Synthesis, sensor activity and logic behavior of a highly water-soluble naphthalimide derivative

Herein we report on the design, synthesis and sensor activity of novel highly water-soluble 9,10-dihydro-7H-imidazo[1,2-b]benz[d,e]isoqionolin-7-one. The novel compound was configured as a “fluorophore-spacer-receptor” system. Due to the simultaneously photoinduced electron transfer and internal charge transfer, the designed fluorophore was able to act as a pH-probe via an “off-on-off” fluorescence sensing mechanism. Several logic functions (INH, XNOR, AND, XOR, NAND and OR) using acid and base as chemical inputs could be performed and combinatorial logic circuits (digital comparator and a half-adder) could be designed on the pH induced changes in spectral properties of the novel molecule. The selectivity of the pH sensor toward protons in commonly used buffer solutions and in the presence of transition metal cations (Co2+, Cu2+, Fe3+, Ni2+, Pb2+, Zn2+, Hg2+ and Ag+) was studied by monitoring the changes of its fluorescence intensity. The tested metal ions exerted a minor quenching effect (below 10%) suggesting that the synthesized compound is highly selective to the proton in the pH range between 3 and 10.