Chemistry Reference
In-Depth Information
SCHEME 11.9
The design and synthesis of “click” CD-containing Cd
2
+
sensor molecules.
(Adapted from ref. 29.)
“click” reaction not only provides a stable linker between the CD and the chelation
functionality, but also contributed the triazole moiety as additional chelation struc-
ture for Cd
2
+
. The high inclusion potential of
-CD to adamantyl group allows the
introduction of a carboxylic group, which contributed to the formation of an even
stronger binding model. Due to its satisfactory solubility and high sensing ability
towards Cd
2
+
, these two fluorescence sensor molecules may have wide application
in clinical diagnosis and environmental monitoring.
The presence of pesticide residues in farm products has been linked to the etiology
of some very devastating diseases, such as cancer and Parkinson's disease [30], which
make the sensitive detection of pesticide residues a critical issue for food safety. To
address this issue, Mallard-Favier et al. developed a fluorescent tripod detection sys-
tem for pesticides such as
-cypermethrin, pendimethalin, thiram, and imidacloprid.
Through microwave-assisted “click” chemistry, they prepared a peracetylated CD
trimer bearing three 1,2,3-triazole linkers, which exhibited two absorption maxima
at 277 nm and 326 nm. They found fluorescence characteristic emissions at 315
nm and 329 nm at an excitation at 227 nm. When complexed with pesticide such as
pendimethalin at increasing concentrations, the fluorescence intensity decreased until
extinction [31]. The absence of wavelength shift excluded the correlations between
the aromatic core of the trimer and the pesticide due to
stacking interactions.
The authors ascribe the quenching of fluorescence to the inclusion of the pesticide
molecules into the CD annulus.
Fujimoto et al. recently developed a group of fluorescent sensors for the detec-
tion of unsaturated fatty acids (Scheme 11.10) [32]. Inspired by the structures of
immunoglobulin antibodies, the sensors are designed to be a pair of complementary-
sequenced oligonucleotides (ODN) possessing the pyrene and guest-binding moi-
eties. Because fatty acids can form 1:2 complexes with CD, one fatty acid can
promote the hybridization of ODNs resulting in the pyrene-emission switching from
monomer to excimer. To implement their design, they first examined the fluorescent
transformation caused by bisadamantyl guest molecule, which can complex with two
-
-CD.
The pyrene-emission switching took place from 379 nm (monomer emission) to
500 nm (excimer emission) and an isoemissive point at 446 nm. Similar emission
-CDs due to the well-known high affinity between adamantyl groups with
Search WWH ::
Custom Search