Spectroscopic Manifestations of (Anti)Aromaticity in Oxidized and Reduced Porphyrin and Norcorrole

Abstract

Abstract Aromaticity and antiaromaticity are foundational principes in organic chemistry, regularly invoked to explain stability, structure, and magnetic and electronic properties. There are ongoing challenges in assigning molecules as aromatic or antiaromatic using optical spectroscopy. Here we report spectroelectrochemical and computational analyses of porphyrin (18π neutral, aromatic) and norcorrole (16π neutral, antiaromatic), and their oxidized (16π porphyrin dication) and reduced (norcorrole 18π dianion) forms. Our results show that while the visible spectra are characteristic of (anti)aromaticity consistent with Hückel’s rules, the IR spectra are much less informative, owing to the relative rigidity of norcorrole. The results have implications for the assignment of (anti)aromaticity in both ground-state and time-resolved spectra.

Stephen Bortolussi

PhD student (2021-); Honours Student (2020)

Stephen is from Sydney, Australia, and originally joined the Peeks group as an honours student in 2020, looking into the properties of liquid crystalline materials. He returned to the group in 2021 to start his PhD in Chemistry at UNSW. The current direction of his research is computational and synthetic studies into the electronic properties of (anti)aromatic molecules. He is also a teaching fellow with the UNSW School of Chemistry, and has an active role in the Students of Chemistry Society (SOCS).

Carmen Zhou

CHEM2999 project student (2020)

Hi, I’m a first-year undergraduate student working with the Peeks group for my CHEM2999 project to metallate porphyrins and to explain the effects of different metals. I hope to pursue a career in research, so I’m excited to be finally getting some experience in the lab! I have a casual job on the weekend, and when I’m not studying for university or working, I like to relax by watching movies/tv-shows or reading.

Nick Lynch

Honours Student (2021)

Nick is currently studying a Bachelor of Medicinal Chemistry (Hons) at UNSW, entering a 4th year of study. He has joined the Peeks Group for a synthetic project, with minor emphasis on advanced characterisation. Nick is currently interested in the synthesis and characterisation of novel antiaromatic compounds.

Martin Peeks

Scientia Senior Lecturer

I am interested in understanding the fundamental chemistry of complex molecules and molecular systems.