When two are better than one: bright phosphorescence from non-stereogenic dinuclear iridium(iii ) complexes
| العنوان: | When two are better than one: bright phosphorescence from non-stereogenic dinuclear iridium( |
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| المؤلفون: | William Clegg, Stacey Culham, Valery N. Kozhevnikov, Ruth Daniels, Marcus C. Durrant, J. A. Gareth Williams, Michael R. Probert, Michael Hunter |
| المصدر: | Dalton transactions, 2016, Vol.45(16), pp.6949-6962 [Peer Reviewed Journal] |
| بيانات النشر: | Royal Society of Chemistry (RSC), 2016. |
| سنة النشر: | 2016 |
| مصطلحات موضوعية: | Denticity, 010405 organic chemistry, Chemistry, Stereochemistry, Ligand, Trans effect, F100, Substituent, chemistry.chemical_element, 010402 general chemistry, 01 natural sciences, 0104 chemical sciences, 3. Good health, Stereocenter, Inorganic Chemistry, chemistry.chemical_compound, Crystallography, Singlet state, Iridium, Phosphorescence |
| الوصف: | A new family of eight dinuclear iridium(iii) complexes has been prepared, featuring 4,6-diarylpyrimidines L(y) as bis-N^C-coordinating bridging ligands. The metal ions are also coordinated by a terminal N^C^N-cyclometallating ligand L(X) based on 1,3-di(2-pyridyl)benzene, and by a monodentate chloride or cyanide. The general formula of the compounds is {IrL(X)Z}2L(y) (Z = Cl or CN). The family comprises examples with three different L(X) ligands and five different diarylpyrimidines L(y), of which four are diphenylpyrimidines and one is a dithienylpyrimidine. The requisite proligands have been synthesised via standard cross-coupling methodology. The synthesis of the complexes involves a two-step procedure, in which L(X)H is reacted with IrCl3·3H2O to form dinuclear complexes of the form [IrL(X)Cl(μ-Cl)]2, followed by treatment with the diarylpyrimidine L(y)H2. Crucially, each complex is formed as a single compound only: the strong trans influence of the metallated rings dictates the relative disposition of the ligands, whilst the use of symmetrically substituted tridentate ligands eliminates the possibility of Λ and Δ enantiomers that are obtained when bis-bidentate units are linked through bridging ligands. The crystal structure of one member of the family has been obtained using a synchrotron X-ray source. All of the complexes are very brightly luminescent, with emission maxima in solution varying over the range 517-572 nm, according to the identity of the ligands. The highest-energy emitter is the cyanide derivative whilst the lowest is the complex with the dithienylpyrimidine. The trends in both the absorption and emission energies as a function of ligand substituent have been rationalised accurately with the aid of TD-DFT calculations. The lowest-excited singlet and triplet levels correlate with the trend in the HOMO-LUMO gap. All the complexes have quantum yields that are close to unity and phosphorescence lifetimes - of the order of 500 ns - that are unusually short for complexes of such brightness. These impressive properties stem from an unusually high rate of radiative decay, possibly due to spin-orbit coupling pathways being facilitated by the second metal ion, and to low non-radiative decay rates that may be related to the rigidity of the dinuclear scaffold. |
| وصف الملف: | application/pdf |
| تدمد: | 1477-9234 1477-9226 |
| URL الوصول: | https://explore.openaire.eu/search/publication?articleId=doi_dedup___::d1336105cb7910aad5def30b729c0091 https://doi.org/10.1039/c6dt00881j |
| حقوق: | OPEN |
| رقم الأكسشن: | edsair.doi.dedup.....d1336105cb7910aad5def30b729c0091 |
| قاعدة البيانات: | OpenAIRE |
| تدمد: | 14779234 14779226 |
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