DNA-flavonoid pH sensitive host–guest mechanism to sense fluoride ions and construction of molecular logic gates

Abstract

A fisetin derivative, 2-(3,4-diethoxyphenyl)-3-hydroxy-4H-benzo[h]chromen-4-one (DEPHBC), binds to the minor groove of DNA-duplex unlike its intercalating precursor. DEPHBC shows efficient excited state intramolecular proton transfer (ESIPT) on binding to the DNA-groove due to facilitation of intramolecular hydrogen bonding. The enhanced tautomer fluorescence of DEPHBC is used to sense fluoride ions (F−) very effectively at physiological pH. The sensibility is found to be significantly affected on minor alteration in the pH of the environment. Moreover, the results were used to fabricate DNA-based molecular logic devices using the threshold fluorescence yields for the ON and OFF signals. An IMPLICATION logic gate is constructed using acid and F− ions while the DNA and F− ion inputs form an INHIBIT logic gate.