Synthesis and anion-sensing property of a family of Ru(II)-based receptors containing functionalized polypyridine as binding site

Article abstract of DOI:10.1016/j.inoche.2010.09.002

A family of fluoroionophores have been synthesized incorporating Ru(II)-bipyridine moiety as fluorogenic unit and amino/benzenesulphonamido functionalized 1,10-phenanthroline moiety, attached to Ru(II), as binding sites. Two of the ligands and one of the complexes have been characterized crystallographically. Anion recognition property, studied by luminescence, UV-vis and ¹H NMR spectroscopy, with a large number of anions exhibit strong complexation with F^-, H₂PO₄^- and AcO^-. Binding constants have been determined from luminescence titration and ¹H NMR study gave insight about binding site of anions. Bidentate chelating nature of the H₂PO₄^- and AcO^- anions and steric crowding created by benzenesulphonamide moiety has significantly influenced binding constants and selectivity.

Full text of DOI:10.1016/j.inoche.2010.09.002

Inorganic Chemistry Communications 13 (2010) 1522–1526
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Inorganic Chemistry Communications
journal homepage: www.elsevier.com/locate/inoche
Synthesis and anion-sensing property of a family of Ru(II)-based receptors
containing functionalized polypyridine as binding site
⁎
Ashish Chakraborty, Ravi Gunupuru, Debdeep Maity, Subrata Patra, E. Suresh, Parimal Paul
Analytical Science Division, Central Salt and Marine Chemicals Research Institute (constituents of CSIR, New Delhi), G. B. Marg, Bhavnagar 364002, India
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 25 June 2010
Accepted 6 September 2010
Available online 16 September 2010
A family of fluoroionophores have been synthesized incorporating Ru(II)-bipyridine moiety as fluorogenic
unit and amino/benzenesulphonamido functionalized 1,10-phenanthroline moiety, attached to Ru(II), as
binding sites. Two of the ligands and one of the complexes have been characterized crystallographically.
Anion recognition property, studied by luminescence, UV–vis and 1H NMR spectroscopy, with a large number
of anions exhibit strong complexation with F−, H2PO−4 and AcO−. Binding constants have been determined
from luminescence titration and 1H NMR study gave insight about binding site of anions. Bidentate chelating
nature of the H2PO−4 and AcO− anions and steric crowding created by benzenesulphonamide moiety has
significantly influenced binding constants and selectivity.
Keywords:
Receptors
Ruthenium complex
Luminescence
Ion-binding
© 2010 Elsevier B.V. All rights reserved.
Crystal structure
The design and synthesis of artificial receptors for recognition and
sensing of anions has received considerable interest in recent years
because of the important role played by anions in biological, envi-
ronmental and industrial processes [1]. In designing of anion
receptors, various noncovalent interactions, such as hydrogen-
bonding, electrostatic, hydrophobicity, are mainly considered to
make interaction between binding sites and anions [2]. To monitor
recognition event, fluorescent technique is gaining increasing atten-
tion because of high sensitivity and easy online monitoring. Binding
of ions to the recognition sites leads to changes in photophysical
properties of the receptors that serve as indicator for ion-recognition
[2,3]. As fluorogenic unit, photoactive organic molecules have been
widely used [1,4], however fluorescent metal complexes such as
ruthenium(II)-polypyridine moiety can also be used [1–3,5]. For anion
recognition, the latter has some advantages over organic molecules,
the positive charge on the metal ion makes electrostatic interaction
with negatively charged species leading to strong host–guest
interaction.
