Dimeric 2,2′-bipyridylruthenium(II) complexes containing 2,2′-bis(1,2,4-triazin-3-yl)-4,4′-bipyridine-like bridging ligands: Syntheses, characterization and DNA-binding

Article abstract of DOI:10.1002/ejic.200300710

Three new bridging ligands 2,2′-bis(1,2,4-triazin-3-yl)-4,4′- bipyridine (btb), 2,2′-bis(1,2,4-triazino[5,6-f] acenaphthylen-3-yl)-4, 4′-bipyridine (btapb), 2,2′-bis(5,6-diphenyl-1,2,4-triazin-3-yl)-4, 4′-bipyridine (bdptb) and their dimeric 2,2′-bipyridylruthenium(II) complexes [Ru(bpy)₂(btb)Ru(bpy)₂]⁴⁺ (1), [Ru(bpy)₂(btapb)Ru(bpy)₂]⁴⁺ (2), [Ru(bpy) ₂(bdptb)Ru(bpy)₂]⁴⁺ (3) have been synthesized and characterized by elemental analysis, fast atom bombardment (FAB) mass spectrometry or electrospray mass spectrometry (ES-MS), ¹H NMR and UV/Visible spectroscopy. The binding behavior of these dimeric complexes with calf thymus DNA (CT-DNA) was investigated by electronic absorption spectroscopy, viscosity measurements, and equilibrium dialysis experiments. The hypochromism of the metal-ligand charge transfer (MLCT) band in the electronic absorption spectra of the dinuclear complexes 1, 2, and 3 is 8.7%, 19% and 33%, respectively, with bathochromic shifts of 5, 5 and 14 nm, respectively. The binding constants are 7.5±10⁴ M^-1, 4.8±10⁵ M^-1 and 7.6±10⁵ M ^-1, respectively. Increasing the size of the plane of the bridging ligand increases the hydrophobicity of their complexes, leading to stronger binding by the complexes to calf thymus DNA. The effect of increasing concentrations of these novel dimeric ruthenium(II) complexes on the relative viscosities of CT-DNA is less notable than that of well-known intercalators such as [Ru(bpy)₂(dppz)]²⁺. The equilibrium experiments showed that ΛΛ-3 binding is stronger than ΛΛ-3 binding to CT-DNA. This is the first example of a dinuclear complex binding enantioselectively to CT-DNA measured by equilibrium dialysis. The experiments suggest that the three complexes may be DNA groove binders. Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004.

Full text of DOI:10.1002/ejic.200300710

FULL PAPER
Dimeric 2,2Ј-Bipyridylruthenium(II) Complexes Containing 2,2Ј-Bis(1,2,4-
triazin-3-yl)-4,4Ј-bipyridine-Like Bridging Ligands: Syntheses, Characterization
and DNA Binding
Cai-Wu Jiang[a]
Keywords: Dinuclear complexes / Ruthenium / DNA binding modes / Enantioselectivity
Three new bridging ligands 2,2Ј-bis(1,2,4-triazin-3-yl)-4,4Ј-
bipyridine (btb), 2,2Ј-bis(1,2,4-triazino[5,6-f]acenaphthylen-
3-yl)-4,4Ј-bipyridine (btapb), 2,2Ј-bis(5,6-diphenyl-1,2,4-tria-
with bathochromic shifts of 5, 5 and 14 nm, respectively. The
−1
binding constants are 7.5×104
M
−1, 4.8×105
M
and 7.6×105
M
−1, respectively. Increasing the size of the plane of the
zin-3-yl)-4,4Ј-bipyridine (bdptb) and their dimeric 2,2Ј-bipyr- bridging ligand increases the hydrophobicity of their com-
idylruthenium(II) complexes [Ru(bpy)2(btb)Ru(bpy)2]4+ (1),
[Ru(bpy)2(btapb)Ru(bpy)2]4+ (2), [Ru(bpy)2(bdptb)Ru(bpy)2]4+
(3) have been synthesized and characterized by elemental
analysis, fast atom bombardment (FAB) mass spectrometry or
