Structural and photophysical characterisation of coordination and optical isomers of mononuclear ruthenium(II) polypyridyl 1,2,4-triazole complexes

Article abstract of DOI:10.1039/b301961f

The X-ray crystal structure of the N² isomers of the Ru(bipy)₂ complexes of Hphpztr (1) and Hpztr (2), (bipy = 2,2′-bipyridine, Hphpztr = 2-(5′-phenyl-4′H-[1,2,4]triazol-3′-yl)pyrazine and Hpztr = 2-(4′H-[1,2,4]triazol-3′-yl)pyrazine) are reported. The molecular structure obtained for 2 demonstrates an interesting structural aspect in the sharing of a single proton between two molecular units. The isolation of the Δ and Λ stereoisomers of 1 and [Ru(phen)₂(pztr)] ⁺ (phen = 1,10-phenanthroline) (3) by semipreparative HPLC is also reported. The compounds obtained are characterised by electronic spectroscopy and particular attention is paid to the photophysical properties of Δ and Λ isomers of 1 and 3, in chiral enantiopure and racemic solvents. The Royal Society of Chemistry 2003.

Full text of DOI:10.1039/b301961f

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Structural and photophysical characterisation of coordination
and optical isomers of mononuclear ruthenium(II) polypyridyl
1,2,4-triazole complexes†
Wesley R. Browne,a Dusan Hesek,‡b John F. Gallagher,c Christine M. O’Connor,a,d
J. Scott Killeen,§a Fumiko Aoki,b Hitoshi Ishida,b Yoshihisa Inoue,b Claudio Villanie and
Johannes G. Vos*a
a National Centre for Sensor Research, School of Chemical Sciences, Dublin City University,
Dublin 9, Ireland. E-mail: johannes.vos@dcu.ie; Fax: 00353-1-7005503; Tel: 00353-1-7005307
b ERATO Photochirogenesis and ICORP Entropy Control Projects, JST, 4-6-3 Kamishinden,
Toyonaka 565-0085, Japan
c National Institute for Cellular Biology, School of Chemical Sciences, Dublin City University,
Dublin 9, Ireland
d School of Chemistry, Dublin Institute of Technology, Kevin Street., Dublin 8, Ireland
e Dipartimento di Studi di Chimica e Tecnologia delle Sostanze Biologicamente Attive,
Universita’ degli Studi di Roma “La Sapienza”, P.le A. Moro 5-00185 Roma, Italy
Received 19th February 2003, Accepted 30th April 2003
First published as an Advance Article on the web 14th May 2003
The X-ray crystal structure of the N2 isomers of the Ru(bipy)2 complexes of Hphpztr (1) and Hpztr (2), (bipy = 2,2Ј-
bipyridine, Hphpztr = 2-(5Ј-phenyl-4ЈH-[1,2,4]triazol-3Ј-yl)pyrazine and Hpztr = 2-(4ЈH-[1,2,4]triazol-3Ј-yl)pyrazine)
are reported. The molecular structure obtained for 2 demonstrates an interesting structural aspect in the sharing of a
single proton between two molecular units. The isolation of the ∆ and Λ stereoisomers of 1 and [Ru(phen)2(pztr)]ϩ
(phen = 1,10-phenanthroline) (3) by semipreparative HPLC is also reported. The compounds obtained are
characterised by electronic spectroscopy and particular attention is paid to the photophysical properties of
∆ and Λ isomers of 1 and 3, in chiral enantiopure and racemic solvents.
