Oligo(U-terpyridines) and their ruthenium(II) complexes: Synthesis and structural properties

Article abstract of DOI:10.1021/jo060387+

A highly efficient domino reaction starting from tetrahydroquinolinone and a series of bisiminium salts provides the corresponding bis(U-terpyridines). These ligands have been treated with [(tpy)RuCl₃] to afford novel dinuclear complexes [(tpy)

Full text of DOI:10.1021/jo060387+

Oligo(U-terpyridines) and Their Ruthenium(II) Complexes:
Synthesis and Structural Properties
Andreas Winter, Johanna Hummel, and Nikolaus Risch*
Paderborn UniVersity, Faculty of Science, Chemistry Department, Warburger Str. 100,
33098 Paderborn, Germany
nikolaus.risch@upb.de
ReceiVed February 24, 2006
A highly efficient domino reaction starting from tetrahydroquinolinone and a series of bisiminium salts
provides the corresponding bis(U-terpyridines). These ligands have been treated with [(tpy)RuCl3] to
afford novel dinuclear complexes [(tpy)Ru(L)Ru(tpy)]4+. The protocol is also applied for the synthesis
of a star-shaped tris(U-terpyridine) and the trinuclear complex [{(tpy)Ru}3(L)]6+. In view of potential
applications in the fields of metallopolymers and molecular devices, the electronic spectra, as well as the
electrochemical potentials of all the complexes have been obtained. According to these data, no significant
intermetal interaction has been observed for the ruthenium complexes presented here.
Introduction
metal complexes as a result of their potential metal-metal
cooperativity. This property is an important aspect in designing
molecular devices and controlling the build-up of supramolecular
structures, metallopolymers, and molecular devices with new
chemical and physical properties.4 The bridging ligands, typi-
cally consisting of two or more chelation sites connected by an
appropriate linker, are the key components in such polynuclear
ensembles. Among others, 2,2′-bipyridines (bpy),5 1,10-phenan-
throlines (phe),6 2,2′:6′,2′′-terpyridines (tpy),7 or closely related
Throughout the last few decades, the development of new
functional materials, such as inorganic-organic or polymeric
structures, has been an increasing field of research.1 A huge
variety of supramolecular systems and synthetic strategies are
known to the literature today.2-4 The basic concepts of
supramolecular chemistry are self-recognition and self-assembly,
and the interactions involved are mainly of a noncovalent nature
(e.g., van der Waals, hydrogen bonding, ionic, or coordinative
interactions). Of special interest are the polynuclear transition
(4) (a) Kaes, C.; Katz, A.; Hosseini, M. W. Chem. ReV. 2000, 100, 3553-
3590. (b) Schubert, U. S.; Eschbaumer, C. Angew. Chem., Int. Ed. 2002,
41, 2893-2936. (c) Steel, P. J. Coord. Chem. ReV. 1990, 106, 227-265.
(d) Balzani, V.; Barigeletti, F.; Belser, P.; Bernhard, S.; De Cola, L.;
Flamigni, L. J. Phys. Chem. 1996, 100, 16786-16788. (e) De Cola, L.;
Belser, P. Coord. Chem. ReV. 1998, 177, 301-346. (f) Barigeletti, F.;
Flamigni, L. Chem. Soc. ReV. 2000, 29, 1-12. (g) Juris, A.; Prodi, L.;
Harriman, A.; Ziessel, R.; Hissler, M.; El-ghayoury, A.; Wu, F.; Riesgo,
E.; Thummel, R. P. Inorg. Chem. 2000, 16, 3590-3598. (h) Balzani, V.;
Credi, A.; Raymo, F. M.; Stoddart, J. F. Angew. Chem., Int. Ed. 2000, 39,
3348-3391.
* To whom correspondence should be addressed. Phone: +49 5251 60-2176.
Fax: +49 5251 60-3245.
(1) (a) Rehahn, M. Acta Polym. 1998, 49, 201. (b) Manners, I. Science
2001, 294, 1664.
(2) Lehn, J.-M. Supramolecular ChemistrysConcepts and PerspectiVes;
VCH: Weinheim, Germany, 1995.
(3) Schubert, U. S. In Tailored Polymers & Applications; Yagci, M. K.
M. Y., Nuyken, O., Ito, K., Wnek, G., Eds.; VSP Publishers: Utrecht, The
Netherlands, 2000; pp 63-85.
10.1021/jo060387+ CCC: $33.50 © 2006 American Chemical Society
Published on Web 05/26/2006
4862
J. Org. Chem. 2006, 71, 4862-4871

Synthesis of Oligo(U-terpyridines)
SCHEME 1. Synthesis of Substituted U-Shaped
Terpyridines 3
derivatives are the most common chelators. Generally, these
binding sites are connected by designed spacers controlling both
the distance between the two metal centers and the electronic
communication between the terminal sites. The distance can
be controlled easily by employing rigid linkers of known
dimensions.8 To attain electronic communication between the
incorporated metal centers, research has focused on the conju-
gating ability of these linkers. Those with one or more π bonds,
such as polyenes, polyphenylenes, polyalkynes, or poly-
thiophene, are widely used, whereas the inclusion of tetrahedral
centers such as sp3-carbon atoms may serve as insulators.9
Our current interest in polytopic terpyridines and their metal
complexes arises from our investigations of the modern ap-
plications of the Mannich reaction in the synthesis of various
rigid pyridine derivatives, which has resulted in different
approaches being developed for these heterocycles.10 The
potential importance of the fields of metallopolymers and novel
molecular devices means that the development of novel and
more flexible synthetic methods is an active area of research.
Our studies in the field of ternary iminium salts have led to the
development of highly efficient, one-pot, domino-type reactions
yielding a wide range of substituted rigid pyridine derivatives,
including bipyridines and terpyridines.11 Domino reactions offer
many advantages compared to traditional syntheses, such as the
minimization of waste and the reduced consumption of solvents,
reagents, adsorbents, and energy. As shown earlier, the reaction
of a ternary iminium salt 2 and two equivalents of 5,6,7,8-
tetrahydroquinolinone 1 in the presence of ammonium acetate,
as a source of ammonia, under appropriate conditions leads to
the formation of rigid U-shaped substituted terpyridines 3,
selectively, whereas the S-shaped isomer is isolated in small
amounts in very few cases (Scheme 1).11l
SCHEME 2. Synthesis of Bridged Bis(U-terpyridines) 34-43
by the so-called “Kro¨hnke” condensation12 or by the cross-
coupling reactions of bromo-terpyridines, especially with
alkynes.13 In addition, our previous studies in the field of bridged
pyridine derivatives have shown that phenyl-linked bisoligo-
pyridines can be easily synthesized using the Suzuki cross-
coupling reaction employing benzene diboronic acid.14 In a
major extension to this, we now establish aromatic bisiminium
salts 24-33 as versatile building blocks in the highly efficient
one-pot synthesis of bis(U-terpyridines) 34-43 (Scheme 2).
To the best of our knowledge, these special types of iminium
salts have not been described in the literature before. According
to Bo¨hme’s protocol, bisaminals 14-23 have been prepared
starting from their corresponding dialdehydes 4-13.15 Subse-
quently, bisiminium salts 24-33 have been obtained in very
good yields (>75%, Scheme 3) by treating the aminals with
acetyl chloride.16 In contrast to other ternary iminium salts,
bisiminium salts derived from bulky secondary amines, such
as morpholine, have been found to be less hygroscopic and can
be stored in a desiccator for months without any sign of
decomposition.
Results and Discussion
Synthesis of Bis(U-terpyridines): A large variety of bis-
terpyridines bearing conjugated linkers has been prepared either
(5) Newkome, G. R.; Patri, A. K.; Holder, E.; Schubert, U. S. Eur. J.
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571-576. (b) Westerwelle, U.; Risch, N. Tetrahedron Lett. 1993, 34, 1775-
1778. (c) Keuper, R.; Risch, N. Z. Naturforsch., B: Chem. Sci. 1995, 50,
1115-1120. (d) Keuper, R.; Risch, N.; Flo¨rke, U.; Haupt, H.-J. Liebigs
Ann. Chem. 1996, 705-715. (e) Keuper, R.; Risch, N. Liebigs Ann. Chem.
1996, 717-723. (f) Keuper, R.; Risch, N. Eur. J. Org. Chem. 1998, 2609,
9-2615. (g) Risch, N.; Keuper, R. J. Prakt. Chem. 1998, 424-429. (h)
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Risch, N. Org. Biomol. Chem. 2004, 2, 863-868. (m) Sielemann, D.;
Winter, A.; Risch, N. Heterocycles 2004, 63, 2615-2621.
Bisiminium salts 24-33 have been employed successfully
in a highly efficient 2-fold domino sequence with 4 equiv of 1
(12) (a) Kro¨hnke, F. Synthesis 1976, 1-24. (b) Potts, K. T.; Cipullo, M.
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J. Org. Chem, Vol. 71, No. 13, 2006 4863

Winter et al.
SCHEME 4. Synthesis of Novel Tris(U-terpyridine) 47
SCHEME 3. Synthesis of Bisiminium Salts 24-33
TABLE 1. Synthesis of Bis(U-terpyridines) Using Bisiminium Salts
a trisiminium salt published in the literature represents a novel
class of iminium derivatives that might serve as key building
blocks in the construction of dendritic structures or two-
dimensional (2D) networks.4b According to our straightforward
procedure, trialdehyde 44 has been transferred subsequently to
the aminal 45 and iminium salt 4615 and converted to star-shaped
tris(U-terpyridine) 47 in good overall yield (25%, Scheme 4).
