New heterobimetallic Au(i)-Pt(ii) polyynes achieving a good trade-off between transparency and optical power limiting performance

Article abstract of DOI:10.1039/c8tc03157f

Two series of new heterobimetallic Au(i)-Pt(ii) polyynes have been easily synthesized by cross-coupling under mild conditions. The absorption profiles of these two series of Au(i)-Pt(ii) polyynes are quite similar. However, the Au(i)-Pt(ii) polyynes with a 1,4-bis(diphenylphosphino)benzene ligand show stronger triplet (T₁) emission and superior optical power limiting (OPL) performance than the corresponding Au(i)-Pt(ii) polyynes with a 1,3-bis(diphenylphosphino)propane ligand. Hence, the 1,4-bis(diphenylphosphino)benzene ligand is more effective than the 1,3-bis(diphenylphosphino)propane ligand for optimizing the transparency and OPL ability of OPL materials. When compared with the corresponding homometallic Pt(ii) polyynes, these heterobimetallic Au(i)-Pt(ii) polyynes display a blue shift in their absorption spectra, showing better transparency in the visible-light region. Besides, these heterobimetallic Au(i)-Pt(ii) polyynes show stronger OPL ability than their corresponding homometallic Pt(ii) polyynes as well as the state-of-the-art OPL material C₆₀, demonstrating their enormous application potential in the nonlinear optics field. In brief, the introduction of Au(i) precursors with tetrahedral diphosphine ligands into the backbone of Pt(ii) polyynes can simultaneously achieve enhanced transparency and high OPL ability for OPL materials, providing a new strategy to optimize OPL materials.

Full text of DOI:10.1039/c8tc03157f

Journal of
Materials Chemistry C
View Article Online
View Journal | View Issue
PAPER
New heterobimetallic Au(I)–Pt(II) polyynes
achieving a good trade-off between transparency
and optical power limiting performance†
Cite this: J. Mater. Chem. C, 2018,
6, 11416
a
Zhuanzhuan Tian,a Xiaolong Yang,
Boao Liu,a Daokun Zhong,a
Guijiang Zhou *a and Wai-Yeung Wong
b
Two series of new heterobimetallic Au(I)–Pt(II) polyynes have been easily synthesized by cross-coupling
under mild conditions. The absorption profiles of these two series of Au(I)–Pt(II) polyynes are quite
similar. However, the Au(I)–Pt(II) polyynes with a 1,4-bis(diphenylphosphino)benzene ligand show stronger
triplet (T1) emission and superior optical power limiting (OPL) performance than the corresponding
Au(I)–Pt(II) polyynes with
a 1,3-bis(diphenylphosphino)propane ligand. Hence, the 1,4-bis(diphenyl-
phosphino)benzene ligand is more effective than the 1,3-bis(diphenylphosphino)propane ligand for
optimizing the transparency and OPL ability of OPL materials. When compared with the corresponding
homometallic Pt(II) polyynes, these heterobimetallic Au(I)–Pt(II) polyynes display a blue shift in their
absorption spectra, showing better transparency in the visible-light region. Besides, these heterobimetallic
Au(I)–Pt(II) polyynes show stronger OPL ability than their corresponding homometallic Pt(II) polyynes as
well as the state-of-the-art OPL material C60, demonstrating their enormous application potential in the
nonlinear optics field. In brief, the introduction of Au(I) precursors with tetrahedral diphosphine ligands into
the backbone of Pt(II) polyynes can simultaneously achieve enhanced transparency and high OPL ability
for OPL materials, providing a new strategy to optimize OPL materials.
Received 27th June 2018,
Accepted 1st October 2018
DOI: 10.1039/c8tc03157f
rsc.li/materials-c
their practical applications. Obviously, solving the conflict
between good transparency and high OPL ability of OPL
Introduction
Lasers are widely used in many fields, such as material pro- materials presents a critical issue in the nonlinear optics field.
cessing, surgery, military activities, etc.1 However, inevitable Due to the interaction between metal centers and organic
damage is caused to human eyes and optical sensors when acetylene ligands, organometallic acetylide compounds show
exposed suddenly to strong laser beams. So, studies of optical unique properties. In addition, Yang’s group reported that
power limiting materials have become more urgent.2,3 Until novel molecular skeletons and self-assembly structures formed
now, many types of OPL materials have been established, such by the new Pt(II) acetylenes also show intriguing properties.17–20
as fullerenes,4 metallophthalocyanines,5,6 metalloporphyrins,7,8 Hence, organometallic acetylides are widely applied in multiple
organic materials,9–12 graphenes,13,14 carbon nanotubes15 and fields.21–24 Importantly, they have great potential in coping with
so on. Most of these materials exhibit high OPL performance this conflict considering their good trade-off between trans-
and fast response speed and allow flexible chemical modifica- parency and OPL performance for OPL materials.25,26
tions. However, their strong absorptions beyond 400 nm result
Recently, Pt(II), Au(I), Hg(II) and Pd(II) acetylide compounds
in poor transparency in the visible-light region,16 restricting as high-performance OPL materials have been developed.16,27–35
Among them, Pt(II) acetylide compounds have been extensively
investigated due to their good transparency in the visible-light
region and high OPL ability. With respect to Pt(II) acetylides,
a MOE Key Laboratory for Nonequilibrium Synthesis and Modulation of Condensed
Matter, State Key Laboratory for Mechanical Behavior of Materials, Department of
Pt(II) polyynes have the advantages of enhanced OPL ability and
good film-forming ability for device fabrication,36,37 suggesting
their greater practical application potential in the OPL field.
However, the transparency of Pt(II) polyynes is inferior to that of
Pt(II) acetylides due to the red shift of the absorption band
caused by polymerization.27,34 To solve this problem, researchers
have explored a new strategy in which Hg(II) or Pd(II) ions were
Chemistry, School of Science, State Key Laboratory for Mechanical Behavior of
Materials, Xi’an Jiaotong University, Xi’an 710049, P. R. China.
