Selective recognition of fluoride ions through fluorimetric and colorimetric response of a first mesitylene based dipodal sensor 15employing thiosemicarbazones

A new dipodal chromo-fluorogenic anion sensor (2Z,2′Z)-2,2′-(((((2,4,6-trimethyl-1,3-phenylene)bis-(methyl-ene))bis-(oxy))bis(2,1-phenylene))bis(methanylylidene))bis(N-methylhydrazinecarbothio-amide) has been synthesized and characterized for the detection of F− ion in DMSO. The sensor has proven to be highly selective and sensitive to F− ion, moreover it can act as naked eye chromogenic sensor. The mechanism involved in the detection of fluoride ion is the deprotonation of the -NH groups, which was confirmed by using TBAOH. The pre-organization of the dipodal receptor provides chelating H-bonds with the spherical F− ion. These strong H-bonding interactions result in fast deprotonation of the sensor, producing an optical response. Employing only a weak fluorescence capability of the imine groups, 1 behaves as a fluorogenic sensor by exhibiting fluorescence enhancement at λex 438 nm upon addition of F− ions.

Graphical abstractA new dipodal chromo-fluorogenic anion sensor (2Z,2′Z)-2,2′-(((((2,4,6-trimethyl-1,3-phenylene)bis-(methyl-ene))bis-(oxy))bis(2,1-phenylene))bis(met-hanylylidene))-bis(N-methylhydrazinecarbothio-amide) has been synthesized and characterized for the detection of F− ion in DMSO. The sensor has proven to be highly selective and sensitive on F− ion, moreover it can act as naked eye chromogenic sensor. The mechanism involved in the detection of fluoride ion is the deprotonation of the -NH groups, which was confirmed by using TBAOH. The pre-organization of the dipodal receptor provides chelating H-bonds with the spherical F− ion. These strong H-bonding interactions result in fast deprotonation of the sensor, producing an optical response. Employing only a weak fluorescence capability of the imine groups, sensor 1 behaves as a fluorogenic sensor by exhibiting fluorescence enhancement at λex 438 nm upon addition of F− ions.Download full-size image