Rational Design of Supramolecular Gridlike Layers and Zigzag Chains

ABSTRACT: Six new Cu(II)-M(I) complexes (M ) Ag, Au) were synthesized to illustrate the role of the convolution of d10-d10. (aurophilic or argentophil...
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CRYSTAL GROWTH & DESIGN

Rational Design of Supramolecular Gridlike Layers and Zigzag Chains through a Unique Interplay of d10-d10 and π-π Stacking Interactions

2006 VOL. 6, NO. 7 1671-1675

Augustin M. Madalan,† Narcis Avarvari,‡ and Marius Andruh*,† Inorganic Chemistry Laboratory, Faculty of Chemistry, UniVersity of Bucharest, Str. DumbraVa Rosie nr. 23, 020464-Bucharest, Romania, and Laboratoire Chimie, Inge´ nierie Mole´ culaire et Mate´ riaux d’Angers (CIMMA) UMR 6200 CNRS - UniVersite´ d'Angers, UFR Sciences, Baˆ t. K, 2 bd. LaVoisier, 49045 Angers, France ReceiVed March 9, 2006

ABSTRACT: Six new Cu(II)-M(I) complexes (M ) Ag, Au) were synthesized to illustrate the role of the convolution of d10-d10 (aurophilic or argentophilic) and π-π stacking interactions in sustaining supramolecular solid-state architectures. Two types of supramolecular synthons are involved: a rectangular one, based on the aurophilic (argentophilic) interactions between the [M(CN) 2]spacers, and a linear one, relying upon π-π contacts between the aromatic ligands. The reactions between [Cu(acac)(BB)(H2O)](ClO4) complexes and K[M(CN)2] in a 2:1 molar ratio (BB ) 2,2′-bipyridine; 1,10-phenanthroline) lead to the following heterotrinuclear complexes: [{Cu(acac)(bipy)}2{Au(CN)2}](ClO4)‚0.5CH3CN (1), [{Cu(acac)(bipy)}2{Ag(CN)2}](ClO4)‚0.5CH3CN (2), [{Cu(acac)(phen)}2{Ag(CN)2}](ClO4) (3), and [{Cu(acac)(phen)}2{Au(CN)2}](ClO4) (4). The recrystallization of 4 from acetonitrile affords [{Cu(acac)(phen)}2{Au(CN)2}](ClO4)‚0.5CH3CN (5), which is isomorphous with the compounds 1-3. By reacting [Cu(sal)(bipy)]ClO4 with K[Ag(CN)2] in a 1:1 molar ratio, a heterobinuclear complex, [{Cu(sal)(bipy)}{Ag(CN)2}] (6), is obtained (sal- is the anion of the salicylaldehyde). The copper(II) ions in compounds 1-6 exhibit a square-pyramidal geometry, with the apical position occupied by the nitrogen atom from the cyano bridge. As expected, the crystallographic investigation of compounds 1-3 and 5 reveals the formation of supramolecular grids resulting from the combination of the two supramolecular synthons. The M‚‚‚M distances in these compounds are 1: 3.295(11) (Au‚‚‚Au); 2: 3.2144(7) (Ag‚‚‚Ag), 3: 3.2789(10) (Ag‚‚‚Ag); 5: 3.389(7) (Au‚‚‚ Au) Å, while the distances associated with the π-π stackings vary between 3.3 and 3.6 Å. The crystal structure of 4 differs from that found in the other trinuclear complexes. It consists of supramolecular chains resulting from the aromatic interaction between the organic ligands attached to the copper ions, without the intervention of the d10-d10 interactions. The analysis of the packing diagram for compound 6 reveals supramolecular zigzag chains, resulting from the convolution of Ag‚‚‚Ag [2.9708(5) Å] and π-π aromatic (3.27-3.55 Å) interactions. Introduction

