Hydrothermal Synthesis and Structure of ... - ACS Publications

DOI: 10.1021/cg801282r

Hydrothermal Synthesis and Structure of Coordination Polymers by Combination of Bipyrazole and Aromatic Dicarboxylate Ligands

2009, Vol. 9 4613–4625

Jens Hunger,*,† Harald Krautscheid,‡ and Joachim Sieler‡ †

Max Planck Institute for Chemical Physics of Solids, Dresden, Germany, and ‡Institute for Inorganic Chemistry of the University, Leipzig, Germany Received November 20, 2008; Revised Manuscript Received July 15, 2009

ABSTRACT: Nine new coordination polymers, namely ¥2[Ag(Hp2CA)(Me4bpz)] (I), ¥3[Zn2(p2CA)2(Me4bpz)] (II), ¥2[Cd(OAc)2(Me4bpz)(H2O)] (III), ¥1[Ag2(m2CA)(Me4bpz)2] (IV), ¥3[Zn(m2CA)(Me4bpz)] (V), ¥2[Cd(m2CA)(Me4bpz)] 3 H2O (VI), 1 3 2 ¥[Ag(OAc)(Me4bpz)2] 3 5.4 H2O (VII), ¥[Zn2(OHm2CA)2(Me4bpz)2] 3 1.75 H2O (VIII), and ¥[Cd(OHm2CA)(Me4bpz)(H2O)] (IX) [Hp2CA, terephthalic acid monoanion; p2CA, terephthalic acid dianion; OAc, acetate; m2CA, isophthalic acid dianion; OHm2CA, 5-hydroxy-isophthalic acid dianion; Me4bpz, 3,30 ,5,50 -tetramethyl-4,40 -bipyrazole], were obtained from acetate hydrates of Agþ, Zn2þ, and Cd2þ and mixed ligand systems consisting of Me4bpz and the respective aromatic dicarboxylic acid by means of hydrothermal synthesis. The compounds were characterized by means of X-ray single-crystal structure analysis, elemental analysis, and IR spectroscopy. The topologies realized in these coordination polymers vary from simple onedimensional polymers to complex three-dimensional frameworks. Hydrogen bonds of different types with influence on the resulting structures are observed in all compounds.

Introduction Inorganic crystal engineering of inorganic-organic hybrid systems has attracted great interest in recent years1-7 because it enables targeted synthesis of coordination polymers with specific properties, allowing potential applications as catalysts,8,9 sorption materials,10-14 solid-state electrolytes, and as optical15,16 and magnetic17 components. The topology of such coordination networks is mainly affected by the strong coordinative bonds between the metal ions and ligands. Therefore, the correct choice of metal centers and the design of the ligands play a decisive role. If the ligands contain uncoordinated heteroatoms, hydrogen bonds between the ligand molecules and also between ligand molecules and solvent molecules may influence the stabilization of specific constitutions. To date, it is difficult to control the dimensionality of coordination polymers by applying specific synthesis conditions. Especially under solvothermal conditions often used for synthesis of single-crystalline samples, the influences of the anions of the employed metal salt and the used solvent on the formation of polymeric structures are often underestimated. In principle, it is observed that dimensionality of coordination polymers increases with rising coordination number of the metal centers, although at high coordination numbers the probability of formation of porous networks required for many applications becomes smaller. Therefore, we used the connectors Agþ, Zn2þ, and Cd2þ with preference for relatively small, but different coordination numbers to be able to analyze the influences on the structure of the resulting polymers. Using anionic ligands neutral porous networks without counterions in the voids can be prepared. The connection of metal centers over only these ligands is often not sufficient for formation of stable three-dimensional networks. A common possibility to solve this problem is the utilization of *Corresponding author. Phone: 49 351 46464217. Fax: 49 351 46464002. E-mail: [email protected]. r 2009 American Chemical Society

mixed-ligand systems composed of anionic and charge-neutral ligands.18-24 Therefore, we used mixed ligand systems consisting of 3,30 ,5,50 -tetramethyl-4,40 -bipyrazole (Me4bpz) and an aromatic dicarboxylic acid (terephthalic acid [p2CA], isophthalic acid [m2CA] or 5-hydroxy-isophthalic acid [OHm2CA]). The latter are characterized by the ability to form different coordination topologies. In addition 5-hydroxy-isophthalic acid features a hydroxyl group, which is not located in coordination spheres of the metal ions coordinated by the carboxylate groups and able to be involved in hydrogen bonding. In coordination compounds, Me4bpz normally appears as an exobidentate ligand, whereby the connected metal centers adopt distances between 9.0 and 10.5 A˚.25-39 The two not coordinated nitrogen atoms normally act as donor atoms in hydrogen bonds, which is a fundamental difference to the triazole-based ligand recently used in a study on mixed ligand systems with an aromatic tricarboxylate.40 The flexibility of this ligand arises from the nearly unhindered torsion of the pyrazole rings along the single bond between the rings and can lead to very different coordination conformations (observed angles between the pseudoaromatic ring planes j are between 55 and 90), where the more topological flexibility of the carboxylate ligands arises from the ability to realize different binding modes to the metal centers. A further aspect of porous coordination polymers is the appearance of interpenetrated networks, which leads to reduction of the pore size, although that does not necessarily prevent structures with available pore volume.41-43 This behavior is mainly observed in compounds with large pore sizes and voids, which are provoked by long inflexible spacer ligands and particular framework topologies. In this contribution, we report the synthesis of the nine coordination polymers ¥2[Ag(Hp2CA)(Me4bpz)] (I), ¥3[Zn2(p2CA)2(Me4bpz)] (II), ¥2[Cd(OAc)2(Me4bpz)(H2O)] (III), 1 3 ¥[Ag2(m2CA)(Me4bpz)2] (IV), ¥[Zn(m2CA)(Me4bpz)] (V), 2 1 ¥[Cd(m2CA)(Me4bpz)] (VI), ¥[Ag(OAc)(Me4bpz)2] 3 5.4 Published on Web 09/30/2009

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Table 1. Results of the Hydrothermal Synthesesa Mnþ

acid H2p2CA H2p2CA H2p2CA H2m2CA H2m2CA H2m2CA H2OHm2CA H2OHm2CA H2OHm2CA

n(Mnþ) (mmol)

n(acid) (mmol)

n(Me4bpz) (mmol)

yield

compound

0.5 1.0 0.5 0.5 0.5 0.5 1.0 1.0 0.5

0.5 1.0 0.5 0.25 0.5 0.5 0.5 1.0 0.5

0.5 0.5 0.5 0.5 0.5 0.5 2.0 1.0 0.5

0.20 g (86%) 0.26 g (80%) 0.18 g (82%) 0.18 g (95%) 0.18 g (86%) 0.19 g (78%) 0.33 g (52%) 0.35 g (78%) 0.22 g (88%)

I II III IV V VI VII VIII IX

þ

Ag Zn2þ Cd2þ Agþ Zn2þ Cd2þ Agþ Zn2þ Cd2þ

a n(Mnþ), employed amount of metal acetate; n(acid), employed amount of aromatic carboxylic acid; n(Me4bpz), employed amount of Me4bpz. Yields in percent are based on metals.

