The water soluble NiII complexes of the cyclam derivatives with 1,3-benzodioxole and 1,2,3-trimethoxybenzene display the fluorescent emission typical of the covalently linked fluorophores, which results from a charge transfer excited state. On oxidation to NiIII, the fluorescence is completely quenched due to the occurrence of an electron transfer (eT) process from the excited fluorogenic fragment FI* to the oxidized metal. Thus, fluorescence can be switched off/on at will, for several cycles, by consecutively oxidizing and reducing the metal center, in controlled potential electrolysis experiments both in acetonitrile and in aqueous 0.1 M HCIO4. Occurrence of an eT process from FI* to NiIII ultimately depends upon the easy oxidation of FI to FI+, whereas failure of the occurrence of an eT process from NiII to FI* has to be ascribed to the particular resistance of FI fragments to the reduction.
Water soluble molecular switches of fluorescence based on the NiIII/NiII redox change
Michele Zema
2002-01-01
Abstract
The water soluble NiII complexes of the cyclam derivatives with 1,3-benzodioxole and 1,2,3-trimethoxybenzene display the fluorescent emission typical of the covalently linked fluorophores, which results from a charge transfer excited state. On oxidation to NiIII, the fluorescence is completely quenched due to the occurrence of an electron transfer (eT) process from the excited fluorogenic fragment FI* to the oxidized metal. Thus, fluorescence can be switched off/on at will, for several cycles, by consecutively oxidizing and reducing the metal center, in controlled potential electrolysis experiments both in acetonitrile and in aqueous 0.1 M HCIO4. Occurrence of an eT process from FI* to NiIII ultimately depends upon the easy oxidation of FI to FI+, whereas failure of the occurrence of an eT process from NiII to FI* has to be ascribed to the particular resistance of FI fragments to the reduction.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
