A comprehensive investigation of the interrelationships between spectroscopy and photochemistry and substituents of some azulenic derivatives.

Several azulenic dyes, including six azulene hydrocarbons, two azulene aldehydes, and two olefinic azulenes, have been synthesized to survey their photophysics and photochemistry. These azulenes display S(2)-->S(0) emission, but with several differences. This is the most remarkable characteristic of the effect of orbital control on color and excited state properties of the azulenic compounds. This paper emphasizes how emission spectra and photochemistry of azulenic compounds are influenced by their chemical structure and solvent. The emission spectra of the azulene hydrocarbons suggest that their excited state properties can be controlled by their molecular structure and size. It was confirmed by emission and (1)H NMR spectroscopy that azulene monoaldehyde is protonated in a strong acid, such as trifluoroacetic acid (TFA). Photochemistry of styrylazulenes was observed during irradiation. Azulenic compounds are thermally stable and color tunable, and hence they are good candidates as non-linear optical materials. Based on their unique photochemical and photophysical characteristics, novel azulenic dyes can be constructed for different uses.