First aggregation-induced emission of a Tb(iii) luminophore based on modulation of ligand-ligand charge transfer bands

Article abstract of DOI:10.1039/d0dt00094a

Herein the aggregation-induced emission (AIE) of a Tb(iii) complex is reported for the first time. The Tb(iii) complex is composed of three anionic ligands (acac: acetylacetonate) and one large hetero-π-conjugated neutral ligand (dpq: dipyrido[3,2-f:2′,3′-h]quinoxaline). The formation of a crystalline J-aggregate of the Tb(iii) complex (CJ-Tb(iii)) was characterized by X-ray crystal structure analysis and absorption spectra. A crystalline H-aggregate (CH-Tb(iii)) was also prepared using the ligand steric effect (tmh: 2,2,6,6-tetramethyl-3,5-heptanedionate). The emission and AIE properties of CJ-Tb(iii) were evaluated using emission spectra, lifetime, and quantum yields, whereas CH-Tb(iii) did not emit photons. Density functional theory calculations predict that the AIE originates from the modulation of ligand-to-ligand charge transfer bands through J-aggregation.

Full text of DOI:10.1039/d0dt00094a

Dalton
Transactions
View Article Online
View Journal
PAPER
First aggregation-induced emission of a Tb(III)
luminophore based on modulation of
Cite this: DOI: 10.1039/d0dt00094a
ligand–ligand charge transfer bands†
Yuichi Kitagawa,
Yasuchika Hasegawa
*
a,b Marina Kumagai,c Takayuki Nakanishi,d Koji Fushimia and
a,b
*
Herein the aggregation-induced emission (AIE) of a Tb(III) complex is reported for the first time. The Tb(III)
complex is composed of three anionic ligands (acac: acetylacetonate) and one large hetero-π-conjugated
neutral ligand (dpq: dipyrido[3,2-f:2’,3’-h]quinoxaline). The formation of a crystalline J-aggregate of the
Tb(III) complex (CJ-Tb(III)) was characterized by X-ray crystal structure analysis and absorption spectra. A
crystalline H-aggregate (CH-Tb(III)) was also prepared using the ligand steric effect (tmh: 2,2,6,6-tetra-
methyl-3,5-heptanedionate). The emission and AIE properties of CJ-Tb(III) were evaluated using emission
spectra, lifetime, and quantum yields, whereas CH-Tb(III) did not emit photons. Density functional theory
calculations predict that the AIE originates from the modulation of ligand-to-ligand charge transfer bands
through J-aggregation.
Received 9th January 2020,
Accepted 22nd January 2020
DOI: 10.1039/d0dt00094a
rsc.li/dalton
shows solvatochromism and cell imaging characteristics.3
Yuan built a singlet oxygen sensor for the targeted photo-
Introduction
Luminescent materials that exhibit aggregation-induced emis- dynamic ablation of cancer cells using an AIE probe.4
sion (AIE) have attracted considerable attention1 since the dis- However, these luminescent materials have short emission life-
covery of the AIE effect by Tang in 2001.1a AIE-active materials times (on the order of nanoseconds) that resemble the emis-
are non-emissive (or weakly emissive) in the solution state but sion lifetimes of biomolecules such as proteins.5 The fabrica-
exhibit strong luminescence in an aggregated state (e.g., supra- tion of AIE-active luminophores with long emission lifetimes
molecular systems in solution, amorphous films, and crystal- (on the order of milliseconds) is required for their developing
line powders). The AIE phenomenon originates from restric- use in bio-applications.
tions to intramolecular rotation induced by aggregation.
Green luminescent Tb(III) complexes are promising mole-
Various types of AIE-based materials for bio-applications have cular materials with narrow 4f–4f emission bands (full-width
been reported. For example, Wen described the heavy-atom- at half maximum < 5 nm) and long emission lifetimes
free 1,1,4,4-tetraphenylbuta-1,3-diene exhibiting the AIE effect (>1 ms).6 Recently, several research groups found that the
for photodynamic cancer therapy.2 Tang demonstrated an AIE- ligand-to-ligand charge transfer (LLCT) band strongly affects
active tetraphenylethene-based chemo-sensor for Hg2+ that the luminescence properties of these complexes.7 Control of
the LLCT band in solution and crystallized states could lead to
the synthesis of Tb(III) luminophores with effective AIE.
