Organometallics
Article
previously reported method.6b Tetraethylammonium tetrafluorobo-
rate (Et4NBF4) for cyclic voltammetry measurements was dried in
vacuo at 100 °C overnight prior to use. Mn was synthesized according
to a previous report. All other reagents were purchased in the highest
available purity and commercially obtained from Kanto Chemical Co.
Inc., Wako Pure Chemical Industries, Ltd., Tokyo Chemical Industry
Co., Ltd., and Sigma-Aldrich Co. LLC.
(CDCl3/δ in ppm): 8.61−7.58 (m, 16H, ArH), 7.34−6.81 (m, 7 H,
ArH), 6.74−6.41 (m, 1H, ArH), 3.88 (br), 3.37 (t, J = 6.0 Hz, 4H,
OCH2), 2.68 (t, J = 7.5 Hz, 4 H, ArCH2), 2.39 (s, 6 H, ArCH3), 1.84
(m, 8 H, CH2). ESI-MS: m/z 871 [M + Na]+ As a side note, the butyl
chain was chosen, because smaller linkers gave low yields during the
coupling reaction or did not allow coupling at all, most likely due to
steric repulsion. The butyl ether, however, gave sufficient yields.
Ru2-BL. RuCl2(dmb)2 (203 mg, 0.4 mmol) and BL1 (240 mg, 0.6
mmol, 1.5 equiv) were dissolved in degassed EtOH/water (4/1) in
the dark and irradiated in the microwave (150 °C, 300 W) for 2 h.
The solvent was then removed in vacuo and the residue purified via
Sephadex chromatography (MeCN/water 1/1, 0−10 mM NH4PF6)
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General Measurements. H NMR spectra were recorded in a
JEOL AL-400 NMR spectrometer. Electrospray ionization mass
spectrometry (ESI-MS) was performed on a Shimadzu LCMS-2010A
system with MeCN as the mobile phase. Electrospray ionization time-
of-flight mass spectrometry (ESI-TOF-MS) was performed on a
Waters LCT Premier spectrometer with MeCN as the mobile phase.
UV−vis absorption spectra were recorded on a JASCO spectrometer.
A Hamamatsu Photonics C-9920-02 integrating sphere with a
multiphotodiode-array detector and a Horiba FluoroHub time-
correlated single photon counting system were used for measuring
emission quantum yields and emission lifetimes, respectively: the
excitation light source was an LED pulse lamp (NanoLED, 510 nm)
with an instrumental response time of less than 0.1 ns. All samples
were degassed using the freeze−pump−thaw method prior to
measurement. Emission quenching experiments (Figure S1) were
performed in DMA/TEOA (4/1 v/v) solutions containing a complex
and four different concentrations of BIH, and the quenching rate
constants were calculated from slopes of the Stern−Volmer plots. An
ALS/CHI Model-760Es electrochemical analyzer was used for
measuring cyclic voltammograms with a glassy-carbon working
electrode, a Pt counter electrode, Et4NBF4 as the supporting
electrolyte, and Ag/AgNO3 (10 mM, DMA) as the reference
electrode in DMA.
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to yield the product as a red solid (241 mg). H NMR (MeCN-d3/δ
in ppm): 8.64−8.56 (m, 4H), 8.39−8.36 (m, 1H), 8.33 (dd, 8.1 Hz,
0.9 Hz, 1H), 8.19−8.15 (m, 1H), 7.79−7.66 (m, 1H), 7.65−7.60 (m,
2H), 7.37−7.28 (m, 10H), 7.06 (dd, 8.0, 0.8 Hz, 1H), 6.94 (dd, 7.9,
1.1 Hz, 1H), 6.77−6.69 (m, 4H), 3.97 (t, 5.0, 6 H), 3.70 (s, 3H), 3.55
(s, 6 H), 2.54−2.43 (m, 17H), 1.64−1.50 (m, 4H); ESI-MS: m/z 554
[M − 2PF6]. TOF-MS: calculated for C64H62F12N8O4P2Ru 554.1978,
found 554.1910.
