Synthesis of new CO2-soluble ruthenium(II) and cobalt(II) polypyridine complexes bearing fluorinated alkyl chains and their application to photoreduction of liq. CO2

Article abstract of DOI:10.1016/j.jfluchem.2010.06.005

Eight types of new CO₂-soluble or CO₂-philic ruthenium(II) and cobalt(II) polypyridine complexes, namely, [M(F84OPh) ₃](BArF)₂, [M(F44OPh)₃](BArF)₂, [M(F62Ph)₃](BArF)₂, and [M(F62O)₃](BArF) ₂ (M = Ru or Co, BArF: tetrakis[3,5-bis(trifluoromethyl)phenyl] borate), were prepared from bipyridine derivatives bearing highly fluorinated alkyl chains and applied to the photoreduction of liq. CO₂ under a high pressure of 6.8 MPa at 35 °C. All these complexes have higher philicity toward liq. CO₂ than the corresponding complexes with PF ^6- as the counteranion. Using the Ru(II)-Co(II) systems of [M(F44OPh)₃](BArF)₂ and [M(F62O)₃](BArF) ₂, direct photoreduction of CO₂ was achieved without the use of any organic solvent.

Full text of DOI:10.1016/j.jfluchem.2010.06.005

Journal of Fluorine Chemistry 131 (2010) 915–921
Contents lists available at ScienceDirect
Journal of Fluorine Chemistry
journal homepage: www.elsevier.com/locate/fluor
Synthesis of new CO2-soluble ruthenium(II) and cobalt(II) polypyridine
complexes bearing fluorinated alkyl chains and their application to
photoreduction of liq. CO2
*
Takuji Hirose , Shuhei Shigaki, Makoto Hirose, Atsushi Fushimi
Graduate School of Science and Engineering, Saitama University, 255 Shimo-ohkubo, Sakura, Saitama 338-8570, Japan
A R T I C L E I N F O
A B S T R A C T
Article history:
Eight types of new CO2-soluble or CO2-philic ruthenium(II) and cobalt(II) polypyridine complexes,
namely, [M(F84OPh)3](BArF)2, [M(F44OPh)3](BArF)2, [M(F62Ph)3](BArF)2, and [M(F62O)3](BArF)2
(M = Ru or Co, BArF: tetrakis[3,5-bis(trifluoromethyl)phenyl]borate), were prepared from bipyridine
derivatives bearing highly fluorinated alkyl chains and applied to the photoreduction of liq. CO2 under a
high pressure of 6.8 MPa at 35 8C. All these complexes have higher philicity toward liq. CO2 than the
corresponding complexes with PF6ꢀ as the counteranion. Using the Ru(II)–Co(II) systems of
[M(F44OPh)3](BArF)2 and [M(F62O)3](BArF)2, direct photoreduction of CO2 was achieved without the
use of any organic solvent.
Received 2 April 2010
Received in revised form 9 June 2010
Accepted 9 June 2010
Available online 16 June 2010
Keywords:
Photoreduction
Liq. CO2
ß 2010 Elsevier B.V. All rights reserved.
CO2-soluble
Ru(II) and Co(II) polypyridine complexes
Fluorinated alkyl chain
1. Introduction
2. Results and discussion
The conversion of solar energy into chemical energy is an
important and promising candidate for addressing the problems of
fossil fuel depletion and global warming. According to Lehn et al.
[1], Ru(II) and Co(II) polypyridine complexes function as photo-
catalysts for the reduction of CO2 dissolved in organic solvents. It is
expected that supercritical CO2 (sc-CO2) or liq. CO2 as solvent and
substrate will enhance the reduction efficiency of the photoreac-
tion. However, the original complexes do not dissolve in a nonpolar
CO2 phase, owing to their ionic property. The development and
application of ‘‘CO2-soluble’’ complexes to CO2 photoreduction are
interesting and attractive because considerable improvement in
reaction efficiency is expected to be possible and the use of harmful
organic solvents can be avoided.
The solubility of polar complexes in sc-CO2 or liq. CO2 is
expected to be enhanced by incorporating ‘‘CO2-philic’’ ligands, an
enhancement that can be achieved by the introduction of
fluoroalkyl chains into the parent ligands to enhance their
lipophilicity [2–7]. In this paper, we present a preliminary report
on the first preparation of CO2-soluble Ru(II) and Co(II) poly-
pyridine complexes bearing fluorinated alkyl chains and their
application to the photoreduction of liq. CO2 under high pressure.
2.1. Synthesis of ligands
Four new ligands, F84OPh, F44OPh, F62Ph, and F62O, were
prepared from appropriate 2,20-bipyridine derivatives and fluoro-
alkyl chains, as shown in Scheme 1, according to the literature [5–
15]: F84OPh and F44OPh were obtained by coupling between 4,40-
bis(p-hydroxyphenyl)-2,20-bipyridine and the corresponding
4-(perfluoroalkyl)butyl tosylates [5–9,11–13,15]. F62Ph was pre-
pared by the Suzuki coupling reaction between 4,40-dibromo-2,20-
bipyridine and p-(2-(perfluorohexyl)ethyl)phenylboronic acid [8–
12,16,17]. On the other hand, F62O was synthesized by the
substitution reaction between 4,40-dinitro-2,20-bipyridine-1,10-di-
oxide and potassium 2-(perfluorohexyl)ethoxide followed by
subsequent deoxygenation with PBr3 (Scheme 1) [8–13].
