IrIII and RuII Complexes Containing Triazole‐Pyridine Ligands: Luminescence Enhancement upon Substitution with β‐Cyclodextrin |
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| Authors: | Marco Felici Pablo Contreras‐Carballada Dr Yolanda Vida Dr Jan M M Smits Roeland J M Nolte Prof Dr Luisa De Cola Prof Dr René M Williams Dr Martin C Feiters Dr |
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| Institution: | 1. Department of Organic Chemistry, Institute for Molecules and Materials, Radboud University Nijmegen, Heijendaalseweg 135, 6525 AJ Nijmegen (The Netherlands), Fax: (+31)?243‐652‐929;2. Molecular Photonic Materials, Van't Hoff Institute for Molecular Sciences, Universiteit van Amsterdam, Nieuwe Achtergracht 129, 1018 WS Amsterdam (The Netherlands), Fax: (+31) 205‐256‐456;3. Physikalisches Institut and CeNTech, Westf?lische Wilhelms‐Universit?t Münster, Mendelstrasse 7, 48149 Münster (Germany), Fax: (+49)?251‐980‐2834;4. Present address: Department of Organic Chemistry, Faculty of Sciences, University of Malaga, 29071 Malaga (Spain);5. Solid State Chemistry, Institute for Molecules and Materials, Radboud University Nijmegen, Heijendaalseweg 135, 6525 AJ Nijmegen (The Netherlands) |
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| Abstract: | Novel 2‐(1‐substituted‐1H‐1,2,3‐triazol‐4‐yl)pyridine (pytl) ligands have been prepared by “click chemistry” and used in the preparation of heteroleptic complexes of Ru and Ir with bipyridine (bpy) and phenylpyridine (ppy) ligands, respectively, resulting in Ru(bpy)2(pytl‐R)]Cl2 and Ir(ppy)2(pytl‐R)]Cl (R=methyl, adamantane (ada), β‐cyclodextrin (βCD)). The two diastereoisomers of the Ir complex with the appended β‐cyclodextrin, Ir(ppy)2(pytl‐βCD)]Cl, were separated. The Ru(bpy)2(pytl‐R)]Cl2 (R=Me, ada or βCD) complexes have lower lifetimes and quantum yields than other polypyridine complexes. In contrast, the cyclometalated Ir complexes display rather long lifetimes and very high emission quantum yields. The emission quantum yield and lifetime (Φ=0.23, τ=1000 ns) of Ir(ppy)2(pytl‐ada)]Cl are surprisingly enhanced in Ir(ppy)2(pytl‐βCD)]Cl (Φ=0.54, τ=2800 ns). This behavior is unprecedented for a metal complex and is most likely due to its increased rigidity and protection from water molecules as well as from dioxygen quenching, because of the hydrophobic cavity of the βCD covalently attached to pytl. The emissive excited state is localized on these cyclometalating ligands, as underlined by the shift to the blue (450 nm) upon substitution with two electron‐withdrawing fluorine substituents on the phenyl unit. The significant differences between the quantum yields of the two separate diastereoisomers of Ir(ppy)2(pytl‐βCD)]Cl (0.49 vs. 0.70) are attributed to different interactions of the chiral cyclodextrin substituent with the Δ and Λ isomers of the metal complex. |
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| Keywords: | click chemistry cyclodextrins iridium luminescence ruthenium |
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