Supramolecular Architectures and Hydrogen-Bond Directionalities of 4

Sep 30, 2010 - Tsuyoshi Murata†, Yumi Yakiyama†, Kazuhiro Nakasuji†‡, and Yasushi Morita*†. † Department of Chemistry, Graduate School of ...
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DOI: 10.1021/cg100958r

Supramolecular Architectures and Hydrogen-Bond Directionalities of 4,40 -Biimidazole Metal Complexes Depending on Coordination Geometries

2010, Vol. 10 4898–4905

Tsuyoshi Murata,† Yumi Yakiyama,† Kazuhiro Nakasuji,†,‡ and Yasushi Morita*,† †

Department of Chemistry, Graduate School of Science, Osaka University, Toyonaka, Osaka 560-0043, Japan, and ‡Fukui University of Technology, Fukui 910-8505, Japan

Received July 20, 2010; Revised Manuscript Received September 15, 2010

ABSTRACT: Assembled metal complexes of 4,40 -biimidazole (4,40 -H2Bim), a ligand exhibiting multidirectional hydrogenbonds, were investigated in AgI, CuII, and NiII complexes. The most intriguing feature of this system is that the directionality of hydrogen-bonds varies depending on the cis/trans-conformations of the ligand and the coordination geometries of the metal atoms. The [AgI2(4,40 -H2Bim)3] complex included ligands of both cis- and trans-conformations, the latter of which linked two metal atoms to form a planar dinuclear complex. The triple N-H 3 3 3 X 3 3 3 H-N hydrogen-bonds across the counteranions (X) formed a one-dimensional hydrogen-bond chain. The [CuII(4,40 -H2Bim)2] complexes showed a square-planar coordination sphere by the chelating coordination of two 4,40 -H2Bim units having the cis-conformation. The complexes were linked by the double N-H 3 3 3 X 3 3 3 H-N hydrogen-bonds across counteranions or solvent molecules to form one-dimensional chains. The [CuII(4,40 -HBim-)2] including the monodeprotonated ligand had a square-planar coordination geometry similar to those of [CuII(4,40 -H2Bim)2] complexes. The deprotonated nitrogen atom acted as a proton acceptor having a tetrahedral geometry. This complex formed a three-dimensional network by the π-stacks and N-H 3 3 3 O-H 3 3 3 N hydrogen-bonds across crystalline water molecules. The [NiII(4,40 -H2Bim)3] complexes had an octahedral coordination sphere including three chelating 4,40 -H2Bim ligands of the cis-conformation. The N-H 3 3 3 X 3 3 3 H-N hydrogen-bonds across counteranions established two- or threedimensional networks.

Scheme 1. Chemical Structures of 2,20 - and 4,40 -H2Bima

Introduction Supramolecular assemblies established by directional intermolecular interactions such as hydrogen-bond (H-bond) and coordination bond have provided promising strategies to control the relative molecular arrangement in the development of molecule-based materials.2,3 2,20 -Biimidazole (2,20 H2Bim, Scheme 1) is a well-known bidentate ligand of transition metal complexes having strong H-bonding ability, and it has achieved a number of well-ordered assembled metal complexes.4-7 Furthermore, the intriguing functions of 2,20 -H2Bim complexes, such as inclusion phenomenon,8 magnetism,9 and proton coupled electron-transfer,10 have been explored. In this context, we have recently designed and synthesized 4,40 -biimidazole (4,40 -H2Bim, Scheme 1), a topological isomer of 2,20 -H2Bim, and its derivatives.1,11-13 4,40 -H2Bim constructed various well-defined assembled structures based on the multidirectional H-bonds intrinsically different from those of 2,20 -H2Bim (Scheme 1). We have also revealed that the H-bond directionality of 4,40 -H2Bim is changed by the cis/ trans-conformations, and 4,40 -H2Bim constructed various network structures. Such a self-assembling ability of 4,40 -H2Bim exhibited remarkable effects on the physical properties (e.g., electrical conductivities of charge-transfer salts with tetracyanoquinodimethane).11b 4,40 -H2Bim exhibits two-step deprotonation processes (Scheme 2), and these deprotonated species are expected to form intermolecular interactions of N-H 3 3 3 N H-bonds and N 3 3 3 M 3 3 3 N coordination bonds which directly connect the complexes and construct diverse and rigid network *To whom correspondence should be addressed. Telephone: (þ81)-66850-5393. Fax: (þ81)-6-6850-5395. E-mail: [email protected]. jp. pubs.acs.org/crystal

Published on Web 09/30/2010

a

Arrows indicate the directionalities of H-bonds and coordination bonds.