2.2. Synthesis of Ru(II) and Co(II) complexes
The Ru(II) and Co(II) complexes were directly prepared from
their corresponding metal chlorides and each of their ligands
following a typical procedure. For the synthesis of Ru complexes
from F84OPh, F62Ph, and F62O and Co complexes from F84OPh
and F62Ph, fluorinated alcohols were necessary to increase the
solubility of the ligand, as shown in Scheme 2. To examine thꢀe
effects of the counteranion on the solubility of the complexes, PF6
was exchanged with BArFꢀ (tetrakis[3,5-bis(trifluoromethyl)phe-
nyl]borate) (Scheme 2) [3,19–24].
* Corresponding author. Tel.: +81 48 858 3522; fax: +81 48 858 3522.
E-mail address: hirose@apc.saitama-u.ac.jp (T. Hirose).
0022-1139/$ – see front matter ß 2010 Elsevier B.V. All rights reserved.
doi:10.1016/j.jfluchem.2010.06.005

[
T. Hirose et al. / Journal of Fluorine Chemistry 131 (2010) 915–921
Scheme 1. Synthesis of 2,20-bipyridine derivatives bearing fluorinated alkyl chains. (a) NaH, dry DMF, 50 8C, 1 h; (b) F(CF2)8(CH2)4OTs or F(CF2)4(CH2)4OTs, 50 8C, 6–15.5 h; (c)
cat. Pd(PPh3)4, dry toluene, r.t., 1 h; (d) p-(2-(perfluorohexyl)ethyl)phenylboronic acid, 4 N KOH aq., 80 8C, 20 h; (e) F(CF2)6(CH2)2OK, 100 8C, 32 h; and (f) PBr3, dry CHCl3,
reflux, 3 h.
All complexes were soluble in fluorinated alcohols as expected.
Interestingly, they were also soluble in common aprotic polar
solvents, such as DMF, CH3CN, and acetone, as seen in Scheme 2
and also have enough solubilities in chloroform to be characterized
by 1H NMR.
were 0.25 mg/100 mg (DMF), 0.25 mg/100 ml (CH3CN) and 0.4 mg/
100 ml (THF). However they seemed to decompose gradually in THF
and both complexes were insoluble in MeOH.
2.3. Solution behavior of metal complexes in sc-CO2
As [M(F84OPh)3](PF6)2 is less soluble than others, its solubilities
were examined for MeOH, DMF, CH3CN, and THF. The solubilities of
[Ru(F84OPh)3](PF6)2 were 0.4 mg/100 mg (DMF), 0.2 mg/100 ml
(CH CN), and 0.4 mg/100 ml (THF) and those of [Co(F84OPh) ](PF )
At present, the solubility of metal complexes in sc-CO2 cannot
be quantitatively measured. Therefore, we attempted to qualita-
tively examine the solution behavior of Ru(II) and Co(II) complexes
[(Schme_2)TD$FIG]
3
3
6 2
Scheme 2. Preparation of Ru(II) and Co(II) complexes.

[
T. Hirose et al. / Journal of Fluorine Chemistry 131 (2010) 915–921
917
are the most soluble in sc-CO2 and that [M(F44OPh)3](BArF)2
compounds are highly CO2-philic.
2.4. Absorption and emission spectra of Ru(II) complexes
Fig. 4 shows the absorption spectra of the Ru(II) complexes.
[Ru(F62O)3](PF6)2 exhibits
comparable to that of Ru(bpy)3Cl2. On the other hand,
a molar extinction coefficient e
[Ru(F84OPh)3](PF6)2, [Ru(F44OPh)3](PF6)2, and [Ru(F62Ph)3](PF6)2
have higher
e values in the visible region than Ru(bpy)3Cl2 and
[Ru(F62O)3](PF6)2. These results are attributable to the introduc-
tion of phenyl groups at the 4,40-positions of 2,20-bipyridine.
The emission spectra of all investigated Ru(II) complexes are
shown in Fig. 5. [Ru(F62O)3](PF6)2 shows a markedly low emission
intensity that was comparable with that of Ru(bpy)3Cl2. It is
thought that excitation energy was lost through nonradiative
deactivation by thermal vibration of the fluoroalkoxy groups
directly attached to the 2,20-bipyridine structure. On the other
Fig. 1. Experimental setup to study the solution behavior of the metal complexes in
sc-CO2.
using a high-pressure reaction vessel (Fig. 1). The experimental
procedure is as follows: a sample bottle containing a Ru(II) or Co(II)
complex (3–4 mg) was set in the reaction vessel and liq. CO2 was
introduced into the vessel (ꢁ10 ml). The complex was steeped in
sc-CO2 at 50 8C under high pressure (ꢁ9.4–10.1 MPa). After about
1 h, sc-CO2 was slowly released as gaseous CO2 and the change in
the appearance of each complex was visually observed.
hand,
the
emission
intensity
of
[Ru(F84OPh)3](PF6)2,
[Ru(F44OPh)3](PF6)2, and [Ru(F62Ph)3](PF6)2 was higher than that
of Ru(bpy)3Cl2. This increase is due to the effects of the phenyl
groups, which increase
motion of the flexible fluoroalkyl chains.
e and prevent deactivation by thermal
Figs. 2 and 3, respectively, show the results of solution
experiments on Ru(II) and Co(II) complexes with the new ligands,
that is, [ML3](PF6)2 and [ML3](BArF)2, in sc-CO2. [M(F62O)3](PF6)2
showed signs of dissolution, while [Ru(F44OPh)3](PF6)2 seemed
soluble to a lesser extent; other complexes did not exhibit any
changes, and thus were considered to be insoluble. It seems that
the introduction of a fluorinated alkoxy group increases solubility,
whereas introduction of an aromatic structure decreases solubility.
