Optical and Electrochemical Properties of Anthraquinone Imine Based Dyes for Dye‐Sensitized Solar Cells

Abstract

Abstract A number of anthraquinone imines ( 1 – 3 , 5 – 8 ) and an anthrone diamine ( 4 ) have been synthesized by the condensation of 9,9‐dimethoxy‐10‐anthrone derivatives ( 13 , 18 , and 23 ) with different primary aromatic amines and, in the case of benzoacridinone 7 , by a subsequent photoinduced 6 electrocyclization. All the compounds were fully characterized by UV/Vis spectroscopy, cyclic voltammetry, and X‐ray diffraction. The XRD analyses proved that the preferred tautomers of 1 , 3 , and 5 have the 9‐amino‐1,10‐anthraquinone or 1‐hydroxy‐9,10‐anthraquinone imine core. Furthermore, aminoanthraquinone 9 and phenoxazine 10 were synthesized by the reaction of 1‐amino‐9,10‐anthraquinone with 3,5‐di‐ tert‐ butylphenyl‐ o ‐benzoquinone, which led to dyes with high molar extinction coefficients of up to 101600 L mol –1 cm –1 . In addition, the absorption maxima of the 1‐hydroxy‐9,10‐anthraquinone imines appear in the range of 246 and 591 nm, at variance with the absorption maxima of the parent 1‐hydroxy‐9,10‐anthraquinone. The cyclic voltammograms of all the compounds show multiple redox processes. In addition, the optical absorption and photoluminescence spectra of 3 show suppressed segregation on mesoporous TiO 2 and an almost pure molecule photoluminescence spectrum containing two main transitions. A new excitonic transition was found in the crystal form.