Polydentate analogues of 8-hydroxyquinoline and their complexes with ruthenium

Article abstract of DOI:10.1021/ic201524j

Selective reduction of 2-nitro-3-methoxybenzaldehyde provides 2-amino-3-methoxybenzaldehyde that undergoes the Friedlaender condensation with a variety of acetyl-substituted derivatives of pyridine and 1,10-phenanthroline. After cleavage of the methyl eth

Full text of DOI:10.1021/ic201524j

ARTICLE
pubs.acs.org/IC
Polydentate Analogues of 8-Hydroxyquinoline and Their Complexes
with Ruthenium
Maya El Ojaimi and Randolph P. Thummel*
Department of Chemistry, 136 Fleming Building, University of Houston, Houston, Texas 77204-5003, United States
S Supporting Information
b
ABSTRACT: Selective reduction of 2-nitro-3-methoxybenzaldehyde
provides 2-amino-3-methoxybenzaldehyde that undergoes the Friedl €a n-
der condensation with a variety of acetyl-substituted derivatives of
pyridine and 1,10-phenanthroline. After cleavage of the methyl ether,
the resulting polydentate analogues of 8-hydroxyquinoline are excellent
ligands for ruthenium. The resulting oxidation state of the metal center
depends on the anionic character of the ligands. The presence of two
electron donating anionic ligands results in a Ru(III) complex as
evidenced by paramagnetic NMR behavior. The electronic absorption
and redox properties of the complexes were measured and found to be
consistent with the anionic character of the 8-HQ moieties. A planar
pentadentate ligand provides two RuꢀO and two RuꢀN bonds in the
equatorial plane. An X-ray structure shows that the central pyridine of
the ligand is oriented toward the metal but held at a distance of 2.44 Å.
’
INTRODUCTION
hydroxyl group replaces a fused pyridine ring. Like phen, 8-HQ is
rigid, planar, and fully conjugated. A major difference is that it
generally binds to metals as its conjugate base, providing an
anionic ligand with distinctly different electronic properties from
the neutral phen.
Out of seven potential quinolinols, only 8-hydroxyquinoline
(8-HQ) can readily form a five-membered chelate complex with
metal ions. The chelate compounds are stable and have been
used in analytical chemistry for the separation and identification
of metal ions as well as in spectrophotometric analysis and metal
0
The parent member of this new ligand series is 2-(pyrid-2 -yl)-
1
ꢀ5
ion sensing.
Medicinal (antiseptic, disinfectant, bactericidal)
8-hydroxyquinoline (6b-H), and several earlier reports of its
31ꢀ35
and agricultural (pesticide, fungicidal) uses of 8-HQ have also
been investigated. In addition 8-HQ has also been explored as
a potential anticancer drug. The electroluminescent tris-(8-
HQ)-aluminum complex plays a critical role in the development
of organic light-emitting diodes (OLEDs)
buildings blocks for flat panel displays. Moreover, platinum com-
plexes of 8-HQ have been used as redox photosensitizers in solar
energy conversion. Ditopic 8-HQ derivatives containing diaza-
synthesis have appeared.
These routes generally involve the
1
,5
multistep, low yield incorporation of a 2-halo group onto 8-HQ
and then subsequent organometallic coupling with either 2-pyr-
idylstannane or 2-pyridyl zinc bromide. We will show that
commercially available 2-nitro-3-methoxybenzaldehyde (1) can
be readily reduced to the corresponding aminoaldehyde that can
then undergo a simple Friedl €a nder condensation with appro-
priate acetyl pyridines to afford 8-methoxyquinoline derivatives
that may be cleaved to provide polydentate analogues of 8-HQ.
The tri-, tetra-, and pentadentate ligands 6b-H, 7b-H, and 8b-2H
are shown to afford interesting complexes with Ru(II).
Synthesis of Ligands. The prerequisite 2-amino-3-methox-
ybenzaldehyde (2) may be readily prepared in 87% yield by the
reduction of 3-methoxy-2-nitrobenzaldehyde (1) with Fe pow-
der in aqueous ethanol.
6
7
ꢀ10
that serve as
1
1
1
8-crown-6 ligands were studied as fluorophoric chemosensors
12,13
as well as for selective metal ion extraction.
based on 8-HQ subunits have been shown to be strong chelators
for Fe(III) over a wide range of pH.
Tripodal ligands
14ꢀ17
However, binding of
18ꢀ30
8
-HQ to Ru(II) has received only moderate attention.
The Friedl €a nder reaction was carried out by heating the
aminoaldehyde 2 together with the precursor carbonyl com-
pound in ethanolic KOH overnight. The 8-methoxyquinolines
were purified by crystallization or chromatography on alumina,
1
and they were readily characterized by their H NMR spectra.
In this work we are interested in the incorporation of the
-HQ subunit into polypyridine ligand systems. In structure,
-HQ strongly resembles 1,10-phenanthroline (phen) where the
8
8
Received: July 18, 2011
Published: October 10, 2011
r 2011 American Chemical Society
10966
dx.doi.org/10.1021/ic201524j
|Inorg. Chem. 2011, 50, 10966–10973

Inorganic Chemistry
ARTICLE
Scheme 1. Synthesis of the Ligands 6b-Hꢀ8b-H
Scheme 2. Synthesis of Ligand 11
By treating ligands 6b-H, 7b-H, and 8b-2H with an appro-
priate source of Ru(II), we have prepared complexes with all
three ligands. When ligand 6b-H is treated with [Ru(tpy)Cl ]
3
0
00
(
tpy = 2,2 ;6.2 -terpyridine) in aqueous ethanol followed by
precipitation with NH PF , the mixed ligand complex [Ru(tpy)-
4
6
1
(
6b)](PF ) is formed in 48% yield (Scheme 3). The H NMR
6
spectrum in acetone-d shows 15 well-resolved peaks, and the
6
proton assignments were made by considering both 1D and 2D
NMR. Due to the symmetry of the tpy ligand, we observe 5 peaks,
each integrating for 2 protons, and a triplet at 8.23 ppm assigned
to H4. The doublet at 7.85 ppm, integrating for 2 protons with
a small coupling constant (5.1 Hz), is assigned to the protons
These spectra were generally well resolved, and the independent
spin systems could be easily identified by 2D techniques. The
final ether cleavage to give the hydroxyquinoline ligands was
accomplished by simply heating the methoxyquinolines in 48%
HBr. We attempted to prepare 11, which would be the planar,
fully conjugated analogue of 6b-H (Schemes 1 and 2). The
Friedl €a nder reaction of 2 with tetrahydro-8-quinolone 9 pro-
ceeded in 84% yield. During the ether cleavage step some
dehydrogenation occurred providing a mixture of 10b-H and
0
0
H6 and H6 of tpy due to their proximity to the nitrogen. The
protons H5, H6, and H7 of the hydroxyquinoline moiety are
shielded due to the anionic 8-oxide and appear at 6.95ꢀ6.39
ppm (Figure SI-10). Further proof of structure was provided by
the positive ion MALDI-TOF mass spectrum that showed a
pattern at m/z 556.28 identical to the simulated isotopic
+
1
1 in a 20/1 ratio. Complete dehydrogenation in the presence of
distribution for [Ru(tpy)(6b)] (Figure SI-20).
Pd/C was problematic so that a pure sample of 11 could not
If the same ligand 6b-H is treated instead with 0.25 equiv
6
easily be obtained.
Ruthenium Complexes. Bhattacharya and co-workers
and Turro and co-workers
of [η -C
H
6
6
)RuCl(μ-Cl)]
2
in acetonitrile in the presence of
2
0ꢀ22
1 equiv of NaOH and KPF
, a dark purple solution results that,
6
18,19
have examined Ru complexes of
after chromatography on alumina, provides a 53% yield of [Ru-
1
2 6 3
8
-HQ. They find that one, two, or three 8-Q ligands can be
(6b) ](PF ). The H NMR spectrum of this material in CD OD
complexed to Ru(II) with the remaining coordination sites being
occupied by one or two bpy (2,2 -bipyridine) or phen ligands.
