A new interpretation of the absorption and the dual fluorescence of Prodan in solution

Author(s)

Vequi-Suplicy, Cintia C. ^{[1, 2]} ; Orozco-Gonzalez, Yoelvis ^{[1, 3]} ; Lamy, M. Teresa ^[1] ; Canuto, Sylvio ^[1] ; Coutinho, Kaline ^[1]

Affiliation

^[1] Univ Sao Paulo, Inst Fis, Rua Matao 1371, BR-05508090 Sao Paulo, SP - Brazil

^[2] Fdn IMDEA Nanociencia Cantoblanco, Madrid 28049 - Spain

^[3] Georgia State Univ, Dept Chem, Atlanta, GA 30302 - USA

• Document type: Journal article
• Source: Journal of Chemical Physics; v. 153, n. 24 DEC 28 2020.
• Web of Science Citations: 0

Abstract

Remarkable interest is associated with the interpretation of the Prodan fluorescent spectrum. A sequential hybrid Quantum Mechanics/Molecular Mechanics method was used to establish that the fluorescent emission occurs from two different excited states, resulting in a broad asymmetric emission spectrum. The absorption spectra in several solvents were measured and calculated using different theoretical models presenting excellent agreement. All theoretical models {[}semiempirical, time dependent density functional theory and and second-order multiconfigurational perturbation theory] agree that the first observed band at the absorption spectrum in solution is composed of three electronic excitations very close in energy. Then, the electronic excitation around 340 nm-360 nm may populate the first three excited states (pi-pi L-{*}(b), n-pi ({*}), and pi-pi L-{*}(a)). The ground state S-0 and the first three excited states were analyzed using multi-configurational calculations. The corresponding equilibrium geometries are all planar in vacuum. Considering the solvent effects in the electronic structure of the solute and in the solvent relaxation around the solute, it was identified that these three excited states can change the relative order depending on the solvent polarity, and following the minimum path energy, internal conversions may occur. A consistent explanation of the experimental data is obtained with the conclusive interpretation that the two bands observed in the fluorescent spectrum of Prodan, in several solvents, are due to the emission from two independent states. Our results indicate that these are the n-pi ({*}) S-2 state with a small dipole moment at a lower emission energy and the pi-pi L-{*}(b) S-1 state with large dipole moment at a higher emission energy. (AU)

• FAPESP's process: 12/15161-7 - Solvent effect on excited electronic states dynamics and on nonradioactive deactivation mechanisms
• Grantee: Yoelvis Orozco González
• Support Opportunities: Scholarships in Brazil - Post-Doctoral
• FAPESP's process: 14/50983-3 - INCT 2014: complex fluids
• Grantee: Antonio Martins Figueiredo Neto
• Support Opportunities: Research Projects - Thematic Grants
• FAPESP's process: 10/08365-0 - Theoretical Study of Lipophilic Nucleosides in Solvents and in Lipid Monolayers Using Hybrid Methods of Quantum Mechanics and Molecular Mechanics.
• Grantee: Cíntia Cristina De Vequi Suplicy
• Support Opportunities: Scholarships in Brazil - Post-Doctoral
• FAPESP's process: 17/11631-2 - CINE: computational materials design based on atomistic simulations, meso-scale, multi-physics, and artificial intelligence for energy applications
• Grantee: Juarez Lopes Ferreira da Silva
• Support Opportunities: Research Grants - Research Centers in Engineering Program