From a blue to white to yellow emitter: A hexanuclear copper iodide nanocluster

Article abstract of DOI:10.1039/c9dt04701h

Highly emissive copper(i) halide nanoclusters showing thermally activated delayed fluorescence (TADF) have been paid much attention, but rarely reported so far. Herein, a hexanuclear copper(i) iodide cluster containing a tridentate N?P?N ligand, [Cu₆I₆(ppda)₂] {ppda = 2-[2-(dimethylamino)phenyl(phenyl)phosphino]-N,N-dimethylaniline}, was synthesized. All six copper atoms are four-coordinate, including four CuPNI₂and two CuI₄units. This complex exhibits intense white emission in the powder state at room temperature and shows a peak at a wavelength of 535 nm (F_PL= 0.36) with a microsecond lifetime (t= 4.4 μs). Emission colors can be largely tuned from blue to white to yellow, from the crystal to powder to film state at 297 K. The emission of [Cu₆I₆(ppda)₂] originates from a combination of MLCT and XLCT transitions. This complex showed good thermal stability. A solution-processed, nondoped device of complex [Cu₆I₆(ppda)₂] exhibits stable yellow emission with the CIE coordinates (x,y) of (0.43, 0.51). [Cu₆I₆(ppda)₂] also shows reasonable photocatalytic H₂evolution activity under visible-light irradiation.

Full text of DOI:10.1039/c9dt04701h

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2020, DOI: 10.1039/C9DT04701H.
Volume 46
Number 10
14 March 2017
Pages 3073-3412
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Page 1 of 28
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DOI: 10.1039/C9DT04701H
From Blue to White to Yellow Emitter: A Hexanuclear
Copper Iodide Nanocluster
Ke Xua, Bu-Lin Chena, Rui Zhangb, Li Liu*a, Xin-Xin Zhong*a, Lei Wang*b, Feng-Yan Li*c,
Guang-Hua Lid, Khalid A. Alamrye, Fa-Bao Lia, Wai-Yeung Wong*f, Hai-Mei Qing
a Hubei Collaborative Innovation Center for Advanced Organic Chemical Materials, Ministry
of Education Key Laboratory for the Synthesis and Application of Organic Functional
Molecules, School of Chemistry and Chemical Engineering, Hubei University, Wuhan
430062, P. R. China. E-mail: liulihubei@hubu.edu.cn; xxzhong@hubu.edu.cn
b
Wuhan National Laboratory for Optoelectronics, Huazhong University of Science and
Technology, Wuhan 430074, P. R. China. E-mail: wanglei@mail.hust.edu.cn
c
Key Laboratory of Polyoxometalates Science of Ministry of Education, College of
Chemistry, Northeast Normal University, Changchun, 130024, P. R. China. E-mail:
lify525@nenu.edu.cn
d
State Key Laboratory of Inorganic Synthesis and Preparative Chemistry, College of
Chemistry, Jilin University, Changchun 130012, P. R. China.
e Chemistry Department, Faculty of Science, King Abdulaziz University, Jeddah 21589, Saudi
Arabia
f
Department of Applied Biology and Chemical Technology, The Hong Kong Polytechnic
University, Hung Hom, Hong Kong, P. R. China. E-mail: wai-yeung.wong@polyu.edu.hk
g Fujian Provincial Key Lab of Theoretical and Computational Chemistry, and Department of
Chemistry, College of Chemistry and Chemical Engineering, Xiamen University, Xiamen
361005, P. R. China.
Ke Xu, Bu-Lin Chen and Rui Zhang contributed equally to this work.
Abstract
Highly emissive copper(I) halide nanoclusters having thermally activated delayed
fluorescence (TADF) have been paid much attention, but rarely reported so far. Here, a
hexanuclear copper(I) iodide cluster containing tridentate N˄P˄N ligand, [Cu6I6(ppda)2] {ppda
= 2-[2-(dimthylamino)phenyl(phenyl)phosphino]-N,N-dimethylaniline}, was synthesized. All
six copper atoms are four-coordinate, including four CuPNI2 and two CuI4 units. This
complex exhibits intense white emission in powder state at room temperature and has peak

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wavelength at 535 nm (ΦPL = 0.36) with microsecond lifetime (τ = 4.4 μs). EmissiDoOnI: c10o.1l0o3r9/cCa9DnT04701H
be largely tuned from blue to white to yellow, from crystal to powder to film state at 297 K.
The emission of [Cu6I6(ppda)2] originates from a combination of MLCT and XLCT
transitions. This complex displayed good thermal stability. A solution-processed, nondoped
device of complex [Cu6I6(ppda)2] exhibits stable yellow emission with CIE(x,y) of (0.43,
0.51). [Cu6I6(ppda)2] also shows a reasonable photocatalytic H2 evolution activity under
visible-light irradiation.
1. Introduction
Copper(I) complexes have been highly attractive due to the superiority in low cost,
pro-environment, high brightness and facile luminescent modulation.[1] The low-lying MLCT
excited states with small singlet-triplet energy gap facilitate Cu(I) complexes efficiently
harvest triplet excitons for thermally activated delayed fluorescence (TADF) emission which
potentially applied in highly efficient organic light-emitting diodes (OLEDs).
Cu(I) complexes usually have a distorted tetrahedral geometry around the Cu atom,
which often exhibit relatively low quantum yield due to increased non-radiative decay.[2] To
overcome the problem, one way is using the trigonal-planar structure with rigid ligands[3] or
two-coordinate Cu(I) complex[4] to hamper the Jahn-Teller distortion, a signifcant example
was reported by Osawa and co-workers, a highly efficient, green, three-coordinate Cu(I)
halide with a EQE over 20%. Another way is to design a firm framework with bulky or
bridged ligands.[3,5] A highly emissive, yellow, four-coordinate mononuclear Cu iodide
complex using a tridentate phosphine ligand with a EQE of 16.3%, and negligible roll-off was