Scheme 1

During the last 15 years, the crystal design and engineering of multidimensional arrays and networks have made considerable progress.1 Chemists learned a lot in manipulating the intermolecular forces, particularly highly directional metalligand and hydrogen bonds, to construct supramolecular solidstate architectures with interesting structures and useful properties. A rich library of tectons (connectors and linkers) and supramolecular synthons is now available for the deliberate construction of various network topologies.2 For instance, gridlike layers can be obtained by assembling linear spacers with either metal ions preferring a square-planar geometry or metal ions displaying an octahedral one. With the second category of metal ions, the spacers are coordinated into the equatorial plane of the octahedron. Among the most popular linear spacers, we mention 4,4′-bipyidine, 1,2-bis-(4-pyridyl)ethylene, bis-(4-pyridyl)-acetylene, etc. The metal-to-spacer molar ratio is 1:2. Most frequently, both spacer molecules are coordinated, leading to a 2-D coordination polymer.3 If only one spacer acts as a bridge, whereas the other one is uncoordinated, the grid motif results from the convolution of coordinative and hydrogen bond interactions established between the spacer and the aqua ligands.4 We now report on an alternative way of constructing gridlike layers, which is based on the interplay of π-π-stacking and * To whom correspondence [email protected]. † University of Bucharest. ‡ CNRS - Universite ´ d’Angers.

should

be

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aurophilic/argentophilic interactions. In a series of recent papers, we have shown that [Cu(AA)(BB)]+ moieties can generate interesting solid-state architectures through aromatic interactions established between the organic ligands (AA ) acetylacetonato; salycilaldehydato; BB ) 2,2′-bipyridine, 1,10-phenanthroline).5 The [Cu(AA)(BB)]+ moieties have been connected through a rich variety of ligands, leading to oligonuclear complexes whose packing in the crystal is driven by π-π interactions. On the other hand, recent works illustrate that [M(CN)2]- (M ) Ag, Au) anions can sustain supramolecular solid-state architectures through both coordinative bonds established between the CN groups and a second metal ion, and argentophilic or aurophilic (d10-d10) interactions.6 Experimental Procedures Synthesis of [{Cu(acac)(bipy)}2{Au(CN)2}](ClO4)‚0.5CH3CN (1), [{Cu(acac)(bipy)}2{Ag(CN)2}](ClO4)‚0.5CH3CN (2), [{Cu(acac)(phen)}2{Ag(CN)2}](ClO4) (3), and [{Cu(acac)(phen)}2{Au(CN)2}](ClO4) (4). Compounds 1-4 were obtained by following the same procedure: a 20 mL solution (acetonitrile) containing 0.2 mmol of [Cu(acac)(bipy)(H2O)](ClO4) for 1 and 2, respectively, [Cu(acac)(phen)(H2O)](ClO4) for 3 and 4, were added to a 10 mL aqueous solution

10.1021/cg060131x CCC: $33.50 © 2006 American Chemical Society Published on Web 06/01/2006

1672 Crystal Growth & Design, Vol. 6, No. 7, 2006

Madalan et al.

Table 1. Crystallographic Data and Structure Refinement Parameters for Compounds 1-6 compound

1

2

3

chemical formula M (g mol-1) temperature (K) wavelength (Å) crystal system space group a (Å) b (Å) c (Å) R (°) β (°) γ (°) V (Å3) Z Dc (g cm-3) µ (mm-1) F(000) goodness-of-fit on F2 final R1, wR2 [I > 2σ(I)] R1, wR2 (all data) largest diff peak and hole (e Å-3)

C33H31.5AuClCu2N6.5O8 1006.64 293(2) 0.71073 triclinic P1h 10.6431(11) 13.1303(14) 27.821(3) 82.913(13) 84.926(13) 71.503(12) 3653.8(7) 4 1.830 5.290 1972 0.956 0.0509, 0.1180 0.0662, 0.1240 3.040, -3.105

C33H31.5AgClCu2N6.5O8 917.55 293(2) 0.71073 triclinic P1h 10.5948(11) 13.1741(13) 27.890(3) 82.883(13) 85.199(13) 71.672(12) 3662.7(7) 4 1.664 1.811 1844 0.901 0.0437, 0.0970 0.0763, 0.1075 0.808, -0.663

C36H30AgClCu2N6O8 945.06 293(2) 0.71073 triclinic P1h 11.2946(10) 13.2756(11) 28.455(3) 82.170(11) 81.393(12) 69.467(10) 3934.4(6) 4 1.595 1.689 1896 0.890 0.0575, 0.1331 0.1202, 0.1571 1.176, -0.629

compound

4

5

6

chemical formula M (g mol-1) temperature (K) wavelength (Å) crystal system space group a (Å) b (Å) c (Å) R (°) β (°) γ (°) V (Å3) Z Dc (g cm-3) µ (mm-1) F(000) goodness-of-fit on F2 final R1, wR2 [I > 2σ(I)] R1, wR2 (all data) largest diff peak and hole (e Å-3)

