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Tweezer‐like Complexes of Crown Ethers with Divalent Metals: Probing Cation‐Size‐Dependent Conformations by Vibrational Spectroscopy in the Gas Phase

Tweezer‐like Complexes of Crown Ethers with Divalent Metals: Probing Cation‐Size‐Dependent... Crown ethers constitute central building blocks for the synthesis of molecular tweezers capable of trapping cationic species. In this study, isolated ternary complexes comprising two (18)crown‐6 (18c6) ether molecules and one divalent cation of varying size (Cu2+, Ca2+, Ba2+) are investigated by means of laser vibrational action spectroscopy and computations. In the ternary (18c6)2–Cu2+ complex, one of the crown units folds tightly around the cation, while the second crown ether unit binds peripherally. Such asymmetrical binding manifests itself as a bimodal splitting of the vibrational bands measured for the complex. The size of the cation in the Ca2+ and Ba2+ complexes leads to a progressively more symmetrical coordination of the two crown ether molecules with the metal. In particular, in the spectrum of the (18c6)2–Ba2+ complex, the two components of the vibrational bands are merged into single‐maximum envelopes. This is consistent with a C2 arrangement predicted by the computation, in which the cation coordinates with the two crown ether units in a fully symmetrical way. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png ChemPlusChem Wiley

Tweezer‐like Complexes of Crown Ethers with Divalent Metals: Probing Cation‐Size‐Dependent Conformations by Vibrational Spectroscopy in the Gas Phase

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References (37)

Publisher
Wiley
Copyright
Copyright © 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim
ISSN
2192-6506
eISSN
2192-6506
DOI
10.1002/cplu.201100044
Publisher site
See Article on Publisher Site

Abstract

Crown ethers constitute central building blocks for the synthesis of molecular tweezers capable of trapping cationic species. In this study, isolated ternary complexes comprising two (18)crown‐6 (18c6) ether molecules and one divalent cation of varying size (Cu2+, Ca2+, Ba2+) are investigated by means of laser vibrational action spectroscopy and computations. In the ternary (18c6)2–Cu2+ complex, one of the crown units folds tightly around the cation, while the second crown ether unit binds peripherally. Such asymmetrical binding manifests itself as a bimodal splitting of the vibrational bands measured for the complex. The size of the cation in the Ca2+ and Ba2+ complexes leads to a progressively more symmetrical coordination of the two crown ether molecules with the metal. In particular, in the spectrum of the (18c6)2–Ba2+ complex, the two components of the vibrational bands are merged into single‐maximum envelopes. This is consistent with a C2 arrangement predicted by the computation, in which the cation coordinates with the two crown ether units in a fully symmetrical way.

Journal

ChemPlusChemWiley

Published: Feb 1, 2012

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