- Email: [email protected]
Eu(III)- and Tb(III)-coordination polymer luminescent thermometers constructed from a π-rich aromatic ligand exhibiting a high sensitivity
Accepted Manuscript Eu(III)- and Tb(III)-coordination polymer luminescent thermometers constructed from a π-rich aromatic ligand exhibiting a high sensitivity Xin-Wen Peng, Qing-Yan Liu, Hui-Hong Wang, Yu-Ling Wang PII:
S0143-7208(18)31975-2
DOI:
https://doi.org/10.1016/j.dyepig.2018.10.055
Reference:
DYPI 7121
To appear in:
Dyes and Pigments
Received Date: 6 September 2018 Revised Date:
22 October 2018
Accepted Date: 25 October 2018
Please cite this article as: Peng X-W, Liu Q-Y, Wang H-H, Wang Y-L, Eu(III)- and Tb(III)-coordination polymer luminescent thermometers constructed from a π-rich aromatic ligand exhibiting a high sensitivity, Dyes and Pigments (2018), doi: https://doi.org/10.1016/j.dyepig.2018.10.055. This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
ACCEPTED MANUSCRIPT Graphical abstract
AC C
EP
TE D
M AN U
SC
RI PT
The 4'-(3,5-dicarboxyphenyl)-2,2',6',2''-terpyridine (H2-DCPTP) ligand serves as a light-harvesting ligand for efficiently sensitizing of Tb3+ and Eu3+ simultaneously, thus enhancing the overall luminescence of Tb0.9064Eu0.0936-DCPTP, which behaves as a high-performance luminescent thermometer with a high relative thermal sensitivity of Sm up to 21.5 % K‒1.
ACCEPTED MANUSCRIPT 1
Eu(III)-
and
Tb(III)-coordination
polymer
luminescent
2
thermometers constructed from a π-rich aromatic ligand exhibiting a
3
high sensitivity
5
Xin-Wen Peng, Qing-Yan Liu*, Hui-Hong Wang, Yu-Ling Wang*
6
RI PT
4
College of Chemistry and Chemical Engineering, Key laboratory of functional small organic
8
molecule of ministry of education, Jiangxi Normal University, Nanchang, Jiangxi 330022, PR
9
China E-mail: [email protected]; [email protected]
M AN U
SC
7
Dedicated to Professor Jin-Shun Huang on the occasion of his 80th birthday.
12
ABSTRACT: A π-rich aromatic organic ligand, 4'-(3,5-dicarboxyphenyl)-2,2',6',2''-terpyridine
13
(H2-DCPTP), and four new lanthanide coordination polymers, {[Ln(DCPTP)(NO3)]·(H2O)}n (Ln
14
= Tb, Eu, Gd) and {[Tb0.9064Eu0.0936(DCPTP)(NO3)]·(H2O)}n (termed Tb0.9064Eu0.0936-DCPTP),
15
were prepared. Compound {[Ln(DCPTP)(NO3)]·(H2O)}n is a 3D framework based on the
16
dinuclear Ln2(µ2-COO)2] units linked by the tridentate DCPTP2‒ ligands. The H2-DCPTP ligand
17
with an appropriate triplet excited state confirmed by DFT calculations and experiments, is a
18
light-harvesting ligand for efficiently sensitizing of Tb3+ and Eu3+ simultaneously, thus enhancing
19
the overall luminescent properties of Tb0.9064Eu0.0936-DCPTP. The Tb0.9064Eu0.0936-DCPTP behaves
20
as a high-performance luminescent thermometer ranging from 150 to 300 K with a large relative
21
thermal sensitivity (Sm) of 21.5 % K‒1 and a high energy transfer efficiency (η) of 84% at 300 K.
AC C
EP
TE D
10 11
22 23
Keywords:
Ratiometric
fluorescent
probe; 1
luminescent
thermometer;
Eu(III)-
and
ACCEPTED MANUSCRIPT 24
Tb(III)-coordination polymer; light-harvesting ligand.
25
1. Introduction The lanthanide-based coordination polymers continue to attract intense attentions due to their
27
potential applications pertaining to the distinctive luminescence and magnetism derived from the
28
lanthanide centers with 4fn configuration [1‒7]. In particular, luminescent lanthanide coordination
29
polymers are highly sought after because of their diverse luminescent properties such as
30
characteristically sharp line emissions, high photoluminescence efficiency as well as long
31
luminescent lifetime, which have been developed for chemical sensors and light-emitting devices
32
[8‒15]. Recently, the lanthanide coordination polymers with the temperature-dependent emissions
33
have been developed for luminescent thermometers [16‒22]. Comparing to the conventional
34
temperature sensors, such luminescence-based thermometers own the distinct advantages of fast
35
response, non-invasive operation and high spatial resolution. Moreover, such thermometers can
36
work in strong electro-magnetic fields due to their inertness to strong electric-magnetic fields.
TE D
M AN U
SC
RI PT
26
As is well-known, luminescent sensing based on relative emission intensity is more reliable and
38
powerful than through single-emission intensity. The accuracy of the sensing based on the
39
absolute intensity of an emission is often susceptible to external factors including the luminophore
40
quantity, excitation power, and the drifts of the optoelectronic systems. Moreover, the intensity
41
ratio for two emissions is almost a constant under a certain condition and thus additional
42
calibration of intensity is not necessary for such a ratiometric method, leading to desirable
43
ratiometric luminescent thermometers. A few mixed lanthanide coordination polymers
44
luminescent thermometers with Tb3+ and Eu3+-dual emissions have been reported recently [23‒27].
45
However, the relative thermal sensitivity of the Tb3+-Eu3+ luminescent thermometers is found to
AC C
EP
37
2
ACCEPTED MANUSCRIPT be lower than 10 % K−1 [28, 29]. Therefore, it is still a challenge to construct lanthanide
47
compounds for temperature sensing with high sensitivity and accurate sensing. As an efficient
48
sensitizer for the lanthanide ions, the organic ligand takes a decisive role in the construction of
49
lanthanide luminescent thermometers. To obtain high-performance luminescent thermometers with
50
Tb3+ and Eu3+ mixed metal ions, the Tb3+ and Eu3+ ions should be efficiently sensitized by the
51
organic ligand simultaneously. The organic ligand for such purpose must have an appropriate
52
triplet excited state energy between 22000 and 27000 cm−1 [1, 30, 31], matching the main
53
accepting energy levels of Tb3+ (5D4, 20500 cm−1) and Eu3+ (5D1, 19030 cm−1) [32].
M AN U
SC
RI PT
46
In this contribution, an organic ligand with a terpyridine backbone and an isophthalic acid,
55
4'-(3,5-dicarboxyphenyl)-2,2',6',2''-terpyridine (H2-DCPTP), was designed for rational preparation
56
of luminescent thermometers. The H2-DCPTP with four carboxylate oxygens has a preferential
57
coordination to the oxophile lanthanide ions and the terpyridine moiety can chelate a lanthanide
58
ion, giving the robust lanthanide coordination polymers. In addition, the H2-DCPTP with
59
extensive aromatic π-systems is expected to be a light-harvesting ligand for efficiently sensitizing
60
of lanthanide ions, which is corroborated by the result of the time-dependent DFT calculations
61
(Fig. S1). The calculated triplet excited state energy for H2-DCPTP is 25217 cm−1, indicating the
62
H2-DCPTP is a suitable organic linker for construction of the Tb3+/Eu3+-coordination polymer
63
luminescent
64
{[Ln(DCPTP)(NO3)]·(H2O)}n (Ln = Tb(1), Eu(2) and Gd(3)) and the Eu-doped Tb-compound of
65
{[Tb0.9064Eu0.0936(DCPTP)(NO3)]·(H2O)}n (termed Tb0.9064Eu0.0936-DCPTP) were presented.
66
Detailed luminescent behavior for these compounds were investigated. Temperature-dependent
67
luminescence of Tb0.9064Eu0.0936-DCPTP show the organic ligands with the extensive aromatic
AC C
EP
TE D
54
thermometers.
Herein
three
3
compounds
with
formula
of
ACCEPTED MANUSCRIPT π-systems transfer the absorbed energy to the Tb3+ and Eu3+ ions efficiently, thus enhancing the
69
overall luminescent properties of Tb0.9064Eu0.0936-DCPTP. As a result, Tb0.9064Eu0.0936-DCPTP
70
behaves a high-performance luminescent thermometers displaying a large relative thermal
71
sensitivity and a high energy transfer efficiency.
RI PT
68
73
2. Experimental
74
2.1. Materials and instrumentations 1
H nuclear magnetic resonance (NMR) spectra were collected on a Bruker AVANCE 400
M AN U
75
SC
72
spectrometer. FT-IR (KBr pellets, cm–1) spectra were performed at a Perkin-Elmer Spectrum One
77
FT-IR spectrometer ranging from 400–4000 cm–1. Elemental analyses were carried out on an
78
Elementar Perkin-Elmer 2400CHN microanalyzer. Thermogravimetric analyses (TGA) were
79
carried out on a PE Diamond instrument under a N2 flow with a heating rate of 10 °C min–1.
80
Powder X-ray diffraction (PXRD) were measured on a Rigaku Miniflex II powder diffractometer
81
(Cu-Kα, λ = 1.5418 Å). Fluorescent spectra and luminescence lifetime were measured with
82
Edinburgh Instruments FLS980 fluorescence spectrometer equipped with an Oxford Instruments
83
liquid nitrogen flow cryostat. Inductively coupled plasma (ICP) (Ultima2, HORIBA Jobin Yvon)
84
spectra were used for determination of the metal concentration after the sample was dissolved in
85
concentrated nitric acid.
AC C
EP
TE D
76
86
X-ray diffraction experiments were carried out on a Rigaku Oxford SuperNova diffractometer
87
with an Eos detector (Mo-Ka radiation, 0.71073 Å) and. The CrysAlisPro software package was
88
used for absorption correction and data reduction [33]. The structures were solved by the direct
89
methods using the SHELXTL [34] and refined by the full-matrix least-squares against F2 [35]. All 4
ACCEPTED MANUSCRIPT atoms except for hydrogen atoms are refined with anisotropic thermal parameters. Aromatic
91
hydrogen atoms were placed in calculated positions. Hydrogen atoms bonded to oxygen atoms
92
couldn’t be located. The R1 and wR2 values are defined as R1 = Σ||Fo| – |Fc|| / Σ|Fo| and wR2 =
93
{Σ[w(Fo2 – Fc2)2] / Σ[w(Fo2)2]}1/2, respectively. The important crystallographic data is listed in
94
Table S1.
95
All chemicals used here were of reagent grade and obtained commercially. The 4'-(3,5-dicarboxyphenyl)-2,2',6',2''-terpyridine (H2-DCPTP) was synthesized in Scheme 1.
M AN U
SC
96
RI PT
90
97
Scheme 1 Preparation of H2-DCPTP ligand.
99
2.2 Synthesis of H2-DCPTP ligand
100
TE D
98
2.2.1 Synthesis of 3-(3′,5′-dimethylphenyl)-1-(pyridin-2′-yl)prop-2-en-1-one (a). All reactants including solvents for this reaction were cooled to 5 oC before use. In a flask, 2.50
102
g (18.7 mmol) of 3,5-dimethylbenzaldehyde and 1.20 g (33.6mmol) of NaOH were mixed with 90
103
mL methanol/water (v/v = 3:1) solution, followed by a 20 mL methanol solution of
104
2-acetylpyridine (18.0 mmol, 2.20 g). The mixture was stirred at 5 oC for 8 h to give yellow solid.
