NMR investigations of the solution structures of Ru–Zn complexes tethered by oligo(aminoethylglycine) chains

[Ru(bpy)3]2+ complexes derivatized with two aminoethylglycine (aeg) chains bearing pendant bipyridine ligands coordinate Zn2+ to form a coordinative interchain crosslink. Although [Zn(bpy)2]2+ is both redox and spectroscopically silent, when bound to [Ru(bpy)3]2+ by the aeg strands it causes quenching of the emissive Ru complex excited state. 1H NMR spectroscopy is used to monitor changes in the structure and environment of the Ru complex during a titration as Zn2+ is added. Using spectral assignments from 1 and 2D NMR spectra, the spectrophotometric titrations reveal that Zn2+ binding causes significant shifts of the peaks assigned to the protons on the [Ru(bpy)3]2+ core that are closest to the Zn2+. These shifts reveal changes in the local environment that are likely a combination of electrostatic interactions between the two dication metal complexes and strain induced by the metal ion crosslinking the strands.

[Ru(bpy)3]2+ complexes derivatized with two aminoethylglycine (aeg) chains bearing pendant bipyridine ligands coordinate Zn2+ to form a coordinative interchain crosslink. Spectrophotometric NMR titrations reveal that Zn2+ binding causes significant shifts of the peaks assigned to the protons on the [Ru(bpy)3]2+ core that are closest to the Zn2+. These shifts reveal changes in the local environment that are likely a combination of electrostatic interactions between the two dication metal complexes and strain induced by the metal ion crosslinking the strands.Figure optionsDownload as PowerPoint slide