Excited state dynamics of photoresponsive betalain-based supramolecular systems

• Grant number: 19/20449-9
• Support Opportunities: Scholarships abroad - Research Internship - Doctorate (Direct)
• Start date: November 01, 2019
• End date: October 31, 2020
• Field of knowledge: Physical Sciences and Mathematics - Chemistry - Organic Chemistry
• Principal Investigator: Erick Leite Bastos
• Grantee: Amanda Capistrano Pinheiro
• Supervisor: Jacinto de Paiva Sá
• Host Institution: Instituto de Química (IQ). Universidade de São Paulo (USP). São Paulo , SP, Brazil
• Institution abroad: Uppsala University (UU), Sweden
• Associated to the scholarship: 15/18474-4 - Functionalization of polysaccharides with photoresponsive betalains, BP.DD

Abstract

Betalains are water-soluble imine/iminium natural pigments whose physicochemical properties can be tailored to specific applications. Depending on their chemical structure, betalains attached to nanostructured materials can promote electron hole transport via proton coupled electron transfer. We designed a photoresponsive and multifunctional betalain that can be covalently attached to metal nanoparticles via its carboxylate moiety and/or Nsp2 atoms. This betalain is the key component of a cucurbit[7]uril hemirotaxane system that can be assembled and disassembled by changing the temperature. Although several analogues and derivatives of this betalain developed in our group share these same fundamental properties, betalain nitrones are far more stable than natural betalains in neutral/alkaline aqueous media and produce a distinct electron paramagnetic resonance spectra upon oxidation. Here, we propose the study of the excited state dynamics of photoexcited betalains focusing on the development of redox mediators and photoresponsive linkers, which are of strategic importance to exploit the full potential of sunlight irradiation in photovoltaic applications and photoredox catalysis. During this one-year research placement at the University of Uppsala under the supervision of Prof. Jacinto Sá the capacity of these systems to modulate electron/hole injection in modular nanostructured systems will be investigated by ultrafast spectroscopy. (AU)