Effects of Alkoxy Substitution on the Optical Properties of 9,10-Anthraquinone and Anthracene: 2,3,6,7-Tetrapropoxy-substituted vs. 2,6-Dipropoxy-substituted Derivatives

2,3,6,7-Tetrapropoxy- and 2,6-dipropoxy-substituted 9,10-anthraquinone (AQ) and anthracene (ANT) derivatives were synthesized, and their optical properties in solution and in the solid state were investigated. In AQs, the tetrapropoxy derivative exhibited a red shift of absorption in comparison with the dipropoxy derivative and ANT. In contrast, in ANTs, the dipropoxy derivative exhibited a red shift of absorption and fluorescence in comparison with the tetrapropoxy derivative and ANT. The electronic effects of alkoxy substitution could be explained by TD-DFT calculations.