The Heteroleptic Cu(I) Photosensitizer-Containing 3,8-Disubstituted Phenanthroline: Synthesis, Photophysical Properties and Photocatalytic Hydrogen Evolution from Water

Article abstract of DOI:10.1002/ejic.202000648

Four novel heteroleptic Cu(I) photosensitizers with 3,8-diaryl-2,9-diisopropyl-1,10-phenanthroline derivatives as electron-donating bidentate N-ligands have been designed and synthesized. The metal copper complexes are studied in light-driven water reduct

Full text of DOI:10.1002/ejic.202000648

European Journal of Inorganic Chemistry
Accepted Article
Title: The heteroleptic Cu(I) photosensitizers containing 3,8-
disubstituted phenanthroline: Synthesis, photophysical properties
and photocatalytic hydrogen generation from water
Authors: Liang-xuan Xu, Tian-qi Wang, Xue-Fen Liu, Hao Chen, Chun-
Jiang Wei, Dan-Dan Xu, Feng Chen, Yang Li, and Shu-Ping
Luo
This manuscript has been accepted after peer review and appears as an
Accepted Article online prior to editing, proofing, and formal publication
of the final Version of Record (VoR). This work is currently citable by
using the Digital Object Identifier (DOI) given below. The VoR will be
published online in Early View as soon as possible and may be different
to this Accepted Article as a result of editing. Readers should obtain
the VoR from the journal website shown below when it is published
to ensure accuracy of information. The authors are responsible for the
content of this Accepted Article.
To be cited as: Eur. J. Inorg. Chem. 10.1002/ejic.202000648
Link to VoR: https://doi.org/10.1002/ejic.202000648
0
1/2020

European Journal of Inorganic Chemistry
10.1002/ejic.202000648
FULL PAPER
The heteroleptic Cu(I) photosensitizers containing 3,8-
disubstituted phenanthroline: Synthesis, photophysical
properties and photocatalytic hydrogen evolution from water
Liang-Xuan Xu+[a], Tian-Qi Wang+[a], Xue-Fen Liu , Hao Chen , Chun-Jiang Wei , Dan-Dan Xu ,
[b]
[a]
[a]
[a]
[a]
[a]
[a]
Feng Chen , Yang Li , Shu-Ping Luo*
[
a]
b]
Mr, Liang-Xuan Xu, Mr, Tian-Qi Wang, Dr. Hao Chen, Mr, Chun-Jiang Wei, Mr. Dan-Dan Xu, Mr, Feng Chen, Mr, Yang Li, Prof. Shu-Ping Luo
State Key Laboratory Breeding Base of Green Chemistry-Synthesis Technology
Zhejiang University of Technology, Hangzhou China, 310014
E-mail: luoshuping@zjut.edu.cn
Dr. Xue-Fen Liu
Qiangjiang College
[
[
Hangzhou Normal University, Hangzhou, China, 310012
+] These authors contributed equally to this work.
Abstract: Four novel heteroleptic Cu(I) photosensitizers with
,8-diaryl-2,9-diisopropyl-1,10-phenanthroline derivatives as
photosensitizers for the noble-metal-free water reduction
system.[10] The structure-activity relationship of copper
photosensitizers and the function of N-ligands and P-ligands
have been mostly investigated. In the previous research works
of phenanthrolines as N-ligands in heteroleptic copper(I)
complexes, the substituent groups at 4,7- or 2,9-sites of
phenanthroline have been synthesized and modified, then been
successfully applied in copper photosensitizers to produce
hydrogen in light-driven water reduction.[11] The electron-
donating substituent groups at 4,7- or 2,9-sites of phenanthroline
were both more useful to increase photosensitization activity of
corresponding copper complexes than electron-withdrawing
3
electron-donating bidentate N-ligands were designed and
synthesized. The metal copper complexes were studied in light-
driven water reduction system. The substituent effect at the 3,8-
positions of N-ligands impacting on photosensitive activity and
photoelectric chemical properties were explored and discussed.
Surprisingly, with the enhancement of electron-donating capacity of
substituent groups at 3,8-sites of 1,10-phenanthroline, the
photosensitive activity of photosensitizer linearly increased, and
turnover numbers (TON) of photocatalytic performance up to 817
was reached combining with water reduction catalyst (WRC),
Fe
3
(CO)12. The photocatalytic performance of these photosensitizers
increased compared to 2,9-diispropyl-1,10-
substituent groups.[12] The [Cu(xantphos)(3,8-Br
phen)][PF ]
2 6
dramatically
compound exhibited yellow emission with photoluminescence
phenanthroline complex (TON=89). Moreover, the introduction of
methoxy substituent to copper complexes, which could increase the
quantum yield of up to 21% for it with an excited state lifetime τ
1/2=8.4 µs.[
13]
Therefore, the photocatalytic activity of
] compound should be improved by modifying
fluorescence lifetimes (τmax=209 ns) and promote hydrogen evolution. [Cu(PˆP)(NˆN)][PF
6
the 3,8-sites of phenanthroline. In view of this, whether this
regularity can be confirmed at 3,8-sites of phenanthroline is of
interest to us. Herein, the 3,8-sites of linear phenanthroline were
modified by a series of aryl groups, which as novel N-ligands for
copper photosensitizers were applied in light-driven water
reduction system. The photoelectric chemical properties of the
synthesized photosensitizers were all discussed in detail.