Ru-Mn. Ru-BL (30 mg, 21 μmol) and MnBr(CO)5 (6 mg, 21
μmol) were suspended in diethyl ether in the dark under an Ar
atmosphere and stirred under reflux for 16 h. After the mixture was
cooled to room temperature, the product was filtered off and washed
with excess diethyl ether. The product was dried in vacuo overnight
and stored in the dark (29 mg, 84% yield). 1H NMR (MeCN-d3/δ in
ppm): 8.53−7.95 (br, 8H, ArH), 7.73−6.88 (br, 18H, ArH), 6.83−
6.49 (br, 4H, ArH), 4.08−3.29 (br, 11H, OCH), 1.92 (s, 17H,
A r C H ) , 1 . 5 2 ( b r ,
4 H , C H ) ; A n a l . C a l c d f o r
C69H65BrF12MnN9O7P2Ru: C, 49.98; H, 3.95; N, 7.60. Found: C,
49.79; H, 3.87; N, 7.79. IR (DMA): 2019, 1933 cm−1. As a side note,
the aromatic ether groups in the supramolecular catalysts should not
isomerize under the presented conditions. Known for isomerization
are typically allyl phenol ethers, which are not present in the
supramolecular photocatalysts.
Ru-BL. RuCl2(dmb)2 (50 mg, 0.06 mmol) and BL2 (64 mg, 0.12
mmol, 2 equiv) were dissolved in degassed EtOH/water (4/1) in the
dark and irradiated in the microwave (150 °C, 300 W) for 2 h. The
solvent was then removed in vacuo and the residue purified via
Sephadex chromatography (MeCN/water 1/1, 0−10 mM NH4PF6)
to yield the product as a red solid (72 mg). 1H NMR (MeCN-d3/δ in
ppm): 8.69−8.62 (m, 16H, ArH), 7.85−7.77 (m, 16H, ArH), 7.40−
7.32 (m, 16H, ArH), 3.62−3.58 (m, 6H, OCH3), 3.39−3.33 (m, 4H,
OCH2), 2.90−2.83 (m, 4H, ArCH2), 2.79−2.76 (m, 6H, ArCH3),
1.86−1.80 (m, 8H, CH2). ESI-MS: m/z 447 [M − 4PF6]. Anal. Calcd
for C103H106Cl2F30N15NaO4P5Ru2: C, 46.88; H, 4.05; N, 7.96. Found:
C, 46.67; H, 3.94; N, 7.88.
Ru2-Mn. Ru2-BL (50 mg, 24 μmol) and MnBr(CO)5 (7 mg, 24
μmol) were suspended in diethyl ether in the dark under an Ar
atmosphere and stirred under reflux for 16 h. After the mixture was
cooled to room temperature, the product was filtered off and washed
with excess diethyl ether. The product was dried in vacuo overnight
and stored in the dark (44 mg, 80% yield). 1H NMR showed
diamagnetic character. Anal. Calcd for C105H100BrF24MnN14O7P4Ru2:
C, 50.93; H, 4.68; N, 7.11. Found: C, 50.92; H, 4.24; N, 7.47. IR
(DMA): 2020, 1933 cm−1.
