Expanded ligands: Bis(2,2′:6′,2″-terpyridine carboxylic acid)ruthenium(ii) complexes as metallosupramolecular analogues of dicarboxylic acids

Article abstract of DOI:10.1039/b709557k

Ligands in which multiple metal-binding domains are linked by a metal-containing moiety rather than a conventional organic group are described as "expanded ligands". The use of 4,4′-difunctionalised {Ru(tpy)₂} units provides a linear spacer bet

Full text of DOI:10.1039/b709557k

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Expanded ligands: bis(2,2ꢀ:6ꢀ,2ꢀꢀ-terpyridine carboxylic acid)ruthenium(II)
complexes as metallosupramolecular analogues of dicarboxylic acids†
Edwin C. Constable,*a Emma L. Dunphy,a Catherine E. Housecroft,a Markus Neuburger,a Silvia Schaffner,a
Frank Schapera,b and Stuart R. Battenc
Received 22nd June 2007, Accepted 19th July 2007
First published as an Advance Article on the web 14th August 2007
DOI: 10.1039/b709557k
Ligands in which multiple metal-binding domains are linked by a metal-containing moiety rather than
a conventional organic group are described as “expanded ligands”. The use of 4,4ꢀ-difunctionalised
{Ru(tpy)2} units provides a linear spacer between metal-binding domains and we have extended this
motif to expanded ligands containing two carboxylic acid metal-binding domains. In this paper, we
describe the synthesis and structural characterisation of ruthenium(II) complexes of
2,2ꢀ:6ꢀ,2ꢀꢀ-terpyridine-4ꢀ-carboxylic acid and 4ꢀ-carboxyphenyl-2,2ꢀ:6ꢀ,2ꢀꢀ-terpyridine. The ability of the
ruthenium(II) centre to charge compensate deprotonation of the carboxylic acid leads to Zwitterionic
complexes and three representative compounds have been structurally characterised.
Introduction
We have recently been developing the concept of “expanded
ligands” in which metal-binding domains are linked through
9
metal-containing scaffolds.1–8 Typical scaffolds are {M(bpy)3}
and {M(tpy)2}10–12 moieties (bpy = 2,2ꢀ-bipyridine, tpy = 2,2ꢀ:6ꢀ,2ꢀꢀ-
terpyridine), which possess different topological and topographi-
cal properties as well as potentially different numbers of attached
metal-binding domains.13,14
aDepartment of Chemistry, University of Basel, Spitalstrasse 51, 4056 Basel,
Switzerland. E-mail: edwin.constable@unibas.ch; Fax: +41 61 267 1018;
Tel: +41 61 267 1001
This paper is concerned with ruthenium complexes of the
carboxylic acid ligands H1 and H2. The origin of the term
“expanded ligands” is seen in Fig. 1 which presents the ideal
carboxylic acid C · · · C distances in oxalic acid, terephthalic acid,
and the complexes [Ru(H1)2]2+ and [Ru(H2)2]2+. The C · · · C
bCurrent address: Department of Chemistry, University of Montreal, CP
6128, succ. Centre-ville, Montreal, Que, Canada, H3C 3J7
cSchool of Chemistry, Monash University 3800, Australia
† CCDC reference numbers 651821–651823. For crystallographic data in
CIF or other electronic format see DOI: 10.1039/b709557k
˚
distance increases by about 20 A or over 1000% on moving from
oxalic acid to [Ru(H2)2]2+.
Fig. 1 The concept of an expanded ligand exemplified by the comparison of oxalic and terephthalic acids with the complex cations bis[Ru(H1)2]2+ and
[Ru(H2)2]2+
.
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Di- and polycarboxylic acids are widely used as bridging ligands
for the construction of coordination polymers and networks
and have been shown to form a wide variety of one-, two-
and three-dimensional simple or interpenetrated structures.15
Carboxylic acid derivatives of oligopyridines are a reasonably
well-known class of ligands and ruthenium complexes of 2,2ꢀ-
bipyridine-4,4ꢀ-dicarboxylic acid H23 and 2,2ꢀ:6ꢀ,2ꢀꢀ-terpyridine-
4,4ꢀ,4ꢀꢀ-tricarboxylic acid H34 have found widespread application
in dye-sensitised photovoltaic cells.16 Our scaffolds of choice
are kinetically inert d6 ruthenium(II) complexes and although
a number of structural determinations of ruthenium complexes
of 2,2ꢀ-bipyridine 4-17–27, 5-28 and 6-carboxylic acids29–31 have
been reported, the only example of a structurally charac-
terised 2,2ꢀ:6ꢀ,2ꢀꢀ-terpyridine carboxylic acid complex is found
for [NEt4]2[Ru(H24)(NCS)3]32,33 which is the active dye for the
preparation of one popular class of dye-sensitized solar cells. In
these structurally characterised species, the inherent ambiguity in
the protonation state of the carboxylic acid substituents is clearly
demonstrated. The structural complexity arising from the use of
bidentate bpy ligands, which typically results in trifurcated or
hexafurcated structures, has led us to concentrate upon {Ru(tpy)2}
scaffolds. We have, therefore, investigated the behaviour of the
linearly expanded ligand acids [Ru(H1)2]2+ and [Ru(H2)2]2+ each
of which can generate [Ru(H1)2]2+, [Ru(H1)(1)]+ or [Ru(1)2] units
in the crystal, where HL represents H1 or H2. In this paper we
report the synthesis of these complexes and describe the hydrogen
bonding interactions that characterise the solid state species.
The complex [Ru(5)2][PF6]2 was conveniently prepared in the
one pot reaction of commercial RuCl3·3H2O with two equivalents
of 5 in ethane-1,2-diol under microwave heating conditions. After
recrystallisation, the compound was obtained analytically pure
as a red microcrystalline solid in 49% yield. The complex was
fully characterised by conventional spectroscopic methods. A
comparison of the free ligand 5 and the complex [Ru(5)2][PF6]2
revealed the typical upfield shifting of H6A upon coordination.
The furyl protons are all shifted downfield upon coordination and
the assignment of the furyl H3C, which was initially based upon
the 3J3,4 coupling constant was confirmed by the observation of a
cross peak between H3B and H3C in the NOESY spectrum (Fig. 2)
After investigating a variety of conditions for the oxidation of
[Ru(5)2]2+ to [Ru(H1)2]2+ we finally developed a protocol involving
oxidation in neutral aqueous solution with KMnO4. The reaction
can be followed by TLC and additional portions of KMnO4 are
added until no trace of the starting complex is observed. After
work-up and recrystallisation, the complex [Ru(H1)2][PF6]2 was
1
obtained in 48% yield as a red crystalline solid. The H NMR
spectrum of the complex indicates that the furyl substituent is no
longer present and the carboxylic acid CO2H protons are observed
as a broad singlet at d 10.66 ppm in CD3CN solution. The synthetic
transformations are summarised in Scheme 1.
