Investigation of Aromaticity and Photophysical Properties in [18]/[20]π Porphycene Derivatives

Abstract

In this study, we have investigated the relationship between aromaticity and photophysical properties of trifluoromethyl-substituted [18]/[20]π porphycenes by using theoretical calculations and various spectroscopic methodologies. Interestingly, we have found that the HOMO-LUMO gap of [20]π porphycene is larger than that of [18]π porphycene, which is in a sharp contrast with those of typical [4n]/[4n+2]π porphyrinoids. Based on our observations, we demonstrate that the origin of this contrasting feature of [20]π porphycene arises from the uniquely large energy splitting between LUMO and LUMO+1 of [18]π porphycene compared with other aromatic [4n+2]π porphyrinoids with nearly degenerate LUMO/LUMO+1. Consequently, we can propose that the energy difference between LUMO and LUMO+1 levels of aromatic [4n+2]π porphyrinoids is an important factor in determining the electronic nature of their corresponding antiaromatic [4n]π porphyrinoids. Moreover, to the best of our knowledge, this is the first study to illustrate the photophysical properties of porphycenes with [4n]π electronic circuits.

The Broken Ring: Reduced Aromaticity in Lys-Trp Cations and High pH Tautomer Correlates with Lower Quantum Yield and Shorter Lifetimes

“…Therefore, we examine QM-MD-derived indole ring isosurfaces, 28,29 which show the ground state π-electron density at specific distances from the ring plane. This exercise reveals a trend in decreased ring charge density and delocalization (i.e, loss of aromaticity) with increased positive charge on the peptide backbone and Lys residue, which is paralleled by decreased quantum yield and fluorescence lifetime.…”

The induced current strengths and aromatic pathways of heteroporphyrins and their antiaromatic derivatives

“…Such discrepancies arise from the interaction between the induced macrocyclic and local heterocyclic circulations . Figure is a reliable outline to elucidate the multifaceted nature of aromaticity for investigated porphyrinoids.…”

Mechanistics and photo‐energetics of macrocycles and photodynamic therapy: An overview of aspects to consider for research

“…As such, they display both strong B‐band (300–450 nm) and Q‐band (600–700 nm) peaks, resulting in extensive studies that have included core metal co‐ordination (particularly, Ni(II), Zn(II) and Fe(II)) and replacement of the bridging nitrogens with oxygens or sulphurs via incorporation of furan, thiophene or imidazole subunits. They have been closely associated with the photoinactivation of viruses and bacteria . Some natural porphycenes such as 5‐aminolevulinic acid (ALA) and methyl‐5‐aminolevulinic acid (MAL) are not the primary catalysts for ablation therapeutics.…”