105
The yellow solid was washed with methanol and water (v/v = 1:4) solution and dried in vacuo at
106
room temperature; yield 4.18 g (95%). 1H NMR (CDCl3, ppm): δ = 8.76 (d, J = 4.0 Hz, 1H), 8.29
107
(d, J = 16.0 Hz, 1H), 8.20 (d, J = 8.0 Hz, 1H), 7.92 (s, 1H), 7.89 (m, J = 16.0 Hz, 1H), 7.50 (m, J
108
= 12.0 Hz, 1H), 7.35 (s, 2H), 7.05 (s, 1H), 2.35 (s, 6H).
AC C
EP
101
5
ACCEPTED MANUSCRIPT 109
2.2.2 Synthesis of (4′-(3,5-dimethylphenyl) -2,2′:6′,2″-terpyridine) (b). Compound a (10.0 mmol, 2.37g), 2-acetylpyridine (10.0 mmol, 1.21 g), and KOH (30.0 mmol,
111
1.68 g) were mixed with 120 mL of ethanol followed by a 75 mL NH4OH solution (30%). The
112
resulting mixture was stirred at 60 °C for 1 d to give a pale yellow solid. The solid was
113
recrystallized from pyridine and water (v/v = 2:1) solvent, and dried in vacuo; yield 1.72 g (51%).
114
1
115
16.8 Hz, 2H), 7.55(d, J = 11.2 Hz, 4H), 7.17(s , 1H), 2.41(s, 6H).
116
2.2.3 Synthesis of 4'-(3,5-dicarboxyphenyl)-2,2',6',2''-terpyridine (H2-DCPTP).
RI PT
110
M AN U
SC
H NMR (DMSO-d6, ppm): δ = 8.77 (d, J = 4.4 Hz, 2H), 8.69 (d, J = 10.0 Hz, 4H), 8.06 (m, J =
1.21 g (3.6 mmol) of compound b and 3.40 g (21.6 mmol) of KMnO4 were mixed with 60 mL
118
pyridine and 30 mL water. The mixture was refluxed for 4 h. Then 3.40 g (21.6 mmol) of KMnO4,
119
10 mL water and 10 mL pyridine were added into the mixture, which was refluxed for another 3 h.
120
The resulting mixture was filtrated and the obtained precipitate was washed with water. The
121
combined filtrates were condensed under reduced pressure and then added by concentrated HCl to
122
give white precipitate. The white precipitate was recrystallized from solvent of pyridine/water (v/v
123
= 1:1) and dried in vacuo; yield 1.23g (86 %). 1H NMR (DMSO-d6, ppm): δ = 8.81 (d, J =4 .4,
124
2H), 8.74 (d, J = 8.4 Hz, 4H), 8.58 (s, 3H), 8.14 (m, J = 15.2 Hz, 2H), 7.64(m, J = 12.0 Hz, 2H).
125
2.3 Synthesis of {[Ln(DCPTP)(NO3)]·(H2O)}n
EP
AC C
126
TE D
117
Lanthanide nitrate (Tb(NO3)3·6H2O (20.4 mg, 0.045 mmol), or Eu(NO3)3·6H2O (20.1 mg,
127
0.045 mmol), or Gd(NO3)3·6H2O (20.3 mg, 0.045 mmol )), H2-DCPTP (18.0 mg, 0.045 mmol ),
128
acetonitrile (4 mL), and HNO3 (0.5 mL, 1 M in H2O) were mixed. The resulting mixture was
129
introduced into a 25 mL Parr Teflon-lined stainless steel vessel, which was heated at 140 °C for 5
130
d. The mixture was cooled to room temperature to give crystals. Yield: 75% for Tb(1); 71% for 6
ACCEPTED MANUSCRIPT Eu(2); 82% for Gd(3). Anal. Calcd for C23H15N4O8Tb (Mr = 634.31): C, 43.55; H, 2.38; N, 8.83%.
132
Found: C, 43.51; H, 2.43; N, 8.81%. Anal. Calcd for C23H15N4O8Eu (Mr = 627.35): C, 44.03; H,
133
2.41; N, 8.93%. Found: C, 44.02; H, 2.39; N, 8.91%. Anal. Calcd for C23H15N4O8Gd (Mr =
134
632.64): C, 43.67; H, 2.39; N, 8.86%. Found: C, 43.62; H, 2.42; N, 8.83%. IR spectrum (cm‒1):
135
for Tb(1), 3394 (m), 1627 (s), 1601 (m), 1586 (m), 1572 (m), 1541 (m), 1449 (s), 1385 (s), 1310
136
(m), 1165 (w), 1105 (w), 1038 (w), 1013 (w), 887 (w), 794 (w), 776 (w), 735 (w), 721 (m), 657
137
(w), 576 (w), 517 (w); for Eu(2), 3420 (m), 1628 (s), 1600 (m), 1586 (m), 1572 (m), 1541 (m),
138
1448 (s), 1383 (s), 1309 (m), 1164 (w), 1104 (w), 1013 (m), 793 (w), 734 (w), 720 (m), 705 (w),
139
657 (w), 637 (w), 573 (w); for Gd(3), 3404 (m), 1626 (s), 1600 (m), 1586 (m), 1572 (m), 1540 (m),
140
1448 (m), 1384 (s), 1308 (m), 1238 (w), 1164 (w), 1104 (m), 1038 (w), 1013 (m), 924 (w), 886
141
(w), 815 (w), 794 (w), 776 (w), 735 (w), 721 (m), 657 (w), 637 (w), 574 (w), 516 (w).
142
2.4 Synthesis of {[Tb0.9064Eu0.0936(DCPTP)(NO3)]·(H2O)}n
TE D
M AN U
SC
RI PT
131
The process for preparation was similar to that of Tb(1) with Tb(NO3)3·6H2O replaced by a
144
mixture of (Tb(NO3)3·6H2O (18.4 mg, 0.0405 mmol) and Eu(NO3)3·6H2O (2.0 mg, 0.0045 mmol).
145
Yield: 77%. IR spectrum (cm‒1): 3410 (m), 1628 (s), 1601 (m), 1587 (m), 1572 (m), 1540 (w),
146
1449 (s), 1384 (s), 1310 (w), 1238 (w), 1165 (m), 1105 (m), 1039 (w), 1013 (m), 925 (w), 886 (w),
147
794 (w), 776 (w), 735 (w), 721 (w), 657 (m), 637 (w), 574 (w), 516 (w).
AC C
148
EP
143
149
3. Results and discussion
150
3.1 Syntheses
151
Reaction of H2-DCPTP and lanthanide salts in CH3CN solvent in the presence of HNO3
152
afforded the isomorphous coordination polymers, {[Ln(DCPTP)(NO3)]·(H2O)}n (Ln = Tb(1), 7
ACCEPTED MANUSCRIPT Eu(2) and Gd(3)). Accordingly, the bimetallic Tb3+/Eu3+ compound of Tb0.9064Eu0.0936-DCPTP can
154
be readily prepared by using the initial molar ratio of 0.9:0.1 for Tb(NO3)3 and Eu(NO3)3 through
155
the similar preparation procedure. The actual molar ratio of Tb3+/Eu3+ (0.9064/0.0936) in the
156
resulting bimetallic coordination polymer, which was determined by inductively coupled plasma
157
spectroscopy, matches well with that of starting materials. As expected, the Eu-doped
158
Tb-compound of Tb0.9064Eu0.0936-DCPTP is isomorphous with the parent ones, which is confirmed
159
by their PXRD patterns (Fig. S2).
160
3.2 Crystal structures
M AN U
SC
RI PT
153
For these isostructural compounds, structure Tb(1) is described representatively. There one Tb3+,
162
one DCPTP2− dianionic ligand, one nitrate anion, and one lattice water molecule are in the
163
asymmetric unit of Tb(1). Tb3+ ion is nine-coordinated by three N atoms of one DCPTP2− ligand,
164
four carboxylate O atoms (O1, O2A, O3C, and O4C) from three DCPTP2− ligands and two O
165
atoms of a NO3− group (Fig. 1a). The Tb–O bond distances vary from 2.286(4) to 2.540(4) Å and
166
Tb–N bond distances range from 2.531(6) to 2.577(6) Å. The nitrate anion chelates a Tb3+ ion
167
through its two O atoms with the third O atom uncoordinated. The DCPTP2− ligand binds four
168
metal ions through a chelating and a bidentate carboxylate groups, and a chelating terpyridyl
169
group (Fig. S3). Two bidentate carboxylate groups bridge two Tb3+ ions to generate a dinuclear
170
Tb2(µ2-COO)2] unit (Fig. 1b), which is connected by the DCPTP2− ligands to generate a 3D
171
framework (Fig. 2). Each dinuclear Tb2(µ2-COO)2] unit is surrounded by six DCPTP2− ligands
172
(Fig. 1b) and each DCPTP2− ligand connects three dinuclear Tb2(µ2-COO)2] units (Fig. S4). In this
173
way, the DCPTP2− ligand and the dinuclear Tb2(µ2-COO)2] unit define a 3- and 6-connected nodes,
174
respectively. Thus the 3D framework of Tb(1) is a 3,6-connected network with
AC C
EP
TE D
161
8
ACCEPTED MANUSCRIPT 175
(42·6)2(44·62·87·102) topology (Fig. S5). When loss of the solvent water molecules, the main
176
framework can stable up to 400 °C (Fig. S6).
M AN U
SC
RI PT
177
178 179
Fig. 1 Coordinated environment of Tb3+ ion (a) and the dinuclear Tb2(µ2-COO)2] unit (b) in Tb(1).
181
AC C
EP
TE D
180
182
Fig. 2 3D framework of Tb(1) (The nitrate anions and lattice water molecules are omitted for
183
clarify).
184 185
3.2 Luminescent properties 9
ACCEPTED MANUSCRIPT Upon excitation at 369 nm, the free H2-DCPTP ligand emits an emission centered at 434 nm in
187
the solid state, which was assigned to the intraligand π*−π electron transitions (Fig. S7). The solid
188
state luminescent emissions of Tb(1) and Eu(2) at room temperature are shown in Fig. S8 and S9,
189
respectively. Tb(1) displays an excitation band centered at 353 nm and no sharp peak of Tb3+ f−f
190
transition appears in the excitation spectrum, indicating the Tb3+ ions are excited via an effective
191
sensitized process involving the organic ligand. Tb(1) emits strong green emission with the
192
characteristic peaks of Tb3+ (5D4 → 7FJ, J = 0 ‒ 6) at 490, 543, 584, 621, 650, 667, and 678 nm
193
(Fig. S8), wherein the 5D4 → 7F5 transition (543 nm) has the most intense intensity. Additionally,
194
the emission of organic ligand is not detected in the emission spectrum of Tb(1), which indicates
195
an energy is transferred from organic ligands to Tb3+ ions efficiently. As case of Eu(2), a excitation
196
band centered at 361 nm overlapping with additional weak intra-4f6 sharp lines is observed,
197
indicating that the Eu3+ ions are mainly excited through a sensitized process but not via a direct
198
excitation process. Eu(2) exhibits typical bands arising from Eu3+ excited levels (5D0 → 7FJ, J = 0,
199
1, 2, 3, 4) at 580, 592, 616, 651, and 698 nm, after excited at 361 nm (Fig. S9). The intensity of
200
the 5D0 → 7F2 emission, which is extremely sensitive to site symmetry, is much more intense
201
than that of the 5D0 →
202
coordination environment.
