Homo- And hetero-metallophilicity-driven synthesis of highly emissive and stimuli-responsive Au(i)-Cu(i) double salts

Article abstract of DOI:10.1039/d1cc01316e

Complex salts composed of cationic Au(i) and anionic Cu(i) species were synthesized by utilizing bis(diphenylarsino)methane (dpam) and bis(diphenylphosphino)methane (dppm) ligands. The discrete tetranuclear complexes were obtained as crystals, and the four-metal chain, Cu?Au?Au?Cu, was linked through homo- and hetero-metallophilic interactions. Three crystal polymorphs were obtained for the dpam- and dppm-complexes, depending on the recrystallization solvent. All the crystals exhibited intense phosphorescence (quantum yields up to 0.97) at room temperature, and the emission color of each crystal was significantly different. The crystals could be interconverted by exposure to solvent vapor, and this was accompanied by a drastic change in the emission color.

Full text of DOI:10.1039/d1cc01316e

View Article Online
View Journal
ChemComm
Chemical Communications
Accepted Manuscript
This article can be cited before page numbers have been issued, to do this please use: R. Kobayashi, T.
Yumura, H. Imoto and K. Naka, Chem. Commun., 2021, DOI: 10.1039/D1CC01316E.
Volume 54
This is an Accepted Manuscript, which has been through the
Number
January 2018
Pages 1-112
1
4
Royal Society of Chemistry peer review process and has been
accepted for publication.
ChemComm
Chemical Communications
rsc.li/chemcomm
Accepted Manuscripts are published online shortly after acceptance,
before technical editing, formatting and proof reading. Using this free
service, authors can make their results available to the community, in
citable form, before we publish the edited article. We will replace this
Accepted Manuscript with the edited and formatted Advance Article as
soon as it is available.
You can find more information about Accepted Manuscripts in the
Information for Authors.
Please note that technical editing may introduce minor changes to the
text and/or graphics, which may alter content. The journal’s standard
Terms & Conditions and the Ethical guidelines still apply. In no event
shall the Royal Society of Chemistry be held responsible for any errors
or omissions in this Accepted Manuscript or any consequences arising
from the use of any information it contains.
ISSN 1359-7345
COMMUNICATION
S. J. Connon, M. O. Senge et al.
Conformational control of nonplanar free base porphyrins:
towards bifunctional catalysts of tunable basicity
rsc.li/chemcomm

Please do not adjust margins
Page 1 of 4
ChemComm
View Article Online
DOI: 10.1039/D1CC01316E
COMMUNICATION
Homo- and hetero-metallophilicity-driven synthesis of highly
emissive and stimuli-responsive Au(I)-Cu(I) double salts
Ryosuke Kobayashi,a Takashi Yumura,b Hiroaki Imoto,ac* and Kensuke Nakaac*
Received 00th January 20xx,
Accepted 00th January 20xx
DOI: 10.1039/x0xx00000x
Complex salts composed of cationic Au(I) and anionic Cu(I) species
Synthesis of complex salts in which a cationic and an anionic
were synthesized by utilizing bis(diphenylarsino)methane (dpam) metal complex form an ion pair are an effective strategy for
and bis(diphenylphosphino)methane (dppm) ligands. The discrete realizing hetero- and homo-metallophilic interactions. Chen
tetranuclear complexes were obtained as crystals, and the four- and coworkers reported the self-assembly of cationic Au(I)
metal chain, Cu···Au···Au···Cu, was linked through homo- and complex and anionic Cu complex through Au···Cu interactions
hetero-metallophilic interactions. Three crystal polymorphs were (Figure 1a).5c,d The cationic Au(I) complex is supported by
obtained for the dpam- and dppm-complexes, depending on the neutral N-heterocyclic carbene (NHC) ligands, and the Cu(I)
recrystallization solvent. All the crystals exhibited intense dihalide, cyanide, or acetylide is used as the counter anion.
phosphorescence (quantum yields up to 0.97) at room The cation-anion metathesis reaction between the [Au(NHC)2]+
temperature, and the emission color of each crystal was and [CuX2]- precursors produces the complex salt, and the
significantly different. The crystals could be interconverted by electrostatic attractions assist the formation of Au···Cu
exposure to solvent vapor, and this was accompanied by a drastic interactions. For further structural diversity, the co-existence
change in the emission color.
of homo- and hetero-metallophilicity is desirable. However, no
molecular design for such a complex using complex salts has
been established yet.
