Manganese-induced triplet blinking and photobleaching of single molecule cyanine dyes

Irradiation of solutions of the cyanine dyes Cy3, Cy3B, and Cy5 in the presence of Mn²⁺ causes an increase in the yield of formation of the triplet state of the dye. This results in increased photobleaching and triplet blinking. Experiments with other divalent ions and paramagnetic molecules suggest that the enhancement in the intersystem-crossing rate is related to the paramagnetic nature of the Mn²⁺ cation. The results are consistent with a model in which the formation of a weak collisional complex between the dye and the ion results in mixing of the singlet and triplet states of the dye. These findings are particularly significant in single-molecule spectroscopy and super-resolution imaging methods, in which photobleaching and blinking play an important role. Triplet blinking: Controlling the triplet-state quantum yield, lifetime, and deactivation pathways of organic dyes is of great interest in single-molecule spectroscopy and super-resolution imaging. Triplet states play a central role in the photobleaching and blinking properties of fluorescent dyes. In this work, the paramagnetic ion Mn²⁺ is found to induce intersystem crossing to the triplet state in Cy3, Cy3B and Cy5, which results in increased photobleaching and triplet blinking.