Scheme 2. Two-Step Deprotonation Processes of 4,40 -H2Bim

structures, as demonstrated in the 2,20 -H2Bim system.8 Furthermore, the robust H-bond networks of oligo(imidazole)s demonstrated the spin-diluted crystal in the quaterimidazole dinuclear helicate (spin-doping into a nonmagnetic crystal),14 realizing the unprecedent material challenge for the matter spin qubits.15 Herein we present the crystal structures of transition metal complexes of 4,40 -H2Bim exhibiting various kinds of coordination geometries, 1,16 and we discuss the H-bond r 2010 American Chemical Society

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Figure 1. Examples of coordination and H-bond modes of 2,20 H2Bim with metal ions. The letters M and X represent the metal atom and counteranion species, respectively.

directionalities depending on the molecular conformation of 4,40 -H2Bim and the coordination geometry of the metal center. Three metal centers, AgI, CuII, and NiII, forming linear, square-planar, and octahedral coordination spheres, respectively, were adopted. H-bonds of these complexes built up diverse and multidimensional networks, demonstrating the intriguing crystal engineering ability of 4,40 -H2Bim with multidirectional interactions. Results and Discussions H-Bond Directionalities of 2,20 - and 4,40 -H2Bim Complexes. Figures 1 and 2 compare the H-bond directionalities of 2,20 and 4,40 -H2Bim in metal complexes, respectively. The H-bond and coordination sites (nitrogen atoms) of 2,20 -H2Bim locate at the long sides of the molecular shape; therefore, interactions elongate along the molecular short axis, forming one-directional interactions. The H-bond directionality of a 2,20 -H2Bim complex further depends on the coordination geometry of the metal center and molecular cis/trans-conformation of 2,20 -H2Bim (Scheme 1). 2,20 -H2Bim in the trans-conformation coordinates to two metal atoms to form a one-dimensional coordination polymer or oligomer.4 H-bonds elongate to the nearly parallel direction of the coordination polymer and connect the complexes through counteranions (Figure 1a). In the cis-conformation, the coordination bonds and H-bonds of 2,20 -H2Bim elongate to the antiparallel directions to each other (Scheme 1). 2,20 -H2Bim of the cis-conformation forms bifurcated coordination bonds in the complex, with two metal atoms forming linear coordination (AgI, etc.),4,5 and the bifurcated H-bonds extend along the side-by-side direction to form a one-dimensional structure (Figure 1b). In a complex with the square-planar coordination metal (CuII, etc.), 2,20 -H2Bim exhibits a chelating coordination, and the complexes are linked by bifurcated H-bonds via counteranions, forming a one-dimensional structure (Figure 1c).6 An octahedral complex composed of a metal atom (NiII, etc.) and three 2,20 -H2Bim ligands of the cis-conformation forms three bifurcated H-bonds with an approximate D3h symmetry, forming a two-dimensional structure (Figure 1d).7 In the case of 4,40 -H2Bim, interactions of N3 atoms elongate along the side-by-side direction, and those of N1

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Figure 2. Examples of coordination and H-bond modes of 4,40 H2Bim with metal ions. The letters M and X represent the metal atom and counteranion species, respectively.

atoms are inclined by ca. 30° from the molecular long axis (Scheme 1). Therefore, coordination bonds and H-bonds of 4,40 -H2Bim extend to two or three directions in the cis- and trans-conformations, respectively. In the trans-conformation, 4,40 -H2Bim coordinates to two metal atoms at the N3 atom to form a coordination chain. The linear bridging N-H 3 3 3 X H-bonds at the N1 atom connect the neighboring coordination chains via counteranions to construct a two-dimensional network (linear bridging mode, Figure 2a). In the cis-conformation, the N3 atoms of 4,40 -H2Bim coordinate to a metal atom, and two N-H 3 3 3 X H-bonds at the N1 atom elongate parallel to the M-N coordination bonds (angular bridging mode, Scheme 1). In a complex of a linear coordination metal (AgI, etc), H-bonds spread to two directions with the angular bridging mode, at the opposite side of which, two N1 atoms form bifurcated coordination bonds (Figure 2b). A square-planar complex forms four N-H 3 3 3 X H-bonds, spreading nearly parallel to the diagonal lines of the square coordination sphere, forming twodimensional H-bonds (Figure 2c). An octahedral complex composed of a metal atom and three 4,40 -H2Bim ligands forms three-dimensional H-bonds extending to six directions parallel to the diagonal lines of the octahedral coordination sphere (Figure 2d). Preparation of Metal Complexes. Preparations of AgI, CuII, and NiII complexes were performed by the mixings of 4,40 -H2Bim with 0.67, 0.5, and 0.33 equimolar amounts of metal sources, respectively, in hot EtOH. Recrystallization of the products by the vapor diffusion method afforded single crystals of complexes [AgI2(4,40 -H2Bim)3](CF3SO3)2 (1), [CuII(4,40 -H2Bim)2](ClO4)2 (2), [CuII(4,40 -H2Bim)2]Cl2(H2O)1.5 (3), [NiII(4,40 -H2Bim)3](NO3)2 (5), and [NiII(4,40 H2Bim)3](ClO4)2 (6). The CuII complex of deprotonated species (4,40 -HBim-), [CuII(4,40 -HBim-)2](H2O)3 (4), was obtained by the reaction of complex 3 with Et3N. The geometric coordination parameters of the complexes are summarized in Table 1. We also prepared the complexes with FeII, CoII, etc.; however, single crystals suitable for X-ray analyses could not be obtained. Crystal Structure of [AgI2(4,40 -H2Bim)3](CF3SO3)2 (1). This crystal has an orthorhombic system and consists of