SC
M AN U
TE D
EP 7
F1 emission, suggesting that the Eu3+ ion is in an asymmetric
AC C
203
RI PT
186
10
RI PT
ACCEPTED MANUSCRIPT
204
Fig. 3 Temperature-dependent emission spectra for Tb(1) between 77 K and 300 K (λex = 361 nm).
M AN U
SC
205
207
TE D
206
Fig. 4 Temperature-dependent emission spectra for Eu(2) between 77 K and 300 K (λex = 361 nm).
AC C
EP
208
209 210
Fig. 5 Solid-state emission spectra of Tb0.9064Eu0.0936-DCPTP between 77 K and 300 K (λex = 361
211
nm).
212 11
ACCEPTED MANUSCRIPT Temperature-dependent photoluminescence emission spectra of Tb(1) and Eu(2) between 77 K
214
and 300 K are presented in Fig. 3 and 4, respectively. For both compounds, the emission intensity
215
and lifetime decrease upon increasing temperature, as a result of the thermal activation of
216
nonradiative-decay. However, the emission intensity and lifetime of Tb3+ in Tb(1) diminish more
217
pronouncedly than those of Eu3+ in Eu(2) upon increasing temperature (Fig. S10). In particular for
218
the lifetime, lifetime of Eu3+ is almost unchanged in the test temperature range (Fig. S10b). Such
219
distinct temperature-dependent luminescent behavior for Tb(1) and Eu(2) can be attributed to the
220
different energy gaps between the triplet excited state of the ligand and the emitting levels of Tb3+
221
and Eu3+ ions. The triplet state energy level T1 for H2-DCPTP is 25445 cm‒1 (393 nm) estimated
222
from the phosphorescence spectrum of Gd(3) (λex = 372 nm) (Fig. S11). The experimental T1
223
value is consistent with the one (25217 cm−1) from DFT calculations. The energy gap between the
224
T1 level and the 5D4 emitting level (20453 cm‒1) of Tb3+ [36] in Tb(1) is much smaller than the
225
energy gap between T1 level and the 5D0 emitting level (17267 cm‒1) of Eu3+ [37] in Eu(2). As a
226
result, the thermally driven depopulation for Eu3+ emitting level is almost prohibited [38–40].
TE D
M AN U
SC
RI PT
213
To obtain more reliable luminescent thermometers based on two emissions with a ratiometric
228
method, the Eu-doped Tb-compound of Tb0.9064Eu0.0936-DCPTP was synthesized. The
229
Tb0.9064Eu0.0936-DCPTP displays characteristic emissions of Tb3+ and Eu3+ ions simultaneously
230
(Fig. S12), indicating the H2-DCPTP with an extensive π-conjugated system is a remarkable
231
sensitizer for sensitizing of Tb3+ and Eu3+ ions. Fig. 5 presents the emission spectra of
232
Tb0.9064Eu0.0936-DCPTP from 77 to 300 K. The intensity of 5D0 → 7F2 (616 nm) transition of Eu3+
233
is enhanced significantly, while that of 5D4 → 7F5 transition (542 nm) of Tb3+ is diminished slowly
234
when increasing temperature (Fig. 6). At 77 K, the intensity of 5D4 → 7F5 (Tb3+) transition is about
AC C
EP
227
12
ACCEPTED MANUSCRIPT 2.7 times more intense than that of 5D0 → 7F2 (Eu3+) transition (Fig. 7), which gives a green color
236
for the compound. In contrast, the intensity of 5D0 → 7F2 (Eu3+) transition is 19.6 times more
237
intense than that of 5D4 → 7F5 (Tb3+) transition at 300 K, indicating the Eu3+ emission is
238
completely dominated in the high temperature region. Thus the temperature-dependent
239
luminescent colors are systematically tuned from green, via yellow to red with increasing
240
temperature (Fig. 8). The dramatic intensity changes of Tb3+- and Eu3+-emissions in opposite
241
directions suggests the Tb0.9064Eu0.0936-DCPTP is an excellent candidate for ratiometric
242
luminescent thermometers. As illustrated in Fig. 7, the emission intensity ratio (∆ = ITb/IEu)
243
between 5D4 → 7F5 transition (Tb3+, 543 nm) and 5D0 → 7F2 transition (Eu3+, 616 nm) remains
244
roughly constant in the temperature range of 77 ‒ 150 K. The relationship between ∆ and
245
temperature (T) is well fitted with the exponential empirical equation (1) in the temperature of 150
246
‒ 300 K (Fig. 7 inset and Fig. S14)
247
∆ = – 0.530 + 24.535e(– 0.013T) (1)
248
The correlation coefficient (R2) of 0.99652 is obtained from the fitting result. The relative thermal
249
sensitivity Sr (Sr = |∂∆/∂T|/∆) [41, 42] is used to characterize the performances of the thermometers.
250
As can be seen from the definition of Sr, the Sr value varies with the temperature. Thus the
251
maximum (Sm) value of Sr in the detection temperature range is proposed for comparing the
252
performances of the coordination compounds thermometers [28]. The Tb0.9064Eu0.0936-DCPTP has
253
a high Sm up to 21.5 % K‒1 at 300 K (Fig. S15), which is the highest value for the lanthanide
254
coordination polymers ratiometric luminescent thermometers (Table S2). Such results suggest the
255
Tb0.9064Eu0.0936-DCPTP is a potentially useful luminescent thermometer and further confirm the
256
present organic ligand is a very effective sensitizer for Tb3+ and Eu3+ ions. It is noted that there is a
AC C
EP
TE D
M AN U
SC
RI PT
235
13
ACCEPTED MANUSCRIPT report claiming the Sm of 31 % K‒1 for the Tb0.95Eu0.05-5-hydroxy-1,2,4-benzenetricarboxylate very
258
recently [43]. However, its Sm value appears at low temperature of 4 K, which is different from the
259
present case and other thermometers (Table S2). Finally, the temperature-dependent emission
260
spectra for Tb0.9064Eu0.0936-DCPTP material are repeatable and reversible (Fig. S16), indicates it is
261
a robust lanthanide coordination polymer luminescent thermometer.
M AN U
SC
262
RI PT
257
TE D
263
Fig. 6 Integrated intensities of 5D4 → 7F5 (538‒555 nm) and 5D0 → 7F2 (605‒630 nm) emission
265
bands versus temperature in Tb0.9064Eu0.0936-DCPTP.
AC C
266
EP
264
267 268
Fig. 7 Integrated intensity ratio between Tb3+ (543 nm) and Eu3+ (616 nm) versus temperature for 14
ACCEPTED MANUSCRIPT 269
Tb0.9064Eu0.0936-DCPTP
(Inset:
Fitted
curve
of
the
270
Tb0.9064Eu0.0936-DCPTP from 150 to 300 K with equation (1).
integrated
intensity
ratio
for
271 A rapid decrease of lifetime for Tb3+ emission is observed in Tb0.9064Eu0.0936-DCPTP with
273
increasing temperature, especially between 150 and 300 K. The lifetime of Tb3+ emission is
274
decreased about 94% as the temperature increasing from 150 to 300 K (Fig. S13). While the
275
lifetime of the Eu3+emission decreases only slightly in Tb0.9064Eu0.0936-DCPTP with increasing the
276
temperature. Such observations indicate the nonradiative Tb3+-to-Eu3+ energy transfer occurs [44].
277
At 150 K, the lifetimes of Tb3+ emission in Tb0.9064Eu0.0936-DCPTP (1.04 ms) (Fig. S13) and in
278
pure Tb(1) (1.16 ms) (Fig. S10b) are similar. In contrast, the lifetime of Tb3+ emission in
279
Tb0.9064Eu0.0936-DCPTP decreases to 0.04 ms at 300 K, which is about one-tenth of that for pure
280
Tb(1) at 300 K (0.41 ms). The energy migration between Tb3+ centers is easier than that of from
281
Tb3+ to Eu3+
TE D
M AN U
SC
RI PT
272
AC C
EP
282
283 284
Fig. 8 The CIE chromaticity diagram showing the luminescence color of Tb0.9064Eu0.0936-DCPTP
285
at different temperatures. 15
286 transform
efficiency
from
to
Eu3+
Fig.
versus
288
Tb0.9064Eu0.0936-DCPTP.
289
because of the larger energy gap between Tb3+ to Eu3+ energy levels. When temperature higher
290
than 150 K, the abrupt decrease of lifetime for Tb3+ emission in Tb0.9064Eu0.0936-DCPTP indicates
291
the energy migration occurred between Tb3+ centers, ultimately resulting in Tb3+ to Eu3+ energy
292
transfer. However, because of the small variations in the energy levels for Tb3+ center, the energy
293
migration between neighboring Tb3+ centers is hampered at lower temperature. Thus in the
294
temperature range from 77 to150 K, the slight changes in the intensity and lifetime of Tb3+
295
emission in Tb0.9064Eu0.0936-DCPTP are not unreasonable. With further increasing the temperature,
296
the energy in the excited state of Tb3+ has more opportunity to transfer to a Tb3+ ion neighboring a
297
Eu3+ center, followed by subsequent energy transfer to Eu3+. As a result, the observation of
298
enhancement of Eu3+ emission and recession of Tb3+ emission in the temperature range 150−300
299
K can be explained by the phonon-assisted Förster transfer mechanism [45]. The energy transfer
300
efficiency (η) from Tb3+ and Eu3+ ions can be calculated from the equation of η = 1 ‒ τ/τ0 (τ and τ0
301
represent the lifetimes of Tb3+ with and without Eu3+ acceptor, respectively) [46]. The
302
temperature-dependent η for Tb0.9064Eu0.0936-DCPTP is presented in Fig. 9, which displays the
SC
Energy
Tb3+
287
temperature
in
AC C
EP
TE D
M AN U
9
RI PT
ACCEPTED MANUSCRIPT
16
ACCEPTED MANUSCRIPT energy transfer efficiency from Tb3+ to Eu3+ is low and almost unchanged in the range of 77‒150
304
K. Then the energy transfer efficiency is dramatically enhanced on going from 150 to 300 K, thus
305
resulting in the increase of the intensity of Eu3+-emission at the cost of the quenching of
306
Tb3+-emission upon temperature increasing. The η value at 300 K is about 84%, which is the
307
highest value for the Eu3+/Tb3+mixed coordination polymers
308 4. Conclusions
SC
309
RI PT
303
In summary, a H2-DCPTP ligand with π-rich conjugated systems and four lanthanide
311
compounds including the mixed lanthanide compound constructed of H2-DCPTP ligand have been
312
prepared and characterized. These isostructural compounds have a 3D framework featuring the
313
dinuclear lanthanide-carboxylate units. The Tb0.9064Eu0.0936-DCPTP serving as a ratiometric
314
luminescent thermometer was evaluated detailedly in terms of luminescence intensity and lifetime.
315
The result shows that Tb0.9064Eu0.0936-DCPTP can be developed as a high-performance temperature
316
sensor in the temperature range of 150−300 K, with higher relative sensitivity and larger energy
317
transfer efficiency than those of previously reported Eu3+/Tb3+ coordination polymers luminescent
318
thermometer. This work demonstrates a strategy for designing of robust luminescent thermometers
319
with high sensitivity and large energy transfer efficiency.
