Highly active and recyclable Pt nanocatalyst for hydrogenation of quinolines and isoquinolines

Article abstract of DOI:10.1016/j.apcata.2018.04.039

Thermoregulated phase-transfer Pt nanocatalyst was shown to be highly active, selective and recyclable in the hydrogenation of quinolines and isoquinolines. The catalyst could be easily separated from the product by simple phase separation and directly reused in the next cycle without evident loss in catalytic activity and selectivity, even after ten recycles. Importantly, for quinoline, the TON of 10,474 is the highest value ever reported among Pt catalysts. More remarkably, for isoquinoline, the TON of 5340 is far ahead of the highest record among transition metal catalysts.

Full text of DOI:10.1016/j.apcata.2018.04.039

Accepted Manuscript
Title: Highly active and recyclable Pt nanocatalyst for
hydrogenation of quinolines and isoquinolines
Authors: Xiuru Xue, Min Zeng, Yanhua Wang
PII:
S0926-860X(18)30211-4
DOI:
Reference:
https://doi.org/10.1016/j.apcata.2018.04.039
APCATA 16645
To appear in:
Applied Catalysis A: General
Received date:
Revised date:
Accepted date:
9-3-2018
26-4-2018
27-4-2018
Please cite this article as: Xue X, Zeng M, Wang Y, Highly active and recyclable Pt
nanocatalyst for hydrogenation of quinolines and isoquinolines, Applied Catalysis A,
General (2010), https://doi.org/10.1016/j.apcata.2018.04.039
This is a PDF file of an unedited manuscript that has been accepted for publication.
As a service to our customers we are providing this early version of the manuscript.
The manuscript will undergo copyediting, typesetting, and review of the resulting proof
before it is published in its final form. Please note that during the production process
errors may be discovered which could affect the content, and all legal disclaimers that
apply to the journal pertain.

Highly active and recyclable Pt nanocatalyst for hydrogenation
of quinolines and isoquinolines
Xiuru Xue, Min Zeng, and Yanhua Wang*
State Key Laboratory of Fine Chemicals, Dalian University of Technology, Dalian 116024, PR China
Corresponding author: Tel./Fax. +86 411 84986033; E-mail address: yhuawang@dlut.edu.cn
Graphical Abstract
Highlights



Highly active and recyclable Pt nanocatalyst was developed for hydrogenation of quinolines and
isoquinolines.
TON of 10,474 for quinoline (the highest value ever reported among Pt catalysts) and TON of 5,340
for isoquinoline (the highest record among transition metal catalysts) were achieved.
Provide a novel approach for simple separation and direct recycling of noble transition metal
catalysts to prepare 1,2,3,4-tetrahydroquinolines and 1,2,3,4-tetrahydroisoquinolines.
Abstract
Thermoregulated phase-transfer Pt nanocatalyst was shown to be highly active, selective and
recyclable in the hydrogenation of quinolines and isoquinolines. The catalyst could be easily separated
1

from the product by simple phase separation and directly reused in the next cycle without evident loss in
catalytic activity and selectivity, even after ten recycles. Importantly, for quinoline, the TON of 10,474 is
the highest value ever reported among Pt catalysts. More remarkably, for isoquinoline, the TON of 5,340
is far ahead of the highest record among transition metal catalysts.
Keywords: thermoregulated phase-transfer catalysis • Pt nanoparticles • hydrogenation • quinolines and
isoquinolines • recycling
1
. Introduction
Quinolines and isoquinolines widely exist in coal, shale stone and tar sands. Their corresponding
hydrogenation products─1,2,3,4-tetrahydroquinolines and 1,2,3,4-tetrahydroisoquinolines, in particular,
are very important skeletons of various biologically active natural products [1,2], chemotherapeutic agents
[
3,4], functional dyes [5,6], pharmacodynamic agents [7-9], ligands [10-12] and many other fine chemicals
13]. Among all the synthesis methods, hydrogenation of quinolines and isoquinolines has been taken for
[
granted as one of the most atomic economic and feasible methods to synthesize
,2,3,4-tetrahydroquinolines and 1,2,3,4-tetrahydroisoquinolines. In recent years, various transition metal
1
nanocatalysts have been widely reported for this type reaction, such as Ru [14-16], Rh [17-19], Pd [20-22],
Pt [23-26], Au [27,28] and Au/Pd [29]. However, due to the aromaticity of reaction substrates and the
poison effect on transition metal catalysts caused by hydrogenation products [30-33], the catalytic
hydrogenation activity for quinolines, especially for isoquinolines, is relatively low, let alone excellent
catalyst recycling.
In our previous studies, a thermoregulated phase-transfer nanoparticle catalysis system, which takes
advantage of both heterogeneous and homogeneous catalysis, has been developed [34-36]. The basic
principle of this system can be described as follows: before reaction, the system is composed of the upper
1
-pentanol phase containing substrates and the lower aqueous phase containing transition metal
nanocatalyst. When reaction temperature exceeds the cloud point, the transition metal nanocatalyst can
transfer from the lower aqueous phase to the upper 1-pentanol phase and the reaction runs efficiently in
the upper 1-pentanol phase (homogeneous reaction). After reaction, when the temperature decreases to
room temperature, the transition metal nanocatalyst will return to the lower aqueous phase again.
2

