Revealing the quantum RC-electrodynamics of push-pull pi-conjugated heterocyclic molecules by impedance-derived electrochemical capacitance spectroscopy

• Grant number: 24/07908-2
• Support Opportunities: Research Grants - Visiting Researcher Grant - International
• Field of knowledge: Physical Sciences and Mathematics - Chemistry - Analytical Chemistry
• Principal Investigator: Paulo Roberto Bueno
• Grantee: Paulo Roberto Bueno
• Visiting researcher: Maria Manuela Marques Raposo
• Visiting researcher institution: Universidade do Minho (UMinho), Portugal
• Host Institution: Instituto de Química (IQ). Universidade Estadual Paulista (UNESP). Campus de Araraquara. Araraquara , SP, Brazil
• Associated research grant: 17/24839-0 - Nanoelectronics and nanoscale electrochemistry: fundaments and applications, AP.TEM

Abstract

Intramolecular charge transfer (ICT) is a fascinating electron property present in a group of À-conjugated organic molecules known as push-pull systems. These organic systems comprise electron donor (D) and acceptor (A) groups, electronically coupled by À-spacers. The electron transfer between the D-A moieties, corresponding to the highest occupied (HOMO) and lowest unoccupied molecular orbitals (LUMO) respectively, is activated under photoexcitation and mediated through À-conjugated bridges. This feature has positioned push-pull molecules as promising systems for various applications in diverse fields such as solar cells, non-linear optics, light-emitting diodes, and sensing. Therefore, the electrodynamics associated with this electron communication between donor and acceptor states in push-pull molecules can be considered an interesting phenomenon to be explored by the quantum rate theory (QRT) approach, which predicts a quantum rate ½ given by the relation between the inverse of the Von Klitzing constant R_K=h/e^2 and the quantum capacitance C_q as ½=e^2/hC_q. In this sense, QRT has allowed access to the pristine electron properties of nanoscale structures using time-dependent electrochemical techniques, such as redox peptide monolayers, semiconducting nanofilms, quantum dots, and graphene, demonstrating that their electron dynamics are governed by quantum principles. Accordingly, we hope that attaching push-pull molecules to electrode surfaces will provide suitable interfaces for measuring and accessing their electron properties, modeled as quantum RC characteristics. In this proposal, one push-pull molecule will be synthesized, containing chemical groups to bond to a peptide-modified electrode. Its quantum capacitance and conductance responses will be measured by electrochemical impedance spectroscopy. (AU)