Spectral, luminescent, and lasing properties of 3-(benzothiazolyl-2)-7-hydroxy-and-8-hydroxycoumarins

Synthesis and electronic spectra of 3‐hetaryl substituted coumarin derivatives 7‐hydroxy‐2H‐chromen‐2‐on and 9‐hydroxy‐2H‐benzo(f)chromen‐2‐on

“…The changes in the pH value of the medium passing from ethanol, through buffer (pH 7) to buffer (pH 8) have a rather low influence on the position of the fluorescence maxima (Table 4). Similar results have been described already for some of the known hydroxy-coumarins [38].…”

“…Their longest wavelength absorption band in ethanol has a maximum reading in the range 390-500 nm; the molar absorptivity is 27 000-42 000 l mol )1 cm )1 ( Table 3). The obtained characteristics of the absorption spectra for compound 4c are in good agreement with those described in the literature [11,38]. The lack of significant changes in the energy of the longest wavelength absorption maxima of hydroxy-coumarins substituted in position 3 with 4-phenyl-thiazole (4d), benzothiazole-(4c) and benzimidazole-(4a and 4b) fragments ( probably because of the similar electron-donating ability of these moieties [39].…”

“…In this case, a slight red shift up to 10 nm is observed only for compounds 4a and 4b (Figure 2). The red shift of the absorption maxima could be explained by the ability of these compounds to form different tautomeric forms, namely hydroxy and oxo forms in ethanol and an anionic form in alkaline media [11,38].…”

Structure and spectral-luminescent properties of 6-isoxazolyl-7-hydroxycoumarins

“…2 and 6). In methylene chloride, they have a universal shape of the curve with a vibrational maximum at the short wavelength edge, which is characteristic of organic dyes [3,4] (Fig. 2, Table 1).…”

“…Derivatives of 7 hydroxycoumarins are unique converters of light energy, as a consequence of which they have been widely applied as active laser media [1,2], fluorescence labels and probes [3], and lumines cent solar concentrators and optical bleaches [4]. Until the present time, their structure has been pre dominantly modified in the pyrone cycle.…”