Therefore, the transition metal nanocatalyst can be easily separated from the product by simple phase
separation and directly reused in the next recycle. Namely, this system can realize not only the
homogeneous reaction but also the separation and recycling of the transition metal nanocatalyst. Till now,
the above-mentioned system has been successfully applied for hydroaminomethylation of olefins [34],
semihydrogenation of diphenylacetylene [35], and selective hydrogenation of α,β-unsaturated aldehydes
and ketones [36] with high catalytic activity, selectivity and reusability.
Encouraged by these results, in this study, the thermoregulated phase-transfer Pt nanocatalyst was
firstly reported for hydrogenation of quinolines and isoquinolines with the aim to achieve high catalytic
activity, selectivity and recyclability of catalyst (Fig. 1).
Fig. 1. Hydrogenation of quinolines and isoquinolines catalyzed by the thermoregulated phase-transfer Pt nanoparticles.
2
2
. Experimental
.1. Materials and analyses
H
2
PtCl
8%), 6-methoxyquinoline (1f, 98%), 8-methylquinoline (1i, 98+%) and 1-methylisoquinoline (3b, 98%)
were from Alfa Aesar. 2-Methylquinoline (1b, 98%), 2,6-dimethylquinoline (1e, 98%), 5-aminoisoquinoline
3c, 99%) and 6-bromoisoquinoline (3d, 97%) were purchased from J&K. 6-Chloroquinoline (1g, 97%),
6
•6H O (20% of Pt), quinoline (1a, 99%), 3-methylquinoline (1c, 98+%), 6-methylquinoline (1d,
2
9
(
methyl quinoline-6-carboxylate (1h, 97%) and isoquinoline (3a, 98%) were from Aladdin. 1-Pentanol and
n-decane were purchased from Kermel. Unless otherwise noted, all chemicals were analytical reagents
without further purification. GC analyses were performed on Tianmei 7890 GC instrument equipped with
an 50 m × 0.25 mm OV-101 column and an FID detector. GC-MS analyses were performed on a HP6890
GC/5973 MSD instrument with a 30 m × 0.25 mm HP-5MS column (He as a carrier gas). TEM images
2
were carried out by using a Tecnai G 20 S-TWIN (120 kV) instrument. HRTEM images were carried out
by using Tecnai F30 (300 kV) instrument. ICP-AES was recorded on Optima 2000 DV (detection limit is
3

