Anti-thermal quenching in NdIII molecular near-infrared thermometers operating at physiological temperatures

abstract

Examples of molecular complexes acting as thermometers operating at room temperature in near infrared region are scarce, therefore this work showcases the anti-thermal quenching effect on neodymium(III) molecular thermometers working in biological windows within the physiological temperature range. A mononuclear complex, [Nd(L)(NO3)3] (1Nd), where L is a macrocyclic ligand, was synthesized and used as a precursor to develop two novel species: a dinuclear, [(Nd(L)(NO3))2(mu -BDC)](NO3)2H2O (2Nd), linked by 1,4-benzenedicarboxylate (BDC), and a hexameric, [(Nd(L))(mu -BTC)(H2O)]635H2O (6Nd), linked with 1,3,5-benzenetricarboxylate (BTC). Thermometric properties were studied in the physiological temperature range (292-332 K), utilizing 804 nm laser excitation (first biological window) and monitoring emissions in the second biological window (908, 1065, and 1340 nm) associated with the 4F3/2 -> 4I9/2, 4I11/2, 4I13/2 transitions, respectively. Among the complexes, the hexamer 6Nd exhibited exceptional performance, with Sr of 2.4%K-1 at 293 K, when luminescence intensity ratio (LIR) of two Stark components of the 4F3/2 -> 4I11/2 emission was used, positioning it as a high-performance NdIII-based thermometer. All complexes displayed anti-thermal quenching behavior, surpassing the current molecular-based thermometers in the near-infrared region. Theoretical calculations using complete active space self consistent field (CASSCF) and Boltzmann population models between Kramers doublets of the 4F3/2 level were performed to rationalize the anti-thermal behavior.

keywords

ENERGY-LEVELS; BASIS-SETS; APPROXIMATION; LANTHANIDES

subject category

Chemistry

authors

Maldonado, MJ; Farias-Carreño, P; Gil, Y; Vega, A; de Santana, RC; Aravena, D; Brites, CDS; Carlos, LD; Neto, ANC; Vetrone, F; Fuentealba, P

Groups

G2 - Photonic, Electronic and Magnetic Materials

Projects

CICECO - Aveiro Institute of Materials (UIDB/50011/2020)

CICECO - Aveiro Institute of Materials (UIDP/50011/2020)

Associated Laboratory CICECO-Aveiro Institute of Materials (LA/P/0006/2020)

Molecular logic devices and computing based on luminescent materials actuated by physical inputs (LogicALL)

acknowledgements

Authors thank ANID-Proyecto Fondecyt de Iniciacion 11200919 and Fondecyt Regular 1241928. Y.G. thanks ANID for the Post-doctoral fellow 3220200. D.A. and P.F. thank Fondecyt Regular 1210325. This study was financed in part by the Brazilian agencies, Conselho Nacional de Desenvolvimento Cientifico e Tecnologico (CNPq, 427164/2018-4), and Fundacao de Amparo a Pesquisa do Estado de Goias (FAPEG, 202310267000236). R.C.S. thanks the CNPq research fellowship 310307/2021-0. The authors thank the Universidad de la Republica, Uruguay, for elemental analysis measurements. This work was also devel-oped within the scope of the project CICECO- Aveiro Institute of Materials, UIDB/50011/2020, UIDP/50011/2020 & LA/P/0006/2020 and LogicALL (PTDC/CTMCTM/0340/2021) financed by Portuguese funds through the FCT/MEC (PIDDAC) Powered@NLHPC: This research was partially supported by the supercomputing infrastructure of the NLHPC (CCSS210001).