Rare-earth coordination polymers with multimodal luminescence on the nano-, micro-, and milli-second time scales

Marius Jakoby; Carolin Beil; Pariya Nazari; Bryce S Richards; Michael Seitz; Andrey Turshatov; Ian A Howard

doi:10.1016/j.isci.2021.102207

Rare-earth coordination polymers with multimodal luminescence on the nano-, micro-, and milli-second time scales

iScience. 2021 Feb 23;24(3):102207. doi: 10.1016/j.isci.2021.102207. eCollection 2021 Mar 19.

Authors

Marius Jakoby¹, Carolin Beil², Pariya Nazari¹, Bryce S Richards^{1

3}, Michael Seitz², Andrey Turshatov¹, Ian A Howard^{1

3}

Affiliations

¹ Institute of Microstructure Technology, Karlsruhe Institute of Technology, Hermann-von-Helmholtz-Platz 1, 76344 Eggenstein-Leopoldshafen, Germany.
² Institute of Inorganic Chemistry, University of Tübingen, Auf der Morgenstelle 18, 72076 Tübingen, Germany.
³ Light Technology Institute, Karlsruhe Institute of Technology, Engesserstrasse 13, 76131 Karlsruhe, Germany.

Abstract

We present a coordination polymer based on rare-earth metal centers and carboxylated 4,4'-diphenyl-2,2'-bipyridine ligands. We investigate Y³⁺, Lu³⁺, Eu³⁺, and a statistical mixture of Y³⁺ with Eu³⁺ as metal centers. When Y³⁺ or Lu³⁺ is exclusively present in the coordination polymer, biluminescence from the ligand is observed: violet emission from the singlet state (417 nm, 0.9 ns lifetime) and orange emission from the triplet state (585 nm, 76 ms (Y³⁺) and 31 ms (Lu³⁺)). When Eu³⁺ is present in a statistical mixture with Y³⁺, red emission from the Eu³⁺ (611 nm, $\sim 500 μs$ ) is observed in addition to the ligand emissions. We demonstrate that this multi-mode emission is enabled by the immobility of singlet and triplet states on the ligand. Eu³⁺ only receives energy from adjacent ligands. Meanwhile, in the broad inhomogeneous distribution of ligand energies, higher energy states favor singlet emission, whereas faster intersystem crossing in the more stabilized ligands enhances their contribution to triplet emission.

Keywords: Optical Materials; Optical Property of Matter; Polymers.