Syntheses of Water-soluble Silver(II)-Phthalocyanines toward Optical Sensing for Thiol Detection

Water-soluble silver(II)-phthalocyanine complexes (AgPcs), tetrakis{4-(N-alkylpyridinium)thio}phthalocyaninato silver(II) tetrafluoroborate, [Ag(tRpySpc)](BF4)4, (R = Me and Et), have been synthesized for the first time by quaternization of pyridyl groups of tetrakis(4-pyridylthio)phthalocyaninato silver(II) by using Meerwein reagents and characterized by ESI-MS, elemental analyses, and optical absorption spectroscopy. They strongly aggregate in water although effectively disaggregate to monomeric species in the presence of appropriate surfactants. They rapidly react with thiols such as cysteine, glutathione, homocysteine, and sodium 2-sulfanylethanesulfonate with a stoichiometric ratio of 1:1 in aqueous solutions at room temperature even on the order of 0.01 mM to liberate the corresponding macrocyclic ligand, H2Pc. Since H2Pcs emit strong red fluorescence while AgIIPcs not, they can be a potent thiol-sensor.