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Vinyl-group alignment along the upper rim of a multi-component resorcin[4]arene
Crystal Engineering, Vol. 2, No. 1, pp. 47–53, 1999 Copyright © 1999 Elsevier Science Ltd Printed in the USA. All rights reserved 1463-0184/99/$–see front matter
PII S1463-0184(99)00006-4
VINYL-GROUP ALIGNMENT ALONG THE UPPER RIM OF A MULTI-COMPONENT RESORCIN[4]ARENE
Leonard R. MacGillivray,1* Jennifer L. Reid,1 Jerry L. Atwood,2 and John A. Ripmeester1 1 Steacie Institute for Molecular Sciences, National Research Council of Canada, Ottawa, Ontario, Canada 2 Department of Chemistry, University of Missouri–Columbia, Columbia, MO 65211, USA (Refereed) (Received February 9, 1999; Accepted March 9, 1999)
ABSTRACT Cocrystallization of C-methylcalix[4]resorcinarene 1 with 4-vinylpyridine obtained from MeNO2 yields a six-component host– guest complex 1䡠4(4-vinylpyridine)䡠MeNO2 2 in which the upper rim of 1 is extended supramolecularly by way of four O–H. . .N(pyridine) hydrogen bonds and the included solvent serves as a guest. The pyridine moieties of 2 assemble along the upper rim of 1 as two stacked dimers in which the vinyl substituents of the aromatic adopt a parallel orientation. The X-ray crystal structure of resorcinol䡠2(4-vinylpyridine) 3 has also been determined and reveals that the vinyl groups of 3 are aligned in an antiparallel fashion. These observations allow us to suggest that multi-component resorcin[4]arenes which possess vinyl-pyridines as cavity extenders may provide a route to aligning olefinic bonds in the solid state. © 1999 Elsevier Science Ltd
KEYWORDS: resorcinarene, hydrogen bonding, inclusion chemistry INTRODUCTION Using a crystal engineering design strategy for molecular self-assembly, we have demonstrated that cocrystallization of C-methylcalix[4]resorcinarene 1 with pyridines (e.g., pyridine, 4-picoline) in the presence of an appropriate guest solvent molecule (e.g., MeCN,
*To whom correspondence should be addressed. 47
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MeNO2) typically yields a discrete, six-component host– guest complex, 1䡠4(pyridine)䡠guest, in which four pyridine units assemble along the upper rim of 1, as two stacked dimers via four O–H. . .N hydrogen bonds (Scheme 1) [1]. In these systems, the cavity of 1, unlike traditional synthetic approaches that involve the making and breaking of covalent bonds [2], is extended supramolecularly which, in effect, provides a route to deep-cavity resorcin[4]arenes in virtually quantitative yield.
With the realization that these multi-component host– guest systems may be exploited for the inclusion of guests different than the supramolecular extenders of 1 achieved [1b], we now focus our attention on the use of substituted pyridines for their design. Indeed, in addition to introducing issues of stereochemistry [3], such an approach allows us to address the robustness and structural parameters that define the resorcinol-based supramolecular synthon studied here [4] and thereby aid the future design of analogous host– guest systems based upon 1 and extended lattices based upon the synthon itself. In this contribution we demonstrate the ability of a vinyl-pyridine—a molecule with a flexible substituent—to serve as a supramolecular extender of a discrete multi-component resorcin[4]arene as revealed by the X-ray crystal structure of 1䡠4(4-vinyl-pyridine)䡠MeNO2 2. In particular, we reveal that the “upper rim” vinyl groups of this complex are aligned in the solid state such that they adopt a parallel orientation. For comparison, we have also determined the X-ray crystal structure of resorcinol䡠2(4-vinyl-pyridine) 3, an assembly held together by two O–H. . .N hydrogen bonds, and show that the vinyl groups of this system are, in contrast to 2, aligned in an antiparallel fashion. In addition to providing insight into the formation and molecular recognition processes involving multi-component resorcin[4]arenes [1], such observations are important because they illustrate a novel manner in which olefinic bonds may be aligned in the crystalline state, which is of considerable interest in the area organic solid state photochemistry [5]. EXPERIMENTAL General Methods. All reagents, unless otherwise stated, were purchased from Aldrich Chemical Co. (Milwaukee, WI) and were used without further purification. 1 was synthesized according to a procedure described in the literature [6]. The formulations of 2 and 3 were confirmed by single-crystal X-ray diffraction and 1H NMR spectroscopy.
