RAPID COMMUNICATIONS IN MASS SPECTROMETRY
Rapid Commun. Mass Spectrom. 2009; 23: 3831–3836
Published online in Wiley InterScience (www.interscience.wiley.com) DOI: 10.1002/rcm.4323
Mass spectrometry and UV-VIS spectrophotometry of
ruthenium(II) [RuClCp(mPTA)2](OSO2CF3)2 complex
in solution
Eladia Marı́a Peña-Méndez1*, Beatriz González2, Pablo Lorenzo2, Antonio Romerosa3
and Josef Havel4,5
1
Department of Analytical Chemistry, Nutrition and Food Science, Faculty of Chemistry, University of La Laguna, Campus de Anchieta, 38071 La
Laguna, Tenerife, Spain
2
Department of Inorganic Chemistry, Faculty of Chemistry, University of La Laguna, Campus de Anchieta, 38071 La Laguna, Tenerife, Spain
3
Section of Inorganic Chemistry, Faculty of Science, Almerı́a University, 04120 Almerı́a, Spain
4
Department of Chemistry, Faculty of Science, Masaryk University, Kotlářská 2, 61137 Brno, Czech Republic
5
Department of Physical Electronics, Faculty of Science, Masaryk University, Kotlářská 2, 61137 Brno, Czech Republic
Received 6 August 2009; Revised 30 September 2009; Accepted 1 October 2009
Ruthenium(II) complexes are of great interest as a new class of cancerostatics with advantages over
classical platinum compounds including lower toxicity. The stability of the [RuClCp(mPTA)2](OSO2CF3)2 complex (I) (Cp cyclopentadienyl, mPTA N-methyl 1,3,5-triaza-7-phosphaadamantane) in
aqueous solution was studied using spectrophotometry, matrix-assisted laser desorption/ionization
(MALDI) and laser desorption/ionization (LDI) time-of-flight (TOF) mass spectrometry (MS).
Spectrophotometry proves that at least three different reactions take place in water. Dissolution
of I leads to fast coordination of water molecules to the Ru(II) cation and then slow hydrolysis and
ligand exchange of chloride and mPTA with water, hydroxide or with trifluoromethane sulfonate
itself. Via MALDI and LDI of the hydrolyzed solutions the formation of singly positively charged
ions of general formula RuClp(Cp)q(mPTA)r(H2O)s(OH)t ( p ¼ 0–1, q ¼ 0–1, r ¼ 0–2, s ¼ 0–5, t ¼ 0–2) and
of some fragment ions was shown. The stoichiometry was determined by analyzing the isotopic
envelopes and computer modelling. The [RuClCp(mPTA)2](OSO2CF3)2 complex can be stabilized in
dilute hydrochloric acid or in neutral 0.15 M isotonic sodium chloride solution. Copyright # 2009
John Wiley & Sons, Ltd.
All drugs used for chemotherapy of cancer have some
drawbacks and undesirable side effects. Many attempts have
been made to increase our understanding of the action of
anti-cancer compounds such as e.g. cis-platinum. Ruthenium
compounds are now of high interest in biology and medicine
due to their great cancerostatic activity1,2 and because they
show lower toxicity than platinum compounds.3 As
ruthenium can mimic iron in binding serum proteins (such
as transferrin or albumin), the ruthenium compounds
interact with DNA4 and are therefore prospective anticancer drugs even if, in contrast to Pt-based drugs, the
mechanisms of the activity of Ru-based compounds are still
not well known and/or understood.5,6 Promising alternatives to platinum anti-tumour drugs in the treatment of
cancer7,8 are those ruthenium compounds which have as
ligand water-soluble phosphines, such as, 1,3,5-triaza-7phospha-adamantane (PTA), for example. In addition, the
influence of pH on the toxicity of chemotherapeutic drugs is
becoming clearer as an outcome of understanding the
*Correspondence to: E. M. Peña-Méndez, Department of Analytical Chemistry, Nutrition and Food Science, Faculty of Chemistry, University of La Laguna, Campus de Anchieta, 38071 La
Laguna, Tenerife, Spain.
E-mail: empena@ull.es
mechanism action of such drugs.5–8 Romerosa et al.9 studied
the DNA binding of cyclopentadienyl ruthenium(II) complexes where N-methyl-1,3,5-triaza-7-phospha-adamantane
(mPTA) and triphenylphosphine (PPh3) were used as
ligands. It was found that water-soluble species containing
{RuClCp} interact more effectively with super-coiled DNA
when mPTA acts as a ligand.10–12 McNae et al.13 recently
studied the physicochemical behavior of the cyclopentadienyl ligand in {Ru(PTA)} half-sandwich complexes and its
pronounced effect on the biological activity was described.
