Determining the Recruiting Rate of Spontaneously Blinking Rhodamines by Density Functional Calculations

A recruiting rate (krc) of 0.1–5 s–1 has been proposed as the criterion for super-resolution spontaneously blinking rhodamines. Accurate prediction of the recruiting rate (krc) of rhodamines is very important for developing spontaneously blinking rhodamines. However, as far as we know, there is no reliable theoretical method to predict the krc. Herein, we meticulously investigated the effect of intermolecular hydrogen bonds on the spirocyclization reactions of rhodamines. Moreover, a theoretical descriptor (ΔEC–T) was proposed to reliably assess the krc. ΔEC–T quantified the ring-opening energy barrier of spirocyclization reactions. A robust linear correlation was established between theoretical ΔEC–T values and experimentally krc values. Based on this correlation, we designed and screened five spontaneously blinking sulfonamide rhodamine dyes with optimized krc values. We expected that these findings could enable the targeted design of spontaneously blinking rhodamines.