Oligoaniline-Functionalized terpyridine ligands and their ruthenium(II) complexes: Synthesis, spectroscopic property and redox behavior

Article abstract of DOI:10.1039/b820392j

A series of oligoaniline-functionalized mono- and bis-topic terpyridine ligands, i.e. C₆H₅[N(R)C₆H₄] _nTPY (R = H, butyl, tert-butyloxycarbonyl; n = 1-4; TPY = 2,2′:6′,2″-terpyridyl) and TPYC₆H ₄[N(R)C₆H₄]_mTPY (R = H, tert-butyloxycarbonyl; m = 2, 4), and the corresponding mono- and bis-nuclear ruthenium(II) complexes have been synthesized and verified. The spectroscopic results indicate that two kinds of π-π* transitions from TPY and oligoaniline fragments of ligands strongly shift to lower energy, and the metal-to-ligand charge-transfer transition (¹MLCT) bands of all obtained complexes are considerably red-shifted (Δλ_max = 22-64 nm) and their intensities become much more intense (approximately 4-6 times), compared with those of the reported complex [Ru(TPY)₂] ²⁺. Moreover, the spectroscopic properties of the ligands and complexes with longer oligoaniline units (n = 3, 4) are markedly influenced by the external stimulus, such as the oxidation and proton acid doping. The characteristic absorption bands in the visual and near infrared (NIR) scales demonstrate the presence of various oxidized and doped states of the oligoaniline unit. All complexes show multiplicate redox processes based on metal center, oligoaniline and terpyridine units. The potential shifts suggest the donor and acceptor (D-A) interaction between the oligoaniline unit and the bis(terpyridine)-Ru²⁺ center.

Full text of DOI:10.1039/b820392j

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www.rsc.org/dalton | Dalton Transactions
Oligoaniline-Functionalized terpyridine ligands and their ruthenium(II)
complexes: synthesis, spectroscopic property and redox behavior†
Dongfang Qiu,a,b Yanxiang Cheng*a and Lixiang Wang*a
Received 14th November 2008, Accepted 18th February 2009
First published as an Advance Article on the web 13th March 2009
DOI: 10.1039/b820392j
A series of oligoaniline-functionalized mono- and bis-topic terpyridine ligands, i.e.
C6H5[N(R)C6H4]nTPY (R = H, butyl, tert-butyloxycarbonyl; n = 1–4; TPY = 2,2¢:6¢,2¢¢-terpyridyl) and
TPYC6H4[N(R)C6H4]mTPY (R = H, tert-butyloxycarbonyl; m = 2, 4), and the corresponding mono-
and bis-nuclear ruthenium(II) complexes have been synthesized and verified. The spectroscopic results
indicate that two kinds of p–p* transitions from TPY and oligoaniline fragments of ligands strongly
shift to lower energy, and the metal-to-ligand charge-transfer transition (1MLCT) bands of all obtained
complexes are considerably red-shifted (Dlmax = 22–64 nm) and their intensities become much more
intense (approximately 4–6 times), compared with those of the reported complex [Ru(TPY)2]2+.
Moreover, the spectroscopic properties of the ligands and complexes with longer oligoaniline units
(n = 3, 4) are markedly influenced by the external stimulus, such as the oxidation and proton acid
doping. The characteristic absorption bands in the visual and near infrared (NIR) scales demonstrate
the presence of various oxidized and doped states of the oligoaniline unit. All complexes show
multiplicate redox processes based on metal center, oligoaniline and terpyridine units. The potential
shifts suggest the donor and acceptor (D–A) interaction between the oligoaniline unit and the
bis(terpyridine)–Ru2+ center.
for a remarkable attenuation of the intercenter interaction, while
the unsaturated and conjugated spacers appear to have good
Introduction
2,2¢:6¢,2¢¢-Terpyridine (TPY) transition metal complexes have
attracted much attention because of their wide applications in
modern coordination chemistry, biology and material science.1,2
Motivated by the fact that the photophysical and redox properties
of TPY–metal complexes depend on the substituent in the ligand,
a great advance has been made in the design of terpyridine
derivatives.3 Introducing the functional groups at the 4¢-position of
terpyridine is the main pathway, due to the synthetic convenience
and the geometrical advantage. In recent years, a novel class of bis-
topic terpyridine ligands (T-S-T), where two terpyridine units (T)
are linked in the back-to-back configuration (via their 4¢ positions)
by a rigid spacer (S), shows a huge potential in the supermolecular
chemistry.4 Various saturated5 or conjugated components, such
as azobenzene,6 diarylethenes,7 polyacetylenes,8 poly(phenylene-
ethynylenes),9 thiophenes,10 oligo(diethylnyl-thiophenes),11 and
oligoferrocenes,12 have been utilized as spacers to incorporate
into d6 transition metal [Ru(II), Os(II), Rh(III) and Ir(III)] ter-
pyridyl complexes. The rod-like homonuclear and heteronuclear
complexes are suitable to simply mimic the photoinduced electron
and energy transfer process in the natural system.13 Concerning
the electronic characteristics, the saturated spacers are responsible
conducting properties. The spectroscopic and electrochemical
properties of the homonuclear complexes are obviously improved
due to the interaction between the spacer and metal–TPY unit.
The vectorial electron- or energy-transfer rate between the donor
and acceptor in the heteronuclear complex can be modulated by
tuning the length and the nature of the spacer.
Oligoaniline is usually used as a modular system to understand
clearly the electrical and optical properties of polyaniline because
of its monodisperse composition and well-defined structure. Like
polyaniline,14 oligoaniline also has various forms, such as the
leucoemeraldine base (LEB), emeraldine base (EB), emeraldine
salt (ES) and pernigraniline base (PNB), which can be easily
controlled by simple redox and acid–base reactions,15 as shown
in Fig. 1. The difference of electronic and/or chemical structures
among the various forms gives rise to remarkable changes in
electrical and optical properties, which suggests that oligoaniline
is a promising class as a photo- and electro-active unit for the
functionalization of the terpyridine systems. In this paper, we
synthesized a novel series of mono- and bis-topic terpyridine
ligands with oligoanilines as functional group and spacer, respec-
tively, and the corresponding mono- and bis-nuclear ruthenium(II)
complexes. The basic studies on their spectroscopic and electro-
chemical behaviors are: (i) to investigate the donor–acceptor
(D–A) interaction between the oligoanline and TPY or metal–
TPY moieties by changing the chain length (n) and the substituted
group in the oligoaniline unit, (ii) to learn about the influence of the
changed electronic and chemical structure in the oligoaniline unit,
resulting from various external stimuli. The information obtained
about the relationship between the chemical/electronic structrures
of oligoanilines and photo/electro-properties of complexes should
aState Key Laboratory of Polymer Physics and Chemistry, Changchun
Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun,
130022, P. R. China. E-mail: yanxiang@ciac.jl.cn, lixiang@ciac.jl.cn;
Fax: +86–431-85684937; Tel: +86–431-85262106
bGraduate University of the Chinese Academy of Sciences, Chinese Academy
of Sciences, Beijing, 100039, P. R. China
† Electronic supplementary information (ESI) available: Experimental
details. CCDC reference number 691744. For ESI and crystallographic
data in CIF or other electronic format see DOI: 10.1039/b820392j
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Among them, the Pd(OAc)2/DPEphos (DPEphos = bis[(2-
diphenylphosphino)phenyl]ether) system has some advantages
over other catalyst/ligand systems, such as the catalyst and ligand
are stable in air and not very expensive. Therefore, we adopted
the Pd(OAc)2/DPEphos system to synthesize the oligoanilines
and oligoaniline-functionalized terpyridines. Compounds 1, 2, 3,
6, 819 (Scheme 1) and 1217c (Scheme 3) were prepared according
to literature methods with improved experimental conditions.
Compounds 4, 7, 9 and 13 were recovered by palladium-catalyzed
hydrogenation from the precursors 3, 6, 8 and 12 in excellent yield
(>90%), respectively.
The syntheses of the ligands explored in this work are shown
in Schemes 2 and 3. Aniline or 1,4-phenylenediamine directly
coupled with 1 or 2 eq. of compound 10,20 followed by protection
with BOC groups, affording L7 in 84% yield or L11 in 62% yield.
Compounds 4, 7, 9 and 13 were coupled with compound 10 via
the same way to afford the BOC-substituted ligands L8, L9,
L10 and L12 in good yields (69~88%). These results suggest that
the catalyst system Pd(OAc)2/DPEphos is also highly efficient
for the synthesis of oligoaniline-functionalized terpyridines. The
reduced state ligands L1– 6, in which the oligoaniline units are
in the LEB form, were generally prepared by thermolysis of the
BOC-substituted ligands under an inert atmosphere at 185 ◦C for
12 h21 or by treatment of the precursors with TMSI22 at room
temperature in DCM solution. L1 and L2 reacted with excess
1-bromobutane to afford the Bu-substituted ligands L13 and L14 in
very good yields (>90%), respectively.
Fig. 1 Principal oxidation states of polyaniline and oligoaniline.
provide a solid basis for further research into the heteronuclear
system.
Results and discussion
Ligand synthesis
In order to facilitate the condensation with the 4¢-(4-bromo-
phenyl)-2,2¢: 6¢,2¢¢-terpyridine, the synthesis of aniline oligomers
with an –NH2 functional end group is a key factor. Compared
with other methods,16 the palladium-catalyzed amination,17 which
was reported as an efficient pathway to synthesize the aniline
oligomers with different functional end groups, can meet the
need. Several catalyst systems have been used in this method.17,18
Complex synthesis
Fig. 2 shows the general structure of the modular systems. The
BOC- and Bu-substituted mononuclear Ru(II) complexes were
prepared by the direct reaction of metal chloride with 2 eq.
Scheme 1
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Scheme 2
Scheme 3
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Fig. 2 Molecular structures of the mono- and dinuclear Ru(II) complexes.
mono-topic ligands L7 –10, L13 and L14, respectively, in EtOH
solutions containing a small amount of N-ethylmorpholine as
a reducing agent, followed by precipitation of the hexafluo-
rophosphate salts and chromatographic purification. Treatment
of bis-topic ligands L11 and L12 with two times the amount
of [Ru(PTPY)Cl3] (PTPY = 4¢-phenyl-2,2¢:6¢,2¢¢-terpyridyl) via
the same way resulted in the formation of the symmetric din-
ligands is 88.8◦ and the angle formed by the Ru atom and the
nitrogen atoms of the central pyridyl groups (N2–Ru–N5) is
176.8(4)◦. The torsional angles between the central pyridyl ring
of the terpyridyl and the linked phenyl ring are 18.1 (C9–C8–
C16–C21) and 27.5◦ (C40–C39–C47–C48), respectively. The sp3
hybridized nitrogen atom and directly bonded three carbon atoms
from the two phenyl and butyl groups nearly form a plane with the
torsional angles 177.7 (C19–C22–C28–N7) and 168.6◦ (C50–C53–
C59–N8). All C–N and C–C distances of the [Ru(TPY)2] moiety
are in the normal range. The Ru–N distances are similar to those
reported in the literature,2 and the bonds to the central pyridyl
1
uclear complexes. All of the complexes exhibit well-resolved H
NMR spectra, in which a number of characteristic peaks are
present and agree with those of other reported Ru(II) com-
plexes with 4¢-substituted terpyridyl ligands.23 In the heterolep-
tic dinuclear complexes {[(PTPY)Ru(L5)Ru(PTPY)](PF6)4 and
[(PTPY)Ru(L6)Ru(PTPY)](PF6)4}, split dd peaks are observed for
both terpyridyl domains (see Fig. S1 and S2 in the ESI†).