The chemical properties, stability and hydrolysis of such
ruthenium complexes are insufficiently described in the
literature, and the hydrolysis of species containing the
{RuClCp(mPTA)2}2þ entity has also not yet been completely
described.14,15 Recently, Akbayeva et al.,25 Dutta et al.,4
McNae et al.13 and Allardyce et al.16 suggested the
importance of hydrolysis for the interaction of rutheniumPTA and ruthenium arene complexes with DNA. However,
such hydrolysis processes are difficult to study. It has,
however, been shown during the last decade that matrixassisted laser desorption/ionization (MALDI) or laser
desorption/ionization (LDI) time-of-flight (TOF) mass spectrometry (MS) can also be used with advantage for the
analysis of inorganic materials, compounds and complexes
Copyright # 2009 John Wiley & Sons, Ltd.
3832 E. M. Peña-Méndez et al.
or even for speciation in solution. For example, these
techniques have been successfully applied for the analysis
of uranium oxides clusters,17 rhenium complexes,18 Rh(III)
chloride hydrolysis speciation,19 speciation of iridium in
aqueous solution,20 arsenic21 and selenium sulfide clusters,22
analysis of the tungstates and molybdates of the rare earth
elements,23 and/or for laser ablation synthesis of selenium
super oxide.24 MALDI and LDI of inorganic complexes
produce almost solely singly charged ions in comparison
with electrospray ionization (ESI)-MS, and MALDI as a soft
ionization technique yields little fragmentation. TOF MS
with sufficiently high mass resolution also enables the
observation of isotopic patterns which can be suitable for the
identification of the species formed.
The ruthenium complex, [RuClCp(mPTA)2](OSO2CF3)2
(I), is readily soluble in water. This is mainly due to the
presence of two mPTA groups in the molecule and the
chloride anion bound to Ru(II). It has been reported that no
great effect on solubility is provided by the CF3SO2O
counter anion.9,25 Good solubility of I in water is important
for the potential use of this compound in medicine and thus
knowledge of its stability and hydrolysis in aqueous solution
is important. Spectrophotometry and MALDI (or LDI) TOF
MS has been applied in this work to characterize the
hydrolysis products of I in aqueous solution and also to
evaluate the stability of the complex with respect to nitrogen
337 nm laser radiation.
matrix solution was pipetted onto the target and then mixed
with 1 mL of solution I. The AnorgPro matrix was prepared
as an aqueous solution (10 mg mL1) and mixed in the ratio
1:1 with 0.1% aqueous TFA solution.
Instrumentation
Spectrophotometric measurement was performed on a
Hewlett Packard HP 84553 diode-array spectrophotometer
(Hewlett Packard, Waldbronn, Germany) furnished with
quartz cells of 1 cm path length and connected to a Vectra
ES computer (Hewlett Packard), via an RS232C interface.
The pH was measured with a Radiometer PHM84 digital pH
meter equipped with a dual glass-saturated calomel
electrode, both from Radiometer (Copenhagen, Denmark).
The pH meter was calibrated with at least two standard
buffer solutions of pH 4.02 and 7.00, also from Radiometer.
The temperature of the solutions was controlled by a Lauda
MS6 thermostat (Königshofen, Germany) at 25 0.058C.
The mass spectra were measured using an AXIMA CFR
TOF instrument (Kratos Analytical, Manchester, UK)
equipped with a nitrogen laser operating at 337 nm from
Laser Science Inc. (Franklin, MA, USA). The laser source was
operated in a repetition mode at 10 Hz frequency with a
pulse width of 3 ns. The maximum average laser power was
6 mW. For external calibration in both negative and positive
ion mode, CHCA and DHB ions were used. Each mass
spectrum was obtained using a minimum accumulation of
100–200 shots.
EXPERIMENTAL
Chemicals
The ruthenium compound [RuClCp(mPTA)2](OSO2CF3)2 (I)
was prepared according to published procedures.9,15 Fresh
aqueous solutions were always used (if not otherwise
mentioned). a-Cyano-4-hydroxycinnamic acid (CHCA)
and 2,5-dihydroxybenzoic acid (DHB) of analytical grade
purity, trifluoroacetic acid (TFA), acetone, and sodium
chloride were obtained from Sigma Aldrich (Steinheim,
Germany). trans-2-[3-(4-tert-Butylphenyl)-2-methyl-2-propenylidene]malononitrile (AnorgPro) and b- or g-cyclodextrins
were purchased from Fluka (Buchs, Switzerland). All other
chemical and solvents were of analytical-reagent grade. The
solutions were prepared using doubly distilled water
prepared using a quartz distillation stand from Heraeus
Quartzschmelze (Hanau, Germany).
