Acetylene-substituted pyrazino[2,3-f][1,10]phenanthrolines and their Ru(II) complexes: Syntheses, electronic properties and an exploration of their suitability as building blocks for metal-coordinated dehydroannulenes

Article abstract of DOI:10.1039/b110660k

Aryl- and silyl-terminated 6,7-dialkynylpyrazino[2,3-f][1,10]phenanthrolines (pyzphen) have been prepared by the condensation of [1,10]phenanthroline-5,6-diamine with appropriately functionalised dialkynyl-1,2-diones. These new ligands were used as chelators in the formation of the corresponding [Ru(bpy)₂(pyzphen)]·2PF₆ and [Ru(phen)₂(pyzphen)]·2PF₆ complexes. The terminally free diethynyl [Ru(bpy)₂(pyzphen)] complex, obtained by protodesilylation of a silyl-protected precursor, was shown to be amenable to oxidative acetylene hetero-coupling reactions with arylacetylenes and allowed the preparation of the corresponding butadiynyl-substituted derivatives. Homo-coupling reactions of the terminally free diethynyl [Ru(bpy)₂(pyzphen)] complex to produce cyclic dehydroannulene-arrays were successful, but furnished an inseparable mixture of compounds of at least two different ring sizes. The photophysical and electrochemical properties of both the free ligands and their Ru(II)-complexes are clearly modified by the presence of the alkynyl substituents. In comparison with non-acetylenic model compounds it was established that acetylene substitution induces bathochromically shifted electronic absorptions and emissions to various degrees in ligands and complexes, leads to increased luminescence lifetimes and quantum yields of the ruthenium pyzphen complexes, and renders the acetylenic ligands and their complexes more susceptible to electrochemical reduction.

Full text of DOI:10.1039/b110660k

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Acetylene-substituted pyrazino[2,3-f ][1,10]phenanthrolines
and their Ru(II) complexes: syntheses, electronic properties
and an exploration of their suitability as building blocks for
metal-coordinated dehydroannulenes
Rüdiger Faust* and Sascha Ott
Department of Chemistry, Christopher Ingold Laboratories, University College London,
20 Gordon Street, London, UK WC1H 0AJ. E-mail: r.faust@ucl.ac.uk
Received 22nd November 2001, Accepted 22nd March 2002
First published as an Advance Article on the web 10th April 2002
Aryl- and silyl-terminated 6,7-dialkynylpyrazino[2,3-f][1,10]phenanthrolines (pyzphen) have been prepared by
the condensation of [1,10]phenanthroline-5,6-diamine with appropriately functionalised dialkynyl-1,2-diones.
These new ligands were used as chelators in the formation of the corresponding [Ru(bpy)2(pyzphen)]ؒ2PF6 and
[Ru(phen)2(pyzphen)]ؒ2PF6 complexes. The terminally free diethynyl [Ru(bpy)2(pyzphen)] complex, obtained by
protodesilylation of a silyl-protected precursor, was shown to be amenable to oxidative acetylene hetero-coupling
reactions with arylacetylenes and allowed the preparation of the corresponding butadiynyl-substituted derivatives.
Homo-coupling reactions of the terminally free diethynyl [Ru(bpy)2(pyzphen)] complex to produce cyclic
dehydroannulene-arrays were successful, but furnished an inseparable mixture of compounds of at least two different
ring sizes. The photophysical and electrochemical properties of both the free ligands and their Ru()-complexes are
clearly modified by the presence of the alkynyl substituents. In comparison with non-acetylenic model compounds
it was established that acetylene substitution induces bathochromically shifted electronic absorptions and emissions
to various degrees in ligands and complexes, leads to increased luminescence lifetimes and quantum yields of the
ruthenium pyzphen complexes, and renders the acetylenic ligands and their complexes more susceptible to
electrochemical reduction.
π-electron system and will therefore lead to modified electron
acceptor properties of the metal-complexed diimine that could
be put to use in fine-tuning metal–ligand interactions according
Introduction
Ruthenium()-diimine complexes have emerged over the years
as key players in the design of light-harvesting devices,1 as
to the requirements of a given application. The first part of this
photonic nanowires2 and as luminescent probes for the study
hypothesis is corroborated by semiempirical MO calculations
of biomolecules such as DNA3,4 and lipid vesicles.5 Much effort
on 2 (R = H, Fig. 1) that show both its highest occupied molec-
has focussed on the design of appropriately functionalised
chelating ligands to enable a specific application of the metal
coordination compound. A prominent example6 of such a
complex is [Ru(bpy)2(dppz)]2ϩ where the chelating dppz
(dipyrido[3,2-a:2Ј,3Ј-c]phenazine) ligand 1 serves, for example,
as a direct probe for the microenvironment (e.g. as a DNA inter-
calator) and as an acceptor of electron density in light-induced
metal-to-ligand charge transfers. Other phenanthroline-based
ligands have been equipped with multiple binding sites for the
formation of polynuclear metal complexes.7 More recently,
electronically modifying substituents have been implemented
on a naphthophenanthroline ligand that is structurally related
to the dppz system.8,9
Fig. 1 Shape of the HOMO (a) and the LUMO (b) of 6,7-diethynyl-
pyzphen as calculated with the PM3 parameter set.
ular orbital (HOMO) and its lowest unoccupied molecular
orbital (LUMO) to have large contributions from the alkynyl
subunits.
Secondly, the acetylenes provide a flexible synthetic handle
for further functionalisations10–12 and may enable the assembly
We wish to present here the dialkynyl-substituted pyrazino-
[2,3-f][1,10]phenanthrolines (pyzphen) 2 as a new structural
motif for chelating diimine ligands. Our interest in these
compounds is twofold: On the one hand, the alkynyl substit-
uents of 2 are an integral part of the ligand’s delocalised
of dehydroannulene scaffolds with a cyclic array of exotopic
metal coordination sites by oxidative acetylene coupling
reactions.13 First examples for architectures of this type have
sporadically emerged in the recent literature,14–16 but in no case
has 2 been exploited as a building block.
1946
J. Chem. Soc., Dalton Trans., 2002, 1946–1953
This journal is © The Royal Society of Chemistry 2002
DOI: 10.1039/b110660k

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Outlined herein are the syntheses of the acetylenic pyzphen
ligands, their conversion into [Ru(bpy)2(pyzphen)]2ϩ and [Ru-
(phen)2(pyzphen)]2ϩ complexes, a discussion of some of their
photophysical and electrochemical properties, and a prelimin-
ary study of the suitability of these complexes for metal-ligated
dehydroannulene frameworks.
Results and discussion
1
Syntheses
by mass spectrometry and H-NMR spectroscopy, but which
was found to be almost insoluble in common organic solvents,
most disappointingly also in those traditionally used for oxid-
ative acetylene coupling reactions (MeOH, CHCl3, acetone,
pyridine, 1,2-dichlorobenzene). The pyzphen system 2c, which
is equipped with the more labile dimethylphenylsilyl groups
at the alkyne termini, led to the same compound when proto-
desilylated by K2CO3 in THF at 0 ЊC. Much to our chagrin, the
triisopropylsilyl-protected ruthenium pyzphen complex 5b did
not prove to be a viable starting point for the generation of
terminally free acetylenic pyzphen systems, as it decomposed
rapidly upon attempted removal of the silyl groups with
fluoride.
The condensation of 5,6-diamino[1,10]phenanthroline 317
(Scheme 1) with vicinal diones was thought to be a facile
Finally, our efforts to generate free terminal acetylene groups
on the pyzphen moiety were met with success when a combin-
ation of cationic Ru() solubilising fragment and labile silyl
terminus was used to balance reactivity and solubility. Thus,
complex 5c was smoothly protodesilylated to 5e by stirring the
former together with K2CO3 in MeCN for 15 min (Scheme 2).
Scheme 1 Reagents and conditions: i, AcOH, rt, 1 h, 2a: 79%, 2b:
72%, 2c: 57%, 2d: 87%; ii, [Ru(bpy)2Cl2]ؒ2H2O, or [Ru(phen)2Cl2]ؒ2H2O,
EtOH, reflux, 16 h, 5a: 78%, 5b: 81%, 5c: 85%, 6a: 84%, 6b: 73%.
method to establish the pyzphen backbone and to study the
effects of varying the substituents in the 6,7-positions. This
strategy was made possible by the availability of the acetylenic
diones 4, a class of compounds which we have recently intro-
duced and which is easily prepared by copper-mediated alkynyl-
ations of oxalyl chloride.18 Of the dialkynyldiones discussed
here, 4a19 and 4b18 have been described previously, whereas 4c
and 4d are new. The dimethylphenylsilyl-terminated dialkynyl-
dione 4c is particularly noteworthy since it is the first stabilised
dialkynyldione from which teminal free acetylenes can be
obtained under the mild conditions of potassium carbonate
mediated protodesilylation.18 We will make use of this bene-
ficial aspect in the course of this study (vide infra).