˚
rings [1.982(7), 1.986(7) A] are evidently shorter than those to the
˚
terminal pyridyl rings [2.049(6)–2.069(8) A]. The cations line two
different columns which partly overlap each other and there are
two forms of p–p stacking interactions between adjacent cations
in the crystal packing (Fig. 3). The face-to-face contacts
The reduced state mono- or dinuclear Ru(II) complexes, in
which the oligoaniline units are in the LEB form, were obtained
by thermolysis of the BOC-substituted complexes under an inert
˚
(C4–C13¢, 3.32; C3–C14¢, 3.51 A) between the two terminal pyridyl
◦
atmosphere at 185 C for 12 h or by treatment of the precursors
rings of neighbouring terpyridyl groups are present in an identical
with TMSI at room temperature in MeCN solution except for
[(PTPY)Ru(L6)Ru(PTPY)](PF6)4, which was decomposed during
the deprotection process. The yields are quantitative and the
structures of these complexes were easily confirmed by the proton
signals at 7–9 ppm from NH groups (see Fig. S3 in the ESI†).
column, while the edge-to-face contacts (C13–C52¢¢, 3.58;
Table 1 Selected bond distances (A) and bond angles (◦) for
˚
[Ru(L13)2](PF6)2
Ru–N1
Ru–N2
Ru–N3
Ru–N4
Ru–N5
Ru–N6
N7–C19
N7–C22
N7–C28
N8–C50
N8–C53
N8–C59
N1–Ru–N2
N1–Ru–N3
N1–Ru–N4
N1–Ru–N5
N1–Ru–N6
2.057(7)
1.982(7)
2.062(6)
2.049(6)
1.986(7)
2.069(8)
1.438(10)
1.413(10)
1.461(10)
1.390(10)
1.406(10)
1.455(11)
78.9(3)
N2–Ru–N3
N2–Ru–N4
N2–Ru–N5
N2–Ru–N6
N3–Ru–N4
N3–Ru–N5
N3–Ru–N6
N4–Ru–N5
N4–Ru–N6
N5–Ru–N6
C19–N7–C22
C19–N7–C28
C22–N7–C28
C50–N8–C53
C50–N8–C59
C53–N8–C59
78.8(3)
102.2(3)
176.8(4)
99.9(3)
87.9(2)
104.5(3)
98.4(3)
78.5(3)
157.8(2)
79.3(3)
120.0(7)
122.2(7)
117.8(6)
120.8(7)
120.4(7)
117.8(6)
Crystal structure of [Ru(L13)2](PF6)2
By using the slow evaporation method, red crystals of
[Ru(L13)2](PF6)2 were deposited from its concentrated solution
in the acetone–methanol system. The molecular structure of the
cation and numbering scheme adopted are depicted in Fig. 3.
Selected bond length and angle data are presented in Table 1.
The ruthenium(II) ion displays the expected distorted-
octahedral geometry with intraligand bite angles (N–Ru–N) in
the range 78.5(3)–79.3(3)◦. The two terpyridyl units are approxi-
mately planar with 0.1–5.6◦ torsional angles (N–C–C–N) between
terminal and central pyridyl rings. The angle between the least-
square planes of central pyridyl rings from the two terpyridyl
157.4(2)
93.4(2)
97.9(3)
88.9(3)
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Fig. 3 ORTEP representation (top) and crystal packing (bottom) of the [Ru(L13)2](PF6)2 complex (30% thermal ellipsoids); hydrogen atoms and PF6
-
anion have been omitted for clarity.
Table 2 TGA Data of the BOC-substituted Ru(II) complexes (PF6- anion
have been omitted for clarity)
˚
C14–C51¢¢, 3.64 A) exist between another terminal pyridyl ring
and the 4-position phenyl ring from the third cation of a different
column. The above facts suggest that strong conjugation exists
in the oligoaniline-functionalized Ru(II) complexes in the solid
state.
Loss [%]
(therotical)
Complex
T1 [◦C]a
T2 [◦C]b
[Ru(L7)2]2+
199
197
184
205
174
175
12.6(14.4)
21.5(22.6)
28.6(27.8)
32.0(31.5)
8.8(8.6)
414
427
413
414
423
393
[Ru(L8)2]2+
[Ru(L9)2]2+
Thermal gravimetric analysis (TGA)
[Ru(L10)2]2+
[(PTPY)Ru(L11)Ru(PTPY)]4+
[(PTPY)Ru(L12)Ru(PTPY)]4+
The reduced state mono- or dinuclear complexes were obtained
by thermolysis of the BOC-substituted precursors under an inert
atmosphere at 185 ◦C for 12 h. In order to prove the cleavage
of the BOC substituents, we conducted TGA measurements. The
TGA data of the BOC-substituted mono- or dinuclear complexes
are listed in Table 2. The BOC-substituted complexes start to lose
weight at 174–205 ◦C, according to the deprotection of the BOC
substituents. For each complex, the total weight loss in the first step
is basically consistent with the theoretical loss. It suggests that the
removal of the BOC groups is essentially quantitative, affording
oligoaniline units in the LEB form. The TGA data also indicate
that the resulting complexes are stable up to around 400 ◦C.
15.2(14.8)
a T1: the start temperature for lossing the BOC protected group; b T2: the
decomposition temperature of the resulting complex.
The shorter-wavelength peak (279–332 nm, log e = 4.41–4.75)
is ascribed to the p–p* transition in the polypyridine ring. In the
arrays of L1–L4 [Fig. 4 (top)] and L13–L14, the longer-wavelength
peak (357–385 nm, log e = 4.41–4.64) gradually red-shifts with
increasing oligoaniline length, suggesting substitution with the
oligoaniline donor group results in a strong shift of the p–
p* transitions to lower energy.24 Compared to the mono-topic
ligands, the bis-topic ligands L5 and L6 [Fig. 4 (top)] show an
opposite trend, which is probably determined by the total effect
of the molecular conjugation and the molecular configuration
in solution. With strong electron-withdrawing groups, the BOC-
substituted ligands display only one distinct absorption band
(279–288 nm, log e = 4.41–4.92) due to the blue-shifted
Electronic absorption spectroscopy
General remarks. The absorption maxima and molar extinc-
tion coefficients of the absorption bands of ligands L1–14 in DMF
solutions are listed in Table 3. All ligands display two intense
UV absorption bands except for the BOC-protected ligands.
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-
Table 3 UV data of the ligands and complexes (PF6 anions have been
omitted for clarity)
lmax [nm] (e ¥ 10-4[M-1 cm-1])b,c
Compound
1MLCT Ligand-based
L1
357(2.8), 295(2.9)
373(2.9), 294(4.3)
371(2.6), 303(4.4)
L2
L3
L4
385(sh, 2.9), 332(5.3), 294(5.6)
L5
386(3.1), 289(3.4)
375(3.5), 291(4.8)
288(2.6)
285(3.5)
279(4.7)
279(5.9)
287(5.3)
283(8.4)
357(4.4), 291(4.5)
363(3.1), 294(4.0)
L6
L7
L8
L9
L10
L11
L12
L13
L14
[Ru(TPY)2]2+a
[Ru(L1)2]2+
474(1.0)
516(5.4) 394(3.2), 344(sh, 4.0),
314(9.4), 278(6.0)
528(5.3) 348(sh, 5.7), 313(9.4), 280(6.4)
531(5.9) 348(sh, 7.7), 313(13.3),
279(8.2)
531(5.4) 350(sh, 8.4), 314(13.3),
279(9.1)
[Ru(L2)2]2+
[Ru(L3)2]2+
[Ru(L4)2]2+
[(PTPY)Ru(L5)Ru(PTPY)]4+ 511(7.7) 348(sh, 5.6), 314(15.5),
286(14.4)
[Ru(L7)2]2+
[Ru(L8)2]2+
[Ru(L9)2]2+
[Ru(L10)2]2+
500(4.0) 330(sh, 7.0), 315(8.4), 289(4.9)
498(3.9) 332(sh, 6.7), 315(8.1), 288(6.1)
498(3.8) 333(sh, 6.5), 315(8.0), 278(7.3)
498(4.3) 333(sh, 7.3), 315(8.9),
278(10.0)
[(PTPY)Ru(L11)Ru(PTPY)]4+ 496(6.6) 330(sh, 11.0), 315(14.4),
288(14.9)
[(PTPY)Ru(L12)Ru(PTPY)]4+ 496(7.0) 334(sh, 10.8), 315(15.7),
288(15.5)
Fig. 4 UV-vis spectra of the ligands (top) and complexes (bottom) in the
LEB form in DMF solutions.
[Ru(L13)2]2+
[Ru(L14)2]2+
529(5.6) 417(2.0), 342(sh, 4.0),
311(9.7), 276(5.3)
538(5.3) 344(sh, 4.2), 311(10.1),
276(5.2)
wavelength regions on passing from the mononuclear complexes
to the dinuclear ones. This indicates that the 1MLCT energy level
of the dinuclear complex is higher than that of the mononuclear
complex. Another most striking feature of the MLCT transitions
in [Ru(Lx)2]2+ (x = 1–4 and 13, 14) complexes is the significant
increase in intensity (around 4–6 times compared to [Ru(TPY)2]2+).
The modification with oligoanilines in these complexes gives an
unexpected e > 50,000 cm3 mol-1 cm-1, the largest value observed,
to our knowledge, for this type of transition in pseudo-octahedral
Ru(II) complexes. The origin of this effect is associated with
a Ref. [25]; b solvent: DMF; c concentration: 10-5 M.
longer-wavelength absorption overlapping with the shorter-
wavelength band (see Fig. S4 in the ESI†).
The maxima and molar extinction coefficients of the absorption
bands for all complexes in DMF solutions are also listed in Table 3.
Each of the complexes displays intense UV absorption bands (276–
417 nm, log e = 4.30–5.20), which are ascribed to ligand-centred
(1LC) transitions from coordinated TPY units, and a less intense
band in the visible region (496–538 nm, log e = 4.58–4.89), which
is attributed to the spin-allowed dp(M) → p*(L), metal-to-ligand
charge-transfer transition (1MLCT).
