Asymmetric ruthenium(II) and osmium(II) complexes with new bidentate polyquinoline ligands. Synthesis and NMR characterization

Article abstract of DOI:10.3390/molecules15031324

A series of Ru(II) and Os(II) tris-chelate complexes with new bidentate 2-pyridylquinoline ligands have been synthesized and fully characterized by EA,¹H-NMR and FAB-MS techniques. The new ligands are: L₁ = 4-p-methoxyphenyl-6-bromo-2-(2'-pyridyl)quinoline (mphbr-pq) and L₂ = 4-p-hydroxyphenyl-6-bromo-2-(2'-pyridyl)-quinoline (hphbr-pq). The complexes studied are: [Ru(bpy)₂L₁](PF₆)₂ (C₁), [Ru(bpy)₂L₂](PF₆)₂ (C₂), [Os(bpy)₂L₁](PF₆)₂ (C₃), [Os(bpy)₂L₂](PF₆)₂ (C₄) (bpy = 2,2'-bipyridine), [Ru(dmbpy)₂L ₁](PF₆)₂ (C₅), [Ru(dmbpy) ₂L₂](PF₆)₂ (C₆), [Os(dmbpy)₂L₁](PF₆)₂ (C ₇), and [Os(dmbpy)₂L₂](PF₆) ₂ (C₈) (dmbpy = 4,4'-dimethyl-2,2'-bipyridine). Moreover, new functionalized complexes C₉-C₁₂ were obtained by the basecatalyzed direct alkylation of C₂, C₄, C₆, and C₈ with 6-bromo-1-hexene. The complete assignment of the ¹H-NMR spectra for the two new ligands (L₁ and L ₂), and their Ru(II) or Os(II) complexes has been accomplished using a combination of one-and two-dimensional NMR techniques. The J_H,H values have been determined for the majority of the resonances.

Full text of DOI:10.3390/molecules15031324

Molecules 2010, 15, 1324-1339; doi:10.3390/molecules15031324
OPEN ACCESS
molecules
ISSN 1420-3049
www.mdpi.com/journal/molecules
Article
Asymmetric Ruthenium(II) and Osmium(II) Complexes with
New Bidentate Polyquinoline Ligands. Synthesis and NMR
Characterization
Antonino Mamo *, Alessandro Aureliano and Antonino Recca
Dipartimento Metodologie Fisiche e Chimiche per l’Ingegneria, Facoltà di Ingegneria, Università
di Catania, Viale A. Doria 6, 95125, Catania, Italy; E-Mail: alessandro.aureliano@gmail.com (A.A.)
* Author to whom correspondence should be addressed; E-Mail: mamo@dmfci.unict.it.
Received: 25 January 2010; in revised form: 11 February 2010 / Accepted: 1 March 2010 /
Published: 5 March 2010
Abstract: A series of Ru(II) and Os(II) tris-chelate complexes with new bidentate
2-pyridylquinoline ligands have been synthesized and fully characterized by EA,1H-NMR
and FAB-MS techniques. The new ligands are: L1 = 4-p-methoxyphenyl-6-bromo-2-(2′-
pyridyl)quinoline (mphbr-pq) and L2 = 4-p-hydroxyphenyl-6-bromo-2-(2′-pyridyl)-
quinoline (hphbr-pq). The complexes studied are: [Ru(bpy)2L1](PF6)2 (C1),
[Ru(bpy)2L2](PF6)2 (C2),
[Os(bpy)2L1](PF6)2
(C3),
[Os(bpy)2L2](PF6)2
(C4)
(bpy = 2,2′-bipyridine), [Ru(dmbpy)2L1](PF6)2 (C5), [Ru(dmbpy)2L2](PF6)2 (C6),
[Os(dmbpy)2L1](PF6)2 (C7), and [Os(dmbpy)2L2](PF6)2 (C8) (dmbpy = 4,4′-dimethyl-2,2′-
bipyridine). Moreover, new functionalized complexes C9-C12 were obtained by the base-
catalyzed direct alkylation of C2, C4, C6, and C8 with 6-bromo-1-hexene. The complete
assignment of the 1H-NMR spectra for the two new ligands (L1 and L2), and their Ru(II) or
Os(II) complexes has been accomplished using a combination of one- and two-dimensional
NMR techniques. The JH,H values have been determined for the majority of the resonances.
Keywords: bidentate quinoline aza-ligands; ruthenium asymmetric complexes; osmium
asymmetric complexes
__________________________________________________________________________________

Molecules 2010, 15
1325
1. Introduction
Transition metal complexes have tremendous potential as diagnostic and therapeutic agents. They
can be exploited for their modularity, reactivity, imaging capabilities, redox chemistry, and precisely
defined three-dimensional structure [1–5]. Several [Ru(bpy)3]-derived
(bpy = 2,2′-bipyridine)
complexes were synthesized and compared electrochemically and spectroscopically in the search for
better luminophores for electrochemiluminescence (ECL)-based analytical applications [6].
Electrochemiluminescence is a kind of sensitive process releasing light during reaction, which has
potential applications in biological, pharmaceutical, and chemical land environmental analysis, due to
its continuance, sensitivity, low-detection limit, reproducibility and relative easiness to be
automatically controlled [7]. However, it is noted that different configurations in metal complexes
affect a variety of activities, and most attention has been focused on symmetric aromatic ligands. . On
the other hand, only a limited number of ruthenium complexes containing asymmetric ligands have so
far been described, and little attention has been paid to the investigation of their DNA-binding
properties [8].
Among the factors governing the binding modes, it appears that the most significant is likely to be
that of molecular shape. Studies reveal that the ligand modifications in geometry, size, hydrophobicity,
planarity, and hydrogen-bonding ability of the complexes, may lead to suitable or spectacular changes
in the binding modes, location, affinity, and to a different cleavage effect [9]. Therefore, inspired by
Vos studies [10], we became interested in the synthesis of new polypyridyl ruthenium(II)/osmium(II)
complexes with asymmetric ligands, with the aim of investigating (i) the effect of asymmetry on the
photophysical properties of such compounds; (ii) their interaction properties with DNA [11]; (iii) their
potential for the fabrication of new monolayers on both silica and Si substrates, namely to transfer
molecular properties to the solid state thus obtaining photoluminescent devices [12–13].
Scheme 1. Ligand moiety.
R1
3''
2''
5''
6''
5
Br
3
N
6'
7
N
8
3'
5'
4'
Ligand
L1
R1
–OCH3
–OH
Nomenclature
Initials
mphbr-pq
hphbr-pq
4-p-methoxyphenyl-6-bromo-2-(2′-pyridyl)quinoline
4-p-hydroxyphenyl-6-bromo-2-(2′-pyridyl)quinoline
L2