In accordance with our projections, the acetylenic pyzphen
ligands 2a–d were smoothly obtained by separately stirring 3
and 4a–d in acetic acid at room temperature. The functionalised
heterocycles are colourless or orange (2d) hygroscopic solids
that rapidly turn yellow or brown upon exposure to the atmos-
phere. Refluxing solutions of 2a–c with [Ru(bpy)2Cl2]ؒ2H2O20
in ethanol for several hours furnished, after anion-exchange
with aqueous NH4PF6, the corresponding metal complexes
5a–c as amorphous, deep orange or red solids. For comparison,
the corresponding [Ru(phen)2] complexes 6a and 6b were
prepared in a similar fashion starting from [Ru(phen)2Cl2]ؒ
2H2O21 and 4a,b respectively.
The non-acetylenic reference complexes 8 and 9 were syn-
thesised along similar routes by the condensation of 3 with
benzil and subsequent coordination of the intermediate 6,7-
diphenyl-pyzphen 7 to the [Ru(bpy)2] or [Ru(phen)2] fragments,
respectively.
Scheme 2 Reagents and conditions: i, K2CO3, MeCN, rt, 15 min, 95%;
ii, 4-tert-butylphenylacetylene (for 10) or 4-N,N-dimethylaminophenyl-
acetylene (for 11), CuCl, TMEDA, O2, acetone, rt, 4 h, 10: 74%, 11:
72%.
Compound 5e was isolated as an orange, air-stable solid that is
soluble in dichloromethane, acetonitrile, acetone and DMSO.
Much to our satisfaction, 5e turned out to be amenable
to oxidative acetylene coupling reactions: Hence, subjecting
an acetone solution of 5e to an excess of the respective aryl-
acetylene in the presence of TMEDA, CuCl and air22 furnished
the butadiynyl-substituted Ru() pyzphen complexes 10 and 11
in yields over 70% (Scheme 2).
The successful preparations of the butadiynyl compounds 10
and 11 by oxidative acetylene hetero-coupling suggest that it
should also be feasible to employ 5e for the assembly of cyclic
polynuclear metal arrays by similar homo-coupling reactions
(Scheme 3). Accordingly, when 5e alone was subjected to the
In an effort to investigate the suitability of the newly gener-
ated acetylenic structures to partake in oxidative acetylene
coupling reactions, we initially attempted to protodesilylate
the triisopropylsilyl-terminated pyzphen ligand 2b with tetra-
butylammonium fluoride in THF. However, these experiments
furnished a grey precipitate, whose constitution was established
J. Chem. Soc., Dalton Trans., 2002, 1946–1953
1947

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Table 1 Electronic absorption data of [Ru()(pyzphen)]-complexesa
Absorption λmax/nm (ε/10Ϫ4 dm3 molϪ1 cmϪ1
)
5a
5b
5c
5e
6a
6b
8
288 (87)
288 (84)
287 (107)
282 (100)
265 (112)
265 (108)
288 (98)
265 (119)
288 (93)
288 (90)
315 (sh)
360 (sh)
358 (21)
346 (21)
295 (sh)
290 (sh)
391 (33)
377 (23)
374 (26)
362 (25)
317 (sh)
361 (sh)
362 (25)
367 (25)
453 (19)
424 (sh)
453 (15)
453 (18)
451 (21)
450 (sh)
449 (21)
453 (21)
450 (22)
465 (sh)
489 (47)
424 (sh)
423 (sh)
393 (45)
377 (45)
421 (sh)
420 (sh)
414 (40)
389 (sh)
9
290 (sh)
10
11
326 (59)
Scheme 3 Reagents and conditions: i, CuCl, TMEDA, O2, acetone,
rt, 4 h.
a All spectra were recorded at room temperature in CH2Cl2.
Hay-coupling conditions, all starting material was rapidly
consumed. Mass spectrometric analysis, using MALDI-TOF
techniques, of the products obtained after chromatographic
purification on alumina confirmed that indeed metal-
coordinated dehydroannulene structures had been formed. Dis-
tinct peaks were observed at m/z ratios of 3919 and 6012,
respectively, corresponding to the molecular ions of tetrameric
dehydro[24]annulene 12 (n = 3) and hexameric dehydro[36]-
annulene 13 (n = 5). Unfortunately, all attempts to isolate
individual [Ru(bpy)2]-coordinated dehydroannulenes from this
mixture by either fractional crystallisation or by size-exclusion
chromatography on Sephadex columns failed. As we did not
succeed in controlling the stoichiometry of the homo-coupling
of 5e to unambiguously prepare just one dehydroannulene ring
size, we are currently exploring alternative synthetic strategies23
to obtain molecular architectures of this type.
Table 2 Electronic emission data of [Ru()(pyzphen)]-complexesa
e
λem/nmb
τf/nsc
τf/nsc, d
Φf
5a
5b
5c
5e
6a
6b
8
602
604
605
610
598
598
595
593
606f
612
350
320
570
490
0.041
0.036
250
240
270
150
330
300
420
190
0.029
0.022
0.028
0.015
9
10
11
a All measurements in CH2Cl2 at rt. b Emission upon excitation at 450
nm. c Luminescence lifetimes 10%. d Dearated solution. e Lumines-
cence quantum yields ( 20%) relative to [Ru(bpy)3Cl2] in aerated H2O
(Φ = 0.028). f λex = 465nm.
Electron absorption and emission data
In agreement with our preliminary PM3-MO calculation on
the electronic structure of the pyzphen ligands (vide supra),
the influence of the acetylene substituents on the electronic
properties of the heterocycles is clearly observable in their
respective electronic absorption spectra (Fig. 2). The longest
donor and the pyzphen acceptor unit. The effect of alkynyl-
substitution is subdued, however, in the emission spectra of
the pyzphen heterocycles, where excitation at wavelengths of
the respective absorption maximum around 320 nm results in
emissions ranging between 408 (2b, 2c) and 415 nm (2a) relative
to 403 nm in 7 (data not shown).
The presence of alkyne substituents is also apparent from
an inspection of the photophysical data of the Ru(pyzphen)-
complexes (Tables 1 and 2, Fig. 3), albeit to varying degrees. In
Fig. 2 Electronic absorption spectra of 2a (–ؒؒ–), 2b (---), 2d (——)
and 7 (ؒ ؒ ؒ) at room temperature in dichloromethane.
wavelength absorptions of 2a,b,d are substantially batho-
chromically shifted (by up to 90 nm in the order 2d > 2a > 2b)
relative to that of the non-acetylenic reference compound 7 and
are more intense than that of the latter. Further fine-tuning of
the absorption properties of the alkynyl pyzphen systems can
be achieved by substituting the terminal aryl group, suggesting
that electron delocalisation is operational throughout the
heterocyclic π-system. Hence, dimethylamino-substituted 2d
displays a significantly red-shifted longest wavelength absorp-
tion relative to that of unsubstituted 2a. The observed red
shift could be further enhanced by the possibility of an
intramolecular charge-transfer between the terminal amine
Fig. 3 Emission spectra of 5a (ؒ ؒ ؒ), 8 (---), and 10 (——) in
dichloromethane at room temperature upon excitation at 450 nm.
all cases, the absorption spectra of the complexes are domin-
ated by intense absorptions at relatively short wavelengths
around 265 nm (series 6 and 9) and 290 nm (series 5 and 8, 10,
11). The longest wavelength absorption maxima in ethynyl-
substituted pyzphen complexes of series 5 and 6, usually
assigned as metal-to-ligand charge transfer bands,24 remain
largely invariant around 450 nm and do not differ significantly
from those of the non-acetylenic reference complexes 8 and 9.