The complexes show increasingly long wavelength metal-to-
ligand transfer (MLCT) absorptions as the number of 8-Q
ligands increases. Similarly the oxidation potential of the com-
plexes decreases due to stabilization of higher oxidation states of
Ru resulting from the anionic nature of the quinolate ligand.
shows several broad peaks characteristic of a Ru(III) complex
(Figure 1, top). The addition of ascorbic acid reduces the Ru(III)
to Ru(II), and the spectrum then shows typical diamagnetic
behavior. Nine well resolved peaks are assigned to the protons of
0
6b in the symmetric complex [Ru(6b) ] (Figure 1, bottom). The
2
proton assignments were made by consideration of the 2D data.
Due to the planar, cisoid conformation of 6b required for
1
0967
dx.doi.org/10.1021/ic201524j |Inorg. Chem. 2011, 50, 10966–10973

Inorganic Chemistry
ARTICLE
Scheme 3. Ru Complexes of Ligand 6b
tridentate coordination, the two 8-oxide functionalities must
assume a cis-orientation in the homoleptic complex such that it
will exist as a racemic mixture. The initial formation of the para-
magnetic Ru(III) species could be explained by the two anionic
ligands stabilizing the higher oxidation state of Ru(III). Further
proof of structure was provided by the positive ion MALDI-TOF
mass spectrum that showed a pattern at m/z 544.16 identical to
the simulated isotopic distribution for C H N O Ru expected
2
8 18 4 2
+
for the cation [Ru(6b) ] (Figure SI-21).
2
In earlier work we have demonstrated that a tetradentate
0
ligand such as 2,9-di(pyrid-2 -yl)-phen will coordinate with Ru-
(
II) such that all four nitrogens bind to the metal in the equatorial
1
Figure 1. Downfield region of the 400 MHz H NMR spectrum in
CD
addition of ascorbic acid.
0
plane. However, the closely related tetradentate ligand 2,2 -
biphen, due to flexibility around the central 2,2 -single bond,
+
3 2 2
OD of [Ru(6b) ] before (top) and [Ru(6b) ] after (bottom) the
0
can act as a bridging ligand and hence does not readily form a 1:1
36
complex with Ru(II). The ligand 7b has an arrangement of
0
ligating centers similar to 2,2 -biphen and in its transoid con-
formation may also act as a bridging ligand, leading to oligomeric
complexes. However, we find that when this ligand is treated with
RuCl and 4-picoline (pic) in the presence of triethylamine
3
(
TEA), followed by NH PF , a low (6%) yield is obtained of the
4 6
mononuclear complex [Ru(7b)(pic) ](PF ) (pic = 4-picoline).
2
6
1
Figure 2. Downfield region of the 400 MHz H NMR spectrum of
Ru(7b)(pic) ](PF ) in CD CN.
[
2
6
3
The ligand 8b-2H is potentially pentadentate, but with two
σ-bonds connecting the two quinolines to the central pyridine, the
molecule has considerable conformational freedom. This free-
dom could lead to some variety in the denticity of its binding to
metal cations. In earlier work it has been demonstrated that the
0
corresponding 2,6-di(quinolin-2 -yl)pyridine will bind Ru(II) as
37
a tridentate. After initial exposure to 1 equiv of NaOH, the
ligand was treated with [Ru(dmso) Cl ] followed by an excess of
4
2
1
The complex was characterized by its H NMR in CD CN
4-picoline. After the addition of NH PF , chromatography and
4 6
1
3
(
Figure 2) where we observe 14 signals in the downfield region
recrystallization provided a black solid in 29% yield. H NMR in
corresponding to the 12 protons of the equatorial anionic ligand
b and 8 protons of the two axial 4-picolines. The proton
acetone-d showed only broad peaks characteristic of a para-
magnetic Ru(III) species. Upon the addition of ascorbic acid and
6
7
assignments were made by considering both 1D and 2D NMR.
The two doublets at 7.96 and 6.83 ppm, each integrating for 4
protons, are assigned to the two axial 4-picolines. The protons
H5 , H6 , and H7 of the hydroxyquinoline moiety are shielded
due to the anionic 8-oxide and appear at 7.07ꢀ6.53 ppm.
Furthermore, the positive ion MALDI-TOF mass spectrum of
warming to 62 °C in CD OD, eight well resolved peaks were
3
observed (Figure SI-13). Two four proton doublets were found
at 8.02 and 6.83 ppm, matching very closely the two doublets for
0
0
0
the 4-picoline protons found in [Ru(7b)(pic)
]PF
. Two doub-
2
6
0
lets and a triplet appeared at 7.06ꢀ7.36 ppm for the protons H5 ,
0
0
H6 , and H7 of the 8-oxyquinoline moiety. Further downfield
0
0
[
Ru(7b)(pic) ](PF ) showed a pattern at m/z 610.43 [M ꢀ
was an AB quartet due to H3 and H4 and a sharp singlet at 8.34
ppm for the H3 proton on the central pyridine. It appears that the
dianionic character of the ligand causes the metal to oxidize to
2
6
+
PF ] identical to the simulated isotopic distribution for
6
C H N ORu (m/z 610.12) (Figure SI-22).
3
3 26 5
1
0968
dx.doi.org/10.1021/ic201524j |Inorg. Chem. 2011, 50, 10966–10973

Inorganic Chemistry
ARTICLE
+
2
Figure 3. (a) Top view of the cation [Ru(8b)(pic) ] showing the atom numbering scheme. Thermal ellipsoids are 40% equiprobability envelopes, with
H atoms omitted. (b) Side view of the cation.
Ru(III). The observation of only six aromatic resonances for 8b
indicates that the ligand is bound in a symmetric disposition. The
Table 1. Selected Geometric Parameters for
[Ru(8b)(pic) ](PF )
2
6
presence of the necessary PF counterion was verified by the
6
1
9
appearance of a F doublet at ꢀ74.80 ppm (J = 750 Hz).
Bond Lengths (Å)
2.030 (5) RuꢀN1
2.031 (5) RuꢀN17
2.097 (6) RuꢀN11
2.100 (7)
The MALDI-TOF mass spectral pattern at m/z 707.55 [M ꢀ
RuꢀO2
RuꢀO1
RuꢀN38
RuꢀN31
2.185 (6)
2.222 (6)
2.440 (6)
+
PF ] was identical to the simulated isotopic distribution for
6
C H N O Ru (Figure SI-23). A complex analogous to
3
9 35 5 2
[
(
Ru(8b)(pic) ]PF was also prepared using 4-t-butylpyridine
tb-py) in place of 4-picoline.
