A new class of high-performance light-emitting materials
Researchers developed a new class of highly luminescent organoaluminium complexes, photo: Grzegorz Krzyżewski
The materials were developed by researchers from the Institute of Physical Chemistry of the Polish Academy of Sciences and Warsaw University of Technology, under the leadership of Professor Janusz Lewiński. The simplicity of the synthesis process combined with the unique optoelectronic properties of these compounds makes them highly promising candidates for practical applications in optoelectronic devices.
The growing demand for artificial light has driven intensive research into light-emitting materials activated by external excitation, as well as the development of energy-efficient solutions based on them, such as optical sensors, displays, and bioimaging systems. As a result, scientists have been actively seeking new luminescent materials, commonly referred to as phosphors.
In recent years, phosphors based on main-group metal complexes have garnered significant attention as phosphor materials. These complexes offer the possibility of tuning their photophysical properties by modifying the metal centre, organic ligands, or the overall complex structure. Aluminium, being abundant in the Earth’s crust, has been of particular interest since the milestone application of Alq₃ (tris (8-hydroxyquinolinato) aluminium) in LED technology in 1987.
Building on this foundation, a team of researchers from IChF PAS and the Faculty of Chemistry at Warsaw University of Technology, in collaboration with Professor Andrew E. H. Wheatley from the University of Cambridge, has recently developed a novel class of highly luminescent organoaluminium complexes. Inspired by reference materials such as Alq₃, the team synthesized a unique series of tetrameric, stereogenic alkylaluminium complexes of the general formula [(R′-anth)AlR]₄, using readily available ligands derived from aromatic amino acids. These anthranilic acid–based aluminium complexes exhibit exceptionally attractive optoelectronic properties.
The results of this research have been published in "Angewandte Chemie International Edition" in the article: "Luminescent Alkylaluminium Anthranilates Reaching Unity Quantum Yield in the Condensed Phase" DOI: https://doi.org/10.1002/anie.202501985.
– In this study, we focused on commercially available anthranilic acid (anth-H₂) and its N-methyl (Me-anth-H₂) and N-phenyl (Ph-anth-H₂) derivatives as model proligands – explains Vadim Szejko from the Faculty of Chemistry at WUT, first author of the publication. – Their reaction with suitable R₃Al compounds in toluene led to the formation of a series of quaternary, stereogenic complexes with distinctive properties.
Photophysical investigations demonstrated that the aluminium-based anthranilates exhibit photoluminescence quantum yields reaching 100% in the solid state. Subtle ligand modifications significantly enhanced emission efficiency, opening new pathways for the design of advanced luminescent materials in this class.
– By substituting the nitrogen atom in the anthranilic scaffold with methyl or phenyl groups, we created a range of luminophores with emission efficiencies ranging from modest to outstanding – notes Iwona Justyniak, PhD, from IChF PAS. – Notably, the [(Ph-anth)AlEt]₄ derivative achieved unity quantum yield in the condensed phase – a breakthrough result for aluminium complexes.
Complementary quantum chemical calculations provided insight into the electronic transitions and helped identify the specific molecular fragments most responsible for the observed photophysical behaviour. The ligand modifications effectively suppressed non-radiative relaxation pathways, improving emission efficiency. In the solid state, intra- and intermolecular non-covalent interactions preserved the structural integrity of the excited-state complexes, minimizing distortion and quenching. The aggregation-induced rigidity of the molecules further supported sustained high luminescence.
This study marks a milestone in the development of easily accessible, high-performance fluorescent materials. The straightforward modification of the ligand framework enables further tuning of chemical stability and optical properties, paving the way for practical applications in OLED technologies, display panels, and optical sensors.
The research was funded by the National Science Centre (NCN) under the OPUS 19 programme (grant no. 2020/37/B/ST4/03310).
Source: ichf.edu.pl