Introduction
The burning of unsustainable fossil fuels is causing rising
environmental pollution and emitting the largest greenhouse
gases in modern society.[1] Their contribution to environmental
disruption has irritated the development of alternative and more
continuable energy carriers such as hydrogen. Hydrogen
possesses abundant global reserves and high combustion
1. Results and discussion
heat.[2] Due attention should be given to the methods of
1
.1. Synthesis and structure
hydrogen generation such as water electrolysis,[
3]
coal
gasification,[ heavy oil and light-driven water splitting and so
on. Water splitting is a benign and sustainable strategy because
only water and light are consumed and no carbon emission
occurs.
4]
[5]
The synthetic route of 3,8-diaryl-1,10-phenanthroline derivatives
was shown in Scheme 1. The synthesis process started with the
Suzuki
cross-coupling
reaction
of
3,8-dibromo-1,10-
phenanthroline in mixed solution (VTHF:VEtOH:VH2O=3:3:1) under
nitrogen atmosphere.[ Then the compounds L1-L4 (N-ligands)
were synthesized by the Nucleophilic addition reaction of
isopropyl lithium to the synthesized 2a-2d. The metal copper
complexes (CuPS 1-4) were achieved by In-situ coordination
To successfully realize the light-driven water splitting reaction,
photosensitizer is regarded as a key component due to it
absorbs the light energy and transfers to the catalyst. For the
last few decades, the research of noble-metal photosensitizers,
such as ruthenium,[6] rhodium,[7] platinum[8] and iridium[9] have
much enhanced the efficiency of hydrogen production by light-
driven water reduction. Since 2012, our group developed a
series of heteroleptic copper(I) complexes as efficient
14]
reaction of N-ligands, P-ligands and Cu(MeCN)
dichloromethane solution.
4
PF
6
in
1
This article is protected by copyright. All rights reserved.

European Journal of Inorganic Chemistry
10.1002/ejic.202000648
FULL PAPER
Scheme 1. The synthetic route of N-ligands and CuPSs.
1
.2. Photophysical properties
The photophysical properties of copper complexes were
recorded using UV-vis absorption and photoluminescence
spectra in tetrahydrofuran solvent in Figure 1. The main data of
the photophysical properties of CuPS 1-4 were listed in Table 1.
Compared to bidentate N-ligand L2, the absorption band
around 390 nm was the typical characteristic absorption band
of copper-based photosensitizer in the visible region, and the
characteristic absorption band was corresponding to a metal-to-
ligand charge-transfer (MLCT) transition.[15] The fluorescence
spectra of four Cu(I) complexes were at 520-555 nm. With the
enhancement of electron-donating capacity of substituent
groups at 3,8-sites of 1,10-phenanthroline, the fluorescence
emission wavelengths of Cu(I) complexes were red-shifted. The
CuPS 4 showed the highest molar absorption coefficient
−1
−1
(
ε=2563 M ·cm ), highest quantum yield (PLQY=8.2%) and
Figure 1. Absorption (left line) and emission (right line) spectra for CuPS 1-4.
Measurements were carried out in THF solution at room temperature.
longest lifetime (τ=221 ns). This was probably a result of the
strong electron-donating group, methoxy group, which made
the cloud density disperse, and the energy of the system then
decreased.[16] The methoxy-containing complexes clearly
demonstrated the existence of higher quantum yields and
longer excitation lifetimes, which might improve the
photocatalytic activities of Cu(I) complexes in light-driven water
reduction
system.
2
This article is protected by copyright. All rights reserved.

European Journal of Inorganic Chemistry
10.1002/ejic.202000648
FULL PAPER
Table 1. Photophysical and electrochemical properties of the Cu(I) complexes CuPS 1-4.
Absorption [a] Emission [a]
λmax
Eox [c]
(V)
Ered[c]
(V)
Entry
Complex
PLQY [b]
τ (ns)
ε
λmax
(nm)
(M−1·cm−1)
2046
(nm)
(%)
1
2
3
4
CuPS 1
CuPS 2
CuPS 3
CuPS 4
384
372
381
374
525
552
536
558
5.1
+1.49
+1.42
+1.43
+1.38
-1.69
-1.70
-1.75
-1.73
201
209
186
221
2154
1709
2563
7.3
4.1
8.2
[
a] Absorption and emission spectra were measured in THF solution at room temperature. [b] Measured with respect to quinine sulfate (1
N, H SO ) as standard (PLQY=54.6%). [c] Eletrochemical measurement was performed at oxygen free condition in acetonitrile vs. Fc/Fc+
2
4
and the redox events were not reversible.