emitting 3MLCT state can be localised on either the pyrazine or
Introduction
2,2Ј-bipyridyl ligands depending on the protonation state of the
There is continuing interest in the photochemical and photo-
triazole ring. In addition dual emission is observed for these
physical properties of ruthenium polypyridyl complexes1 due to
complexes over a wide temperature range.9 One complication in
their well-recognised role in photomolecular devices.2 The issue
the study of these compounds is the formation of coordination
of isomerism in terms of both stereochemistry3 and co-
isomers due to the presence of two inequivalent nitrogen atoms
ordination mode4 is of particular relevance to the large and
in the triazole ring, (i.e. N2 and N4, see Fig. 1). NMR studies
often complex systems employed in these studies.5,6 The
were used to tentatively assign the coordination mode of the
importance of stereochemistry and, in particular, chirality is
triazole rings, however, so far no X-ray data have been reported
well illustrated in the studies carried out on the stereoselective
for Ru() polypyridyl complexes of this type to confirm this
assignment. Another intriguing observation is that under cer-
interaction of transition metal complexes with DNA7 and pro-
teins.8 The isolation of the stereoisomers of mono- and poly-
tain conditions ruthenium complexes containing ‘pyrazine-
nuclear ruthenium() and osmium() diimine complexes has
triazole’ ligands are obtained with 1½ PF6Ϫ counter ions, rather
been reviewed recently.3
than one or two as expected from the two possible protonation
states of the triazole ring. Finally, no efforts have been made to
isolate and investigate the optical isomers in compounds of this
One class of compounds, which has been investigated in great
detail, are Ru() polypyridyl complexes of ligands such as
2-(4ЈH-[1,2,4]triazol-3Ј-yl)pyrazine) and its analogues (see
type.
Fig. 1). These compounds show very unusual photophysical
In the present contribution these structural issues are
behaviour and detailed investigations have shown that the
addressed. The X-ray crystal structures of the compounds
[Ru(bipy)2(phpztr)]PF6ؒCH3OH (1) and H([Ru(bipy)2(pztr)])2-
(PF6)3ؒH2O (2) (bipy = 2,2Ј-bipyridine, Hphpztr = 2-(5Ј-phenyl-
4ЈH-[1,2,4]triazol-3Ј-yl)pyrazine and Hpztr = 2-(4ЈH-[1,2,4]-
triazol-3Ј-yl)pyrazine) are reported. The resolution of the ∆
and Λ stereoisomers of 1 and [Ru(phen)2(pztr)]ϩ 3 (phen = 1,10-
phenathroline), by semipreparative HPLC is described also.
The electronic properties of the compounds obtained are dis-
cussed and particular attention is given to the photophysical
Fig. 1 Structures of compounds 1–4.
properties of the enantiomers of 1 and 3.
Results and discussion
† Electronic supplementary information (ESI) available: analytical and
semipreparative HPLC chromatograms, CD and UV/vis spectra. See
http://www.rsc.org/suppdata/dt/b3/b301961f/
Synthetic considerations
‡ Present address: Institute for Drug Design, Department of Chemistry,
Wayne State University, Detroit, Michigan 48202-3489, USA.
§ Present address: Unilever Research Laboratory, Olivier van Noort-
laan 120, 3133 AT, Vlaardingen, The Netherlands.
The preparation of compounds 1–3 was carried out using
standard procedures.4,6 As expected from steric considerations,
the presence of a phenyl group in the 5 position of the 1,2,4-
T h i s j o u r n a l i s © T h e R o y a l S o c i e t y o f C h e m i s t r y 2 0 0 3
D a l t o n T r a n s . , 2 0 0 3 , 2 5 9 7 – 2 6 0 2
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triazole ring results in one main fraction being obtained for
1. This was further purified by column chromatography and
recrystallisation.4 The molecular structure (vide infra) obtained
for the compound indicates that, as expected, in the isomer
obtained the triazole ring is coordinated via the N2 atom
(Fig. 1). For compounds 2 and 3, in which the 5 position of the
1,2,4-triazole ring is an –H, the absence of steric constraints
results in equimolar amounts of both N2 and N4 isomers. After
separation on neutral alumina the pure isomers were obtained
upon crystallisation of the appropriate fraction. The com-
pounds obtained are pure as evidenced from NMR and HPLC
analysis, however, elemental analysis indicates the presence of
1½ PF6Ϫ counter ions for every ruthenium centre. To investigate
this rather surprising observation crystals of 2 (N2 isomer) were
grown and its molecular structure was determined.
pyrazine-N and N2 of the triazole ring (Fig. 1), as predicted by
1H NMR spectroscopy.