To investigate the effect of counterions, the anion was
exchanged with BArFꢀ containing 24 fluorine atoms. As clearly
shown in Fig. 3, [M(F62Ph)3](BArF)2, [M(F44OPh)3](BArF)2, and
[M(F62O)3](BArF)2 (M = Ru and Co) were more soluble than their
corresponding complexes with PF6ꢀ. In addition, the solubility of
the Ru complexes was higher than that of the Co complexes. On the
other hand, [M(bpy)3](BArF)2 compounds were insoluble. These
results indicate that both the ligand and the counteranion must be
CO2-philic to solubilize the Ru(II) and Co(II) complexes in sc-CO2. It
(M = Ru and Co) compounds
2.5. Photoreduction of CO2 under high pressure
New CO2-philic and sc-CO2-soluble Ru(II) and Co(II) com-
plexes, namely, [M(F44OPh)3](BArF)2 and [M(F62O)3](BArF)2
(M = Ru and Co), were applied to CO2 photoreduction experi-
ments in liq. CO2 and a DMF–CO2 mixture under high pressure.
The results are summarized in Table 1, and the appearance of
the reaction mixtures in the vessel is shown in Fig. 6. For the
[M(F44OPh)3](BArF)2 system in liq. CO2 (Entry 1), the production
of CO and H2 was detected but the TNCO was about one-fifth of
that in DMF–CO2 (Entry 2). It was observed that a small amount
of the complexes dissolved in liq. CO2; however, most of the
complexes remained at the bottom of the vessel (Fig. 6a), while
all complexes dissolved in DMF–CO2. On the other hand,
[M(F62O)3](BArF)2 in liq. CO2 showed the same TNCO as that
in DMF–CO2 (Entries 3 and 4) because all the complexes
[(g._2)TD$FIG]
wi as shown that [M(F62O) ](BArF)
3
2
Fig. 2. Solution experiments of Ru (a) and Co complexes (b) in sc-CO2.
From the left: [M(F84OPh)3](PF6)2, [M(F62Ph)3](PF6)2, [M(F44OPh)3](PF6)2, and [M(F62O)3](PF6)2 (M = Ru (a) or Co (b)) were shown. The complexes in bottles in the back row
and those in cut-bottles in the front were before sc-CO and after sc-CO2 exposure, respectively.
[(ig._3)TD$FIG]
2
Fig. 3. Solution experiments of Ru (a) and Co complexes (b) in sc-CO2. From the left, [M(F62Ph)3](BArF)2, [M(F44OPh)3](BArF)2, [M(F62O)3](BArF)2, and [M(bpy)3](BArF)2
(M = Ru (a) or Co (b)) were shown. The complexes in bottles in the back row and those in cut-bottles in the front were before sc-CO2 and after sc-CO2 exposure, respectively.

[
T. Hirose et al. / Journal of Fluorine Chemistry 131 (2010) 915–921
)
Fig. 4. Absorption spectra of Ru(bpy)3Cl2, [Ru(F44OPh)3](PF6)2, [Ru(F62O)3](PF6)2,
[Ru(F62Ph)3](PF6)2, and [Ru(F84OPh)3](PF6)2 (2 ꢂ 10ꢀ5 M) in degassed and N2
saturated CH3CN at room temperature.
Fig. 5. Emission spectra of Ru(bpy)3Cl2, [Ru(F44OPh)3](PF6)2, [Ru(F62O)3](PF6)2,
[Ru(F62Ph)3](PF6)2 and [Ru(F84OPh)3](PF6)2 (2 ꢂ 10ꢀ5 M) in degassed and N2
saturated CH3CN at room temperature. The excitation wavelength is 450 nm.
[(ig._6)TD$FIG]
Fig. 6. Photos of the photoreduction systems of liq. CO2 in the high-pressure reaction vessel. (a) [Ru(F44OPh)3](BArF)2 and [Co(F44OPh)3](BArF)2 system at 35 8C and 6.8 MPa,
(b) [Ru(F62O)3](BArF)2 and [Co(F62O)3](BArF)2 system at 35 8C and 6.8 MPa, and (c) [Ru(F62O)3](PF6)2 and [Ru(F62O)3](PF6)2 system at 25 8C and 5.6 MPa.
dissolved in liq. CO2 (Fig. 6b). For [M(F62O)3](PF6)2, however, no
CO or H2 was detected (Entry 5) because only small amounts of
the complexes dissolved in sc-CO2 (Fig. 6c), which was due to
PF6ꢀ, as mentioned above. The modification of both the ligand
and counteranion of the complexes resulted in high solubility
and high CO production for [M(F62O)3](BArF)2 (M = Ru and Co).
The lower TNCO of the [M(F62O)3](BArF)2 system than that of the
[M(F44OPh)3](BArF)2 system in DMF–CO2 (Entry 2 vs Entry 4) is
due to the lower absorption and emission properties of the
former system, which arises from the aliphatic side chain of
F62O, as mentioned above.
3. Conclusion
Four 2,20-bipyridine derivatives with highly fluorinated side
chains were synthesized and their Ru(II) and Co(II) complexes
were prepared. The CO2-soluble or CO2-philic Ru(II) and Co(II)
complexes [M(F62O)3](BArF)2 and [M(F44OPh)3](BArF)2 were
synthesized with new 2,20-bipyridines bearing fluorinated alkyl
chains, namely, F62O and F44OPh. The solubilities of these
complexes were enhanced in combination with a highly fluorinat-
ed counteranion, BArFꢀ. Applying the new Ru(II) and Co(II)
complexes, we successfully realized CO2 photoreduction in sc-
CO2 without the use of any other organic solvent.
