Copper-catalyzed, silver-mediated formal [3+2] cycloaddition of simple alkynes with β-ketoesters through propargylic C(sp3)-H functionalization

Article abstract of DOI:10.1039/c8cc08013e

A copper-catalyzed propargylic [3+2] cycloaddition of simple alkynes with β-ketoesters through the propargylic C(sp³)-H functionalization has been realized. Under catalysis by CuI in combination with 1,10-phenanthroline hydrate as the ligand and Ag₂CO₃ as a bifunctional reagent (oxidant and base), the reaction proceeds smoothly with a broad substrate scope, thus providing a variety of highly functionalized furans in moderate to high yields. This represents the first successful example of the catalytic propargylic cycloaddition of simple alkynes with bisnucleophiles based on the propargylic C(sp³)-H functionalization strategy.

Full text of DOI:10.1039/c8cc08013e

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Strongly luminescent inorganic–organic hybrid
semiconductors with tunable white light
emissions by doping†
Cite this:DOI: 10.1039/c8tc05020a
ab
ba
Wei Liu,
Debasis Banerjee,b Fang Lina and Jing Li
*
A series of copper bromide based inorganic–organic hybrid semiconductors have been synthesized by
doping a trace amount of a secondary ligand into their parent structures. Upon near-ultraviolet
excitation, these structures emit broadband bluish (‘‘cold’’) to yellowish (‘‘warm’’) white light. The color
temperature can be systematically tuned by controlling the type and amount of the dopant. Our studies
show that the observed white emission is emitted directly from the doped sample, and is not a
combined effect from mixed phases. The internal quantum yields (IQYs) of these white-light-emitting
hybrids are as high as 68%, which are significantly higher than those of most direct white-light-emitting
phosphors reported to date. In addition, these copper halide staircase chain based hybrid structures
exhibit interesting thermochromic luminescence. The high quantum efficiencies coupled with facile and
low-cost synthesis and strong optical tunability of this materials group suggest its considerable promise
for lighting-related applications.
Received 4th October 2018,
Accepted 3rd December 2018
DOI: 10.1039/c8tc05020a
rsc.li/materials-c
In the recent years, single-phase, non-rare-earth, direct white-
light-emitting phosphors have been developed and are attracting
Introduction
Energy-efficient white-light-emitting-diodes (WLEDs) are commonly increasing attention due to their considerable potential for
produced by coating blue LED chips with blue-excitable phosphors. lighting-related applications.13–25 For example, II–VI (e.g. Zn, Cd
Such systems are regarded as phosphor-converted WLEDs and S, and Se) group based nano-crystal quantum dots (QDs) of
(pc-WLEDs).1,2 A simplest pc-WLED makes use of a yellow very small size can generate white light.26–28 However, their
phosphor, cerium-doped yttrium aluminium garnet (YAG:Ce). internal quantum yields (IQYs) are generally low. Their emissions
However, light emitted from this device typically lacks the lower are highly dependent on the particle sizes, which also require
energy (red) emission, resulting in an elevated correlated color complicated synthesis procedures. These drawbacks limit their
temperature (CCT) that is too ‘‘cold’’ for indoor illumination.1,3 practical use. Inorganic–organic hybrid semiconductors are a
An alternative approach is the excitation of a direct white light- unique family of semiconductor bulk materials that exhibit
emitting phosphor using a near ultraviolet LED chip. Such enhanced properties with respect to their parent structures.29–36
phosphors are typically a blend of several monochromic emitters. Unique properties, especially luminescence, have emerged as a
This design has several advantages such as better light quality, facile result of combining both the inorganic and organic components
device fabrication, etc.4–6 However, there are also disadvantages in a single crystal lattice.14,37–40 The structures built on II–VI
including significant self-absorption and color change due to the group based semiconductors and alkyl-amines emit white light in
decomposition of one component in the blends.7–10 Besides these their bulk phases. Their IQYs reach 37% upon Mn2+ doping.14,41,42
issues, nearly all commercial phosphors in today’s market contain Layered halide perovskites, on the other hand, exhibit intrinsic
rare-earth elements (REEs), which bring up potential supply, cost, white light emission with an IQY of 9%.37,43,44 However, compared
and environmental issues.11,12
to the IQYs of commercial phosphors, which are usually higher
than 80%, the photoluminescence efficiency of these structures
needs to be further improved for practical applications.