Complex Synthesis and Characterization: U-terpyridines
are known to form stable octahedral complexes with most of
the transition metals.19 If cations, such as Re(I), Cu(I), Pt(II),
Zn(II), Ru(II), Os(II), or Ir(III), are added, metal-containing
aggregates are obtained that are photo- and electroactive and
may find applications in molecular electronics.4 Terpyridine-
ruthenium complexes are of special interest, because they display
interesting photophysical, photochemical, and electrochemical
properties, which can be revealed easily by their absorption and
emission spectra.4,13,17 In regard to possible applications in the
synthesis of supramolecular assemblies, such as molecular wires,
energy transfer along the molecular axis between the metal
centers is a fundamental requirement that can be varied by the
nature of the spacer unit.20 It has been our goal to incorporate
ligands 34-43 into coordination polymers and to investigate
the photophysical and electrochemical properties of the metal-
lopolymers obtained. Therefore, the novel bi- and tridental
a Isolated yield after flash column chromatography on neutral Al2O3.
b In addition, the S-isomer11l has also been obtained in 5% yield.
and NH4OAc, as a source of ammonia, to give bis(U-ter-
pyridines) 34-43 in good yields (Scheme 2, Table 1). The
proposed mechanism for the selective formation of U-ter-
pyridines has already been discussed elsewhere.11l When
optimized reaction conditions are used,11l the formation of the
undesired bis(S-terpyridine) in small amounts has only been
observed in a single case (43, 5%). Our results show that the
length and the substitution pattern of the linker can be tuned
easily depending on the structure of the iminium compound.
The solubility of the rigid bis(U-terpyridines) can be increased
significantly by introducing glycol or amine groups (42/43),
although electronic communication between the terminal sites
is hindered in the case of these insulating spacers. A minor
drawback of the strategy presented here is that it is limited only
to aromatic ternary bisiminium salts so far. Hence, future work
will focus on the synthesis of bisiminium salts bearing alkyne
or oligothiophene linkers, as these groups are known to attain
better electronic communication than polyphenylene linkers.17
Our strategy has also been applied for the synthesis of the
novel star-shaped tris(U-terpyridine) 47. This first example of
(17) (a) Harriman, A.; Hissler, M.; Ziessel, R. Phys. Chem. Chem. Phys.
1999, 1, 4203-4211. (b) Harriman, A.; Hissler, M.; Khatyr, A.; Ziessel,
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A.; Ziesse, R. Chem.sEur. J. 1999, 5, 3366-3381. (d) El-ghayoury, A.;
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Suffert, J.; Youinou, M.-T. J. Org. Chem. 1996, 61, 6535-6546.
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C. C.; Ng, M.-K. Tetrahedron 1996, 52, 4277-4290. (c) Armspach, C.;
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(19) (a) Thummel, R. P.; Jahng, Y. Inorg. Chem. 1986, 25, 2527-2534.
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Flamigni, L.; Balzani, V.; Collin, J.-P.; Sauvage, J.-P.; Sour, A.; Constable,
E. C.; Cargill Thompson, A. M. W. J. Am. Chem. Soc. 1994, 116, 7692-
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4864 J. Org. Chem., Vol. 71, No. 13, 2006

Synthesis of Oligo(U-terpyridines)
1
FIGURE 1. One-dimensional (top) and COSY H NMR (bottom) of [(tpy)Ru(38)Ru(tpy)](PF6)4 (500 MHz, CD3CN, 298 K).
and the COSY 1H NMR spectra of [(tpy)Ru(38)Ru(tpy)](PF6)4
is presented in Figure 1.
SCHEME 5. Synthesis of Di- and Trinuclear Ruthenium
Complexes
All complexes have been characterized additionally by mass
spectrometry. They show the characteristic [M - PF6]+ peaks
in their MALDI-TOF mass spectra, revealing successful coor-
dination. No dissociation of the coordinative bonds has been
observed during the laser desorption/ionization process, indicat-
ing high stability of these complexes. The representative spectra
of complexes [(tpy)Ru(38)Ru(tpy)](PF6)4 and [(tpy)Ru(42)Ru-
(tpy)](PF6)4 are shown in Figure 2. The ESI spectra, as shown
in the Supporting Information, are also in accordance with the
assigned structures.
The IR vibration spectra are dominated by a strong band at
around 850 cm-1 being characteristic for the hexafluorophos-
phate counterion.19a The other IR bands have been assigned to
the vibrations of the respective bis(U-terpyridine) and 2,2′:6′,2′′-
terpyridine ligands.
Absorption Spectroscopy: In Table 2, the absorption maxima
and corresponding intensities for the solutions of [(tpy)Ru(L)-
Ru(tpy)](PF6)4 in MeCN are summarized. All complexes show
a set of two distinct absorption bands at shorter wavelengths
(270-310 nm, log ꢀ ) 4.3-5.1; Figure 3), which can be
assigned to characteristic ligand-centered 1LC transitions (π f
π* and n f π*) in ruthenium-terpyridine complexes. This band
is slightly shifted to a longer wavelength compared to those of
complex [Ru(tpy)2]2+. This effect is due to the greater delo-
calization of the excited electron on the ligand bearing a
conjugated moiety stabilizing the LUMO orbital (π*).19f The
less-intense band in the visible region (approximately 480 nm,
log ꢀ ) 3.1-4.6)19a is due to the allowed metal to ligand charge-
transfer transitions (1MLCT), where an electron is promoted
from the metal t2g orbital to a π* antibonding orbital of the
ligand.24 These transitions appear at lower energy as for the
reference substrate [Ru(tpy)2]2+. The donor-effect of the sub-
stituents in 7-position lowers the energy gap between HOMO
and LUMO orbitals of the parent complexes.19
ligands have been further used to make a set of di- and trinuclear
complexes [(tpy)Ru(L)Ru(tpy)]4+ and [{tpy)Ru}3(L)]6+, as
illustrated in Scheme 5.
The dinuclear complexes have been prepared by the direct
reaction of the ligand L with an appropriate metal precursor.
Therefore, bis(U-terpyridines) 34-43 have been treated with 2
equiv of [(tpy)RuCl3]21 in ethanol under reducing conditions,22
resulting in the formation of dark-red symmetric, dinuclear
complexes [(tpy)Ru(L)Ru(tpy)](PF6)4 in very high yields (Scheme
5). The trinuclear complex [{(tpy)Ru}3(L)](PF6)6 has been
obtained by the same protocol using 3 equiv of [(tpy)RuCl3].
1
In general, all complexes exhibit well-resolved H NMR
spectra, and a number of characteristic features are present. In
many cases, all the peaks can be assigned completely by 2D
analysis supported by comparison to the spectra of mono- and
dinuclear complexes published in the literature.19a,20 On coor-
dination, a significant shift of the proton resonances is observed.
The A6/C6 protons are directed toward the shielding region of
the central pyridine ring of the orthogonal neighboring ligand,
resulting in some considerable upfield shielding of these protons
(approximately 1.4 ppm). The shielding of the more remote A5/
C5 protons (about 0.2 ppm) can be explained in a similar
fashion.20,23 As an example, the aromatic region of the 1H NMR
(20) (a) Encinas, S.; Flamigni, C.; Barigelletti, F.; Constable, E. C.;
Housecroft, C. E.; Schofield, E. R.; Figgemeier, E.; Fenske, D.; Neuburger,
M.; Vos, J. G.; Zehnder, M. Chem.sEur. J. 2002, 8, 137-150. (b) Barbieri,
A.; Ventura, B.; Barigeletti, F.; De Nicola, A.; Quesada, M.; Ziessel, R.
Inorg. Chem. 2004, 43, 7359-7368. (c) Azhari, E.; Penaud-Berruyer, F.;
Azhari, D.; A¨ıt-Haddou, H.; Fontenas, C.; Bejan, E.; Daran, J.-C.; Balavoine,
G. G. A. New J. Chem. 1998, 373-380.
(21) (a) Sulliva, B. P.; Calvert, J. M.; Meyer, T. J. Inorg. Chem. 1980,
19, 1404-1407. (b) Constable, E. C.; Cargill Thompson, A. M. W. J. Chem.
Soc., Dalton Trans. 1994, 1409-1418.
(22) Maestri, M.; Armaroli, N.; Balzani, V.; Constable, E. C.; Cargill
Thompson, A. M. W. Inorg. Chem. 1995, 34, 2759-2767.
Additionally, a band centered around 360 nm is present,
1
which results from mixed LC-1MLCT transitions. The data
(23) Constable, E. C.; Cargill Thompson, A. M. W.; Tocher, D. A.;
Daniels, M. A. M. New J. Chem. 1992, 16, 855.
J. Org. Chem, Vol. 71, No. 13, 2006 4865

Winter et al.
FIGURE 2. MALDI-TOF mass spectra of [(tpy)Ru(L)Ru(tpy)](PF6)4; L ) 38 (left) and L ) 42 (right).
