Metal-organic frameworks derived CuONPs@C nanocatalysts for synthesizing optoelectronic triarylamine molecules

Article abstract of DOI:10.1016/j.inoche.2020.108301

Carbon encapsulated copper oxide nanoparticles (CuONPs@C) fabricated using copper metal organic frameworks (Cu-MOFs) used as reusable nanocatalysts in Ullmann C[sbnd]N coupling reactions for synthesizing optoelectronic triphenylamine (TPA) and carbazole (CBZ) derivatives. The formation of CuONPs in carbon matrix was confirmed by powder X-ray diffraction (PXRD), X-ray photoelectron spectroscopy (XPS) and high-resolution transmission electron microscopy (HR-TEM). The catalytic activity of CuONPs@C was performed with diphenylamine/carbazole with substituted aryl halides in presence of mild K₂CO₃ base that produced triarylamines with 63–83% yields. Carbazole triarylamines exhibited strong solid state fluorescence (Φ_f = 14.54–36.32%) with λ_max between 370 and 420 nm.

Full text of DOI:10.1016/j.inoche.2020.108301

Inorganic Chemistry Communications xxx (xxxx) xxx
Contents lists available at ScienceDirect
Inorganic Chemistry Communications
journal homepage: www.elsevier.com/locate/inoche
Short communication
Metal-organic frameworks derived CuONPs@C nanocatalysts for
synthesizing optoelectronic triarylamine molecules
Anu Kundu, Vadivel Vinod Kumar, Savarimuthu Philip Anthony*
School of Chemical and Biotechnology, SASTRA Deemed University, Thanjavur 613402, Tamil Nadu, India
A R T I C L E I N F O
A B S T R A C T
Keywords:
Carbon encapsulated copper oxide nanoparticles (CuONPs@C) fabricated using copper metal organic frame-
Copper oxide nanoparticles
Nanocatalysts
–
works (Cu-MOFs) used as reusable nanocatalysts in Ullmann C N coupling reactions for synthesizing opto-
electronic triphenylamine (TPA) and carbazole (CBZ) derivatives. The formation of CuONPs in carbon matrix was
confirmed by powder X-ray diffraction (PXRD), X-ray photoelectron spectroscopy (XPS) and high-resolution
transmission electron microscopy (HR-TEM). The catalytic activity of CuONPs@C was performed with diphe-
nylamine/carbazole with substituted aryl halides in presence of mild K2CO3 base that produced triarylamines
with 63–83% yields. Carbazole triarylamines exhibited strong solid state fluorescence (Φf = 14.54–36.32%) with
λmax between 370 and 420 nm.
Metal organic frameworks
Luminescence
Nanocomposites
Carbon encapsulated nanoparticles
Polyaromatic amines such as triphenylamine and carbazole have
been used as important core units to build molecules for optoelectronic
applications such as organic light emitting diodes (OLEDs), displays,
dye-sensitized solar cells, smart materials, sensors, data storage and
optical switches because of their strong hole-transporting and fluores-
cence property [1,2]. The non-planar molecular geometry of triphe-
nylamine can be utilized to generate strong solid state fluorescent and
mechano/thermofluorochromic materials [3–5]. Palladium-catalyzed
Buchwald–Hartwig coupling, [6] copper-catalyzed Ullmann reaction,
[7] other transition-metal-mediated reactions primarily utilizing iron
[8] or nickel-based catalysts [9] are some of the most used methods for
synthesizing arylamines. However, harsh reaction conditions such as
high temperature (200 ◦C), expensive and/or highly air-sensitive com-
pounds such as phosphine-based ligands, catalytic sensitivity and low
yields often posed great challenge [10]. Ullmann-type coupling re-
actions have been employed as important tool for preparing numerous
biologically active natural products [11], pharmaceutical compounds
and polymers [12]. Cu-catalysed arylation reactions especially using
organic chemical transformation received significant attention since the
catalysts can easily be recovered, reused and also allowed easy separa-
tion of product [17,18]. Among different solid support, porous carbon is
more desirable in catalysis due to their large surface area, high thermal
and mechanical stability [18]. The low cost, abundant availability, good
stability and easy synthesis of copper oxide nanomaterials (CuONPs)
have been used as catalysts for different organic chemical trans-
–
formation including for C N Ullmann coupling reactions [19–22].
However, most of the reaction employed strong base along with
expensive ligands and mainly restricted to synthesizing diaryl amines.
Metal organic frameworks (MOFs) with exciting topology offered op-
portunities for fabricating metal/metal oxide NPs in carbon matrix. The
regularly arranged metal coordination in the MOFs can be transformed
into metal/metal oxide NPs in-situ by thermolysis induced carboniza-
tion whereas the diverse organic bridging ligands tend to produce highly
porous carbon matrices. The carbon matrix provides size controlling
structure for nanoaprticles along with increased stability. Herein, we
report the fabrication of CuONPs@C using Cu-MOFs as precursors that
was generated using valine amino acid based reduced Schiff base ligand
by simple calcination and utilized as nanocatalysts for synthesizing
optoelectronic triphenylamine/carbazole molecules. CuONPs@C
–
copper salts as catalysts have been explored extensively for C C and
–
C
N bonds (Ullmann-type couplings) formation [13]. Nevertheless, the
classic Ullmann-type reactions require harsh reaction conditions, stoi-
chiometric use of copper compounds, strong bases, and bipyridine or
phosphine-type costly ligands [14–16]. Therefore, developing mild,
simple and cost-efficient methods are still highly desirable.
–
exhibited good catalytic activity in Ullmann C N coupling reaction
between diphenylamine/carbazole and aryl halides in presence of mild
base that resulted in the formation of fluorescent triarylamines in good
yield (63–83%).
In recent years, fabrication of heterogeneous nanocatalysts for
* Corresponding author.
E-mail address: philip@biotech.sastra.edu (S.P. Anthony).
https://doi.org/10.1016/j.inoche.2020.108301
Received 20 July 2020; Received in revised form 16 October 2020; Accepted 18 October 2020
Available online 22 October 2020
1387-7003/© 2020 Elsevier B.V. All rights reserved.
Please cite this article as: Anu Kundu, Inorganic Chemistry Communications, https://doi.org/10.1016/j.inoche.2020.108301