Molecules 2010, 15
1326
By continuing our previous studies in this field [14–17], we have designed two new asymmetric
ligands (L1, L2), shown in Scheme 1, from which twelve aza-bidentate complexes with transition
metals like ruthenium or osmium have been derived (See Scheme 2 and Scheme 5). This paper reports,
as a first step, the synthesis and characterization of all the new compounds, while preliminary data on
their luminescent properties, DNA binding, and solid state photoluminescent devices [18] will be
1
reported elsewhere. All the compounds were characterized by EA, EI/FAB-MS and H-NMR
1
spectroscopy. Complete assignments of the H spectra of the various compounds were accomplished
by using a combination of one- and two-dimensional NMR techniques.
2. Result and Discussion
2.1. Ligands
Following the synthetic pathway previously used for the preparation of the parent ligand 4-phenyl-
2-(2′-pyridyl)quinoline (ph-pq) [19], namely the acid-catalyzed condensation of o-amino-
benzophenone with 2- acetylpyridine, we have synthesized ligand L1 in a three synthetic steps as
shown in Scheme 2.
Scheme 2. Synthesis of L1.
OMe
'
5
'
'
3
6
Br
CH2CN
OMe
'
2
4
7
KOH
Br
+
O
6
MeOH / THF
N
NO2
1
CH3COOH
Fe
OMe
OMe
'
'
'
5
3
2
5"
6"
3"
2"
'
6
5
N
6
Br
Br
3
O
O
N
7
4
N
m-cresol / P2O5
NH2
6'
8
3
3'
5'
4'
2
L1

Molecules 2010, 15
1327
4’-Methoxy-2-amino-5-bromobenzophenone (2) was obtained by condensation of p-nitrobromo-
benzene with p-methoxyphenylacetonitrile in a basic ethanol/tetrahydrofuran medium to give 3-p-
methoxyphenyl-5-bromo-2,1-benzisoxazole (1) (66%), which upon reductive cleavage
(Fe/CH3COOH) of the benzoisoxazole ring was converted to the desired aminoketone 2 (70%). A
subsequent Friedlander reaction [20,21] of the o-aminobenzophenone 2 with 2-acetylpyridine, using a
mixture of m-cresol and phosphorous pentoxide gave ligand L1 (71%). The subsequent demethylation
of L1 with boron tribromide [22] afforded a new ligand 4-p-hydroxyphenyl-6-bromo-2-(2’-pyridyl)-
quinoline (brhph-pq) (L2) as is shown in Scheme 3.
Scheme 3. Synthesis of L2.
OMe
OH
5"
6"
3"
2"
5"
6"
3"
2"
BBr3
5
5
Br
3
Br
3
CH2Cl2
N
7
N
N
6'
7
8
N
6'
3'
8
5'
3'
5'
4'
L1
4'
L2
1
The H-NMR spectroscopy proved to be a useful tool to check the structure of the synthesized
1
ligands. By taking advantage of our previous H-NMR studies on similar compounds [16], we were
able to make by comparison the overall proton assignments for our ligands that are reported in Table 1.
Table 1. 1H-NMR spectral data for ligands L1 and L2. Coupling constants in italic.
Proton
L1
3
5
7
8
3′
4′
5′
6′
2′′/6′′ 3′′/5′′ OCH3
OH
8.51 s 8.13 d 7.80 dd 8.10 d 8.60 d 7.89 dt 7.38 dt 8.73 d 7.52 d 7.09 d
3.92 s
-
J = 2.0 J = 9.0 J = 8.0 J = 8.0 J = 8.0 J = 9.0 J = 4.0 J = 9.0 J = 9.0
J = 2.0
7.91
J = 1.5 J = 1.5
L2
8.61 s 8.16 d
8.14 d 8.73 d 8.01 dt 7.50 dt 8.74 d 7.53 d 7.12 d
J = 9.0 J = 8.0 J = 8.0, J = 8.5, J = 4.0 J = 9.0 J = 9.0
J = 1.5 J = 1.5
-
8.79
bs
J = 2.5
dd
J = 9.0,
J = 2.0
Notes: The spectra were obtained in (CD3)2CO, chemical shifts in ppm, and coupling constants (J) in Hz.
Numbering pattern as shown in Scheme 3. Abbreviations used: s = singlet, d = doublet, dd = double doublet,
t = triplet, dt = double triplet, bs = broad singlet, bd = broad doublet.
The 1H-NMR spectra of the synthesized ligands show the same trend in the region 7.0–9.0 ppm and
in Figure 1 is reported an expanded section of the 1H-NMR spectrum in (CD3)2CO of L2, showing the
assignments of all peaks as gathered in Table 1. In all cases, the spectra were found to be consistent
with the expected structures. The 1H-NMR spectrum (Figure 1) of L2 shows the expected pattern for a

Molecules 2010, 15
1328
2,4′′,6-trisubstituted 4-phenylquinoline moiety. In fact the two doublets at 8.60 and 8.73 ppm and two
double triplets at 7.89 and 7.38 ppm, assigned to H3′, H6′, H4′ and H5′, respectively, is of diagnostic
value for the presence of an -pyridinyl group linked to the quinoline unit. Furthermore, one AA′XX′
system (two doublets at 7.52 and 7.09 ppm) –easily recognized because of its symmetry and apparent
simplicity– accounts for a 1,4-disubstituted benzene ring having the 4′′ position occupied by the
hydroxyl group (broad resonance at 8.79 ppm). Finally, the lack of any signal for a hypothetic H6
proton along with the multiplicity of H8, H7 and H5 protons is in agreement with the presence of the
bromine substituent, as confirmed by elemental analysis.
Figure 1. The 1H-NMR spectrum (500 MHz, (CD3)2CO) and peak assignments of ligand L2.
2.2. Complexes
According to Scheme 4, by crossing the ligands L1 or L2 with the starting cis form of bis-chelate
Ru(bpy)2Cl2, Os(bpy)2Cl2, Ru(dmpy)2Cl2, and Os(dmbpy)2Cl2 complexes where the two bpy or dmbpy
(dmbpy = 4,4′-dimethyl-2,2′bipyridine) units lie on orthogonal planes and the chlorine atoms occupy
adjacent coordination sites, we have synthesized eight new tris-chelate complexes C1–C8.