a Hoffmann Institute of Advanced Materials, Shenzhen Polytechnic,
7098 Liuxian Blvd, Nanshan District, Shenzhen, 518055, China
Our recent studies on I–VII binary metal halide (Cu, Ag and I, Br,
and Cl) based inorganic–organic hybrid semiconductors demon-
strate their strong potential as general lighting phosphors.38,45–47
This family of compounds have a number of advantages compared
to commercial and other phosphor classes, such as strong lumines-
cence, earth-abundance, REE-free, and facile one-step synthesis.
b Department of Chemistry and Chemical Biology, Rutgers University,
610 Taylor Road, Piscataway, NJ, 08854, USA. E-mail: jingli@rutgers.edu
† Electronic supplementary information (ESI) available: Crystal images, structural
plots, PXRD patterns, TGA data, DFT calculation results, UV-vis absorption spectra
and PL spectra. CCDC 1506741, 1506742 and 1506745. For ESI and crystallographic
data in CIF or other electronic format see DOI: 10.1039/c8tc05020a
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Fig. 1 Schematic illustration of the ligand doping approach in designing
white emitting 1D-CuBr(py)1Àx(pz)x compounds.
The emission profiles of nearly all of these structures are single-
band type, with a full width at half maximum (FWHM) of around
100 nm.48,49 Broadened emission spectra can be obtained by doping
a secondary ligand onto pristine hybrids.38 Herein, we report a
series of one dimensional (1D) staircase chain-like copper(I) bro-
mide based inorganic–organic hybrid compounds with the general
formula 1D-CuBr(pyridine)1Àx(pyrazine derivatives)x (x o 0.01),
where pyrazine (pz) derivatives are the dopants (Fig. 1). These
doped compounds exhibit tunable white light emission as well
as significantly enhanced IQYs, a 6-fold improvement compared
to previously reported copper iodide based analogues.38
A
comprehensive analysis has been done by varying the doping
amount and by modifying the dopants with different functional
groups. The results demonstrate that the light temperature of
the doped compounds is adjustable. Bluish (‘‘cold’’) to yellowish
(‘‘warm’’) white light from the single crystals of these structures
was observed, indicating that the white light is emitted directly
from the doped bulk materials (Fig. 2). Moreover, we observed
reversible thermochromic behavior in all white-light-emitting
compounds. This behavior has never been reported previously
for copper halide staircase chain based structures. The advantages
of high IQYs, facile synthesis and optical tunability make this type of
Fig. 2 Single crystals of 2 (a), 2c (c), 2f (e), 2g (g) under natural light and
2 (b), 2c (d), 2f (f), 2g (h) under UV light (365 nm).
Table 1 Summary of the crystal data of new 1D-CuBr(L) structures
(L = py functionalized ligand)
1D-CuBr
(3,5-dm-py) (1)
1D-CuBr
(3-Cl-py) (3)
1D-CuBr
(3-Br-py) (4)
Compound
Empirical formula
FW
Space group
C7H9BrCuN
250.60
C2/c
C5H4BrClCuN
256.99
P21/n
C5H4Br2CuN
301.44
P21/n
phosphor promising candidates as lighting phosphors, and their a (Å)
13.910(17)
15.111(18)
8.107(10)
90.00
99.455(17)
90.00
1681(4)
8
298(2)
8.7438(19)
3.9296(9)
21.002(5)
90.00
100.837(3)
90.00
708.7(3)
4
298(2)
8.720(9)
3.933(4)
21.11(2)
90.00
100.603(13)
90.00
711.6(12)
4
298(2)
b (Å)
thermochromic behavior may lead to new applications.
c (Å)
A (1)
B (1)
g (1)
Results and discussion
V (Å3)
Z
T (K)
l (Å)
Attempts to synthesize copper bromide based hybrid semi-
conductors led to the formation of compounds 1–4. They are
0.71073
0.0396
0.0973
0.71073
0.0306
0.0817
0.71073
0.0479
0.1207
all copper bromide staircase chain based structures (Fig. S4–S9, R1
wR2
CCDC
ESI†). Important crystallographic data of these compounds are
listed in Table 1. Their phase purities were evaluated and
1506745
1506742
1506741
confirmed by elemental analysis (Table S1, ESI†). Optical
absorption spectra for compounds 1–4 were recorded at room This trend corresponds to the decreasing LUMO energies of the
temperature and converted to the Kubelka–Munk function organic ligands in the structures, which are À1.039, À1.120, À1.473
(Fig. S12, ESI†). Their band gaps were estimated using their and À1.492 eV for 3,5-dm-py, py, 3-Cl-py and 3-Br-py, respectively
absorption edges, and are 3.1, 2.8, 2.7 and 2.5 eV, respectively. (Table S2, ESI†). As shown in Fig. S15 and Table S3 (ESI†),
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these structures emit strongly in the visible light region and significantly compared to that of the parent structure (Fig. 3c).
