Synthese, spektroskopische Eigenschaften und elektrochemisches Verhalten von Ruthenium(II)‐Komplexen mit zweizähnigen Stickstoffliganden

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Abstract
Synthesis, Spectroscopic Data and Electrochemical Behavior of Ruthenium(II) Complexes with Bidentate LigandsThe syntheses of coordination compounds of ruthenium (II) with bidentate nitrogen donors (aa) is described. The ligands (aa) used are related to dipyridyl, but differ from the latter in size of the π‐electron systems. In some ligands, e.g. 10, the two halves of the molecule are forced to be non planar by the aliphatic bridge between the two rings accomodating the nitrogen ligand atoms. The syntheses of the complexes Ru(dipy)2(aa)2+, Ru(dipy)(aa)2+2 and Ru(aa)2+3 ((aa) 1–17) are described. Generally the crystalline salts with PF−6 as counter‐ion have been obtained. The complexes are characterized by elementary analysis, electronic spectra, infrared spectra, cyclic voltammograms, proton nuclear magnetic resonance spectra and, for those which have been obtained in optically active forms also by circular dichroism. In the discussion special emphasis is given to the change of properties compared to the well investigated Ru(dipy)2+3 complex. In the visible range of the spectrum all complexes show one or several spin allowed charge transfer transitions at longer wave lengths then Ru(dipy)2+3. The ground state oxidation potential to the 3+ state are little affected by substitution of one or more of the dipy ligands in Ru(dipy)2+3 by the ligands (aa), whereas the reduction behavior is strongly influenced by such substitutions. The 1H‐NMR. spectra indicate rigid conformations of some of the nonplanar (aa)‐ligands in the complexes.