1948
J. Chem. Soc., Dalton Trans., 2002, 1946–1953

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Table 3 Electrochemical data of pyzphen ligands and their Ru()-
The differences are more marked when comparing the absorp-
tions of 8 and those of the butadiynyl pyzphen complexes 10
and 11, which show red-shifted longest wavelength absorptions
at 465 nm and 489 nm, respectively.
a
complexes
E1/2(RuII/III)/V
Ered/V
Alkynyl-substitution of the chelating pyzphen ligands also
effects the luminescence properties of the corresponding Ru()
coordination compounds (Table 2, Fig. 3). For example, the
emissions of the [Ru(bpy)2(pyzphen)] complexes 5a–c, 5e, 10
and 11 are slightly bathochromically shifted (up to 17 nm) with
respect to that of non-acetylenic 8. A similar, although less
pronounced trend can be noted when the auxiliary chelating
ligands of the ruthenium complexes are changed from bpy to
phen. Thus, when comparing the stimulated emissions of com-
plexes 6a,b and 9, a bathochromic shift of ca. 5 nm is observed
in the case of the acetylenic pyzphen complexes 6a,b. As the
emissions in Ru-diimine complexes are thought to arise from
excited MLCT states24 it therefore appears that the nature of
the distal pyzphen ligand substituents does have a small, but
non-negligible, influence on the electronic interaction between
metal and ligand. This is in agreement with the behaviour of
[Ru(bpy)2(dppz)]2ϩ whose MLTC transitions were shown to be
vectorial and involve the more readily electron-accepting dppz
ligand.6 The emission observed in this complex at 610 nm there-
fore arises from excited states localised on the dppz moiety,
although the exact nature of these states (a singlet MLCT
dppz radical anion or a triplet ππ* state) is still a contentious
issue.25–28
The notion that alkynyl-substitution does impinge on the
electronic properties of [Ru(pyzphen)]-complexes is further
corroborated upon inspection of their luminescence lifetimes
and quantum yields (Table 2). In the compounds investigated
here, alkynyl-substitution generally results in extended lumin-
escence lifetimes and increased luminescence quantum yields in
both the bpy and the phen series. Thus, whereas τ of acetylenic
5a,b in air-equilibrated solutions are 350 ns and 320 ns
respectively, the corresponding value for 8 is, with τ = 270 ns,
considerably shorter. A similar trend is observed in the series of
[Ru(phen)2(pyzphen)]-complexes, where the luminescence life-
time differences between 6a,b and 9 amount to 100 ns and 90 ns,
respectively. The differences in the luminescence lifetimes
between acetylenic and non-acetylenic systems becomes equally
apparent in the absence of oxygen, where the lifetimes of 5a
and 5b are increased by 63% and 53% to 570 ns and 490 ns,
respectively, whereas that of 8 increases by 56% to 420 ns with
respect to those measured in aerated solutions. The extended
luminescence lifetimes of dialkynyl-pyzphen complexes are
accompanied by increased luminescence quantum yields, most
prominently so within the series of the phen complexes, in
which ꢀ almost doubles on going from non-acetylenic 9 (ꢀ =
0.015) to acetylenic 6a (ꢀ = 0.029). Again, the highest value is
observed in case of phenylethynyl-substituted 5a (ꢀ = 0.041).
Clearly, all alkynyl-pyzphen bearing ruthenium-complexes
presented here are more efficient fluorophores than [Ru(bpy)2-
(dppz)]2ϩ (τ = 270 ns, ꢀ = 0.021 in EtOH),6 a conclusion which
suggests an evaluation of the suitability of the new systems in
biological applications similar to those of the latter.
2a
2b
2d
7
Ϫ1.49b
Ϫ1.53b
Ϫ1.56b
Ϫ1.81b
Ϫ1.13d
Ϫ1.16
c
5a
5b
5e
6a
6b
8
1.24
1.25
1.24
1.25
1.25
1.23
1.23
1.24
1.24e
Ϫ1.56d
Ϫ1.53
Ϫ1.11d
Ϫ1.14d
Ϫ1.17d
Ϫ1.36
Ϫ1.57d
Ϫ1.50d
Ϫ1.49d
Ϫ1.59
9
Ϫ1.38d
Ϫ0.95d
Ϫ1.00d
Ϫ1.53d
10
11
a Potentials were determined by cyclovoltammetry with a scan rate of
0.05 V sϪ1 on a Pt working electrode vs. Fc/Fcϩ at rt in deaerated MeCN
(Ru-complexes) or CH2Cl2 (ligands) using 0.1 M NBu4BF4 as support-
ing electrolyte. b Redox potentials E1/2 c Irreversible oxidation at 0.83 V.
.
d Irreversible. e Additional oxidation at 0.87 V.
tion pattern is possible. Coordination of these ligands to the
[Ru(bpy)2]2ϩ-fragment leads to less negative first reduction
potentials, although the differences in the case of the acetylenic
ligands are relatively small (cf. Ϫ1.49 V for 2a and Ϫ1.13 V for
5a). It is more pronounced for the non-acetylenic reference
compounds 7 and 8 (∆E = 0.54 V). A potential difference of
∆E = 0.32 V was observed for the dppz/[Ru(bpy)2(dppz)]2ϩ
system and was interpreted as a reflection of the limited elec-
tronic coupling between the ruthenium cation and the dppz
ligand.6 Apparently, the electrochemical behaviour of acetylenic
[Ru(pyzphen)]-complexes seems to mirror that of the [Ru(bpy)2-
(dppz)]2ϩ system, and it is perhaps not surprising, therefore,
that the redox potential of the Ru()/Ru()-couple remains
largely unaffected by the nature of the pyzphen ligands.
There is little variation between the reduction potentials of
bpy- and phen-ligated [Ru(pyzphen)]-complexes, suggesting
that in all cases the pyzphen ligand serves as the initial electron
acceptor. In agreement with the electrochemical behaviour of
the uncoordinated pyzphen heterocycles, the complexes are
more easily reduced if the pyzphen ligands are acetylene substi-
tuted (cf. Ϫ1.13 V for 5a vs. Ϫ1.36 V for 8). The introduction of
a second acetylene unit further facilitates electron uptake,
as can be observed from the reduction potential of the
butadiynyl-system 10 (Ϫ0.95 V) and 11 (Ϫ1.00 V). However,
while secondary, presumably bpy- and phen-centred reductions
are found around potentials of ca. Ϫ1.5 V for the ethynyl-
complexes of series 5 and 6, the radical-anions of 10 and 11
rapidly decompose and a subsequent reduction of their bpy
ligands is not observed even at scan rates of up to 300 mV sϪ1
.
Conclusions
This work has established a convenient route to acetylene-
substituted pyzphen heterocycles and their corresponding
[Ru(bpy)2]- and [Ru(phen)2]-complexes. The condensation
between phen-diamine and the functionalised dialkynyl-1,2-
diones, which lies at the core of the pyzphen construction, can
be readily adapted to provide a variety of substituted dialkynyl
pyzphen ligand systems. While oxidative acetylene coupling
reactions are feasible with terminally free acetylenic Ru-
pyzphen complexes and lead to the corresponding butadiynyl
derivatives, the absence of stoichiometry control during
analogous homo-coupling reactions prevented the isolation of
discrete metal-coordinated dehydroannulenes, pointing at the
need for a different synthetic strategy to access these complex
architectures.
Electrochemical data
The electrochemical data (Table 3) also reflect a marked influ-
ence of the alkynyl substituents on the electronic properties of
the pyzphen ligands and their ruthenium complexes. Due to
their expanded π-systems,29 reduction of the acetylenic com-
pounds 2a,b and 2d occurs at potentials that are ca. 300 mV less
negative than that of 7. Not unexpectedly, the most facile
reduction along the series occurs at the extended π-system of
phenyl-terminated 2a. Electron-donor substituted 2d, on the
other hand, exhibits a first reduction potential that is 70 mV
lower, thereby reemphasising the fact that a fine-tuning of the
ligand’s electronic properties by variation of the aryl substitu-
The presence of alkynyl substituents on the pyzphen core
clearly manifests itself in the optical and electrochemical
J. Chem. Soc., Dalton Trans., 2002, 1946–1953
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properties of both the free ligands and their corresponding
ruthenium complexes. Alkynyl substitution leads to batho-
chromically shifted absorptions and emissions, increased
luminescence lifetimes and luminescence quantum yields as
well as to more readily reducible systems. In particular the
luminescence and the electrochemical behaviour of the
ruthenium dialkynyl-pyzphen complexes resemble those of
[Ru(bpy)2(dppz)]2ϩ, a compound widely used as a luminescent
probe. Compared to related peripherally substituted dppz-
ligands that have been employed for this purpose,4 the ease
with which the new pyzphen systems can be structurally
varied renders them a valuable alternative for this type of
application.
dimethylphenylsilylacetylene,33 3,17 p-ethynyl-N,N-dimethyl-
aniline,34 p-tert-butylphenyl-acetylene,35 [Ru(bpy)2Cl2]ؒ2H2O,20
and [Ru(phen)2Cl2]ؒ2H2O21) were synthesised according to
the literature procedures. All other reagents are available
from commercial suppliers and were used without further
purification.