aFaculty of Engineering, Hokkaido University, Kita-13 Jo, Nishi-8 Chome, Sapporo,
Hokkaido, 060-8628, Japan. E-mail: hasegaway@eng.hokudai.ac.jp,
y-kitagawa@eng.hokudai.ac.jp
In general, crystal packing structures are classified into
slipped-stacked configurations (J-aggregates) and face-to-face
configurations (H-aggregates) in terms of molecular align-
ment.8 The H-aggregates of Tb(III) complexes promote the for-
mation of quenching states such as excimers,9 whereas the
J-aggregates induce effective red-shifts of absorption bands
without the formation of a quenching state.10 In this study, we
report the first observation of AIE from a Tb(III) complex.
To prepare a Tb(III) complex with LLCT-controlled states, we
selected β-diketonate ligands (acac: acetylacetonate or tmh:
2,2,6,6-tetramethyl-3,5-heptanedionate) and dipyrido[3,2-f:2′,3′-
h]quinoxaline (dpq) as energy donating and accepting parts,
bInstitute for Chemical Reaction Design and Discovery (WPI-ICReDD),
Hokkaido University, Sapporo, Hokkaido 001-0021, Japan
cGraduate School of Chemical Sciences and Engineering, Hokkaido University,
Kita-13 Jo, Nishi-8 Chome, Sapporo, Hokkaido, 060-8628, Japan
dFaculty of Industrial Science and Technology, Tokyo University of Science, 6-3-1,
Niijuku, Katsushika-ku, Tokyo 125-8585, Japan
†Electronic supplementary information (ESI) available: Experimental detail,
emission spectra, electronic absorption spectra, thermogravimetric analysis,
X-ray crystal data, shape measure calculations, emission lifetimes, DFT calcu-
lations. CCDC 1867203, 1867204, 1911406 and 1975471. For ESI and crystallo-
graphic data in CIF or other electronic format see DOI: 10.1039/d0dt00094a
This journal is © The Royal Society of Chemistry 2020
Dalton Trans.

View Article Online
Paper
Dalton Transactions
Fig. 1 (a) Chemical structures and schematic images of Tb(III) com-
plexes. Schematic images of (b) Tb(III) complex in solution, (c) Tb(III)-
based J-aggregates, and (d) Tb(III) based H-aggregates.
Fig. 3 Main T1 state configurations (>10%) of Tb(acac)3dpq (HOMO−4
→ LUMO+1: 27%, HOMO−6 → LUMO: 15%, HOMO−5 → LUMO: 11%).
DFT calculations were performed using Al(III) ions instead of Tb(III)
ions.7a,15
respectively (Fig. 1a and b). The large π-conjugated dpq ligand
is also expected to aid in building the Tb(III)-based aggregates.
We prepared crystalline Tb(III)-based J-aggregates (CJ-Tb(III),
Fig. 1c) and H-aggregates (CH-Tb(III), Fig. 1d) by controlling
the steric structure of the β-diketonate ligands. This discovery
of AIE, based on LLCT control of the Tb(acac)3dpq complex,
represents a frontier field for molecular materials chemistry,
photophysical chemistry, and coordination chemistry.
levels of dpq and acac (tmh) ligands as 23 500 cm−1 and 25 000
(24 400) cm−1 11–13
respectively. Time-dependent density func-
,
tional theory (TD-DFT) (CAM-B3LYP/6-31G(d), IPCM-CH2Cl2)14
calculations revealed that the T1 states are mainly composed of
transitions from the delocalized orbital between dpq and
β-diketonate to dpq orbitals, thus inducing LLCT characteristic
(Fig. 3, see the ESI† for details). This interpretation is consist-
ent with the observed characteristically broad emission
bands.16 These results suggest that Tb(acac)3dpq and Tb
(tmh)3dpq in solution do not emit photons for quenching into
the LLCT state.
Results and discussion
Tb(III) complexes in solution states
To analyze the lowest excited triplet (T1) levels, we prepared Gd
(acac)3dpq and Gd(tmh)3dpq. By using Gd(III) complexes, the
T1 levels of Tb(acac)3dpq and Tb(tmh)3dpq in CH2Cl2 were
found to be 19 200 cm−1 and 19 100 cm−1, respectively (Fig. 2).