1
0 μg/L).
2
.2. Preparation of the thermoregulated phase-transfer Pt nanocatalyst
As a typical example, a mixture of water (4 mL, Ph
2
P(CH
10 mmol of Pt) and 1-pentanol (4 mL) was added to a 75 mL stainless-steel autoclave. The autoclave
and then inflated to 4.0 MPa with H . After being stirred at 70
2
CH
2
O)22CH
3
/Pt = 2 (mol/mol), containing 1.93
-3
×
was flushed for three times with 2.0 MPa H
2
2
ºC for 2 h, the reactor was cooled to room temperature and depressurized. The colour of the mixture
changed from claret to brown, indicating the formation of the thermoregulated phase-transfer Pt
nanocatalyst.
2
.3. Hydrogenation of quinolines and isoquinolines
In a typical experiment, the above-prepared thermoregulated phase-transfer Pt nanocatalyst, n-decane
(100 mg) and a certain amount of substrates were added in the autoclave. Then the reactor was replaced
three times with 2 MPa H and stirred under hydrogen pressure at a designated temperature for an
2
appointed time. After reaction, the reactor was cooled to room temperature and depressurized. The upper
product phase was easily separated from the lower catalyst phase and directly analysed by GC and
GC-MS.
3
. Results and discussion
We initially explored the catalytic performance of the thermoregulated phase-transfer Pt nanocatalyst
for this hydrogenation reaction by using quinoline 1a as a model substrate (Table 1). Firstly, the effect of
the reaction temperature was studied and the results showed that the conversion of quinoline increased
o
with increasing temperature in the range of 80 to 130 C until the >99% conversion was achieved at 130
oC. While the selectivity of 1,2,3,4-tetrahydroquinoline completely unaffected by this temperature variation
and always remained >99% (entries 1-5). Subsequently, we investigated the effect of the molar ratio of
quinoline to Pt on the reaction and observed that the conversion of quinoline descended gradually with
the molar ratio raised from 1000 to 5000, but the selectivity of 1,2,3,4-tetrahydroquinoline still unaffected
in this process (entries 5-8). Hence, based on our studies, the best molar ratio of quinoline to Pt was
defined as 1000 in view of the separation of products from reaction substrates. In addition, the
4

dependence of the conversion and the selectivity on hydrogen pressure was examined (entries 9-11 and
5
). The data showed that the conversion of quinoline increased from 51% to >99% and the selectivity of
,2,3,4-tetrahydroquinoline was always >99% when the hydrogen pressure increased from 0.5 to 3 MPa.
1
Further studies indicated that prolonging reaction time led to an increase from 67% to >99% in the
conversion of quinoline and had no influence on the selectivity of 1,2,3,4-tetrahydroquinoline (entries
1
2-14 and 5). The catalytic profile of the conversion vs. time for the hydrogenation of quinoline was
provided (Fig. S1a, see Supplementary Material for details) and the result showed that the hydrogenation
rate was progressively decreased with the increase of reaction time. What’s more, when the molar ratio of
ligands to Pt was decreased from 2 to 1 (entries 5 vs. 15), the conversion was only 49% resulting from the
aggregation of Pt nanoparticles. On the other hand, increasing the molar ratio of ligands to Pt from 2 to 3
also decreased the conversion from >99% to 95 (entries 5 vs.16). This may be due to the fact that more
surface of Pt was covered. Therefore, the optimized reaction conditions for the thermoregulated
phase-transfer Pt nanoparticles-catalyzed hydrogenation of quinoline 1a were established with
1,2,3,4-tetrahydroquinoline selectivity of >99% at the >99% conversion of quinoline (entry 5).
Having established the optimized reaction conditions for hydrogenation of quinoline 1a, we paid our
attention to expanding the substrate scope by using the thermoregulated phase-transfer Pt nanoparticles
as catalyst. As shown in Table 2, except for methyl 1,2,3,4-tetrahydroquinoline-6-carboxylate (Table 2,
2
h) with >99% selectivity at 95% substrate conversion, all other quinolines afforded their corresponding
1,2,3,4-tetrahydroquinolines with excellent selectivity of >99% as well as high conversion of >99% (2b-g
and 2i). From literature results we knew that isoquinoline is more difficult to be hydrogenated due to the
special structure characteristics [30-32]. What’s more, isoquinolines and hydroisoquinolines are more
strongly alkaline and more likely to cause metals poisoning in comparison to that of quinolines and
hydroquinolines [30-33]. Therefore, we turned our attention to hydrogenation of isoquinolines by using
isoquinoline, 1-methylisoquinoline, 5-aminoisoquinoline and 6-bromoisoquinoline as substrates. Under
the optimized reaction conditions, the conversion of isoquinolines reached up to 98%->99% and the
selectivity of their corresponding 1,2,3,4-tetrahydroisoquinolines was as high as >99% (4a-d). Namely,
the thermoregulated phase-transfer Pt nanocatalyst exhibited good catalytic performance not only for
hydrogenation of quinolines but also for isoquinolines.
5