E-mail: zhougj@mail.xjtu.edu.cn; Fax: +86-29-8266-3914
b Department of Applied Biology and Chemical Technology, The Hong Kong
Polytechnic University, Hung Hom, Hong Kong, P. R. China
† Electronic supplementary information (ESI) available: Synthetic details for
organic ligands, AuI acetylides and some photophysical data. See DOI: 10.1039/
c8tc03157f
11416 | J. Mater. Chem. C, 2018, 6, 11416--11426
This journal is ©The Royal Society of Chemistry 2018

View Article Online
Paper
Journal of Materials Chemistry C
introduced into the backbone of homometallic Pt(II) polyynes.34 Physical measurements
It is worth noting that introducing Hg(II) ions into the backbone
All the NMR spectra were measured in CDCl3 solvent using a
Bruker AXS 400 MHz NMR spectrometer with the H and 13C
of homometallic Pt(II) polyynes with fluorene-based ligands can
not only improve their transparency, but also offer them
comparable OPL performance with that of homometallic Pt(II)
polyynes. However, introducing Pd(II) ions into the backbone of
homometallic polyynes cannot significantly enhance the OPL
properties and transparency. The high toxicity of Hg(II) ions38,39
and the poor effect of introducing Pd(II) ions into the backbone
of Pt(II) polyynes limit the application of these ions in OPL
materials development. Therefore, effective strategies have to
be developed for optimizing the transparency and OPL perfor-
mance of Pt(II) polyynes.
1
NMR chemical shifts quoted relative to SiMe4 and the 31P
chemical shifts relative to the 85% H3PO4 external standard.
Fast atom bombardment (FAB) mass spectra were characterized
using a Finnigan MAT SSQ710 system. UV-Vis spectra were
recorded on a PerkinElmer Lambda 950 spectrophotometer at
298 K. The photoluminescent (PL) properties were charac-
terized using an Edinburgh Instruments FLS920 fluorescence
spectrophotometer. The lifetimes at 298 K for the excited states
were measured using a single photon counting spectrometer
from Edinburgh Instruments FLS920 with a 360 nm picosecond
LED lamp as the excitation source, while those at 77 K were
obtained with the excitation from a xenon flash lamp. The low-
temperature PL spectra and lifetimes at 77 K were measured by
dipping the degassed CH2Cl2 solution in a thin quartz tube into
a liquid nitrogen Dewar and the data were recorded after
allowing it to stand for 3 minutes. The fluorescence quantum
yields (FF) were measured in CH2Cl2 solutions at 298 K against
quinine sulfate in 1.0 M H2SO4 as the reference (FF ca. 0.56 at
334 nm and ca. 0.55 at 365 nm).41 The molecular weights were
determined using Waters 2695 GPC in CHCl3 and estimated by
using a calibration curve of polystyrene standards.
Au(I) acetylide compounds usually exhibit excellent trans-
parency in the visible-light region,27,31,40 which can be attri-
buted to the weak interaction between the 5d orbitals of the
Au(I) centers and the p orbitals of the organic ligands. Goswami
et al. reported one thienyl-carbazole-based Au(I) acetylide with
high transparency comparable to its organic ligand.27 This is
because the absorption band of this Au(I) acetylide only shows a
very slight red-shift compared with that of its organic ligand.
In addition, the transparency of the concerned OPL materials
can be successfully improved by introducing tetrahedral diphos-
phine ligands to the backbone of the Pt(II) polyyne due to their
conjugation-breaking ability. Recently, we have reported a series
of new Au(I) polyynes with tetrahedral diphosphine ligands with
excellent transparency in the visible-light region and some of
them even outperform C60 as OPL materials.40 So, the introduc-
tion of Au(I) ions and tetrahedral diphosphine ligands into
homometallic Pt(II) polyynes should be a promising protocol to
reduce the red shift effect after polymerization. On the basis of
these advantages, by combining monomeric Pt(II) acetylides and
the dinuclear Au(I) complex precursors with tetrahedral diphos-
phine ligands, two series of new heterobimetallic Au(I)–Pt(II)
polyynes have been developed. Compared with the corres-
ponding homometallic Pt(II) polyynes, these new polyynes can
not only show better transparency, but also achieve stronger
optical limiting performances by effectively maintaining the
density of the metal atom of the polyyne chain. Hence, the
results of the concerned polyynes should provide a new means
for achieving comprehensive optimization between good trans-
parency and high OPL ability.
Optical power limiting measurements
The optical power limiting properties were characterized by
Z-scan measurements, which were performed at 532 nm for the
Gaussian mode laser beam with a repetition frequency of 20 Hz
from a Q-switched Quantel Q-Smart 100 Nd:YAG laser. The laser
beam was split into two beams by a beam splitter. One was used
as the reference beam, which was directly received by a power
detector (D1), and the other was focused with a lens ( f = 20 cm)
for sample measurement. After starting the position control
device, the light beam through the sample was collected imme-
diately by another power detector (D2). The sample to be
measured was moved automatically along a rail to change the
incident irradiance with its distance (Z-position). The incident
and transmitted powers were detected simultaneously using
D1 and D2, separately. The OPL performance of each solution
sample was measured in CH2Cl2 with ca. 90% transmittance
solution filled in a 1 mm quartz cell. OPL devices based on
P1-FLU and P2-FLU were prepared by casting the polystyrene
(PS) solution (0.2 g mLÀ1) in CHCl3 with a ca. 1.0 wt% doping
level into a PTFE mould, respectively. Then, they were left on a
clean bench for 3 days at room temperature to obtain solid
plates as prototype OPL devices.
Experimental
General information
Commercially available reagents were used directly as received.
The solvents were refined through a normative process under
dry nitrogen for use. All reactions were completed under a
Computational details
nitrogen atmosphere. The reactions were monitored by thin- Geometrical optimizations were conducted using the popular
layer chromatography (TLC) using Merck pre-coated aluminum B3LYP density functional theory (DFT). The basis set used
plates. Flash column chromatography and preparative TLC for C, H, O, N and P atoms was 6-311G(d, p), whereas effective
were carried out using silica gel. All Sonogashira reactions core potentials with a LanL2DZ basis set were employed for
were completed using Schlenk techniques under a nitrogen Au and Pt atoms.42,43 The energies of the excited states of
atmosphere.
the complexes were computed by TD-DFT based on all the
This journal is ©The Royal Society of Chemistry 2018
J. Mater. Chem. C, 2018, 6, 11416--11426 | 11417

View Article Online
Journal of Materials Chemistry C
Paper
ground-state geometries. All calculations were carried out by 7.16–7.00 (m, 10H, Ar), 6.96–6.78 (m, 14H, Ar), 3.92 (br, 4H,
using the Gaussian 09 program.44
–OCH2–), 2.81 (br, 4H), 2.12–2.11 (br, 12H, PBu3), 1.95–1.90 (m,
2H), 1.77 (m, 4H, –CH2–), 1.57–1.54 (m, 12H, PBu3), 1.46–1.40 (m,
12H, PBu3), 1.33–1.26 (m, 36H, –CH2–), 0.92–0.86 (m, 24H, PBu3
Synthesis
Monomeric Pt(II) acetylides (FLU-Pt-FLU, TPA-Pt-TPA and CAZ- and –CH3); 31P NMR (161.9 MHz, CDCl3): d (ppm) 35.28, 2.65;
Pt-CAZ) were obtained using a modified method.34,40 L-P1-Au GPC: Mn = 2.4 Â 104 g molÀ1, PDI = 1.5 (against polystyrene
and L-P2-Au were synthesized as in a published reaction.45,46 standards); anal. found: C 60.96, H 5.68.