The MLCT absorption bands of all complexes in this work
are considerably red-shifted (Dlmax = 22–64 nm) compared with
those of [Ru(TPY)2]2+.25 The phenomenon suggests oligoanilines
act as good donors in these complexes.23a In the array of the
mononuclear ruthenium complexes, the MLCT maximum is con-
vergent to 531 nm with the increasing chain length in oligoaniline
[Fig. 4 (bottom)]. Owing to the electron-withdrawing effect, the
bathochromic effect of the BOC-substituted complexes is smaller
than that of the reduced state and Bu-substituted complexes (see
Fig. S4 in the ESI†). From the absorption data in Table 3, we
also find that the MLCT bands are displaced towards the shorter
1
a mix of MLCT with the pp* excited state.24 As expected,
the molar absorption coefficient of the MLCT transition in the
dinuclear complexes approximately doubles, compared to that in
the mononuclear complexes.
Effect of oxidant and dopant. Oxidation of the pale yellow
solution of L3 [Fig. 5 (a)] by silver(I) oxide results in a blue–purple
solution with hypsochromic shifts of the two waves in the UV
region and the growth of a broad absorption band at 562 nm, which
is attributed to the characteristic electronic transition related
to quinoid and benzenoid units (the EB state), i.e. the pb–pq
transition.26,27 The addition of a drop of hydrochloric acid (a
large excess) to the above solution produces a greenish yellow
color. Protonation causes the shorter-wavelength absorption band
to split. The longer-wavelength absorption band at 562 nm is
broadened and its maximum is red-shifted to 797 nm. And two
new bands at 424 and 1047 nm, respectively, are observed which
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Fig. 5 Influence of oxidant and dopant on the UV-vis-NIR spectra of the ligands and complexes in DMF solutions. (a) L3; (b) [Ru(L3)2](PF6)2; (c) L4;
(d) [Ru(L4)2](PF6)2: the LEB state (1); the EB state (2); the doped state (3); the PNB state (4).
Table 4 Oxidation potentials (Ep in V vs Fc+/Fc) of the ligands in CV
are attributed to the polaron absorption in aniline oligomers or
polymers.17,28
spectra
During oxidation of ligand L4 [Fig. 5 (c)], initial formation of
c
c
Ligand
Ep,ox
Ligand
Ep,ox
the pb–pq transition band at 569 nm is observed. With further
oxidation, the solution color turns to pink. The absorption peak
at 569 nm considerably blue-shifts to 500 nm (Dlmax = 69 nm).
The strongly hypsochromic effect reflects the decreased charge-
transfer absorption in the PNB state.15 Protonation of the EB
form of L4 causes similar changes to those of L3, besides the
absorbance in the near-IR region becomes much more intense
with a definite maximum at 1039 nm. The intensity of this band is
usually regarded to be directly proportional to the conductivity of
polyaniline,27,28 suggesting the doped state of L4 is more conductive
than that of L3.
L1
L2
L3
L4
L5
L6
L7
+0.48a
L8
+1.02b
+0.08a
L9
+1.07b
-0.08, +0.41a
-0.17(sh), -0.08, +0.12a
+0.08a
L10
L11
L12
L13
L14
+1.06b
+1.01b
+1.03b
-0.08, +0.24a
+1.21b
+0.64b
+0.02, +0.55b
a DMF solvent; b DCM solvent; c concentration: 10-3 M; supporting
electrolyte: 0.1 M nBu4NClO4.
electrochemical window of the used solvents, just the oligoaniline-
based oxidation waves were observed. From the data in Table 4,
ligand L1 shows a single oxidation peak at +0.48 V (vs Fc+/Fc), in
accordance with forming a radical cation species.30 Similar to the
voltammetric behavior of the tri-aniline analogue,31 two oxidation
waves with basically equal amplitude are observed at -0.08 V
and +0.41 V (vs Fc+/Fc) for L3 in this study, attributed to the
formation of the benzoquinoid dication. For L2, L4, L5 or L6,
including even-numbered oligoaniline units, the electron transfer
prefers to occur in pairs. Like the oxidation behavior of N,N¢-
diphenyl-p-phenylenediamine in an aqueous electrolyte (pH 2.5),32
a combined two-electron transfer process is observed for L2 and
L5, respectively, in accordance with the formation of the quinoid
structure. The phenyl-capped aniline tetramer33 and polyaniline34
usually show two two-electron transfer processes, in which the
first wave is assigned to a two-electron transfer process to form
the di(cation radical) tetraamine (the EB state) and the second is
attributed to another two-electron transfer process followed by a
four-proton loss to form the PNB structure. Ligand L6 exhibits
the above similar behavior with two oxidation waves at -0.08 and
The changes in the UV-vis-NIR spectra of complexes
[Ru(L3)2](PF6)2 [Fig. 5 (b)] and [Ru(L4)2](PF6)2 [Fig. 5 (d)], arising
from oxidation and the doping effect, are essentially identical to
those of the free ligands L3 and L4 respectively. Owing to overlap
with the MLCT band, the characteristic wave of the EB or PNB
state is just shown as a shoulder peak for each of them. Protonation
leads the MLCT band to blue-shift and decrease in intensity,
suggesting the higher p*(L) energy in the doped state decreases
1
the blending degree of the MLCT and pp* excited states. The
effects of oxidant and dopant on other ligands and complexes are
shown in Fig. S5 in the ESI.†
Electrochemistry
Cyclic voltammetry (CV) has been widely used to characterize
the electrochemical properties of poly- or oligoanilines, affording
valuable insights into the electronic structures of the oxidized
states.29 Electrochemical data of the ligands are listed in Table 4.
Because the redox potentials of the TPY moiety are beyond the
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Table 5 Electrochemical data (Ep in V vs Fc+/Fc) of the Ru(II) complexes. (All complexes were used as hexafluorophosphate salts and PF6- anions have
been omitted for clarity)
CV
Ep,ox
Ep,red
Complex
Metal-based
Oligoaniline-based
Ligand-based
a
[Ru(TPY)2]2+
+0.92d
+0.95
+0.84
+0.91
+0.84
+0.83
+0.84d
+0.85d
+0.83d
-1.67d
b
[Ru(L1)2]2+
+0.59
+0.09
-0.04, +0.50
-0.17, +0.01, +0.24
+0.16
+0.64
+1.06, +1.30
+1.18
+1.13
+1.09
-1.73, -1.96, -2.47
-1.76, -1.97, -2.45, -2.80f
-1.70, -1.92, -2.39, -2.80f
-1.70, -1.90, -2.47
-1.71, -1.96, -2.42, -2.74
-1.63d, -1.93
b
[Ru(L2)2]2+
b
[Ru(L3)2]2+
b
[Ru(L4)2]2+
[(PTPY)Ru(L5)Ru(PTPY)]4+
b
c
[Ru(L7)2]2+
c
[Ru(L8)2]2+
-1.61d, -1.89
c
[Ru(L9)2]2+
-1.62d, -1.90
[Ru(L10)2]2+
–
-1.62d, -1.91
c
e
[(PTPY)Ru(L11)Ru(PTPY)]4+
[(PTPY)Ru(L12)Ru(PTPY)]4+
+0.84d
+0.85d
+0.89d
+0.90d
-1.63d, -1.89
c
c
+1.12
+0.58
+0.09, +0.51
-1.63d, -1.90
c
[Ru(L13)2]2+
-1.69d, -1.96
c
[Ru(L14)2]2+
-1.69d, -1.92
a Ref. [25]; b DMF solvent; c CH3CN solvent; d reversible, values calculated as averages of the cathodic and anodic peaks; e overlapped; f shoulder peak.
+0.24 V (vs Fc+/Fc), while three oxidation waves at -0.17 (sh),
-0.08 and +0.12 V (vs Fc+/Fc) are observed for L4, arising from
the distinct splitting of the first two-electron transfer processes.
The difference should be attributed to the unsymmetric structure
formed by the TPY moiety on one end in L4. The second oxidative
wave in L6 is apparently higher than that in L4, suggesting the
oxidation of the EB state to the PNB state in L6 is more difficult.
Compared with those of ligands L1– 6, the oligoaniline-based
oxidation waves of ligands L7–12 are markedly shifted to positive
potentials due to the strong electron-withdrawing ability of the
BOC substituents. L13 shows a single oxidation peak at +0.64 V
(vs Fc+/Fc), in accordance with forming a radical cation species,
while L14 displays two oxidation peaks at +0.02 and +0.55 V (vs
Fc+/Fc), relative to the formation of di(cation radical) species.35
Besides the oligoaniline-based oxidation waves as mentioned
above, each complex shows the voltammetric responses ex-
pected for the [Ru(TPY)2]2+ core, typically Ru3+/2+ couple, and
two terpyridyl-centred reduction processes {the [Ru(TPY)2]2+/
[Ru(TPY)(TPY-)]+ and [Ru(TPY)(TPY-)]+/[Ru(TPY-)2]◦ couples
at approximately -1.7 and -1.9 V respectively}. The voltammetric
responses for the [Ru(TPY)2]2+ core are relatively well known23
and, rather than give a detailed description, assignments are sum-
marized in Table 5. However, introduction of the oligoaniline unit
in each of [Ru(L1 –4)2]2+ and [(PTPY)Ru(L5)Ru(PTPY)]4+ lowers
the reversibility of the redox waves for the [Ru(TPY)2]2+ core, and
extra reduction processes at more negative potentials are present.
Similar phenomena are observed in the analogue of monomeric36
or dimeric37 Ru(II) complexes with an amine donor group.
Fig. 6. The metal-centred oxidation potentials slightly shift to the
negative direction, while the terpyridyl-centred reduction waves
show the reverse tendency in the BOC-substituted complexes.
Fig. 6 Substituent effect (R) on the oxidation behavior of aniline dimer
in ligands and complexes. (a) R = -H (L2 (left) and [Ru(L2)2](PF6)2 (right));
(b) R = -Bu (L14 (left) and [Ru(L14)2](PF6)2 (right)); (c) R = -BOC (L8 (left)
and [Ru(L8)2](PF6)2 (right)).
