Quenching mechanism of the UO22+ excited state by phenols and related compounds in aqueous solutions

Quenching rate constants, kq, of the uranyl excited state by phenolic compounds were determined in H3PO4 1M by luminescence techniques. A plot of log kq vs. ΔG2 for the photo-induced electron transfer reaction rendered a slope value of 4.0 eV-1 which was much smaller than that predicted from the Rehm-Weller correlation (16.9 eV-1). This value is similar to those found for aromatic quenchers that fail to interact with the UO22+ ground state, and quench the uranyl luminescence through a non-radiative donor-acceptor complex formation. (author)