We note that although [Ru(5)2]2+ is stable in the solid state, some
decomposition occurs when a CD3CN solution of [Ru(5)2][PF6]2
is exposed to sunlight over several days. Most NMR signals of the
tpy remained unaffected, while the signals of the furanyl group
were absent in the decomposition product, whose NMR spectra
was nevertheless different from that of [Ru(5)2]2+. We have not
investigated this reaction in detail, but note that the changes are
in accord with partial oxidation of the furan.
Results and discussion
Synthesis of [Ru(H2)2][PF6]2 and related compounds
Synthesis of [Ru(H1)2][PF6]2
A
number of reports have appeared describing ester40
2,2ꢀ:6ꢀ,2ꢀꢀ-Terpyridine-4ꢀ-carboxylic acid H1 is not readily
accessible34–36 and we have developed a new and convenient
synthesis of the complex cation [Ru(H1)2]2+. The key intermediate
is 4ꢀ-(2-furyl)-2,2ꢀ:6ꢀ,2ꢀꢀ-terpyridine 537–39 which has been obtained
from 2-acetylpyridine and 2-furaldehyde under various conditions.
We have optimised the reaction conditions and obtain 5 in 86%
yield from the reaction of 2-acetylpyridine with furaldehyde in
ethanol in the presence of ammonia at 60 ◦C. Beley and coworkers
have shown that the furyl substituent in the complex [Ru(5)(6)]2+
can be oxidised to give the complex [Ru(H1)(6)]2+ directly38 and
we have extended this reaction to the oxidation of [Ru(5)2]2+ to
[Ru(H1)2]2+.
and amide41–44 derivatives of 4ꢀ-(4-carboxyphenyl)-2,2ꢀ:6ꢀ,2ꢀꢀ-
terpyridine H2 together with descriptions of iridium45 and
ruthenium40,46–49 complexes and the use of the ruthenium com-
plexes as carboxylate donor ligands in dirhodium complexes.47 We
have investigated a number of methods for the optimal preparation
of [Ru(H2)2]2+. We originally considered the synthesis of the free
ligand H2 from the ester 7, which was prepared in modest yield
from 2-acetylpyridine and 4-methoxycarbonylbenzaldehyde using
the solvent free conditions introduced by Raston and coworkers50
followed by cyclisation with ammonium acetate in ethanol. The
ester 7 was obtained in 25% yield after recrystallisation which
represents an improvement over our previously reported 15% yield
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Scheme 1
We experienced severe difficulties in defining reproducible condi-
tions for the hydrolysis of the free ligand 7 and under apparently
identical reaction conditions obtained yields varying between 0
and 80%. We have, however, found a reproducible method for
the preparation of the free acid H2 from 2-acetylpyridine and
4-methoxycarbonylbenzaldehyde in aqueous ethanol containing
ammonia and NaOH. After acidic work-up, the desired acid
is obtained in 49% yield as a white microcrystalline material.
The overall yield of 12% over two steps is lower than the 22%
reported by Campagna45 but using a conventional (“non-Green”)
preparation of ester 740,48 the overall yield is raised to >25%. We
speculate that the low yields associated with the preparation of 7
might be associated with concurrent ester hydrolysis, although we
have not isolated any acid from the reaction conditions reported
in the experimental section.
The reaction of two equivalents of H2 with commercial ruthe-
nium trichloride in a pressure vessel in basic ethanol, followed by
work-up in basic conditions gave the fully deprotonated complex
[Ru(2)2] as a deep red solid. The work-up of the complex is critical
to the protonation state and under various conditions it is possible
to obtain [Ru(2)2], [Ru(2)(H2)]+ or [Ru(H2)2]2+.
An alternative strategy for the synthesis of derivatives of
[Ru(H2)2]2+ involves the preliminary synthesis of the ester complex
[Ru(7)2]2+ and subsequent hydrolysis directly to complexes of H2.
The ester complexes [Ru(7)2][PF6]2 and [Ru(7)2]Cl2 were prepared
in acceptable yield by standard methods (microwave synthesis in
ethane-1,2-diol or thermal reaction in methanol) and isolated as
red crystalline solids. The reaction of [Ru(7)2][PF6]2 with sodium
hydroxide in aqueous acetonitrile gave the salt [Ru(H2)2][PF6]2 as a
red solid in 64% yield. After drying in vacuo an approximately 8 : 2
mixture of [Ru(H2)2][PF6]2 and [Ru(H2)(2)][PF6] was obtained.
Although the two tpy ligands of this complex are formally
different, proton transfer is apparently fast in DMSO-d6 (the
only suitable solvent) and a single set of tpy signals are observed
in the 1H NMR spectrum. The synthetic transformations are
summarised in Scheme 2.
Fig. 2 Coordination shifts of ligand 5 on changing from the free ligand
(upper trace, in CDCl3, 400 MHz) to [Ru(5)2][PF6]2 (middle trace, CD3CN,
500 MHz). The typical upfield shift of H6A (black) is observed, together
with a downfield shifting of all the furyl protons (grey) and H3B (black).
The lower spectrum shows the cross peak between H3B and H3C in the
NOESY spectrum of [Ru(5)2][PF6]2 confirming the assignment of H3C
.
Structural characterisation of ruthenium complexes of carboxylic
acid derivatives
in a two step reaction.40 The ligand was fully characterised by
conventional spectroscopic and analytical methods.
We then considered two alternative routes for the preparation
of [Ru(H2)2]2+ derivatives. Firstly, the direct hydrolysis of 7 to give
the free acid H2 with subsequent coordination to ruthenium and,
secondly, the preparation and subsequent hydrolysis of [Ru(7)2]2+.
We have structurally characterised the precursor ester complex
[Ru(7)2]Cl2·4H2O and hydrates of [Ru(1)2] and [Ru(2)2], the
latter being obtained from reactions aiming at the formation of
coordination polymers or metal organic frameworks by reaction
with additional metal salts in basic conditions.51
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Scheme 2 (a) (i) KOH (ii) EtOH, NH4OAc (b) (i) NH3, H2O, NaOH (ii) HCl (c) RuCl3·3H2O, HOCH2CH2OH, N-ethylmorpholine, microwave or
RuCl3·3H2O, MeOH, 150 ◦C (d) NaOH, MeCN (e) HCl, NH4PF6 (f) RuCl3·3H2O, NEt3, EtOH.
The ester complex [Ru(7)2]Cl2·4H2O
˚
plane of the other being in the range 3.3 – 3.6 A. The presence of
the additional aromatic ring at the 4ꢀ-position results in a lattice
in which there are no typical tpy embraces.52–54
The ester complex [Ru(7)2]2+ provides an excellent model for the
carboxylic acid complexes without the ambiguity of protona-
tion state and without a very strong hydrogen bond acceptor
or donor in the coordination unit. X-Ray quality crystals of
[Ru(7)2]Cl2·4H2O were obtained directly from the reaction mixture
upon cooling.