Compared with those in free ligands, the oligoaniline-based
oxidation waves in most of the complexes shift to more positive
potentials. For example, the third oxidative wave in L4 is present
at +0.12 V (vs Fc+/Fc), while the counterpart in [Ru(L4)2](PF6)2
is observed at +0.24 V (vs Fc+/Fc). The significant shift (DEp =
0.12 V) reflects the phenyl-capped aniline tetramer in the latter is
more difficult to be fully oxidized to the PNB form, arising from
the interaction between the oligoaniline unit and the [Ru(TPY)2]2+
core. The substituent effect on the oligoaniline-based oxidation
in complexes is similar to that in ligands, typically shown in
Like other reported binuclear Ru2+ complexes linearly arranged
with p-conjugated organic oligomers as spacers,18b,38 each
of the obtained binuclear complexes, such as [(PTPY)Ru-
(L5)Ru(PTPY)](PF6)2, [(PTPY)Ru(L11)Ru(PTPY)](PF6)2 and
[(PTPY)Ru(L12)Ru(PTPY)](PF6)2, shows a single-wave for the
3254 | Dalton Trans., 2009, 3247–3261
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Table 6 Energy levels and Eg of the Ru(II) complexes. (All complexes
were used as hexafluorophosphate salts and PF6- anions have been omitted
for clarity)
Complex
HOMOa (eV) LUMOa (eV) Eg (eV)
b
b
b
b
[Ru(L1)2]2+
[Ru(L2)2]2+
[Ru(L3)2]2+
[Ru(L4)2]2+
,
,
,
,
5.22
4.77
4.61
4.51
4.84
5.31
5.56
5.57
5.58
5.56
5.57
5.29
4.78
3.17
3.15
3.22
3.15
3.20
3.23
3.25
3.24
3.25
3.24
3.23
3.19
3.18
2.05
1.62
1.39
1.36
1.64
2.08
2.31
2.33
2.33
2.32
2.34
2.10
1.60
[(PTPY)Ru(L5)Ru(PTPY)]4+
,
b
c
[Ru(L7)2]2+
[Ru(L8)2]2+
[Ru(L9)2]2+
,
,
,
c
c
c
[Ru(L10)2]2+
,
[(PTPY)Ru(L11)Ru(PTPY)]4+
,
,
c
[(PTPY)Ru(L12)Ru(PTPY)]4+
c
c
[Ru(L13)2]2+
[Ru(L14)2]2+
,
,
c
a HOMO = {4.8 + [Eox,onset-E1/2(Fc+/Fc)]}(eV); LUMO = {4.8 + [Ered,onset
-
E
1/2(Fc+/Fc)]}(eV), where E1/2(Fc+/Fc) = (Ep,a+Ep,c)/2, Eox,onset and
Ered,onset were calculated from the onset value of the first oxidation wave
in the anodic segment and the first reduction wave in the cathodic segment
of the CV spectrum respectively; b DMF solvent; c CH3CN solvent.
Fig. 7 Oxidative electropolymerization of [Ru(L13)2](PF6)2. (a) Top:
Repetitive cyclic voltammograms on a Pt electrode; (b) Bottom: SEM
images of poly-[Ru(L13)2]2+-coated ITO after 20 segments (left) and 100
segments (right).
Ru3+/Ru2+ couple, which might indicate that the electronic
coupling between the two Ru2+ centers is comparatively weak.
The HOMO-LUMO gaps (Eg) of Ru(II) complexes, calculated
from the electrochemical measurements,39 are listed in Table 6.
For unsubstituted and Bu-substistuted oligoaniline functionalized
Ru(II) complexes, the Eg values gradually decrease with increasing
chain length of oligoaniline unit, arising from the decrease of the
HOMO level but with no change in the LUMO level. With the
introduction of a strong electron-withdrawing substituent (BOC),
the Eg value considerably increases. But in the BOC-substituted
series it is essentially unchanged. The dinuclear Ru(II) complexes
possess slightly larger gaps than the corresponding mononuclear
ones. These results are well in line with those of the spectroscopic
studies.
Experimental
General
Melting points were recorded on a hot stage apparatus and
are uncorrected. 1H and 13C NMR spectra were recorded on
Bruker AV 300 spectrometers and referenced with respect to TMS
internal standard. Elemental analyses were carried out using a
Bio-Rad Co’s elemental analytical instrument. UV-Vis spectra
were obtained using a Perkin-Elmer UV-35 spectrophotometer. PL
spectra were performed on a Perkin-Elmer LS50B spectrometer.
CV measurements were conducted on a EG & 283 electrochemical
workstation with a three-electrode electrochemical cell using SCE
or AgCl/Ag and Pt wire as the reference and counter electrode,
respectively. nBu4NClO4 (0.1 mol cm-3) was used as the supporting
electrolyte. The scan rate was 100 mV s-1. Thermal analyses
were carried out in a nitrogen atmosphere with a heating rate
Oxidative electropolymerization
◦
With incorporation of the diphenylamine unit in the ter-
pyridine ligand, complexes [Ru(L1)2](PF6)2, [Ru(L7)2](PF6)2 and
[Ru(L13)2](PF6)2 display interesting electro-polymerization be-
haviours. Continuous cycling of the working Pt or ITO electrode
potential from 0 to 1.8 V in a CH3CN solution containing
0.5 mmol cm-3 [Ru(L13)2](PF6)2 resulted in the formation of a
red adherent film on the electrode surface. A wave at +1.02 V
(vs SCE) is observed in the first oxidation segment [Fig. 7 (a)]. As
the cyclic scan proceeds, it gradually shifts to positive potentials
with increasing intensities and finally combines with the metal-
based oxidation wave. The SEM images [Fig. 7 (b)] indicate the
formation of the polymer film. Similar phenomena were also
present in [Ru(L1)2](PF6)2 and [Ru(L7)2](PF6)2. It is believed that
the waves at +1.17 V (vs SCE) for [Ru(L13)2](PF6)2, +1.02 V (vs
SCE) for [Ru(L13)2](PF6)2 and +1.08 V (vs SCE) for [Ru(L7)2](PF6)2
are attributed to the formation of a radical cation species, which
trigger the polymerization process, and the [Ru(TPY)]2+ cores in
these complexes play a key role in the stabilization of the radical
cation species.40
of 10 C min-1 on a thermal gravimetric analysis (TGA) Perkin-
Elmer 7 series instrument.
Reactions under an argon atmosphere were carried out in oven-
dried glassware using standard Schlenk techniques. Tetrahydrofu-
ran (THF) was distilled under argon from sodium benzophenone
ketyl. Toluene was distilled under argon from molten sodium.
N,N-Dimethylformamide (DMF) was treated with 5 A molecular
sieves and distilled under reduced pressure. All other solvents were
analytical reagent grades and used as supplied.
All the reagents were analytical grades. 1,4-Phenylenediamine
was sublimed while aniline was distilled before use. p-Amino-
diphenylamine, benzophenone, palladium acetate (Pd(OAc)2),
sodium tert-butoxide (NaOBut) (Acros), bis[(2- diphenylphos-
phino)phenyl]ether (DPEphos) (Acros), di-tert-butyl bicarbon-
ate ((BOC)2O) (Acros), 4-(dimethylamino)pyridine (4-DMAP)
(Acros), palladium on carbon (Pd/C, 10%), ammonium formate,
2-acetylpyridine, 4-bromo-phenylaldehyde, NaH (>52%, in min-
eral oil), n-bromobutylane were all used as received without
further purification.
˚
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4¢-(4-Bromophenyl)-2,2¢:6¢,2¢¢-terpyridine (10), 4¢-phenyl-
2,2¢:6¢,2¢¢-terpyridine (PTPY),22 N-diphenylmethylene-4-bromo-
aniline (5),15 N-(diphenylmethylene-N¢-(tert-butoxycarbonyl)-N¢-
(4-bromophenyl)-p-phenylenediamine (2), N-(diphenylmethylene-
N¢-(tert-butoxycarbonyl)-N¢-(phenyl)-p-phenylenediamine (3),
N-(diphenylmethylene-N¢-(tert-butoxycarbonyl)-N¢-[4-(N-tert-
butoxycarbonylanilino)]phenyl-p-phenylenediamine (6) and
compound 819 were synthesized according to literature methods.
(50 cm3), and (BOC)2O (1M in THF) (16 cm3, 16.0 mmol) and
4-DMAP (0.18 g, 1.5 mmol) were added. The reaction mixture
was refluxed for 24 h. The solvent was removed, and L8 was
separated by column chromatography [Al2O3, PE/DCM = 5:1
(V/V) containing 5% (V) triethylamine] as white powder. (6.1 g,
88%); mp 190 ◦C; Found: C, 74.94; H, 6.00; N, 9.78. Calc. for
1
C43H41N5O4: C, 74.65; H, 5.97; N, 10.12%; H NMR (300 MHz,
DMSO-d6): d 8.76 (d, J = 4.0 Hz, 2 H; H6, 6¢¢, terpy), 8.70 (s, 2 H;
H
3¢, 5¢, terpy), 8.67 (d, J = 7.9 Hz, 2 H; H3, 3¢¢, terpy), 8.04 (t, J =
7.7 Hz, 2 H; H4, 4¢¢, terpy), 7.93 (d, J = 8.6 Hz, 2 H), 7.53 (t, J =
7.0 Hz, 2 H; H5, 5¢¢, terpy), 7.42 – 7.34 (m, 4 H), 7.24 – 7.20 (m, 7 H;
Ar), 1.42 (s, 9 H, -OC(CH3)3), 1.38 (s, 9 H, -OC(CH3)3); 13C NMR
(75 MHz, CDCl3): d 156.6, 156.4, 154.1 (-C=O), 154.0 (-C=O),
149.5, 144.1, 143.2, 141.0, 140.5, 137.3, 136.1, 129.2, 128.1, 127.5,
126.2, 124.2, 121.8, 119.1, 82.0 (-OC(CH3)3), 81.7 (-OC(CH3)3),
28.6 (-CH3).
Preparations
The ligand L7. 4¢-(4-Bromophenyl)-2,2:6¢,2¢¢-terpyridine (10)
(3.88 g, 10 mmol), Pd(OAc)2 (15.0 mg, 0.067 mmol) and DPEphos
(49.0 mg, 0.091 mmol) were charged into a flask and purged with
argon. Aniline (1.2 cm3, 13 mmol) was added via syringe, followed
by toluene (30 cm3). NaOBut (1.63 g, 17 mmol) was added in
one portion. The reaction mixture was heated to 80 ◦C with
stirring for 3–4 h (as monitored by thin layer chromatography).
The solvent was removed by rotary evaporation. The residue was
dissolved in dichloromethane, washed with distilled water, dried
over anhydrous sodium sulfate and concentrated.
The residue was dissolved in THF (80 cm3), and (BOC)2O (1M
in THF) (15 cm3, 15.0 mmol) and 4-DMAP (0.15 g, 1.2 mmol)
were added. The reaction mixture was refluxed for 24 h and
cooled to room temperature and concentrated. The residue was
separated by column chromatography [Al2O3, PE/DCM = 5:1
(V/V) containing 5% (V) triethylamine]. Product L7 was obtained
as a white powder. (4.2 g, 84%); mp 166 ◦C; Found: C, 76.87; H,
5.50; N, 10.85. Calc. for C32H28N4O2: C, 76.78; H, 5.64; N, 11.19%;
L9 and L10 were prepared by the same procedures besides using
compound 6 and 8 as starting materials and using THF instead of
toluene as solvent.