We performed Stern-Volmer quenching study in order to
establish the quenching mode of the excited state of the PS in
Figure 2 and Figure 3. The quenching of the excited state of PS
could either be an oxidative quenching by the catalyst
electrochemical properties to be further understood in Figure 4.
In the complete cyclic voltammetry system, the entire process
was a single electron reduction process. The irreversible
oxidation potential at -0.28 V was mostly attributed to the
oxidation of Cu / Cu . By comparing the four complexes, it was
discovered that the different functional groups at 3,8-positions
of phenanthroline had minimal effect on the redox potential of
copper complexes, which might have been because of the
overall skeleton of the copper complexes determined the
approximate value of the redox potential.
I
II
Fe
3
(CO)12 or a reductive quenching by single electron transfer
from TEA. In fact, we discovered that PS was quenched by
7
TEA with a rate constant (k
q
) of 3.24×10 (Figure 3a). With an
increasing concentration of Fe
3
(CO)12, the luminescence ratio
of PS was totally unaffected (Figure 3b). The quenching
mechanism of PS was consistent with our previous works,
which exhibited reductive quenching by TEA.
#
###
##
a
a
4
2
0
a10
7
0.00 mM
0.05 mM
0.10 mM
0.15mM
0.20 mM
4×
10
3.
2
=
Kq
8
6
4
0
.0
0.1
0.2
0.3
0.4
c/M
b 2
2
0
0
0
.00
0.05
0.10
c/mM
0.15
0.20
5
00
600
700
Figure 3. Stern-Volmer plots. The concentration of CuPS 1 in THF was
.0∙10-5 M; quenching reagents: TEA (a); Fe (CO) (b).
7
Wavelength(nm)
3
12
1
0
b
0
.0mM
00mM
00mM
1
2
8
300mM
400mM
6
4
2
0
5
00
550
600
650
700
750
Wavelength(nm)
Figure 2. Photoluminescence spectra of a 7.0∙10-5 M CuPS 1 solution in
THF containing different concentrations of Fe CO12 (a) and TEA (b).
3
Figure 4. Cyclic voltammetry of different copper photosensitizers
1
.3. Electrochemical studies
The cyclic voltammetry of different copper photosensitizers was
measured in acetonitrile under nitrogen, in order for the
3
This article is protected by copyright. All rights reserved.

European Journal of Inorganic Chemistry
10.1002/ejic.202000648
FULL PAPER
1
.4. Photocatalytic hydrogen production
The heteroleptic copper complexes were prepared in situ and
the water splitting reduction reaction was carried out in an
argon atmosphere. Initially, CuPS 1 was selected as model PS
and TEA as SR in light-driven water reduction system. The
results were shown in Table 2. Pd, Ni and Co catalysts, which
were active applying metal-based PS, only displayed poor
activities (Table 2, entries 1-4). Surprisingly, the highest
photocatalytic performance of CuPS 1 was obtained with
0
.5mM 299TON
nCuPS1=0.35mM
300
0
.25mM 275TON
1
mM 238TON
2
1
00
00
0
2mM 151TON
0.125mM 121TON
Fe
TON) of 299. Next, the concentration of Fe
changed in Figure 5. Interestingly, the changes in the TON of
3
(CO)12 (Table 2, entry 5), which gave a turnover number
(
3
(CO)12 was
CuPS
1
showed
a
parabolic
trend
with
0
5
10
Time/h
a maximum TON of 299 when the concentration of Fe
3
(CO)12
increased from 0.125 mM to 2.0 mM. Referring to previous
works, the optimal system conditions were established to be
Figure 5. Photocatalytic hydrogen production (TON) as a function of time
CuPS
(3.5
μmol),
Fe
3
(CO)12
(5.0
μmol)
and
from a reaction solution (10 mL) under Xe-light irradiation in the presence of
CuPS
3
1 (3.5 μmol) and with various concentrations of Fe (CO)12.
VTHF:VTEA:VH2O=4:3:1 in this work (see the Supporting
Information for more details).
Table 2. Results for the photocatalytic hydrogen evolution using CuPS 1
in the presence of TEA as SR. Screening of WRC. [a]
[b]
TON
H
Entry
WRC
Time(h)
Vol.H
2
(mL)
1 [c]
2
PdCl
+PPh
6
8
8.6
4.8
201
112
187
159
299
2
3
3
Co(bpy) Cl
2
3
NiCl
PdCl
Fe (CO)12
2
3
(PPh )
2
7
8.0
4
2
5
6.8
5
3
10
12.8
[
a] Reaction conditions: CuPS 1 (3.5 μmol), catalyst (5 μmol), 10 mL
THF/TEA/H O (4:3:1), 25 °C, Xe-light irradiation (output 5 W), without
2
light filter, gas evolution quantitatively measured via automatic gas
burettes, gas analysis via GC. All given values are the averages of at
Figure 6. The TON of hydrogen production of system with CuPS 1 was
studied under different wavelengths.
least two experiments. [b] TON
1:1).