2 6
Bond Angles (deg)
O1ꢀRuꢀN1
O2ꢀRuꢀN17
O1ꢀRuꢀO2
N1ꢀRuꢀN17
76.4 (2)
75.1 (2)
78.3 (2)
O2ꢀRuꢀN1
154.6 (2)
153.3 (2)
111.4 (6)
111.7 (6)
113.6 (6)
113.9 (6)
O1ꢀRuꢀN17
N11ꢀC16ꢀC18
130.3 (2) N11ꢀC12ꢀC10
C12ꢀC10ꢀN1
C16ꢀC18ꢀN17
Dihedral Angles (deg)
N11ꢀC16ꢀC18ꢀN17 ꢀ3.5 (9)
N17ꢀC26ꢀC25-O2 3.4 (10)
N11ꢀC12ꢀC10ꢀN1
C25ꢀO2ꢀRuꢀN17
N1ꢀRuꢀO1ꢀC3
2.3 (10)
2.6 (5)
N1ꢀC2ꢀC3-O1
ꢀ3.4 (11)
4.3 (9)
C16ꢀC18ꢀN17-Ru
C12ꢀC10ꢀN1-Ru
ꢀ6.7 (5)
ꢀ2.5 (10)
Monocrystals of Ru(8b)(pic) ](PF ) suitable for X-ray dif-
2
6
fraction were obtained by slow evaporation of an acetone/
toluene solution. The X-ray data confirm the NMR spectrum,
indicating that ligand 8b is bound in a symmetrical fashion to the
central Ru(III) using both 8-HQ moieties. The ORTEP plot of
the complex is shown in Figure 3, and selected bond lengths,
bond angles, and torsion angles are collected in Table 1. An
interesting geometrical situation is found in the disposition of 8b
around the metal. The two RuꢀO bonds are both 2.03 Å, and
the two axial RuꢀN bonds involving the 4-picolines are typical
at 2.10 Å. The interior RuꢀN bonds involving N1 and N17
are quite long, averaging about 2.20 Å. These bond lengths
can be compared to the four equatorial RuꢀN bonds in
of 8b whose lone pair electrons are oriented toward the metal
center. Due to constraints imposed by the four coordinative
bonds between Ru and 8b, N11 is held 2.44 Å from the metal
center, a distance normally considered too long for effective
binding. Orvig and co-workers have recently reported a similar
pentadentate ONNNO ligand that does not use the central
nitrogen in metal binding. The two oxygens and two nitrogens
that bind to Ru form a planar trapazoid with OꢀRuꢀN angles
that average 75.7°, O1ꢀRuꢀO2 at 78.3°, and N1ꢀRuꢀN17 at
130.3° for a total of 360.1° indicating a planar arrangement of all
five atoms as illustrated in Figure 3b. The two 8-HQ moieties
are pulled toward the metal center causing distortion of the
trigonal carbons that form the C10ꢀC12 and C16ꢀC18 bonds.
38
2
+
0
Ru(dpp)(pic) ] [dpp = 2,9-di(pyrid-2 -yl)phen] where one
2
[
observes two short interior RuꢀN bonds at 1.94 Å and two long
exterior ones at 2.17 Å. What is most intriguing is the central N11
1
0969
dx.doi.org/10.1021/ic201524j |Inorg. Chem. 2011, 50, 10966–10973

Inorganic Chemistry
Table 2. Electronic Absorption and Cyclic Voltammetric Data for Ru Complexes and Ligands
ARTICLE
a
b
c
cyclic voltammetric data
abs/nm (ε ꢁ 10ꢀ
3
M
ꢀ1
cm
ꢀ1
)
Ru /Ru
II
III
Ru /Ru
III
IV
reduction
compd
λ
6
7
8
b-H
264 (30), 280 (24), 314 (5)
b-H
290 (28), 327 (13), 337 (14)
267 (93), 308 (27), 364 (7.4)
308 (54), 475 (13)
b-2H
c,d
[
[
[
[
[
[
Ru(tpy)
2
](PF
6
)
2
+1.38
ꢀ1.41(120), ꢀ1.67(200)
ꢀ1.44(83), ꢀ1.73(94)
c
ir
ir
Ru(6b)(tpy)](PF
6
)
313 (46), 374 (8), 514 (14)
302 (49), 414 (10), 565 (11)
346 (17), 481 (4.4), 609 (2)
342 (17), 450 (2.6), 556 (1.5)
+0.54
+1.06
c
ir
ir
Ru(6b)
2
](PF
6
)
+0.09(71)
ꢀ1.67 , ꢀ1.85
ir
Ru(7b)(pic)
Ru(8b)(pic)
2
](PF
6
)
)
+0.60
ꢀ1.17(124)
ꢀ1.57(90)
ꢀ1.54(135)
ir
2
](PF
6
ꢀ0.39(277)
ꢀ0.23(138)
+0.70
Ru(8b)(tb-py)
2
](PF
6
)
341 (15), 454 (3.9)
0.51(352)
a
ꢀ5
b
+
Measured in CH CN (5 ꢁ 10 M) at room temp. Recorded in CH CN (except [Ru(6b) ] in 9:1 CH CN/CH OH) containing 0.1 M NBu PF ;
3
3
2
3
3
4
6
c
E
1/2 in V vs SCE and ΔE in mV; scan rate = 100 mV/s; irreversible process (ir) estimated by differential peaks. Electronic absorption data measured in
5 d
OH (5 ꢁ 10ꢀ M) at room temp. Cyclic voltammetric data from ref 39.
CH
3
observed at 403 and 414 nm with stronger absorbance for the
+
homoleptic complex [Ru(6b) ] . For complexes involving the
2
tetradentate 7b or the pentadentate 8b the situation is less clear
and the longer wavelength absorbances are considerably less
intense (Figure 5-SI).
The electrochemical behavior of the Ru complexes of 8-HQ
derivatives is highly dependent on the charge on the central metal
atom that will strongly influence its ground state oxidation
potential. Studies by two different groups on complexes of the
type [Ru(bpy)3‑n(8-HQ) ] (n = 0ꢀ3) have demonstrated
n
the effectofthe anionic8-HQligandon the redox properties of the
system although there seem to be some discrepancies in the
1
8ꢀ22
reported potentials.
tency to the results that we report in Table 2. For the series
Ru(tpy)2 (6b) ] (n = 0ꢀ2), we observe a steady decrease in
There is considerable internal consis-
Figure 4. Long wavelength region of the electronic absorption spectra
of [Ru(tpy) ](PF (black), [Ru(tpy)(6b)](PF ) (red), and [Ru(6b) ]-
PF ) (blue).
[
‑n
n
2
6
)
2
6
2
II
III
2+
the Ru /Ru oxidation potential from +1.38 V for [Ru(tpy) ] ,
to +0.54 V for [Ru(tpy)(6b)] , to 0.09 V for [Ru(6b) ] as the
2
(
6
+
+
2
number of anionic 6b ligands around Ru increases from 0 to 2.
III
IV
Ideally, the interior angles centered on these carbons should measure
A second oxidation wave (Ru /Ru ) at +1.06 V is observed for
+
1
20°, but in this complex, they are compressed to 111.4ꢀ113.9°.
[Ru(tpy)(6b)] . Due to solubility problems, the measurement
] was made in 9:1 CH
potential measured for [Ru(6b) ] indicates that this species
might exist as either Ru(II) or Ru(III). From its paramagnetic
NMR behavior we observe that the Ru(III) species is formed
initially, but after reduction with ascorbic acid the resulting Ru(II)
complex is stable for more than one month.
The tetradentate complex [Ru(7b)(pic) ] involves only one
+
Photophysical and Electrochemical Behavior. The electro-
nic absorption maxima and extinction coefficients of the ligands
and their Ru complexes are listed in Table 2 together with the
electrochemical data for the Ru complexes. Due to its extended
conjugation, the pentadentate ligand 8b-2H shows a longer
wavelength πꢀπ* absorption at 364 nm than the tetradentate
for [Ru(6b)
2
3
CN/MeOH. The near zero
+
2
+
7
b-H at 337 nm and tridentate 6b-H at 314 nm. For the Ru
2
II
III
complexes, relatively intense peaks in the region 302ꢀ346 nm
are attributed to πꢀπ* transitions of the ligands. A progressive
red-shift in the lowest energy absorption band from 475 to 519 to
anionic ligand. Its Ru /Ru potential of +0.60 V matches well
with the +0.54 V measured for [Ru(tpy)(6b)] . The pentaden-
tate ligand 8b presents two anionic 8-HQ moieties, and so, we
+
2+
5
65 nm is observed as we substitute a tpy ligand in [Ru(tpy)2]
would expect considerable stabilization of higher oxidation states.