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DOI: 10.1039/C9DT04701H
made by Xu’s group.[6]
In comparison to mono- and dinuclear Cu(I) complexes (n = 1, 2),[7-14] nanoclusters ( n
≥ 3)[15-18] have advantages of rigidity, and therefore thermo- and photostability. However,
only one Cu4I4 cluster was used as emitter in OLED to date.[19] The main challenge is their
poor processability and weak eletroactivities.
Based on the high luminescence efficiency of the Cu(I) halide complexes,[20-26]
rigid/congested structure is important to avoid structural changes in the excited state. For this
reason, tridentate ligand,
N˄P˄N
a
a
2-[2-(dimthylamino)phenyl(phenyl)phosphino]-N,N-dimethylaniline is employed, likely
obtain high efficiency emissive Cu(I) complex. Reported here is a luminescent
four-coordinate copper(I) iodide cluster, the molecular structure and photophysical and
photocatalytic properties are investigated.
2. Experimental
2.1. Materials
All reagents and solvents are of commercial reagent grade and used without further
purification except where noted. Tetrahydrofuran (THF) was distilled under nitrogen in the
presence of sodium chips using benzophenone ketyl as an indicator.
2-bromo-N,N-dimethylaniline was synthesized according to the literature method.[27]
2.2. Instrumentation
1H, 13C and 31P NMR spectra were recorded on a Varian 600 or 400 MHz NMR spectrometer
using deuterated solvents as the lock and reference. Chemical shifts were reported in ppm

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DOI: 10.1039/C9DT04701H
relative to SiMe4 for the 1H and 85% H3PO4 for the 31P nucleus. High-resolution mass spectra
reported as m/z were obtained on a Bruker Autoflex MALDI-TOF mass spectrometer. C and
H analyses were determined using a Vario Micro Cube elemental analyzer. The single crystal
structure of the complex [Cu6I6(ppda)2] was measured at room temperature using Bruker P4
Venture diffractometer. The powder X-ray diffraction data were obtained from a Bruker-D8
Advance diffractometer. UV–vis spectra were recorded on a Unicam Helios α spectrometer.
Photoluminescence spectra were recorded on a FLS920 steady state & time-resolved
fluorescence spectrometer. Solid-state ΦPL values were determined using a Hamamatsu
system for absolute PL quantum yield measurements equipped with an integrating sphere with
Spectralon inner surface coating. The PL lifetimes were measured by a single photon counting
spectrometer from Edinburgh Instruments (FLS920) with a Picosecond Pulsed UVLASTER
(LASTER377) as the excitation source. The samples were carefully degassed by at least five
freeze-pump-thaw cycles. Thermogravimetric analysis (TGA) was performed on a
Perkin-Elmer Diamond TG/DTA thermal analyzer. The elemental composition was
determined with SEM/EDS (Hitachi SU-800 FE-SEM). The hydrogen evolved was analyzed
with a gas chromatograph (Agilent 6890GC, thermal conductivity, Ar carrier).
2.3. Syntheses
2.3.1. Synthesis of 2-[2-(dimthylamino)phenyl(phenyl)phosphino]-N,N-dimethylaniline
(ppda)
n-BuLi (2.5 M in hexane, 2 mL, 5 mmol) was added dropwise to a solution of
2-bromo-N,N-dimethylaniline (1 g, 5 mmol) in THF/Et2O (1:1, 20 mL) at 110°C, the

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DOI: 10.1039/C9DT04701H
reaction mixture was stirred at 110°C for 5 min. PhPCl2 (0.34 mL, 2.5 mmol) was added
during 5 min. The resulted pale yellow solution was gradually warmed to room temperature
and stirred for 8 h. The reaction was then quenched by addition of water (10 mL). The
mixture was treated with aqueous NH4Cl and extracted with CH2Cl2 (3×10 mL). The extracts
were combined and dried over anhydrous Na2SO4. After removal of solvent, the residue was
purified by flash chromatography to afford the white powder of 0.436 g with a yield of 50%.
1H NMR (600 MHz, CDCl3): δ: 7.32-7.26 (m, 5H), 7.21-7.17 (m, 4H), 6.96 (t, J = 6 Hz, 2H),
6.81-6.78 (m, 2H), 2.63 (s, 12H). 13C NMR (100 MHz, d6-DMSO), δ = 157.45, 138.92,
134.93, 133.58, 133.07, 129.70, 128.21, 127.97, 124.09, 120.31, 44.97. 31P NMR (200 M,
CDCl3) δ: 17.45 (s). Anal. Calcd for C22H25N2P: C, 75.84; H, 7.23; N, 8.04. Found: C,
75.90; H, 7.18; N, 8.09. MS (MALDI-TOF): m/z calcd for [C22H25N2P+H]+, 349.1755, found:
349.1767.
2.3.2. Synthesis of [Cu6I6(ppda)2]
A suspension of copper(I) iodide (0.057 g, 0.30 mmol) and ppda (0.105 g, 0.30 mmol) in
30 mL of CH3CN was stirred for 3 days at room temperature to form a white precipitate. The
precipitate was filtered off, and [Cu6I6(ppda)2] was crystallized from the filtered solution after
slow evaporation at room temperature to give colorless crystals of 0.066 g with a yield of
1
72%. H NMR (600 MHz, CDCl3) δ: 7.84-7.76 (m, 2H), 7.68-7.55 (m, 6H), 7.47-7.39 (m,
12H), 7.20-7.15 (m, 6H), 2.67 (s, 24H). 31P NMR (200 M, CDCl3) δ: 31.73. Anal. Calcd for
C44H50Cu6I6N4P2: C, 28.73; H, 2.74. Found: C, 28.77; H, 2.71. MS (MALDI-TOF): m/z calcd
for [Cu2I(dppa)+H]+, 601.9392, found: 601.3938. A solution of [Cu6I6(ppda)2] crystals

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DOI: 10.1039/C9DT04701H
dissolved in CH3CN was evaporated to remove organic solvent under vacuum, a powder
sample is obtained. Anal. Calcd for C44H50Cu6I6N4P2: C, 28.73; H, 2.74. Found: C, 28.78; H,
2.73. A solution of [Cu6I6(ppda)2] dissolved in CH3CN (10 mg/mL) was spin coated onto the
substrate at 2000 r.p.m for 50 s, a film sample is obtained.
2.4. X-ray crytallography
Colorless crystals of complex [Cu6I6(ppda)2] suitable for X-ray diffraction study were
grown by slow evaporation of its solution in acetonitrile at room temperature. Geometric and
intensity data were collected using graphite-monochromated Mo Kα radiation (λ = 0.71073
Å) on a Bruker AXS APEX II CCD area detector. The collected frames were processed with
the software SAINT[28], and an absorption correction was applied (SADABS)[29] to the
collected reflections. The structures were solved by direct methods (SHELXTL)[30] in
conjunction with standard difference Fourier techniques and subsequently refined by
full-matrix least-squares analyses on F2. All non-hydrogen atoms were assigned with
anisotropic displacement parameters.
2.5. Theoretical calculations
The structural parameters for complex [Cu6I6(ppda)2] were obtained from the crystal data
which are listed in Tables 1 and 2. The ground-state (S0) geometry was then optimized at
theoretical level of B3LYP-D3(BJ)/6-311+G(d,p) (LANL2D2 for Cu and I atoms), where
D3(BJ) was Grimme's D3 dispersion correction with Becke-Jonson damping. To calculate the
adiabatic excitation energies, the optimized geometries of S1 and T1 are required, which were
obtained
at
theoretical
levels
of
TD-B3LYP-D3(BJ)/6-31+G(d)
and

