报告人: Martin J. Stillman

Stillman Bioinorganic Group, Department of Chemistry, The University of Western Ontario, London, Ontario, Canada 

时间：2018年10月10日（周三） 上午10:00—11:30

地点：北京大学化学学院A区717报告厅.

Abstract:

The glorious colors of the natural tetrapyrroles, from the purples and greens of bacteriochlorophylls, to the greens of the chlorophylls and then the reds and yellows of the hemes, and the deep reds of the corrinoids have attracted immense technological activity focused on a myriad of possible functions.  What is startling is that Nature was quite economical in tuning the electronic properties of the aromatic ring using not only specific metals, oxidation and spin state and axial ligands, but also electronically-active peripheral groups, and pi ring reduction to optimize functionality.  The key to the colors and redox properties of the tetrapyrroles is the electronic structure of the aromatic ring and its moderation by the central metal, the axial ligands and the peripheral decoration.  Quantifying this range of function activators has been a challenge for many decades being based on the interpretation of the origins of a wide range of redox and spectroscopic data and the use of ever more sophisticated computational approaches.  However, with quantification comes the opportunity for modeling properties and then predicting properties of novel structures (1).  With detailed absorption, emission and magnetic circular dichroism spectral data we have begun to characterize the specific electronic effects of the tuning of tetrapyrroles.  By quantifying the effects of individual activators, we can provide guidance as to the choice of activator.   By connecting specific properties to parameters in the electronic structure (through trend lines) we can identify the electronic structure properties required for a desired property.  This leads to electronic structure guided design. 

Work funded by NSERC of Canada.

REFERENCES

1.  A. Zhang, L. Kwan, and M.J. Stillman “The spectroscopic impact of interactions with the four Gouterman orbitals from peripheral decoration of porphyrins with simple electron withdrawing and donating groups”, Org. Biomol. Chem., 2017,15, 9081-9094.  DOI : 10.1039/C7OB01960B.

A Zhang, MJ Stillman “Exploring function activated chlorins using MCD spectroscopy and DFT methods: design of a chlorin with a remarkably intense, red Q band”. Physical Chemistry Chemical Physics 20 (18), 12470-12482  DOI: 10.1039/C8CP01010B