C36H30AuClCu2N6O8 1034.16 293(2) 0.71073 triclinic P1h 12.2575(13) 13.6244(8) 23.0234(17) 90.406(6) 100.333(8) 94.192(5) 3771.7(5) 4 1.821 5.128 2024 0.974 0.0529, 0.0931 0.1556, 0.1166 0.672, -0.635

C37H31.5AuClCu2N6.5O8 1054.68 293(2) 0.71073 triclinic P1h 11.1506(12) 13.4704(12) 28.350(3) 83.315(8) 82.568(8) 68.127(8) 3907.7(7) 4 1.793 4.951 2068 0.996 0.0580, 0.1132 0.1450, 0.1361 0.975, -0.981

C38H26Ag2Cu2N8O4 1001.51 293(2) 0.71073 monoclinic C2/c 20.2704(8) 10.2540(4) 17.7320(8) 90.00 94.988(3) 90.00 3671.7(3) 4 1.812 2.246 1976 0.984 0.0384, 0.0568 0.0697, 0.1172 0.443, -0.361

Table 2. Selected Bond Length for Compounds 1-6 compound

1

2

4

5

6

Cu(1)-O(1) Cu(1)-O(2) Cu(1)-N(1) Cu(1)-N(2) Cu(1)-N(3) Cu(1)-N(9) Cu(2)-O(3) Cu(2)-O(4) Cu(2)-N(3) Cu(2)-N(4) Cu(2)-N(10) Cu(3)-O(5) Cu(3)-O(6) Cu(3)-N(5) Cu(3)-N(6) Cu(3)-N(11) Cu(4)-O(7) Cu(4)-O(8) Cu(4)-N(7) Cu(4)-N(8) Cu(4)-N(12) Au‚‚‚Au/Ag‚‚‚Ag contacts

1.913(5) 1.924(6) 2.007(6) 2.006(7)

1.924(3) 1.910(3) 2.010(4) 2.019(4)

1.919(5) 1.922(5) 1.992(6) 2.017(6)

1.896(5) 1.902(4) 2.012(6) 2.025(5)

1.906(4) 1.919(4) 2.004(5) 2.024(5)

1.9626(18) 1.9022(17) 1.997(2) 2.003(2) 2.296(2)

2.391(6) 1.908(5) 1.913(5) 1.997(5) 2.008(6) 2.372(6) 1.921(5) 1.914(5) 2.000(5) 1.993(5) 2.463(8) 1.907(5) 1.937(5) 1.989(6) 2.014(6) 2.276(7) 3.295(11)

2.374(4) 1.919(3) 1.923(3) 2.010(4) 2.004(4) 2.348(4) 1.932(3) 1.912(3) 2.002(4) 2.005(4) 2.258(5) 1.911(3) 1.917(3) 1.993(4) 2.005(4) 2.398(4) 3.2144(7)

2.295(6) 1.914(6) 1.906(5) 2.027(6) 2.031(6) 2.266(6) 1.906(5) 1.911(4) 2.000(5) 2.012(5) 2.331(6) 1.903(8) 1.899(5) 2.030(8) 2.009(7) 2.207(7) 3.2789(10)

2.320(5) 1.899(4) 1.921(5) 2.017(5) 2.009(6) 2.323(5) 1.906(4) 1.902(5) 2.015(5) 2.011(6) 2.286(5) 1.906(5) 1.894(4) 2.017(6) 2.007(5) 2.326(5)

2.313(5) 1.925(4) 1.922(4) 2.022(5) 1.999(5) 2.283(6) 1.913(4) 1.900(4) 2.004(5) 2.001(5) 2.358(6) 1.898(5) 1.920(4) 2.020(6) 2.025(5) 2.236(6) 3.389(7)

containing 0.1 mmol of K[Au(CN)2] (for 1 and 4) or K[Ag(CN)2] (for 2 and 3). The [Cu(acac)(phen)(H2O)](ClO4) and [Cu(acac)(bipy)(H2O)](ClO4) mononuclears have been obtained as already reported.5 The green crystals of 1-4 are obtained by slow evaporation of the resulting mixtures at room temperature.