electrospray mass spectrometry (ES-MS), 1H NMR and
UV/Visible spectroscopy. The binding behavior of these di-
meric complexes with calf thymus DNA (CT-DNA) was in-
vestigated by electronic absorption spectroscopy, viscosity
measurements, and equilibrium dialysis experiments. The
hypochromism of the metal-ligand charge transfer (MLCT)
band in the electronic absorption spectra of the dinuclear
complexes 1, 2, and 3 is 8.7%, 19% and 33%, respectively,
plexes, leading to stronger binding by the complexes to calf
thymus DNA. The effect of increasing concentrations of these
novel dimeric ruthenium(II) complexes on the relative viscos-
ities of CT-DNA is less notable than that of well-known inter-
calators such as [Ru(bpy)2(dppz)]2+. The equilibrium experi-
ments showed that ΛΛ−3 binding is stronger than ∆∆−3 bind-
ing to CT-DNA. This is the first example of a dinuclear com-
plex binding enantioselectively to CT-DNA measured by
equilibrium dialysis. The experiments suggest that the three
complexes may be DNA groove binders.
( Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim,
Germany, 2004)
Introduction
[3; bdptb ϭ 2,2Ј-bis(5,6-diphenyl-1,2,4-triazin-3-yl)-4,4Ј-bi-
pyridine] that displays enantiopreferential DNA-binding
behavior after equilibrium dialysis.[10] We describe here the
synthesis of the three new bridging ligands 2,2Ј-bis(1,2,4-
The design of molecules that target particular DNA se-
quences is one of the major challenges in the field of molec-
ular recognition. The potential application of ruthenium
complexes with polypyridyl ligands in the design and devel-
opment of photophysical and stereoselective probes of nu-
cleic acid structure has been explored extensively in recent
years.[1Ϫ6] However, this work has focused primarily on
mononuclear complexes, with di- or polynuclear complexes
attracting limited attention. Dimeric ruthenium() com-
plexes have some advantages over other complexes as
photo- and stereochemical probes for nucleic acids, such as
greater variations in size and shape. Additionally, the incor-
poration of two chiral centers into a single dimeric complex
may enable amplification of the chiral discrimination. More
recently, non-intercalating dinuclear ruthenium() com-
plexes have been synthesized as probes of DNA
structure.[7Ϫ10]
triazin-3-yl)-4,4Ј-bipyridine
(btb),
2,2Ј-bis(1,2,4-triaz-
ino[5,6-f]acenaphthylen-3-yl)-4,4Ј-bipyridine (btapb), bdptb
and their dimeric 2,2Ј-bipyridylruthenium() complexes
[Ru(bpy)2(btb)Ru(bpy)2]4ϩ
(1),
[Ru(bpy)2(btapb)Ru-
(bpy)2]4ϩ (2) and 3. The binding behavior of these com-
pounds with calf thymus DNA (CT-DNA) is also pre-
sented.
Results and Discussion
1. Syntheses and Characterization
The synthetic routes to the bidentate bridging ligands
and their complexes with bpy diruthenium() are summar-
ized in Scheme 1. The synthesis of the bridging ligands was
based on the method for the 1,2,4-triazine ring preparation
established by Case.[11,12] The condensation of bahmb with
glyoxal, acenaphthenequinone or benzil produced btb,
btapb and bdptb, respectively, in 78%, 72% and 75% yields.