namide derivatives (L2–L4) were prepared following the modified
published procedure (Scheme 1) used for other systems [7]. It may be
noted that the excess benzenesulfonylchloride used in the reaction
was hydrolyzed under the reaction conditions to benzenesulfonic
acid, the acidic hydrogen atom of which combined with ―NH2 of the
ligand to form ―NH+3 and isolated as organic salt with deprotonated
benzenesulfonic acid as counter anion, [L2H+][C6H5SO3−], [L3H+
]
[C7H7SO−3 ] and [L4H+][C6H4NSO−5 ]. The elemental analysis (C, H, and
N) and mass spectrometric data are in excellent agreement with the
compositions of the ligands. As expected, the mass spectrometric data
are corresponding to the cationic part of the ligand. In the 1H NMR
spectra, the signals for ―NH+3 and NH protons appeared around δ 6.5
and 10.0, respectively and the deprotonated benzenesulfonic acid
exhibits two doublets in the regions δ 7.4–7.7. The metal complexes
[Ru(bpy)2(L)][PF6]2.2H2O (L=L1 (1), L2 (2), L3 (3) and L4 (4)) were
synthesized by the reaction of cis-[Ru(bpy)2Cl2].2H2O with the
respective ligand (L1 and salts of L2/L3/L4) in ethanol-water under
reflux, isolated as PF−6 salt and purified by column chromatography
[8]. The complexes, however did not show the presence of ―NH+3 , the
deprotonation took place under the reaction conditions with the
building block cis-[Ru(bpy)2Cl2]. The elemental analysis (C, H and N)
are in agreement with the compositions of the complexes and the
We have designed fluoroionophores incorporating Ru(II)-
polypyridine moiety as fluorogenic unit and functionalized 1,10-
phenanthroline moiety containing amino (―NH2) and benzenesul-
phonamide groups as binding sites for anion recognition. We report
here synthesis, characterization, electrochemical and ion-recognition
properties of these fluoroionophores.
mass spectrometric data correspond to the mass of [M-PF6− +
and
]
the 1H NMR spectral data are consistent to the structures shown in
Fig. 1.
The compound 5,6-diamino-1,10-phenanthroline (L1) was pre-
pared following the literature procedure [6] and the benzenesulpho-
Crystals for [L2H+][C6H5SO3−] and [L3H+][C7H7SO−3 ] were grown
from CH3CN/MeOH and the data analysis [9] confirmed the structures
shown in Fig. 2. The ORTEP views of these compounds clearly show
that the amino nitrogen of the ligand is protonated forming cation and
deprotonated benzenesulphonic acid acts as counter anion. Crystals
⁎
Corresponding author. Tel.: +91 278 2567760; fax: +91 278 2567562.
E-mail address: ppaul@csmcri.org (P. Paul).
1387-7003/$ – see front matter © 2010 Elsevier B.V. All rights reserved.
doi:10.1016/j.inoche.2010.09.002

A. Chakraborty et al. / Inorganic Chemistry Communications 13 (2010) 1522–1526
1523
Scheme 1. Synthetic route for the ligands L2–L4.
for the complex 1 were grown from the acetonitrile solution, into
which Et2O was allowed to diffuse slowly. The molecular structure of
1, derived from the crystal data [10], is shown in Fig. 3. The Ru(II) is
coordinated to two bipyridine and a 1,10-phenanthroline ligands
forming a distorted octahedral geometry, as evident from bond
angles.
(a)
Absorption spectra of 1–4 in acetonitrile exhibit a band in the
region 440–453 nm (Table 1), which is assigned to metal-to-ligand
⁎
(bpy) charge-transfer (MLCT) transitions (dπ→π ) [11]. They also
exhibit a high-energy band around 286 nm, which can be assigned to
⁎
ligand-centered charge transfer (CT) due to π → π transitions. The
luminescence spectra in acetonitrile (excitation at 450 nm) exhibit a
band in the region 603–609 nm (Table 1), which is attributed to
3MLCT emission [5,11].
Cyclic voltammograms (CV) of 1–4 were recorded in acetonitrile in
a three-electrode cell consisting of a platinum working electrode, a
platinum-wire auxiliary electrode, and a SCE reference electrode. The
solution containing 0.1 M tetrabutylammonium tetrafluoroborate as
supporting electrolyte was deaerated by bubbling nitrogen for 10 min
prior to the experiment. The CV exhibit a metal-based oxidation
(RuII →RuIII) in the potential range 1.50 to 1.55 V, and two ligand-
based one-electron redox couples in the potential range −1.24 to
−1.57 V (Table 1) [11].
