ORGANIC
LETTERS
2013
Vol. 15, No. 7
1452–1455
Selective Redox-Active Molecular
Receptors for Kþ and Agþ
Karina R. Larsen,† Carsten Johnsen,† Ole Hammerich,‡ and Jan O. Jeppesen*,†
Department of Physics, Chemistry, and Pharmacy, University of Southern Denmark,
Campusvej 55, DK-5230, Odense M, Denmark, and Department of Chemistry,
University of Copenhagen, Universitetsparken 5, DK-2100 Copenhagen Ø, Denmark
Received January 18, 2013
ABSTRACT
Two new tetrathiafulvalene based receptors in which the favorable redox properties of the tetrathiafulvalene unit are coupled to either a benzo-
crown (X = O) or a dithiabenzo-crown (X = S) ether binding site were designed and synthesized as receptors for Kþ and Agþ. The receptors display
a good (Kþ, X = O) to strong (Agþ, X = S) affinity toward the cation and a high discrimination against other metal cations.
The advent of supramolecular chemistry1 has aroused
the interest of chemists of many different persuasions in the
development ofmolecularreceptorscapableofrecognizing
specific chemicalsubstrates. Redox-activereceptors2 are of
particular interest because their affinity toward different
substrates are reflected by the redox properties of the
receptor allowing supramolecular systems capable of per-
forming controlled uptake and release of substrates to be
constructed. Redox-active molecular receptors are typi-
cally designed to allow the detection of substrates by
binding-induced changes in the redox properties and are
generally being built by the covalent association of an
appropriate binding site and a redox-active unit. In the
context of redox-active receptors, tetrathiafulvalene3
(TTF) constitutes a unique building block on account of
the fact that it can exist in three stable redox states (i.e., as
neutral TTF, as the radical cation TTF•þ, and the dica-
tionic TTF2þ) and TTF and its derivatives have been used
as the redox-active unit in a number of anion4 and cation5
responsive receptors. A majority of the cation responsive
receptors involve a binding site made of a crown-ether
cavity or a coordinating acyclic ether moiety.6 Although
a huge amount of work has been devoted to create TTF
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† University of Southern Denmark.
‡ University of Copenhagen.
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r
10.1021/ol303308e
Published on Web 03/19/2013
2013 American Chemical Society