Hydrothermal Syntheses and Structural Diversity of Cobalt Complexes

Nov 17, 2008 - Copyright © 2008 American Chemical Society ... coordination modes at high temperature, however, a chelating mode at low temperature...
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Hydrothermal Syntheses and Structural Diversity of Cobalt Complexes with 2,2′-Bibenzimidazole Ligand by Temperature Tuning Strategy Hao-Jun Mo, Yong-Rui Zhong, Man-Li Cao, Yong-Cong Ou, and Bao-Hui Ye* MOE Key Laboratory of Bioinorganic and Synthetic Chemistry, School of Chemistry and Chemical Engineering, Sun Yat-Sen UniVersity, Guangzhou 510275, China

CRYSTAL GROWTH & DESIGN 2009 VOL. 9, NO. 1 488–496

ReceiVed July 11, 2008; ReVised Manuscript ReceiVed August 14, 2008

ABSTRACT: Five different cobalt complexes were synthesized by the combination of the multidentate ligand 2,2′-bibenzimidazole (H2bbim) and the coordination plasticity of cobalt ion in the presence of 4-cyanopyridine under hydrothermal conditions using temperature as the only independent variable. The structural features of theses complexes, which ranged from zero-dimensional (0D) in [Co(Hbbim)3] · 3H2O (1) and [Co(ina)2(H2O)4] (5) to two-dimensional (2D) layer in {[Co4(Hbbim)4(bbim)2] · 2H2O}n (2) or three-dimensional (3D) networks in [Co2(Hbbim)(bbim)2(H2O)]n (3) and [Co5(Hbbim)(bbim)3(ina)2(µ3-OH)]n (4), were extremely dependent on the reaction temperature. At 130 °C, discrete 1 was the unique product. However, 4 was the main product when the reaction temperatures were set in the range of 160-200 °C. 2 and 3 yielded at 140 °C as main products. In spite of the structural diversity of this system, crystallographic studies reveal that the H2bbim ligand typically displays tridentate (Hbbim-) and/or tetradentate (bbim2-) coordination modes at high temperature, however, a chelating mode at low temperature. The ligands Hbbim- and bbim2offering donor atoms and charge balance may have both advantages of bipyrimidine and oxalate in the assembly of high-dimensional structures. Indeed, 2 is the first instance of 2D honeycomb (6,3), neutral coordination polymer constructed by only one type of ligand and one type of metal ion. Magnetic properties of 3 and 4 have been studied in the temperature range of 2-300 K. Both compounds exhibit antiferromagnetic interactions between metal ions through the bridging ligand. Introduction In the past two decades, considerable attention has been paid to the design and assembly of Metal-Organic Framework materials (MOFs) not only because of their advantages from organic polymers and coordination compounds, giving diverse structures and particular properties, but also because of their potential applications in the developments of optical, magnetic, superconductive, and catalytic materials.1 Compared to the classical microporous inorganic materials, such as zeolites, structures of MOFs are easy to be tailored and the pores can be functionalized through modification of the ligands. However, rational design and synthesis of MOFs with a unique structure and function are still a challenge. In our quest of new ligands for the construction of MOFs with novel structural features, we are aware that the imidazolate and benzimidazolate ligands have succeeded in the assembly of porous complexes because these ligands can be deprotonated in basic condition and further bind to a second metal ion into oligomers or high dimensional frameworks.2-6 On the other hand, both 2,2′-bipyrimidine (bpm) and oxalate (ox) bisdidentate bridging ligands have been extensively employed in the assembly of a great variety of multidimensional polynuclear complexes that exhibit interesting structures and properties.7 The analogous ligands 2,2′-biimidazole (H2biim) and 2,2′-bibenzimidazole (H2bbim) offering donor atoms and charge-balance may have both advantages of bpm and ox in the design of new functional compounds (see Chart 1). Furthermore, they are potential multidentate ligands and can serve as neutral bidentate (H2biim/H2bbim), tridentate (Hbiim-/Hbbim-) or tetradentate (biim2-/bbim2-) ligands, depending on the reaction conditions. However, the assembly of multidimensional coordination polymer based on the H2biim or H2bbim ligand is relatively rare.8-12 We have reported the supramolecular assembly of M(II)-H2biim in the presence of carboxylate.10,13 As part of an ongoing study, * To whom correspondence should be addressed. Fax: (86)-20-84112245. Tel: (86)-20-84112469. E-mail: [email protected].

we extend the insight into the H2bbim ligand. Compared with the H2biim ligand, the side-by-side steric repulsion between the H7 of the H2bbim ligands should effectively prevent the selfaggregation via complementary hydrogen bonds, which have been widely observed in H2biim complexes in crystal engineering.14-16 On the other hand, the pKa values of M-H2bbim are much lower than those of M-H2biim,17 indicating that the former may be easily deprotonated to form the Hbbim- and bbim2anions. These anionic ligands further connect to other metal ions resulting in cyclic or high-dimensional structures and also display coordination diversity. At least eight coordination modes, including bidentate, tridentate, and tetradentate, have been found in the CSD (see Scheme 1).18 Among them the chelating types A and F are the most adopted modes.11,12,19-21 The other coordination modes are relatively rare, only one instance for types G and H,22 two instances for types B,23 C,23,24 and D,9,12 and three examples for type E20a,25 have been documented. One of the major challenges in the design and synthesis of MOFs is the control of topology and dimensionality, because the final structure is frequently modulated by various factors such as medium, temperature, metal-ligand ratio, template, and counterion. Temperature tuning has been proven to be an effective approach to achieve them.26 Here, we describe how the combination of the multidentate ligand H2bbim with the coordination plasticity of cobalt(II) ion in the presence of 4-cyanopyridine under different temperatures yielded a variety of extended coordination compounds exhibiting structures ranging from 0D in [Co(Hbbim)3] · 3H2O (1) and [Co(ina)2(H2O)4] (5, where ina ) isonicotinate) to 2D layer in {[Co4(Hbbim)4(bbim)2] · 2H2O}n (2) or 3D networks in [Co2(Hbbim)(bbim)2(H2O)]n (3) and [Co5(Hbbim)(bbim)3(ina)2(µ3OH)]n (4). These systems were structurally characterized using single-crystal X-ray crystallographic methods, and the magnetic properties of 3 and 4 were evaluated.