III
IV
with one or two anionic tridentate ligands 6b (Figure 4). This
long wavelength band is normally associated with a metal-to-
ligand charge transfer (MLCT) state in which an electron is
promoted from a metal d-orbital to the π*-orbital of the most
electronegative ligand. The bathochromic shift is most likely due
to increased electron donation from the ligand that serves to
destabilize the metal-centered HOMO and raise its energy. This
observation is reinforced by the dramatic increase in the first
oxidation potential that is observed for this same series of
complexes. It is also noteworthy that for the complexes involving
ligand 6b a higher energy component of the MLCT state is
The first oxidation is the Ru /Ru couple that we observe at
II III
+0.70 V. The first reduction is the Ru /Ru couple that occurs at
the very low potential of ꢀ0.39 V. Changing the axial ligand from
4-picoline to the somewhat better donor 4-t-butylpyridine raises
IV
II
III
III
the Ru /Ru potential (ꢀ0.23 V) and lowers the Ru /Ru
potential (+0.51 V).
For the series [Ru(tpy)2‑n(6b) ] (n = 0ꢀ2), the reduction
n
potential corresponds to the addition of an electron to the most
+
electronegative ligand which is the tpy. For [Ru(6b) ] that
contains only anionic ligands, we observe two irreversible waves
at ꢀ1.67 and ꢀ1.85 V. The first reduction of the two complexes
2
1
0970
dx.doi.org/10.1021/ic201524j |Inorg. Chem. 2011, 50, 10966–10973

Inorganic Chemistry
ARTICLE
2 3 3
), 4.11 (s, 3H, CH ). Similar HNMR(CDCl ) valuesfor2
1
involving 8b is consistent with adding an electron to the axial
pyridine ligand.
It has been reported that mono- and dianionic ligands derived
6.40 (s, 2H, NH
have been reported.
45
0
8-Methoxy-2-(pyrid-2 -yl)quinoline (6a). To a mixture of 2
(1.30 g, 8.60 mmol) and 2-acetylpyridine (3, 0.96 mL, 8.60 mmol) in
EtOH (80 mL) was added a solution of KOH (1.3 g) in EtOH (5 mL),
and the mixture was heated at reflux for 15 h. The mixture was then
cooled to room temperature, and the solvent was evaporated. The
from bpy and phen as their Ru complexes can be used as catalysts
4
0
for water oxidation. It has been suggested that the lower oxi-
dation potentials of these complexes might improve their per-
41
formance in this regard. In line with our own work in this area,
we have examined appropriate Ru complexes derived from
ꢀ8b, but found only modest activity toward water oxidation.
These studies will be reported in an upcoming publication.
residue was dissolved in CH
and concentrated. Purification by chromatography on alumina and
elution with CH Cl /MeOH (100:1) afforded 6a as a light brown oil
1.71 g, 84%). H NMR (CDCl ): δ 8.71 (m, 2H), 8.59 (d, 1H, J = 8.7
2 2 4
Cl , washed with water, dried over MgSO ,
6
2
2
1
(
3
Hz), 8.25 (d, 1H, J = 8.7 Hz), 7.85 (dt, 1H, J = 7.8, 1.8 Hz), 7.44 (AB, 2H,
J = 8.2 Hz), 7.33 (m, 1H), 7.07 (dd, 1H, J = 7.3, 1.4 Hz), 4.11 (s, 3H,
’
CONCLUSIONS
1
34
A two-step Friedl €a nder approach has been used to prepare a
CH
3
). Similar H NMR (CDCl
3
) values for 6a have been reported.
0
series of tri-, tetra-, and pentadentate analogues of 8-hydroxy-
quinoline. These ligands form stable complexes with Ru whose
oxidation state depends on the overall anionic character of
the 8-HQ analogue. Consistent behavior is observed both in the
electronic absorption spectra and in the redox properties of these
systems. A Ru(III) complex of the pentadentate ligand 8b shows
an unusual geometry in which the central pyridine on 8b is orien-
ted toward the metal but held at a distance that would normally
preclude effective binding. Future work will reveal other coordi-
nation chemistry of this interesting family of ligands.
2-(Pyrid-2 -yl)-8-hydroxyquinoline (6b-H). A solution of 6a
(120 mg, 0.50 mmol) in HBr (48%, 25 mL) was heated at 120 °C for 16
h. The mixture was cooled to room temperature, and then cold water
(200 mL) was added. The precipitate was collected, extracted with
CH Cl , and washed with NaHCO and water. The combined organic
2
2
3
phase was dried over MgSO and concentrated to afford 6b-H as a white
4
3
4
1
solid (88 mg, 86%): mp 128ꢀ130 °C (lit. mp 119ꢀ121 °C). H NMR
(
CDCl ): δ 8.74 (d, 1H, J = 4.1 Hz), 8.60 (t, 2H, J = 8.7 Hz), 8.28 (d, 1H,
3
J = 8.7 Hz), 8.27 (s, 1H, OH), 7.89 (dt, 1H, J = 7.8, 4.6 Hz), 7.47 (t, 1H,
1
J = 7.8 Hz), 7.37 (m, 2H), 7.20 (dd, 1H, J = 8.2, 0.9 Hz). Similar H NMR
3
1 13
(CDCl
3
) values for 6b-H have been reported.
3
C NMR (CDCl ): δ
1
1
55.4, 153.8, 152.4, 149.2, 137.6, 136.9, 136.8, 128.5, 128.0, 124.1, 121.4,
ꢀ
1
’
EXPERIMENTAL SECTION
19.6, 117.9, 110.3; IR 3391, 1590, 1504, 1482, 1452, 1229, 783 cm
.
+
1
13
19
10 2
MS (MALDI-TOF): m/z 223.23 [M + H] , 222.08 calcd for C14H N O.
The H, C, and F NMR spectra were recorded at room tempera-
ture, except for those of [Ru(8b)(pic) ](PF ) and [Ru(8b)(tb-py) ]-
PF ) that were recorded at 62 °C, on a JEOL ECX-400 spectrometer at
0
0
2-(8 -Methoxyquinolin-2 -yl)-1,10-phenanthroline (7a). In
the manner described for 6a, 2 (606 mg, 4.01 mmol), 2-acetyl-1,10-
phenanthroline (4, 823 mg, 3.97 mmol), and KOH (600 mg) in EtOH
(50 mL) provided 7a as a yellow solid after recrystallization from
CH
9.26 (dd, 1H, J = 4.9, 1.8 Hz), 9.24 (d, 1H, J = 8.6 Hz), 9.16 (d, 1H, J =
8.0 Hz), 8.42 (d, 1H, J = 8.0 Hz), 8.35 (d, 1H, J = 8.6 Hz), 8.29 (dd, 1H,
J = 8.0, 1.7 Hz), 7.85 (AB, 2H, J = 8.6 Hz), 7.66 (dd, 1H, J = 8.2, 4.6 Hz),
7.48 (m, 2H), 7.10 (dd, 1H, J = 7.7, 1.7 Hz), 4.16 (s, 3H, CH
NMR (CDCl ): δ 156.3, 155.7, 155.1, 150.6, 146.5, 145.7, 139.8, 137.0,
136.9, 136.3, 129.9, 129.1, 129.0, 127.3, 127.0, 126.7, 123.0, 121.8, 121.0,
119.8, 108.8, 56.3; IR 1548, 1489, 1461, 1255, 1109, 852, 755 cm . MS
15 3
(MALDI-TOF): m/z 338.39 [M + H] , 337.12 calcd for C22H N O.
