Ground-State, Excited-Singlet-State, and Excited-Triplet-State Energy Levels and Photophysics of the Three Rotational Isomers of Isophthalaldehyde Vapor

Abstract

Emission, excitation, and absorption spectra of isophthalaldehyde (benzene-1,3-dicarboxaldehyde) vapor have been measured at different temperatures, along with the UV-vis and IR absorption spectra in solution. Analyses of the temperature dependence of the phosphorescence and excitation spectra of isophthalaldehyde vapor revealed the energetic relationships among the three rotational isomers in the T1(n, pi*), S1(n, pi*), and ground states. This appears to be the first example of the system where the S0, T1, and S1 energy levels are determined for the three rotational isomers. The phosphorescence, fluorescence, and excitation origins of the three rotamers were assigned on the basis of the results of the density functional theory (DFT) and semiempirical SCF-MO calculations and infrared data as well as on the basis of the temperature dependence of the emission and excitation spectra.

Thermal response and thermochromism of methyl red-based copolymer systems – coupled responsiveness in critical solution behaviour and optical absorption properties

“…Second possibility: A temperature-induced shift of the equilibrium between several stable rotamers causes the sub-band structure. This effect has been ascribed to the features in the fine structure of the optical absorption of isophthalaldehyde, 64 but also to absorption 65 or fluorescence characteristics of stilbenes 66–68 and to azo compounds. 69…”

“…Second possibility: A temperature-induced shift of the equilibrium between several stable rotamers causes the sub-band structure. This effect has been ascribed to the features in the fine structure of the optical absorption of isophthalaldehyde, 64 but also to absorption 65 or fluorescence characteristics of stilbenes [66][67][68] and to azo compounds. 69 Third possibility: The thermal peak shift may be associated with a temperature-induced change in the structure of the solvent shell, which has been reported for the related azo dye methyl orange.…”

Emission spectra of 3,4- and 3,5-difluorobenzaldehyde vapors: Conformer-specific phosphorescence from the 3,4-derivative

“…Perhaps, it might be possible to obtain the sharp emission spectra for these phosphorescent molecules in a jet, but it is generally not easy to measure the dispersed phosphorescence spectra in a jet. On the other hand, molecules such as benzaldehyde, fluorobenzaldehydes, pyridinecarboxaldehydes and isophthalaldehyde are known to exhibit comparatively sharp phosphorescence bands in the vapor phase [1,4,5].…”