Issue 11, 2014

The redox series [Ru(bpy)2(L)]n, n = +3, +2, +1, 0, with L = bipyridine, “click” derived pyridyl-triazole or bis-triazole: a combined structural, electrochemical, spectroelectrochemical and DFT investigation

Abstract

The compounds [Ru(bpy)2(L1)](ClO4)2 (1(ClO4)2), [Ru(bpy)2(L2)](ClO4)2 (2(ClO4)2), [Ru(bpy)2(L3)](ClO4)2 (3(ClO4)2), [Ru(bpy)2(L4)](ClO4)2 (4(ClO4)2), [Ru(bpy)2(L5)](ClO4)2 (5(ClO4)2), and [Ru(bpy)2(L6)](ClO4)26(ClO4)2 (bpy = 2,2′-bipyridine, L1 = 1-(4-isopropyl-phenyl)-4-(2-pyridyl)-1,2,3-triazole, L2 = 1-(4-butoxy-phenyl)-4-(2-pyridyl)-1,2,3-triazole, L3 = 1-(2-trifluoromethyl-phenyl)-4-(2-pyridyl)-1,2,3-triazole, L4 = 4,4′-bis-{1-(2,6-diisopropyl-phenyl)}-1,2,3-triazole, L5 = 4,4′-bis-{(1-phenyl)}-1,2,3-triazole, L6 = 4,4′-bis-{1-(2-trifluoromethyl-phenyl)}-1,2,3-triazole) were synthesized from [Ru(bpy)2(EtOH)2](ClO4)2 and the corresponding “click”-derived pyridyl-triazole or bis-triazole ligands, and characterized by 1H-NMR spectroscopy, elemental analysis, mass spectrometry and X-ray crystallography. Structural analysis showed a distorted octahedral coordination environment about the Ru(II) centers, and shorter Ru–N(triazole) bond distances compared to Ru–N(pyridine) distances in complexes of mixed-donor ligands. All the complexes were subjected to cyclic voltammetric studies, and the results were compared to the well-known [Ru(bpy)3]2+ compound. The oxidation and reduction potentials were found to be largely uninfluenced by ligand changes, with all the investigated complexes showing their oxidation and reduction steps at rather similar potentials. A combined UV-vis-NIR and EPR spectroelectrochemical investigation, together with DFT calculations, was used to determine the site of electron transfer in these complexes. These results provided insights into their electronic structures in the various investigated redox states, showed subtle differences in the spectroscopic signatures of these complexes despite their similar electrochemical properties, and provided clues to the unperturbed redox potentials in these complexes with respect to ligand substitutions. The reduced forms of the complexes display structured absorption bands in the NIR region. Additionally, we also present new synthetic routes for the ligands presented here using Cu-abnormal carbene catalysts.

Graphical abstract: The redox series [Ru(bpy)2(L)]n, n = +3, +2, +1, 0, with L = bipyridine, “click” derived pyridyl-triazole or bis-triazole: a combined structural, electrochemical, spectroelectrochemical and DFT investigation

Supplementary files

Article information

Article type
Paper
Submitted
14 Oct 2013
Accepted
21 Nov 2013
First published
22 Nov 2013

Dalton Trans., 2014,43, 4437-4450

The redox series [Ru(bpy)2(L)]n, n = +3, +2, +1, 0, with L = bipyridine, “click” derived pyridyl-triazole or bis-triazole: a combined structural, electrochemical, spectroelectrochemical and DFT investigation

S. Hohloch, D. Schweinfurth, M. G. Sommer, F. Weisser, N. Deibel, F. Ehret and B. Sarkar, Dalton Trans., 2014, 43, 4437 DOI: 10.1039/C3DT52898G

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