Hydrogen-Bonded One-Dimensional Zigzag Pairs and Helical Dimers

Hydrogen-Bonded One-Dimensional Zigzag Pairs and Helical Dimers in an Enolic 4-Terpyridone Based Nickel(II) Dicyanamide Supramolecule. Malabika ...
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Hydrogen-Bonded One-Dimensional Zigzag Pairs and Helical Dimers in an Enolic 4-Terpyridone Based Nickel(II) Dicyanamide Supramolecule Malabika Nayak,† Rajesh Koner,† Helen Stoeckli-Evans,‡ and Sasankasekhar Mohanta*,†

CRYSTAL GROWTH & DESIGN 2005 VOL. 5, NO. 5 1907-1912

Department of Chemistry, University of Calcutta, 92 A. P. C. Ray Road, Kolkata 700 009, India, and Institut de Chimie, Universite´ de Neuchaˆ tel, Av. de Bellevaux 51, Case postale 2, CH-2007 Neuchaˆ tel, Switzerland Received April 26, 2005

ABSTRACT: The synthesis, characterization, and crystal engineering of an enolic 4-terpyridone (L1) based threedimensional supramolecule, [NiII(L1)2](dicyanamide)2‚2H2O, have been described. One aim of this study has been to demonstrate that the H-O-pyridine-M-pyridine-O-H moiety in [M(L1)2]n+ can participate in extended hydrogenbonding interactions and, thus, can act as a building block to generate supramolecular frameworks. A second objective has been to stabilize a coordination compound containing dicyanamide in only noncoordinating form, which in turn would get involved in extended hydrogen bondings. The title compound crystallizes in the triclinic space group P1 h with the following unit cell parameters: a ) 8.7482(9) Å, b ) 9.0810(7) Å, c ) 20.5411(18) Å, R ) 92.143(7)°, β ) 93.011(8)°, γ ) 94.315(7)°, and Z ) 2. In this compound, the metal center is hexacoordinated by the three pyridine nitrogens of each of the two enolic 4-terpyridones. A number of hydrogen bonds, involving the H-O-pyridine-Mpyridine-O-H moiety and a few C-H hydrogens of the dication as well as the two noncoordinating dicyanamide anions and two waters of crystallization, results in the generation of three-dimensional assembly in this molecule. The fragment analyses reveal the existence of helical dimers and a pair of one-dimensional chains. The overall three-dimensional structure of the title compound can be considered as the stitching of the two-dimensional sheets, which consist of the interlinked pairs of one-dimensional chains, by the second type of one-dimensional chains created due to the attachment of the helical dimers, which in turn consist of the hydrogen-bonded monomers. Introduction The crystal engineering of self-assembled supramolecular architectures is currently of great interest, due to their intriguing topologies and their applications in materials chemistry, in particular in optoelectronics, conductivity and superconductivity, charge-transfer and magnetism, nanoporus materials, and biomimetic materials.1,2 In supramolecules, the molecular building blocks are self-assembled by covalent or coordinate bonds1 as well as by several types of noncovalent interactions such as π-π stacking, hydrogen bonds (both strong and weak), halogen-halogen, sulfur-sulfur, gold-gold, etc.2 Bridging organic or inorganic ligands play the key role in the creation of coordination polymers, and in this area, dicyanamide and hexacyanometalates are known as important inorganic stitching units to develop varieties of topologies.1d,3-7 As dicyanamide and hexacyanometalates have a high potential to coordinate a number of metal ions, coordination compounds containing these units as noncoordinating anions are very rare.2h,5,6f,7 There are a few compounds which contain hexacyanometalates only as noncoordinating anions2h,7 or as both the bridging and noncoordinating forms.6f However, the reported examples containing noncoordinating dicyanamides are also associated with the bridging forms of this unit.5 In any case, the noncoordinating nitrogens * To whom correspondence should be addressed. [email protected]. Fax: 91-33-23519755. † University of Calcutta. ‡ Universite ´ de Neuchaˆtel.