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DOI: 10.1039/C9DT04701H
UB3LYP-D3(BJ)/6-31+G(d) (LANL2D2 for Cu and I atoms), respectively. The absorption
spectrum based on the optimized S0 geometry was obtained at the
TD-B3LYP-D3(BJ)/6-311+G(d,p) (LANL2D2 for Cu and I atoms) level. In addition, the
solvent effect was taken into account by the polarizable continuum model (PCM,
solvent=acetonitrile) for the purpose of comparing with the experimental spectrum. All the
calculations were manipulated by the Gaussian 16 suite.[31]
Table 1. Crystallographic data and details for [Cu6I6(ppda)2]
[Cu6I6(ppda)2]
Empirical formula
Formula weight
Temperature (K)
Wavelength (Å)
Crystal system
Space group
a (Å)
C44H50Cu6I6N4P2
1839.46
293(2)
0.71073
Monoclinic
P2(1)/n
12.7527(40)
13.5827(38)
15.2564(41)
2637.9(9)
b (Å)
c (Å)
V (Å3)
Z
2
ρ (g cm-3)
2.316
µ (mm-1)
5.982
F (0 0 0)
1728
θ range for data collection (°)
Index ranges
3.00 to 27.47
16 ≤ h ≤ 16
17 ≤ k ≤ 17
19 ≤ l ≤ 19
24543 [R(int) = 0.0953]
99.4 %
Independent reflections
Completeness to θ = 25.242°
Max. and min. transmission
Gof
0.3478 and 0.2864
1.082
Final R indices [I > 2σ(I)]
R1= 0.0536
wR2= 0.1263
R1= 0.0598
wR2= 0.1304
2.772 and 2.281
R (all data)
Max/min (e Å3)

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Table 2. Selected bond lengths [Å] and angles (°) for [Cu6I6(ppda)2] DOI: 10.1039/C9DT04701H
[Cu6I6(ppda)2]
2.5854(9) , 2.6067(10), 2.6287(8),
2.6947(11), 2.6756(10), 2.6461(12),
2.7664(10), 2.7782(11)
Cu
2.3447(14) , 2.5008(15)
CuP
2.098(4), 2.121(5)
CuN
Cu…Cu
2.4135(13), 2.7424(11), 2.8334(11),
3.0259(18)
104.16(3), 105.48(3), 107.66(3), 108.01(4),
108.06(3), 111.41(4), 114.73(3), 116.98(4)
53.14(3), 61.29(2), 61.46(2), 62.00(2),
65.57(3), 68.59(4), 120.66(3)
106.68(12), 109.12(13), 110.70(12),
116.37(13)
Cu
CuCu
CuN
106.95(5), 116.95(4), 117.96(5), 131.75(4)
83.66(13), 86.51(12)
CuP
PCuN
CuPCu
59.65(4)
2.6. Device Fabrication
Patterned indium tin oxide (ITO) glass substrates with the sheet resistance less than 15 Ω/sq
were successively cleaned with alkaline cleaner diluted with deionized water, acetone and
isopropanol by ultrasonic cleaning and then oven-dried for more than 3 hours after quick
drying with N2. The ITO glass substrates were then treated with the oxygen plasma for 5 min
in air. Poly(3,4-ethylenedioxythiophene)/poly(styrenesulfonate) (PEDOT: PSS) solutions
(Baytron PVP Al 4083, filtered through a 0.22 μm filter) were spin-coated onto the
o
ITO-coated glass substrates at the speed of 2000 r.p.m. for 50 s and baked at 120 C for 30
min in the air. The PEDOT: PSS-coated substrates were transferred into a nitrogen-filled
glove box (O2﹤1p.p.m., H2O﹤1p.p.m.). Then a solution of [Cu6I6(ppda)2] dissolved in DMF
(15 mg/mL) was spin coated onto the substrates at 2000 r.p.m for 50 s and baked at 100 oC for
10 min in the glove box to volatilize the DMF and acquire a smooth film of emitting layer

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(EML) material. Finally, the substrates were transferred to a vacuum chamber aDnOdI: a10f.t1e03r9/tCh9aDtT04701H
1,3,5- tris(1-phenyl-1H-benzimidazole-2-yl)benzene (TPBi, 30 nm) and LiF/Al electrodes (1
nm/100 nm) were deposited using a thermal evaporation system through a shadow mask
under a high vacuum of ≈ 4 × 10−4 Pa. The current density-voltage and luminance-voltage
were measured using a Keithley 2400 source measurement unite and in the meanwhile the
efficiency was measured with a PhotoResearch spectroradiometer (PR655), and all the tests
were conducted in the air without encapsulation.
2.7. Photocatalytic hydrogen production
The photocatalytic hydrogen production test was performed in a closed system with a 200 mL
quartz flask at room temperature. A 300 W xenon lamp (Beijing Perfectlight Technology
Corp., China) was used as the light source with an AM 1.5 optical filter and photocurrent
density was 100 mW cm-2. In a typical photocatalytic experiment, 50 mg of the prepared
photocatalyst (Cu6I6(ppda)2 in powder state) was suspended in 200 mL mixed solution
containing CH3OH (20 vol%) as sacrificial reagents and DI water. Nitrogen was purged
through the cell for 30 minutes to remove oxygen before photocatalytic reaction. The blank
experiments showed no appreciable hydrogen evolution in the absence of irradiation or
photocatalyst. After a continuous reaction for 3h, the photocatalyst was centrifuged and
redispersed in a new reaction solution with fresh sacrificial reagents.
3. Results and discussion
3.1. Description of syntheses and structures
The synthetic routes for ligand ppda and complex [Cu6I6(ppda)2] are outlined in Scheme 1.