Ion-binding property of 1–4 has been investigated with a series of
(b)
anions (F−, Cl−, Br−, I−, H2PO−4 , ClO4−, NO3−, BF4−, AcO−, and HSO−4
)
and the host–guest interactions monitored by luminescence, UV–vis
and 1H NMR spectral changes. The luminescence spectra of 1–4 were
recorded in acetonitrile upon addition of tetrabutylammonium salts
of various anions (100 fold excess). Commercially obtained (Aldrich)
tetrabutylammonium salts were anhydrous, except F− salt, which was
hydrated (xH2O). The anions, F−, H2PO4− and AcO− exhibited
substantial quenching in emission intensity (65–80%) for all the
receptors, whereas other anions did not show any significant change,
except 1, which also exhibits 35–45% quenching in presence of I− and
HSO−4 . The quenching in emission intensity of the 3MLCT (d-π*)
transition indicates strong interaction of the anions with the
Fig. 2. ORTEP views of [L2H+][C6H5SO3−] (a) and [L3H+][C7H7SO−3 ] (b) with atom
numbering scheme (40% probability factor for the thermal ellipsoids).
on NH and NH2, which subsequently propagates to metal bound 1,10-
phenanthroline ring causing increase of the intramolecular quenching
in emission intensity [1,2,5]. The UV–vis spectra for 1–4 were re-
corded upon addition of increasing amount of all the anions studied,
among which F− and AcO− exhibit significant changes (Fig. 4), H2PO−4
also shows minor changes, whereas other anions do not show any
considerable change.
fluoroionophores [1,2,5]. The strong to moderate bases such as F−
,
The 1H NMR spectra of 1–4 were recorded upon addition of in-
creasing concentration of F− and AcO−. In case of phosphate, pre-
cipitate was formed in the NMR tube even before addition of one
equivalent of anion in acetonitrile and therefore 1H NMR spectral
changes could not be recorded. In presence of F− and AcO−, sig-
nificant change in chemical shift for NH2 protons and some of the
aromatic protons were observed. It may be noted that the sulphona-
mide N–H signal for all three complexes could not be located, because
of high acidity it might be too broad to observe or might have ex-
changed with deuterated solvent due to the presence of trace amount
of water in the solvent. In case of F−, the chemical shift for NH2
protons move significantly to upfield with increasing the concentra-
tion of anion (Fig. 5). The aromatic protons associated to 1,10-
phenanthroline (phen) moiety have also moved slightly upfield. The
AcO− and H2PO−4 are hydrogen binding acceptors and in this case they
formed complexes with NH and NH2 through N–H…F−/O− interac-
tion [2]. The strong basicity of the anions enhanced electron density
F
−, on interaction with NH2/NH, enhanced electron density on
nitrogen atom and also on neighbouring phen ring, causing shielding
effect on these protons. However, low field shift of a doublet of the
phen moiety at higher concentration of anion is noted for 2–4, which
Fig. 1. Structural drawing for the fluoroionophores 1–4.

1524
A. Chakraborty et al. / Inorganic Chemistry Communications 13 (2010) 1522–1526
Fig. 4. Uv–vis spectral change for 2 in acetonitrile (1×10−5 M) upon addition of
increasing amount of F− (TBAF.xH2O).
Fig. 3. ORTEP diagram of 1 (40% probability factor for the thermal ellipsoids, lattice
acetonitile molecule is omitted for clarity). Bond distances in the coordination sphere: Ru
(1)–N(1)=2.047(8), Ru(1)–N(2)=2.073(9), Ru(1)–N(3)=2.065(9), Ru(1)–N(4)=
2.062(10), Ru(1)–N(5)=2.074(9) and Ru(1)–N(6)=2.057(9).