H H 2 3
= n /nCu . [c] WRC (5 μmol , PdCl /PPh
=
three complexes CuPS 1-3, which were applied in light-driven
water reduction system. With the enhancement of electron-
donating capacity of substituents, the photosensitive activity of
photosensitizer increased linearly. Further, CuPS 4 having
stronger electron-donating capacity was synthesized according
to CuPS 2. The CuPS 4 showed highest photocatalytic activity
with 817 TON (Table 3, entry 4). Noticeably, by means of data
of hydrogen evolution, it was established that the introduction of
electron-donating substituents contributed most significantly to
the photocatalytic activities of these complexes. Compared with
XT-CuPS, the modification at 3,8-positions of phenanthroline
greatly improved the photocatalytic activity of the complexes
Table 3. Results for the photocatalytic water reduction using CuPS in the
(CO)12 as WRC and TEA as SR. [
a]
presence of Fe
3
Time
Vol.H
(mL)
2
[b]
TON
H
Entry
Complex
(h)
1
2
3
4
CuPS 1
CuPS 2
CuPS 3
CuPS 4
10
18
15
20
12.8
24.1
18.6
35
299
563
435
817
i
[
Cu(Xantphos)(2,9-Pr
phen)]PF
2
5
3
3.8
89
6
[
a] Reaction conditions: CuPS (3.5 μmol), [Fe
3
(CO)12] (5 μmol), 10 mL
THF/TEA/H
2
O (4:3:1), 25°C, Xe-light irradiation (output 5 W), without light
filter, gas evolution quantitatively measured via automatic gas burettes, gas
analysis via GC. All given values are the averages of at least two
experiments. The results of each same experiment differ between 1 and
(
Table 3, entry 5). It could be noted that this strategy was likely
to promote a more stable photocatalytic H production system,
2
17%. [b] TON
H
= nH /nCu
suggesting superior performances as a PS.
Under the exploring conditions, the CuPS 1 (3.5 µmol) or
Fe (CO)12 (5.0 µmol) were added to reconstruct the
photocatalytic H production system after 20 h (Fig. S50). The
most effective wavelength was explored under Xe-light
irradiation, and the data showed that the incident photon to
hydrogen efficiency (IPE) was higher at 400 nm with the
maximum of 2.61% in Figure 6 and Table S3.
3
2
Conclusion
In summary, the heteroleptic copper photosensitizers with linear
bidentate N-ligands were synthesized and applied to
photocatalytic proton reduction using Fe
3
(CO)12 as a water
These novel copper complexes had resulted in significant
hydrogen production in Table 3. Initially, we only synthesized
reduction catalyst for the first time. The complex of cationic Cu
4
This article is protected by copyright. All rights reserved.

European Journal of Inorganic Chemistry
10.1002/ejic.202000648
FULL PAPER
(s, 2H), 7.90 (s, 2H), 6.93 (s, 4H), 3.98 (s, 12H), 3.92 (s, 6H). 13C NMR
with N-ligand L4 was used in visible-light-driven hydrogen
evolution, which showed highly effective photosensitizer to
display turnover numbers (TON) up to 817. The new
photosensitizers introduced herein were fully characterized by
using photophysical technique and cyclic voltammetry, and
exhibited the typical MLCT transition of copper complex.
Notably, CuPS 4 displayed the best photocatalytic performance
to generate hydrogen from water due to the longer lifetimes of
the excited states and higher stability towards atmospheric
conditions. Interestingly, the modification at 3,8-sites of
phenanthroline was positive to steady steric bulk of copper
complex, and electron-donating groups at 3,8-sites markedly
(125 MHz, CDCl
3
) δ (ppm): 153.59, 148.89, 144.08, 135.85, 133.36,
1
28.28, 126.91, 104.60, 60.69, 56.09. ESI-MS: m/z: calcd for
+
+
30 28 6 2
C H O N : 513.2 [M+H] ; found:513.2 [M+H] .
Synthesis of N ligand. Isopropyl lithium (5 mmol) was added dropwise
slowly to a solution of N ligand precursor (1 mmol) in dry ether (10 mL)
at 0°C for 10 min, which was stirred at 0 ℃ for 30 minutes, then was
transferred to room temperature and stirred for 24 hours. The dark red
2
reaction mixture was quenched by slow addition of H O (5 mL). It was
2 2
then extracted with CH Cl (4 x 15 mL), concentrated and dried in vacuo.
The crude product was purified by column chromatography on silica gel
to afford the products.
2
increased the output of H generation. The results of this work
will provide a reference for the design and development of new
efficient cuprous complex.
3
,8-diphenyl-2,9-diisopropyl-1,10-phenanthroline(L1).
(0.129
g,
1
31%) H NMR (500 MHz, CDCl
3
) δ (ppm): 8.02 (s, 2H), 7.74 (d, J = 7.6
Hz, 2H), 7.51 (q, J = 7.5 Hz, 4H), 7.48 (d, J = 7.3 Hz, 4H), 7.46 (q, J =
.6 Hz, 2H), 3.34-3.36 (m, 2H), 1.49 (m, 12H); 13C NMR (125 MHz,
CDCl ) δ(ppm): 164.84, 140.22, 136.51, 136.27, 129.37, 128.37, 127.48,
126.82, 125.71, 32.71, 22.69. ESI-MS: m/z: calcd for C30 : 417.2
7
3
Experimental Section
28 2
H N
+
+
[M+H] ; found: 417.2 [M+H] .
