Synthesis of heteroleptic phosphine-copper(i) complexes: Fluorescence sensing and catalytic properties

Article abstract of DOI:10.1039/d0nj06095j

Heteroleptic copper(i)-phosphine complexes have attracted considerable attention because of their diverse structures, and photophysical and catalytic properties. In this work, a series of heteroleptic diimine-diphosphine Cu(i) complexes (C1-C10) were synthesized quantitively using the designed bipyridine (L1-L4) and bidentate polyphosphine (L5-L8) as functional ligands. These mixed ligand-copper(i) complexes were fully characterized by 1H and 13C NMR spectroscopy, electrospray ionization mass spectrometry (ESI-MS) and elemental analysis. The detailed structures of complexes C1, C2, C5, C6, C9 and C10 were confirmed by single-crystal X-ray diffraction analysis. Moreover, these phosphine-Cu(i) complexes exhibited intense emissions either in the solid state or in solution under UV light excitation. The emissive complexes C1-C4 displayed highly sensitive luminescence sensing towards silver ions in a quenching fashion (turn-off). Furthermore, all the phosphine-protected copper(i) complexes exhibited high catalytic activity towards azide-alkyne cycloaddition (CuAAC) in water.

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Synthesis of heteroleptic phosphine–copper(I)
complexes: fluorescence sensing and catalytic
properties†
Cite this: DOI: 10.1039/d0nj06095j
Chen-Lin Luo,‡a Chu-Xing Hu,‡a Ping Shang,*a Guan-Zhao Wen,b Jia-Jun Zhu,a
Ya-Hui Xuan,a Bang-Lian Xia,a Yu-Chen Liu,a Zi-Hao Jiang,a Geng Dong,b
ae
Wei Zhang,c Liu-Cheng Gui*d and Xuan-Feng Jiang
*
Heteroleptic copper(I)–phosphine complexes have attracted considerable attention because of their
diverse structures, and photophysical and catalytic properties. In this work, a series of heteroleptic
diimine–diphosphine Cu(I) complexes (C1–C10) were synthesized quantitively using the designed bipyri-
dine (L1–L4) and bidentate polyphosphine (L5–L8) as functional ligands. These mixed ligand–copper(I)
complexes were fully characterized by 1H and 13C NMR spectroscopy, electrospray ionization mass
spectrometry (ESI-MS) and elemental analysis. The detailed structures of complexes C1, C2, C5, C6, C9
and C10 were confirmed by single-crystal X-ray diffraction analysis. Moreover, these phosphine–Cu(I)
complexes exhibited intense emissions either in the solid state or in solution under UV light excitation.
The emissive complexes C1–C4 displayed highly sensitive luminescence sensing towards silver ions in a
quenching fashion (turn-off). Furthermore, all the phosphine-protected copper(I) complexes exhibited
high catalytic activity towards azide–alkyne cycloaddition (CuAAC) in water.
Received 15th December 2020,
Accepted 1st April 2021
DOI: 10.1039/d0nj06095j
rsc.li/njc
so on. In these mixed-ligand cooperative coordination systems,
the photophysical properties and stability of copper(I) com-
Introduction
Cu(I) complexes have received extensive attention because of plexes can be effectively improved by subtle structural modifi-
their unusual structures and intriguing properties.1–6 Among cations and coordination mode change of chelating diimine or
them, heteroleptic diimine–diphosphine copper(I)-based com- phosphine ligands.17 Therefore, in the past two decades, many
plexes not only exhibited various structures including poly- efforts have been devoted to the development of stable hetero-
nuclear clusters,5–9 metallocycles,10 and cages,11 but also leptic Cu(I) complexes supported by mixed diimine–phosphine
displayed promising applications in the fields of long-lived ligands.1–8,18,19 In such a Cu(I)–phosphine coordination system,
excited materials,12 catalytic chemistry,13–15 medicine16 and the structural conformation and electron-donating ability of
diimine and phosphine ligands played a crucial role in achiev-
ing controlled synthesis and tunable properties of heteroleptic
a Key Laboratory of Green Preparation and Application for Functional Materials,
Cu(I) complexes.1–10
Ministry of Education, Hubei Key Laboratory of Polymer Science, School of
In this work, a series of novel diimine ligands (L1–L4) were
rationally designed and synthesized through multi-step reac-
Materials Science and Engineering, Hubei University, Wuhan, Hubei, 430062,
P. R. China. E-mail: pingshang02@126.com, xuanfengjiang@hubu.edu.cn
b School of Physics and Materials Science, Guangzhou University, GuangZhou,
tions at the bipyridine backbone (as shown in Scheme S1, ESI†).
Combined with bisphosphine ligands (L5, POP; L6, dppm; L7,
dppe; L8, dppp), ten heteroleptic diimine–diphosphine Cu(I)
complexes (C1–C10) were precisely synthesized in a single step
(Scheme 1). These well-defined copper(I) complexes were fully
characterized by 1H and 13C NMR spectroscopy and mass
spectrometry. The structural features of the mononuclear
complexes C1–C6 and dinuclear complexes C7–C10 were
also confirmed by X-ray single-crystal diffraction analysis.