Table 2. Selected Distances (A˚) and Angles (deg) in the Crystal Structures of the Silver Coordination Polymers I, IV, and VII 2

¥[Ag(Hp2CA)(Me4bpz)]

Ag1-N1 Ag1-N3 Ag1-O1 Ag1-O3 O1-Ag1-O3 N3-Ag1-O3 N3-Ag1-O1 N1-Ag1-O3 N1-Ag1-O1 N1-Ag1-N3

(I)

2.138(2) 2.168(2) 2.461(2) 2.656(2) 79.22(6) 84.17(7) 90.86(7) 98.72(7) 115.71(7) 153.39(8)

1 ¥[Ag2(m2CA)(Me4bpz)2]

Ag2-N7 Ag2-N3 Ag2-O3 Ag2-O4 O3-Ag2-O4 N3-Ag2-O4 N7-Ag2-O3 N3-Ag2-O3 N7-Ag2-O4 N3-Ag2-N7 Ag1-N5 Ag1-N1 Ag1-O1 N1-Ag1-O1 N5-Ag1-O1 N1-Ag1-N5

H2O (VII), ¥3[Zn2(OHm2CA)2(Me4bpz)2] 3 1.75 H2O (VIII), and ¥2[Cd(OHm2CA)(Me4bpz)(H2O)] (IX) from the respective metal acetate hydrates and mixed-ligand systems by means of hydrothermal synthesis. The single-crystal structures of all the above-mentioned coordination polymers were determined. Additionally, the compounds were characterized by means of elemental analysis and IR spectroscopy. Experimental Section 0

0

3,3 ,5,5 -tetramethyl-4,40 -bipyrazole (Me4bpz) was synthesized according to literature methods,31 using acetyl acetone (Acros, 99þ%), sodium hydride (Acros, 60% dispersion in mineral oil), iodine (Sigma-Aldrich, 99,8%), and hydrazine hydrate (Merck, ca. 100%). Diethyl ether was dried with sodium/benzophenone and preserved under nitrogen atmosphere. All other solvents were used as obtained. The aromatic dicarboxylic acids terephtalic acid (Fluka, 99%), isophthalic acid (Sigma-Aldrich, 99%), and 5-hydroxy-isophthalic acid (Acros, 99%) as well as the metal acetates were used as obtained from the distributors stated above. Metal acetates, aromatic dicarboxylic acid, and 3,30 ,5,50 -tetramethyl-4,40 -bipyrazole were reacted under hydrothermal conditions (solvent volume of 5 mL) in amounts specified in Table 1. The autoclaves of type 4749 (Parr, volume 23 mL, Teflon liner, Tmax = 250 C, pmax = 124 bar) were tempered using a drying oven ULE400 (Memmert) with RS232-interface and the control software CELSIUS2000 (Memmert). The reaction vessels were heated to 150 C within 10 h. After a further 20 h at 150 C, the autoclaves were cooled to 25 C within 120 h with a constant cooling rate. The generated colorless crystalline solids were filtrated from the liquids and washed with 50 mL of hot water and 50 mL of hot methanol. Thereafter, the products were dried at 120 C in a drying oven. All syntheses were performed at least two times to ensure reproducibility of the results. The products were characterized by means of IR spectroscopy and elemental analysis. IR spectra were recorded from KBr pellets in transmission geometry on a Perkin-Elmer FT-IR Spectrum 2000.

(IV)

2.175(2) 2.196(2) 2.615(2) 2.672(2) 49.36(6) 95.84(7) 102.23(7) 110.60(8) 120.27(6) 142.11(8) 2.152(2) 2.174(2) 2.409(2) 103.22(7) 117.25(8) 139.31(8)

1

¥[Ag(OAc)(Me4bpz)2] 3 5.4

Ag1-N5 Ag1-N7 Ag1-N1 Ag1-O1 N7-Ag1-O1 N1-Ag1-O1 N1-Ag1-N7 N5-Ag1-O1 N1-Ag1-N5 N5-Ag1-N7

H2O (VII) 2.214(2) 2.226(2) 2.334(2) 2.537(2) 89.28(7) 93.33(7) 104.16(8) 104.93(7) 120.04(8) 131.98(8)

Elemental analyses were determined on a VARIO EL apparatus (Heraeus). The results are summarized in the Supporting Information, Tables 1 and 2, respectively. Measurement of single-crystal diffraction intensities using Mo KR radiation (λ = 0,71073 A˚) was carried out at a CCD diffractometer SMART1K (BRUKER-AXS; ω-Scans) and IP diffractometers IPDS-1 and IPDS-2T (STOE, j-Scans and ω-Scans). The data were reduced by means of the data reduction software SAINT (BRUKER-AXS) and X-AREA (STOE), respectively. An empirical absorption correction was applied to the data from the CCD diffractometer using the software SADABS (BRUKER-AXS). A numerical absorption correction was applied to the data from the IP diffractometers by measurement of the crystal faces using the program FACEIT (STOE) and calculation using the program XRED (STOE). The crystal structures were solved by direct methods using the program SHELXS44 and the refinements and all further calculations were carried out using SHELXL-97,44 included in the WINGX package.45 The H-atoms were included in calculated positions and treated as riding atoms using SHELXL default parameters. The nonH atoms were refined anisotropically, using weighted full-matrix least-squares on F2. Details of the crystal structure determinations are summarized in Tables 3-5 in the Supporting Information. Visualization of crystal structures was carried out with the program DIAMOND3.1 (Crystal Impact). The topological analysis of the crystal structures was done using the TOPOS program package.46 Crystallographic data (excluding structure factors) for the structures reported in this paper have been deposited with the Cambridge Crystallographic Data Center as supplementary publication no. CCDC-703520-703528. Copies of the data can be obtained free of charge on application to CCDC, 12 Union Road, Cambridge CB2 1EZ, UK (fax: (_44)1223-336-033; e-mail: deposit@ccdc. cam.ac.uk).