Molecules 2010, 15
1329
Scheme 4. Synthesis of complexes C1–C8.
R2
R2
R1
3''
2''
5''
6''
N
N
N
N
5
+
Br
Cl
Me
Cl
3
N
6'
7
N
8
3'
5'
4'
R2
R2
Ethanol
Reflux
R1
3''
2''
5''
6''
5
3
Br
3'
7
R2
4'
5'
5'A
N
8
4'A
3'A
6'A
N
N
(PF6)2
6'
Me
6B
3A
N
5B
4B
N
6A
N
4A
6'B
5'B
R2
R2
5A
3B
3'B
4'B
R2
Abpy
Bbpy
Complex
C1
Ligand
Me
Ru
Ru
Os
Os
Ru
Ru
Os
Os
R1
-OCH3
-OH
-OCH3
-OH
-OCH3
-OH
R2
H
H
H
H
CH3
CH3
CH3
CH3
Chemical Formula
[Ru(bpy)2L1] (PF6)2
[Ru(bpy)2L2] (PF6)2
[Os(bpy)2L1] (PF6)2
[Os(bpy)2L2] (PF6)2
[Ru(dmbpy)2L1] (PF6)2
[Ru(dmbpy)2L2] (PF6)2
[Os(dmbpy)2L1] (PF6)2
[Os(dmbpy)2L2] (PF6)2
L1
L2
L1
L2
L1
L2
L1
L2
C2
C3
C4
C5
C6
C7
C8
-OCH3
-OH

Molecules 2010, 15
1330
The syntheses were accomplished by reacting equimolar amounts of the reagents in refluxing
ethanol for 8 h, followed by dropwise addition of a 20% water solution of NH4PF6, in order to get the
red-orange complexes. These were collected by filtration and purified by crystallization. Owing to the
ability of alkene molecules to covalently bond to hydrogen-terminated crystalline silicon (111) by
thermally induced hydrosilylation [23], the required cis octahedral coordinated complexes C9–C12
were prepared by direct alkylation of C2, C4, C6, and C8, respectively, with 6-bromo-1-hexene in
K2CO3/CH3CN mixture, as shown in Scheme 5. These new tris-chelate complexes exhibit, besides the
two bpy or dmbpy moieties, the new 4-p-(5-hexen-1-yloxy)phenyl-6-bromo-2-(2′-pyridyl)quinoline
ligand (L3).
Scheme 5. Synthesis of complexes C9–C12.





OH
O
3''
2''
5''
6''
3''
2''
5''
6''
(PF6)2
(PF6)2
5
5
3
Br
3
Br
3'
3'
7
7
R2
4'
5'
5'A
R2
4'
5'
5'A
N
N
8
8
4'A
3'A
6'A
4'A
3'A
6'A
N
K2CO3
N
N
N
Br
6'
+
6'
Me
Me
CH3CN
6B
6B
3A
3A
N
N
5B
4B
5B
4B
N
N
6A
6A
N
N
4A
6'B
5'B
6'B
5'B
R2
4A
R2
R2
R2
5A
5A
3B
3B
3'B
3'B
4'B
4'B
R2
R2
Complex
C9
Ligand
L3
Me
Ru
Os
Ru
Os
R1
R2
H
H
CH3
CH3
Chemical Formula
[Ru(bpy)2L3](PF6)2
[Os(bpy)2L3](PF6)2
[Ru(dmbpy)2L3](PF6)2
[Os(dmbpy)2L3](PF6)2
O(CH2)4CH=CH2
O(CH2)4CH=CH
O(CH2)4CH=CH
O(CH2)4CH=CH
C10
C11
C12
L3
L3
L3
The synthesized complexes were generally stable, diamagnetic, and kinetically inert. The 1H-NMR
spectra of Ru(bpy)2Cl2 and Os(bpy)2Cl2 show [24,25] eight different signals for the aromatic
hydrogens, that become six for Ru(dmbpy)2Cl2, and Os(dmbpy)2Cl2, consistently with the presence in
solution of two non-interconverting enantiomers possessing C2 symmetry. Substitution of the two
chlorine atoms with ligands mphbr-pq (L1) or hphbr-pq (L2) yields the corresponding tris-chelate
complexes which, in a cis octahedral coordination, are also capable of existing in two enantiomeric
propeller conformations, but, in contrast to the above cited bis-chelate complexes, do not possess a C2
axis of symmetry.

Molecules 2010, 15
1331
Figure 2. The 1H-NMR spectrum (500 MHz, (CD3)2CO) and peak assignments of complex C1.
40
30
20
10
0
3
3"/ 5"
2"/ 6"
8
4B
4A
5' A
7
5B
5A
4' B
5
3A
4'
6' A
3'
6A
6B
3B
6'
4'
5'
3'
6' B
3' B
5' B
9.50
9.00
8.50
8.00
7.50
ppm (t1)
The reduced symmetry of these complexes removes the degeneracies associated with the C2 axis in
the starting Ru(bpy)2Cl2, giving rise to a structure of the general type [Me(bpy)2L](PF6)2, (being
Me = Ru or Os) and L is an unsymmetrical bidentate ligand like L1 or L2. As a consequence, howing
to the asymmetry of the complexes, and to the kinetically restricted interconversion of the two
enantiomers on the NMR time-scale, the 1H-NMR spectra of complexes C1–C12 are quite complicated
showing 16 signals for the diastereomeric protons of the two bpy moieties (Abpy and Bbpy) in
addition to 13 signals for the ligand L1 or L2 and 18 for L3, as reported in Table 2.
1
As an example, Figure 2 shows the downfield aromatic section of the H NMR spectrum of
complex C1. The twentyeight methine resonances, arising from the two bipyridyl units (Abpy and
Bbpy) and to the bidentate ligand (mphbr-pq) (L1) are spread out over a 2.5 ppm interval. As
described in the following, each signal has been assigned to the respective proton with the aid of mono
and two-dimensional techniques. Chemical shifts and assignments are reported in Table 2 and
Figure 3.
The assignment of the sole singlet in the spectrum (8.98 ppm, H3) is straightforward. In fact, it is
worth to note that the 3-positioned aromatic proton of the pyridine moiety in Ru(II) complexes
displays a remarkable deshielding of ca 0.45 ppm, as compared to the free ligands, that is considered
diagnostic for their formation.
In the COSY-45 spectrum of C1 (see Figure 3) correlations between ortho, meta and para protons
1
2
3
are normally observable; differentiation among J, J and J couplings has been greatly aided by the

