Bright and Photostable TADF-Emitting Zirconium(Ⅳ) Pyridinedipyrrolide Complexes: Efficient Dyes for Decay Time-Based Temperature Sensing and Imaging

摘要

Luminescence thermometry represents a technique of choice formeasurements in small objects and imaging of temperature distribution.However, most state-of-the-art luminescent probes are limited in spectralcharacteristics, brightness, photostability, and sensitivity. Molecularthermometers of the new generation utilizing air and moisture-stablezirconium(IV) pyridinedipyrrolide complexes can address all these limitations.The dyes emit pure thermally activated delayed fluorescence without anyprompt fluorescence and show a unique combination of attractive features:a) visible light excitation and emission in the orange/red region, b) highluminescence brightness (quantum yields ≈0.5 in toluene and 0.8–1.0 inpolystyrene matrix), c) excellent photostability, d) suitability for two-photonexcitation and e) mono-exponential decay on the order of tens to hundredsof microseconds with strongly temperature-dependent lifetimes (between?2.5 and ?2.9% K~(?1) in polystyrene at 25 ℃). Immobilization in gas-blockingpolymers yields sensing materials for self-referenced decay time read-outthat are manufactured in two common formats: planar optodes and waterdispersiblenanoparticles. Positively charged nanoparticles are demonstratedto be suitable for nanothermometry in live cells and multicellular spheroids.Negatively charged nanoparticles represent advanced analytical toolsfor imaging temperature gradients in samples of small volumes such asmicrofluidic devices.