Exploring the Reversible Equilibrium State between ³CS and ³CSS in a Ru(phen)-Naphthalene Diimide Dyad

Author(s):Show less -

Pereira, Lorena Maria Borges ; de Oliveira, Diego Franca ; Tiburcio, Marco Antonio ; Ribeiro, Gabriel H. ; Moraes, Carlos Andre Ferreira ; Neto, Flavio Olimpio Sanches ; Camargo, Ademir Joao ; De Boni, Leonardo ; Nascimento, Otaciro Rangel ; Homem, Manoel G. P. ; Carlos, Rose Maria

• Document type: Journal article
• Source: Inorganic Chemistry; v. 64, n. 17, p. 10-pg., 2025-04-21.

Abstract

This study explores the dynamics of charge separation (CS) and recombination in the photoinduced electron transfer of the [Ru(phen)(2)(pNDIp)](2+) dyad, focusing on the thermal equilibrium between rapid charge separation (CS) and the slower charge-separated state (CSS). The pNDIp component is a naphthalene diimide linked to one of the phen ligands, providing nearly unrestricted orthogonal freedom between the {[Ru(phen)(3)](2+)} and {pNDIp} units. The investigation employs steady-state and time-resolved spectroscopic techniques, electrochemical methods, and DFT/TD-DFT computational calculations. The results show that selective excitation of the {[Ru(phen)(3)](2+)} at 450 nm partially quenches the (MLCT)-M-3 emission due to thermal equilibrium with the (CSS)-C-3 state, (3){Ru3+(phen(center dot-))(2)(pNDIp)} reversible arrow 3{Ru3+(phen)(2)(pNDIp(center dot-) )}. This equilibrium is attributed to a combination of nonradiative forward (tau(CT) = 10 ps) and reverse (tau(-CT) = 140 ps) time decays, driven by the intramolecular charge transfer. The long-lived (MLCT)-M-3 state, the reduced distance between the donor and acceptor, and the vibrational structure of the dyad provide sufficient time for (CS)-C-3 reversible arrow (CSS)-C-3 equilibrium. These findings support Marcus theory and highlight key parameters such as -Delta G CS = 0.279 eV, lambda = 0.49 eV, and HDA = 0.28 eV. Additionally, the dyad's ability to generate singlet oxygen under 450 nm light suggests potential applications in photodynamic therapy and oxidative processes. Its ability to form radical anion RupNDIp(center dot-) upon 350 nm light exposure further demonstrates its versatility in photocatalytic applications. (AU)

• FAPESP's process: 19/21143-0 - Amyloid protein aggregates and the relationship between Alzheimer's Disease and type 2 Diabetes investigated by Ru(II) luminescent complexes
• Grantee: Rose Maria Carlos
• Support Opportunities: Regular Research Grants
• FAPESP's process: 20/16036-8 - Ultrafast spectroscopy: degenerated and non-degenerated pump-probe resolved in polarization
• Grantee: Rafael de Queiroz Garcia
• Support Opportunities: Scholarships in Brazil - Master
• FAPESP's process: 21/04675-9 - Therapeutic properties of luminescent Ru (II) to amyloid proteins fibrillation
• Grantee: Lorena Maria Borges Pereira
• Support Opportunities: Scholarships in Brazil - Doctorate
• FAPESP's process: 21/07350-3 - Optical and time-resolved spectroscopic studies on new free-based Corrol molecules
• Grantee: Diego França de Oliveira
• Support Opportunities: Scholarships in Brazil - Scientific Initiation
• FAPESP's process: 18/11283-7 - Nonlinear photonics: spectroscopy and advanced processing of materials
• Grantee: Cleber Renato Mendonça
• Support Opportunities: Research Projects - Thematic Grants
• FAPESP's process: 23/05917-1 - Study of the optical properties of photosensitizers: Triplet formation, two-photon absorption and molecular interaction
• Grantee: Diego França de Oliveira
• Support Opportunities: Scholarships in Brazil - Master
• FAPESP's process: 22/06637-0 - Association between Alzheimer's Disease and Diabetes Mellitus-2: interaction between amyloid proteins, cellular toxicity and development of theranostic agents
• Grantee: Rose Maria Carlos
• Support Opportunities: Regular Research Grants