The second principal packing motif is a hydrogen bonding
network involving the lattice water molecules, the chloride coun-
terions and the carbonyl oxygen atoms. Each of the cations
is hydrogen bonded to two water molecules through each of
the carbonyl groups (O4 · · · O10, O8 · · · O11, O2 · · · O13 and
The structure of the two crystallographically independent
but chemically very similar cations is presented in Fig. 3 and
confirms the expected {Ru(tpy)2] structural motif with pendant
methoxycarbonylphenyl groups. The {Ru(tpy)2} motifs are typical
with the tpy ligands being essentially coplanar and the least
squares planes angles between any two bonded pyridine rings not
being greater than 7◦ and most being below 4◦. Bond lengths and
angles within the coordination sphere and within the ligands are
typical. The methoxycarbonylphenyl substituents show a rather
different behaviour; two of the phenyl substituents are almost
coplanar with the pyridine rings to which they are attached (rings
containing N5 and N8, least squares planes angles 5 and 4◦)
whilst the other two make least squares planes angles of 36 and
40◦ with the directly bonded pyridine rings. The near coplanar
phenyl substituents are p-stacked with a terminal pyridine of the
independent cation, the one attached to the ring containing N8
with that containing N6, and that attached to the ring containing
N5 with that containing N7. The stacked rings are offset and near
coplanar with distances of atoms in one ring from the least squares
◦
˚
O6 · · · O15: O · · · O, 2.80–2.95 A; ∠O–H · · · O, 137–165 ). The
water and chloride ions form two distinct types of motif in the
lattice. The first is a one dimensional hydrogen-bonded chain
in the sequence Cl1 · · · O9 · · · Cl2 · · · O11 · · · O12 · · · O13 · · · Cl1A
˚
with typical Cl · · · O distances in the range 3.10–3.22 A and O · · · O
˚
distances 2.73, 2.92 A (Fig. 4). The remaining water and chloride
ions have some positional disorder, but form discrete clusters with
further hydrogen bonds to the cation carbonyl oxygen atoms.
The deprotonated complex [Ru(1)2]·4H2O
Dark red rhombic crystals of the complex [Ru(1)2]·4H2O were
obtained from a reaction of [Ru(H1)2][PF6]2 with zinc nitrate in
aqueous DMF under autoclave conditions.
The structure of the neutral [Ru(1)2] molecule is shown in Fig. 5.
The {Ru(tpy)2} motif is very much as expected and the Ru–N
distances are very similar to those in the ester complex [Ru(7)2]Cl2
discussed above. The carboxylate substituent is planar and near
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coplanar with the central ring of the terpyridine to which it is
attached (least squares planes, 20◦). The carboxylate C–O bond◦s
˚
are equal with a bond length of 1.226(2) A and O–C–O of 127.0(3)
fully consistent with a delocalised carboxylate.
The lattice comprises hydrogen bonded sheets of water
molecules and carboxylate groups separated by layers of the
{Ru(tpy)2} units. Fig. 6a shows a view of the hydrogen-bonded
sheet along c and illustrates the formation of a net of 12-membered
(non-hydrogen atoms) rings. Reducing the network to a nodal
representation, the sheets are an example of the (6, 3) network in
which the three-connected nodes are the lattice water molecules.
The corrugated water–carboxylate sheets separate the {Ru(tpy)2}
motifs as shown in Fig. 6b.
Fig. 3 The two crystallographically independent [Ru(7)2]2+ cations
present in the lattice of [Ru(7)2]Cl2·4H2O. Hydrogen atoms have been
omitted for clarity and thermal ellipsoid◦s are plotted at 50% probability.
˚
Selected bond lengths (A) and angles ( ): Ru1–N1, 2.067(3); Ru1–N2,
1.969(2); Ru1–N3, 2.064(3); Ru1–N4, 2.069(3); Ru1–N5, 1.971(2);
Ru1–N6, 2.069(3); Ru2–N7, 2.076(3); Ru2–N8, 1.973(3); Ru2–N9,
2.068(3); Ru2–N10, 2.058(3); Ru2–N11, 1.971(3); Ru2–N12, 2.066(3);
N1–Ru1–N2, 78.85(10); N1–Ru1–N3, 158.27(10); N2–Ru1–N3,
79.41(10); N1–Ru1–N4, 94.50(10); N2–Ru1–N4, 101.32(10); N3–Ru1–N4,
89.81(10); N1–Ru1–N5, 100.04(10); N2–Ru1–N5, 178.82(10); N3–Ru1–
N5, 101.69(10); N4–Ru1–N5, 79.15(10); N1–Ru1–N6, 91.07(10); N2–
Ru1–N6, 100.52(10); N3–Ru1–N6, 92.81(10); N4–Ru1–N6, 158.12(10);
N5–Ru1–N6, 79.04(10); N7–Ru2–N8, 78.50(10); N7–Ru2–N9, 157.45(10);
N8–Ru2–N9, 79.13(10); N7–Ru2–N10, 92.99(10); N8–Ru2–N10,
101.91(11); N9–Ru2–N10, 88.85(10); N7–Ru2–N11, 101.89(10); N8–Ru2–
N11, 178.75(11); N9–Ru2–N11, 100.54(10); N10–Ru2–N11, 79.28(11);
N7–Ru2–N12, 91.99(10); N8–Ru2–N12, 100.14(11); N9–Ru2–N12,
94.69(10); N10–Ru2–N12, 157.94(10); N11–Ru2–N12, 78.67(11).
Fig. 4 The one dimensional chain of chloride ions and water molecules in
the lattice of [Ru(7)2]Cl2·4H2O. The chain is linked to the cations through
additional hydrogen bonds from O13 and O11. The symmetry description
refers to atoms generated by the symmetry operator x + 1/2, −y, z.
Fig. 6 (a) The (6, 3) net formed in the hydrogen-bonded sheets of
water molecules and carboxylate in the lattice of [Ru(1)2]·4H2O and (b)
a projection orthogonal to part a showing the alternating layers of water
sheets and {Ru(tpy)2} motifs.