All the synthetic procedures are provided in the ESI.†
P2-CAZ. (Yield: 58%). 1H NMR (400 MHz, CDCl3): d (ppm)
8.27–8.17 (m, 2H, Ar), 8.00–7.96 (m, 2H, Ar), 7.75 (m, 8H, Ar),
7.63–7.57 (m, 2H, Ar), 7.46–7.34 (m, 14H, Ar), 7.27–7.20 (m, 4H,
A general synthetic procedure for Au(I)–Pt(II) polyynes
Under a N2 atmosphere, L-P1-Au/L-P2-Au (1.0 equiv.) and the Ar), 4.21 (br, 4H, –NCH2–), 2.85 (br, 4H), 2.23 (br, 12H, PBu3),
corresponding Pt(II) acetylides (1.0 equiv.) were mixed in 2.00 (br, 2H), 1.84 (br, 4H, –CH2–), 1.68 (br, 12H, PBu3), 1.51–
CH2Cl2/MeOH (v : v = 2 : 1). Then, sodium methoxide solution 1.44 (m, 12H, PBu3), 1.33–1.24 (m, 36H, –CH2–), 0.96–0.86 (m,
(3.0 equiv., 0.3 M) was added. The reaction mixture was kept 24H, PBu3 and –CH3); 31P NMR (161.9 MHz, CDCl3): d (ppm)
stirring for 5 h at room temperature. After removing the 35.36, 2.94; GPC: Mn = 3.1 Â 104 g molÀ1, PDI = 1.5 (against
solvent, the obtained residue was dissolved in a small amount polystyrene standards); anal. found: C 60.96, H 5.68.
of CH2Cl2 and filtered using a syringe filter (PTFE, 0.45 mm)
to remove the insoluble part. Then, it was precipitated in MeOH
and this procedure was repeated two times. The heterobimetallic
Results and discussion
Synthesis and structural characterization
Au(I)–Pt(II) polyynes were obtained as an off-white solid.
P1-FLU. (Yield: 56%). 1H NMR (400 MHz, CDCl3): d (ppm)
7.64–7.58 (m, 8H, Ar), 7.55–7.44 (m, 22H, Ar), 7.21 (m, 6H, Ar), The synthetic routes to monomeric Pt(II) acetylides (FLU-Pt-
2.20 (br, 12H, PBu3), 1.86 (br, 8H, –CH2–), 1.66 (br, 12H, PBu3), FLU, TPA-Pt-TPA and CAZ-Pt-CAZ), L-P1-Au and L-P2-Au are
1.50–1.44 (br, 12H, PBu3), 1.25–0.99 (m, 72H, –CH2–), 0.94 provided in Scheme S1 (ESI†). Ethynyl aromatic ligands (L-FLU,
(t, 18H, PBu3), 0.88–0.84 (m, 12H, –CH3), 0.57 (br, 8H, –CH2–); L-TPA and L-CAZ) are prepared first. Then monomeric Pt(II)
31P NMR (161.9 MHz, CDCl3): d (ppm) 42.45, 2.83; GPC: Mn
=
acetylides can be easily synthesized through the Sonogashira
1
2.4 Â 104 g molÀ1, PDI = 1.6 (against polystyrene standards); cross-coupling in high yields. In the H NMR spectra of these
anal. found: C 60.96, H 5.68.
Pt(II) acetylides, the signals at ca. 3.1 ppm are from the alkynyl
P1-TPA. (Yield: 60%). 1H NMR (400 MHz, CDCl3): d (ppm) group of ethynyl aromatic ligands and three sets of multiple
7.63–7.46 (m, 22H, Ar), 7.35–7.31 (m, 10H, Ar), 7.10–6.91 (m, peaks in the range of ca. 2.2–1.4 ppm are from PBu3 groups. In
6H, Ar), 6.86–6.79 (m, 10H, Ar), 3.92 (t, 4H, –OCH2–), 2.12 (br, their 31P NMR spectra, the peaks at ca. 2.8 ppm are attributed to
12H, PBu3), 1.76–1.75 (br, 4H, –CH2–), 1.57–1.54 (m, 12H, PBu3 groups. The above results can demonstrate that monomeric
PBu3), 1.46–1.40 (m, 12H, PBu3), 1.35–1.26 (m, 36H, –CH2–), Pt(II) acetylides are successfully obtained.
0.93–0.86 (m, 24H, PBu3 and –CH3); 31P NMR (161.9 MHz,
Scheme 1 shows the synthetic pathways of the hetero-
bimetallic Au(I)–Pt(II) polyynes. Using a similar synthetic strategy
CDCl3): d (ppm) 42.44, 2.70; GPC: Mn = 2.7 Â 104 g molÀ1
,
PDI = 1.3 (against polystyrene standards); anal. found: C 60.96, for homometallic polyynes,34 these polyynes have been prepared
H 5.68.
by the cross-coupling between L-P1-Au/L-P2-Au and the corres-
P1-CAZ. (Yield: 52%). 1H NMR (400 MHz, CDCl3): d (ppm) ponding monomeric Pt(II) acetylides. The chemical structures
8.24–8.22 (m, 2H, Ar), 7.96–7.87 (m, 2H, Ar), 7.64–7.48 (m, 26H, of these Au(I)–Pt(II) polyynes have been fully characterized by 1H
Ar), 7.38 (m, 2H, Ar), 7.25–7.19 (m, 4H, Ar), 4.20 (t, 4H, –NCH2–), and 31P NMR spectra. In the 1H NMR spectra of these Au(I)–Pt(II)
2.23 (br, 12H, PBu3), 1.83–1.81 (m, 4H, –CH2–), 1.68 (br, 12H, polyynes, the peaks at ca. 3.1 ppm from the proton of alkyne
PBu3), 1.55–1.47 (m, 12H, PBu3), 1.33–1.24 (m, 36H, –CH2–), groups disappear, compared with those from the monomeric
0.99–0.94 (t, 18H, PBu3), 0.89–0.86 (m, 6H, –CH3); 31P NMR Pt(II) acetylides. Two sets of resonance peaks at ca. 2.8 ppm
(161.9 MHz, CDCl3): d (ppm) 42.56, 3.03; GPC: Mn = 2.9 Â from PBu3 groups and at ca. 42.4 ppm from L-P1-Au/L-P2-Au
104 g molÀ1, PDI = 1.4 (against polystyrene standards); anal. can clearly show the simultaneous existence of the trans-
found: C 60.96, H 5.68.