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Table 1. Selected Bond Lengths (A˚) and Angles (deg) in Complexes 1-6

1-A (cis) 1-B (trans) M-N3 (A˚)

2.222(4)

2.155(5)

N3-M-N3 (deg) 157.0(2)

2 1.995(4)

3 (complex A)

3 (complex B)

2.007(3), 2.007(3) 2.019(4), 1.991(4)

2.019(4), 2.019(3) 1.995(4), 2.023(4)

4 2.020(3) 1.975(3)

5 2.076(3), 2.089(3) 2.075(3)

81.9(2)

82.0(1), 81.6(1)

81.5(1), 81.3(1)

82.4(1)

79.1(2), 79.2(2)

C2-N3-C4 (deg) 105.5(4)

105.7(3)

106.1(4)

106.4(3), 106.0(3) 106.8(4), 105.1(4)

105.6(3), 106.2(3) 105.2(3), 105.7(3)

105.7(3) 104.3(3)

105.8(3), 106.7(3) 104.8(3)

C2-N1-C5 (deg) 107.8(5)

107.3(5)

108.9(5)

108.1(4), 108.5(4) 108.2(4), 108.3(4)

108.7(4), 109.4(4) 107.9(4), 108.1(4)

109.1(3) 104.8(3)

107.8(3), 108.6(3) 107.6(3)

three 4,40 -H2Bim, two AgI, and two CF3SO3-. This complex has a C2v symmetry, and one 4,40 -H2Bim skeleton (4,40 -H2Bim-A) and one imidazole-ring (a half of 4,40 -H2Bim, 4,40 -H2Bim-B) are crystallographically independent. 4,40 -H2 Bim-A has the cis-conformation with a small torsion angle of 0.6°, while the flat 4,40 -H2Bim-B has the trans-conformation. 4,40 H2Bim-A chelates to the Ag1 atom, and the linear bridging coordination of 4,40 -H2Bim-B forms the dinuclear complex (Figure 3a). The Ag1-N2 distance (2.412(4) A˚, gray line in Figure 3a) is considerably longer than those of Ag1-N4 (2.222(4) A˚) and Ag1-N6 (2.155(5) A˚), and this is responsible for the N2-Ag1-N6 angle (157.0(2)°). 4,40 -H2Bim-A and 4,40 -H2Bim-B ligands are nearly parallel to each other (dihedral angle = 4.2°) to form a planar complex. The Ag 3 3 3 Ag distance within the dinuclear complex is 6.79 A˚. 4,40 -H2Bim-A having the cis-conformation interacts with two CF3SO3- with angular bridging H-bonds (N1 3 3 3 O2 and N3 3 3 3 O1 distances = 2.94 and 2.88 A˚, respectively). 4,40 H2Bim-B having the trans-conformation forms linear bridging H-bonds with two CF3SO3- (N5 3 3 3 O4 distance = 2.92 A˚). A set of one three-centered N-H 3 3 3 O 3 3 3 H-N and two NH 3 3 3 O-S-O 3 3 3 H-N H-bonds connect the complexes to form a one-dimensional chain along the b-axis (Figure 3b). The [AgI2(4,40 -H2Bim)3] complex forms a uniform π-stacking column along the c-axis with a face-to-face distance of 3.17 A˚ (Figure 3c). Crystal Structure of [CuII(4,40 -H2Bim)2](ClO4)2 (2). This crystal has a monoclinic system and consists of two 4,40 H2Bim, one CuII, and two ClO4-. The inversion center locates at the CuII ion, and one imidazole-ring (a half of 4,40 -H2Bim) is crystallographically independent. 4,40 -H2Bim ligand has the cis-conformation, and two imidazole-rings of the ligand are slightly twisted by 4.4°. The ligand acts in a bidentate coordination fashion, and the CuII ion is coordinated by four nitrogen atoms from two 4,40 -H2Bim ligands (Cu-N distance = 1.995(4) A˚, N-Cu-N angle = 81.9(2)°, Table 1) to furnish a square-planar coordination geometry (Figure 4a). The N-H groups of 4,40 -H2Bim interact with two ClO4by angular bridging H-bonds, and the three-centered double H-bonds of N1-H 3 3 3 O1 3 3 3 H-N1 (N 3 3 3 O distance=2.90 A˚) across the counteranion formed a one-dimensional chain along the b-axis (Figure 4b). In addition to the H-bond formation, 4,40 -H2Bim ligands interact with adjacent molecules through

