title: Sticking and patching: tuning and anchoring cyclometallated ruthenium(II) complexes.
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, S(t)Bu, 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 (1)H 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.
authors.affiliation: Department of Chemistry, University of Basel, Spitalstrasse 51, 4056 Basel, Switzerland. catherine.housecroft@unibas.ch.
authors.forename: Cathrin D
authors.initials: CD
authors.lastname: Ertl
authors.forename: Daniel P
authors.initials: DP
authors.lastname: Ris
authors.forename: Stefan C
authors.initials: SC
authors.lastname: Meier
authors.forename: Edwin C
authors.initials: EC
authors.lastname: Constable
authors.forename: Catherine E
authors.initials: CE
authors.lastname: Housecroft
authors.forename: Markus
authors.initials: M
authors.lastname: Neuburger
authors.forename: Jennifer A
authors.initials: JA
authors.lastname: Zampese