L9. obtained as white solid in 76% yield. mp 195 ◦C; Found:
C, 73.47; H, 6.18; N, 9.13. Calc. for C54H54N6O6: C, 73.45; H, 6.16;
N, 9.52%; 1H NMR (300 MHz, DMSO-d6): d 8.76 (d, J = 4.2 Hz,
2 H; H6, 6¢¢, terpy), 8.70 (s, 2 H; H3¢, 5¢, terpy), 8.67 (d, J = 8.0 Hz,
2 H; H3, 3¢¢, terpy), 8.04 (t, J = 7.7 Hz, 2 H; H4, 4¢¢, terpy), 7.91 (d, J =
8.6 Hz, 2 H), 7.53 (t, J = 4.9 Hz, 2 H; H5, 5¢¢, terpy), 7.41 – 7.32
(m, 4 H), 7.23 – 7.19 (m, 11 H; Ar), 1.47 (s, 9 H, -OC(CH3)3),
1.42 (s, 9 H, -OC(CH3)3), 1.37(s, 9 H, -OC(CH3)3); 13C NMR
(75 MHz, CDCl3): d 156.6, 156.4, 154.2 (-C=O), 154.1 (-C=O),
154.0 (-C=O), 150.0, 149.5, 144.1, 143.2, 140.9, 140.8, 140.6,
140.5, 137.3, 136.1, 129.1, 128.1, 127.6, 127.4, 126.2, 124.2, 121.8,
119.1, 82.0 (-OC(CH3)3), 81.8 (-OC(CH3)3), 81.6 (-OC(CH3)3),
28.6 (-CH3).
1H NMR (300 MHz, DMSO-d6): d 8.75 (d, J = 4.5 Hz, 2 H; H6, 6¢¢
,
,
terpy), 8.68 (s, 2 H; H3¢, 5¢, terpy), 8.65 (d, J = 7.8 Hz, 2 H; H3, 3¢¢
terpy), 8.02 (t, J = 7.7 Hz, 2 H; H4, 4¢¢, terpy), 7.89 (d, J = 8.4 Hz,
2 H), 7.51 (t, J = 6.9 Hz, 2 H; H5, 5¢¢, terpy), 7.43 – 7.37 (m, 4 H),
7.28 – 7.21 (m, 3 H; Ar), 1.47(s, 9 H, -OC(CH3)3); 13C
NMR(75 MHz, CDCl3): d 156.6, 156.4, 154.0 (-C=O), 150.0,
149.5, 144.4, 143.2, 137.2, 135.9, 129.3, 128.0, 127.5, 127.4, 126.3,
124.2, 121.8, 119.1, 81.9 (-OC(CH3)3), 28.7 (-CH3).
L10. obtained as white solid in 69% yield. mp 196 ◦C; Found:
C, 72.88; H, 6.20; N, 8.94. Calc. for C65H67N7O8: C, 72.67; H,
1
6.29; N, 9.13%; H NMR (300 MHz, DMSO-d6): d 8.76 (d, J =
4.0 Hz, 2 H; H6, 6¢¢, terpy), 8.70 (s, 2 H; H3¢, 5¢, terpy), 8.67 (d, J =
8.0 Hz, 2 H; H3, 3¢¢, terpy), 8.04 (t, J = 7.6 Hz, 2 H; H4, 4¢¢, terpy),
L8. Compoud 3 (12.0 g, 26.8 mmol), ammonium formate
(25.0 g, 396.5 mmol), and palladium on carbon (10%) (2.3 g,
1.1 mmol) were charged into a round-bottomed flask and purged
with argon. THF (50 cm3) and methanol (125 cm3) were added,
and the reaction mixture was refluxed until conversion to amine
4 was complete (as monitored by thin layer chromatography).
The reaction mixture was cooled to room temperature and
concentrated. The residue was dissolved in dichloromethane,
filtered through Celite, and then concentrated. The solid was
washed with hexanes and filtered. The white powder was dried
in vacuum at 50 ◦C for 24 h. Yield of product 4 was 7.5 g (98%).
7.92 (d, J = 8.5 Hz, 2 H), 7.53 (t, J = 5.8 Hz, 2 H; H5, 5¢¢
,
terpy), 7.40 (d, J = 8.5 Hz, 4 H), 7.32 – 7.16 (m, 17 H; Ar),
1.41 (s, 9 H, -OC(CH3)3), 1.38 (s, 9 H, -OC(CH3)3), 1.36 (s,
9 H, -OC(CH3)3), 1.36 (s, 9 H, -OC(CH3)3); 13C NMR (75 MHz,
CDCl3): d 156.2, 156.0, 153.8 (-C=O), 153.7 (-C=O), 153.6
(-C=O), 149.6, 149.1, 143.7, 142.9, 140.5, 140.4, 140.3, 140.1,
136.9, 135.7, 128.7, 128.2, 127.7, 127.2, 127.0, 125.8, 123.8, 121.4,
118.8, 81.6 (-OC(CH3)3), 81.4 (-OC(CH3)3), 81.3 (-OC(CH3)3),
81.2 (-OC(CH3)3), 28.2 (-CH3), 27.9 (-CH3).
Compound
4
(3.41 g, 12 mmol), Pd(OAc)2 (16.2 mg,
L11. 1,4-Phenylenediamine (0.52 g, 4.8 mmol), 4¢-(4-
bromophenyl)-2,2:6¢,2¢¢- terpyridine (10) (3.88 g, 10 mmol),
Pd(OAc)2 (15.0 mg, 0.067 mmol) and DPEphos (49.0 mg,
0.091 mmol) were charged into a flask and purged with argon.
THF (40 cm3◦) was added via syringe, and the suspension was
warmed to 50 C to aid the dissolution. NaOBut (1.63 g, 17 mmol)
was added in one portion. The reaction mixture was refluxed with
stirring for 3–4 h (as monitored by thin layer chromatography).
The solvent was removed by rotary evaporation. The residue was
dissolved in dichloromethane, washed with distilled water, dried
over anhydrous sodium sulfate and concentrated. The obtained
0.072 mmol) and DPEphos (62.9 mg, 0.117 mmol) were charged
into a flask and purged with argon. Compound 10 (3.88 g,
10 mmol) was added, ◦followed by toluene (40 cm3). The solution
was warmed to 50 C to aid dissolution. NaOBut (1.73 g,
18 mmol) was added in one portion. The reaction mixture was
heated to 80 ◦C with stirring for about 5 h (as monitored
by thin layer chromatography). The solvent was removed by
rotary evaporation. The residue was dissolved in dichloromethane,
washed with distilled water, dried over anhydrous sodium sulfate
and concentrated. The obtained solid was dissolved in THF
3256 | Dalton Trans., 2009, 3247–3261
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solid was dissolved in THF (80 cm3), and (BOC)2O (1M in THF)
(15 cm3, 15.0 mmol) and 4-DMAP (0.15 g, 1.2 mmol) were added.
The reaction mixture was refluxed for 24 h. Product L11 was
separated by column chromatography [Al2O3, PE/DCM = 5:1
(V/V) containi◦ng 5% (V) triethylamine] as white powder. (2.7 g,
62%). mp 221 C; Found: C, 75.25; H, 5.56; N, 11.98. Calc. for
(300 MHz, DMSO-d6): d 8.76 (d, J = 4.1 Hz, 4 H; H6, 6¢¢, terpy),
8.74 (s, 4 H; H3¢, 5¢, terpy), 8.69 (d, J = 8.0 Hz, 4 H; H3, 3¢¢, terpy),
7.94 – 7.87 (m, 8 H), 7.41 – 7.36 (m, 8 H), 7.22 – 7.20 (m, 12 H;
Ar), 1.50 (s, 18 H, -OC(CH3)3), 1.48 (s, 18 H, –OC(CH3)3); 13C
NMR(75 MHz, CDCl3): d 156.2, 155.9, 153.7 (–C=O), 153.6
(–C=O), 149.6, 149.1, 143.7, 140.4, 140.2, 136.9, 135.6, 127.7,
127.2, 127.1, 123.8, 121.4, 118.8, 81.6 (–OC(CH3)3), 81.4
(–OC(CH3)3), 28.3 (–CH3).
1
C58H50N8O4: C, 75.47; H, 5.46; N, 12.14%; H NMR (300 MHz,
DMSO-d6): d 8.76 (d, J = 4.2 Hz, 4 H; H6, 6¢¢, terpy), 8.71 (s, 4 H;
H
3¢, 5¢, terpy), 8.67 (d, J = 8.0 Hz, 4 H; H3, 3¢¢, terpy), 8.03 (t, J =
L13. The BOC-protected ligand L7 (2.16 g, 4.3 mmol) was
4.7 Hz, 4 H; H4, 4¢¢, terpy), 7.94 (d, J = 8.6 Hz, 4 H), 7.53 (t, J =
6.0 Hz, 4 H; H5, 5¢¢, terpy), 7.43 (d, J = 8.5 Hz, 4 H), 7.30 (s, 4 H;
Ar), 1.44 (s, 18 H, -OC(CH3)3); 13C NMR (75 MHz, DMSO-d6):
d 156.6, 155.8, 153.9 (–C=O), 150.2, 149.5, 144.8, 141.5, 138.3,
135.7, 129.2, 128.6, 128.2, 125.4, 121.8, 118.6, 81.6 (–OC(CH3)3),
28.7 (–CH3).
◦
placed in a flask under argon. The system was heated to 185 C
for 12 h. After cooling to room temperature, THF (20 cm3) was
added to dissolve the solid. NaH (0.41 g, >52% in mineral oil) was
added and purged with argon. The reaction mixture was stirred
for 1 h at room temperature, and then 1-bromobutylane (10 cm3,
8 mmol) was added dropwise via syringe. The solution was refluxed
until the conversion was complete (as monitored by thin layer
chromatography). The solution was cooled to room temperature
and poured onto ice-water mixture, extracted with DCM until
the water phase was colorless. The combined organic solutions
were washed with distilled water, dried over anhydrous sodium
sulfate and concentrated. The residue was separated by column
chromatography [silica gel, PE/DCM = 8:1 (V/V) containing
5% (V) triethylamine]. Product L13 was obtained as white powder
(1.8 g, 93%). mp 126 ◦C; Found: C, 81.79; H, 6.20; N, 11.98. Calc.
for C31H28N4: C, 81.55; H, 6.18; N, 12.27%; 1H NMR (300 MHz,
DMSO-d6): d 8.76 (d, J = 4.7 Hz, 2 H; H6, 6¢¢, terpy), 8.68 – 8.65
(m, 4 H; H3¢, 5¢, 3, 3¢¢, terpy), 8.03 (t, J = 8.6 Hz, 2 H; H4, 4¢¢, terpy),
7.79 (d, J = 8.8 Hz, 2 H), 7.52 (t, J = 6.6 Hz, 2 H; H5, 5¢¢, terpy),
7.41 (t, J = 7.8 Hz, 2 H), 7.22 (d, J = 7.6 Hz, 2 H), 7.15 (t, J =
7.3 Hz, 1 H), 6.99 (d, J = 8.8 Hz, 2 H; Ar), 3.77 (t, J = 7.5 Hz,
2 H, a (–CH2)), 1.61 (m, 2 H, b (–CH2)), 1.36 (m, 2 H, g (–CH2)),
0.90 (t, J = 7.3 Hz, 3 H, –CH3); 13C NMR(75 MHz, CDCl3): d
156.5, 155.8, 149.9, 149.2, 149.1, 147.4, 136.8, 129.5, 128.8, 128.1,
124.0, 123.6, 123.3, 121.3, 117.9, 52.2 (a(-CH2)), 29.7 (b(-CH2)),
20.3 (g(-CH2)), 13.9 (–CH3).