6 2.082(5), 2.094(5) 2.120(5), 2.088(6) 2.083(5), 2.085(5) 79.0(2), 78.9(2) 79.6(2) 107.4(7), 105.5(7) 106.3(6), 108.4(6) 105.3(6), 104.6(6) 107.0(9), 108.9(9) 108.4(6), 108.3(6) 105.9(7), 108.3(6)

Figure 3. (a) Molecular structure of the dinuclear complex [AgI2(4,40 -H2Bim)3] in 1. (b) Crystal packing viewed along the c-axis showing the H-bond structure. (c) Crystal packing viewed along the b-axis showing the stacking columns. The relatively longer Ag1-N2 bonds are indicated by gray lines.

π-stacks of a face-to-face distance of 3.26 A˚. These interactions form a three-dimensional structure of this crystal (Figure 4c). Crystal Structure of [CuII(4,40 -H2Bim)2]Cl2(H2O)1.5 (3). This crystal has a triclinic system and consists of crystallographically four independent 4,40 -H2Bim ligands having

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Figure 4. (a) Molecular structure of the square-planar complex [CuII(4,40 -H2Bim)2] in 2. (b) One-dimensional H-bond chain viewed along the a-axis (a = 0). (c) Crystal packing viewed along the b-axis showing π-stacking interactions.

the cis-conformation, two CuII, four Cl-, and three crystalline water molecules. Two imidazole-rings of each ligand are slightly twisted, with dihedral angles of 3.6-5.9°. The ligands act in a bidentate coordination fashion (Cu-N distances = 1.991(4)-2.023(4) A˚, N-Cu-N angles = 81.3(1)-82.0(1)°, Table 1) and form two crystallographically independent molecules having a distorted square-planar coordination geometry (denoted complexes-A and -B, Figure 5a). Two 4,40 -H2Bim ligands in complexes-A and -B are twisted by 12.0 and 14.0°, respectively. The Cu1 and Cu2 atoms interact with chlorine atoms at the apical positions, with the Cu-Cl distances of 2.709(2) and 2.632(2) A˚, respectively, which are considerably longer than those of Cu-N distances (Table 1). All N-H groups of the 4,40 -H2Bim ligands interact with Cl- or water molecules by angular bridging H-bonds. Complexes-A and -B are alternately connected by a couple of three-centered double H-bonds of N-H 3 3 3 Cl 3 3 3 H-N and N-H 3 3 3 O 3 3 3 H-N to form a one-dimensional H-bond chain along the [011] direction (Figure 5b). The H-bond distances are 3.06-3.28 A˚ for N-H 3 3 3 Cl and 2.86-2.88 A˚ for N-H 3 3 3 O bonds. Furthermore, Cu-Cl interactions and π-stacks between 4,40 -H2Bim ligands (face-to-face distances = 3.3-3.5 A˚) connect the H-bond chains (Figure 5b and c). This crystal has a one-dimensional channel (ca. 7 A˚  3 A˚) parallel to the a-axis (Figure 5c), in which noncoordinating Cl- (Cl3 and Cl4) and water molecules (O1 and O2) form a one-dimensional H-bond chain along the a-axis (Figure 5d).

Figure 5. (a) Molecular structures of the square-planar complexes [CuII(4,40 -H2Bim)2] in 3. (b) One-dimensional H-bond structures. (c) Crystal packing viewed along the a-axis showing channel structures. (d) Crystal packing viewed along the H-bond chain direction ([110]) showing π-stacks of the ligands and one-dimensional chains of water and Cl-. The relatively longer Cu-Cl bonds are indicated by gray lines.

