TY - JOUR
T1 - [C-H···O] interactions as a control element in supramolecular complexes
T2 - Experimental and theoretical evaluation of receptor affinities for the binding of bipyridinium-based guests by catenated hosts
AU - Houk, K. N.
AU - Menzer, Stephan
AU - Newton, Simon P.
AU - Raymo, Françisco M.
AU - Stoddart, J. Fraser
AU - Williams, David J.
PY - 1999/2/24
Y1 - 1999/2/24
N2 - Macrocyclic receptors incorporating two facing π-electron-rich aromatic surfaces, held at a distance of approximately 7 Å by polyether spacers, bind bipyridinium-based guests. This recognition motif, which is dictated by π- π stacking and [C-H···O] hydrogen-bonding interactions, has led to the development of efficient template-directed syntheses of mechanically interlocked molecules, such as catenanes and rotaxanes. By employing a supramolecularly assisted synthetic methodology based on these interactions, we have self-assembled two novel [3]catenanes, each incorporating two 1,5- dioxynaphtho-38-crown-10 components and one bipyridinium-based tetracationic cyclophane component. Single-crystal X-ray analyses of these [3]catenanes revealed that they possess internal cavities bounded on two opposite sites by π-electron-rich 1,5-dioxynaphthalene units separated by a distance of approximately 7-8 Å. Despite the presence of apparently ideal 'binding pockets', these mechanically interlocked compounds steadfastly refuse to bind bipyridinium-based guests in solution, as demonstrated by both 1H NMR and UV-vis spectroscopy. AMBER* and HF/321G calculations on appropriate models show that the absence of [C-H···O] hydrogen-bonding interactions is responsible for the instability of these geometrically ideal complexes. The [C-H···O] bond appears to be quantitatively much more important than π- π stacking interactions in these particular systems.
AB - Macrocyclic receptors incorporating two facing π-electron-rich aromatic surfaces, held at a distance of approximately 7 Å by polyether spacers, bind bipyridinium-based guests. This recognition motif, which is dictated by π- π stacking and [C-H···O] hydrogen-bonding interactions, has led to the development of efficient template-directed syntheses of mechanically interlocked molecules, such as catenanes and rotaxanes. By employing a supramolecularly assisted synthetic methodology based on these interactions, we have self-assembled two novel [3]catenanes, each incorporating two 1,5- dioxynaphtho-38-crown-10 components and one bipyridinium-based tetracationic cyclophane component. Single-crystal X-ray analyses of these [3]catenanes revealed that they possess internal cavities bounded on two opposite sites by π-electron-rich 1,5-dioxynaphthalene units separated by a distance of approximately 7-8 Å. Despite the presence of apparently ideal 'binding pockets', these mechanically interlocked compounds steadfastly refuse to bind bipyridinium-based guests in solution, as demonstrated by both 1H NMR and UV-vis spectroscopy. AMBER* and HF/321G calculations on appropriate models show that the absence of [C-H···O] hydrogen-bonding interactions is responsible for the instability of these geometrically ideal complexes. The [C-H···O] bond appears to be quantitatively much more important than π- π stacking interactions in these particular systems.
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U2 - 10.1021/ja982748b
DO - 10.1021/ja982748b
M3 - Article
AN - SCOPUS:0033599295
VL - 121
SP - 1479
EP - 1487
JO - Journal of the American Chemical Society
JF - Journal of the American Chemical Society
SN - 0002-7863
IS - 7
ER -