L12.
A solution of 1,4-phenylenediamine (11) (1.62 g,
15.0 mmol), bromide 5 (10.83 g, 32.2 mmol), Pd(OAc)2 (116.4 mg,
0.52 mmol), DPEphos (514.6 mg, 0.96 mmol) and NaOBut
(5.0 g, 52 mmol) in THF (40 cm3) was refluxed for 5 h under
argon. The solution was concentrated, and the residue was
dissolved in dichloromethane, washed with distilled water, dried
over anhydrous sodium sulfate and concentrated. The residue was
dissolved in THF (200 cm3), and (BOC)2O (1M in THF) (50 cm3,
50.0 mmol) and 4-DMAP (0.60 g, 4.9 mmol) were added. The
reaction mixture was refluxed for 24 h. The solvent was removed,
and the residue was separated by column chromatography [silica
gel, PE/DCM = 1:8 (V/V)]. Product 12 was obtained as yellow
powder: 10.7 g (87%).
Compound 12 (3.27 g, 4.0 mmol), ammonium formate (7.0 g,
111.0 mmol), and palladium on carbon (10%) (0.85 g, 0.8 mmol)
were charged into a round-bottomed flask and purged with argon.
THF (100 cm3) and methanol (100 cm3) were added. The reaction
mixture was refluxed until conversion to diamine 13 completely
(as monitored by thin layer chromatography). The solvent was
removed by rotary evaporation. The residue was dissolved in a
hot mixture of isopropanol (500 cm3), CHCl3 (100 cm3) and water
(50 cm3), then allowed to stand at room temperature for 12 h. The
precipitate which formed was collected by filtration, and washed
with distilled water followed by isopropanol. The solid was dried
under vacuum to afford the compound 13 as a white powder (1.9 g,
94%).
Ligand L14 was obtained by the same procedures except using
compound L8 as the starting material.
L14. obtained as yellow solid in 92% yield. mp 143 ◦C; Found:
C, 81.72; H, 6.54; N, 11.73. Calc. for C41H41N5: C, 81.56; H, 6.84;
N, 11.60%; 1H NMR (300 MHz, DMSO-d6): d 8.72 (d, J = 3.9 Hz,
2 H; H6, 6¢¢, terpy), 8.63 – 8.61 (m, 4 H; H3¢, 5¢, 3, 3 ”, terpy), 7.99 (t, J =
8.6 Hz, 2 H; H4, 4¢¢, terpy), 7.74 (d, J = 8.7 Hz, 2 H), 7.48 (t, J =
6.1 Hz, 2 H; H5, 5¢¢, terpy), 7.26 (t, J = 7.9 Hz, 2 H), 7.10 (d, J =
8.8 Hz, 2 H), 7.00 – 6.86 (m, 7 H; Ar), 3.65 (m, 4 H, a (-CH2)), 1.54
(m, 4 H, b (–CH2)), 1.34 (m, 4 H, g (–CH2)), 0.89 (m, 6 H, –CH3);
13C NMR(75 MHz, CDCl3): d 156.6, 155.7, 149.9, 149.6, 149.1,
148.2, 144.7, 140.7, 136.8, 129.3, 128.0, 127.3, 126.6, 123.6, 122.4,
121.3, 120.8, 120.4, 117.7, 115.9, 52.25 (a(-CH2)), 29.7 (b(-CH2)),
20.3 (g(-CH2)), 14.0 (–CH3).
A solution of diamine 13 (1.53 g, 3.12 mmol), compound 10
(2.54 g, 6.54 mmol), Pd(OAc)2 (44.0 mg, 0.20 mmol), DPEphos
(158 mg, 0.29 mmol) and NaOBut (1.57 g, 16.35 mmol) in THF
(40 cm3) and triethylamine (10 cm3) was refluxed for 48 h under
argon. After this period, the heat was temporarily removed, and
4-DMAP (0.12 g, 0.98 mmol), THF (40 cm3), and a 1.0 M solution
of (BOC)2O (20.0 mmol) in THF (20 cm3) were added. The
reaction mixture was refluxed for 24 h. The solvent was removed by
rotary evaporation. The residue was dissolved in dichloromethane,
washed with distilled water, dried over anhydrous sodium sulfate
and concentrated. The solid was re-dissolved in the boiling THF
(50 cm3) and was poured into hot MeOH (200 cm3) and allowed
to stand for 12 h at room temperature. The precipitate formed was
collected by filtration and the procedure was operated for one more
time. The solid was dried under vacuum to afford a white powder
(L12) (3.1 g, 76%). mp 214 ◦C; Found: C, 73.29; H, 5.83; N, 10.50.
General method for mononuclear complexes [Ru(L)2](PF6)2
(L = L7, L8, L9, L10, L13 and L14)
The appropriate metal chloride (RuCl3·3H2O) and ligand L
(2.1 eq.) were heated at reflux in EtOH (150 cm3) containing
several drops of N-ethylmorpholine for 12 h. After cooling to room
temperature, aqueous NH4PF6 was added and the precipitate
was purified by column chromatography (silica gel, CH3CN/sat.
1
Calc. for C80H76N10O8: C, 73.60; H, 5.87; N, 10.73%; H NMR
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Dalton Trans., 2009, 3247–3261 | 3257
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aqueous KNO3/H2O). The major red fraction was collected and
reduced to half its volume in vacuo and treated with aqueous
NH4PF6. The precipitate was collected by filtration. The solid was
redissolvedinCH3CN, to which water was addeduntilaprecipitate
was obtained. The precipitate was dried under vacuum to give a
red solid.
(t, J = 7.4 Hz, 4 H, a(-CH2)), 1.58 (m, 4 H, b(-CH2)), 1.32 (m, 4 H,
g(-CH2)), 0.85 (t, J = 7.3 Hz, 6 H, –CH3); 13C NMR (75 MHz,
DMSO-d6): d 159.1, 155.7, 152.9, 150.5, 147.8, 147.2, 138.7, 130.7,
129.6, 128.5, 126.0, 125.4, 120.6, 117.1, 52.2 (a(–CH2)), 30.1
(b(-CH2)), 20.5 (g(-CH2)), 14.7 (–CH3).
[Ru(L14)2](PF6)2. obtained as deep red solid in 74% yield;
[Ru(L7)2](PF6)2. obtained as red solid in 67% yield; Found: C,
54.95; H, 3.87; N, 8.20. Calc. for C64H56F12N8O4P2Ru: C, 55.21;
H, 4.05; N, 8.05%; 1H NMR (300 MHz, DMSO-d6): d 9.46 (s, 4 H;
Found: C, 61.72; H, 5.36; N, 8.51. Calc. for C82H82F12N10P2Ru:
1
C, 61.61; H, 5.17; N, 8.76%; H NMR (300 MHz, DMSO-d6): d
9.34 (s, 4 H; H3¢, 5¢, terpy), 9.04 (d, J = 8.1 Hz, 4 H; H3, 3¢¢, terpy),
8.27 (d, J = 8.5 Hz, 4 H), 8.05 (t, J = 7.7 Hz, 4 H; H4, 4¢¢, terpy), 7.51
(d, J = 5.3 Hz, 4 H), 7.35 – 7.20 (m, 12 H), 7.08 – 6.99 (m, 14 H; Ar),
3.83 – 3.72 (m, 8 H, a (-CH2)), 1.69 – 1.60 (m, 8 H, b(-CH2)),
1.45 – 1.37 (m, 8 H, g(-CH2)), 0.99 – 0.90 (m, 12 H, –CH3); 13C
NMR (75 MHz, DMSO-d6): d 158.3, 154.8, 152.1, 150.2, 147.5,
147.0, 145.0, 139.0, 137.8, 129.4, 128.7, 127.6, 127.3, 124.5, 124.1,
121.5, 121.2, 120.8, 119.4, 114.7, 67.0, 51.3 (a(-CH2)), 29.2
(b(-CH2)), 19.6 (g(-CH2)), 13.9 (–CH3).
H
3¢, 5¢, terpy), 9.09 (d, J = 8.2 Hz, 4 H; H3, 3¢¢, terpy), 8.39 (d, J =
8.6 Hz, 4 H), 8.07 (t, J = 7.9 Hz, 4 H; H4, 4¢¢, terpy), 7.60 – 7.45 (m,
10 H), 7.37 – 7.04 (m, 12 H; Ar), 1.48 (s, 18 H, –OC(CH3)3); 13
C
NMR (75 MHz, DMSO-d6): d 158.9, 155.9, 153.7 (–C=O), 153.1,
147.2, 145.6, 143.4, 138.9, 134.0, 130.0, 129.1, 128.6, 128.1, 127.2,
125.7, 122.0, 81.8 (–OC(CH3)3), 28.7 (CH3).
[Ru(L8)2](PF6)2. obtained as red solid in 60% yield; Found: C,
57.97; H, 4.56; N, 7.83. Calc. for C86H82F12N10O8P2Ru: C, 58.20;
1
H, 4.66; N, 7.89%; H NMR (300 MHz, DMSO-d6): d 9.46 (s,
General method for homo-dinuclear complexes
4 H; H3¢, 5¢, terpy), 9.08 (d, J = 8.2 Hz, 4 H; H3, 3¢¢, terpy), 8.39
(d, J = 8.6 Hz, 4 H), 8.07 (t, J = 7.5 Hz, 4 H; H4, 4¢¢, terpy),
7.60 – 7.53 (m, 8 H), 7.43–7.38 (m, 4 H), 7.34–7.24 (m, 18 H;
Ar), 1.48 (s, 18 H, –OC(CH3)3), 1.41 (s, 18 H, –OC(CH3)3);
13C NMR (75 MHz, DMSO-d6): d 158.9, 155.9, 153.8 (-C=O),
153.6 (-C=O), 153.0, 147.2, 145.4, 143.5, 141.6, 140.8, 138.9,
134.1, 129.8, 129.2, 128.5, 128.3, 128.0, 126.9, 125.7, 122.0, 82.0
(-OC(CH3)3), 81.4 (-OC(CH3)3), 28.7 (CH3).