TABLE 2. Absorption Data of Complexes in MeCN
λ
1LC
max [nm] (ꢀ × 104 [M-1 cm-1])
complex
LC-1MLCT 1MLCT
[Ru(tpy)]2+ (ref 2l)
[(tpy)Ru(3a)]2+ a
[(tpy)Ru(3b)]2+ a
272 (2.8) 307 (5.2)
269 (2.1) 311 (4.8)
273 (3.6) 309 (5.1)
475 (1.3)
477 (1.2)
481 (1.9)
[(tpy)Ru(34)Ru(tpy)]4+ 271 (3.5) 308 (4.8) 359 (1.7)
[(tpy)Ru(35)Ru(tpy)]4+ 269 (4.8) 309 (7.4) 358 (2.2)
[(tpy)Ru(36)Ru(tpy)]4+ 268 (3.9) 308 (6.7) 358 (1.9)
[(tpy)Ru(37)Ru(tpy)]4+ 269 (4.5) 310 (7.2) 357 (2.3)
[(tpy)Ru(38)Ru(tpy)]4+ 270 (5.2) 309 (8.9) 359 (2.8)
[(tpy)Ru(39)Ru(tpy)]4+ 269 (5.7) 310 (7.9) 357 (3.0)
[(tpy)Ru(40)Ru(tpy)]4+ 270 (7.5) 308 (12.3) 359 (3.3)
[(tpy)Ru(41)Ru(tpy)]4+ 271 (5.6) 309 (8.4) 357 (2.5)
[(tpy)Ru(42)Ru(tpy)]4+ 271 (6.6) 309 (10.8) 359 (3.7)
[(tpy)Ru(43)Ru(tpy)]4+ 272 (8.1) 310 (13.6) 358 (5.3)
477 (1.7)
480 (1.9)
481 (1.7)
483 (2.1)
482 (2.3)
479 (2.8)
478 (3.1)
479 (2.1)
478 (2.8)
480 (3.9)
483 (2.5)
[{(tpy)Ru}3(47)]6+
a 3a: R1 ) Ph;26 3b: R1 ) thiophene-2-yl.26
269 (6.1) 311 (9.6) 357 (4.2)
FIGURE 4. Emission spectra of the dinuclear complexes [(tpy)Ru-
(40)Ru(tpy)]4+, [(tpy)Ru(41)Ru(tpy)]4+, and [(tpy)Ru(43)Ru(tpy)]4+. All
solutions are 10-5 M in CH3CN at 25 °C.
Upon functionalization with electron-donating groups at the
central pyridine ring, the corresponding Ru(II) complexes
become more luminescent at room temperature. In Figure 4 the
emission properties of some selected complexes [(tpy)Ru(L)-
Ru(tpy)](PF6)4 in dilute MeCN solution are shown. Excitation
of the compounds at 340 nm reveals broad emission bands for
1
the solutions that are basically derived from MLCT transi-
tions.20a,c For all complexes, an unstructured band with a
maximum between 400 and 500 nm is revealed upon excitation
at 340 nm. These maxima are shifted significantly in comparison
to those of the reference complex [Ru(tpy)2]2+ for which the
emission maximum is observed at about 360 nm.19f,20a The
strongest effect is observed for the thienyl-bridged complex (L
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Compounds; Kalyanasundaram, K., Gra¨tzel, M., Eds.; Kluwer: Dordrecht,
The Netherlands, 1993. (f) Schanze, K. S.; MacQeen, D. B.; Perkins, T.
A.; Cabana, L. A. Coord. Chem. ReV. 1993, 122, 63. (g) Didier, P.; Ortmans,
I.; Kirsch-De Mesmaeker, A.; Watts, R. Inorg. Chem. 1993, 32, 5239. (h)
Nallas, G. N. A.; Jones, S. W.; Brewer, K. J. Inorg. Chem. 1996, 25, 6974.
(i) Bignozzi, C. A.; Schoonover, J. N.; Scandola, F. Prog. Inorg. Chem.
1997, 44, 1.
FIGURE 3. Absorption spectra of the dinuclear complexes [(tpy)Ru-
(40)Ru(tpy)]4+, [(tpy)Ru(41)Ru(tpy)]4+, and [(tpy)Ru(43)Ru(tpy)]4+. All
solutions are 10-5 M in CH3CN at 25 °C.
reveal that on passing from the mononuclear to the dinuclear
complexes the bands become more intense, on the other hand,
no significant shift of the absorption bands can be observed.
1
This indicates that the MLCT levels are equal in energy for
both types of complexes. Therefore, from a spectroscopic point
of view, the coordinated metal centers have to be described as
electronically isolated chromophores.25
(25) Balzani, V.; Scandola, F. Supramolecular Photochemistry; Ellis
Horwood: Chichester, 1991.
(26) Winter, A. Oligotope Ligands and NicotinonitrilessModern Ap-
plications of the Mannich reaction in the Synthesis of Pyridine Derivatives.
Ph.D. Thesis, Paderborn University, 2003.
Emission Spectroscopy: It is known from the literature that
[Ru(tpy)2]2+ only shows weak emission at room temperature.22
4866 J. Org. Chem., Vol. 71, No. 13, 2006

Synthesis of Oligo(U-terpyridines)
TABLE 3. Emission Data of Complexes in MeCN (Room
Temperature)
identical and, more importantly, noninteracting. If there were
significant interactions between the metal centers, then the
oxidation of the first ruthenium center would affect the potential
at which the other centers in the complex are oxidized.18a,27 In
other words, in electronic terms, the bridging ligands L
effectively behave as simple aryl-substituted U-terpyridines, and
there is no electronic interaction between the U-terpyridyl
substituents or the metals coordinated to them.
λmax,em
[nm]
λmax,em
complex
complex
[nm]
[Ru(tpy)]2+ (ref 20a)
357
368
380
382
379
380
[(tpy)Ru(39)Ru(tpy)]4+
[(tpy)Ru(40)Ru(tpy)]4+
[(tpy)Ru(41)Ru(tpy)]4+
[(tpy)Ru(42)Ru(tpy)]4+
[(tpy)Ru(43)Ru(tpy)]4+
[{(tpy)Ru}3(47)]6+
385
500
451
397
423
386
[(tpy)Ru(34)Ru(tpy)]4+
[(tpy)Ru(35)Ru(tpy)]4+
[(tpy)Ru(36)Ru(tpy)]4+
[(tpy)Ru(37)Ru(tpy)]4+
[(tpy)Ru(38)Ru(tpy)]4+
In all cases, two reduction waves in the region of (-)1.2-
(-)1.3 V and (-)1.45-(-)1.6 V, corresponding to the Ru(II)/
Ru(I) and Ru(I)/Ru(0) couples, respectively, are also ob-
served.28,29 Generally, the first reduction is shifted by 0.2 V to
TABLE 4. Electrochemical Data for Complexes in MeCNa
E
1/2 [V]
a more negative potential compared to that of [(tpy2)Ru]2+
,
complex
oxidation
reduction
which can be explained by the high electron density caused by
the rigid ligands L.19b The reductive behavior of the thienyl-
bridged complex (L ) 40) is complicated by irreproducible
processes between 0.6 and 0.8 V associated with surface binding
to the electrodes.20
[Ru(tpy)]2+ (ref 18b)
[(tpy)Ru(3a)]2+ b
+1.20
+1.25
+1.19
+1.22
+1.27
+1.25
+1.21
+1.26
+1.25
+1.18
+1.20
+1.26c
+1.24
+1.25
-0.96
-1.21
-1.33
-1.26
-1.22
-1.23
-1.24
-1.23
-1.25
-1.35
-1.28
-1.32
-1.29
-1.26
-1.49
-1.46
-1.73
-1.48
-1.46
-1.45
-1.47
-1.46
-1.45
-1.71
-1.51
-1.49
-1.46
-1.46
[(tpy)Ru(3b)]2+ b
[(tpy)Ru(34)Ru(tpy)]4+
[(tpy)Ru(35)Ru(tpy)]4+
[(tpy)Ru(36)Ru(tpy)]4+
[(tpy)Ru(37)Ru(tpy)]4+
[(tpy)Ru(38)Ru(tpy)]4+
[(tpy)Ru(39)Ru(tpy)]4+
[(tpy)Ru(40)Ru(tpy)]4+
[(tpy)Ru(41)Ru(tpy)]4+
[(tpy)Ru(42)Ru(tpy)]4+
[(tpy)Ru(43)Ru(tpy)]4+
[{(tpy)Ru}3(47)]6+
Conclusion
The novel oligo(U-terpyridines) 34-43 and 47 presented in
this paper have been synthesized by a highly efficient domino
reaction sequence, introducing iminium salts 24-33 and 46 as
key building blocks. This extension of prior work is well suited
for the design of bridged terpyridine ligands with highly variable
spacer properties. In regard to potential applications in the fields
of molecular devices, a set of di- and trinuclear ruthenium(II)
complexes have been synthesized, and their electronic and
electrochemical behaviors have been investigated. These com-
plexes have been found to be light-emitting upon excitation at
340 nm, with broad emission maxima between 400 and 500
nm. Thus, no metal-metal interaction along the molecular axis
could be observed so far. Our strategy promises to be a valuable
approach toward the synthesis of ligands capable of transporting
energy over large distances on a molecular scale and for use in
photophysical applications.
a [n-Bu4N](BF4) as the supporting electrolyte; potentials in V vs Fc+/
Fc. All solutions are 10-5 M in CH3CN at 25 °C. b 3a: R1 ) Ph;25 3b: R1
) thiophene-2-yl.25 c Oxidation of the amino group interferes with this
process.
) 40) and the naphthyl-bridged analogue (L ) 41), with the
emission maxima occurring at 500 and 451 nm, respectively.
As summarized in Table 3, only slight differences for the
position of the emission maximum for the oligophenyl-bridged
derivatives (L ) 35-39) can be observed, indicating the minor
influence of the length and substitution pattern of the corre-
sponding spacer units. Our first results indicate that the di- and
trinuclear Ru(II) complexes derived from oligo(U-terpyridines)
are promising structures with respect to potential photophysical
applications.
Electrochemistry: The electrochemical data obtained are
reported in Table 4 (potentials vs Fc+/Fc). The electrochemical
behavior is well-documented for both mono- and dinuclear
ruthenium complexes and is explained in terms of localized
metal- and ligand-centered processes.24 This general approach
has been put to use in the present cases.