3+8.0 eqv
/ /
3+6.0 eqv
/ /
probably due to intramolecular C–H…O interaction between the
proton at 4- or 7-position of phen and oxygen atom of SO2, induced by
conformational change of the molecule due to complex formation
with F−. The other possibility is due to intermolecular interaction
involving proton at the 4- or 7-position of phen and F− in presence of
excess anions. For AcO−, the NH2 signal moved slightly to upfield and
then significantly broadens with increasing the concentration of anion
and after addition of 5 fold excess it is too broad to observe, which
3+4.0 eqv
/ /
3+2.0 eqv
/ /
3
indicates strong interaction of the NH2 protons with the AcO−
.
/ /
Chemical shift of some of the aromatic protons also changed slightly
but it is less prominent compared to F−. The sulphonamide N–H
probably also binds with anions but could not be confirmed from 1H
NMR data due to difficulty to locate the signal. It is interesting to note
that the two protons of the NH2 behave similarly to make interaction
with anions, indicating that either both of the protons are involved in
making interaction or there is fast exchange of interaction between
the two protons. The stochiometry of the complex formed (1:1) was
determined from Job's plot (Fig. 6) and Yoe and Jones' method from
luminescence data [12].
8.5
8.0
7.5
ppm 6.0
5.5
ppm
Fig. 5. Selected portion of the 1H NMR spectrum for 3 upon addition of increasing
amount of F− (TBAF.xH2O).
that the binding constants are in the range 3.2×103 to 4.9×104 M−1
which are comparable to the values (1.0×103 to 1.0×106 M−1
,
)
found for many other Ru(II)-polypyridine based fluoroionophores for
F−, AcO− and H2PO−4 [1,2,5]. The variation in binding constant for a
particular ion is mainly due to differences in binding sites in the
ionophore moiety attached to the fluorogenic unit. The present study
shows that the binding constants (Ks) for AcO− and H2PO4− are higher
compared to that of F−. The stronger binding ability of these two anions
are probably due to their bidentate chelating nature, two oxygen atoms
with delocalized negative charge can interact simultaneously with two
hydrogen atoms of NH2/NH forming stable complex by chelating effect.
It also may be noted that the fluoroionophore 1 exhibited higher binding
Binding constants for all three anions were determined from
n
emission titration data using the equation (F0–F)/(F–F∞)=([M]/Kdiss
)
[5,13], the titration experiments were carried out following the method
reported earlier [5]. The value of log[M] at log[(F0–F)/(F–F∞)]=0 gives
the value of log(Kdiss), the reciprocal of which is the binding constant
(Ks). The spectral changes due to emission titration and the plots log
[(F0–F)/(F–F∞)] versus log[M] are shown in the Figs. 7 and 8; and
the binding constants are summarized in Table 2. The table shows
Table 1
Absorption, emission, quantum yield and redox potentials for the receptors 1–4.
Complex
Absorption maxima
(λmax, MLCT), nm
(ε, dm3 mol−1 cm−1
Emission maxima
(φ)
Redox potential
Ru(II)/Ru(III) (ΔEp, mV)
Ligand reduction
(ΔEp, mV)
)
1
2
3
4
440 (4.08×103)
451 (3.94×103)
452 (3.17×103)
452 (2.89×103)
613 (0.028)
605 (0.051)
603 (0.044)
605 (0.044)
1.55 (155)
1.56 (228)
1.55 (191)
1.55 (130)
−1.24 (114),–1.47 (115)
−1.31 (228),–1.57 (220)
−1.29 (175),–1.55 (194)
−1.23 (205),–1.52 (110)

A. Chakraborty et al. / Inorganic Chemistry Communications 13 (2010) 1522–1526
1525
1.2x106
6.0x105
0.0
0.0
0.3
0.6
0.9
Mole fraction
Fig. 6. Job's plot for 3 from luminescence data upon addition of F− (TBAF.xH2O).