These energy levels are lower than the emission level of the Tb
(III) ion (5D4: 20 500 cm−1), indicating the formation of quench-
ing states for Tb(III) emission. Previous reports state the T1
Tb(III) complexes in aggregation states
Single crystals of Tb(acac)3dpq and Tb(tmh)3dpq (Fig. 4) were
obtained by recrystallization from CH2Cl2/hexane solution.
Single-crystal X-ray analysis revealed the structures of the J-
and H-aggregates of Tb(acac)3dpq (CJ-Tb) and Tb(tmh)3dpq
(CH-Tb), respectively (Fig. 4, Table 1). Two patterns of inter-
molecular dipole–dipole interactions (Fig. 4a, 1.0 nm and
1.2 nm) were observed for the Tb(acac)3dpq crystal structure,
which correspond to the slipped-stacked configuration
(J-aggregation: CJ-Tb(III)). On the other hand, strong inter-
molecular π–π interactions (Fig. 4b, 0.3 nm) between two dpq
ligands were observed for Tb(tmh)3dpq, which correspond to
the face-to-face configuration (H-aggregation: CH-Tb(III)). The
strong π–π interaction induces the formation of an effective
quenching state for Tb(III) emission (Fig. 5, T1 = 17 200 cm−1).
This energy shift is thought to originate from charge reso-
nance interactions between dpq ligands.17 The triplet level of
CJ-Tb(III) was calculated via TD-DFT, and the estimated T1
Fig. 2 Phosphorescence spectra of Gd(acac)3dpq (black line) in CH2Cl2
(1.0 × 10−3 M, delay: 20 ms, 185 K, λex = 350 nm) and Gd(tmh)3dpq (red
line) in CH2Cl2 (1.0 × 10−3 M, delay: 10 ms, 180 K, λex = 350 nm).
Dalton Trans.
This journal is © The Royal Society of Chemistry 2020

View Article Online
Dalton Transactions
Paper
metry from the solution to solid state. To determine the
coordination geometry around the Tb(III) ion, we performed
continuous shape measure calculations (Table S1, see ESI† for
the detail).18 The continuous shape measure factor S was
calculated to estimate the distortion degree of the coordi-
nation structure in the first coordination sphere based on the
crystal structure data. The S value is given by the following
equation.
N
P
2
jQk ꢀ Pkj
k
S ¼ min
ꢁ100
N
P
2
jQk ꢀ Q0j
k
where Qk is the vertices of the actual structure, Q0 is the center
of mass of the actual structure, N is the number of vertices,
and Pk is the vertices of the ideal structure. Eight-coordinated
lanthanide complexes exhibit a square antiprism (SAP, point
group: D4d), trigonal dodecahedron (TDH, point group: D2d),
or biaugmented trigonal prism (BTP, point group: C2v) struc-
ture according to the S value. Based on the calculations, Tb
(acac)3dpq was categorized as SAP coordination geometries
(Table S1,† S = 0.581). On the other hand, the S value of the
isolated Tb(III) complex obtained by theoretical calculations
was categorized as TDH coordination geometry (S = 4.569),
indicating different coordination geometry of between Tb(III)
complexes in solution and solid states. The coordination geo-
metry changes lead to LLCT band modulation, which should
induce AIE property (Fig. 6).
Fig. 4 X-ray crystal structures of (a) Tb(acac)3dpq and (b) Tb(tmh)3dpq.
Table 1 Crystallographic data of Tb(acac)3dpq and Tb(tmh)3dpq
Tb(acac)3dpq
Tb(tmh)3dpq
Chemical formula
Formula weight
C29H29N4O6Tb
688.49
C47H65N4O6Tb
937.92
Crystal system
Space group
Triclinic
P1
Triclinic
P1
ˉ
ˉ
a/Å
b/Å
c/Å
α/°
β/°
γ/°
Volume/Å
9.3675(2)
9.4780(2)
15.8705(3)
100.326(2)
92.661(2)
99.070(2)
1364.86(5)
2
1.675
20
0.0235
0.0776
10.9111(2)
12.2969(2)
19.3981(3)
104.160(2)
93.820(2)
110.125(2)
2336.81(8)
2
1.337
20
0.0240
0.0832
Aggregation-induced emission of Tb(III) luminophore
The emission photograph of Tb(acac)3dpq in solution (CH2Cl2,
1.0 × 10−3 M) and solid states under UV-light are shown in
Fig. 7a. We successfully observed the green emission of CJ-Tb
(III), although Tb(acac)3dpq in solution did not emit photons.
