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DOI:10.1002/ejic.201500077
Ferrocenyl–Bipyridinium Cations and Their Platinum
Complexes Related to Viologens – Preparation, Redox
Properties, and Crystal Structures
Tomoyuki Mochida,*[a,b] Yusuke Funasako,[a] Yukiko Nezu,[b]
Koji Hagiwara,[b] and Ryo Horikoshi[b,c]
Keywords: Metallocenes / Viologens / Platinum / Donor–acceptor systems / Electrochemistry
N-R1-NЈ-R2-4,4Ј-Bipyridinium and N-R1-4,4Ј-bipyridinium
these compounds are independently affected by molecular
modifications, which indicates that conjugation between the
salts containing ferrocenyl substituents were prepared as
donor–acceptor compounds (R1 = ferrocenyl, ferrocenyl- donor and acceptor moieties is less effective. Single-crystal
phenyl; R2 = ferrocenyl, ferrocenylphenyl, phenyl, methyl).
Platinum(II)-bridged diferrocene compounds were prepared
X-ray diffraction analyses revealed large twist angles be-
tween the two moieties in the solid state. The compounds
by using the N-R1-4,4Ј-bipyridinium ligands. These com- exhibit broad charge-transfer absorption bands in the range
pounds display multistage redox properties. The redox
potentials of the ferrocenyl and bipyridinium moieties in
450–800 nm. No electronic communication was observed be-
tween the terminal ferrocenes in the diferrocene complexes.
and solid-state physical properties have been evaluated.[9]
Recently, several other ferrocene-based donor–acceptor
molecules have been reported.[10]
Herein, we report the preparation of a series of diferro-
cenyl– and ferrocenyl–bipyridinium cations, shown in Fig-
ure 1. Hexafluorophosphate was used as the counter anion.
The salts of viologen-bridged diferrocenes [1x][PF6]2 as well
as mono-ferrocenyl viologen derivatives [2x][PF6]2 and
Introduction
Donor–acceptor molecules have attracted significant
interest in terms of their molecular design towards non-
linear optical properties, functional dyes, electrochromic de-
vices, and photoinduced-electron-transfer systems. Ferro-
cenes are electron donors that have been widely applied in
the fabrication of molecular functional materials.[1] In par-
ticular, diferrocenes bridged by π-conjugated spacers or
through coordination bonds have garnered interest because
of the electronic communication observed between Fe
atoms in the mixed-valent state.[2,3] Viologens are electron
acceptors that undergo two-step redox processes and have
been used as redox indicators, in electrochemical devices,
and as components of ion-pair compounds.[4,5] The elec-
tronic properties of molecules containing ferrocenes and
viologens are of great interest because of their potential
applications as donor–acceptor multistage redox systems.
To this end, several ferrocene–viologen compounds have
been prepared, and their electrochromic properties,[6] redox
control of internal rotations,[7] nonlinear optical activities,[8]
[a] Department of Chemistry, Graduate School of Science, Kobe
University, Kobe,
Hyogo 657-8501, Japan
E-mail: tmochida@platinum.kobe-u.ac.jp
[b] Department of Chemistry, Faculty of Science, Toho University,
Miyama, Funabashi,
Chiba 274-8510, Japan
[c] Department of Chemistry, College of General Education,
Osaka Sangyo University, Nakagaito,
Daito, Osaka 574-8530, Japan
Supporting information for this article is available on the
Figure 1. Structures of ferrocenyl–bipyridinium cations investigated
in this study.
Eur. J. Inorg. Chem. 2015, 2330–2337
2330
© 2015 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim