Development of Aldehyde-Based Fluorescent Probes for Highly Selective Recognition of 1,3-Diaminopropane

The 1,1'-bi-2-naphthol (BINOL)-based aldehydes 5 and 6 are synthesized. It is found that 1,3-diaminopropane (DAP) can greatly enhance the fluorescence of these compounds in methanol, but other monoamines and diamines cause much smaller fluorescent response under the same conditions. H-1 NMR analyses show that 6 reacts with DAP to form a six-membered ring aminal as the major product but other amines and diamines can only generate the corresponding imines. A molecular modelling study indicates that formation of the aminal product can inhibit the photoinduced electron transfer of the BINOL-based aldehydes, which leads to the observed selective fluorescence enhancement. These molecules represent the first highly selective fluorescent probes for the recognition of DAP and their further development should be useful for the study of the biological functions of the polyamines.