Experimental Section
General. All reagents were purchased from commercial sources
and used without prior purification unless specified. All solvents
were dried and distilled according to standard procedures and stored
under argon. All reactions were conducted under argon. 5,6,7,8-
Tetrahydroquinolinone 130 and aldehydes 7-1331 and 4432 were
prepared by procedures described in the literature. Chromatographic
separation was performed on neutral aluminum oxide. 1H and 13C
NMR (500 and 125 MHz, respectively) were obtained in CDCl3
All ruthenium complexes exhibit a single one-electron
reversible wave for the Ru(II)/Ru(III) oxidation in the range
1.20-1.30 V, which is shifted to a more positive potential than
what is observed for [Ru(tpy)2]2+ (1.18 V).19b The data comply
with those obtained for analogous structures known to the
literature.19c,e,27 The electronic influence of the aromatic sub-
stituents results in the metal centers being more resistant to
oxidation.28 The observed potentials for the metal-centered
oxidation do not change significantly on passing from mono-
nuclear to dinuclear species. The presence of a single oxidative
process within the solvent window at any scan rate supports
the conclusion that the metal centers in each complex are
(29) (a) Balzani, V.; De Cola, L.; Barigeletti, F. Top. Curr. Chem. 1990,
158, 31-71. (b) Grosshenny, V.; Ziessel, R. Tetrahedron Lett. 1992, 33,
8075-8078. (c) Arana, C.; Yan, S.; Keshavarz-K., M.; Potts, K. T.; Abrun˜a,
H. D. Inorg. Chem. 1992, 31, 3680-3682. (d) Flanagan, J. B.; Margel, S.;
Bard, A. J.; Anson, F. C. J. Am. Chem. Soc. 1978, 100, 4248-4253.
(30) (a) Crabb, T. A.; Turner, C. H. J. Chem. Soc, Perkin Trans. 1 1980,
1778-1782. (b) Thummel, R. P.; Lefoulon, F.; Cantu, D.; Mahadevan, R.
J. Org. Chem. 1984, 49, 2208-2212.
(31) (a) Helm, A.; Heiler, D.; McLendon, G. J. Am. Chem. Soc. 1992,
114, 6227-6238. (b) Lourak, M.; Vanderesse, R.; Fort, Y.; Caubere, P. J.
Org. Chem. 1989, 54, 4840-4844. (c) Feringa, B. L.; Hulst, R.; Rikers,
R.; Brandsma, L. Synthesis 1988, 316-318. (d) Hagiya, K.; Mitsui, S.;
Taguchi, H. Synthesis 2003, 823-828. (e) Katritzky, A. R.; Belyakov, S.
A.; Denisko, O. V.; Maran, U.; Dalal, N. S. J. Chem. Soc., Perkin Trans.
2 1998, 611-616. (f) Mayence, A.; Eynde, J. J. V.; Krogstad, F. M.;
Krogstad, D. J.; Cushion, M. T.; Huang, T. L. J. Med. Chem. 2004, 47,
2700-2705.
(27) Collin, J.-P.; Laine, P.; Sauvage, J.-P., Sour, A. J. Chem. Soc., Chem.
Commun. 1993, 434-435.
(28) Elliot, C. M.; Hershenhart, E. J. J. Am. Chem. Soc. 1982, 104, 7519.
(32) Weber, E.; Hecker, M.; Koepp, E.; Orlia, W.; Czugler, M.; Csoeregh,
I. J. Chem. Soc., Perkin Trans. 2 1988, 1251-1258.
J. Org. Chem, Vol. 71, No. 13, 2006 4867

Winter et al.
(unless otherwise stated) with TMS as internal standard. Mass
spectroscopy was carried out by electron impact (EI, 70 eV), matrix
assisted laser desorption/ionization time-of-flight (MALDI-TOF,
matrix substance DCTB), and electrospray ionization (ESI) tech-
niques. UV/vis and emission spectra were measured at 298 K in
outgassed CH3CN.
General Procedure for the Synthesis of Aminals 14-23 and
45. A mixture of an aromatic dialdehyde (0.1 mol) and morpholine
(35.7 mL, 0.41 mol) was stirred for 12 h at room temperature. The
solid so obtained was recrystallized from Et2O.15
1H NMR (500 MHz, CDCl3) δ 6.80 (s, 2H), 3.92 (s, 2H), 3.67-
3.75 (m, 16H), 2.46-2.56 (m, 16H); 13C NMR (125 MHz, CDCl3)
δ 143.8, 125.9, 88.2, 66.9, 50.2. Anal. Calcd for C22H36N4O4S
(452.6): C, 58.38; H, 8.02; N, 12.38. Found: C, 58.32; H, 7.97;
N, 12.36.
2,6-Bis(dimorpholinomethyl)naphthalene (21). Reaction of 2,6-
diformylnaphthalene 11 (4.2 g, 22.6 mmol) and morpholine (8 mL,
91 mmol) afforded 7.73 g (69%) of a yellow powder: mp > 250
°C after recrystallization from EtOH; IR (KBr) ν 2956, 2910, 2884,
2848, 2821, 2796, 1724, 1450, 1392, 1303, 1290, 1272, 1137, 1110,
1
1016, 867; H NMR (500 MHz, CDCl3) δ 7.80-8.17 (m, 4H),
1,1,2,2-Tetramorpholinoethane (14). Reaction of glyoxal 4 (23
mL, 40% aq solution, 0.2 mol) and morpholine (70 mL, 0.8 mol)
afforded 56.3 g (76%) as a yellow powder: mp 109 °C (lit.33 mp
7.38-7.60 (m, 2H), 4.02 (s, 2H), 3.71-3.84 (m, 16H), 2.40-2.65
(m, 16H); 13C NMR (125 MHz, CDCl3) δ 135.3, 133.1, 132.7,
129.5, 125.9, 123.5, 89.6, 67.9, 52.7. Anal. Calcd for C28H40N4O4
(496.6): C, 67.71; H, 8.12; N, 11.28. Found: C, 67.67; H, 8.01;
N, 11.20.
1
112 °C) after recrystallization from Et2O; H NMR (500 MHz,
CDCl3) δ 4.26 (s, 2H), 3.51-3.64 (m, 16H), 2.37-2.41 (m, 16H).
1,4-Bis(dimorpholinomethyl)benzene (15). Reaction of tereph-
thaldehyde 5 (26.8 g, 0.2 mol) and morpholine (70 mL, 0.8 mol)
afforded 74.1 g (83%) as a pale yellow powder: mp 214 °C (lit.34
mp 216 °C) after recrystallization from Et2O; 1H NMR (500 MHz,
CDCl3) δ 7.14 (s, 4H), 3.52-3.66 (m, 18H), 2.35-2.46 (m, 16H).
1,3-Bis(dimorpholinomethyl)benzene (16). Reaction of iso-
phthaldehyde 6 (6.7 g, 0.05 mol) and morpholine (10.5 mL, 0.12
mol) afforded 19.4 g (87%) as a yellow powder: mp 198 °C after
recrystallization from Et2O; 1H NMR (500 MHz, CDCl3) δ 6.91-
7.13 (m, 4H), 3.57-3.65 (m, 16H), 3.55 (s, 2H), 2.38-2.46 (m,
16H).
1,5-Bis-(4-dimorpholinomethylphenoxy)-3-oxopentane (22).
Reaction of 1,5-(di-(4-formyl-phenoxy)-3-oxopentane 12 (31.44 g,
0.1 mol) and morpholine (35 mL, 0.4 mol) afforded 47.02 g (75%)
of a yellow powder: mp 223 °C after recrystallization from Et2O;
IR (KBr) ν 2944, 2835, 2815, 1526, 1412, 1272, 1251, 1155, 1106,
1
3
1023; H NMR (500 MHz, CDCl3) δ 7.13 (d, J ) 8.2 Hz, 4H),
6.91 (d, 3J ) 8.2 Hz, 4H), 4.11-4.24 (m, 4H), 3.90-4.02 (m, 4H),
3.64-3.76 (m, 16H), 3.61 (s, 2H), 2.33-2.55 (m, 16H); 13C NMR
(125 MHz, CDCl3) δ 158.7, 130.3, 126.9, 114.2, 88.9, 70.3, 68.3,
67.6, 49.9. Anal. Calcd for C34H50N4O7 (626.8): C, 65.51; H, 8.04;
N, 8.94. Found: C, 65.44; H, 8.08; N, 8.89.
4,4′-Bis(dimorpholinomethyl)biphenyl (17). Reaction of 4,4′-
diformylbiphenyl 7 (8.4 g, 0.04 mol) and morpholine (10.5 mL,
0.12 mol) afforded 20.1 g (96%) of a pale yellow powder: mp >
250 °C after recrystallization from Et2O; IR (KBr) ν 2959, 2805,
N,N′-Bis(4-dimorpholinophenyl)piperazine (23). Reaction of
N,N′-di(4-formylphenyl)piperazine 13 (29.43 g, 0.1 mol) and
morpholine (35 mL, 0.4 mol) afforded 50.97 g (84%) of an orange
powder: mp 209 °C after recrystallization from Et2O; IR (KBr) ν
1
1492, 1452, 1394, 1301, 1290, 1207, 1138, 1016, 1001, 876; H
1
3
3
2933, 2811, 2795, 1510, 1460, 1233, 1150, 1090, 1023, 876; H
NMR (500 MHz, CDCl3) δ 7.52 (d, J ) 8.3 Hz, 4H), 7.14 (d, J
) 8.3 Hz, 4H), 3.54-3.72 (m, 18H), 2.37-2.48 (m, 16H); 13C
NMR (125 MHz, CDCl3) δ 135.2, 134.9, 129.2, 127.1, 89.3, 67.7,
50.4; EI-MS (70 eV) m/z 522 (3, M+), 435 (100), 349 (49), 292
(26), 277 (22), 175 (71). Anal. Calcd for C30H42N4O4 (522.7): C,
68.94; H, 8.10; N, 10.72. Found: C, 69.01; H, 8.07; N, 10.75.
