Preparation and characterization of a phenothiazine oligomers as low bandgap organic system

• Grant number: 23/00271-6
• Support Opportunities: Scholarships in Brazil - Scientific Initiation
• Start date: March 01, 2023
• End date: February 29, 2024
• Field of knowledge: Physical Sciences and Mathematics - Physics - Condensed Matter Physics
• Principal Investigator: Thiago Branquinho de Queiroz
• Grantee: Bruno Silva Simão
• Host Institution: Centro de Ciências Naturais e Humanas (CCNH). Universidade Federal do ABC (UFABC). Ministério da Educação (Brasil). Santo André , SP, Brazil
• Associated research grant: 20/13466-1 - Design, synthesis and characterization of molecular systems for light harvesting and charge separation, AP.JP

Abstract

The design and preparation of low bandgap molecular systems is a crucial step towards the implementation of organic electronic and photovoltaic applications. In particular, pi-conjugated systems exhibit bandgap lowering as building blocks with different electron affinities are associated. In this scientific initiation plan the candidate will synthesize phenothiazine oligomers by interfacial oxidative polymerization (IOP) of the monomer and characterize their structural and optical properties. The oligomers will be prepared according to the IOP procedure described by S. Zh. Ozkan et al. (Polymer Science Series B , 51(5):149, 156, 2009), using ammonium persulfate as an oxidant agent in toluene-isopropanol solution. Interestingly, this procedure leads to the neutral form of oligophenothiazines composed by a mixture of the quinoid imine and benzoid imine structures, with the quinoid to benzoid ratios depending on the amount of oxidant and time of reaction. The benzoid units are electron donor while the quinoid are acceptor, establishing a ``pull-push'' mechanism, useful in the preparation of low bandgap oligomers. The structural investigation will be performed by liquid state nuclear magnetic resonance (NMR) spectroscopy in order to determine the quinoid/benzoid ratios and isomerism and correlated to optical absorption. The electronic structure and optical properties will be further described by time-dependent density functional theory (TD-DFT) calculations using the optimally tuned range separated functional, OT-RSH TDDFT, (already in progress). This investigation aims to establish designing rules for applications of oligophenothiazines in photo-induced donor-acceptor molecular systems.