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DOI: 10.1039/C9DT04701H
First, methyl iodide was used to methylate the 2-bromoaniline to furnish
2-bromo-N,N-dimethylaniline in 70% yield. Then the synthesis of
2-dimethylaminophenyllithium was carried out in a mixture with the mole ratio of 1:1 for
2-bromo-N,N-dimethylaniline and n-butyllithium. By the addition of
dichlorophenylphosphine to 2-dimethylaminophenyllithium in THF at −110 °C under
nitrogen, ppda was synthesized in 50% yield. Complex [Cu6I6(ppda)2] was prepared by
mixing a suspension of CuI in acetonitrile with 1 equivalent of ppda. A new hexanuclear
Cu(I) iodide complex was obtained as air stable crystal in high purity and found to be
generally soluble in acetonitrile, methanol, chloroform and DMF. It was characterized by
MALDI-TOF spectrometry, single crystal X-ray diffraction, and NMR spectroscopy and gave
satisfactory analytical data.
Br
Li
n-BuLi
PhPCl2
THF
P
THF
NMe2
NMe2
NMe2 NMe2
ppda
CuI
MeCN
Me
Me
Me Me
I
N
N
Cu

u
I
C
Cu
I
Cu
P
P
Cu
u
C

N
I
N
Me
Me
Me
Me
[Cu6I6(ppda)2]
Scheme 1. Synthetic pathways to ligand ppda and complex [Cu6I6(ppda)2].

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DOI: 10.1039/C9DT04701H
3.2. X-ray crystallographic study
Perspective view of complex [Cu6I6(ppda)2] is shown in Fig.1. Crystallographic data and
selected bond lengths and angles are given in Tables 1 and 2, respectively. X-ray
crystallographic study on complex [Cu6I6(ppda)2] reveal a hexanuclear Cu6I6 cluster, in which
four Cu atoms are involved in tetrahedral geometries and each Cu atom is coordinated by two
iodide atoms and a nitrogen and a phosphor atoms from the ppda ligand. The remaining two
Cu atoms are in tetrahedrally coordinated by four iodide atoms. The distances of Cu-I bonds
are from 2.5854 to 2.7782, which are within the normal ranges as the data reported before.[32]
The average Cu-N distance is 2.1095 Å, slightly shorter than those observed in
[Cu(µ-I)(PNMe2)]2 (2.250 and 2.232 Å),[25] reflecting the enhanced coordination strength.
Accordingly, the distances of CuP are from 2.3447 to 2.5010 Å, which are longer than those
observed in [Cu(µ-I)(PNMe2)]2 (2.210 and 2.213 Å),[25] displaying the highly congested
environment around phosphorus atoms. Two copper(I) centers (Cu3 and Cu3’) are bridged by
two iodide atoms (I2 and I2’) with a planar four-membered Cu2X2 ring. The centroid of the
Cu3I2Cu3’I2’ ring is also the centre of symmetry of the complex, with two iodide atoms (I1
and I1’) take on the trigonal pyramidal geometries symmetrically. It is noted that the
metallophilic interactions exist in two trigonal pyramidal geometries, with the Cu …Cu
distances (2.4135 Å for Cu1…Cu2 and Cu1’…Cu2’, 2.7424 Å for Cu3…Cu2 and Cu3’…Cu2’)
shorter than the van der Waals distance (2.80 Å), and weaker Cu…Cu interactions for Cu1…
Cu3,
Cu1’ … Cu3’ (2.8334 Å) and Cu3 … Cu3’ (3.0259 Å). Furthermore, complex
[Cu6I6(ppda)2] has an elliptical configuration with diameters of 1.7 and 2.0 nm (Fig.S6),

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making it competent as a nanoemitter for super-resolution display. IntermoleculDaOrI:h10y.1d0r3o9/gCe9DnT04701H
bonds can be observed in [Cu6I6(ppda)2], with the closest H-to-I distance of 3.120 Å.
Complex [Cu6I6(ppda)2] also shows the intermolecular C-H …π interactions between phenyl
rings with the closest C-to-H distance of 2.760 Å. Overall, all these intermolecular
interactions are incorporated into 2-D sheet for complex [Cu6I6(ppda)2] (Supporting
Information Fig.S7).
Fig.1. ORTEP diagram of complex [Cu6I6(ppda)2], H atoms were omitted for clarity.
3.3. Photophysical properties and theoretical calculations
The absorption spectra of complex [Cu6I6(ppda)2] and ppda in CH3CN (5.5 × 10-6 M) at
room temperature are shown in Fig.2. The absorption spectrum of ppda exhibits a broad,
intense band at 211 nm (ε = 2.80 × 104 M−1 cm−1), which is characteristic of an aryl phosphine
and amine compound. This band is assigned to a mixed transition of n–π* and π–π*; the
former one involves the transition of an electron from the lone pair orbital on phosphorus or
nitrogen to an empty antibonding π* orbital on a phenyl ring and the latter is the electron

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transition from a phenyl ring to the same or another phenyl ring. Complex [Cu6I6D(OpIp: 1d0a.1)023]9/hC9aDsT04701H
an intense absorption band with a maximum at 245 nm [ε = 1.87 × 104 M−1 cm−1] and a
weaker band tail at 280–350 nm. The weaker band tail may be attributed to the electronic
transition being affected by the copper ions, the halide ligands, or both, or intraligand charge
transfer (n→π*, π→π* or both). The absorption spectrum of complex [Cu6I6(ppda)2] in
CH3CN from our TDDFT calculations is shown in Fig.S18 in supporting information, which
is consistent with the experimental data. According to the excitation properties (Table S2, Fig.
S19) for complex [Cu6I6(ppda)2], the main contributions to the lowest excited state are
identified as the mixed transitions from HOMO (highest occupied molecular orbital) and
HOMO1 to LUMO+1 (LUMO: lowest unoccupied molecular orbital). As shown in Fig.3,
the contour plots of HOMO1, HOMO and LUMO+1 at optimized S0 geometry reveal that
the electrons in HOMO and HOMO1 are mainly distributed over the copper and halogen
atoms, while the holes in LUMO+1 are mainly localized on the phenyl rings of ppda. We can
thus conclude that the lowest excited state of [Cu6I6(ppda)2] (280–350 nm) consists of
metal-to-ligand charge transfer (MLCT) and halogen-to-ligand charge transfer (XLCT) state
transition, analogous to those in Cu(I) halides complexes containing di- and tri-phosphine
ligand such as [CuI(dppb)(PPh3)] and TTPPCuX.[21-23,33]. We also measured the UV-Vis
absorption spectra of [Cu6I6(ppda)2] in CH3CN with the concentration range from 2.0 × 10-5
to 2.5 × 10-7 M (Fig.S9). The concentration dependence of the absorption intensity follows
Beer’s law, which confirms the solution stability and indicates the maintaining of the
hexanuclear cluster structure.