Crystal Structure of [CuII(4,40 -HBim-)2](H2O)3 (4). This crystal has an orthorhombic system and consists of two 4,40 HBim-, one CuII, and three crystalline water molecules. The inversion center locates at the Cu1 atom, and one 4,40 -HBimis crystallographically independent. The C-N-C angle of the N3 atom (104.8(3)°) is significantly smaller than that of the N1 atom (109.1(3)°), indicating the deprotonated state of the N3 atom (Table 1). 4,40 -HBim- has the cis-conformation, and two imidazole-rings of a ligand are slightly twisted by 5.2°. 4,40 -HBim- ligand acts in a bidentate coordination fashion, and the Cu1 atom is coordinated by four nitrogen atoms from two 4,40 -HBim- (Cu-N distances = 2.020(3) and 1.975(3) A˚, N2-Cu1-N4 angle = 82.4(1)°, Table 1) to furnish a square-planar coordination geometry (Figure 6a). No distinguishable difference from the complexes of neutral 4,40 -H2Bim (2 and 3) is found in the coordination parameters (Cu-N distances and N-Cu-N angles, Table 1).

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Figure 6. (a) Molecular structure of the square-planar complex [CuII(4,40 -HBim-)2] in 4. (b) Crystal structure viewed nearly along the b-axis showing the H-bond network and one-dimensional stacking column. (c) Crystal packing viewed along the c-axis showing one-dimensional columns. 0

-

The [Cu (4,4 -HBim )2] complex forms a uniform π-stacking column along the b-axis with a face-to-face distance of 3.09 A˚ (Figure 6b and c). The protonated N1 atom forms an N-H 3 3 3 O H-bond (2.78 A˚) with a water molecule (O1) (Figure 6b), while the deprotonated N3 atom interacts with two water molecules (O1 and O2) with N 3 3 3 H-O H-bonds (2.74 and 2.98 A˚, respectively), forming a tetrahedral geometry (Figure 6b). π-Stacking columns are connected by these N1-H 3 3 3 O1-H 3 3 3 N3 and N3 3 3 3 H-O2-H 3 3 3 N3 H-bonds along the c-axis to form a two-dimensional array (Figure 6b). Water molecules (O1) form a zigzag one-dimensional H-bond chain (O1-H 3 3 3 O1 distance; 2.85 A˚) parallel to the π-stacking column (b-axis, Figure 6b). These H-bonds and π-stacks construct a three-dimensional network structure of this crystal. Crystal Structure of [NiII(4,40 -H2Bim)3](NO3)2 (5). This crystal has a monoclinic system and consists of three 4,40 H2Bim, one NiII, and two NO3-. The complex has a C2v symmetry, and one 4,40 -H2Bim skeleton and one imidazolering (a half of 4,40 -H2Bim) are crystallographically independent (Figure 7a). In the 4,40 -H2Bim ligands having the cisconformation, two imidazole-rings are slightly twisted by 4.9 and 6.4°. 4,40 -H2Bim ligands act in a bidentate coordination fashion, and the Ni1 atom is coordinated by six nitrogen II

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Figure 7. (a) Molecular structure of the octahedral complex [NiII(4,40 H2Bim)3] (Δ isomer) in 5. (b) Two dimensional sheet structure of the Λ isomers formed by N3-H 3 3 3 O1 3 3 3 H-N5 H-bonds (c = 0). (c) Crystal structure viewed along the b-axis showing the N1-H 3 3 3 O2 H-bond connecting H-bond sheet of the Λ isomer depicted in part b (c = 0 and 1). Light colored molecules are the Δ isomers locating in the c = 0.5 layer.

atoms from three 4,40 -H2Bim ligands (Ni-N distances = 2.075(3)-2.089(3) A˚, N-Ni-N angles = 79.1(2) and 79.2(2)°, Table 1) to furnish an octahedral coordination geometry (Figure 7a). The complex has an approximate point group of D3 symmetry. The Δ and Λ isomers are included in the crystal (Figure 8). The N3-H and N5-H groups in a 4,40 -H2Bim moiety form angular bridging H-bonds with NO3- (N 3 3 3 O distance = 2.90 and 2.79 A˚, respectively, Figure 7b). Three-centered H-bonds of N3-H 3 3 3 O1 3 3 3 H-N5 across NO3- connect the complexes along the [110] and [110] directions to form a two-dimensional sheet (Figure 7b). H-bond sheets are connected by H-bonds between the N1-H group and the O2 atom of NO3- to construct a three-dimensional network (Figure 7c). The Δ and Λ isomers form H-bond networks individually, and only small π-overlaps of 4,40 -H2Bim ligands (3.3-3.5 A˚) are observed between Δ and Λ isomers (Figure 7c). The three-dimensional H-bond networks of Δ and Λ isomers

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Figure 8. Δ and Λ isomers of octahedral [NiII(4,40 -H2Bim)3]2þ.