321
TE D
EP
AC C
320
M AN U
310
Acknowledgements
322
This work was supported by the NSF of China (Grants 21661014, 21561015 and 21861020),
323
the NSF of Jiangxi Province (Grant 20171ACB20008 and 20181BAB203001). We thank
324
Professor Xingfa Gao for the DFT calculations 17
ACCEPTED MANUSCRIPT 325 326 327
Appendix A. Supplementary data Supplementary data related to this article can be found at http://dx.doi.org/10.1016/j.dyepig.
RI PT
328 329
References
330
[1] Rocha J, Carlos LD, Almeida Paza FA, Ananias D. Luminescent multifunctional
333 334 335 336 337
SC
[2] Binnemans K. Lanthanide-Based Luminescent Hybrid Materials. Chem Rev 2009;109:4283–
M AN U
332
lanthanides-based metal-organic frameworks. Chem Soc Rev 2011;40:926−940.
4374.
[3] Kreno LE, Leong K, Farha OK, Allendorf M, Van Duyne RP, Hupp JT. Metal-Organic Framework Materials as Chemical Sensors. Chem Rev 2012;112:1105−1125. [4] Bünzli J-CG. Lanthanide Luminescence for Biomedical Analyses and Imaging. Chem Rev 2010; 110:2729–2755
TE D
331
[5] Zhou L-J, Deng W-H, Wang Y-L, Xu G, Yin S-G, Liu Q-Y. Lanthanide-Potassium
339
Biphenyl-3,3′-disulfonyl-4,4'-dicarboxylate Frameworks: Gas Sorption, Proton Conductivity,
340
and Luminescent Sensing of Metal Ions. Inorg Chem 2016;55:6271−6277.
AC C
EP
338
341
[6] Yan X-H, Cai Z-H, Yi C-L, Liu W-S, Tan M-Y, Tang Y. Anion-Induced Structures and
342
Luminescent Properties of Chiral Lanthanide-Organic Frameworks Assembled by an Achiral
343
Tripodal Ligand. Inorg Chem 2011;50:2346–2353.
344
[7] Liu T-F, Zhang W-J, Sun W-H, Cao R. Anion-Induced Structures and Luminescent Properties
345
of Chiral Lanthanide-Organic Frameworks Assembled by an Achiral Tripodal Ligand. Inorg
346
Chem 2011;50:5242–5248. 18
ACCEPTED MANUSCRIPT 347 348
[8] Cui Y, Yue Y, Qian G, Chen B. Luminescent Functional Metal–Organic Frameworks. Chem Rev 2012;112:1126−1162. [9] He R, Wang Y-L, Ma, H-F, Yin, S-G, Liu Q-Y, Eu3+-functionalized metal-organic framework
350
composite as ratiometric fluorescent sensor for highly selective detecting urinary
351
1-hydroxypyrene, Dyes Pigments 2018;151:342–347.
353
[10] Wu W-T, Dong J, Ni W-Y, Zhang B-W, Cui J-Z, Zhao B. Unique Chiral Interpenetrating d-f Heterometallic MOFs as Luminescent Sensors. Inorg Chem 2015;54:5266−5272.
SC
352
RI PT
349
[11] Zhou Y, Chen H-H, Yan B. An Eu3+ post-functionalized nanosized metal-organic framework
355
for cation exchange-based Fe3+-sensing in an aqueous environment. J Mater Chem A 2014;2:
356
13691−13697.
M AN U
354
[12] Dong X-Y, Wang R, Wang J-Z, Zang S-Q, Mak TCW. Highly selective Fe3+ sensing and
358
proton conduction in a water-stable sulfonate-carboxylate Tb-organic-framework. J Mater
359
Chem A 2015; 3:641−647.
TE D
357
[13] Li Y-J, Wang Y-L, Liu Q-Y. The Highly Connected MOFs Constructed from Nonanuclear and
361
Trinuclear Lanthanide-Carboxylate Clusters: Selective Gas Adsorption and Luminescent pH
362
Sensing. Inorg Chem 2017;56:2159−2164.
AC C
EP
360
363
[14] Armelao L, Quici S, Barigelletti F, Accorsi G, Bottaro G, Cavazzini M, et al. Design of
364
luminescent lanthanide complexes: From molecules to highly efficient photo-emitting materials.
365
Coord Chem Rev 2010;254:487−505.
366 367 368
[15] Allendorf MD, Bauer CA, Bhaktaa RK, Houk RJT. Luminescent metal-organic frameworks. Chem Soc Rev 2009;38:1330–1352. [16] Wei Y, Sa R, Li Q, Wu K. Highly stable and sensitive LnMOF ratiometric thermometers 19
ACCEPTED MANUSCRIPT 369 370 371
constructed with mixed ligands. Dalton Trans 2015;44:3067–3074. [17] Ananias D, Brites CD, Carlos LD, Rocha J. Cryogenic Nanothermometer Based on the MIL-103(Tb,Eu) Metal-Organic Framework. Eur J Inorg Chem 2016;1967–1971. [18] Zhao D, Rao X, Yu J, Cui Y, Yang Y, Qian G. Design and Synthesis of an MOF Thermometer
373
with High Sensitivity in the Physiological Temperature Range. Inorg Chem 2015;54:11193–
374
11199.
RI PT
372
[19] Miyata K, Konno Y, Nakanishi T, Kobayashi A, Kato M, Fushimi K, et al. Chameleon
376
Luminophore for Sensing Temperatures: Control of Metal-to-Metal and Energy Back Transfer
377
in Lanthanide Coordination Polymers. Angew Chem Int Ed 2013;52:6413−6416.
380 381
M AN U
379
[20] Brites CDS, Lima PP, Silva NJO, Millán A, Amaral VS, Fernando P, et al. Lanthanide-based luminescent molecular thermometers. New J Chem 2011;35:1177–1183. [21] Wang X-D, Wolfbeis OS, Meier RJ. Luminescent probes and sensors for temperature. Chem
TE D
378
SC
375
Soc Rev 2013;42:7834–7869.
[22] Zhou Y, Yan B, Lei F. Postsynthetic lanthanide functionalization of nanosized metal-organic
383
frameworks for highly sensitive ratiometric luminescent thermometry. Chem Commun 2014;50:
384
15235–15238.
386
AC C
385
EP
382
[23] Cui Y, Xu H, Yue Y, Guo Z, Yu J, Chen Z, et al. A Luminescent Mixed-Lanthanide Metal-Organic Framework Thermometer. J Am Chem Soc 2012;134:3979−3982.
387
[24] Han Y-H, Tian C-B, Li Q-H, Du S-W. Highly chemical and thermally stable luminescent
388
EuxTb1-x MOF materials for broad-range pH and temperature sensors. J Mater Chem C 2014;2:
389
8065–8070.
390
[25] Yang Y, Chen L, Jiang F, Yu M, Wan X, Zhang B, et al. A family of doped lanthanide 20
ACCEPTED MANUSCRIPT 391
metal-organic frameworks for wide-range temperature sensing and tunable white light emission.
392
J Mater Chem C 2017;5:1981−1989.
394
[26] Cui Y-J, Zhu F-L, Chen B-L, Qian G-D. Metal-organic frameworks for luminescence thermometry. Chem Commun 2015;51:7420–7431.
RI PT
393
[27] Zhao S-N, Li L-J, Song X-Z, Zhu M, Hao Z-M, Meng X, et al. Lanthanide Ion Codoped
396
Emitters for Tailoring Emission Trajectory and Temperature Sensing. Adv Funct Mater 2015;25:
397
1463–1469.
399
[28] Rocha J, Brites CDS, Carlos LD. Lanthanide Organic Framework Luminescent
M AN U
398
SC
395
Thermometers. Chem Eur J 2016;22:14782–14795.
[29] Cui Y-J, Zou W-F, Song R-J, Yu J-C, Zhang W-Q, Yang Y, et al. A ratiometric and
401
colorimetric luminescent thermometer over a wide temperature range based on a lanthanide
402
coordination polymer. Chem Commun 2014;50:719–721.
TE D
400
[30] Latva M, Takalo H, Mukkala VM, Matachescu C, Rodríguez-Ubis JC , Kankare J.
404
Correlation between the lowest triplet state energy level of the ligand and lanthanide(III)
405
luminescence quantum yield. J Lumin 1997;75:149−169.
EP
403
[31] Døssing A. Luminescence from Lanthanide(3+) Ions in Solution. Eur J Inorg Chem 2005;
407
1425−1434.
408
[32] Parker D. Luminescent lanthanide sensors for pH, pO2 and selected anions. Coord Chem Rev
409
AC C
406
2000;205:109−130.
410
[33] CrysAlisPro; Rigaku Oxford Diffraction 2015.
411
[34] Sheldrick GM. HELXT-Integrated space-group and crystal-structure determination. Acta
412
Cryst 2015;A71:3–8. 21
ACCEPTED MANUSCRIPT 413
[35] Sheldrick GM. Crystal structure refinement with SHELXL. Acta Cryst 2015;C71:3–8.
414
[36] Carnall WT, Fields PR, Rajnak K. Electronic Energy Levels of the Trivalent Lanthanide Aquo
418 419 420 421
Ions. IV. Eu3+. J Chem Phys 1968;49:4450−4455.
RI PT
417
[37] Carnall WT, Fields PR, Rajnak K. Electronic Energy Levels of the Trivalent Lanthanide Aquo
[38] Carlos LD, Ferreira RAS, de Zea Bermudez V, JulianLopez B, Escribano P. Progress on lanthanide-based organic-inorganic hybrid phosphors. Chem Soc Rev 2011;40:536−549.
SC
416
Ions. III. Tb3+. J Chem Phys 1968;49:4447−4449.
[39] Kolodner P, Tyson JA. Remote thermal imaging with 0.7-µm spatial resolution using
M AN U
415
temperature-dependent fluorescent thin flims. Appl Phys Lett 1983;42:117–119. [40] Brites CDS, Lima PP, Silva NJO, Millan A, Amaral VS, Palacio F, et al. A Luminescent
423
Molecular Thermometer for Long-Term Absolute Temperature Measurements at the Nanoscale.
424
Adv Mater 2010;22:4499−4504.
427 428
Absolute Temperature Measurements at the Nanoscale. J Appl Phys 2003;94:4743–4756. [42] Brites CDS, Lima PP, Silva NJO, Millán A, Amaral VS, et al. Thermometry at the nanoscale.
EP
426
[41] Wade SA, Collins SF, Baxter GW. A Luminescent Molecular Thermometer for Long-Term
Nanoscale 2012;4:4799–4829.
AC C
425
TE D
422
429
[43] Liu X, Akerboom S, Jong M de, Mutikainen I, Tanase S. Meijerink A, et al.
430
Mixed-Lanthanoid Metal-Organic Framework for Ratiometric Cryogenic Temperature Sensing.
431
Inorg Chem 2015; 54:11323−11329.
432
[44] Marciniak L, Bednarkiewicza A. The influence of dopant concentration on temperature
433
dependent emission spectra in LiLa1−x−yEuxTbyP4O12 nanocrystals: toward rational design of
434
highly-sensitive luminescent nanothermometers. Phys Chem Chem Phys 2016;18:15584– 22
ACCEPTED MANUSCRIPT 435 436 437
15592. [45] Auzel F. Upconversion and Anti-Stokes Processes with f and d Ions in Solids. Chem Rev 2004; 104:139−173. [46] Rodrigues M O, Dutra JDL, Nunes LAO, de Sá GF, de Azevedo WM, Silva P, et al. Tb3+→
439
Eu3+ Energy Transfer in Mixed-Lanthanide-Organic Frameworks. J Phys Chem C 2012;116:
440
19951−19957.