2 -(1,10-Phenanthrolin-2-yl)quinolin-8 -ol (7b-H). In the
manner described for 6b-H, 7a (120 mg, 0.35 mmol) in HBr (48%,
25 mL) provided 7b-H (90 mg, 78%) as an orange solid after recry-
2
6
2
(
6
1
13
19
400 MHz for H, 100 MHz for C, and 376 MHz for F, and on a JEOL
1
13
ECA-500 spectrometer at 500 MHz for H and 125 MHz for C. The
NMR data of [Ru(6b) ](PF ), [Ru(8b)(pic) ](PF ), and [Ru(8b)(tb-
py) ](PF ) were collected in the presence of ascorbic acid. Chemical
1
Cl
2
(865 mg, 64%): mp 212 °C (dec). H NMR (CDCl
3
): δ
2
6
2
6
2
2
6
shifts are referenced to the residual solvent peak and were reported in
parts per million (ppm), and the J values are (0.5 Hz. Melting points
were measured on a Thomas-Hoover capillary melting point apparatus
and were not corrected. Electronic absorption spectra were recorded
with a Varian Cary 50 Bio UVꢀvis spectrophotometer. Infrared spectra
were measured on a Perkin-Elmer Spectrum 100 FT-IR spectrophot-
ometer. Mass spectra were obtained on a Voyager-DE-STR MALDI-TOF
mass spectrometer using α-cyano-4-hydroxycinnamic acid as matrix.
Electrochemical measurements were carried out using a BAS Epsilon
electroanalytical system. Cyclic voltammetry (CV) experiments were
performed at room temperature in a one-compartment cell equipped
with a glassy carbon working electrode, a saturated calomel reference elec-
trode (SCE), and a platinum wire as the auxiliary electrode in CH
containing (n-butyl) N(PF ) (0.1 M) at a scan rate of 100 mV s . CHN
analyses were performed by Quantitative Technologies Inc., White-
house, NJ. All reagents and solvents were purchased from commercial
sources and were used as received except 6,7-dihydroquinolin-8(5H)-
13
3
).
C
3
ꢀ
1
+
0
0
1
stallizationfrom EtOH/hexane: mp184 °C (dec). H NMR (DMSO-d
):
6
δ 9.93 (s, 1H, OH), 9.48 (d, 1H, J = 8.2 Hz), 9.18 (dd, 1H, J = 4.6, 1.8
Hz), 9.03 (d, 1H, J = 8.7 Hz), 8.66 (d, 1H, J = 8.7 Hz), 8.54 (d, 1H, J = 8.7
Hz), 8.52 (dd, 1H, J = 8.4, 1.8 Hz), 8.04 (AB, 2H, J = 8.7 Hz), 7.81 (dd,
3
CN
ꢀ
1
4 6
13
1H, J = 8.4, 4.1 Hz), 7.48 (m, 2H), 7.16 (dd, 1H, J = 6.8, 4.3 Hz).
NMR (DMSO-d ): δ 155.3, 154.2, 153.9, 150.4, 145.9, 145.3, 138.4,
137.5, 137.4, 136.9, 129.4, 129.3, 129.2, 128.8, 127.7, 127.0, 123.8, 122.0,
119.9, 118.15, 112.2. IR 3394, 2923, 2854, 1502, 1444, 1108, 845,
C
6
42
43
one (7), 4-tert-butyl-2,6-diacetylpyridine (8), 2-acetyl-1,10-phenan-
throline (9), and [Ru(tpy)Cl
published procedures.
2
40c
44
ꢀ1
+
3
]
that were prepared according to
749 cm . MS (MALDI-TOF): m/z 324.07 [M + H] , 323.11 calcd for
O.
4-t-Butyl-2,6-di(8 -methoxy-quinolin-2 -yl)pyridine (8a).
21 13 3
C H N
0
0
-Amino-3-methoxybenzaldehyde (2). Iron powder (5.55 g,
9
3
9.3 mmol) and conc HCl (0.1 mL) were added to a solution of
-methoxy-2-nitrobenzaldehyde (11, 1.80 g, 9.93 mmol) in EtOH/
In the manner described for 6a, 2 (527 mg, 3.48 mmol), 4-t-butyl-2,6-
diacetylpyridine (5, 382 mg, 1.75 mmol), and KOH (550 mg) in EtOH
(40 mL) provided 8a as a beige solid (558 mg, 71%): mp > 230 °C. H
3
NMR (CDCl ): δ 8.80 (dd, 2H, J = 6.9, 1.8 Hz), 8.79 (s, 2H), 8.20 (dd,
1
water (4/1, 40 mL), and the mixture was heated at reflux for 2 h. After
cooling to room temperature, the solid was removed by filtration, and
the filtrate was extracted with EtOAc. The combined organic phase was
2H, J = 8.1, 2.8 Hz), 7.36 (m, 4H), 6.99 (m, 2H), 4.05 (s, 6H, CH ), 1.53
3
1
3
dried over MgSO and concentrated. The residue was purified by
(s, 9H, CH3). C NMR (CDCl ): δ 162.1, 155.8, 155.6, 139.8, 136.8,
4
3
chromatography on alumina, eluting with CH
2
Cl
): δ 9.89 (s, 1H, CHO), 7.12
dd, 1H, J= 8.4, 1.4 Hz), 6.88 (d, 1H, J= 7.3, 0.9 Hz), 6.68 (t, 1H, J=7.8Hz),
2
to afford 2 as a
129.5, 127.0, 120.2, 119.6, 119.4, 108.0, 56.2, 35.6, 30.9; IR 2957, 1603,
1
ꢀ1
yellow oil (1.30 g, 87%). H NMR (CDCl
3
1503, 1262, 1097, 836, 747 cm . MS (MALDI-TOF): m/z 450.38
+
(
[M + H] , 449.21 calcd for C H N O .
2
9 27 3 2
1
0971
dx.doi.org/10.1021/ic201524j |Inorg. Chem. 2011, 50, 10966–10973

Inorganic Chemistry
ARTICLE
0
0
4
-t-Butyl-2,6-di(8 -hydroxy-quinolin-2 -yl)pyridine (8b-2H).
[Ru(7b)(pic) ](PF ). A mixture of 7b-H (40 mg, 0.125 mmol) and
2
6
In the manner described for 6b-H, 8a (558 mg, 1.24 mmol) in HBr
48%, 65 mL) provided 8b-2H (300 mg, 58%) as a yellow solid: mp
RuCl3 3H O (32.6 mg, 0.125 mmol) in EtOH (20 mL) was refluxed for
30 min, and then Et N (0.2 mL) was added and the reflux continued
3
3
2
(
1
2
8
8
60 °C. H NMR (CD
3
OD/CDCl
3
): δ 8.73 (s, 2H), 8.62 (d, 2H, J =
for 90 min. Water (7 mL), 4-picoline (0.4 mL), and LiCl (10 mg) were
added to the dark solution, and the mixture was refluxed for 16 h.
NH PF (60 mg, 0.5 mmol) was added, and the mixture was concen-
.7 Hz), 8.40 (d, 2H, J = 8.7 Hz), 7.45 (t, 2H, J = 8.2 Hz), 7.38 (d, 2H, J =
1
3
.2 Hz), 7.16 (d, 2H, J = 8.7 Hz), 4.8 (br s, OH), 1.56 (s, 9H, CH3).
OD/CDCl ): δ 164.3, 153.1, 152.1, 138.6, 136.6, 129.2,
28.6, 120.3, 119.3, 118.0, 112.0. IR 3500, 3415, 2959, 1610, 1243, 840,
C
4
6
NMR (CD
1
7
3
3
trated to about 5 mL. The precipitate was collected, washed with water,
and purified by chromatography on alumina. The column was eluted
first with CH Cl to remove the impurities, and the complex was re-
ꢀ1
+
61 cm . MS (MALDI-TOF): m/z 422.10 [M + H] , 421.18 calcd for
2
2
C
27
H
1
23
N
3
O
2
.
