Ruthenium redox properties

The results presented here seem to indicate that 1) the local order about ruthenium centers in the polymers is essentially unchanged from that in the monomer complex and 2) that the interaction with the electrode surface occurs without appreciable electronic and structural change. This spectroscopic information corroborates previous electrochemical results which showed that redox properties (e.g. as measured by formal potentials) of dissolved species could be transferred from solution to the electrode surface by electrodepositions as polymer films on the electrode. Furthermore, it is apparent that the initiation of polymerization at these surfaces (i.e. growth of up to one monolayer of polymer) involves no gross structural change. 

The redox properties of a transition metal complex may change dramatically if it has absorbed energy and exisis in an excited state. One of the most famous and widely studied complexes in this area is tr]s(2.2 -bipyridine)ruthenium(il) cation. 

Levason, W., Quirk, J. J., Reid, G., Smith, S. M., Synthesis, spectroscopic and redox properties of ruthenium complexes with selenoether macrocycles crystal structures of cis-[RuCl2([16]aneSe4)] and trans-[RuCl(PPh3)([16]aneSe4)]PF6 ([16]aneSe4 = 1,5,9,13-tetraselenacyclohexadecane). J. Chem. Soc., Dalton Trans. 1997, 3719-3724. 

Fraysse et al. have synthesized a derivative with two ruthenium centers, 29, and have investigated its photochromic and redox properties [27]. The closed form of this complex is obtained with 254-nm light irradiation in 75%... 

The redox properties of ruthenium(II) sarcophaginates are discussed in Refs. 324 and 327. The [Ru(sar)] + cation oxidized readily to the corresponding ruthenium (III) complex, which spontaneously disproportionated to the initial cation and a monodeprotonated intermediate ruthenium(IV) complex. This complex quickly produced the imine ruthenium(II) clathrochelate by both base- and acid-catalyzed pathways (Scheme 118). Intermediate di- and triimine species were also observed. The kinetic and thermodynamic data for the disproportionation process demonstrated that the secondary amino group in [Ru(sar)] + cation is quite acidic (pRTa = 5-r6) and that the ruthenium(IV) state is stabilized at more than 2000 mV. 

There is much interest in transition metal polypyridyl complexes, largely due to their numerous applications in a variety of fields (247-250). In particular, ruthenium(II) tris(2,2 -bipyridyl) has been one of the most extensively studied complexes of the last decade due to its chemical stability, redox properties, excited-state reactivity, and luminescent emission (251, 252). 

Special interest was focused on the photochemistry and redox properties of mononuclear ruthenium complexes.20 Examples show the nucleophilic attack of one of the N atoms of 1,8-naphthyridine on the coordinated CO in [Ru(bipy)2(napy)(CO)]2+ upon le reduction of the napy moiety (Scheme 2). Such a type of metallacyclization enables the reduction of the CO group, derived from the electrochemical reduction of C02 catalyzed by [Ru(bipy)(napy)2(CO)2](PF6)2, to produce acetone in the presence of Me4NBF4.21,22 An unusual result is the simultaneous formation of a carbene ligand and the addition of the methoxo group to the naphthyridine ring upon reaction of [Ru(bipy)2(napy)]2+ with propiolic acid in methanol (Scheme 2).23... 

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