219135-61-2Relevant academic research and scientific papers
Structures, electrochemical and spectroscopic properties of ternary ruthenium(II)-polypyridyl complexes with additional carboxylate, biguanide or sulfonamide donors
Couchman, Samantha M.,Dominguez-Vera, Jose M.,Jeffery, John C.,McKee, Colin A.,Nevitt, Simon,Pohlman, Matthias,White, Claire M.,Ward, Michael D.
, p. 3541 - 3550 (1998)
The following complexes have been prepared: [Ru(bipy)2(pic)][PF6] (bipy=2,2′-bipyridine; Hpic= picolinic acid); [Ru(terpy)(dipic)] (terpy=2,2′:6′,2″-terpyridine; H2dipic=dipicolinic acid); [Ru(bipy)2 (Hbig)][PF6]2 (Hbig=biguanide); and [Ru(bipy)2(apps)][PF6] [where Happs is the p-tolylsulfonamide of 2-(2-aminophenyl)-pyridine]. The latter three have been characterised by X-ray crystallography and are all mononuclear pseudo-octachedral complexes. Electrochemical studies reveal the relationship between the potential of the metal-based Ru(II)Ru(III) couple, with the potential values being clearly related to the σ-donor or π-acceptor capabilities of the ligands. The energies of the lowest-energy m.l.c.t. maxima in the electronic spectra also correlate with ligand properties. [Ru(bipy)2(Hbig)][PF6]2, which has a dissociable proton on the biguanide ligand, undergoes deprotonation in strongly basic conditions (pKa=12.3±0.2), which results in a red-shift of the m.l.c.t. transition consistent with weakening of the ligand field due to the increased π-donor capability of the deprotonated ligand.