their emission colors range from blue to green. Their emission The blue-green emission band from their parent structure
spectra are all single-band type, with an average full width at remains in the higher energy (HE) region, while the second
half maximum (FWHM) of around 100 nm. Their emission band emerges in the spectra in the lower energy (LE) region,
energies are related to their band gap values and the LUMO resulting from doping. The HE and LE bands combine to give a
energies of the incorporated ligands. The internal quantum broad emission spanning over the entire visible light region
yields (IQYs) of 1–4 were determined at room temperature, and (400–700 nm). Centimeter-long single crystals of the doped
the values obtained with 360 nm as the excitation wavelength samples were obtained by a layering approach and all optical
are 56%, 48%, 27% and 21% for 1, 2, 3 and 4, respectively. measurements of the doped samples were from the single-phase
These results demonstrate that the varying functional groups samples. It was observed that the white light is emitted directly
on the py ligands significantly influence the quantum yields of from the single crystals, suggesting that it is a bulk property of the
the hybrid structures. Electron donating groups, such as methyl material. We also grinded the single crystals of 1D-CuBr(py)1Àx(pz)x
groups, enhance the emission, while electron-withdrawing groups, (x = 0.0012) into fine powder. No changes in the emission
such as chlorine or bromine, lower the emission efficiency. The were observed before and after grinding, confirming that the
structures’ band gaps, emission energies, IQY and ligand LUMO luminescence is not a surface property.
energies are highly related to each other and are in agreement with
our previous studies on 1D-CuI(L). The optical properties of these collected and all show a single, sharp absorption edge, indicating
structures can be tuned by ligand design and selection. that they are single-phase compounds (Fig. S13, ESI†). All of the
The absorption spectra for doped structures 2a–2h were
Compound 2 or 1D-CuBr(py) (space group P21) was chosen doped compounds have nearly the same band gap values as that of
as the parent structure for the doping study.50 It exhibits intense their parent structure 1D-CuBr(py). The possible impurities from
blue-green emission (lem = 494 nm) under near-UV excitation the dopants under these conditions are 2D-CuBr(L)0.5 (Fig. S5b,
(lex = 360 nm) with an IQY of 48%. In the case of the parent ESI†), which have band gaps around 2.0 eV, significantly lower
structure, adding a trace amount of pz afforded doped products than that of 1D-CuBr(py).51 However, no absorption at the lower
1D-CuBr(py)1Àx(pz)x (x o 0.01) (compounds 2a–2d). The PXRD energy part was observed in any of the spectra of the doped
analysis confirmed that the crystal structures of these doped structures. This confirms that the second bidentate ligands have
samples remain the same (Fig. 3a). Photoluminescence measure- been doped into the parent structure, and are not forming the
ments of the doped samples show that their emissions change second impurity phase. Further increasing the doping level to
Fig. 3 (a) PXRD patterns of the parent and doped structures of 1D-CuBr(py) compared with their simulated patterns. From bottom to top: simulated 2,
as-synthesized 2, and as-synthesized 2a–2h. The dopant concentrations are listed in Table 2. (b) Calculated density of states (DOS) of 1D-CuBr(py) (2) by
the DFT method: total DOS (black); Cu 3d orbitals (light blue); Br 4p orbitals (pink); C 2p orbitals (grey); and N 2p orbitals (blue). (c) Photoluminescence
spectra of 2a (solid), 2b (dash), 2c (dash dot dot) and 2d (short dash dot). Inset: Photo images of the doped samples under UV light. Samples from left to
right: parent 1D-CuBr(py), 0.004%, 0.008%, 0.02%, 0.05%, 0.07%, 0.12%, 0.32% pz doped 1D-CuBr(py). lex = 365 nm. (d) Relative intensities of the HE
band at 494 nm (blue) and the LE band at 545 nm (green), respectively, for 2c, as a function of excitation wavelengths. The intensity of the HE band at
360 nm is set to 1. Inset: PL spectra of 2c at various excitation wavelengths. (e) Luminescence decay spectra of 2c at 494 nm (blue) and 545 nm (green).
l
ex = 360 nm. (f) PL spectra of 2c at room temperature (red) and at 77 K (black). Inset: Images of 2c taken immediately after removing the sample from
liquid nitrogen (left) and at room temperature (right).
