Synthesis and photophysical properties of 3,8-disubstituted 1,10-phenanthrolines and their ruthenium (II) complexes

Article abstract of DOI:10.1002/ejic.200900310

The palladium-catalysed cross-coupling reaction between 3,8-dibromo-1,10-phenanthroline with phenylacetylene or 3, 5-bis (trifluoromethyl) phenylboronic acid gives good yields of the 3, 8-disubstituted products. These 1,10-phenanthroline derivatives are used for the formation of novel ruthenium complexes of the type [(tbbpy)₂Ru(phenR ₂)]²⁺ [where tbbpy = 4, 4′-di-tert-butyl-2,2′- bipyridine, phen = 1, 10-phenanthroline, R represents the substituents at the 3, 8 positions with bromine, phenylacetylene or 3, 5-bis (trifluoromethyl)phenyl]. All compounds are completely characterised by NMR and UV/Vis spectroscopy, MS, electrochemical measurements and Raman and resonance Raman spectroscopy. The photophysical properties indicate a strong influence of the substitution of the phenanthroline ligand on the absorption, emission and Raman properties. With resonance Raman spectroscopy the localisation of the singlet metal-to-ligand charge-transfer (¹MLCT) excited state is determined. The solid-state structures of 3, 8-dibromo-1, 10-phenanthroline (phenBr₂) and the corresponding ruthenium complex [(tbbpy)₂Ru(phenBr₂)] ²⁺ and a structural motif of f(tbbpy)_2- Ru[phen-3,8-bis[3, 5-bis (trifluoromethyl)phenyl]}]²⁺ are also reported.

Full text of DOI:10.1002/ejic.200900310

FULL PAPER
DOI: 10.1002/ejic.200900310
Synthesis and Photophysical Properties of 3,8-Disubstituted
1,10-Phenanthrolines and Their Ruthenium(II) Complexes
Michael Karnahl,[a] Sven Krieck,[a] Helmar Görls,[a] Stefanie Tschierlei,[b]
Michael Schmitt,[b] Jürgen Popp,*[b,c][‡] Daniel Chartrand,[d] Garry S. Hanan,[d]
Robert Groarke,[e] Johannes G. Vos,[e] and Sven Rau*[a,f][‡‡]
Keywords: Phenanthroline / Ruthenium / Pd catalysis / Luminescence / Resonance Raman spectroscopy
The palladium-catalysed cross-coupling reaction between
3,8-dibromo-1,10-phenanthroline with phenylacetylene or
3,5-bis(trifluoromethyl)phenylboronic acid gives good yields
of the 3,8-disubstituted products. These 1,10-phenanthroline
derivatives are used for the formation of novel ruthenium
complexes of the type [(tbbpy)2Ru(phenR2)]2+ [where tbbpy
The photophysical properties indicate a strong influence of
the substitution of the phenanthroline ligand on the absorp-
tion, emission and Raman properties. With resonance Raman
spectroscopy the localisation of the singlet metal-to-ligand
charge-transfer (1MLCT) excited state is determined. The
solid-state structures of 3,8-dibromo-1,10-phenanthroline
=
4,4Ј-di-tert-butyl-2,2Ј-bipyridine, phen = 1,10-phenan- (phenBr2) and the corresponding ruthenium complex
throline, R represents the substituents at the 3,8 positions
with bromine, phenylacetylene or 3,5-bis(trifluoromethyl)-
phenyl]. All compounds are completely characterised by
NMR and UV/Vis spectroscopy, MS, electrochemical mea-
surements and Raman and resonance Raman spectroscopy.
[(tbbpy)2Ru(phenBr2)]2+ and a structural motif of [(tbbpy)2-
Ru{phen-3,8-bis[3,5-bis(trifluoromethyl)phenyl]}]2+ are also
reported.
(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim,
Germany, 2009)
tion-metal complexes.[5–8] Phenanthrolines are an interest-
ing scaffold and are very versatile building blocks as they
offer several positions that can be manipulated (Fig-
ure 1).[9–15]
Introduction
Ruthenium coordination compounds, based on polypyr-
idine ligands, play a central role in the design of lumines-
cent and redox-active assemblies. Therefore, the develop-
ment of photochemical molecular devices (PMD)[1–3] with
ligands of the 1,10-phenanthroline type (phen) has been in-
vestigated extensively.[4] It is of fundamental importance to
possess a variety of synthetic methods to obtain derivatives
of the phen ligand in order to be able to introduce substitu-
ents that can tune the photophysical properties of its transi-
Figure 1. Structure of 1,10-phenanthroline (phen) and the applied
numbering scheme. The two arrows mark the desired 3,8 positions.
[a] Institut für Anorganische und Analytische Chemie,
Friedrich-Schiller-Universität,
For example, oxidation of phen at the 5,6 positions leads
to the corresponding 1,10-phenanthroline-5,6-dione, which
is an important building block for the construction of oligo-
pyridophenazines, such as di- and tetrapyridophenazine li-
gands.[16–20] Their ruthenium complexes may be used as lu-
minescent probes for DNA (DNA sensors)[21,22] or light-
harvesting centres for intramolecular photocatalytic hydro-
gen formation.[23–27] In this contribution, we wish to report
novel methods for the introduction of substitution at the 3
and 8 positions of the 1,10-phenanthroline ring (Figure 1).
It is important to note that introduction of substituents at
the 2,9 positions can render the corresponding ruthenium
complexes photolabile,[13,15,18,28,29] while substitution at the
3,8 positions will influence the photophysical properties
without interfering with the coordination sphere.[10,30]
August-Bebel-Str. 2, 07743 Jena, Germany
[b] Institut für Physikalische Chemie, Friedrich-Schiller-Uni-
versität,
Helmholzweg 4, 07743 Jena, Germany
Fax: +49-3641-948302
E-mail: juergen.popp@uni-jena.de
[c] Institute of Photonic Technology Jena e.V.,
Albert-Einstein-Straße 9, 07749 Jena, Germany
[d] Département de Chimie, Université de Montréal,
2900 Edouard-Montpetit, Montréal, Québec H3T-1J4, Canada
[e] Solar Energy Conversion SRC, School of Chemical Sciences,
Dublin City University,
Dublin 9, Ireland
[f] Department for Chemistry and Pharmacy,
Friedrich-Alexander-University Erlangen-Nürnberg,
Egerlandstraße 1, 91058 Erlangen, Germany
Fax: +49-9131-8527367
E-mail: sven.rau@chemie.uni-erlangen.de
[‡] Correspondence for Raman and resonance Raman spectra.
[‡‡] Correspondence for the synthesis and the materials.