The deprotonated complex [Ru(2)2]·5H2O
X-Ray quality crystals of the complex [Ru(2)2]·5H2O were ob-
tained from the reaction of the complex [Ru(H2)2][PF6]2 with
europium(III) nitrate in aqueous DMF in an autoclave. The
compound is topologically equivalent to [Ru(1)2] discussed above,
although the incorporation of the 1,4-phenylene residue is ex-
pected to increase the C-carboxylate-to-C-carboxylate distance
Fig. 5 The structure of [Ru(1)2] in the compound [Ru(1)2]·4H2O. Selected
◦
˚
bond lengths (A) and angles ( ): Ru1–N1, 2.0667(19); Ru1–N2, 1.9768(16);
C9–O1, 1.226(2); N1–Ru1–N2, 78.84(5); N2–Ru1–N2A, 180.0(0);
N1–Ru1–N1A, 92.148(17); N1–Ru1–N1B, 157.67(9); N2–Ru1–N1A,
101.16(5); O1–C9–O1B, 127.0(3). The symmetry labels A, B and C refer to
the symmetry operators (y, −x, −z), (−x, −y, z) and (−y, x, −z). Hydrogen
atoms have been omitted for clarity. Thermal ellipsoids at 50% probability
level.
˚
˚
from ∼13 A to ∼21 A. This expansion of the ligand is expected to
result in differences in packing consistent with the Kitaigorodsky
close packing model.55 The structure of the neutral [Ru(2)2]
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species present in the lattice is presented in Fig. 7. The typical
features of the {Ru(tpy)2} core are present and the structural
features of the coordination unit closely resemble those in
[Ru(7)2]Cl2·4H2O. Once again, there is no significant influence
of the remote charged carboxylate substituent on the Ru–N
distances. The average Ru–Nterminal and Ru–Ncentral distances for
˚
˚
[Ru(7)2]Cl2·4H2O are 2.07 A and 1.97 A and for [Ru(2)2]·5H2O
˚
˚
2.07 A and 1.97 A respectively. The phenylene rings are not
coplanar with the pyridine to which they are bonded but make least
squares planes angles of 19◦ (ring bonded to pyridine with N5)
and 29◦ (ring bonded to pyridine with N2). As in [Ru(1)2]·4H2O,
the carboxylate substituent is planar and near coplanar with the
ring to which it is bonded (least squares planes, 17 and 10◦). The
carboxylate C–O bonds are equivalent with a bond lengths◦in the
˚
range 1.25–1.26 A and O–C–O of 125.4(3) and 125.7(3) fully
consistent with a delocalised carboxylate.
Fig. 8 The two hydrogen-bonding motifs involving carboxylate and water
found in [Ru(2)2]·5H2O. (a) The (4.82) sheets constructed from water
molecules containing O130, O150 and O11 and carboxylate oxygen atoms
O3 and O4 and (b) the chains constructed from water molecules containing
O120, O140 and O10 and carboxylate oxygen atoms O1 and O2. The nets
have been idealised by the omission of symmetry related atoms from half
occupancy positions.
Fig. 7 The [Ru(2)2]·5H2O unit present in [Ru(2)2]·5H2O showing the
partial numbering scheme adopted. Hydrogen atoms have been omitted
◦
˚
for clarity. Selected bond lengths (A) and angles ( ): Ru1–N1, 2.080(2);
Ru1–N2, 1.978(2); Ru1–N3, 2.065(2); Ru1–N4, 2.063(2); Ru1–N5,
1.971(2); Ru1–N6, 2.067(2); C37–O1, 1.252(4); C37–O2, 1.256(4);
C44–O3, 1.265(4); C44–O4, 1.256(4); N1–Ru1–N2, 78.56(9); N1–Ru1–N3,
157.39(9); N2–Ru1–N3, 78.88(9); N1–Ru1–N4, 91.73(9); N2–Ru1–N4,
98.99(9); N3–Ru1–N4, 93.24(9); N1–Ru1–N5, 104.46(9); N2–Ru1–N5,
176.23(10); N3–Ru1–N5, 98.14(9); N4–Ru1–N5, 78.79(10); N1–Ru1–N6,
91.70(9); N2–Ru1–N6, 103.30(10); N3–Ru1-N6, 92.02(9); N4–Ru1–N6,
157.69(9); N5–Ru1–N6, 79.01(10); C34–C37–O2, 116.6(3); O3–C44–O4,
125.4(3). Thermal ellipsoids at 50% probability level.
Conclusions
We have shown that the expanded ligands [Ru(H1)2]2+ and
[Ru(H2)2]2+ may be prepared and that they behave as analogues
of phthalic acids. The ability of the ruthenium(II) centre in
these compounds to charge compensate the deprotonation of
the carboxylic acid has been established and the solid state
structures of two Zwitterionic compounds have been determined.
The introduction of a 1,4-phenylene spacer between the tpy and
the carboxylic acid leads to a significantly more open sub-lattice
which gives a three-fold interpenetrated structure.
The expanded ligand principle can be a powerful tool in
supramolecular chemistry and crystal engineering allowing a
subtle control over the topological and topographical properties
of molecular and extended constructs to be achieved. In this paper,
we have shown that the combination of metal-containing and
hydrogen-bonding motifs gives access to significant solid state
diversity and offers new approaches to the construction of network
structures.
As in [Ru(1)2]·4H2O, the carboxylate oxygen and water
molecules build a complex hydrogen bonded network. Two sepa-
rate substructures are present. The first is a two-dimensional sheet
(Fig. 8a) which exhibits the net structure (4.82) constructed from
water and carboxylate residues. The formation of the (4.82) net is
a remarkable validation of the expanded ligand concept as exactly
this motif is found in the tetra-n-butylammonium terephthalate
hydrate.56 The second motif is a one dimensional chain (Fig. 8b).
The two motifs are bridged by the [Ru(2)2] molecules and the end
result is a 3D lattice (Fig. 9a). In the same way that [Ru(1)2] may
be regarded as an expanded terephthalate ligand in which the C-
carboxylate · · · C-carboxylate distance has been increased from ∼6
˚
to ∼13 A, [Ru(2)2] may be seen as a super-expanded terephthalate
or as an expanded [Ru(1)2], in which the C-carboxylate · · · C-
Experimental
˚
carboxylate distance has further increased from ∼13 to ∼21 A. The
incorporation of longer spacers is expected to lead to increasingly
porous structures and eventually lead to interpenetrating sub-
lattices57–63 as shown by Yaghi for terephthalate analogues.64 As
Fig. 9b shows, the introduction of the 1,4-phenylene spacer into the
expanded ligand results in the formation of large voids, resulting
in the formation of three identical interpenetrating nets (Fig. 9c).
General
Infrared spectra were recorded on a Shimadzu FTIR-8400 S
spectrophotometer with samples as solids using a Golden Gate
ATR accessory. 1H and 13C NMR spectra were recorded on Bruker
Avance DRX 500 or 400 spectrometers and chemical shifts are
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2-acetylpyridine (2.7 mL, 24 mmol) and aqueous ammonia solu-
tion (28–30%, 5 mL, 80 mmol) were added to the solution, which
was then heated to 80 ◦C and stirred vigorously at that temperature
for 24 h in a flask open to air. The brown solution so obtained was
poured into water (200 mL) and cooled to ambient temperature.