[Pt(PBu3)2] unit and L-P1-Au/L-P2-Au in their 31P NMR spectra.
P2-FLU. (Yield: 55%). 1H NMR (400 MHz, CDCl3): d (ppm) Hence, the above results reveal their successful coupling between
7.76–7.72 (m, 6H, Ar), 7.57–7.38 (m, 22H, Ar), 7.22–7.20 (d, 4H, L-P1-Au/L-P2-Au and the corresponding monomeric Pt(II)
Ar), 2.85 (br, 4H), 2.19 (br, 12H, PBu3), 1.97–1.88 (br, 10H), 1.66 acetylides. In the 1H NMR spectra of these Au(I)–Pt(II) polyynes,
(br, 12H, PBu3), 1.52–1.44 (m, 12H, PBu3), 1.25–1.21 (m, 72H, the multiple peaks in the range of ca. 1.5–0.8 ppm can be
–CH2–), 0.94 (t, 18H, PBu3), 0.87–0.84 (m, 12H, –CH3), 0.58 (br, assigned to the n-dodecyl groups and the PBu3 groups in these
8H, –CH2–); 31P NMR (161.9 MHz, CDCl3): d (ppm) 35.18, 2.77; polyynes. In the 1H NMR spectra of P1-TPA and P2-TPA, the
GPC: Mn = 2.1 Â 104 g molÀ1, PDI = 1.3 (against polystyrene signals at ca. 3.9 ppm can be induced by the protons from
standards); anal. found: C 60.96, H 5.68.
the –OCH2– unit. The signals at ca. 4.2 can be ascribed to the
P2-TPA. (Yield: 65%). 1H NMR (400 MHz, CDCl3): d (ppm) –NCH2– group in the 1H NMR spectra of P1-CAZ and P2-CAZ. The
7.71–7.68 (m, 6H, Ar), 7.44–7.42 (m, 8H, Ar), 7.37–7.29 (m, 6H, Ar), broad peaks at ca. 2.8 ppm come from the –CH2CH2CH2– unit of
11418 | J. Mater. Chem. C, 2018, 6, 11416--11426
This journal is ©The Royal Society of Chemistry 2018

View Article Online
Paper
Journal of Materials Chemistry C
Scheme 1 Synthesis of heterobimetallic Au(I)–Pt(II) polyynes.
This journal is ©The Royal Society of Chemistry 2018
J. Mater. Chem. C, 2018, 6, 11416--11426 | 11419

View Article Online
Journal of Materials Chemistry C
Paper
L-P2-Au in the 1H NMR spectra of P2-FLU, P2-TPA and P2-CAZ.
All these NMR data clearly indicate the successful synthesis of
these new heterobimetallic Au(I)–Pt(II) polyynes.
Photophysical properties
The absorption spectra of the Au(I)–Pt(II) polyynes have been
characterized in CH2Cl2 at 298 K and the corresponding data
are summarized in Table 1. Obviously, the maximum absorp-
tion wavelengths (lmax) of two series of Au(I)–Pt(II) polyynes
(P1 and P2 series, Fig. 1) show a blue shift compared with those
of the corresponding homometallic Pt(II) polyynes (Fig. S1 and
Table S1, ESI†). Besides, the cut-off absorption wavelengths
(lcut-off) of P1 and P2 series show a slight blue shift compared
with those of the corresponding homometallic Pt(II) polyynes.
When compared with that of the corresponding monomeric
Pt(II) acetylides, the absorption bands of these Au(I)–Pt(II) poly-
ynes show a weaker red shift than those of the homometallic
Pt(II) polyynes (Fig. S2 and Table S1, ESI†). Therefore, these
Fig. 1 UV-Vis absorption spectra for heterobimetallic Au(I)–Pt(II) polyynes
in CH2Cl2 at 298 K.
Au(I)–Pt(II) polyynes exhibit better transparency than homo- (lcut-off, 411 nm),34 P1-FLU, P1-TPA, P2-FLU and P2-TPA
metallic Pt(II) polyynes, indicating the validity of introduction (Table 1) can show comparable transparency and P1-CAZ
of Au(I) precursors with tetrahedral diphosphine ligands to and P2-CAZ (Table 1) can show better transparency in the
improve transparency. The improvement of transparency can visible-light region. Importantly, compared with the reported
be attributed to the weak interaction between 5d orbitals of the heterobimetallic Pd(II)–Pt(II) and Pd(II)–Hg(II) polyynes with
Au(I) centers and p orbitals of the ethynyl aromatic ligands, as fluorene-based ligands (lcut-off, 438 nm and 435 nm, respectively),34
well as the conjugation-breaking ability of tetrahedral diphos- all the Au(I)–Pt(II) polyynes show much better transparency in
phine ligands.
the visible-light region.
In the UV-Vis absorption spectra, all the Au(I)–Pt(II) polyynes
Based on the fact that the transition properties of the
exhibit intense absorption peaks with lmax before 400 nm and transition metal polyynes can show similarity to their repeating
a weak absorption tail after 400 nm (Fig. 1), indicating their units,47 the molecular orbital (MO) patterns of the repeating
excellent optical transparency in the visible light region units of these Au(I)–Pt(II) polyynes have been obtained by time-
(ca. 400–700 nm). Their intense absorption peaks can be mainly dependent density functional theory (TD-DFT) calculations
assigned to the metal disturbed p–p* transitions from the to interpret their photophysical properties. Due to their large
ethynyl aromatic ligands.34 The profiles of P1 series and P2 contribution to the transition of the S1 states above 84%
series are similar in their absorption spectra. But the lmax and (Table 2), the transitions between the key molecular orbitals
lcut-off in the absorption spectra of P2 series show a slight blue- can represent the feature of the S1 states of the repeating units
shift compared with those of the corresponding P1 series, for these Au(I)–Pt(II) polyynes. From the MO patterns of the
which is caused by the –CH2CH2CH2– group of L-P2-Au posses- Au(I)–Pt(II) polyynes (Fig. 2), their S1 states should show obvious
sing a stronger conjugation-breaking ability. These results ligand–ligand charge transfer (LLCT) features from the p orbitals
show that these new polyynes still maintain good transparency of diethynyl aromatic ligands to the p* orbitals of 1,4-bis-
after polymerization. Besides, compared with the reported hetero- (diphenylphosphino)benzene (L-P1)/1,3-bis(diphenylphosphino)-
bimetallic Hg(II)–Pt(II) polyyne with fluorene-based ligands propane (L-P2) ligands coordinated with the Au(I) centers.