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3,8-Disubstituted 1,10-Phenanthrolines and Their Ruthenium(II) Complexes
Furthermore, 1,10-phenanthroline ligands substituted at
the 4,7 positions are already known and applied in rutheni-
um(II) complexes as luminescent sensors for oxygen.[31,32]
The introduction of bromine functions into the ligand
framework is especially interesting as they allow the appli-
cation of palladium-catalysed Suzuki[33–36] and Sonoga-
shira[37] cross-coupling reactions thus enabling the intro-
duction of phenyl or alkynyl derivatives at predesignated
positions. In addition, nucleophilic substitution at these po-
sitions allows the introduction of alkoxides[12] and amino
acids.[38] Recently we reported that these reactions can also
be
employed
for
3,5,6,8-tetrabromophenanthroline
(phenBr4), where a stronger influence of the alkynyl moiety
than that of the aryl moiety on the photophysical proper-
ties, such as absorption and emission maxima, was ob-
served.[12,14]
Scheme 2. Synthesis and labelling of the presented ruthenium com-
plexes.
The combination of electron-rich bipyridine ligands,
such as tbbpy, with electron-deficient bipyridine ligands,
like 4,4Ј-bis(methoxycarbonyl)-2,2Ј-bipyridine, leads to
interesting photophysical properties of the corresponding
complexes such as excitation-wavelength-dependent
switches of the localisation of the singlet metal-to-ligand
charge-transfer state.[39] The introduction of alkynyl- or aryl
groups into the phenanthroline frames at the 3,8 positions
leads to an expansion of the conjugated π system, which
lowers the energy of the phenanthroline-based excited state.
Here, we present the synthesis, characterisation and photo-
Figure 2. Solid-state structure and numbering of L2, relevant bond
lengths and angles are given in Table 1, solvent molecules are omit-
ted for clarity.
physical properties of three different mononuclear ruthe- 3,8-bis[{3,5-bis(trifluoromethyl)}phenyl]-1,10-phenanthrol-
nium polypyridine complexes based on 3,8-disubstituted ine [L3, phen(tfmp)2] in very good yields. The combination
1,10-phenanthroline ligands.
of Pd2(dba)3 and S-Phos (in the ratio of 1:2) was found to
be the most effective catalytic system for preparation of L3
(yield = 95%). The alternative use of Pd(PPh3)4 and
Na2CO3 under comparable reaction conditions resulted in
incomplete conversion and diminished yields of only 25%.
L2 can also be transformed into the 3,8-bis(arylethynyl)-
1,10-phenanthroline L4 by using an ultrasonic activated
Sonogashira coupling reaction.[37] It has to be mentioned
that the application of sonication is essential for the effec-
tive palladium-catalysed C–C bond formation.[10,37] Thus,
the reaction mixture was sonicated at 40 °C under argon
atmosphere for 8 h before the suspension was heated to
60 °C for 1 d. After workup and purification by column
chromatography, it was possible to isolate 3,8-bis(phenyl-
acetylene)-1,10-phenanthroline [L4, phen(phac)2] in yields
of 81% (Scheme 1).
Results and Discussion
Synthesis
The desired compounds were synthesised according to
Schemes 1 and 2. 3,8-Dibromo-1,10-phenanthroline, L2,
was obtained by using literature methods[8] starting from
1,10-phenanthroline, L1. The solid-state structure of L2 is
depicted in Figure 2.
NMR measurements and mass spectra are all in good
agreement with the proposed structure. The regioselective
addition of two arylethynyl groups in the 3,8 positions leads
to an increased conjugated aromatic system, that has not
only an influence on the solubility, it further affects the
photophysical properties, as discussed later.
Scheme 1. Synthesis and naming of disubstituted phenanthroline
ligands.
The coordination of these new ligands to the [(tbbpy)2-
Ru]2+ core was accomplished by using microwave-assisted
The two bromine functions in L2 can be modified by reaction conditions with short reaction times of only two
using different types of palladium-catalysed carbon–carbon hours, to afford the target complexes in yields of above
bond-forming reactions. Reaction of L2 with 2 equiv. 3,5- 70%. Furthermore, purification from side products by col-
bis(trifluoromethyl)phenylboronic acid under Suzuki[33,36] umn chromatography was not necessary as simple
cross-coupling conditions (in thf, Cs2CO3, 80 °C, 3 d) gives recrystallisation sufficed.
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J. Popp, S. Rau et al.
FULL PAPER
1
Figure 3. H NMR spectrum (400 MHz, 300 K) of RuL3 in CD3CN and the assignment of the NMR values.
The structural characterisation of the new ruthenium
complexes was performed with multidimensional NMR
methods (H,H-COSY), MS (ESI), UV/Vis, emission and
Raman spectroscopy and, wherever possible, X-ray analysis.
The results of the investigation of the complexes RuL2–
RuL4 by ESI mass spectroscopy always confirm the compo-
sition of the complexes. In each case the [M – 1PF6]+ and
the [(M – 2PF6)/2]+ peak can be assigned to the correspond-
ing fragment with matching isotopic pattern. One represen-
tative example for a 1H NMR spectrum is given in Figure 3.
The signals corresponding to the hydrogen atoms of the
phenanthroline ligand of RuL3 are marked with numbers.
As expected, the phen moiety provides three different pro-
ton signals with a characteristic shape (two doublets and
one singlet, marked with Latin numbers) and equal peak
–
Figure 4. Solid-state structure of RuL2. Hydrogen atoms, PF6
anions and solvent molecules are omitted for clarity.
1
areas. This H NMR pattern indicates the formation of a
symmetrical octahedral complex, which is in agreement
with the crystallographic characterisation (Figure 5).
In addition to the characterisation of the novel mononu-
clear compounds RuL2–RuL4 by means of NMR spec-
troscopy, the X-ray structures of RuL2 and RuL3 are de-
picted in Figures 4 and 5. The structural analysis of RuL2
indicates a conventional octahedral coordination environ-
ment around the ruthenium centre, which is common for
these classes of coordination compounds.[12] A detailed
comparison of the results of the X-ray crystallographic
analysis (Table 1) reveals only slight differences between L2
and the corresponding ruthenium complex RuL2. All se-
lected bond lengths and angles are in the same range, and
the phenanthroline frame is nearly ideally planar (deviation
from planarity is 9 pm). There are also no significant differ-
ences in the bond lengths and angles when RuL1 and RuL2
are compared. The same trend can be found for the analo-
gous tetrabromo-substituted ruthenium complex RuBr4
([(tbbpy)2Ru(phenBr4)]2+), with four bromine functions at
the positions 3, 5, 6 and 8.[12] The Ru–N bond lengths (de-
picted in Table 1) are in the same range as those found for
related Ru complexes.[12] Hence, it is obvious that bromine
Figure 5. Solid-state structural motif of RuL3. Hydrogen atoms,
–
PF6 anions and solvent molecules are omitted for clarity.
substitution (neither its position nor the number) has no where the phenyl rings are twisted out of the phen-
significant influence on the solid-state structure. anthroline plane. This is caused by rotation of the aromatic
The structural motif of RuL3 is depicted in Figure 5, rings to avoid steric strain, which results in a potential lack
which was obtained by crystallisation from an acetone/ of delocalisation of the conjugated π system. Unfortunately,
water mixture. The ruthenium centre is octahedrally sur- the quality of this structural motif is not high enough for
rounded by two tbbpy chelate ligands and one 3,8-bis[{3,5- a more detailed discussion of the bond lengths and bond
bis(trifluoromethyl)}phenyl]-1,10-phenanthroline
ligand, angles.