Moreover, these phosphine–Cu(I) complexes exhibit good
photophysical properties either in the solid state or in solution.
The heteroleptic copper(I) complexes C1–C6 presented sensitive
510006, China
c Medical Informatics Research Center, Shantou University Medical College,
Shantou 515041, China
d State Key Laboratory for the Chemistry and Molecular Engineering of Medicinal
Resources, School of Chemistry & Pharmaceutical Sciences, Guangxi Normal
University, Guilin, Guangxi, 541004, P. R. China.
E-mail: guiliucheng2000@163.com
e Hubei Key Laboratory of Processing and Application of Catalytic materials,
Huanggang Normal University, Huanggang, Hubei, 438000, P. R. China
† Electronic supplementary information (ESI) available. CCDC 2050236–2050238,
2050240, 2070930 and 2070931. For ESI and crystallographic data in CIF or other
electronic format see DOI: 10.1039/d0nj06095j
‡ These authors contributed equally.
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Scheme 1 The synthesis routes of the heteroleptic phosphine–copper(I)
complexes C1–C10. The carton parts represent bipyridine and bispho-
sphine (green: bipyridine; purple: bisphosphine; blue ball: Cu+ atom).
luminescence sensing towards silver ions in a quenching
fashion (turn-off). Furthermore, all the phosphine-protected
copper(I) complexes exhibited good catalytic activity towards
azide–alkyne cycloaddition (CuAAC) performed in water.
Results and discussion
Synthesis of the ligands
Scheme 1 presents four new bipyridine and two common
bisphosphine ligands used in this work. The bipyridine ligands
(L1–L4) were synthesized using a method reported in previous
studies.16,17 Four bisphosphine ligands (L5–L8) were purchased
from a chemical company.
Fig. 1 1H NMR spectrum of C1ꢀBF4ꢁ in CDCl3 at room temperature (a)
and ESI-MS spectrum in acetonitrile solution (b).
Self-assembly and characterization of heteroleptic Cu(I)
complexes C1–C10
spectrum, suggesting that the heteroleptic copper(I) complex
C1 has good thermodynamic stability in solution (Fig. S19,
ESI†). Moreover, the formation of the heteroleptic [(POP)-
A mixture of bipyridine ligand, bisphosphine and copper(I) salt
([Cu(CH3CN)4]ꢀBF4) in equal amounts was added into 4 mL of
acetonitrile solution and stirred for 24 hours at room tempera-
ture. The resulting clear solution was filtered and precipitated
with 30 ml of diethyl ether. A yellow powder was afforded in
quantitative yield after freeze-drying treatment. High-quality
single crystals of complexes C1–C10 were obtained by vapor
diffusion of diethyl ether into their acetonitrile solution for
one week.
The mononuclear Cu(I) complex C1 was fully characterized
by NMR spectroscopy, ESI-MS and X-ray crystallography. The 1H
and 13C NMR spectra indicated that complex C1 was success-
fully synthesized as a single highly symmetrical species. As
shown in Fig. 1a and Fig. S16 (ESI†), the integration of proton
Cu(bpy)]+-type complex was further supported by electrospray
ꢁ +
ionization mass spectrometry (ESI-MS): 868.9 for [C1-BF4
]
(Fig. 1b). A similar procedure used for the preparation of C1
was used to synthesize C2–C10 (Scheme 1). The NMR and
ESI-MS spectra of C2–C10 were fully characterized and con-
firmed the copper(I) complex structures (Fig. S21–S49, ESI†).
These experimental results indicated that the hetero-
leptic [(P4P)Cu(bpy)]+-type complexes C1–C10 were stable and
retained complete molecular structures in solution.
Crystal structures of heteroleptic phosphine-copper(I)
complexes
signals revealed a 1 : 1 : 1 ratio between the three components, High-quality single crystals of complexes C1, C2, C5, C6, C9 and
namely, the dipyridine ligand (L1), Cu(I) central atom and C10 suitable for X-ray crystallography were successfully grown
diphosphine-based ligand (L5). The resonance of the aromatic via the diffusion of diethyl ether into their acetonitrile solution
rings of the pyridine ligand appeared at 8.24, 7.82, and at room temperature. The crystal structures of complexes C1
7.46 ppm and the chemical shifts corresponding to the term- and C2 are displayed in Fig. 2a and the selected structural data
inal alkene groups were also found at 5.82, 5.19, and 4.27 ppm are summarized in Tables S2 and S3 (ESI†). The X-ray diffrac-
in the upfield. Four sets of multiplets observed at 7.24, 7.13, tion analysis revealed that C1 and C2 are mononuclear com-
6.91 and 6.68 ppm can be attributed to the proton signals of the plexes composed of one copper(I) ion, the bipyridine ligand and
diphosphine ligand (POP). Furthermore, no remarkable signal the bisphosphine ligand L5 (POP). The central copper ion
change was observed in the temperature-dependent 1H NMR adopted tetrahedral coordination conformation to interact with
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Cu–N bond length is 2.080 Å. The Cu(1)–P(2) and Cu(1)–P(3)
bond lengths in C9 are slightly shorter (2.247 and 2.226 Å,
respectively) than those observed in the similar complex C10.