Table 1 Photophysical data for heterobimetallic Au(I)–Pt(II) polyynes
FF
Lifetime of excited statesc S1
lcut-off
b
Compound Absorptiona labs (nm) 298 K
Emissiona lem (nm) 298 K/77 K
(%) state (ns)/T1 state (ms)
(nm)
P1-FLU
P1-TPA
P1-CAZ
P2-FLU
P2-TPA
P2-CAZ
270, 276, 305, 319, 345, 362, 387 417, 438, 450, 539/548, 587, 625, 642
1.03 0.71 ns (438 nm)/181.63 ms (548 nm)
416
264, 276, 316sh, 377
504/504, 545, 563
0.62 10.37 ms (504 nm)d/130.80 ms (504 nm) 414
253, 262, 276sh, 317, 335
275, 305, 319, 344, 361, 384
268, 275, 314sh, 373
405, 425, 455, 495, 534/456, 492, 507, 527 0.27 0.99 ns (455 nm)/44.31 ms (456 nm)
389
413
412, 432, 449sh, 542, 584/548, 586, 619
504/503, 529, 603
1.66 0.63 ns (412 nm)/137.84 ms (548 nm)
1.69 6.46 ms (504 nm)d/165.23 ms (503 nm) 412
253, 261, 316, 334
402, 421, 438, 455, 503/457, 493, 507
0.30 0.72 ns (421 nm)/40.14 ms (457 nm)
386
a
b
Measured in CH2Cl2 at a concentration of ca. 10À5 M. sh: shoulder. Measured using quinine sulfate in 1.0 M H2SO4 as the standard. According
to the UV-Vis absorption of the compounds, the excitation wavelengths were set at 334 nm and 365 nm while the FF of the standard is 56% and
c
55%. The numbers in parentheses are the emission wavelengths of the S1 and T1 states. The lifetime of the S1 state was measured at 298 K in
degassed CH2Cl2 with the excitation at 360 nm and that of the T1 state was measured at 77 K in the same solvent with the same excitation
d
wavelength. The lifetime of P1-TPA and P2-TPA at 298 K should be a mixture of S1 and T1 states.
11420 | J. Mater. Chem. C, 2018, 6, 11416--11426
This journal is ©The Royal Society of Chemistry 2018

View Article Online
Paper
Journal of Materials Chemistry C
The results of TD-DFT can give insight into the blue shift from
P1 series to P2 series in the absorption process, which coincides
well with the experimental results.
In CH2Cl2 solution at 298 K, the photoluminescent (PL)
spectra of P1-FLU and P2-FLU exhibit two emission bands
(Fig. 3a). The high-energy emission bands should be fluores-
cent signals from the radiative decay of the singlet states (S1)
associated with the metal disturbed organic ligand p–p* transi-
tions. This result can be attributed to their short lifetime in the
order of nanoseconds (ns). However, the long-wavelength emis-
sion bands should be induced by the decay of the triplet states
(T1) due to their longer lifetimes in the order of microseconds
(ms) with large Stokes shift 4100 nm. P1-FLU possesses stronger
triplet emission compared with P2-FLU, which can be associated
with its lower FF (1.03% for P1-FLU and 1.66% for P2-FLU,
Table 1). The PL spectra of P1-CAZ and P2-CAZ show two
emission bands as well (Fig. 3c). It is obvious that P1-CAZ
exhibits stronger triplet emission than P2-CAZ, which is also
attributed to its lower FF (0.27% for P1-CAZ and 0.30% for
P2-CAZ). The PL spectra of P1-TPA and P2-TPA merely show
one emission band at 298 K (Fig. 3b), but they should be the
overlapping of singlet and triplet emission. This can be explained
by the fact that P1-TPA and P2-TPA possess a long lifetime in
the order of microseconds at 298 K (10.37 ms for P1-TPA and
6.46 ms for P2-TPA) and the emission bands of P1-TPA and
P2-TPA at 77 K (Fig. S3b in the ESI†) completely overlap with the
corresponding emission band at 298 K. Although the emission
profiles of P1-TPA and P2-TPA are quite similar, the emission
profile of P1-TPA becomes wider after 550 nm than that of
P2-TPA (Fig. 3b). In addition, the FF of P1-TPA (0.60%) is lower
than that of P2-TPA (1.69%). So P1-TPA should possess stronger
T1 emission compared with P2-TPA. The improvement of triplet
emission in P1 series might be related to the phenyl group of
L-P1-Au that can extend the conjugation of the backbone in the
Au(I)–Pt(II) polyynes. Furthermore, the feature of T1 emission
for these Au(I)–Pt(II) polyynes can also be obviously indicated by
enhanced long-wavelength emission signals at 77 K.
In order to clearly interpret the PL behaviors of these
Au(I)–Pt(II) polyynes, the natural transition orbital (NTO) results
for their repeating units have been obtained based on the
optimized T1 geometries for the S0 - T1 excitation.40 The
NTO patterns for the repeating unit of P1-FLU and P2-FLU
(Fig. 4a and d) show that both hole (H) and particle (P) orbitals
are mainly located on fluorene-based diethynyl ligands. Then,
based on the large percentage of H - P transition for P1-FLU
and P2-FLU (91.45% and 90.73%, respectively) (Table 3), they
should indicate a ligand-centered 3p–p* feature for the T1
emission. However, the L-P1 ligands of P1-CAZ and the L-P2
ligands of P2-CAZ have noticeable contribution (62.62% and
61.67%, respectively) to the particles of the NTO patterns for
their corresponding repeating units. So the T1 emission of
P1-CAZ and P2-CAZ should exhibit LLCT character. In addition,
the T1 emission of P1-TPA and P2-TPA also exhibits LLCT
character due to the contribution of L-P1 (63.3%) and L-P2
(44.34%) to the particle of the NTO patterns for their corres-
ponding repeating units. Due to the contribution (22.56%) of
This journal is ©The Royal Society of Chemistry 2018
J. Mater. Chem. C, 2018, 6, 11416--11426 | 11421

View Article Online
Journal of Materials Chemistry C
Paper
Fig. 2 Molecular orbital (MO) patterns for the repeating units of the heterobimetallic Au(I)–Pt(II) polyynes based on their optimized S0 geometries.
