N,N′dimethylformamide), and [Co2(5-iipa)2(bbi)2·2DMAc]n (4) (DMAc = N,N′-dimethylacetamide).

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EXPERIMENTAL SECTION

Materials and Physical Measurements. 5-Iodo-isophthalic acid was prepared according to the literature.16 All other starting materials were of analytical grade and obtained from commercial sources without further purification. Elemental analysis for C, H, and N were performed on a Perkin-Elmer 240 elemental analyzer. The FT-IR spectra were recorded from KBr pellets in the range from 4000 to 400 cm−1 on a Bruker VECTOR 22 spectrometer. Thermal analyses were performed on a SDT 2960 thermal analyzer from room temperature to 800 °C at a heating rate of 20 °C/min under nitrogen flow. X-ray powder diffraction (XRD) data were collected on a Rigaku D/Max-2500PC diffractometer with Cu Kα radiation (λ = 1.5406 Å) over the 2θ range of 5−60° with a scan speed of 5°/min at room temperature. Solid UV−visible spectra were obtained in the 200−800 nm range on a JASCO UVIDEC-660 spectrophotometer. Syntheses. The reactions of 5-iodo-isophthalic acid (5-iipa) and 1,1′-(1,4-butanediyl)bis(imidazole) (bbi) with divalent cobalt ions under hydro(solvo)thermal conditions yielded four purple X-ray suitable crystals by using distilled water, glycol, DMF, and DMAc solvents, respectively. When we attempted other solvents, poor blue crystals were obtained in acetonitrile, methanol, or 1,4-dioxane systems, and precipitates were obtained in other reactions. Unfortunately, such blue crystals can’t be used to collect X-ray data. Interestingly, purple single crystals of [Co(5-iipa)(bbi)·3(H2O)]n (1) were obtained when the blue ones were placed in distilled water for 3 days at room temperature, which share completely the same structure as that obtained directly from the distilled water. We also obtained [Co(5-iipa)(bbi)·3(H2O)]n (1) from a mixture system of methanol and water. The changes induced between similar solvent pairs (water/ethylene glycol and DMF/DMAc) were investigated, namely, complex 1 was dipped in glycol and 2 was placed in distilled water for seven days, 3 and 4 were treated with DMAc and DMF respectively, but no amazing phenomenon was observed. [Co(5-iipa)(bbi)·3(H2O)]n (1). A mixture of 5-iodo-isophthalic acid (0.0146 g, 0.05 mmol), 1,1′-(1,4-butanediyl)bis(imidazole) (bbi) (0.0095 g, 0.05 mmol), CoCl2·6H2O (0.0119 g, 0.05 mmol), and LiOH·H2O (0.0042 g, 0.1 mmol) in distilled water (7 mL) was placed in a Teflon-lined stainless steel container, heated to 120 °C for 3 days, and then cooled to room temperature. Purple needle crystals of 1 were obtained in 76% yield based on cobalt. Anal. Calcd for C18H23CoIN4O7 (593.23): C, 36.44; H, 3.91; N, 9.44%. Found: C, 36.48; H, 3.88; N, 9.49%. IR/cm−1 (KBr): 3420(m), 3128(m), 2941(w), 1610(vs), 1548(s), 1421(m), 1340(vs), 1235(m), 1091(s), 773(m), 716(s), 657(m).

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RESULTS AND DISCUSSION [Co(5-iipa)(bbi)·3(H2O)]n (1). X-ray crystallographic analysis revealed that complex 1 crystallizes in monoclinic space group P21/c and has some intriguing features. The asymmetric unit contains one four-coordinated Co(II) center, one 5-iipa2− ligand, one bbi ligand,and three lattice water molecules. Among them, the site occupancies of both O3W and O4W are 0.5, and O2W have two disordered positions with occupancy ratios of 0.5:0.5. Each Co(II) center is located in a distorted tetrahedral environment shaped by two oxygen atoms of two monodentated carboxylate groups from different 5-iipa2− ligands, and two nitrogen atoms from two different bbi molecules, as depicted in Figure 1a. At the first glance, the 5-iipa-Co chains are joined together by μ2-bridged bbi ligands to form a layer with a (4,4) lattice, which is common in the structure of the coordination polymer based on isophthalic acid and its derivatives.20 Additional investigation for this structure indicates that the Co atoms are interlinked through bbi ligands in TGT conformation with the dihedral angles between the imidazole rings of ∼46.6° to form a helix along the [010] direction with the pitch of 17.401 Å, and 1240