3,3′-Bis(dimorpholinomethyl)biphenyl (18). Reaction of 3,3′-
diformylbiphenyl 8 (3.0 g, 14 mmol) and morpholine (4.9 mL, 56
mmol) afforded 6.9 g (95%) of a colorless powder: mp 231 °C
after recrystallization from Et2O; IR (KBr) ν 2976, 2856, 2821,
3
3
NMR (500 MHz, CDCl3) δ 6.95 (d, J ) 7.9 Hz, 4H), 6.89 (d, J
) 7.9 Hz, 4H), 3.52-3.73 (m, 26H), 2.31-2.49 (m, 16H); 13C
NMR (125 MHz, CDCl3) δ 146.5, 130.1, 128.8, 116.9, 88.6, 68.4,
50.1, 49.3. Anal. Calcd for C34H50N6O4 (606.8): C, 67.30; H, 8.31;
N, 13.85. Found: C, 67.25; H, 8.22; N, 13.94.
1,3,5-Tris(4′,4′′,4′′′-bismorpholinomethylphenyl)benzene (45).
Reaction of 1,3,5-tris(4′,4′′,4′′′-formylphenyl)benzene 44 (1.42 g,
3.6 mmol) and morpholine (1.9 mL, 21.6 mmol) afforded 3.01 g
(97%) of a yellow powder: mp 250 °C after recrystallization from
Et2O; IR (KBr) ν 2952, 2848, 2807, 1504, 1452, 1394, 1270, 1139,
1114, 1016, 875; 1H NMR (500 MHz, CDCl3) δ 7.82 (s, 3H), 7.72
1
1475, 1348, 1270, 1205, 1141, 1114, 1018, 869, 756; H NMR
(500 MHz, CDCl3) δ 7.38-7.51 (m, 6H), 7.16-7.22 (m, 2H),
3.62-3.75 (m, 18H), 2.37-2.45 (m, 16H); 13C NMR (125 MHz,
CDCl3) δ 141.2, 135.0, 128.6, 127.9, 127.2, 89.5, 67.6, 50.0; EI-
MS (70 eV) m/z 436 (9), 211 (15), 88 (100), 57 (98). Anal. Calcd
for C30H42N4O4 (522.7): C, 68.94; H, 8.10; N, 10.72. Found: C,
68.89; H, 8.15; N, 10.68.
3
3
(d, J ) 8.0 Hz, 6H), 7.34 (d, J ) 8 Hz, 6H), 3.59-3.73 (m,
27H), 2.39-2.52 (m, 24H); 13C NMR (125 MHz, CDCl3) δ 142.3,
141.0, 133.9, 129.7, 127.2, 125.4, 89.2, 67.6, 50.0. Anal. Calcd
for C51H66N6O6 (859.1): C, 71.30; H, 7.74; N, 9.78. Found: C,
71.26; H, 7.78; N, 9.83.
General Procedure for the Synthesis of Iminium Salts 24-
33 and 46. A solution of acetyl chloride (1 equiv per aminal group)
in absolute Et2O (25 mL) was added slowly to a suspension of an
aminal (0.05 mol) in absolute Et2O (150 mL) at 0 °C. The reaction
mixture was then kept at room temperature for 12 h. The bisiminium
salt was filtered off, washed rapidly with absolute Et2O (50 mL),
and dried in vacuo. Due to their hygroscopic nature and low
solubility in organic solvents, bisiminium salts were used in the
synthesis of U-terpyridines 34-43 and 47 without any further
purification and characterization.16
General Procedure for the Synthesis of Bis(U-terpyridines)
34-43. A solution of 5,6,7,8-tetrahydroquinolinone 1 (6 mmol)
and ammonium acetate (6.1 mmol) in dry DMSO (15 mL) was
heated for 5 min at 85 °C. In a second flask, a suspension of 1 (6
mmol) and a bisiminium salt (3.05 mmol) in dry DMSO (10 mL)
was heated until a clear solution was formed. The solution of the
bisiminium salt and the ketone was then added to the first flask
and heated at 150 °C for 16 h. The reaction mixture was cooled,
and water (40 mL) was added. The solution was extracted with
CH2Cl2 (3 × 25 mL). The combined organic layers were washed
with water (3 × 20 mL) and dried over MgSO4. After removal of
4,4′′-Bis(dimorpholinomethyl)-p-terphenyl (19). Reaction of
4,4′′-diformyl-p-terphenyl 9 (14.3 g, 50 mmol) and morpholine
(17.5 mL, 0.2 mol) afforded 26.3 g (88%) of a pale yellow
powder: mp > 250 °C after recrystallization from EtOH; IR (KBr)
ν 2954, 2854, 2813, 1701, 1602, 1484, 1398, 1274, 1105, 1016,
1
877, 821, 765; H NMR (500 MHz, CDCl3) δ 7.63 (s, 4H), 7.36
3
3
(d, J ) 8.4 Hz, 4H), 7.22 (d, J ) 8.4 Hz, 4H), 3.83 (s, 2H),
3.59-3.72 (m, 16H), 2.35-2.46 (m, 16H); 13C NMR (125 MHz,
CDCl3) δ 140.5, 140.1, 133.6, 129.7, 127.8, 127.4, 89.2, 67.6, 50.0;
EI-MS (70 eV) m/z 327 (68), 267 (55), 242 (100), 87 (36). Anal.
Calcd for C36H46N4O4 (598.8): C, 72.21; H, 7.74; N, 9.36. Found:
C, 72.25; H, 7.70; N, 9.41.
2,5-Bis(dimorpholinomethyl)thiophene (20). Reaction of 2,5-
thiophenedicarbaldehyde 10 (0.5 g, 3.57 mmol) and morpholine
(0.62 mL, 7.14 mmol) afforded 1.58 g (98%) of a yellow powder:
mp 203 °C after recrystallization from Et2O; IR (KBr) ν 2951, 2915,
2881, 2855, 2800, 1735, 1466, 1442, 1397, 1278, 1143, 1023, 914;
(33) Duhamel, L.; Duhamel, P.; Ple´, G. C. R. Hebd. Seances Acad. Sci.
Ser. C 1970, 271, 751-753.
(34) Kerfanto, M. Bull. Soc. Chim. Fr. 1975, 196-200.
4868 J. Org. Chem., Vol. 71, No. 13, 2006

Synthesis of Oligo(U-terpyridines)
the solvent, the residue was purified by chromatography on Al2O3
(elution with CH2Cl2/methanol, 50:1).11l
0.98 g (41%) as a brownish powder: mp > 270 °C (lit.11m mp >
250 °C) after recrystallization from EtOH; IR (KBr) ν 2935, 2812,
1
1631, 1549, 1441, 1370, 1199, 1108, 777; H NMR (500 MHz,
5,5′,6,6′,8,8′,9,9′-Octahydro-7,7′-biquino[8,7-b]-1,10-phenan-
throline (34). Reaction of 1 (1.76 g, 12 mmol), ammonium acetate
(0.5 g, 6.5 mmol), and 24 (0.82 g, 3.05 mmol) according to the
predescribed protocol resulted in the isolation of 0.44 g (26%) as
a brownish powder: mp > 270 °C after recrystallization from
EtOAc; IR (KBr) ν 3028, 2935, 2883, 2829, 1563, 1442, 1400,
CDCl3/CD3OD, 20:1) δ 8.52 (d, 3J ) 4.7 Hz, 4H), 7.79-7.84 (m,
4H), 7.57-7.63 (m, 4H), 7.21-7.35 (m, 12H), 2.89-2.92 (m, 8H),
2.75-2.83 (m, 8H); 13C NMR (125 MHz, CDCl3/CD3OD, 20:1) δ
152.1, 150.3, 148.5, 140.7, 136.6, 136.3, 129.5, 128.0, 127.9, 124.3,
27.6, 25.6. Anal. Calcd for C50H36N6 (767.0): C, 84.40; H, 5.06;
N, 10.55. Found: C, 84.36; H, 5.01; N, 10.44.
1
1225, 1176, 845, 778, 759; H NMR (500 MHz, CDCl3) δ 8.67
(m, 4H), 7.18-7.39 (m, 8H), 2.88-3.09 (m, 16H); 13C NMR (125
MHz, CDCl3) δ 156.2, 152.1, 148.8, 147.5, 136.4, 136.3, 133.9,
123.9, 27.8, 27.6. Anal. Calcd for C38H28N6 (568.67): C, 80.26;
H, 4.96; N, 14.78. Found: C, 80.31; H, 5.02; N, 14.89.