Non-covalent metal-metal interaction, also known as
metallophilicity, can be utilized to generate unique structures
and/or advanced functionalities.1-4 Homo-metallophilicity,
such as aurophilicity (Au···Au),2 argentophilicity (Ag···Ag),3 and
cuprophilicity (Cu···Cu),4 has been traditionally utilized for the
construction of metal clusters. On the other hand, hetero-
metallophilicity allows the generation of diverse structures and
functionalities, particularly in the d10-d10 heterometallic
complexes.5 Among them, supramolecular architectures
through Au···Cu interactions have been developed for
luminescent materials to utilize their phosphorescence
properties. Metallophilic interactions are susceptible to
external stimuli, and Au-Cu complexes exhibiting luminescent
vapochromism and thermochromism have been reported so
far.5b,d,6 On the other hand, Au···Au homo-metallophilicity and
Au···Cu hetero-metallophilicity often co-exist in a complex
manner,7 and thus the resultant structures resemble a roll of
the dice.
Fig. 1 (a) Example of a complex salt containing hetero-
metallophilic interactions. (b) Discrete tetranuclear complex
containing mixed homo- and hetero-metallophilic interactions.
Recently, we found that diarsine ligands are effective in the
precise design of inter- and intramolecular metallophilic
interactions for AuCl or CuI complexes.8 The length and
flexibility of the linker between the arsenic atoms determine
the form of the metallophilic interactions. Importantly, arsenic
ligands can form less directional coordinated bonds than the
corresponding phosphine ligands because the lone pair of an
arsenic ligand has a higher s-character than that of a
phosphorus ligand.9 As a result, the coordination direction of
arsenic ligands can be effectively adjusted to realize
metallophilic interactions.
In
this
work,
it
has
been
shown
can
that
support
bis(diphenylarsino)methane
(dpam)10
intramolecular Au···Au interaction and that the covalently
bonded chlorides of the Au(I) cations can be captured by CuCl
Please do not adjust margins

Please do not adjust margins
ChemComm
Page 2 of 4
COMMUNICATION
Journal Name
to form intermolecular Au···Cu interactions (Figure 1b). Thus, Å, respectively. In contrast, the Au···Cu interaction was absent
View Article Online
DOI: 10.1039/D1CC01316E
the co-existence of homo-metallophilic Au···Au and hetero- from the other conformer (γ-2-2) probably because of the long
metallophilic Au···Cu interactions was achieved in the obtained distance (4.7413(7) Å), while the Au···Au interactions
complex salt [Au2(dpam)2]-[CuCl2]2. This molecular design was (2.9594(4) Å) were present in it. We then focused on the
expanded
bis(diphenylphosphino)methane (dppm). As expected, crystals, the angles were similar to each other: 134.50(2)° (α-
[Au2(dppm)2]-[CuCl2]2 was readily synthesized from ), 133.14(2)° (α- ), 140.70(2)° (β- ), 140.22(2)° (β- ). The
Au2Cl2(dppm)2 and CuCl, and Au···Au and Au···Cu interactions Cu···Au···Au···Cu chain of γ- was highly distorted, considering
to
the
phosphorus
ligand, Cu···Au···Au angles in the complexes. In the α- and β-type
1
2
1
2
1
were formed as well. Both [Au2(dpam)2]-[CuCl2]2 and the small angle (114.99(3)°). It is probable that this distortion
[Au2(dppm)2]-[CuCl2]2 exhibited strong luminescence with originated because of the less directional coordination of the
diverse colors and stimuli-responsiveness. Particularly, highly arsenic atoms, as reported for some transition metal
efficient near infrared (NIR) emission was observed for one of complexes.12 In the case of the diphosphine ligand, the
the polymorphs of [Au2(dpam)2]-[CuCl2]2, whose molecular Cu···Au···Au···Cu chain of γ-
2 was cleaved in one conformer,
packing was probably supported by the less directional while a non-distorted chain (Cu···Au···Au angle = 130.21(2)°)
coordination of the arsenic ligand, dpam.