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of these anions usually act as hydrogen bond acceptors.2h,4,5,6f For the compounds containing only the noncoordinating forms of these anions, the probability of the number of hydrogen bonds as well as of the creation of interesting types of topologies should be enhanced. At this point, it may be noted that a novel example of strongly hydrogen bonded interlocked infinite double helices has been reported recently in a compound that contains hexacyanoferrate(III) in only noncoordinating form.2h 4-Terpyridone is known to coordinate to the metal ions in its enolic form (L1) and behaves, like terpyridine (L2), as a tridentate chelating ligand.8,9 In the complex cations [M(L1)2]n+ and [M(L2)2]n+, the coordination environment of the metal ions as well as the relative positions of the six pyridine rings should be similar. However, unlike in the terpyridine complexes, there will be the fragment H-O-pyridine-M-pyridine-O-H in [M(L1)2]n+. The two O-H moieties in this fragment may behave as potential hydrogen bond donors. In addition, these moieties may also interact, through its oxygen center, with hydrogens of suitable donors. Evidently, due to the presence of the H-O-pyridine-M-pyridine-O-H fragment, the enolic 4-terpyridone complexes may be a potential supramolecular synthon. It may be noted that there are only a few structurally characterized coordination compounds derived from enolic 4-terpyridone and, in these examples, the supramolecular interactions of the above-mentioned fragment have not been enlightened.8 As discussed above, noncoordinating dicyanamide (or hexacyanometalates) and [M(L1)2]n+ (L1 ) enolic 4-terpy-

10.1021/cg050182e CCC: $30.25 © 2005 American Chemical Society Published on Web 07/13/2005

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Table 1. Crystallographic Data of 1 empirical formula fw cryst syst space group a, Å b, Å c, Å R, deg β, deg γ, deg V, Å3 Z T, K λ(Mo KR), Å Fcalcd, g cm-3 µ, mm-1 no. of rflns collected no. of indep rflns R1a/wR2b (I > 2σ(I) data) R1a/wR2b (all data)a a

C34H26N12NiO4 725.38 triclinic P1 h 8.7482(9) 9.0810(7) 20.5411(18) 92.143(7) 93.011(8) 94.315(7) 1623.6(3) 2 173(2) 0.710 73 1.484 0.658 16 808 6107 0.0394/0.0756 0.0677/0.0810

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

ridone) should behave, respectively, as a potential hydrogen bond donor and acceptor. Therefore, as a result of hydrogen-bonding interactions, a coordination compound containing [M(L1)2]n+ and noncoordinating dicyanamide may consist of interesting types of topologies. In the case of the presence of solvent molecules (water) of crystallization, the probability of the creation of supramolecular networks should be enhanced. With the aim of obtaining a coordination compound containing noncoordinating dicyanamide and [M(L1)2]n+, nickel(II) chloride, 4-terpyridone, and dicyanamide were allowed to react in a ratio of 1:2:3 and a compound having the composition [NiII(L1)2](dicyanamide)2‚2H2O (1) has been isolated. Herein, we report the synthesis, structural characterization, and crystal engineering of this compound. Experimental Section Materials and Methods. All the reagents and solvents were purchased from commercial sources and used as received. Elemental (C, H, and N) analyses were performed on a PerkinElmer 2400 II analyzer. IR spectra were recorded in the region 400-4000 cm-1 on a Perkin-Elmer RXIFT spectrophotometer with samples as KBr disks. Synthesis of 1. A methanol solution (25 mL) containing 4-terpyridone (0.249 g, 1 mmol) and nickel(II) chloride (0.065 g, 0.5 mmol) was refluxed for 2 h. After the mixture was cooled to room temperature, an aqueous solution (5 mL) of sodium dicyanamide (0.134 g, 1.5 mmol) was added dropwise with stirring to the resulting light blue solution. The stirring was continued for an additional period of 1 h. Then the mixture was filtered to remove any suspended particles and kept at room temperature for slow evaporation. After a few days, a brown crystalline compound containing diffractable single crystals deposited that was collected by filtration, washed with methanol, and air-dried. Yield: 0.175 g (48%). Anal. Calcd for C34H26N12O4Ni: C, 56.30; H, 3.61; N, 23.17. Found: C, 56.39; H, 3.52; N, 23.31. IR (KBr/cm-1): dicyanamide 2252 m, 2204 w, 2139 vs. Determination of Crystal Structure. Pertinent crystallographic data for 1 are summarized in Table 1. The intensity data were collected at 173 K on a Stoe Mark II-image plate diffraction system10 equipped with a two-circle goniometer and using graphite-monochromated Mo KR radiation. The details of the data collection are as follows: image plate distance, 100 mm; ω rotation scans, 0-180° at φ ) 0° and 0-64° at φ ) 90°; step ∆ω ) 1.0°; 2θ range, 1.76-52.59°; dmin-dmax ) 23.1070.802 Å. The structure was solved by direct methods using the

