The importance of the modular structure ‘fluor-spacer-amine ’is pointed out for the design of fluorescent molecular sensors for pH according to the principle of photoinduced electron transfer (PET). Anthracen-9-yl methylamines (24) and some azacrown ether analogues (15 and 23) are examined in this context. They show pH-dependent fluorescence quantum yields describable by eqn. (5) while all other electronic spectral parameters remain essentially pH-invariant. The range of pKa values of these sensors are understandable in terms of macrocyclic effects and the transmission of electric fields across the anthracene short axis. Phase-shift fluorometric determination of the fluorescence lifetimes of these sensors allows the calculation of the rate constant of PET in their proton-free form to be 1010–1011 s–1, with the diamines 23 and 24b exhibiting the faster rates.
Bissell, Richard A. ; Calle, Emilio ; de Silva, Amilra Prasanna ; De Silva, Saliya A. ; Gunaratne, H.Q.Nimal ; et. al. Luminescence and charge transfer. II. Aminomethyl anthracene derivatives as fluorescent PET (Photoinduced Electron Transfer) sensors for Protons. In: Royal Society of Chemistry. Journal: Perkin Transactions 2, Vol. 2, no. 9, p. 1559 (1992)
