Conclusions
The optical and electrochemical properties of tricarbonylrhe-
nium(I) complexes of a new electroactive NNN-tridentate ligand
can be gated by reactions with Brønsted acids or bases which
serve to modulate energetic access to the lone pair of electrons on
the central nitrogen that govern the electrochemical activity and
associated electronic (n–p* or dp–pp) transitions. It is hoped that
appropriate modifications of the ligand on either the pyrazolyls
or the diarylamine portion will address the current issues of
small signal losses observed during cycling reactions. From this
perspective, the PNP ligands or PNN hybrids of Fig. 1 may also
Fig. 4 Overlay of absorption spectra of 2·PF
6
(grey), 3 (violet), and
+
∑
(
3 )(SbCl ) (red) in CH Cl
6
2
2
.
offer some advantages for Re(CO)
examined.
3
-based systems that should be
References
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Fig. 5 UV-Vis spectral (top) and voltammetric (bottom, 100 mV s )
changes attendant upon titration of CH Cl solutions of 3 first with a
methanolic solution of HBF and then with (NEt )(OH) in MeOH to in
2
2
4
4
situ generated 2. A minimum of three cycles are shown for each.
7
+
∑
The significant differences in the optical spectra of 2·X, 3, and 3
(
Fig. 4) and the electrochemical activity of these species prompted
8
9
J. I. von der Vlugt and J. N. H. Reek, Angew. Chem., Int. Ed., 2009, 48,
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8
832and references.
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4
) and (NEt
4
)(OH)
were monitored by both electronic absorption and voltammetric
experiments (Fig. 5). While these initial titration experiments
showed the viability of performing switching operations, the
reversibility over multiple reaction cycles was variable, being
dependent upon the concentration mandated by the analytical
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11 See ESI† for more details. The quasi-reversible nature of the wave (and
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is likely a result of slow structural reorganization on the time-scale of
the cyclic voltammetry experiment, as will be detailed in the full paper.
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2
5
3
-
5
-4
technique being employed (10 M 3 for UV, 10 M for CV).
The more concentrated samples afforded higher reversibility as
indicated by the quantity of acid or base required to achieve the
maximum signal intensity indicative of 3. Currently the origin of
the signal degradation is not clear and is the subject of ongoing
investigations in our laboratory.
1
1
1
985, 24, 4180.
3 Compare also to: L. A. DeLearie, R. C. Haltiwanger and C. G.
Pierpont, Inorg. Chem., 1989, 28, 644.
This journal is © The Royal Society of Chemistry 2010
Dalton Trans., 2010, 39, 3167–3169 | 3169