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Table 1. Crystal Data and Structure Refinement for Complexes 1−4 formula fw cryst syst space group a (Å) b (Å) c (Å) β (deg) V (Å3) Z Dc (g·cm−3) F(000) R(int) GOF R1a (I > 2σ(I)) R2b (I > 2σ(I)) max/min (e Å−3) a

1

2

3

4

C18H23CoIN4O7 593.23 monoclinic P21/c 8.0435(6) 17.4010(18) 17.9545(14) 110.689(6) 2350.9(4) 4 1.676 1180 0.0410 1.025 0.0604 0.1440 1.186/−0.635

C42H52Co2I2N8O10 1264.58 monoclinic P21/c 15.131(4) 19.269(10) 18.433(6) 108.89(3) 5085(3) 4 1.652 2528 0.0522 0.986 0.0538 0.1082 1.101/−0.914

C21H24CoIN5O5 612.28 monoclinic P21/c 10.2864(4) 24.1852(19) 9.8258(5) 99.757(5) 2409.1(2) 4 1.688 1220 0.0343 1.019 0.0513 0.0983 1.324/−1.097

C44H52Co2I2N10O10 1252.62 orthorhombic Pna21 24.7094(17) 19.5965(10) 11.1511(6) 90 5399.6(5) 4 1.541 2504 0.0299 0.995 0.0673 0.1596 1.727/−0.881

R1 = ∑||Fo| − |Fc||/∑|Fo|. bR2 = {∑[w(Fo2 − Fc2)2]/∑[w(Fo2)2]}1/2.

Table 2. Selected Bond Lengths (Å) and Angles (deg) for 1−4 compound 1a Co(1)−O(4A) Co(1)−N(4B) O(4A)−Co(1)−O(1) O(4A)−Co(1)−N(4B)

1.966(5) 2.012(6) 104.6(2) 99.8(2)

Co(1)−O(5) Co(1)−N(1) Co(2)−N(4) O(5)−Co(1)−O(8A) O(5)−Co(1)−N(1) O(2B)−Co(2)−O(4) O(2B)−Co(2)−N(8C)

1.963(3) 2.033(4) 2.016(5) 109.5(2) 95.4(2) 110.7 (2) 95.7(2)

Co(1)−O(4A) Co(1)−N(1) O(4A)−Co(1)−O(1) O(4A)−Co(1)−N(1) Co(1)−O(1) Co(1)−N(1) Co(2)−O(3B) O(1)−Co(1)−O(5) O(1)−Co(1)−N(1) O(7A)−Co(2)−N(4) O(7A)−Co(2)−N(8C)

1.991(4) 2.052(5) 103.5(2) 109.5(2) 1.990(7) 2.032(9) 2.019(6) 94.4(3) 110.8(3) 116.4(3) 116.9(3)

Co(1)−O(1)

1.976(5)

Co(1)−N(1)

O(4A)−Co(1)−N(1) O(1)−Co(1)−N(4B) compound 2b

110.1(3) 110.0(2)

O(1)−Co(1)−N(1) N(1)−Co(1)−N(4B)

Co(1)−O(8A) Co(2)−O(2B) Co(2)−N(8C) O(5)−Co(1)−N(5) O(8A)−Co(1)−N(1) O(2B)−Co(2)−N(4) O(4)−Co(2)−N(8C) compound 3c

1.980(4) 1.954(3) 2.017(5) 110.0(2) 106.6(2) 108.8(2) 108.1(2)

Co(1)−N(5) Co(2)−O(4)

Co(1)−O(1)

1.998(3)

O(4A)−Co(1)−N(4B) O(1)−Co(1)−N(1) compound 4d

112.8(2) 106.5(2)

Co(1)−O(5) Co(2)−O(7A) Co(2)−N(8C) O(1)−Co(1)−N(5) O(5)−Co(1)−N(1) O(7A)−Co(2)−O(3B) N(4)−Co(2)−N(8C)