Results and Discussion Description of the Single-Crystal Structures. In the following, the substantial aspects of the crystal structures will be reviewed. In the structure discussion, a simplified representation

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Figure 2. Asymmetric unit of ¥2[Ag(Hp2CA)(Me4bpz)]. Figure 1. Symbolic representation of the ligands (left) and color code used for metal cations, ligand components, and water molecules (right).

of packing graphs (connectivities) is necessary, which is introduced here briefly. The aromatic rings and pyrazole rings of the ligands are represented by a dummy atom in the center of gravity of the rings. Also the centers of gravity of the carboxylate groups are drawn as a dummy atom. The following color code is used: blue for bipyrazole ligands, red for carboxylate groups, and black for the aromatic rings. Accordingly, connections between two pyrazole rings and pyrazole units and metal cations, respectively, are drawn blue, whereas connections between carboxylate groups and aromatic rings as well as between carboxylate groups and metal cations are drawn in red. The carboxylate anions and the bipyrazole ligand used in this work are depicted in Figure 1, left side. The metal cations are drawn in different colors, depending on the type of the cation (Figure 1, right side). If water molecules are present, those as well as the hydroxyl group of 5-hydroxyisophthalic acid are symbolized as green dummy atoms on the location of the oxygen atoms. The hydrogen bonds observed in all cases are represented by green dashed lines. For classification of hydrogen bonds, a code consisting of three letters is used. The first two letters are symbols for the donor and the acceptor atoms of the hydrogen bond, which are N (nitrogen), O (carboxylate oxygen), W (water oxygen), and H (hydroxyl oxygen). The last letter symbolizes the location of the hydrogen bond, which is either I (intrapolymer) or E (interpolymer) or M (also intrapolymer, but donor and acceptor ligand are coordinated to the same metal center). Catena-((μ2-hydrogen-benzene-1,4-dicarboxylato)-( μ2-3,30 ,5,50 -tetramethyl-4,40 -bipyrazole)-silver(I)): ¥2[Ag(Hp2CA)(Me4bpz)] (I). ¥2[Ag(Hp2CA)(Me4bpz)] crystallizes in the monoclinic space group P21/c with four formula units per unit cell. The metal cations have the coordination number four and are coordinated by two bipyrazole ligands and two carboxylate ligands (Tables 2 and 5). The angle between the two oxygen donor atoms on the silver ion amounts to 79.22(6) where the nitrogen donor atoms are arranged nearly perpendicular to the O-M-O plane with an angle of 153.39(8) on the metal cation (Figure 2). The catenation of metal cations by bipyrazole ligands along crystallographic a-axis (d(Ag-Ag) = 9.969(1) A˚) and monovalent terephtalate ligands along the c direction (d(Ag-Ag) = 9.583(1) A˚) leads to formation of heterogenic two-dimensional (4,4)-nets. These frameworks are oblique

Figure 3. Heterogenic (4,4)-net in the crystal structure of ¥2[Ag(Hp2CA)(Me4bpz)].

angled caused by substantial deviations from quadratic planar coordination environment on the silver cations (Figure 3). Within the nets relatively strong hydrogen bonds between the terephthalate anions (d(D-A)=2.447(2) A˚) are observed. In the crystal packing, hydrogen bonds between bipyrazole ligands and carboxylate ligands (d(D-A) =2.792(3) A˚) cause the formation of double layers where the bipyrazole ligands are located in the interior of these double layers. The distance between two neighbored cations located in different layers of a double layer is 3.0814(4) A˚, which is relatively short and suggests contribution of argentophilic interactions.47 The connection of the double layers is also effected by weaker N-H 3 3 3 O hydrogen bonds (d(D-A) = 2.870(3) A˚), where two neighboring double layers are translated ca. 3 A˚ relative to the planes spanned by the cations (Figure 4). Catena-(bis(μ4-benzene-1,4-dicarboxylato)-(μ2-3,30 ,5,50 tetramethyl-4,40 -bipyrazole)-dizinc(II)): ¥3[Zn2(p2CA)2(Me4bpz)] (II). ¥3[Zn2(p2CA)2(Me4bpz)] crystallizes in the monoclinic

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space group C2/c with four formula units per unit cell. The metal cations are coordinated quadratic pyramidal by four equatorial carboxylate ligands and one axial bipyrazole ligand (Tables 3 and 5). This is in difference to the already described related coordination polymer48 ¥3[Zn2(p2CA)2(Me4bpz)2] 3 Me4bpz with a higher ligand/metal ratio of two, where interestingly the cations have a coordination number of only four, resulting in interpenetrated networks with diamondoid topology. Through 4-fold connection of two metal centers by μ2 coordinated carboxylate groups so-called paddle wheel motifs are formed with an Zn-Zn distance of 2.9937(6) A˚ (Figure 5). These topological structure units are catenated by two axial bipyrazole ligands and the four carboxylic acid bodies resulting in a simple (4,6)-net (Figure 6). Thereby zinc(II) carboxylate layers, consisting of not quadratic (4,4)nets (angle between nodes 100 and 80, respectively) parallel to the crystallographic a-b plane, are connected by bipyrazole ligands in the c direction. The coordination environment

of the cations is stabilized by weak hydrogen bonds between bipyrazole and carboxylate ligands (d(D-A) = 3.024(2) A˚). The bipyrazole ligands are disordered, where only one position is found for the nitrogen atoms coordinated to the cations and the carbon atoms bridging the two pyrazole rings. Therefore, the disorder can be described by a rotation of the pyrazole rings about the axis through these two atoms. The angle between the ring planes of the pyrazole units of the two observed possible positions (occupation ratio 1:1.17) is 25.6(3). On the more occupied position A, Me4bpz shows an torsion angle of 85.1(3), where that angle amounts to 46.9(2) in the other position, B. In the crystal structure, two of the frameworks are interpenetrated. They are translated against each other a half unit cell edge length in the c direction and two-fifths of the edge length in the b direction (Figure 7). Between the two

Figure 4. Crystal packing of ¥2[Ag(Hp2CA)(Me4bpz)]. View along the crystallographic c axis.

Figure 5. Structural motif of ¥3[Zn2(p2CA)2(Me4bpz)].