1,6-Bis(dimethylphenylsilyl)hexa-1,5-diyne-3,4-dione (4c)
To a cooled (0 ЊC) solution of dimethylphenylsilylacetylene33
(1.334 g, 8.33 mmol) in THF (10 ml) was added BuLi (5.2 ml of
a 1.6 M solution in hexane, 8.33 mmol). After stirring for 15
min at 0 ЊC this solution was added to a solution of pre-dried
LiBr (1.45 g, 16.67 mmol) and CuBr (1.195 g, 8.33 mmol) in
THF (50 ml) at 0 ЊC via cannula. After stirring for a further
15 min at 0 ЊC an ice-cold solution of oxalyl chloride (480 mg,
3.78 mmol) in THF (10 ml) was added via cannula. Stirring
was continued for one hour before the reaction mixture was
hydrolysed by the addition of a mixture of saturated aqueous
ammonium chloride solution (40 ml) and 1 M HCl (10 ml). The
layers were separated and the aqueous layer was extracted with
diethyl ether (3 × 50 ml). The combined organic layers were
washed with brine (50 ml) and dried over Na2SO4. After evap-
oration of the solvent, the resulting yellow–red oil was filtered
through a plug of silica (eluted with 10% ethyl acetate in
hexane) to furnish an orange oil, yield 633 mg (1.69 mmol,
45%). The compound decomposed slowly even when stored
under argon at Ϫ20 ЊC. (Found: 375.1230. C22H23O2Si2 requires
375.1237); λmax/nm (CH2Cl2) 260 (ε/dm3 molϪ1 cmϪ1 9000);
Experimental
General details
Cyclic voltammetry was carried out on an Autolab PGStat
100 (Ecochimie, Netherlands), controlled by GPES software
(version 4.8). A platinum disc electrode BAS (diameter 1.6 mm)
was used as the working electrode and was polished prior to
each experiment using a suspension of alumina powder in
water. A platinum wire (diameter 0.5 mm) served as a counter
and a silver wire (diameter 0.5 mm) as a quasi reference
electrode. All potentials are given vs. the Fc/Fcϩ couple as
internal standard at 0.31 V vs. SCE.30 Melting points were
determined on a Reichert hotstage and are uncorrected. Micro-
analyses were carried out on a Perkin-Elmer 2400 CHN
machine. UV/Vis–absorption spectra were taken on a Perkin-
Elmer Lambda 40 instrument in dichloromethane. Lumin-
escence spectra were recorded on a Perkin-Elmer LS50B
spectrometer fitted with a red-sensitive R928 photomultiplier
tube. Emission spectra are corrected for photomultiplier
response using calibration curves provided by the manu-
facturer. Luminescence quantum yields were determined on a
SPEX Fluorolog 2 spectrofluorimeter (equipped with an RCA
C31034 Peltier-cooled GaAs photomultiplier) by excitation at
450 nm. The emission spectra are corrected for photomultiplier
response. Luminescence quantum yields were calculated
according to eqn. (1), where s and r stand for sample and
νmax/cmϪ1 (CH Cl ) (CH) 2965 (s), (C᎐C) 2150 (s), (C᎐O) 1680
᎐
᎐
᎐
2
2
(s); δH (400 MHz, CDCl3) 7.60 (2 H, m, Ph), 7.40 (3 H, m,
Ph), 0.51 (6 H, s, CH3); δC (100 MHz, CDCl ) (C᎐O) 171.6,
᎐
3
᎐
(aromatic C) 133.9, 133.8, 130.2, 128.2, (C᎐C) 107.1, 99.8,
᎐
(CH3) Ϫ1.9; m/z (EI-MS) 374 (11%, Mϩ), 187 (36%, Mϩ/2), 159
(100%, Mϩ/2 Ϫ CO).
1,6-Bis(4-N,N-dimethylaminophenyl)hexa-1,5-diyne-3,4-dione
(4d)
The synthesis was performed in analogy to that of 4c. The
reaction was quenched by the addition of a saturated aqueous
ammonium chloride solution (50 ml). The organic layer was
separated and the aqueous layer extracted with dichlorometh-
ane (3 × 50 ml). After removal of the solvents the black residue
was dissolved in dichloromethane (200 ml), washed with water
(3 × 100 ml), brine (50 ml) and dried over Na2SO4. The crude
product, obtained by evaporation of the solvent, was triturated
with boiling ethyl acetate to yield 4d as a deep red solid, yield
703 mg (2.04 mmol, 54%), mp 221–223 ЊC (decomp.) (Found:
C, 76.8; H, 5.9; N, 8.0. C22H20N2O2 requires C, 76.7; H, 5.9;
N, 8.1%); λmax/nm (CH2Cl2) 321 (ε/dm3 molϪ1 cmϪ1 36500), 457
(40000); νmax/cmϪ1 (KBr disc) (C᎐C) 2165 (s), (C᎐O) 1662 (s);
Φs/Φr = Arns2 (area)s/Asnr2 (area)r
(1)
reference standard, respectively, A is the absorbance adjusted
to be ≤0.1 at the selected excitation wavelength and n is
the refractive index of the solvent. [Ru(bpy)3Cl2] was chosen as
the reference standard (ꢀs = 0.028 in air-equilibrated water).31
Time-resolved emission experiments were performed using
a 450 nm pump light delivered by a tunable nanosecond pulsed
solid-state laser (Coherent Infinity XPO and frequency
doubling). The width of the pulse was approximately 2 ns
(fwhm), and its energy was less than 2 mJ/pulse. The emission
was recorded with a streak camera (Hamamatsu C5680–21)
equipped with a M 5677 sweep unit. Infrared spectra were taken
on a Perkin-Elmer 1600 FT-IR instrument either as KBr discs
or in dichloromethane solution. NMR-spectra were recorded
on Bruker AMX400 and Bruker DRX500 machines in CDCl3
᎐
᎐
δH (400 MHz, CDCl3) 7.56 (4 H, d, J = 9.1 Hz, Ph), 6.62 (4 H, d,
J = 9.1 Hz, Ph), 3.04 (12 H, s, CH3); δC (100 MHz, CDCl3)
᎐
(C᎐O) 172.9, (aromatic C) 152.3, 136.2, 111.5, (C᎐C) 105.0,
᎐
᎐
᎐
(aromatic C) 104.7, (C᎐C) 89.2, (CH ) 40.0; m/z (EI-MS) 344
᎐
3
(2%, Mϩ), 172 (100%, Mϩ/2).
or DMSO-d6. Residual protic solvent signals of CHCl3 (δH
=
General procedure for the synthesis of the pyrazino[2,3-f ][1,10]-
phenanthroline ligands
7.24 ppm, δC = 77.0 ppm) and DMSO (δH = 2.49 ppm, δC = 39.5
ppm) were used as internal reference. Signal assignments
in the 1H-NMR were assisted by correlation spectroscopy
(COSY). Mass spectra were recorded on a VG ZAB SE
machine (EI, FAB).
All reactions were conducted in oven-dried glassware under
an atmosphere of argon. Solvents were purified and dried
according to standard procedures32 and were freshly distilled
prior to use. Amines were freshly distilled from KOH. Lithium
bromide was dried at 160 ЊC at 0.1 mmHg for two hours
immediately prior to usage. Known compounds (4a,b,18
To a deaerated solution of the respective 1,2-diketone 4 or
benzil (0.5 mmol) in acetic acid (15 ml) was added phen-
anthroline-5,6-diamine 317 (0.5 mmol) in one portion. The
reaction mixture was stirred for one hour during which time
the colour changed from deep brown to red. The solvent was
removed in vacuo and the red residue was recrystallised from
1
methanol unless otherwise stated. α, β and γ H-NMR signals
refer to protons in the 2, 3 and 4 positions relative to the
phenanthroline nitrogen.
1950
J. Chem. Soc., Dalton Trans., 2002, 1946–1953

View Article Online
6,7-Bis(phenylethynyl)pyrazino[2,3-f ][1,10]phenanthroline (2a)
s, CH3); δC (100 MHz, CDCl3) (aromatic C) 152.0, 151.0, 147.5,
᎐
141.5, 137.3, 133.9, 133.5, 126.7, 123.8, 111.7, 108.2, (C᎐C)
᎐
Yellow solid, yield 171 mg (0.395 mmol, 79%), mp 281–283 ЊC
(decomp.) (Found: C, 83.3; H, 3.6; N, 12.9. C30H16N4 requires
C, 83.3; H, 3.7; N, 13.0%); λmax/nm (CH2Cl2) 284 (ε/dm3 molϪ1
99.3, 86.5, (CH3) 40.1; m/z (EI-MS) 519 (100%, Mϩ).
