Synthesis, spectroscopic and photophysical studies of xanthene derivatives

We report on the experimental, crystal structure and computational investigation of a new class of xanthenes obtained by the reaction of salicylaldehyde and its derivatives with, 5,5-Dimethylcyclohexane-1,3-dione (Dimedone). The synthesized xanthenes were characterized by state-of-the-art techniques, such as IR, Raman, 1H and 13C NMR, Single Crystal X-ray crystallography, UV-Vis and photophysical measurements. The structure, ground- and excited-state properties of one xanthene derivative was investigated using Density Functional Theory (DFT) and Time-Dependent DFT (TD-DFT) calculations with and without solvent (ethanol). The optimized geometries and predicted IR frequencies were in good agreement with experimental data. Hirshfeld surface analyses were carried out to gain insight on the close-contact interactions of the crystal, where hydrogen showed the highest contribution (66.1%). The synthetic route proposed in this work does not use any catalysts and leads to high yields (75-85%), therefore being an interesting alternative to synthesize xanthene derivatives.