Table 3. Selected Distances (A˚) and Angles (deg) in the Crystal Structures of the Zinc Coordination Polymers II, V, and VIII 3 ¥ [Zn2(p2CA)2(Me4bpz)]

Zn1-N1 Zn1-O4 Zn1-O2 Zn1-O3 Zn1-O1 O3-Zn1-O4 O2-Zn1-O4 O1-Zn1-O2 O1-Zn1-O3 N1-Zn1-O1 N1-Zn1-O2 N1-Zn1-O3 N1-Zn1-O4 O1-Zn1-O4 O2-Zn1-O3

(II)

2.024(2) 2.041(2) 2.051(2) 2.053(2) 2.061(2) 85.73(8) 87.86(8) 88.24(7) 89.70(8) 93.52(7) 95.95(7) 105.18(8) 109.77(8) 156.67(8) 158.86(8)

3 ¥ [Zn(m2CA)(Me4bpz)]

Zn1-O3 Zn1-O1 Zn1-N1 Zn1-N3 N1-Zn1-O3 N3-Zn1-O1 N3-Zn1-O3 N1-Zn1-O1 N1-Zn1-N3 O1-Zn1-O3

(V)

1.928(2) 1.936(2) 1.988(2) 1.998(2) 103.76(7) 106.69(7) 108.17(7) 111.38(7) 112.41(7) 114.52(7)

3 ¥ [Zn2(OHm2CA)2(Me4bpz)2] 3 1.75

Zn1-O3 Zn1-O8 Zn1-N5 Zn1-N3 N3-Zn1-O8 O5-Zn1-O8 O5-Zn1-O3 N3-Zn1-O3 N3-Zn1-N5 O3-Zn1-O8 Zn2-O1 Zn2-N7 Zn2-N1 Zn2-O6 Zn2-O7 O6-Zn2-O7 N1-Zn2-O7 N7-Zn2-O6 O1-Zn2-O6 N1-Zn2-O1 N1-Zn2-N7 O1-Zn2-O7 N7-Zn2-O1 N7-Zn2-O7 N1-Zn2-O6

H2O (VIII) 1.9285(15) 1.9732(14) 2.0464(15) 2.0509(17) 93.35(7) 97.74(6) 106.08(6) 106.33(7) 113.45(7) 139.23(7) 1.9929(13) 2.0265(16) 2.0636(17) 2.1952(17) 2.1964(17) 59.08(6) 92.25(6) 93.00(6) 94.96(6) 99.18(6) 103.92(7) 104.76(6) 115.24(6) 133.16(6) 150.57(6)

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polymers, very weak hydrogen bonds are observed (d(D-A) = 3.200(2) A˚) that compete against the intrapolymer hydrogen bonds. Presumably this is the reason for the observed disorder of the pyrazole rings discussed above: In case of occupation of the preferred ring position (A), only hydrogen bonds within the polymers are realized, whereas in the other case, the hydrogen bonds between the frameworks are formed in conjunction with a relatively small torsion angle of bipyrazole ligands, which is disadvantageous from an energy standpoint. Catena-((μ2-acetato)-(μ2-3,30 ,5,50 -tetramethyl-4,40 -bipyrazole)acetato-aqua-cadmium(II)): ¥2[Cd(OAc)2(Me4bpz)(H2O)] (III). 2 ¥[Cd(OAc)2(Me4bpz)(H2O)] crystallizes in the monoclinic space group P21/c with four formula units per unit cell. The cations are coordinated octahedrally by two bipyrazol ligands in trans position, three acetate anions and one aqua ligand (Tables 4 and 8). The coordination environment of the metal centers is stabilized by two hydrogen bonds between Me4bpz ligands and acid anions (d(D-A)=2.890(2) A˚ and 2.690(2) A˚; Figure 8). Because of only two of the three acid anions coordinated to each cation are bridging ligands, zigzag chains along the Figure 7. Interpenetration of two frameworks (red and blue) in the crystal structure of ¥3[Zn2(p2CA)2(Me4bpz)]. View along the crystallographic c axis.

Figure 6. Heterogenic (4,6)-net with dimeric units as nodes in the crystal structure of ¥3[Zn2(p2CA)2(Me4bpz)].

Figure 8. Structural motif of ¥2[Cd(OAc)2(Me4bpz)(H2O)].

Table 4. Selected Distances (A˚) and Angles (deg) in the Crystal Structures of the Cadmium Coordination Polymers III, VI, and IX 2 ¥ [Cd(OAc)2(Me4bpz)(H2O)]

Cd1-O5 Cd1-O1 Cd1-O3 Cd1-O4 Cd1-N3 Cd1-N1 O3-Cd1-O4 N1-Cd1-O1 N3-Cd1-O5 N1-Cd1-O4 N1-Cd1-O5 N3-Cd1-O3 O4-Cd1-O5 N3-Cd1-O1 O1-Cd1-O3 N1-Cd1-O3 O1-Cd1-O5 N3-Cd1-O4 O1-Cd1-O4 O3-Cd1-O5 N1-Cd1-N3

(III)

2.3135(17) 2.3161(14) 2.3216(15) 2.3403(14) 2.3412(17) 2.3566(19) 74.31(5) 78.62(6) 80.82(6) 87.18(6) 90.13(6) 91.76(6) 92.30(6) 93.24(6) 95.57(5) 99.49(6) 100.13(6) 102.88(6) 161.06(5) 162.95(6) 166.64(6)

2 ¥ [Cd(m2CA)(Me4bpz)]

Cd1-N1 Cd1-O3 Cd1-N3 Cd1-O4 Cd1-O1 Cd1-O2 O1-Cd1-O2 N3-Cd1-O4 N3-Cd1-O2 O1-Cd1-O3 N3-Cd1-O1 N3-Cd1-O3 N1-Cd1-O2 N1-Cd1-O4 O2-Cd1-O4 N1-Cd1-O1 N1-Cd1-O3 O3-Cd1-O4 O2-Cd1-O3 O1-Cd1-O4 N1-Cd1-N3

(VI)

2.2796(18) 2.2832(14) 2.3179(17) 2.3690(15) 2.3804(14) 2.3931(15) 55.20(5) 76.98(6) 83.58(6) 84.09(5) 87.03(6) 89.86(6) 91.17(6) 91.89(6) 93.19(5) 99.44(6) 101.56(6) 124.73(5) 138.94(5) 146.28(5) 167.35(6)

2 ¥ [Cd(OHm2CA)(Me4bpz)(H2O)]