The Cu–N bond lengths in C9 are in the range of 2.064–2.105 Å.
The N–Cu–P bond angles vary from 100.001 to 105.241, and the
N–Cu–N bond angle is 78.721 for C9, while the N–Cu–P bond
angles for C10 vary from 96.131 to 105.751, and the N–Cu–N
bond angle is 79.31. The dihedral angles of Cu–N–N and Cu–P–P
are 85.421 and 83.871, respectively, which are slightly larger than
those in the mononuclear complexes C1 and C2. In the dinuclear
complexes C9 and C10, the Cu–Cu distances of two Cu(I) atoms
are 4.123 and 4.393 Å, respectively.
Inspired by the structural diversity of the aforementioned
Cu(I) heteroleptic complexes C1–C2 and C9–C10, two linear
diphosphine ligands with a longer alkyl chain (L7, dppe; L8,
dppp) were reacted with copper(I) salt and bipyridine ligands
(L1–L4) in acetonitrile solution. Interestingly, two mononuclear
copper–phosphine complexes were obtained in high yields
(480%). As shown in Fig. S54 (ESI†), in complex C5, the
copper(I) central atom coordinated with two nitrogen atoms
(Cu01–N6, 2.033 Å, and Cu01–N7, 2.042 Å) and phosphine
atoms (Cu01–P003, 2.2503 Å, and Cu01–P15, 2.2532 Å) in a
distorted tetrahedral geometry. Similar structure and coordina-
tion moiety can be found in complex C6 after the replacement
of L7 with the more flexible diphosphine ligand L8 (Fig. S55,
ESI†). These structural differences of complexes C1–C10
Fig. 2 Crystal structures of mononuclear complexes C1 (a), C2 (b), C9 (c)
and C10 (d) drawn in the ball-stick mode. Green, carbon; blue, nitrogen;
purple, phosphor; red, oxygen; brown, copper. The terminal carbon atoms
at the bipyridine ligands are shown in deep violet.
two phosphine donors from the distorted organophosphorus revealed that the flexibility of diphosphine ligands plays a
ligand (POP) and two nitrogen atoms from the bipyridine crucial role in the synthesis of heteroleptic Cu(I) complexes.
ligands (L1 and L2) forming [(POP)Cu(bpy)]+-type triple-
Spectroscopic properties
component complexes.
Taking C1 and C2 for example, in the distorted The photophysical data of the heteroleptic Cu(I)–phosphine
[(P^P)Cu(N^N)]+ tetrahedral coordination moiety, the bond complexes C1–C10 are displayed in Table S6 (ESI†). The elec-
distances of Cu1–P2 and Cu1–N2 in complex C1 are about tronic absorption spectra of complexes C1–C10 in the solid
2.25 and 2.10 Å, respectively, which are slightly shorter than state are depicted in Fig. S104 (ESI†). Complexes C1–C10 dis-
those found in complex C2 (2.24 Å for Cu1–P2, 2.049 Å for Cu1– play intense absorption bands over a wide range from 250 to
N2). The N1–Cu–N2 angles of 79.171 and 80.191 are observed in 450 nm; the lower energy bands (350–450 nm) could have
the tetrahedra of C1 and C2, respectively. In a distorted eight- possibly been caused by the exciton coupling of metal-to-
membered ring, the P1–Cu1–P2 angles are 112.341 and 111.971, ligand charge transfer (MLCT).18–25 The mononuclear Cu(I)
and the P1–Cu1–N2 bond angles in these two complexes are in complexes C1–C4 in MeCN show a similar absorption band at
the range of 101–1281. The dihedral angles of triangular planes 310–400 nm (Fig. S106–S108, ESI†), which arises from the ILCT
composed of Cu1–N1–N2 and Cu1–P1–P2 are 81.271 and 81.401, and p–p* charge transfer transitions. The electronic absorption
respectively (Tables S2 and S3, ESI†). These structural features spectra of the dinuclear complexes C7–C10 in MeCN (Fig. S107
indicate that the mononuclear heteroleptic complexes C1–C4 and S108, ESI†) show two absorption bands near 260–290 nm
have
geometry.
a
similar [(P^P)Cu(N^N)]+ tetrahedral coordination and 310–330 nm which can be attributed to the MLCT (1[3d(Cu)
- p*(N-heteroaromatic ligand)]) transitions.23–25 Fig. 3a shows
In order to precisely control the structures of the hetero- the emission spectra of complexes C1–C10 in the solid state.