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x = 0.01 leads to the formation of the second phase, identified than 2.8 Å),48,52–54 as far as we are aware, such behavior has not
using the UV-vis absorption spectra as a new absorption band been reported for staircase chain based structures. For example,
appeared in addition to that of 2D-CuBr(pz)0.5 (Fig. S14, ESI†). a typical cubane cluster, 0D-Cu4I4(py)4, exhibits LE (yellow)
Therefore, we keep the doping amount significantly lower than emission at room temperature originated from ‘‘cluster centered’’
1% to ensure their single phase purity.
(CC) luminescence, and at low temperature (77 K), the
Upon varying the doping level of pz, from 0.05% to 0.32% LE emission is quenched and HE (blue) emission emerges as a
molar ratio to that of py, the peak positions of the HE and LE combination of MLCT and XLCT.48 The LE band emission in
bands remain unchanged while their intensities vary based on doped 1D-CuBr(py) samples is similar to that of cubane based
the doping level. With an increase in the doping amount, we structures, indicating that they might also be attributed to the
observe a gradual intensity decrease of the HE band along with CC luminescence mechanism. Single crystal X-ray diffraction is not
an intensity increase of the LE band. When the doping level capable of providing an answer as the doping level is too low to
reaches 0.32%, the HE is almost totally quenched, resulting in form an ordered structure. We also noted that the dopants must be
intense ‘‘yellowish’’ white light.
multidentate ligands in order to achieve the broadening effect of
The intense blue-green emission of the parent structure the spectra. Other multidentate ligands, including pyrimidine (pm)
1D-CuBr(py) is primarily attributed to a combination of metal- and 1,3,5-triazine (tz), exhibit a similar behavior to that of
to-ligand charge-transfer (MLCT) and halide-to-ligand charge pz derivatives (Fig. S17, ESI†). However, upon replacing these
transfer (XLCT) luminescence mechanism, as confirmed by Density dopants with monodentate ligands having lower LUMO energies,
Functional Theory (DFT) calculations (Fig. 3b and Fig. S11, ESI†). such as 3-cyano-py and 4-cyano-py (Table S2, ESI†), no broadening
The band gap and emission energy of this type of structure are effect was observed. The full understanding of the broadening effect
correlated to the LUMO energy of the ligand. Further calculations of through doping is still limited, and a further in-depth investigation
the LUMO energies show that pz has a distinctly lower energy of the luminescence mechanism is now underway.
(À1.857 eV) compared to that of py (À1.120 eV), indicating that the
The direct application of these white-lighting-emitting materials
parent ligand and the dopant might be responsible for the dual is their use as lighting phosphors. The quality of the white light
emissions (Table S2, ESI†). To understand this, we kept the parent from these phosphors is readily tunable by selecting suitable
ligand py, and changed the pz to pz derivatives (2-et-pz, 2-me-pz, dopants and doping amount. The performance of the doped
2-Cl-pz, 2-Br-pz) with different LUMO energies. Single crystals of compounds as lighting phosphors was evaluated by measuring their
2e–2h were obtained with these dopants, and PXRD analysis IQY, CIE (International Commission on Illumination) color coordi-
along with a UV-vis absorption experiment was conducted to nates, Color Rendering Index (CRI) and CCT under excitation with
confirm their phase correctness and purity. Based on their photo- near-ultraviolet light (365 nm) and the results are summarized in
luminescence measurements, all compounds show a two-band type Table 2. It is interesting to observe that the IQYs of most doped
spectrum (Fig. S16, ESI†). The emission energies of the HE band structures are higher than that of their parent structure, with the
remain constant for all of them, proving that the HE band is from highest IQY value of 68% for compound 2e. Compared to other
the parent ligand py. The energies of the LE band, however, changes reported direct white light emitting phosphors, which generally
accordingly based on the LUMO energies of the dopants, providing suffer from low IQYs, most of these compounds have IQYs higher
strong evidence that the LE band is originated from the dopants.
than 60%. More interestingly, their color temperature can also be
Furthermore, the relative intensities of the HE and LE bands tuned, from bluish (cold) to yellowish (warm) white light, as evident
at various excitation wavelengths were studied (Fig. 3d). The from their CCT values (Fig. 4). The current commercial white light
observation of their excitation-wavelength dependent emissions LEDs made from YAG:Ce produce ‘‘cold’’ white light with CCT
suggests that the HE band and the LE band are from the isolated values higher than 5000 K, which may not be suitable for indoor
luminous centers. Time-resolved PL measurements were conducted illumination.1 The color temperatures of the doped 1D-CuBr(py)
on the doped sample at an excitation wavelength of 360 nm at the samples, on the other hand, range from 3360 K to 5792 K, making
emission maximum of the two bands. The lifetime values for these materials usable under various environments.
