Extended ligand conjugation and dinuclearity as a route to efficient platinum-based near-infrared (NIR) triplet emitters and solution-processed NIR-OLEDs

Near infrared (NIR) emission from molecular materials is typically targeted by using more extended conjugated systems compared to visible-emitting materials. But efficiencies usually fall off due to the combined effects of increasing non-radiative and lower oscillator strengths as the energy of emis...

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Published in:Journal of materials chemistry. C, Materials for optical and electronic devices Materials for optical and electronic devices, 2021-01, Vol.9 (1), p.127-135
Main Authors: Shafikov, Marsel Z, Pander, Piotr, Zaytsev, Andrey V, Daniels, Ruth, Martinscroft, Ross, Dias, Fernando B, Williams, J. A. Gareth, Kozhevnikov, Valery N
Format: Article
Language:English
Subjects:
Conjugation
Coordination compounds
Coupling (molecular)
Crystallography
Emission
Emitters
Excitation
Fluorescence
Heavy metals
Ligands
Near infrared radiation
Organic light emitting diodes
Oscillator strengths
Phosphorescence
Photoluminescence
Platinum
Quantum efficiency
Radiosity
Spin-orbit interactions
Toluene
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Summary:Near infrared (NIR) emission from molecular materials is typically targeted by using more extended conjugated systems compared to visible-emitting materials. But efficiencies usually fall off due to the combined effects of increasing non-radiative and lower oscillator strengths as the energy of emissive excited states decreases. Efficient NIR-emitting organic light emitting diodes (OLEDs) are rare compared to the huge progress that has been made for visible-light devices. For organometallic emitters that contain a heavy metal ion to promote phosphorescence through the effect of enhanced spin-orbit coupling (SOC), the problem is typically exacerbated by decreased metal character in the S n and T 1 excited states as the conjugation in a bound ligand increases. Here we show how the use of a dinuclear metal complex with an extended conjugated ligand allows such effects to be mitigated compared to analogous structures with just one metal centre. The complex Pt 2 (bis-dthpym)(dpm) 2 (complex 5 ) is readily prepared by a double N^C cyclometallation of 4,6-bis(dithienyl)-pyrimidine (H 2 bis-dthpym), with the coordination sphere of each Pt centre being completed by O^O-coordinating dipivaloylmethane (dpm). This new complex displays intense NIR emission in solution, λ max = 725 nm, with essentially no "contamination" by visible light
ISSN:2050-7526
2050-7534
DOI:10.1039/d0tc04881j