Cd1-N1 Cd1-O1 Cd1-O6 Cd1-O1* Cd1-O3 Cd1-O4 O3-Cd1-O4 O1-Cd1-O1* O1*-Cd1-O4 O3-Cd1-O6 N1-Cd1-O6 N1-Cd1-O1* O1-Cd1-O6 O1-Cd1-O4 N1-Cd1-O1 O4-Cd1-O6 O1*-Cd1-O3 N1-Cd1-O3 O1-Cd1-O3 N1-Cd1-O4 O1*-Cd1-O6

(IX)

2.2726(12) 2.2755(10) 2.2779(10) 2.3419(9) 2.3446(9) 2.3879(10) 55.54(3) 79.92(3) 81.37(3) 85.48(4) 86.23(4) 87.70(4) 89.68(4) 90.41(3) 101.60(4) 107.25(4) 107.87(3) 115.78(4) 141.82(3) 162.13(4) 166.65(4)

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Table 5. Selected Distances (A˚) and Angles (deg) in the Crystal Structures of the Terephthalate Coordination Polymers I and II 2 ¥ [Ag(Hp2CA)(Me4bpz)]

hydrogen bonds N2-O1 N4-O4 O3-O2

distance D 3 3 3 A 2.792(3) 2.870(3) 2.447(2)

j (Me4bpz) d(M 3 3 3 M) (Me4bpz) d(M 3 3 3 M) (acid)

62.34(8) 9.969(1) 9.583(1)

a

3 ¥ [Zn2(p2CA)2(Me4bpz)]

(I)

angle D-H 3 3 3 A 171(3) 147(3) 172(4)

type code NO-E NO-E OO-M

hydrogen bonds

(II)

N2A-O2 N2B-O2

distance D 3 3 3 A 3.024(2) 3.200(2)

angle D-H 3 3 3 A 119(3) 142(6)


85.1(3) [A] 9.7014(8) 10.9357(8)

46.9(3) [B] 11.2660(8) 11.4097(8)

type code NO-M NO-E

2.9937(6)a

Entry in italics is the distance of two cations bridged by one and the same carboxylate group of the acid anion.

Figure 9. Two-dimensional (4,4)-net in the crystal structure of

2 ¥[Cd(OAc)2(Me4bpz)(H2O)].

Figure 10. Crystal packing of ¥2[Cd(OAc)2(Me4bpz)(H2O)], view along the crystallographic a axis.

crystallographic c direction, consisting of cadmium acetate, are formed. These chains are stabilized by hydrogen bonds between aqua ligands and the bridging acetate anions (d(D-A) = 2.809(3) A˚; Figure 9). They are linked together along a direction by bipyrazole ligands resulting in heterogenic (4,4)-nets perpendicular to b direction. In the crystal packing these nets are oriented antiparallel and linked by hydrogen bonds between aqua ligands and nonbridging acid anions (d(D-A) = 2.704(2) A˚; Figure 10). Catena-((μ2-benzene-1,3-dicarboxylato)-bis(μ2-3,30 ,5,50 -tetramethyl-4,40 -bipyrazole)-disilver(I)): ¥1[Ag2(m2CA)(Me4bpz)2] (IV). ¥1[Ag2(m2CA)(Me4bpz)2] crystallizes in the monoclinic

Figure 11. Rope-ladder motif in the crystal structure of ¥1[Ag2(m2CA)(Me4bpz)2].

space group C2/c with eight formula units per unit cell. The cations are linked by bipyrazole ligands resulting in chains (d(Ag-Ag) = 9.813(1) and 9.876(1) A˚), which are connected pairwise to one-dimensional strands with rope-ladder motif by the bivalent acid anions (d(Ag-Ag)=10.864(1) A˚, Figure 11). Two crystallographic independent silver sites are observed, where Ag1 is coordinated in η1-mode and Ag2 in η2-mode by the carboxylate ligands (Tables 2 and 6). Thus, Ag1 has the coordination number 3 and Ag2 has the coordination number 4. Within the polymers no hydrogen bonds are observed. In the crystal packing the strands are located parallel to each other and connected by hydrogen bonds between bipyrazole ligands and acid anions (d(D-A)=2.719(3) and 2.779(3) A˚; Figure 12). Catena-((μ2-benzene-1,3-dicarboxylato)-(μ2-3,30 ,5,50 -tetramethyl-4,40 -bipyrazole)-zinc(II)): ¥3[Zn(m2CA)(Me4bpz)] (V). 3 ¥[Zn(m2CA)(Me4bpz)] crystallizes in the orthorhombic noncentrosymmetric space group P212121 with four formula units per unit cell. The cations with pseudo 2-fold symmetry are coordinated tetrahedrally by two bipyrazole ligands and two carboxylate ligands (Tables 3 and 6). Between the ligands hydrogen bonds are formed (d(D-A) = 2.692(2) and 2.778(2) A˚), which stabilize the coordination environment on the metal ions (Figure 13). The connection of the metal centers by carboxylate anions leads to formation of zigzag chains along the crystallographic c direction (d(Zn-Zn)=10.6106(5) A˚). These chains are linked together by Me4bpz ligands in b direction (d(ZnZn)=9.4768(4) A˚). This is how three-dimensional (6,4)-nets with diamondoid topology are formed (Figure 14). Examining only the connection by bipyrazole ligands right-handed helices in the b direction are formed, which are reminiscent of

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Figure 12. Hydrogen bonds in the crystal structure of ¥1[Ag2(m2CA)(Me4bpz)2] (left, hydrogen atoms omitted for clarity) and packing of the strands, which are linked together by hydrogen bonds.


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the helical motifs in the acentric polymorphs and solvates of Me4bpz.25 In the crystal structure, three of these nets interpenetrate each other, each translated one unit cell edge length in the crystallographic a direction (Figure 15). There are no strong interactions observed between the polymers, except a CH-π interaction between a methyl group of the bipyrazole ligands and the aromatic π-system of the carboxylate ligands (d(Haromatic ring center)=2.90(1) A˚). Using the same mixed-ligand system but zinc sulfate hydrate as metal source and a maximum temperature of 120 C during hydrothermal treatment, the distantly related two-dimensional coordination polymer ¥2[Zn2(m2CA)(Me4bpz)(Me4bpz2-)] was obtained.48 Obviously, the usage of sulfate provokes partial deprotonation of the bitopic bipyrazole ligand to tetratopic Me4bpz2-, which indicates that the metal acetates are more desirable metal sources in this type of mixed ligand systems. Catena-((μ3-benzene-1,3-dicarboxylato)-(μ2-3,30 ,5,50 -tetramethyl-4,40 -bipyrazole)-cadmium(II) monohydrate): ¥2[Cd(m2CA)(Me4bpz)] 3 H2O (VI). ¥2[Cd(m2CA)(Me4bpz)] 3 H2O

Figure 13. Structural motif of ¥3[Zn(m2CA)(Me4bpz)]. Figure 15. Interpenetration of three (6,4)-nets (blue, red and green) in the crystal structure of ¥3[Zn(m2CA)(Me4bpz)]. View along the crystallographic c axis.

