Hole polaron of small radius in assemblies of hydrated mono-protonated meso-tetraphenylporphine dimers at 77 K

Abstract

Polaron theory is often used for the study of electrons and holes mobility in semiconductors when longitudinal optical (LO) phonons are generated upon the charge carriers moving. The polaron theory was applied to explain long-wavelength absorptions observed nearby Soret band in the electronic spectra of assemblies of mono-protonated meso-tetraphenylporphine dimer (TPP2H+) that are interpreted as LO-phonons originated due to proton movement. The energy of hole polaron is found to be 1.50eV at 77K. Energy of Franck–Condon transitions of LO-phonons generated by hole polaron moving through water confined in the assemblies with distortions of O–H bonds is 0.2653eV (2138cm−1). A broad band around 2127cm−1 corresponding the same energy of O–H bonds vibrations is observed in IR spectra of the assemblies consisting of water and mainly of TPP2H+ species in the solid state indicating the presence of similar distortions of the hydrogen bonds. The radius of protonic sphere of 0.202Å, which was estimated as a polaron quasiparticle moving through the confined water at 77K, is found in agreement with earlier evaluated one of 0.265Å that was obtained for proton diffusion at 298K in similar assemblies.