Issue 17, 2014

Stereoselective formation of a meso-diruthenium(ii,ii) complex and tuning the properties of its monoruthenium analogues

Abstract

A novel bis(bidentate) ligand dgpm (dgpm = diguanidylpyrimidine) was synthesized by a catalyst-free C–N bond forming reaction in high yield (90%) by microwave-assisted heating. The ligand was coordinated to two [Ru(bpy)2]2+ cores to afford a meso-di-Ru(II,II) complex (1-meso) with high diastereoselectivity over its homochiral form. Three mononuclear ether-functionalized Ru(II) complexes (2: ethoxyether; 3: butoxyether; 4: 2-hydroxy-1-ethoxyether) were also isolated. The ligand and complexes were fully characterized by a variety of techniques including X-ray crystallography. In cyclic voltammetric studies, the complexes exhibit a RuIII/II couple, which is ∼500 mV less positive than the RuIII/II couple in Ru(bpy)32+. The 1MLCT absorption maxima of all the complexes (510–550 nm) are considerably red-shifted as compared to that of Ru(bpy)32+ (450 nm). The 3MLCT emission maxima of complexes 1-meso and 3 are also red-shifted by about 120 nm compared to that of Ru(bpy)32+ (620 nm), whereas the corresponding maxima for complexes 2 and 4 are shifted by 75 nm and 25 nm, respectively. These relative trends in redox potentials and 1MLCT maxima are in good agreement with DFT and TD-DFT calculations, performed for all complexes. Complexes 1-meso and 3 display emission from a RuII-to-bpy 3MLCT state, which is rarely the emitting state at λ > 700 nm in [Ru(bpy)2(N-N)]2+ complexes when the ancillary ligand is neutral.

Graphical abstract: Stereoselective formation of a meso-diruthenium(ii,ii) complex and tuning the properties of its monoruthenium analogues

Supplementary files

Article information

Article type
Paper
Submitted
13 Jan 2014
Accepted
31 Jan 2014
First published
13 Mar 2014

Dalton Trans., 2014,43, 6567-6577

Stereoselective formation of a meso-diruthenium(II,II) complex and tuning the properties of its monoruthenium analogues

A. K. Pal and G. S. Hanan, Dalton Trans., 2014, 43, 6567 DOI: 10.1039/C4DT00112E

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