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DOI: 10.1039/C9DT04701H
6
4
2
0
ppda
Cu6I6(ppda)2
200
250
300
350
400
Wavelength (nm)
Fig.2. Absorption spectra of ppda and complex [Cu6I6(ppda)2] in CH3CN at 297 K.
The optimized S0
geometry
HOMO
LUMO+1
HOMO1
E =  eV
E =  eV
E = 1.48 eV
Fig.3. The optimized S0 geometry, electron cloud distribution of HOMO1, HOMO and
LUMO+1 for complex [Cu6I6(ppda)2].
The emission spectra of complex [Cu6I6(ppda)2] in crystal and powder state measured at
297 K and 77 K are shown in Fig.4 and the emission maxima, lifetimes and quantum yields of
the complex at 297 K and 77 K are summarized in Table 3. Complex [Cu6I6(ppda)2] in crystal
state shows intense blue emission at 476 nm (λex= 372 nm, τ = 2.7 μs, ΦPL = 0.0035 in air) with
a weaker shoulder at 420 nm, and a relatively weak low energy emission at 716 nm (τ = 73.3
ns). In powder state it shows intense white emission at 535 nm (λex= 350 nm, ΦPL = 0.36 in
vacuum) with a weaker shoulder at 450 nm. The weaker shoulder emission at 450 nm in

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powder state is from the ligand ppda when compared with the emission of ligDaOnId: 10p.1p03d9a/C9iDnT04701H
powder state at 297 K (Fig.S16). In film state, the emission color changes to yellow with
wavelength maxima at 563 nm and a much weaker peak at 415 nm. From crystal to powder to
film state, structural relaxation should take place at 297 K, rending a bathochromic shift to the
emission (λemcrystal = 476 → λempowder = 535 → λemfilm = 563 nm). The PXRD patterns of the
powder and film samples confirm some structural changes in the crushed state and large
changes in amorphous state when compared to the simulated peaks from the single-crystal
data (Fig.S8). Much lower quantum yield of complex [Cu6I6(ppda)2] in crystal state than that
in powder state under vacuum, the main reason is due to the reduction of intermolecular
interaction-induced quenching through the transformation from crystal to powder state as
evidenced by powder X-ray diffraction analysis, analogous to copper iodide nanocluster
[DBFDP]2Cu4I4[19]. Based on the PL data in crystal, powder and film state at 297 K, the
Commission Internationale de L’Eclairage color coordinates are (0.2278, 0.2784), (0.2938,
0.3707) and (0.3990, 0.4613), respectively (Fig.5). The CIE value for the powder state is quite
near to the saturated white point of (0.33, 0.33). As far as we know, this is the first report on
efficient white light and the nearest to saturated white emission from neutral Cu(I) halide
complexes and the PLQY is the highest among Cu(I) halide clusters.
The emission properties of complex [Cu6I6(ppda)2] were also estimated based on the
optimized S1 geometries using the TDDFT method. The calculated emission wavelength of
complex [Cu6I6(ppda)2] (Table 3) suggests the reliability of our TDDFT method as the
theoretical value (463 nm) agrees well with the experimental one (476 nm). The

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DOI: 10.1039/C9DT04701H
LUMOHOMO transition is identified as the main contribution to the emission; the contour
plots of the HOMO and LUMO based on the S1 state geometry are in Fig.6. The LUMO is
mainly from Cu and X, and the HOMO is mainly confined to the phenyl rings in ppda. These
indicate that the luminescence mainly arises from XLCT and MLCT transitions.
At 77 K, the emission maxima of complex [Cu6I6(ppda)2] is located at 470 nm both in
the crystal and powder states. A relatively weak emission at 711 nm is observed in the crystal
state, similar as it at 297 K (716 nm), which may be from the difference of structures between
the crystal and powder. We analyzed the effect of molecular aggregates on the emission
spectra through the electronic structure calculations using TDDFT method. Owing to
hundreds of atoms, the optimized geometries of S1 and T1 cannot be obtained. However, the
absorption spectra of one, two and three molecules based on the crystal data were calculated
to present the effect of molecular aggregates. The results (Supporting Information Table S3)
showed that the absorptions at 297 K and 77 K are both red-shifted with the number of
molecules increasing, therefore, we can conclude that the molecular aggregates will result in
the emissions at 716 nm and 711 nm of the crystal. The molecular aggregates are possibly
ascribed to the intermolecular hydrogen bonds (H-to-I) and intermolecular C-H … π
interactions between phenyl rings which are discussed in X-ray crystallographic study. The
excitation spectrum with emission wavelength at 716 nm of complex [Cu6I6(ppda)2] in crystal
state is quite different from that with emission wavelength at 474 nm, indicating different
emission origin at 474 and 716 nm (Fig.S15). The intense, longer excitation wavelength at
404 nm is possibly due to the the molecular aggregates. In addition, the emission lifetime at

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DOI: 10.1039/C9DT04701H
716 nm of complex [Cu6I6(ppda)2] in crystal state is very short (73.3 ns), which might support
the molecular aggregates as well. The emission bands (470 and 711 nm) at 77 K are
blue-shifted in comparison to the bands (476 and 716 nm) at 297 K upon cooling possibly due
to suppression of the excited state energy relaxation caused by structural changes involving
vibrations and rotations.[20]
The S1 and T1 energy levels of 3.3244 and 3.2208 eV are estimated according to the
emission peak onsets at 297 K and 77 K (Fig.S17). The resulted ΔE(S1-T1) of 0.1036 eV is
very small to make RISC feasible. We found that the lifetime of luminescence from the solid
state at 297 K is 2 orders of magnitude shorter than those at 77 K, which is also consistent
with the TADF mechanism.[25,34] Fig.7 shows the temperature dependence of the decay times
in the solid state for the complex. In the temperature range between 77 and 317 K, the decay
is two-exponential. At 77 K, the emissive state is dominated by the lowest triplet state (T1).
The corresponding transition has long decay time because the transition from the lowest
triplet state to the singlet ground state is spin-forbidden. With the temperature increase, a
strong reduction of the emission decay time is observed. The thermal activation of the
short-lived singlet state S1 that decay irradiatively to give the TADF, is evidenced.
The radiative rate constant kr of complex [Cu6I6(ppda)2] was calculated to be 8.18 × 104
s1 in powder state, and 1.33 × 103 s1 in crystal state at 297 K, respectively. The value in
powder state is similar with those Cu(I) halide containing tridentate phosphine complex
TTPPCuX [22b], and copper iodide nanocluster [DBFDP]2Cu4I4[19]. Copper iodide nanocluster
[DBFDP]2Cu4I4 in crystal state is nonluminous[19]
.