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TABLE 1 Crystallographic Data
CCDC deposit no. Formula Formula weight Crystal system Space group T, °C a, Å b, Å c, Å , deg V, Å3 Z calc, g cm⫺3 , mm⫺1 Ra WR2a
2
3
CCDC-1294/82 O10N5C61H63 1026.14 Monoclinic P2/c ⫺100 11.7351(8) 7.7492(5) 31.195(2) 100.637(1) 2716.1(3) 2 1.26 0.089 0.073 0.199
CCDC-1294/83 O2N5C20H20 362.41 Monoclinic C2/c ⫺100 15.182(1) 13.686(1) 9.060(4) 112.941(2) 1733.7(3) 4 1.23 0.080 0.042 0.107
Inet ⬎ 2.0 (Inet)
a
Synthesis of 2. Addition of 1 (0.020 g) to a boiling aliquot of 4-vinyl-pyridine (2 mL) yielded a yellow precipitate. The precipitate was then heated and MeNO2 was added dropwise, with continuous heating, until the solid dissolved. Yellow crystals of 2 suitable for X-ray analysis formed, upon cooling, within approximately two days. Synthesis of 3. Addition of 4-vinyl-pyridine (2 mL) to a mixture of resorcinol (0.010 g) and boiling CHCl3 (5 mL) resulted in dissolution of the solid which, upon slow cooling, yielded colorless crystals of 3. X-ray Crystallography. Single crystals of 2 and 3 were individually mounted on the end of a glass fiber and optically centered in the X-ray beam of a Siemens SMART system for data collection. Initial sets of cell constants were calculated from reflections harvested from three sets of 25 frames. Final cell constants were calculated from reflections obtained from the data collection. All structures were solved using direct methods. After anisotropic refinement of all nonhydrogen atoms, methine, methyl, aromatic, and hydroxyl hydrogen atoms were placed by modeling the moieties as rigid groups with idealized geometry, maximizing the sum of the electron density at the calculated hydrogen positions. A summary of data collection parameters for both structures is given in Table 1. Structure solutions were accomplished with the aid of SHELXS-86 [7] and refinement was conducted using SHELXL93 [8] locally implemented on a pentium-based IBM compatible computer. All crystallographic manipulations were performed with the aid of RES2INS [9].
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FIG. 1 Space-filling view of the X-ray crystal structure of (a) 2 and (b) 3.
RESULTS AND DISCUSSION Discrete Assemblies. A space-filling view of the X-ray crystal structure of 2 is shown in Figure 1a. As in 1䡠4(pyridine)䡠pyridine 4 [1a] and 1䡠4(4-picoline)䡠MeNO2 5 [1b], four pyridines have assembled, as two symmetry-related stacked dimers (Cent. . .Cent 4.21 Å), along the upper rim of 1 such that they participate in four O–H. . .N hydrogen bonds with four hydroxyl groups of two resorcinol units of the macrocycle (O(1). . .N(1) 2.72(1) Å, O(2). . .N(2) 2.74(1) Å).1 This, in turn, gives rise to a fivecomponent extended-cavity resorcin[4]arene that is bisected by a crystallographic twofold rotation axis in which a molecule of MeNO2, which lies disordered across two sites, has assembled within 1, interacting with 1 via C–H. . . interactions. Notably, the pyridine units are twisted by 127.6° (N1) and 112.1° (N2) with respect to the upper rim of 1, and the vinyl groups of each stacking pyridine dimer adopt an approximate parallel orientation in which the olefinic bonds are twisted by 3.8° with respect to each other. The carbon pairs, as determined by bond center– center separations, span a gap of 4.18 Å. A space-filling view of the X-ray crystal structure of 3 is shown in Figure 1b. In a way similar to 2, two symmetry-related pyridines, as a stacked dimer (Cent. . .Cent 3.89 Å), participate in two O–H. . .N hydrogen bonds with two hydroxyl groups of the resorcinol molecule (O(1). . .N(1) 2.74(2) Å), the twist angle between the pyridine rings and the resorcinol moiety being 71.0°. As a result, a three-component assembly, which is bisected by a crystallographic twofold rotation axis, has formed. Unlike 2, however, the vinyl groups of the stacking pyridines are aligned in an antiparallel fashion such that the angle between the two olefinic bonds is 103.3°, and the alkene carbon pairs are separated by 3.87 Å.