(a) Repeating unit for P1-FLU, (b) repeating unit for P1-TPA, (c) repeating unit for P1-CAZ, (d) repeating unit for P2-FLU, (e) repeating unit for P2-TPA,
and (f) repeating unit for P2-CAZ.
the triphenylamine ligand, P2-TPA also shows a ligand-centered Au(I)–Pt(II) polyynes. Moreover, the T1 emission of these
3p–p* feature for the T1 emission. From the results of NTO in Au(I)–Pt(II) polyynes showing a ligand-centered 3p–p* feature
Table 3, the Au and Pt centers make negligible contribution to and LLCT characteristics can be indicated by the structured
the transition process responsible for the T1 emission of these line-shape of their PL spectra at 77 K (Fig. S3, ESI†). The above
11422 | J. Mater. Chem. C, 2018, 6, 11416--11426
This journal is ©The Royal Society of Chemistry 2018

View Article Online
Paper
Journal of Materials Chemistry C
characterizing their OPL properties against the 532 nm laser
beam. Then the OPL behaviors of these Au(I)–Pt(II) polyynes
have been characterized with a linear transmittance To of
ca. 90% (Fig. 5) through the Z-scan with the open-aperture mode
in CH2Cl2. Incident irradiance upon the Au(I)–Pt(II) polyynes
varies from their Z-position to focal point (Z = 0). Obviously,
the transmittance (T) of the sample in solution remains constant
when the incident irradiance upon the sample is weak, showing
linear optical properties (i.e. obeying Beer’s law). However, when
the sample gradually approaches the focus with an increase in
incident irradiance, the transmittance (T) of the sample
decreases to show an OPL effect (Fig. 5). The OPL behaviors of
these Au(I)–Pt(II) polyynes can be interpreted by the reverse
saturable absorption (RSA) mechanism of the T1 states (Fig. S3,
ESI†). Due to the strong SOC effect induced by the Au(I) and Pt(II)
centers, the S1 states formed through the weak absorption of
laser irradiance can be rapidly transformed into the T1 states
through a fast inter-system crossing (ISC) process. After accu-
mulating a certain population, these T1 states absorb much
more laser energy to reach the higher triplet state Tn to induce
the OPL effect, especially for the nano-second laser pulse. The
lifetime of the S1 state is very short, so that the energy absorption
from the S1 - Sn transition can be neglected in the contribution
to the nano-second OPL response. Therefore, the OPL ability
mainly depends on the strong absorption from the T1 - Tn
transition, showing that these Au(I)–Pt(II) polyynes with a higher
T1 emission ability can show better OPL performances.
The OPL performances of these Au(I)–Pt(II) polyynes based
on the reverse saturable absorption can be compared by using
the figure of merit factor sex/so = ln Tsat/ln To, in which so and
sex stand for the ground-state absorption cross-section and the
effective excited-state absorption cross-section, respectively. To
is the linear transmittance as aforementioned and Tsat is the
transmittance at the saturation fluence. The sex/so values of
P1-FLU, P1-TPA and P1-CAZ are 9.98, 8.39 and 4.01, respec-
tively. The sex/so values of P2 series (7.92 for P2-FLU, 6.66 for
P2-TPA and 3.72 for P2-CAZ) are lower than those of P1 series.
Based on the RSA mechanism of T1 states, the higher T1
quantum yield associated with P1 series should enhance their
OPL ability effectively. So the higher OPL behaviors of P1 series
are correlated with their lower FF at 298 K. Obviously, the
performances of these Au(I)–Pt(II) polyynes are better than that
of the state-of-the-art OPL material C60 (ca. 3.39), showing their
great potential for application in the OPL field. In addition,
compared with the reported heterobimetallic Hg(II)–Pt(II), Pd(II)–
Pt(II) and Pd(II)–Hg(II) polyynes with fluorene-based ligands,34
these Au(I)–Pt(II) analogs can successfully cope with the toxicity
problem of the Hg(II) ions and the poor transparency-enhancing
Fig. 3 Photoluminescent (PL) spectra for heterobimetallic Au(I)–Pt(II)
polyynes in CH2Cl2 solution at 298 K. (a) P1-FLU and P2-FLU (b) P1-TPA
and P2-TPA (c) P1-CAZ and P2-CAZ.
results demonstrate the good consistency between the experi- ability of the Pd(II) ions.
mental and theoretical results.
What is more, the sex/so values of two series of Au(I)–Pt(II)
polyynes are higher than those of the corresponding homo-
metallic Pt(II) polyynes (7.36 for FLU-Pt, 5.46 for TPA-Pt and 3.45
Optical power limiting behaviors
From their UV-Vis spectra, these Au(I)–Pt(II) polyynes show for CAZ-Pt) (Fig. S5, ESI†), indicating their better OPL behav-
exceptional optical transparency at 532 nm, indicating their iors. As mentioned before, the absorption bands of two series of
extremely low ground-state absorption at this wavelength. Their Au(I)–Pt(II) polyynes show a blue shift compared with the
absorption behaviors fully meet the basic test requirements for corresponding homometallic Pt(II) polyynes, showing enhanced
This journal is ©The Royal Society of Chemistry 2018
J. Mater. Chem. C, 2018, 6, 11416--11426 | 11423

View Article Online
Journal of Materials Chemistry C
Paper
Fig. 4 Natural transition orbital (NTO) patterns for S0 - T1 excitation of the repeating units from the heterobimetallic Au(I)–Pt(II) polyynes based on their
optimized T1 geometries. (a) Repeating unit for P1-FLU, (b) repeating unit for P1-TPA, (c) repeating unit for P1-CAZ, (d) repeating unit for P2-FLU,
(e) repeating unit for P2-TPA, and (f) repeating unit for P2-CAZ.
transparency. Therefore, these results fully illustrate that intro- (81% for P1-FLU and 82% for P2-FLU) (inset Fig. 6), respec-
ducing Au(I) precursors with tetrahedral diphosphine ligands tively. As the input fluence increases, the normalized trans-
into the backbone of homometallic Pt(II) polyynes successfully mittance of the P1-FLU doped PS plate continuously drops to
achieve a good trade-off between transparency and optical power 0.48, reaching an OPL threshold of ca. 0.18 J cmÀ2, while that
limiting performance.
of the P2-FLU doped PS plate is ca. 0.2 J cmÀ2. Obviously, as
Because OPL materials in solution are inconvenient to make a prototype OPL device, the P1-FLU doped PS plate shows
practical devices, it is highly valuable to use them in the solid enhanced OPL ability compared to the P2-FLU doped PS plate,
state. P1-FLU and P2-FLU have been doped into polystyrene (PS) which is similar to their OPL performance in solution. In addi-
with a ca. 1.0 wt% doping level to make two prototype devices to tion, the PL spectra of P1-FLU and P2-FLU in the PS matrix
characterize its OPL ability for the 532 nm laser. The prepared (Fig. S6, ESI†) show stronger T1 emission than those of their
doped PS thin plates with a thickness of 0.2 mm show very high corresponding solutions, indicating their advantage in the fabri-
transparency, possessing a linear transmittance of ca. 80% cation of OPL devices.
