F−- and H+-triggered reversible supramolecular self-assembly/disassembly probed by a fluorescent Ru2+ complex

A new strategy was proposed to monitor transition behavior involved in F−- and H+-triggered reversible supramolecular self-assembly/disassembly by using a Ru2+ complex (Ru(Phen)32+) as a fluorescent probe. N,N-Dibenzoyl-L-cystine (DBC) was used as gelator to form supramolecular gels. Fluorescent images of the fluorescent-labelled DBC gels indicate that Ru(Phen)32+ is dispersed in the gapping place of three-dimensional networks formed by fibrillar DBC aggregates. In a certain range of F− concentrations, it was found that there is a good linear relationship (R2 = 0.999) between F− concentrations and the fluorescent intensity difference between the DBC gels and corresponding solutions. The phase transition temperature of DBC gels is increased with a decrease of F− concentration. Interestingly, the addition of H+ to disassembled systems results in reassembly of DBC. The rate of H+-triggered reassembly is increased with an increase of the H+ concentration. SEM images of reassembled aggregates show no substantial difference in comparison with that of original DBC aggregates, indicating that the F−- and H+-triggered disassembly/reassembly is completely reversible. Time-dependent fluorescent spectra indicate that monitoring self-assembly/disassembly transitions by using the Ru2+ complex as a fluorescent probe is a fast and precise strategy.