Table 1
4. Experimental
CO2-photoreduction using sc-CO2 soluble and CO2-philic Ru(II) and Co(II)
complexes under high pressure.
4.1. General
Entry Ligand
Counteranion Solvents
Temp. Pressure TNa TNa
(8C)
(MPa)
CO
H2
Dry solvents used in the reactions were freshly distilled from
appropriate drying agents before use. Chemicals used were
obtained from commercial suppliers and used without further
purifications including fluorinated compounds from Daikin
Industries, Ltd. All compounds were characterized by 1H NMR
(Bruker AC-300P or AVANCE500) and ESI–MS (Mariner). IR
spectra were recorded on and a JASCO FT/IR 400. UV–vis and
emission spectra of the complexes were recorded as an
acetonitrile solution on a JASCO V-550 and a JASCO V-750,
respectively.
c
1
2
3
4
5
F44OPh BArF
F44OPh BArF
CO2
35
50
35
50
25
6.8
7.3
6.8
6.6
5.6
6.0 1.2
27.1 3.3
17.7 1.8
15.6 0.5
b
b
DMF–CO2
c
F62O
F62O
F62O
BArF
BArF
PF6
CO2
DMF–CO2
c
CO2
–
–
Reaction conditions: Ru complex, 2.5
mmol; Co complex, 2.5 mmol; light, Xe lamp
(400–750 nm: HOYA L39, HA50); reaction time, 48 h.
a
Turnover number (TN) refers to the mol of CO or H2 generated per mol of the Co
complex.
b
Liq. CO2 (5 ml), trietanolamine (1 ml), DMF (4 ml).
Liq. CO2 (8 ml), triethylamine (2 ml).
c

T. Hirose et al. / Journal of Fluorine Chemistry 131 (2010) 915–921
919
4.2. Synthesis of the ligands
4.2.4. Synthesis of 4,40-bis[2-(perfluorohexyl)ethoxy]-2,20-bipyridine-
1,10-dioxide (4) [13]
4.2.1. Synthesis of 4,40-bis(p-(4-(perfluorooctyl)butoxy)phenyl))-
2,20-bipyridine (F84OPh)
Potassium metal (261 mg, 6.68 mmol) was cut into small pieces
and immediately added to the solution of 2-(perfluorohexyl)etha-
nol (6.0 ml, 27.7 mmol) in diethyl ether (6.0 ml) under nitrogen
atmosphere. The mixture was stirred at r.t. for several hours until
potassium dissolved completely. 4,40-Dinitro-2,20-bipyridine-1,10-
dioxide 3 (600 mg, 2.16 mmol) was added to the solution and
diethyl ether was removed by distillation, then the suspension was
stirred at 100 8C for 32 h. The mixture was cooled to r.t., acidified to
pH 4 by conc. HCl aq. and concentrated under vacuum. Large
amount of chloroform was added to the residue and the suspension
was sonicated several times to dissolve the brownish yellow solid.
Insoluble precipitate was removed by filtration and the filtrate was
concentrated. The residue was sonicated three times in hexane
(30 ml), then the suspension was filtered again to obtain yellow
Under nitrogen, 4,40-bis(p-hydroxyphenyl)-2,20-bipyridine 1
(50.0 mg, 0.147 mmol) was suspended in dry DMF (6 ml) and
stirred at 80 8C. After adding large excess amount of NaH (51.1 mg,
1.28 mmol) and stirring for 1 h, 4-(perfluorooctyl)butyl p-tolue-
nesulfonate (301 mg, 0.466 mmol) was added. The suspension was
stirred for 15.5 h. After cooling to r.t., the precipitate was filtered
through a 0.45-
amount of H2O, methanol and chloroform to obtain a gray solid in
72% (137 mg, 0.106 mmol). 1H NMR (300 MHz, CDCl3):
8.84 (d,
mm membrane filter and washed with a large
d
J = 6.54 Hz, 2H; 6-Py-H and 60-Py-H), 8.71 (s, 2H; 3-Py-H and 30-Py-
H), 8.35 (d, J = 6.54 Hz, 2H; 5-Py-H and 50-Py-H), 7.93 (d, J = 9.09 Hz,
4H; Ar-H), 7.15 (d, J = 9.09 Hz, 4H; Ar-H), 4.17 (t, J = 5.82 Hz, 4H;
Ar-OCH2), 2.08–2.23 (m, 4H; CF2CH2, 4H), 1.82–1.93 (m, 8H;
ArOCH2CH2CH2); IR (KBr): 1592, 1205, 1041 cmꢀ1; mp 226.2–
227.1 8C.
powder (1.17 g, 1.28 mmol, 59%). 1H NMR (300 MHz, CDCl3):
d 8.24
(d, J = 7.26 Hz, 2H; 6-H and 60-H), 7.48 (d, J = 3.62 Hz, 2H; 3-H and
30-H), 6.93 (dd, J1 = 7.26 Hz, J2 = 3.62 Hz, 2H; 5-H and 50-H), 4.34 (t,
J = 6.44 Hz, 4H; OCH2), 2.58–2.74 (m, 4H; OCH2CH2); IR (KBr):
1202, 1015 cmꢀ1; mp 157.3–160.3 8C.