10.1021/cg800747t CCC: $40.75  2009 American Chemical Society Published on Web 11/17/2008

Cobalt Complexes with 2,2′-Bibenzimidazole

Crystal Growth & Design, Vol. 9, No. 1, 2009 489 Chart 1

Scheme 1. Schematic Representation of the Coordination Modes for Metal 2,2′-Bibenzimidazole Complexes

Table 1. Crystal Data and Structure Refinement for 1-6 formula fw cryst syst space group a (Å) b (Å) c (Å) V (Å3) Z Dc (g cm-3) µ (mm-1) no. of reflns collected no. of independent reflns data/restraints/params R1a (I > 2σ) wR2b (all data) GOF ∆Fmax/∆Fmin (e Å3) a

1

2

3

4

C42H33N12O3Co 812.73 cubic I4j3d 24.6815(10) 24.6815(10) 24.6815(10) 15035.4(11) 16 1.436 0.516 24725 2477 2140/0/170 0.0494 0.1085 1.04 0.33/-0.23

C84H52N24O2Co4 1665.22 orthorhombic P212121 17.774(9) 18.964(10) 23.806(12) 8024(7) 4 1.378 0.876 28194 14578 9512/0/1045 0.0957 0.2074 1.07 0.81/-0.55

C42H27N12OCo2 833.62 cubic P213 16.0970(5) 16.0970(5) 16.0970(5) 4168.5(2) 4 1.328 0.843 17080 2743 1744/0/167 0.0617 0.1677 1.01 0.57/-0.32

C68H42N18O5Co5 1485.83 orthorhombic Aba2 17.9653(18) 19.8784(19) 17.6947(19) 6319.2(11) 4 1.560 1.353 14202 5142 4474/1/444 0.0465 0.1221 1.01 0.77/-0.36

R1 ) ∑|Fo| - |Fc|/∑|Fo|. b wR2 ) [∑w(Fo2 - Fc2)2/∑w(Fo2)2]1/2.

Experimental Section Materials and Methods. The reagents and solvents employed were commercially available and were used as received without further purification. The C, H, and N microanalyses were carried out with a Vario EL elemental analyzer. 1H NMR spectra were recorded on a Varian 300 MHz spectrometer at 25 °C. The FT-IR spectra were recorded from KBr pellets in the range of 400-4000 cm-1 on a BrukerEQUINOX 55 FT-IR spectrometer. Powder X-ray diffraction patterns were recorded on a D/Max-2200 diffractometer with Cu KR radiation (λ ) 1.5409 Å) at a scanning rate of 5° min-1 with 2θ ranging from 5 to 50°. Magnetic susceptibility data of powder samples were collected in the temperature range of 2-300 K on a Quantum Design MPMS7 SQUID magnetometer. The diamagnetic corrections were estimated from the Pascal’s constants.27 The effective magnetic moment was calculated from the equation µeff ) 2.828(χMT)1/2. The H2bbim ligand was synthesized with the published procedures28 and was checked with elemental analysis and NMR spectra. Synthesis of [Co(Hbbim)3] · 3H2O (1), {[Co4(Hbbim)4(bbim)2] · 2H2O}n (2),[Co2(Hbbim)(bbim)2(H2O)]n (3),[Co5(Hbbim)(bbim)3(ina)2(µ3OH)]n (4), and [Co(ina)2H2O4]n (5). Co(NO3)2 · 6H2O (0.145 g, 0.5 mmol), H2bbim (0.176 g, 0.75 mmol), and 4-cyanopyridine (0.104 g, 1 mmol) were added into an ethanol-aqueous solution (10 mL, 1:1). The resulting mixture was stirred for 30 min at room temperature, and

Figure 1. Coordination environment of Co(III) ion in 1. Phenyl rings and most of the hydrogen atoms are omitted for clarity. Symmetry code: A, -z + 3/2, -x + 1, y + 1/2; B, -y + 1, z - 1/2, -x + 3/2. then, transferred and sealed in a 23 mL Teflon reactor. The mixture was heated at 130, 140, 150, 160, 170, 180, 190, or 200 °C for 3 days and then cooled to room temperature at a rate of 5 °C · h-1. The final

