Triplet state direct excitation on trivalent lanthanide complexes

• Grant number: 19/23763-6
• Support Opportunities: Scholarships in Brazil - Post-Doctoral
• Start date: December 01, 2020
• End date: August 27, 2024
• Field of knowledge: Physical Sciences and Mathematics - Chemistry - Inorganic Chemistry
• Principal Investigator: Fernando Aparecido Sigoli
• Grantee: Airton Germano Bispo Júnior
• Host Institution: Instituto de Química (IQ). Universidade Estadual de Campinas (UNICAMP). Campinas , SP, Brazil
• Associated research grant: 21/08111-2 - Development of rare earth based light converters: luminescent markers, optical sensors, and amplifiers, AP.TEM
• Associated scholarship(s): 21/09755-0 - Multifunctional LnIII complexes featuring magneto-chiral dichroism and direct excitation of triplet state, BE.EP.PD

Abstract

Luminescent complexes based on organic ligands and lanthanide(III) ions (Ln3+) find a broad range of applications within the photonic field such as solar cells, biological markers, temperature sensors, solid-state lighting, photodynamic therapy, photothermal therapy, etc. One of the basic mechanisms of the luminescence in such complexes involves the absorption of electromagnetic radiation by the ligands through S0’Sn transitions related to singlet (S) excited states, followed by Sn’Tn transitions related to triplet states (T), energy transfer from the ligands to the Ln3+, and then the photon emission by the Ln3+. Although this mechanism is currently one of high importance for the luminescence of Ln3+-based complexes, it typically features intrinsic non-radiative losses, decreasing the overall emission quantum yield of the Ln3+. To avoid such non-radiative losses, in this proposal, our aim is to induce a new excitation channel in Ln3+-based complexes through direct excitation of the triplet excited state by using S0’T1 transitions. Among the main advantages of this new mechanism of excitation are decreased non-radiative energy losses, decrease of the excitation energy of the complexes and decrease of the pseudo-Stokes shift, probably leading to the enhancement of the overall emission quantum yield of the complexes. However, the main challenge is how to favor the S0’T1 transition since it is forbidden by the spin selection rule, featuring low probability to occur. To overcome such drawback and based on several literature precedents about the possibility of transitions S0’T1 on ligands, we get motivated in modifying the structure of ligands based on H2dipicCBZ (-(9H-carbazol-9-yl-)pyridine-2,6-dicarboxylate), synthesizing new families of ligands containing bromine and/or heteroaromatic rings since bromine, heteroatoms in conjugated systems and the lanthanides may relax the selection rule of the S0’T1 transition through spin-orbital coupling. Those new ligands will then be applied to synthesize new Ln3+ complexes (Ln3+ = Eu3+ ou Tb3+) displaying S0’T1 excitation transition aiming to evaluate their new properties for applications in the photonic field.

Scientific publications

(References retrieved automatically from Web of Science and SciELO through information on FAPESP grants and their corresponding numbers as mentioned in the publications by the authors)

GARCIA, A. B. S.; BISPO-JR, A. G.; LIMA, S. A. M.; PIRES, A. M.. Effects of the Pechini's modified synthetic route on structural and photophysical properties of Eu3+ or Tb3+-doped LaAlO3. Materials Research Bulletin, v. 143, NOV 2021. (19/23763-6, 17/13688-1)

BISPO-JR, AIRTON G.; GALICO, DIOGO A.; DIAZ-RODRIGUEZ, ROBERTO M.; OVENS, JEFFREY S.; SIGOLI, FERNANDO A.; MURUGESU, MURALEE. The role of terminal ligands in the slow relaxation of magnetisation and luminescence thermometry of dinuclear Nd-III complexes. INORGANIC CHEMISTRY FRONTIERS, v. 10, n. 13, p. 11-pg., 2023-06-06. (21/08111-2, 12/11382-9, 21/06326-1, 19/23763-6, 21/09755-0)

BISPO-JR, AIRTON GERMANO; YEH, LAURENCE; ERRULAT, DYLAN; GALICO, DIOGO ALVES; SIGOLI, FERNANDO APARECIDO; MURUGESU, MURALEE. Improving the performance of & beta;-diketonate-based Dy-III single-molecule magnets displaying luminescence thermometry. CHEMICAL COMMUNICATIONS, v. 59, n. 56, p. 4-pg., 2023-06-16. (19/23763-6, 21/09755-0, 21/06326-1, 21/08111-2)