3

2.9708(5)

Synthesis of [{Cu(acac)(phen)}2{Au(CN)2}](ClO4)‚0.5CH3CN 5. Compound 5 was obtained by recrystallization of compound 4 from acetonitrile. Synthesis of [{Cu(sal)(bipy)}{Ag(CN)2}] 6. The reaction between 0.2 mmol of [Cu(sal)(bipy)](ClO4) in 20 mL of acetonitrile and 0.2

Rational Design of Supramolecular Gridlike Layers

Crystal Growth & Design, Vol. 6, No. 7, 2006 1673 Scheme 2

mmol of K[Ag(CN)2] in 15 mL of water leads (after slow evaporation of the resulted mixture) to green crystals of 6. X-ray Structure Determination. X-ray diffraction measurements were performed on a STOE IPDS diffractometer for compounds 1-3 and on a Nonius Kappa CCD diffractometer for compounds 4-6, using graphite-monochromated MoKR radiation (λ ) 0.71073 Å). The structures were solved by direct methods and refined by full-matrix least squares techniques based on F2. The non-H atoms were refined with anisotropic displacement parameters. The crystallographic data are collected in Table 1. Calculations were performed using SHELX-

97 crystallographic software package. CCDC reference numbers are as follows: crystal 1: 289517; crystal 2: 289518; crystal 3: 600994; crystal 4: 600995; crystal 5: 600996;.crystal 6: 289518.

Figure 1. View of the two trinuclear [{Cu(acac)(bipy)}2{Au(CN)2}]+ isomers in crystal 1, showing the formation of the rectangular synthon through Au‚‚‚Au contacts.

Figure 3. View of the two trinuclear [{Cu(acac)(phen)}2{Ag(CN)2}]+ isomers in crystal 3, showing the formation of the rectangular synthon through Ag‚‚‚Ag contacts.

Results and Discussion Our synthetic approach relies upon two useful tools in crystal engineering: the d10-d10 and the π-π stacking interactions. Two supramolecular synthons can be defined: a linear one, based on aromatic interactions, and a rectangular one, resulting

Figure 2. Packing diagram in crystals 1 and 2 showing the formation of the supramolecular gridlike layer (a) and a side view of the supramolecular grid (b).

1674 Crystal Growth & Design, Vol. 6, No. 7, 2006

Figure 4. View of the two trinuclear [{Cu(acac)(phen)}2{Au(CN)2}]+ isomers in crystal 4.

Figure 5. Packing diagram in crystal 4 showing the formation of supramolecular chains.

from the d10-d10 contacts (Scheme 1). The linear synthon arises from the aromatic interactions established between the aromatic ligands coordinated to the copper ions in the [Cu(AA)(BB)]+ moieties. The rectangular synthon is a classical motif encountered in the packing diagrams for many complexes containing [M(CN)2]- ions.7 Supramolecular Grids. If the [M(CN)2]- ion bridges two copper(II) ions, then the packing of the resulting trinuclear complexes in crystal, driven by the two types of intermolecular interactions, will be a supramolecular grid (Scheme 2) The reactions between [Cu(acac)(bipy)(H2O)](ClO4) in acetonitrile and K[MI(CN)2] (M ) Au, Ag) in water (2:1 molar ratio) lead

Figure 6. View of a supramolecular zigzag chain in crystal 6.

Madalan et al.