Software and computation
The STATISTICA V.6 software package from STAT soft Inc.
(Tulsa, OK, USA) was used for factor analysis to estimate the
number of species in solution.26 Structure modelling via a
semi-empirical approach was carried out using the
HYPERCHEMTM program (release 5.1, 1998) from Hypercube Inc. (Gainesville, FL, USA). All computation was
performed on a Pentium-based IBM compatible personal
computer.
Sample preparation
For LDI TOF measurements, 1 mL of a solution of I was
deposited onto a target and dried at room temperature in a
stream of air. For the MALDI TOF measurements, 1 mL of the
Copyright # 2009 John Wiley & Sons, Ltd.
RESULTS AND DISCUSSION
Spectrophotometric study of
[RuClCp(mPTA)2](OSO2CF3)2 hydrolysis in
aqueous solution
The complex [RuClCp(mPTA)2](OSO2CF3)2 (I), in the form of
its trifluoromethane sulfonate salt, is readily soluble in
organic solvents such as acetone, and also in water. The
optimized structure of the complex cation is given in Fig. 1.
The solution of the compound in dry acetone shows an
absorption maximum at 345 nm and an absorption band at
410 nm. On adding even a small amount of water to the
acetone solution of I, the absorbance at the absorption
maximum at 345 nm is slightly increased (10%). This is
probably due to the fast addition of water to the
ruthenium(II) complex.
Absorption spectra in aqueous solution at different
concentrations (0.078 to 0.41 mM) were measured in order
to check for possible dimer formation (Fig. 2(A)) but no
substantial changes in the character of the spectra were
observed when increasing the concentration of I. Factor
analysis (FA) of the spectra was performed, calculating
Eigenvalues of the absorbance matrix. It is well known that
the number of non-zero Eigenvalues is equal to the rank of
the matrix and this gives an estimate of the number of species
formed in solution26 without any a priori suggestions. The FA
results shown in Fig. 2(A) indicate that the value of the rank
is equal to two. Thus, in spite of the apparently same spectra
being obtained when the concentration of I is increased, there
is an indication of some changes in the solution. Therefore,
the kinetics of the spectra change when the complex is
Rapid Commun. Mass Spectrom. 2009; 23: 3831–3836
DOI: 10.1002/rcm
Study of Ru(II) [RuClCp(mPTA)2](OSO2CF3)2 complex in solution
3833
suggested that the [RuClCp(mPTA)2](OSO2CF3)2 complex
when dissolved in water first undergoes fast addition of
water and then slower hydrolysis forming several products.
Mass spectrometry
We attempted to elucidate the hydrolysis processes taking
place after dissolution of I in water and to determine the
composition of the hydrolysis products. Either MALDI or
LDI MS was used for this purpose.
MALDI-TOF MS study of the
[RuClCp(mPTA)2](OSO2CF3)2 complex
Figure 1. Structure of the [RuClCp(mPTA)2]2þ cation as
optimized by the Hyperchem program.
dissolved in water were further studied in detail. The UV-VIS
spectra of the aqueous solution of I show three isosbestic
points (IP) at 300, 355 and 405 nm within 1 h (Fig. 2(B)).
These changes indicate that several chemical equilibria (at
least three) occur after the dissolution of the compound in
water. In this case FA gives the value of rank equal to three or
four (Fig. 2(B), inset in the right upper corner). This means
that in the aqueous solution of I several other species (three
or four) are formed from the original complex. It could be
(B)
1
t=0
Absorbance
0.8
f
e
0.6
d
0.4
c
b
0.2
a
0
Eigenvalue
0.12
Absorbance
(A)
Various matrices were examined for the MALDI TOF MS
of I with the aim of developing a MALDI method for the
detection and/or determination of the compound. The
hydrolysis of I in solution was also studied. Of the matrices
(CHC, DHB, AnorgPro) examined, AnorgPro was found to
be the most suitable: DHB and CHC were found to react with
the complex while AnorgPro did not. The ‘thin-layer’ sample
preparation method was applied: 1 mL of the AnorgPro
matrix solution was dropped onto the target, allowed to dry,
and then 1 mL of an aqueous solution of I (1.5 mM) was
added and the mixture was dried in a stream of air at room
temperature. The sample was analyzed after the vacuum had
dropped below 104 Pa. The mass spectra were recorded in
linear positive and negative ion modes, as well as in
the reflectron mode. Spectra in the negative ion mode were
of low intensity and are therefore not shown here. The
MALDI mass spectra in positive ion mode revealed the
presence of singly charged ruthenium species detected in
both linear and in reflectron mode. Figure 3(A) shows a
MALDI TOF mass spectrum of I. The main peak in
the mass spectrum is at m/z 660 but down to m/z 330
there are several other minor peaks demonstrating the
formation of other Ru-containing hydrolysis species. The
group of the peaks at m/z 660 was found to correspond
approximately to a hydrate of I, [RuClCp(mPTA)2](H2O)n.