In this conformation, 1 forms four O-H. . .O hydrogen bonds along the upper rim.
1
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FIG. 2 Views of the X-ray crystal structures of (a) self-inclusion displayed by 2, (b) O–H. . .N, O–H. . .O, and C–H. . .O interactions involving the components of 2, (c) 2D layered structure of 3, and (d) C–H. . .O and O–H. . .N interactions involving the components of 3. Note: dotted lines represent hydrogen bonds. Extended Structures. Views depicting the extended structure of 2 are shown in Figures 2a and 2b. As in 5 [1b] but unlike 4 [1a], 2 self-assembles in the solid state such that adjacent complexes, which are related by translation symmetry, self-include and lie in an antiparallel fashion along the crystallographic b axis. As a result, a layered architecture, which is composed of alternating columns of stacking pyridines and resorcin[4]arenes, has formed (Fig. 2a). Notably, the vinyl groups of each pyridine column are slightly interdigitated such that two vinylic hydrogen atoms (i.e., CH⫽CH2) of one of the two symmetry independent vinyl substituents lie inserted between two vinyl groups of an adjacent stacking pyridine dimer (Fig. 2b). The second vinyl substituent is then observed to form a C–H. . .O hydrogen bond (C(23). . .O(3) 3.36(1) Å) with an oxygen atom of a molecule of 1 located in an adjacent layer.2 Views depicting the extended structure of 3 are shown in Figures 2c and 2d. 3 has self-assembled in the solid state such that nearest neighbor resorcinol molecules interact via
We also note, as in 4, an O4. . .O4’ (O4’ –x⫹0.5, ⫹y, -z⫹0.5) separation of 3.11(4) Å between self-included strands of adjacent layers which suggests a weak hydrogen bond involving a disordered hydroxyl hydrogen atom.
2
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C–H. . .O hydrogen bonds (C(2). . .O(1) 3.73(2) Å) and the pyridine dimers form infinite 1D face-to-face - stacking arrays. This, in turn, gives rise to a layered structure in which the complexes are aligned in a head-to-tail fashion along the crystallographic b axis (Fig. 2c). Interestingly, adjacent layers stack offset such that the pyridine dimers of one layer occupy the grooves defined by the resorcinol units of an another, and each pyridine participates in an edge-to-face - interaction with a single resorcinol molecule. As a consequence of these forces, the vinyl groups of 3 are positioned such that they form two C–H. . .O hydrogen bonds (C(11). . .O(1) 3.57(4) Å) with two resorcinol molecules of two adjacent layers and, as a result, are directed to opposite sides of each layer, being aligned in an anti parallel fashion (Fig. 2d). Cavity Extension and Vinyl Group Alignment. The observation that a substituted pyridine that possesses a flexible substituent, such as the vinyl group of 2, assembles along the upper rim of 1, via four O–H. . .N hydrogen bonds, in a way similar to 4 and 5, provides further evidence demonstrating the utility of the resorcinol-based supramolecular synthon studied here for elaborating 1 via rational solid-state design [1]. In the case of 2, the upper rim vinyl groups of 1, unlike 3, adopt a parallel orientation, owing to the fit displayed by the stacking pyridine and resorcin[4]arene columns of 2 and the presence of C–H. . .O hydrogen bonds,3 such that the substituents are directed away from the cavity of 1. Indeed, approaches that utilize supramolecular hosts to promote alignment of olefinic bonds in the crystalline state, for conducting [2⫹2] photochemical reactions, for example, are rare [10], and such observations suggest that similar complexes based upon 1 may provide a route to achieving this goal. CONCLUSION In conclusion, we have demonstrated the ability of 4-vinyl-pyridine to serve as a supramolecular extender of 1 in the solid state in the formation of a six-component host– guest complex. The vinyl groups of 2, in contrast to 3, adopt a parallel orientation, which suggests that these and related systems based upon 1 may be exploited for aligning carbon– carbon double bonds in the crystalline state. REFERENCES 1. 2. 3. 4. 5.
