A series of binuclear complexes of general formula
L
m
Ru−BL−RuL‘
m
n
+
where L and L‘ are monodentate or
bidentate ligands bound to one metal center and BL is a bridging ligand
are analyzed with the recently reported
unified solvation model (USM). The solvent dependence of
ΔE
1/2 and E
IT data
are analyzed for cases where L
is the same as L‘ and where L and L‘ differ. Data for the change
in E
1/2 and E
IT as the
Lewis base, B, is varied
in (bpy)2ClRupyz
Ru(NH3)4B (where bpy is 2,2‘-bipyridine
and pyz is pyrazine) are also correlated. The USM
provides the relative contributions of specific and nonspecific
solvation to the solvent dependence of the
physicochemical property. The factoring of the solvent dependence
permits the construction of potential energy
surfaces providing unprecedented detail concerning the influence of
solvent donor−acceptor and solvation
contributions to these measurements. The ability of USM to
correlate Franck−Condon energies and the failure
of donor numbers (DN) to do so emphasizes the need for a dual parameter
treatment of the specific interaction.
In contrast to nonsymmetrical binuclear complexes, the solvent
dependence of the E
IT bands for
symmetrical
complexes is not correlated by solvent donor and polarity parameters
but is fit to the dielectric constants and
refractive indices of the Marcus−Hush dielectric continuum model.
A rationale for this disparate behavior of
symmetrical and unsymmetrical binuclear complexes is
given.
The unified solvation model has been
extended to solvent sensitive electronic transitions in metal carbonyls
and new polycyclic aromatics. The contribution from specific and
nonspecific interactions is obtained. An explanation is offered
for cases where the two effects go in opposite directions and cases
where the electrostatic and covalent contribution go in opposite
directions. The addition of these new probes leads to several new
solvent S‘ values.
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