Table 1. Hydrogenation of quinoline 1a using thermoregulated phase-transfer Pt nanoparticles as catalyst.a
o
Conv. (%)b
Sel. (%)b
TONc
Entry
T ( C)
1a/Pt (mol/mol)
PH2 (MPa)
t (h)
1
2
3
4
5
6
7
8
9
80
1000
1000
1000
1000
1000
1500
2500
5000
1000
1000
1000
1000
1000
1000
1000
1000
3
3
3
3
3
3
3
3
3
3
3
3
3
3
3
3
3
3
3
0.5
1
2
3
3
48
78
85
95
>99
98
81
44
51
84
96
67
81
97
49
95
>99
>99
>99
>99
>99
>99
>99
>99
>99
>99
>99
>99
>99
>99
>99
>99
480
780
850
950
990
1470
2025
2200
510
840
960
670
810
970
490
950
100
110
120
130
130
130
130
130
130
130
130
130
130
130
130
0.5
1
1
0
11
2
1
1
1
1
1
a
2
3
3
3
4
3
5d
6e
3
3
Reaction conditions: 1-pentanol 4 mL, water 4 mL (containing 1.93 × 10-3 mmol of Pt, Ph
2
2 2 3
P(CH CH O)22CH /Pt = 2
(mol/mol)), and corresponding amount of 1a, 100 mg of n-decane as internal standard;
b
c
d
e
Determined by GC and GC-MS;
Turnover Number (TON): moles of product formed per mole of Pt, TON = n × Conversion × Selectivity (n = 1a/Pt).
Ph
Ph
2
2
P(CH
2
2
CH
2
2
O)22CH
3
3
/Pt = 1 (mol/mol), the aggregation of Pt nanoparticles appeared.
/Pt = 3 (mol/mol)
P(CH
CH
O)22CH
Table 2. Hydrogenation of various quinolines and isoquinolines using
thermoregulated phase-transfer Pt nanoparticles as catalyst.a
6

a
Reaction conditions: 1-pentanol 4 mL, water 4 mL (containing 1.93 × 10-3
mmol of Pt, Ph
2
P(CH
2
CH
2
O)22CH
3
/Pt = 2 (mol/mol)), substrate/Pt = 1000
o
(
mol/mol), 100 mg of n-decane as internal standard; T = 130 C, PH2 = 3
MPa; conversion and selectivity were determined by GC and GC-MS;
Turnover Number (TON): moles of product formed per mole of Pt, TON = n ×
Conversion × Selectivity (n = substrate/Pt).
b
Substrate/Pt = 500 (mol/mol).
The lifetime is an important factor to evaluate the use of the transition metal catalysts [37-39],
especially for hydrogenation of quinolines and isoquinolines due to the toxic effect on catalysts caused by
reaction substrates and hydrogenation products. Therefore, with the optimized reaction conditions in
hand, the recycling efficiency of the thermoregulated phase-transfer Pt nanocatalyst in the hydrogenation
of quinoline and isoquinoline was examined. After reaction, the lower catalyst phase was easily separated
from the upper product phase by simple phase separation and directly reused in the next reaction run. As
show in Fig. 2, the thermoregulated phase-transfer Pt nanocatalyst in the hydrogenation of quinoline and
isoquinoline could be reused ten recycles without evident loss in catalytic activity and selectivity. More
importantly, for quinoline, the TON is up to 10,474, which is the highest value ever reported among Pt
catalysts. Especially for isoquinoline, the TON is as high as 5,340, which is far ahead of the highest
record among transition metal catalysts. In addition, the recycling efficiency of the catalyst was also tested
near 80% substrate conversion and similar results were achieved compared with >99% conversion (Fig.
S2, see Supplementary Material for details). TEM and HRTEM images showed that the particle size of the
7

Pt nanoparticles in the hydrogenation of quinoline remained nearly the same between the newly prepared
and after ten recycles (Fig. 3a-b vs. 3c-d). As for isoquinoline, after ten catalytic recycles the particle size
increased from 2.1 to 3.1 nm (Fig. 3a-b vs. 3e-f). This can be ascribed to the stronger alkalinity and
poison effect of isoquinoline and 1,2,3,4-tetrahydroisoquinoline compared with quinoline and
1
,2,3,4-tetrahydroquinoline. In addition, ICP-AES analyses of the upper organic phase after the first run
indicated that the leaching of Pt in the hydrogenation of quinoline and isoquinoline were 5.62 wt.% and
.81 wt.%, respectively, and from the second run on the leaching of Pt decreased obviously until the
1
leaching was below the detection limit (Table S1, see Supplementary Material for details). Although
further optimization is necessary to minimize the Pt leaching, the above-mentioned results still confirmed
that the thermoregulated phase-transfer Pt nanocatalyst was highly active, selective and recyclable for
hydrogenation of quinolines, especially for isoquinolines.
Fig. 2. Recycling efficiency of the thermoregulated phase-transfer Pt nanocatalyst in the hydrogenation of quinoline (a) and
isoquinoline (b).
8