Their identities were confirmed by elemental analysis, fast
atom bombardment (FAB) mass spectrometry and NMR
In a previous communication, we reported a novel di-
meric ruthenium() complex [Ru(bpy)2(bdptb)Ru(bpy)2]4ϩ
[a]
Guangxi Traditional Chinese Medical University,
Nanning 530001, P. R. China
Fax: (internat.) ϩ86-771-313-7377
E-mail: cwjiang@gxtcmu.edu.cn
Eur. J. Inorg. Chem. 2004, 2277Ϫ2282
DOI: 10.1002/ejic.200300710
 2004 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
2277

C.-W. Jiang
FULL PAPER
Scheme 1. The synthetic routes to the bidentate bridging ligands and bpy diruthenium() complexes
spectroscopy. Their complexes were also synthesized and intraligand π-π* transition by comparison with the spectra
characterized by elemental analysis and spectroscopic meth- of the uncoordinated bridging ligand.[14]
ods. The bridging ligands and their dimeric complexes give
highly resolved 1H NMR spectra in [D6]DMSO and all pro-
2. DNA-Binding Studies
1
ton resonance signals could be assigned by H-1H COSY
Electronic Absorption Titrations
experiments. The 1H NMR spectral data of the dimeric
1
complexes are listed in the Exp. Sect. The H-1H COSY
The interaction of the diruthenium() complexes with
NMR spectrum of the dimeric complex 2 is given in Fig- DNA was investigated by electronic absorption spec-
ure 1 as an example. troscopy. The absorption spectra of complexes 1, 2 and 3
Electrospray mass spectrometry (ES-MS) has recently in the absence and presence of CT-DNA (with the same
been shown to be a powerful tool for measuring the molec- concentrations of the complexes) are given in Figure 2. The
ular mass of nonvolatile, thermally unstable compounds.[13] absorption spectrum of complex 3 has been reported pre-
In the ES-MS spectra for the diruthenium() complexes, viously.[10] These results are summarized in Table 2.
intense signals for [M Ϫ 2ClO4]2ϩ, [M Ϫ 3ClO4]3ϩ and [M
As the concentration of DNA is increased, the MLCT
Ϫ 4ClO4]4ϩ were observed. The ES-MS results are given in transition bands of the complexes 1, 2 and 3 at 483, 523
the Exp. Sect. The observed molecular weights are consist- and 492 nm, respectively, exhibit hypsochromic shifts of
ent with the expected values.
about 8.7%, 19% and 33%, and a bathochromism of 5, 5
The electronic absorption spectra of the new bridging li- and 14 nm, respectively. These spectral characteristics
gands and their dimeric complexes were recorded in chloro- suggest that the complexes exhibit a high affinity for
form and acetonitrile, respectively. The absorption data are DNA.
shown in Table 1. The lowest energy absorption bands at
In order to compare quantitatively the binding strength
502, 532 and 506 nm for the dimeric complexes are assigned of the diruthenium() complexes, the intrinsic binding con-
to the metal-ligand charge transfer (MLCT) transition. The stants Kb of the complexes 1, 2 and 3 with calf thymus
high energy absorption bands are attributed to the intense DNA were determined from the decrease of the absorbance
2278
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Eur. J. Inorg. Chem. 2004, 2277Ϫ2282

Dimeric 2,2Ј-Bipyridylruthenium(II) Complexes
FULL PAPER
Figure 2. Absorption spectra of complexes 1 and 2 in Tris-HCl
buffer upon addition of calf thymus DNA; [Ru] ϭ 4 µM, [DNA] ϭ
(0Ϫ60) µM; the arrow shows the absorbance change upon increas-
ing DNA concentrations
Table 2. Electronic absorption spectral changes upon addition of
CT-DNA
Complexes λmax/nm
free bound ∆λ/ nm
Bathochromism Hypochromism Kb/Ϫ1
%
1
2
3
483 488
422 426
284 274
5
4
Ϫ10
8.7
8.2
12
7.5ϫ104
4.8ϫ105
7.6ϫ105
523 528
388 402
283 285
5
4
2
19
28.2
24
492 506
426 427
280 282
14
1
2
33
26
31
parent absorption coefficients εa, ε and εb correspond to
f
Aobsd/[Ru], the extinction coefficient for the free ruthenium
complex and the extinction coefficient for the ruthenium
complex in the fully bound form, respectively. The slope
and y intercept of the linear fit of [DNA]/(εa Ϫ εf) versus
[DNA] give 1/(εb Ϫ εf) and 1/Kb·(εb Ϫ εf), respectively. The
