USE OF EPR SPECTROSCOPY FOR THE CHARACTERIZATION OF BIOMIMETIC SYSTEMS FOR SOLAR ENERGY CONVERSION AND QUANTUM INFORMATION SCIENCE APPLICATIONS

The following thesis focuses on the study of the photophyisics and photochemistry of organic biomimetic systems. The systems investigated mimic the chromophores involved in photosynthesis, e.g. porphyrins, and/or the photoinduced electron transfer chain that occurs in photosynthetic centres, e.g. molecular donor-acceptor1-acceptor2 triads, and have been proposed as viable molecules for solar energy conversion and Quantum Information Science. A special focus has been given to the photoexcited triplet state populated following the absorption of light and intersystem crossing. Given their paramagnetic nature, triplet states can be studied using Electron Paramagnetic Resonance (EPR). By means of EPR spectroscopy, the properties of these chromophores in their triplet state, the mechanisms by which they are populated, and their spin dynamics have been investigated. Another class of compounds that have been studied by EPR spectroscopy, consists of donor-acceptor1-acceptor2 molecular triads. In these molecules, following the absorption of light it is possible to observe photoinduced electron transfer from the electron donor to the final acceptor. This process leads to the formation of two radicals in the molecule which can be used as a spin qubit pair. The features of these spin qubit pairs have been studied and one of them has been proposed as a possible system for the implementation of the controlled-NOT gate. The information and results gathered on these systems is crucial for a deeper understanding of the processes governing their photophysics and photochemistry and, thus, their applications for efficient solar energy conversion and Quantum Information Science systems.