Presenter: Prof. Martin Stillman
The University of Western Ontario, Canada
Topic: Computational and Spectroscopic Studies in the Design of Novel Porphyrins for Solar Cell Applications
Time: 9:30 a.m., May 10th, 2016
Location: Conference Room B, BLDG 909-1F
Abstract
Porphyrins are a diverse group of bioinorganic molecules with a complex cyclic structure composed of four pyrrole rings. They have many unique applications in medicine and energy conversion such as photodynamic therapies and in solar cells. Inclusion of specific functional groups in porphyrins can add new properties. 
The effects of peripheral substituents on the electronic structure of chlorophylls and Zn-anthraquinonoporphyrins was investigated using UV-visible absorption spectroscopy, magnetic circular dichroism (MCD) spectroscopy, and computational modeling methods. The key to a successful solar cell is to model the photochemical properties of chlorophyll. Our DFT and optical measurements identify the key factors in the success of chlorophyll as a solar cell – except it only works in a leaf! Optical and DFT results showed that introduction of peripherally attached anthraquinone functional groups distort the symmetry of porphyrins but more importantly caused a distortion of the excited states as well. This results in red-shifting of the porphyrin absorption bands and an intensification of the Q-band, just like in chlorophyll. These properties are essential in developing and extending photo-cell properties of these dyes.
Biography
Martin Stillman is Professor of Biology and Chemistry in the Department of Chemistry, at The University of Western Ontario, London, Ontario, Canada. He received his B. Sc. and Ph. D. from the School of Chemical Sciences, University of East Anglia, Norwich, UK supervised by Prof. Andrew Thomson, FRS. His Ph. D. research focused on the application of magnetic circular dichroism spectroscopy to porphyrins, phthalocyanines and the protein myoglobin. He was a postdoctoral fellow at the University of Alberta, Canada studying the optical properties of phthalocyanines and the heme enzyme horseradish peroxidase.
Three areas of research continue to be the focus in Stillman’s laboratory; (i) the metal binding mechanism and metal binding structural properties in the protein metallothionein, (ii) the electronic properties of tetrapyrroles as a function of ring size, ring substitution, deformation, leading to an understanding of the chemical and physical properties of all tetrapyrroles from the electronic structure standpoint, and (iii) interpreting the mechanism of action of the recently-discovered series of Isd wall and membrane bound proteins, which have a proposed role in iron scavenging for the human pathogenic Staphylococcus aureus bacterium.
Contact: Prof. Qiao Zhang
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