Photophysical Characterization of Free-Base N-Confused Tetraphenylporphyrins

Abstract

We report the photophysical characterization of the two tautomers (1e and 1i) of 5,10,15,20-tetraphenyl N-confused free-base porphyrin, potential building blocks in assemblies designed for artificial photosynthesis, using a combination of steady state and time-resolved techniques. Tautomer 1e was found to have a significantly higher quantum yield of fluorescence than tautomer 1i (Φ Fl ) 0.036 vs Φ Fl ) 0.0016, respectively), despite the fact the fluorescence lifetimes were quite similar (i.e., 1.98 ns vs 1.60 ns, respectively). These differences were attributed to a more rapid rate of internal conversion or intersystem crossing in 1i due to steric conditions in the interior of the macrocycle. The absorption spectra of these porphyrins were also examined using the results from B3LYP/6-31G(d)//B3LYP/3-21G(d) calculations and interpreted using the four electron four orbital model.

Developments in the metal chemistry of N-confused porphyrin

“…In our group, we have reexamined the electronic structures of both tautomers using DFT methods at the B3LYP/6-31G(d)//B3LYP/3-21G(d) level using the observed crystal structures as a starting point for the geometry optimization [37]. We also carried out these calculations in the context of Gouterman's four orbital model (HOMO-1, HOMO, LUMO, LUMO+1), which provides some insight into how these macrocycles can function as ligands for metals [38,39].…”

“…Visible absorption spectra of internally protonated (a) and externally protonated (b) tautomers of H 2 NCTPP[37].…”

The Direct Synthesis of 2-N-Methyl-5,10,15,20-tetrakis-(4′-sulfophenyl)-2-aza-21-carbaporphyrin J-Aggregates

“…[20] Porphyrinoids with inverted porphyrin platform H 2 IP (2-aza-21-carbaporphyrin derivatives) [21,22] attract a great interest through its unique molecular structure. [23][24][25][26][27][28][29][30][31] Water soluble N-confused porphyrin derivatives are very interesting objects for researchers due to their potential medical and biological application. [32][33][34][35][36] Previously it was established that porphyrinoids with inverted pyrrole ring possess an ability to form anion complexes [ 4 ] n [39] in acidic media.…”

Decorating Metal Oxide Surfaces with Fluorescent Chlorosulfonated Corroles

“…em for tetraphenylporphyrin is 0.11. 3 All relative fluorescence quantum yields were calculated based on the corresponding fluorescence spectra of the samples and the standard according to the equation [4][5][6] : where Φ em (s) and Φ em (x) are the relative fluorescence quantum yield of the standard and sample, respectively; A s and A x are the absorbance at the excitation wavelength for the standard and sample, respectively; F s and F x are the area under the corrected emission curve for the standard and sample, respectively; and s and x are the refractive index of the solvent used for the standard and sample, respectively. Mass Spectrometry.…”