All chemicals were purchased from commercial sources and used
without further purification. Solvents were freshly distilled over
3,8-bis(4-methoxyphenyl)-2,9-diisopropyl-1,10-phenanthroline(L2).
1
13
1
appropriate drying reagents. H NMR and C NMR spectra were
recorded on Bruker Avance III operated at 500 MHz and 125 MHz
respectively. The samples used for NMR measurement were obtained
after the crystalline products of the studied com. Absorption spectra
were recorded using a Specord 50 (Analytic Jena) UV-vis spectrometer.
(0.133 g, 28%) H NMR (500 MHz, CDCl
3
) δ (ppm): 8.05 (s, 2H), 7.90 (s,
2H), 7.38 (d, J = 7.6 Hz, 4H), 7.04 (d, J = 7.7 Hz, 4H), 3.92 (s, 6H),
3.55-3.60 (m, 2H), 1.47-1.49 (m, 12H); 13C NMR (125 MHz, CDCl
3
)
δ(ppm): 165.08, 159.06, 144.63, 136.50, 132.30, 130.45, 126.80,
125.61, 113.80, 55.35, 32.64, 22.68. ESI-MS: m/z: calcd for
+
+
Luminescence spectra were measured with
FluoroMax-4P, Horiba Scientific).
a
spectrofluorometer
32 32 2 2
C H O N : 477.2 [M+H] ; found: 477.3 [M+H] .
(
3
,8-bis(3,5-dimethylphenyl)-2,9-diisopropyl-1,10-phenanthroline(L3).
1
Synthesis of Ligands: Bidentate N-ligands were synthesized by
multistep reaction as shown in Scheme 1.
(0.165 g, 35%) H NMR (500 MHz, CDCl
3
) δ (ppm): 7.98 (d, J = 7.7 Hz,
2H), 7.71 (d, J = 7.5 Hz 2H), 7.72 (s, 4H), 7.10 (s, 2H), 3.55-3.61 (m,
H), 2.45 (s, 12H), 1.49-1.51 (m, 12H); 13C NMR (125 MHz, CDCl
)
3
2
δ(ppm): 164.86, 144.66, 140.18, 137.80, 136.35, 129.04, 127.13,
Synthesis of N-ligand precursor. A mixture of Na
2.25 mmol), Pd(PPh (0.8667 g, 0.75 mmol), 3,8-dibromo-1,10-
phenanthroline (1.69 g, 5 mmol) and 12.5 mmol alkyl phenylboric acid in
the mixed solution of THF/EtOH/H O (35 mL) was stirred under an
2 3
CO (1.3249 g,
+
1
26.80, 125.60. ESI-MS: m/z: calcd for C34
H
36
N
2
: 473.3 [M+H] ; found:
1
3 4
)
4
73.3 [M+H]+.
2
argon atmosphere and then refluxed for 18 h. The reaction was
quenched with water (5 mL). The reaction mixture was then extracted
3,8-bis(3,4,5-trimethoxyphenyl)-2,9-diisopropyl-1,10-
phenanthroline(L4). (0.089 g, 15%) 1H NMR (500 MHz, CDCl
3
) δ
with CH
2
Cl
2
(4 x 15 mL), concentrated and dried in vacuo. The crude
(ppm): 8.01 (d, J = 7.3 Hz, 2H), 7.72 (d, J = 7.6 Hz, 2H), 6.64 (s, 4H),
product was purified by column chromatography on silica gel to afford
the product.
3.96 (s, 6H), 3.92 (s, 12H), 3.58 (s, 2H), 1.51 (s, 12H).13C NMR (125
MHz, CDCl
3
) δ (ppm): 164.76, 153.01, 144.80, 137.44, 136.06, 135.70,
1
26.60, 125.63, 106.57, 60.93, 56.22, 32.71, 22.90. ESI-MS: m/z: calcd
+
+
,8-diphenyl-1,10-phenanthroline(2a). (0.964 g, 58%) 1H NMR (500
MHz, CDCl ) δ (ppm): 9.40 (d, J = 8.2 Hz, 2H), 8.34 (d, J = 7.5 Hz, 2H),
.85 (d, J = 7.4 Hz, 2H), 7.73 (m, 4H), 7.65 (m, 2H), 7.42-7.48 (m, 4H);
) δ (ppm): 152.31, 145.12, 136.45, 135.32,
32.46, 129.27, 128.71, 127.65, 127.52. ESI-MS: m/z: calcd for
40 6 2
for C36H O N : 596.29 [M+H] ; found: 596.3 [M+H] .