intrinsic binding constant Kb can be obtained from the ratio
of the slope and the y intercept. The intrinsic binding con-
stants Kb of complexes 1, 2 and 3 were calculated from the
decrease of the absorbance to be 7.5ϫ104, 4.8ϫ105 and 7.6
ϫ105 Ϫ1, respectively. The Kb’s of complexes 1, 2 and 3
are smaller than that observed for [Ru(bpy)2(dppz)]2ϩ
1
Figure 1. H-1H COSY spectra of [Ru(bpy)2(btapb)Ru(bpy)2]]4ϩ
Table 1. Electronic absorption spectroscopic data of the ligands
and complexes
Compound
λmax/nm(εmax/Ϫ1 ·cmϪ1
)
btb[a]
284.6(6540) 242(9630)
316.6(11031) 235.8(10901)
304.4(7733) 240.8(10898)
502(23847) 421(27100) 284(109494) 244(69100)
532(24553) 434(26883) 386(41176) 284(101211)
506(32406) 425(32964) 284(119788) 245(64400)
btapb[a]
bdptb[a]
(Ͼ106

Ϫ1),[15] but larger than that observed for ∆-
Ϫ1).[15] The experiments suggest
[b]
1
2
[b]
[Ru(phen)3]2ϩ (6.2ϫ103

[b]
3
that the three complexes may be bound to DNA by groove
binding and that increasing the size of the plane of the
bridging ligand increases the hydrophobicity of their com-
plexes, leading to stronger binding by the complexes to calf
thymus DNA.
[a] The solvent is chloroform for the ligands. [b] The solvent is aceto-
nitrile for the complexes.
monitored, for the complexes 1, 2 and 3, at 483, 523 and
492 nm, respectively. The intrinsic binding constant Kb of
the complex with CT-DNA was determined from the equa-
Enantioselectivity of DNA-Binding
Equilibrium dialysis experiments offer the opportunity to
tion:[14] [DNA]/(εa Ϫ εf) ϭ [DNA]/(εb Ϫ εf) ϩ 1/Kb·(εb Ϫ examine the enantioselectivities of DNA-binding by the
εf) by a plot of [DNA]/(εa Ϫ εf) versus [DNA], where complexes. Figure 3 shows the UV region of the CD spectra
[DNA] is the concentration of DNA as base pairs. The ap- for the dimeric ruthenium complexes 1, 2 and 3 after their
Eur. J. Inorg. Chem. 2004, 2277Ϫ2282
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C.-W. Jiang
FULL PAPER
racemic solutions had been dialyzed against calf thymus graphic data.[17] A classical intercalation model demands
DNA with stirring for 48 h. An interesting phenomenon that the DNA helix must lengthen as base pairs are sepa-
was observed in the equilibrium dialysis of the complexes. rated to accommodate the binding ligand, leading to an in-
After dialysis against calf thymus DNA with stirring for crease in DNA viscosity. In contrast, a partial and/or non-
48 h, the dialyzate of complex 3 shows two strong CD sig- classical intercalating ligand could bend (or kink) the DNA
nals, with a positive peak at 263 nm and a negative peak at helix, reducing its effective length and, concomitantly, its
289.5 nm, which are the CD signals of the ∆∆-enantiomer viscosity.[18] The effects of complexes 1, 2 and 3 on the vis-
of complex 3 assigned by comparison with the CD spec- cosity of rod-like DNA are shown in Figure 4 together with
trum of the chiral complex 3.[16] The presence of these sig- the corresponding data for ethidium bromide (EB) and
nals indicates enrichment of the isomer which is less likely [Ru(bpy)3]2ϩ
to bind DNA, indicating that the ΛΛ-enantiomer binds
DNA more strongly than the ∆∆-enantiomer. The other
complexes, 1 and 2, don’t show strong CD signals for their
enantiomers indicating that complexes 1 and 2 do not bind
DNA stereoselectively. The results indicate that complex 3
is an enantioselective binder of DNA while complexes 1
and 2 are not, which may be explained by the differences in
the bridging ligand of the complexes: the plane of the bridg-
ing ligand for 3 is the largest of the three complexes. To the
best of our knowledge, complex 3 is the first example of a
dinuclear ruthenium() complex binding enantioselectively
to CT-DNA measured by equilibrium dialysis. Further-
more, it is interesting to observe that the ΛΛ-bpy complex
was found to bind DNA more strongly than the ∆∆-bpy
complex, as indicated by the presence of CD signals. This
contrasts with previous reports in which the ∆∆-diru-
thenium() complexes show preferential DNA binding.[10]
.