2,5-Di-(5,6,8,9-tetrahydrochino[8,7-b][1,10]phenanthrolin-7-
yl)thiophene (40). Reaction of 1 (1.17 g, 8 mmol), ammonium
acetate (0.63 g, 8.2 mmol), and 30 (1.30 g, 3.7 mmol) according
to the predescribed protocol resulted in the isolation of 0.92 g (38%)
as a brownish powder: mp > 270 °C after recrystallization from
EtOH; IR (KBr) ν 2959, 2802, 1633, 1512, 1444, 1120, 1023, 765,
1,4-Di-(5,6,8,9-tetrahydrochino[8,7-b][1,10]phenanthrolin-7-
yl)benzene (35). Reaction of 1 (1.76 g, 12 mmol), ammonium
acetate (0.5 g, 6.5 mmol), and 25 (1.05 g, 3.05 mmol) according
to the predescribed protocol resulted in the isolation of 0.70 g (36%)
as a brownish powder: mp > 270 °C (lit.35 mp > 300 °C) after
recrystallization from EtOH; IR (KBr) ν 3035, 2927, 2825, 1555,
1437, 1388, 1236, 1174, 853, 752; 1H NMR (500 MHz, CDCl3) δ
8.76-8.85 (m, 4H), 7.51-7.58 (m, 4H), 7.33 (s, 4H), 7.16-7.24
(m, 4H), 2.93-3.09 (m, 8H), 2.74-2.89 (m, 8H); 13C NMR (125
MHz, CDCl3) δ 152.5, 150.9, 149.2, 147.5, 137.3, 136.0, 133.9,
132.6, 129.5, 124.0, 27.9, 25.9. Anal. Calcd for C44H32N6
(644.77): C, 81.96; H, 5.00; N, 13.03. Found: C, 81.91; H, 5.07;
N, 13.01.
1,3-Di-(5,6,8,9-tetrahydrochino[8,7-b][1,10]phenanthrolin-7-
yl)benzene (36). Reaction of 1 (1.76 g, 12 mmol), ammonium
acetate (0.5 g, 6.5 mmol), and 26 (1.05 g, 3.05) according to the
predescribed protocol resulted in the isolation of 0.60 g (31%) as
a brown powder: mp > 270 °C (lit.35 mp > 300 °C) after
recrystallization from EtOH; IR (KBr) ν 3031, 2931, 2846, 1549,
1432, 1377, 1234, 1167, 861, 759; 1H NMR (500 MHz, CDCl3) δ
8.79-8.92 (m, 4H), 7.55-7.62 (m, 4H), 7.08-7.29 (m, 8H), 2.77-
3.12 (m, 16H); 13C NMR (125 MHz, CDCl3) δ 152.3, 150.8, 149.1,
147.5, 138.8, 136.2, 133.7, 132.5, 129.1, 127.5, 125.3, 124.0, 27.8,
25.8. Anal. Calcd for C44H32N6 (644.77): C, 81.96; H, 5.00; N,
13.03. Found: C, 82.03; H, 5.05; N, 13.10.
1
649; H NMR (500 MHz, CDCl3) δ 8.65-8.69 (m, 2H), 7.10-
7.75 (m, 10H), 2.89-3.00 (m, 2H), 2.70-2.88 (m, 8H); 13C NMR
(125 MHz, CDCl3) δ 153.5, 150.6, 147.1, 142.8, 135.6, 132.4,
131.9, 126.9, 121.6, 28.1, 25.9. Anal. Calcd for C42H30N6S
(650.8): C, 77.51; H, 4.56; N, 12.91. Found: C, 77.49; H, 4.61;
N, 12.88.
2,6-Di-(5,6,8,9-tetrahydrochino[8,7-b][1,10]phenanthrolin-7-
yl)naphthalene (41). Reaction of 1 (1.17 g, 8 mmol), ammonium
acetate (0.63 g, 8.2 mmol), and 31 (1.62 g, 3.7 mmol) according
to the predescribed protocol resulted in the isolation of 1.81 g (63%)
as a brown solid: mp > 270 °C after recrystallization from EtOH;
IR (KBr) ν 3052, 2940, 2836, 1721, 1575, 1550, 1438, 1390, 1280,
1
1249, 1214, 815, 779, 757, 715, 657, 480; H NMR (500 MHz,
CDCl3) δ 8.76-8.87 (m, 4H), 8.07-8.12 (m, 2H), 7.57-7.69 (m,
4H), 7.35-7.51 (m, 8H), 2.90-3.08 (m, 8H), 2.68-2.90 (m, 8H);
13C NMR (125 MHz, CDCl3) δ 151.4, 149.7. 149.4, 147.6, 137.3,
136.5, 135.2, 132.7, 131.0, 130.0, 128.8. 128.4, 128.2, 123.9, 27.2,
25.1. Anal. Calcd for C48H34N6 (694.8): C, 82.97; H, 4.93; N, 12.10.
Found: C, 82.91; H, 4.88; N, 12.21.
[4,4′-Di-(5,6,8,9-tetrahydrochino[8,7-b][1,10]phenanthrolin-
7-yl)-1,7-diphenyl]-1,4,7-trioxaheptan (42). Reaction of 1 (1.17
g, 8 mmol), ammonium acetate (0.63 g, 8.2 mmol), and 32 (1.87
g, 4.1 mmol) according to the predescribed protocol resulted in
the isolation of 0.92 g (29%) as a brown powder: mp > 270 °C
after recrystallization from EtOH; IR (KBr) ν 3288, 3052, 2929,
2877, 2836, 1662, 1606, 1509, 1438, 1388, 1243, 1220, 1110, 842,
4,4′-Di-(5,6,8,9-tetrahydrochino[8,7-b][1,10]phenanthrolin-7-
yl)biphenyl (37). Reaction of 1 (1.76 g, 12 mmol), ammonium
acetate (0.5 g, 6.5 mmol), and 27 (1.29 g, 3.05 mmol) according
to the predescribed protocol resulted in the isolation of 0.81 g (37%)
as a brownish powder: mp > 270 °C after recrystallization from
EtOH; IR (KBr) ν 2950, 2829, 1637, 1557, 1550, 1438, 1390, 1214,
815, 777, 613, 530; 1
H NMR (500 MHz, CDCl3) δ 8.69-8.70 (m,
4H), 7.49-7.65 (m, 4H), 7.19-7.31 (m, 4H), 6.90-7.12 (m, 8H),
4.19-4.38 (m, 4H), 3.97-4.10 (m, 4H), 2.62-2.90 (m, 16H); 13
C
1
1112, 815, 782, 615; H NMR (500 MHz, CDCl3) δ 8.72-8.78
NMR (125 MHz, CDCl3) δ 158.8, 152.8, 151.1, 149.3, 147.7, 135.5,
(m, 4H), 7.55-7. 62 (m, 4H), 7.03-7.28 (m, 12H), 2.97-3.06 (m,
8H), 2.81-2.92 (m, 8H); 13C NMR (125 MHz, CDCl3) δ 156.3,
153.1, 150.7, 140.5, 136.8, 136.3, 134.6, 132.9, 129.7, 124.0, 27.8,
25.8. Anal. Calcd for C50H36N6 (720.9): C, 83.31; H, 5.03; N, 11.66.
Found: C, 83.37; H, 5.08; N, 11.77.
3,3′-Di-(5,6,8,9-tetrahydrochino[8,7-b][1,10]phenanthrolin-7-
yl)biphenyl (38). Reaction of 1 (1.76 g, 12 mmol), ammonium
acetate (0.5 g, 6.5 mmol), and 28 (1.29 g, 3.05 mmol) according
to the predescribed protocol resulted in the isolation of 0.91 g (42%)
as a brownish powder: mp > 270 °C after recrystallization from
EtOH; IR (KBr) ν 2933, 2817, 1625, 1555, 1431, 1375, 1222, 1116,
819, 781, 615; 1H NMR (500 MHz, CDCl3) δ 8.75-8.81 (m, 4H),
7.47-7.58 (m, 6H), 7.28-7.37 (m, 6H), 7.05-7.09 (m, 4H), 2.79-
2.93 (m, 16H); 13C NMR (125 MHz, CDCl3) δ 156.7, 153.8, 150.2,
148.7, 138.1, 137.4, 136.5, 136.1, 133.0, 129.6, 127.5, 125.8, 124.9,
123.7, 27.6, 25.8. Anal. Calcd for C50H36N6 (720.9): C, 83.31; H,
5.03; N, 11.66. Found: C, 83.27; H, 4.99; N, 11.58.
133.5, 133.0, 130.3, 129.8, 123.5, 115.2, 70.3, 67.7, 27.8, 25.9.
Anal. Calcd for C54H44N6O3 (825.1): C, 78.62; H, 5.38; N, 10.19.
Found: C, 78.59; H, 5.32; N, 10.18.
4,4′-Di-(5,6,8,9-tetrahydrochino[8,7-b][1,10]phenanthrolin-7-
yl)-N,N′-diphenylpiperazine (43). Reaction of 1 (1.17 g, 8 mmol),
ammonium acetate (0.63 g, 8.2 mmol), and 33 (2.07 g, 4.1 mmol)
according to the predescribed protocol resulted in the isolation of
0.73 g (22%) as a brown solid: mp > 270 °C after recrystallization
from EtOH; IR (KBr) ν 3290, 3052, 3002, 2937, 2834, 1662, 1643,
1608, 1575, 1515, 1440, 1388, 1222, 1186, 1110, 1000, 815, 781,
707, 661, 615; 1H NMR (500 MHz, CDCl3) δ 8.61-8.77 (m, 4H),
7.58-7.66 (m, 8H), 7.37-7.48 (m, 8H), 7.21-7.28 (m, 4H), 3.63-
3.73 (m, 8H), 2.88-2.97 (m, 8H), 2.74-2.85 (m, 8H); 13C NMR
(125 MHz, CDCl3) δ 156.5, 152.8, 152.2, 150.8, 148.6, 147.4,
147.1, 135.1, 129.6, 128.1, 123.6, 123.2, 46.7, 40.0, 27.8, 25.9.
Anal. Calcd for C54H44N8 (805.0): C, 80.57; H, 5.51; N, 13.92.
Found: C, 80.55; H, 5.49; N, 13.96.
