Color‐Tunable Fluorescent Dyes Based on Benzo[c]coumarin

Abstract

Hurtley condensation was shown to be a perfect tool with which to assemble a diversified library of derivatives of benzo[c]coumarin. Not only do simple resorcinols and ortho‐bromobenzoic acids undergo this reaction, but also dihydroxynaphthalenes and 3‐bromothiophene‐2‐carboxylic acid, affording the desired compounds in moderate yields. In the case of naphthalenediols, intriguing regioselectivity is observed, which holds promise for its utilization in the synthesis of previously inaccessible molecules. Further transformation made it possible to obtain benzo[c]coumarin bearing amino and nitro groups at various positions, which served as entry points to prepare complex hybrids of 1,4‐benzoxazin‐2‐ones and benzo[c]coumarins. The hydroxyl group proved to be the synthetic handle, enabling the synthesis of strongly solvatochromic, soluble analogues. The effect of structural variation on photophysical properties was studied in detail for almost 30 compounds. The relationship between the structure and photophysical properties was thoroughly elucidated by comparison with simple analogues (coumarins, benzoxazinones). All of the obtained compounds exhibit moderate to large Stokes shifts (3300–12500 cm–1). The type of π‐expansion of the chromophore strongly influences the overall optical phenomena. Compounds possessing alkyl substituents on the benzo[c]coumarin core have much higher fluorescence quantum yields than their analogues bearing amino, fluorine, and other complex substituents. Interestingly, the product possessing a fused coumarin–thiophene skeleton exhibits over twofold higher fluorescence quantum yield than any of its coumarin–benzene analogues.

Photophysics of Derivatives of 3-Hydroxybenzo[c]coumarin

“…32 Both compounds appeared to have broad, unstructured fluorescence bands with large Stokes shifts with respect to the absorption, and their fluorescence quantum yields were rather low. Absorption and emission spectra of compounds 1 and 2 in n-nonane matrixes at 5 K are presented in Fig.…”

“…The spectrum resembled the room temperature spectrum of 1 in acetonitrile, with the low energy band located at 30120 cm -1 , as previously reported. 32 The broad fluorescence band of 1 in n-nonane at 5 K has a maximum at about 22500 cm -1 (23040 cm -1 in acetonitrile at room temperature) 32 with high energy onset at 26200 cm -1 .…”

“…0.18), 32 we calculated that the radiative rate constant (k r = Φ fl /τ fl ) would be 0.68·10 8 [s -1 ], whereas the nonradiative value would be k nr = 3.11·10 8 [s -1 ].…”

NLOphoric Red Emitting Bis Coumarins with O-BF2-O core - Synthesis, Photophysical Properties and DFT Studies

“…The importance of coumarins in the field of optoelectronics [1][2][3], fluorescent markers for proteins [4], cellular imaging [5] and lasers [6] and optical whitening [7] is well documented in the literature. The typical absorbance and emission wavelengths of coumarin derivatives lies in the blue-green region (400-520 nm) and the molecules of coumarin class are known to be highly fluorescent [8] with moderate to good quantum yields [9]. The red emitting dyes are of importance in OLEDs to complement their blue and green counterparts, in bio-labelling to achieve greater penetration [10,11] and more cell viability.…”

Red Emitting Coumarins: Insights of Photophysical Properties with DFT Methods

“…Design and synthesis of red emitting dyes are gaining interest in recent years [34][35][36][37][38]. The molecules of coumarin class are known to be highly fluorescent [39] with moderate to good quantum yields [40] and are used in biological applications such as fluorescent markers for proteins [41], cellular imaging [42] and lasers [43]. Coumarin dyes are known to have blue to green fluorescence and there are successful attempts reported in the literature to shift the excitation and emission wavelength Electronic supplementary material The online version of this article (doi:10.1007/s10895-015-1602-5) contains supplementary material, which is available to authorized users.…”