leptic phosphine–copper(I) complexes, a linear diphosphine With reference to the luminescence studies of heteroleptic
ligand, L6, was used as a linker to assemble the dinuclear Cu(I)–phosphide complexes reported in previous work,26–33
complexes C9 and C10 under similar conditions. Compared the solid-state emissions of the mononuclear complexes
with the mononuclear complexes C1–C4, the dimeric com- C1–C6 observed in the range of 556–598 nm are derived from
plexes C9 and C10 contain two bipyridine-protected copper(I) the [(P^P)Cu(N^N)]+ framework, and the origins are tentatively
centers doubly bridged by two polyphosphoric ligands L6 attributed to the triplet ligand-to-metal charge transfer (LMCT)
(dppm) as depicted in Fig. 2b and Tables S6 and S7 (ESI†). In transitions. Compared with C1–C4, the dinuclear complexes
these heteroleptic di-copper(I) complexes, three components C7–C10 exhibit intense solid-state emissions over a narrow
also formed two [(P^P)Cu(N^N)]+ tetrahedral geometries. In range of 503–546 nm upon excitation at 384 nm and 398 nm.
C10, the average bond length of Cu–P is 2.24 Å and the average In CH2Cl2 solution, complexes C1–C4 show emission peaks
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Fig. 4 Selected frontier orbitals and their energies for the mononuclear
complexes C1 and C6, and the dinuclear complex C10.
Silver ions are widely dispersed in industrial wastewater.
Highly sensitive and selective luminescence sensing towards
silver ions is still a challenging problem. However, because
silver ions are luminescence-silent, ideal fluorescent probes for
sensitively detecting silver ions in solution have rarely been
reported to date.22,26,27 The heteroleptic [(POP)Cu(bpy)]+-type
complexes C1–C10 exhibit good stability and strong emission
in solution, suggesting that these complexes can be used as
potential fluorescent probes for detecting silver ions. As shown
in Fig. 5, the fluorescence intensity of C1 at 610 nm decreased
gradually upon the dropwise addition of Ag+ (from 0 to 3.4
equivalents) into the DCM solution. When the concentration
of Ag+ in the mixture solution was below 0.8 ꢂ 10ꢁ6 M, the
fluorescence intensity of C1 changed slowly. When the Ag+
concentration reached 3.4 uM, the emission intensity is no
longer significantly weakened. In order to rule out the possible
interference from organic solvents, more than 4.0 equivalents
of acetonitrile was added into the DCM solution of complex C1.
The emission intensity of C1 at 610 nm did not change
remarkably, suggesting that the luminescence quenching beha-
viour was most likely to be caused by the strong interactions
between the silver ions and complex C1 in solution. Moreover,
similar fluorescence sensing and solvent interference experi-
ments were also carried out using complexes C2–C8 as probes.
As shown in Fig. S109–S112 (ESI†), upon the addition of silver
ions, the emission intensities of C2–C4 decreased gradually
in DCM/CH3CN solution. In contrast, the dinuclear complexes
C7–C10 did not exhibit ‘‘turn-off’’ fluorescence sensing
towards silver ions. To gain insights into possible interaction
Fig. 3 (a) Emission spectra of complexes C1–C10 in the solid state and (b)
in CH2Cl2 solution (1 ꢂ 10ꢁ6 M) at 298 K.
(610 nm, 610 nm, 615 nm and 640 nm) based on excitation at
421 nm, 421 nm, 415 nm and 398 nm, respectively (Fig. 3b and
Fig. S71–S75, ESI†). However, C7–C10 in CH2Cl2 solution show
broad emission peaks at 543 nm, 560 nm, 501 nm and 543 nm,
respectively. The remarkable red-shifted emission could have
possibly been caused by the merely changing nature of the
tetrahedron coordination geometry when the Cu(I) center inter-
acts with different diphosphine ligands, L5–L8. The lifetimes
and quantum yields of complexes C1–C10 were measured and
are summarised in Table S8 (ESI†). All complexes exhibit life-
times in a broad range of 1.07–1008 ms either in the solid state
or in DCM solution at room temperature, suggesting that the
electron transfer originated from the triplet MLCT transitions.
In order to gain insights into the electron transfer beha-
viours observed in the heteroleptic complexes C1–C10 in the
solid state, the gap energy between the LUMO and HOMO was
calculated using the DFT/B3LYP/Def2-SVP method. As shown in
Fig. 4 and Table S9 (ESI†), the HOMO–LUMO energy gaps of the
mononuclear complexes C1 and C6 and the dinuclear complex
C10 are 4.02, 3.38, and 3.81 eV, respectively. These theoretical
calculation results indicated that electron transfer can be
possibly attributed to a mixture of triplet MLCT {d(Cu) -
p*[bpy]} and LLCT transitions which are in good agreement
with the experimental results observed from the UV-vis absorp-
tion and solid-state emission spectra.