For both 1 [N(1)–Ru(1)–N(2) 78.2(4)Њ] and 2 [N(1)–Ru(1)–
N(4) 78.18(18)Њ] the bite angle corresponds well with the
bite angle obtained for [Ru(bipy)2(3,5-bis(pyridin-2-yl)-1,2,4-
triazole)]PF6ؒ½H2O of 78(1)Њ, 77.98(6)Њ for [Ru(bipy)2(3-
(pyrazin-2Ј-yl)-5-(pyridin-2Љ-yl)-1,2,4-triazole)]PF6ؒMeOH,10
and 77.9(1)Њ for [Ru(bipy)2(3-(2-hydroxyphenyl)-5-(pyridin-2-
yl)-1,2,4-triazole)]PF6ؒCH3COCH3.11 Bite angles of 78.4(4) and
78.6(4)Њ {1} and 79.0(2) and 79.01(19)Њ {2} for bipyridyl ligands
are typical for this class of complex. Ruthenium–nitrogen dis-
tances of 2.036(10)–2.069(9) Å {1} and 2.023(4)–2.071(4) Å {2}
are also comparable to those found in other complexes.12 For
both 1 (Ru(1)–N(1) 2.069(9) Å) and 2 (Ru(1)–N(4) 2.071(4) Å),
the ruthenium–pyrazine bond is the longest Ru–N bond in the
complex.
An interesting crystallographic feature observed for 2 is the
presence of a shared hydrogen atom between the N3 of two
molecular units (Fig. 3). That both nitrogens are bonded to the
same proton is evident from the intermolecular nitrogen to
nitrogen separation (see Fig. 3). The intermolecular N ؒ ؒ ؒ N
distance for the N–H ؒ ؒ ؒ N hydrogen bond is 2.672(7) Å. This
observation is important and is in agreement with CHN analy-
sis (see Experimental section). A common feature of pyrazine-
triazole based Ru() complexes is their tendency to crystallise
from aqueous solutions to give CHN analysis suggesting a
mixed protonation state. The X-ray structural data presented
here provides considerable support to the validity of this
assumption.
X-Ray crystallography
The molecular structures of 1 and 2 are shown in Figs. 2 and 3,
respectively. Complex 1 co-crystallised with disordered ethanol/
water molecules, and a hexafluorophosphate counter anion (not
shown). Complex 2 co-crystallised with disordered water mole-
cules, and hexafluorophosphate counter anions (not shown).
(see Experimerntal section). From the crystal structure it is
clear that for both 1 (via N(1) and N(2) in Fig. 2) and 2
(via N(1) and N(4) in Fig. 3), the ligand is bound through the
Separation of the stereoisomers
The ∆ and Λ stereoisomers of 1 were separated using HPLC
employing a chiral carbamate stationary phase. The separation
achieved using this column is excellent with retention times of
12.5 min (Λ) and 25.2 min (∆) (see ESI,† Fig. S1). Similar results
were observed on an analytical column for the related complex,
[Ru(bipy)2(mepztr)]ϩ (4) (Hmepztr = 2-(5Ј-methyl-4ЈH-[1,2,4]-
triazol-3Ј-yl)pyrazine) (Fig. 1), however it is very noticeable
that the retention times (7.61 and 10.28 min) for the enantio-
mers of this complex were much shorter than for 1. This is not
unexpected considering the reversed phase nature of the
column would favour the retention of the more lipophillic
phenyl containing complex 1.
The analytical separation of the stereoisomers of 2 has been
reported earlier by Gasparrini et al.13,14 The analytical and semi-
preparative separation of 3 was carried out using a non-
commercial teicoplanin based column (see ESI,† Fig. S2 and
S3).13
Fig. 2 Molecular structure and labelling scheme for 1.
Circular dichroism spectroscopy
The CD spectra for the ∆ and Λ stereoisomers 3 are shown
in Fig. 4. As expected both stereoisomers exhibit very strong
opposite (but equal) Cotton effects. Identification of each of
the stereoisomers as either Λ or ∆ is made by comparison with
CD spectra of [Ru(bipy)3]2ϩ and [Ru(phen)3]2ϩ of known
Fig. 3 Diagram of the hydrogen bridged dimer for 2.
D a l t o n T r a n s . , 2 0 0 3 , 2 5 9 7 – 2 6 0 2
Fig. 4 CD spectra for the ∆ and Λ stereoisomers of 3 in CH3CN.