Molecules 2010, 15
1332
careful examination of shape and intensity of the cross-peaks. Starting from the peak at 9.51 (H3′), the
sequence of signals at 8.29 (H4′), 7.63 (H5′) and 8.04 ppm (H6′) can be assigned; another set of
connectivities (signals at 8.18/7.50/7.74 ppm) allows to assign the sequence H5, H7, and H8 of the
ligand mphbr-pq. Unambiguous identification of H8 (7.74) is based on the upfield shift observed for
1
this proton in H NMR spectrum of the Ru(II) complex C1 with respect to the free ligand L1 (see
Table 1), probably due to the shielding effect of a pyridine ring approximately orthogonal to this
proton; H5 shows, on the contrary, a negligible downfield shift. The intense peaks at 7.73 and
7.22 ppm indicate the presence of an AA′XX ′ system diagnostic of p-disubstituted benzene ring, and
may be easily attributed to the resonances of four phenyl protons of mphbr-pq.
Figure 3. 1H/1H COSY-45 spectrum (500 MHz, (CD3)2CO) of C1.
7.50
8.00
8.50
9.00
9.50
ppm (t1)
9.50
ppm (t2)
9.00
8.50
8.00
7.50

Molecules 2010, 15
Table 2. 1H-NMR spectral data for complexes C1–C12. Coupling constants in italic.
1333
C1
8.98
s
8.18
d
C2
8.79
s
8.23
d
C3
8.94
s
8.12
d
C4
8.75
s
8.17
d
C5
9.01
s
8.18
d
C6
8.76
s
8.21
d
C7
8.97
s
8.12
d
C8
8.58
s
8.10
d
C9
8.81
s
8.18
d
C10
8.80
s
8.15
d
C11
8.84
s
8.18
d
C12
8.83
s
8.15
d
H3
H5
J = 2.0
7.50
dd
J = 9.0,
2.0
J = 2.0
7.50
dd
J = 9.0,
2.0
J = 2.0
7.46
dd
J = 9.0,
2.0
J = 2.0
7.46
dd
J = 8.5,
2.0
J = 2.0
7.49
dd
J = 9.0,
2.0
J = 2.0
7.50
m
J = 2.0
7.45
dd
J = 9.0,
2.0
J = 2.0
7.50
m
J = 2.5
7.50
dd
J = 9.0,
2.0
J = 2.0
7.45
dd
J = 8.5,
2.0
J = 2.0
7.49
dd
J = 9.0,
2.0
J = 2.0
7.46
dd
J = 9.0,
2.0
H7
7.74
d
7.73
d
7.69
d
7.68
d
7.82
d
8.11
d
7.77
d
7.97
d
7.73
d
7.67
d
8.10
d
7.84
d
H8
J = 9.0
9.51
d
J = 9.5
9.23
d
J = 9.0
9.46
d
J = 9.0
9.16
d
J = 9.0
9.57
d
J = 9.0
9.18
d
J = 9.0
9.52
d
J = 9.0
9.18
d
J = 9.5
9.23
d
J = 9.0
9.36
d
J = 9.5
9.29
d
J = 9.0
9.42
d
H3′
J = 8.5
8.29
dt
J = 8.0,
1.5
7.63
dt
J = 7.0,
1.5
J = 9.0
8.32
m
J = 8.5
8.07
m
J = 8.0
8.10
m
J = 9.0
8.23
dt
J = 8.5
8.27
dt
J = 8.0,
2.0
7.60
t
J = 8.0
J = 9.0
8.01
m
J = 8.5
8.18
m
J = 9.0
8.32
dd
J = 8.0
2.0
J = 8.5
8.07
t
J = 8.5
8.26
t
J = 9.0
8.01
t
H4′
H5′
J = 8.0, 1.5
J = 8.0
J = 8.0
J = 8.0
7.65
t
J = 7.5,
1.5
7.61
dt
J = 7.5,
1.5
7.63
m
7.62
dt
J = 7.0,
1.5
7.60
dt
J = 7.0,
1.5
7.62
t
J = 8.0
7.62
m
7.62
m
7.61
t
J = 7.0
7.61
t
J = 7.0
8.04
d
8.06
d
8.04
d
8.06
d
8.02
d
8.02
d
8.02
d
7.96
d
8.05
d
7.88
d
8.03
d
7.86
d
H6′
J = 5.0
7.73
d
J = 9.0
7.22
d
J = 9.0
9.13
d
J = 5.5
7.55
d
J = 8.5
7.14
d
J = 8.5
8.76
d
J = 5.0
7.72
d
J = 9.0
7.20
d
J = 9.0
9.08
d
J = 5.0
7.54
d
J = 8.5
7.12
d
J = 8.5
8.71
d
J = 5.0
7.71
d
J = 8.5
7.21
d
J = 8.5
9.28
bs
J = 5.5
7.55
d
J = 8.0
7.13
d
J = 8.0
8.62
bs
J = 5.0
7.70
d
J = 8.5
7.19
d
J = 8.5
9.23
bs
J = 5.0
7.53
d
J = 8.5
7.14
d
J = 8.5
8.60
bs
J = 5.0
7.70
d
J = 8.5
7.23
d
J = 9.0
8.77
d
J = 5.0
7.54
d
J = 8.5
7.15
d
J = 8.5
8.98
d
J = 5.5
7.68
d
J = 8.5
7.22
d
J = 8.5
8.92
bs
J = 5.0
7.52
d
J = 8.5
7.14
d
J = 8.5
9.13
bs
H2”/6”
H3′′/5′′
H3A
J = 8.0
8.24
m
J = 8.0
8.26
m
J = 8.0
8.03
m
J = 8.5
8.05
m
J = 8.0
8.24
dd
J = 8.0
2.0
J = 8.5
8.05
m
H4A
7.53
m
8.48
d
7.58
m
8.52
d
7.43
m
8.35
d
7.48
m
8.39
d
7.48
m
8.22
bd
7.50
m
7.75
bd
7.38
m
8.09
m
7.44
m
7.78
m
7.55
m
8.50
d
7.46
m
8.38
d
7.50
m
7.76
d
7.41
m
7.64
d
H5A
H6A
J = 5.0
9.06
d
J = 6.0
8.68
d
J = 5.0
8.99
d
J = 5.5
8.61
d
J = 6.0
8.69
d
J = 5.5
8.87
d
J = 5.5
8.83
bs
J = 5.0
9.01
bs
9.19
bs
8.53
bs
9.12
bs
8.48
bs
H3′A
J = 8.0
8.08
dt
J = 8.0,
1.0
J = 8.0
8.11
t
J = 8.0
7.89
t
J = 8.0
7.92
t
J = 9.0
8.11
t
J = 8.0
7.92
t
H4′A
J = 7.5
J = 8.0
J = 8.0
J = 7.5
J = 8.0
7.52
m
7.87
d
J = 5.0
9.43
d
7.56
m
7.91
d
J = 6.0
8.96
d
7.37
m
7.81
d
J = 5.5
9.39
d
7.41
m
7.85
d
J = 5.0
8.92
bs
7.31
m
7.35
d
J = 5.0
9.61
bs
7.32
m
7.38
d
J = 5.5
8,78
bs
7.16
m
7.29
d
J = 5.5
9.57
bs
7.24
m
7.42
m
7.52
m
7.89
d
J = 5.5
8.97
d
7.44
m
7.76
d
J = 7.5
9.26
d
7.31
m
7.37
d
J = 6.0
9.15
bs
7.23
m
7.24
m
H5′A
H6′A
8.74
bs
9.44
bs
H3B
J = 8.0
8.23
m
J = 8.0
8.28
m
J = 8.0
8.02
m
J = 8.0
8.27 dt
J = 8.0
1.5
7.54
m
J = 8.0
8.07
m
8.07
m
H4B
H5B
H6B
7.53
m
7.93
d
7.57
m
7.99
d
7.30
m
7.84
d
7.44
m
7.90
bd
7.31
m
7.66
d
7.34
m
7.73
d
7.18
m
7.67
bd
7.30
m
8.16
bd
7.43
m
7.85
d
7.32
m
7.21
m
7.97
d
7.70
d
7.58
d
J = 5.0
9.41
d
J = 8.0
8.23
m
J = 5.0
8.93
d
J = 7.5
8.30
m
J = 5.0
9.39
d
J = 7.5
8.04
m
J = 5.0
9.60
bs
J = 5.0
8.75
bs
J = 5.5
8.94
d
J = 8.5
8.28 dd
J = 8.0
1.5
J = 5.0
9.24
bd
J = 6.0
9.13
bs
J = 5.5
9.43
bs
8.91
bd
9.56
bs
8.70
bs
H3′B
H4′B
8.09
m
8.09
m