Complex salts [Au2(dpam)2]-[CuCl2]2
[CuCl2]2 were synthesized according to Scheme 1.
was present in the other.
(1) and [Au2(dppm)2]-
(2)
AuCl(dms) (dms = dimethyl sulfide) was mixed with bidentate
ligand dpam or dppm in dichloromethane (CH2Cl2) at room
temperature for 1 h to afford Au2Cl2(
CH2Cl2 solution of Au2Cl2( ) and additional ligand was mixed
with an acetonitrile (MeCN) solution of CuCl at room
temperature for 1 h to produce [Au2(dpam)2]-[CuCl2]2 ( ) and
[Au2(dppm)2]-[CuCl2]2 ). Notably, the isolated yields were
high; the total yields were 80% ( ) and 89% ( ).
L) (L = dpam or dppm). A
L
1
(
2
1
2
Scheme 1. Synthesis of complex salts 1 and 2.
Fig. 2 ORTEP (at 50% probability) and lengths and angles of the
Single crystals suitable for X-ray diffraction (XRD) analysis
were grown by the slow mixing of CH2Cl2 solution with poor
solvents (Figure 2). Depending on the poor solvents for
metallophilic interactions of
by wireframe, and hydrogen atoms are omitted for clarity.
1 and 2. Phenyl groups are shown
The photoluminescence (PL) spectra of and were
recorded in the solid states (Table 1 and Figure 3). The α- and
β-type crystals showed green and greenish-yellow emissions,
respectively, and the emission colors of γ-1 and γ-2 were near-
infrared and white, respectively. This difference in emission
1
2
recrystallization, different crystals were obtained for both
1
and under the same conditions. Hexane, acetonitrile
2
(MeCN)/diethyl ether (Et2O), and methanol (MeOH) gave the
α-, β-, and γ-forms, respectively; the space groups were P-1 (α-
1
, α-
conformations were similar, except for γ-
3.1408(4) Å, β- : 3.1636(7) Å, γ- : 3.1192(7) Å, α-
Å, β- : 3.0835(7) Å) and Au···Cu (α-
2.7868(7) Å, γ- : 2.861(1) Å, α-
2
, and γ-
2
) and C2/c (β-
1
, γ-
1
, and β-
2). The observed
wavelength (λem) can be attributed to the distance and angles
2
. The Au···Au (α-
1
:
of the metallophilic interactions. λem of γ-
long; the emission peak was above 1100 nm. The white
emission of γ- was composed of two peaks that are derived
1 was remarkably
1
1
2
: 3.0656(4)
2
1
: 2.7491(9) Å, β-1
:
2
1
2
: 2.7705(6) Å, β-
2
: 2.8117(7) Å)
from the two conformers indicated in the XRD pattern.
Notably, the quantum yields (Φ) of the complexes were
distances were within the sum of the van der Waals radii of
the atoms (Au: 2.10 Å, Cu: 1.92 Å),11 indicating the coexistence
of homo- and hetero-metallophilic interactions. The Au···Au
interactions were supported by the ligand backbones, while
the Au···Cu interactions were supported by the electrostatic
interactions. These results demonstrate that the combination
of methylene-linked bidentate ligands and complex salt
formation is effective for realizing the co-existence of homo-
Table 1. PL properties of 1 and 2.