1.992(6) 2.000(7) 2.044(8) 118.4(3) 106.1(3) 113.8(3) 108.8(3)

O(8A)−Co(1)−N(5) N(5)−Co(1)−N(1) O(4)−Co(2)−N(4) N(4)−Co(2)−N(8C) Co(1)−N(4B) O(1)−Co(1)−N(4B) N(4B)−Co(1)−N(1) Co(1)−N(5) Co(2)−N(4) O(5)−Co(1)−N(5) N(5)−Co(1)−N(1) N(4)−Co(2)−O(3B) O(3B)−Co(2)−N(8C)

1.999(7) 120.2(3) 110.0(3) 2.021(4) 1.959(4) 124.4(2) 107.0(2) 118.9(2) 112.1(2) 2.015(4) 105.8(2) 117.5(2) 2.014(8) 2.018(8) 120.3(3) 106.1(4) 92.1(3) 105.7(3)

Symmetry codes: A x,−y + 3/2, z + 1/2; B −x + 2, y − 1/2, −z + 1/2. bSymmetry codes: A x, −y + 3/2, z + 1/2; B x, −y + 5/2, z + 1/2; C x, y + 1, z. Symmetry codes: A x + 1, y, z; B −x + 2, y − 1/2, −z + 3/2. dSymmetry codes: A −x + 1, −y + 2, z − 1/2; B −x + 1, −y + 1, z − 1/2; C x, y, z − 1.

a c

the bbi ligands as rods, a (4, 3)-connected network with a Schläfli symbol of (64·82)(6·82) topology can be invoked (Figure 1d). Of particular interest, three identical 3D single nets are interlocked with each other, thus directly leading to the formation of a 3-fold interpenetrated architecture (Figure 1e). The most striking feature of complex 1 is that there exist rectangular channels running along the a-axis direction with ∼9.318 × 13.472 Å apertures in the 3D supramolecular frameworks. The channels are mainly occupied by the guest water molecules. Approximately 20.2% of the crystal volume is

both left and right-handed helices exist in the same layer with an ABAB pattern, thus a mesomeric pillared 2D network is generated (Figure 1b). It is worth noting that adjacent layers are arranged parallel each other with the I···I distance being 3.735 Å, which is shorter than the sum of the van der Waals radiis of the two atoms (∼4.12 Å),21 indicating the exist of the I···I interactions; thus the 2D covalent network is expanded to a 3D supramolecular structure, as shown in Figure 1c. Taking account of the I···I interactions, taking the Co centers as 4-connected nodes and 5-iipa2− ligands as 3-connected nodes, 1241



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Figure 2. (a) A view of the whole network along the a-axis with water chains shown in space filling mode occupying the channels. All hydrogen atoms are omitted for clarity. (b) A quasiplanar cyclic water octamer in complex 1. (Symmetry codes: #1 −1 + x, 1.5 − y, −0.5 + z; #2 x, 1.5 − y, −0.5 + z; #3 x, 0.5 − y, −0.5 + z; #4 1 − x, −0.5 + y, −0.5 − z.)

Table 3. Hydrogen-Bonding Parameters in 1−4 (in Å and deg) D−H···A O(1W)−H(1WA)···O(1)i O(1W)−H(1WB)···O(3)ii O(2W)−H(2WA)···O(1W) O(2W)−H(2WB)···O(2) O(3W)−H(3WB)···O(1W)iii O(4W)−H(4WA)···O(2W)iv O(4W)−H(4WB)···O(3W)v

Figure 1. (a) Metal coordination and atom labeling in complex 1 (thermal ellipsoids at 50% probability level). All hydrogen atoms and lattice water molecules are omitted for clarity. Symmetry codes: A x, − y + 3/2, z + 1/2; B −x + 2, y − 1/2, −z + 1/2. (b) The 2D layer composed of 5-iipa-Co chains and bbi-Co helices. (c) The 3D net connected by interlayer I···I interactions. (Dotted lines represent I···I interactions.) (d) Schematic presentation of a single 3D structure: Aqua and purple balls represent Co atoms and 5-iipa2− ligands, respectively. (e)The space-filling mode of the 3-fold interpentration.