Molecules 2010, 15
1334
Table 2. Cont.
7.68
dt
J = 7.0,
1.5
7.70
t
J = 7.0
7.64
dt
J = 7.0,
1.5
7.66
m
7.64
d
J = 7.0
7.65
d
J = 7.5
7.60
d
J = 7.0
7.36
m
7.68
t
J = 7.5
7.66
t
J = 7.5
7.64
d
J = 7.5
7.62
d
J = 7.0
H5′B
8.32
d
J = 6.0
8.36
d
J = 5.0
8.16
d
J = 6.0
8.20
d
J = 5.5
8.22
d
J = 6.0
8.23
d
J = 6.5
8.06
d
J = 6.0
7.70
d
J = 6.0
8.34
d
J = 5.5
8.21
d
J = 6.5
8.20
d
J = 6.0
7.62
d
J = 6.0
H6′B
2.49
bs
2.45
bs
2.44
bs
2.50
bs
2.48
bs
2.47
bs
′
CH3 A
2.60
bs
2.60
bs
2.54
bs
2.55
bs
2.53
bs
2.53
bs
2.70
bs
2.71
bs
2.59
bs
2.60
bs
2.53
bs
2.53
bs
CH3B
CH3A
2.60
bs
2.56
bs
2.53
bs
2.72
bs
2.61
bs
2.53
bs
′
CH3 B
4.17 t
J = 6.5
1.87
t
4.17 t
J = 6.5
1.86
t
4.17 t
J = 6.5
1.87
t
4.17 t
J = 6.5
1.87
t
αCH2
βCH2
J = 6.5
1.63
t
J = 6.5
2.17
dt
J = 6.5
1.62
t
J = 6.5
2.15
dt
J = 6.5
1.63
t
J = 6.5
2.17
dt
J = 6.5
1.63
t
J = 6.5
2.16
dt
γCH2
δCH2
J = 7.0,
1.5
J = 7.0,
1.5
J = 7.0,
1.5
J = 7.0,
1.5
5.00
dd
J = 10.0,
2.0
5.04
dd
J = 10.0,
2.0
5.02
dd
J = 10.0,
2.0
5.00
dd
J = 10.0,
2.0
εCH2
5.87
m
5.88
m
5.87
m
5.87
m
-CH
OCH3
-OH
3.95
s
3.95
s
3.95
s
3.95
s
9.95
bs
9.96
bs
9.95
bs
9.96
bs
Notes: The spectra were obtained in deuterated acetone (CD3)2CO, chemical shifts in ppm, and coupling constants (J) in
Hz. Numbering pattern as shown in Schemes 4 and 5. Abbreviations used: s = singlet, d = doublet, dd = double doublet,
t = triplet, dt = double triplet, bs = broad singlet, bd = broad doublet.
Following inspection of the COSY spectrum, further sequences of isolated four-spin systems can be
analyzed. Using low-field signals as convenient starting points, it is possible to establish the complete
set of connectivities for the following sequences of signals: 9.43/8.22/8.54/7.93 ppm,
9.41/8.23/7.68/8.32 ppm, 9.13/8.24/7.54/8.48 ppm and 9.06/8.08/7.52/7.87 ppm. Owing to a
combination of inductive and steric effects, the proton H7, H8, and H6’ of the asymmetric ligands
experience, upon complexation, an upfield effect with respect to the free ligands as is shown in
Table 2. It is also worth noting that in the case of complexes with dmbpy moieties (C5–C8) we
observe two different signals for the four methyl groups in the ratio 1:3 (with the less intense signal
experiencing an upfield effect), suggestive of the presence of a clear steric effect between the big
bromo substituent linked to the quinoline moiety of the asymmetric ligands and the methyl group
linked to the nearest pyridine ring of the Abpy moiety. (See Scheme 4)
On the basis of this evidence, after inspection of the molecular models and taking into account the
resonances of H6 and/or H6′ bpy protons, we assume that binding of the asymmetric ligands (L1 or L2)
is expected to strongly shield these protons and shift them to higher field. In other words, upon
complexation the nearest is the proton of the bpy units to the asymmetric ligand, the stronger is the
upfield effect experienced. As a consequence, in accord with the numbering pattern shown in Scheme