The luminescence and excitation spectra of Tb(acac)3dpq are
shown in Fig. 7b. Sharp emission bands at 488, 545, 581, 619,
and 648 nm were observed for Tb(acac)3dpq, which are
Z
Density/g cm−3
Temperature/°C
Ra
b
wR2
2 1/2
a R = ∑||Fo| − |Fc||/∑|Fo|. b wR2 = [∑w(|Fo| − |Fc|)2/∑wFo
]
.
5
7
7
5
7
5
7
assigned to the D4 → F6, 5D4 → F5, D4 → F4, D4 → F3,
and 5D4 → 7F2 transitions of the Tb(III) ion, respectively.
The excitation spectrum has broad bands in the UV-visible
region, indicating an effective energy transfer from the
J-aggregate to the Tb(III) ion (Φ = 16%, τ = 0.47 ms, Table 2).
Fig. 5 Phosphorescence spectrum of Gd(tmh)3dpq in solid state (λex
=
350 nm).
energy (22 900 cm−1) was sufficiently higher than the emission
level of the Tb(III) ion (20 500 cm−1). The T1 states correspond
to localized dpq states (Fig. S12†), indicating that the excited
Fig. 6 Schematic images of energy diagram of Tb(acac)3(dpq) in solu-
LLCT energy increased with the change in coordination geo- tion (a) and solid (b) states.
This journal is © The Royal Society of Chemistry 2020
Dalton Trans.

View Article Online
Paper
Dalton Transactions
(Fig. 8), demonstrating the potential of the AIE-active Tb(III)
luminophore as a thermometer.
Finally, we determined the water solubility of the complex
between CJ-Tb(III) and sodium dodecyl sulfate (SDS) for poss-
ible future applications. DLS measurements of the complex in
SDS-water (SDS: 2.0 × 10−2 M) revealed a nano-order particle
size (Fig. 9a, dave = 196 nm). Effective Tb(III) emission in SDS-
water was also observed (Fig. 9b, τ = 0.38 ms).
Conclusions
In this paper, we reported a novel strategy to fabricate emis-
sion materials exhibiting the AIE effect by using the orien-
tation control of ligands around the Tb(III) ion. The Tb(III)
complex has the advantage of prominent luminescence with
narrow emission bands and long emission lifetimes based on
Fig. 7 (a) Photographs of Tb(acac)3(dpq) in solution and solid states
under UV-light. (b) Emission (solid line, λex = 350 nm) and excitation
(broken line, λem = 545 nm) spectra of Tb(acac)3(dpq). Photographs in
casting solutions of (c) Tb(acac)3(dpq) and (d) Tb(tmh)3(dpq) under UV-
light.
Fig. 8 Temperature-dependent emission lifetime of CJ-Tb(III) (λex
356 nm).
=
The luminescence lifetime of CH-Tb(III) was much shorter (τ =
0.02 ms) due to aggregation-induced quenching of the Tb(III)
ion.
The AIE behavior of CJ-Tb(III) during the solidification of
the luminescent species in solution is shown in Fig. 7c. We
observed green luminescence from the edge of the solution at
21 s, and then bright green luminescence at 56 s. In contrast
to the AIE effect of Tb(acac)3dpq, we did not observe green
luminescence from CH-Tb(III) (Fig. 7d). We also found that the
emission lifetime was strongly dependent on temperature
Fig. 9 (a) DLS graph of Tb(acac)3(dpq)-SDS, (b) Photographs and sche-
matic image of Tb(acac)3(dpq)-SDS in H2O.
Table 2 Photophysical properties of Tb(III) complexes
State
Compounds
T1/cm−1
Aggregation type
Absorption edge/cm−1
Φtot b/%
τc/ms
CJ-Tb(III)
CH-Tb(III)
Solution
Solution
Tb(acac)3dpq
Tb(tmh)3dpq
Tb(acac)3dpq
Tb(tmh)3dpq
22 900a
17 200
19 200
19 100
J-Aggregation
H-Aggregation
Monomer
16 800
20 300
—
16
<1
ND
ND
0.47
0.02
ND
Monomer
—
ND
a Theoretical calculation value. b λex = 360 nm. c λex = 355 nm
Dalton Trans.