λex[a] [nm]
λem[b] [nm]
Ф[c]
τ[d] [μs]
α-1
β-1
γ-1
α-2
β-2
γ-2
397
341
348
397
327
400
533
551
0.96
0.97
0.11
0.91
0.95
0.82
8.8
12.0
8.6
814
522
8.8
and hetero-metallophilic interactions. The XRD pattern of γ-
2
533
9.9
indicated the presence of two conformations, γ-2-1 and γ-2-2
,
527, 624
11.8
as shown in Figure 2f. The structure of the γ-2-1 conformer
was similar to those of the α- and β-type crystals, and the
Au···Au and Au···Cu distances were 2.9785(5) Å and 2.8465(6)
[a] Excitation maxima corresponding to the emission maxima. [b] Emission
maxima corresponding to the excitation maxima. [c] Absolute quantum yield.
[d] Emission lifetimes monitored at the emission maxima.
2 | J. Name., 2012, 00, 1-3
This journal is © The Royal Society of Chemistry 20xx
Please do not adjust margins

Page 3 of 4
ChemComm
Please do not adjust margins
Journal Name
remarkably high even at room temperature in the solid states;
COMMUNICATION
No emission (Φ < 0.01) was observed from 1 VaienwdArticlfeoOrnlainlel
2
Φ = 0.82–0.97 (visible region) and 0.11 (near-infrared region). the polymorphs (α-, β-, and γ-forms)DuOpI:o10n.10g3r9in/Dd1iCnCg01i3n16aE
The μs-order emission lifetimes implied that the emissions mortar. The PXRD pattern showed significantly weakened
were attributed to phosphorescence. Since phosphorescent signals after grinding, suggesting the occurrence of crystal-to-
dyes exhibiting highly efficient solid-state emission at room amorphous transition. In the amorphous phases, the
temperature are desired for luminescent materials, this series metallophilic chains responsible for the emission could be
of complexes are promising. In particular, γ-1, which exhibits cleaved, thus turning off the emission. It is also possible that
intense emission in the near-infrared region,13 is beneficial for the amorphous phases gave sufficient space for molecular
bio-imaging14 because its PL spectrum reaches the second motions to quench the energies of the excitons. Then,
window.
exposure to CH2Cl2 and MeOH vapor for 1 h induced
crystallization of the amorphous samples, forming the α- and
γ-forms, respectively, as determined from the PL spectra and
PXRD patterns. After exposure to the vapors, the emission of
and were turned on, and the emission colors were green (α-
and α- ), near-infrared (γ- ), or white (γ-
1
1
2
2
1
2
). This was well-
consistent with the aforementioned vapor-induced crystal-to-
crystal transitions. Turn-on sensing is an important strategy to
develop visually recognizable systems, and thus, the
amorphous samples of
detection.
1 and 2 are promising for vapor
Finally, we conducted dispersion-corrected density
functional theory (DFT) calculations (B3LYP-D3 functional) to
reveal the importance of the co-existence of homo-
metallophilic Au···Au and hetero-metallophilic Au···Cu
Fig. 3 PL spectra of
temperature. The minor peak around 500 nm of γ-
from the crashed samples generated during the measurement.
1
and
2
in the crystalline states at room
is derived
1
We next examined luminescent vapochromism (Figure 4).
The crystalline samples were exposed to CH2Cl2 or MeOH
vapor for sufficient time (around one day). The powder XRD
interactions in the electronic properties of
used the atomic coordination of and obtained from the X-
ray analyses. Average interaction energies between the
[Au2( )2] and [CuCl2] moieties were obtained (Table S10).
1 and 2. For this, we
1
2
(PXRD) pattern showed that the β- and γ-crystals of
1 and 2
L
were converted to the α-crystals by CH2Cl2 vapor (Figures S1
and S2), being a good solvent. The α-forms might be more
stable than the β- and γ-forms, and thus the crystalline
samples were converted to the α-forms by CH2Cl2 vapor
regardless of the starting crystalline polymorph. Additionally,
Negative Einteract values were observed for all the structures,
indicating the presence of attractive interactions between the
[Au2(L)2] and [CuCl2]2 moieties to stabilize their structures. All
the structures, except that of γ-2-2, have Au···Cu coupling
around 2.8 Å; at the same time, they are stabilized by
attractive interactions between the [Au2(L)2] and [CuCl2]
MeOH vapor converted the α-crystals of
1 and 2 to the γ-
crystals, while exposure to the β-crystals gave a complex
mixture. MeOH was employed as a poor solvent to grow the γ-
crystals through recrystallization, and thus it is rational that
MeOH vapor produced the γ-crystals. According to the crystal-
moieties. Therefore, they exhibit hetero-metallophilicity.