6,7-Diethynylpyrazino[2,3-f ][1,10]phenanthroline. Tetrabutyl-
ammonium fluoride (1.04 ml of a 1 M solution in THF,
1.04 mmol) was added to a deaerated solution of 2b (310 mg,
0.52 mmol) in THF (10 ml) at 0 ЊC. The grey solid, formed
instantly during the addition, was filtered and washed with
CH2Cl2 (3 × 30 ml), yield 105 mg (0.38 mmol, 72%). The com-
pound was found to be very hygroscopic and almost insoluble
in common organic solvents. It was characterised by 1H-NMR
and EI-MS. δH (400 MHz, CDCl3) 9.46 (2 H, dd, J = 8.2, 1.8 Hz,
γ CH), 9.29 (2 H, dd, J = 4.5, 1.8 Hz, α CH), 7.79 (2 H, dd,
J = 8.2, 4.5 Hz, β CH), 3.70 (2 H, s, acetylenic H); m/z (EI-MS)
280 (100%, Mϩ).
cmϪ1 55500), 322 (sh), 335 (37000), 394 (32000); νmax/cmϪ1
᎐
(CH Cl ) (CH) 3050 (s), 2983 (m), (C᎐C) 2207 (s); δ (400 MHz,
᎐
2
2
H
CDCl3) 9.49 (2 H, dd, J = 8.2, 1.7 Hz, γ CH), 9.25 (2 H, dd,
J = 4.4, 1.7 Hz, α CH), 7.75 (2 H, dd, J = 8.2, 4.4 Hz, β CH),
7.70 (4 H, m, Ph), 7.40 (6 H, m, Ph); δC (100 MHz, CDCl3)
(aromatic C) 152.5, 147.7, 141.0, 138.0, 133.7, 132.3, 129.9,
᎐
128.6, 126.3, 124.0, 121.6, (C᎐C) 96.8, 86.8; m/z (EI-MS) 432
᎐
(100%, Mϩ).
6,7-Bis(triisopropylsilylethynyl)pyrazino[2,3-f ][1,10]phen-
anthroline (2b). The red residue obtained after standard workup
was subjected to column chromatography (neutral aluminium
oxide, hexane–dichloromethane–triethylamine = 65 : 30 : 5).
After recrystallisation from methanol, 2b was isolated as white,
hygroscopic needles, which turned yellow upon exposure to
the ambient conditions, yield 214 mg (0.36 mmol, 72%), mp
175–177 ЊC (Found: C, 72.4: H, 8.2; N, 9.3. C36H48N4Si2
requires C, 72.9; H, 8.2; N, 9.5%); (Found: 593.3495.
C36H49N4Si2 requires 593.3496); λmax/nm (CH2Cl2) 277 (ε/dm3
molϪ1 cmϪ1 62000), 315 (27000), 350 (sh), 358 (sh), 366 (19000),
6,7-Diphenylpyrazino[2,3-f ][1,10]phenanthroline (7). White
solid, yield 131 mg (0.34 mmol, 68%), mp > 300 ЊC (Found: C,
80.9; H, 4.1; N, 14.6. C26H16N4 requires C, 81.2; H, 4.2; N,
14.6%); λmax/nm (CH2Cl2) 269 (ε/dm3 molϪ1 cmϪ1 52000), 311
(21000), 364 (20000); νmax/cmϪ1 (CH2Cl2) (CH) 3060 (s); δH (400
MHz, CDCl3) 9.54 (2 H, dd, J = 8.1, 1.7 Hz, γ CH), 9.26 (2 H,
dd, J = 4.4, 1.7 Hz, α CH), 7.76 (2 H, dd, J = 8.1, 4.4 Hz, β CH),
7.67 (4 H, m, Ph); 7.40 (6 H, m, Ph); δC (100 MHz, CDCl3)
(aromatic C) 152.5, 152.0, 147.6, 138.7, 137.8, 133.3, 130.0,
129.1, 128.3, 127.0, 123.9; m/z (EI-MS) 384 (100%, Mϩ).
376 (20000), 385 (28000); νmax/cmϪ1 (CH2Cl2) (CH) 2946 (s),
᎐
2867 (s), (C᎐C) 2159 (w); δH (400 MHz, CDCl3) 9.42 (2 H, dd,
᎐
J = 8.2, 1.6 Hz, γ CH), 9.23 (2 H, dd, J = 4.5, 1.6 Hz, α CH),
7.75 (2 H, dd, J = 8.2, 4.5 Hz, β CH), 1.28–1.05 (42 H, m, i-Pr);
δC (100 MHz, CDCl3) (aromatic C) 152.5, 147.7, 138.8, 138.0,
General procedure for the preparation of [Ru(bpy)2(pyzphen)]
and [Ru(phen)2(pyzphen)] complexes
᎐
133.7, 126.3, 124.0, (C᎐C) 103.4, 100.2, (CH ) 18.7, (Si–CH)
᎐
3
11.3; m/z (EI-MS) 592 (7%, Mϩ), 549 (23%, Mϩ Ϫ i-Pr), 507
(100%, Mϩ Ϫ 2 i-Pr].
To a stirred, deaerated solution of pyzphen ligands 2 or 7
(0.2 mmol) in ethanol (20 ml) was added either [Ru(bpy)2Cl2]ؒ
2H2O20 (97 mg, 0.2 mmol) or [Ru(phen)2Cl2]ؒ2H2O21 (113 mg,
0.2 mmol). The reaction mixture was heated under reflux for 16
hours in an argon atmosphere. After cooling to 0 ЊC an aqueous
solution of NH4PF6 was added until no further precipitate was
formed. The suspension was stored for 2 hours at Ϫ20 ЊC before
the precipitate was filtered, washed successively with H2O
(10 ml), ethanol (10 ml) and diethyl ether (20 ml) to furnish the
metal complexes as analytically pure orange to red solids.
6,7-Bis(dimethylphenylsilylethynyl)pyrazino[2,3-f ][1,10]phen-
anthroline (2c). The red residue obtained after standard workup
was subjected to column chromatography (silica, 5% methanol
in dichloromethane) and recrystallised from methanol to give
2c as a white, hygroscopic solid, which turned yellow upon
exposure to the ambient conditions, yield 156 mg (0.285 mmol,
57%), mp 157–160 ЊC (decomp.) (Found: C, 74.4; H, 5.0; N,
10.2. C34H28N4Si2 requires C, 74.4; H, 5.1; N, 10.2%); (λmax/nm
(CH2Cl2) 276 (ε/dm3 molϪ1 cmϪ1 60000), 315 (21000), 349 (sh),
357 (sh), 365 (14000), 376 (15000), 384 (21000); (νmax/cmϪ1
[Ru(bpy)2(6,7-bis(phenylethynyl)pyzphen)]ؒ2PF6 (5a). Red
solid, yield 177 mg (0.16 mmol, 78%), mp 265–268 ЊC (decomp.)
(Found: C, 52.0; H, 2.8; N, 9.6. RuC50H32N8(PF6)2ؒH2O
requires C, 52.1; H, 2.8; N, 9.7%); λmax/nm (CH2Cl2) 288 (ε/dm3
᎐
(CH Cl ) (CH) 2975 (s), 2967 (s), (C᎐C) 2158 (w); δ (400
᎐
2
2
H
MHz, CDCl3) 9.44 (2 H, dd, J = 8.2, 1.8 Hz, γ CH), 9.24 (2 H,
dd, J = 4.4, 1.8 Hz, α CH), 7.74 (2 H, dd, J = 8.2, 4.4 Hz, β CH),
7.71 (4 H, m, Ph), 7.40–7.35 (6 H, m, Ph), 0.54 (12 H, s, CH3);
δC (100 MHz, CDCl3) (aromatic C) 152.7, 147.7, 140.2, 138.2,
molϪ1 cmϪ1 87000), 315 (sh), 391 (33000), 453 (19000); νmax
/
cmϪ1 (KBr disc) (CH) 3074 (s), (C᎐C) 2209 (s); δ (500 MHz,
᎐
᎐
H
DMSO-d6) 9.49 (2 H, dd, J = 8.3, 1.3 Hz, lig), 8.87 (2 H, d,
J = 8.3 Hz, bpy), 8.84 (2 H, d, J = 8.3 Hz, bpy), 8.27 (2 H, dd,
J = 5.3, 1.3 Hz, lig), 8.22 (2 H, m, bpy), 8.13 (2 H, m, bpy), 8.02
(2 H, dd, J = 8.3, 5.3 Hz, lig), 7.81 (2 H, m, bpy), 7.77 (4 H, m,
Ph), 7.70 (2 H, m, bpy), 7.61–7.40 (8 H, m, Ph, bpy), 7.38 (2 H,
m, bpy); δC (100 MHz, DMSO-d6) (aromatic C) 156.8, 156.5,
153.8, 151.9, 151.4, 149.3, 141.2, 138.1, 138.0, 137.6, 133.2,
132.1, 131.0, 129.3, 128.7, 127.9, 127.8, 127.7, 124.5, 124.4,
᎐
135.5, 133.9, 133.8, 129.8, 128.0, 126.1, 124.1, (C᎐C) 102.2,
᎐
101.4, (CH3) Ϫ1.2; m/z (EI-MS) 448 (100%, Mϩ), 433 (42%,
Mϩ Ϫ CH3).
