Luminescent metal complexes featuring photophysically innocent boron cluster ligands

• Published in: Chemical science (Cambridge) 2016-01, Vol.7 (8), p.5132-5138
• Main Authors: Kirlikovali, Kent O, Axtell, Jonathan C, Gonzalez, Alejandra, Phung, Alice C, Khan, Saeed I, Spokoyny, Alexander M
• Format: Article
• Language: English
• Subjects: Charge transfer; Clusters; Coordination compounds; Emission; Ligands; Mathematical analysis; Organic light emitting diodes; X-rays
• ISSN: 2041-6520; 2041-6539
• DOI: 10.1039/c6sc01146b

We report the synthesis and characterization of a series of d 8 metal complexes featuring robust and photophysically innocent strong-field chelating 1,1′-bis( o -carborane) ( bc ) ligand frameworks. A combination of UV-Vis spectroscopy, single crystal X-ray structural analysis, and DFT calculations of these species suggest that the dianionic bc ligand does not contribute to any visible metal-to-ligand charge transfer (MLCT) transitions, yet it provides a strong ligand field in these complexes. Furthermore, a bc -based Pt( ii ) complex containing a 4,4′-di- tert -butyl-2,2′-bipyridine ligand (dtb-bpy) has been prepared and was found to display blue phosphorescent emission dominated by MLCT from the Pt( ii ) center to the dtb-bpy ligand. Importantly, the bulky three-dimensional nature of the bc ligand precludes intermolecular Pt( ii ) Pt( ii ) interactions in the solid state where the resulting compounds retain their emission properties. This study opens a potentially new avenue for designing organic light-emitting diode (OLED) materials with tunable properties featuring photophysically innocent boron-rich cluster ligands. We report the synthesis and characterization of a series of d 8 metal complexes featuring robust and photophysically innocent strong-field chelating 1,1′-bis( o -carborane) ( bc ) ligand frameworks.