495 nm and 550 nm emissions are 17.5 ms and 26.3 ms, respectively
(Fig. 3e). The difference in the lifetime values reflects their different solution processability. Using a commercial binder, they can be
excited states. easily coated onto different substrates. Prototype WLED bulbs
Moreover, the water stability of these materials ensures their
The temperature-dependent emission spectra of the doped were fabricated by coating 5 mm 365 nm LED chips with doped
samples show that they all display thermochromic behavior samples having various CCT values. These bulbs display white
(Fig. 3f). The intensity of the LE band completely quenched light from ‘‘cold’’ to ‘‘warm’’ as their CCT values decrease from
when the sample was dipped in liquid nitrogen (77 K), while the 5024 K to 3360 K (Fig. 4).
intensity of the HE band became much stronger. After removing
the crystals from liquid nitrogen, the initial emission intensities
of the two bands regained as the sample temperature returned
to RT, indicating that the thermochromic luminescence is fully
reversible. Though thermochromic behavior for copper halide
Experimental
Materials
cubane cluster-based hybrid materials has been well studied CuBr (98%, Alfa Aesar), KBr (499%, Alfa Aesar), acetonitrile (499%,
and is attributed to the short Cu–Cu bond distances (smaller Alfa Aesar), pyridine (py, 499%, Alfa Aesar), 3,5-dimethylpyridine
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Table 2 Summary of the composition and optical properties of the white-light-emitting structures
#
Dopant
pz
Doping amount
0.05
Band gap (eV)
3.0
lem (nm) (298 K)
lem (nm) (77 K)
IQYs (%) 360 nm
60
CIE
CRI
CCT (K)
5792
2a
494 (HE)
545 (LE)
494
0.34, 0.41
68.4
2b
2c
2d
2e
2f
pz
0.07
0.12
0.32
0.12
0.12
0.12
0.12
3.0
3.0
3.0
3.0
3.0
3.0
3.0
494 (HE)
545 (LE)
494
494
494
494
494
494
494
64
61
54
68
66
35
24
0.35, 0.42
0.39, 0.43
0.42, 0.46
0.26, 0.36
0.28, 0.37
0.43, 0.42
0.44, 0.40
67.0
67.2
58.0
65.4
65.5
77.2
75.6
5024
3888
3658
4259
3940
3697
3360
pz
484 (HE)
545 (LE)
pz
494 (HE)
545 (LE)
2-et-pz
2-me-pz
2-Cl-pz
2-Br-pz
494 (HE)
520 (LE)
494 (HE)
525 (LE)
2g
2h
494 (HE)
556 (LE)
494 (HE)
575 (LE)
vials or tubes (Fig. S1–S3, ESI†). The bottom, middle and top
layers were a CuBr/KBr saturated aqueous solution, aceto-
nitrile, and a ligand in ethanol, respectively. The crystals formed
in the middle layer over 3–5 days at room temperature. Pure
phase powder samples were obtained by direct mixing of CuBr
(0.1 mmol) in a saturated KBr solution (2.0 ml) with the ligand
(0.1 mmol) in ethanol (2.0 ml). The pure phase powder generally
formed immediately after stirring.
General procedures for the synthesis of the doped structures
The synthesis of doped compounds 1D-CuBr(py)1Àx(pz derivatives)x
(x o 0.01) is similar to that of their parent structures. A stock
solution of 10À4 M pz derivatives in ethanol was pre-prepared.
Single crystals of the doped structures were obtained by a
layering method. The ligand in an ethanol solution was made
by mixing the pz derivative stock solution with py at various
molar ratios, from 0% to 1.0% of py. Pure phase powder
samples were made by directly mixing the ligand solution with
CuBr in a KBr saturated solution while stirring at room temperature.
The doped structures obtained are 1D-CuBr(py)1Àx(pz)x (x = 0.0005,
2a; x = 0.0007, 2b; x = 0.0012, 2c; x = 0.0032, 2d) and
1D-CuBr(py)0.9988(pz derivatives)0.0012, (pz derivatives) = 2-et-pz
(2e); 2-me-pz (2f); 2-Cl-pz (2g); and 2-Br-pz (2h). All products
were collected by filtration and dried in an vacuum oven for
further characterization.
Fig. 4 CIE coordinates of all white-light-emitting structures. Inset:
Photos of the LED bulbs under working condition.
(3,5-dm-py, 498%, Alfa Aesar), 3-chloropyridine (3-Cl-py, 99%, Alfa
Aesar), 3-bromopyridine (3-Br-py, 498%, Alfa Aesar), pyrazine
(pz, 98%, Alfa Aesar), 2-ethyl-pyrazine (2-et-pz, 98%, Alfa Aesar),
2-methyl-pyrazine (2-me-pz, 98%, TCI), 2-chloro-pyrazine (2-Cl-
pz, 98%, Alfa Aesar), 2-bromo-pyrazine (2-Br-pz, 98%, TCI), and
sodium salicylate (SS, 99%, Merck).
