Unraveling the photophysical processes in supramolecular tetraruthenated thienyl porphyrins

Abstract

In the present work, we investigated two supramolecular tetraruthenated porphyrins. The first originates from the decoration of the thienyl sites of a meso-tetra-thienyl free base (TThP) porphyrin with the RuCl2(dppb)(5,5′-Mebipy) ruthenium complex (named RuT) (yielding the sample TThP-RuT), whereas the second is a variant form in which besides accommodating the RuT moieties, the thienyl also undergoes methylation, resulting in the sample TThP(me)-RuT. The structure-dependent response of the photophysical processes was inspected through steady-state and time-resolved spectroscopies, revealing significant effects in the electronic spectra, vibronic progressions, fluorescence quantum yields, radiative (non-radiative) deactivation rate and excited-state lifetimes of the pristine porphyrin. The solvatochromic analysis also allowed exploring the variations introduced by the supramolecular constitution to the dipole moments of the porphyrin's singlet states. We also demonstrated the relationship between the samples´ structure and their singlet oxygen quantum yields. Finally, we confirmed that all samples are photostable under high pulsed laser fluences, supporting their potential practical uses in the future.