O(9)−H(9)···O(11)i O(10)−H(10A)···O(14)ii O(11)−H(11)···O(7)iii O(12)−H(12)···O(1)iv O(13)−H(13C)···O(10)iii O(14)−H(14A)···O(3)iv

occupied by lattice water molecules with a volume of ∼474.6 Å3 in each cell unit (Figure 2a) based on a PLATON calculation.22 As shown in Figure 2b, four pairs of symmetric related water molecules are linked together through O−H···O hydrogen bonds forming a quasiplanar cyclic water octamer. Such octamers are fixed to the framework through numerous hydrogen contacts involving O1W, O2W, and some carboxylate oxygen atoms. The parameters of the hydrogen bonds are list in Table 3. [Co2(5-iipa)2(bbi)2·3(C2H6O2)]n (2). Complex 2 crystallizes in monoclinic space group P21/c and exists rectangular channels in the 3D supramolecular frameworks, too. Different from complex 1, there are two crystallographic independent

C(21)−H(21C)···O(5)i C(9)−H(9)···O(5)ii C(18)−H(18)···O(2)iii C(20)−H(20A)···O(4)i C(23)−H(23B)···O(10)ii C(30)−H(30A)···O(9)iii C(40)−H(40C)···O(6)iv

d(D···H)

d(D···A)

∠DHA

2.01 2.11 1.93 1.96 2.18 2.06 1.97

2.858(1) 2.693(1) 2.750(2) 2.820(1) 3.30(2) 2.87(3) 2.62(4)

179.5 125.3 165.5 178.4 178.8 159.5 132.1

2.16 1.92 1.98 2.07 1.99 1.99

2.910(1) 2.729(8) 2.770(6) 2.828(7) 2.785(3) 2.782(7)

152.9 169.2 161.1 153.9 154.8 163.3

2.61 2.54 2.45

3.431(1) 3.333(3) 3.264(7)

143.5 143.9 146.0

2.59 2.46 2.39 2.63

3.353(4) 3.409(3) 3.333(5) 3.485(5)

136.1 167.5 164.0 148.4

d(H···A)

compound 1a 0.85 0.85 0.84 0.86 0.85 0.85 0.85 compound 2b 0.82 0.82 0.82 0.82 0.85 0.82 compound 3c 0.96 0.93 0.93 compound 4d 0.97 0.97 0.97 0.96

Symmetry codes: i x + 1, y, z; ii x + 1, −y + 3/2, z + 1/2; iii x − 1, y, z; iv −x + 1, −y + 1, −z; v x, y − 1, z. bSymmetry codes: i x + 1, y, z; ii x, −y + 1/2, z − 1/2; iii −x + 1, y − 1/2, −z + 1/2; iv x, y − 1, z. c Symmetry codes: i x, −0.5 − y, −0.5 + z; ii −x + 1, 0.5 + y, 0.5 − z; iii x, 1.5 − y, −0.5 + z. dSymmetry codes: i 1.5 − x, 0.5 + y, −0.5 + z; ii x, y, −1 + z; iii x, 1 + y, z; iv x, −1 + y, z. a