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3,8-Disubstituted 1,10-Phenanthrolines and Their Ruthenium(II) Complexes
Table 1. Bond lengths [pm] and angles [°] of L2, RuL1 and RuL2. For atom numbering see also Figure 2.
[a]
L2
RuL1[a]
RuL2
RuBr4
Br1–C2
Br2–C9
C1–N1
C3–C4
Ru1–N1
Ru1–N2
Ru1–N3
Ru1–N4
Br1–C2–C3
C3–C4–C5
C1–N1–C12
N1–Ru1–N2
N1–Ru1–N3
N3–Ru1–N4
189.4Ϯ2.4
187.9Ϯ2.4
131.4Ϯ3.0
142.0Ϯ3.3
–
–
–
–
121.2Ϯ1.8
122.3Ϯ2.1
118.9Ϯ2.1
–
–
–
–
–
188.6Ϯ2.1
189.9Ϯ2.1
135.5Ϯ2.4
139.0Ϯ3.3
204.0Ϯ1.5
205.8Ϯ1.5
204.9Ϯ1.2
204.8Ϯ1.5
120.4Ϯ1.5
124.0Ϯ2.1
118.5Ϯ0.9
79.7Ϯ0.6
189.1Ϯ1.8
187.7Ϯ1.8
133.4Ϯ2.1
140.7Ϯ2.7
204.6Ϯ1.5
206.0Ϯ1.5
206.4Ϯ1.5
205.2Ϯ1.5
122.2Ϯ1.5
125.0Ϯ1.8
118.6Ϯ1.5
79.3Ϯ0.6
135.7Ϯ2.7
139.4Ϯ4.5
206.1Ϯ1.5
205.6Ϯ1.5
205.3Ϯ1.2
205.5Ϯ1.2
–
126.1Ϯ3.0
117.6Ϯ1.8
79.9Ϯ0.6
91.2Ϯ0.5
77.9Ϯ0.5
87.8Ϯ0.5
78.8Ϯ0.5
91.8Ϯ0.6
78.2Ϯ0.6
[a] The data of RuL1 and RuBr4 are taken from Rau et al.[12] and are given for comparison.
Electrochemistry
sion, RuL2 with the bromine substitution in positions 3 and
8 exhibits clear differences in its redox potentials relative
to the unsubstituted complex RuL1. Therefore, it would be
interesting if differences can also be found in the photo-
physical properties, which are discussed below.
The electrochemical measurements were carried out in
anhydrous and nitrogen-purged acetonitrile with 0.1  tet-
rabutylammonium tetrafluoroborate as supporting electro-
lyte. The resulting cyclic voltammograms of RuL1–RuL4
are consistent with a metal-based reversible oxidation step
and several ligand-based reduction steps, which are pre-
sented in Table 2. In comparison to the unsubstituted phen-
anthroline ligand in RuL1 [EoxRu(II/III) = 0.79 V], all the oxi-
dation potentials of the RuII/RuIII couple in RuL2–RuL4
lie towards more positive values, but they are only slightly
affected by the substitution pattern. This suggests that the
introduction of substituents has a comparatively moderate
influence on the metal-based ground state. The most pro-
nounced of the oxidation potentials of the RuII/RuIII cou-
ple, with a difference of 90 mV, is for RuL2, which clearly
shows that the two bromine substituents decrease the elec-
tron density at the metal centre.
Electronic Properties
The clear influence of the different substituents on the
absorption and emission properties, as well as on the lumi-
nescence lifetimes, is listed in Table 3. The absorption spec-
tra of L1–L4 dissolved in dichloromethane are shown in
Figure 6. All four ligands display two absorption maxima,
independent of their substitution, in the wavelength range
from 230 to 400 nm. The ligands L2–L4 exhibit a consider-
able redshift of the π–π* transitions, and an increased inten-
sity of these two bands relative to 1,10-phenanthroline, L1.
For L1, the difference between these two absorption bands
at 233 and 265 nm is 32 nm. A comparable behaviour can
be found for the absorption maxima of the ligand L2 with
a bathochromic shift from 233 to 246 nm and from 265 nm
to 275 nm relative to the unsubstituted ligand L1, and for
L3, the maxima occur at 278 and 321 nm. These spectro-
scopic properties are comparable to related 3,5,6,8-tet-
raphenyl-1,10-phenanthroline ligands.[14] Substitution with
phenylacetylene (L4) results in a significant variation in the
absorption properties as discussed by Tzalis et al.[10] These
Table 2. Electrochemical data: half-wave potentials E [V] (vs. Fc/
Fc+).
Ru(II/III)
I
II
III
IV
Compound
Eox
Ered
Ered
Ered
Ered
RuL1
RuL2
RuL3
RuL4
0.79
0.88
0.81
0.85
–1.79
–1.53
–1.69
–1.46
–1.99
–2.02
–1.95
–2.02
–2.26
–2.27
–2.21
–2.30
–
–
–2.56
–
The first reduction processes of RuL2, RuL3 and RuL4 absorption maxima are located at 284 and 347 nm with a
occur at markedly less cathodic potentials relative to that shoulder at 359 nm.[10] It seems that the phenylacetylene
of RuL1, with a shift of 0.35 V for RuL2 and 0.33 V for substituents have the strongest influence on the π system of
RuL4, which arises because of the more pronounced π ac- the phenanthroline moiety.
ceptance by the substituted phen ligand. The second and
An influence of the substitution pattern on the emission
third reductions at around –2.0 V and –2.3 V are ascribable features of L1–L4 dissolved in dichloromethane, excited at
to the stepwise one-electron tbbpy-based reductions. These their long-wavelength absorption maxima, is also clearly
values are in good agreement with the potentials obtained visible. The emission maxima display a significant redshift
for the recently described systems RuL1.[12,14] The complex on going from L1 to L4 as shown in Table 3. The emission
RuL3 shows an additional reduction step at –2.56 V, which maxima for L1 and L2 are located at 365 and 368 nm,
is in accordance to reported complexes with a tetrasubsti- respectively, and a bathochromic shift from 365 to 391 and
tuted phenanthroline moiety [(tbbpy)2Ru(phenBr4)](PF6)2 414 nm occurs for the emission of L3 and L4, respectively.
and [(tbbpy)2Ru{phen(Ph-4-tBu)4}](PF6)2.[12,14] In conclu- Similar redshifts of the emission wavelength have been ob-
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J. Popp, S. Rau et al.
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Table 3. Absorption, emission properties, lifetimes and quantum yields of the 1,10-phenanthroline ligands L1–L4 and the corresponding
ruthenium complexes RuL1–RuL4 dissolved in dichloromethane.