[(PTPY)Ru(L)Ru(PTPY)](PF6)4 (L = L11 and L12)
A suspension of ligand L11 or L12 and 2 eq. [(PTPY)RuCl3] was
heated at reflux in EtOH (200 cm3) containing several drops of
N-ethylmorpholine for 12 h. The reaction mixture was poured
into aqueous NH4PF6, and the precipitated solid was purified
by column chromatography (silica gel, CH3CN/sat. aqueous
KNO3/H2O). The major fraction was concentrated and ion-
exchanged with aqueous NH4PF6 to precipitate the product as
a red solid.
[Ru(L9)2](PF6)2. obtained as deep red solid in 63% yield;
Found: C, 59.74; H, 4.99; N, 7.74. Calc. for C108H108F12N12O12P2Ru:
[(PTPY)Ru(L11)Ru(PTPY)](PF6)4. obtained as deep red solid
in 58% yield; Found: C, 51.37; H, 3.49; N, 8.21. Calc. for
C100H80F24N14O4P4Ru2: C, 51.69; H, 3.47; N, 8.44%; 1H NMR
(300 MHz, DMSO-d6): d 9.51 (s, 4 H; H3¢, 5¢, terpy), 9.49 (s, 4 H;
1
C, 60.13; H, 5.05; N, 7.79%; H NMR (300 MHz, DMSO-d6):
d 9.46 (s, 4 H; H3¢, 5¢, terpy), 9.08 (d, J = 8.1 Hz, 4 H; H3, 3¢¢
,
terpy), 8.39 (d, J = 8.2 Hz, 4 H), 8.08 (t, J = 7.73 Hz, 4 H;
H
4, 4¢¢, terpy), 7.60 – 7.53 (m, 8 H), 7.40 – 7.23 (m, 30 H; Ar), 1.47
H
3¢, 5¢, terpy), 9.12 (dd, J = 8.52 Hz, 8 H; H3, 3¢¢, terpy), 8.45 (d, J =
(s, 18 H, –OC(CH3)3), 1.41 (s, 18 H, –OC(CH3)3), 1.39 (s, 18 H,
–OC(CH3)3); 13C NMR (75 MHz, DMSO-d6): d 158.9, 155.9, 153.8
(–C=O), 153.6 (–C=O), 153.0, 147.2, 145.4, 143.5, 141.3, 140.9,
138.9, 134.1, 129.8, 129.2, 128.6, 128.4, 128.1, 128.0, 126.9, 125.6,
122.0, 82.0 (–OC(CH3)3), 81.6 (–OC(CH3)3), 81.4 (–OC(CH3)3),
28.6 (CH3).
7.59 Hz, 8 H), 8.09 (t, J = 7.55 Hz, 8 H; H4, 4¢¢, terpy), 7.78 (d, J =
7.11 Hz, 4 H), 7.67 (m, 6 H), 7.57 (s, 8 H), 7.32 (s, 4 H), 7.30
(t, J = 6.08 Hz, 8 H; Ar), 1.51 (s, 18 H, –OC(CH3)3); 13C NMR
(75 MHz, DMSO-d6): d 158.9, 156.0, 153.7 (-C=O), 153.1, 148.0,
147.2, 145.4, 141.3, 138.9, 137.1, 134.3, 131.2, 130.3, 129.2, 128.6,
128.2, 125.7, 122.1, 82.0 (–OC(CH3)3), 28.8 (–CH3).
[Ru(L10)2](PF6)2. obtained as deep red solid in 57% yield;
[(PTPY)Ru(L12)Ru(PTPY)](PF6)4. obtained as deep red solid
Found: C, 61.19; H, 5.41; N, 7.51. Calc. for C130H134F12N14O16P2Ru:
1
in 83% yield; Found: C, 53.87; H, 3.86; N, 8.59. Calc. for
C, 61.48; H, 5.32; N, 7.72%; H NMR (300 MHz, DMSO-d6): d
1
9.46 (s, 4 H; H3¢, 5¢, terpy), 9.08 (d, J = 8.3 Hz, 4 H; H3, 3¢¢, terpy), 8.38
(d, J = 8.6 Hz, 4 H), 8.06 (t, J = 7.5 Hz, 4 H; H4, 4¢¢, terpy), 7.59 – 7.53
(m, 8 H), 7.33 – 7.19 (m, 38 H; Ar), 1.46 (s, 18 H, –OC(CH3)3), 1.40
(s, 18 H, –OC(CH3)3), 1.37 (s, 18 H, –OC(CH3)3), 1.35 (s, 18 H,
–OC(CH3)3); 13C NMR (75 MHz, DMSO-d6): d 158.9, 155.9, 153.8
(–C=O), 153.6 (–C=O), 153.1, 147.2, 145.4, 143.5, 141.3, 141.2,
141.1, 140.8, 138.9, 134.1, 129.7, 129.2, 128.5, 128.4, 128.1, 127.9,
126.8, 125.7, 122.0, 81.9 (–OC(CH3)3), 81.6 (–OC(CH3)3), 81.5
(–OC(CH3)3), 81.3 (–OC(CH3)3), 28.7, 28.6 (CH3).
C122H106F24N16O8P4Ru2: C, 54.15; H, 3.95; N, 8.28%; H NMR
(300 MHz, DMSO-d6): d 9.50 (s, 4 H; H3¢, 5¢, terpy), 9.46 (s, 4 H;
H
3¢, 5¢, terpy), 9.11 (dd, J = 8.2 Hz, 8 H; H3, 3¢¢, terpy), 8.43 (dd, J =
7.6 Hz, 8 H), 8.07 (t, J = 7.4 Hz, 8 H; H4, 4¢¢, terpy), 7.79 (t, J =
7.1 Hz, 4 H), 7.68 (t, J = 8.1 Hz, 2 H), 7.57 (m, 12 H), 7.31 (m, 20 H;
Ar), 1.46 (s, 18 H, –OC(CH3)3), 1.41 (s, 18 H, -OC(CH3)3); 13C
NMR (75 MHz, DMSO-d6): d 158.9, 156.0, 153.8 (–C=O), 153.6
(–C=O), 153.1, 147.9, 147.2, 145.4, 141.3, 141.1, 140.9, 138.9,
137.0, 134.1, 131.2, 130.3, 129.2, 128.6, 128.2, 128.0, 125.7, 122.1,
82.0 (–OC(CH3)3), 81.6 (–OC(CH3)3), 28.7 (–CH3).
[Ru(L13)2](PF6)2. obtained as red solid in 74% yield; Found: C,
56.97; H, 4.52; N, 8.36. Calc. for C62H56F12N8P2Ru: C, 57.10; H,
General procedure for deprotection of ligands or complexes by
thermolysis or by treatment with TMSI
1
4.33; N, 8.59%; H NMR (300 MHz, DMSO-d6): d 9.25 (s, 4 H;
H
3¢, 5¢, terpy), 8.95 (d, J = 8.1 Hz, 4 H; H3, 3¢¢, terpy), 8.17 (d, J =
8.9 Hz, 4 H), 7.94 (t, J = 8.4 Hz, 4 H; H4, 4¢¢, terpy), 7.42 – 7.35 (m,
The protected ligands or complexes were heated in a Schlenk
tube under argon for 12 h at 185 ◦C, and then cooled to
8 H), 7.22 – 7.01 (m, 10 H), 6.99 (d, J = 8.9 Hz, 4 H; Ar), 3.78
3258 | Dalton Trans., 2009, 3247–3261
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©

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room temperature or treated with TMSI at room temperature
in DCM or MeCN solution. The deprotected ligands or com-
plexes were obtained as powders in quantitative yield, except
[(PTPY)Ru(L6)Ru(PTPY)](PF6)4.
4 H), 8.06 (t, J = 7.8 Hz, 4 H; H4, 4¢¢, terpy), 7.54 (d, J = 5.4 Hz,
4 H), 7.39 (m, 8 H), 7.28 (m, 8 H), 7.01 (t, J = 7.5 Hz, 2 H; Ar).
[Ru(L2)2](PF6)2. Found: C, 57.41; H, 3.62; N, 10.29. Calc.
1
for C66H50F12N10P2Ru: C, 57.69; H, 3.67; N, 10.19%; H NMR
L1. Found: C, 81.05; H, 4.89; N, 14.02. Calc. for C27H20N4: C,
80.98; H, 5.03; N, 13.99%; 1H NMR (300 MHz, DMSO-d6): d 8.77
(d, J = 4.1 Hz, 2 H; H6, 6¢¢, terpy), 8.69 (s, 2 H; H3¢, 5¢, terpy), 8.67
(d, J = 7.4 Hz, 2 H; H3, 3¢¢, terpy), 8.57 (s, 1 H, N-H), 8.03 (t, J =
8.5 Hz, 2 H; H4, 4¢¢, terpy), 7.85 (d, J = 8.6 Hz, 2 H), 7.53 (dd, J =
5.0 Hz, 2 H; H5, 5¢¢), 7.3 – 7.18 (m, 6 H), 6.93 (t, J = 7.2 Hz, 1 H;
Ar); 13C NMR (75 MHz, DMSO-d6): d 156.4, 156.1, 150.1, 149.9,
146.1, 143.2, 138.2, 130.1, 128.7, 128.3, 125.2, 121.7, 119.0, 117.5,
117.0.
(300 MHz, DMSO-d6): d 9.36 (s, 4 H; H3¢, 5¢, terpy), 9.08 (d, J =
8.4 Hz, 4 H; H3, 3¢¢, terpy), 8.56 (s, 2 H, N-H), 8.33 (d, J = 8.7 Hz,
4 H), 8.05 (m, 6 H), 7.53 (d, J = 5.4 Hz, 4 H), 7.27 – 7.06 (m,
20 H), 7.05 (d, J = 7.7 Hz, 4 H), 6.85 (t, J = 7.5 Hz, 2 H; Ar).
[Ru(L3)2](PF6)2. Found: C, 60.30; H, 3.61; N, 11.20. Calc.
1
for C78H60F12N12P2Ru: C, 60.19; H, 3.89; N, 10.80%; H NMR
(300 MHz, DMSO-d6): d 9.35 (s, 4 H; H3¢, 5¢, terpy), 9.07 (d, J =
8.2 Hz, 4 H; H3, 3¢¢, terpy), 8.49 (s, 2 H, N-H), 8.31 (d, J = 8.5 Hz,
4 H), 8.05 (t, J = 7.7 Hz, 4 H; H4, 4¢¢, terpy), 7.86 (s, 2 H, N-H),
7.85 (s, 2 H, N-H), 7.53 (d, J = 5.4 Hz, 4 H), 7.27 (t, J = 6.5 Hz,
4 H), 7.18 (m, 12 H), 7.11 (m, 12 H), 6.95 (d, J = 8.0 Hz, 4 H),
6.72 (t, J = 6.0 Hz, 2 H; Ar).
