Dicyanostilbene-based two-photon thermo-solvatochromic fluorescence probes with large two-photon absorption cross sections: Detection of solvent polarities, viscosities, and temperature

The unusually sensitive solvatochromic probes (P1 and P2) derived from 4-methyl-2,5-dicyano-4′-amino stilbene (DCS) whose emission maxima and two-photon absorption cross sections (δ) vary from 445 and 452 nm, and 5560 and 6670 GM in cyclohexane to 641 and 604 nm, and 980 and 2040 GM in DMSO, respectively are described. P1 and P2 exhibit very strong polarity-, viscosity-, and temperature-dependence of fluorescence, and can be used to detect polarities, viscosities, and temperature. P1 and P2 possess small molecule-size, wide solvatochromism (445–641 nm, 452–641 nm), large δ (980–5560 GM, 2040–6670 GM), and high fluorescence quantum yields, and are ideal two-photon fluorescence solvatochromic probes.