This journal is © The Royal Society of Chemistry 2020

View Article Online
Dalton Transactions
Paper
4f–4f transition. This study provides new insights into AIE (433 mg), and the mixed solution was refluxed for 12 h. The
materials based on lanthanide(III) complexes.
resulting precipitate was filtrated, washed with methanol and
ethanol, and dried under vacuum to afford a cream-colored
solid (yield: 349 mg).
ESI-MS: m/z calcd for C29H29N4O6Tb, [M-acac]+ = 589.09;
found: 589.07; elemental analysis calcd (%) for C 50.59, H
4.25, N 8.14; found: C 50.33, H 4.14, N 7.98.
Experimental section
General method
1H-NMR spectra were recorded in CDCl3 on a JEOL ECS-400
(400 MHz) spectrometer; CHCl3 (δH = 7.26 ppm) was used as
the internal reference. Electrospray ionization (ESI) mass spec-
trometry was performed using JEOL JMS-T100 LP instrument.
Elemental analyses were performed using MICRO CORDER
JM10. Thermogravimetric analyses (TGA) were performed
using an EXSTAR 6000 TG/DTA 6300 instrument (Seiko
Instruments Inc.). UV-vis absorption spectra were measured
using a JASCO V-670 spectrophotometer. Diffuse-reflection
spectra was recorded with a JASCO V-670 spectrophotometer
equipped with an integrating-sphere unit (JASCO ISN-723).
Luminescence spectra, excitation spectra, and luminescence
lifetimes for Tb(acac)3dpq and Tb(tmh)3dpq were measured
using a Horiba FluoroLog®3 spectrofluorometer. Temperature-
dependent luminescence lifetimes for Tb(acac)3dpq were
measured using a Horiba FluoroLog®3 spectrofluorometer
with a cryostat (Thermal Block Company, SA-SB245 T) and a
temperature controller (Oxford, Instruments, ITC 502S).
Luminescence quantum yields were measured using a FP-6300
spectrofluorometer with an integration sphere (ILF-533). DLS
measurement was performed using nanotracWave II = UT151-
SPHG.
Preparation of Tb(tmh)3dpq. Tb2(tmh)6 was prepared accord-
ing to a previous report.14 A methanol solution (50 ml) con-
taining dpq (233 mg, 1.00 mmol) was added to a methanol
solution (50 ml) containing Tb2(tmh)6 (710 mg, 0.501 mmol),
and the mixed solution was refluxed for 12 h. The resulting
precipitate was filtrated, washed with methanol and ethanol,
and dried under vacuum to afford a cream-colored solid (yield:
692 mg, 74%).
ESI-MS: m/z calcd for C47H65N4O6Tb, [M-tmh]+ = 757.28;
found: 757.25; elemental analysis calcd (%) for C 59.99, H
6.96, N 5.95; found: C 59.83, H 6.96, N 5.93.
Preparation of Gd(acac)3dpq. A methanol solution (40 ml)
containing dpq (235 mg, 1.01 mmol) was added to
a
methanol solution (20 ml) containing Gd(acac)3·nH2O
(458 mg), and the mixed solution was refluxed for 12 h. The
resulting precipitate was filtrated, washed with methanol and
ethanol, and dried under vacuum to afford a cream-colored
solid (yield: 434 mg).
ESI-MS: m/z calcd for C29H29GdN4O6, [M-acac]+ = 588.09;
found: 588.08; elemental analysis calcd (%) for C 50.71, H
4.26, N 8.16; found: C 50.27, H 4.15, N 8.05.
Preparation of Gd(tmh)3dpq. Gd2(tmh)6 was prepared
according to a previous report.19 A methanol solution (40 ml)
containing dpq (237 mg, 1.02 mmol) was added to a methanol
Materials
Magnesium sulfate, anhydrous (>98.0% (titration)), methanol solution (20 ml) containing Gd(tmh)6 (709 mg, 0.501 mmol),
(guaranteed reagent), ethanol (guaranteed reagent), and and the mixed solution was refluxed for 12 h. The resulting
chloroform-d1 (99.8%) were purchased from Kanto Chemical precipitate was filtrated, washed with methanol and ethanol,
Co., Inc. Dichloromethane (spectroscopic grade), chloroform and dried under vacuum to afford a cream-colored solid (yield:
(spectroscopic grade), and 1,2-dichloroethane (spectroscopic 812 mg, 85%).
grade) were purchased from Wako Pure Chemical Industries,
ESI-MS: m/z calcd for C47H65GdN4O6, [M-tmh]+ = 756.28;
Ltd. 1,10-Phenanthroline-5,6-dione (>98.0%), 2,2,6,6-tetra- found: 756.32; elemental analysis calcd (%) for C 60.10, H
methyl-3,5-heptanedione, and ethylenediamine anhydrous 6.98, N 5.96; found: C 59.39, H 6.87, N 5.82.