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Crystal Structure of [NiII(4,40 -H2Bim)3](ClO4)2 (6). This crystal has an orthorhombic system and consists of three 4,40 -H2Bim, one NiII, and two ClO4-. Three 4,40 -H2Bim skeletons having the cis-conformation are crystallographically independent (Figure 9a). Two imidazole-rings of each ligand are slightly twisted by 4.3-5.9°. 4,40 -H2Bim ligands act in a bidentate coordination fashion, and the NiII center is coordinated by six nitrogen atoms from three 4,40 -H2Bim ligands (Ni-N distances = 2.082(5)-2.120(5) A˚, N-Ni-N angles = 78.9(2)-79.6(2)°, Table 1) to furnish an octahedral coordination geometry with an approximate point group of D3 symmetry (Figure 9a). This crystal consists of the Δ and Λ isomers of the complex (Figure 8). All N-H groups of 4,40 -H2Bim ligands form angular bridging H-bonds with ClO4- (N 3 3 3 O distances = 2.85-3.10 A˚, Figure 9b). The Δ and Λ isomers are alternately connected by the triple three-centered N-H 3 3 3 O 3 3 3 H-N and N-H 3 3 3 O-Cl-O 3 3 3 H-N H-bonds along the a-axis to form a onedimensional motif (Figure 9b and c). The N11-H 3 3 3 O7-Cl-O9 3 3 3 H-N7 and N1-H 3 3 3 O5 3 3 3 H-N5 H-bonds connect the one-dimensional motifs along the c-axis to construct a two-dimensional H-bond network (Figure 9b). No H-bonds and π-overlaps of 4,40 -H2Bim ligands are observed between two-dimensional networks (Figure 9c). Conclusion

Figure 9. (a) Molecular structure of the octahedral complex [NiII(4,40 -H2Bim)3] in 6. (b) Crystal packing viewed along the b-axis (b = 0) showing the two-dimensional H-bond sheet. (c) Crystal packing viewed along the c-axis. Light colored molecules belong to the c = 0.5 layer.

are interpenetrated to each other (Figure S6 in the Supporting Information).

Assembled metal complexes of 4,40 -H2Bim with AgI, CuII, and NiII were investigated, where diverse H-bond networks were constructed with the aid of multidirectional H-bonds. 4,40 -H2Bim exhibited coordination modes identical to those observed in 2,20 -H2Bim complexes, and it afforded linear bridging (AgI, 1), square-planar (CuII, 2-4), and octahedral coordination spheres (NiII, 5 and 6). In contrast to the coordination modes, the H-bond directionalities of 4,40 -H2Bim complexes were distinct from those of 2,20 -H2Bim complexes and were changed depending on cis/trans-conformations. The cis-conformation was observed for all metal ions (1-6), and 4,40 -H2Bim exhibited angular-bridging H-bonds (Figure 2c and d). The N-H 3 3 3 X 3 3 3 H-N type H-bonds across counteranions or solvent molecules constructed multidimensional H-bond networks: one-dimensional chains (2 and 3, Figures 4b and 5b), two-dimensional sheets (5, Figure 7b), and a threedimensional network (6, Figure 9b). Deprotonation of an N-H group resulted in the formation of two N 3 3 3 H-O type H-bonds with a tetrahedral geometry, increasing the variation and directionality of H-bond patterns (4, Figure 6b). The trans-conformation was observed only in 1, where the bridging coordination formed a dinuclear complex. The triple N-H 3 3 3 X 3 3 3 H-N H-bonds of angular bridging (cis-conformation) and linear bridging (trans-conformation) connected the neighboring complexes to form a one-dimensional chain. We emphasize that these results are achieved by the multiple directionality and diversity of the H-bond nature of the 4,40 H2Bim, and we confirm the high potential of this system as a building block of functional metal complexes based on the supramolecular structures. The present work elucidating the supramolecular architectures of neutral 4,40 -H2Bim metal complexes with N-H 3 3 3 X 3 3 3 H-N H-bonds is the first step of our research directing toward the development of new functional materials in the assembled metal complexes with multidimensional network structures. Investigations are in progress for the construction of supramolecular architectures of assembled metal complexes of deprotonated 4,40 -H2Bim

