Calixpyrroles as Sensors:A Review
Aparna Sharma1*, Sangeeta Obrai2 and Rakesh Kumar2
Journal Title:Journal of Chemical, Biological and physical sciences
Molecules with specific binding sites serve as sensors. Calixpyrrole is one
such class, which holds a great promise in the fields of sensors, and their unique behaviour as
sensors owe to its structural flexibility. Anion binding ability of calixpyrrole has been
modified in a variety of ways. Introduction of electron-releasing and electron-withdrawing
groups at the meso- position or at ?-pyrrolic positions lead to calixpyrrole with deep
cavities and fixed walls which shows increased selectivity and modified binding effects.
Strapping of calixpyrrole is another way to modify its structural behaviour which is
responsible for its binding behaviour. Choice of strap could play a profound role not only in
increasing the intrinsic anion binding affinity of calixpyrrole, but also in modulating the
receptor anion stoichiometry, thereby modifying potentially the inherent anion binding
selectivity. Calix[n]pyrroles with extended cavities have also been synthesized. Such as
Calixbipyrrole binds bromide substantially with high affinity than calixpyrrole.
Calixpyrrole has also been used to produce anion sensors that can report the presence of
anion by means of a colour change. The medium effect on the complexation of
calixpyrrole and anion has been investigated in various solvents. Calixpyrrole has also
been used to increase the ionic conductivity of solid polymer electrolyte by anion
complexation of the metal salt. Calixpyrrole has been used to obtain optical sensors using
surface plasmon resonance technique. Composite films of cellulose acetate containing
calixpyrrole has also been reported which has potential usage in packaging, storage and
preservation. In nut shell, cailxpyrrole can be modified in a variety of ways to form
versatile sensors which can be used in variety of ways in various areas.