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Catalytic activity toward the CuAAC reaction in water
Metal-catalyzed azide–alkyne cycloaddition reactions are widely
used in organic synthesis, medicinal chemistry, high polymer
chemistry and biological coupling.25 In particular, Cu(I) com-
plexes exhibited high catalytic activity towards azide–alkyne
cycloaddition reactions (CuAAC) carried out in aqueous
solutions.26–28 However, a few heteroleptic Cu(I) complexes
stabilized with diimine–polyphosphine ligands have been used
as efficient catalysts for CuAAC reactions carried out in water
under mild conditions.29–35 As shown in Table 1, seven aro-
matic alkynyl-based substrates 1a–1g, respectively, reacted with
benzyl azide (2a) at 80 1C for 8 h. The experimental yields were
calculated based on the target triazolyl compounds 3a–3g
purified by column chromatography (DCM as the eluent).
Alkyne substrates 1a–1c with electron-donating groups dis-
played good reactivity towards benzyl azide, and the highest
yields of the corresponding triazole reached 97% (3b) and 95%
(3d). In order to study the circulation of the catalyst, the
catalytic yield remains 60% after recycling four times in
the reaction of phenylacetylene (1a) with benzyl azide (2a). All
the triazolyl compounds 3a–3g were fully characterized by NMR
spectroscopy and mass spectrometry (Fig. S116–S134, ESI†).
Based on previous studies,32–35 as shown in Fig. S135 (ESI†), we
proposed a mechanistic pathway for the CuAAC reaction cata-
lyzed by heteroleptic complexes. The azide and alkyne sub-
strates possibly coordinate with the copper(I) atom via Cu–N
Fig. 5 Fluorescence spectra of C1 (1 ꢂ 10ꢁ6 M) upon titration with Ag+
(0–3.4 ꢂ 10ꢁ6 M) in CH2Cl2 solution at room temperature.
mechanisms between complexes C1–C4 and silver ions in
solution, the 1H-NMR titration experiment was performed.
When 10 eq. of AgPF6 was added into the DCM solution of
complex C1, the proton signals from the terminal alkene
groups in the range from 5.0 to 6.2 ppm moved toward the
lower field with a maximum shift of 0.7 ppm (Fig. 6). Three
resonance signals from the bipyridine ligand L1 in the range of
7.5–8.3 ppm shifted to one set of multiple signals at 7.48 ppm.
Furthermore, five sets of chemical shifts in the range from 6.7
to 7.5 ppm, attributed to protons from the POP ligand L5,
changed to three dominant signals at 6.8, 7.1, and 7.3 ppm.
Based on these results, we speculated that the silver ions could
have possibly interacted with complex C1 through multiple
Ag+ꢀ ꢀ ꢀp interactions in solution. These weak interactions inter-
Table 1 The CuAAC reaction catalyzed by complex C1 at 80 1C
fered with the metal-to-ligand charge transfer behaviour Entry Alkyne
between the copper center and the bipyridine and diphosphine
Azide
Producta
Yieldb (%)
96
ligands, leading to luminescence quenching.
1
2
3
97
92
4
95
5
6
85
88
90
7
a
Reaction conditions: azide (0.1 mmol), alkyne (0.11 mmol), complex
C1 as catalyst (1 mmol %), water (2 mL), CH3CN (1 mL), 80 1C, 8 h.
Fig. 6 1H-NMR spectra of the mononuclear complex C1 before (a) and
after the addition of silver ions (4 eq.) in CD3CN. The dashed lines show the
change in chemical shifts before and after complexation.
b
The isolated product yield was calculated through recrystallization
from the reaction solution and determined using 1H NMR and ESI mass
spectra.
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and Cu–C bonds, leading to the formation of intermediates B was concentrated under reduced pressure. The afforded solid
and C, respectively. After the [2+3]-cycloaddition and the clea- was dissolved in CH2Cl2 and washed with water, then brine,
vage of the C–Cu bond, the triazole product was produced and dried (Na2SO4), and the solvent was evaporated in a vacuum.
separated from intermediate D.
Flash chromatography (SiO2, AcOEt: light petroleum) afforded
L1 as a pale-yellow solid (80.50 mg, 0.30 mmol, 57%). 1H NMR
(500 MHz, chloroform-d) d 8.33 (d, J = 3.0 Hz, 2H, Hg), 8.22 (d,
J = 8.8 Hz, 2H, Hf), 7.30 (d, J = 3.0 Hz 2H, He), 6.07 (brs, 2H, Hc),
5.47(d, J = 18.4 Hz, 2H, Hb), 5.35 (d, J = 11.4 Hz, 2H, Ha), 4.62
(d, J = 5.0 Hz 4H. Hd). 13C NMR (100 MHz, chloroform-d)
d 154.70, 149.22, 137.33, 132.65, 122.26, 121.09, 118.49, 69.33.
[L1 + H]+, calcd m/z =269.12, found m/z = 269.12. This com-
pound was directly subjected to the next step of synthesis
without further purification. A similar method was used to
prepare ligands L2–L4.
