The switching of a Rhenium(I) complex from turn-off to turn-on sensor system through protein binding

Abstract

New luminescent Re(I)-polypyridine complexes (1a and 1b) containing an amide-pyridine pendant carrying the N-H group have been synthesized, characterized and used as an anion sensor by utilizing UV-visible and luminescence titration methods. Both the complexes exhibit luminescence quenching upon addition of anions and the binding constants are in the range of 10(3)-10(5) M-1. Thus these probes act as a turn off sensor for anions in acetonitrile and show a color change from colorless to yellow on the addition of the fluoride ion. This turn-off sensor becomes a turn-on sensor for F- in the presence of bovine serum albumin (BSA) which serves as a platform for the sensor design. The study of the interaction between Re(I) complexes (1a and 1b) and BSA in buffer (pH = 7.4) shows that 1a and 1b bind BSA strongly with a binding constant of 10(4) M-1.