Solvent effects on the electrochemistry and spectroelectrochemistry of diruthenium complexes.: Studies of Ru2(L)4Cl where L=2-CH3ap, 2-Fap, and 2,4,6-F3ap, and ap is the 2-anilinopyridinate anion

Three Ru-2(5+) diruthenium complexes, (4,0) Ru-2(2-CH(3)ap)(4)Cl, (3,1) Ru-2(2-Fap)(4)Cl, and (3,1) Ru-2(2,4,6-F(3)ap)(4)Cl where ap is the 2-anilinopyridinate anion, were examined as to their electrochemical and spectroelectrochemical properties in five different nonaqueous solvents (CH2Cl2, THF, PhCN, DMF, and DMSO). Each compound undergoes a single one-electron metal-centered oxidation in THF, DMF, and DMSO and two one-electron metal-centered oxidations in CH2Cl2 and PhCN. The three diruthenium complexes also undergo two reductions in each solvent except for CH2Cl2, and these electrode processes are assigned as Ru-2(5+/4+) and Ru-2(4+/3+). Each neutral, singly reduced, and singly oxidized species was characterized by UV-vis thin-layer spectroelectrochemistry, and the data are discussed in terms of the most probable electronic configuration of the compound in solution. The three neutral complexes contain three unpaired electrons as indicated by magnetic susceptibility measurements using the Evans method (3.91-3.95 mu(B)), and the electronic configuration is assigned as sigma(2)pi(4)delta(2)pi*(2)delta, independent of the solvent. The three singly oxidized compounds have two unpaired electrons in CD2Cl2, DMSO-d(6), or CD3CN (2.65-3.03,mu(B)), and the electronic configuration is here assigned as sigma(2)pi(4)delta(2)pi*(2). The singly reduced compound also has two unpaired electrons (2.70-2.80 mu(B)) in all three solvents, consistent with the electronic configuration sigma(2)pi(4)delta(2)pi*(2)delta*(2) or sigma(2)pi(4)delta(2)pi*(3)delta*. Finally, the overall effect of solvent on the number of observed redox processes is discussed in terms of solvent binding, and several formation constants were calculated.