Single crystal X-ray diffraction (SXRD) and powder X-ray
diffraction (PXRD) analysis
Single crystal X-ray diffraction data of 1, 3, and 4 were collected
at low temperature (100 K) on a Bruker-AXS smart APEX I CCD
diffractometer with graphite-monochromated MoKa radiation
General procedures for the synthesis of undoped structures (1)
to (4)
Single crystals of 1D-CuBr(3,5-dm-py) (1), 1D-CuBr(py) (2), (l = 0.71073 Å) at room temperature. The structures were solved
1D-CuBr(3-Cl-py) (3) and 1D-CuBr(3-Br-py) (4) were acquired by direct methods and refined by full-matrix least-squares on
by a layering method. The reactions were conducted in glass F2 using the Bruker SHELXTL package. The structures were
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deposited in the Cambridge Structural Database (CSD), and the Notes and references
file numbers are 1506741, 1506742, and 1506745.† A summary
1 X. Huang, Nat. Photonics, 2014, 8, 748–749.
of the crystal data of all five compounds are given in Table 1. PXRD
patterns of these structures were obtained using a Rigaku Ultima-IV
automated diffraction system with Cu Ka radiation. Measurements
were made in the 2y range of 3–501. The data were collected at room
temperature with a step size of 0.021 (2y) and a counting time of
0.2 s/step. The operating power was 40 kV/44 mA.
2 Y. H. Kim, P. Arunkumar, S. H. Park, H. S. Yoon and
W. B. Im, J. Mater. Sci. Eng. B, 2015, 193, 4–12.
3 H. Zhu, C. C. Lin, W. Luo, S. Shu, Z. Liu, Y. Liu, J. Kong,
E. Ma, Y. Cao, R.-S. Liu and X. Chen, Nat. Commun., 2014, 5.
4 B. Song, Y. Zhong, S. Wu, B. Chu, Y. Su and Y. He, J. Am.
Chem. Soc., 2016, 138, 4824–4831.
5 N. Horiuchi, Nat. Photonics, 2010, 4, 738.
Characterization and DFT calculations
6 M. Yoshihiko, K. Masahiro and N. Suguru, Semicond. Sci.
Technol., 2014, 29, 084004.
7 N. C. George, K. A. Denault and R. Seshadri, Annu. Rev.
Mater. Res., 2013, 43, 481–501.
8 A. Moazzam, C. Soma, N. Angshuman, K. Akshay, S. Sameer,
S. Chakraborty and D. D. Sarma, Nanotechnology, 2007,
18, 075401.
9 P. Thiyagarajan, M. Kottaisamy and M. S. R. Rao, J. Phys. D:
Appl. Phys., 2006, 39, 2701.
Optical diffuse reflectance spectra were measured at room
temperature on a Shimadzu UV-3600 spectrophotometer. Data
were collected in the wavelength range of 300–1000 nm and the
% reflectance was converted to the Kubelka–Munk function.
Photoluminescence (PL) measurements were carried out on a
Varian Cary Eclipse spectrophotometer at room temperature.
Thermogravimetric (TG) analyses were performed on a computer-
controlled TG Q5000 analyzer (TA Instruments) at a ramp rate of
10 1C minÀ1 from room temperature to 400 1C. The internal
quantum yield (IQY) was measured for the samples in the powder
form using a C9920-03 absolute quantum yield measurement
system (Hamamatsu Photonics) with a 150 W xenon monochromatic
light source and a 3.3 inch integrating sphere. Sodium salicylate
(99%, Merck) was used as the standard with an IQY value of 60%
when excited at 360 nm. The IQY value of the standard was
measured to be 65%, indicating an experimental error of less than
10%. The luminescence lifetime was measured using an FLS920
Edinburgh fluorimeter (Edinburgh Instruments, Livingston, United
Kingdom) with a microsecond mF900 xenon flash lamp as the
excitation source and by time-correlated single photon counting.
Instrumental response function (IRF) was applied if the instru-
mental response could not be neglected for shorter lifetimes.