Figure 1. ORTEP representation of 1 with atom-labeling schemes. Except for the O-H hydrogens of enolic 4-terpyridone, hydrogen atoms are omitted for clarity. Table 2. Selected Bond Lengths (Å) and Angles (deg) of 1 Ni(1)-N(1) Ni(1)-N(2) Ni(1)-N(3) Ni(1)-N(4) Ni(1)-N(5) Ni(1)-N(6) C(31)-N(31)

2.126(2) 1.982(2) 2.106(2) 2.102(2) 1.985(2) 2.110(2) 1.165(4)

N(1)-Ni(1)-N(3) N(2)-Ni(1)-N(5) N(4)-Ni(1)-N(6) N(1)-Ni(1)-N(2) N(1)-Ni(1)-N(4) N(1)-Ni(1)-N(5) N(1)-Ni(1)-N(6) N(2)-Ni(1)-N(3) N(2)-Ni(1)-N(4) N(2)-Ni(1)-N(6) N(3)-Ni(1)-N(4)

156.01(8) 175.33(10) 155.59(8) 77.77(9) 92.49(8) 97.68(8) 93.84(8) 78.31(9) 102.95(8) 101.43(8) 90.92(8)

C(32)-N(32) C(31)-N(30) C(32)-N(30) C(41)-N(41) C(42)-N(42) C(41)-N(40) C(42)-N(40) N(3)-Ni(1)-N(5) N(3)-Ni(1)-N(6) N(4)-Ni(1)-N(5) N(5)-Ni(1)-N(6) C(31)-N(30)-C(32) N(30)-C(31)-N(31) N(30)-C(32)-N(32) C(41)-N(40)-C(42) N(40)-C(41)-N(41) N(40)-C(42)-N(42)

1.134(4) 1.291(4) 1.300(4) 1.127(5) 1.119(4) 1.309(6) 1.288(5) 106.26(9) 92.79(8) 78.17(8) 77.63(8) 122.2(3) 173.8(4) 173.9(4) 120.2(4) 174.7(5) 173.3(4)

program SHELXS-97.11a The refinement and all further calculations were carried out using SHELXL-97.11b The hydroxyl and water H atoms were located from Fourier difference maps and refined isotropically. The remainder were included in calculated positions and treated as riding atoms using SHELXL default parameters. The non-hydrogen atoms were refined anisotropically, using weighted full-matrix least squares on F2. The final least-squares refinements (R1) based on I > 2σ(I) converged to 0.0394.

Results and Discussion Description of the Structure of 1. An ORTEP representation of [NiII(L1)2](dca)2‚2H2O (1) is shown in Figure 1, while selected bond lengths and angles are listed in Table 2. The structure of 1 contains five independent units: the dication, [NiII(4-terpyridone)2]2+, two dicyanamide anions, N(41)tC(41)-N(40)-C(42)t N(42) (dca1) and N(31)tC(31)-N(30)-C(32)tN(32) (dca2), and two water molecules, water1 (H2O(1w)) and water2 (H2O(2w)), as solvents of crystallization. The nickel(II) center in 1 is hexacoordinated. Three nitrogens of each of the two enolic 4-terpyridones chelate to the metal ion. The Ni-N distances fall into two distinct ranges; those involving the central pyridine rings are

A 4-Terpyridone-Based Ni(II) Dicyanamide Supramolecule

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Table 3. Geometries (Distances in Å and Angles in deg) of the Hydrogen Bonds in 1a D-H‚‚‚A

H‚‚‚A

D‚‚‚A

D-H‚‚‚A

O(1)-H(1A)‚‚‚O(1WP) O(2)-H(2A)‚‚‚O(2WL) O(1W)-H(1WA)‚‚‚N(42F) O(1W)-H(1WB)‚‚‚N(41) O(2W)-H(2WA)‚‚‚N(31B) O(2W)-H(2WB)‚‚‚N(31I) C(1)-H(1)‚‚‚N(32L) C(3)-H(3)‚‚‚N(41L) C(9)-H(9)‚‚‚O(1V)