Conclusions
A series of bipyridine ligands with various side chains were
synthesized and used to synthesize ten diphosphine-supported
heteroleptic complexes C1–C10. The mononuclear conforma-
tion was changed to dinuclear by replacing the semi-rigid
bisphosphine ligand POP with a flexible linear linker, Dppm,
in the assembly process. These discrete triple-component com-
plexes were fully characterized by NMR spectroscopy, ESI-MS
and X-ray crystallography. These heteroleptic Cu(I) complexes
exhibited good stability and intense wide-range emissions
either in the solid state or in solution. The mononuclear
complexes C1–C4 with modified bipyridine displayed ‘‘turn-
off’’ fluorescence sensing towards silver ions in DCM/CH3CN
solution. The possible luminescence probing mechanism was
proposed based on the NMR titration experimental results.
Furthermore, all these water-stable phosphine–copper(I) com-
plexes exhibit high catalytic activity towards the CuAAC reac-
tion in water/CH3CN solution.
Synthesis of ligand L2
Yield, 51%. 1H NMR (500 MHz, DMSO-d6) d 8.32 (d, J = 2.8 Hz,
2H, Hh), 8.20 (d, J = 8.8 Hz, 2H, Hg), 7.48 (d, J = 11.6 Hz, 2H, Hf),
5.91 (brs, 2H, Hc), 5.21 (d, J = 17.2 Hz, 2H, Hb), 5.11 (d, J =
10.2 Hz, 2H, Ha), 4.15 (t, J = 6.6 Hz, 4H, He), 3.35 (s, 4H, Hd). 13
C
Experimental section
NMR (100 MHz, chloroform-d) d 149.11, 137.17, 134.09, 121.99,
121.08, 117.55, 67.81, 33.66. [L2 + H]+, calcd m/z =297.15, found
m/z = 297.10. This compound was directly subjected to the next
step of synthesis without further purification.
All reactions and manipulations were performed under an
atmosphere of prepurified nitrogen using Schlenk techniques.
All the organic solvents were purchased from a commercial
chemical company and were used after being distilled over 4 Å
molecular sieves under an argon atmosphere. All other chemi-
cals were used as received without any further purification.
NMR spectra were recorded using either a Bruker AVIII 400
MHz spectrometer or a Bruker AVIII 500 MHz spectrometer and
referenced to residual solvent peaks. The working frequencies
were 400 or 500 MHz for 1H and 100/125 MHz for 13C. The
fluorescence spectral analyses were carried out using Edin-
burgh FLS980 and Gangdong FL-320 spectrometers. The X-ray
diffraction single-crystal data of the Cu(I)–POP complexes C1–
C6 and Cu(I)–Dppm complexes C7–C10 were collected using a
Bruker D8 Venture APEX II CCD single-crystal diffractometer.
Synthesis of ligand L3
Yield, 64%. 1H NMR (500 MHz, chloroform-d) d 8.39 (s, 2H, He),
8.27 (d, J = 8.8 Hz, 2H, Hd), 7.40 (d, J = 8.7 Hz, 2H, Hc), 7 4.78
(s, 4H, Hb), 2.57 (s, 2H, Ha). 13C NMR (100 MHz, chloroform-d)
d 153.63, 149.63, 137.41, 122.47, 121.06, 77.80, 76.60, 56.26.
[L3 + H]+, calcd m/z =265.28, found m/z = 265.10. This com-
pound was directly subjected to the next step of synthesis
without further purification.
Synthesis of ligand L1
(2,2’-Bipyridine)-5,50-diol (100 mg, 0.53 mmol), K2CO3 (2.50 g,
18.12 mmol), KI (20 mg, 0.12 mmol) and allyl bromide (0.8 mL,
Synthesis of ligand L4
9.26 mmol) were dissolved in dry THF (20 mL) in a sealed tube. The compound was synthesized by reference. 1H NMR (400 MHz,
The mixture was stirred at 85 1C for 48 hours. Next, the solution DMSO-d6) d 8.60 (s, 2H, He), 8.34 (d, J = 8.1 Hz, 2H, Hd),
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7.86 (d, J = 8.2 Hz, 2H, Hc), 5.40 (t, J = 5.7 Hz, 2H, Ha), 4.59 141.14, 137.37, 132.70, 130.87, 129.61, 122.76, 60.43, 25.16.
(d, J = 5.5 Hz, 4H, Hb).
ERSI-MS: [C5-BF4ꢁ]+, calcd m/z = 678.21, found m/z = 678.1.
Synthesis of the Cu(I)–DPPP complex C6
Synthesis of the Cu(I)–POP complex C1
1H NMR (500 MHz, DMSO-d6) d 8.66 (s, 4Hd/e), 8.15 (s, 2Hc),
7.41 (s, 4Hf), 7.32 (s, 16Hg/h), 5.57 (s, 2Ha), 4.61 (s, 4Hb), 2.84
(s, 4Hi), 2.20–1.99 (m, 2Hj). 13C NMR (100 MHz, acetonitrile-d3)
d 150.60, 148.53, 140.93, 137.14, 134.00, 132.25, 130.45, 129.29,
122.61, 60.40, 27.24, 19.48. ESI-MS: [C6-BF4ꢁ]+, calcd m/z =
692.24, found m/z = 692.1.
