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Issue 4, 2015
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Sticking and patching: tuning and anchoring cyclometallated ruthenium(II) complexes

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Abstract

A series of [Ru(bpy)2(C^N)][PF6] (HC^N = 2-phenylpyridine derivative) complexes functionalized in the cyclometallating C^N phenyl ring with F, Me, OMe, CO2Me, StBu, SO2Me (ligands H1–H6) or in the C^N pyridine ring with 4-CO2Me or 4-C6H4P(O)(OEt)2 substituents (ligands H7 or H9) have been prepared and characterized; representative crystal structures confirm the structural features of the complexes. When the C^N ligand contains a CO2H substituent (ligand H28), deprotonation in addition to cyclometallation occurs to give a neutral, zwitter-ionic complex [Ru(bpy)2(8)]. The synthesis of the cationic complexes requires addition of a silver(I) salt (AgPF6 or AgBF4) to abstract Cl from cis-[Ru(bpy)2Cl2] and 1H NMR spectroscopic data are consistent with interactions between Ag+ and the coordinated C^N ligand in [Ru(bpy)2(C^N)]+. The absorption spectra of [Ru(bpy)2(C^N)][PF6] (C^N = 1–6) are similar, but the introduction of the anchoring domains in [Ru(bpy)2(C^N)][PF6] with C^N = 7 or 9 enhances the absorption response; the greatest influence is observed in [Ru(bpy)2(9)]+ with the introduction of the 4-C6H4P(O)(OEt)2 substituent. Trends in emission and electrochemical behaviours of the complexes are interpreted in terms of the influence of the electronic properties of the C^N ligand substituents on the energies of the HOMO which is localized on the C^N ligand and Ru centre. This study provides an optimized synthetic route to the phosphonate ester derivative [Ru(bpy)2(9)][PF6], designed to anchor to a semiconductor surface; this complex also exhibits the most favourable absorption properties among the complexes studied.

Graphical abstract: Sticking and patching: tuning and anchoring cyclometallated ruthenium(ii) complexes

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Publication details

The article was received on 12 Sep 2014, accepted on 11 Nov 2014 and first published on 20 Nov 2014


Article type: Paper
DOI: 10.1039/C4DT02797C
Author version available: Download Author version (PDF)
Citation: Dalton Trans., 2015,44, 1557-1570
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    Sticking and patching: tuning and anchoring cyclometallated ruthenium(II) complexes

    C. D. Ertl, D. P. Ris, S. C. Meier, E. C. Constable, C. E. Housecroft, M. Neuburger and J. A. Zampese, Dalton Trans., 2015, 44, 1557
    DOI: 10.1039/C4DT02797C

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