The slightly brown precipitate was isolated by filtration, washed
with water and recrystallised from hot ethanol (100 mL) at −20 ◦C
to yield 5 as off-white needles (1.46 g, 4.88 mmol, 41%).
Method 3. 2-Furaldehyde (1.92 g, 0.02 moles) and 2-acetyl-
pyridine (4.84 g, 0.0400 moles) were dissolved in EtOH (100 mL).
To this was added, KOH (3.08 g, 0.055 moles) and aqueous
ammonia solution (60 mL, 25%). The solution was then stirred at
60 ◦C for 24 h after which about half of the solvent was removed
under reduced pressure and the solution filtered yielding an off-
white solid. Recrystallisation from EtOH–MeOH gave 5 as white
needles. (5.12 g, 0.0171 mmol, 86%).
(Found: C, 76.16; H, 4.32; N, 13.92. C19H13N3O requires C,
76.24; H, 4.38; N, 14.04%); dH/ppm (400 MHz, CDCl3): 8.74 (d,
2H, J = 4.8 Hz, H6A), 8.72 (s, 2H, H3B), 8.64 (d, 2H, J = 8.0 Hz,
H3A), 7.87 (dt, 2H, J = 1.9, 7.8 Hz, H4A), 7.59 (d, 1H, J = 1.2 Hz,
H5C), 7.35 (ddd, 2H, J = 1.0 , 4.8, 7.4 Hz, H5A), 7.11 (d, 1H,
J = 3.2 Hz, H3C), 6.57 (dd, 1H, J = 1.8, 3.4 Hz, H4C); dC/ppm
(100 MHz, CDCl3): 156.1, 155.9, 151.9, 149.1, 143.7, 139.5, 136.8,
123.8, 121.3, 115.1, 112.1, 109.1; m/z (EIMS) 299 (M+, 100%),
271 (26%), 192 (6%), 149.5 (M2+, 5%), 78 ([C5H4N]+, 5%).
[Ru(5)2][PF6]2. RuCl3·3H2O (100 mg, 0.38 mmol), 4ꢀ-(2-furyl)-
2,2ꢀ;6ꢀ,2ꢀꢀ-terpyridine (250 mg, 0.84 mmol) and N-ethylmorpholine
(8 drops) were dissolved in ethane-1,2-diol (50 mL) and the
suspension homogenized in an ultrasonic bath. Heating to reflux
in the microwave oven (6 min, 400 W) yielded a red solution,
which was treated with excess ammonium hexafluorophosphate
in water (0.4 M, 9.5 mL) while still hot. After cooling to
ambient temperature the suspension was filtered over Celite,
washed several times with ethanol and ether and extracted with
acetonitrile. After evaporation of the solvent, the residue was
recrystallised from methanol–acetone (1 : 1) to yield [Ru(5)2][PF6]2
as a red, microcrystalline powder (185 mg, 0.187 mmol, 49%);
(Found: C, 46.13; H, 2.92; N, 8.30. C38H26F12N6O2P2Ru requires
C, 46.12; H, 2.65; N, 8.49%); dH/ppm (500 MHz, CD3CN): 8.97
(s, 4H, H3B), 8.61 (ddd, 4H, J = 0.8, 1.3, 8.3 Hz, H3A), 7.94 (m, 4H,
H4A,H5C), 7.62 (dd, 2H, J = 0.5, 3.5 Hz, H3C), 7.42 (ddd, 4H, J =
0.5, 1.5, 5.5 Hz, H6A), 7.17 (ddd, 4H, J = 1.5, 5.5, 7.5 Hz, H5A),
6.88 (dd, 2H, J = 1.5, 3.5 Hz, H4C); dC/ppm (100 MHz, CD3CN):
159.0, 156.5, 153.5, 151.3, 147.0, 139.1, 138.2, 128.5, 125.5, 118.4,
114.4, 113.1; m/z (FABMS) 845 (82%, [M − PF6]+), 700 (100%,
[M − 2PF6]+).
Fig. 9 (a) The construction of an interpenetrating net in which the
water–carboxylate sheets and chains are connected by the central complex
core (represented schematically by the black lines between carboxylate
carbon atoms). (b) Space filling representation of a single net, with
hydrogen bonded sheets shown in pink, and hydrogen bonded chains
shown in blue. The voids into which the interpenetrating networks fit
are clear. (c) The three interpenetrating networks, with complexes shown
schematically as in part (a).
referenced with respect to residual solvent peaks (CD3CN, dH
1.49 ppm dC 1.24 ppm; DMSO-d6, dH 2.50 ppm, dC 39.43 ppm)
and quoted with respect to TMS = d 0 ppm. MALDI-TOF
mass spectra were recorded using Finnigan MAT LCQ and
PerSeptive Biosystems Voyager mass spectrometers, respectively.
Electronic absorption spectra were recorded on a Varian-Cary
5000 spectrophotometer.
Syntheses
Method 1. 2-Furaldehyde (1.0 mL, 12 mmol), 2-acetylpyridine
(2.7 mL, 24 mmol) and aqueous ammonia solution (28–30%, 5 mL,
80 mmol) were dissolved in ethanol (40 mL) and a solution of
NaOH (1.0 g, 25 mmol) in H2O (1 mL) added to the yellow
mixture. The resulting dark yellow–brown solution was stirred
vigorously open to the air and after 30 min a white precipitate
started to appear. Stirring in air was continued for 2 d, after which
the precipitate was isolated by filtration and washed with H2O to
give 5 as an off-white powder (2.36 g, 7.89 mmol, 65%).
[Ru(H1)2][PF6]2. RuCl3·3H2O (381 mg, 1.46 mmol), 5 (873 mg,
2.92 mmol) and N-ethylmorpholine (14 drops) were suspended
in ethanol (40 mL) and the mixture heated to reflux for 24 h
after which the suspension turns bright red. After evaporation
of the solvent a red–violet precipitate was obtained, which was
transferred into a round bottom flask containing a solution of
KMnO4 (450 mg) in water (50 mL). After stirring for 3 h at
room temperature TLC analysis showed significant amounts of the
[Ru(5)2]2+ remained (SiO2, CH3CN –saturated aqueous KNO3 –
H2O 7 : 1 : 0.5, Rf = 0.45) and another portion of KMnO4
(500 mg) was added. A further portion of KMnO4 (1100 mg) was
Method 2. Sodium hydroxide (1.09 g, 27 mmol) was dissolved
in ethane-1,2-diol (50 mL) and 2-furaldehyde (1.0 mL, 12 mmol),
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added after an additional 3.5 h as TLC analysis still showed the
presence of [Ru(5)2]2+. After stirring overnight, no [Ru(5)2]2+could
be detected by TLC, but still two red spots remained in the TLC
(assumed to be [Ru(5)(H1)]2+ and the desired [Ru(H1)2]2+. KMnO4
(1.54 g) was added over a period of 2 h and stirring continued for an
additional 7 h, after which the suspension was filtered and washed
with water. The residue was extracted with aq. H2SO4 (2 M) and
reacted with NH4PF6 (0.4 M aq. solution, 10 mL) to yield a red
precipitate. The suspension was stirred overnight, filtered over
Celite, washed with aqueous NH4PF6 solution (0.02 M) and a
little water and extracted with acetonitrile. After evaporation of
the solvent, [Ru(H1)2][PF6]2 was obtained as a red microcrystalline
solid (667 mg, 0.0704 mmol, 48%); (Found: C, 40.18; H, 2.50; N,
8.78. C32H22F12N6O4P2Ru requires C, 40.65; H, 2.35; N, 8.89%);
dH/ppm (400 MHz, CD3CN): 10.66 (br s, 2H, CO2H), 9.21 (s, 2H,
H3B), 8.65 (d, 2H, J = 8.4 Hz, H3A), 7.94 (dt, 2H, J = 1.5 Hz, 7.9,
H4A), 7.33 (d, 2H, J = 4.8 Hz, H6A), 7.18 (ddd, 2H, J = 1.3, 5.7,
7.5 Hz, H5A); m/z (ESMS) 801 (7%, [M − PF6]+), 655 (12%, [M −
2PF6]+).