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Figure 2. Views of (a) the tetrahedral water tetramer and its hydrogen bonding with the Hbbim- ligands, (b) the eight-membered ring constructed by the (H2O)4 (tetrahedron) and [Co(Hbbim)3] (octahedron) via hydrogen bonding, (c) the 3D hydrogen bonded network, and (d) the cubic-C3N4 net ((83)4(86)3, the red nodes are the (H2O)4 and the blue nodes are [Co(Hbbim)3]) in 1 (phenyl rings and most of the hydrogen atoms are omitted for clarity). Selected distances and angles: O(1W) · · · N(2) ) 2.829(4)Å, ∠O(1W)-H · · · N(2) ) 168.4°; N(3) · · · O(1WB) ) 2.797(4)Å, ∠N(3)-H · · · O(1WB) ) 166.9°; O(1W) · · · O(1WA) ) 3.245(6), O(1W) · · · O(1WB) ) 3.319(7), O(1W) · · · O(1WC) ) 3.319(6) Å. Symmetry code: A, -x + 3/2, y, -z + 1; B, z + 1/4, -y + 3/4, -x + 5/4; C, -z + 5/4, -y + 3/4, x - 1/4. solution was filtered. The crystals were dried at room temperature and collected by manual separation under a microscope. At 130 °C, only red 1 was obtained in 50% based on the H2biim ligand. Anal. Calcd (%) for 1: C42H33N12O3Co: C, 62.07; H, 4.09; N, 20.68. Found: C, 62.36; H, 4.15; N, 20.49. At 140 °C, three compounds, 2 (light green), 3 (dark green), and 5 (yellow),29 were obtained in 3, 20, and 5% yield, respectively, on the basis of Co(II) salt. Anal. Calcd (%) for 2: C84H52N24O2Co4: C, 60.54; H, 3.15; N, 20.19. Found: C, 61.07; H, 3.31; N, 20.02. Anal. Calcd (%) for 3: C42H27N12OCo: C, 60.51; H, 3.26; N, 20.16. Found: C, 60.74; H, 3.68; N, 20.39. Anal. Calcd (%) for 5: C12H18N2O8Co: C, 38.21; H, 4.81; N, 7.43. Found: C, 38.49; H, 5.03; N, 7.25. At 150 °C, four compounds, 2, 3, 4 (black), and 5, were obtained in 1, 10, 50, and 7% yield, respectively, on the basis of Co(II) salt. Anal. Calcd (%) for 4: C68H42N18O5Co: C, 54.95; H, 2.83; N, 16.97. Found: C, 55.31; H, 3.11; N, 17.20. FT-IR data for 4 (cm-1): 3476 vs, 3420 sh, 1639 s, 1616s, 1595 vs, 1546 s, 1472 m, 1393 m, 1346 m, 1005 m, 850 vs, 776 s, 746 m, 653 m, 593 m. From 160 to 200 °C, only 4 and 5 were obtained in ∼70% and 7-10% yields, respectively, on the basis of Co(II) salt. X-ray Crystallography. Diffraction intensities for the compounds were collected at 293 K on a Bruker Apex CCD area-detector diffractometer (Mo KR, 0.71073 Å). Absorption corrections were applied by using the multiscan program SADABS.30 The structures were solved with direct methods and refined with the full-matrix leastsquares technique with the SHELXTL program package.31 Anisotropic thermal parameters were applied to all the non-hydrogen atoms. The organic hydrogen atoms were generated geometrically (C-H 0.96 Å, N-H 0.86 Å) and refined with isotropic temperature factors. Hydrogen atoms on oxygen and nitrogen atoms were located from difference maps

and refined isotropically; the O-H distances involving the water molecules were refined with an AFIX restraint of 0.85-0.95 Å. Analytical expressions of neutral atom scattering factors were employed, and anomalous dispersion corrections were incorporated. In 2, the water molecules in the void of the structure were high disorder. In 4, the Co(3) ion was disordered over two positions and refined isotropically with occupation factors of 0.5 and 0.5, respectively. Crystallographic data as well as details of data collection and refinement for the complexes are summarized in Table 1. Selected bond lengths and angles are listed in Table S1 in the Supporting Information.

Results and Discussion Crystal Structure of 1. The title complex consists of one neutral [Co(Hbbim)3] unit and three water molecules. As shown in Figure 1, the Co(III) ion is coordinated by six nitrogen atoms from three Hbbim- ligands to furnish an octahedral geometry. The distance Co(1)-N(1) 1.939(2) Å is slightly shorter than that of Co(1)-N(4) 1.965(2) Å, indicating that the nitrogen atom of imidazolate ring has a strong coordination ability. The bond lengths are comparable to the previous reports for [Co(Hbiim)3] (1.899-1.946 Å),14b,32 but markedly shorter than those of [Co(H2bbim)3]2+ (2.10∼2.22 Å)33 and [Co(H2biim)3]2+ (2.15 Å).10 Each Hbbim- ligand adopts a type B coordination mode, which further forms a pair of hydrogen bonds (O(1W)-H · · · N(2) ) 2.83, N(3)-H · · · O(1WB) ) 2.79 Å) from the water molecules.

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Figure 3. Views of (a) the coordination environment of Co(II) ion (phenyl rings and hydrogen atoms are omitted for clarity) (b) the 2D (6, 3) sheet with the 6-membered ring of Co(II) on the ab plane (the phenyl rings are omitted for clarity), and (c) the packing of the 2D sheets with 1D channels filled with water molecules (red balls) along the c-axis in 2. Symmetry code: A, x - 0.5, -y + 1.5, -z + 1; B, x - 1, y, z; C, x - 0.5, -y + 0.5, -z + 1; D, x + 0.5, -y + 0.5, -z + 1; E, x + 0.5, -y + 1.5, -z + 1; F, x + 1, y, z.

The most interesting feature is that the [Co(Hbbim)3] units link with water molecules into a 3D hydrogen-bonded network. Each [Co(Hbbim)3] unit links with six water molecules via 6-fold hydrogen bonds and every four [Co(Hbbim)3] units enclose into a cavity. Four water molecules in a tetrahedral motif with edge lengths of 3.26-3.32 Å embed in the cavity, as shown in Figure 2a. Therefore, each [Co(Hbbim)3] molecule links with three water tetramers, and each water tetramer links with four [Co(Hbbim)3] molecules into a 3D hydrogen-bonded network, as shown in Figure 2c. In a simplified view, it is composed of alternating tetrahedral four-connected (H2O)4 and triangular three-connected [Co(Hbbim)3] nodes. The two types of nodes are linked to each other to form an extended network where the shortest ring comprises eight nodes (see Figure 2b). Such a network with 3- and 4-connected nodes can be specified by Schla¨fli symbol (83)(86) or cubic-C3N3 net (see Figure 2d).34 At this point, it is worth emphasizing the difference between [Co(Hbbim)3] and [Co(Hbiim)3]. Though both deprotonated ligands Hbbim- and Hbiim- serve as hydrogen-bonded acceptor and donator, the [Co(Hbiim)3] building blocks link together via a pair of complementary N-H · · · N hydrogen bonds into 1D chain14b or 3D network.32 Here, the Hbbim- ligands form N-H · · · O and O-H · · · N hydrogen bonds with water molecules instead of complementary N-H · · · N hydrogen bonds. These may be attributed to the additional phenyl hydrogen repulsion from the assembly of [Co(Hbbim)3]. Crystal Structure of 2. As shown in Figure 3a, four crystallographically independent Co(II) ions locate on an

