Optical properties of free base tetrasulfonatofenil porphyrin (H2TPPS4), and tetrapyridyl porphyrin (H2TPyP) with ruthenium group

Recently we proposed new insight to the absorption and fluorescence (FL) of free base tetrapyridyl porphyrin (H₂TPyP). In this project, we extend our study to the free base tetrasulfonatofenil porphyrin (H₂TPPS₄), and to supramolecular structure composed by H₂TPyP and four ruthenium groups ([RuCl(terpy)(PPh₃)₂]PF₆). Despite the fact that literature has reported the transitions observed in porphyrins’ absorption and fluorescence spectra, a more accurate interpretation has been evasive and still needed for H₂TPPS₄ and [RuCl(terpy)(PPh₃)₂]PF₆ systems. We found that these systems follow our recent findings for H₂TPyP where each of the absorption Q-bands consist of two quasi-degenerated bands namely Q_x1, Q_x2 and Q_y1, Q_y2, respectively. We also explore the FL and its polarization degree (polarization components) via the Stokes spectroscopy method. Using the Stokes method, we found that the FL polarization degree depends on the concentration of the molecules in the solvent. In order to elucidate the polarization mechanisms, further investigations are being conducted via polarization-resolved, temperature-dependent and lifetime spectroscopy experiments.