Spectroscopic and electrochemical investigations have
been carried out on a collection of hydrogen-bonded
mixed-valence adducts of ruthenium complexes. The electron donors
(H-bond acceptors) are Ru(II) cyano species
and the electron acceptors (H-bond donors) are Ru(III)
ethylenediamine species, and NIR spectroscopic transitions
in the adducts are assigned to intervalence transfer through the
hydrogen bonds holding the adducts together (HBIT).
Spectroscopic studies using Job's method indicate that the
adducts are 2:1 ternary aggregates of formulations such
as
[((trpy)(bpy)RuII(CN))2,(en)2RuIII(bpy)]5+
and
[((bpy)2RuII(CN)2)2,(en)2RuIII(bpy)]3+.
Voltammetric investigations
show substantial repulsion of the redox waves of the parent complexes
in mixtures containing both donor and acceptor.
Comparison with known electronic coupling data for mixed-valence
ruthenium dimers covalently bound through
dithiaspiroalkane bridging ligands indicates that the electronic
coupling through H bonds of this type is 65−75% as
strong as through σ-covalent bonds.
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