(d, 2H, J = 8.4 Hz, H3C), 8.07 (d, 2H, J = 8.8 Hz, H2C), 8.05 (dt,
2H, J = 1.7, 7.7 Hz, H4), 7.54 (ddd, 2H, J = 1.2, 4.8, 7.6 Hz, H5A);
m/z (EIMS) 353 (M+, 100%), 308 ([M − CO2H]+, 26%).
[Ru(7)2][PF6]2. RuCl3·3H2O (100 mg, 0.38 mmol), 7 (281 mg,
0.76 mmol) and N-ethylmorpholine (8 drops) were dissolved in
ethane-1,2-diol (50 mL) and heated to reflux in a microwave
oven (6 min, 400 W). The resulting red solution was cooled to
room temperature and treated with excess aqueous ammonium
hexafluorophosphate. The red suspension so obtained was col-
lected over Celite, washed several times with water and extracted
with acetonitrile. After evaporation of the MeCN, the residue was
purified by column chromatography (SiO2, CH3CN – saturated
aqueous KNO3 – H2O 7 : 1 : 0.5). The collected fractions
were concentrated and treated with ammonium hexafluorophos-
phate to give [Ru(7)2][PF6]2 as a red microcrystalline powder
(318 mg, 0.275 mmol, 73%); (Found: C, 46.06; H, 3.00; N, 7.07.
C46H34F12N6O4P2Ru.4H2O requires C, 46.12; H, 3.53; N, 7.02%);
dH/ppm (500 MHz, CD3CN): 9.06 (s, 4H, H3B), 8.67 (d, 4H, J =
7.5 Hz, H3A), 8.37 (d, 4H, J = 9.0 Hz, H3C), 8.31 (d, 4H, J =
8.5 Hz, H2C), 7.96 (dt, 4H, J = 1.7, 7.6 Hz, H4A), 7.44 (dd, 4H, J =
1.3, 5.3 Hz, H6A), 7.19 (ddd, 4H, J = 1.5, 5.8, 7.5 Hz, H5A), 3.99
(s, 6H, CH3); m/z (MALDI-TOF MS) 838 ([M + H]+, 100%).
4ꢀ-(4-Methoxycarbonylphenyl)-2,2ꢀ:6ꢀ,2ꢀꢀ-terpyridine 7. Pow-
dered potassium hydroxide (2.5 g, 44 mmol), 4-methoxycarbonyl-
benzaldehyde (6.82 g, 42 mmol) and 2-acetylpyridine (9.2 mL,
82 mmol) were ground together in a pestle and mortar for 15 min
to give a sticky yellow solid, which was left standing for 30 min,
ground again and dispersed in water. The solid was collected
by filtration, washed with water and dried in air for 1 h. The
off-white precipitate was dispersed in a suspension of ammonium
acetate (16.0 g, 208 mmol) in ethanol (125 mL) and the mixture
stirred for 8 d at room temperature in a flask open to air and the
resulting precipitate isolated by filtration and recrystallised twice
from hot ethanol to give 4ꢀ-(4-methoxycarbonylphenyl)-2,2ꢀ:6ꢀ,2ꢀꢀ-
terpyridine 7 as very pale yellow fibres (3.85 g, 10.1 mmol, 25%);
(Found: C, 74.21; H, 4.66; N, 11.29. C23H17N3O·0.25H2O requires
C, 74.28; H, 4.74; N, 11.30%); dH/ppm (400 MHz, CDCl3): 8.76
(2H, s, H3B), 8.74 (2H, d, J = 4.8 Hz, H6A), 8.68 (2H, d, J =
8.0 Hz, H3A), 8.18 (2H, d, J = 8.0 Hz, H3C), 7.97 (2H, d, J =
8.4 Hz, H2C), 7.89 (2H, dt, J = 1.7, 7.7 Hz, H4A), 7.37 (2H, ddd,
J = 1.0,4.8,7.4 Hz, H5A), 3.97 (3H, s, Me); dC/ppm (125 MHz,
CDCl3): 166.8, 156.1, 156.0, 149.2, 149.18, 142.9, 136.9, 130.5,
130.2, 127.4, 124.0, 121.4, 118.9, 52.2; m/z (EIMS) 367 (M+,
100%).
[Ru(7)2]Cl2. RuCl3·3H2O (100 mg, 0.38 mmol) and 7 (337 mg,
0.76 mmol) were suspended in methanol (5 mL) and the suspension
heated in a Teflon-lined Parr reaction vessel for 15 h to 150 ◦C
and then cooled slowly to room temperature. The microcrystalline
material (suitable for X-ray diffraction study) was isolated by filtra-
tion and extracted with methanol. Evaporation of the solvent gave
[Ru(7)2]Cl2 as a red microcrystalline powder (234 mg, 0.250 mmol,
66%); (Found: C, 55.44; H, 4.37; N, 8.19. C46H34Cl2N6O4Ru·5H2O
requires C, 55.42; H, 4.45; N, 8.43%); dH/ppm (400 MHz, DMSO-
d6): 9.56 (s, 4H, H3B), 9.13 (d, J = 8.0 Hz, 4H, H3A), 8.59 (d, J =
8.4 Hz, 4H, H3C), 8.33 (d, J = 8.4 Hz, 4H, H2C), 8.08 (dt, J = 1.3,
7.9 Hz, 4H, H4A), 7.57 (d, J = 6.0 Hz, 4H, H6A), 7.29 (ddd, J =
0.7, 5.5, 7.7 Hz, 4H, H5A), 3.98 (s, 6H, Me); m/z (FABMS) 871
([M − Cl]+, 24%).