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It is interesting that each double-layer is bicatenated by two other such motifs in a parallel fashion to produce a 2D → 3D entanglement which is different from the 3-fold interpenetrated architecture in 1, as depicted in Figure 3c. There exist slightly distorted rectangular channels running along the a-axis direction in the 3D supramolecular frameworks with two longer side being ∼13.719 and 13.846 Å and two shorter ones being ∼9.455 and 9.417 Å respectively, which are mainly occupied by the guest glycol molecules (Figure 3d). As shown in Figure 3e, two O10 atoms from a pair of symmetry related glycol molecules act as both hydrogen donors and acceptors bridging another pair of symmetry related solvent molecules forming a fourteen-membered ring. Furthermore, two O9 atoms work as hydrogen donors linking the third pair of glycol molecules, and then the fourteen-membered ring is further extended to a (C2H6O2)6 cluster which is rather unusual in coordination compounds. The (C2H6O2)6 clusters are hydrogen bonded to carboxylate groups of the framework. The parameters of the hydrogen bonds are list in Table 3. Approximately 24.8% of the crystal volume is occupied by solvent molecules with a volume of ∼1262.8 Å3 in each cell unit (5085.0 Å3) based on a PLATON calculation.22 [Co(5-iipa)(bbi)·DMF]n (3). When the DMF was utilized in place of the water and glycol under similar synthetic conditions, a different structure was formed in 3, in which no iodine-related interaction was detected. As in complexes 1 and 2, complex 3 crystallizes in monoclinic space group P21/c, the metallic coordination geometry is tetrahedral environment (Figure 4a), and there exist rectangular channels in the supramolecular structures. The asymmetric unit contains one four-coordinated Co(II) center, one 5-iipa2− ligand, one bbi ligand, and one uncoordinated DMF molecule. Among them, both C13 and C14 have two disordered positions with occupancy ratios of 0.6:0.4. Adjacent 5-iipa-Co chains are centrosymmetric and connected by bbi ligands in GTG conformation with the dihedral angles between the imidazole rings of ∼18.9° to form a complanated sheet (Figure 4b), showing a rectangular window with the dimensions of 10.286 Å × 12.399 Å. Different from 1 and 2, the bbi-Co chain in the sheet is a zigzag chain, not a helix. Neighboring sheets are interlaced parallel with a translation vector [0,1,0] (3.89 Å) and connected by C18− H18···O2iii23 hydrogen bonding and face-to-face π···π interactions (intercentroid distances are 3.765 Å and 3.883 Å, respectively) (Figure 4e). Viewed down the c-axis, rectangular channels with dimensions of ∼8.40 × 10.29 Å are detected in the structure, which are mainly occupied by DMF molecules, as shown in Figure 4c. The solvent molecules are linked together by C21− H21···O5i hydrogen bonding to form a chain that is fixed on the framework through C9−H9···O5i hydrogen bonding and C19−H19···π interaction with the distance between the H19 atom and adjacent phenyl ring of the 5-iipa2− ligand being 2.776 Å. Approximately 22.9% of the crystal volume is occupied by solvent molecules with a volume of ∼550.6 Å3 in each cell unit (2409.1 Å3) on the basis of a PLATON calculation.22 There are no iodine-related interactions in the structure of complex 3, which may be attributed to the competition of the halogen bonding and other supramolecular interactions in the process of coordination assembly in this solvent. [Co2(5-iipa)2(bbi)2·2DMAc]n (4). When DMF was replaced with DMAc and CoCl 2·6H2O was replaced with Co(NO3)2·6H2O, a distinct structure has been obtained. Complex 4 crystallizes in orthorhombic space group Pna21, which is

Co(II) centers with a tetrahedral coordinated environment, two 5-iipa2− ligands, two bbi ligands and three glycol molecules in the asymmetric unit (Figure 3a). The mesomeric pillared 2D

Figure 3. (a) Metal coordination and atom labeling in complex 2 (thermal ellipsoids at 50% probability level). All hydrogen atoms are omitted for clarity. Symmetry codes: A x, −y + 3/2, z + 1/2; B x, −y + 5/2, z + 1/2; C x, y + 1, z. (b) The double-layer connected by interlayer I···I interactions. (Dotted lines represent I···I interactions.) (c) The space-filling mode of the 2D → 3D interpentration. (d) A view of the whole network along the a-axis with glycol molecules shown in space filling mode occupying the channels (I1, lime; I2, pink). (e) A (C2H6O2)6 cluster in complex 2. (Symmetry codes: #1 1 − x, 0.5 + y, 0.5 − z; #2 x, 0.5 − y, −0.5 + z; #3 x, 1.5 − y, −0.5 + z; #4 1 + x, +y, z; #5 2 − x, −0.5 + y, 0.5 − z; #6 1 + x, −1 + y, z.).

network in 2 is similar to that in 1, which is also composed of 5iipa-Co chains and bbi-Co helices. Adjacent Co1 atoms are bridged by I2-containing ligands to form a 5-iipa-Co chain, while adjacent Co2 atoms are bridged by I1-containing ligands to form another 5-iipa-Co chain. Two kind of 5-iipa-Co chains are parallel and alternate, which are interlinked through two kinds of bbi ligands vicissitudinary to form a helix along the [010] direction with the pitch of 19.269 Å. The bbi ligands also present TGT conformation with the dihedral angles between the imidazole rings of ∼42.5, 54.7°, respectively. It should be noted that the distances between adjacent iodine atoms from different layers are 4.6061(18) Å(I1···I1) and 3.8740(15) Å (I2···I2), respectively, indicating the layer is only extended to a supramolecular double-layer structure through I···I interactions (Figure 3b). The I···I distances may be effected by the bulk of the glycol molecules. 1243



