Exploring electronic delocalization in porphyrin oligomers

Thesis

The general theme of this thesis is a study of electronic communication within porphyrin oligomers. Chapter 1 reviews briefly the porphyrins: their chemical structure, advantages of their use in supramolecular chemistry and some of their basic photo-physical properties. Chapter 2 discusses a study of the origin of an unusual intensity of certain IR bands in two porphyrin oligomer cations. The study uses a polarised time-resolved IR (TR-IR) to understand relative orientation of the intensified vibrations, corroborated with DFT calculations. Coupling between individual IR modes and with the electronic band is documented by 2D-IR spectroscopy and further understanding of the system dynamics upon excitation is understood thanks to the detail kinetic analysis. Chapter 3 focuses on aromaticity. The basis of aromaticity as a concept is reviewed and examples of theoretical and experimental investigations of aromaticity of some π-conjugated species is presented. The experimental part discusses the preparation of large globally (anti)aromatic species via oxidation of the otherwise globally non-aromatic nanorings and its evaluation with NMR. All these studies are supported with DFT calculations corroborating the correct interpretation. Chapter 4 discuses the design and synthesis of a large Möbius-strip-shaped porphyrin nanoring. Firstly, a brief overview of the concept of Möbius aromaticity is reviewed, followed by examples of various designs and reported syntheses of Möbius molecules. This is followed by the design and synthesis and study of two novel nanorings, one which is suspected of adopting Möbius confirmation.

Authors: Jirasek, M

• Type of award: DPhil
• Level of award: Doctoral
• Awarding institution: University of Oxford
• Language: English
• Keywords: porphyrins; aromaticity; 2D-IR; Möbius topology; ring current; ultrafast spectroscopy
• Subjects: Physical organic chemistry