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

A recruiting rate (k_rc) of 0.1-5 s^-1 has been proposed as the criterion for super-resolution spontaneously blinking rhodamines. Accurate prediction of the recruiting rate (k_rc) 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 k_rc. Herein, we meticulously investigated the effect of intermolecular hydrogen bonds on the spirocyclization reactions of rhodamines. Moreover, a theoretical descriptor (ΔE_C-T) was proposed to reliably assess the k_rc. ΔE_C-T quantified the ring-opening energy barrier of spirocyclization reactions. A robust linear correlation was established between theoretical ΔE_C-T values and experimentally k_rc values. Based on this correlation, we designed and screened five spontaneously blinking sulfonamide rhodamine dyes with optimized k_rc values. We expected that these findings could enable the targeted design of spontaneously blinking rhodamines.