to the isostructural trinuclear heterometallic complexes 1 and 2, whose crystal structures have been solved. As expected, two {Cu(acac)(bipy)} moieties are connected through the linear [MI(CN)2]- (M ) Au, Ag) anions, via coordination of the cyano groups into the apical position of the Cu(II) centers (Figure 1). The copper ions exhibit a square-pyramidal geometry, with the basal plane formed by two oxygen and two nitrogen atoms arising from the chelating ligands. The apical position is thus occupied by one cyano group from the spacer [Cu(1)-N(9) ) 2.391(6), Cu(2)-N(10) ) 2.372(6), Cu(3)-N(11) ) 2.463(8), Cu(4)-N(12) ) 2.276(7) Å for 1, and Cu(1)-N(9) ) 2.374(4), Cu(2)-N(10) ) 2.348(4), Cu(3)-N(11) ) 2.258(5), Cu(4)-N(12) ) 2.398(4) Å for 2]. An interesting feature of these structures is the presence of two isomeric cationic complexes: in one of them the acac (bipy) ligands are disposed in the same direction with respect to the bridge [Cu(3)-Au(2)-Cu(4) for 1 and Cu(3)-Ag(2)-Cu(4) for 2], while in the other one, they are oriented in opposite directions [Cu(1)-Au(1)-Cu(2) for 1, and Cu(1)-Ag(1)-Cu(2) for 2]. In crystal 1, the average intramolecular distance between the copper and the gold atoms in the two isomers is 5.32 Å. The analysis of the packing diagram reveals the formation of the targeted gridlike supramolecular layers (Figure 2). The distances between the gold and the silver atoms in compounds 1 and 2 are 3.2946(6) and 3.2144(8) Å, respectively. The distances associated with the π-π contacts range between 3.37 and 3.62 Å in 1 and between 3.40 and 3.64 Å in 2. The reactions between [Cu(acac)(phen)(H2O)](ClO4) and K[MI(CN)2] (M ) Ag, Au) in a 2:1 molar ratio lead also to trinuclear heterometallic complexes, 3 and 4, but only in compound 3 do the trinuclear cations have a similar arrangement with 1 and 2 (Figure 3), generating supramolecular gridlike layers. In crystal 4, there are two independent crystallographic types of [{Cu(acac)(phen)}2{Au(CN)2}]+ trinuclears (Figure 4) with a parallel orientation, and not a perpendicular one. The copper ions exhibit the same square-pyramidal geometry, with the basal plane formed by two oxygen and two nitrogen atoms arising from the chelating ligands, and one nitrogen from a cyano group in the apical position. Selected bond distances concerning the copper(II) ions stereochemistry are collected in Table 2. Every trinuclear [{Cu(acac)(phen)}2{Au(CN)2}]+ unit interacts through the chelatic ligands with two other trinuclear units generating supramolecular chains, running along the crystallographic b-axis. Every supramolecular chain contains only one type of crystallographically independent [Cu2Au] complex, the distances associated with the π-π contacts ranging between 3.30 and 3.56 Å (Figure 5). The packing diagram for crystal 4 does not confirm our expectations, since no gold-gold interaction is present. There are several other compounds in the literature with no interactions between the dicyanoaurate or dicyanoargentate ions.8

Rational Design of Supramolecular Gridlike Layers

Crystal Growth & Design, Vol. 6, No. 7, 2006 1675

References

Scheme 3

Upon slow evaporation of the solution resulted by dissolving compound 4 in acetonitrile, green crystals of 5 were obtained, in which the trinuclear [{Cu(acac)(phen)}2{Au(CN)2}]+ units interact as in crystals 1-3; the packing diagram shows the gridlike arrangement. Supramolecular Zigzag Chains. What about the 1:1 Cu(II)-M(I) complexes (M ) Ag, Au)? They can be obtained by assembling [Cu(AA)(BB)]+ and [M(CN)2]- ions in a 1:1 molar ratio. These compounds can in principle generate, through the cooperativity of π-π stacking and d10-d10 interactions, either supramolecular squares or supramolecular zigzag chains (Scheme 3). To validate the structural type, we synthesized and crystallographically characterized a binuclear [CuAg] compound: [{Cu(sal)(bipy)}{Ag(CN)2}] (6). Similar to complexes 1-5, the copper(II) ions display a square-pyramidal stereochemistry, with the chelatic ligands forming the basal plane and one nitrogen atom from the cyano group coordinating in the apical position [Cu(1)-N(3) ) 2.296(2) Å]. The intramolecular Cu‚‚‚Ag distances are Cu(1)‚‚‚Ag(1) ) 5.4864(4) Å. The analysis of the packing diagram shows the self-assembling of the supramolecular zigzag chains (Figure 6). As previously, the Ag‚‚‚Ag rectangular synthon is formed again [Ag(1)‚‚‚Ag(1′) ) 2.9708(5) Å]. This is a quite short Ag‚‚‚Ag distance (the typical silver-silver distance in cyanoargentate complexes varies currently between 3.05 and 3.26 Å, while the Ag-Ag distance in metallic silver is 2.89 Å).9 The separation between the aromatic fragments involved in π-π stacking interactions is 3.27-3.55 Å. The results presented herein illustrate that the combination of weak and rather peculiar organizing forces, such as aromatic and d10-d10 interactions, can be successfully employed to design solid-state architectures. Acknowledgment. Financial support from the CERES Program (Project 4/130) is gratefully acknowledged. Supporting Information Available: Crystallographic information files (CIF) are available free of charge via the Internet at http:// pubs.acs.org.

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