RI PT
438
AC C
EP
TE D
M AN U
SC
441
23
ACCEPTED MANUSCRIPT Highlights
EP
TE D
M AN U
SC
RI PT
{[Ln(DCPTP)(NO3)](H2O)}n and {[Tb0.9064Eu0.0936(DCPTP)(NO3)](H2O)}n were presented. The H2-DCPTP ligand is a light-harvesting ligand for efficiently sensitizing of Tb3+ and Eu3+. Tb0.9064Eu0.0936-DCPTP behaves as a high-performance luminescent thermometer. Luminescent thermometer with a high relative thermal sensitivity of Sm up to 21.5 % K‒1.
AC C
• • • •
S0143-7208(18)31975-2
DOI:
https://doi.org/10.1016/j.dyepig.2018.10.055
Reference:
DYPI 7121
To appear in:
Dyes and Pigments
Received Date: 6 September 2018 Revised Date:
22 October 2018
Accepted Date: 25 October 2018
Please cite this article as: Peng X-W, Liu Q-Y, Wang H-H, Wang Y-L, Eu(III)- and Tb(III)-coordination polymer luminescent thermometers constructed from a π-rich aromatic ligand exhibiting a high sensitivity, Dyes and Pigments (2018), doi: https://doi.org/10.1016/j.dyepig.2018.10.055. This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
ACCEPTED MANUSCRIPT Graphical abstract
AC C
EP
TE D
M AN U
SC
RI PT
The 4'-(3,5-dicarboxyphenyl)-2,2',6',2''-terpyridine (H2-DCPTP) ligand serves as a light-harvesting ligand for efficiently sensitizing of Tb3+ and Eu3+ simultaneously, thus enhancing the overall luminescence of Tb0.9064Eu0.0936-DCPTP, which behaves as a high-performance luminescent thermometer with a high relative thermal sensitivity of Sm up to 21.5 % K‒1.
ACCEPTED MANUSCRIPT 1
Eu(III)-
and
Tb(III)-coordination
polymer
luminescent
2
thermometers constructed from a π-rich aromatic ligand exhibiting a
3
high sensitivity
5
Xin-Wen Peng, Qing-Yan Liu*, Hui-Hong Wang, Yu-Ling Wang*
6
RI PT
4
College of Chemistry and Chemical Engineering, Key laboratory of functional small organic
8
molecule of ministry of education, Jiangxi Normal University, Nanchang, Jiangxi 330022, PR
9
China E-mail: [email protected]; [email protected]
M AN U
SC
7
Dedicated to Professor Jin-Shun Huang on the occasion of his 80th birthday.
12
ABSTRACT: A π-rich aromatic organic ligand, 4'-(3,5-dicarboxyphenyl)-2,2',6',2''-terpyridine
13
(H2-DCPTP), and four new lanthanide coordination polymers, {[Ln(DCPTP)(NO3)]·(H2O)}n (Ln
14
= Tb, Eu, Gd) and {[Tb0.9064Eu0.0936(DCPTP)(NO3)]·(H2O)}n (termed Tb0.9064Eu0.0936-DCPTP),
15
were prepared. Compound {[Ln(DCPTP)(NO3)]·(H2O)}n is a 3D framework based on the
16
dinuclear Ln2(µ2-COO)2] units linked by the tridentate DCPTP2‒ ligands. The H2-DCPTP ligand
17
with an appropriate triplet excited state confirmed by DFT calculations and experiments, is a
18
light-harvesting ligand for efficiently sensitizing of Tb3+ and Eu3+ simultaneously, thus enhancing
19
the overall luminescent properties of Tb0.9064Eu0.0936-DCPTP. The Tb0.9064Eu0.0936-DCPTP behaves
20
as a high-performance luminescent thermometer ranging from 150 to 300 K with a large relative
21
thermal sensitivity (Sm) of 21.5 % K‒1 and a high energy transfer efficiency (η) of 84% at 300 K.
AC C
EP
TE D
10 11
22 23
Keywords:
Ratiometric
fluorescent
probe; 1
luminescent
thermometer;
Eu(III)-
and
ACCEPTED MANUSCRIPT 24
Tb(III)-coordination polymer; light-harvesting ligand.
25
1. Introduction The lanthanide-based coordination polymers continue to attract intense attentions due to their
27
potential applications pertaining to the distinctive luminescence and magnetism derived from the
28
lanthanide centers with 4fn configuration [1‒7]. In particular, luminescent lanthanide coordination
29
polymers are highly sought after because of their diverse luminescent properties such as
30
characteristically sharp line emissions, high photoluminescence efficiency as well as long
31
luminescent lifetime, which have been developed for chemical sensors and light-emitting devices
32
[8‒15]. Recently, the lanthanide coordination polymers with the temperature-dependent emissions
33
have been developed for luminescent thermometers [16‒22]. Comparing to the conventional
34
temperature sensors, such luminescence-based thermometers own the distinct advantages of fast
35
response, non-invasive operation and high spatial resolution. Moreover, such thermometers can
36
work in strong electro-magnetic fields due to their inertness to strong electric-magnetic fields.
TE D
M AN U
SC
RI PT
26
As is well-known, luminescent sensing based on relative emission intensity is more reliable and
38
powerful than through single-emission intensity. The accuracy of the sensing based on the
39
absolute intensity of an emission is often susceptible to external factors including the luminophore
40
quantity, excitation power, and the drifts of the optoelectronic systems. Moreover, the intensity
41
ratio for two emissions is almost a constant under a certain condition and thus additional
42
calibration of intensity is not necessary for such a ratiometric method, leading to desirable
43
ratiometric luminescent thermometers. A few mixed lanthanide coordination polymers
44
luminescent thermometers with Tb3+ and Eu3+-dual emissions have been reported recently [23‒27].
45
However, the relative thermal sensitivity of the Tb3+-Eu3+ luminescent thermometers is found to
AC C
EP
37
2
ACCEPTED MANUSCRIPT be lower than 10 % K−1 [28, 29]. Therefore, it is still a challenge to construct lanthanide
47
compounds for temperature sensing with high sensitivity and accurate sensing. As an efficient
48
sensitizer for the lanthanide ions, the organic ligand takes a decisive role in the construction of
49
lanthanide luminescent thermometers. To obtain high-performance luminescent thermometers with
50
Tb3+ and Eu3+ mixed metal ions, the Tb3+ and Eu3+ ions should be efficiently sensitized by the
51
organic ligand simultaneously. The organic ligand for such purpose must have an appropriate
52
triplet excited state energy between 22000 and 27000 cm−1 [1, 30, 31], matching the main
53
accepting energy levels of Tb3+ (5D4, 20500 cm−1) and Eu3+ (5D1, 19030 cm−1) [32].
M AN U
SC
RI PT
46
In this contribution, an organic ligand with a terpyridine backbone and an isophthalic acid,
55
4'-(3,5-dicarboxyphenyl)-2,2',6',2''-terpyridine (H2-DCPTP), was designed for rational preparation
56
of luminescent thermometers. The H2-DCPTP with four carboxylate oxygens has a preferential
57
coordination to the oxophile lanthanide ions and the terpyridine moiety can chelate a lanthanide
58
ion, giving the robust lanthanide coordination polymers. In addition, the H2-DCPTP with
59
extensive aromatic π-systems is expected to be a light-harvesting ligand for efficiently sensitizing
60
of lanthanide ions, which is corroborated by the result of the time-dependent DFT calculations
61
(Fig. S1). The calculated triplet excited state energy for H2-DCPTP is 25217 cm−1, indicating the
62
H2-DCPTP is a suitable organic linker for construction of the Tb3+/Eu3+-coordination polymer
63
luminescent
64
{[Ln(DCPTP)(NO3)]·(H2O)}n (Ln = Tb(1), Eu(2) and Gd(3)) and the Eu-doped Tb-compound of
65
{[Tb0.9064Eu0.0936(DCPTP)(NO3)]·(H2O)}n (termed Tb0.9064Eu0.0936-DCPTP) were presented.
66
Detailed luminescent behavior for these compounds were investigated. Temperature-dependent
67
luminescence of Tb0.9064Eu0.0936-DCPTP show the organic ligands with the extensive aromatic
AC C
EP
TE D
54
thermometers.
Herein
three
3
compounds
with
formula
of
ACCEPTED MANUSCRIPT π-systems transfer the absorbed energy to the Tb3+ and Eu3+ ions efficiently, thus enhancing the
69
overall luminescent properties of Tb0.9064Eu0.0936-DCPTP. As a result, Tb0.9064Eu0.0936-DCPTP
70
behaves a high-performance luminescent thermometers displaying a large relative thermal
71
sensitivity and a high energy transfer efficiency.
RI PT
68
73
2. Experimental
74
2.1. Materials and instrumentations 1
H nuclear magnetic resonance (NMR) spectra were collected on a Bruker AVANCE 400
M AN U
75
SC
72
spectrometer. FT-IR (KBr pellets, cm–1) spectra were performed at a Perkin-Elmer Spectrum One
77
FT-IR spectrometer ranging from 400–4000 cm–1. Elemental analyses were carried out on an
78
Elementar Perkin-Elmer 2400CHN microanalyzer. Thermogravimetric analyses (TGA) were
79
carried out on a PE Diamond instrument under a N2 flow with a heating rate of 10 °C min–1.
80
Powder X-ray diffraction (PXRD) were measured on a Rigaku Miniflex II powder diffractometer
81
(Cu-Kα, λ = 1.5418 Å). Fluorescent spectra and luminescence lifetime were measured with
82
Edinburgh Instruments FLS980 fluorescence spectrometer equipped with an Oxford Instruments
83
liquid nitrogen flow cryostat. Inductively coupled plasma (ICP) (Ultima2, HORIBA Jobin Yvon)
84
spectra were used for determination of the metal concentration after the sample was dissolved in
85
concentrated nitric acid.
AC C
EP
TE D
76
86
X-ray diffraction experiments were carried out on a Rigaku Oxford SuperNova diffractometer
87
with an Eos detector (Mo-Ka radiation, 0.71073 Å) and. The CrysAlisPro software package was
88
used for absorption correction and data reduction [33]. The structures were solved by the direct
89
methods using the SHELXTL [34] and refined by the full-matrix least-squares against F2 [35]. All 4
ACCEPTED MANUSCRIPT atoms except for hydrogen atoms are refined with anisotropic thermal parameters. Aromatic
91
hydrogen atoms were placed in calculated positions. Hydrogen atoms bonded to oxygen atoms
92
couldn’t be located. The R1 and wR2 values are defined as R1 = Σ||Fo| – |Fc|| / Σ|Fo| and wR2 =
93
{Σ[w(Fo2 – Fc2)2] / Σ[w(Fo2)2]}1/2, respectively. The important crystallographic data is listed in
94
Table S1.
95
All chemicals used here were of reagent grade and obtained commercially. The 4'-(3,5-dicarboxyphenyl)-2,2',6',2''-terpyridine (H2-DCPTP) was synthesized in Scheme 1.
M AN U
SC
96
RI PT
90
97
Scheme 1 Preparation of H2-DCPTP ligand.
