Equilibria and spectroelectrochemical studies on the formation of multibridged tris(bipyrazine) ruthenium(II) complexes with ruthenium-edta groups.
The tris(bipyrazine) ruthenium(II) complex forms a series of complexes containing [Ru(II/III)EDTA](2-/-) groups coordinated to the peripheral nitrogen atoms of the bipyrazine bridging ligand. These groups exhibit similar redox potentials (E(0) = 0.38 V vs. SHE) and a very weak electronic coupling through the central complex. When the peripheral Ru(III) groups are reduced to the Ru(II) state, strong charge-transfer bands appear at 490 and 670 nm and the stability constants increase by 7 orders of magnitude due to d(pi) -p(*)(pi) back-bonding interactions involving the peripheral ions and the bipyrazine ligand.
Toma
H E
HE
Instituto de Química, Universidade de São Paulo, Caixa Postal 20780, CEP 01498, São Paulo, Sp, Brazil.
Sernaglia
R L
RL