Molecules 2010, 15
1335
4 and/or Scheme 5, resonances at 7.87, 7.93, 8.32,and 8.48 ppm were assigned to H6′A, H6B, H6′B and
H6A, respectively. Therefore the former pair of sequence signals is assigned to the protons H3B and H3'B
of the same bpy unit, respectively, and the latter one to H3A and H3′A of the other bpy unit. The
assignments of the above cited signals to the sequences from position 3 to position 6 of the bpy ligands
are reported in Table 2.
3. Experimental
3.1. General
The starting materials, 2-acetylpyridine, 2-aminobenzophenone, p-nitrobromobenzene,
p-methoxyphenylacetonitrile, 4,4’-dimethylbpy, and 6-bromo-1-hexene, were purchased from Aldrich.
All other chemicals were reagent grade. Os(bpy)2Cl2, Ru(dmbpy)2CL2 and Os(dmbpy)2CL2 were
synthesized by the method of Togano et al. for Ru(bpy)2Cl2 and were used without purification [26].
All reactions were performed under an inert atmosphere of nitrogen except when otherwise stated and
the solvents were dried and stored under nitrogen and over 4Å molecular sieves. Melting points are
uncorrected. Elemental analyses were determined commercially. The analytical and FAB-MS data of
complexes C1–C12 are gathered in Table 3. Proton spectra were performed in (CD3)2CO or CDCl3 by
1
using a Varian INOVA 500 MHz instrument. H-NMR spectra were calibrated relative to the solvent
resonance considered at 2.05 or 7.26 ppm for residual (CH3)2CO or CHCl3, respectively. The analysis
of the proton spectra was carried out according to the rules for the first-order splitting with the help of
integral intensities, and resonance splitting patterns are abbreviated by using s for singlet, d for
doublet, dd for doublet of doublets, t for triplet, and m for multiplet. Positive ion FAB mass spectra
were obtained on a Kratos MS 50 S double-focusing mass spectrometer equipped with a standard FAB
1
source, using 3-nitrobenzyl alcohol as the matrix. The H spectra with assigned signals are given in
Table 2.
Table 3. Analytical and Positive ion FAB-MS Spectral Data for the Complexes C1–C12.
Yield (%)
(XXX)
%C
Found
(Calcd)
44.96
%H
Found
(Calcd)
3.00
%N
Found
(Calcd)
7.56
Molecular Formula
(M.W.)
FAB – MS
Complex.
m/z
Me2CO/Et2O
72
C1
C2
C3
C4
C5
C6
C7
Ru(C41H31BrF12N6OP2)
(1094.50)
949
[Ru(bpy)2L1](PF6)+
935
(45.00)
44.33
(2.85)
2.85
(7.67)
7.47
63
69
71
95
80
73
Ru(C40H29BrF12N6OP2)
(1080.47)
(44.46)
42.01
(2.70)
2.22
(7.77)
7.37
[Ru(bpy)2L2](PF6)+
Os(C41H31BrF12N6OP2)
(1183.66)
1038
(41.62)
41.74
(2.64)
2.09
(7.10)
7.33
[Os(bpy)2L1](PF6)+
1024
Os(C40H29BrF12N6OP2)
(1169.63)
(41.41)
46.91
(2.50)
3.57
(7.18)
6.94
[Os(bpy)2L2](PF6)+
Ru(C45H39BrF12N6OP2)
(1150.60)
1005
(46.97)
46.11
(3.40)
3.19
(7.30)
7.41
[Ru(dmbpy)2L1](PF6)+
991
Ru(C44H37BrF12N6OP2)
(1136.57)
(46.49)
46.52
(3.28)
2.49
(7.39)
6.74
[Ru(dmbpy)2L2](PF6)+
Os(C45H39BrF12N6OP2)
(1239.76)
1094
(46.13)
(2.90)
(6.78)
[Os(dmbpy)2L1](PF6)+

Molecules 2010, 15
1336
Table 3. Cont.
C8
C9
80
99
94
83
88
Os(C44H37BrF12N6OP2)
42.98
(43.11)
47.63
2.85
(3.04)
3.49
6.92
(6.89)
6.93
1080
(1225.73)
Ru(C46H39BrF12N6OP2)
(1162.61)
[Os(dmbpy)2L2](PF6)+
1017
(47.52)
44.52
(3.38)
3.06
(7.23)
6.58
[Ru(bpy)2L3](PF6)+
1106
C10
C11
C12
Os(C46H39BrF12N6OP2)
(1251.77)
(44.13)
48.91
(3.14)
4.11
(6.71)
6.87
[Ru(bpy)2L3](PF6)+
Ru(C50H47BrF12N6OP2)
(1218.65)
1099
(49.27)
46.09
(3.89)
3.36
(6.89)
6.80
[Ru(dmbpy)2L3](PF6)+
1188
Os(C50H47BrF12N6OP2)
(1307.81)
(45.91)
(3.62)
(6.42)
[Os(dmbpy)2L3](PF6)+
3.2. Syntheses
3-p-Methoxyphenyl-5-bromo-2,1-benzoisoxazole (1). To a vigorously stirred solution containing
potassium hydroxide (17.76 g, 310 mmol) in methanol (35 mL) at room temperature, was slowly
added p-methoxyphenylacetonitrile (1.75 g, 15 mmol). After dissolution was complete, a
methanol/tetrahydrofuran (2:1, v/v) solution (36 mL) containing p-nitrobromobenzene (3.0 g,
15 mmol) was added dropwise at 0 °C. The resulting dark mixture was stirred at 0 °C for 3 h, at room
temperature for 4 h, refluxed overnight, and then poured into ice-water (300 mL) to afford, after
filtration, cold water and methanol washings and methanol recrystallization, compound 1 as yellow
crystals; 2.22 g (66%); m.p. 112 °C; 1H-NMR (CDCl3) : 8.05 (bs, 1H, H4 of benzoisoxazole); 7.94 (d,
2H, J = 8.5 Hz, H2’/H6’of phenyl), 7.50 (dd, 1H, J = 9.5, 1.0 Hz, H7 of benzoisoxazole); 7.36 (dd, 1H,
J = 9.5, 1.5 Hz, H6 of benzoisoxazole); 7.09 (d, 2H, J = 8.5 H3’/H5’of phenyl), 3.92 (s, OCH3); MS, m/z
304 (MH+); Anal. Calcd. for C14H10BrNO: C, 56.95; H, 2.92; N, 5.11. Found: C, 57.19; H, 3.03;
N, 4.86.
4’-Methoxy-2-amino-5-bromobenzophenone (2). A solution containing 1 (0.44 g, 1.6 mmol) in acetic
acid (70 mL), was heated on a water-bath, and iron powder (1.0 g, 18 mmol) was added over 2.5 h,
during which time water (12 mL) was also added. The mixture was filtered while hot and then water
(100 mL) was added. The yellow precipitate was collected by filtration, washed with cold water until
the water washings were clear and dried. The product was purified by column chromatography (silica;
cyclohexane/ethyl acetate 9:1) followed by recrystallization from ethanol-water to afford 2 as a yellow
1
powder; 031 g (70%); m.p. 105 °C; H-NMR (CDCl3) : 7.68 (d, 2H, J = 9.0 Hz, H2’/H6’of phenyl);
7.55 (d, 1H, H6 of benzene); 7.35 (dd, 1H, J = 8.5, 2.5 Hz, H4of benzene); 6.98 (d, 2H, J = 9.0 Hz,
H3’/H5’of phenyl); 6.65 (d, 1H, J = 9.0 H3 of benzene) 5.83 (bs, 2H, of amino) 3.90 (s, CH3 of
methoxy); MS, m/z 406 (MH+); Anal. Calcd. for C14H11BrNO: C, 56.54; H, 3.62; N, 5.07. Found: C,
56.28; H, 3.59; N, 4.95
4-p-Ethoxyphenyl-6-bromo-2-(2’-pyridyl)quinoline (brmph-pq, L1). A mixture of m-cresol (25 mL)
and phosphorus pentoxide (0.81 g, 5.7 mmol) was stirred at 145 °C for 2.5 hours to afford a
homogeneous solution. After cooling, 4-methoxy-2-amino-5-bromobenzophenone (4.08 g, 15 mmol)
and 2-acetylpyridine (2.03 g, 15 mmol) were added, followed by m-cresol (20 mL) to rinse the powder
funnel. The reaction mixture was heated at 135 °C overnight. After cooling, the dark solution was