(>98.0%) were purchased from Tokyo Chemical Industry Co.,
Ltd. Terbium(III) acetylacetonate hydrate was purchased from
Sigma-Aldrich (99.9%).
Single-crystal X-ray structure determination
Preparation of dpq (dipyrido[3,2-f:2′,3′-h]quinoxaline). We X-ray crystal structures and crystallographic data for Tb
prepared the dpq ligand according to a previous report.11,19 (acac)3dpq and (for Tb(tmh)3dpq are shown in Fig. 4 and
1,10-Phenanthroline-5,6-dione (627 mg, 2.99 mmol) and ethy- Table 1. Single crystals of the compounds were mounted on
lenediamine (1.0 mL, 15.0 mmol) were dissolved in water micromesh (MiTeGen M3-L19–25L) using paraffin oil.
(40 ml), and the mixed solution was stirred for 12 h at 60 °C. Measurements were made by using a Rigaku RAXIS RAPID
The resulting precipitate was filtrated, washed with water, and imaging-plate area detector or XtaLAB AFC11 (RCD3) with
dried under vacuum to afford a cream-colored solid (yield: graphite-monochromated Mo-Kα radiation. Non-hydrogen
559 mg, 80%).1H-NMR (400 MHz, CDCl3/TMS) δ/ppm = 9.52 atoms were anisotropically refined. All calculations were per-
(d, J = 8.4 Hz, 2H), 9.30 (d, J = 4.4 Hz, 2H), 9.00 (s, 2H), 7.81 formed using a crystal-structure crystallographic software
(dd, J = 8.0, 4.0 Hz, 2H).
package. The CIF data were confirmed by the check CIF/
Preparation of Tb(acac)3dpq. Tb(acac)3dpq was prepared PLATON service. CCDC 1867203 (for Tb(acac)3dpq), 1867204
according to our previous report.11,19 A methanol solution (for Tb(tmh)3dpq), 1975471 (for Gd(acac)3dpq), and 1911406
(20 ml) containing dpq (143 mg, 0.616 mmol) was added to a (for Gd(tmh)3dpq) contain the supplementary crystallographic
methanol solution (20 ml) containing Tb(acac)3·nH2O data for this paper.†
This journal is © The Royal Society of Chemistry 2020
Dalton Trans.

View Article Online
Paper
Dalton Transactions
J.-C. G. Bünzli and V. K. Pecharsky, Elsevier, Amsterdam,
2005, vol. 35, p. 107.
Conflicts of interest
There are no conflicts to declare.
7 (a) P. P. F. da Rosa, T. Nakanishi, Y. Kitagawa, T. Seki,
H. Ito, K. Fushimi and Y. Hasegawa, Eur. J. Inorg. Chem.,
2018, 2018, 2031; (b) M. Räsänen, H. Takalo, J. Rosenberg,
J. Mäkelä, K. Haapakka and J. Kankare, J. Lumin., 2014,
146, 211; (c) R. T. Golkowski, N. S. Settineri, X. K. Zhao and
D. R. McMillin, J. Phys. Chem. A, 2015, 119, 11650;
(d) C.-L. Liu, R.-L. Zhang, C.-S. Lin, Li.-P. Zhou, Li.-X. Cai,
J.-T. Kong, S.-Q. Yang, Ke.-Li Han and Q.-F. Sun, J. Am.
Chem. Soc., 2017, 139, 12474; (e) G.-L. Law, D. Parker,
S. L. Richardson and K.-L. Wong, Dalton Trans., 2009, 8481.
8 N. J. Hestand and F. C. Spano, Acc. Chem. Res., 2017, 50,
341.
9 F. Nuesch and M. Gratzel, Chem. Phys., 1995, 193, 1.
10 Y. Kitagawa, J. Hiromoto and K. Ishii, J. Porphyrins
Phthalocyanines, 2013, 17, 703.
11 S. Dasari, S. Singh, S. Sivakumar and A. K. Patra, Chem. –
Eur. J., 2016, 22, 17387.