Figure 14. Three-dimensional (6,4)-net of ¥3[Zn(m2CA)(Me4bpz)]. View along the crystallographic b axis.

Figure 16. Structural motif of ¥2[Cd(m2CA)(Me4bpz)].

2.801(3) 2.778(3) 2.735(4) 2.719(3)

distance D3 3 3A

a

66.13(9) 9.813(1) 10.864(1)

angle D-H 3 3 3 A 157(3) 163(3) 168(3) 167(3) 64.60(9) 9.876(1)

NO-E NO-E NO-E NO-E

type code 2.692(2) 2.778(2)

N2-O2 N4-O4


distance D3 3 3A

hydrogen bonds

(V)

56.28(8) 9.4768(4) 10.6106(5)

angle D-H 3 3 3 A 167(3) 160(2)

3 ¥ [Zn(m2CA)(Me4bpz)]

Entry in italics is the distance of two cations bridged by one and the same carboxylate group of the acid anion.


N2-O2 N6-O2 N4-O3 N8-O4

hydrogen bonds

(IV)

O5-O3 N2-O5 N4-O4 O5-O1

NO-M NO-M

2.802(2) 2.707(2) 2.743(2) 2.689(2)

distance D3 3 3A


hydrogen bonds

type code

(VI)

68.56(7) 10.2185(5) 10.2022(4)

angle D-H 3 3 3 A 164(4) 168(3) 131(2) 146(3)

2 ¥ [Cd(m2CA)(Me4bpz)]

Table 6. Selected Distances (A˚) and Angles (deg) in the Crystal Structures of the Isophthalate Coordination Polymers IV, V, and VI

1 ¥ [Ag2(m2CA)(Me4bpz)2]

3.9730(2)a

WO-E NW-E NO-M WO-E

type code

4620 Crystal Growth & Design, Vol. 9, No. 11, 2009 Hunger et al.

2 ¥[Cd(m2CA)(Me4bpz)].

Figure 17. Double layer arises from connection of two (4,4)-nets in

Figure 18. Crystal packing of the double layers in ¥2[Cd(m2CA)(Me4bpz)] linked together by hydrogen bonds to water molecules located between the layers.

Figure 19. Structural motif of ¥1[Ag(OAc)(Me4bpz)2] 3 5,4 H2O.

crystallizes in the monoclinic space group P21/c with four formula units per unit cell. The cations are coordinated

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distorted octahedrally by three equatorial carboxylate ligands and two axial bipyrazole ligands (Tables 4 and 6; Figure 16). Thereby, one carboxylate group coordinates in η2-mode and the two others in η1-mode. As structural motif heterogenic (4,4)-nets are observed. These nets are linked together pairwise by the η1-coordinated carboxylate groups resulting in double layers (Figure 17). Thus, dimeric cadmium units are formed (d(Cd-Cd) = 3.9730(2) A˚). Alternatively, the double layers could be understood as cadmium(II)carboxylate chains linked together by Me4bpz. The double layers are connected by hydrogen bonds to water molecules located between the double layers. Thereby the water molecules link two carboxylate groups coordinated to one and the same cation (as donor, d(D-A) = 2.689(2) and 2.802(2) A˚) with a pyrazole unit of a neighboring layer (as acceptor, d(D-A) = 2.707(2) A˚; Figure 18). The second not-involved pyrazole unit of the bipyrazole ligands acts as donor of an hydrogen bond (d(D-A) = 2.743(2) A˚) to the oxygen atom of the η1-coordinated carboxylate group, which connects the cation dimers.

Figure 20. Helical chains in ¥1[Ag(OAc)(Me4bpz)2] 3 5.4 H2O (top) and helix bundle arises from twisting three helices with same chirality (bottom).

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Catena-((μ2-3,30 ,5,50 -tetramethyl-4,40 -bipyrazole)-(3,30 ,5,50 tetramethyl-4,40 -bipyrazole)-acetato-silver(I) hydrate): ¥1[Ag(OAc)(Me4bpz)2] 3 5.4 H2O (VII). ¥1[Ag(OAc)(Me4bpz)2] 3 5.4 H2O crystallizes in the tetragonal space group I41/a with 16 formula units per unit cell. The cations are coordinated tetrahedrally by three bipyrazole ligands and one acetate anion (Tables 2 and 8; Figure 19). The coordination environment of the silver ions is stabilized by hydrogen bonds between two of the Me4bpz ligands and the anions (d(D-A)=2.813(3) and 2.841(3) A˚). In the crystal structure, there are two water molecules per metal center in the asymmetric unit, which are not coordinated to the cations, but connected with the bipyrazole ligands and the acid anions by hydrogen bonds, respectively (d(D-A) = 2.786(3), 2.817(4), and 2.867(3) A˚; 2.650(3) and 2.745(3) A˚). Because only two of the Me4bpz ligands are bridging ligands, one-dimensional helical chains along the crystallographic c axis are formed (Figure 20).

Figure 21. Crystal packing of the helix bundles and linkage of the bundles through hydrogen bonds to water molecules located in the voids in the crystal structure of ¥1[Ag(OAc)(Me4bpz)2] 3 5.4 H2O.