Ligand L1 (20 mg, 0.074 mmol) and tetrafluoro–borate
tetra(acetonitrile) copper (23 mg, 0.074 mmol) were
dissolved in acetonitrile (3 mL) in an assembly tube and stirred
at room temperature for
2
hours. Then, L5 bis(2-
diphenylphosphinophenyl)ether (40 mg, 0.074 mmol) was
added and the mixture was stirred at room temperature for 8
hours. The solution was divided into three parts. It was grown
by a solvent diffusion method with ethyl ether as the diffusion
agent. A week later, the Cu(I)–POP complex C1 was obtained.
1H NMR (400 MHz, chloroform-d) d 8.24 (d, J = 9.0 Hz, 2H, He),
7.82 (s, 2H, Hf), 7.46 (d, J = 11.7 Hz, 2H, Hd), 7.24 (m, 6H, Hj/k/m),
7.13 (m, 8H, Hi), 6.91 (m, 12H, Hg/h), 6.68 (m, 2H, Hl), 5.82 (m, 2H,
Hb), 5.19 (m, 4H, Ha), 4.26 (d, J = 5.3 Hz, 4H, Hc). 13C NMR
(100 MHz, chloroform-d) d 155.67, 144.88, 136.97, 134.38, 133.11,
132.08, 131.70, 130.71, 130.20, 128.83, 125.30, 124.09, 122.87,
120.41, 118.78, 69.39. [C1-BF4ꢁ]+, calcd m/z = 868.93, found
m/z = 868.90. Complexes C2–C10 were prepared according to
the same procedure as that used for C1.
Synthesis of the Cu(I)–Dppm complex C7
1H NMR (400 MHz, acetonitrile-d3) d 7.82 (brs, 8H, Hf/g), 7.42 (d,
J = 9.7 Hz, 4H, He), 7.23 (brs, 8H, Hh), 7.05 (brs, 32H, Hi/j), 6.01
(m, 4H, Hc), 5.31 (m, 8H, Ha/b), 4.55 (d, J = 7.5 Hz, 8H, Hd), 3.65
(s, 4H, Hk). 13C NMR (100 MHz, chloroform-d) d 155.52, 138.06,
132.42, 132.10, 130.04, 128.71, 123.79, 122.36, 118.52, 69.56.
TOF-ESI-MS: fragment of C7 with a formula of [L1 + Cu +
Dppm]+, calcd m/z = 715.17, found m/z = 715.17.
Synthesis of the Cu(I)–Dppm complex C8
1H NMR (400 MHz, acetonitrile-d3) d 7.79 (brs, 4H, Hg), 7.69
(s, 4H, Hh), 7.39 (d, J = 6.3 Hz, 4H, Hf), 7.24 (brs, 8H, Hi), 7.06
(brs, 32H, Hg/k), 5.93 (m, 4H, Hc), 5.19 (m, 8H, Ha/b), 4.00 (t,
J = 9.5 Hz, 8H, He), 3.66 (s, 4H, Hl), 2.56 (m, 8H, Hd).13C NMR
(100 MHz, acetonitrile-d3) d 156.76, 145.33, 138.73, 135.22,
133.22, 131.05, 123.79, 123.13, 117.88, 69.03, 33.93, 26.79.
TOF-ESI-MS: fragment of C8 with the formula [L2 + Cu +
Dppm]+, calcd m/z = 743.20, found m/z = 743.19.
Synthesis of the Cu(I)–POP complex C2
1H NMR (400 MHz, chloroform-d) d 8.24 (d, J = 9.0 Hz, 2H, Hf),
7.79 (s, 2H, Hg), 7.43 (d, J = 8.9 Hz, 2H, He), 7.24 (m, 6H, Hk/l/n),
7.13 (m, 8H, Hj), 6.94 (m, 12H, Hh/i), 6.67 (s, 2H, Hm), 5.69
(m, 2H, Hb), 5.05 (m, 4H, Ha), 3.72 (t, J = 6.6 Hz, 4H, Hd), 2.37
(m, 4H, Hc). 13C NMR (100 MHz, chloroform-d) d 158.10,
155.98, 144.84, 136.72, 134.41, 133.71, 133.17, 132.08, 130.72,
130.23, 128.85, 125.35, 123.97, 122.92, 120.39, 117.60, 68.00,
33.14. [C2-BF4ꢁ]+, calcd m/z = 896.91, found m/z = 896.90.