asymmetric unit, where Co(1) ion is four-coordinated by two nitrogen atoms from a chelating bbim2- ligand (Co(1)-N(1) ) 2.004(7) and Co(1)-N(4)) 2.033(7) Å) and two nitrogen atoms from two Hbbim- ligands (Co(1)-N(5C) ) 2.008(7) and Co(1)-N(9) ) 1.983(7) Å) to give a distorted tetrahedral coordination geometry. Co(2) and Co(3) ions are 5-coordinated by four nitrogen atoms from two chelating bbim2- ligands (Co(2)-N(2) ) 2.005(7), Co(2)-N(3) ) 2.525(7), Co(2)-N(17) ) 2.134(7), Co(2)-N(20) ) 2.032(7) Å; Co(3)-N(14A) ) 2.044(7), Co(3)-N(15A) ) 2.167(7), Co(3)-N(18) ) 1.993(7), Co(3)-N(19)) 2.323(7) Å) and one nitrogen atom from one Hbbim- ligand (Co(2)-N(13) ) 2.035(7) Å; Co(3)-N(21B) ) 2.057(8) Å) to furnish an elongated trigonal bipyramid (τCo(2) ) 0.71, τCo(3) ) 0.83). N(3) and N(17), and N(15A) and N(19) are at the apical positions of the trigonal bipyramids, respectively. Co(4) ion is 6-coordinated by six nitrogen atoms from three chelating Hbbim- ligands to give an octahedral coordination sphere. The distances of Co(4)-N(6) ) 2.148(7), Co(4)-N(10) ) 2.153(7), and Co(4)-N(22) ) 2.127(7) Å are shorter than those of Co(4)-N(7) ) 2.210(7), Co(4)-N(11) ) 2.201(7), and Co(4)-N(23) ) 2.183(7) Å, indicating that the nitrogen atom of imidazolate ring has a strong coordination ability. In 2, all 6-coordinated Co(4) ions adopt in a Λ configuration, and thus it crystallizes in chiral space group P212121. Interestingly, two coordination modes D and F were found in 2. Two bbim2- and four Hbbim- ligands link to six Co ions into a 6-membered ring which further extend into a chiral (6,3)

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Figure 4. Views of (a) the coordination environment of Co ions (phenyl rings and hydrogen atoms are omitted for clarity), (b) the intramolecular hydrogen bonding of Co(II)-OH2 part (phenyl rings are omitted for clarity), (c) the 3D framework, and (d) topological structure (black nodes are Co(1) and blue nodes are Co(2)) of 3. Symmetry code: A, z, x, y; B, y, z, x; C, -z + 1, x - 0.5, -y + 0.5; D, y + 0.5, -z + 0.5, -x + 1; E, -x + 1, y + 0.5, -z + 0.5; F, -y + 0.5, -z + 1, x - 0.5; G, x - 0.5, -y + 0.5, -z + 1; H, -z + 0.5, -x + 1, y + 0.5; I, -y + 1, z - 0.5, -x + 0.5; J, z + 0.5, -x + 0.5, -y + 1.

honeycomb 2D neutral net on the ab plane because of the adoption of Co(4) ion in an unique Λ configuration, as shown in Figure 3b. Two water molecules embed in a hexagonal ring. The phenyl rings of Hbbim- and bbim2- ligands hang on both sides of the sheet. Within the layers, Co · · · Co distances across the bbim2-, Hbbim- ligands and through the diagonal of the hexagonal ring are ∼5.42, ∼6.0, and ∼11.0 Å, respectively. It should be noted that the (6,3) sheets are stacked in a face-toface fashion along the c-axis with 1D channels and the shortest Co · · · Co interlayer separation along the c-axis is ca. 12 Å. Although the 2D honeycomb networks such as [MIIMIII(ox)3]-,7 [M2(pymca)3]+ (M ) Co2+ and Fe2+, pymca ) pyrimidine-2carboxylato)),35 [Mn(4-mepy)2(N3)2],36 {Co3Cl4(H2O)[Co(Hbbim)3]2}9 and [M(bpm)(ox)2] (M ) Cu2+ and Mn2+),37 and the 3D framework8 Fe(Hbiim)2 have been synthesized, the 2D honeycomb, neutral coordination polymer containing only one type of ligand and one type of metal ion has never been reported so far. These may be attributed to the coordination diversity of H2bbim ligand and coordiantion plasticity of cobalt(II) ion, in which the H2bbim ligand exhibits in tridentate (Hbbim-) and tetradentate (bbim2-) coordination modes and the coordination number of Co(II) ion varies from 4 to 6. Crystal Structure of 3. Two crystallographically independent Co ions locate on an asymmetric unit. Co(1) ion is 6-coordinated by six nitrogen atoms from three chelating ligands that adopt a

left rotation, generating a Λ configuration. Thus, 3 crystallizes in a chiral space group P213. The bond distances Co(1)-N(1) 1.943(4) and Co(1)-N(2) 1.945(4) Å are in accordance with the observations in 1 (1.939 and 1.965 Å), and [Co(Hbiim)3] (1.899∼1.946 Å),14b,32 but significantly shorter than those in [Co(H2bbim)3]2+ (2.10∼2.22 Å)33 and [Co(H2biim)3]2+ (2.15 Å),10 indicating that Co(1) is a trivalent ion. Whereas Co(2) is coordinated by three nitrogen atoms and one oxygen atom to give a CoN3O tetrahedral geometry with the angles of O(1)-Co(2)-N(3) ) 106.0(1) and N(3C)-Co(2)-N(3) ) 112.7(1)°, as shown in Figure 4a. The bond length Co(2)-N(3) 1.997(4) Å is in agreement with the previous report for the four coordinated Co(II), [CoL(OH2)]+ (2.015(2) Å, L ) 3-tert-butyl5-methylpyrazolyl).38 The bond distance Co(2)-O(1W) 1.988(4) Å is comparable with the observation in [CoL(OH2)]+ (1.963(2) Å), but markedly longer than that of [CoL(OH)] (1.859(2) Å).38 In addition to the coordination bond Co(2)-OH2 in 3, three intramolecular hydrogen bonds to the aqua ligand are present between the oxygen atom and the NH/N groups (see Figure 4b). The distance of N(2) · · · O(1W) ) 2.599(3) Å, and the O(1W)-H · · · N(2) and O(1W) · · · H-N(2C) angles of 166(2) and 156(3)° are indicative of strong hydrogen bonds. It should be noted that the Co ions in 3 are mixed valent, which is also confirmed by its magnetic behavior.