(a) L.R. MacGillivray and J.L. Atwood, J. Am. Chem. Soc. 119, 6931 (1997); (b) L.R. MacGillivray and J.L. Atwood, Chem. Commun., 181 (1999). R.K. Juneja, K.D. Robinson, C.P. Johnson, and J.L. Atwood, J. Am. Chem. Soc. 115, 3818 (1993). D.M. Rudkevich, G. Hilmersson, and J. Rebek, Jr., J. Am. Chem. Soc. 120, 12216 (1998). Y. Aoyama, K. Endo, T. Anzai, Y. Yamaguchi, T. Sawaki, K. Kobayashi, N. Kanehisa, H. Hashimoto, Y. Kai, and H. Masuda, J. Am. Chem. Soc. 118, 5562 (1996). G.W. Coates, A.R. Dunn, L.M. Henling, J.W. Ziller, E.B. Lobkovsky, and R.H. Grubbs, J. Am. Chem. Soc. 120, 3641 (1998).
3 Further studies are underway to delineate those factors which promote alignment of olefinic bonds in these and similar systems based upon 1.
Vol. 2, No. 1
6.
MULTI-COMPONENT RESORCIN[4]ARENES
53
D.J. Cram, S. Karbach, H.-E. Kim, C.B. Knobler, E.F. Maverick, J.L. Ericson, and R.C. Helgeson, J. Am. Chem. Soc. 110, 2229 (1988). 7. G.M. Sheldrick, Acta. Crystallogr. A46, 467 (1990). 8. G.M. Sheldrick, SHELXL93, University of Go¨ttingen, Go¨ttingen, Germany (1993). 9. L.J. Barbour, RES2INS, University of Missouri–Columbia, Columbia, Missouri, USA (1997). 10. F. Toda, Top. Curr. Chem. 149, 211 (1988).
PII S1463-0184(99)00006-4
VINYL-GROUP ALIGNMENT ALONG THE UPPER RIM OF A MULTI-COMPONENT RESORCIN[4]ARENE
Leonard R. MacGillivray,1* Jennifer L. Reid,1 Jerry L. Atwood,2 and John A. Ripmeester1 1 Steacie Institute for Molecular Sciences, National Research Council of Canada, Ottawa, Ontario, Canada 2 Department of Chemistry, University of Missouri–Columbia, Columbia, MO 65211, USA (Refereed) (Received February 9, 1999; Accepted March 9, 1999)
ABSTRACT Cocrystallization of C-methylcalix[4]resorcinarene 1 with 4-vinylpyridine obtained from MeNO2 yields a six-component host– guest complex 1䡠4(4-vinylpyridine)䡠MeNO2 2 in which the upper rim of 1 is extended supramolecularly by way of four O–H. . .N(pyridine) hydrogen bonds and the included solvent serves as a guest. The pyridine moieties of 2 assemble along the upper rim of 1 as two stacked dimers in which the vinyl substituents of the aromatic adopt a parallel orientation. The X-ray crystal structure of resorcinol䡠2(4-vinylpyridine) 3 has also been determined and reveals that the vinyl groups of 3 are aligned in an antiparallel fashion. These observations allow us to suggest that multi-component resorcin[4]arenes which possess vinyl-pyridines as cavity extenders may provide a route to aligning olefinic bonds in the solid state. © 1999 Elsevier Science Ltd
KEYWORDS: resorcinarene, hydrogen bonding, inclusion chemistry INTRODUCTION Using a crystal engineering design strategy for molecular self-assembly, we have demonstrated that cocrystallization of C-methylcalix[4]resorcinarene 1 with pyridines (e.g., pyridine, 4-picoline) in the presence of an appropriate guest solvent molecule (e.g., MeCN,
*To whom correspondence should be addressed. 47
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MeNO2) typically yields a discrete, six-component host– guest complex, 1䡠4(pyridine)䡠guest, in which four pyridine units assemble along the upper rim of 1, as two stacked dimers via four O–H. . .N hydrogen bonds (Scheme 1) [1]. In these systems, the cavity of 1, unlike traditional synthetic approaches that involve the making and breaking of covalent bonds [2], is extended supramolecularly which, in effect, provides a route to deep-cavity resorcin[4]arenes in virtually quantitative yield.