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Figure 4. (a) Metal coordination and atom labeling in complex 3 (thermal ellipsoids at 50% probability level). All hydrogen atoms and lattice DMF molecules are omitted for clarity. Symmetry codes: A x + 1, y, z; B −x + 2, y − 1/2, −z + 3/2. (b) The layer structure in 3. (c) A view of the whole network along the c-axis with DMF molecules shown in space filling mode occupying the channels. (d) A DMF chain in complex 3. (Symmetry code: i x, −0.5 − y, −0.5 + z.) (e) The supramolecular interactions in 3. (Symmetry codes: ii −x + 1, 0.5 + y, 0.5 − z; iii x, 1.5 − y, −0.5 + z.)

Figure 5. (a) Metal coordination and atom labeling in complex 4 (thermal ellipsoids at 50% probability level). All hydrogen atoms and lattice DMAc molecules are omitted for clarity. Symmetry codes: A −x + 1, −y + 2, z − 1/2; B −x + 1, −y + 1, z − 1/2; C x, y, z−1. (b) The double-layer structure in 4. (c) A view of the whole network along the c-axis with DMAc molecules shown in space filling mode occupying the channel. (Symmetry codes: #1 1.5 − x, 0.5 + y, −0.5 + z; #2 1.5 − x, 0.5 + y, 0.5 + z.) (d) The hydrogen bonding in 4. (Symmetry codes: #3 x, −1 + y, z; #4 x, −1 + y, 1 + z.).

different from the former three complexes. The structure of 4 contains two kinds of crystallographic independent Co(II) centers, 5-iipa2− ligands, bbi ligands and DMAc molecules. Each Co(II) ion shows a tetrahedral coordinated environment which is completed by two carboxylate oxygen atoms from different 5-iipa2− anions and two nitrogen atoms from two bbi ligands (Figure 5a). Two kinds of 5-iipa2− anions and Co(II) cations are interlinked by alternate means with the Co···Co distance being ∼9.989 and 9.623 Å, respectively, to form a chain running along the b-axis, and there are 2-fold axes between adjacent chains. All bbi ligands are μ2-bridges and take GTG conformation. Two kinds of bbi ligands are arranged alternatively with the dihedral angles between the corresponding imidazole rings of ∼85.5° and 50.2° respectively, connecting 5-iipa-Co chains to result in a double layer structure (Figure 5b). Interestingly, the bbi-Co chain looks like a waving ribbon running along the c-axis, in which the Co···Co distances are ∼7.963 and 7.636 Å, respectively. It is worth noting that rectangular channels are also detected in the structure viewed down the c-axis with the dimension being ∼7.92 × 9.86 Å, which are mainly occupied by DMAc molecules. Adjacent layers are associated together through C(20)−H(20A)···O(4)i hydrogen bonding and interlayer I···π interactions, as shown in Figure 5c. The two lattice DMAc molecules and their symmetric entities exhibit hydrogen

bonding interaction with the framework. As depicted in Figure 5d, O9 and O10 atoms from DMAc molecules are hydrogen bonded to the C30 and C23 donors of the bbi ligand respectively, and C40 atom acts as donor to contact adjacent O6 acceptor of carboxylate group from 5-iipa2− anion. The parameters of the hydrogen bonds are listed in Table 3. Approximately 30.5% of the crystal volume is occupied by solvent molecules with a volume of ∼1648.1 Å3 in each cell unit (5399.6 Å3) based on a PLATON calculation.22