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The selected bond lengths and angles in the optimized S0, and S1 geometriesDfOoIr: 1c0o.10m39p/Cle9DxT04701H
[Cu6I6(ppda)2] are collected in Table S1. The S1 coordination geometries of the copper center
of [Cu6I6(ppda)2] are highly distorted tetrahedral, with I-Cu-N, I-Cu-P, P-Cu-N and Cu-P-P
bond angles essentially unchanged in comparison to the ground state (S0) due to the rigid
structure of tridentate ligand ppda. Some changes are observed in I-Cu-I and Cu-I-Cu bond
angles, which possibly results in some nonradiative processes cause by Jahn-Teller distortion
of emissive excited states[3] and not very high quantum efficiency. Structural relaxation in
I-Cu-I and Cu-I-Cu bond angles possibly results in a bathochromic shift to the emission, from
crystal to powder to film state at 297 K.
297 K-Crystal
77 K-Crystal
1.0
297 K-Powder
77 K-Powder
297 K-Film
0.8
0.6
0.4
0.2
0.0
400
500
600
700
800
Wavelength (nm)
Fig.4. Normalized emission spectra of [Cu6I6(ppda)2] in crystal state at 297 K (λex = 372 nm)
and 77 K (λex = 350 nm), in powder state at 297 K (λex = 350 nm) and 77 K (λex = 320 nm)
and in film state (λex = 370 nm)
Table 3. Photophysical data of [Cu6I6(ppda)2] in the solid state.
krd
λmax (nm)a
τ (µs)b
Φc
λ
(104s1)
(nm)e
[Cu6I6(ppda)2]
Crystal
297 K
476
77 K
470
297 K
2.7
77 K
214
297 K 77 K
0.0035
/
0.133*
463
(0.0036*)

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DOI: 10.1039/C9DT04701H
Powder
Film
535
563
470
4.4
717
0.36* 0.73*
0.15
8.18*
a Emission peak wavelength in crystal and powder state.
b Average lifetime was used and calculated by the equation τave = ƩBiTi2/ƩBiTi, Bi and Ti are
are shown in Figures S8-S12. Experimental errors are ± 5%.
c Absolute emission quantum in crystal in air, asterisk indicates under vacuum. Experimental
errors are ± 5%.
d Radiative decay rate constant in crystal and powder state. kr = Ф/τave.
e Calculated emission wavelengths based on the optimized S1 geometries.
Fig. 5. CIE graph of complex [Cu6I6(ppda)2] in crystal, powder and film state.
The optimized S1 geometry
HOMO E =  eV
LUMO E = 2.11 eV
Fig.6. The optimized S1 geometry, electron cloud distribution of HOMO and LUMO at S1
geometry for complex [Cu6I6(ppda)2].

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800
600
400
200
0
50
100
150
200
250
300
350
Temperature (K)
Fig.7. Temperature dependence of decay time for complex [Cu6I6(ppda)2] in powder state.
3.4. Thermal properties
Since good thermal stabilities of the complexes are important for OLED applications, the
onset decomposition temperature (Tdec) of [Cu6I6(ppda)2] was determined by
thermogravimetric analysis (TGA) under a stream of nitrogen. From the onset of the TGA
curve (Fig.8), [Cu6I6(ppda)2] shows good thermal stability with its Tdec value at 248 °C with
weight loss of ca. 2%. The first-step weight loss for the complex [Cu6I6(ppda)2] of ca. 21%
was observed at 395 °C, which is due to the removal of two I atoms and eight methyls from
two ppda. The second-step weight loss was observed at 524 °C, which is ascribed to the
removal of four I atoms and further decomposition of two ppda ligands.

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DOI: 10.1039/C9DT04701H
Fig.8. TGA trace of complex [Cu6I6(ppda)2].
3.5 Electroluminescent properties
The solution-processed devices based on complex [Cu6I6(ppda)2] were fabricated with the
structure of ITO/ PEDOT:PSS (40 nm)/ complex [Cu6I6(ppda)2] (40 nm)/ TPBi (30 nm)/ LiF
(1 nm)/ Al (100 nm). In the device, ITO (indium tin oxide) was used as the anode, PEDOT:
PSS (Poly(3,4-ethylenedioxythiophene)：poly(styrenesulfonate)) used as hole injection and
hole
transport
layer,
complex
[Cu6I6(ppda)2]
used
as
the
EML,
1,3,5-Tris(1-phenyl-1H-benzimidazol-2-yl)benzene (TPBi) used as the electron transport
layer, LiF served as electron injection layer and Al as cathode. The energy-level diagram of
the device is shown in Fig.9(a). This device exhibits yellow emission at 564 nm with CIE (x,
y) of (0.43, 0.51). The EL spectrum of the device is shown in Fig.9(b). The device gives
maximum external quantum efficiency (EQE) of 0.31% and presented maximum current
efficiency (CE) of 0.85 cd/A. The performance of the device is less satisfactory than we
expected. We speculate the energy levels don't match up very well and further work should be
made to find more suitable transporting materials for [Cu6I6(ppda)2]. In addition, we have

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tried
CBP
(4,4'-bis(carbazol-9-yl)biphenyl),
DPEPO
(bis{2-[di(phenyl)phosphino]phenyl}etheroxide), mCP (N,N-dicarbazolyl-3,5-benzene) and
mCBP (3,3-di(9H-carbazol-9-yl)biphenyl) as the host materials, and complex [Cu6I6(ppda)2]
as the emitter to fabricate doped devices to improve the luminescence performance of OLED
devices. However, we found that due to the limited solubility of the complex [Cu6I6(ppda)2],
the solvent DMF or DMSO used could not dissolve the above host materials. Then we also
came up with a way to use mixed solvents by dissolving the complex [Cu6I6(ppda)2] in DMF
or DMSO accompanied with dissolving host material mCBP in acetone, and then mixing to
prepare the doped device. Due to the different evaporation rates of the two solvents, the
quality of the film is poor, which results in OLED device without emitting light.
Fig.9. (a) Energy-level diagram of the device based on [Cu6I6(ppda)2]; (b) the EL spectra of
the device at 5V, and the inset is the corresponding CIE; (c) current density–voltage–
luminance (J–V–L) characteristics; (d) EQE–luminance and CE–luminance characteristics.