1-Methoxy-5,6-dihydrobenzo[b][1,10]phenanthroline (10a).
covered by eluting with CH
2
Cl
CN): δ 9.50 (dd, 1H, J = 5.4, 1.1 Hz, H
(dd, 1H, J = 8.7, 0.9 Hz, H ), 8.34 (d, 1H, J = 8.2 Hz), 8.14 (d, 1H, J = 8.7
Hz), 8.07 (d, 1H, J = 8.7 Hz) 7.98 (d, 1H, J = 9.1 Hz), 7.96 (d, 4H, J = 6.4
Hz, Hpic, 7.90 (d, 1H, J = 9.1 Hz), 7.86 (dd, 1H, J = 8.2, 5.0 Hz, H ), 7.80
), 6.83 (d, 4H, J = 6.4 Hz,
2
/acetone (1:1) (6 mg, 6%): mp >
1
260 °C. H NMR (CD
3
9
), 8.38
In the manner described for 6a, 2 (459 mg, 3.03 mmol), 6,7-dihydro-
quinolin-8(5H)-one (9, 447 mg, 3.03 mmol), and KOH (450 mg) in
EtOH (30 mL) provided 10a as a beige solid (673 mg, 84%): mp
7
8
1
(d, 1H, J = 9.1 Hz), 7.07 (t, 1H, J = 7.8 Hz, H 0
6
9
7
7
2
1
6ꢀ98 °C. H NMR (CDCl
3
): δ 8.74 (d, 1H, J = 4.6 Hz), 7.89 (s, 1H),
H
pic), 6.60 (d, 1H, J = 7.8 Hz, H 0
(s, 6H, CH
). MS (MALDI-TOF): m/z 610.29 [M ꢀ PF
[M ꢀ PF ꢀ 2 pic] , 610.12 calcd for C33
OPRu HPF : C, 43.94; H, 3.01; N, 7.76. Found: C, 44.78;
), 6.53 (d, 1H, J = 8.2 Hz, H7
0
), 2.07
.51 (d, 1H, J = 7.3 Hz), 7.38 (t, 1H, J = 7.8 Hz), 7.26 (d, 1H, J = 7.8 Hz),
5
+
.18 (dd, 1H, J = 7.8, 4.6 Hz), 6.93 (d, 1H, J = 7.8 Hz), 4.01 (s, 3H, CH ),
.09 (m, 2H, CH
51.8, 151.0, 149.3, 139.9, 136.0, 135.4, 134.9, 134.1, 132.1, 129.4, 127.3,
3
6
] , 424.20
26 5
H N ORu. Anal. Calcd for
3
13
+
2
), 2.98 (m, 2H, CH
2
). C NMR (CDCl
3
): δ 156.1,
6
C
33
H
26
F
6
N
5
6
3
+
127.1, 123.8, 118.6, 106.9, 55.7. MS (MALDI-TOF): m/z 263.12 [M + H] ,
H, 3.25; N, 7.60.
2
62.11 calcd for C H N O.
[Ru(8b)(pic) ](PF ). A mixture of 8b-2H (65 mg, 0.15 mmol) and
17
14
2
2
6
1
1-Hydroxy-5,6-dihydrobenzo[b][1,10]phenanthroline
10b-H). In the manner described for 6b-H, 10a (150 mg, 0.45 mmol)
in HBr (48%, 30 mL) provided a white solid as a mixture of 10b-H and
NaOH (6 mg, 0.15 mmol) in EtOH (7 mL) was stirred at 50 °C for 10
min. [Ru(dmso) Cl ] (74.6 mg, 0.15 mmol) was added, and the mixture
was refluxed for 2 h. Then, 4-picoline (0.5 mL), LiCl (10 mg), and Et
(0.1 mL) were added, and the reflux was continued for 6 h. The solution
was concentrated, NH PF (100 mg, 0.8 mmol) was added, and the
resulting black solid was collected, washed with water, and purified by
chromatography on alumina, eluting first with CH Cl followed by
acetone and acetonitrile. Recrystallization from acetone/hexane afforded
[Ru(8b)(pic) ](PF ) as a black solid (38 mg, 29%): mp > 285 °C.
H NMR (CD OD, ascorbic acid): δ 8.34 (s, 2H), 8.26 (d, 2H, J =
9.7 Hz, H ), 8.16 (d, 2H, J = 8.7 Hz, H ), 8.03 (d, 4H, J = 6.9 Hz, HPic),
.36 (t, 2H, J = 8.2 Hz, H ), 7.14 (d, 2H, J = 8.2 Hz, H ), 7.06 (d, 2H, J =
.2 Hz, H ), 6.83 (d, 4H, J = 6.8 Hz, Hpic), 2.06 (s, 6H, CH ), 1.58 (s,
(
4
2
N
3
1
1
1 in a 20/1 ratio (123 mg, 85%). Data follow for 10b-H. H NMR
CDCl ): δ 9.10 (dd, 1H, J = 5.7, 1.7 Hz), 8.80 (d, 1H, J = 3.9 Hz), 8.09
dd, 1H, J = 8.6, 1.7 Hz), 7.99 (s, 1H), 7.59 (d, 1H, J = 7.5 Hz), 7.41 (dd,
H, J = 8.0, 4.0 Hz), 7.28 (dd, 1H, J = 9.7, 4.6 Hz), 3.17 (m, 2H, CH ),
): δ 9.34 (dd,
H, J = 5.7, 2.8 Hz), 9.23 (d, 1H, J = 3.8 Hz), 8.78 (s, 1H), 8.39 (dd, 1H,
(
(
3
4
6
1
3
1
2
2
2
1
2 3
.04 (m, 2H, CH ). Data for 11 follow. H NMR (CDCl
2
6
1
J = 8.6, 1.7 Hz), 8.21 (d, 1H, J = 7.5, 3.7 Hz), 7.72ꢀ7.86 (AB, 2H, J =
.1 Hz), 7.67 (dd, 1H, J = 8.0, 4.6 Hz), 7.54 (dd, 1H, J = 8.0, 4.0 Hz).
Ru(6b) ](PF ). Under argon and shielded from light by aluminum
3
9
3
0
0
4
7
8
9
6
0
0
5
[
2
6
6
0
foil, a suspension of [η -C
55 mg, 0.25 mmol), NaOH (10 mg, 0.25 mmol), and KPF (90 mg,
6 6 2
H )RuCl(μ-Cl)] (31 mg, 0.125 mmol), 6b-H
7
3
1
9
H, CH3). F NMR (CD OD): δ ꢀ74.80 (d, J = 750 Hz). MS
(
3
6
+
+
(
MALDI-TOF): m/z 707.55 [M ꢀ PF
6
] , 521.39 [M ꢀ PF
6
ꢀ 2 pic] ,
0
.49 mmol) in dry MeCN (6 mL) was stirred at 50 °C for 16 h. The
using
CH Cl /MeOH (90/10) as the eluant. The dark purple fraction was
7
07.12 calcd for C39
[Ru(8b)(tb-py)
(pic) ](PF ), a mixture of 8b-2H (65 mg, 0.15 mmol), NaOH (6 mg,
0.15 mmol), [Ru(dmso) Cl ] (74.6 mg, 0.15 mmol), 4-t-butylpyridine
(0.75 mL), LiCl (10 mg), Et N (0.1 mL), and NH PF (100 mg, 0.8
mmol) afforded a black solid that was purified by chromatography on
alumina, eluting first with CH Cl followed by acetone and acetonitrile.
Recrystallization from acetone/hexane afforded [Ru(8b)(tb-py) ](PF
OD, ascorbic
), 8.12 (d, 2H, J = 8.6
), 8.08 (d, 4H, J = 6.3 Hz, Htb‑py), 7.38 (t, 2H, J = 7.45 Hz, H ),
7.21 (d, 2H, J = 8.6 Hz, H ), 7.04 (m, 2H), 7.03 (d, 4H, J = 6.3 Hz,
tb‑py), 1.59 (s, 9H, CH ), 1.04 (s, 18H, CH ). MS (MALDI-TOF):
m/z 521.39 [M ꢀ PF ꢀ 2 tb-py] , 521.07 calcd for C27 Ru.