Table 7. Selected Distances (A˚) and Angles (deg) in the Crystal Structures of the 5-Hydroxy-Isophthalate Coordination Polymers VIII and IX 3 ¥ [Zn2(OHm2CA)2(Me4bpz)2] 3 1.75

hydrogen bonds N2-O9 N4-O11 N6-O12A N6-O12B N8-O2 O5-O6 O10-O1 O11-O4 O13-O5 O13-O8 O12B-O13

distance D 3 3 3 A 2.845(3) 2.821(3) 2.807(10) 2.773(10) 2.747(3) 2.649(2) 2.999(2) 2.748(3) 2.643(22) 2.823(22) 2.845(36)


89.08(9) 9.6768(9) 9.5591(10)

a

2 ¥ [Cd(OHm2CA)(Me4bpz)(H2O)]

H2O (VIII)

angle D-H 3 3 3 A type code 157(3) NO-E 166(3) NW-E 168(3) NW-E 155(3) NW-E 153(2) NO-M 169(1) HO-E 165(3) HO-E 171(2) WO-E a WH-E a WO-E a WW-E 57.20(7) 9.2026(9) 8.9013(9)

hydrogen bonds N4-O3 N2-O4 O5-N3 O6-O5 O6-O2


distance D 3 3 3 A 2.838(2) 2.875(2) 2.682(2) 2.769(1) 2.660(2)

62.99(5) 9.6946(12)b 9.0189(4)

(IX)

angle D-H 3 3 3 A type code 171(2) NO-E 169(2) NO-I 166(2) HN-E 176(2) WH-I 159(2) WO-M

10.3523(4)

3.5395(2)c

Hydrogen atoms of H2O(12A), H2O(12B) and H2O(13) were not refineable. b Distance between cation and oxygen atom of the water molecule hydrogen bonded to Me4bpz. c Entry italics is the distance of two cations bridged by one and the same carboxylate group of the acid anion.

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In the crystal structure, the helices are twisted to bundles, where each bundle consists of three chains with same chirality. Between the helices of a bundle, no hydrogen bonds are observed. The bundles are stacked parallel, so that every bundle is surrounded by four bundles of helices with complementary chirality (Figure 21). There are no hydrogen bonds observed between the bundles, the contact between them is realized in fact over hydrogen bonds to water molecules mentioned earlier. In the voids between the bundles, further disordered water molecules are located, which

are connected to a framework by multiple hydrogen bonding. Catena-(bis(μ2-5-hydroxy-benzene-1,3-dicarboxylato)-bis(μ23,30 ,5,50 -tetramethyl-4,40 -bipyrazole)-dizinc(II) hydrate): ¥3[Zn2(OHm2CA)2(Me4bpz)2] 3 1.75 H2O (VIII). ¥3[Zn2(OHm2CA)2(Me4bpz)2] 3 1.75 H2O crystallizes in the monoclinic space group C2/c with eight formula units per unit cell. Two crystallographic independent zinc positions are located in the asymmetric unit. Zn1 is coordinated tetrahedrally by two bipyrazole ligands and two carboxylate ligands, whereas Zn2 is coordinated trigonalbipyramidal by two bipyrazole ligands and two carboxylate ligands in η1-mode and η2-mode, respectively (Tables 3 and 7). The coordination environment of Zn1 is stabilized by a hydrogen bond between a Me4bpz ligand and an acid anion (d(D-A)= 2.747(3) A˚; Figure 22). Because of both the bipyrazole ligands and the acid anions being bridging ligands, a heterogenic three-dimensional framework is formed consisting of vertices with a connectivity of four bearing a shortest circuit of four (Figure 23). The topology of the coordination polymer is related to the bimodal PtS structure, which is also known as cooperite. In the crystal, the voids in the framework structure parallel to crystallographic c axis are diminished through interpenetration of two identical nets. These two coordination polymers are connected via hydrogen bonds between the

Figure 22. Structural motif of ¥3[Zn2(OHm2CA)2(Me4bpz)2] 3 1.75 H2O.

Figure 23. Three-dimensional framework of ¥3[Zn2(OHm2CA)2(Me4bpz)2] 3 1.75 H2O. View along the crystallographic b axis.

Figure 24. Interpenetration of two frameworks with linkage through hydrogen bonding in the crystal structure of ¥3[Zn2(OHm2CA)2(Me4bpz)2] 3 1.75 H2O.

Table 8. Selected Distances (A˚) and Angles (deg) in the Crystal Structures of the Acetate Coordination Polymers III and VII 2 ¥ [Cd(OAc)2(Me4bpz)(H2O)]

hydrogen bonds N2-O3 N4-O2 O5-O4 O5-O2

distance D3 3 3A 2.890(2) 2.690(2) 2.809(3) 2.704(2)


64.63(9) 10.4707(7) 5.5579(4)

a

1 ¥ [Ag(OAc)(Me4bpz)2] 3 5.4

(III)

angle D-H 3 3 3 A 139(3) 176(3) 172(3) 174(4)

type code NO-M NO-M WO-I WO-E

H2O (VII)

hydrogen bonds

distance angle D3 3 3A D-H 3 3 3 A N2-O2 2.813(3) 175(2) N4-O3 2.817(3) 174(3) N6-O3 2.786(3) 170(3) N8-O2 2.841(3) 168(3) O3-O1 2.650(3) 172(5) O3-O5 2.726(4) 155(4) O4-O2 2.745(3) 165(3) O4-N3 2.867(3) 170(3) There are more hydrogen bonds between water molecules in the voids not listed here.


68.27(9) 9.9151(4)

type code NO-M NW-E NW-E NO-M WO-E WO-E WO-E WN-E

62.70(9) 10.498(2)a

Distance between Agþ and the oxygen atom of the water molecule hydrogen bonded to the nitrogen acceptor atom of the bipyrazole ligand.

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Figure 25. Structural motif of ¥2[Cd(OHm2CA)(Me4bpz)(H2O)].

Figure 27. Crystal packing of ¥2[Cd(OHm2CA)(Me4bpz)(H2O)]. View along the crystallographic c axis.

framework, two-dimensional (4,4)-nets are formed by linking the cations with the carboxylate ligands (Figure 26). The coordination environment of the cadmium ions is stabilized by hydrogen bonds between the aqua ligands and the carboxylate anions (d(D-A) = 2.660(2) A˚). Within the polymers further hydrogen bonds are realized between bipyrazole and carboxylate ligands (within an dimeric unit, d(D-A)=2.875(2) A˚) as well as aqua ligands and OH groups of the carboxylic acids (d(D-A)=2.769(1) A˚). In the crystal packing the layers are linked together by hydrogen bonds between aqua ligands and bipyrazole ligands (d(D-A) = 2.682(2) A˚) as well as between Me4bpz ligands and acid anions (d(D-A)=2.838(2) A˚; Figure 27). Figure 26. (4,4)-net with dimeric units as nodes in the crystal structure of ¥2[Cd(OHm2CA)(Me4bpz)(H2O)].

