A remarkable ligand orientational effect in osmium-atom-induced blue phosphorescence

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DOIResolve DOI: http://doi.org/10.1002/chem.200400598
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TypeArticle
Journal titleChemistry - A European Journal
Volume10
Issue24
Pages62556264; # of pages: 10
AbstractA new series of OsII-based carbonyl complexes cis(CO),trans(Npy,Npy),cis(Ntz,Ntz)-[Os(CO)2(bptz)2] (1), cis(CO),cis(Npy,Npy),trans(Ntz,Ntz)-[Os(bptz)2(CO)2] (2), and cis(CO),trans(Npy,Npy),cis(Ntz,Ntz)-[Os(CO)2(fptz)2] (3), where bptz and fptz denote 3-tert-butyl-5-(2-pyridyl)- and 3-trifluoromethyl-5-(2-pyridyl)-1,2,4-triazolate, respectively, have been designed and synthesized in an effort to achieve high efficiency, room-temperature blue phosphorescence. Although 1 and 2 are geometric isomers, remarkably different excited-state relaxation pathways were observed. Complex 1 exhibits strong phosphorescence in CH3CN (Phipsim0.47) and as a single crystal at room temperature, whereas complex 2 is nearly nonemissive under similar conditions. The associated relaxation dynamics have been comprehensively investigated by spectroscopic and relaxation dynamics as well as by theoretical approaches. Our results lead us to the conclusion that for complex 2, the ldquoloose boltrdquo effect of metal-ligand bonding interactions plays a crucial role in the fast radiationless deactivation of this type of geometrical isomer. Fine adjustment can also be achieved by functionalizing the ligands so that the electron-withdrawing nature of the CF3 group in 3 stabilizes the HOMO of the triazolate moiety, thus moving the emission further into the pure ldquobluerdquo region; this results in highly efficient phosphorescence and renders 3 particularly attractive for application in blue OLED devices.
Publication date
LanguageEnglish
AffiliationNational Research Council Canada; NRC Steacie Institute for Molecular Sciences
Peer reviewedNo
NPARC number12335879
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Record identifier914065ec-dd6f-4b4b-8598-8b57467a75db
Record created2009-09-10
Record modified2016-05-09
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