Tuning carotenoid photophysics by changes in structure and local environment

Emrah ÖZCAN

Doctoral thesis

Carotenoid Photophysics: Influence of environment properties on excited-state dynamics

Abstract:

This thesis investigates the complex dynamics of excited states in carotenoids, focusing on the origins and properties of certain dark states and how they are affected by external disturbances such as metal interactions, pH changes, applied voltage, and chemical modifications. Paper I demonstrates the creation of stable astaxanthin-metal complexes and their altered excited-state dynamics, revealing shortened lifetimes and enhanced ICT bands due to metal-ion interactions. Paper II explores the effect of external voltage on 8-apo--carotenal, showing that applied voltage can control the ICT state amplitude and extend its lifetime. Paper III examines pH-dependent effects on crocin, finding significant pH-induced shifts and stabilization at basic pH levels. Paper IV presents the synthesis and analysis of bis-phenylhydrazone astaxanthin, highlighting its modified excited-state dynamics and the potential for organic modification to study new effects. These findings enhance our understanding of carotenoid excited states and suggest new research approaches.

Abstract:

This thesis investigates the complex dynamics of excited states in carotenoids, focusing on the origins and properties of certain dark states and how they are affected by external disturbances such as metal interactions, pH changes, applied voltage, and chemical modifications. Paper I demonstrates the creation of stable astaxanthin-metal complexes and their altered excited-state dynamics, revealing shortened lifetimes and enhanced ICT bands due to metal-ion interactions. Paper II explores the effect of external voltage on 8-apo--carotenal, showing that applied voltage can control the ICT state amplitude and extend its lifetime. Paper III examines pH-dependent effects on crocin, finding significant pH-induced shifts and stabilization at basic pH levels. Paper IV presents the synthesis and analysis of bis-phenylhydrazone astaxanthin, highlighting its modified excited-state dynamics and the potential for organic modification to study new effects. These findings enhance our understanding of carotenoid excited states and suggest new research approaches.

Keywords

Carotenoids, Metal complexes, Ultrafast spectroscopy, Charge transfer state, Cyclic voltammetry, 8'-apo--carotenal, Spectroelectrochemistry, Crocin, pH-dependence.

Language used: English

Date on which the thesis was submitted / produced: 23. 7. 2024

Thesis defence

• Supervisor: prof. RNDr. Tomáš Polívka, Ph.D.

UNIVERSITY OF SOUTH BOHEMIA IN ČESKÉ BUDĚJOVICE

Faculty of Science

Doctoral programme / field:
Biophysics / Biophysics