However, careful analysis and modelling of the isotopic
envelopes enabled this main product to be to identified
as a mixture (1:1) of [RuClCp(mPTA)2](H2O)4(OH)Naþ
with other [Ru(OH)Cp(mPTA)2](H2O)5(OH) species not
250
300
350
400
Wavelength (nm)
IP2
0.08
Rank
Rank
0.04
IP1
60 min
0
0
2
4
6
8
Number of Factors
t=0
IP3
t=0
450
500
Wavelength (nm)
Figure 2. Absorption spectra of aqueous solutions of the [RuClCp(mPTA)2](OSO2CF3)2 complex. (A) Spectra
recorded at various concentrations of I (pH 5.56): a 0.078, b 0.15, c 0.18, d 0.24, e 0.34, f 0.41 mM. (B) Changes in
absorption spectra at pH 8.50. Concentration of 0.34 mM.
Copyright # 2009 John Wiley & Sons, Ltd.
Rapid Commun. Mass Spectrom. 2009; 23: 3831–3836
DOI: 10.1002/rcm
3834 E. M. Peña-Méndez et al.
(B)
(A)
658.8
Na+
RuCp(mPTA)2(H2O)5(OH)2
RuClCp(mPTA)2(H2O)4(OH) Na+
Reelative Inteensity (%)
100 EXPERIMENT
C ( S 2CF
C 3)(H
)( 2O)(OH)
)(
)2+
70 RuCl(OSO
RuCp(OSO2CF3)Na+
RuClCp(mPTA)
p(
)2((H2O))5+
50
RuCp(mPTA)2(H2O)4OH+
30
RuClCp(mPTA)Na+
RuCp(mPTA)(H2O)3H+
10
0
350
400
450
500
m/z
550
80
60
636.7
40
20
600.3
0
100 MODEL
Peaks of the matrix
600
650
700
Relative Intensitty (%)
Rellative Inteensity (%)
100
RuClCp(mPTA)2(H2O)3(OH)Na+
RuCp(mPTA)2(H2O)5(OH)2Na+
80
60
40
RuCp(mPTA)2(H2O)4OH+
RuCp(mPTA)2(H2O)5+
20
0
595 605 615 625 635 645 655 665
m/z
Figure 3. MALDI TOF mass spectra of the [RuClCp(mPTA)2](OSO2CF3)2 complex. (A) An overview of the
positive ion mode mass spectrum obtained using AnorgPro matrix. (B) Comparison of experimental spectra with
theoretical isotopic envelopes.
containing chloride. It seems that two water molecules are
stepwise dissociating forming one or two OH groups while,
in the second case, the chloride is replaced by one OH group.
The remaining water molecules exceeding the maximum
coordination number of Ru(II) will either be present in the
second coordination sphere or are just adducts. A comparison of experimental mass spectra with calculated isotopic
envelopes of species in the range m/z 590–670 is shown in
Fig. 3(B). Of the other identified species, [Ru(OH)Cp(mPTA)2]þ(H2O)4 (m/z 600.3) and [RuClCp(mPTA)2]þ(H2O)5
(m/z 636.7), only the second one contains chloride. This is
the original molecule I with five water molecules attached.
The chloride in the first species was eliminated by ligand
exchange with a water molecule in the first stage of hydrolysis.
The stoichiometry of the other species in the range m/z 320–600
was also confirmed by analyzing isotopic envelopes and
comparison with theoretical models. An example of such a
comparison of the theoretical isotopic envelopes with the
experimental ones is shown in Fig. 3(B) and excellent
agreement can be observed. The group of the peaks at m/z
335 was identified as an overlay of {RuCl(OSO2CF3)
(H2O)(OH)2} and RuCp(OSO2CF3)Naþ ions and that at
m/z 395 as RuClCp(mPTA)þ with {RuCp(mPTA)(H2O)3H}þ
species.