Figure 4. Effect of increasing amounts of complexes 1, 2, 3, ethid-
ium bromide (EB) and the parent complex [Ru(bpy)3]2ϩ on the
relative viscosities of CT-DNA at 28.0 (Ϯ 0.1) °C, [DNA]ϭ 0.5 m
 and r ϭ [Ru]/[DNA]
The experiments suggest that the dimeric ruthenium()
complexes bind to the polyanionic DNA via a non-intercal-
ating mode and may be bound to DNA by groove binding.
Conclusion
Figure 3. CD spectrum of complexes 1, 2,and 3 after 48 h of dialy-
sis against calf thymus DNA with stirring of the solution
Three new asymmetric binuclear ligands 2,2Ј-bis(1,2,4-
triazin-3-yl)-4,4Ј-bipyridine (btb), 2,2Ј-bis(1,2,4-triazino-
[5,6-f]acenaphthylen-3-yl)-4,4Ј-bipyridine (btapb), 2,2Ј-
bis(5,6-diphenyl-1,2,4-triazin-3-yl)-4,4Ј-bipyridine (bdptb)
and their binuclear bpy complexes [Ru(bpy)2(btb)Ru(bpy)2]-
(ClO4)4 (1), [Ru(bpy)2(btapb)Ru(bpy)2](ClO4)4 (2), [Ru-
(bpy)2(bdptb)Ru(bpy)2](ClO4)4 (3) were synthesized and
The equilibrium dialysis results indicate that complex 3
is a good candidate as an enantioselective binder of DNA.
Viscosity Measurements
In order to further clarify the interaction of the com- characterized. Binding behavior of these dimeric complexes
plexes 1, 2 and 3 with DNA, viscosity measurements were with calf thymus DNA was investigated by electronic ab-
carried out. Optical probes provide essential, but insuf- sorption spectroscopy, viscosity measurements and equilib-
ficient, evidence to support a binding model. Hydrody- rium dialysis experiments. The results indicate that the three
namic measurements, which are sensitive to changes in mo- complexes bind to polyanionic DNA in a non-intercalating
lecular length (i.e. viscosity and sedimentation), are re- mode and may be bound to DNA by groove binding, and
garded as the least ambiguous and the most critical tests of that complex 3 is a good candidate as an enantioselective
a binding model in solution in the absence of crystallo- binder of DNA.
2280
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Dimeric 2,2Ј-Bipyridylruthenium(II) Complexes
FULL PAPER
1
(C36H18N8 requires 563). H NMR (CDCl3): 9.29 (d, J ϭ 7.5 Hz,
2 H), 9.17 (d, J ϭ 5 Hz, 2 H), 8.65 (dd, 2 H, J1 ϭ 5.5, J2 ϭ12 Hz),
8.31 (d, J ϭ 8.5 Hz, 2 H), 8.24 (d, J ϭ 8 Hz, 2 H), 8.18 (d, 2 H,
J1 ϭ 2.5, J2 ϭ 9 Hz), 8.04 (d, J ϭ 8 Hz, 2 H), 7.82 (t, J ϭ 8 Hz, 2
H), 7.70 (t, J ϭ 8 Hz, 2 H) ppm.