3
3
7
2,9-diisopropyl-1,10-phenanthroline. (0.726 g, 55%) 1H NMR (400
MHz, CDCl ) δ 8.13 (d, J = 8.3 Hz, 2H), 7.67 (s, 2H), 7.53 (d, J = 8.3 Hz,
2H), 3.57 (d, J = 6.9 Hz, 2H), 1.47 (s, 12H). 13C NMR (101 MHz,
CDCl ) δ 167.86, 145.31, 136.42, 127.31, 125.47, 120.12, 37.30, 22.90.
1
3C NMR (125 MHz, CDCl
3
3
1
+
+
C
24
H
16
N
2
: 333.1 [M+H] ; found: 333.1 [M+H] .
3
3
,8-bis(4-methoxyphenyl)-1,10-phenanthroline(2b). (1.472 g, 75%)
1
H NMR (500 MHz, CDCl
3
) δ (ppm): 9.38 (s, 2H), 8.28 (s, 2H), 7.79 (s,
H), 7.68-7.71 (d, J = 7.6 Hz, 4H), 7.05 (d, J = 7.3 Hz, 4H), 3.87(s,6H);
) δ(ppm): 159.95, 149.08, 144.40, 135.16,
32.53, 129.80, 128.54, 126.96, 114.67, 55.37. ESI-MS: m/z: calcd for
In-situ synthesis of copper(I) complexes. The corresponding
copper(I) complexes were obtained by in-situ coordination reaction
according to the previous work. N^N ligand (1 mmol), P^P ligand
2
1
3C NMR(125 MHz, CDCl
3
1
Xanphos (1 mmol) and Cu(MeCN)
4
PF
6
(1 mmol) were added to CH
2 2
Cl
+
+
C
26
H
20 2
O N
2
: 393.2 [M+H] ; found: 393.2 [M+H] .
(10 mL). The reaction mixture was stirred for 2
hours at room
temperature and then concentrated under reduced pressure. It was
washed thoroughly with n-hexane and dried in vacuo. The copper(I)
complexes could be directly used in light-driven water reduction system.
3
,8-bis(3,5-dimethylphenyl)-1,10-phenanthroline(2c). (0.795 g, 47%)
1
3
H NMR (500 MHz, CDCl ) δ (ppm): 9.38-9.41 (s, 2H), 8.34 (s, 2H), 7.82
(
s, 2H), 7.35-7.37 (s, 4H), 7.10 (s, 2H), 2.24 (s,12H); 13C NMR(125 MHz,
CDCl
3
) δ(ppm): 151.50, 144.50, 138.80, 136.31, 133.30, 132.02, 130.14,
CuPS 1 1H NMR (400 MHz, CDCl
) δ 8.21 (s, 2H), 8.00 (s, 2H), 7.46
3
1
29.49, 127.00, 125.31, 21.40. ESI-MS: m/z: calcd for C28
H
24
N
2
: 389.2
(dd, J = 12.4, 8.1 Hz, 14H), 7.35 (d, J = 6.0 Hz, 8H), 7.19 (dd, J = 8.4,
4.8 Hz, 6H), 7.05 (t, J = 7.4 Hz, 8H), 3.27 – 3.16 (m, 2H), 1.96 (s, 6H),
+
+
[M+H] ; found: 389.2 [M+H] .
0
1
.88 (d, J = 7.0 Hz, 12H). 13C NMR (101 MHz, CDCl
41.15, 140.74, 133.37, 133.30, 133.23, 133.04, 132.96, 130.08, 130.00,
3
) δ 164.61, 154.40,
3
,8-bis(3,4,5-trimethoxyphenyl)-1,10-phenanthroline(2d). (2.256 g,
1
128.86, 128.82, 128.78, 128.47, 128.42, 128.38, 127.77, 127.72, 126.58,
88%) H NMR (500 MHz, CDCl
3
) δ (ppm): 9.37 (d, J = 8.6 Hz, 2H), 8.37
5
This article is protected by copyright. All rights reserved.

European Journal of Inorganic Chemistry
10.1002/ejic.202000648
FULL PAPER
1
25.22, 36.04, 33.31, 23.30, 23.20, 21.45. 31P NMR (162 MHz, CDCl
3
) δ
+
-
11.89. ESI-MS: m/z: calcd for C69
H60CuN
2
OP
2
(M ): 1057.3471; found:
[1]
A. K. Karmaker, M. M. Rahman, M. A. Hossain, M. R. Ahmed, J Clean
Prod 2020, 244, 118645.
1057.3505.
[
2]
a) B. C. R. Ewan, R. W. K. Allen, Int J Hydrogen Energ 2005, 30, 809-
819; b) X. Yalan, F. Baizeng, A. Bonakdarpour, Z. Shichao, D. P.
CuPS 2 1H NMR (400 MHz, CDCl
3
) δ 7.97 (s, 2H), 7.83 (d, J = 8.7 Hz,
H), 7.75 – 7.40 (m, 12H), 7.24 (d, J = 3.4 Hz, 6H), 7.13 (d, J = 2.7 Hz,
H), 7.03 (s, 4H), 3.89 (s, 6H), 3.20 (p, J = 7.0 Hz, 2H), 1.96 (s, 6H),
.88 (d, J = 7.1 Hz, 12H). 13C NMR (101 MHz, CDCl
) δ 159.56, 154.40,
Wilkinson, Int
J Hydrogen Energ 2014, 39, 7859-7867; c) A.
