Polarity-Driven Isomerization of a Hydroxynaphthalimide-Containing Spiropyran at Room Temperature

Abstract

Design of spiropyrans showing spontaneous isomerization driven by the polarity of solvents is an important consideration for the synthesis of optical sensory materials. Although some spiropyrans undergo polarity-driven isomerization, they must be heated owing to the high activation energy required for isomerization. In this study, we describe that a spiropyran containing a hydroxynaphthalimide unit (1) exhibits a polarity-driven isomerization at room temperature. It exists as a colorless spirocyclic (SP) form in less polar solvents but is isomerized to a colored merocyanine (MC) form in polar solvents. The equilibrium amount of the MC form increases with an increase in the polarity of solvents. The MC form involves two resonance structuresthe quinoidal and zwitterionic forms. In polar media, the zwitterionic form dominates mainly owing to solvation by polar molecules. Solvation stabilizes the negative charge of the zwitterionic form and decreases its ground state energy, thereby enhancing SP → MC isomerization. The SP ⇌ MC isomerization terminates within barely 30 s even at room temperature because the naphthol moiety with high π-electron density lowers the activation energy for the rate-determining rotational step.

Multiparameter Assessment of Foam Cell Formation Progression Using a Dual-Color Switchable Fluorescence Probe

“…Stimuli involving pH and polarity can initiate this isomerization. , Under nonpolar conditions, spiropyran compounds prefer the ring-closed form, while in polar conditions, they prefer the ring-opened form. An acidic environment can induce the protonation reactions of spiropyran compounds, leading to a more stable ring-opened form. , To obtain the dual responses to both polarity and pH, the benzospiropyran-julolidine derivative-based probe BSJD was designed in this work. Both the polarity and pH can reversibly adjust the ring-closed and ring-opened forms of BSJD (Figure c), and the probe fluorescence changes induced by them are synchronous with the dissimilarities of lysosomes and LDs, that is, lysosomes and LDs can be discriminated by either polarity or pH; enhanced discrimination will be obtained when the two are used together.…”

A novel fluorescence probe for simultaneous detection of mitochondrial viscosity in hepatic ischemia reperfusion injury models

“…31,32 Vinyl linked to naphthalimide derivatives through s-bonds, functions as a viscositydependent cohort, allowing PN to signal variations in viscosity. 33,34 A near-infrared with a large stroke shi (190 nm) uorescent probe, PN, was successfully prepared and applied for bioimaging. In settings with low or non-viscous characteristics, donor cohort freely rotates around C-C bond, leading to excited state non-radiative quenching.…”