[Ru(2)2]. H2 (342 mg, 0.97 mmol), RuCl3·3H2O (126.5 mg,
0.48 mmol), and NEt3 (0.3 mL, 2.2 mmol) were suspended in
ethanol (3 mL) and heated in a Teflon-lined Parr-vessel for 18 h
◦
to 150 C. After cooling to ambient temperature the precipitate
formed is filtered over Celite, and washed with ethanol (5 mL),
water containing 10 drops of 2 M NaOH (10 mL), and water
(10 mL). The remaining residue was extracted with boiling
methanol (350 mL) and evaporation of the solvent yielded [Ru(2)2]
as a red powder (254 mg, 0.315 mmol, 65%); (Found: C, 63.71; H,
4.30; N, 10.23. C44H28N6O4Ru·1.25H2O requires C, 63.76; H, 3.77;
N, 10.14%); dH/ppm (400 MHz, DMSO-d6): 9.53 (4H, s, H3B), 9.14
(4H, d, J = 8.0 Hz, H3A), 8.48 (4H, d, J = 8.4 Hz, H3C), 8.24 (4H,
d, J = 8.4 Hz, H2C), 8.06 (4H, dd, J = 7.4, 14.6 Hz, H4A), 7.56
(4H, d, J = 6.0 Hz, H6A), 7.28 (4H, t, J = 6.6 Hz, H5A).
[Ru(H2)2][PF6]2. Aqueous sodium hydroxide (2 M, 5 mL) was
added to a suspension of [Ru(7)2][PF6]2 (150 mg, 0.13 mmol) in
acetonitrile (80 mL) and the mixture refluxed overnight. After
cooling to room temperature, 2 M hydrochloric acid (5 mL) and
aqueous ammonium hexafluorophosphate (0.4 M, 5 mL, 2 mmol)
were added to the suspension, which was then filtered over Celite,
washed with water and extracted with acetonitrile and methanol.
4ꢀ-(4-Carboxyphenyl)-2,2ꢀ:6ꢀ,2ꢀꢀ-terpyridine H2. 30% NH3 so-
lution (1 mL) and NaOH (0.488 g, 12.2 mmol) dissolved
in a minimum amount of water were added to a solution
of 4-methoxycarbonylbenzaldehyde (1.0 g, 6.1 mmol) and 2-
acetylpyridine (1.37 mL, 12.2 mmol) in ethanol (25 mL). After the
addition of the NaOH, the solution turned yellow and after about
1 h red. The solution was stirred vigorously at room temperature
in a flask open to air for 17 h, after which a yellow suspension was
obtained. Water (50 mL) was added to the solution, which was then
neutralized with conc. HCl to yield a slightly yellow precipitate
and a red solution. The precipitate was collected by filtration and
washed with water. For further purification it was refluxed for 1 h
in 50 mL EtOH, and the solid collected by filtration and dried in
vacuum. (1.06 g, 3.00 mmol, 49%); (Found: C, 74.41; H, 4.25; N,
11.68. C22H15N3O2 requires C, 74.78; H, 4.28; N, 11.89%); dH/ppm
(400 MHz, DMSO-d6): 13.2 (br s, 1H, CO2H), 8.77 (d, 2H, J =
4.8 Hz, H6A), 8.76 (s, 2H, H3B), 8.69 (d, 2H, J = 8.0 Hz, H3A), 8.14
4330 | Dalton Trans., 2007, 4323–4332
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©

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The solvents were evaporated to yield “[Ru(2)2][PF6]2” as a
red solid of variable constitution between [Ru(H2)(2)][PF6] and
[Ru(H2)2][PF6]2 (88 mg, 0.080 mmol, 61%); dH/ppm (400 MHz,
DMSO-d6): 9.57 (4H, s, H3B), 9.15 (4H, d, J = 8.0 Hz, H3A), 8.58
(4H, d, J = 8.4 Hz, H3C), 8.30 (4H, d, J = 8.4 Hz, H2C), 8.09 (4H,
dt, J = 0.9, 7.7 Hz, H4A), 7.57 (4H, d, J = 5.2 Hz, H6A), 7.29 (4H,
t, J = 6.2 Hz, H5A); m/z (FABMS) 953 ([M − PF6]+, 808 ([M −
2PF6]+).
Notes and references
1 E. C. Constable and A. M. W. Cargill Thompson, J. Chem. Soc., Dalton
Trans., 1992, 2947.
2 E. C. Constable and A. M. W. Cargill Thompson, J. Chem. Soc., Dalton
Trans., 1994, 1409.
3 E. C. Constable, C. E. Housecroft, A. M. W. C. Thompson, P. Passaniti,
S. Silvi, M. Maestri and A. Credi, Inorg. Chim. Acta, 2007, 360, 1102.
4 E. C. Constable and E. Schofield, Chem. Commun., 1998, 403.
5 E. C. Constable, C. E. Housecroft, M. Neuburger, D. Phillips, P. R.
Raithby, E. Schofield, E. Sparr, D. A. Tocher, M. Zehnder and Y.
Zimmermann, J. Chem. Soc., Dalton Trans., 2000, 2219.
6 E. C. Constable, E. L. Dunphy, C. E. Housecroft, W. Kylberg, M.
Neuburger, S. Schaffner, E. R. Schofield and C. B. Smith, Chem.–Eur. J.,
2006, 12, 4600.
7 J. E. Beves, E. C. Constable, C. E. Housecroft, C. J. Kepert and D. J.
Price, CrystEngComm, 2007, 456.
8 E. C. Constable, Coord. Chem. Rev., manuscript submitted.
9 C. Laes, A. Katz and M. W. Hosseini, Chem. Rev., 2000, 100, 3553.
10 U. S. Schubert, H. Hofmeier and G. R. Newkome, Modern Terpyridine
Chemistry, Wiley-VCH, Weinheim, 2006.
11 E. C. Constable, Chem. Soc. Rev., 2007, 36, 246.
12 R. P. Thummel, in Comprehensive Coordination Chemistry II, ed.
J. A. McCleverty and T. J. Meyer, Elsevier, Oxford, 2004, vol. 1,
p. 41.
13 E. C. Constable, A. M. W. Cargill, Thompson and D. A. Tocher, in
Supramolecular Chemistry, ed. V. Balzani and L. De Cola, Kluwer
Academic Press, Dordrecht, 1992, p. 219.
Crystal structure determination†
Data were collected on an Enraf Nonius Kappa CCD instrument;
data reduction, solution and refinement used the programs
COLLECT,65 SIR9266 and CRYSTALS.67
CCDC reference numbers 651821–651823.