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Table 2. Crystallographic Data of 1-6 crystal formula formula weight crystal system space group a (A˚) b (A˚) c (A˚) R (deg) β (deg) γ (deg) V (A˚3) Z Dcalcd (g cm-3) μ (cm-1) temp (K) unique reflns reflns used parameters R1, wR2 GOF a

1

2

3

4

5

6

C20H18F6Ag2N12O6S2 916.29 orthorhombic Pnma 22.302(8) 23.455(6) 5.550(1)

C12H12Cl2Cu1N8O8 530.73 monoclinic C2/m 13.038(1) 10.7926(6) 7.4191(5)

C24H30Cl4Cu2N16O3 859.51 triclinic P1 7.569(7) 11.62(1) 19.40(2) 93.78(7) 85.04(7) 98.66(7) 1678(2) 2 1.701 16.42 200 7529 4133a 442 0.048, 0.118 0.863

C12H16Cu1N8O3 383.86 orthorhombic Pbcn 14.921(7) 4.993(2) 20.56(1)

C18H18Ni1N14O6 585.13 monoclinic C2/c 17.373(2) 13.845(2) 10.509(1)

C18H18Cl2Ni1N12O8 660.03 orthorhombic Pmc21 19.669(1) 14.514(1) 9.7746(7)

117.496(7) 2903(1) 4 2.096 15.89 200 3329 2593a 229 0.057, 0.171 1.106

926.0(1) 2 1.903 15.33 296 1114 901b 89 0.070, 0.212 1.100

98.052(2) 1531(1) 4 1.665 14.58 200 1754 1020a 111 0.039, 0.101 0.774

2503.0(5) 4 1.553 8.40 150 2861 1605a 177 0.041, 0.095 0.689

2790.3(3) 4 1.571 9.52 200 6568 5073a 388 0.077, 0.216 1.038

I > 2.0σ(I). b I > 3.0σ(I).

species (Scheme 2), where complexes are directly connected by N-H 3 3 3 N H-bonds and N-M-N coordination bonds, which are more robust and selective than the N-H 3 3 3 X 3 3 3 H-N H-bonds of neutral 4,40 -H2Bim complexes. Furthermore, the oligomerization of 4,40 -H2Bim produces intriguing coordination architectures exhibiting the self-assembling ability.12,14 The octahedral coordination geometry with three 4,40 -H2Bim ligands of NiII complexes (5 and 6) bears a resemblance to those of triple-stranded helicates based on oligo(bipyridine)s first demonstrated by Professor J. M. Lehn.2a The successful molecular design for matter spin qubit based on the triple-stranded helicate of quaterimidazole (a dimer of 4,40 -H2Bim)14 is one of the most typical examples of the development for the application of supramolecular assemblies of oligo(imidazole)-based metal complexes. Experimental Section 0

Materials. 4,4 -H2Bim was prepared according to our previous paper,11a and metal sources were used as purchased. Measurements. Elemental analyses were performed at the Graduate School of Science, Osaka University. Infrared (IR) and electronic spectra were measured using KBr plates on JASCO FT/IR-660 M and Shimadzu UV/vis scanning spectrophotometer UV-3100PC, respectively. Typical Synthetic Procedure for Metal Complexes of 4,40 -H2Bim: [CuII(4,40 -H2Bim)2](ClO4)2 (2). 4,40 -H2Bim (100 mg, 0.74 mmol) was placed in a 50-mL round-bottomed flask and dissolved with EtOH (5 mL). To this mixture was added CuII(ClO4)2 3 6H2O (138 mg, 0.37 mmol) in EtOH (5 mL), and the reaction mixture was refluxed for 0.5 h. After being cooled to room temperature, the resulting precipitate was collected by filtration and washed with EtOH (3 mL) and ether (5 mL), to give the complex (191 mg, 97%) as a dull green powder. Green crystals suitable for X-ray measurements were obtained by the vapor diffusion method using ethyl acetate;10:1 mixture of EtOH and DMSO. mp >300 °C; IR (KBr) ν = 3600-2700, 1660, 1566, 1121, 1086, 1046 cm-1; UV (KBr) λmax = 218, 268(sh) nm. Elemental analysis. Calcd (%) for C12H12Cl2N8O8Cu: C, 27.16; H, 2.28; N, 21.10. Found: C, 27.10; H, 2.24; N, 20.97. [AgI2(4,40 -H2Bim)3](CF3SO3)2 (1). White powder (78% yield). Colorless crystals suitable for X-ray measurements were obtained by the vapor diffusion method using ether-EtOH. mp >300 °C; IR (KBr) ν = 3366, 3081, 2973, 3000-2300, 1793, 1663, 1533, 1257 cm-1. Elemental analysis. Calcd (%) for C20H18N12F6O6S2Ag2: C, 26.22; H, 1.98; N, 18.34. Found: C, 26.38; H, 1.97; N, 18.38.