4.2.2. Synthesis of 4,40-bis(p-(4-(perfluorobutyl)butoxy)phenyl)-2,20-
bipyridine (F44OPh)
Under nitrogen, 4,40-bis(p-hydroxyphenyl)-2,20-bipyridine 1
(251 mg, 0.737 mmol) was suspended in dry DMF (40 ml) and
stirred at 60 8C for 30 min. After adding large excess amount of
NaH (258 mg, 6.45 mmol) and stirring for 10 min, 4-(perfluor-
obutyl)butyl p-toluenesulfonate (879 mg, 1.97 mmol) was
added and the suspension was stirred for 5 h. After cooling to
r.t., the mixture was concentrated, suspended in water and
extracted with chloroform (50 ml ꢂ 4). The organic layer was
dried with anhyd. Na2SO4 and concentrated. The residue was
filtered again and washed with large amount of water and small
amount of hexane to obtain brownish white solid. The residue
was purified by recrystallization from ethanol/water (v/v, 10/1)
to obtain white solid in 40% (263 mg, 0.296 mmol). 1H NMR
4.2.5. Synthesis of 4,40-bis(2-(perfluorohexyl)ethoxy)-2,20-bipyridine
(F62O) [10]
Phosphorus tribromide (0.7 ml, 6.64 mmol) was added to the
suspension of 4,40-bis[2-(perfluorohexyl)ethoxy]-2,20-bipyridine-
1,10-dioxide 4 (1.10 g, 1.21 mmol) in dry chloroform (50 ml). After
refluxing for 3 h, the suspension was cooled in a water bath,
basified with 6 N NaOH aq. and extracted with chloroform
(80 ml ꢂ 4). The organic layer was combined, dried with anhyd.
Na2SO4, and concentrated. The residue was sonicated in ethyl
acetate and the suspension was filtered to obtain white solid in 82%
(878 mg, 1.00 mmol). 1H NMR (300 MHz, CDCl3):
d 8.66 (d,
J = 6.27 Hz, 2H; 6-Py-H and 60-Py-H), 8.63 (s, 2H; 3-Py-H and 30-
Py-H), 7.18 (d, J = 6.27 Hz, 2H; 5-Py-H and 50-Py-H), 4.74 (t,
J = 5.88 Hz, 4H; OCH2), 2.71–2.85 (m, 4H; OCH2CH2); IR (KBr):
1587, 1242, 1036 cmꢀ1; mp 189.3–191.4 8C.
(300 MHz, CDCl3):
d
8.71 (d, J = 5.14 Hz, 2H; 6-Py-H and 60-Py-
H), 8.69 (d, J = 1.60 Hz, 2H; 3-Py-H and 30-Py-H), 7.75 (d,
J = 8.63 Hz, 4H; Ar-H), 7.52 (dd, J1 = 5.14 Hz, J2 = 1.60 Hz, 2H; 5-
Py-H and 50-Py-H), 7.01 (d, J = 8.63 Hz, 4H; Ar-H), 4.07 (t,
J = 5.70 Hz, 4H; OCH3), 2.09–2.30 (m, 4H; CF2CH2), 1.78–2.00 (m,
8H, OCH2CH2 CH2); IR (KBr): 1592, 1237, 1040 cmꢀ1; mp 139.0–
141.8 8C.
4.3. Preparation of Ru(II) and Co(II) complexes [19,25,26]
4.3.1. Ru(4,40-bis(p-(4-(perfluorooctyl)butoxy)phenyl)-2,20-
bipyridine)3(PF6)2 [Ru(F84OPh)3](PF6)2
Under nitrogen, RuCl3ꢃnH2O (5.0 mg, 22.9
40-bis(p-(4-(perfluorooctyl)butoxy)phenyl)-2,20-bipyridine F84OPh
(109 mg, 84.6 mol) were reacted in a mixture of degassed ethylene
mmol as n = 3) and 4,
4.2.3. Synthesis of 4,40-bis(p-(2-perfluorohexyl)ethylphenyl)-2,20-
bipyridine (F62Ph) [18]
m
Under nitrogen, Pd(PPh3)4 (256 mg, 0.222 mmol, 12 mol%) was
added to the solution of 4,40-dibromo-2,20-bipyridine 2 (580 mg,
1.85 mmol) in dry toluene (100 ml). After stirring for 1 h, p-(2-
(perfluorohexyl)ethyl)phenylboronic acid (1.90 g, 4.06 mmol)
and 4 N KOH aq. (9.2 ml, 36.8 mmol) were added and the mixture
was stirred at 80 8C. After stirring for 20 h, the mixture was cooled
to r.t. and 1 N Na2CO3 aq. (15.0 ml) and NH3 aq. (8.0 ml) were
added to the mixture. The precipitate was filtered and washed
with large amount of acetone and the filtrate was concentrated.
Water was added and the mixture was extracted with chloroform
(50 ml ꢂ 3). The organic layer was dried with anhyd. Na2SO4 and
concentrated again. The residue was purified by silica gel column
chromatography (chloroform to ethyl acetate) and alumina
column chromatography with chloroform to obtain a white solid
glycol (2 ml) and degassed 1H,1H,7H-dodecafluoroheptanol (6 ml)
at 150 8Cfor21 h. Allsolventswereremoved under vacuumtoobtain
dark-red solid. The residue was purified by molecular sieve type
chromatography (Sephadex LH-20) using MeOH/acetone (v/v, 1/1)
and the counteranion was exchanged by adding sat. KPF6 aq. The
precipitate was filtered through a 0.45-
obtain red solid (41.9 mg, 9.84 mol, 43%). ESI–MS: m/z = 1984
(100%, [M-2(PF6)]2+);1HNMR(500 MHz, CDCl3):
8.49(br, 6H;3-Py-
mm membrane filter to
m
d
H and 30-Py-H), 7.91 (d, J = 6.00 Hz, 6H; 6-Py-H and 60-Py-H), 7.69 (d,
J1 = 6.00 Hz, J2 = 1.50 Hz, 6H; 5-Py-H and 50-Py-H), 7.76 (d,
J = 8.50 Hz, 12H; Ar-H), 7.04 (d, J = 8.50 Hz, 12H; Ar-H), 4.07 (t,
J = 6.00 Hz, 12H; Ar-OCH2), 2.10–2.26 (m, 12H; CF2CH2, 4H), 1.79–
1.98 (m, 24H; ArOCH2CH2CH2); IR (KBr): 1604, 1208, 851 cmꢀ1; mp
284.4–287.1 8C.