Synthesis of the Cu(I)–Dppm complex C9
1H NMR (400 MHz, acetonitrile-d3) d 7.93 (brs, 2H, Hd), 7.79
(s, 2H, He), 7.50 (d, J = 13.4 Hz, 2H, Hc), 7.22 (brs, 4H, Hf), 7.03
(brs, 16H, Hg/h), 4.81 (s, 4H, Hb), 3.66 (s, 2H, Ha), 2.90 (s, 2H,
Hi).13C NMR (100 MHz, acetonitrile-d3) d 155.47, 139.22, 133.20,
131.03, ꢁ129.46, 124.06, 123.13, 78.25, 57.44, 26.45. TOF-ESI-MS:
[C9-BF4 + H2O]+, calcd m/z = 1528.32, found m/z = 1528.13.
Synthesis of the Cu(I)–POP complex C3
1H NMR (400 MHz, chloroform-d) d 8.32 (d, J = 9.0 Hz, 2H, Hd),
7.98 (s, 2H, He), 7.60 (d, J = 14.7 Hz, 2H, Hc), 7.30 (m, 6H, Hi/k/l),
7.18 (m, 8H, Hh), 7.02 (m, 12H, Hf/g), 6.72 (m, 2H, Hj), 4.49
(s, 2H, Hb), 2.42 (s, 2H, Ha). 13C NMR (100 MHz, chloroform-d)
d 158.21, 154.78, 145.38, 137.17, 134.39, 133.07, 132.12, 130.26,
128.87, 125.28, 124.40, 123.06, 120.53, 78.48, 76.84, 56.57.
[C3-BF4ꢁ]+, calcd m/z = 865.28, found m/z = 865.17.
Synthesis of the Cu(I)–Dppm complex C10
1H NMR (400 MHz, acetonitrile-d3) d 8.09 (brs, 2H, Hd), 7.85
(brs, 4H, He/c), 7.19 (brs, 4H, Hf), 7.01 (brs, 16H, Hg/h), 5.07
(s, 2H, Ha), 4.56 (s, 4H, Hb), 3.71 (s, 2H, Hi).13C NMR (100 MHz,
acetonitrile-d3) d 150.69, 139.13, 133.13, 130.53, 129.18, 62.23,
26.40. TOF-ESI-MS: [C10-BF4ꢁ]+, calcd m/z = 1413.28 found
1
Synthesis of the Cu(I)–POP complex C4. H NMR (400 MHz,
acetonitrile-d3) d 8.26 (d, J = 8.0 Hz, 2H, Hd), 8.18 (s, 2H, He),
7.88 (d, J = 11.5 Hz, 2H, Hc), 7.26 (m, 6H, Hi/k/l), 7.14 (d, J =
9.4 Hz, 8H, Hh), 6.95 (m, 12H, Hf/g), 6.67 (m, 2H, Hj), 4.38
(d, J = 14.5 Hz, 4H, Hb), 3.48 (s, 2H, Ha). 13C NMR (100 MHz,
acetonitrile-d3) d 157.49, 149.79, 147.06, 139.19, 135.75, 133.46,
132.43, 131.47, 130.15, 129.40, 128.07, 124.45, 123.01, 121.14,
119.81, 116.40, 59.98. TOF-MS: fragment of C4 with the formula
[C4-L4-BF4ꢁ]+, calcd m/z = 601.09, found m/z = 601.34.
m/z = 1413.07; [C10-BF4 + CH3CH2OH]+, calcd m/z = 1459.32,
ꢁ
found m/z = 1459.03.
Conflicts of interest
There are no conflicts to declare.
Synthesis of the Cu(I)-DPPE complex C5
Acknowledgements
1H NMR (500 MHz, DMSO-d6) d 8.76 (m, 2Hd), 8.46 (m, 2He),
8.21 (m, 2Hc), 7.46 (brs, 20Hf/g/h), 5.56 (m, 2Ha), 4.61 (m, 4Hb), We thank the National Natural Science Foundation of China
2.77 (s, 4Hi). 13C NMR (100 MHz, DMSO-d6) d 150.86, 148.69, (No. 21971058, 21907063) for financial support and SSRF for
This journal is © The Royal Society of Chemistry and the Centre National de la Recherche Scientifique 2021
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Paper
NJC
II. Copper(I) Chemistry of Phosphines, Functionalized Phos-
phines and Phosphorus Heterocycles, ed. M. S. Balakrishna,
Elsevier, 2019, pp. 83–107.
the crystal structure determination using synchrotron radiation
X-ray diffraction analysis. This project was also supported by
the Hubei Province Fund for Distinguished Young Scholars
(2020CFA085), the research funds of ‘‘Chu-Tian Distinguished
Professor Scholar’’ and the ‘‘Hundred-Talent Program’’ youth
project (No. 430-090177) at Hubei University. We also thank the
Natural Science Foundation of Guangdong Province (Grant No.
2019A1515010783), the Young Talents Program of Guangzhou
University (Grant No. RQ2020080), and the Guangzhou Science
and Technology Plan Project (Grant No. 202001010002).
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