1.63(4) 1.73(4) 1.87(5) 1.83(6) 2.01(5) 2.04(4) 2.59 2.50 2.47

2.540(4) 2.591(3) 2.739(5) 2.797(5) 2.900(4) 2.835(4) 3.327(4) 3.293(4) 3.389(4)

173(3) 178(4) 170(4) 164(6) 171(4) 179(7) 134.00 141.00 162.00

a

For symmetry codes, see Figures 2 and 3.

almost the same (1.982(2) and 1.985(2) Å), while those involving the other four rings lie in the range 2.102(2)-2.126(2) Å. The stereochemistry of the metal ion, due to the rigidity of the donor environment of 4-terpyridone, deviates appreciably from an ideal octahedron. In addition to the differences in the metal-ligand bond distances, the reduction of the transoid angles (155.59(8), 156.01(8), and 175.33(10)°) and the wide range of cisoid angles (77.63(8)-106.26(9)°) are indicative of the high distortion of the coordination environment. The deviations of the metal ion or the donor centers from N(2)N(4)N(5)N(6) and N(1)N(2)N(3)N(5) coordination planes, the latter of which is the best least-squares plane, are not very high (0.4 Å) is in parallel with the large distortion of the coordination environment. The CtN or C-N distances in either of the two crystallographically different dca anions are very similar (Table 2). In addition, the values of the C-N-C angles of 120.2(4)° in dca1 and 122.2(3)° in dca2 indicate the pseudo-C2v symmetry of the dicyanamides. Nine hydrogen bonds, two of the O-H‚‚‚O type, four of the O-H‚‚‚N type, three of the C-H‚‚‚N type, and one of the C-H‚‚‚O type, link the components into a three-dimensional framework (vide infra). One terminal nitrogen (N(31)) of dca2 acts as a bifurcated acceptor and forms hydrogen bonds with two water molecules, symmetry related to water2, while the second terminal nitrogen (N(32)) of this dca interacts with one C-H hydrogen of one 4-terpyridone. The water2 molecule, in addition to being a double donor, also interacts with the hydrogen bonded to one oxygen, symmetry related to O(2), of one 4-terpyridone. The terminal nitrogens of dca1 form hydrogen bonds with hydrogens bonded to two different water molecules, symmetry related to water1. In addition, one terminal nitrogen (N(41)) of this dca weakly interacts with one C-H hydrogen. The oxygen of water1, similar to that of water2, also forms hydrogen bonds with the hydrogen of one oxygen, symmetry related to O(1). In contrast to O(2), which behaves only as a single donor, O(1) acts as a single donor and single acceptor; it interacts also with one C-H hydrogen. The geometries of the hydrogen bonds are summarized in Table 3. The analyses of the patterns of the interlinking of the individual units and the supramolecular structure can be better understood as fragments. Excluding dca1 and water1, the structure is one-dimensional, consisting of interlinked helical dimers (Figure 2 and Figure S1

Figure 2. Perspective view to demonstrate the one-dimensional chain formed due to the hydrogen bonds involving dca2, water2, and the O(2)-H(2A) and C(1)-H(1) parts of the dication. A terminal pyridine ring of one 4-terpyridone and both pyridine rings of the second 4-terpyridone as well as H2O(1W) and dca1 are omitted for clarity. The hydrogens bonded to C(1), O(1), O(2), and O(2W) are the only ones shown. Symmetry codes: (A) 1 + x, y, z; (B) 1 - x, 1 - y, 1 - z; (C) 2 - x, 1 - y, 1 - z; (D) 1 - x, -y, 1 - z; (E) 1 + x, 1 + y, z; (F) x, 1 + y, z; (G) 2 - x, -y, 1 - z; (H) -x, 1 - y, 1 - z; (I) x - 1, y, z; (J) - x, -y, 1 - z; (K) 2 + x, 1 + y, z.

