Cationic dye dimers: a theoretical study

In this work we present a quantum-mech- anical study on the structure and electronic spectra of three cationic dyes monomers and dimers: acridine orange (AO), proflavine (PF) and methylene blue (MB). The geometries were obtained from crystallographic data, the electronic properties were calculated with DFT (B3LYP functional) and the theoretical spectra were obtained with ZINDO. The solvation methodology adopted was the Integral Equation Formalism (IEF) version of the Polarizable Continuum Model (PCM). This study shows that the differences, even small, bet- ween optimized and crystal geometries are responsible for important spectral characteristics. Also, it indicates possible structures for interacting dimers.