Dynamic Equilibrium of a Supramolecular Dimeric Rhomboid and Trimeric Hexagon and Determination of Its Thermodynamic Constants
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- Takuya Yamamoto
- Contribution from the Department of Chemistry, University of Utah, 315 South 1400 East, Salt Lake City, Utah 84112
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- Atta M. Arif
- Contribution from the Department of Chemistry, University of Utah, 315 South 1400 East, Salt Lake City, Utah 84112
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- Peter J. Stang
- Contribution from the Department of Chemistry, University of Utah, 315 South 1400 East, Salt Lake City, Utah 84112
書誌事項
- 公開日
- 2003-09-13
- DOI
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- 10.1021/ja0302984
- 公開者
- American Chemical Society (ACS)
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説明
A supramolecular dimeric rhomboid and its trimeric counterpart, a hexagon, are generated by design via the directional bonding methodology of self-assembly. The different-sized supramolecular macrocycles formed by Pt-coordination undergo a concentration- and temperature-dependent dynamic equilibrium. The two structures are characterized by multinuclear NMR and ESI-MS. Extensive study of the dynamic equilibrium of the two species in solution is performed to obtain its thermodynamic properties. By varying the ionic strength, mu, of the solutions, the true thermodynamic equilibrium constant, K, is determined at each experimental temperature (K(253) = 36 +/- 7, K(273) = 18 +/- 6, K(293) = 10 +/- 3, K(313) = 9 +/- 2, K(333) = 5 +/- 2, and K(353) = 3.0 +/- 0.2). By applying these values of true K at the respective temperatures to the van't Hoff equation extended with the entropy term, the standard enthalpy and entropy changes are determined for the equilibrium: with Delta H degrees = -18 +/- 1 kJ mol(-1) and Delta S degrees = -43 +/- 4 J mol(-1) K(-1), respectively, for the forward reaction (rhomboid to hexagon) of the equilibrium. The rhomboid is selectively crystallized, and its crystal structure is determined by X-ray diffraction. The structure reveals a significant amount of porosity as well as distortion of the rhomboid from planarity, leading to channels that can be observed from two viewing positions of the packing.
収録刊行物
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- Journal of the American Chemical Society
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Journal of the American Chemical Society 125 (40), 12309-12317, 2003-09-13
American Chemical Society (ACS)