With the realization that these multi-component host– guest systems may be exploited for the inclusion of guests different than the supramolecular extenders of 1 achieved [1b], we now focus our attention on the use of substituted pyridines for their design. Indeed, in addition to introducing issues of stereochemistry [3], such an approach allows us to address the robustness and structural parameters that define the resorcinol-based supramolecular synthon studied here [4] and thereby aid the future design of analogous host– guest systems based upon 1 and extended lattices based upon the synthon itself. In this contribution we demonstrate the ability of a vinyl-pyridine—a molecule with a flexible substituent—to serve as a supramolecular extender of a discrete multi-component resorcin[4]arene as revealed by the X-ray crystal structure of 1䡠4(4-vinyl-pyridine)䡠MeNO2 2. In particular, we reveal that the “upper rim” vinyl groups of this complex are aligned in the solid state such that they adopt a parallel orientation. For comparison, we have also determined the X-ray crystal structure of resorcinol䡠2(4-vinyl-pyridine) 3, an assembly held together by two O–H. . .N hydrogen bonds, and show that the vinyl groups of this system are, in contrast to 2, aligned in an antiparallel fashion. In addition to providing insight into the formation and molecular recognition processes involving multi-component resorcin[4]arenes [1], such observations are important because they illustrate a novel manner in which olefinic bonds may be aligned in the crystalline state, which is of considerable interest in the area organic solid state photochemistry [5]. EXPERIMENTAL General Methods. All reagents, unless otherwise stated, were purchased from Aldrich Chemical Co. (Milwaukee, WI) and were used without further purification. 1 was synthesized according to a procedure described in the literature [6]. The formulations of 2 and 3 were confirmed by single-crystal X-ray diffraction and 1H NMR spectroscopy.
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TABLE 1 Crystallographic Data
CCDC deposit no. Formula Formula weight Crystal system Space group T, °C a, Å b, Å c, Å , deg V, Å3 Z calc, g cm⫺3 , mm⫺1 Ra WR2a
2
3
CCDC-1294/82 O10N5C61H63 1026.14 Monoclinic P2/c ⫺100 11.7351(8) 7.7492(5) 31.195(2) 100.637(1) 2716.1(3) 2 1.26 0.089 0.073 0.199
CCDC-1294/83 O2N5C20H20 362.41 Monoclinic C2/c ⫺100 15.182(1) 13.686(1) 9.060(4) 112.941(2) 1733.7(3) 4 1.23 0.080 0.042 0.107
Inet ⬎ 2.0 (Inet)
a
Synthesis of 2. Addition of 1 (0.020 g) to a boiling aliquot of 4-vinyl-pyridine (2 mL) yielded a yellow precipitate. The precipitate was then heated and MeNO2 was added dropwise, with continuous heating, until the solid dissolved. Yellow crystals of 2 suitable for X-ray analysis formed, upon cooling, within approximately two days. Synthesis of 3. Addition of 4-vinyl-pyridine (2 mL) to a mixture of resorcinol (0.010 g) and boiling CHCl3 (5 mL) resulted in dissolution of the solid which, upon slow cooling, yielded colorless crystals of 3. X-ray Crystallography. Single crystals of 2 and 3 were individually mounted on the end of a glass fiber and optically centered in the X-ray beam of a Siemens SMART system for data collection. Initial sets of cell constants were calculated from reflections harvested from three sets of 25 frames. Final cell constants were calculated from reflections obtained from the data collection. All structures were solved using direct methods. After anisotropic refinement of all nonhydrogen atoms, methine, methyl, aromatic, and hydroxyl hydrogen atoms were placed by modeling the moieties as rigid groups with idealized geometry, maximizing the sum of the electron density at the calculated hydrogen positions. A summary of data collection parameters for both structures is given in Table 1. Structure solutions were accomplished with the aid of SHELXS-86 [7] and refinement was conducted using SHELXL93 [8] locally implemented on a pentium-based IBM compatible computer. All crystallographic manipulations were performed with the aid of RES2INS [9].