(Supporting Information)). As demonstrated in Figure 2, one terminal nitrogen (N(31)) of dca2 interacts with one hydrogen of each of the two water molecules, H2O(2WA) and H2O(2WB). Each of these two water molecules forms another hydrogen bond, via their second hydrogen, with the terminal nitrogen (N(31C)) of another dca2 anion. In the tetragon N(31)O(2WA)N(31C)O(2WB), the N‚‚‚O distances (2.83 and 2.89 Å) are almost equal, and the N‚‚‚O‚‚‚N and O‚‚‚N‚‚‚O angles (101.8 and 78.2°, respectively) do not deviate much from 90°. Clearly, the bifurcated acceptor nature of one terminal nitrogen (N(31)) and the double-donor behavior of the water2 molecule form approximate squares. In addition to behaving as a double donor, O(2WA) and O(2WB) also act as single acceptors and interact with the hydrogens bonded to, respectively, O(2E) and O(2D). Evidently, due to the O(2E)‚‚‚O(2WA) type of interactions, two monomeric metal complexes are linked to the water‚‚‚dca squares to form dimers, consisting of hydrogen-bonded monomers. The second terminal nitrogens (N(32) and N(32C)) of dca2’s, forming the squares, link the dimer with two other dimers via C(1F)-H(1F)‚ ‚‚N(32) and C(1G)-H(1G)‚‚‚N(32C) interactions. These interactions result in the creation of one-dimensional chains that propagate along the crystallographic a axis. As evidenced from the view along the crystallographic a axis (Figure S1), the one-dimensional chains resulting from the hydrogen bonds involving dca2, water2, and the dication in 1 can be considered as interlinked helical dimers consisting of hydrogen-bonded monomers.

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Figure 3. Perspective view to demonstrate the two-dimensional sheet formed due to the hydrogen bonds involving dca1, water1, and the O(1)-H(1A), C(3)-H(3), and C(9)-H(9) parts of the dication. One 4-terpyridone and one ring of the second 4-terpyridone as well as dca2 and water2 have been deleted for clarity. Only those hydrogens participating to create the two-dimensional sheets are shown. Symmetry codes: (A), (E), (F), (I), as in Figure 2; (L) x, y - 1, z; (M) 2 - x, 1 - y, -z; (N) 2 - x, 2 - y, -z; (O) 1 - x, 2 - y, -z; (P) 1 - x, 1 - y, -z; (Q) 1 - x, -y, -z; (R) x - 1, 1 + y, z; (S) x - 1, y - 1, z; (T) 2 - x, -y, -z; (U) -x, -y, -z; (V) -x, 1 - y, -z.

Excluding dca2 and water2, the structure is twodimensional, consisting of interlinked pairs of onedimensional chains (Figure 3 and Figure S2 (Supporting Information)). As demonstrated in Figure 3, one water1 molecule (O(1W)) acts as a double donor to two terminal nitrogens (N(41) and N(42F)) of two dca1’s, and the atoms at the other end (N(42) and N(41F)) interact with two other different water1 molecules (H2O(1WL) and H2O(1WF), respectively) to result in the formation of one-dimensional zigzag chains that propagate along the crystallographic b axis. In addition to the formation of two hydrogen bonds with nitrile nitrogens, H2O(1W) also interacts with the hydrogen bonded with O(1P) and, due to this type of interaction, the dications are appended with the water1‚‚‚dca1 one-dimensional chains. In Figure 3, four one-dimensional chains (I, O(1WF)‚‚‚O(1W)‚‚‚O(1WL)‚‚‚N(40L); II, N(40N)‚‚‚ O(1WN)‚‚‚O(1WM)‚‚‚O(1WT); III, O(1WR)‚‚‚O(1WI)‚‚‚ O(1WS)‚‚‚N(40S); IV, N(40O)‚‚‚O(1WO)‚‚‚O(1WP)‚‚‚ O(1WQ)) along with the appended dications are shown to demonstrate the patterns of interlinking between them as well as their relative positions. The oxygen atom, O(1P), which is the part of the dication appended with chain I, interacts with the hydrogen bonded with C(9A), which is the part of the dication appended with the chain II. Clearly, due to the O(1P)‚‚‚C(9A) type of interactions, chains I and II or III and IV are interlinked with each other through the appended dications. Again, the chains I and IV are stitched with each other due to C(3F)-H(3F)‚‚‚N(41) types of hydrogen bonds to create the second dimension along the crystallographic a axis. The water1 oxygens of the chains I and II, as well as of III and IV, belong to two perfect and mutually parallel planes; the oxygens of the second plane deviate from the first plane by -6.14 Å. Similarly, the water1 oxygens of the chains I and III, as well as of II and IV, define two perfect and mutually parallel planes, sepa-

