A theoretical study on magnesium ion-selective two-photon fluorescent probe based on benzo [h] chromene derivatives

The geometrical structure, electronic structure, and one-photon absorption (OPA) properties of a series of magnesium ion (Mg2+)-selective fluorescent probes based on benzo [h] chromene derivatives have been theoretically studied by using density functional theory (DFT) method and Zerner's intermediate neglect of differential overlap (ZINDO) methods. Their two-photon absorption (TPA) properties are also calculated by using the method of ZINDO/sum-over-states. Results show that all studied probe molecules exhibit large TPA cross-section (delta(max)) in response to Mg2+ in 700- to 1,200-nm range. Furthermore, the delta(max) can be greatly enhanced by introducing acceptor groups to the lateral side of benzo [h] chromene. And that probes with stronger acceptor group show larger delta(max) and result in 70-fold enhancing when coordinate with Mg2+. Significantly, probe molecules with good cell permeability were also studied by replacing the hydrogen group with acetoxymethyl ester, but delta(max) changed slightly. These results shed light into the design strategy of efficient TP fluorescent probes with large delta(max) and good cell permeability for Mg2+ sensing in living systems.