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configuration.3,15 The CD spectra of the stereoisomers of 1
(see ESI,† Fig. S4) and 3 are, to a first approximation, very
similar and show only very minor differences in the position of
maxima and minima. The first enantiomer of 1 to elute on the
carbamate based chiral HPLC column has a CD spectrum
featuring two bisignate couplets in the LCT (ligand centred
tansitions, π–π*) (250–300 nm) and MLCT (350–520 nm)
regions, with negative signs for the lower wavelength bands
within each couplet. These spectral features are characteristic
of complexes having Λ configuration (see ESI,† Fig. S4). The
elution order on the carbamate column is thus Λ before ∆ for 1.
The same elution order was obtained for the enantiomers of 3
on the teicoplanin column.
ments were recorded under identical conditions of solvent and
temperature.
The excited MLCT state of [Ru(bipy)3]2ϩ is known to pos-
sess a considerable amount of charge transfer to solvent char-
acter (CTTS)18 and this is expected to be the case for other
ruthenium() polypyridyl complexes. Hence for the systems
under examination, excited state interaction with the solvent
would be expected to be substantial. The use of chiral solvents
amenable to intermolecular interactions such as π-stacking and
hydrogen bonding could in principle, affect the electronic
structure of stereoisomers of transition metal complexes.
3
However, for such intermolecular interactions to produce
measurable differences in the photophysical properties of such
complexes, they must be sufficiently strong/non-random to
affect the complex over the timescale of the lifetime of the
excited states of such molecules. In fluid solutions, and indeed
in glassy matrices, the randomness of the solvent orientation
around the complex is almost complete. Hence, if solvent–sol-
ute interactions significantly effect the excited state lifetime then
multi-exponential behaviour would be anticipated. Only if such
intermolecular interactions are significant will differences in the
photophysical properties of the stereoisomers be observed. For
each of the enantiomeric pairs of 1, or 3 both intramolecular
and intermolecular interactions (in achiral solvents) are identi-
cal and hence no differences in their photophysical properties
are expected. However, the use of enantiopure hosts could, in
principle, result in differential stabilisation of the enantiomers.
No differences are observed in the photophysical properties of
the stereoisomers of 1 or 3 in both achiral and chiral solvents.
Electronic properties
The absorption and emission properties of all complexes are
reported in Table 1. The lowest energy absorption feature for
the ruthenium complexes is assigned to a singlet metal-to-
ligand charge-transfer (1MLCT) transition (logε ∼ 4) by
comparison with similar Ru() polypyridyl complexes.2–6 All
compounds show strong absorptions (logε ∼ 5) at about 280 nm
which are π–π* in nature. Overall the electronic properties of all
complexes are typical for pyrazyl-1,2,4-triazole complexes.6 All
complexes examined are luminescent in acetonitrile at room
temperature and at 77 K. The ruthenium complexes examined
all emit in the 650–700 nm region and a large blue shift is
3
observed between 300 and 77 K, typical for MLCT emission
(Table 1).4
The photophysical properties of the stereoisomers of 1 and 3
have been examined in racemic 1-phenylethanol, in (S)-(Ϫ)-1-
phenylethanol (Table 2) and in acetonitrile (Table 1). 1-Phenyl-
ethanol was chosen as a solvent for two reasons. First the
solvent is inherently chiral and can be obtained in enantio-
merically pure form. Secondly the presence of a phenyl group
and a hydroxyl moiety allows for the possibility of a π-stacking
interaction and hydrogen bonding interaction between the
pyridyl/phenyl/pyrazyl-rings of the complex and the solvent
phenyl group and hydroxyl group, respectively. Such inter-
actions have been reported by Patterson and Keene16 and by
Hesek et al..17
For both 1 and 3 no differences in the electronic or photo-
physical properties between the enantiomeric pairs and a
racemic mixture were observed as is apparent from Table 2. The
slight increase in lifetime observed in (S)-(Ϫ)-1-phenylethanol
compared with the racemic solvent is probably due to different
H2O contents in the solvents employed. In each case measure-
Conclusions
The confirmation of the coordination mode in two Ru() poly-
pyridyl complexes containing pyrazine-triazole based ligands as
being via the N2 position justifies previous assignments. In
addition, the X-ray structure of 2 in a mixed protonation state
confirms the interpretation of CHN results for this class of
complex. The photophysical results reported here are in agree-
ment with those obtained for [(Ru(bipy)2)2(bpt)]3ϩ (Hbpt = 2,5-
bis(pyrid-2Ј-yl)-4H-1,2,4-triazole), and indicate that the pres-
ence of stereoisomers does not affect the general photophysical
properties in both mononuclear and binuclear complexes. That
no differences in the photophysical properties of the stereo-
isomers are observable either at 77 K or at room temperature
in both racemic and enantiomerically pure solvents, suggests
strongly that the differences between the stereoisomers in either
ground or excited state structure are not significant.