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FIG. 1 Space-filling view of the X-ray crystal structure of (a) 2 and (b) 3.
RESULTS AND DISCUSSION Discrete Assemblies. A space-filling view of the X-ray crystal structure of 2 is shown in Figure 1a. As in 1䡠4(pyridine)䡠pyridine 4 [1a] and 1䡠4(4-picoline)䡠MeNO2 5 [1b], four pyridines have assembled, as two symmetry-related stacked dimers (Cent. . .Cent 4.21 Å), along the upper rim of 1 such that they participate in four O–H. . .N hydrogen bonds with four hydroxyl groups of two resorcinol units of the macrocycle (O(1). . .N(1) 2.72(1) Å, O(2). . .N(2) 2.74(1) Å).1 This, in turn, gives rise to a fivecomponent extended-cavity resorcin[4]arene that is bisected by a crystallographic twofold rotation axis in which a molecule of MeNO2, which lies disordered across two sites, has assembled within 1, interacting with 1 via C–H. . . interactions. Notably, the pyridine units are twisted by 127.6° (N1) and 112.1° (N2) with respect to the upper rim of 1, and the vinyl groups of each stacking pyridine dimer adopt an approximate parallel orientation in which the olefinic bonds are twisted by 3.8° with respect to each other. The carbon pairs, as determined by bond center– center separations, span a gap of 4.18 Å. A space-filling view of the X-ray crystal structure of 3 is shown in Figure 1b. In a way similar to 2, two symmetry-related pyridines, as a stacked dimer (Cent. . .Cent 3.89 Å), participate in two O–H. . .N hydrogen bonds with two hydroxyl groups of the resorcinol molecule (O(1). . .N(1) 2.74(2) Å), the twist angle between the pyridine rings and the resorcinol moiety being 71.0°. As a result, a three-component assembly, which is bisected by a crystallographic twofold rotation axis, has formed. Unlike 2, however, the vinyl groups of the stacking pyridines are aligned in an antiparallel fashion such that the angle between the two olefinic bonds is 103.3°, and the alkene carbon pairs are separated by 3.87 Å.
In this conformation, 1 forms four O-H. . .O hydrogen bonds along the upper rim.
1
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FIG. 2 Views of the X-ray crystal structures of (a) self-inclusion displayed by 2, (b) O–H. . .N, O–H. . .O, and C–H. . .O interactions involving the components of 2, (c) 2D layered structure of 3, and (d) C–H. . .O and O–H. . .N interactions involving the components of 3. Note: dotted lines represent hydrogen bonds. Extended Structures. Views depicting the extended structure of 2 are shown in Figures 2a and 2b. As in 5 [1b] but unlike 4 [1a], 2 self-assembles in the solid state such that adjacent complexes, which are related by translation symmetry, self-include and lie in an antiparallel fashion along the crystallographic b axis. As a result, a layered architecture, which is composed of alternating columns of stacking pyridines and resorcin[4]arenes, has formed (Fig. 2a). Notably, the vinyl groups of each pyridine column are slightly interdigitated such that two vinylic hydrogen atoms (i.e., CH⫽CH2) of one of the two symmetry independent vinyl substituents lie inserted between two vinyl groups of an adjacent stacking pyridine dimer (Fig. 2b). The second vinyl substituent is then observed to form a C–H. . .O hydrogen bond (C(23). . .O(3) 3.36(1) Å) with an oxygen atom of a molecule of 1 located in an adjacent layer.2 Views depicting the extended structure of 3 are shown in Figures 2c and 2d. 3 has self-assembled in the solid state such that nearest neighbor resorcinol molecules interact via
We also note, as in 4, an O4. . .O4’ (O4’ –x⫹0.5, ⫹y, -z⫹0.5) separation of 3.11(4) Å between self-included strands of adjacent layers which suggests a weak hydrogen bond involving a disordered hydroxyl hydrogen atom.