Acknowledgements
This work was supported by Grant-in-Aid for Grant Number
17K14467, 19H04556, 18H04497 and 18H02041. This work was
also supported by the Institute for Chemical Reaction Design
and Discovery (ICReDD), established by the World Premier In-
ternational Research Initiative (WPI) of MEXT, Japan. This
study was supported in part by Grants-in-Aids for regional R&D
Proposal-Based Program from Northern Advancement Center
for Science & Technology of Hokkaido Japan.
Notes and references
1 (a) J. Luo, Z. Xie, J. W. Y. Lam, L. Cheng, H. Chen, C. Qiu,
H. S. Kwok, X. Zhan, Y. Liu, D. Zhu and B. Z. Tang, Chem. 12 D. A. Hardy, R. A. Tigaa, R. E. Ortega, J. R. McBride and
Commun., 2001, 1740; (b) H.-T. Feng, Y.-X. Yuan, G. F. Strouse, J. Phys. Chem. C, 2019, 123, 31175.
J.-B. Xiong, Y.-S. Zheng and B.-Z. Tang, Chem. Soc. Rev., 13 K. Yanagisawa, Y. Kitagawa, T. Nakanishi, T. Akama,
2018, 47, 7452; (c) M. Gao and B. Z. Tang, ACS Sens., 2017,
2, 1382; (d) J. Qian and B. Z. Tang, Chem, 2017, 3, 56;
M. Kobayashi, T. Seki, K. Fushimi, H. Ito, T. Taketsugu and
Y. Hasegawa, Eur. J. Inorg. Chem., 2017, 2017, 3843.
(e) J. Mei, N. L. Leung, R. T. Kwok, J. W. Lam and 14 (a) C. Lee, W. Yang and R. G. Parr, Phys. Rev. B: Condens.
B. Z. Tang, Chem. Rev., 2015, 115, 11718.
2 H. Wen, J. Ma, J. Chen, Z. Ke, D. Zou and Q. Li, New J.
Chem., 2019, 43, 9183–9187.
3 A. L. Tang, Z. Chen, D. D. Deng, G. Liu, Y. Y. Tu and
S. Z. Pu, RSC Adv., 2019, 9, 11865.
Matter Mater. Phys., 1988, 37, 785; (b) A. D. Becke, J. Chem.
Phys., 1993, 98, 5648.
15 S. Omagari, T. Nakanishi, T. Seki, Y. Kitagawa, Y. Takahata,
K. Fushimi, H. Ito and Y. Hasegawa, J. Phys. Chem. A, 2015,
119, 1943–1947.
4 Y. Yuan, C.-J. Zhang, S. Xu and S. B. Liu, Chem. Sci., 2016, 16 H. Tanaka, K. Shizu, H. Nakanotani and C. Adachi, Chem.
7, 1862. Mater., 2013, 25, 3766.
5 J. R. Alcala, E. Gratton and F. G. Prendergast, Biophys. J., 17 N. J. Hestand and F. C. Spano, Acc. Chem. Res., 2017, 50,
1987, 51, 597. 341–350.
6 (a) F. S. Richardson, Chem. Rev., 1982, 82, 541; (b) J.-C. 18 D. Casanova, M. Llunell, P. Alemany and S. Alvarez, Chem.
G. Bünzli, Chem. Rev., 2010, 110, 2729; (c) S. J. Butler and – Eur. J., 2005, 11, 1479.
D. Parker, Chem. Soc. Rev., 2013, 42, 1652; (d) J.-C. 19 (a) G. J. Chen, Z. G. Wang, X. Qiao, J. Y. Xu, J. L. Tian and
G. Bünzli, Coord. Chem. Rev., 2015, 293–294, 19;
(e) Y. Hasegawa and Y. Kitagawa, J. Mater. Chem. C, 2019, 7,
7494; (f) K. Binnemans, in Handbook on the Physics and
Chemistry of Rare Earths, ed. K. A. Gschneidner Jr.,
S. P. Yan, J. Inorg. Biochem., 2013, 127, 39; (b) F. Fulgêncio,
F. C. De Oliveira, F. F. Ivashita, A. Paesano, D. Windmöller,
A. Marques-Netto, W. F. Magalhães and J. C. MacHado,
Spectrochim. Acta, Part A, 2012, 92, 415.
Dalton Trans.
This journal is © The Royal Society of Chemistry 2020