Multipoint recognition of catecholamines by hydrindacene-based receptors accompanied by the complexation-induced conformational switching |
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Authors: | Kawai Hidetoshi Katoono Ryo Fujiwara Kenshu Tsuji Takashi Suzuki Takanori |
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Institution: | Division of Chemistry, Graduate School of Science, Hokkaido University, Sapporo 060-0810, Japan. kawai@sci.hokudai.ac.jp |
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Abstract: | The molecular recognition of catecholamines by hydrindacene-based receptors 1 and 2, as well as the durene-based receptor 3, and the guest-induced conformational changes are reported. These receptors selectively bind adrenaline and dopamine salts through the guests' ammonium group and 3-hydroxyl group on the aromatic ring. In the case of adrenaline, an additional hydrogen bond with a benzylic hydroxyl group is formed. In 2 % CD3CN/CDCl3, the association constants are of the order of 10(4) M(-1), which is much larger than with guests without the 3-hydroxyl groups (10(3) M(-1)). The two amide groups of receptor 1 can rotate freely around the C(aromatic)--C(amide) bond, whereas the tert-amide in 2 changes between two stable conformations at a slow enough rate to allow detection by (1)H NMR spectroscopy. In the absence of a guest molecule, the syn-conformer is less stable than the anti-conformer. On complex formation with adrenaline, the syn-conformer becomes dominant due to an intramolecular dipole-reversal effect in addition to multipoint hydrogen bonding. |
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Keywords: | adrenalines amides atropisomerism dopamines molecular recognition receptors |
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