A ring‐controlled fluorescent platform for visualizing polymer degradation

Abstract

The creation of a new photoluminescent platform to study their photo physics and further applications is important in the fields of chemistry, material, physics, etc. In this work, we developed benzene-based fluorophores generated by chemical reactions on conjugate acceptor precursors. Their optical properties have been studied, and the large Stokes shifts, high molar extinction coefficients and quantum yields have been revealed. The starting precursors containing bis-intercalated vinyl thioester shows no luminescence, which is turned on by the chemically triggered cyclization. From spectroscopic, crystallographic, and computational studies, cyclization-induced emission enhancement is proposed as a mean to explain the photoluminescent performances, a principle extended in the substituent incorporated fluorophores. Furthermore, they were applied to the chemically triggered degradation of a polymer and achieved visual tracking, quantifying, and downcycling of the processes. The method for designing and developing series fluorophores and visually tracking polymer degradation represents a new photoluminescent platform, allowing its further applications.

Fluorometric detection of volatile amines using an indanonalkene platform

“…2), the HOMO-LUMO gap of CA-NH 2 was found to be 4.35 eV while that of CA-SCH 3 was 3.93 eV, which matched the experimental blue shift in absorbance. As reported in our previous work, 28 the fluorescence quenching due to vibrational energy loss from the bis-vinylogous thioester of CA-SCH 3 accounted for the initial state of the probe. When the thiol group was substituted by the amine, the quenching factor was diminished which truned on the photoluminescence output.…”

“…Previously, we established a photoluminescent platform based on indanonalkene luminogens (Scheme 1A). 28,29 On this basis, we employed CA-SCH 3 , an indanonalkene molecule containing a bis-vinylogous thioester group, as an amine receptor for the fluorescence detection of volatile amines via aminethiol scrambling (Scheme 1B). [30][31][32] As such, the luminescent precursor CA-SCH 3 was turned on in the presence of ammonia in both solution and solid states to generate the luminophore CA-NH 2 , exhibiting a strong green emission (Scheme 1B).…”

Visualizing Drug Release from a Stimuli-Responsive Soft Material Based on Amine–Thiol Displacement

“…For the amine coupled luminogens, the positive charge on the amine(s) can be stabilized (Figure B). It was proposed that the bis-vinylogous thioesters substituents, i.e., 2RS– (R represents alkyl groups), resulted in excited state energy loss of CA most probably through free vibration or rotation, thus quenching the fluorescence through energy internal conversion after excitation . The displacement of bis-vinylogous thioesters by electron-rich amino groups reduces the quenching and allows the energy from the excited state to transfer to the ground state by a radiative transition (Figure B).…”

“…It was proposed that the bisvinylogous thioesters substituents, i.e., 2RS− (R represents alkyl groups), resulted in excited state energy loss of CA most probably through free vibration or rotation, thus quenching the fluorescence through energy internal conversion after excitation. 30 The displacement of bis-vinylogous thioesters by electron-rich amino groups reduces the quenching and allows the energy from the excited state to transfer to the ground state by a radiative transition (Figure 3B). Noticeably, with two amine scrambled fluorophores D/G or replacement of one thiol with oxygen such as cyclic E, the fluorophores required higher excitation energy and emitted stronger fluorescence (Figure 3B and Table 1).…”

“…Previously, we developed photoluminogens, which worked in an organic medium with/without catalyst or alkaline conditions, for tracking macroscopic fabrication of soft materials or chemosensing. − However, the photoluminecent mechanism remains underdeveloped, limiting additional application. With this research, we explored the indanonalkene photoluminescent platform, investigated the optical properties and proposed an optical mechanism involving amine–thiol scrambling with CA to generate a range of diverse fluorophores (Scheme ).…”