Fig. 8. Emission spectral changes for 4 (4.5×10−5 M) upon addition of increasing
concentration of H2PO−4 (TBAP). Inset: linear regression fit (double-logarithmic plot) of
the titration data as a function of concentration of H2PO4−
.
constants for all three anions compared to 2–4, which is ascribed to
steric hindrance created by sulphonamide moiety. However, the steric
hindrance resulted in better selectivity for 2–4, as the quenching in
emission intensity for these receptors in presence of I− and HSO4− is
negligible compared to 1.
Table 2
Binding constants (Ks) for the receptors 1–4.
Complex
Binding constant (Ks) M−1 ×10−3
In summary, a number of fluoroionophores incorporating [Ru
(bpy)2(phen)]+ as fluorogenic unit and NH2/NH as binding site have
been synthesized and their ion-binding ability have been investigated
with a large number of anions. Luminescence and UV–vis study sug-
gest strong complexation with F−, H2PO4− and AcO−, the positive
charge of the fluorogenic unit enhances binding of anions due to
strong electrostatic interaction. Binding constants suggest that
bidentate chelating nature of H2PO−4 and AcO− provide advantage
over F− to form strong complexes. 1H NMR study indicates involve-
ment of NH2 in binding with anions. Incorporation of benzenesul-
phonamide moiety gave better selectivity, as no other anions, except
three mentioned above, exhibits any considerable quenching in
emission intensity.
Anion
F−
H2PO−4
CH3COO−
1
2
3
4
22.9
11.8
7.3
25.4
12.3
3.2
49.4
19.2
12.7
16.4
17.9
14.6
competency development. S.P. gratefully acknowledges the CSIR for
awarding Senior Research Fellowship (SRF). We thank A. K. Das, V. P.
Boricha and V. Agrawal for recording mass, IR and NMR spectra,
respectively.
Appendix A. Supplementary material
Acknowledgements
CCDC 781990-781992 contain the supplementary crystallographic
data for [L2H+][C6H5SO3−], [L3H+][C7H7SO3−] and 1. These data can be
obtained free of charge via www.ccdc.cam.ac.uk/data_request/cif.
Other supplementary data associated with this article can be found in
the online version. doi:10.1016/j.inoche.2010.09.002.
We are grateful to the Department of Science and Technology
(DST), Government of India, for financial support. We thank CSIR,
New Delhi for generous support towards infrastructures and core
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N, 10.28. Found: C, 41.34; H, 2.98; N, 10.08. 1H NMR (CD3CN, 500MHz, ppm ): δ
8.63 (d,1H, J=8.5 Hz, Ar-H); 8.46-8.53 (m, 4H, Ar-H); 8. 04-8.10 (m, 3H, Ar-H);
7.9-8.03 (m, 2H, Ar-H); 7.83 (d, 1H, J=5.0 Hz, Ar-H), 7.76-7.78 (m, 2H, Ar-H);
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Characterization data for 3: Anal. Calcd for C39H36F12N8O4P2RuS: C, 42.45; H, 3.29;
N, 10.14. Found: C, 42.29; H, 3.01; N, 10.29. 1H NMR (CD3CN, 500MHz, ppm): δ
8.62 (d, 1H, J=8.5Hz, Ar-H); 8.47-8.547(m, 4H, Ar-H); 7.99-8.10 (m, 4H, Ar-H);
7.85 (d, 1H, J=5.0 Hz, Ar-H); 7.67-7.76 (m, 3H, Ar-H), 7.49-7.54 (m, 4H, Ar-H);
7.39-7.43 (m, 2H, Ar-H); 7.24-7.29 (m, 2H, Ar-H); 7.15-7.20 (m, 3H, Ar-H); 7.06
(d,2H, J=8.0 Hz, Ar-H); 5.8 (s,2H, NH2); 2.34 (s, 3H, CH3). ESI-MS m/z: 922.76 [3-
1+
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(calc. 922.14). UV-Vis (MeCN) λ ) 452
max/nm (ɛ/dm3 mol–1 cm–1
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Characterization data for L2: Anal. Calc. for C24H20N4O5S2: C, 56.68; H, 3.96; N, 11.02.