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Figure 5. Views of (a) the coordination environment of Co(II) ion containing the hydrogen bonding with µ3-OH (phenyl rings are omitted for clarity), (b) the 2D layer on the ac-plane, (c) the 3D network along the c-axis, and (d) topological structure (SBUs are assigned as black nodes, Co(1) ions are assigned as blue nodes) in 4. Symmetry code: A, x - 1/2, -y + 1, z + 1/2; B, -x + 5/2, y - 1/2, z; C, -x + 3, -y + 1, z; D, x + 1/2, -y + 1, z - 1/2; E, -x + 5/2, y + 1/2, z; F, -x + 5/2, y, z - 1/2.

Scheme 2. Syntheses of 1, 2, 3, 4 and 5 under Different Temperatures

Moreover, each chiral [Co(Hbbim)(bbim)2] unit further links to three Co(2) ions, alternately, each Co(2) ion binds to three [Co(Hbbim)(bbim)2] fragments and expands the chiral configuration, generating a chiral 3D network, as shown in Figure 4c. The distance of Co(1) · · · Co(2) across the bbim2- ligand is 5.76 Å. Topological analysis reveals that it is a common (3,3)connected, chiral (10,3)-a net (SrSi2, see Figure 4d).

Crystal Structure of 4. X-ray crystallographic analysis reveals that there are three types of Co ions located on an asymmetric unit. Co(1) is 5-coordinated by four nitrogen atoms from two bbim2- ligands and one nitrogen atom from an ina ligand to furnish a slightly distorted trigonal bipyramidal geometry (τ ) 0.81). The N(7) and N(4A) are at the apical positions of the trigonal bipyramid (see Figure 5a). Co(2) is

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Figure 6. (a) Temperature dependence of χMT (left) and χ-1 (right), and (b) field dependence of magnetization for 3 at 2.0 K.

Figure 7. Temperature dependence of χMT (left) and χ-1 (right) for 4.

also 5-coordinated by two nitrogen atoms from two bbim2ligands, two oxygen atoms from two ina ligands, and one oxygen atom from the µ3-OH group, giving a slightly distorted trigonal bipyramidal geometry (τ ) 0.97). The bond distances of Co(2)-O(1) 2.268(3) Å at the apical positions are markedly enlongated, whereas Co(3) is 4-coordinated by two nitrogen atoms from two bbim2- ligands, one oxygen atom from an ina anion, and one oxygen atom from the µ3-OH group to form a distorted tetrahedral geometry. The hydroxide O(5) group is coordinated to three Co ions to form a trinuclear cluster of formula [Co3(µ3-OH)], which can be considered as a secondary building unit (SBU) for construction of the metal-organic architecture of 4. Each SBU connects to six Co(1) ion through four bbim2-/Hbbim- bridges on the ac-plane as a layer (see Figure 5b) and two ina ligands as pillars along the b-axis into a 3D network (see Figure 5c). A better insight into the 3D network of 4 can be achieved by the application of a topological appproach. As mentioned above, each SBU can be regarded as a 6-connected node and each Co(1) ion is a 3-connected node. The two types of nodes are linked to each other via bbim2-/ Hbbim- and ina ligands, adopting an unprecedented topology specified by Schla¨fli symbol (63)(611.84). It should be noted that two coordination modes D and E are found in 4, which is rare in H2bbim chemistry. Syntheses. We noticed that the reaction of H2bbim and Fe(II) salt at 65 °C yielded a 0D complex [Fe(H2bbim)3](ClO4)2.8 However, the reaction of H2bbim and CoCl2 in the presence of KOH at 110 °C offered a 2D complex.9 Recently, two research groups have reported the reactions of of H2bbim and M(II) salt in the presence of polycarboxylic acids offered 1D, 2D and 3D

coordination polymers in different conditions.11,12 The synthetic conditions may play an important role in the formation of fascinating new compounds. However, a detailed understanding of the role of them in the synthesis of MOFs is still a challenging work, particularly under hydrothermal conditions. Lu’s group has observed the influence of pH value on the reaction of H2bbim and metal ions.12 We have also observed the effect of metal ions and anions on the formation of the metal-H2bbim complex.33 Rao’s group has systematically studied on the Zn(II)-ox system to elucidate the role of temperature.26b By judicious control of temperature, 1D, 2D and 3D coordination polymers were obtained at 100, 165, and 180 °C, respectively. In fact, hydrothermal synthesis is a straightforward and effective method for the preparation of metal-H2bbim complex because the poor solubility problem of H2bbim ligand could be easily solved. We examined herein the reactions of Co(NO3)2 with H2bbim ligand in the presence of 4-cyanopyridine at different temperatures. The summary is briefly outlined in Scheme 2. The starting materials and molar ratio in the syntheses are the same, and the only difference is the reaction temperature. When the temperature was set at 130 °C, only discrete 1 was obtained in a moderate yield. In this case, the metal ion is excessive; however, the H2bbim ligand in 1 is monodeprotonated in type B coordination mode, which can further coordinate to metal ion as a metalloligand. This stimulates us to examine the reaction at high temperature. It is well-known that hydrothermal synthesis is a powerful tool for the construction of high-dimensional MOFs.39 In these cases, it is more probable that the metastable kinetic phases are isolated rather than the thermodynamically stable ones.40 First, the reaction temperature was increased to 150 °C. Four complexes 2, 3, 4, and 5 were obtained and collected by manual separation under a microscope in different yields (the purity was confirmed by powder XRD, see the Supporting Information). Surprisingly, no 1 was found at this temperature, and the main product was 4 in 50% yield, indicating that the H2bbim ligand prefers multidentate coordination at high temperature. These also encourage us to observe what would happen in the range of 130-150 °C. Indeed, 2, 3, and 5 were given at 140 °C; 1 and 4 were not obtained under this condition. We also found that the yields of 2 (3%) and 3 (20%) at 140 °C were higher than those at 150 °C. These seem to imply that 2 and 3 may be metastable kinetic products and stable at this temperature. Moreover, we also examine the reaction at 160-200 °C. Only 4 and 5 were obtained, and 4 was the main product in about 70% yield, indicating that the deprotonation process of H2bbim ligand gets easier when the