11424 | J. Mater. Chem. C, 2018, 6, 11416--11426
This journal is ©The Royal Society of Chemistry 2018

View Article Online
Paper
Journal of Materials Chemistry C
Table
3
NTO results for repeating units from the heterobimetallic
Conclusions
Au(I)–Pt(II) polyynes based on their optimized T1 geometries
Two series of heterobimetallic Au(I)–Pt(II) polyynes have been
successfully prepared. On the premise of transparency approxi-
mation of two series of Au(I)–Pt(II) polyynes, P1 series exhibit
stronger T1 emission and superior OPL performances than P2
series. This result indicates that the 1,4-bis(diphenylphosphino)-
benzene ligand is more favorable for optimizing the optical
transparency and OPL ability of OPL materials than the 1,3-bis-
(diphenylphosphino)propane ligand. Importantly, the absorp-
tion bands of these Au(I)–Pt(II) polyynes are blue-shifted by
introducing Au(I) precursors with tetrahedral phosphine
ligands into the homometallic Pt(II) polyynes backbone, indi-
cating better transparency in the visible-light region. Moreover,
the OPL performances of these polyynes are not only superior to
the corresponding homometallic Pt(II) polyynes, but also out-
perform the state-of-the-art OPL material C60. When compared
with the reported heterobimetallic polyynes with fluorene-based
ligands, the heterobimetallic Au(I)–Pt(II) polyynes with fluorene-
based ligands show a lower toxicity and even achieve consistency
between excellent, good transparency and high OPL performances.
The concerned results provide valuable information for the com-
prehensive optimization of OPL materials.
Contribution percentages of metal dp orbitals
and p orbitals of ligands to NTOsb (%)
Compound
NTOa
Pt
Au1
Au2
L1
L2
P1-FLU
H
P
H
P
H
P
H
P
H
P
H
P
1.28
0.54
1.25
0.00
5.16
0.00
1.25
0.64
1.24
0.30
2.46
0.01
1.87
5.27
1.70
1.51
2.25
2.06
1.87
5.02
1.88
8.55
2.70
7.03
0.00
0.06
0.00
1.11
0.00
1.44
0.00
0.01
0.00
1.31
0.00
1.44
95.54
87.81
95.66
0.56
87.30
0.70
95.60
91.39
95.36
25.56
87.53
7.77
0.00
1.80
0.07
63.32
0.08
62.62
0.19
1.77
0.25
44.34
0.37
61.67
P1-TPA
P1-CAZ
P2-FLU
P2-TPA
P2-CAZ
a
H and P represent the NTO hole and particle orbital, respectively.
Pt represents the Pt(II) centers, and Au1 and Au2 represent the two
Au(I) centers, while L1 indicates the aromatic diacetylene ligands and
b
L2 represents the organic phosphine ligands (L-P1 and L-P2).
Conflicts of interest
There are no conflicts to declare.
Acknowledgements
This research was financially supported by the National Natural
Science Foundation of China (no. 21572176 and 21602170),
the Fundamental Research Funds for the Central Universities
(cxtd2015003 and xjj2016061), the Key Creative Scientific
Research Team in Yulin City, Shaanxi Province, the China Post-
doctoral Science Foundation (2015M580831) and the Program
for New Century Excellent Talents in University, the Ministry of
Education of China (NECT-09-0651). The financial support from
the State Key Laboratory for Mechanical Behavior of Materials
is also acknowledged. The characterizations of materials are
supported by the Instrument Analysis Center of Xi’an Jiaotong
University.
Fig. 5 Open-aperture Z-scan results for heterobimetallic Au(I)–Pt(II) polyynes
(To ca. 90%) together with that for C60 (To ca. 89%).
Notes and references
1 J. Hecht, Opt. Eng., 2010, 49, 99.
2 C. W. Spangler, J. Mater. Chem., 1999, 9, 2013.
3 L. W. Tutt and T. F. Boggess, Prog. Quantum Electron., 1993,
17, 299.
4 X. Liu, D. Wang, H. Gao, Z. Yang, Y. Xing, H. Cao, W. He,
H. Wang, J. Gu and H. Hu, Phys. Chem. Chem. Phys., 2016,
18, 7341.
5 A. Y. Tolbin, A. V. Dzuban, E. V. Shulishov, L. G. Tomilova
and N. S. Zefirov, New J. Chem., 2016, 40, 8262.
6 P. Zhao, Z. Wang, J. Chen, Y. Zhou and F. Zhang, Opt.
Mater., 2017, 66, 98.
Fig. 6 Normalized transmittance of the P1-FLU and P2-FLU (To ca. 80%)
doped PS plate. (a) P1-FLU doped PS plate and (b) P2-FLU doped PS plate.
This journal is ©The Royal Society of Chemistry 2018
J. Mater. Chem. C, 2018, 6, 11416--11426 | 11425

View Article Online
Journal of Materials Chemistry C
Paper
7 N. V. Krishna, P. T. Anusha, S. V. Rao and L. Giribabu, 32 K. B. Manjunatha, V. M. Shelar, R. Dileep, G. Umesh,
J. Porphyrins phthalocyanines, 2016, 20, 1173.
8 X. Liu, D. Wang, H. Gao, Z. Yang, Y. Xing, H. Cao, W. He,
H. Wang, J. Gu and H. Hu, Dyes Pigm., 2016, 134, 155.
9 D. Dini, M. J. F. Calvete and M. Hanack, Chem. Rev., 2016,
116, 13043.
M. N. Satyanarayan and B. R. Bhat, Synth. React. Inorg.
Met.-Org. Chem., 2014, 44, 282.
33 W.-Y. Wong, L. Liu and J.-X. Shi, Angew. Chem., Int. Ed.,
2003, 42, 4064.
34 G. Zhou, W.-Y. Wong, C. Ye and Z. Lin, Adv. Funct. Mater.,
2007, 17, 963.
10 K. M. Hijas, S. M. Kumar, K. Byrappa, T. Geethakrishnan,
S. Jeyaram and R. Nagalakshmi, J. Mol. Struct., 2018, 35 P. I. P. Elliott, Annu. Rep. Prog. Chem., Sect. A: Inorg. Chem.,
1155, 249. 2012, 108, 389.
11 Z. Xiao, Y. Shi, R. Sun, J. Ge, Z. Li, Y. Fang, X. Wu, J. Yang, 36 W.-Y. Wong, J. Inorg. Organomet. Polym. Mater., 2005,
M. Zhao and Y. Song, J. Mater. Chem. C, 2016, 4, 4647. 15, 197.
12 C. R. Ma, J. Xiao and G. W. Yang, J. Mater. Chem. C, 2016, 37 W.-Y. Wong, S.-Y. Poon, A. W. Lee, J.-X. Shi and K.-W.
4, 4692. Cheah, Chem. Commun., 2004, 2420.
