Theoretical study of the effects of hydrogen bonds and interactions with ions on the ground, electronically excited states and energetic barriers of the sulfonamide photodegradation reaction

• Grant number: 22/14780-7
• Support Opportunities: Scholarships in Brazil - Doctorate
• Start date: June 01, 2023
• End date: August 31, 2026
• Field of knowledge: Physical Sciences and Mathematics - Chemistry - Physical-Chemistry
• Principal Investigator: Roberto Luiz Andrade Haiduke
• Grantee: José Luiz Felix Santos
• Host Institution: Instituto de Química de São Carlos (IQSC). Universidade de São Paulo (USP). São Carlos , SP, Brazil

Abstract

Due to the importance of developing and improving techniques for the removal of contaminants, such as antibiotics, which, consequently, can avoid or mitigate problems to the environment and human health, this project will focus on the computational study of the effects of explicit solvation and the interactions with ions on the ground and electronically excited states and also on the energetic barriers of the rate-determining steps of the photodegradation mechanism of sulfonamides. Density functional theory will be used to calculate equilibrium geometries of ground states and vibrational frequencies, and time-dependent density functional theory will be used to calculate excited state geometries, oscillator strengths and verticals excitation energies, both being combined with different modeling levels to assess the effect of explicit hydrogen bonding of water molecules and interactions with ions on such properties. The coupled cluster theory with iterative single and double excitations, including the perturbative correction for triple substitutions (CCSD(T)), will beused to improve the description of the activation energies for the rate-determining steps of the photodegradation reaction. These results will also be evaluated from the perspective of the quantum theory of atoms in molecules (QTAIM), which will provide us with data on the distribution of electron density in the ground and excited states and along the reaction coordinate. From these results, it is expected to reach a deeper understanding of this category of molecular systems in the presence of water and dissolved ions and the effects of these interactions on their properties. Thus, with this, it is intended to suggest more advanced theoretical approaches for studies of this nature and, if possible, to indicate more efficient routes for the elimination of such contaminants.