High-Resolution Rotational Spectroscopy of a Cyclic Ether.
The conformational landscape of crown ethers has constituted a central topic in the development of host-guest supramolecular chemistry. We report a high-resolution rotational study of a crown ether, 1,4,7,10,13-pentaoxacyclopentadecane (15-crown-5), by means of molecular beam Fourier transform microwave spectroscopy. The considerable size and the broad range of conformations allowed by the flexibility of the cyclic backbone of this ether pose important challenges to spectroscopy approaches. In this investigation, three stable rotamers of the 15-crown-5 ether have been identified and characterized through their rotational constants and centrifugal distortion coefficients. Ab initio quantum calculations at the MP2 level predict these conformers as the most stable ones for the title system and reproduce accurately their distinct structural features. The results pave the ground for an extensive survey of the conformational landscape of the 15-crown-5 and related cyclic ethers in the near term.
†Department of Physical, Chemical and Natural Systems, Universidad Pablo de Olavide, 41013 Seville, Spain.
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Gámez
†Department of Physical, Chemical and Natural Systems, Universidad Pablo de Olavide, 41013 Seville, Spain.
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Martínez-Haya
‡Grupo de Espectroscopía Molecular, Edificio Quifima, Área de Química Física, Campus Miguel Delibes, Universidad de Valladolid, 47011 Valladolid, Spain.
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Blanco
‡Grupo de Espectroscopía Molecular, Edificio Quifima, Área de Química Física, Campus Miguel Delibes, Universidad de Valladolid, 47011 Valladolid, Spain.
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López
‡Grupo de Espectroscopía Molecular, Edificio Quifima, Área de Química Física, Campus Miguel Delibes, Universidad de Valladolid, 47011 Valladolid, Spain.
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Alonso
conformers; inclusion complexes; macrocycles; molecular recognition; molecular structure