For crystallographic data in CIF or other electronic format see
DOI: 10.1039/b709557k
[Ru(7)2]Cl2·4H2O. Crystals were obtained on cooling the
solution from the preparation of the compound in methanol
at 150 ◦C. Crystal data for: C46H62Cl2N6O8Ru, M = 977.84,
monoclinic, space group P2/c, a = 25.857(3), b = 8.8662(13),
◦
3
˚
˚
c = 39.775(4) A, b = 106.393(7) ; U = 8747.7(2) A , Z = 8,
Dc = 1.485 Mg m−3, l(Mo-Ka) = 0.542 mm−1, T = 173 K,
22 134 reflections collected. Refinement of 11 491 reflections (1158
parameters) with I > 3.0r (I) converged at final R1 = 0.0367
(0.0784 all data), wR2 = 0.0388 (0.0576 all data), gof = 1.081.
14 E. C. Constable and A. M. W. Cargill Thompson, J. Chem. Soc., Dalton
Trans., 1992, 3467.
15 S. Kitagawa and S. Noro, in Comprehensive Coordination Chemistry II,
ed. J. A. McCleverty and T. J. Meyer, Elsevier, Oxford, 2004, vol. 7,
p. 231.
16 M. Gra¨tzel, Inorg. Chem., 2005, 44, 6841.
17 R. Caspar, L. Musatkina, A. Tatosyan, H. Amouri, M. Gruselle, C.
Guyard-Duhayon, R. Duval and C. Cordier, Inorg. Chem., 2004, 43,
7986.
[Ru(1)2]·4H2O. [Ru(H1)2][PF6]2 (10 mg, 10.6 lmol) and
Zn(NO3)2·6H2O (31.5 mg, 106 lmol) was dissolved in a glass vessel
in DMF (1.5 mL). The vessel was placed in a Teflon-lined Parr
autoclave and heated to 150 ◦C for 1 d, after which the vessel was
slowly cooled to ambient temperature to give red rhombic crystals.
Crystal data: C32H28N6O8Ru, M = 725.68, tetragonal, space
18 E. Eskelinen, P. Da, Costa and M. Haukka, J. Electroanal. Chem., 2005,
579, 257.
19 S. Luukkanen, M. Haukka, E. Eskelinen, T. A. Pakkanen, V.
Lehtovuori, J. Kallioinen, P. Myllyperkio and J. Korppi-Tommola,
Phys. Chem. Chem. Phys., 2001, 3, 1992.
20 V. Shklover, T. Haibach, B. Bolliger, M. Hochstrasser, M. Erbudak,
H.-U. Nissen, S. M. Zakeeruddin, M. K. Nazeeruddin and M. Gratzel,
J. Solid State Chem., 1997, 132, 60.
21 S. M. Zakeeruddin, M. K. Nazeeruddin, R. Humphry-Baker, M.
Gratzel and V. Shklover, Inorg. Chem., 1998, 37, 5251.
22 R. Caspar, H. Amouri, M. Gruselle, C. Cordier, B. Malezieux, R. Duval
and H. Leveque, Eur. J. Inorg. Chem., 2003, 499.
23 E. Coronado, J. R. Galan-Mascaros, C. Marti-Gastaldo, E. Palomares,
J. R. Durrant, R. Vilar, M. Gratzel and M. K. Nazeeruddin, J. Am.
Chem. Soc., 2005, 127, 12351.
24 P. Homanen, M. Haukka, M. Ahlgren and T. A. Pakkanen, Inorg.
Chem., 1997, 36, 3794.
25 E. Eskelinen, S. Luukkanen, M. Haukka, M. Ahlgren and T. A.
Pakkanen, J. Chem. Soc., Dalton Trans., 2000, 2745.
26 V. Shklover, Yu, E. Ovchinnikov, L. S. Braginsky, S. M. Zakeeruddin
and M. Gratzel, Chem. Mater., 1998, 10, 2533.
27 C. M. Hartshorn, K. A. Maxwell, P. S. White, J. M. DeSimone and T. J.
Meyer, Inorg. Chem., 2001, 40, 601.
28 C. J. Matthews, M. R. J. Elsegood, G. Bernardinelli, W. Clegg and A. F.
Williams, Dalton Trans., 2004, 492.
29 A. I. Philippopoulos, E. Chatzivasiloglou, A. Terzis, C. P. Raptopoulou,
P. Tisnes, C. Picard and P. Falaras, Inorg. Chem. Commun., 2005, 8, 162.
30 T. Norrby, A. Borje, P. B. Akermark, L. Hammarstrom, J. Alsins,
K. Lashgari, R. Norrestam, J. Martensson and G. Stenhagen, Inorg.
Chem., 1997, 36, 5850.
˚
group I42d, a = 8.6013(4), b = 8.6013(4), c = 40.033(2) A;
3
−3
˚
U = 2961.7(2) A , Z = 4, Dc = 1.627 Mg m , l(Mo-Ka) =
0.595 mm−1, T = 173 K, 2158 reflections collected. Refinement
of 1455 reflections (116 parameters) with I > 3.0r (I) converged
at final R1 = 0.0211 (0.0418 all data), wR2 = 0.0218 (0.0304 all
data), gof = 1.093.
[Ru(2)2]·5H2O. [Ru(H2)][PF6]2, (4.7 mg) and Eu(NO3)3·5 H2O
(2.7 ◦mg) were dissolved in DMF and heated in a glass vessel to
180 C in a Teflon-lined Parr autoclave for 1 d. After cooling to
ambient temperature red crystals were isolated from the solution
by filtration.
Crystal data: C44H32N6O9Ru, M = 889.84, triclinic, space group
¯
˚
P1, a = 8.6945(2), b = 13.4822(3), c = 16.5345(4) A, a = 93.118(1),
◦
3
˚
b = 97.373(1), c = 90.915(2) ; U = 1918.80(8) A , Z = 2,
Dc = 1.540 Mg m−3, l(Mo-Ka) = 0.477 mm−1, T = 123 K,
9123 reflections collected. Refinement of 5963 reflections (580
parameters) with I > 2.0r (I) converged at final R1 = 0.0393
(0.0730 all data), wR2 = 0.0364 (0.1043 all data), gof = 1.144.
31 T.-J. J. Kinnunen, M. Haukka and T. A. Pakkanen, J. Organomet.
Chem., 2002, 654, 8.
32 M. K. Nazeeruddin, P. Pechy, T. Renouard, S. M. Zakeeruddin, R.
Humphrey-Barker, P. Comte, P. Liska, L. Cevey, E. Costa, V. Shklover,
L. Spiccia, G. B. Deacon, C. A. Bignozzi and M. Gratzel, J. Am. Chem.
Soc., 2001, 123, 1613.
Acknowledgements
We thank the Swiss National Science Foundation and the Univer-
sity of Basel for financial support. We would also like to thank Dr
Jorge Sague´ Doimeadios (University Fribourg, Switzerland) for
helpful discussions.
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