“…These results indicate an extra nonradiative deactivation of PM597, which is not governed by the solvent viscosity. Figure shows a correlation between the k nr value and the fluorescence wavenumber of PM597 by changing the nature of the solvent, indicating similar solvent parameters affecting both photophysical characteristics, as was also proposed for other aromatic systems. − 7 Correlation between the rate constant of nonradiative deactivation (log k nr ) with the fluorescence wavenumbers (υ fl ) in several solvents. Solvent numbers are given in Table .…”
UV-vis absorption spectroscopy and fluorescence (steady-state and time-resolved) techniques were used to study the photophysical properties of the pyrromethene 597 (PM597) dye in several solvents, which include a wide range of apolar, polar, and protic media. This dye presents a lower fluorescence quantum yield than the well-known PM567 dye because of an increase in the nonradiative deactivation rate constant. This is attributed to a loss of planarity in the excited state provided by the steric hindrance of the tert-butyl groups at positions 2 and 6 of the chromophore core. Such a geometrical change in the excited state leads to an important Stokes shift, reducing the reabsorption and reemission effects in the detected emission in highly concentrated dye solutions. The highest fluorescence quantum yield of PM597 is observed in polar media.
“…These results indicate an extra nonradiative deactivation of PM597, which is not governed by the solvent viscosity. Figure shows a correlation between the k nr value and the fluorescence wavenumber of PM597 by changing the nature of the solvent, indicating similar solvent parameters affecting both photophysical characteristics, as was also proposed for other aromatic systems. − 7 Correlation between the rate constant of nonradiative deactivation (log k nr ) with the fluorescence wavenumbers (υ fl ) in several solvents. Solvent numbers are given in Table .…”
UV-vis absorption spectroscopy and fluorescence (steady-state and time-resolved) techniques were used to study the photophysical properties of the pyrromethene 597 (PM597) dye in several solvents, which include a wide range of apolar, polar, and protic media. This dye presents a lower fluorescence quantum yield than the well-known PM567 dye because of an increase in the nonradiative deactivation rate constant. This is attributed to a loss of planarity in the excited state provided by the steric hindrance of the tert-butyl groups at positions 2 and 6 of the chromophore core. Such a geometrical change in the excited state leads to an important Stokes shift, reducing the reabsorption and reemission effects in the detected emission in highly concentrated dye solutions. The highest fluorescence quantum yield of PM597 is observed in polar media.
“…1 H NMR spectrum (DMSO-d 6 (6). A mixture of aldehyde 5 (0.272 g, 1 mmol) and indenochromene 1 (0.218 g, 1 mmol) in acetic anhydride (10 ml) was heated to boiling, then cooled, 70% HClO 4 (0.1 ml) was added, and the mixture boiled for 5 min.…”
“…These systems retain an aromatic character and possess physical and chemical properties mainly analogous to azulene. The pseudoazulenes are of significant interest for synthesis and investigation of polymethine dyes, since they have characteristic absorption bands in the visible region [3][4][5], their fluorescence corresponds to a rare type of S 2 -S 0 transitions [2,[6][7][8][9], and some of them display nonlinear optical properties [10].…”
Starting from the products of formylation and vinylformylation of indeno [2,1-b]chromene a series of new symmetrical and unsymmetrical polymethine dyes have been synthesized with a residue of indeno [2,1-b]chromene as the terminal group. It was shown that the unsymmetrical dyes obtained have two absorption bands in the visible region, the position, intensity, and shape of which depend on the nature of the second terminal group.Pseudoazulenes are π-isoelectronic analogs of azulene and are formally obtained by the replacement of a CH=CH fragment in the seven-membered ring of azulene by an O or S heteroatom or an NR group [1,2]. These systems retain an aromatic character and possess physical and chemical properties mainly analogous to azulene. The pseudoazulenes are of significant interest for synthesis and investigation of polymethine dyes, since they have characteristic absorption bands in the visible region [3][4][5], their fluorescence corresponds to a rare type of S 2 -S 0 transitions [2, 6-9], and some of them display nonlinear optical properties [10].Polymethine dyes containing pseudoazulene residues as terminal groups have not been investigated systematically up to the present time. Information in this area, in essence, is restricted to two studies, in which cationoid polymethine dyes of symmetrical [11] and unsymmetrical [12] structure, derivatives of 2,4-diphenylindeno[2,1-b]pyran, are described. In addition, a symmetrical monomethine cyanine, containing an indeno-[2,1-b]chromene residue, is known [13].The problem of the present work comprises the synthesis of new cyanine dyes having a residue of a pseudoazulene as terminal group and the study of their spectral properties. The system of the most available pseudoazulene, indeno[2,1-b]chromene (1), was selected for investigation [14]. There is information on the instability of 6H-indeno[2,1-b]chromenium perchlorate (2) preventing its isolation in the pure state [14], and also some data on salt 2, obtained however on its incomplete protonation [15]. O O CF 3 COOH CF 3 COO 1 3 11 _ +
“…At first this appears to contradict the fact that the ratio of the electronic non-adiabatic coupling to the transition dipole moment, τ /µ, decreases. However, the reason for the fluorescence quenching in the oligomers is the lower energy gap 20 and the vastly higher density of states. The reduction in the electronic non-adiabatic coupling per porphyrin unit is more than compensated by the increase of accessible final vibrational states.…”
In this study, two different simple and intuitive semiempirical schemes for computing approximate non-adiabatic coupling vectors (NACVs) between the ground and excited electronic states are presented. The first approximation makes use of Mulliken
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