Although the stabilization of γ-2-2 is comparable to that of the
other conformers, it does not exhibit hetero-metallophilicity
due to the lack of Au···Cu coupling around 2.8 Å.
The presence or absence of hetero-metallophilicity plays an
essential role in determining the electronic properties of the
to-crystal transitions, the emission colors were green (α-
1 and
α- ), near-infrared (γ- ), or white (γ- ). The PL spectra (Figures
2
1
2
S5 and S6) as well as the PXRD patterns were almost
completely altered upon exposure to the solvent vapors,
indicating that the crystal-to-crystal transitions progressed
efficiently. This sharp response implies that the synthesized
complexes are susceptible to a particular change in the
surrounding, reflecting the characteristics of the structures in
which unsupported metallophilic interactions coexists.
frontier orbitals of
amplitude of the frontier occupied and unoccupied orbitals
appears on the [Au2(
metallophilicity (i.e.,
the HOMO and LUMO in
based orbitals can overlap due to the Au···Au coupling around
3.0 Å, which can be induced by binding methylene-linked
1 and 2, as shown in Figure S7. The
L
)2] moiety in the conformers with hetero-
and , except γ-2-2). Figure S8 shows
-1. In the frontier orbitals, the Au-
1
2

bidentate ligands to the Au cations. On the other hand, γ-2-2
,
with no hetero-metallophilicity, has frontier occupied orbital
appearing on [CuCl2]2, although the LUMO has amplitude on
the [Au2(
metallophilicity in
L
)2] moiety. Thus, we confirmed that the hetero-
and , except γ-2-2, is responsible for their
1
2
homo-metallophilicity; detailed discussion has been included
in the supporting information. As listed in Table S11, time-
dependent DFT calculations revealed that the combination
between Au-based frontier occupied and unoccupied orbitals,
Fig. 4 Emission behavior of (a)
external stimuli such as solvent vapor and grinding (irradiation
at 365 nm for obtaining the photographs).
1 and (b) 2 in response to
which can be seen in
1
and
2
, except γ-2-2, is responsible for
This journal is © The Royal Society of Chemistry 20xx
J. Name., 2013, 00, 1-3 | 3
Please do not adjust margins

Please do not adjust margins
ChemComm
Page 4 of 4
COMMUNICATION
Journal Name
Schier, Chem. Soc. Rev., 2012, 41, 370; d) E. E. Langdon-Jones
and S. J. A. Pope, Chem. Commun., 20D1O4,I:5100,.1100393/4D31;CeC)0J1.3G16ilE-
Rubio and J. Vicente, Chem. Eur. J., 2018, 24, 32.
For a review, see: H. Schmidbaur and A. Schier, Angew. Chem.
Int. Ed., 2015, 54, 746.
For reviews, see: a) P. C. Ford, Coord. Chem. Rev., 1994, 132,
129; b) R. Peng, M. Li and D. Li, Coord. Chem. Rev., 2010, 254,
1; c) K. Tsuge, Chem. Lett., 2013, 42, 204; d) N. V. S.
Harisomayajula, S. Makovetskyi and Y.-C. Tsai, Chem. Eur. J.,
2019, 25, 8936.
the electronic transition, which is the first step for photo-
emission. On the other hand, no electronic transition with
substantial oscillator strength was observed for γ-2-2 due to
the absence of the Au-based frontier occupied orbitals.