6,7-Bis(4-N,N-dimethylaminophenylethynyl)pyrazino[2,3-f ]-
[1,10]phenanthroline (2d). The red residue obtained after
standard workup was dissolved in dichloromethane, the solu-
tion was washed with water and dried (Na2SO4). After removal
of the solvent in vacuo the remaining brown residue was filtered
through a short plug of silica gel. Eluting first with 1% meth-
anol in dichloromethane afforded unreacted diketone, changing
the eluent to 5% methanol in dichloromethane afforded 2d as
an orange solid, yield 225 mg (0.43 mmol, 87%), mp 252–254 ЊC
(decomp.) (Found: C, 78.2: H, 5.0; N, 16.0. C34H26N6 requires
C, 78.7; H, 5.1; N, 16.7%); (Found: 519.2285. C34H27N6 requires
519.2297); λmax/nm (CH2Cl2) 272 (ε/dm3 molϪ1 cmϪ1 38000), 281
ϩ
᎐
120.1, (C᎐C) 97.7, 86.4; m/z (FAB-MS) 846 (34%, M Ϫ 2 PF ).
᎐
6
[Ru(bpy)2(6,7-bis(triisopropylsilylethynyl)pyzphen)]ؒ2PF6
(5b). Orange solid, yield 210 mg (0.16 mmol, 81%), mp > 300 ЊC
(Found: C, 51.1; H, 4.9; N, 8.6. RuC56H64N8Si2(PF6)2ؒH2O
requires C, 51.2; H, 4.9, N, 8.5%); λmax/nm (CH2Cl2) 288 (ε/dm3
molϪ1 cmϪ1 84000), 360 (sh), 377 (23000), 424 (sh), 453 (15000);
νmax/cmϪ1 (KBr disc) (CH) 2945 (s), 2866 (s), (C᎐C) 2156 (w);
᎐
᎐
δH (500 MHz, DMSO-d6) 9.37 (2 H, dd, J = 8.3, 1.2 Hz, lig),
(sh), 294 (sh), 327 (sh), 375 (32000), 439 (41000);); νmax/cmϪ1
8.88 (2 H, d, J = 8.3 Hz, bpy), 8.85 (2 H, d, J = 8.3 Hz, bpy), 8.27
(2 H, dd, J = 5.3, 1.2 Hz, lig), 8.23 (2 H, m, bpy), 8.14 (2 H, m,
bpy), 8.03 (2 H, dd, J = 8.3, 5.3 Hz, lig), 7.83 (2 H, m, bpy), 7.68
(2 H, m, bpy), 7.60 (2 H, m, bpy), 7.37 (2 H, m, bpy), 1.30–1.19
(42 H, m, i-Pr); δC (100 MHz, DMSO-d6) (aromatic C) 156.8,
᎐
(KBr disc) (CH) 3034 (s), 2891 (m), (C᎐C) 2183 (s); δ (400
᎐
H
MHz, CDCl3) 9.48 (2 H, d, J = 8.1 Hz, γ CH), 9.22 (2 H, d,
J = 4.2 Hz, α CH), 7.74 (2 H, dd, J = 8.1, 4.2 Hz, β CH), 7.61
(4 H, d, J = 8.7 Hz, Ph), 6.67 (4 H, d, J = 8.7 Hz, Ph), 3.03 (12 H,
J. Chem. Soc., Dalton Trans., 2002, 1946–1953
1951

View Article Online
156.5, 153.9, 151.7, 151.5, 149.3, 139.5, 138.1, 138.0, 137.9,
DMSO-d6) 9.32 (2 H, dd, J = 8.3, 1.2 Hz, lig), 8.78 (2 H, dd,
J = 8.3, 1.2 Hz, phen), 8.76 (2 H, dd, J = 8.3, 1.2 Hz, phen), 8.38
(4 H, s, phen), 8.20 (2 H, dd, J = 5.4, 1.2 Hz, lig), 8.17 (2 H, dd,
J = 5.2, 1.2 Hz, phen), 8.04 (2 H, dd, J = 5.2, 1.1 Hz, phen), 7.90
(2 H, dd, J = 8.3, 5.4 Hz, lig), 7.77 (4 H, m, phen), 1.28–1.08 (42
H, m, i-Pr); δC (100 MHz, DMSO-d6) (aromatic C) 154.3, 152.9,
᎐
133.2, 128.5, 127.9, 127.8, 127.7, 124.5, 124.4, (C᎐C) 103.0,
᎐
101.1, (CH3) 18.5, (Si–CH) 10.7; m/z (FAB-MS) 1151 (73%, Mϩ
Ϫ PF6), 1005 (38%, Mϩ Ϫ 2 PF6).
[Ru(bpy)2(6,7-bis(dimethylphenylsilylethynyl)pyzphen)]ؒ2PF6
(5c). Orange solid, yield 213 mg (0.17 mmol, 85%), mp 213–215
ЊC (decomp.) (Found: C, 51.1; H, 3.5; N, 9.0. RuC54H44N8Si2-
(PF6)2ؒH2O requires C, 51.1; H, 3.5; N, 8.8%); λmax/nm (CH2Cl2)
287 (ε/dm3 molϪ1 cmϪ1 107000), 358 (21000), 374 (26000), 424
(sh), 453 (18000); νmax/cmϪ1 (KBr disc) (CH) 3088 (s), 2862 (s),
152.6, 149.6, 147.1, 147.0, 139.4, 137.8, 136.9 (2 C), 133.1, 130.4
᎐
(2 C), 128.3, 128.0 (2 C), 127.5, 126.2, 126.1, (C᎐C) 102.9,
᎐
101.1, (i-Pr) 18.4, 10.7; m/z (FAB-MS) 1199 (12%, Mϩ Ϫ PF6),
1054 (9%, Mϩ Ϫ 2 PF6).
᎐
(C᎐C) 2160 (w); δ (400 MHz, DMSO-d ) 9.44 (2 H, dd, J = 8.3,
[Ru(bpy)2(6,7-diphenylpyzphen)]ؒ2PF6 (8). Orange solid, yield
155 mg (0.14 mmol, 71%), mp 258–260 ЊC (Found: C, 50.0; H,
2.7; N, 9.9. RuC46H32N8(PF6)2ؒH2O requires C, 50.0; H, 2.9; N,
10.1%); λmax/nm (CH2Cl2) 288 (ε/dm3 molϪ1 cmϪ1 98000), 362
(25000), 421, (sh), 453 (21000); νmax/cmϪ1 (KBr disc) (CH) 3087
(s); δH (500 MHz, DMSO-d6) 9.59 (2 H, dd, J = 8.2, 1.3 Hz, lig),
8.89 (2 H, d, J = 8.2 Hz, bpy), 8.86 (2 H, d, J = 8.2 Hz, bpy), 8.27
(2 H, dd, J = 5.3, 1.3 Hz, CH), 8.24 (2 H, m, bpy), 8.14 (2 H, m,
bpy), 8.03 (2 H, dd, J = 8.2, 5.3 Hz, lig), 7.86 (2 H, m, bpy), 7.73
(2 H, m, bpy), 7.70 (4 H, m, Ph), 7.62 (2 H, m, bpy), 7.54–7.47
(6 H, m, Ph), 7.38 (2 H, m, bpy); δC (100 MHz, DMSO-d6)
(aromatic C) 156.6, 156.3, 153.4, 153.1, 151.6, 151.2, 148.8,
137.9, 137.8 (2C), 136.9, 132.9, 129.6, 129.4, 129.1, 128.3, 127.7,
127.5, 127.2, 125.3, 125.2; m/z (FAB-MS) 1088 (1%, Mϩ), 944
(100%, Mϩ Ϫ PF6), 798 (32%, Mϩ Ϫ 2 PF6).
᎐
H
6
1.3 Hz, lig), 8.88 (2 H, d, J = 8.3 Hz, bpy), 8.85 (2 H, d, J = 8.3
Hz, bpy), 8.26 (2 H, dd, J = 5.4, 1.3 Hz, lig), 8.23 (2 H, m, bpy),
8.14 (2 H, m, bpy), 7.99 (2 H, dd, J = 8.3, 5.4 Hz, lig), 7.81 (2 H,
m, bpy), 7.73 (4 H, m, Ph), 7.69 (2 H, m, bpy), 7.50–7.43 (8 H,
m, Ph, bpy), 7.39 (2 H, m, bpy), 0.54 (12 H, s, CH3); δC (100
MHz, DMSO-d6) (aromatic C) 156.7, 156.5, 153.9, 151.8,
151.4, 149.4, 140.3, 138.1, 138.0, 137.8, 134.6, 133.7, 133.5,
᎐
130.1, 128.5, 128.2, 127.9, 127.7 (2C), 124.5, 124.4, (C᎐C)
᎐
102.7, 101.7, (CH3) Ϫ1.6; m/z (FAB-MS) 1107 (14%,
Mϩ Ϫ PF6), 962 (14%, Mϩ Ϫ 2 PF6), 135 (100%, PDMSϩ).