in 39% (720 mg, 0.720 mmol). 1H NMR (300 MHz, CDCl3):
d 8.75
(dd, J1 = 5.15 Hz, J2 = 0.75 Hz, 2H; 6-Py-H and 60-Py-H), 8.72 (dd,
J1 = 1.83, J2 = 0.75 Hz, 2H; 3-Py-H and 30-Py-H), 7.76 (d, J = 8.45 Hz,
4H; Ar-H), 7.55 (dd, J1 = 5.15 Hz, J2 = 1.83 Hz, 2H; 5-Py-H and 50-
Py-H), 7.37 (d, J = 8.45 Hz, 4H; Ar-H), 2.98–3.03 (m, 4H; ArCH2),
2.35–2.53 (m, 4H, ArCH2CH2); IR (KBr): 1592, 1221 cmꢀ1; mp
152.3–153.9 8C.
4.3.2. Co(4,40-bis(p-(4-(perfluorooctyl)butoxy)phenyl)-2,20-
bipyridine)3(PF6)2 [Co(F84OPh)3](PF6)2
Under nitrogen, CoCl2ꢃ6H2O (24.6 mg, 103
mmol) was dissolved
in a mixture of degassed acetonitrile (8 ml) and 1H,1H,3H-
tetrafluoropropanol (17 ml) at r.t. After the mixture became clear
blue solution, 4,40-bis(p-(4-perfluorooctyl)butoxyphenyl)-2,20-

920
T. Hirose et al. / Journal of Fluorine Chemistry 131 (2010) 915–921
bipyridine F84OPh (400 mg, 310
110 8C for 5 h. Filtration through a 0.45-
m
mol) was added and stirred at
m membrane filter was
4.3.6. Co(4,40-bis(p-(2-(perfluorohexyl)ethyl)phenyl)-2,20-
m
bipyridine)3(PF6)2 [Co(F62Ph)3](PF6)2
performed to remove unreacted F84OPh, then the solvents were
removed under reduced pressure to obtain brownish-yellow solid.
The residue was purified by molecular sieve type chromatography
(Sephadex LH-20) using MeOH/acetone (v/v, 1/1) and the counter-
anion was exchanged by adding sat. KPF6 aq. The precipitate was
Under nitrogen, CoCl2ꢃ6H2O (12.3 mg, 51.7
mmol) was dis-
solved in a mixture of degassed acetonitrile (10 ml) and degassed
chloroform (10 ml) at r.t. After the mixture became clear blue
solution,
dine F62Ph (180 mg, 180
4,40-bis(p-(2-perfluorohexyl)ethylphenyl)-2,20-bipyri-
mol) was added and refluxed for 5 h.
m
filtered through a 0.45-
m
m membrane filter to obtain yellow solid
All solvents were removed under reduced pressure to obtain
yellow solid. The residue was purified by molecular sieve type
chromatography (Sephadex LH-20) using MeOH/acetone (v/v, 1/1)
and the counteranion was exchanged by adding sat. KPF6 aq. The
(289 mg, 68.6
m
mol, 67%). ESI–MS: m/z = 1962 (100%, [M-
2(PF6)]2+), 1308 (10%, [M-2(PF6)]3+); IR (KBr): 1604, 1205,
845 cmꢀ1; mp 199.2–201.8 8C.
precipitate was filtered through a 0.45-mm membrane filter to
4.3.3. Ru(4,40-bis(p-(4-(perfluorobutyl)butoxy)phenyl)-2,20-
bipyridine)3(PF6)2 [Ru(F44OPh)3](PF6)2
obtain beige solid (101 mg, 30.1 mmol, 58%). ESI–MS: m/z = 1528
(100%, [M-2(PF6)]2+); IR (KBr): 1611, 1199, 845 cmꢀ1; mp 198.0–
Under nitrogen, RuCl3ꢃnH2O (8.2 mg, 37.6
4,40-bis(p-(4-perfluorobutyl)butoxyphenyl)-2,20-bipyridine
F44OPh (100 mg, 113 mol) were reacted in a mixture of degassed
ethylene glycol (4 ml), degassed DMF (4 ml) and degassed 1,1,2,2-
tetrachloroethane (2 ml) at 140 8C for 20 h. All solvents were
removed under vacuum to obtain wine red solid. The residue was
purified by molecular sieve type chromatography (Sephadex LH-
20) using MeOH/acetonitrile (v/v, 1/1) and the counteranion was
exchanged by adding sat. KPF6 aq. The precipitate was filtered
m
mol as n = 3) and
201.1 8C.
