example, ruthenium(II) complexes of dipyrroloylquinoxaline
phenanthroline8 and ferrocene-imidazophenanthroline9 have
been developed as efficient anions chemosensors.
p-quinodimethane analogues of TTF usually exhibit high
π-donating ability, characterized by a one-stage two-electron
oxidation process.15 To our knowledge, an exTTF has never
been associated to a heterocyclic sp2 nitrogen-donor chelating
ligand. On this ground, we report here the synthesis and
characterizationsoftheruthenium(II)complex[Ru(bpy)2(exTTF-
dpq)](PF6)2 (1) based on the redox-active exTTF and
dipyrido[3,2-f:2′,3′-h]-quinoxaline (dpq) ligand.16 Compound
4, described by Yamashita et al. to reach organic field-effect
transistors, can be considered as a unique example to date
combining an exTTF and a quinoxaline moiety.17
First we developed an efficient synthesis of the ligand
Nqphen 7.18 This key building block was previously prepared
in five steps and in an overall 30% yield from 2,3-
dichloronaphthoquinone.19 We performed the synthesis of
this ligand in three steps in an overall 79% yield (Scheme
2). Compound 5 was prepared in 85% yield according to a
Owing to their unique π-donor properties, tetrathiaful-
valene (TTF) and its derivatives have been associated with
a large range of electron acceptor units in the search for
specific intramolecular electronic interactions.10 The use of
a TTF molecule associating an aromatic heterocyclic sp2
nitrogen-donor chelating ligand (pyridine, bipyridine, phenan-
throline, etc.) has been extensively developed, but corre-
sponding transition metal complexes are still rare.11 With
the aim of developing new systems showing long-lived
charge-separated state and photoredox switches, ruthe-
nium(II) complexes of TTF-dppz dyad 2 were synthesized
by Liu and co-workers. One of the synthetic approaches
involved the condensation of a diamino-functionalized TTF
ligand with the phendione ruthenium bipyridyl complex to
reach dyad 2 (Scheme 1).12 Very recently, fused TTF-1,10-
Scheme 2. Synthesis of the Complex
[Ru(bpy)2(exTTF-dpq)](PF6)2 1
Scheme 1
.
Structures of Complex 1 and Some Related
Complexes
phenanthroline and related ruthenium(II) bipyridyl complex
3 were also reported.13 Tetrathiafulvalenes with extended
π-conjugation (exTTF) constitute a well-known class of
electron donors.14 It is well-established that the insertion of
a quinodimethane structure into the TTF skeleton enhances
the donor ability, since an aromatic ring is formed upon
oxidation, thus stabilizing the cationic species. Consequently,
two-step procedure from commercially available 2,3-dichlo-
ronaphtoquinone.20 On the other hand, Phendione 6 was
(14) (a) TTF Chemistry. Fundamentals and Applications of Tetrathi-
afulValene; Yamada, J., Sugimoto, T., Eds.; Springer Verlag: New Yorker,
2004. (b) Gorgues, A.; Hudhomme, P.; Salle´, M. Chem. ReV. 2004, 104,
5151–5184. (c) Mart´ın, N.; Sa´nchez, L.; Herranz, M. A.; Illescas, B.; Guldi,
D. M. Acc. Chem. Res. 2007, 40, 1015–1024. (d) Wenger, S.; Bouit, P.-A.;
Chen, Q.; Teuscher, J.; Di Censo, D.; Humphry-Baker, R.; Moser, J.-E.;
Delgado, J. L.; Mart´ın, N.; Zakeeruddin, S. M.; Gra¨tzel, M. J. Am. Chem.
Soc. 2010, 132, 5164–5169.
(8) Mizuno, T.; Wei, W.-H.; Eller, L. R.; Sessler, J. L. J. Am. Chem.
Soc. 2002, 124, 1134–1135.
(9) Zapata, F.; Caballero, A.; Espinosa, A.; Ta´rraga, A.; Molina, P. J.
Org. Chem. 2008, 73, 4034–4044.
(10) (a) Segura, J. L.; Mart´ın, N. Angew. Chem., Int. Ed. 2001, 40, 1372–
1409. (b) Bendikov, M.; Wudl, F.; Perepichka, D. F. Chem. ReV. 2004,
104, 4891–4945. (c) Canevet, D.; Salle´, M.; Zhang, G.; Zhang, D.; Zhu, D.
Chem. Commun. 2009, 2245–2269.
(15) (a) Yamashita, Y.; Kobayashi, Y.; Miyashi, T. Angew. Chem., Int.
Ed. Engl. 1989, 28, 1052–1053. (b) Bryce, M. R.; Moore, A. J.; Hasan,
M.; Ashwell, G. J.; Fraser, A. T.; Clegg, W.; Hursthouse, M. B.; Karaulov,
A. I. Angew. Chem., Int. Ed. Engl. 1990, 29, 1450–1452. (c) Mart´ın, N.;
Sa´nchez, L.; Seoane, C.; Ort´ı, E.; Viruela, P. M.; Viruela, R. J. Org. Chem.
1998, 63, 1268–1279.
(11) Lorcy, D.; Bellec, N.; Fourmigue´, M.; Avarvari, N. Coord. Chem.
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(12) Goze, C.; Leiggener, C.; Liu, S.-X.; Sanguinet, L.; Levillain, E.;
Hauser, A.; Decurtins, S. ChemPhysChem 2007, 8, 1504–1512.
(13) Keniley, L. K.; Ray, L.; Kovnir, K.; Dellinger, L. A.; Hoyt, J. M.;
Shatruk, M. Inorg. Chem. 2010, 49, 1307–1309.
(16) Dipyrido[3,2-f:2′,3′-h]-quinoxaline (dpq) is sometimes also refer-
enced as pyrazino[2,3-f][1,10]-phenanthroline (ppl): D´ıaz, R.; Francois, A.;
Leiva, A. M.; Loeb, B.; Norambuena, E.; Yao`ez, M. HelV. Chim. Acta 2006,
89, 1220–1230.
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