Computational studies of the thermodynamic properties, and global and reactivity descriptors of fluorescein dye derivatives in acetonitrile using density functional theory

This work reports density functional theory calculations of the optimized geometries, molecular reactivity, energy gap, and thermodynamic properties of molecular dyes fluorescein (FS), fluorescein attached with methoxy (FSO), fluorescein attached with amine (FSA), fluorescein attached with methane (FSM), fluorescein attached with ethene (FSE), and fluorescein attached with thiophene (FST) using the hybrid functional B3LYP and 6-311G basis sets. When donating groups are attached to the molecular dye, the bond lengths are slightly decreased which is important for easy transfer of electron from donating to the accepting group. For all dyes, highest occupied molecular orbital/lowest occupied molecular orbital analysis results in positive outcomes upon electron injection to semiconductors and subsequent dye regeneration by the electrolyte. The ionization potential increases with increasing conjugation; therefore, the molecular dye attached to thiophene has the highest ionization potential. Meanwhile, a donating group with increased conjugation results in low electron affinity.