[Ru(bpy)2(6,7-diethynylpyzphen)]ؒ2PF6 (5e). Potassium carb-
onate (83 mg, 0.6 mmol) was added to a solution of 5c (250 mg,
0.2 mmol) in acetonitrile (25 ml). After stirring for 15 minutes
at rt, the reaction was hydrolysed with water (25 ml). The result-
ing solution was extracted with dichloromethane (3 × 50 ml).
Drying over Na2SO4, filtration and removal of the solvent
in vacuo afforded a red solid, which was recrystallised from a
mixture of acetonitrile, dichloromethane and diethyl ether. The
orange solid was collected and dried, yield 187 mg (0.19 mmol,
95%), mp > 300 ЊC (Found: C, 45.2; H, 2.5; N, 10.8. RuC38-
H24N8(PF6)2ؒH2O requires C, 45.5; H, 2.4; N, 11.2%); λmax/nm
(CH2Cl2) 282 (ε/dm3 molϪ1 cmϪ1 100000), 346 (21000), 362
[Ru(phen)2(6,7-diphenylpyzphen)]ؒ2PF6 (9). Orange solid,
yield 178 mg (0.16 mmol, 78%), mp > 250 ЊC (Found: C, 52.2;
H, 2.8; N, 9.6. RuC50H32N8(PF6)2ؒH2O requires C, 52.0; H, 2.8;
N, 9.7%); λmax/nm (CH2Cl2) 265 (ε/dm3 molϪ1 cmϪ1 119000), 290
(sh), 367 (25000), 420 (sh), 450 (22000); νmax/cmϪ1 (KBr disc)
(CH) 3086 (s); δH (500 MHz, DMSO-d6) 9.54 (2 H, dd, J = 8.2,
1.1 Hz, lig), 8.78 (2 H, dd, J = 8.2, 1.0 Hz, phen), 8.77 (2 H, dd,
J = 8.2, 1.0 Hz, phen), 8.39 (4 H, s, phen), 8.23 (2 H, dd, J = 5.2,
1.0 Hz, phen), 8.20 (2 H, dd, J = 5.3, 1.1 Hz, lig), 8.07 (2 H, dd,
J = 5.2, 1.0 Hz, phen), 7.89 (2 H, dd, J = 8.2, 5.3 Hz, lig), 7.78
(4 H, m, phen), 7.67 (4 H, m, Ph,), 7.46 (6 H, m, Ph); δC (100
MHz, DMSO-d6) (aromatic C) 153.7, 153.5, 153.0, 152.6,
149.4, 147.1 (2C), 137.8, 137.0, 136.9 (2C), 133.0, 130.4 (2C),
129.7, 129.5, 129.1, 128.4, 128.2, 128.0, 127.2, 126.2, 126.1; m/z
(FAB-MS) 991 (10%, Mϩ Ϫ PF6), 846 (34%, Mϩ Ϫ 2 PF6).
(25000), 423 (sh), 451 (21000); νmax/cmϪ1 (KBr disc) (C᎐CH)
᎐
᎐
᎐
3275 (s), (CH) 3086 (m), (C᎐C) 2113 (s); δ (400 MHz, DMSO-
᎐
H
d6) 9.42 (2 H, dd, J = 8.2, 1.0 Hz, lig), 8.87 (2 H, d, J = 8.3 Hz,
bpy), 8.83 (2 H, d, J = 8.3 Hz, bpy), 8.26 (2 H, dd, J = 5.3, 1.0
Hz, lig), 8.21 (2 H, m, bpy), 8.12 (2 H, m, bpy), 8.00 (2 H, dd,
J = 8.2, 5.3 Hz, lig), 7.80 (2 H, m, bpy), 7.66 (2 H, m, bpy), 7.58
(2 H, m, bpy), 7.35 (2 H, m, bpy), 5.28 (2 H, s, acetylenic H);
δC (100 MHz, DMSO-d6) (aromatic C) 156.7, 156.4, 153.8,
151.7, 151.3, 149.3, 140.4, 138.0, 137.9, 137.8, 133.2, 128.4,
General procedure for oxidative acetylene coupling reactions of
5e and arylacetylenes
᎐
127.8, 127.6 (2C), 124.4, 124.3, (C᎐C) 89.6, 79.7; m/z (FAB-MS)
᎐
839 (66%, Mϩ Ϫ PF6), 694 (56%, Mϩ Ϫ 2 PF6).
Copper() chloride (124 mg 1.25 mmol) was added to a solution
of tetramethylethylenediamine (148 mg, 1.25 mmol) in dry
acetone (5 ml) and the mixture was stirred for 30 minutes. The
resulting deep green solution was added to a solution of 5e (50
mg, 0.05 mmol) and the respective arylacetylene (1.25 mmol)
in dry acetone (150 ml). While stirring, a constant stream of dry
air was bubbled through the reaction mixture. After 4 hours, the
reaction mixture was concentrated in vacuo and filtered through
a plug of alumina. Eluting the plug with dichloromethane
furnished the 1,4-diarylbutadiyne, changing the eluent to a 10
mM solution of NH4PF6 in acetonitrile afforded the product.
[Ru(phen)2(6,7-bis(phenylethynyl)pyzphen)]ؒ2PF6 (6a). Red
solid, yield 200 mg (0.17 mmol, 84%), mp > 250 ЊC (decomp.)
(Found: C, 54.2; H, 2.7; N, 9.3. RuC54H32N8(PF6)2ؒH2O requires
C, 54.0; H, 2.7; N, 9.3%); λmax/nm (CH2Cl2) 265 (ε/dm3 molϪ1
cmϪ1 112000), 295 (sh), 317 (sh), 393 (45000), 450 (sh); νmax
/
cmϪ1 (KBr disc) (CH) 3085 (m), (C᎐C) 2205 (s); δH (400 MHz,
᎐
᎐
DMSO-d6) 9.46 (2 H, dd, J = 8.3, 1.2 Hz, lig), 8.79 (2 H, dd, J =
8.3, 1.2 Hz, phen), 8.77 (2 H, dd, J = 8.3, 1.2 Hz, phen), 8.39
(4 H, s, phen), 8.23 (2 H, dd, J = 5.3, 1.2 Hz, phen), 8.21 (2 H,
dd, J = 5.3, 1.2 Hz, lig), 8.05 (2 H, dd, J = 5.3, 1.2 Hz, phen),
7.89 (2 H, dd, J = 8.3, 5.3 Hz, lig), 7.81 (2 H, dd, J = 8.3, 5.3 Hz,
phen), 7.78–7.75 (6 H, m, phen, Ph), 7.60–7.54 (6 H, m, Ph);
δC (100 MHz, DMSO-d6) (aromatic C) 154.2, 153.1, 152.5,
149.6, 147.1 (2C), 141.1, 137.5, 136.9, 133.1, 132.0 (2C), 130.8,
130.4 (2C), 129.2, 128.5, 128.0, 127.9, 127.4, 126.2, 126.1, 120.1,
[Ru(bpy)2(6,7-bis(4-tert-butylphenylbutadiynyl)pyzphen)]ؒ2PF6
(10). Orange solid, yield 49 mg (0.038 mmol, 74%), mp 198–200
ЊC (decomp.) (Found: C, 56.2; H, 3.8; N, 8.4. RuC62H48N8(PF6)2ؒ
H2O requires C, 56.6; H, 3.6; N, 8.5%); λmax/nm (CH2Cl2) 288
ϩ
᎐
(C᎐C) 97.6, 86.3; m/z (FAB-MS) 894 (3%, M Ϫ 2 PF ).