2
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C–H. . .O hydrogen bonds (C(2). . .O(1) 3.73(2) Å) and the pyridine dimers form infinite 1D face-to-face - stacking arrays. This, in turn, gives rise to a layered structure in which the complexes are aligned in a head-to-tail fashion along the crystallographic b axis (Fig. 2c). Interestingly, adjacent layers stack offset such that the pyridine dimers of one layer occupy the grooves defined by the resorcinol units of an another, and each pyridine participates in an edge-to-face - interaction with a single resorcinol molecule. As a consequence of these forces, the vinyl groups of 3 are positioned such that they form two C–H. . .O hydrogen bonds (C(11). . .O(1) 3.57(4) Å) with two resorcinol molecules of two adjacent layers and, as a result, are directed to opposite sides of each layer, being aligned in an anti parallel fashion (Fig. 2d). Cavity Extension and Vinyl Group Alignment. The observation that a substituted pyridine that possesses a flexible substituent, such as the vinyl group of 2, assembles along the upper rim of 1, via four O–H. . .N hydrogen bonds, in a way similar to 4 and 5, provides further evidence demonstrating the utility of the resorcinol-based supramolecular synthon studied here for elaborating 1 via rational solid-state design [1]. In the case of 2, the upper rim vinyl groups of 1, unlike 3, adopt a parallel orientation, owing to the fit displayed by the stacking pyridine and resorcin[4]arene columns of 2 and the presence of C–H. . .O hydrogen bonds,3 such that the substituents are directed away from the cavity of 1. Indeed, approaches that utilize supramolecular hosts to promote alignment of olefinic bonds in the crystalline state, for conducting [2⫹2] photochemical reactions, for example, are rare [10], and such observations suggest that similar complexes based upon 1 may provide a route to achieving this goal. CONCLUSION In conclusion, we have demonstrated the ability of 4-vinyl-pyridine to serve as a supramolecular extender of 1 in the solid state in the formation of a six-component host– guest complex. The vinyl groups of 2, in contrast to 3, adopt a parallel orientation, which suggests that these and related systems based upon 1 may be exploited for aligning carbon– carbon double bonds in the crystalline state. REFERENCES 1. 2. 3. 4. 5.
(a) L.R. MacGillivray and J.L. Atwood, J. Am. Chem. Soc. 119, 6931 (1997); (b) L.R. MacGillivray and J.L. Atwood, Chem. Commun., 181 (1999). R.K. Juneja, K.D. Robinson, C.P. Johnson, and J.L. Atwood, J. Am. Chem. Soc. 115, 3818 (1993). D.M. Rudkevich, G. Hilmersson, and J. Rebek, Jr., J. Am. Chem. Soc. 120, 12216 (1998). Y. Aoyama, K. Endo, T. Anzai, Y. Yamaguchi, T. Sawaki, K. Kobayashi, N. Kanehisa, H. Hashimoto, Y. Kai, and H. Masuda, J. Am. Chem. Soc. 118, 5562 (1996). G.W. Coates, A.R. Dunn, L.M. Henling, J.W. Ziller, E.B. Lobkovsky, and R.H. Grubbs, J. Am. Chem. Soc. 120, 3641 (1998).
3 Further studies are underway to delineate those factors which promote alignment of olefinic bonds in these and similar systems based upon 1.
Vol. 2, No. 1
6.
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53
D.J. Cram, S. Karbach, H.-E. Kim, C.B. Knobler, E.F. Maverick, J.L. Ericson, and R.C. Helgeson, J. Am. Chem. Soc. 110, 2229 (1988). 7. G.M. Sheldrick, Acta. Crystallogr. A46, 467 (1990). 8. G.M. Sheldrick, SHELXL93, University of Go¨ttingen, Go¨ttingen, Germany (1993). 9. L.J. Barbour, RES2INS, University of Missouri–Columbia, Columbia, Missouri, USA (1997). 10. F. Toda, Top. Curr. Chem. 149, 211 (1988).