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3.6 Photocatalytic properties
The photocatalytic H2 evolution experiments were carried out using complex
[Cu6I6(ppda)2] as the light photosensitizer and photocatalyst. Methanol was employed as a
sacrificial electron donor, being the source of the electrons required in the reduction
semi-reaction of water. The photocatalytic activity of complex [Cu6I6(ppda)2] could be
recovered owing to the re-exposed active-sites and the renewed sacrificial reagents. As shown
in Fig.10, the H2 evolution rate of complex [Cu6I6(ppda)2] was 22.30, 21.67 and 20.00 μmol/h,
respectively. The total amount of evoluted H2 during 9h was 191.9 μmol, which demonstrates
that complex [Cu6I6(ppda)2] shows photocatalytic H2 evolution activity under visible-light
irradiation. The activity of the photocatalyst is presumably attributed to the enhanced visible
light harvesting of complex [Cu6I6(ppda)2] and the effective electron-hole separation in the
complex. SEM-EDS for the Cu6I6 cluster was exhibited in Fig.S20 before and after the
photocatalysis. The atom (%) have no obviously change, which indicated that the Cu6I6
cluster undecomposed during the photocatalysis.

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Fig.10. Time course of H2 evolution from photocatalytic reaction with complex
[Cu6I6(ppda)2].
4. Conclusion
This is the first report on efficient white light and the nearest to saturated white emission
from the single-molecule hexanuclear Cu(I) iodide nanoclusters with the highest PLQY.
Emission color can be largely tuned from blue to white to yellow, by changing the solid state
from crystal to powder to film, due to the large structural relaxation, rending a bathochromic
shift to the emission. Small S1–T1 energy gaps in the solid state indicate that the emission
occurs from a thermally activated excited singlet state at ambient temperature. The emission
of [Cu6I6(ppda)2] originates from a combination of MLCT and XLCT transitions. Good
solubility in organic solvents allows it firstly applied in solution-processed device for
hexanuclear Cu iodide nanoclusters. In addition, it shows photocatalytic H2 evolution activity
under visible-light irradiation. This work manifests the great potential of cheap and abundant

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DOI: 10.1039/C9DT04701H
neutral Cu(I) halide nanoclusters for emitters in OLEDs and patent light photosensitizer and
photocatalyst in H2 evolution. Obviously, the EQE of device leaves a huge space for further
improving the EL performance of copper iodide clusters. Better solubility of the Cu(I) halide
nanoclusters in nonpolar solvents is needed to match the requirement for the common host
materials.
Conflicts of interest
There are no conflicts to declare.
Acknowledgements
This work was supported by the National Natural Science Foundation of China [grant number
21671061] and application foundation frontier special project by Wuhan Science and
Technology Bureau [grant number 2019010701011414]. W.-Y.W. thanks the Hong Kong
Research Grants Council (C4006-17G), the Hong Kong Polytechnic University (1-ZE1C) and
Ms Clarea Au for the Endowed Professorship in Energy (847S) for the financial support. We
thank senior engineer Mingxing Chen (Peking University) for his measurement of
photoluminescence property of complex.
Reference
[1] N. Armaroli, G. Accorsi, F. Cardinali, and A. Listorti, In Photochemistry and
Photophysics of Coordination Compounds I; Eds. V. Balzani, S. Campagna, Springer:
Berlin Heidelberg, 2007, 280, pp 69−115.
[2] Y. Tao, K. Yuan, T. Chen, P. Xu, H. Li, R. Chen, C. Zheng, L. Zhang, and W. Huang,
Adv. Mater., 2014, 26, 7931.

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Page 26 of 28
[3] M. Hashimoto, S. Igawa, M. Yashima, I. Kawata, M. Hoshino, and M. Osawa, J.VieAwmArt.icle Online
DOI: 10.1039/C9DT04701H
Chem. Soc., 2011, 133, 10348.
[4] R. Hamze,J.L. Peltier, D. Sylvinson, M. Jung, . Cardenas, R. Haiges, M. Soleihavoup, R.
Jazzar, P. I. Djurovic, G. Bertrand and M. E. Thompson. Science, 2019, 363, 601-606.
[5] D. Volz, Y. Chen, M. Wallesch, R. Liu,C. Fléchon, D. M. Zink, J. Friedrichs, H. Flügge ,
R. Steininger, J. Göttlicher, C. Heske, L. Weinhardt, S. Bräse, F. So, and T. Baumann,
Adv. Mater., 2015, 27, 2538.
[6] J. Zhang, C. Duan, C. Han, H. Yang, Y. Wei, and H. Xu, Adv. Mater., 2016, 28, 5975.
[7] Q. Zhang, Q. Zhou, Y. Cheng, L. Wang, D. Ma, X. Jing, and F. Wang, Adv. Mater.,
2004, 16, 432.
[8] N. Armaroli, G. Accorsi, M. Holler, O. Moudam, J. F. Nierengarten, Z. Zhou, R. T.
Wegh, and R. Welter, Adv. Mater., 2006, 18, 1313.
[9] D. G. Cuttell, S. M. Kuang, P. E. Fanwick, D. R. McMillin, and R. A. Walton, J. Am.
Chem. Soc., 2002, 124, 6.
[10] 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.
[11] D. Asil, J. A. Foster, A. Patra, X. de Hatten, J. del Barrio, O. A. Scherman, J. R.
Nitschke, and R. H. Friend, Angew. Chem. Int. Ed., 2014, 53, 8388.
[12] X. de Hatten, D. Asil, R. H. Friend, and J. R. Nitschke, J. Am. Chem. Soc., 2012, 134,
19170.
[13] W. Liu, Y. Fang, G. Z. Wei, S. J. Teat, K. Xiong, Z. Hu, W. P. Lustig, and J. Li, J. Am.
Chem. Soc., 2015, 137, 9400.
[14] T. Hasegawa, A. Kobayashi, H. Ohara, M. Yoshida, and M. Kato, Inorg. Chem., 2017,
56, 4928.
[15] C. W. Hsu, C. C. Lin, M. W. Chung, Y. Chi, G. H. Lee, P. T. Chou, C. H. Chang, and P.
Y. Chen, J. Am. Chem. Soc., 2011, 133, 12085.
[16] X. C. Shan, F. I. Jiang, D. Q. Yuan, H. B. Zhang, M. Y. Wu, L. Chen, J. Wei, S. Q.
Zhang, J. Pan, and M. C. Hong, Chem. Sci., 2013, 4, 1484.
[17] Y. Fang, W. Liu, S. J. Teat, G. Dey, Z. Shen, L. An, D. Yu, L. Wang, D. M. O’Carroll,
and J. Li, Adv. Funct. Mater., 2017, 27, 1603444.
[18] L. Ma, W. Chen, G. Schatte, W. Wang, A. G. Joly, Y. Huang, R. Sammynaiken, and M.
Hossu, J. Mater. Chem. C, 2014, 2, 4239.
[19] M. Xie, C. Han, J. Zhang, G. Xie, and H. Xu, Chem. Mater., 2017, 29, 6606.
[20] (a) M. Osawa, M. Hoshino, M. Hashimoto, I. Kawata, S. Igawa, and M. Yashima,
Dalton Trans., 2015, 44, 8369; (b) Q. Wei, R. Zhang, L. Liu, X. Zhong, L. Wang, G. Li,
F. Li, K. A. Alamry and Y. Zhao, Dalton Trans., 2019, 48, 11448; (c) B. K. Guo, F.
Yang, Y. Q. Wang, Q. Wei, L. Liu, X. X. Zhong, L. Wang, J. K. Gong, F. B. Li, W. Y.
Wong, K. A. Alamry, Y. Zhao, J. Lumin. 2020, 220, 116963.
[21] X. Hong, B. Wang, L. Liu, X. X. Zhong, F. B. Li, L. Wang, W. Y. Wong, H. M. Qin,
and Y. H. Lo, J. Lumin., 2016, 180, 64.
[22] (a) W. J. Zhang, Z. X. Zhou, L. Liu, X. X. Zhong, A. M. Asiri, K. A. Alamry, F. B. Li,
N. Y. Zhu, W. Y. Wong, and H. M. Qin, J. Lumin., 2018, 196, 425; (b) J. Zhang, C.
Duan, C. Han, H. Yang, Y. Wei, and H. Xu, Adv. Mater., 2016, 28, 5975.