10 H. J. Yu, K. Park, W. Chung, J. Kim, B.-H. Chun and
S. H. Kim, Polym. J., 2009, 41, 1076–1079.
11 B. Sprecher, I. Daigo, S. Murakami, R. Kleijn, M. Vos and
G. J. Kramer, Environ. Sci. Technol., 2015, 49, 6740–6750.
12 A. Tukker, Environ. Sci. Technol., 2014, 48, 9973–9974.
13 Y.-C. Liao, C.-H. Lin and S.-L. Wang, J. Am. Chem. Soc., 2005,
127, 9986–9987.
14 W. Ki and J. Li, J. Am. Chem. Soc., 2008, 130, 8114–8115.
15 T. Ogi, H. Iwasaki, A. B. D. Nandiyanto, F. Iskandar, W. N.
Wang and K. Okuyama, J. Mater. Chem. C, 2014, 2, 4297–4303.
16 T. Nakajima, M. Isobe, Y. Uzawa and T. Tsuchiya, J. Mater.
Chem. C, 2015, 3, 10748–10754.
17 Z.-Y. Mao, F. Wang, J.-J. Chen and D.-J. Wang, J. Am. Ceram.
Soc., 2015, 98, 3856–3862.
18 W. Liu, K. Zhu, S. J. Teat, G. Dey, Z. Shen, L. Wang, D. M.
O’Carroll and J. Li, J. Am. Chem. Soc., 2017, 139, 9281–9290.
19 W. Liu, Y. Fang and J. Li, Adv. Funct. Mater., 2018, 28, 1705593.
20 M.-S. Wang, S.-P. Guo, Y. Li, L.-Z. Cai, J.-P. Zou, G. Xu,
W.-W. Zhou, F.-K. Zheng and G.-C. Guo, J. Am. Chem. Soc.,
2009, 131, 13572–13573.
21 Z.-F. Liu, M.-F. Wu, S.-H. Wang, F.-K. Zheng, G.-E. Wang,
J. Chen, Y. Xiao, A. Q. Wu, G.-C. Guo and J.-S. Huang,
J. Mater. Chem. C, 2013, 1, 4634–4639.
22 G.-E. Wang, G. Xu, M.-S. Wang, L.-Z. Cai, W.-H. Li and
G.-C. Guo, Chem. Sci., 2015, 6, 7222–7226.
23 M.-S. Wang and G.-C. Guo, Chem. Commun., 2016, 52,
13194–13204.
24 N.-N. Zhang, C. Sun, X.-M. Jiang, X.-S. Xing, Y. Yan, L.-Z. Cai,
M.-S. Wang and G.-C. Guo, Chem. Commun., 2017, 53,
9269–9272.
25 M.-S. Wang, G.-C. Guo, W.-T. Chen, G. Xu, W.-W. Zhou,
K.-J. Wu and J.-S. Huang, Angew. Chem., Int. Ed., 2007, 46,
3909–3911.
Conclusions
In summary, a series of copper bromide inorganic–organic
hybrid semiconductors have been synthesized and structurally
characterized. Upon doping with a trace amount of the second,
multidentate ligand, they exhibit bright and tunable white light
emissions. The color quality of their white emission can be
precisely controlled and tuned by varying the dopant and doping
amount, generating a range of ‘‘cold’’ to ‘‘warm’’ emissions. All
doped compounds also exhibit thermochromic behavior as a
function of temperature. This work provides the first example
of a systematic study that demonstrates a dopant effect on the
photoluminescence of copper bromide based hybrid structures.
Conflicts of interest
There are no conflicts to declare.
26 T. E. Rosson, S. M. Claiborne, J. R. McBride, B. S. Stratton
and S. J. Rosenthal, J. Am. Chem. Soc., 2012, 134, 8006–8009.
27 M. J. Bowers, Ii, J. R. McBride, M. D. Garrett, J. A. Sammons,
A. D. Dukes Iii, M. A. Schreuder, T. L. Watt, A. R. Lupini,
Acknowledgements
Financial support from the National Science Foundation
(Grant no. DMR-1507210) is gratefully acknowledged.
J. Mater. Chem. C
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Paper
S. J. Pennycook and S. J. Rosenthal, J. Am. Chem. Soc., 2009, 42 M. Roushan, X. Zhang and J. Li, Angew. Chem., Int. Ed., 2012,
131, 5730–5731. 51, 436–439.
28 A. D. Dukes, P. C. Samson, J. D. Keene, L. M. Davis, J. P. Wikswo 43 E. R. Dohner, A. Jaffe, L. R. Bradshaw and H. I. Karunadasa,
and S. J. Rosenthal, J. Phys. Chem. A, 2011, 115, 4076–4081. J. Am. Chem. Soc., 2014, 136, 13154–13157.