Anal. Calcd for C H F N O PRu 3H O: C, 54.60; H, 5.35; N, 7.07.
35 5 2
H N O Ru.
2 3
resulting purple suspension was filtered through a plug of Al O
](PF ). In the manner described for [Ru(8b)-
6
2
2
2
collected and concentrated, and the residue was precipitated by the addi-
tion of n-hexane to provide [Ru(6b)] as a purple solid (37 mg, 53%).
OD, ascorbic acid): δ 8.30 (d, 1H, J = 9.1 Hz, H or H ),
.19 (d, 1H, J = 8.2 Hz, H6 ), 8.05 (d, 1H, J = 9.1 Hz, H or H ), 7.55
t, 1H, J = 7.9 Hz, H ), 7.27 (dt, 1H, J = 7.8, 3.9 Hz, H
), 7.05 (dd, 1H, J = 7.8, 4.6 Hz, H ), 6.90 (t, 1H, J = 6.4 Hz,
), 6.55 (dd, 1H, J = 9.6, 4.6 Hz, H ). MS (MALDI-TOF): m/z 544.16
2
6
2
4
2
1
H NMR (CD
3
3
4
3
4
6
8
0
3
4
(
5
0
6
), 7.14 (d, 1H, J =
2
2
5
.5 Hz, H
3
0
5
2
6
)
1
H
[
4
0
7
as a black solid (22 mg, 16%): mp > 285 °C. H NMR (CD
acid): δ 8.39 (s, 2H), 8.32 (d, 2H, J = 9.15 Hz, H
Hz, H
3
+
M ꢀ PF ] , 544.05 calcd for C H N O Ru. Anal. Calcd for
0
3
6
28 18 4 2
C
4
28
H
18
F
6
N
4
O
2
PRu 2H
2
O: C, 46.60; H, 3.03; N, 7.73. Found: C,
4
0
0
6
3
6.46; H, 2.71; N, 7.29.
5
0
[Ru(6b)(tpy)](PF ). A mixture of 2-H (48 mg, 0.21 mmol),
H
3
3
6
+
[
Ru(tpy)Cl ] (95 mg, 0.21 mmol), and Et N (0.2 mL) in EtOH/
6
H N O
21 3 2
3
3
H
2
O (2:1, 30 mL) was refluxed for 90 min, and then the solvent was
PF (100 mg, 0.8 mmol) was added, and the dark red
solid was collected, washed with water, and purified by chromatography
on alumina. The column was eluted first with CH Cl , and the complex
was recovered by eluting with acetone. Recrystallization from acetone/
hexane affords [Ru(6b)(tpy)](PF ) as a red solid (73 mg, 48%): mp >
85 °C. H NMR (acetone-d ): δ 8.72 (d, 2H, J = 8.0 Hz), 8.56 (d, 2H,
45 47
6
5
2
3
2
evaporated. NH
4
6
Found: C, 54.47; H, 4.77; N, 6.57.
X-ray Determination of[Ru(8b)(pic)
](PF ) C H O 0.5C H .
6 3 6 7 8
2
3
3
All measurements were made with a Siemens SMART platform dif-
fractometer equipped with a 4K CCD APEX II detector. A hemisphere
of data (1271 frames at 6 cm detector distance) was collected using a
narrow-frame algorithm with scan widths of 0.30% in ω and an exposure
time of 40 s/frame. The data were integrated using the Bruker-Nonius
SAINT program, with the intensities corrected for Lorentz factor,
polarization, air absorption, and absorption due to variation in the path
length through the detector faceplate. A ψ scan absorption correction
was applied on the basis of the entire data set. Redundant reflections
were averaged. Final cell constants were refined using 2912 reflections
having I > 10σ (I), and these, along with other information pertinent to
2
2
6
1
2
6
J = 8.0 Hz), 8.37 (AB, 2H, J = 9.1 Hz), 8.23 (m, 2H), 7.97 (dt, 2H, J = 9.1,
.7 Hz), 7.84 (d, 2H, J = 5.1 Hz), 7.70 (dt, 1H, J = 8.0, 1.7 Hz), 7.35
m, 3H), 7.10 (d, 1H, J = 8.0 Hz), 6.94 (d 1H, J = 5.15 Hz), 6.87 (dt, 1H,
J = 6.9, 1.1 Hz), 6.40 (d, 1H, J = 8.0). MS (MALDI-TOF): m/z 556.28
1
(
+
[
M ꢀ PF
6
] , 556.07 calcd for C29
OPRu H O: C, 48.47; H, 3.06; N, 9.74. Found: C,
8.60; H, 2.90; N, 9.12.
20 5
H N ORu. Anal. Calcd for
C
4
29
H
20
F
6
N
5
2
3
1
0972
dx.doi.org/10.1021/ic201524j |Inorg. Chem. 2011, 50, 10966–10973

Inorganic Chemistry
ARTICLE
data collection and refinement, are listed in Table S-1. The Laue
symmetry was determined to be ꢀ1, and the space group was shown
to be either P1 or P1. The asymmetric unit consists of one cation and one
molecule of acetone solvent in general positions, two half-molecules of
(14) Thomas, F.; Baret, P.; Imbert, D.; Pierre, J.-L.; Serratrice, G.
Bioorg. Med. Chem. Lett. 1999, 9, 3035–3040.
(15) Caris, C.; Baret, P.; Pierre, J.-L.; Serratrice, G. Tetrahedron
1
996, 52, 4659–72.
(16) Serratrice, G.; Boukhalfa, H.; Beguin, C.; Baret, P.; Caris, C.;
ꢀ
PF6 on inversion centers, and one-half molecule of toluene solvent on
Pierre, J.-L. Inorg. Chem. 1997, 36, 3898–3910.
17) Hayashi, M.; Ishii, M.; Hiratani, K.; Saigo, K. Tetrahedron Lett.
998, 39, 6215–6218.
18) Warren, J. T.; Johnston, D. H.; Turro, C. Inorg. Chem. Commun.
999, 2, 354–357.
19) Warren, J. T.; Chen, W.; Johnston, D. H.; Turro, C. Inorg.
Chem. 1999, 38, 6187–6192.
20) Lahiri, G. K.; Bhattacharya, S.; Ghosh, B. K.; Chakravorty, A.
Inorg. Chem. 1987, 26, 4324–31.
an inversion center. The t-butyl group of the cation and the toluene
solvent molecule are both disordered over two different positions. One
of the PF anions is heavily disordered, and the acetone is so massively
6
disordered that only 80% of the total electron density could be located.
Ideal rigid body models were used to refine most of the disordered
moieties, with population factors estimated by comparison of isotropic
displacement parameters. The acetone solvent site is presumed to be
fully occupied for all calculations.
(
1
1
(
(
(
(
(
(
21) Pramanik, N. C.; Bhattacharya, S. J. Chem. Res., Synop. 1997, 98–99.
22) Bhattacharya, S. Polyhedron 1993, 12, 235–239.
23) Harada, F.; Onozuka, T.; Tomizawa, H.; Tanaka, M.; Miki, E.
’
ASSOCIATED CONTENT
Inorg. Chim. Acta 2006, 359, 665–672.
24) Brissard, M.; Convert, O.; Gruselle, M.; Guyard-Duhayon, C.;
Thouvenot, R. Inorg. Chem. 2003, 42, 1378–1385.
25) Slugovc, C.; Koppitz, A.; Pogantsch, A.; Stelzer, F. Inorg. Chim.