Page 27 of 28
Dalton Transactions
View Article Online
[23] A. Tsuboyama, K. Kuge, M. Furugori, S. Okada, M. Hoshino, and K. Ueno, Inorg.
DOI: 10.1039/C9DT04701H
Chem., 2007, 46, 1992.
[24] D. M. Zink, M. Bächle, T. Baumann, M. Nieger, M. Kühn, C. Wang, W. Klopper, U.
Monkowius, T. Hofbeck, H. Yersin, and S. Bräse, Inorg. Chem., 2013, 52, 2292.
[25] M. J. Leitl, F. R. Küchle, H. A. Mayer, L. Wesemann, and H. Yersin, J. Phys. Chem. A,
2013, 117, 11823.
[26] T. Hofbeck, U. Monkowius, and H. Yersin, J. Am. Chem. Soc., 2015, 137, 399.
[27] I. Bonnaventure, and A. B. Charette, J. Org. Chem., 2008, 73, 6330.
[28] SAINT Reference Manual, Siemens Energy and Automation, Madison, WI, 1994.
[29] G. M. Sheldrick, SADABS, Empirical Absorption Correction Program, University of
Göttingen, Göttingen, Germany, 1997.
[30] G. M. Sheldrick, SHELXTL Reference Manual, Version 5.1, Siemens Energy and
Automation, Madison, WI, 1997.
[31] (a) M. J. Frisch, G. W. Trucks, H. B. Schlegel, G. E. Scuseria, M. A. Robb, J. R.
Cheeseman, G. Scalmani, V. Barone, B. Mennucci, G. A. Petersson, H. Nakatsuji, M.
Caricato, X. Li, H. P. Hratchian, A. F. Izmaylov, J. Bloino, G. Zheng, J. L. Sonnenberg,
M. Hada, M. Ehara, K. Toyota, R. Fukuda, J. Hasegawa, M. Ishida, T. Nakajima, Y.
Honda, O. Kitao, H. Nakai, T. Vreven, J. A. Montgomery Jr, J. E. Peralta, F. Ogliaro, M.
Bearpark, J. J. Heyd, E. Brothers, K. N. Kudin, V. N. Staroverov, R. Kobayashi, J.
Normand, K. Raghavachari, A. Rendell, J. C. Burant, S. S. Iyengar, J. Tomasi, M. Cossi,
N. Rega, J. M. Millam, M. Klene, J. E. Knox, J. B. Cross, V. Bakken, C. Adamo, J.
Jaramillo, R. Gomperts, R. E. Stratmann, O. Yazyev, A. J. Austin, R. Cammi, C.
Pomelli, J. W. Ochterski, R. L. Martin, K. Morokuma, V. G. Zakrzewski, G. A. Voth, P.
Salvador, J. J. Dannenberg, S. Dapprich, A. D. Daniels, O. Farkas, J. B. Foresman, J.V .
Ortiz, J. Cioslowski, and D. J. Fox, Gaussian 09, Revision A.1, Gaussian Inc.,
Wallingford, CT, 2016; (b) G. M. Sheldrick. Acta Cryst., 2008, 112, A64.
[32] Q. Hou, J. H. Yu, J. N. Xu, Q. F. Yang, and J. Q. Xu, Cryst. Eng. Comm., 2009, 11,
2452.
[33] C. Kutal, Coord. Chem. Rev., 1990, 99, 213.
[34] H. Yersin, A. F. Rausch and R. Czerwieniec, in Physics of Organic Semiconductors, ed.
W. Bruetting, C. Adachi and R. J. Holmes, Wiley-VCH, Weinheim, 2012, p. 371.

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TOC Graphic
DOI: 10.1039/C9DT04701H
Crystal
Powder
Film
1.0
0.8
0.6
0.4
0.2
0.0
Me
Me
Me
Me
I
N
N
Cu

u
C
Cu
I
P
I
P
Cu
N
Cu
u
C

I
N
Me
Me
Me
Me
[Cu6I6(ppda)2]
400
500
600
700
800
900 1000 1100
Wavelength (nm)
Emission color can be largely tuned from blue to white to yellow, by changing the
solid state from crystal to powder to film.