Table 1 Electronic properties
Experimental
λmax(abs.)/nm (logε)a
λmax(em.)/nm (τ/ns)a
λmax/nm (τ/µs)b
Materials
1
2
3
453 (4.02)
456 (3.81)
430 (3.68)
670 (220)
668 (250)
654 (860)
645 (6.7)
640 (6.0)
595 (9.2)
All solvents employed were of HPLC grade. For emission
measurements UVASOL grade solvents were employed.
Racemic and enantiopure (S)-(Ϫ)-1-phenylethanol (Aldrich)
were used as received. All reagents employed in synthetic
procedures were of reagent grade or better. Hpztr6 and
N2 isomers only. a All measurements in deaerated acetonitrile at 298 K.
b In EtOH–MeOH (1 : 1) at 77 K.
Table 2 Spectroscopic data
(S)-(Ϫ)-1-Phenylethanol
τ/ns (λmax/nm) 298 Ka
rac-1-Phenylethanol
τ/ns (λmax/nm) 298 Ka
τ/µs (λmax/nm) 77 K
1a
1b
3a
3b
160 (680)
161 (680)
230 (657)
229 (656)
165 (680)
168 (680)
223 (657)
219 (657)
5.0 (610)
5.2 (610)
7.6 (590)
7.6 (590)
N2 isomers only. a Samples deaerated by argon purge, λ 5 nm (τ 5%).
D a l t o n T r a n s . , 2 0 0 3 , 2 5 9 7 – 2 6 0 2
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Table 3 X-Ray experimental crystal data for 1 and 2
1
2
Empirical formula
RuC32H24N9ؒPF6ؒ0.7C2H5OHؒ0.5H2O
RuC26H20.5N9ؒ1.5PF6ؒ0.75H2O
Formula weight/g molϪ1
821.90
293(2)
0.71073
791.52
293(2)
0.71073
Orthorhombic, B2cb
Temperature/K
Wavelength/Å
Symmetry, space group
¯
Triclinic, P1
Unit cell dimensions:
a/Å
b/Å
c/Å
12.232(17)
12.301(2)
13.296(2)
17.4944(15)
17.5143(16)
19.5605(19)
α/Њ
β/Њ
78.996(12)
64.996(10)
γ/Њ
77.151(10)
1757.0(5), 2
1.554
V/Å3, Z
5993.4(10), 8
1.738
Dc/Mg mϪ3
Crystal dimensions/mm
0.15 × 0.15 × 0.1
0.566
0.25 × 0.15 × 0.1
0.697
µ/mmϪ1
F(000)
830
1.9–25.3
3126
2.1–27.1
0 ≤ h ≤ 22; 0 ≤ k ≤ 22; 0 ≤ l ≤ 25
3430
θ range for data collection/Њ
Limiting indices
No. reflections collected
Ϫ14 ≤ h ≤ 1; Ϫ14 ≤ k ≤ 14;Ϫ15 ≤ l ≤ 14
7145
Independent reflections (Rint
∆ρ/σ (mean)
Data/restraints/parameters
GOF F 2
)
4344 (0.0433)
0.063 (0.005)
6202/162/596
1.023
2184 (0.052)
0.027 (0.004)
3430/88/533
0.977
Final R1 [I > 2σ(I )]
Final R1 (all data)
0.0653
0.1540
1.31/Ϫ0.76
0.0351
0.0568
0.303/Ϫ0.368
Largest difference peak and hole/e ÅϪ3
cis-[Ru(LL)2Cl2]ؒ2H2O19 (LL = 2,2Ј-bipyridine or 1,10-phenan-
throline) were prepared by literature methods. [Ru(bipy)2-
(mepztr)](PF6) 4 was available from earlier studies.6
from acetone–water (5 : 1). The N2 isomer was isolated by
column chromatography as for 1 (720 mg, 90% {both N2 and N4
isomer combined}) (Found: C, 39.3; H, 2.70; N, 15.48.