[a]
Compound
Absorption λmax [nm] (ε/103 –1 cm–1)
Emission λmax [nm] Lifetime, τ[b] [ns]
Quantum yield, f
L1
L2
L3
L4
233 (33), 265 (32)
246 (52), 275 (42)
278 (37), 321 (23)
284 (51), 347 (55), 359 (51)
365
368
391
414
–
–
–
–
Ͻ0.01
Ͻ0.01
0.03
0.47
RuL1
RuL2
RuL3
RuL4
267 (64), 288 (69), 426 (16), 455 (19)
282 (59), 289 (83), 440 (19), 470 (16)
286 (98), 322 (31), 441(12), 485 (11)
287 (109), 371 (68), 440 (19), 502 (11)
602
638
652
657
272
525
480
591
0.03
0.05
0.05
0.05
[a] L1–L4: λexc at the long-wavelength maximum, RuL1–RuL4: λexc = 440 nm. [b] λexc = 337 nm.
mine groups are located at the 3, 5, 6 and 8 positions,[14]
and for the complex [Ru(bpy)2(phenBr2)]2+ without tert-bu-
tyl groups.[30] A further bathochromic shift of the absorp-
tion occurs for RuL3. The band maxima located at 286 and
322 nm are assigned to ligand-centred π–π* transitions of
tbbpy and L3, respectively. The other two maxima at 441
and 486 nm can be assigned to electronic transitions be-
tween orbitals of the ruthenium and the π* orbitals either
tbbpy or L3. Comparable properties have been observed for
complexes with different fourfold phenyl substitutions at
the 3, 5, 6 and 8 positions.[14] The absorption properties of
RuL4 differ from the other presented coordination com-
pounds. A particular feature is the band at 371 nm for
RuL4, which can be assigned to the ligand-centred π–π*
transition of L4 (by comparison, the absorption of the un-
bound ligand L4 occurs at 359 nm, Figure 6). Furthermore
a bathochromic shift of the absorption band with the lowest
energy is clearly visible, because the absorption maximum
Figure 6. Absorption spectra of L1 (solid), L2 (dashed), L3 (dot-
ted), L4 (dash–dotted) dissolved in dichloromethane.
1
of this MLCT transition is located at 502 nm with a red-
served in fourfold-substituted phenanthroline ligands.[14]
The Stokes shift decreases in the order L1 (1.28 eV), L2
(1.14 eV), L3 (0.69 eV) and L4 (0.46 eV).
On the basis of these investigations, it is apparent that
substitution at the 3,8 positions of the 1,10-phenanthroline
ligand has a pronounced influence on the photophysical
properties of phenanthroline ligands. The strongest effect is
observed for the alkynyl substituent, which likely correlates
with the most increased delocalisation of the conjugated π
system.[10]
shift of 47 nm relative to the unsubstituted complex RuL1
and 16 nm to RuL3. Very similar absorption properties
have been reported for a ruthenium complex with a 3,5,6,8-
tetrakis[(triisopropylsilyl)acetylene]-1,10-phenanthroline li-
gand and for a structurally related osmium complex with a
All four complexes RuL1–RuL4 dissolved in dichloro-
methane exhibit absorption properties that are common for
the class of ruthenium polypyridine compounds (Fig-
ure 7).[40] The absorption spectra of RuL1 and RuL2 are
very similar. RuL1 exhibits four absorption maxima at 267,
288, 426 and 455 nm. The maxima at 267 and 288 nm can
be assigned to ligand-centred π–π* transitions of L1 and
4,4Ј-bis(tert-butyl)-2,2Ј-bipyridine (tbbpy), respectively.[10]
Furthermore, the two maxima at 426 and 455 nm correlate
to metal-to-ligand charge-transfer (1MLCT) transitions be-
tween the ruthenium ion and the coordinated ligands.[40]
The complex RuL2 displays very similar properties; for in-
stance, a notable shift in the lowest-energy absorption band
from 426 and 455 nm for RuL1 to 440 and 470 nm for
RuL2 is observed. This shift is very comparable with data
Figure 7. Absorption spectra of RuL1 (solid), RuL2 (dashed),
RuL3 (dotted) and RuL4 (dash–dotted) in dichloromethane; an en-
obtained for the [Ru(tbbpy)2(phenBr4)]2+, where the bro- largement of the MLCT region is depicted in the inset.
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3,8-Disubstituted 1,10-Phenanthrolines and Their Ruthenium(II) Complexes
3,8-bis(phenylacetylene)-1,10-phenanthroline ligand where electronic transition, are selectively enhanced. The enhance-
the absorption maxima are shown at 505[41] and 497 nm,[42] ment factor is about 106 relative to off-resonance measure-
respectively.
ments.[45] Therefore, rR spectroscopy is the method of
The emission maxima and emission lifetimes of com- choice of examining which particular ligand of the investi-
plexes RuL1–RuL4 dissolved in dichloromethane were also gated heteroleptic ruthenium complexes is involved in the
investigated (Table 3). When the data obtained for the sub- metal-to-ligand charge-transfer (1MLCT) processes.[39,46–48]
stituted complexes are compared with that of RuL1, a ba-
Prior to resonance Raman spectroscopy, the analysis of
thochromic shift of the emission wavelengths from 602 nm the off-resonance Raman spectra is required to identify
(RuL1) to 638 nm (RuL2), 652 nm (RuL3) and 657 nm marker bands of the different ligands. This will facilitate the
(RuL4) is observed. The largest bathochromic shifts of the analysis of the rR data obtained for the complexes. There-
emission maxima appear for RuL3 and RuL4, which indi- fore, the solid-state Raman spectra of the complexes RuLR
cates that the phenyl and phenylacetylene groups have the were compared with the Raman spectrum of [Ru-
strongest influence on the π system of the phenanthroline (tbbpy)3]2+ (Figure 8). The Raman bands located in the
system. Similar bathochromic shifts of the emission max- range of the ring vibrations at 1617, 1541, 1483, 1420, 1372
ima have been observed for a ruthenium complex with a and 1316 cm–1 of the homoleptic complex can clearly be
3,5,6,8-tetrakis[(triisopropylsilyl)acetylene]-1,10-phenan- assigned to the 4,4Ј-bis(tert-butyl)-2,2Ј-bipyridine (tbbpy)
throline ligand with a maximum at 692 nm.[41] For com- ligand. When this spectrum is compared with the Raman
plexes with a dual phenylacetylene substitution at the 4 and bands of RuL1–RuL4, differences are detected, and the new
7 positions, similar properties with an emission maximum bands can be assigned to the different 1,10-phenanthroline
at 672 nm have been observed.[43] The analysis of the lumi- ligands. However, a similarity between the Raman spectra
nescence lifetimes, recorded in aerated dichloromethane of RuL1–RuL4 is observed in this investigated range, which
with an excitation wavelength of 337 nm, shows that all indicates that substitution at the 3,8 positions has only
substituted complexes display significantly longer lifetimes small influence on the vibrations of the 1,10-phenanthroline
than the unsubstituted RuL1. However, the type of substi- system. Some new Raman bands of RuL3 located at 1390
tution has no significant influence on the emission lifetime. and 1001 cm–1 can be assigned to vibrations of the phenyl
This surprising finding might be explained by the combined groups of the substituents. Furthermore, comparison of the
effect of the substitution at the 3,8 positions, together with spectra of RuL1 with RuL4 shows differences; some Raman
the deactivating effect of the large substituents, which might bands of the substituent at 1578, 1147 and 999 cm–1 for the
offer additional nonradiative relaxation pathways.