The changes in the UV-Vis spectra of the alkaline solution
of I (at pH 8.50, after adding 0.1 M NaOH) provide evidence
that hydrolysis reactions also take place at basic pH. MALDI
TOF MS analysis of the solution at basic pH as a function of
time (Fig. 4) shows that the relative abundance of the hydrolytic
species containing Ru(II) changes significantly with time and
thus also clearly demonstrates that hydrolysis processes take
place. The first spectrum (time ¼ 0) shows the same main peaks
Copyright # 2009 John Wiley & Sons, Ltd.
as those shown in Fig. 3. The most intense group at m/z 658
corresponds to a mixture of RuClCp(mPTA)2(H2O)3(OH)Naþ
with RuCp(mPTA)2(H2O)5(OH)2Naþ, species, etc. As the
time increases up to 2 h, the abundance of the species around
m/z 658 diminishes and lower mass species in the range
m/z 520–540 eventually prevail.
LDI-MS study
In addition to MALDI measurements LDI of I was also
carried out. The sample preparation was similar: 1 mL of the
solution of I (2.6 105 M) was deposited onto the target plate
and dried as described in the Experimental section. Several
Ru-containing ions were observed in the LDI mass spectra in
both positive and negative ion mode. The stoichiometry of
these singly charged ions was identified using isotopic
pattern modelling, as described above.
The LDI mass spectra of I show some differences from the
MALDI spectra. They are of lower signal intensity and no
peaks with m/z > 660 were observed. Figure 5 shows an LDI
TOF mass spectrum of I where it can be seen that the most
intense peaks are observed in the m/z range 250–600. The
species containing ruthenium at m/z values around 250, 265,
295, 335, 350–400, 429 and 600 were identified, respectively,
as Ru(OSO2CF3)þ, Ru(OSO2CF3)H2Oþ, RuCp(OSO2CF3)Naþ,
RuCpCl(mPTA)Naþ, RuCp(mPTA)(H2O)OHþ, RuCl(mPTA)(H2O)þ
3
and a mixture of RuClCp(mPTA)2(H2O)þ
with
3
RuCp(mPTA)2(H2O)þ
5 . Generally, the presence here of up
to five water molecules in the identified species is further
evidence of the strong addition of water molecules to Ru(II)
in the original [RuClCp(mPTA)2]2þ cation after dissolution in
water. These results showing coordination of water to the
[RuClCp(mPTA)2] complex are in agreement with other
Rapid Commun. Mass Spectrom. 2009; 23: 3831–3836
DOI: 10.1002/rcm
Study of Ru(II) [RuClCp(mPTA)2](OSO2CF3)2 complex in solution
3835
100
Relative Intenssity (%)
80
180 min
60
120 min
40
90min
60 min
20
0 min
0
520
540
560
580
600
620
640
660 680
m/z
Figure 4. MALDI TOF mass spectra of an alkaline solution of I as a function of time.
Conditions: pH 8.50, concentration 0.34 mM.
reports. For example, [Ru(H2O)2(mPTA)4]6þ has been
structurally characterized27 and [RuI2(H2O)(mPTA)3]I3 is
also known.28 The RuCp(mPTA)2(H2O)5 species identified in
this work might correspond to the [Ru(H2O)Cp(mPTA)2]
complex synthesized recently.15
Even if the composition of some of the hydrolysis species
differs slightly from those found in MALDI, the ligand
exchange of chloride, Cp or mPTA with water, and OH or
OSO2CF
3 anions is confirmed. Partial decomposition of I and
its hydrolysis products via 337 nm laser radiation can also
occur and so cannot be excluded.
Stability of the aqueous solution of
[RuClCp(mPTA)2](OSO2CF3)2
In view of the possible applications of [RuClCp(mPTA)2](OSO2CF3)2 in medicine and considering that we have shown
that I undergoes hydrolysis in aqueous solution, possible
ways for the stabilization of I in aqueous solution were
studied. When the pH of an aqueous solution of I was
decreased below pH 3–4 using dilute hydrochloric acid, the
UV-Vis spectra of aqueous solution of I do not show any
changes with time. The possibility of the stabilization of I in
neutral solution has also been examined. For example, the
RuCp(OSO2CF3)Na+
80
40
20
RuCll(mPTA)C
CpNa+
RuCpp(mPTA)((H2O)OH+
60
A)Na+
RuCp
pCl(mPTA
RuCl(mPTA)(H2O)3+
Ru
u(OSO2CF
F3)+
O2CF3)(H2O)+
Ru(OSO
Relattive Inteensity (%
%)
100
RuCp(mPTA)2(H2O)5+
RuClCp(mPTA)2(H2O)3+
0
250
300
350
400
450
m/z
500
550
600
650 700
Figure 5. LDI positive ion mass spectrum of [RuClCp(mPTA)2](OSO2CF3)2.
