Co-effects of the electron transfer and intersystem crossing on the photophysics of a phenothiazine based Hg2+ sensor

Abstract In the field of fluorescence sensing for metal ions, coordination between the sensor and the analyte is always observed. The formations of organometallic compounds generally induce significant changes to the fluorescence spectra. However, the underlying detecting mechanism always remains uncovered. From the view point of orbital interaction between Hg2+ and a newly designed sensor P, the fluorescence quenching detection mechanism of P is comprehensively investigated. The whole photophysical process of the organometallic compound formed by P and Hg2+ is fully analyzed. Strong orbital coupling between the sensor P and Hg2+ is observed, which opens up two non-emissive channels, namely, the intramolecular electron transfer and intersystem crossing. The co-effect of the two channels induced high degree of fluorescence quenching, which makes P a good candidate in the fabricating of Hg2+ sensor. This mechanism is insightful and intrinsically different from the previously proposed mechanism, which would help to understand the photophysics of the organometallic compounds and provide a piece of guidance for the design of Hg2+ sensors.