π‐Aryl/heteroaryl conjugated coumarin‐thiazoles: Synthesis, optical spectral and nonlinear optic properties

Abstract

A series of -aryl/heteroaryl conjugated coumarin-thiazole systems 8a-f has been synthesized by using Hantzsch thiazole protocol and Wittig olefination as the keys. In the UV-Visible spectra of 8a-f, a main absorption band associated with a dominant -* transition is observed in the region of 338 to 390 nm. Qualitatively, the values of max have been found to correlate satisfactory with the donor/acceptor characteristics of the -attached chromophores. Marked changes observed in the absorption maxima of 8a under acidic conditions are rationalized on the basis of mono-or bis-protonation and modification of the donor/acceptor properties of chromophores undergoing protonation. The emission spectra of 8a-f, obtained by exciting the molecules at their main absorption bands showed emission maxima in the region of 429 nm to 537 nm, with relatively high Stokes shifts of 145 and 171 nm being observed for 8a and 8e, carrying a -donor, dimethylaminophenyl and a -acceptor, p-nitrophenyl chromophore, respectively. Although, the first hyperpolarisability , measured by the hyper-Reileigh scattering (HRS) technique are modest (12 to 23 10 -30 esu), all the compounds exhibited complete transparency in the frequency doubling region at 532 nm and showed high thermal stability (T d from 330 to 365 °C).

Synthesis and biological evaluation of novel conjugated coumarin‐thiazole systems

“…In the last few years, researchers have renewed interest in 3‐(thiazol‐4‐yl)coumarins [1–6] for their industrial applications as fluorescent probes and laser dyes [7], for their biological activity as pharmaceutical agents [8–10] and because they could be useful for the construction of the diazepinone ring [11]. In addition, π‐conjugated systems are known to show interesting electronic, optical, and electric properties [12]. On the basis of our experience in the synthesis of thiazole and coumarin [13, 14] derivatives, we were pursued, therefore, to synthesize a series of novel heterocyclic systems characterized by the association of a coumarin nucleus with a thiazole ring linked to a cycloaliphatic group, whose presence and influence on this kind of molecules have not been described so far (Table 1).…”

Synthesis and X‐ray Characterization of 4,5‐Dihydropyrazolyl‐Thiazoles Bearing a Coumarin Moiety: On the Importance of Antiparallel π‐Stacking

“…[25] Moreover, coumarin derivatives are used in dyes due to their excellent optical and photophysical properties. [26,27] Coumarin-thiazoles dyes are exploited as optical brighteners, [28,29] fluorescence labels, [30,31] non-linear optical materials, [32] solar energy absorbers, laser dyes and as two-photon absorption (TPA) materials. [33] Similar properties have been also described for substituted pyrazolyl thiazolyl coumarin dyes.…”

Recurrent π–π stacking motifs in three new 4,5-dihydropyrazolyl–thiazole–coumarin hybrids: X-ray characterization, Hirshfeld surface analysis and DFT calculations

“…25 Apart from the pharmacological properties, 26 substituted coumarin derivatives also find applications in dyes due to their unique optical and photophysical properties. 27 Coumarin-thiazoles based dyes are used as fluorescence labels, 28 optical brighteners, 29 non-linear optical materials, 30 solar energy absorbers, laser dyes and as two-photon absorption (TPA) materials. 31 3-Substituted pyrazolyl thiazolyl based coumarin dyes have also been used as fluorescent brightening agents, 32 red, green and blue dopants in organic light-emitting diodes.…”