Fig. 3. TEM images, particle size histograms and HRTEM images of the thermoregulated phase-transfer Pt nanocatalyst
newly prepared (a, b), after ten recycles for hydrogenation of quinoline (c,d) and isoquinoline (e,f).
4
. Conclusion
In summary, the thermoregulated phase-transfer Pt nanocatalyst was firstly reported for hydrogenation
of quinolines and isoquinolines. More excitingly, the catalyst not only was highly active (>99% conversion)
and selective (>99% selectivity) but also can be easily separated from products by simple phase
separation and directly recycled for ten times without evident loss in activity and selectivity. To the best of
our knowledge, in this paper, the TON for quinoline is up to 10,474, which is the highest value ever
reported among Pt catalysts. Even more remarkably, for isoquinoline, the TON is as high as 5,340, which
is far ahead of the highest record among transition metal catalysts.
Acknowledgements
This work was supported by the National Natural Science Foundation of China (21373039, 21173031).
9

References
[
[
[
1] S. Dhanasekaran, V. Bisai, R. A. Unhale, A. Suneja, V. K. Singh, Org. Lett. 16 (2014) 6068-6071.
2] T. Jiang, W-W. Chen, M-H. Xu, Org. Lett. 19 (2017) 2138-2141.
3] R. T. Skerlj, G. J. Bridger, A. Kaller, E. J. McEachern, J. B. Crawford, Y. Zhou, B. Atsma, J. Langille, S. Nan, D. Veale,
Trevor Wilson, C. Harwig, S. Hatse, K. Princen, E. D. Clercq, D. Schols, J. Med. Chem.53 (2010) 3376-3388.
4] Z. Wang, Y. Zhang, S. G. Bartual, J. Luo, T. Xu, W. Du, Q. Xun, Z. Tu, R. A. Brekken, X. Ren, A. N. Bullock, G. Liang, X.
Lu, K. Ding, ACS Med. Chem. Lett. 8 (2017) 327-332.
[
[
[
[
[
5] K. Yamashita, S. Imahashi, S. Ito, Dyes Pigm. 76 (2008) 748-753.
6] J-X. Jiang, Y. Li, X. Wu, J. Xiao, D. J. Adams, A. I. Cooper, Macromolecules 46 (2013) 8779-8783.
7] M. Thevis, M. Kohler, W. Schänzer, Drug Discov. Today 13 (2008) 59-66.
8] R. Burai, C. Ramesh, M. Shorty, R. Curpan, C. Bologa, L. A. Sklar, T. Oprea, E. R. Prossnitz, J. B. Arterburn, Org.
Biomol. Chem. 8 (2010) 2252-2259.
[
9] T. Y. Taha, S. M. Aboukhatwa, R. C. Knopp, N. Ikegaki, H. Abdelkarim, J. Neerasa, Y. Lu, R. Neelarapu, T. W. Hanigan,
G. R. J. Thatcher, P. A. Petukhov, ACS Med. Chem. Lett. 8 (2017) 824-829.
[
[
10] S. Bell, B. Wüstenberg, S. Kaiser, F. Menges, T. Netscher, A. Pfaltz, Science 311 (2006) 642-644.
11] Y. Xu, M. A. Celik, A. L. Thompson, H. Cai, M. Yurtsever, B. Odell, J. C. Green, D. M. P. Mingos, J. M. Brown, Angew.
Chem. Int. Ed. 48 (2009) 582-585.
[
12] T. Pullmann, B. Engendahl, Z. Zhang, M. Hölscher, A. Zanotti-Gerosa, A. Dyke, G. Franciò, Walter Leitner, Chem. Eur. J.
1
6 (2010) 7517-7526.
[
[
[
[
[
[
[
[
[
13] V. Sridharan, P. A. Suryavanshi, J. C. Menéndez, Chem. Rev., 111 (2011) 7157-7259.
14] M. Fang, N. Machalaba, R. A. Sánchez-Delgado, Dalton Trans. 40 (2011) 10621-10632.
15] B. Sun, F-A. Khan, A. Vallat, G. Süss-Fink, Appl. Catal. A-Gen. 467 (2013) 310-314.
16] L. Zhang, X. Wang, Y. Xue, X. Zeng, H. Chen, R. Li, S. Wang, Catal. Sci. Technol. 4 (2014) 1939-1948.
17] I. S. Park, M. S. Kwon, K. Y. Kang, J. S. Lee, J. Parka, Adv. Synth. Catal. 349 (2007) 2039-2047.
18] M. Niu, Y. Wang, P. Chen, D. Du, J. Jiang, Z. Jin, Catal. Sci. Technol. 5 (2015) 4746-4749.
19] A. Karakulina, A. Gopakumar, İ. Akçok, B. L. Roulier, T. LaGrang, Angew. Chem. Int. Ed. 55 (2016) 292-296.
20] K. Okamoto, R. Akiyama, H. Yoshida, T. Yoshida, S. Kobayashi, J. Am. Chem. Soc. 127 (2005) 2125-2135.
21] N. Hashimoto, Y. Takahashi, T. Hara, S. Shimazu, T. Mitsudome T. Mizugaki, K. Jitsukawa, K. Kaneda, Chem. Lett. 39
(2010) 832-834.
1
0