latter compound have a high intensity and thus change the
The quantum yields of the emission for all complexes are appearance of the Raman spectrum. These Raman bands
in the range expected for ruthenium polypyridyl complexes. can be assigned to vibrations of the phenyl rings. In ad-
The bromine substituent seems to lower the quantum yield dition, the CϵC stretch vibration occurs at 2220 cm–1.
to some extent. In summary, the substitution in the 3,8 po-
sitions of the non-coordinated and the coordinated 1,10-
phenanthroline ligand has a considerable influence on its
photophysical properties, such as absorption and emission
wavelengths and luminescence lifetimes. The obtained val-
ues indicate that the expansion of the 1,10-phenanthroline
frame by phenyl and phenylacetylene leads to a lowering of
the energies of the excited states. To further elucidate the
influence of the substituents on the excited states of the
corresponding complexes, detailed Raman spectroscopic in-
vestigations were performed.
Raman and Resonance Raman Spectroscopy
An extremely capable method of analysing the locali-
sation of the 1MLCT excited state is resonance Raman (rR)
spectroscopy, which is an excellent tool to characterise the
molecular degrees of freedom involved in the initial struc-
Figure 8. Off-resonance Raman spectra of RuL1–RuL4 and
tural changes of photochemically active systems, e.g. to
[Ru(tbbpy)3]2+ in the solid state recorded at an excitation wave-
analyse the Franck–Condon point of an electronic transi-
length of 830 nm. The spectra are normalised to the band at
tion.[44,45] It is important to consider the Franck–Condon
point because the subsequent excited state relaxations will
be initiated at this point. If the Raman excitation wave-
1031 cm–1.
1
The localisation of the MLCT excited state was investi-
length lies within the absorption band, the resonance condi- gated for the complexes RuL2–RuL4, dissolved in dichloro-
tion is achieved and the vibrational modes, involved in the methane, with resonance Raman spectroscopy (Figure 9).
Eur. J. Inorg. Chem. 2009, 4962–4971
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4967

J. Popp, S. Rau et al.
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The resonance Raman spectrum of the homoleptic complex vent band at 1423 cm–1. The Raman bands located at 1624,
[Ru(tbbpy)3]2+, measured at an excitation wavelength of 1562, 1489 and 1437 cm–1 can be associated to vibrations
458 nm, is displayed in Figure 9 for comparison and exhib- of L2. The remaining bands can be assigned to tbbpy. It is
its enhanced Raman bands located at the tbbpy ligand. The noticeable that the intensity of all Raman bands of the spec-
excitation wavelength of 488 nm for RuL4 lies within the tra measured at 458, 476 and 488 nm decrease with increas-
first absorption band (Figure 5), and the obtained spectrum ing excitation wavelength. The enhancement maximum for
of RuL4 shows new bands that can clearly be associated the Raman bands located at tbbpy seems to be at 458 nm,
with the newly introduced ligand L4 by comparing them close to the absorption maximum of this complex (Figure 7,
with the spectrum of [Ru(tbbpy)3]2+. The Raman bands lo- Table 3). In contrast, the Raman bands that can be assigned
cated at 2220, 1625, 1576, 1497, 1449, 1373, 1352, 1208, to L2 show their maximum intensity at an excitation wave-
1
1146, 1111 and 999 cm–1 can be assigned to MLCT pro- length of 476 nm. Thus, resonance Raman spectroscopy
cesses to L4 in RuL4. Thus, an excitation of both ligands, shows that the lowest-energy absorption maximum can be
1
tbbpy and L4 is observable with excitation at 488 nm, and assigned to a MLCT process to the bromine-substituted
notably, the vibrational modes of the phenylacetylene sub- phenanthroline L2.
stituent at 2220, 1576 and 999 cm–1 are involved. This is in
contrast to the results from the rR investigations of the
1
complex [Ru(bpy)2(phen)]2+, in which the MLCT transi-
Conclusions
tion is favoured for the bpy ligand.[49] A similar localisation
1
of the MLCT process, in comparison to RuL4, can be ob-
The synthesis of ruthenium(II) complexes with regiose-
served for RuL3. For this compound, the rR spectra ob- lective functionalised 1,10-phenanthroline derivatives is fac-
tained at 488 nm show enhanced Raman bands of the two ile and results in high yields of up to 95%. The 3,8-dibro-
ligands tbbpy and L3.
mine-substituted phenanthroline, L2, is easily transformed
into the aryl-substituted phenanthroline by using organo-
metallic Suzuki coupling with an optimised phosphane li-
gand system. The electrochemical investigations indicate
that the new substituents at the phenanthroline ligands have
a limited influence on the redox properties of the ruthenium
centre, but a pronounced effect can be observed for the re-
dox properties of the phenanthroline ligand. The photo-
physical data indicate that the newly introduced functionali-
ties induce a bathochromic shift of the absorption and emis-
sion maxima of ligands and complexes alike. This general
trend has been observed for the 3,5,6,8-tetrasubstituted
phenanthroline complexes already.[12,14] On the basis of a
comparison of these results, it is clear that substitution in
the 5,6 positions in the latter complex has a far less pro-
nounced effect on the photophysical properties of the corre-
sponding complexes than substitution in the 3,8 positions.
The resonance Raman investigation of the complexes shows
that the tbbpy ligand and the substituted phenanthrolines
are involved in the 1MLCT transition. The detailed analysis
of the data obtained for RuL2 shows that the lowest-energy
1
section of the MLCT band is increasingly localised on the
bromine-substituted phenanthroline ligand. In general, the
greater ease of reduction of the substituted phenanthrolines
1
correlates quite well with their involvement in the MLCT
process. In conclusion, the results obtained indicate that
bromine substitution at the 3 and 8 positions of 1,10-phen-
anthroline yields an excellent starting material for the syn-
thesis of more extensive molecular structures that have dif-
ferent emission wavelengths and allow for the tuning of the
localisation of the lowest-energy 1MCLT level. From a syn-
Figure 9. Resonance Raman spectra of RuL2, RuL3, RuL4 and,
for comparison, of [Ru(tbbpy)3]2+ dissolved in dichloromethane
(solvent bands are marked with *). The complexes were excited at
different wavelengths lying within the first absorption band (Fig-
ure 7). The spectra of RuL2 are normalised to the solvent band at
702 cm–1.