Molecules 2010, 15
1337
poured into ethanol (200 mL) containing triethylamine (20 mL). The light grey precipitate was
collected by filtration, continuosly extracted with a solution of ethanol/triethylamine for 24 h, and
recrystallized from n-hexane/methylene chloride to give brmph-pq (L1) as an off white powder;
+
3.96 g (71%); m.p. = 212 °C.; MS, m/z 375 (MH ).
4-p-Hydroxyphenyl-6-bromo-2-(2’-pyridyl)quinoline (brhph-pq, L2). A mixture of of L1 (0.5 g,
1.27 mmol), 1 M boron tribromide in dichloromethane ((5.69 mL, 5.08 mmol) and dichloromethane
(dry, 30 mL) was stirred at −75 °C for 0.5 h and room temperature for 24 h. The reaction mixture was
poured into ice and cold water (800 mL) and stirred for 0.5 h. The red precipitate was filtrated and
suspended in ethanol (250 mL). The turbid red mixture was neutralized by some drops of 1N NaOH
(colour changing from red to light-blue). The light-blue precipitate was collected by filtration, washed
with cold water and ethanol until the water washings were clear and dried under vacuum on P2O5 at
40 °C to give 0.42 g (72%) of L2 as a white solid.
The synthesis of complex C1 is given below as a general procedure for the synthesis of C1-C8
complexes.
[Ru(bpy)2(brmph-pq)] (PF6)2. (C1). To a refluxing solution of cis-Ru(bpy)2Cl2 2H2O (0.156 g,
0.3 mmol) in ethanol (20 mL), was added dropwise a solution of brmph-pq (0.1 g, 0.35 mmol) in
EtOH (20 mL), and the mixture was allowed to reflux for 8 h. After concentration and addition of
water (15 mL), the mixture was refluxed for 5 min and filtered while hot. After cooling, the complex
was precipitated by dropwise addition of a 20% water solution of NH4PF6 (5 mL). The red precipitate
was collected, washed with cold water and Et2O, and purified by gel filtration on a column of
Sephadex LH-20 in EtOH followed by recrystallization from acetone-Et2O, to give 0.22 g (72%) of C1
as red orange crystals.
The synthesis of complex C9 is given below as a general procedure for the synthesis of C9–C12
complexes.
[Ru(bpy)2(L2-hexene)](PF6)2. To a refluxing solution of K2CO3 (0,2 g, 14.5 mmol) in CH3CN (20 mL)
was added dropwise a solution of [Ru(bpy)2(brhph-pq)](PF6)2 (0.06g. 0.055 mmol) in CH3CN
(10 mL) and a solution of 6-bromo-1-hexene (0.018 g. 0.111 mmol) in CH3CN (10 mL) and the
mixture was allowed to reflux for 48 h. Then the reaction mixture was filtered while hot to remove
carbonate-salt, rotoevaporated to dryness, dissolved with a minumum quantity of acetone and poured
into Et2O. The red-brown precipitate was collected by filtration, washed with Et2O, and purified by
recrystallization from acetone-Et2O, to give 0.06 g (99%) of C9 as dark-red crystals.
4. Conclusions
A series of Ru(II) and Os(II) complexes with new polyquinoline asymmetric aza-bidentate ligands
1
have been synthesized and characterized by EA, EI-FAB Mass and NMR techniques. Complete H
NMR assignments have been obtained by the use of two-dimensional techniques. The results indicate
that steric hindrance on Ru(II) or Os(II) metal has to be carefully considered in designing new

