ELECTROCHEMICAL REDUCTION OF (2,2'-BIPYRIDINE) AND BIS((2-PYRIDYL)PYRAZINE)RUTHENIUM(II) COMPLEXES USED AS BUILDING-BLOCKS FOR SUPRAMOLECULAR SPECIES - REDOX SERIES MADE OF 8, 10, AND 12 REDOX STEPS
S. Roffia et al., ELECTROCHEMICAL REDUCTION OF (2,2'-BIPYRIDINE) AND BIS((2-PYRIDYL)PYRAZINE)RUTHENIUM(II) COMPLEXES USED AS BUILDING-BLOCKS FOR SUPRAMOLECULAR SPECIES - REDOX SERIES MADE OF 8, 10, AND 12 REDOX STEPS, Inorganic chemistry, 32(14), 1993, pp. 3003-3009
The electrochemical reduction of the [Ru(2,3-dpp)n(bpy)3-n]2+ complexe
s (n = 1-3), which are extensively used as building blocks for the syn
thesis of polynuclear compounds, has been investigated at -54-degrees-
C in DMF solution up to a limit of -3.1 V vs SCE (dpp is the potential
bridging ligand bis(2-pyridyl)pyrazine and bpy is 2,2'-bipyridine). F
or comparison purposes, the electrochemical behavior of the free 2,3-d
pp ligand has also been investigated. The results obtained have been d
iscussed and compared with those previously reported for bpy and Ru(bp
y)3(2+). Convolutive analysis and simulation of the cyclic voltammetri
c curves have been performed to obtain the redox potentials in the cas
e of overlapping waves. [Ru(2,3-dpp)3]2+, [Ru(2,3-dpp)2(bpy)]2+, and [
Ru(2,3-dpp)(bpy)2]2+ display 12, 10, and 8 reduction steps, respective
ly, in the potential window examined. The corresponding redox series a
re thus noticeably more extended than those exhibited by [Ru(bpy)3]2and related complexes not containing bridging-type ligands. The analys
is of the genetic diagram which relates the redox potentials observed
for 2,3-dpp, [Ru(2,3-dpp)3]2+, [Ru(2,3-dpp)2(bpy)]2+, [Ru(2,3-dpp)(bpy
)2]2+, [Ru(bpy)3]2+, and bpy shows that each redox step in the metal c
omplexes is essentially localized on a specific ligand. A satisfactory
assignment of the redox sites has been proposed, and their mutual int
eractions have been discussed. The results obtained show that in order
to arrive at a satisfactory assignment of the redox series for a comp
lex containing redox-active ligands a comparison with the behavior of
complexes of the same family is as much instructive as a comparison wi
th the behavior of the free ligands.