New insights into oxidation properties and band structure of fluorescein dyes from ab initio calculations

During recent years, several publications have investigated the electrical bistability of spin cast films of halogenated fluorescein dyes. In the present contribution, we simulate the excited states of single fluorescein dyes with time-dependent density functional theory (TD-DFT) and we analyzed the band structure of the corresponding molecular crystals with DFT. More precisely, the molecules examined are fluorescein, erythrosine B, and rose bengal. We consider the molecular crystals of fluorescein in salt and lactone forms as well as erythrosine B. Rose bengal showed high quantum yield of the triplet state and high electronic affinity. Therefore, the rose bengal has very strong oxidation properties and it is able to form electrically bistable thin oxide layer. The poor crystal order and small bandwidths of fluorescein in salt form and erythrosine B indicated high resistivity for both crystals.