m
4.3.7. Ru(4,40-bis(2-(perfluorohexyl)ethoxy)-2,20-bipyridine)3(PF6)2
[Ru(F62O)3](PF6)2
Under nitrogen, RuCl3ꢃnH2O (10.0 mg, 45.8
4,40-bis(2-(perfluorohexyl)ethoxy)-2,20-bipyridine F62O (150 mg,
170 mol) were reacted in a mixture of ethylene glycol (6 ml) and
mmol as n = 3) and
m
1H,1H,7H-dodecafluoroheptanol (5 ml) 150 8C for 16 h. Dark
orange suspension gradually became clear red solution. All
solvents were removed under vacuum to obtain red solid. The
residue was purified by molecular sieve type chromatography
(Sephadex LH-20) using MeOH/acetone (v/v, 1/1) and the counter-
anion was exchanged by adding sat. KPF6 aq. The precipitate was
filtered through a 0.45-
(57.0 mg, 18.8
mol, 41%). ESI–MS: m/z = 881 (100%, [F62O + H]+),
1371 (40%, [M-2(PF6)]2+); 1H NMR (500 MHz, CDCl3):
8.50 (d,
J = 5.75 Hz, 6H; 3-Py-H and 30-Py-H), 8.00 (d, J = 2.50 Hz, 6H; 6-Py-
H and 60-Py-H), 6.87 (dd, J1 = 5.75 Hz, J2 = 2.50 Hz 6H; 5-Py-H and
50-Py-H), 4.46 (t, J = 6.50 Hz, 12H; OCH2), 2.61–2.78 (m, 12H;
OCH2CH2); IR (KBr): 1618, 1235, 843 cmꢀ1; mp 267.2–272.1 8C.
through a 0.45-
29.2
mol, 78%). ESI–MS: m/z = 1383 (100%, [M-2(PF6)]2+); 1H
NMR (500 MHz, CDCl3):
8.49 (br, 6H; 3-Py-H and 30-Py-H), 7.91
mm membrane filter to obtain red solid (89.3 mg,
m
d
(d, J = 6.00 Hz, 6H; 6-Py-H and 60-Py-H), 7.76 (d, J = 9.00 Hz, 12H;
Ar-H), 7.70 (dd, J1 = 6.00 Hz, J2 = 2.00 Hz, 6H; 5-Py-H and 50-Py-H),
7.04 (d, J = 9.00 Hz, 12H; Ar-H), 4.07 (t, J = 5.75 Hz, 12H; OCH3),
2.10–2.29 (m, 12H; CF2CH2), 1.79–2.00 (m, 24H, OCH2CH2 CH2); IR
(KBr): 1604, 1237, 843 cmꢀ1; mp 271.1–274.3 8C.
mm membrane filter to obtain orange solid
m
d
4.3.4. Co(4,40-bis(p-(4-(perfluorobutyl)butoxyphenyl)-2,20-
bipyridine)3(PF6)2 [Co(F44OPh)3](PF6)2
Under nitrogen, CoCl2ꢃ6H2O (5.3 mg, 22.3
mmol) was dissolved
mixture of degassed acetonitrile (1 ml) and degassed
in
a
4.3.8. Co(4,40-bis(2-(perfluorohexyl)ethoxy)-2,20-bipyridine)3(PF6)2
[Co(F62O)3](PF6)2
chloroform (4 ml) at r.t. After the mixture became clear blue
solution, 4,40-bis(p-(4-perfluorobutyl)butoxyphenyl)-2,20-bipyri-
Under nitrogen, CoCl2ꢃ6H2O (12.3 mg, 51.7
mmol) was dis-
dine F44OPh (60.9 mg, 68.5
m
mol) was added and stirred at
solved in a mixture of degassed acetonitrile (1 ml) and degassed
chloroform (1 ml) at r.t. After the mixture became clear blue
solution, 4,40-bis(2-(perfluorohexyl)ethoxy)-2,20-bipyridine F62O
70 8C for 5 h. All solvents were removed under reduced pressure to
obtain yellow solid. The residue was purified by molecular sieve
type chromatography (Sephadex LH-20) using MeOH/acetonitrile
(v/v, 1/1) and the counteranion was exchanged by adding sat. KPF6
(208 mg, 236
mmol) and 1H,1H,3H-tetrafluoropropanol (2 ml)
were added and refluxed for 5 h. Blue solution gradually became
yellow and all solvents were removed under reduced pressure to
obtain yellow solid. The residue was purified by molecular sieve
type chromatography (Sephadex LH-20) using MeOH/acetone (v/v,
1/1) and the counteranion was exchanged by adding sat. KPF6 aq.
aq. The precipitate was filtered through a 0.45-
m
m membrane
filter to obtain yellow solid (52.2 mg, 17.3
mmol, 78%). ESI–MS: m/
z = 1362 (100%, [M-2(PF6)]2+), 1308 (20%, [M-2(PF6)]3+); IR (KBr):
1603, 1236, 843 cmꢀ1; mp 244.7–248.7 8C.
The precipitate was filtered through a 0.45-mm membrane filter to
4.3.5. Ru(4,40-bis(p-(2-(perfluorohexyl)ethyl)phenyl)-2,20-
bipyridine)3(PF6)2 [Ru(F62Ph)3](PF6)2
obtain beige solid (110 mg, 37.0 mmol, 72%). ESI–MS: m/z = 1350
(100%, [M-2(PF6)]2+), 900 (80%, [M-2(PF6)]3+), 1423 (30%, [M-
Under nitrogen, RuCl3ꢃnH2O (8.4 mg, 32.1
4,40-bis(p-(2-(perfluorohexyl)ethyl)phenyl)-2,20-bipyridine F62Ph
(100 mg, 100 mol) were reacted in a mixture of degassed ethylene
mmol as n = 3) and
(PF6)]2+); IR (KBr): 1617, 1237, 839 cmꢀ1; mp 240.0–243.9 8C.
m
4.4. Procedure of solution behavior study of Ru(II) and Co(II)
complexes in sc-CO2
glycol (5 ml) and degassed 1H,1H,7H-dodecafluoroheptanol (5 ml)
at 150 8C for 16 h. Dark orange suspension gradually became clear
red solution, and all solvents were removed under vacuum to obtain
red solid. The residue was purified by molecular sieve type
chromatography (Sephadex LH-20) using MeOH/acetone (v/v, 1/
1) and the counteranion was exchanged by adding sat. KPF6 aq. The
Solution behavior of new complexes in sc-CO2 was investigated
according to the following procedure (Fig. 1).
