Molecular Reorganization Energy as a Key Determinant of J-Band Formation in J-Aggregates of Polymethine Dyes.

This work demonstrates the feasibility of the theory of extended multiphonon electron transitions for the description of optical spectra of polymethine dyes and J-aggregates using quantum chemistry. The formation of a strong absorption band in dye monomers and a J-band in their aggregates is uniformly explained from the electron-nuclear resonance condition. The redistribution of optical band intensities among cyanine dyes with the solvent is also explained. The dependence of the possibility of J-band formation in aggregates on the dye structure is successfully predicted. The results presented provide an insight for rational molecular design and application of polymethine dyes.