4,4′′-Di-(5,6,8,9-tetrahydrochino[8,7-b][1,10]phenanthrolin-7-
yl)-[1,1′;4′,1′′]terphenyl (39). Reaction of 1 (1.76 g, 12 mmol),
ammonium acetate (0.5 g, 6.5 mmol), and 29 (1.52 g, 3.05 mmol)
according to the predescribed protocol resulted in the isolation of
1,3,5-Tris-[(5,6,8,9-tetrahydroquino[8,7-b][1,10]phenantrolin-
7-yl]phenyl]benzene (47). Reaction of 1 (1.76 g, 12 mmol),
ammonium acetate (0.94 g, 12.2 mmol), and 46 (1.41 g, 2 mmol)
according to the predescribed protocol resulted in the isolation of
0.58 g (25%) as a brown solid: mp > 270 °C after recrystallization
from EtOH; IR (KBr) ν 2935, 2883, 2806, 1564, 1440, 1222, 1176,
(35) Hegde, V.; Jahng, Y.; Thummel, R. P. Tetrahedron Lett. 1987, 28,
4023-4026.
1
820, 789, 705 cm-1; H NMR (500 MHz, CDCl3) δ 8.71-8.85
J. Org. Chem, Vol. 71, No. 13, 2006 4869

Winter et al.
(m, 6H), 7.48-7.62 (m, 21H), 7.05-7.11 (m, 4H), 2.76-2.95 (m,
24H); 13C NMR (125 MHz, CDCl3) δ 156.4, 152.6, 150.7, 147.3,
136.2, 135.8, 134.2, 133.3, 133.0, 132.2, 131.6, 128.4, 127.9, 125.2,
122.5, 35.3, 26.4. Anal. Calcd for C81H57N9 (1156.4): C, 84.13;
H, 4.97; N, 10.90. Found: C, 84.05; H, 5.03; N, 10.92.
Synthesis of [(tpy)RuCl3]. A mixture of RuCl3‚H2O (262 mg,
1 mmol) and 2,2′:6′,2′′-terpyridine (234 mg, 1 mmol) in absolute
ethanol (125 mL) was heated at reflux for 3 h. After this time, the
reaction was cooled to room temperature and the fine brown powder
was filtered off. The product was washed with ethanol (3 × 25
mL) and Et2O (3 × 25 mL) and dried in vacuo to give 440 mg
(88%) of [(tpy)RuCl3].21
General Procedure for the Synthesis of Complexes [(tpy)-
Ru(L)Ru(tpy)](PF6)4. A mixture of the bis(U-terpyridine) (0.1
mmol), [(tpy)RuCl3] (0.2 mmol), and N-ethylmorpholine in ethanol
(7 mL) was heated at reflux for 24 h. After cooling to room
temperature, the mixture was filtered to remove the remainder of
the unreacted ligand. The filtrate was then treated with an excess
of NH4PF6 (150 mg). The red-orange solid was isolated and purified
by recrystallization from toluene/acetonitrile (1:1) and/or flash
column chromatography on Al2O3 using the same solvents.22
[(tpy)Ru(34)Ru(tpy)](PF6)4. Reaction of 34 (114 mg, 0.2 mmol),
[(tpy)RuCl3] (185 mg, 0.42 mmol), and NH4PF6 (150 mg, 0.92
mmol) according to the predescribed protocol resulted in the
isolation of 287 mg (79%) as a red solid. IR (KBr) ν 3653, 3586,
3098, 2992, 2835, 1607, 1453, 1418, 1234, 850, 762 cm-1; 1H NMR
(500 MHz, CD3CN) δ 8.75 (d, 3J ) 7.9 Hz, 4H, B3/5), 8.51-8.55
(m, 4H, A3), 8.42-8.47 (m, 2H, B4), 8.01-8.06 (m, 4H, A4),
7.63-7.77 (m, 8H, A6/C4), 7.19-7.25 (m, 4H, A5), 7.01-7.14
(m, 4H, C6), 6.79-6.98 (m, 4H, C5), 3.11-3.41 (m, 16H); UV/
vis λmax (ꢀ) 477 (17 320), 359 (16 980), 308 (48 250), 271 (35 130);
MALDI-TOF MS m/z 1673 [M - PF6]+. Anal. Calcd for
C68H50F24N12P4Ru2 (1817.2): C, 44.94; H, 2.77; N, 9.25. Found:
C, 45.07; H, 2.81; N, 9.33.
357 (23 040), 310 (72 160), 269 (45 250); MALDI-TOF MS m/z
1825 [M - PF6]+. Anal. Calcd for C80H58F24N12P4Ru2 (1969.4):
C, 48.79; H, 2.97; N, 8.53. Found: C, 48.71; H, 2.92; N, 8.60.
[(tpy)Ru(38)Ru(tpy)](PF6)4. Reaction of 38 (144 mg, 0.2 mmol),
[(tpy)RuCl3] (185 mg, 0.42 mmol), and NH4PF6 (150 mg, 0.92
mmol) according to the predescribed protocol resulted in the
isolation of 358 mg (91%) as a red solid. IR (KBr) ν 3441, 3111,
2942, 1617, 1452, 1421, 1013, 851, 761, 559 cm-1; 1H NMR (500
3
MHz, CD3CN) δ 8.77 (d, J ) 8.0 Hz, 4H, B3/5), 8.51-8.57 (m,
4H, A3), 8.37-8.46 (m, 2H, B4), 8.12 (s, 2H, E2), 7.95-8.05 (m,
4H, A4), 7.57-7.81 (m, 10H, A6/C4/E5), 7.20-7.31 (m, 6H, A5),
7.02-7.22 (m, 4H, C6), 6.81-7.00 (m, 4H, C5), 3.10-3.39 (m,
16H); UV/vis λmax (ꢀ) 482 (23 160), 359 (28 410), 309 (89 120),
270 (51 980); MALDI-TOF MS m/z 1825 [M - PF6]+, 840 [M -
2 PF6]2+. Anal. Calcd for C80H58F24N12P4Ru2 (1969.4): C, 48.79;
H, 2.97; N, 8.53. Found: C, 48.84; H, 3.02; N, 8.47.
[(tpy)Ru(39)Ru(tpy)](PF6)4. Reaction of 39 (159 mg, 0.2 mmol),
[(tpy)RuCl3] (185 mg, 0.42 mmol), and NH4PF6 (150 mg, 0.92
mmol) according to the predescribed protocol resulted in the
isolation of 384 mg (94%) as a red solid. IR (KBr) ν 3437, 3108,
2951, 1612, 1441, 1411, 1025, 876, 751, 549 cm-1; 1H NMR (500
3
MHz, CD3CN) δ 8.73 (d, J ) 7.7 Hz, 4H, B3/5), 8.49-8.56 (m,
4H, A3), 8.32-8.45 (m, 2H, B4), 8.02-8.09 (m, 4H, A4), 7.54 (s,
4H), 7.39-7.81 (m, 12H), 7.21-7.33 (m, 8H), 7.02-7.16 (m, 4H,
C6), 6.79-6.97 (m, 4H, C5), 3.14-3.38 (m, 16H); UV/vis λmax
(ꢀ) 479 (27 880), 357 (29 780), 310 (79 230), 269 (57 120);
MALDI-TOF MS m/z 1901 [M - PF6]+, 878 [M - 2 PF6]2+. Anal.
Calcd for C86H62F24N12P4Ru2 (2045.5): C, 50.50; H, 3.06; N, 8.22.
Found: C, 50.54; H, 3.11; N, 8.29.
[(tpy)Ru(40)Ru(tpy)][PF6]4. Reaction of 40 (130 mg, 0.2 mmol),
[(tpy)RuCl3] (185 mg, 0.42 mmol), and NH4PF6 (150 mg, 0.92
mmol) according to the predescribed protocol resulted in the
isolation of 330 mg (87%) as a dark red solid. IR (KBr) ν 3106,
3072, 2852, 1600, 1448, 1405, 1388, 853, 765, 557 cm-1; 1H NMR
(500 MHz, CD3CN) δ 8.78 (d, 3J ) 8.0 Hz, 4H, B3/5), 8.52-8.55
(m, 4H, A3), 8.47 (s, 2H), 8.39-8.44 (m, 2H, B4), 7.97-8.03 (m,
4H, A4), 7.53-7.75 (m, 8H, A6/C4), 7.23-7.27 (m, 4H, A5),
7.06-7.21 (m, 4H, C6), 6.84-7.01 (m, 4H, C5), 3.08-3.44 (m,
16H); UV/vis λmax (ꢀ) 478 (30 910), 359 (33 130), 308 (122 500),
270 (75 450); MALDI-TOF MS m/z 1755 [M - PF6]+. Anal. Calcd
for C72H52F24N12P4Ru2S (1899.3): C, 45.53; H, 2.76; N, 8.85.
Found: C, 45.48; H, 2.72; N, 8.89.
[(tpy)Ru(35)Ru(tpy)](PF6)4. Reaction of 35 (129 mg, 0.2 mmol),
[(tpy)RuCl3] (185 mg, 0.42 mmol), and NH4PF6 (150 mg, 0.92
mmol) according to the predescribed protocol resulted in the
isolation of 352 mg (93%) as a red solid. IR (KBr) ν 3644, 3591,
3081, 2955, 1621, 1432, 1408, 1214, 851, 766 cm-1; 1H NMR (500
3
MHz, CD3CN) δ 8.76 (d, J ) 8.1 Hz, 4H, B3/5), 8.49-8.53 (m,
4H, A3), 8.33-8.41 (m, 2H, B4), 7.95-8.04 (m, 4H, A4), 7.52 (s,
4H), 7.51-7.66 (m, 8H, A6/C4), 7.17-7.21 (m, 4H, A5), 6.99-
7.15 (m, 4H, C6), 6.81-6.95 (m, 4H, C5), 3.09-3.39 (m, 16H);
UV/vis λmax (ꢀ) 480 (19 050), 358 (22 300), 309 (74 020), 269
(48 210); MALDI-TOF MS m/z 1749 [M - PF6]+, 802 [M - 2
PF6]2+. Anal. Calcd for C74H54F24N12P4Ru2 (1893.3): C, 46.94; H,
2.87; N, 8.88. Found: C, 46.87; H, 2.81; N, 8.95.