Conditions: pH 5.56, concentration 0.34 mM.
Copyright # 2009 John Wiley & Sons, Ltd.
Rapid Commun. Mass Spectrom. 2009; 23: 3831–3836
DOI: 10.1002/rcm
3836 E. M. Peña-Méndez et al.
use of b- and g-cyclodextrins to stabilize I in solution via
formation of supramolecular host-guest complexes was
studied; however, no stabilizing effect was found probably
because no host-guest complexes are formed. As described
above, ligand exchange of chloride is the main effect of
hydrolysis. Therefore, the effect of chloride was studied in
detail and it was found that by greatly increasing the chloride
concentration the solution of I can be stabilized. For example,
in an isotonic solution of 0.15 M NaCl the ruthenium complex
is stable for at least 72 h within a relative error of 0.01% in the
range 25–378C. This finding is similar to the stabilization of
cis-platinum and/or other platinum-containing drugs at
increased chloride concentration. The stabilization probably
occurs because the high chloride level is preventing
coordinated chloride exchange in the ruthenium complex I
with water, hydroxyl or with trifluoromethylsulfate.29 In
other words, the excess of chloride is blocking ligand
exchange of the chloride with water and with other possible
ligands in solution. Our results are in agreement with
findings for a similar Ru complex with the PTA ligand, where
[RuCpCl(PTA)2] and its aqueous parent complex
[RuCp(H2O)(PTA)2]þ were found to exist in partial equilibrium.30 This also supports our explanation for the
stabilization of I in isotonic NaCl solution. The stabilization
of I might be important for the use of the compound in
medical practice.
CONCLUSIONS
The behavior of the ruthenium complex in aqueous
solution, as studied by UV-Vis spectrophotometry and
TOF MS, proved that compound I first undergoes fast
addition of water, coordinating 2–5 water molecules to
form [RuClCp(mPTA)2] (H2O)x (x ¼ 3, 5) hydrates while
probably water molecules are coordinated in the 2nd
coordination sphere forming an outer-sphere complex. This
is in agreement with finding of Bešker et al.31 In slightly
acidic, neutral and also in alkaline solutions, the ligand
exchange starts immediately. The mPTA ligand and/or
chloride and cyclopentadiene are exchanged with water,
hydroxyl and/or also with the counter anion. The trifluoromethylsulfate present as an anionic species outside the
coordination sphere of the ruthenium(II) complex can also
attack the ruthenium(II) coordination sphere to replace either
mPTA or chloride. The major hydrolysis products include
RuClCp(mPTA)2(H2O)4(OH)Naþ, RuCp(mPTA)2(H2O)5(OH)2Naþ,
and RuCp(mPTA)2(H2O)4OHþ,
RuClCp(mPTA)2(H2O)þ
5
where some of them are Naþ adducts. Some other species,
especially those observed by LDI, can be formed by laser
fragmentation. The stoichiometry of all the species was
identified using isotopic pattern modelling. The ruthenium
complex can be stabilized in isotonic 0.15 M sodium chloride
solution where it remains stable for at least 72 h within 0.01%
relative error in the range 25 to 378C. The trifluoromethylsulfate as a counter anion in I is not suitable for use in
medical applications and, for such applications, its replacement with either a less or a non-complexing anion such as
BF
4 is recommended. The complex [RuClCp(mPTA)2](BF4)2
was recently synthesized.15
Copyright # 2009 John Wiley & Sons, Ltd.
Acknowledgements
B. González thanks the Consejerı́a de Educación, Cultura y
Deportes (Canarian Government, Spain) for a predoctoral
grant and MCYT (Spain) project CTQ2006-06552/BQU and J.
Havel to the University of La Laguna for supporting his stay
at ULL. Financial support of the work from project
MSM0021622411 of the Ministry of Education, Czech Republic and the Academy of Sciences of the Czech Republic,
project KAN 101630651 is gratefully acknowledged. The
English was kindly revised by Mr Vickery.
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DOI: 10.1002/rcm
Pablo Lorenzo-luis