Tailoring C-6-Substituted Coumarin Scaffolds for Novel Photophysical Properties and Stimuli-Responsive Chromism

Abstract

A judicious strategy was utilized to envision the substantial regio-positional effects of substituents on the photophysical properties of the 2H-chromen-2-one-3-benzothiazole scaffold-based push–pull framework, named 6-X-CUMs. Among them, 6-NEt 2 -CUM reveals prominent excited-state intramolecular charge transfer with a large change of dipole moment (Δμ ∼ 18.23 D), hence displaying remarkable emission solvatochromism from the green (536 nm in cyclohexane) to far-red region (714 nm in dimethyl sulfoxide) and a high-temperature sensitivity (−0.23 nm °C–1). These, together with unique basicity and acido-/vaporchromism upon acidification elucidated by NMR and photospectroscopic studies, show stark contrast to the conventional 7-NEt 2 -CUM. The new series of these tailored 6-X-CUMs represents a new dimension in tailoring the photophysical properties for the development of a promising class of multistimuli-responsive materials.

Strongly emitting, centrosymmetric, ladder-type bis-coumarins with crankshaft architecture

“…The above mentioned photophysical characteristics corresponds well with the one observed for many aminocoumarins 10,19 and aminobenzo[g]coumarins 20 and the low-energy band that is typically assigned to the intramolecular charge transfer (ICT). The emission maxima of bis-coumarins 7 (Et 2 N) and 9 (Oct 2 N) in toluene displayed identical l max em at 580 nm.…”

Modulating the Microenvironment of Coumarin Dyes within Multihierarchical Supraparticles: En Route toward Versatile Luminescent Dual‐Threshold Temperature Indicators with Ratiometric Readout

“…According to the literature, C6 shows a large bathochromic shift in its absorption and fluorescence upon protonation due to intramolecular charge transfer interactions from the electron-rich diethylamino moiety to the ring-protonated benzothiazole. [31,50] The reported emission maximum of the monocationic species of C6 (𝜆 max ≈ 560 nm) corresponds to the herein observed second emission band after exposure to higher temperatures (> 120 °C).…”

Conformation of the Ester Group Governs the Photophysics of Highly Polarized Benzo[g]coumarins

“…In the context of excited-state CT and conformational dynamics that may lead to dual fluorescence, we turn our attention to aminocoumarins. Developed as strongly fluorescent and photostable laser dyes, they have become popular photoprobes for biomedical imaging. , The amine and the electron-deficient pyrone ring form a donor–acceptor pair efficiently mediating ICT in the excited state and producing broad CT fluorescence with a huge Stokes’ shift. − Although studied for more than a century, coumarins and π-expanded coumarins are well-known to produce emission from their low-lying CT states with no traces of dual fluorescence from upper states.…”