Cobalt Complexes with 2,2′-Bibenzimidazole

temperature is increased. In 4, the H2bbim ligands are monoand bideprotonated in tridentate (D) and tetradentate (E) coordination modes, respectively. It should be pointed out that 4-cyanopyridine is indispensable under these conditions.33 It has long been known that nitriles can be hydrolyzed to carboxylic acids and ammonia. In neutral solution the rate of this reaction is very slow. However, the hydrothermal conditions (high pressure and temperature) dramatically increase the rate of this reaction.41 Metal ions are powerful activators of nitriles toward nucleophilic attack by OH-/H2O. This activation results in an enhancement of the rate of hydrolysis.42 4-Cyanopyridine and/ or ina trap proton from H2bbim under the reaction condition. At high temperature, ina also participates in the coordination to metal ion, finally forming 4 and 5. Magnetic Properties. The magnetic properties of 3 were investigated over the temperature range of 2.0-300.0 K at 5000 Oe. The χMT value of 2.67 cm3 mol-1 K at 300 K is higher than the expected value for one Co(II) ion with S ) 3/2 (1.88 cm3 mol-1 K), indicating an important orbital contribution due to the tetrahedral coordination geometry of Co(II) ion. Upon cooling, the χMT value decreases slowly above 50 K and drastically below that (see Figure 6a). The magnetic susceptibility in the range 2-300 K obeys the Curie-Weiss law χM ) C/(T - θ) with a Curie constant C ) 2.56 cm3 mol-1 K and θ ) -3.7 K. The field dependence of magnetization at 2 K and 7 T is 2.69 Nβ, lower than the saturated value 3.0 Nβ. All of the above indicate that 3 shows weak antiferromagnetic interaction and the Co(II) ion is at high spin state. The magnetic properties of 4 were also investigated over the temperature range of 2.0-300.0 K at 1000 Oe. The χMT value of 9.22 cm3 mol-1 K at room temperature is close to the expected value for five Co(II) ions with S ) 3/2 (9.40 cm3 mol-1 K). Upon cooling, the χMT value decreases more and more rapidly (see Figure 7). The magnetic susceptibility in the range 150-300 K obeys the Curie-Weiss law with a Curie constant C ) 11.56 cm3 mol-1 K and θ ) -76.59 K, indicating a moderate antiferromagnetic coupling between the metallic centers along the bridging ligands.

Crystal Growth & Design, Vol. 9, No. 1, 2009 495

(2) (3)

(4)

(5) (6) (7)

(8) (9) (10) (11) (12) (13)

(14)

Conclusion We have demonstrated the successful construction of a series of cobalt complexes with multidentate H2bbim ligand under hydrothermal conditions. Their structures varying from 0D to 2D or 3D were extremely dependent on the reaction temperature. Crystallographic studies reveal that the H2bbim ligand typically displays tridentate and/or tetradentate coordination modes at high temperature, however, a chelating mode at low temperature. The ligands Hbbim- and bbim2- offering donor atoms and chargebalance may have both advantages of bipyrimidine and oxalate in the assembly of high-dimensional structures. Acknowledgment. This work was supported by the NSF of China (20771104) and Guangdong Province (20623086), the Doctoral Programs Foundation of Ministry of Education of China, (20070558009) and the National Foundation for Fostering Talents of Basic Science (J0730420). Supporting Information Available: Powder XRD patterns of 1, 3, and 4 (PDF); X-ray crystallographic files in CIF format for 1-4. This material is available free of charge via the Internet at http://pubs.acs.org.

References (1) (a) Leininger, S.; Olenyuk, B.; Stang, P. J. Chem. ReV. 2000, 100, 853. (b) Moulton, B.; Zaworotko, M. J. Chem. ReV. 2001, 101, 1629.

(15) (16) (17) (18) (19)

(20)

(21)