RuP1.5F9N9C30H21ؒH2O requires C, 39.25; H, 2.64; N, 15.85 %).
Syntheses
H([Ru(phen)2(pztr)])2(PF6)3ؒH2O (3). cis-[Ru(phen)2Cl2]ؒ
2H2O (0.53 g, 1 mmol) and Hpztr (0.3 g, 2 mmol) were heated at
reflux in 50 cm3 of ethanol for 8 h, after which the ethanol was
removed by evaporation and the product redissolved in water a
precipitated with saturated aqueous NH4PF6. The complex was
collected by vacuum filtration and recrystallised from acetone–
water (5 : 1). The N2 isomer was isolated by column chromato-
graphy as for 1 (600 mg, 72% combined yield of N4 and N2
isomers) (Found: C, 42.86; H, 2.65; N, 14.55. RuP1.5F9N9-
C30H20ؒH2O requires C, 42.70; H, 2.49; N, 14.95%).
2-(5Ј-Phenyl-4ЈH-[1,2,4]triazol-3Ј-yl)pyrazine
(Hphpztr).
Sodium metal (0.8 g) were added (carefully) to 35 cm3 of
methanol followed by the addition of 2-pyrazine carbonitrile
(10.9 g, 104 mmol). The solution was heated at reflux for 3 h
after which, it was allowed to cool and phenyl hydrazide (17 g,
104 mmol) was added and the solution refluxed for a further
15 min yielding a dark yellow solution. Yellow crystals formed
on cooling to room temperature overnight and were filtered
under vacuum and air dried for one hour. The crystals were
dissolved in 40 cm3 of ethylene glycol and refluxed for 3 h. On
cooling overnight the white target ligand precipitated and was
collected by vacuum filtration, followed by washing with 50 cm3
methanol. The product was recrystallised from hot ethanol.
X-Ray crystallography
Data for 1 was collected on a Bruker P4 diffractometer using
the XSCANS20 software with graphite monochromated
Mo-Kα radiation (Table 3). Data for 2 was collected on a Enraf
Nonus CAD4 diffractometer with graphite monochromated
Mo-Kα radiation (Table 3)21 using the NRCVAX system of
programs. Relevant experimental data are presented in Table 3.
The structures were solved using direct methods and refined
with the SHELXL-97 program22 and the non-hydrogen atoms
were refined with anisotropic thermal parameters. There is con-
siderable disorder in the molecular structures of 1 and 2. In 1
the hexafluorophosphate anion [PF6]Ϫ anion is present as two
half molecules residing on inversion centres both of which are
disordered over two sites and which refine to site occupancy
factors of 0.81(5)/0.19(5) and 0.58(13)/0.42(13) in the final
refinement cycles. A partial occupancy molecule of ethanol was
discerned and modelled in the penultimate stages of refinement
with occupancies of 0.35 : 0.35 site occupancy together with a
water molecule with occupancies of 0.25 : 0.25. Loose restraints
using DFIX controls were used for the P–F/cis-F ؒ ؒ ؒ F dis-
tances in the hexafluorophosphate anion, the C–O and O–H
bond lengths, as well as DELU/ISOR controls for the com-
ponents of the displacement ellipsoids in all three disordered
moieties (anion/ethanol/water). In 2, disorder is present in the
hexafluorophosphate anions with the [PF6]Ϫ anion which
resides on a general position disordered over two sites with
Yield of Hphpztr (15 g, 64%); m/z 224 (HMϩ); H NMR (400
1
MHz, D6-DMSO): δ 9.35 (d, 1H, pz-H3), 8.795 (dd, 1H, pz-H5),
8.765 (d, 1H, pz-H6), 8.11 (d, 2H, Ph-H2/H6), 7.54 (dd, 2H,
Ph-H3/H5), 7.49 (t, 1H, Ph-H4)
[Ru(bipy)2(phpztr)](PF6)ؒ2H2O (1). Hphpztr (0.63 g, 2.8
mmol) and cis-[Ru(bipy)2Cl2]ؒ2H2O (1 g, 2.1 mmol) in 80 cm3