[CuII(4,40 -H2Bim)2]Cl2 3 (H2O)1.5 (3). Bright bluish green powder (83% yield). Green crystals suitable for X-ray measurements were obtained by the vapor diffusion method using acetone-water. mp >300 °C; IR (KBr) ν = 3600-3300, 3300-2500, 1648, 1560 cm-1; UV (KBr) λmax = 262 nm. Elemental analysis. Calcd (%) for (C12H12N8Cl2Cu)(H2O)1.5: C, 33.54; H, 3.52; N, 26.07. Found: C, 33.92; H, 3.35; N, 26.34. Preparation of [CuII(4,40 -HBim-)2](H2O)3 (4). Complex 2 (60.0 mg, 0.12 mmol) was placed in a vial and dissolved with water (30 mL). To this mixture was added Et3N (0.1 M aqueous solution, 6.0 mL, 0.60 mmol), and the reaction mixture was left standing under the vapor-diffusion condition using acetone at room temperature. After it was left standing for 3 weeks, the resulting precipitate was collected by filtration and washed with water (3 mL) and acetone (5 mL), to give the complex (34.1 mg, 83%) as light purplish gray microcrystals. mp 280-282 °C (dec); IR (KBr) ν = 36002600, 1639, 1539 cm-1; UV (KBr) λmax = 254 nm. Elemental analysis. Calcd (%) for (C12H10N8Cu)(H2O)3: C, 37.55; H, 4.20; N, 29.19. Found: C, 37.90; H, 3.90; N, 29.14. [NiII(4,40 -H2Bim)3](NO3)2 (5). (Purple powder, 90% yield). Violet crystals suitable for X-ray measurements were obtained by the aerial evaporation from EtOH. mp >300 °C; IR (KBr) ν = 3600-2800, 1642, 1553, 1384 cm-1; UV (KBr) λmax = 212, 221(sh), 254(sh) nm. Elemental analysis. Calcd (%) for (C18H18N14O6Ni)(H2O)0.6: C, 36.28; H, 3.25; N, 32.91. Found: C, 36.40; H, 3.11; N, 32.68. Due to the high hygroscopic nature of this complex, elemental analysis did not give the appropriate value. [NiII(4,40 -H2Bim)3](ClO4)2 (6). (Purple powder, 81% yield). Violet crystals suitable for X-ray measurements were obtained by the vapor diffusion method using ether-EtOH. mp >300 °C; IR (KBr) ν = 3600-2800, 1643, 1553, 1502, 1086 cm-1; UV (KBr) λmax = 234 nm. Elemental analysis. Calcd (%) for (C18H18N12Cl2O8Ni)(H2O)0.8: C, 32.06; H, 2.93; N, 24.92. Found: C, 32.24; H, 2.77; N, 24.76. Due to the high hygroscopic nature of this complex, elemental analysis did not give the appropriate value. X-ray Crystallography. X-ray crystallographic measurements were made on a Rigaku Mercury CCD area detector for 5 and on a Rigaku Raxis-Rapid imaging plate for the other compounds with graphite monochromated Mo KR (λ = 0.71070 A˚). Structures were determined by direct methods using SIR-9217 for 5, SIR-9718 for 2 and 4, SHELXS-8619 for 1 and 3, and SHELXS-9720 for 5. Refinements were performed by full-matrix least-squares on F2 using the teXsan crystallographic software package21 for 5 and SHELXL9722 for the others. All non-hydrogen atoms were refined anisotropically, and all hydrogen atoms were included but not refined. Empirical absorption corrections were applied. Selected crystal data and data collection parameters are given in Supporting Information Table 2.

Article

Crystal Growth & Design, Vol. 10, No. 11, 2010

Acknowledgment. This work was partly supported by Grants-in-Aid for Scientific Research (20550051) and Challenging Exploratory Research (21655015) from the Japan Society for the Promotion of Science, and for Scientific Research on Innovative Area (20110006) from the Ministry of Education, Culture, Sports, Sciences and Technology, Japan. Supporting Information Available: Overlap modes of complexes 1-5 and schematic drawing of the interpenetrated network of 5 in PDF format and X-ray crystallographic data for each structure in CIF format. This material is available free of charge via the Internet at http://pubs.acs.org.

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