Found: C, 55.65; H, 3.78; N, 11.17. 1H NMR ( 500 MHz, [D6]DMSO, ppm) : δ 10.22
(s, 1H, NH), 9.24 (d, 1H, J=4.0 Hz, 2-H), 9.00 (d, 1H, J=8.0 Hz, 4-H), 8.76 (d, 1H,
J=4.5 Hz, 9-H), 8.51 (d, 1H, J=8.5 Hz, 7-H), 8.05 (m, 1H, 3-H), 7.87 (m, 1H, 8-H),
7.77–7.45 (m, 10 H, Ph), 6.6 (br s, 3H, NH3+ ). ESI-MS m/z: 351.6 [L1+H+] (calc.
351.4).
(3.17×103), 286 (1.10×104).
Characterization data for 4: Anal. Calcd for C38H33F12N9O6P2SRu: C, 40.23; H, 2.93;
N, 11.11. Found: C, 40.03; H, 2.79; N, 10.96. 1H NMR (CD3CN, 500MHz, ppm): δ
8.46-8.54 (m, 4H, Ar-H); 8.41 (d,1H, J=8.5, Ar-H); 7.97-8.06 (m, 6H, Ar-H); 7.84
(t, 2H, Ar-H) 7.78-7.81 (m, 3H, Ar-H); 7.51-7.57 (m, 4H, Ar-H); 7.40-7.42 (m, 2H,
Ar-H); 7.25-7.31 (m, 4H, Ar-H); 5.25 (s, 2H, NH2). ESI-MS m/z: 954.53 [4-PF-6] +
(calc. 954.11). UV-Vis (MeCN) λmax/nm (ɛ/dm3 mol–1 cm–1) 452 (2.89×103), 286
(1.26×104).
Characterization data for L3: Anal. Calc. for C28H27N5O5S2: C, 58.22; H, 4.71; N, 12.12.
Found: C, 57.60; H, 4.66; N, 11.89. 1H NMR ( 500 MHz, [D6]DMSO, ppm) : δ 9.85 (s,
1H, NH), 9.26 (d, 1H, J=4.5 Hz, 2-H), 9.0 (d, 1H, J=8.0 Hz, 4-H), 8.78 (d, 1H,
J=4.5 Hz, 9-H), 8.47 (d, 1H, J=8.0 Hz, 7-H), 8.09 (m, 1H, 3-H), 7.9 (m, 1H, 8-H), 7.54
(d, 2H, J=8.0 Hz, p-CH3-Ph), 7.48 (d, 2H, J=8.0 Hz, p-CH3-Ph), 7.54 (d, 2H,
J=8.0 Hz, p-CH3-Ph), 7.48 (d, 2H, J=8.0 Hz, p-CH3-Ph), 6.4 (br s, 3H, NH3+), 2.35 (s,
3H, CH3), 2.28 (s, 3H, CH3), 2.08 (s, 3H, CH3CN). ESI-MS m/z: 365.44 [L2+H+] (calc.
365.42).
[9] The crystal data were collected on a SMART APEX diffractometer with graphite
monochromated MoKα radiation (λ=0.71073Å). Refinement method was Full-
matrix least-squares on F2 using SHELXTL-97 programm.
Crystal data for L2: C24H20N4O5S2, M=508.56, monoclinic, P2(1)/n, Z=4,
T=293(2)K, a=15.142(3) Å, b=10.467(2) Å, c=16.197(4) Å, α=γ = 90o, β =
116.374(4)o. V = 2299.9(9) Å3, Dcalc = 1.469 Mg/m3, μ=0.277 mm–1, F(000)=
1056. collected reflections=11283, independent reflections=4032, R1=0.0817,
wR2=0.1929;
Characterization data for L4: Anal. Calc. for C24H18N6O9S2: C, 48.07; H, 3.19; N, 14.01.