99
2.2 Synthesis of H2-DCPTP ligand
100
TE D
98
2.2.1 Synthesis of 3-(3′,5′-dimethylphenyl)-1-(pyridin-2′-yl)prop-2-en-1-one (a). All reactants including solvents for this reaction were cooled to 5 oC before use. In a flask, 2.50
102
g (18.7 mmol) of 3,5-dimethylbenzaldehyde and 1.20 g (33.6mmol) of NaOH were mixed with 90
103
mL methanol/water (v/v = 3:1) solution, followed by a 20 mL methanol solution of
104
2-acetylpyridine (18.0 mmol, 2.20 g). The mixture was stirred at 5 oC for 8 h to give yellow solid.
105
The yellow solid was washed with methanol and water (v/v = 1:4) solution and dried in vacuo at
106
room temperature; yield 4.18 g (95%). 1H NMR (CDCl3, ppm): δ = 8.76 (d, J = 4.0 Hz, 1H), 8.29
107
(d, J = 16.0 Hz, 1H), 8.20 (d, J = 8.0 Hz, 1H), 7.92 (s, 1H), 7.89 (m, J = 16.0 Hz, 1H), 7.50 (m, J
108
= 12.0 Hz, 1H), 7.35 (s, 2H), 7.05 (s, 1H), 2.35 (s, 6H).
AC C
EP
101
5
ACCEPTED MANUSCRIPT 109
2.2.2 Synthesis of (4′-(3,5-dimethylphenyl) -2,2′:6′,2″-terpyridine) (b). Compound a (10.0 mmol, 2.37g), 2-acetylpyridine (10.0 mmol, 1.21 g), and KOH (30.0 mmol,
111
1.68 g) were mixed with 120 mL of ethanol followed by a 75 mL NH4OH solution (30%). The
112
resulting mixture was stirred at 60 °C for 1 d to give a pale yellow solid. The solid was
113
recrystallized from pyridine and water (v/v = 2:1) solvent, and dried in vacuo; yield 1.72 g (51%).
114
1
115
16.8 Hz, 2H), 7.55(d, J = 11.2 Hz, 4H), 7.17(s , 1H), 2.41(s, 6H).
116
2.2.3 Synthesis of 4'-(3,5-dicarboxyphenyl)-2,2',6',2''-terpyridine (H2-DCPTP).
RI PT
110
M AN U
SC
H NMR (DMSO-d6, ppm): δ = 8.77 (d, J = 4.4 Hz, 2H), 8.69 (d, J = 10.0 Hz, 4H), 8.06 (m, J =
1.21 g (3.6 mmol) of compound b and 3.40 g (21.6 mmol) of KMnO4 were mixed with 60 mL
118
pyridine and 30 mL water. The mixture was refluxed for 4 h. Then 3.40 g (21.6 mmol) of KMnO4,
119
10 mL water and 10 mL pyridine were added into the mixture, which was refluxed for another 3 h.
120
The resulting mixture was filtrated and the obtained precipitate was washed with water. The
121
combined filtrates were condensed under reduced pressure and then added by concentrated HCl to
122
give white precipitate. The white precipitate was recrystallized from solvent of pyridine/water (v/v
123
= 1:1) and dried in vacuo; yield 1.23g (86 %). 1H NMR (DMSO-d6, ppm): δ = 8.81 (d, J =4 .4,
124
2H), 8.74 (d, J = 8.4 Hz, 4H), 8.58 (s, 3H), 8.14 (m, J = 15.2 Hz, 2H), 7.64(m, J = 12.0 Hz, 2H).
125
2.3 Synthesis of {[Ln(DCPTP)(NO3)]·(H2O)}n
EP
AC C
126
TE D
117
Lanthanide nitrate (Tb(NO3)3·6H2O (20.4 mg, 0.045 mmol), or Eu(NO3)3·6H2O (20.1 mg,
127
0.045 mmol), or Gd(NO3)3·6H2O (20.3 mg, 0.045 mmol )), H2-DCPTP (18.0 mg, 0.045 mmol ),
128
acetonitrile (4 mL), and HNO3 (0.5 mL, 1 M in H2O) were mixed. The resulting mixture was
129
introduced into a 25 mL Parr Teflon-lined stainless steel vessel, which was heated at 140 °C for 5
130
d. The mixture was cooled to room temperature to give crystals. Yield: 75% for Tb(1); 71% for 6
ACCEPTED MANUSCRIPT Eu(2); 82% for Gd(3). Anal. Calcd for C23H15N4O8Tb (Mr = 634.31): C, 43.55; H, 2.38; N, 8.83%.
132
Found: C, 43.51; H, 2.43; N, 8.81%. Anal. Calcd for C23H15N4O8Eu (Mr = 627.35): C, 44.03; H,
133
2.41; N, 8.93%. Found: C, 44.02; H, 2.39; N, 8.91%. Anal. Calcd for C23H15N4O8Gd (Mr =
134
632.64): C, 43.67; H, 2.39; N, 8.86%. Found: C, 43.62; H, 2.42; N, 8.83%. IR spectrum (cm‒1):
135
for Tb(1), 3394 (m), 1627 (s), 1601 (m), 1586 (m), 1572 (m), 1541 (m), 1449 (s), 1385 (s), 1310
136
(m), 1165 (w), 1105 (w), 1038 (w), 1013 (w), 887 (w), 794 (w), 776 (w), 735 (w), 721 (m), 657
137
(w), 576 (w), 517 (w); for Eu(2), 3420 (m), 1628 (s), 1600 (m), 1586 (m), 1572 (m), 1541 (m),
138
1448 (s), 1383 (s), 1309 (m), 1164 (w), 1104 (w), 1013 (m), 793 (w), 734 (w), 720 (m), 705 (w),
139
657 (w), 637 (w), 573 (w); for Gd(3), 3404 (m), 1626 (s), 1600 (m), 1586 (m), 1572 (m), 1540 (m),
140
1448 (m), 1384 (s), 1308 (m), 1238 (w), 1164 (w), 1104 (m), 1038 (w), 1013 (m), 924 (w), 886
141
(w), 815 (w), 794 (w), 776 (w), 735 (w), 721 (m), 657 (w), 637 (w), 574 (w), 516 (w).
142
2.4 Synthesis of {[Tb0.9064Eu0.0936(DCPTP)(NO3)]·(H2O)}n
TE D
M AN U
SC
RI PT
131
The process for preparation was similar to that of Tb(1) with Tb(NO3)3·6H2O replaced by a
144
mixture of (Tb(NO3)3·6H2O (18.4 mg, 0.0405 mmol) and Eu(NO3)3·6H2O (2.0 mg, 0.0045 mmol).
145
Yield: 77%. IR spectrum (cm‒1): 3410 (m), 1628 (s), 1601 (m), 1587 (m), 1572 (m), 1540 (w),
146
1449 (s), 1384 (s), 1310 (w), 1238 (w), 1165 (m), 1105 (m), 1039 (w), 1013 (m), 925 (w), 886 (w),
147
794 (w), 776 (w), 735 (w), 721 (w), 657 (m), 637 (w), 574 (w), 516 (w).
AC C
148
EP
143
149
3. Results and discussion
150
3.1 Syntheses
151
Reaction of H2-DCPTP and lanthanide salts in CH3CN solvent in the presence of HNO3
152
afforded the isomorphous coordination polymers, {[Ln(DCPTP)(NO3)]·(H2O)}n (Ln = Tb(1), 7
ACCEPTED MANUSCRIPT Eu(2) and Gd(3)). Accordingly, the bimetallic Tb3+/Eu3+ compound of Tb0.9064Eu0.0936-DCPTP can
154
be readily prepared by using the initial molar ratio of 0.9:0.1 for Tb(NO3)3 and Eu(NO3)3 through
155
the similar preparation procedure. The actual molar ratio of Tb3+/Eu3+ (0.9064/0.0936) in the
156
resulting bimetallic coordination polymer, which was determined by inductively coupled plasma
157
spectroscopy, matches well with that of starting materials. As expected, the Eu-doped
158
Tb-compound of Tb0.9064Eu0.0936-DCPTP is isomorphous with the parent ones, which is confirmed
159
by their PXRD patterns (Fig. S2).
160
3.2 Crystal structures
M AN U
SC
RI PT
153
For these isostructural compounds, structure Tb(1) is described representatively. There one Tb3+,
162
one DCPTP2− dianionic ligand, one nitrate anion, and one lattice water molecule are in the
163
asymmetric unit of Tb(1). Tb3+ ion is nine-coordinated by three N atoms of one DCPTP2− ligand,
164
four carboxylate O atoms (O1, O2A, O3C, and O4C) from three DCPTP2− ligands and two O
165
atoms of a NO3− group (Fig. 1a). The Tb–O bond distances vary from 2.286(4) to 2.540(4) Å and
166
Tb–N bond distances range from 2.531(6) to 2.577(6) Å. The nitrate anion chelates a Tb3+ ion
167
through its two O atoms with the third O atom uncoordinated. The DCPTP2− ligand binds four
168
metal ions through a chelating and a bidentate carboxylate groups, and a chelating terpyridyl
169
group (Fig. S3). Two bidentate carboxylate groups bridge two Tb3+ ions to generate a dinuclear
170
Tb2(µ2-COO)2] unit (Fig. 1b), which is connected by the DCPTP2− ligands to generate a 3D
171
framework (Fig. 2). Each dinuclear Tb2(µ2-COO)2] unit is surrounded by six DCPTP2− ligands
172
(Fig. 1b) and each DCPTP2− ligand connects three dinuclear Tb2(µ2-COO)2] units (Fig. S4). In this
173
way, the DCPTP2− ligand and the dinuclear Tb2(µ2-COO)2] unit define a 3- and 6-connected nodes,
174
respectively. Thus the 3D framework of Tb(1) is a 3,6-connected network with
AC C
EP
TE D
161
8
ACCEPTED MANUSCRIPT 175
(42·6)2(44·62·87·102) topology (Fig. S5). When loss of the solvent water molecules, the main
176
framework can stable up to 400 °C (Fig. S6).
M AN U
SC
RI PT
177
178 179
Fig. 1 Coordinated environment of Tb3+ ion (a) and the dinuclear Tb2(µ2-COO)2] unit (b) in Tb(1).
181
AC C
EP
TE D
180
182
Fig. 2 3D framework of Tb(1) (The nitrate anions and lattice water molecules are omitted for
183
clarify).
184 185
3.2 Luminescent properties 9
ACCEPTED MANUSCRIPT Upon excitation at 369 nm, the free H2-DCPTP ligand emits an emission centered at 434 nm in
187
the solid state, which was assigned to the intraligand π*−π electron transitions (Fig. S7). The solid
188
state luminescent emissions of Tb(1) and Eu(2) at room temperature are shown in Fig. S8 and S9,
189
respectively. Tb(1) displays an excitation band centered at 353 nm and no sharp peak of Tb3+ f−f
190
transition appears in the excitation spectrum, indicating the Tb3+ ions are excited via an effective
191
sensitized process involving the organic ligand. Tb(1) emits strong green emission with the
192
characteristic peaks of Tb3+ (5D4 → 7FJ, J = 0 ‒ 6) at 490, 543, 584, 621, 650, 667, and 678 nm
193
(Fig. S8), wherein the 5D4 → 7F5 transition (543 nm) has the most intense intensity. Additionally,
194
the emission of organic ligand is not detected in the emission spectrum of Tb(1), which indicates
195
an energy is transferred from organic ligands to Tb3+ ions efficiently. As case of Eu(2), a excitation
196
band centered at 361 nm overlapping with additional weak intra-4f6 sharp lines is observed,
197
indicating that the Eu3+ ions are mainly excited through a sensitized process but not via a direct
198
excitation process. Eu(2) exhibits typical bands arising from Eu3+ excited levels (5D0 → 7FJ, J = 0,
199
1, 2, 3, 4) at 580, 592, 616, 651, and 698 nm, after excited at 361 nm (Fig. S9). The intensity of
200
the 5D0 → 7F2 emission, which is extremely sensitive to site symmetry, is much more intense
201
than that of the 5D0 →
202
coordination environment.