S
Supporting Information. X-ray crystallographic data
b
(
for [Ru(8b)(pic) ](PF ) C H O 0.5C H (CIF file and
Table S1). H and C NMR spectra for ligands 6b, 7b, and
2
6
3
3
6
3
7
8
1
13
(
8
b and their Ru complexes. MALDI-TOF MS and simulated
Acta 2005, 358, 2718–2724.
MS for Ru complexes. Electronic absorption spectra for Ru
complexes. This material is available free of charge via the
Internet at http://pubs.acs.org.
(26) Leung, C.-F.; Wong, C.-Y.; Ko, C.-C.; Yuen, M.-C.; Wong,
W.-T.; Wong, W.-Y.; Lau, T.-C. Inorg. Chim. Acta 2009, 362, 1149–1157.
(
27) Holligan, B. M.; Jeffery, J. C.; Norgett, M. K.; Schatz, E.; Ward,
M. D. J. Chem. Soc., Dalton Trans. 1992, 3345–51.
28) Leung, C.-F.; Ng, S.-M.; Xiang, J.; Wong, W.-Y.; Lam, M. H.-W.;
Ko, C.-C.; Lau, T.-C. Organometallics 2009, 28, 5709–5714.
29) Sears, R. B.; Joyce, L. E.; Turro, C. Photochem. Photobiol. 2010,
6, 1230–1236.
30) Malecki, J. G.; Kruszynski, R.; Tabak, D.; Kusz, J. Polyhedron
007, 26, 5120–5130.
31) Corsini, A.; Louch, W. J.; Thompson, M. Talanta 1974,
(
’
AUTHOR INFORMATION
(
Corresponding Author
8
2
2
*E-mail: thummel@uh.edu.
(
(
’
ACKNOWLEDGMENT
1, 252–255.
We acknowledge support from the Robert A. Welch Founda-
(32) Corsini, A.; Cassidy, R. M. Talanta 1979, 26, 297–301.
(33) Barnham, K. J.; Gautier, E. C. L.; Kok, G. B.; Krippner, G.
tion (Grant E-621) and the Division of Chemical Sciences,
Geosciences, and Biosciences, Office of Basic Energy Sciences
of the U.S. Department of Energy (Grant DE-FG02-07ER15888).
We also thank Dr. James Korp for assistance with the X-ray
determination and Nattawut Kaveevivitchai for assistance with
the cyclic voltammetry.
Preparation of 8-Hydroxyquinolines for Treatment of Neurological Condi-
tions. Patent 2004007461, 2004.
(34) Verniest, G.; Wang, X.; De Kimpe, N.; Padwa, A. J. Org. Chem.
2
010, 75, 424–433.
(
(
35) Sigouin, O.; Beauchamp, A. L. Can. J. Chem. 2005, 83, 460–470.
36) Zhang, G.; Zong, R.; Tseng, H.-W.; Thummel, R. P. Inorg.
Chem. 2008, 47, 990–998.
(
(
37) Thummel, R. P.; Jahng, Y. Inorg. Chem. 1986, 25, 2527–2534.
38) Boros, E.; Lin, Y.-H. S.; Ferreira, C. L.; Patrick, B. O.; Hafeli,
’
REFERENCES
(
(
1) Phillips, J. P. Chem. Rev. 1956, 56, 271–97.
2) Ballardini, R.; Varani, G.; Indelli, M. T.; Scandola, F. Inorg. Chem.
U. O.; Adam, M. J.; Orvig, C. Dalton Trans. 2011, 40, 6253–6259.
39) Sarkar, S.; Sarkar, B.; Chanda, N.; Kar, S.; Mobin, S. M.; Fiedler,
J.; Kaim, W.; Lahiri, G. K. Inorg. Chem. 2005, 44, 6092–6099.
40) (a) Xu, Y.; Aakermark, T.; Gyollai, V.; Zou, D.; Eriksson, L.;
Duan, L.; Zhang, R.; Aakermark, B.; Sun, L. Inorg. Chem. 2009, 48,
(
1
986, 25, 3858–65.
3) Bartocci, C.; Sostero, S.; Traverso, O.; Cox, A.; Kemp, T. J.;
Reed, W. J. J. Chem. Soc., Faraday Trans. 1 1980, 76, 797–803.
4) Palacios, M. A.; Wang, Z.; Montes, V. A.; Zyryanov, G. V.;
Hausch, B. J.; Jursikova, K.; Anzenbacher, P., Jr. Chem. Commun. 2007,
708–3710.
5) Hollingshead, R. G. W. Oxine and Its Derivatives; Butterworths:
London; Vols. IꢀIV, pp 1954ꢀ1956.
6) Shen, A.-Y.; Wu, S.-N.; Chiu, C.-T. J. Pharm. Pharmacol. 1999,
1, 543–548.
(
(
(
2
2
717–2719. (b) Duan, L.; Fischer, A.; Xu, Y.; Sun, L. J. Am. Chem. Soc.
009, 131, 10397–10399. (c) Tong, L.; Duan, L.; Xu, Y.; Privalov, T.;
Sun, L. Angew. Chem., Int. Ed. 2011, 50, 445–449. (d) Xu, Y.; Fischer, A.;
Duan, L.; Tong, L.; Gabrielsson, E.; Åkermark, B.; Sun, L. Angew. Chem.
010, 122, 9118–9121.
3
(
2
(
(41) (a) Tseng, H.-W.; Zong, R.; Muckerman, J. T.; Thummel, R.
5
Inorg. Chem. 2008, 47, 11763–11773. (b) Deng, Z.; Tseng, H.-W.; Zong,
R.; Wang, D.; Thummel, R. Inorg. Chem. 2008, 47, 1835–1848. (c) Zong,
R.; Thummel, R. P. J. Am. Chem. Soc. 2005, 127, 12802–12803.
(
(
(
(
7) Chen, C. H.; Shi, J. Coord. Chem. Rev. 1998, 171, 161–174.
8) Kido, J.; Kimura, M.; Nagai, K. Science 1995, 267, 1332–4.
9) Tang, C. W.; VanSlyke, S. A. Appl. Phys. Lett. 1987, 51, 913–15.
10) Humbs, W.; van Veldhoven, E.; Zhang, H.; Glasbeek, M. Chem.
(42) Thummel, R. P.; Lefoulon, F.; Cantu, D.; Mahadevan, R. J. Org.
Chem. 1984, 49, 2208–12.
Phys. Lett. 1999, 304, 10–18.
11) Donges, D.; Nagle, J. K.; Yersin, H. Inorg. Chem. 1997,
6, 3040–3048.
12) Su, N.; Bradshaw, J. S.; Zhang, X. X.; Song, H.; Savage, P. B.; Xue,
G.; Krakowiak, K. E.; Izatt, R. M. J. Org. Chem. 1999, 64, 8855–8861.
13) Prodi, L.; Bargossi, C.; Montalti, M.; Zaccheroni, N.; Su, N.;
Bradshaw, J. S.; Izatt, R. M.; Savage, P. B. J. Am. Chem. Soc. 2000, 122,
769–6770.
(43) Nueckel, S.; Burger, P. Organometallics 2001, 20, 4345–4359.
(44) Sullivan, B. P.; Calvert, J. M.; Meyer, T. J. Inorg. Chem. 1980,
19, 1404–1407.
(45) Doherty, E. M.; Fotsch, C.; Bannon, A. W.; Bo, Y.; Chen, N.;
Dominguez, C.; Falsey, J.; Gavva, N. R.; Katon, J.; Nixey, T.; Ognyanov,
V. I.; Pettus, L.; Rzasa, R. M.; Stec, M.; Surapaneni, S.; Tamir, R.; Zhu, J.;
Treanor, J. J. S.; Norman, M. H. J. Med. Chem. 2007, 50, 3515–3527.
(
3
(
(
6
1
0973
dx.doi.org/10.1021/ic201524j |Inorg. Chem. 2011, 50, 10966–10973