Found: C, 47.43; H, 3.07; N, 13.86. 1H NMR ( 500 MHz, [D6]DMSO, ppm) : δ = 10.18
(s, 1H, NH), 9.27 (d, 1H, J=5.5 Hz, 2-H), 8.95 (d, 1H, J=9.0 Hz, 4-H), 8.8 (d, 1H,
J=5.5 Hz, 9-H), 8.5 (d, 1H, J=9.0 Hz, 7-H), 8.28(d, 2H, J=9.0 Hz, p-NO2-Ph), 8.19
(d, 2H, J=9.0 Hz, p-NO2-Ph), 8.10 (m, 1H, 3-H), 7.96 (m, 1H, 8-H), 7.91 (d, 2H,
J=8.0 Hz, p-NO2-Ph), 7.83 (d, 2H, J=8.0 Hz, p-NO2-Ph), 6.58 (br s, 3H, NH3+). ESI-
MS m/z: 396.49 [L3+H+] (calc. 396.40).
Crystal data for L3: C28H27N5O5S2, M=577.67, monoclinic, P2(1)/c, Z=4,
T = 100(2)K, a = 15.2592(17) Å, b = 10.9366(12) Å, c = 17.3677(19) Å,
o
α = γ = 90o, β = 111.441(2)
. ,
V = 2697.8(5) Å3 Dcalc = 1.422 Mg/m3,
μ=0.247 mm-1
, F(000)=1208, collected reflections=15745, independent
reflections=6221, R1 =0.0548, wR2 =0.1442.
[10] Crystal data for 1: C34H29N9F12P2Ru, M=954.67, monoclinic, P2(1)/c, Z=4,
T=100(2)K, a=19.950(4)Å, b=14.978(3)Å, c=12.798(3)Å, α=γ=90o,
β=107.816(5)o. V=3640.8(13)Å3, Dcalc =1.742 Mg/m3, μ=0.622 mm−1, F(000)=
1912, collected reflections=16462, independent reflections=5699, R1=0.0964,
wR2=0.1556.
[11] (a) P. Paul, B. Tyagi, A.K. Bilakhiya, P. Dastidar, E. Suresh, Inorg. Chem. 39 (2000)
14;
(b) A.K. Bilakhiya, B. Tyagi, P. Paul, P. Natarajan, Inorg. Chem. 41 (2002) 3830.
[12] J.M. Bosque-Sendra, E. Almansa-Lopez, N.M. Garcia-Campana, L. Cuadros-
Rodriguez, Anal. Sci. 19 (2003) 1431.
[8] General procedure for the synthesis of 1-4: A mixture of cis-[Ru(bpy)2Cl2].2H2O
(0.13 g, 0.25 mmol ) and respective ligand (L1/L2/L3/L4, 0.25 mmol) in ethanol-
water (2:1, 60 mL) was refluxed for 10 h. The reaction mixture was then allowed
to cool to room temperature; volume was reduced to ca. 20 mL by rotary
evaporation, filtered and to the filtrate was added solid NH4PF6 (0.815g, 5 mmol).
The precipitate thus separated was washed with water and diethyl ether and
purified by column chromatography using a column packed with deactivated (2%
water) alumina and acetonitrile-toluene (0.3:0.7) as eluent. Yield: 60-70%.
Characterization data for 1: Anal. Calcd for C32H30F12N8O2P2Ru: C, 40.39; H, 3.17;
N, 11.77. Found: C, 40.14; H, 3.27; N, 11.41. 1H NMR (CD3CN, 500MHz, ppm ): δ
8.46-8.51 (m, 6H, Ar-H); 8.07 (t, 2H, Ar-H), 7.97 (t, 2H, Ar-H); 7.79-7.82 (m, 4H,
[13] A.C. Tedesco, D.M. Oliveria, Z.J.M. Lacava, R.B. Azevedo, E.C.D. Lima, P.C. Morais, J.
Magn. Magn. Mater. 272–276 (2004) 2404.