Experimental Section
Materials: All reagents and solvents were purchased commercially
and used without further purification unless otherwise noted. Solu-
tions of calf thymus DNA in 50 m NaCl/5 m Tris-HCl (pH 7.2)
gave a ratio of UV absorbance at 260 and 280 nm of 1.8Ϫ1.9:1,
indicating that the DNA was sufficiently free of protein.[19] The
DNA concentration per nucleotide was determined by electronic
absorption spectroscopy using the molar absorption coefficient
2,2Ј-Bis(5,6-diphenyl-1,2,4-triazin-3-yl)-4,4Ј-bipyridine (bdptb):
Α
mixture of bahmb (0.27 g, 1.0 mmol), benzil (0.4 g, 1.9 mmol), and
ethanol (40 cm3) was refluxed with stirring for 4 h. The resulting
(6600 Ϫ1·cmϪ1) at 260 nm.[20] Doubly distilled water was used to yellow precipitate was collected by filtration while hot, washed with
prepare buffers.
ethanol (3ϫ5 mL), then dried at 50 °C in vacuo. Yield: 75%.
C40H26N8 (618.7): calcd. C 77.6, H 4.2, N 18.1; found C 78.0, H
3.9, N 18.2. FAB-MS: m/z ϭ 619 (C40H26N8 requires 618). 1H
NMR (CDCl3): 9.13 (d, J ϭ 2.5 Hz, 2 H), 9.11 (d, 2 H, J ϭ 5 Hz),
7.9 (dd, 2 H, J1 ϭ 2, J2 ϭ5 Hz), 7.72 (dd, 4 H, J1 ϭ 1, J2 ϭ 8.5 Hz),
7.66 (dd, 4 H, J1 ϭ 1, J2 ϭ 8 Hz), 7.47 (t, J ϭ 8 Hz, 4 H), 7.41 (t,
J ϭ 8 Hz, 4 H), 7.39 (t, J ϭ 7 Hz, 4 H) ppm.
Physical Measurements: Microanalysis (C, H, and N) was carried
out with a PerkinϪElmer 240Q elemental analyzer. Fast atom
bombardment mass spectra were recorded on a VG ZAB-HS spec-
trometer using 3-nitrobenzyl alcohol as the matrix. Electrospray
mass spectra were recorded on an LCQ system (Finnigan MAT,
USA) using methanol as the mobile phase. The spray voltage, tube
lens offset, capillary voltage and capillary temperature were set at
4.50 kV, 30.00 V, 23.00 V and 200 °C, respectively, and the quoted
m/z values are for the major peak in the isotope distribution. 1H
NMR spectra were recorded on a Varian-500 spectrometer. All
chemical shifts are relative to tetramethylsilane (TMS). UV/Vis
spectra were recorded on a Shimadzu UV-3101PC or Agilent 8453
spectrophotometer. Emission spectra were recorded at room tem-
perature on a Shimadzu RF-5000 luminescence spectrometer.
[Ru(bpy)2(btb)Ru(bpy)2](ClO4)4
(1):
cis-[Ru(bpy)2Cl2]·2H2O
(1 mmol, 0.432 g), btb (0.5 mmol, 0.157 g) and ethylene glycol (20
cm3) were refluxed under argon for 6 h. The solution was cooled
to room temperature, and H2O (50 cm3) was added. After filtration,
a dark red precipitate was obtained by dropwise addition of
aqueous NaClO4 solution. The product was purified by column
chromatography on alumina using acetonitrile/ethanol, 2:1
(v/v) as eluent and then dried in vacuo. Yield: 66%.
