Photophysical transformations in molecules studied by ultrafast multi-pulse spectroscopy /

This dissertation aims at exploring excited state photoevolution of three different systems by the means of transient absorption spectroscopy. First two chapters are dedicated to the theoretical background, the description of the objects of the study and the experimental tools used. The following three chapters correspond to three different systems explored by ultrafast spectroscopy. First, photochromic indolo-benzoxazines, which are considered as the fastest molecular switches, are investigated. It was found that the current understanding must be redefined, as these compounds do not actually undergo ring-opening in acetonitrile solutions, therefore they are not “switches” by definition. Instead, it is shown that the induced absorption is assigned to the triplet form. Additionally, photoexcitation in alcohol solutions was investigated, where ring-opening was observed. Second, another chapter is devoted to peridinin-chlorophyll-a protein (PCP), which is a light-harvesting protein with complex excited state dynamics. Within the protein complex, carotenoid peridinin absorbs the radiation and transfers the excitation energy to chlorophyll-a. The exact involvement of peridinin states in the process of energy transfer was rather obscure. In this work, the results of pump-dump-probe (PDP) experiments revealed the main channel of energy transfer in PCP and explained the relationship between the peridinin excited states. Finally, the third object of investigation was the photoisomerization reaction of two symmetric polymethine dye compounds. PDP experiments demonstrated for the first time the presence of emissive and non-emissive state and the equilibrium between them. The non-emissive state is the main channel of photoisomer formation, while the emission of a photon returns the molecule to the original ground state.

Grantor dc:publisher

Institutional Repository of Vilnius University

Year dc:date

2015

Author dc:creator

• Voiciuk, Vladislava,

Contributors dc:contributor

• Vengris, Mikas

• Photochemistry ; ultrafast spectroscopy ; photochromism

Statement dc:rights

• info:eu-repo/semantics/openAccess

Language dc:language

eng

Repository record dc:identifier

https://repository.vu.lt/VU:ELABAETD15052161&prefLang=en_US

OAI identifier oai:identifier

oai:vu.lt:elaba:15052161