[(tpy)Ru(41)Ru(tpy)][PF6]4. Reaction of 41 (139 mg, 0.2 mmol),
[(tpy)RuCl3] (185 mg, 0.42 mmol), and NH4PF6 (150 mg, 0.92
mmol) according to the predescribed protocol resulted in the
isolation of 354 mg (91%) as a dark red solid; IR (KBr) ν 3110,
3077, 2948, 1627, 1600, 1448, 1409, 1388, 1284, 855, 765, 557;
3
[(tpy)Ru(36)Ru(tpy)](PF6)4. Reaction of 36 (129 mg, 0.2 mmol),
[(tpy)RuCl3] (185 mg, 0.42 mmol), and NH4PF6 (150 mg, 0.92
mmol) according to the predescribed protocol resulted in the
isolation of 322 mg (85%) as a red solid. IR (KBr) ν 3438, 3111,
3052, 2946, 1616, 1541, 1429, 1401, 1345, 1298, 1012, 855, 714,
1H NMR (500 MHz, CD3CN) δ 8.83 (d, J ) 7.9 Hz, 4H, B3/5),
8.54-8.61 (m, 4H, A3), 8.35-8.45 (m, 2H, B4), 7.95 (s, 2H),
7.92-8.01 (m, 4H, A4), 7.39-7.72 (m, 12H), 7.21-7.31 (m, 4H,
A5), 7.03-7.17 (m, 4H, C6), 6.79-6.97 (m, 4H, C5), 3.15-3.39
(m, 16H); UV/vis λmax (ꢀ) 479 (21 310), 359 (25 200), 309 (83 870),
271 (56 400); MALDI-TOF MS m/z 1799 [M - PF6]+, 972 [M -
2 PF6]2+. Anal. Calcd for C78H56F24N12P4Ru2 (1943.4): C, 48.21;
H, 2.90; N, 8.65. Found: C, 48.16; H, 2.93; N, 8.71.
1
3
543 cm-1; H NMR (500 MHz, CD3CN) δ 8.81 (d, J ) 7.8 Hz,
4H, B3/5), 8.55-8.61 (m, 4H, A3), 8.41-8.47 (m, 2H, B4), 7.92-
8.05 (m, 4H, A4), 7.73 (s, 1H), 7.37-7.68 (m, 11H), 7.19-7.26
(m, 4H, A5), 7.02-7.17 (m, 4H, C6), 6.84-6.99 (m, 4H, C5),
3.16-3.41 (m, 16H); UV/vis λmax (ꢀ) 481 (17 270), 358 (19 050),
308 (67 240), 268 (39150); MALDI-TOF MS m/z 1749 [M - PF6]+.
Anal. Calcd for C74H54F24N12P4Ru2 (1893.3): C, 46.94; H, 2.87;
N, 8.88. Found: C, 46.99; H, 2.95; N, 8.81.
[(tpy)Ru(42)Ru(tpy)][PF6]4. Reaction of 42 (165 mg, 0.2 mmol),
Ru(tpy)Cl3 (185 mg, 0.42 mmol), and NH4PF6 (150 mg, 0.92 mmol)
according to the predescribed protocol resulted in the isolation of
323 mg (78%) as a dark red solid; IR (KBr) ν 3075, 2921, 2834,
1639, 1517, 1448, 1405, 1386, 1346, 1228, 1195, 851, 765, 557
1
3
[(tpy)Ru(37)Ru(tpy)](PF6)4. Reaction of 37 (144 mg, 0.2 mmol),
[(tpy)RuCl3] (185 mg, 0.42 mmol), and NH4PF6 (150 mg, 0.92
mmol) according to the predescribed protocol resulted in the
isolation of 374 mg (95%) as a red solid. IR (KBr) ν 3435, 3117,
2955, 1610, 1466, 1441, 857, 763, 563 cm-1; 1H NMR (500 MHz,
cm-1; H NMR (500 MHz, CD3CN) δ 8.82 (d, J ) 8.2 Hz, 4H,
B3/5), 8.49-8.57 (m, 4H, A3), 8.33-8.46 (m, 2H, B4), 8.06-
8.11 (m, 4H, A4), 7.59-7.75 (m, 8H, A6/C4), 7.21-7.38 (m, 8H),
7.01-7.17 (m, 4H, C6), 6.85-6.97 (m, 4H, C5), 6.82 (d, 3J ) 7.9
Hz, 4H), 4.12-4.23 (m, 4H), 3.69-3.74 (m, 4H), 3.14-3.32 (m,
16H); UV/vis λmax (ꢀ) 480 (39 420), 359 (52 640), 310 (13 620),
271 (81 490); MALDI-TOF MS m/z 1929 [M - PF6]+; 1784 [M
+ H - 2 PF6]+. Anal. Calcd for C84H66F24N12O3P4Ru2 (2073.5):
C, 48.66; H, 3.21; N, 8.11. Found: C, 48.61; H, 3.25; N, 8.17.
3
CD3CN) δ 8.72 (d, J ) 8.2 Hz, 4H, B3/5), 8.54-8.59 (m, 4H,
A3), 8.35-8.42 (m, 2H, B4), 8.02-8.09 (m, 4H, A4), 7.52-7.82
(m, 12H), 7.21-7.37 (m, 8H), 7.11-7.17 (m, 4H, C6), 6.87-6.98
(m, 4H, C5), 3.02-3.35 (m, 16H); UV/vis λmax (ꢀ) 483 (21 160),
4870 J. Org. Chem., Vol. 71, No. 13, 2006

Synthesis of Oligo(U-terpyridines)
[(tpy)Ru(43)Ru(tpy)][PF6]4. Reaction of 43 (161 mg, 0.2 mmol),
[(tpy)RuCl3] (185 mg, 0.42 mmol), and NH4PF6 (150 mg, 0.92
mmol) according to the predescribed protocol resulted in the
isolation of 398 mg (97%) as a dark red solid; IR (KBr) ν 2956,
2925, 2856, 1724, 1604, 1513, 1448, 1388, 1286, 1245, 1124, 849,
765, 557; H NMR (500 MHz, CD3CN) δ 8.79 (d, J ) 8.0 Hz,
4H, B3/5), 8.51-8.62 (m, 4H, A3), 8.35-8.42 (m, 2H, B4), 8.12-
8.23 (m, 4H, A4), 7.55-7.82 (m, 8H, A6/C4), 7.16-7.36 (m, 8H),
7.06-7.13 (m, 4H, C6), 6.88-7.03 (m, 8H), 3.51-3.69 (m, 8H),
3.09-3.29 (m, 16H); UV/vis λmax (ꢀ) 478 (28 500), 359 (37 220),
309 (108 330), 271 (66 200); MALDI-TOF MS m/z 1909 [M -
PF6]+. Anal. Calcd for C84H66F24N14P4Ru2 (2053.5): C, 49.13; H,
3.24; N, 9.55. Found: C, 49.19; H, 3.30; N, 9.48.
8.01-8.13 (m, 6H, A4), 7.66 (s, 3H), 7.51-7.82 (m, 24H), 7.33-
7.41 (m, 6H, A5), 7.16-7.27 (m, 6H, C6), 6.89-7.08 (m, 6H, C5),
3.01-3.52 (m, 24H); UV/vis λmax (ꢀ) 483 (25 120), 357 (41 870),
311 (96 040), 269 (60 800); MALDI-TOF MS m/z 2885 [M -
PF6]+, 865 [M - 3 PF6]3+. Anal. Calcd for C126H90F36N18P6Ru3
(3029.2): C, 49.96; H, 2.99; N, 8.32. Found: C, 50.07; H, 3.04;
N, 8.22.
1
3
Acknowledgment. Financial support of this work by the
Fonds der Chemischen Industrie and the Deutsche Forschungs-
gemeinschaft is gratefully acknowledged. The authors also thank
Dr. Matthias Letzel from the University of Bielefeld, Germany,
for performing the MALDI-TOF and ESI MS measurements.
[{(tpy)Ru}3(47)](PF6)6. Reaction of 47 (231 mg, 0.2 mmol),
[(tpy)RuCl3] (278 mg, 0.63 mmol), and NH4PF6 (225 mg, 1.38
mmol) according to the predescribed protocol resulted in the
isolation of 382 mg (63%) as a dark red-purple solid; IR (KBr) ν
3430, 3092, 2961, 1630, 1574, 1429, 1395, 1308, 1175, 1071, 847,
Supporting Information Available: Selected electrospray
ionization mass spectra (ESI MS) of dinuclear complexes [(tpy)-
Ru(L)Ru(tpy)](PF6)4. This material is available free of charge via
the Internet at http://pubs.acs.org.
1
721, 704, 635 cm-1; H NMR (500 MHz, CD3CN) δ 8.75-8.81
(m, 6H, B3/5), 8.49-8.57 (m, 6H, A3), 8.31-8.43 (m, 4H, B4),
JO060387+
J. Org. Chem, Vol. 71, No. 13, 2006 4871