Solvation Structures and Deactivation Pathways of Luminescent Isothiazole-Derived Nucleobases: (tz)A, (tz)G, and I-tz

Author(s)

de Araujo, Adalberto Vasconcelos Sanches ^[1] ; Valverde, Danillo ^[2] ; Canuto, Sylvio ^[2] ; Borin, Antonio Carlos ^[1]

Affiliation

^[1] Univ Sao Paulo, Dept Fundamental Chem, Inst Chem, BR-05508000 Sao Paulo, SP - Brazil

^[2] Univ Sao Paulo, Inst Phys, BR-05508090 Sao Paulo, SP - Brazil

• Document type: Journal article
• Source: Journal of Physical Chemistry A; v. 124, n. 34, p. 6834-6844, AUG 27 2020.
• Web of Science Citations: 0

Abstract

The photophysical relaxation pathways of (tz)A, (tz)G, and I-tz luminescent nucleobases were investigated with the MS-CASPT2 quantum-chemical method and double-zeta basis sets (cc-pVDZ) in gas and condensed phases (1,4-dioxane and water) with the sequential Monte Carlo/CASPT2 and free energy gradient (FEG) methods. Solvation shell structures, in the ground and excited states, were examined with the pairwise radial distribution function (G(r)) and solute-solvent hydrogen-bond networks. Site-specific hydrogen bonding analysis evidenced relevant changes between both electronic states. The three luminescent nucleobases share a common photophysical pattern, summarized as the lowest-lying 1(pi pi{*}) bright state that is populated directly after the absorption of radiation and evolves barrierless to the minimum energy structure, from where the excess of energy is released by fluorescence. From the (1)(pi pi{*})(min) region, the conical intersection with the ground state ((pi pi{*}/GS)(CI)) is not accessible due to the presence of high energetic barriers. By combining the present results with those reported earlier by us for the pyrimidine fluorescent nucleobases, we present a comprehensive description of the photophysical properties of this important class of new fluorescent nucleosides. (AU)

• FAPESP's process: 17/02612-4 - Dynamics of excited states and spectroscopic properties of natural and synthetic DNA and RNA derivatives in solvent environment
• Grantee: Danillo Pires Valverde
• Support type: Scholarships in Brazil - Doctorate
• FAPESP's process: 14/50983-3 - INCT 2014: complex fluids
• Grantee: Antonio Martins Figueiredo Neto
• Support type: Research Projects - Thematic Grants
• FAPESP's process: 18/19454-5 - Structure and Photochemistry of Fluorescent Nucleobaseas and Metal Mediated Base Pairs
• Grantee: Antonio Carlos Borin
• Support type: Regular Research Grants