Donor-acceptor electronic coupling as a function of bridging group: Mixed- valence diruthenium(II,III) complexes bridged by isonicotinato and isonicotinamido ligands

Journal Article · Wed Jun 10 04:00:00 EDT 1992 · Inorganic Chemistry; (United States)

DOI:https://doi.org/10.1021/ic00038a007· OSTI ID:6915584

Creutz, C; Sutin, N ^[1]

---

1. Brookhaven National Lab., Upton, NY (United States)

Binuclear, mixed-valence [mu]-isonicotinato and [mu]-isonicotinamido complexes capped by pentaammineruthenium(II) at the pyridine site and pentaammineruthenium(III) at the carboxylato or amido site have been synthesized and characterized. On the basis of their electronic absorption spectra and redox properties, the amido complexes are assigned as the N-bonded (Ru[sup III]-NHC(O)R) isomers. The mixed-valence complexes exhibit intervalance charge-transfer bands at 720 nm ([epsilon] = 2.6 [times] 10[sup 2]M[sup [minus]1] cm[sup [minus]1]) and 761 nm (0.9 [times] 10[sup 3] M[sup [minus]1] cm[sup [minus]1]), respectively, in aqueous acetate buffer at pH 4.8. The redox potentials of the two sites differ by 0.44 V in the isonicotinato and by 0.54 V in the isonicotinamido complexes in the above medium, and the donor-acceptor coupling elements, evaluated from the intesities of the intervalence bands, are 300 and 510 cm[sup [minus]1], respectively. Solvent dependences of the electronic spectra and the electrochemical parameters are also reported. Both bridges provide significant coupling between the Ru(II) and Ru(III) metal centers in the mixed-valence complexes. These coupling energies serve as a point of departure for a consideration of coupling mechanisms in related polyproline-bridged systems for which thermal electron-transfer rates have been determined. It is concluded that 'hole' transfer pathways predominate when osmium(II) pentaammine is the donor and cobalt(III) or ruthenium(III) pentaammine is the electron acceptor.

• DOE Contract Number: AC02-76CH00016
• OSTI ID: 6915584
• Journal Information: Inorganic Chemistry; (United States), Journal Name: Inorganic Chemistry; (United States) Vol. 31:12; ISSN 0020-1669; ISSN INOCAJ
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400400* -- Electrochemistry
ABSORPTION SPECTRA
ALKALOIDS
AZINES
BINDING ENERGY
BUFFERS
CHARGE TRANSPORT
CHEMICAL PREPARATION
CHEMICAL PROPERTIES
CHEMICAL REACTION KINETICS
CHEMICAL REACTIONS
CHEMISTRY
COMPLEXES
ELECTROCHEMISTRY
ELECTRON TRANSFER
ELECTRONS
ELEMENTARY PARTICLES
ENERGY
FERMIONS
HETEROCYCLIC COMPOUNDS
ISOMERS
KINETICS
LEPTONS
LIGANDS
ORGANIC COMPOUNDS
ORGANIC NITROGEN COMPOUNDS
ORGANOMETALLIC COMPOUNDS
OSMIUM COMPLEXES
PH VALUE
PYRIDINES
REACTION KINETICS
REDOX REACTIONS
RUTHENIUM COMPLEXES
SOLVENT PROPERTIES
SPECTRA
SYNTHESIS
TRANSITION ELEMENT COMPLEXES
VALENCE