Lanthanide coordination polymers as luminescent thermometers: integrating theoretical modeling with experimental analysis to tune the thermal response

Abstract

Temperature measurements are crucial in numerous industries, spurring ongoing innovations in sensing technology. Among the myriad techniques being explored, luminescence thermometry using lanthanide(III) (Lnⁱⁱⁱ) coordination polymers has garnered considerable interest. However, there remains a scarcity of mapping design strategies for optimizing luminescent temperature probes. To address this issue, theoretical models that examine photophysical dynamics can offer valuable insights into the thermal response of luminescence. In this work, we show a detailed study that integrates theoretical modelling with experimental analysis of the thermal dependence of luminescence in two coordination polymers: [Ln(tfa)₃(μ-dppeo)]_n (1) and [Ln(tfa)₃(μ-dppbo)]_n (2) (Ln = Eu and Tb, tfa⁻ = trifluoroacetylacetonate, and the bridge ligands are [(diphenylphosphoryl)R](diphenyl)phosphine oxide, R = ethyl − dppeo − or butyl − dppbo). By combining experimental and theoretical methods, the mechanisms governing intramolecular and intermolecular energy transfer are investigated. The thermal behaviours of ligand-to-Ln^III and Ln^III-to-Ln^III energy transfer processes are dissected upon direct ligand or Tb^III excitation, shedding light on their contributions to luminescence thermometry and enabling control of the thermal response. Additionally, we adapted and experimentally validated a theoretical protocol for mapping temperature sensing based on the population dynamics of emitting states, demonstrating its feasibility for designing molecular thermometers with enhanced sensitivity. Overall, this study sets the stage for unfolding thermal response mechanisms across multiple excitation channels, offering a foundation for the development of luminescent temperature probes.