2
4
0
1
1
1
Magnuson, M. Anderlund, O. Johansson, P. Lindblad, R. Lomoth, T.
Polivka, S. Ott, K. Stensjö, V. Sundström, L. Hammarström, Acc Chem
Res 2009, 42, 1899-1909.
3
41.48, 141.13, 138.21, 133.04, 132.35, 131.13, 130.32, 130.25, 130.05,
28.76, 128.35, 127.34, 127.14, 126.46, 126.15, 125.21, 121.10, 113.18,
13.12, 55.43, 55.37, 43.82, 43.75, 36.05, 33.31, 23.31, 23.21, 21.43.
[
3]
D. Guilbert, S. M. Collura, A. Scipioni, Int J Hydrogen Energ 2017, 42,
23966-23985.
3
1
[4]
[5]
G. J. Stiegel, M. Ramezan, Int J Coal Geol 2006, 65, 173-190.
K. K., Kasem, J Mater Sci Technol 2010.
P NMR (162 MHz, CDCl
3
) δ -12.10, -144.29. ESI-MS: m/z: calcd for
+
C
71
H
64CuN
O P
2 3 2
(M ): 1117.3683; found: 1117.3737.
[
6]
a) K. Kitamoto, M. Ogawa, G. Ajayakumar, S. Masaoka, K. Sakai,
Inorg Chem Front 2016, 3, 671-680; b) Kyoji, Kitamoto, Ken, Sakai,
Chem Commun 2016; c) B. Probst, M. Guttentag, A. Rodenberg, P.
Hamm, R. Alberto, Inorg. Chem. 2011, 50, 3404-3412.
1
CuPS 3 H NMR (400 MHz, CDCl
3
) δ 8.15 (s, 2H), 7.95 (s, 2H), 7.64 (d,
J = 7.3 Hz, 4H), 7.33 (s, 14H), 7.15 (d, J = 7.7 Hz, 14H), 3.23 – 3.16 (m,
H), 2.39 (s, 12H), 1.72 (s, 6H), 1.19 (t, J = 7.1 Hz, 12H). 13C NMR (101
MHz, CDCl ) δ 137.28, 133.93, 133.38, 133.30, 133.09, 130.36, 130.23,
30.06, 129.78, 129.72, 129.65, 128.81, 128.40, 127.87, 127.36, 127.15,
2
[
[
7]
8]
K. Yamauchi, S. Masaoka, K. Sakai, Dalton Trans 2011, 40, 12447-
3
12449.
1
1
2
a) K. Kitamoto, K. Sakai, Angew. Chem. Int. Ed. 2014, 53, 4618-4622;
b) K. Yamamoto, K. Kitamoto, K. Yamauchi, K. Sakai, Chem Commun
2015, 51, 14516-14519; c) H. N. Kagalwala, E. Gottlieb, G. Li, T. Li, R.
Jin, S. Bernhard, Inorg. Chem. 2013, 52, 9094-9101.
26.44, 125.19, 43.85, 36.03, 34.44, 33.33, 23.23, 22.75, 21.46, 21.38,
1.27, 21.22, 14.75. 3 P NMR (162 MHz, CDCl
1
3
) δ -12.16, -16.71. ESI-
(M ): 1113.4097; found: 1113.4152.
+
MS: m/z: calcd for C73
H
68CuN
2
OP
2
[
[
9]
a) H. Lv, Y. Gao, W. Guo, S. M. Lauinger, Y. Chi, J. Bacsa, K. P.
Sullivan, M. Wieliczko, D. G. Musaev, C. L. Hill, Inorg. Chem. 2016, 55,
CuPS 4 1H NMR (400 MHz, CDCl
.44 (m, 12H), 7.20 (d, J = 7.6 Hz, 8H), 7.15 (d, J = 7.4 Hz, 6H), 6.38 (d,
J = 4.6 Hz, 4H), 3.80 (s, 12H), 3.79 (s, 6H), 3.13 (dt, J = 13.1, 6.8 Hz,
H), 1.67 (s, 6H), 1.40 (s, 6H), 1.27 (d, J = 10.9 Hz, 6H). 13C NMR (101
MHz, CDCl ) δ 154.40, 152.49, 152.44, 133.95, 133.86, 133.78, 133.20,
31.49, 130.42, 129.95, 129.77, 128.83, 127.32, 126.60, 125.12, 121.16,
08.27, 108.24, 108.17, 108.16, 56.43, 43.81, 23.33, 21.63. 31P NMR
-12.12, -17.65. ESI-MS: m/z: calcd for
(M ): 1237.4105; found: 1237.4169.