The rR spectra of complex RuL2 dissolved in dichloro- thetic point of view, it is very interesting that the introduc-
methane were obtained by using excitation wavelengths of tion of bromine substituents alone is sufficient to induce
1
488, 476 and 458 nm, which lie within the first absorption some degree of directional electron transfer in the MLCT
band (Figure 9). These spectra are normalised to the sol- state. This finding may form the basis for the development
vent band at 702 cm–1. It can be seen that the spectrum at of photochemical molecular devices relying on directional
488 nm shows enhanced Raman bands relative to the sol- energy or electron transfer.[1–3]
4968
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© 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Inorg. Chem. 2009, 4962–4971

3,8-Disubstituted 1,10-Phenanthrolines and Their Ruthenium(II) Complexes
provided by an argon ion laser (Modell Coherent Innova 300C Mo-
Experimental Section
toFreD Ion Laser) served as the resonant excitation in the range
of the MLCT absorption band. A rotating cell was utilised to pre-
vent the heating of the samples. No changes in the absorption spec-
tra of the complexes could be observed after exposure to the reso-
nant laser light. The scattered light was collected with a lens (f1 =
35 mm) and subsequently focussed (f2 = 50 mm) onto the entrance
slit of an Acton SpectraPro 2758i spectrometer. The dispersed Ra-
man stray light was detected with a CCD-camera from Princeton
Instruments, labelled with a Spec-10 400B/LN back-illuminated
CCD. The concentration of the solutions was optimised to obtain
a maximum signal-to-noise ratio and was in the millimolar range.
If not stated otherwise, all Pd-catalysed cross-coupling reactions
were conducted under argon or nitrogen by using standard Schlenk
techniques. The Sonogashira[37] and Suzuki[33–36] reactions were
carried out in anhydrous, freshly distilled solvents. Toluene and tri-
ethylamine were distilled from sodium benzophenone ketyl under
argon prior to use. Methanol was dried with magnesium. All other
solvents were of HPLC grade. 1,10-Phenanthroline monohydrate,
phenylacetylene,
3,5-bis(trifluoromethyl)phenylboronic
acid,
NH4PF6 and all other materials were of commercial grade and used
without further purification. [Ru(tbbpy)2Cl2], 3,8-bis(phenylace-
tylene)-1,10-phenanthroline and S-Phos were prepared according
to literature methods.[8,10,36,50]
Crystal-Structure Analyses: The structure determinations were car-
ried out on an Enraf Nonius Kappa CCD diffractometer, by using
graphite monochromated Mo-Kα radiation. The crystals were
mounted in a stream of cold nitrogen, with a distance of 29 mm to
the crystal detector. Data were corrected for Lorentz and polarisa-
tion effects but not for absorption.[52,53] The structures were solved
by direct methods (SHELXS[54]) and refined by full-matrix least-
1H NMR and 13C NMR spectra were recorded at ambient tem-
perature on a Bruker AC 200 or AC 400 MHz spectrometer (1H:
400.25 MHz, 13C: 100.65 MHz). All spectra were referenced to tms
or deuterated solvent as an internal standard (measured values for
δ are given in ppm and for J in Hz). Mass spectra were performed
on a Finnigan MAT SSQ 710 instrument at the Friedrich-Schiller
University, Jena. UV/Vis spectra (accuracy Ϯ2 nm) were obtained
by using a Specord S600 from Analytik Jena. Emission spectra were
measured at 298 K by using a Perkin–Elmer LS50B equipped with
a Hamamatsu R928 red-sensitive detector. Quartz cells with a
10 mm pathlength were used for recording UV/Vis and emission
spectra. Luminescence quantum yields were measured with diluted
solutions (optical density Ͻ 0.05) with [Ru(bpy)3]Cl2 in nonde-
gassed water (Φ = 0.028)[51] and quinine sulfate (Φ = 0.55) as refer-
ences.
2
squares techniques against Fo (SHELXL-97[55]). The hydrogen
atoms were included at calculated positions with fixed thermal pa-
rameters during the final stages of the refinement. All non-hydro-
gen atoms were refined anisotropically.[55] The molecular illustra-
tions were drawn with the program XP (SIEMENS Analytical X-
ray Instruments, Inc.). CCDC-676105 (L2), and CCDC-676106
(RuL2) contains the supplementary crystallographic data for this
paper. These data can be obtained free of charge from The Cam-
bridge Crystallographic Data Centre via www.ccdc.cam.ac.uk/
data_request/cif.
The microwave-assisted reactions were carried out by using the Mi-
crowave Laboratory Systems MLS EM-2 microwave system. Ele-
mental analyses were performed by the Microanalytical Laboratory
of the University Jena. For the sonication reaction, a Bandelin
Sonorex Super RK 156 BH ultrasonic bath with a HF power of P
= 150 W and a HF frequency f = 35 kHz was used.
Crystal Data for phenBr2 (L2): Crystals suitable for X-ray analysis
were obtained from chloroform. C12H6Br2N2·CHCl3, Mr
=
457.38 gmol–1, colourless prism, size 0.04ϫ0.04ϫ0.03 mm, ortho-
rhombic, space group Pnma, a = 21.149(4), b = 6.7797(14), c =
10.982(2) Å, V = 1574.6(6) Å3, T = –90 °C, Z = 4, ρcalcd.
=
1.929 gcm–3, µ (Mo-Kα) = 56.46 cm–1, F(000) = 880, 10336 reflec-
tions in h(–26/27), k(–8/8), l(–13/14), measured in the range
1.93°ՅΘՅ27.47°, completeness Θmax = 99.9%, 1957 independent
reflections, Rint = 0.0545, 1444 reflections with Fo Ͼ 4σ(Fo), 118
Electrochemical data were obtained with cyclic voltammetry by
using a conventional single-compartment, three-electrode cell ar-
rangement in combination with a potentiostat “AUTOLAB®, Eco
Chemie”. A 0.196 cm2 Pt disk was used as an auxiliary electrode,
the working electrode was glassy carbon and the reference electrode
Ag/AgCl (3  KCl). The measurements were carried out in anhy-
drous and nitrogen-purged acetonitrile with 0.1  terabutylammon-
ium tetrafluoroborate as supporting electrolyte. All potentials are
referenced by the ferrocenium/ferrocene couple [E(Fc/Fc+) =
0.45 V].
parameters, 0 restraints, R1obs = 0.0606, wR2obs = 0.1596, R1all
=
0.0868, wR2all = 0.1773, GOOF = 1.042, largest difference peak
and hole 3.285/–1.082 eÅ–3.
Crystal Data for [(tbbpy)2Ru(phenBr2)](PF6)2 (RuL2): Crystals suit-
able for X-ray analysis were obtained from acetone/water.
C48H54Br2F12N6P2Ru·1.25C3H6O·0.5H2O, Mr = 1322.87 gmol–1,
red–brown prism, size 0.05ϫ0.05ϫ0.04 mm, triclinic, space group
Luminescence lifetime measurements were obtained by using an
Edinburgh Analytical Instrument (EAI) time-correlated single-
photon-counting apparatus (TCSPC) comprised of two model J-
yA monochromators (emission and excitation), a single-photon-
photomultiplier detection system model 5300 and a F900 nanose-
cond flashlamp (nitrogen filled at 1.1 atm pressure, 40 kHz or
0.3 atm pressure, 20 kHz) interfaced with a personal computer by
a NorlandMCA card. A 410-nm cut-off filter was used for the
emission measurements to attenuate scatter of the excitation light
(337 nm); luminescence was monitored at the λmax of the emission.