1. The high-pressure vessel was completely replaced with CO2.
2. Under CO2 stream, a sample bottle containing Ru or Co complex
(3–4 mg) was set in a vessel and the vessel was closed tightly.
3. Liq. CO2 (10 ml) was introduced and the temperature was raised
to 50 8C to change liq. CO2 into sc-CO2.
4. After 1 h, the vessel was cooled to r.t. and sc-CO2 was released as
gaseous CO2.
5. The change of complex was examined by sight.
precipitate was filtered through a 0.45-
obtain orange solid (67.0 mg, 19.7 mol, 61%). ESI–MS: m/z = (100%,
1549 [M-2(PF6)]2+); 1H NMR (300 MHz, CDCl3):
8.53 (br, 6H; 3-Py-
mm membrane filter to
m
d
H and 30-Py-H), 7.99 (d, J = 6.00 Hz, 6H; 6-Py-H and 60-Py-H), 7.71–
7.82 (m, 18H; 5-Py-H and 50-Py-H and Ar-H), 7.41 (d, J = 8.40 Hz,
12H; Ar-H), 2.92–3.09 (m, 12H; ArCH2), 2.30–2.57 (m, 12H,
ArCH2CH2); IR (KBr): 1611, 1200, 841 cmꢀ1; mp 238.0–240.7 8C.

T. Hirose et al. / Journal of Fluorine Chemistry 131 (2010) 915–921
[13] N. Sato, M. Kobayashi, Bull. Chem. Soc. Jpn. 57 (1984) 3015–3016.
921
References
[14] N. Lu, Y.-C. Lin, J.-Y. Chen, C.-W. Fan, L.-K. Liu, Tetrahedron 63 (2007) 2019–2023.
[15] M. Kotora, M. Ha´cek, B. Ameduri, B. Boutevin, J. Fluor. Chem. 68 (1994) 49–56.
[16] S. Kainz, Z. Luo, D.P. Curran, W. Leitner, Synthesis (1998) 1425–1427.
[17] N. Miyaura, A. Suzuki, Chem. Rev. 95 (1995) 2457–2483.
[18] B. Pe´es, M. Sindt, J.M. Paul, J.L. Mieloszynski, Eur. Polym. J. 38 (2002) 921–931.
[19] P.D. Beer, S.E. Stokes, Polyhedron 14 (1995) 873–879.
[20] D.L. Reger, T.D. Wright, C.A. Little, J.J.S. Lamba, M.D. Smith, Inorg. Chem. 40 (2001)
3810–3814.
[21] N.A. Yakelis, R.G. Bergman, Organometallics 24 (2005) 3579–3581.
[22] H. Nishida, N. Takada, M. Yoshimura, T. Sonoda, H. Kobayashi, Bull. Chem. Soc. Jpn.
57 (1984) 2600–2604.
[23] C.A. Grapperhaus, J.A. Bellefeuille, J.H. Reibenspies, M.Y. Darensbourg, Inorg.
Chem. 38 (1999) 3698–3703.
[1] R. Ziessel, J. Hawecher, J.-M. Lehn, Helv. Chim. Acta 69 (1986) 1065–1084.
[2] D. Koch, W. Leitner, J. Am. Chem. Soc. 120 (1998) 13398–13404.
[3] S. Kainz, A. Brinkmann, W. Leitner, A. Pfaltz, J. Am. Chem. Soc. 121 (1999) 6421–
6429.
[4] G. Francio`, K. Wittmann, W. Leitner, J. Organomet. Chem. 621 (2001) 130–142.
[5] Y. Akiyama, X. Meng, S. Fujita, Y.-C. Chen, N. Lu, H. Cheng, F. Zhao, M. Arai, J.
Supercrit. Fluids 51 (2009) 209–216.
[6] T. Osswald, S. Schneider, S. Wang, W. Bannwarth, Tetrahedron Lett. 42 (2001)
2965–2967.
[7] M.D. Doherty, D.C. Grills, E. Fujita, Inorg. Chem. 48 (2009) 1796–1798.
[8] J. Haginiwa, Yakugaku Zasshi 75 (1955) 731–733 (Japanese).
[9] G. Maerker, F.H. Case, J. Am. Chem. Soc 80 (1958) 2745–2748.
[10] D. Wenkert, R.B. Woodward, J. Org. Chem. 48 (1983) 283–289.
[11] M.J. Cook, A.P. Lewis, G.S.G. McAuliffe, V. Skarda, A.J. Thomson, J.L. Glasper, D.J.
Robbins, J. Chem. Soc. Perkin Trans. II (1984) 1293–1301.
[24] B. Guzel, M.A. Omary, J.P. Fackler Jr., A. Akgerman, Inorg. Chim. Acta 325 (2001)
45–50.
[25] D.A. Freedman, J.K. Evju, M.K. Pomije, K.R. Mann, Inorg. Chem. 40 (2001) 5711–
5715.
[12] C.L. Donnici, D.H.M. Filho, L.L.C. Moreira, G.T. dos Reis, E.S. Cordeiro, I.M.F. de
Oliveira, S. Carvalho, E.B. Paniago, J. Braz. Chem. Soc. 9 (1998) 455–460.
[26] J.A. Zampese, F.R. Keene, P.J. Steel, Dalton Trans. (2004) 4124–4129.