A. Kundu et al.
Inorganic Chemistry Communications xxx (xxxx) xxx
Fig. 1. (a) Powder X-ray diffractogram of Cu-MOFs and high resolution XPS spectra of (a) Cu2p, (b) C1s and (c) O1s orbitals.
Fig. 2. (a, b) HR-TEM images of CuONPs and (c) solid state fluorescence.
Cu-MOFs was prepared by following the reported procedure
531.79 eV [Fig. 1d]. Further energy dispersive X-ray (EDX) analysis also
confirmed the presence of copper in the carbon matrix (Fig. S2). The
amount of copper present in the carbon matrix is 35.9%. HR-TEM image
showed dispersion of 10–15 nm size of CuONPs in the carbon matrix
[Fig. 2a, S3]. The magnified image clearly showed the encapsulation of
crystalline CuNPs in the carbon matrix that thickness ranged between 9
and 11 nm. Raman studies of CuONPs@C did not show any character-
istic peaks for graphitic carbon and hence amorphous normal carbon
matrix has been formed by decomposition of Cu-MOF (Fig. S4).
[Scheme S1, Fig. S1], [23]. CuONPs encapsulated in carbon matrix was
prepared by calcination of Cu-MOFs at 330 ◦C for 12 h in presence of air
and confirmed by PXRD [Fig. 1a]. The appearance of clear peaks in
PXRD pattern indicates the formation crystalline nanoparticles with
monoclinic phase (JCPDS#45-0937). XPS spectra of CuONPs@C
revealed Cu2+ 2p3/2 peaks at 935.18 eV and Cu2+ 2p1/2 peak at 955.08
eV with separation of 20.0 eV that indicates the presence of oxidized
state of copper [Fig. 1b], [24]. The appearance of shakeup satellites at
945.58 and 943.18 eV further established the formation of copper ox-
ides. High resolution C1s spectra revealed peaks at 284.58 and 288.18
eV [Fig. 1c]. The O1s binding energy peaks were observed at 530.19 and
The catalytic reaction was performed by mixing aryl halides and
diphenylamine/carbazole in presence of mild K2CO3 base and
CuONPs@C nanocatalysts in dichlorobenzene solvent under N2
2

A. Kundu et al.
Inorganic Chemistry Communications xxx (xxxx) xxx
calcination. Importantly, CuONPs@C exhibited good catalytic activity
for synthesizing triarylamine derivatives. The synthesized carbazole
derivatives exhibited strong solid state fluorescence. Thus easily acces-
sible CuONPs were prepared and used as catalyst for synthesising op-
toelectronic molecules.
Table 1
Synthesising different triarylamine derivatives using CuONPs nanocatalysts.
Entry
Aryl halide
R1
Time (hr)
Yield (%)e
R2
R3
TPA-1
TPA-2
TPA-3
TPA-4
TPA-5
CBZ-1
CBZ-2
CBZ-3a
CBZ-3b
CBZ-3c
CBZ-3d
CBZ-4
CBZ-5
CBZ-6
OCH3
H
H
H
12
12
14
10
16
8
68
63
65
64
66
72
74
73
72
70
68
76
83
80
OCH3
H
H
CRediT authorship contribution statement
H
OCH3
H
H
H
NO2
OCH3
H
H
H
Anu Kundu: Investigation, Data curation. Vadivel Vinod Kumar:
Investigation, Data curation, Writing - original draft. Savarimuthu
Philip Anthony: Writing - review & editing, Supervision, Project
administration, Funding acquisition.
H
H
OCH3
H
H
9
H
OCH3
OCH3
OCH3
OCH3
H
10
10
10
10
6
H
H
H
H
H
H
H
H
Declaration of Competing Interest
NO2
H
H
H
3
H
NO2
4
None.
a
Catalyst (I cycle).
b
c
Recycled catalyst (II cycle).
Recycled catalyst (III cycle).
Recycled catalyst (IV cycle).
Isolated yield.
Acknowledgments
d
e
Financial support from the Nanomission, Department of Science and
Technology, New Delhi, India (DST-Nanomission scheme no. SR/NM/
NS-1053/2015) is acknowledged with gratitude.
atmosphere [Table 1]. The reaction mixture was refluxed for 3–16 h
depending on the substrates. The triarylamines (triphenylamine/
carbazole) was isolated and purified using column chromatography that
showed yield between 63 and 83% [See supporting information for re-
action condition and NMR spectra]. The completion of each reaction
was monitored using thin layer chromatography. Diphenylamine/
carbazole starting material was disappeared at different times for
different aryl halide substrates that were taken as reaction time. Further
increasing reaction did not show any increase of yield. As a represen-
tative case, the reaction time for TPA-1 was increased from 12 to 16 h
but obtained the same yield (68%). The efficiency of CuONPs@C for
Appendix A. Supplementary material
Supplementary data to this article can be found online at https://doi.
org/10.1016/j.inoche.2020.108301.
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In conclusion, we have used Cu-MOFs as precursor as well as carbon
source for synthesising carbon encapsulated CuONPs by simple
3