Data correlation and manipulation was carried out by using EAI
F900 software version 6.24. Emission lifetimes were calculated with
a single-exponential fitting function, Levenberg–Marquardt algo-
rithm with iterative deconvolution (Edinburgh instruments F900
software). The reduced χ2 (Ͻ1.05) and residual plots were used to
judge the quality of the fits. Lifetimes are Ϯ5%.
¯
P1, a = 16.6627(3), b = 19.7941(5), c = 19.9314(5) Å, α = 83.234(1),
β = 65.869(1), γ = 81.967(1)°, V = 5927.1(2) Å3, T = –90 °C, Z =
4, ρcalcd. = 1.482 gcm–3, µ (Mo-Kα) = 17.45 cm–1, F(000) = 2670,
42776 reflections in h(–21/21), k(–25/25), l(–25/23), measured in the
range 2.69°ՅΘՅ27.46°, completeness Θmax = 99.2%, 26922 inde-
pendent reflections, Rint = 0.0346, 18497 reflections with Fo
4σ(Fo), 1252 parameters, 0 restraints, R1obs = 0.0785, wR2obs
Ͼ
=
0.2096, R1all = 0.1176, wR2all = 0.2452, GOOF = 1.011, largest
difference peak and hole 2.049/–2.074 eÅ–3.
Crystal Data for [(tbbpy)2Ru{phen(tfmp)2}](PF6)2 (RuL3): Crystals
suitable for X-ray analysis were obtained from acetone/water.
C67H66F24N6OP2Ru, Mr
=
1590.27 gmol–1, red prism, size
¯
0.38ϫ0.10ϫ0.01 mm, triclinic, space group P1, a = 16.3058(2), b
= 19.910(3), c = 24.570(3) Å, α = 94.772(7), β = 90.300(6), γ =
104.524(5)°, V = 7691.9(17) Å3, Z = 4, ρcalcd. = 1.373 gcm–3, µ
(Mo-Kα) = 2.944 mm–1, F(000) = 3232, 116847 reflections mea-
sured in the range 1.80°ՅΘՅ70.09°, 24257 independent reflec-
The resonance Raman spectra were measured with a conventional
90°-scattering arrangement. The excitation lines at 488 and 458 nm
Eur. J. Inorg. Chem. 2009, 4962–4971
© 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
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4969

J. Popp, S. Rau et al.
FULL PAPER
tions, 1823 parameters, R1obs = 0.1908, wR2obs = 0.4320, GOOF =
1.266, largest difference peak and hole 2.591/–1.102 eÅ–3.
and LR: All prepared complexes contain tbbpy to increase the solu-
bility in less polar organic solvents and were prepared by using a
somewhat modified standard procedure.[14,50] For the complexation
reaction, [(tbbpy)2RuCl2] (0.05 g, 0.07 mmol) and the correspond-
ing ligand LR (R = 1, 2, 3, 4; 0.07 mmol) were suspended in eth-
anol/water (50 mL/30 mL) and heated at reflux for 2 h with micro-
wave irradiation (microwave setup: 30 s, 400 W; 2 h, 150 W, 10 min
ventilation). After cooling to room temperature, the red solution
was filtered, followed by evaporation of 90% of the solvent on the
rotary evaporator. An aqueous solution of NH4PF6 was then
added, and the precipitate was removed by filtration, washed with
water and a small amount of EtOH and Et2O and dried in air.
3,8-Dibromo-1,10-phenanthroline (L2): For this synthesis a slightly
modified literature procedure was used.[8] 1,10-Phenanthroline
monohydrate was treated with Br2 in the presence of S2Cl2 and
pyridine to afford 3,8-dibromo-1,10-phenanthroline. The workup
procedure was slightly modified relative to reported approaches.
First, the crude product was purified with column chromatography
(with silica and chloroform) and then recrystallised from a mixture
of carbon tetrachloride and chloroform. At the end, a white pow-
der was obtained. Yield: 6.01 g (64%). 1H NMR (CDCl3,
400 MHz): δ = 9.126 (d, J = 2.4 Hz, 2 H), 8.594 (d, J = 2.4 Hz, 2
H), 7.743 (s, 2 H) ppm. MS (DEI): m/z (%) = 338 (100) [M + H+],
259 (65) [M – Br + H+], 178 (34) [M – 2Br + H+].
[(tbbpy)2Ru(phenBr2)](PF6)2 (RuL2): Yield: 0.08 g (91%).
C48H54Br2F12N6P2Ru (1265.80): calcd. C 43.00, H 4.33, N 6.69;
found C 43.17, H 4.52, N 6.35. 1H NMR ([D3]CD3CN, 400 MHz):
δ = 8.805 (d, J = 1.6 Hz, 2 H), 8.486 (d, J = 1.6 Hz, 2 H), 8.452
(d, J = 1.6 Hz, 2 H), 8.173 (s, 2 H), 7.997 (d, J = 1.6 Hz, 2 H),
7.623 (d, J = 6.0 Hz, 2 H), 7.452 (dd, J = 5.6, 2.0 Hz 2 H), 7.437
(d, J = 6.0 Hz, 2 H), 7.215 (dd, J = 6.0, 2.0 Hz, 2 H), 1.438 (s, 18 H,
tert-butyl), 1.379 (s, 18 H, tert-butyl) ppm. 13C NMR ([D3]CD3CN,
100 MHz): δ = 30.43, 30.47, 36.27, 36.36, 122.04, 122.62, 125.34,
125.60, 129.36, 132.41, 139.57, 147.23, 152.23, 152.63, 154.23,
157.64, 158.10, 163.80, 163.92 ppm. MS (ESI in CH3CN and
MeOH): m/z (%) = 1121.1 (100) [M – 1PF6]+ with matching iso-
topic pattern, 487.8 (10) [M – 2PF6/2]2+ with matching isotopic
pattern.
3,8-Bis[{3,5-bis(trifluoromethyl)}phenyl]-1,10-phenanthroline (L3):
The catalytic reaction was run under a nitrogen atmosphere. 3,8-
dibromo-1,10-phenanthroline (L2, 0.08 g, 0.24 mmol), 3,5-bis(tri-
fluoromethyl)phenylboronic acid (0.13 g, 0.50 mmol), Cs2CO3
(3.2 g, 0.01 mol), S-Phos (6 mg, 0.014 mmol, 6 mol-%) were placed
together into a Schlenk tube. Thereafter, freshly distilled tertrahyd-
rofuran (70 mL) and deoxygenated water (5 mL) were added. The
mixture was stirred and degassed with nitrogen for 30 min. After
addition of Pd2(dba)3 (6 mg, 0.007 mmol, 3 mol-%), the yellow re-
action mixture was heated at reflux under nitrogen for 3 d. The
suspension was then cooled to room temperature, taken up into
water and extracted with chloroform. The solvent of the combined
organic layers was removed, and the crude product was dried under
vacuum. The residue was cleaned by column chromatography by
collecting the main fluorescent band (silica and chloroform). Yield:
0.14 g (95%). 1H NMR (CDCl3, 400 MHz): δ = 9.438 (d, J =
2.0 Hz, 2 H); 8.488 (d, J = 2.0 Hz, 2 H), 8.192 (m, 4 H), 7.990 (m, 4
H) ppm. 13C NMR (CDCl3, 100 MHz): δ = 120.10, 125.52, 127.26,
128.40, 132.18, 132.84, 133.12, 133.97, 139.37, 145.50, 148.64 ppm.