Furthermore, Figure S7 shows that γ-1 has energetically close
occupied orbitals as well as energetically close unoccupied
orbitals in the frontier orbital region; the orbitals are shown in
View Article Online
3
4
Figure S9. The energetically close frontier orbitals in γ-1, with
the smallest Cu∙∙∙Au∙∙∙Au angles that are unique from the other
conformers with larger Cu∙∙∙Au∙∙∙Au angles, can contribute to
the electronic transition, as seen in Table S11. This can
differentiate it from the other structures in terms of the
emission properties.
In conclusion, we have synthesized Au(I)···Cu(I) double salts
containing homo- and hetero-metallophilic interactions based
on bidentate ligands, dpam and dppm. X-ray crystallography
revealed the structures of the discrete tetranuclear complexes
5
For recent papers, see: a) R. Donamaría, E. J. Fernández, J. M.
López-de-Luzuriaga, M. Monge, M. E. Olmos, D. Pascual and
M. Rodríguez-Castillo, Dalton Trans., 2017, 46, 10941; b) A.
Belyaev, T. Eskelinen, T. M. Dau, Y. Yu. Ershova, S. P. Tunik, A.
S. Melnikov, P. Hirva and I. O. Koshevoy, Chem. Eur. J., 2018,
24, 1404; c) Q. Liu, Mo Xie, X. Chang, S. Cao, C. Zou, W.-F. Fu,
C.-M. Che, Y. Chen and W. Lu, Angew. Chem. Int. Ed., 2018, 57,
6279; d) Y. Cao, J.-G. Yang, Y. Deng, S. Wang, Q. Liu, C. Shen,
W. Lu, C.-M. Che, Y. Chen and L. He, Angew. Chem. Int. Ed.,
2020, 59, 2080.
a) C. E. Strasser and V. J. Catalano, J. Am. Chem. Soc., 2010,
132, 10009; b) I. O. Koshevoy, Y.-C. Chang, A. J. Karttunen, M.
Haukka, T. Pakkanen and P.-T. Chou, J. Am. Chem. Soc., 2012,
134, 6564.
For example, see: a) I. O. Koshevoy, A. J. Karttunen, S. P. Tunik,
M. Haukka, S. I. Selivanov, A. S. Melnikov, P. Y. Serdobintsev,
M. A. Khodorkovskiy and T. A. Pakkanen, Inorg. Chem., 2008,
47, 9478; b) I. O. Koshevoy, A. J. Karttunen, S. P. Tunik, J.
Jänis,a M. Haukka, A. S. Melnikov, P. Y. Serdobintsev and T. A.
Pakkanen, Dalton Trans., 2010, 39, 2676; c) I. O. Koshevoy, C.-
L. Lin, A. J. Karttunen, J. Jänis, M. Haukka, S. P. Tunik, P.-T.
Chou and T. A. Pakkanen, Chem. Eur. J., 2011, 17, 11456; d) J.
R. Shakirova, E. V. Grachova, V. V. Gurzhiy, I. O. Koshevoy, A. S.
Melnikov, O. V. Sizova, S. P. Tunik and A. Laguna, Dalton
Trans., 2012, 41, 2941; e) D. V. Krupenya, P. A. Snegurov, E. V.
Grachova, V. V. Gurzhiy, S. P. Tunik, A. S. Melnikov, P. Yu.
Serdobintsev, E. G. Vlakh, E. S. Sinitsyna and T. B. Tennikova,
Inorg. Chem., 2013, 52, 12521.
a) H. Imoto, S. Nishiyama, T. Yumura, S. Watase, K.
Matsukawa and K. Naka, Dalton Trans., 2017, 46, 8077; b) H.
Imoto, S. Nishiyama and K. Naka, Bull. Chem. Soc. Jpn., 2018,
91, 349; c) R. Kobayashi, T. Fujii, H. Imoto and K. Naka, Eur. J.
Inorg. Chem., 2021, 2021, 217; d) R. Kobayashi, H. Kihara, T.
Kusukawa, H. Imoto and K. Naka, Chem. Lett., 2021, 50, 382.
W. Levason, G. Reid, Comprehensive Coordination Chemistry
II; J. A. McCleverty, T. J. Meyer, Eds.; Elsevier Science:
Amsterdam, The Netherlands, 2004; Vol. 1, Chapter 1.12, pp
253.