rated by 4.50 Å. Evidently, in comparison to the chains I and II, the chains III and IV lie in a lower bc plane (Figure S2). Again, the chains I and III, as well as II and IV, belong to the same ab plane (Figure S2). As the chains I and II, as well as III and IV, are interlinked through direct interactions between the appended dications, these can be considered as two pairs of onedimensional chains. Therefore, the supramolecular structure involving dca1, water1, and the dication in 1 can be summarized as two-dimensional sheets (in the bc plane) consisting of the interlinked pairs of onedimensional chains (along the b axis). As discussed above, one oxygen center (O(2)) of the dication interacts with dca2/water2 to result in onedimensional chains, while two-dimensional sheets are created due to the interaction of the second oxygen (O(1)) of the dication with dca1/water1. However, as the two oxygens are linked by a pyridine-nickel(II)-pyridine moiety, the superposition of the two assemblies results in the formation of the three-dimensional network in the title compound. In Figure 4, the construction of the three dimensions is demonstrated by a simplified diagram. In this illustration, I and II, as well as V and VI, are two pairs of one-dimensional chains (dca1‚‚‚ water1) and, evidently, are parts of two different twodimensional sheets. The region X in this figure consists of the helical dimers, which are parts of the onedimensional chains resulting from the interactions involving O(2), C(1), O(2W), and dca2. The stitching of the chains II and V by the helical dimers implies the linking of the two-dimensional sheets by the onedimensional chains. Therefore, the overall three-dimensional structure of the title compound can be considered as the stitching of the two-dimensional sheets, which consist of the interlinked pairs of one-dimensional chains, by the second type of one-dimensional chains,

A 4-Terpyridone-Based Ni(II) Dicyanamide Supramolecule

Crystal Growth & Design, Vol. 5, No. 5, 2005 1911 Supporting Information Available: Crystallographic data in CIF format and Figures S1 and S2. This material is available free of charge via the Internet at http://pubs.acs.org.

References

Figure 4. Perspective view along the crystallographic a axis to demonstrate, in a simplified way (see text), the creation of the three dimensions in the structure of 1. Two terminal pyridine rings of each of the two 4-terpyridones and the atoms, other than N(31), of dca2 are omitted for clarity.

created by the attachment of the helical dimers, which consist of the hydrogen-bonded monomers. Conclusions The synthesis, characterization, and crystal engineering of an enolic 4-terpyridone (L1) based hydrogenbonded supramolecule, [NiII(L1)2](dca)2‚2H2O (1), have been described in this report. To the best of our knowledge, the title compound is the first example of a coordination compound containing dicyanamide in only a noncoordinating form. As expected, the O-H groups of L1 in 1 behave as hydrogen bond donors. Not only that, but these hydrogen bonds are quite strong (D‚‚‚A < 2.6 Å). In addition, one O-H group also acts as an hydrogen bond acceptor. Therefore, regarding the ability to create a multidimensional assembly, the H-Opyridine-M-pyridine-O-H moiety (as in 1) can be considered as similar to 4,4′-bipyridine or 4,4′-bipyridine-N,N′-dioxide;1b,12 the nature of the interactions is hydrogen bonding for the H-O-pyridine-M-pyridineO-H fragment, while in the latter cases, supramolecular structures are created due to coordinate bonds. Evidently, new systems containing this organic moiety may result in interesting types of topologies. The involvements of the H-O-pyridine-M-pyridine-O-H fragment, a few C-H hydrogens, noncoordinating dca, and water molecules in strong or weak hydrogenbonding interactions create a three-dimensional assembly in 1. The fragment analyses reveal the existence of helical dimers and a pair of one-dimensional chains in this molecule. Acknowledgment. Financial support from the DST (SR/S1/IC-27/2002), the Government of India, and the Swiss National Science Foundation is gratefully acknowledged. M.N. thanks the CSIR, Government of India, for providing a fellowship.

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