were heated at reflux in ethanol–water (2 : 1) for 4 h. The
ethanol was subsequently removed and the product precipitated
with concentrated NH4PF6(aq) solution. The precipitate was
collected under vacuum and recrystallised from 30 cm3 acetone–
water (5 : 1) with two drops of conc. ammonia solution. The N2
isomer was isolated by column chromatography on neutral
alumina with acetonitrile as eluent (0.55 g, 25%). Crystals for
X-ray studies were grown from ethanol solution (Found: C,
46.92; H, 3.02; N, 15.54; P, 3.47. RuPF6N9C32H24ؒ2H2O requires
C, 47.06; H, 3.19; N, 15.44; P, 3.80%); m/z 635 (Mϩ).
H([Ru(bipy)2(pztr)])2(PF6)3ؒH2O (2). cis-[Ru(bipy)2Cl2]ؒ2H2O
(0.5 g, 1 mmol) and Hpztr (0.3 g, 2 mmol) were heated at reflux
in 50 cm3 of ethanol for 8 h, after which the ethanol was
removed by evaporation and the product redissolved in 10 cm3
of water and precipitated with saturated aqueous NH4PF6. The
complex was collected by vacuum filtration and recrystallised
D a l t o n T r a n s . , 2 0 0 3 , 2 5 9 7 – 2 6 0 2
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occupancies of 0.522(16) and 0.478(16), respectively, and 0.33 :
0.17 for the half occupancy anion (per unit cell anion). Partial
occupancy water is present which refines to a site occupancy
factor of 0.75: the H atoms on water were located from differ-
ence maps and were treated as riding atoms with loose O–H
bond length DFIX restraints.
CCDC reference numbers 204725 and 204726.
See http://www.rsc.org/suppdata/dt/b3/b301961f/ for crystal-
lographic data in CIF or other electronic format.
apparatus (TCSPC) comprising of two model J-yA mono-
chromators (emission and excitation), a single photon photo-
multiplier detection system model 5300, and F900
a
nanosecond flashlamp (N2 filled at 1.1 atm pressure, 40 kHz),
interfaced with a personal computer via a Norland MCA card.
A 500 nm cut-off filter was used in emission to attenuate scatter
of the excitation light (337 nm) luminescence was monitored at
650 nm. Data correlation and manipulation was carried out
using EAI F900 software version 5.1.3. Samples were deaerated
for 20 min using Ar gas before measurements were carried out,
followed by repeated deaeration to ensure total oxygen exclu-
sion. Emission lifetimes were calculated using a single exponen-
tial fitting function; Levenberg–Marquardt algorithm with
iterative reconvolution (Edinburgh instruments F900 software).
The reduced χ2 and residual plots were used to judge the quality
of the fits. Lifetimes are 5%.
Chromatography
Separation of the ∆ and Λ stereoisomers of 1 was carried out
using a JASCO Gulliver system equipped with a single-wave-
length UV-visible detector set to 290 nm, Rheodyne injection
valve and a Daicel Chiralcel OD–RH stainless steel (15 cm ×
4.6 mm i.d.) carbamate based semi-preparative column. The
column temperature was set at 28 ЊC and column pressure 40 kg
cmϪ2. Elution was with 0.1 M NaPF6 water–acetonitrile (60 : 40
v/v). Separation of the ∆ and Λ stereoisomers of 3 was carried
out with semi-preparative HPLC using a chiral stationary
phase (CSP 1) containing Teicoplanin bonded to silica gel
Acknowledgements
We thank Enterprise Ireland for financial support.
microparticles, packed in a 250 × 10 mm i.d. column.13,14
A
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