29 X. Huang, J. Li and H. Fu, J. Am. Chem. Soc., 2000, 122, 44 M. D. Smith and H. I. Karunadasa, Acc. Chem. Res., 2018, 51,
8789–8790. 619–627.
30 X. Huang and J. Li, J. Am. Chem. Soc., 2007, 129, 3157–3162. 45 W. Liu, Y. Fang, G. Z. Wei, S. J. Teat, K. Xiong, Z. Hu,
31 C. R. Kagan, D. B. Mitzi and C. D. Dimitrakopoulos, Science,
1999, 286, 945–947.
32 D. B. Mitzi, S. Wang, C. A. Feild, C. A. Chess and
A. M. Guloy, Science, 1995, 267, 1473–1476.
W. P. Lustig and J. Li, J. Am. Chem. Soc., 2015, 137, 9400–9408.
46 Z. Liu, M. F. Qayyum, C. Wu, M. T. Whited, P. I. Djurovich,
K. O. Hodgson, B. Hedman, E. I. Solomon and M. E. Thompson,
J. Am. Chem. Soc., 2011, 133, 3700–3703.
33 X. Zhang, M. Hejazi, S. J. Thiagarajan, W. R. Woerner, 47 Z. Liu, J. Qiu, F. Wei, J. Wang, X. Liu, M. G. Helander,
D. Banerjee, T. J. Emge, W. Xu, S. J. Teat, Q. Gong,
A. Safari, R. Yang, J. B. Parise and J. Li, J. Am. Chem. Soc.,
2013, 135, 17401–17407.
S. Rodney, Z. Wang, Z. Bian, Z. Lu, M. E. Thompson and
C. Huang, Chem. Mater., 2014, 26, 2368–2373.
48 P. C. Ford, E. Cariati and J. Bourassa, Chem. Rev., 1999, 99,
3625–3648.
34 X. Huang, M. Roushan, T. J. Emge, W. Bi, S. Thiagarajan,
J.-H. Cheng, R. Yang and J. Li, Angew. Chem., Int. Ed., 2009, 49 K. Tsuge, Y. Chishina, H. Hashiguchi, Y. Sasaki, M. Kato,
48, 7871–7874.
S. Ishizaka and N. Kitamura, Coord. Chem. Rev., 2016, 306(Part 2),
636–651.
50 P. Healy, J. Kildea, B. Skelton and A. White, Aust. J. Chem.,
1989, 42, 93–105.
51 J. Pospisil, I. Jess, C. Nather, M. Necas and P. Taborsky, New
J. Chem., 2011, 35, 861–864.
52 S. Perruchas, C. Tard, X. F. Le Goff, A. Fargues, A. Garcia,
S. Kahlal, J.-Y. Saillard, T. Gacoin and J.-P. Boilot, Inorg.
Chem., 2011, 50, 10682–10692.
35 Z.-J. Zhang, G.-C. Guo, G. Xu, M.-L. Fu, J.-P. Zou and
J.-S. Huang, Inorg. Chem., 2006, 45, 10028–10030.
36 G.-E. Wang, G. Xu, B.-W. Liu, M.-S. Wang, M.-S. Yao and
G.-C. Guo, Angew. Chem., Int. Ed., 2016, 55.
37 E. R. Dohner, E. T. Hoke and H. I. Karunadasa, J. Am. Chem.
Soc., 2014, 136, 1718–1721.
38 X. Zhang, W. Liu, G. Z. Wei, D. Banerjee, Z. Hu and J. Li,
J. Am. Chem. Soc., 2014, 136, 14230–14236.
39 C. Sun, G. Xu, X.-M. Jiang, G.-E. Wang, P.-Y. Guo, M.-S. Wang 53 S. Perruchas, X. F. Le Goff, S. Maron, I. Maurin, F. Guillen,
and G.-C. Guo, J. Am. Chem. Soc., 2018, 140, 2805–2811.
40 C. Sun, M.-S. Wang, P.-X. Li and G.-C. Guo, Angew. Chem.,
Int. Ed., 2017, 56, 554–558.
41 X. Fang, M. Roushan, R. Zhang, J. Peng, H. Zeng and J. Li,
Chem. Mater., 2012, 24, 1710–1717.
A. Garcia, T. Gacoin and J.-P. Boilot, J. Am. Chem. Soc., 2010,
132, 10967–10969.
54 Q. Benito, X. F. Le Goff, S. Maron, A. Fargues, A. Garcia,
C. Martineau, F. Taulelle, S. Kahlal, T. Gacoin, J.-P. Boilot
and S. Perruchas, J. Am. Chem. Soc., 2014, 136, 11311–11320.
This journal is ©The Royal Society of Chemistry 2018
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