[(tbbpy)2Ru{phen(tfmp)2}](PF6)2 (RuL3): Yield: 0.08 g (74%).
C64H60F24N6P2Ru·1H2O: calcd. C 49.58, H 4.03, N 5.42; found C
49.11, H 3.82, N 5.31. 1H NMR ([D3]CD3CN, 400 MHz): δ = 8.979
(d, J = 2.0 Hz, 2 H), 8.483 (d, J = 2.0 Hz, 2 H), 8.447 (d, J =
2.0 Hz, 2 H), 8.351 (s, 2 H), 8.155 (m, 4 H), 8.137 (d, J = 2.0 Hz,
2 H), 7.755 (d, J = 6.0 Hz, 2 H), 7.576 (d, J = 6.0 Hz 2 H), 7.479
(dd, J = 5.6, 1.6 Hz, 2 H), 7.229 (dd, J = 6.0, 2.0 Hz, 2 H), 1.399
(s, 18 H, tert-butyl), 1.338 (s, 18 H, tert-butyl) ppm. 13C NMR
([D3]CD3CN, 100 MHz): δ = 30.41, 36.25, 36.33, 122.54, 122.67,
122.97, 123.94, 125.25, 125.39, 125.68, 129.38, 129.96, 131.96,
132.81, 133.15, 133.48, 135.97, 136.74, 139.08, 148.13, 151.86,
152.72, 157.86, 158.29, 163.57, 163.82 ppm. MS (ESI in CH3CN
and MeOH): m/z (%) = 1387.1 (29) [M – 1PF6]+ with matching
isotopic pattern, 621.1 (100) [M – 2PF6/2]2+ with matching isotopic
pattern.
MS (DEI): m/z (%) = 605 (100) [M + H+], 302 (23) [M/2]2+
.
3,8-Bis(phenylacetylene)-1,10-phenanthroline (L4): The synthetic
procedure used for 3,8-bis(phenylacetylene)-1,10-phenanthroline is
based on the report by Tor et al., but was slightly changed.[10] The
Pd-catalysed Sonogashira cross-coupling reactions were carried out
under an argon atmosphere. Furthermore, the use of ultrasound
and a temperature of 40 °C were necessary to introduce the alkyne
functions. At first a standard Schlenk vessel was charged with 3,8-
dibromo-1,10-phenanthroline (0.2 g, 0.59 mmol), Pd(PPh3)2Cl2
(0.042 g, 0.06 mmol, 10.0 mol-%), copper iodide CuI (0.023 g,
0.12 mmol, 20.0 mol-%), methanol (12 mL) and dry triethylamine
(18 mL). Finally, excess phenylacetylene (0.15 mL, 1.37 mmol) was
added. The yellowish suspension was then sonicated at 40 °C under
argon for 8 h. Thereafter, the reaction mixture was heated to 50 °C
and stirred for 1 d. The suspension was then cooled to room tem-
perature, taken up into an aqueous solution of potassium cyanide
(0.02 g, 0.31 mmol) and dichloromethane. The water phase was
well extracted with dichloromethane, and the solvent of the com-
bined organic layers was removed. The crude product was then
dried under vacuum. The residue was cleaned by column
chromatography by collecting the main fluorescent band (silica and
[(tbbpy)2Ru{phen(phac)2}](PF6)2 (RuL4): Yield: 0.065 g (71%).
C64H64F12N6P2Ru (1308.24): calcd. C 58.76, H 4.93, N 6.42; found
C 58.98, H 4.45, N 6.24. 1H NMR ([D3]CD3CN, 400 MHz): δ =
8.687 (d, J = 1.6 Hz, 2 H), 8.521 (d, J = 2.0 Hz, 2 H), 8.479 (d, J
= 2.0 Hz, 2 H), 8.217 (s, 2 H), 8.060 (d, J = 2.0 Hz, 2 H), 7.700 (d,
J = 6.0 Hz, 2 H), 7.541 (m, 10 H), 7.519 (d, J = 6.4 Hz, 2 H), 7.468
(dd, J = 6.4, 2.0 Hz, 2 H), 7.244 (dd; J = 6.0, 2.0 Hz, 2 H), 1.431
(s, 18 H, tert-butyl), 1.358 (s, 18 H, tert-butyl) ppm. 13C NMR
([D3]CD3CN, 100 MHz): δ = 30.42, 30.49, 36.26, 36.37, 85.43,
96.61, 122.26, 122.59, 122.64, 123.33, 125.39, 125.66, 129.50,
129.89, 130.95, 131.58, 132.67, 139.11, 147.31, 152.22, 152.52,
154.84, 157.71, 158.13, 163.66, 163.76 ppm. MS (ESI in MeOH):
m/z (%) = 1163.2 (100) [M – 1PF6]+ with matching isotopic pattern,
1017.2 (11) [M – 2PF6 – H]+ with matching isotopic pattern.
1
CH2Cl2/MeOH in a ratio of 20:1). Yield: 0.18 g (81%). H NMR
(CDCl3, 400 Hz): δ = 9.283 (d, J = 1.6 Hz, 2 H), 8.390 (d, J =
2.0 Hz, 2 H), 7.803 (s, 2 H), 7.605 (m, 4 H), 7.393 (m, 6 H) ppm.
13C NMR (CDCl3, 100 MHz): δ = 30.89, 85.78, 94.90, 120.47,
122.13, 127.02, 128.33, 128.55, 129.22, 131.89, 138.76, 151.88 ppm.
Acknowledgments
This work was financially supported by the Deutsche Forschungs
gemeinschaft (DFG) and the Deutscher Akademischer Austausch
Dienst (DAAD). D. C. and G. S. H. thank the Natural Sciences
MS (DEI): m/z (%) = 380 (100) [M + H+], 190 (8) [M/2]2+
.
Typical Procedure for Preparation of RuLR (R = 1, 2, 3, 4) from
[(tbbpy)2RuCl2] (where tbbpy = 4,4Ј-di-tert-butyl-2,2Ј-bipyridine) and Engineering Research Council of Canada (NSERC) and the
4970 Eur. J. Inorg. Chem. 2009, 4962–4971
www.eurjic.org
© 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

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Received: April 3, 2009
Published Online: October 13, 2009
Eur. J. Inorg. Chem. 2009, 4962–4971
© 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjic.org
4971