Stepwise structural and fluorescent colour conversion in rhodamine analogues based on light and acid stimulations

Abstract

The research and development of multi-stimuli, multi-responsive molecules have attracted considerable attention in chemistry, biology, and material science. Herein, we propose a multi-stimuli-responsive multi-fluorescence system in a single molecule.

Spirocyclic rhodamine B benzoisothiazole derivative: a multi-stimuli fluorescent switch manifesting ethanol-responsiveness, photo responsiveness, and acidochromism

“…These spectral and color changes indicate that RHBIT isomerizes to a zwitterionic form by cleavage of the C–N bond in spironolactone resulting in an open form by a photoinduced ring-opening mechanism along with an extended conjugated structure with strong absorbance and emission intensities. 41 Moreover, the electron-withdrawing nitro group attached to the benzenoisothiazole moiety of RHBIT facilitates less conjugation into an extended conjugated structure; also chlorinated solvents like CHCl 3 and DCM have a hydrogen-bonding character; they are able to behave as H-bond donors. 42 Hence, RHBIT exhibits typical rhodamine spirolactam ring-opening behavior in the presence of acid and also under UV light illumination.…”

“…The color of the solution changed from yellow to prominent pink in deuterated CDCl 3 after short-wavelength UV illumination. From the spectral behavior, it is presumed that photoisomerization takes place from the closed ring to the open form 41 of RHBIT and a plausible mechanism for the photoinduced ring-opening process is proposed in Scheme 2 . Variation of pH, quantum yield, and lifetime decay in the above-mentioned solvents, studied before and after UV irradiation, disclosed that pH in CHCl 3 , DCM, and DMSO was reduced to an acidic range (3.3–5.5) ( Table 1 ), which as mentioned before is evocative of strong protonation of the spirocyclic form of RHBIT, which further transforms to an open form in an acidic environment.…”

Structural, DFT calculations and photophysical and photochemical characteristics of 1-((E)-2-phenylethenyl)-2-(4-(2-((E)-2-phenylethenyl) phenoxy) butoxy) benzene (PPPBB)

“…Assuming the ground and excited states dipole moments are parallel, the values of 𝜇 𝑔 and 𝜇 𝑒 can be obtained using Eqs. ( 15) and ( 16) [60,61].…”

A double-spiro ring-structured mechanophore with dual-signal mechanochromism and multistate mechanochemical behavior: non-sequential ring-opening and multimodal analysis

“…Moreover, a new issue arises: how to assign the complicated absorption peaks? Tanioka et al 56 have reported the unique photochemistry of ABPX that can only transform to the ABPX OC form under UV light irradiation and displays three absorption peaks at about 450 nm, 480 nm, and 510 nm in CHCl 3 solution. The accepted sequential acidichromism shows the main absorption peaks at about 530 nm, 500 nm, and 465 nm for monocationic ABPX and about 600 nm, 550 nm, and 515 nm for dicationic ABPX in CHCl 3 solution.…”