(c) Eddaoudi, M.; Moler, D. B.; Li, H.; Chen, B.; Reineke, T. M.; O’Keeffe, M.; Yaghi, O. M. Acc. Chem. Res. 2001, 34, 319. (d) Holliday, B. J.; Mirkin, C. A. Angew. Chem., Int. Ed. 2001, 40, 2023. (e) Roesky, H. W.; ruh, M. Coord. Chem. ReV. 2003, 236, 91. (f) Barnett, S. A.; Chempness, N. R. Coord. Chem. ReV. 2003, 246, 145. (g) Kitagawa, S.; Kitaura, R.; Noro, S.-I. Angew. Chem., Int. Ed. 2004, 43, 2334. Rettig, S. J.; Storr, A.; Summers, D. A.; Thompson, R. C.; Trotter, J. J. Am. Chem. Soc. 1997, 119, 8675. (a) Tian, Y.-Q.; Cai, C.-X.; Ji, Y.; You, X.-Z.; Peng, S.-M.; Lee, G.H. Angew. Chem., Int. Ed. 2002, 41, 1384. (b) Tian, Y.-Q.; Cai, C.X.; Ren, X.-M.; Duan, C.-Y.; Xu, Y.; Gao, S.; You, X.-Z. Chem.sEur. J. 2003, 9, 5673. (c) Tian, Y.-Q.; Zhao, Y.-M.; Chen, Z.-X.; Zhang, G.-N.; Weng, L.-H.; Zhao, D.-Y. Chem.sEur. J. 2007, 13, 4146. (a) Huang, X.-C.; Zhang, J.-P.; Lin, Y.-Y.; Yu, X.-L.; Chen, X.-M. Chem. Commun. 2004, 1100. (b) Huang, X.-C.; Zhang, J.-P.; Chen, X.-M. J. Am. Chem. Soc. 2004, 126, 13218. (c) Huang, X.-C.; Zhang, J.-P.; Lin, Y.-Y.; Yu, X.-L.; Chen, X.-M. Chem. Commun. 2005, 2232. (d) Huang, X.-C.; Lin, Y.-Y.; Zhang, J.-P.; Chen, X.-M. Angew. Chem., Int. Ed. 2006, 45, 1557. Park, K. S.; Ni, Z.; Cote, A. P.; Choi, J. Y.; Huang, R.; Uribe-Romo, F. J.; Chae, H. K.; O’Keeffe, M.; Yaghi, O. M. Proc. Natl. Acad. Sci. U.S.A. 2006, 103, 10186. Zhang, J.; Cai, R.; Chen, Z.; Zhou, X. Inorg. Chem. 2007, 46, 321. (a) Some reviews: Decurtins, S.; Pellaux, R.; Hauser, A.; Von Arx, M. E. In Magnetism: A Supramolecular Function; Kahn, O., Ed.; Kluwer: Dordrecht, The Netherlands, 1996; p 487, and references therein. (b) Pilkington, M.; DecurtinsS. Crystal Design: Structure and Function; Desiraju, G. R., Ed.; Perspectives in Supramolecular Chemistry; Wiley: West Sussex, U.K., 2003; Vol 7, pp 275-323. (c) Cle´ment, R.; Decurtins, S.; Gruselle, M.; Train, C. Monastsh. Chem. 2003, 134, 117, and references therein. Martinez-Lorente, M. A.; Daham, F.; Sanakis, Y.; Petrouleas, V.; Bousseksou, A.; Tuchagues, J.-P. Inorg. Chem. 1995, 34, 5346. Gala´n-Mascaro´s, J. R.; Dunbar, K. R. Angew. Chem., Int. Ed. 2003, 42, 2289. (a) Ye, B.-H.; Ding, B.-B.; Weng, Y.-Q.; Chen, X.-M. Cryst. Growth Des. 2005, 5, 801. (b) Ding, B.-B.; Weng, Y.-Q.; Mao, Z.-W.; Lam, C.-K.; Chen, X.-M.; Ye, B.-H. Inorg. Chem. 2005, 44, 8836. Wen, L.; Li, Y.; Dang, D.; Tian, Z.; Ni, Z.; Meng, Q. J. Solid State Chem. 2005, 178, 3336. Xia, C.-K.; Lu, C.-Z.; Yuan, D.-Q.; Zhang, Q.-Z.; Wu, X.-Y.; Xiang, S.-C.; Zhang, J.-J.; Wu, D.-M. CrystEngComm 2006, 8, 281. (a) Ye, B.-H.; Xue, F.; Xue, G.-Q.; Ji, L.-N.; Mak, T. C. W. Polyhedron 1999, 18, 1785. (b) Ye, B.-H.; Ding, B.-B.; Weng, Y.-Q.; Chen, X.M. Inorg. Chem. 2004, 43, 6866. (c) Ding, B.-B.; Weng, Y.-Q.; Cui, Y.; Chen, X.-M.; Ye, B.-H. Supramol. Chem. 2005, 17, 475. (a) Tadokoro, M.; Nakasuji, K. Coord. Chem. ReV. 2000, 98, 205. (b) Tadokoro, M.; Kanno, H.; Kitajima, T.; Shimada-Umemoto, H.; Nakanishi, N.; Isobe, K.; Nakasuji, K. Proc. Natl. Acad. Sci. U.S.A. 2002, 99, 4950. ¨ hrstro¨m, L.; Larsson, K. Dalton Trans. 2004, 347. O Ghosh, A. K.; Jana, A. D.; Ghoshal, D.; Mostafa, G.; Chaudhuri, N. R. Cryst. Growth Des. 2006, 6, 701. (a) Rillema, D. P.; Sahai, R.; Matthews, P.; Edwards, A. K.; Shaver, R. J.; Morgan, L. Inorg. Chem. 1990, 29, 167. (b) Akutagawa, T.; Saito, G. Bull. Chem. Soc. Jpn. 1995, 68, 1753. Cambridge Structural Database, version 5.29; Cambridge Crystallographic Data Centre: Cambridge, U.K., 2007. (a) Boinnard, D.; Cassoux, P.; Petrouleas, V.; Savariault, J.-M.; Tuchagues, J.-P. Inorg. Chem. 1990, 29, 4114. (b) Souza; Lemos, S.; de; Bessler, K. E.; Schulz Lang, E. Z. Anorg. Allg. Chem. 1998, 624, 30. (c) Rau, S.; Bo¨ttcher, L.; Schebesta, S.; Stollenz, M.; Go¨rls, H.; Walther, D. Eur. J. Inorg. Chem. 2002, 2800. (a) Carmona, D.; Ferrer, J.; Mendoza, A.; Lahoz, F. J.; Oro, L. A.; Vigura, F.; Reyes, J. Organometallics 1995, 14, 2066. (b) Souza Lemos, S.; de; Bessler, K. E.; Schulz Lang, E. Z. Anorg. Allg. Chem. 1998, 624, 701. (c) Rau, S.; Ruben, M.; Buttner, T.; Temme, C.; Dautz, S.; Gorls, H.; Rudolph, M.; Walther, D.; Brodkorb, A.; Duati, M.; O’Connor, C.; Vos, J. G. J. Chem. Soc., Dalton Trans. 2000, 3649. (d) Lemos, S. S.; Deflon, V. M.; Bessler, K. E.; Abbott, M. P.; Niquet, E. Transition Met. Chem. 2004, 29, 46. (e) Yin, J.; Elsenbaumer, R. L. Inorg. Chem. 2007, 46, 6891. (a) Benkstein, K. D. T.; Hupp, J.; Stern, C. L. Angew. Chem., Int. Ed. 2000, 39, 2891. (b) Dinolfo, P. H.; Williams, M. E.; Stern, C. L.; Hupp, J. T. J. Am. Chem. Soc. 2004, 126, 12989. (c) Dinolfo, P. H.; Benkstein, K. D.; Stern, C. L.; Hupp, J. T. Inorg. Chem. 2005, 44, 8707. (d) Dinolfo, P. H.; Coropceanu, V.; Bredas, J.-L.; Hupp, J. T. J. Am. Chem. Soc. 2006, 128, 12592.

