Inorganic Chemistry
Article
UV−vis spectrophotometer, respectively. The IR spectra were taken
on the Nicolet 6700 FTIR spectrometer (from Thermo Electron
Corporation). All gaseous and liquid products produced from
photoreaction were analyzed by gas chromatography (GC) and
Waters high-performance liquid chromatography (HPLC) equipped
with RSpak KC-811 column, respectively.
merry-go-round apparatus and then irradiated under magnetic stirring
with an LED lamp (60 W, model Fc-6051, Cree Inc.). For the LED
lamp, the incident light (λ > 500 nm) was obtained by passing the
light through a K CrO solution layer of 1.0 cm path length. A
2
4
homogeneous-solution photoreaction was performed in 3 mL DMF/
TEOA solution (16.7 vol % TEOA) containing 0.1 mM IrPS, 0.025−
Synthesis and Characterization. The heteroleptic Ir(III)
0.2 mM RuPE, and 0.1 M BIH. The gaseous products that evolved in
∧
∧
+
∧
complex, [Ir(C N) (N N)] (C N = 1-phenylisoquinoline (piq);
2
the overhead space of the cell were identified by GC (7890B GC
equipped with a TCD detector) using a SUPELCO Carboxen 1010
PLOT fused silica capillary column. The liquid phase of the irradiated
samples was subjected to HPLC analysis using a Waters 515 pump, a
Waters 486 UV detector operated at 210 nm, an RSpak KC-811
column (Shodex), and 0.05 M H PO aqueous solution eluent.
∧
4 8
N N
(
=
4, 4′-dimethyl-2, 2′-bipyridine),
4, 4′-bis-
4
5
49
diethoxyphosphorylmethyl)-2,2′-bipyridine, [Ru(CO) Cl ] ,
2
2 n
50
and sacrificial electron donor (BIH) were prepared according to
methods reported in previous work. Two types of monobipyridyl
Ru(II) complexes (RuPE and RuP) were prepared by modifying
47,49
synthetic protocols described by previous reports,
the details of
3
4
Electrochemical Measurements. The cyclic voltammetry (CV)
experiment was performed in distilled, Ar-degassed DMF containing 1
mM RuPE and 0.1 M tetrabutylammonium perchlorate (TBAP) at
room temperature using an electrochemical analyzer (CH Instru-
ments, CHI660e). Glassy carbon (diameter 1.6 mm), platinum wire,
and saturated calomel electrode (SCE) were used as the working,
counter, and reference electrodes, respectively.
Operando UV−vis Spectroscopy for Identification of Ru−Ru
Polymerization. The absorption spectra of Ru polymer (Figure 2c)
were monitored at 800 nm (λdet of Ru polymer) with a bandwidth of 1
nm on a Scinco S-3150 spectrometer operated at an averaged
sampling time of 3 s. Polymeric Ru complex was generated during
photoirradiation (>495 nm) of 4 mL of Ar-purged DMF/TEOA
mixed solvent (16.7 vol % TEOA) containing 100 μM RuPE, 100 μM
IrPS, and 0.1 M BIH.
which are described below (see Scheme 3 and the Experimental
Section).
trans(Cl)-[Ru(4,4′-bis(diethoxyphosphorylmethyl)-2,2′-
bipyridine)(CO) Cl ] (RuPE). An ethanol solution (30 mL)
2
2
containing a mixture of 4,4′-bis(diethoxyphosphorylmethyl)-2,2′-
bipyridine (0.260 g, 0.570 mmol) and [Ru(CO) Cl ] (0.100 g,
2
2 n
0.438 mmol) was refluxed for 8 h under a nitrogen atmosphere and
then cooled to room temperature. After cooling to room temperature,
the solvent was evaporated under reduced pressure. The remaining
solid was dried in vacuo. The crude product obtained was purified by
silica gel chromatography using dichloromethane/methanol (20:1 v/
v) as eluent to give RuPE as a pale yellow solid. Yield 36% (0.108 g).
1
H NMR (300 MHz, CHCl -d) δ 9.08 (d, J = 5.7 Hz, 2H), 8.26 (s,
3
2
4
H), 7.57 (d, J = 5.7 Hz, 2H), 4.13 (m, 8H), 3.33 (d, J = 22.8 Hz,
H), 1.32 (t, J = 6.6 Hz, 12H). ESI-MS (m/z): Calcd for
−
C H Cl N O P Ru [M]: 683.9898. Found [M − H] : 682.9327.