SC
M AN U
TE D
EP 7
F1 emission, suggesting that the Eu3+ ion is in an asymmetric
AC C
203
RI PT
186
10
RI PT
ACCEPTED MANUSCRIPT
204
Fig. 3 Temperature-dependent emission spectra for Tb(1) between 77 K and 300 K (λex = 361 nm).
M AN U
SC
205
207
TE D
206
Fig. 4 Temperature-dependent emission spectra for Eu(2) between 77 K and 300 K (λex = 361 nm).
AC C
EP
208
209 210
Fig. 5 Solid-state emission spectra of Tb0.9064Eu0.0936-DCPTP between 77 K and 300 K (λex = 361
211
nm).
212 11
ACCEPTED MANUSCRIPT Temperature-dependent photoluminescence emission spectra of Tb(1) and Eu(2) between 77 K
214
and 300 K are presented in Fig. 3 and 4, respectively. For both compounds, the emission intensity
215
and lifetime decrease upon increasing temperature, as a result of the thermal activation of
216
nonradiative-decay. However, the emission intensity and lifetime of Tb3+ in Tb(1) diminish more
217
pronouncedly than those of Eu3+ in Eu(2) upon increasing temperature (Fig. S10). In particular for
218
the lifetime, lifetime of Eu3+ is almost unchanged in the test temperature range (Fig. S10b). Such
219
distinct temperature-dependent luminescent behavior for Tb(1) and Eu(2) can be attributed to the
220
different energy gaps between the triplet excited state of the ligand and the emitting levels of Tb3+
221
and Eu3+ ions. The triplet state energy level T1 for H2-DCPTP is 25445 cm‒1 (393 nm) estimated
222
from the phosphorescence spectrum of Gd(3) (λex = 372 nm) (Fig. S11). The experimental T1
223
value is consistent with the one (25217 cm−1) from DFT calculations. The energy gap between the
224
T1 level and the 5D4 emitting level (20453 cm‒1) of Tb3+ [36] in Tb(1) is much smaller than the
225
energy gap between T1 level and the 5D0 emitting level (17267 cm‒1) of Eu3+ [37] in Eu(2). As a
226
result, the thermally driven depopulation for Eu3+ emitting level is almost prohibited [38–40].
TE D
M AN U
SC
RI PT
213
To obtain more reliable luminescent thermometers based on two emissions with a ratiometric
228
method, the Eu-doped Tb-compound of Tb0.9064Eu0.0936-DCPTP was synthesized. The
229
Tb0.9064Eu0.0936-DCPTP displays characteristic emissions of Tb3+ and Eu3+ ions simultaneously
230
(Fig. S12), indicating the H2-DCPTP with an extensive π-conjugated system is a remarkable
231
sensitizer for sensitizing of Tb3+ and Eu3+ ions. Fig. 5 presents the emission spectra of
232
Tb0.9064Eu0.0936-DCPTP from 77 to 300 K. The intensity of 5D0 → 7F2 (616 nm) transition of Eu3+
233
is enhanced significantly, while that of 5D4 → 7F5 transition (542 nm) of Tb3+ is diminished slowly
234
when increasing temperature (Fig. 6). At 77 K, the intensity of 5D4 → 7F5 (Tb3+) transition is about
AC C
EP
227
12
ACCEPTED MANUSCRIPT 2.7 times more intense than that of 5D0 → 7F2 (Eu3+) transition (Fig. 7), which gives a green color
236
for the compound. In contrast, the intensity of 5D0 → 7F2 (Eu3+) transition is 19.6 times more
237
intense than that of 5D4 → 7F5 (Tb3+) transition at 300 K, indicating the Eu3+ emission is
238
completely dominated in the high temperature region. Thus the temperature-dependent
239
luminescent colors are systematically tuned from green, via yellow to red with increasing
240
temperature (Fig. 8). The dramatic intensity changes of Tb3+- and Eu3+-emissions in opposite
241
directions suggests the Tb0.9064Eu0.0936-DCPTP is an excellent candidate for ratiometric
242
luminescent thermometers. As illustrated in Fig. 7, the emission intensity ratio (∆ = ITb/IEu)
243
between 5D4 → 7F5 transition (Tb3+, 543 nm) and 5D0 → 7F2 transition (Eu3+, 616 nm) remains
244
roughly constant in the temperature range of 77 ‒ 150 K. The relationship between ∆ and
245
temperature (T) is well fitted with the exponential empirical equation (1) in the temperature of 150
246
‒ 300 K (Fig. 7 inset and Fig. S14)
247
∆ = – 0.530 + 24.535e(– 0.013T) (1)
248
The correlation coefficient (R2) of 0.99652 is obtained from the fitting result. The relative thermal
249
sensitivity Sr (Sr = |∂∆/∂T|/∆) [41, 42] is used to characterize the performances of the thermometers.
250
As can be seen from the definition of Sr, the Sr value varies with the temperature. Thus the
251
maximum (Sm) value of Sr in the detection temperature range is proposed for comparing the
252
performances of the coordination compounds thermometers [28]. The Tb0.9064Eu0.0936-DCPTP has
253
a high Sm up to 21.5 % K‒1 at 300 K (Fig. S15), which is the highest value for the lanthanide
254
coordination polymers ratiometric luminescent thermometers (Table S2). Such results suggest the
255
Tb0.9064Eu0.0936-DCPTP is a potentially useful luminescent thermometer and further confirm the
256
present organic ligand is a very effective sensitizer for Tb3+ and Eu3+ ions. It is noted that there is a
AC C
EP
TE D
M AN U
SC
RI PT
235
13
ACCEPTED MANUSCRIPT report claiming the Sm of 31 % K‒1 for the Tb0.95Eu0.05-5-hydroxy-1,2,4-benzenetricarboxylate very
258
recently [43]. However, its Sm value appears at low temperature of 4 K, which is different from the
259
present case and other thermometers (Table S2). Finally, the temperature-dependent emission
260
spectra for Tb0.9064Eu0.0936-DCPTP material are repeatable and reversible (Fig. S16), indicates it is
261
a robust lanthanide coordination polymer luminescent thermometer.
M AN U
SC
262
RI PT
257
TE D
263
Fig. 6 Integrated intensities of 5D4 → 7F5 (538‒555 nm) and 5D0 → 7F2 (605‒630 nm) emission
265
bands versus temperature in Tb0.9064Eu0.0936-DCPTP.
AC C
266
EP
264
267 268
Fig. 7 Integrated intensity ratio between Tb3+ (543 nm) and Eu3+ (616 nm) versus temperature for 14
ACCEPTED MANUSCRIPT 269
Tb0.9064Eu0.0936-DCPTP
(Inset:
Fitted
curve
of
the
270
Tb0.9064Eu0.0936-DCPTP from 150 to 300 K with equation (1).
integrated
intensity
ratio
for
271 A rapid decrease of lifetime for Tb3+ emission is observed in Tb0.9064Eu0.0936-DCPTP with
273
increasing temperature, especially between 150 and 300 K. The lifetime of Tb3+ emission is
274
decreased about 94% as the temperature increasing from 150 to 300 K (Fig. S13). While the
275
lifetime of the Eu3+emission decreases only slightly in Tb0.9064Eu0.0936-DCPTP with increasing the
276
temperature. Such observations indicate the nonradiative Tb3+-to-Eu3+ energy transfer occurs [44].
277
At 150 K, the lifetimes of Tb3+ emission in Tb0.9064Eu0.0936-DCPTP (1.04 ms) (Fig. S13) and in
278
pure Tb(1) (1.16 ms) (Fig. S10b) are similar. In contrast, the lifetime of Tb3+ emission in
279
Tb0.9064Eu0.0936-DCPTP decreases to 0.04 ms at 300 K, which is about one-tenth of that for pure
280
Tb(1) at 300 K (0.41 ms). The energy migration between Tb3+ centers is easier than that of from
281
Tb3+ to Eu3+
TE D
M AN U
SC
RI PT
272
AC C
EP
282
283 284
Fig. 8 The CIE chromaticity diagram showing the luminescence color of Tb0.9064Eu0.0936-DCPTP
285
at different temperatures. 15
286 transform
efficiency
from
to
Eu3+
Fig.
versus
288
Tb0.9064Eu0.0936-DCPTP.
289
because of the larger energy gap between Tb3+ to Eu3+ energy levels. When temperature higher
290
than 150 K, the abrupt decrease of lifetime for Tb3+ emission in Tb0.9064Eu0.0936-DCPTP indicates
291
the energy migration occurred between Tb3+ centers, ultimately resulting in Tb3+ to Eu3+ energy
292
transfer. However, because of the small variations in the energy levels for Tb3+ center, the energy
293
migration between neighboring Tb3+ centers is hampered at lower temperature. Thus in the
294
temperature range from 77 to150 K, the slight changes in the intensity and lifetime of Tb3+
295
emission in Tb0.9064Eu0.0936-DCPTP are not unreasonable. With further increasing the temperature,
296
the energy in the excited state of Tb3+ has more opportunity to transfer to a Tb3+ ion neighboring a
297
Eu3+ center, followed by subsequent energy transfer to Eu3+. As a result, the observation of
298
enhancement of Eu3+ emission and recession of Tb3+ emission in the temperature range 150−300
299
K can be explained by the phonon-assisted Förster transfer mechanism [45]. The energy transfer
300
efficiency (η) from Tb3+ and Eu3+ ions can be calculated from the equation of η = 1 ‒ τ/τ0 (τ and τ0
301
represent the lifetimes of Tb3+ with and without Eu3+ acceptor, respectively) [46]. The
302
temperature-dependent η for Tb0.9064Eu0.0936-DCPTP is presented in Fig. 9, which displays the
SC
Energy
Tb3+
287
temperature
in
AC C
EP
TE D
M AN U
9
RI PT
ACCEPTED MANUSCRIPT
16
ACCEPTED MANUSCRIPT energy transfer efficiency from Tb3+ to Eu3+ is low and almost unchanged in the range of 77‒150
304
K. Then the energy transfer efficiency is dramatically enhanced on going from 150 to 300 K, thus
305
resulting in the increase of the intensity of Eu3+-emission at the cost of the quenching of
306
Tb3+-emission upon temperature increasing. The η value at 300 K is about 84%, which is the
307
highest value for the Eu3+/Tb3+mixed coordination polymers
308 4. Conclusions
SC
309
RI PT
303
In summary, a H2-DCPTP ligand with π-rich conjugated systems and four lanthanide
311
compounds including the mixed lanthanide compound constructed of H2-DCPTP ligand have been
312
prepared and characterized. These isostructural compounds have a 3D framework featuring the
313
dinuclear lanthanide-carboxylate units. The Tb0.9064Eu0.0936-DCPTP serving as a ratiometric
314
luminescent thermometer was evaluated detailedly in terms of luminescence intensity and lifetime.