[
[
[
[
[
[
[
22] Y. Gong, P. Zhang, X. Xu, Y. Li, H. Li, Y. Wang, J. Catal. 297 (2013) 272-280.
23] D. Ge, L. Hu, J. Wang, X. Li, F. Qi, J. Lu, X. Cao, H. Gu, ChemCatChem 5 (2013) 2183-2186.
24] L. Bai, X. Wang, Q. Chen, Y. Ye, H. Zheng, J. Guo, Y. Yin, C. Gao, Angew. Chem. Int. Ed. 55 (2016) 15656-15661.
25] S. K. Moromi, S.M.A. H. Siddiki, K. Kona, T. Toyao, K. Shimizua, Catal. Today 281 (2017) 507-511.
26] S. Zhang, Z. Xia, T. Ni, Z. Zhang, Y. Ma, Y. Qu, J. Catal. 359 (2018) 101-111.
27] D. Ren, L. He, L. Yu, R-S. Ding, Y-M. Liu, Y. Cao, H-Y. He, K-N. Fan, J. Am. Chem. Soc. 134 (2012) 17592-17598.
28] M. Yan, T. Jin, Q. Chen, H. E. Ho, T. Fujita, L-Y. Chen, M. Bao, M-W. Chen, N. Asao, Y. Yamamoto, Org. Lett. 15 (2013)
1
484-1487.
[
[
[
[
29] S. Zhang, Z. Xia, T. Ni, H. Zhang, C. Wu, Y, Qu, J. Mater. Chem. A 5 (2017) 3260-3266.
30] D-S. Wang, Q-A. Chen, S-M. Lu, Y-G. Zhou, Chem. Rev. 112 (2012) 2557-2590.
31] X-C. Zhang, Y-H. Hu, C-F. Chen, Q. Fang, L-Y. Yang, Y-B. Lu, L-J. Xie, J. Wu, W. Fan, Chem. Sci. 7 (2016) 4594-4599.
32] R. Adam, J. R. Cabrero-Antonino, A. Spannenberg, K. Junge, R. Jackstell, M. Beller, Angew. Chem. Int. Ed. 56 (2017)
3
216-3220.
[
[
[
[
[
[
[
33] H. Konnerth, M. H. G. Prechtl, Green Chem. 19 (2017) 2762-2767.
34] K. Li, Y. Wang, J. Jiang, Z. Jin, Catal. Commun. 11 (2010) 542-546.
35] W. Li, Y. Wang, M. Zeng, J. Jiang, Z. Jin, RSC Adv. 6 (2016) 6329-6335.
36] W. Li, Y. Wang, P. Chen, M. Zeng, J. Jiang, Z. Jin, Catal. Sci. Technol. 6 (2016) 7386-7390.
37] Liu J., He K., Wu W., Song T-B., Kanatzidis M. G., J. Am. Chem. Soc. 139 (2017) 2900-2903.
38] Lu S., Hu Y., Wan S., McCaffrey R., Jin Y., Gu H., Zhang W., J. Am. Chem. Soc. 139 (2017) 17082-17088.
39] Chen Y., Yang X., Kitta M., Xu Q., Nano Res. 10 (2017) 3811-3816.
11