Applications of Fluorescent Displacement-Based ... - Jacobs University

CHAPTER 1
Introduction
A large variety of water-soluble fluorescent dyes exist and their
combination with macrocycles has been recently reviewed. [57] Among them, the
dyes exhibiting strong fluorescence and absorbing light at long wavelengths are
particularly desirable for sensing applications.
CH 3
N
N
N
CH3
O
HN
HO O
O
O
OH HO
OHO
OH
HO
HO
O
OH O
O
OH
HO
O
OH
OH
O
OH
OH
O OH
OH
OH O
O
OOH
HO
O
OH
Figure 1.3.1. The first combination between a macrocycle (β-cyclodextrin) and
an indicator dye (methyl red), covalently attached to each other, for selective
sensing of analytes (in this case adamantane carboxylic acid) via the indicator
displacement strategy. [58]
One of the original indicator displacement sensor studies involving
macrocycles is that of Ueno and coworkers where the indicator, methyl red, a
known pH indicator dye, has been attached to a β-cyclodextrin wall. [58] Addition
of the guest, in this case adamantane carboxylic acid induces a displacement or
relocation of the dye from the macrocyclic cavity to the bulk solvent, signaling
the analyte. This example has further inspired the design of similar covalently
linked macrocycle/dye sensing systems. [59] The covalent tethering of a macrocycle
to a fluorophore is advantageous for the fact that due to the local proximity, a high
concentration of the complex is insured. This may be particularly relevant under
conditions where concentrations cannot be perfectly adjusted, for instance when
working with biological samples, such as tissues or cells. However, several
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