(ε/dm3 molϪ1 cmϪ1 93000), 414 (40000), 465 (sh); νmax/cmϪ1 (KBr
᎐
6
᎐
disc) (CH) 2961 (s), (C᎐C) 2202 (s); δ (500 MHz, DMSO-d6)
᎐
H
[Ru(phen)2(6,7-bis(triisopropylsilylethynyl)pyzphen)]ؒ2PF6
(6b). Red solid (196 mg, 73%), mp 245–247 ЊC (Found: C, 53.1;
H, 4.8; N, 8.2. RuC60H64N8Si2(PF6)2ؒH2O requires C, 52.9; H,
4.7; N, 8.2%); λmax/nm (CH2Cl2) 265 (ε/dm3 molϪ1 cmϪ1 108000),
9.44 (2 H, dd, J = 8.2, 0.9 Hz, lig), 8.87 (2 H, d, J = 8.3 Hz, bpy),
8.83 (2 H, d, J = 8.3 Hz, bpy), 8.27 (2 H, dd, J = 5.2, 0.9 Hz, lig),
8.22 (2 H, m, bpy), 8.13 (2 H, m, bpy), 8.01 (2 H, dd, J = 8.2, 5.2
Hz, lig), 7.81 (2 H, m, bpy), 7.68 (2 H, m, bpy), 7.68 (4 H, d,
J = 8.4 Hz, Ph), 7.58 (2 H, m, bpy), 7.51 (4 H, d, J = 8.4 Hz, Ph),
7.36 (2 H, m, bpy), 1.29 (18 H, s, t-Bu); δC (100 MHz, DMSO-
290 (sh), 361 (sh), 377 (45000), 449 (21000); νmax/cmϪ1 (KBr
᎐
disc) (CH) 2943 (s), 2865 (s), (C᎐C) 2155 (w); δ (400 MHz,
᎐
H
1952
J. Chem. Soc., Dalton Trans., 2002, 1946–1953

View Article Online
10 H. S. Joshi, R. Jamshidi and Y. Tor, Angew. Chem., Int. Ed., 1999, 38,
d6) (aromatic C) 156.7, 156.4, 154.3, 154.1, 151.8, 151.4, 149.5,
140.3, 138.1, 137.9, 137.6, 133.3, 132.9, 128.4, 127.9, 127.7 (2C),
2722–2725.
11 D. Tzalis and Y. Tor, J. Am. Chem. Soc., 1997, 119, 852–853.
12 A. Harriman and R. Ziessel, Chem. Commun., 1996, 1707–1716.
13 P. Siemsen, R. C. Livingston and F. Diederich, Angew. Chem.,
Int. Ed., 2000, 39, 2632–2657.
᎐
126.0, 124.5, 124.4, 116.1, (C᎐C) 87.5, 81.3, 77.2, 72.0, (CCH )
᎐
3
34.8, (CCH3) 30.7; m/z (FAB-MS) 1151 (81%, Mϩ Ϫ PF6), 1006
(100%, Mϩ Ϫ 2 PF6).
14 M. Schmittel and H. Ammon, Synlett, 1999, 750–752.
15 J.-J. Lagref, M. W. Hosseini, J.-M. Planeix, A. De Cian and
J. Fischer, Chem. Commun., 1999, 2155–2156.
16 S.-S. Sun and A. J. Lees, Organometallics, 2001, 20, 2353–2358.
17 S. Bodige and F. M. MacDonnell, Tetrahedron Lett., 1997, 47,
8159–8160.
18 R. Faust, C. Weber, V. Fiandanese, G. Marchese and A. Punzi,
Tetrahedron, 1997, 53, 14655–14670.
19 R. Faust and C. Weber, Liebigs Ann., 1996, 1235–1238.
20 B. P. Sullivan, D. J. Salmon and T. J. Meyer, Inorg. Chem., 1978, 17,
3334–3341.
21 Prepared in analogy to [Ru(bpy)2Cl2]ؒ2H2O as described in ref. 20.
The compound has been previously described in P. J. Giordano,
C. R. Bock and M. S. Wrighton, J. Am. Chem. Soc., 1978, 100,
6960–6965.
22 G. E. Jones, D. A. Kendrick and A. B. Holmes, Org. Synth., 1987,
65, 52–57.
23 W. B. Wan, S. C. Brand, J. J. Pak and M. M. Haley, Chem. Eur. J.,
2000, 6, 2044–2052.
24 A. Juris, V. Balzani, F. Barigeletti, S. Campagna, P. Belser and
A. von Zelewsky, Coord. Chem. Rev., 1988, 84, 85–277.
25 C. G. Coates, P. L. Callaghan, J. J. McGarvey, J. M. Kelly,
P. E. Kruger and M. E. Higgins, J. Raman Spectrosc., 2000, 31,
283–288.
[Ru(bpy)2(6,7-bis(4-N,N-dimethylaminophenylbutadiynyl)-
pyzphen)]ؒ2PF6 (11). The product was found to be hygroscopic.
Red solid, yield 47 mg (0.037 mmol, 72%), mp > 300 ЊC (Found:
C, 52.3; H, 3.1; N, 10.4. RuC58H42N10(PF6)2ؒ3 H2O requires C,
52.6; H, 3.2; N, 10.6%); λmax/nm (CH2Cl2) 288 (ε/dm3 molϪ1
cmϪ1 90000), 326 (59000), 349 (sh), 489 (47000); νmax/cmϪ1 (KBr
᎐
disc) (CH) 3080 (w), (C᎐C) 2180 (s); δH (400 MHz, DMSO-d6)
᎐
9.43 (2 H, dd, J = 8.2, 1.0 Hz, lig), 8.87 (2 H, d, J = 8.2 Hz, bpy),
8.84 (2 H, d, J = 8.2 Hz, bpy), 8.25 (2 H, dd, J = 5.4, 1.0 Hz, lig),
8.21 (2 H, m, bpy), 8.13 (2 H, m, bpy), 7.99 (2 H, dd, J = 8.2,
5.4 Hz, lig), 7.80 (2 H, m, bpy), 7.68 (2 H, m, bpy), 7.58 (2 H, m,
bpy), 7.53 (4 H, d, J = 8.9 Hz, Ph), 7.37 (2 H, m, bpy), 6.73 (4 H,
d, J = 8.9 Hz, Ph), 3.00 (12 H, s, CH3); δC (100 MHz, DMSO-d6)
(aromatic C) 156.7, 156.4, 153.8, 151.8, 151.5, 151.4, 149.3,
140.5, 138.1, 138.0, 137.6, 134.5, 134.3, 133.3, 128.5, 127.9,
᎐
127.7, 124.5, 124.4, 111.8, 103.8, (C᎐C) 90.7, 83.0, 77.9, 71.8,
᎐
(CH3) 41.3; m/z (FAB-MS) 980 (4% Mϩ Ϫ 2 PF6).
Acknowledgements
26 J. J. McGarvey, P. Callaghan, C. G. Coates, J. R. Schoonover, J. M.
Kelly, L. Jacquet and K. C. Gordon, J. Phys. Chem. B, 1998, 102,
5941–5942.
27 W. Chen, C. Turro, L. A. Friedman, J. K. Barton and N. J. Turro,
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28 E. J. C. Olson, D. Hu, A. Hormann, A. M. Jonkman, M. R. Arkin,
E. D. A. Stemp, J. K. Barton and P. F. Barbara, J. Am. Chem. Soc.,
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29 C. Boudon, J. P. Gisselbrecht, M. Gross, J. Anthony, A. M. Boldi,
R. Faust, T. Lange, D. Philp, J.-D. Van Loon and F. Diederich,
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30 A. J. Bard and L. R. Faulkner, Electrochemical Methods, J. Wiley &
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31 K. Nakamaru, Bull. Chem. Soc. Jpn., 1982, 55, 2697.
32 D. D. Perrin and W. L. F. Armarego, Purification of Laboratory
Chemicals, Pergamon Press, Oxford, 1988.
33 L. Brandsma, Preparative Acetylenic Chemistry, Elsevier,
Amsterdam, 1988.
34 M. J. Bowden and S. R. Turner, Polymers for high technology, ACS
Symposium series, Washington DC, 1987, pp. 453–457.
35 Obtained by bromination of 4-tert-butylstyrene and subsequent
dehydrobromination according to: Organikum, H. G. O. Becker,
W. Berger, G. Domschke, E. Fanghänel, J. Faust, M. Fischer,
F. Gentz, K. Gewald, R. Gluch, R. Mayer, K. Müller, D. Pavel,
H. Schmidt, K. Schollberg, K. Schwetlick and E. Seiler, eds.,
Johann Ambrosius Barth, Heidelberg, 1993. The compound
has been previously described in R. W. Bott, C. Eaborn and
D. R. A. Wilson, J. Chem. Soc., 1965, 384–387.
We wish to thank Daren J. Caruana, UCL, for his help with the
electrochemical measurements, Hans Hofstraat, Luisa de Cola
and Mara Staffilani at the University of Amsterdam for deter-
mining the photophysical data of selected compounds, and a
referee for valuable comments. We wish to acknowledge UCL
for the provision of a Provost studentship to S. O. We are grate-
ful for support from the EPSRC (Grant No. GR/N09503).
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1953