C56H42N16Cl4O16Ru2·2H2O (1570.0): calcd. C 42.7, H 2.9, N
14.2%; found C 42.3, H 3.3, N 14.1%. ES-MS [CH3OH, m/z]: 670.6
Viscosity measurements were carried out using an Ubbelodhe vis-
cometer maintained at a constant temperature of 28.0 Ϯ 0.1 °C in
a thermostatted water bath. DNA samples of approximately 200
base pairs average length were prepared by sonication in order to
minimize complexities arising from DNA flexibility.[21] Flow time
was measured with a digital stopwatch. Each sample was measured
three times and an average flow time was calculated. Data are pre-
sented as (η/η°)1/3 versus binding ratio,[22] where η is the viscosity
of DNA in the presence of complex and η0 is the viscosity of
DNA alone.
1
[M Ϫ 2ClO4]2ϩ, 413.4 [M Ϫ 3ClO4]3ϩ, 285.6 [M Ϫ 4ClO4]4ϩ. H
NMR ([D6]DMSO): δ ϭ 9.33 (d, J ϭ 6 Hz, 2 H), 9.18 (s, J ϭ 6 Hz,
2 H), 9.16 (d, J ϭ 6 Hz, 2 H), 8.91 (d, J ϭ 10.5 Hz, 2 H), 8.88 (d,
J ϭ 7.5 Hz, 2 H), 8.85 (d, J ϭ 12.5 Hz, 2 H), 8.81 (d, J ϭ 8 Hz, 2
H), 8.27 (t, J ϭ 8 Hz, 2 H), 8.24Ϫ8.19 (m, 6 H), 8.17 (d, J ϭ 4 Hz,
2 H), 8.12 (d, J ϭ 8 Hz, 4 H), 7.85 (d, J ϭ 8 Hz, 4 H), 7.64 (t, J ϭ
1 Hz, 4 H), 7.35 (dd, 4 H, J1 ϭ 7.5, J2 ϭ12 Hz) ppm.
[Ru(bpy)2(btapb)Ru(bpy)2](ClO4)4 (2): This complex (dark red) was
synthesized in a similar manner to that described for complex 1,
with btapb (0.5 mmol, 0.286 g) in place of btb. Yield: 65%.
C76H50Cl4N16O16Ru2·3H2O (840.0): calcd. C 49.6, H 3.1, N 12.2;
found C 50.0, H 2.9, N 12.4. ES-MS [CH3OH, m/z]: 793.4 [M Ϫ
Equilibrium dialyses were conducted at room temperature with
5 mL of CT-DNA (1.0 m) sealed in a dialysis bag and 10 mL of
the dinuclear rac complexes (10 µM) outside the bag. The solution
containing the dialysis bag was stirred for 48 h.
1
2ClO4]2ϩ, 496.5 [M Ϫ 3ClO4]3ϩ, 347.7 [M Ϫ 4ClO4]4ϩ. H NMR
Syntheses of Complexes
([D6]DMSO): δ ϭ 9.31 (s, 2 H), 8.98 (d, J ϭ 8.5 Hz, 2 H), 8.93 (d,
J ϭ 8.5 Hz, 2 H), 8.87 (d, J ϭ 7.5 Hz, 2 H), 8.83 (d, J ϭ 8.5 Hz,
2 H), 8.75 (d, J ϭ 7 Hz, 2 H), 8.59 (d, J ϭ 8.5 Hz, 2 H), 8.52 (d,
J ϭ 8.5 Hz, 2 H), 8.33Ϫ8.27 (m, 8 H), 8.19 (dd, 6 H, J1 ϭ 7.5,
J2 ϭ 19.5 Hz), 8.14 (t, J ϭ 8 Hz, 2 H), 8.00 (dd, 4 H, J1 ϭ 6.5,
J2 ϭ14 Hz), 7.94 (t, J ϭ 5 Hz, 4 H), 7.82 (d, J ϭ 5 Hz, 2 H), 7.70
(t, J ϭ 7 Hz, 2 H), 7.64 (t, J ϭ 7 Hz, 2 H), 7.56 (dd, 2 H, J ϭ
7 Hz), 7.46 (dd, 2 H, J1 ϭ 6, J2 ϭ 11.5 Hz) ppm.
2,2Ј-Bis[amino(hydrazono)methyl]-4,4Ј-bipyridine (bahmb),[16] cis-
Ru(bpy)2Cl2 were prepared as described previously.