OH groups of the acid anions and carboxylate groups (d(D-A) = 2.649(2) and 2.999(2) A˚) as well as between a bipyrazole ligand and a carboxylate group (d(D-A) = 2.845(3) A˚). Further partially linking hydrogen bonds are formed toward water molecules in the voids (d(D-A) = 2.75-3.00 A˚, Figure 24), which are also connected via hydrogen bonds. Catena-((μ3-5-hydroxy-benzene-1,3-dicarboxylato)-aqua(3,30 ,5,50 -tetramethyl-4,40 -bipyrazole)-cadmium(II)): ¥2[Cd(OHm2CA)(Me 4bpz)(H 2O)] (IX). ¥2 [Cd(OHm2CA)(Me 4 bpz)(H2O)] crystallizes in the monoclinic space group P21/c with four formula units per unit cell. The cations are coordinated octahedrally by one terminal bipyrazole ligand, three carboxylate ligands, and an aqua ligand (Tables 4 and 7). Thereby two of the carboxylate groups are coordinated with only one oxygen atom and the third one with both of the oxygen atoms (Figure 25). One of the carboxylate groups is bridging two metal centers to dimeric units (d(Cd-Cd) = 3.5395(2) A˚). If those dimers are understood as vertices in a

Summary and Conclusions Nine new coordination polymers were obtained from acetate hydrates of Agþ, Zn2þ, and Cd2þ and mixed-ligand systems consisting of 3,30 ,5,50 -tetramethyl-4,40 -bipyrazole and an aromatic dicarboxylic acid (terephthalic acid, isophthalic acid and 5-hydroxy-isophthalic acid, respectively) by means of hydrothermal synthesis. Two of these coordination polymers contain acetate ions instead of the corresponding dicarboxylate anions (III and VII). The topologies realized in the coordination polymers are very manyfold, varying from simple one-dimensional polymers to complex three-dimensional frameworks (Table 9). The coordination number of the metal center has to be regarded as only a maximum possible topological connectivity of the center as vertex in a framework, because in many cases, the connectivity is diminished by μ2-coordination of carboxylate groups of acid anions and coordination of nonbridging ligands (H2O, but also terminal bipyrazole ligands, which means located between a metal center and a hydrogen bond donor, for example, in VII and IX). This can finally lead to the reduction of dimensionality of the coordination polymers, although it is not directly

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Table 9. Topological Overviewa

a SG, space group; D, dimensionality; CN, cation coordination number; C, topological connectivity of the metal centre; coordination sphere, N (bipyrazole), O (carboxylate), and W (water) as well as indices subscript T (terminal) and digit (number of metal centres coordinated to the carboxylate group) and superscript digit (η, number of O-M bonds per metal centre); WELLS symbol, total (first line), linkage by carboxylate (second line), and linkage by Me4bpz (third line); SCHLA¨FLI symbol, {short} and [long]; TD10, number of nodes within a topological radius of ten (topological density TD ≈ (TD10 - 1)(385ND), with ND being dimensionality of crystal space); IP, interpenetration (type, number of nets); * Dimeric units [M - (OCO)2 - M] as nodes.

correlated to the connectivity. For example, with metal centers possessing a connectivity equal to four, both two-dimensional (I and III) and three-dimensional (V and VIII) coordination polymers are formed. However, it is noticeable that in all coordination polymers containing cations with a coordination number of six (Cd2þ: III, VI, and IX), the metal centers show smaller connectivities between three and five, resulting in twodimensional coordination polymers in all cases. The cations are coordinated by one to three, but mostly two bipyrazole ligands. The carboxylate groups of the aromatic acid anions are predominantly coordinated to the metal center with only one oxygen atom. If such a carboxylate group is coordinated to only one metal center, the second oxygen atom normally acts as acceptor atom in a hydrogen bond within the coordination sphere of the metal center. But also μ2-coordinated carboxylate groups are observed independently from the type of polycarboxylic acid (II, III, VI, and IX). The realization of that coordination mode with aromatic polycarboxylate ligands causes in either case formation of dimeric [M-(OCO)2-M] units with relatively short M-M distances. This also has a bearing on the topology of the coordination polymers, because in that case more metal centers are bridged by the carboxylate ligand than the number of carboxylate groups at the ligand. For simplification of the structure description, in most cases such dimers could be regarded as a topological unit. The results of analyses of the obtained crystal structures strongly suggest that the formation of hydrogen bonds between bipyrazole and carboxylate ligands coordinated to the

same metal center could be regarded as being a new supramolecular synthon (see, for example, Figures 5, 8, 13, 16, 19, and 22). This structural motif is observed at six of the coordination polymers considered here, although the formation of this type of hydrogen bonds in all three-dimensional frameworks is noticeable. Furthermore, intrapolymeric and interpolymeric hydrogen bonds can be distinguished. Only oxygen atoms are involved in hydrogen bonds as acceptor atoms. That means no hydrogen bonds are observed between bipyrazole ligands. The carboxylate groups coordinated with both oxygen atoms to one and the same metal center are not appearing as acceptor for a hydrogen bond with a bipyrazole ligand coordinated to the same cation. That conclusion seems to be nearly universally valid. Thus, in the CSD, only five structures49-52 can be found where this type of hydrogen bonding is observed. This is independent from the type of the atom coordinated to the cation within the ligand containing the nitrogen donor atom (only structures with a resulting “ring size” smaller than nine were considered). Interestingly, a combination of carboxylate groups coordinated with both oxygen atoms to one and the same metal center and μ2-coordinated carboxylate groups is realized only by usage of Cd2þ as metal center (VI and IX). These coordination polymers are two-dimensional, whereas the cations are coordinated by three carboxylate groups in each case. Two of the carboxylate groups are coordinated in a η1-μ2 mode and the remaining one in a η2-μ1 mode, hence a coordination in a η2-μ2 mode is not realized. In all coordination polymers, at least two

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cations are linked together by carboxylate ligands, resulting in M 3 3 3 M distances between 8.9 A˚ (VIII) and 11.3 A˚ (II). The interaction between the different used ligands with their different coordination and hydrogen-bonding properties provokes a broad range of structure types. Because of interplay of many different interactions, it is difficult to obtain general statements about the respective influences on the resulting structures. However, we were able to extract some structural motifs formed in coordination polymers with combination of bipyrazole and aromatic carboxylate ligands, which have to be established by further investigations. Supporting Information Available: Full crystallographic data in CIF format for compounds I-IX. Listing of crystallographic details, detailed listings of infrared spectroscopic data, and results of elemental analyses (PDF). This material is available free of charge via the Internet at http://pubs.acs.org.

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