6
7
1
and 2. They formed three types of crystalline polymorphs,
i.e., α-, β-, and γ-forms, depending on the recrystallization
solvents. All the crystals exhibited remarkably strong
phosphorescence at room temperature (quantum yields up to
0.97), and various emission colors were observed including
near-infrared and white. Vapor-induced crystal-to-crystal
transitions resulted in diverse interconversion of emission
colors. Grinding the crystals in a mortar gave amorphous
samples that did not exhibit emission, while CH2Cl2 and MeOH
vapors converted the amorphous samples to the α- and γ-
forms crystals, respectively, turning on the emission with the
corresponding colors. DFT calculations indicated that the co-
existence of homo- and hetero-metallophilicity plays pivotal
roles in the electronic structures responsible for the
luminescence. The present work proposes a novel molecular
design for highly emissive and stimuli responsive hetero-
multinuclear d10 complexes. We are currently investigating the
detailed mechanism for the efficient emissions, phase
transition behaviors, and different effects of diarsine and
diphosphine ligands on the properties of this kind of
complexes.
8
9
Conflicts of interest
10 H. Imoto, M. Konishi, S. Nishiyama, H. Sasaki, S. Tanaka, T.
Yumura and K. Naka, Chem. Lett., 2019, 48, 1312.
There are no conflicts to declare.
11 S. Nag, K. Banerjee and D. Datta, New J. Chem., 2007, 31, 832.
12 a) H. Kihara, S. Tanaka, H. Imoto and K. Naka, Eur. J. Inorg.
Chem., 2020, 2020, 3662; b) R. Kobayashi, H. Imoto and K.
Naka, Eur. J. Inorg. Chem., 2020, 2020, 3548.
13 When the emission maxima are longer than 800 nm, the NIR
dyes exhibiting the quantum yields higher than 0.10 are rare.
For detail, see: A. Zampetti, A. Minotto andv F. Cacialli, Adv.
Funct. Mater., 2019, 29, 1807623.
14 For recent reviews, see: a) S. Shimizu, Chem. Commun., 2019,
55, 8722; b) L. Wang, W. Du, Z. Hu, K. Uvdal, L. Li and W.
Huang, Angew. Chem. Int. Ed., 2019, 58, 14026; c) G.-Q. Jin, Y.
Ning, J.-X. Geng, Z.-F. Jiang, Y. Wang and J.-L. Zhang, Inorg.
Chem. Front., 2020, 7, 289; d) Z. Wang and B. Xing, Chem.
Asian J., 2020, 15, 2076; e) D. Chen, Z. Zhong, Q. Ma, J. Shao,
W. Huang and X. Dong, ACS Appl. Mater. Interfaces, 2020, 12,
26914.
Acknowledgement
This work was supported by JSPS KAKENHI, grant Number
19H04577 (Coordination Asymmetry) and 20H02812 (Grant-in-
Aid for Scientific Research (B)) to HI.
Notes and references
1
Recent reviews, see: a) A. Aliprandi, D. Genovese, M. Mauro
and L. D. Cola, Chem. Lett., 2015, 44, 1152; b) A. K. Gupta and
A. Orthaber, Chem. Eur. J., 2018, 24,7536; c) S. A. Beach and L.
H. Doerrer, Acc. Chem. Res., 2018, 51, 1063; d) V. K. Jain, New
J. Chem., 2019, 43, 11034; e) J. Zheng, Z. Lu, K. Wu, G.-H. Ning
and D. Li, Chem. Rev., 2020, 120, 9675.
For reviews, see: a) H. Schmidbaur and A. Schier, Chem. Soc.
Rev., 2008, 37, 1931; b) M. J. Katz, K. Sakai and D. B. Leznof,
Chem. Soc. Rev., 2008, 37, 1884; c) H. Schmidbaur and A.
2
4 | J. Name., 2012, 00, 1-3
This journal is © The Royal Society of Chemistry 20xx
Please do not adjust margins