| Emissive Osmium(II) Complexes Supported by N-Heterocyclic Carbene-based C(∧)C(∧)C-Pincer Ligands and Aromatic Diimines. | |
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MedLine Citation:
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PMID: 22873818    Owner: NLM    Status: Publisher    |
Abstract/OtherAbstract:
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Osmium(II) complexes containing N-heterocyclic carbene (NHC)-based pincer ligand 1,3-bis(1-methylimidazolin-2-ylidene)phenyl anion (C(1)(∧)C(∧)C(1)) or 1,3-bis(3-methylbenzimidazolin-2-ylidene)phenyl anion (C(2)(∧)C(∧)C(2)) and aromatic diimine (2,2'-bipyridine (bpy), 1,10-phenanthroline (phen), or 4,4'-diphenyl-2,2'-bipyridine (Ph(2)bpy)) in the form of [Os(C(∧)C(∧)C)(N(∧)N)(CO)](+) have been prepared. Crystal structures for these complexes show that the Os-C(NHC) bonds are essentially single (Os-C(NHC) distances = 2.079(5)-2.103(7) Å). Spectroscopic comparisons and time-dependent density functional theory (TD-DFT) calculations suggest that the lowest-energy electronic transition associated with these complexes (λ(max) = 493-536 nm, ε(max) = (5-10) × 10(3) dm(3) mol(-1) cm(-1), solvent = CH(3)CN) originate from a d(π)(Os(II)) → π*(N(∧)N) metal-to-ligand charge transfer transition, where the d(π)(Os(II)) and π*(N(∧)N) levels contain significant contribution from the C(∧)C(∧)C ligands. All these complexes are emissive in the red-spectral region (674-731 nm) with quantum yields of 10(-4)-10(-2) and emission lifetimes of around 1-6 μs. Transient absorption spectroscopy and spectroelectrochemical measurements have also been used to probe the nature of the emissive excited-states. Overall, this joint experimental and theoretical investigation reveals that the C(∧)C(∧)C ligands can be used to modulate the photophysical properties of a [Os(N(∧)N)] core via the formation of the hybrid [Os + C(∧)C(∧)C] frontier orbitals. |
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Authors:
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Lai-Hon Chung; Siu-Chung Chan; Wing-Chun Lee; Chun-Yuen Wong |
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Publication Detail:
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Type:Â JOURNAL ARTICLE Â Â Â Date:Â 2012-8-8 |
Journal Detail:
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Title: Inorganic chemistry    Volume: -    ISSN: 1520-510X    ISO Abbreviation: Inorg Chem    Publication Date: 2012 Aug |
Date Detail:
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Created Date:Â 2012-8-9 Â Â Â Completed Date:Â - Â Â Â Revised Date:Â - Â Â Â |
Medline Journal Info:
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Nlm Unique ID: 0366543    Medline TA: Inorg Chem    Country: -    |
Other Details:
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Languages:Â ENG Â Â Â Pagination:Â - Â Â Â Citation Subset:Â - Â Â Â |
Affiliation:
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Department of Biology and Chemistry, City University of Hong Kong , Tat Chee Avenue, Kowloon, Hong Kong SAR, People's Republic of China. |
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From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine
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