Molecules 2010, 15
1338
bidentate asymmetric ligands. Because of their intrinsic asymmetry, the racemic complexes obtained,
when resolved into their enantiomeric forms, will provide interesting species for DNA binding studies,
the development of solid state photoluminescent devices, light harvesting compounds, and useful
energy traps when inserted into supramolecular arrays.
Acknowledgements
We would like to thank R. Purrello and A. Gulino for helpful discussions. This work was supported
by PRA funds of Catania University, Italy.
References and Notes
1. Smalley, S.; Waterland, M.; Telfer, S. Heteroleptic dipyrrin/bipyridine complexes of
ruthenium(II). Inorg. Chem. 2009, 1, 13–15.
2. Bolink, H.; Coronado, E.; Costa, R.; Lardiés, N.; Orti. E. Near-Quantitative internal quantum
efficiency in a light-emitting electrochemical cell. Inorg. Chem. 2008, 47, 9149–9151.
3. Flamigni, L.; Collin, J.P.; Sauvage, J.P. Iridium terpyridine complexes as functional assembling
units in arrays for the conversion of light energy, Acc. Chem. Res. 2008, 41, 857–871.
4. Puckett, C.; Barton, J. Mechanism of cellular uptake of a ruthenium polypyridyl complex.
Biochemistry 2008, 47, 11711–11716.
5. Pradhan, B.; Das, S. Role of new bis(2,2’-bipyridyl)(triazolopyridyl)ruthenium(II) complex in the
organic bistable memory application. Chem. Mater. 2008, 20, 1209–1211.
6. Zhou, M.; Robertson, G.; Roovers, J. Comparative study of ruthenium(II) tris(bipyridine)
derivatives for electrochemiluminescence application. Inorg. Chem. 2005, 44, 8317–8325.
7. Richter, M.M. Electrochemiluminescence (ECL). Chem. Rev. 2004, 104, 3003–3036
8. Wang, X.; Chao, H.; Li, H.; Hong, X.; Liu, Y.; Tan, L.; Ji, L. DNA interactions of cobalt(III)
mixed-polypyridyl complexes containing asymmetric ligands. J. Inorg. Biochem. 2004,
98, 1143–1150.
9. Ji, L.; Zou, X.; Liu, J. Shape and enantioselective interaction of Ru(II)/Co(III) polypyridyl
complexes with DNA. Coord. Chem. Rev. 2001, 216–217, 513–536.
10. Fanni, S.; Keyes, T.; O’Connor, C.; Hughes, H.; Wang, R.; Vos, J. Excited – states properties of
ruthenium (II) polypyridyl complexes containing asymmetric triazole ligands. Coord. Chem. Rev.
2000, 208, 77–86.
11. Deng, H.; Cai, J.; Xu, H.; Zhang, H.; Ji, L. Ruthenium (II) complexes containing asymmetric
ligands: synthesis, characterization, crystal structure and DNA–binding. J. Chem. Soc. Dalton
Trans. 2003, 325–330.
12. Sortino, S.; Petralia, S.; Conoci, S.; Di Bella, S. Novel self-assembled monolayers of dipolar
ruthenium (III/II) pentaamine (4,4’-bipyridinium) complexes on ultrathin platinum films as redox
molecular switches. J. Am. Chem. Soc. 2003, 125, 1122–1123.
13. Shukla, A.; Das, A.; Van der Boom, M.E. Electrochemical addressing of the optical properties of
a monolayer on a trasparent conducting substrate. Angew. Chem. Int. Ed. 2005, 44, 3237–3240.

Molecules 2010, 15
1339
14. Mamo, A. Synthesis and characterization of new substituted terdendate 2,6-pyridylquinolines and
1,3-benzenequinoline ligands. J. Heterocyclic. Chem. 2000, 37, 1225–1231.
15. Mamo A.; Stefio I.; Parisi M. F.; Di Pietro C.; Campagna S. Luminescent and redox-active
iridium (III)-cyclometallated compounds with terdentate ligands. Inorg. Chem. 1997,
36, 5947–5950.
16. Mamo, A.; Stefio, I.; Poggi, A.; Tringali, C.; Di Pietro, C.; Campagna, S. Ruthenium (II) and
osmium (II) complexes with new terdentate polyquinoline and cyclometalating ligands. Synthesis,
NMR characterization, luminescence properties, and electrochemical behavior. New J. Chem.
1997, 21, 1173–1185.
17. Mamo, A.; Pappalardo, A. Synthesis and characterization of acyclic and cyclic aza-bridged
ligands incorporating 2,2'-bipyridine subunits and their complexes with copper (II), cobalt (II),
and nickel (II). Molecules 2003, 8, 521–535.
18. Lupo, F.; Fragalà, M.; Gupta, T.; Mamo, A.; Aureliano, A.; Bettinelli, M.; Speghini, A.; Gulino,
A. Optical selective CO sensing by a ruthenium monolayer covalently assembled on silica
substrates . J. Mat. Chem. 2010, in press.
19. Campagna, S.; Mamo, A.; Stille, J.K. Synthesis, characterization, luminescence properties, and
electrochemical behavior of ruthenium (II) complexes with two new bidentate and tridentate 2-
pyridyl-quinoline ligands. J. Chem. Soc. Dalton Trans. 1991, 2545–2551.
20. Riego, E. C.; Jin, X.; Thummel, R.P. Introduction of benzo[h]quinoline and 1,10-phenanthroline
subunits by Friedlander methodology J. Org. Chem. 1996, 61, 3017–3022.
21. Hu, Y.Z.; Zhang, G.; Thummel R.P. Friedlander approach for the incorporation of
6-bromoquinoline into novel chelating ligands. Org. Lett. 2003, 5, 2251-2253.
22. McOmie, J.F.; Watts, M.L.; West, D.E. Demethylation of aryl methyl ethers by boron tribromide.
Tetrahedron 1968, 24, 2289–2292.
23. Lehner, A.; Steinhoff, G.; Brandt, M.; Eickhoff, M.; Stutzmann, M. Hydrosilylation of crystalline
silicon (111) and hydrogenated amorphous silicon surfaces: A comparative x-ray photoelectron
spectroscopy study. J. Appl. Phys. 2003, 94, 2289–2294.
24. Constable, E.C. Homoleptic complexes of 2,2’ bipyridine. Adv. Inorg. Chem. 1989, 34, 1–63.
25. Lay, P.; Harmer, W.D. Recent advances in osmium chemistry. Adv. Inorg. Chem. 1991,
37, 219–379.
26. Togano,T.; Nagao, N.; Tsuchida, M.; Kumakura, H.; Hisamatsu, K.; Howell, F.; Mukaida, M.
One pot and selective synthesis of a series of [RuCl6-2nLn] (L bidentate ligand n = 0–3) types of
complexes with polypyridyl ligands, another example of the synthetic utility of ‘ruthenium-blue’
solution. Inorg. Chim. Acta 1992, 195, 221–225.
Sample Availability: Available from the authors.
© 2010 by the authors; licensee Molecular Diversity Preservation International, Basel, Switzerland.
This article is an open-access article distributed under the terms and conditions of the Creative
Commons Attribution license (http://creativecommons.org/licenses/by/3.0/).