22
30
2
2
8 2
AQY Measurement. The apparent quantum yields (AQYs) for
trans(Cl)-[Ru(4,4′-bis(dihydroxyphosphorylmethyl)-2,2′-
CO/formate production (ΦCO/formate) were determined for the
bipyridine)(CO) Cl ] (RuP). Bromotrimethylsilane (TMSBr) (6.9
2
2
heterobinary system (IrPS+ TiO /RuP). A band-pass filter with
2
mL, 52.6 mmol) was added dropwise to a dry CHCl solution (30
3
3
95−405, 435−445, 495−505, and 595−605 nm passthrough
mL) containing a mixture of RuPE (0.500 g, 0.731 mmol). The
reaction mixture was refluxed for 24 h. After cooling to room
temperature, methanol (17 mL) was added, and the reaction was
stirred for an additional 3 h. The yellow solid precipitated was
collected by filtration. After evaporation under reduced pressure, the
remaining solid was recrystallized from boiling methanol to give the
frequencies was used to isolate the emission light of a high-pressure
Xenon Arc lamp (450 W, model 6279NS, Ozone Free, Newport
Corporation), and the incident light flux was measured using a 0.20 M
5
3
−
ferrioxalate actinometer solution. The AQYs of CO/HCOO
formation (Φproduct) for the heterobinary hybrid and homogeneous
systems were measured in a linear time−conversion region, according
to eq 1.
1
product (RuP) as a yellow solid. Yield 65% (0.270 g). H NMR (300
MHz, DMSO-d ) δ 9.11 (d, J = 4.5 Hz, 2H), 8.56 (s, 2H), 7.70 (d, J =
6
4
.5 Hz, 2H), 3.28 (d, J = 22.2 Hz, 4H). ESI-MS (m/z): Calcd for
−
C H Cl N O P Ru [M]: 571.8646. Found [M − H] : 570.9200.
Crystal Structure Determination. Orange crystals of RuPE
were obtained from a CH Cl /n-hexane solution, sealed in glass
14
14
2
2
8
2
AQY or QY (%)
−
amount of CO/HCOO generated per unit time
2
2
=
× 100
capillaries under argon, and mounted on the diffractometer. The
preliminary examination and data collection were performed on a
Bruker SMART CCD X-ray diffractometer equipped with a sealed-
tube X-ray source (50 kV × 30 mA) using graphite-monochromated
Mo Kα radiation (λ = 0.71073 Å). The preliminary unit cell constants
were determined using a set of 45 narrow-frame (0.3° in ω) scans.
The double-pass method of scanning was used to exclude noise. The
collected frames were integrated using an orientation matrix
determined from the narrow-frame scans. The SMART software
package was used for data collection, and SAINT was used for frame
number of incident photons per unit time
(1)
In Situ FTIR Spectroscopy. A homemade in situ FTIR
spectroscopy tool was designed and fabricated for analyzing chemical
2
47
parts specialized for this study. Three mirror reflectance accessories
were put in the Nicolet 6700 FTIR spectrometer (Thermo Electron
Corporation). After the PTFE gasket-type ring was placed in the cell
51
integration. The final cell constants were determined through global
refinement of the xyz centroids of the reflections harvested from the
entire data set. Structure solution and refinement were performed
base body, a CaF window was inserted, and a Teflon spacer was
2
positioned on the CaF window. To carry out the in situ FTIR study
2
in an environment similar to the actual photolysis conditions of the
52
using the SHELXTL-PLUS software package. Crystallographic data
heterobinary system, a mesoporous TiO film was deposited on a
2
CaF plate and then sequentially treated with solutions of RuP for
2
immobilization of the component on the TiO film. The composite
2
plate was set at the center of the active cell of the in situ FTIR tool.
After the DMF or mixed DMF/TEOA solution (16.7 vol % TEOA)
Photocatalytic CO -to-CO Conversion. The hybrid catalyst
2
(
TiO /RuP) was prepared by anchoring of RuP on TiO particles as
2
2
45,47
containing 0.50 mM IrPS and 0.1 M BIH was purged with CO gas in
described in our previous papers.
Suspensions of 10 mg of TiO2/
2
the dark for 30 min, 0.05 mL of the purged solution was injected into
IR peaks under LED irradiation (>495 nm), were traced over time
(0−30 min).
RuP particles (0.025−0.6 μmol on 10 mg TiO ) in 3.0 mL of DMF or
2
a mixed DMF/TEOA solution (16.7 vol % TEOA) containing 0.01−
1
.0 mM IrPS and 0.10 M BIH were placed in a Pyrex cell (1.0 cm pass
length; 12.8 mL total volume), bubbled with CO for 30 min, and
2
sealed with a septum. A series of samples was set on a homemade
1
0238
Inorg. Chem. 2021, 60, 10235−10248
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