Polaronic exciton in self-organized assemblies of protonated meso-tetraphenylporphine dimers and water at room temperature

Abstract

Assemblies consisting of protonated meso-tetraphenylporphine (TPP) dimers and water have been investigated by UV–vis and infrared (IR) spectroscopy and by atomic force microscopy (AFM) in thin layers. Features of electronic absorption spectra of the assemblies are interpreted in terms of hole polaron combined with exciton theory using quantum well with parameters obtained from the dimer structure. It appears to be hole polaron moving defines kinetic energy of polaronic exciton confined in a quantum well when the electron absorbs photon. Hole polaron characteristics such as polaron self-energy, energy of Frank–Condon transitions, and radius of hole polaron moving through water are found to be 1.38 eV, 0.2445 eV, and 0.246 Å, respectively. A doublet at 1944, 1960 cm−1 (0.2412, 0.2432 eV) observed in IR spectra matches the energy of Frank–Condon transitions. Excitation energies estimated using molecular parameters for polaronic excitons in pure water and in the TPP dimers are found in a good agreement with the experimental data.