496 Crystal Growth & Design, Vol. 9, No. 1, 2009 (22) Tzeng, B.-C. D.; Li, Peng, S.-M.; Che, C.-M. J. Chem. Soc., Dalton Trans. 1993, 2365. (23) Cui, Y.; Niu, Y.-L.; Cao, M.-L.; Wang, K.; Mo, H.-J.; zhong, Y.-R.; Ye, B.-H. Inorg. Chem. 2008, 47, 5616. (24) (a) Bae, J. Y.; Tadokoro, M.; Sato, K.; Shiomi, D.; Takui, T.; Itoh, K. Synth. Met. 1997, 85, 1741. (b) Rau, S.; Buttner, T.; Temme, C.; Ruben, M.; Gorls, H.; Walther, D.; Duati, M.; Fanni, S.; Vos, J. G. Inorg. Chem. 2000, 39, 1621. (25) (a) Uson, R.; Oro, L. A.; Gimeno, J.; Ciriano, M. A.; Cabeza, J. A.; Tiripicchio, A.; Tiripicchio Camellini, M. J. Chem. Soc., Dalton Trans. 1983, 323. (b) Walther, D.; Bottcher, L.; Blumhoff, J.; Schebesta, S.; Gorls, H.; Schmuck, K.; Rau, S.; Rudolph, M. Eur. J. Inorg. Chem. 2006, 2385. (26) (a) Forster, P. M.; Burbank, A. R.; Livage, C.; Fe´rey, G.; Cheetham, A. K. Chem. Commun. 2004, 368. (b) Dan, M.; Rao, C. N. R. Angew. Chem., Int. Ed. 2006, 45, 281. (c) Dong, Y.-B.; Jiang, Y.-Y.; Li, J.; Ma, J.-P.; Liu, F.-L.; Tang, B.; Huang, R.-Q.; Batten, S. R. J. Am. Chem. Soc. 2007, 129, 4520. (d) Zhang, J.; Bu, X. Chem. Commun. 2008, 444. (e) Chen, S.-M.; Lu, C.-Z.; Zhang, Q.-Z.; Liu, J.-H.; Wu, X.-Y. Eur. J. Inorg. Chem. 2005, 423. (27) Kahn, O. Molecular Magnetism; VCH: New York, 1993. (28) Muller, E.; Bernardinelli, G.; Reedijk, J. Inorg. Chem. 1995, 34, 5979. (29) The unit cell was measured: crystal system, triclinic; space group, P1j; a ) 6.3531(17) Å, b ) 6.9047(19) Å, c ) 9.249(3) Å, R ) 96.182(4)°, β ) 104.655(4)°, γ ) 113.027(16)°, V ) 351.4(2) Å3. This has been published. See: Waizumi, K.; Takuno, M.; Fukushima, N.; Masuda, H. J. Coord. Chem. 1998, 44, 269.

Mo et al. (30) Sheldrick, G. M. SADABS 2.05; University of Go¨ttingen: Go¨ttingen, Germany. (31) SHELXTL 6.10; Bruker Analytical Instrumentation: Madison, WI, 2000. ¨ hrstro¨m, L.; Larsson, K.; Borg, B.; Norberg, S. T. Chem.sEur. J. (32) O 2001, 7, 4805 (f). (33) Zhong, Y.-R.; Cao, M.-L.; Mo, H.-J.; Ye, B.-H. Cryst. Growth Des. 2008, 8, 2282. ¨ hrstrom, L.; Larsson, K. Molecule-Based Materials: The Struc(34) (a) O tural Network Approach; Elsevier: Amsterdam, 2005. (b) Dybtsev, D. N.; Chun, H.; Kim, K. Chem. Commun. 2004, 14, 1594. (35) Rodrı´guez-Die´guez, A.; Cano, J.; Kiveka1s, R.; Debdoubi, A.; Colacio, E. Inorg. Chem. 2007, 46, 2503. (36) Escuer, A.; Cano, J.; Goher, M. A. S.; Journaux, Y.; Lloret, F.; Mautner, F. A.; Vicente, R. Inorg. Chem. 2000, 39, 4688. (37) (a) De Munno, G.; Julve, M.; Nicolo, F.; Lloret, F.; Faus, J.; Ruiz, R.; Sinn, E. Angew. Chem., Int. Ed. 1993, 32, 613. (b) De Munno, G.; Ruiz, R.; Lloret, F.; Faus, J.; Sessoli, R.; Julve, M. Inorg. Chem. 1995, 34, 408. (38) Bergquist, C.; Fillebeen, T.; Morlok, M. M.; Parkin, G. J. Am. Chem. Soc. 2003, 125, 6189. (39) Cheetham, A. K.; Rao, C. N. R.; Feller, R. K. Chem. Commun. 2006, 4780. (40) Hagrman, P. J.; Finn, R. C.; Zubieta, J. Solid State Sci. 2001, 3, 745. (41) Zhang, X.-M. Coord. Chem. ReV. 2005, 249, 1201. (42) Kukushkin, V. Y.; Pombeiro, A. J. L. Inorg. Chim. Acta 2005, 358, 1.

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