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DISCUSSION

A total of four novel cobaltic coordination polymers based on 5-iodo-isophthalic acid (5-iipa) and 1,1′-(1,4-butanediyl)bis(imidazole) (bbi) have been solvothermally synthesized by using various solvents. Although all complexes exhibit layer structures which expand to 3D supramolecular architectures by interlayer interactions with the presence of channels within them, there are many differences between their structures (Table 4). Halogen-related interactions have been found in 1, 2, and 4, indicating 5-iipa is a good ligand which can introduce halogen bonding into metal organic complex. The different interlayer interactions in these complexes have shown that 1244



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Table 4. Comparision of the Four Structures compound

solvent

conformation of bbi ligand

1

water

TGT

helix

2

glycol

TGT

helix

3 4

DMF DMAc

GTG GTG

zigzag chain waving ribbon

bbi-Co chain

interlayer interactions

2D structure mesomeric 2D network mesomeric 2D network complanated sheet double-layer structure

influence

I···I

2D → 3D, 3-fold interpentration

I···I

layer → double-layer, 3-fold interpenetrated 2D → 3D network 2D → 3D 2D → 3D

C−H···O π···π C−H···O I···π

interaction in the assembly of coordination polymers and the conformations of flexible ligand can be influenced by different solvents. The combination of the rigid and flexible ancillary ligands can be used to obtain diverse networks in different solvents and can be considered as candidate to design more intriguing architectures. Following research will further focus on other factors of the role of halogen-related interaction on the coordination assembly.

solvents have important effect on the formation of halogen bonding. In compounds 1 and 2, although the compositions, the conformations of the ligands and metal coordinated environments are essentially identical in both coordination networks, the I···I distances may be effected by the different molecular bulkiness of solvents. It is interesting to notice that adjacent layers in 1 are connected by I···I interactions to form a 3D supramolecular framework, whereas in 2 only double-layer structure is formed through I···I interactions. As the guest molecules located in the channels of the coordinated polymers, solvents with different nature, such as molecular volume, polarity, the capability of the formation of H-bonding, may induce the formation of diverse crystalline products.11 When we utilized the DMF or DMAc instead of the water and glycol under similar synthetic conditions, distinct net structures were obtained. Structural analyses reveal that the compositions and metal coordinated environments in 3 and 4 are similar to that in 1 and 2, while the conformations and the dihedral angles between the imidazole rings of the flexible bbi ligands are different, which result in the different layer structure. I···π interactions were detected in the structure of 4, while only π···π stacking was found in complex 3. The reason for this phenomenon may be that the assembled processes are impacted by a synergy effect of the larger volume of DMF or DMAc molecules and their polarity as well as weak proton donation capabilities. When we attempted other solvents in the syntheses, such as acetonitrile, methanol, ethanol, tetrahydrofuran and 1,4dioxane, poor blue crystals which are unsuitable for X-ray analyses were obtained in acetonitrile, methanol, or 1,4-dioxane systems and precipitates were obtained in other reactions. It is apparent that the solvents have significant influence on the assembly of the coordination polymers. On the other hand, the use of the bbi auxiliary ligand also plays an important role in the assembly of the structures. Compared with other auxiliary ligands in our previous report, the longer bbi ligand makes it easy to form larger voids, and more flexible −(CH2)4− spacers between two imidazole rings lead to more conformations, which result in different arcitectures.

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ASSOCIATED CONTENT

S Supporting Information *

X-ray crystallographic files (CIF), thermogravimetric analysis and X-ray powder diffraction, TG curves, the XRD patterns, and UV−vis absorption spectra and properties. This material is available free of charge via the Internet at http://pubs.acs.org.

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AUTHOR INFORMATION

Corresponding Author

*E-mail: [email protected]. Fax: (+86)-371-6778 0136.

ACKNOWLEDGMENTS We gratefully acknowledge financial support by the National Natural Science Foundation of China (No. 20901070) and Zhengzhou University (P. R. China).

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CONCLUSION In this paper, we present the results of our investigation on a series of four coordination polymers by using different solvents under solvothermal conditions. All compounds display 3D supramolecular structures, in which the open channels are occupied by different guest molecules. The interlayer I···I, I···π interactions in compounds 1, 2, and 4 indicated that the tethered iodine atom in 5-iipa plays an important role in the assembly of the coordination polymers with increasing in dimensionality. In addition, the role of the halogen-related 1245



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Four Cobaltic Coordination Polymers Based on 5-Iodo-Isophthalic Acid

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