L2. Found: C, 80.31; H, 4.99; N, 14.43. Calc. for C33H25N5: C,
80.63; H, 5.13; N, 14.25%; 1H NMR (300 MHz, DMSO-d6): d 8.76
(d, J = 4.2 Hz, 2 H; H6, 6¢¢, terpy), 8.67 (s, 2 H; H3¢, 5¢, terpy), 8.66
(d, J = 7.2 Hz, 2 H; H3, 3¢¢, terpy), 8.33 (s, 1 H, N-H), 8.03 (t, J =
7.9 Hz, 2 H), 8.00 (s, 1 H, N-H), 7.80 (d, J = 8.7 Hz, 2 H), 7.52
(dd, J = 5.0 Hz, 2 H; H5, 5¢¢, terpy), 7.20 (t, J = 7.5 Hz, 2 H), 7.13 –
7.00 (m, 8 H), 6.76 (t, J = 7.2 Hz, 1 H; Ar); 13C NMR (75 MHz,
DMSO-d6): d 156.3, 156.2, 150.1, 147.6, 145.4, 138.5, 138.1, 135.9,
130.0, 128.6, 127.1, 125.1, 122.0, 121.7, 120.0, 119.6, 117.3, 116.4,
115.7.
[Ru(L4)2](PF6)2. Found: C, 61.91; H, 3.84; N, 11.31. Calc.
1
for C90H70F12N14P2Ru: C, 62.17; H, 4.06; N, 11.28%; H NMR
(300 MHz, DMSO-d6): d 9.40 (s, 4 H; H3¢, 5¢, terpy), 9.08 (d, J =
7.6 Hz, 4 H; H3, 3¢¢, terpy), 8.38 (d, J = 8.1 Hz, 4 H), 8.05 (t, J =
7.4 Hz, 4 H; H4, 4¢¢, terpy), 7.54 (d, J = 3.6 Hz, 6 H), 7.42 – 6.89 (m,
40 H; Ar).
[(PTPY)Ru(L5)Ru(PTPY)](PF6)4. Found: C, 51.16; H, 2.97;
N, 9.37. Calc. for C90H64F24N14P4Ru2: C, 50.90; H, 3.04; N, 9.23%;
1H NMR (300 MHz, DMSO-d6): d 9.50 (s, 4 H; H3¢, 5¢, terpy),
9.41(s, 4 H; H3¢, 5¢, terpy), 9.12 (dd, J = 7.4 Hz, 8 H; H3, 3¢¢, terpy),
8.75 (s, 2 H, N-H), 8.42 (dd, J = 7.3 Hz, 8 H), 8.08 (t, J = 7.5 Hz,
8 H; H4, 4¢¢, terpy), 7.81 – 7.56 (m, 15 H), 7.35 – 7.29 (m, 15 H; Ar).
L3. Found: C, 80.49; H, 4.87; N, 14.42. Calc. for C39H30N6: C,
80.39; H, 5.19; N, 14.42%; 1H NMR (300 MHz, DMSO-d6): d 8.76
(d, J = 4.7 Hz, 2 H; H6, 6¢¢, terpy), 8.67 (s, 2 H; H3¢, 5¢, terpy), 8.66
(d, J = 7.8 Hz, 2 H; H3, 3¢¢, terpy), 8.24 (s, 1 H, N-H), 8.03 (t, J =
7.8 Hz, 2 H; H4, 4¢¢, terpy), 7.81 (d, J = 5.7 Hz, 2 H), 7.79 (s, 1 H,
N-H), 7.76 (s, 1 H, N-H), 7.52 (dd, J = 4.8 Hz, 2 H; H5, 5¢¢, terpy),
7.16 (t, J = 7.4 Hz, 2 H), 7.09 (m, 4 H), 7.02 (m, 6 H), 6.93 (d, J =
7.7 Hz, 2 H), 6.70 (t, J = 7.2 Hz, 1 H; Ar).
Crystallography
[Ru(L13)2](PF6)2. C62H56F12N8P2Ru, MW = 1304.16, red
needle, 0.28 ¥ 0.16 ¥ 0.05 mm3, triclinic, P1, a = 9.3421(14),
L4. Found: C, 80.31; H, 5.11; N, 14.69. Calc. for C45H35N7: C,
80.21; H, 5.24; N, 14.55%; 1H NMR (300 MHz, DMSO-d6): d 8.76
(d, J = 4.7 Hz, 2 H; H6, 6¢¢, terpy), 8.67 (s, 2 H; H3¢, 5¢, terpy), 8.65
(d, J = 7.8 Hz, 2 H; H3, 3¢¢, terpy), 8.22 (s, 1 H, N-H), 8.03 (t, J =
8.6 Hz, 2 H; H4, 4¢¢, terpy), 7.78 (d, J = 8.8 Hz, 2 H), 7.76 (s, 1 H,
N-H), 7.70 (s, 1 H, N-H), 7.63 (s, 1 H, N-H), 7.52 (dd, J = 6.3 Hz,
2 H; H5, 5¢¢, terpy), 7.15 (t, J = 7.5 Hz, 2 H), 7.07 (m, 4 H), 6.98 (m,
12 H), 6.68 (t, J = 7.1 Hz, 1 H; Ar).
˚
b = 10.3691(15), c = 15.427(2) A, a = 77.133(2), b = 89.628(2),
◦
g = 80.524(2) , V = 1436.3(4) A , Z = 1, Dcalcd = 1.508 g/cm3,
3
˚
m = 0.417 mm-1, The intensity data were collected with the w
scan mode (186 K) on a Bruker Smart APEX diffractometer
˚
with CCD detector using Mo Ka radiation (l = 0.71073A).
Lorentz, polarization factors were made for the intensity data
and absorption corrections were performed using the SADABS
program.41 The number of reflections collected was 8118, of which
6835 were independent (Rint = 0.0414). The crystal structures
were solved using the SHELXTL program and refined using
full matrix least squares.42 The positions of hydrogen atoms
were calculated theoretically and included in the final cycles of
refinement in a riding model along with attached carbons. The
Flack parameter is 0.28(4) and 0.72(4) with the configuration
inverted in space group P1, indicating that the complex is a
twinned racemate crystal. R1/wR2 [I>2s(I)]: 0.0593/0.1047.
R1/wR2 [all reflections]: 0.0697/0.1100. S = 1.008. Residual
L5. Found: C, 79.34; H, 4.62; N, 15.34. Calc. for C48H34N8: C,
79.76; H, 4.74; N, 15.50%; 1H NMR (300 MHz, DMSO-d6): d 8.77
(d, J = 4.2 Hz, 4 H; H6, 6¢¢, terpy), 8.69 – 8.65 (m, 8 H; H3¢, 5¢, 3, 3¢¢
,
terpy), 8.41 (s, 2 H, N-H), 8.03 (t, J = 8.6 Hz, 4 H; H4, 4¢¢, terpy),
7.82 (d, J = 8.6 Hz, 4 H), 7.52 (dd, J = 4.9 Hz, 4 H; H5, 5¢¢, terpy),
7.20 – 7.17 (m, 8 H, Ar).
L6. Found: C, 79.29; H, 4.78; N, 15.55. Calc. for C60H44N10:
C, 79.62; H, 4.90; N, 15.48%; 1H NMR (300 MHz, DMSO-d6): d
8.76 (d, J = 3.5 Hz, 4 H; H6, 6¢¢, terpy), 8.66 – 8.64 (m, 8 H; H3¢, 5¢, 3, 3¢¢
,
terpy), 8.19 (s, 2 H, N-H), 8.02 (t, J = 7.7 Hz, 4 H; H4, 4¢¢, terpy),
7.78 (d, J = 8.6 Hz, 4 H), 7.70 (s, 2 H, N-H), 7.51 (dd, J = 4.7 Hz,
4 H; H5, 5¢¢, terpy), 7.10 – 7.06 (m, 8 H), 7.01 – 6.98 (m, 8 H; Ar).
-3
˚
electron density: 0.850 and -0.616 e A .
Conclusion
[Ru(L1)2](PF6)2. Found: C, 54.37; H, 3.30; N, 9.56. Calc.
for C54H40F12N8P2Ru: C, 54.41; H, 3.38; N, 9.40%; 1H NMR
(300 MHz, DMSO-d6): d 9.39 (s, 4 H; H3¢, 5¢, terpy), 9.09 (d, J =
8.1 Hz, 4 H; H3, 3¢¢, terpy), 8.79 (s, 2 H, N-H), 8.37 (d, J = 8.7 Hz,
In this study, a series of mono- and bis-topic terpyridine ligands
and the corresponding mono- and bis-nuclear ruthenium(II)
complexes have been successfully synthesized by incorporating
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oligoaniline units at the para-position of a 4¢-phenyl substituted
terpyridine ligand. The palladium-catalyzed aromatic amination
with Pd(OAc)2/DPEphos as catalyst has proved to be an efficient
method for synthesizing these compounds.
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The introduction of electron-rich oligoaniline groups into
electron-deficient terpyridine moieties can strengthen the donor–
acceptor (D–A) interaction in Ru(II) complexes, resulting in
much more intense and strongly red-shifted 1MLCT bands in
the absorption spectra. The 1MLCT absorption maximum can be
tuned over a span of 42 nm by changing the chain length and the
substituent group in oligoaniline units. The shifts in potentials of
the metal-based and oligoaniline-based oxidation waves suggest an
interaction between the oligoaniline unit and the bis(terpyridine)–
Ru2+ center. The dinuclear complexes with oligoaniline units as
spacers possess higher 1MLCT energy levels than the correspond-
ing mononuclear complexes, while no apparent electronic coupling
between two Ru2+ centers is observed.
Moreover, with incorporation of photo- and electro-active
oligoaniline units, the ligands and Ru(II) complexes are endowed
with other interesting properties. The characteristic absorption
bands in the visual and NIR scales, relating to various states of
oligoaniline units (n = 3, 4) in ligands and complexes, are easily
modulated by the oxidation and doping effect. Single aniline moi-
ety in Ru(II) complexes trigger the oxidative electropolymerization
reaction to form a hybrid polymer film on the electrode surface.
The Ru(II) complexes with longer oligoaniline chains are provided
with multiplicate redox processes based on various components.
All of these unique spectroscopic and redox properties suggest
that this novel class of Ru(II) complexes is worthy of further
investigation for photoelectronic materials.
Acknowledgements
This work is supported by the National Natural Science Foun-
dation of China (No. 20874098 and 50673088), Science Fund
for Creative Research Groups (No. 20621401) and 973 Project
(2002CB613400).
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