Photophysical and theoretical studies of photoisomerism and rotamerism of trans-styrylphenanthrenes

Abstract

The photophysical and photochemical properties and the ground-state conformational equilibrium of fz-azzi-rz-styrylphenanthrene (n-StPh, with zi = 1, 2, 3, 4, 9) have been studied in inert solvents. The kinetic parameters of the competitive radiative and reactive decay processes have been obtained. A detailed analysis of the fluorimetric behavior as a function of the excitation wavelength and temperature has allowed the distinct decay parameters and the ground-state energy difference of the two rotamers of zrazu-3-StPh to be obtained. Parallel theoretical calculations of the potential energy curves for the internal rotation of the phenanthryl group in the ground state, of the energies and oscillator strengths of the lowest transitions, and of the activation energies for trans -*• cis isomerization in the ground and lowest excited singlet states have been carried out with a modified (CS) INDO method. The results of the experimental and theoretical studies are in satisfactory agreement and provide a general description of the photophysical and photochemical behavior of this class of compounds.

Photoisomerization and Photocyclization of 5-Styryloxazole

“…The fluorescence spectra were measured with a Spex Fluorolog-2 F112AI spectrofluorimeter using dilute solutions (absorbance < 0.1 at the excitation wavelength,  exc ). The fluorescence quantum yield ( F , uncertainty  15 %) was determined at  exc corresponding to the maximum of the first absorption band ( max ) using -NPD ( F = 0.70) 23 in de-aerated CH as fluorimetric standard. For photochemical measurements (potassium ferrioxalate in water was used as actinometer) a 150 W high pressure xenon lamp coupled with a monochromator was used.…”

Photophysics and (E/Z)-Photoisomerization of 1-(2-Naphthyl)-2-(2-benzothiazolyl)ethenes

“…Ar, " Ar naphthyl) has received much attention [1,2] because of the two effects exerted by the naphthyl substituent in 2-styrylnaphthalene: (i) the lowest excited state of the aromatic moiety noticeably increases the¯uorescence quantum yield but decreases the photoisomerization yield at room temperature and (ii) the strong steric interaction between the naphthyl group and the ethylenic hydrogen is important in determining the mixtures of conformers originating from rotation of the naphthyl group about a quasi-single bond between the aryl group and the ethylenic carbon atom.…”

P‐Type Photochromism of New Helical Naphthopyrans: Synthesis and Photochemical, Photophysical and Theoretical Study

“…The emission spectra were collected by using aS pex Fluorolog-2 1680/1 equipped with as ystem for spectral correction;t he quantum yields were determined by using 9,10-diphenylanthracene (DPA) in cyclohexane (quantum yield f F = 0.90 [62] )a sas tandard. The corrected areas of the sample and the standard emissions were compared by using Equation (6), which accounts for the differences in absorbance and refraction index of the sample (A S , n S ) and standard (A ST , n ST )solutions.…”