[23]
2,2Ј-Bis(1,2,4-triazin-3-yl)-4,4Ј-bipyridine (btb):
Α mixture of
bahmb (0.27 g, 1 mmol), 30% aqueous glyoxal (5 mL), and ethanol
(20 mL) was refluxed with stirring for 2 h. After cooling to room
temperature, the yellow precipitate was collected by filtration,
washed with ethanol (3ϫ5 cm3), then dried at 50 °C in vacuo.
Yield: 78%. C16H10N8 (314.3): calcd. C 61.1, H 3.2, N 35.7; found
C 59.8, H 2.9, N 36.2. FAB-MS: m/z ϭ 315 (C16H10N8 requires
314). 1H NMR ([D6]DMSO): 9.55 (d, J ϭ 2.5 Hz, 2 H), 9.08 (d,
J ϭ 2.5 Hz, 2 H), 9.03 (dd, 2 H, J ϭ 2.5, J1 ϭ 1, J2 ϭ 5.5 Hz),
8.90 (dd, J1 ϭ 0.5, J2 ϭ 1.5 Hz, 2 H), 8.19 (s, 2 H) ppm.
[Ru(bpy)2(bdptb)Ru(bpy)2](ClO4)4 (3): This complex (dark red) was
synthesized in a similar manner to that described for complex 1,
with bdptb (0.5 mmol, 0.307 g) in place of btb. Yield: 68%.
C80H58Cl4N16O16Ru2·H2O (1856.1): calcd. C 51.6, H 3.3, N 12.0%;
found C 51.8, H 3.6, N 12.3%. ES-MS [CH3OH, m/z]: 821.6 [M Ϫ
2,2Ј-Bis(1,2,4-triazino[5,6-f]acenaphthylen-3-yl)-4,4Ј-bipyridine 2ClO4]2ϩ, 516 [M Ϫ 3ClO4]3ϩ, 361.7 [M Ϫ 4ClO4]4ϩ
.
1H NMR
(btapb): Α mixture of bahmb (0.27 g, 1 mmol), acenaphthenequi- ([D6]DMSO): δ ϭ 9.17 (s, J ϭ 2 Hz, 2 H), 8.93 (d, J ϭ 8 Hz, 2 H),
none (0.346 g, 1.9 mmol) and ethanol (40 mL) was refluxed with
stirring for 4 h. The resulting yellow precipitate was collected by
filtration while hot, washed with ethanol (3ϫ5 mL), then dried at
50 °C in vacuo. Yield: 72%. C36H18N8 (562.6): calcd. C 76.9, H
8.88 (d, J ϭ 8 Hz, 2 H), 8.78 (t, J ϭ 8 Hz, 4 H), 8.29 (dd, 6 H,
J1 ϭ 7.5, J2 ϭ 9 Hz), 8.14 (dd, 2 H, J1 ϭ 1, J2 ϭ 5.5 Hz), 7.94 (t,
J ϭ 9 Hz, 2 H), 7.88 (d, J ϭ 5.5 Hz, 2 H), 7.75 (t, J ϭ 5.5 Hz, 6
H), 7.67 (t, J ϭ 5.5 Hz, 2 H), 7.60Ϫ7.52 (m, 8 H), 7.48Ϫ7.40 (m,
3.2, N 19.9; found C 77.3, H 3.6, N 20.2. FAB-MS: m/z ϭ 564 6 H), 7.11 (d, J ϭ 7.5 Hz, 4 H) ppm.
Eur. J. Inorg. Chem. 2004, 2277Ϫ2282
www.eurjic.org
 2004 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
2281

C.-W. Jiang
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2282
 2004 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjic.org
Eur. J. Inorg. Chem. 2004, 2277Ϫ2282