Fluorescent sensors design principles

Klymchenko AS, Demchenko AP (2002) Electrochromic modulation of excited-state intramolecular proton transfer the new principle in design of fluorescence sensors. J Am Chem Soc 124 12372-12379... 

Valeur B., Leray I., Design principles of fluorescent molecular sensors for cation recognition, Coord. Chem. Rev. 2000 205 3. 

E-3 (Figure 10.26) is the first example of an ionophoric calixarene with appended fluorophores, demonstrating the interest in this new class of fluorescent sensors. The lower rim contains two pyrene units that can form excimers in the absence of cation. Addition of alkali metal ions affects the monomer versus excimer emission. According to the same principle, E-4 was designed for the recognition of Na+ the Na+/K+ selectivity, as measured by the ratio of stability constants of the complexes, was indeed found to be 154, while the affinity for Li+ was too low to be determined. 

In Chapter 10, fluorescent pH indicators and fluorescent molecular sensors for cations, anions and neutral molecules are described, with an emphasis on design principles in regard to selectivity. 

Valeur, B. Leray, I. Design Principles of Fluorescent Molecular Sensors for Cation Recognition. Coord. Chem. Rev. 2000, 205, 3—40... 

This knowledge has been adapted to allow molecular switches to be designed into fluorescent sensors through the use of amine donor groups proximal to suitable fluorophore acceptor groups, separated by methylene bridges. This design principle was first applied to a sensory system by de Silva et al. who reported the pH sensor 77. ... 

Fluorescent PET (photoinduced electron transfer) sensors are considered to be those molecular systems where the binding of ions and other species leads to the perturbation of the competition between the de-excitation pathways of fluorescence and electron transfer. The early developments in this field are traced and the design logic of these sensors is detailed. A variety of examples drawn from different areas of chemistry are classified according to the fluorophore-spacer-receptor format and their photophysical behaviour is rationalized in terms of fluorescent PET sensor principles. Cases are pointed out where such experimental data are unavailable but desirable. During these discussions, the relevance of twisted fluorophore-receptor systems and the contrast with integrated fluorophore-receptor systems is noted. The utility of the fluorescence on-ofP phenomenon in these PET sensors for the area of molecular photoionic devices is pointed out. 

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