3
) δ 8.23 (s, 2H), 7.97 (s, 2H), 7.91 –
7
6750-6758; b) Y. Yuan, Z. Yu, X. Liu, J. Cai, Z. Guan, Z.-G. Zou, Sci
Rep-UK 2014, 4, 4045; c) Q. Wu, H. Chen, D. Huang , L. Xia, X. Wang,
W. Lou, X. Wu, S. Luo, Chinese J Inorg Chem 2018, 34(002):270-276.
2
3
10] a) A. J. J. Lennox, S. Fischer, M. Jurrat, S. Luo, N. Rockstroh, H.
Junge, R. Ludwig, M. Beller, Chem. Eur. J. 2016, 22, 1233-1238; b) E.
Mejía, S. Luo, M. Karnahl, A. Friedrich, S. Tschierlei, A. E. Surkus, H.
Junge, S. Gladiali, S. Lochbrunner, M. Beller, Chem. Eur. J. 2013, 19,
1
1
3
(162 MHz, CDCl ) δ
+
C
75 2 7 2
H72CuN O P
15972-15978; c) M. Karnahl, E. Mejía, N. Rockstroh, S. Tschierlei, S.
Luo, K. Grabow, A. Kruth, V. Brüser, H. Junge, S. Lochbrunner, M.
Beller, ChemCatChem 2014, 6, 82-86.
2
,9-diispropyl-1,10-phenanthroline complex. 1H NMR (400 MHz,
CDCl ) δ 8.47 (d, J = 8.4 Hz, 2H), 8.29 (d, J = 8.5 Hz, 2H), 7.85 (d, J =
.7 Hz, 2H), 7.57 (dd, J = 18.9, 8.5 Hz, 4H), 7.20 (t, J = 7.7 Hz, 14H),
.81 (s, 4H), 6.68 (s, 4H), 3.69 (p, J = 6.7 Hz, 2H), 1.47 (s, 6H), 1.08 (d,
) δ 138.78, 138.42, 133.26,
33.19, 133.11, 132.92, 132.84, 132.76, 130.44, 130.08, 130.02, 129.78,
3
[
[
11] a) S. Luo, E. Mejía, A. Friedrich, A. Pazidis, H. Junge, A. E. Surkus, R.
Jackstell, S. Denurra, S. Gladiali, S. Lochbrunner, M. Beller, Angew.
Chem. Int. Ed. 2013, 52, 419-423; b) N. Chen, L. Xia, A. J. J. Lennox,
Y. Sun, H. Chen, H. Jin, H. Junge, Q. Wu, J. Jia, M. Beller, S. Luo,
Chem. Eur. J. 2017, 23, 3631-3636.
8
6
J = 6.8 Hz, 12H). 13C NMR (101 MHz, CDCl
3
1
1
1
28.84, 128.29, 127.35, 126.09, 125.25, 121.40, 121.28, 121.22, 121.18,
21.16, 40.69, 40.34, 36.15, 33.24, 23.80, 23.42, 22.21. 31P NMR (162
12] a) L. Xia, H. Chen, Q. Wu, X. Wang, W. Lou, B. Xu, S. Luo, Chinese J
Inorg Chem 2017; b) Z. Yu, H. Chen, A. J. J. Lennox, L. Yan, X. Liu, D.
Xu, F. Chen, L. Xu, Y. Li, Q. Wu, S. Luo, Dyes Pigments 2019, 162,
MHz, CDCl3) δ -11.85. ESI-MS: m/z: calcd for C57
05.2845; found: 905.2876.
H52CuN
2
OP2 (M+):
9
771-775.
[
[
[
13] I. Nohara, A. Keller, N. Tarassenko, A. Prescimone, E. C. Constable, C.
E. Housecroft, Inorganics 2020, 8, 4.
14] M. Mörtel, T. Lindner, A. Scheurer, F. W. Heinemann, M. M.
Khusniyarov, Inorg. Chem. 2020, 59, 2659-2666.
Acknowledgements
15] Y. Sun, H. Wang, N. Chen, A. J. J. Lennox, A. Friedrich, L. Xia, S.
Lochbrunner, H. Junge, M. Beller, S. Zhou, S. Luo, ChemCatChem
2016, 8, 2340-2344.
Financial support by the National Natural Science Foundation
of China (No. 21376222), the Natural Science Foundation of
Zhejiang Province (No. LY18B060011).
[16] P. Day, N. Sanders, J. Chem. Soc. A 1967, 1536-1541.
Keywords: Photosensitizer; Substituent effect; Photosensitive
activity; Hydrogen evolution
6
This article is protected by copyright. All rights reserved.

European Journal of Inorganic Chemistry
10.1002/ejic.202000648
FULL PAPER
Entry for the Table of Contents
Key Topic: Heteroleptic Cu(I) photosensitizer; Homogeneous catalysis.
Graphic abstract
The novel heteroleptic Cu(I) photosensitizers were synthesized by Suzuki cross-coupling, Nucleophilic substitution and In-situ
coordination reaction, and then used as photosensitizers to study hydrogen generation in photocatalytic water reduction.
Heteroleptic Cu(I) photosensitizer; Homogeneous catalysis.
7
This article is protected by copyright. All rights reserved.