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In recent times fluorescence-quenching-based detection of
nitroaromatics, which are the chemical signatures of many explosives,
is gaining momentum in chemical sensing. Various fluorescent
compounds can prove to be efficient tools for such sensing.
Conjugated polymers are used as redox sensors for nitroaromatic
detection as they are electron donors [40-42]. Porous polyethynyl
compounds have been investigated as potential fluorescent sensors
for nitroaromatics. Porous polymers are better sensors than simple
nonporous analogues as the porous nature of the polymers produces
a large free volume in the structure, which imparts permeability
and allows small nitroaromatics vapor to penetrate quickly into the
polymer. Thus, combining all these properties of compounds used
for nitroaromatic sensing, discrete supramolecular assemblies have
been designed.
9.4.1
Nitroaromatic Sensing by the Macrocyclic
Rectangle 12
π
Ethynyl functionality was introduced to make the final
-electron-
rich metallocycle
, which indeed shows interesting fluorescence
behavior. On excitation at 400 nm, macrocycle
12
12
showed strong
emission band at 440 nm in CHCl
medium. The fluorescence
intensity at 440 nm was quenched efficiently upon gradual addition
of TNT solutions having concentrations on the order of 10
3
-5
M (Fig.
9.19). Analysis of the normalized fluorescence intensity (
I
/
I
) as
0
Figure 9.19
Quenching of emission intensity of
12
[5
×
10
-5
M in CHCl
] on
3
gradual increase of quencher TNT (in CHCl
) concentration.
3
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