13 Y. Du, N. Dong, M. Zhang, K. Zhu, R. Na, S. Zhang, N. Sun, 38 D. W. Boening, Chemosphere, 2000, 40, 1335.
G. Wang and J. Wang, Phys. Chem. Chem. Phys., 2017, 19, 39 L. Liu, W.-Y. Wong, S.-Y. Poon, J.-X. Shi, K.-W. Cheah and
2252.
14 R. Liu, J. Hu, S. Zhu, J. Lu and H. Zhu, ACS Appl. Mater. 40 Z. Tian, X. Yang, B. Liu, J. Zhao, D. Zhong, Y. Wu, G. Zhou
Interfaces, 2017, 9, 33029. and W.-Y. Wong, J. Mater. Chem. C, 2018, 6, 6023.
15 Y. Xiong, J. Si, L. Yan, H. Song, W. Yi and X. Hou, Laser Phys. 41 W. R. Dawson and M. W. Windsor, J. Phys. Chem., 1968,
Z. Lin, Chem. Mater., 2006, 18, 1369.
Lett., 2014, 11, 115904.
72, 3251.
16 G. Zhou and W.-Y. Wong, Chem. Soc. Rev., 2011, 40, 2541.
42 W. R. Wadt and P. J. Hay, J. Chem. Phys., 1985, 82, 284.
17 W. Wang, L. J. Chen, X. Q. Wang, B. Sun, X. Li, Y. Zhang, 43 P. J. Hay and W. R. Wadt, J. Chem. Phys., 1985, 82, 299.
J. Shi, Y. Yu, L. Zhang, M. Liu and H. B. Yang, Proc. Natl. 44 M. J. Frisch, G. W. Trucks, H. B. Schlegel, G. E. Scuseria,
Acad. Soc. U. S. A., 2015, 112, 5597.
M. A. Robb, J. R. Cheeseman, J. A. Montgomery, T. Vreven Jr,
K. N. Kudin, J. C. Burant, J. M. Millam, S. S. Iyengar,
J. Tomasi, V. Barone, B. Mennucci, M. Cossi, G. Scalmani,
N. Rega, G. A. Petersson, H. Nakatsuji, M. Hada, M. Ehara,
K. Toyota, R. Fukuda, J. Hasegawa, M. Ishida, T. Nakajima,
Y. Honda, O. Kitao, H. Nakai, M. Klene, X. Li, J. E. Knox,
H. P. Hratchian, 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, P. Y.
Ayala, K. Morokuma, G. A. Voth, P. Salvador, J. J.
Dannenberg, V. G. Zakrzewski, S. Dapprich, A. D. Daniels,
M. C. Strain, O. Farkas, D. K. Malick, A. D. Rabuck,
K. Raghavachari, J. B. Foresman, J. V. Ortiz, Q. Cui,
A. G. Baboul, S. Clifford, J. Cioslowski, B. B. Stefanov,
G. Liu, A. Liashenko, P. Piskorz, I. Komaromi, R. L.
Martin, D. J. Fox, T. Keith, M. A. Al-Laham, C. Y. Peng,
A. Nanayakkara, M. Challacombe, P. M. W. Gill, B. Johnson,
W. Chen, M. W. Wong, C. Gonzalez and J. A. Pople, Gaussian 09,
revision A.2, Gaussian, Inc., Wallingford, CT, 2009.
18 B. Jiang, J. Zhang, J. Q. Ma, W. Zheng, L. J. Chen, B. Sun,
C. Li, B. W. Hu, H. Tan, X. Li and H. B. Yang, J. Am. Chem.
Soc., 2016, 138, 738.
19 L. Xu and H. B. Yang, Chem. Rec., 2016, 16, 1274.
20 W. Wang and H. B. Yang, Chem. Commun., 2014, 50, 5171.
21 H. Zhang, X. Yan, J. Zhao, X. Yang, Z. Huang, G. Zhou and
Y. Wu, RSC Adv., 2015, 5, 88758.
22 Z. Huang, B. Liu, Y. He, X. G. Yan, X. Yang, X. Xu, G. Zhou,
Y. Ren and Z. Wu, J. Organomet. Chem., 2015, 794, 1.
23 W.-Y. Wong and C.-L. Ho, Acc. Chem. Res., 2010, 43, 1246.
24 B. Jiang, L. J. Chen, G. Q. Yin, Y. X. Wang, W. Zheng, L. Xu
and H. B. Yang, Chem. Commun., 2017, 53, 172.
25 I. R. Whittall, M. G. Humphrey, S. Houbrechts, J. Maes,
A. Persoons, S. Schmid and D. C. R. Hockless, J. Organomet.
Chem., 1997, 544, 277.
26 N. J. Long, Angew. Chem., Int. Ed. Engl., 1995, 34, 21.
27 S. Goswami, G. Wicks, A. Rebane and K. S. Schanze, Dalton
Trans., 2014, 43, 17721.
28 Y. Du, N. Dong, M. Zhang, B. Jiang, N. Sun, Y. Luo, S. Zhang, 45 C. K. Mirabelli, D. T. Hill, L. F. Faucette, F. L. McCabe,
G. Wang and J. Wang, J. Mater. Chem. C, 2018, 6, 7317.
29 T. Kindahl, P. G. Ellingsen, C. Lopes, C. Brannlund,
M. Lindgren and B. Eliasson, J. Phys. Chem. A, 2012, 116, 11519.
G. R. Girard, D. B. Bryan, B. M. Sutton, J. O. Bartus,
S. T. Crooke and R. K. Johnsonl, J. Med. Chem., 1987,
30, 2181.
¨
30 T. Kindahl, J. Ohgren, C. Lopes and B. Eliasson, Tetrahedron 46 M.-C. Brandys, M. C. Jennings and R. J. Puddephatt,
Lett., 2013, 54, 2403. J. Chem. Soc., Dalton Trans., 2000, 24, 4601.
31 B. Liu, Z. Tian, F. Dang, J. Zhao, X. Yan, X. Xu, X. Yang, 47 G. Zhou, Y. He, B. Yao, J. Dang, W.-Y. Wong, Z. Xie, X. Zhao
G. Zhou and Y. Wu, J. Organomet. Chem., 2016, 804, 80. and L. Wang, Chem. – Asian J., 2010, 5, 2405.
11426 | J. Mater. Chem. C, 2018, 6, 11416--11426
This journal is ©The Royal Society of Chemistry 2018