Photochemical Reactions. A 4 mL DMA/TEOA mixed solution
containing the photocatalyst (0.05 mM or 0.5 mM) and BIH (0.1 M)
was saturated with CO2 for 30 min. The catalyst solution was
irradiated with either an Ushio Optical Module (BA-H500) high-
pressure Hg lamp equipped with a 546 nm band-pass filter or a Xe
short arc lamp (SX-U1500H) with a 546 nm band-pass filter. In both
cases, the light intensity was adjusted by ND filters. The accurate light
intensities were then determined by using K3Fe(C2O4)3 actinometry
(4.8 × 10−7 einstein s−1 for the Hg lamp and 4.2 × 10−8 einstein s−1
for the Xe lamp), and adjusted with appropriate ND filters for the
photochemical reaction. Spectral changes were monitored on a Photal
MCPD-6800 photodiode array detector equipped with a MC-2530
light source. For quantum yield measurements, a Shimadzu QYM-01
quantum yield evaluation system was used in combination with an
Synthesis. 4-(4-(2-(6′-(2,6-Dimethoxyphenyl)[2,2′-bipyridin]-6-
yl)-3-methoxyphenoxy)butyl)-4′-methyl-2,2′-bipyridine (BL1). 1
(400 mg, 2.0 mmol), 2 (301 mg, 2.0 mmol), and potassium
carbonate (140 mg, 2.0 mmol) were suspended in dry MeCN (20
mL) and refluxed for 16 h under an Ar atmosphere. The solvent was
then removed in vacuo, the residue was redissolved in 20 mL DCM,
washed with water, and dried over MgSO4, and the solvent was again
removed in vacuo. Recrystallization from hot acetone led to
precipitation of the product, which was used in the next step without
further purification. The obtained phenol (400 mg, 0.6 mmol) in 5
mL of dry THF was slowly added to a suspension of NaH (60% in
mineral oil, 28 mg, 0.7 mmol, 1.1 equiv) in 10 mL of dry THF under
an Ar atmosphere at room temperature. After the mixture was stirred
for 5 min, MeI (60 μL, 0.96 mmol, 1.5 equiv) was slowly added and
the mixture stirred for 16 h. After quenching with water, the aqueous
phase was extracted with DCM (3 × 10 mL), the organic layer dried
over MgSO4, and the solvent removed in vacuo. Column
chromatography (SiO2, 100% DCM, 1% MeOH in DCM) yielded
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the desired compound BL1 as a yellow solid. H NMR (CDCl3/δ in
ppm): 8.54−8.48 (m, 2H, ArH), 8.40 (t, J = 5.2 Hz, 1H, ArH), 8.35−
8.31 (m, 1H, ArH), 8.25−8.04 (m, 3H, ArH), 7.77−7.65 (m, 2H,
ArH), 7.35−7.26 (m, 3H, ArH), 7.14−7.06 (m, 2H, ArH), 6.89−6.83
(m, 1H, ArH), 6.69−6.59 (m, 3H, ArH), 3.97−3.89 (m, 3H,
ArOCH3), 3.75−3.68 (m, 8H, ArOCH), 2.43 (s, 3H, ArCH3), 2.41−
2.39 (m, 2H, ArCH2), 0.90−0.80 (m, 4H, CH2). ESI-MS: m/z 639
[M + H]. TOF-MS: calculated for C40H39N4O4 639.2971, found
639.3007. As a side note, the butyl chain was chosen, because smaller
linkers gave low yields during the coupling reaction or did not allow
coupling at all, most likely due to steric repulsion. The butyl ether,
however, gave sufficient yields.
6,6′-Bis(2-methoxy-6-(4-(4′-methyl[2,2′-bipyridin]-4-yl)butoxy)-
phenyl)-2,2′-bipyridine (BL2). Following the synthesis for BL1, 1
(250 mg, 0.6 mmol), 2 (424 mg, 1.87 mmol, 3 equiv), and NaH (60%
in mineral oil, 120 mg, 2.5 mmol, 4 equiv) were suspended in dry
THF (20 mL) and stirred for 16 h under an Ar atmosphere at room
temperature. The solvent was then removed in vacuo, the residue was
redissolved in DCM, washed with water, and dried over MgSO4, and
the solvent was again removed in vacuo. Column chromatography
(SiO2, 100% DCM, 10% MeOH in DCM) yielded the desired
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compound BL2 as a brown solid (423 mg, 80% yield). H NMR
F
Organometallics XXXX, XXX, XXX−XXX