315
The result shows that Tb0.9064Eu0.0936-DCPTP can be developed as a high-performance temperature
316
sensor in the temperature range of 150−300 K, with higher relative sensitivity and larger energy
317
transfer efficiency than those of previously reported Eu3+/Tb3+ coordination polymers luminescent
318
thermometer. This work demonstrates a strategy for designing of robust luminescent thermometers
319
with high sensitivity and large energy transfer efficiency.
321
TE D
EP
AC C
320
M AN U
310
Acknowledgements
322
This work was supported by the NSF of China (Grants 21661014, 21561015 and 21861020),
323
the NSF of Jiangxi Province (Grant 20171ACB20008 and 20181BAB203001). We thank
324
Professor Xingfa Gao for the DFT calculations 17
ACCEPTED MANUSCRIPT 325 326 327
Appendix A. Supplementary data Supplementary data related to this article can be found at http://dx.doi.org/10.1016/j.dyepig.
RI PT
328 329
References
330
[1] Rocha J, Carlos LD, Almeida Paza FA, Ananias D. Luminescent multifunctional
333 334 335 336 337
SC
[2] Binnemans K. Lanthanide-Based Luminescent Hybrid Materials. Chem Rev 2009;109:4283–
M AN U
332
lanthanides-based metal-organic frameworks. Chem Soc Rev 2011;40:926−940.
4374.
[3] Kreno LE, Leong K, Farha OK, Allendorf M, Van Duyne RP, Hupp JT. Metal-Organic Framework Materials as Chemical Sensors. Chem Rev 2012;112:1105−1125. [4] Bünzli J-CG. Lanthanide Luminescence for Biomedical Analyses and Imaging. Chem Rev 2010; 110:2729–2755
TE D
331
[5] Zhou L-J, Deng W-H, Wang Y-L, Xu G, Yin S-G, Liu Q-Y. Lanthanide-Potassium
339
Biphenyl-3,3′-disulfonyl-4,4'-dicarboxylate Frameworks: Gas Sorption, Proton Conductivity,
340
and Luminescent Sensing of Metal Ions. Inorg Chem 2016;55:6271−6277.
AC C
EP
338
341
[6] Yan X-H, Cai Z-H, Yi C-L, Liu W-S, Tan M-Y, Tang Y. Anion-Induced Structures and
342
Luminescent Properties of Chiral Lanthanide-Organic Frameworks Assembled by an Achiral
343
Tripodal Ligand. Inorg Chem 2011;50:2346–2353.
344
[7] Liu T-F, Zhang W-J, Sun W-H, Cao R. Anion-Induced Structures and Luminescent Properties
345
of Chiral Lanthanide-Organic Frameworks Assembled by an Achiral Tripodal Ligand. Inorg
346
Chem 2011;50:5242–5248. 18
ACCEPTED MANUSCRIPT 347 348
[8] Cui Y, Yue Y, Qian G, Chen B. Luminescent Functional Metal–Organic Frameworks. Chem Rev 2012;112:1126−1162. [9] He R, Wang Y-L, Ma, H-F, Yin, S-G, Liu Q-Y, Eu3+-functionalized metal-organic framework
350
composite as ratiometric fluorescent sensor for highly selective detecting urinary
351
1-hydroxypyrene, Dyes Pigments 2018;151:342–347.
353
[10] Wu W-T, Dong J, Ni W-Y, Zhang B-W, Cui J-Z, Zhao B. Unique Chiral Interpenetrating d-f Heterometallic MOFs as Luminescent Sensors. Inorg Chem 2015;54:5266−5272.
SC
352
RI PT
349
[11] Zhou Y, Chen H-H, Yan B. An Eu3+ post-functionalized nanosized metal-organic framework
355
for cation exchange-based Fe3+-sensing in an aqueous environment. J Mater Chem A 2014;2:
356
13691−13697.
M AN U
354
[12] Dong X-Y, Wang R, Wang J-Z, Zang S-Q, Mak TCW. Highly selective Fe3+ sensing and
358
proton conduction in a water-stable sulfonate-carboxylate Tb-organic-framework. J Mater
359
Chem A 2015; 3:641−647.
TE D
357
[13] Li Y-J, Wang Y-L, Liu Q-Y. The Highly Connected MOFs Constructed from Nonanuclear and
361
Trinuclear Lanthanide-Carboxylate Clusters: Selective Gas Adsorption and Luminescent pH
362
Sensing. Inorg Chem 2017;56:2159−2164.
AC C
EP
360
363
[14] Armelao L, Quici S, Barigelletti F, Accorsi G, Bottaro G, Cavazzini M, et al. Design of
364
luminescent lanthanide complexes: From molecules to highly efficient photo-emitting materials.
365
Coord Chem Rev 2010;254:487−505.
366 367 368
[15] Allendorf MD, Bauer CA, Bhaktaa RK, Houk RJT. Luminescent metal-organic frameworks. Chem Soc Rev 2009;38:1330–1352. [16] Wei Y, Sa R, Li Q, Wu K. Highly stable and sensitive LnMOF ratiometric thermometers 19
ACCEPTED MANUSCRIPT 369 370 371
constructed with mixed ligands. Dalton Trans 2015;44:3067–3074. [17] Ananias D, Brites CD, Carlos LD, Rocha J. Cryogenic Nanothermometer Based on the MIL-103(Tb,Eu) Metal-Organic Framework. Eur J Inorg Chem 2016;1967–1971. [18] Zhao D, Rao X, Yu J, Cui Y, Yang Y, Qian G. Design and Synthesis of an MOF Thermometer
373
with High Sensitivity in the Physiological Temperature Range. Inorg Chem 2015;54:11193–
374
11199.
RI PT
372
[19] Miyata K, Konno Y, Nakanishi T, Kobayashi A, Kato M, Fushimi K, et al. Chameleon
376
Luminophore for Sensing Temperatures: Control of Metal-to-Metal and Energy Back Transfer
377
in Lanthanide Coordination Polymers. Angew Chem Int Ed 2013;52:6413−6416.
380 381
M AN U
379
[20] Brites CDS, Lima PP, Silva NJO, Millán A, Amaral VS, Fernando P, et al. Lanthanide-based luminescent molecular thermometers. New J Chem 2011;35:1177–1183. [21] Wang X-D, Wolfbeis OS, Meier RJ. Luminescent probes and sensors for temperature. Chem
TE D
378
SC
375
Soc Rev 2013;42:7834–7869.
[22] Zhou Y, Yan B, Lei F. Postsynthetic lanthanide functionalization of nanosized metal-organic
383
frameworks for highly sensitive ratiometric luminescent thermometry. Chem Commun 2014;50:
384
15235–15238.
386
AC C
385
EP
382
[23] Cui Y, Xu H, Yue Y, Guo Z, Yu J, Chen Z, et al. A Luminescent Mixed-Lanthanide Metal-Organic Framework Thermometer. J Am Chem Soc 2012;134:3979−3982.
387
[24] Han Y-H, Tian C-B, Li Q-H, Du S-W. Highly chemical and thermally stable luminescent
388
EuxTb1-x MOF materials for broad-range pH and temperature sensors. J Mater Chem C 2014;2:
389
8065–8070.
390
[25] Yang Y, Chen L, Jiang F, Yu M, Wan X, Zhang B, et al. A family of doped lanthanide 20
ACCEPTED MANUSCRIPT 391
metal-organic frameworks for wide-range temperature sensing and tunable white light emission.
392
J Mater Chem C 2017;5:1981−1989.
394
[26] Cui Y-J, Zhu F-L, Chen B-L, Qian G-D. Metal-organic frameworks for luminescence thermometry. Chem Commun 2015;51:7420–7431.
RI PT
393
[27] Zhao S-N, Li L-J, Song X-Z, Zhu M, Hao Z-M, Meng X, et al. Lanthanide Ion Codoped
396
Emitters for Tailoring Emission Trajectory and Temperature Sensing. Adv Funct Mater 2015;25:
397
1463–1469.
399
[28] Rocha J, Brites CDS, Carlos LD. Lanthanide Organic Framework Luminescent
M AN U
398
SC
395
Thermometers. Chem Eur J 2016;22:14782–14795.
[29] Cui Y-J, Zou W-F, Song R-J, Yu J-C, Zhang W-Q, Yang Y, et al. A ratiometric and
401
colorimetric luminescent thermometer over a wide temperature range based on a lanthanide
402
coordination polymer. Chem Commun 2014;50:719–721.
TE D
400
[30] Latva M, Takalo H, Mukkala VM, Matachescu C, Rodríguez-Ubis JC , Kankare J.
404
Correlation between the lowest triplet state energy level of the ligand and lanthanide(III)
405
luminescence quantum yield. J Lumin 1997;75:149−169.
EP
403
[31] Døssing A. Luminescence from Lanthanide(3+) Ions in Solution. Eur J Inorg Chem 2005;
407
1425−1434.
408
[32] Parker D. Luminescent lanthanide sensors for pH, pO2 and selected anions. Coord Chem Rev
409
AC C
406
2000;205:109−130.
410
[33] CrysAlisPro; Rigaku Oxford Diffraction 2015.
411
[34] Sheldrick GM. HELXT-Integrated space-group and crystal-structure determination. Acta
412
Cryst 2015;A71:3–8. 21
ACCEPTED MANUSCRIPT 413
[35] Sheldrick GM. Crystal structure refinement with SHELXL. Acta Cryst 2015;C71:3–8.
414
[36] Carnall WT, Fields PR, Rajnak K. Electronic Energy Levels of the Trivalent Lanthanide Aquo
418 419 420 421
Ions. IV. Eu3+. J Chem Phys 1968;49:4450−4455.
RI PT
417
[37] Carnall WT, Fields PR, Rajnak K. Electronic Energy Levels of the Trivalent Lanthanide Aquo
[38] Carlos LD, Ferreira RAS, de Zea Bermudez V, JulianLopez B, Escribano P. Progress on lanthanide-based organic-inorganic hybrid phosphors. Chem Soc Rev 2011;40:536−549.
SC
416
Ions. III. Tb3+. J Chem Phys 1968;49:4447−4449.
[39] Kolodner P, Tyson JA. Remote thermal imaging with 0.7-µm spatial resolution using
M AN U
415
temperature-dependent fluorescent thin flims. Appl Phys Lett 1983;42:117–119. [40] Brites CDS, Lima PP, Silva NJO, Millan A, Amaral VS, Palacio F, et al. A Luminescent
423
Molecular Thermometer for Long-Term Absolute Temperature Measurements at the Nanoscale.
424
Adv Mater 2010;22:4499−4504.
427 428
Absolute Temperature Measurements at the Nanoscale. J Appl Phys 2003;94:4743–4756. [42] Brites CDS, Lima PP, Silva NJO, Millán A, Amaral VS, et al. Thermometry at the nanoscale.
EP
426
[41] Wade SA, Collins SF, Baxter GW. A Luminescent Molecular Thermometer for Long-Term
Nanoscale 2012;4:4799–4829.
AC C
425
TE D
422
429
[43] Liu X, Akerboom S, Jong M de, Mutikainen I, Tanase S. Meijerink A, et al.
430
Mixed-Lanthanoid Metal-Organic Framework for Ratiometric Cryogenic Temperature Sensing.
431
Inorg Chem 2015; 54:11323−11329.
432
[44] Marciniak L, Bednarkiewicza A. The influence of dopant concentration on temperature
433
dependent emission spectra in LiLa1−x−yEuxTbyP4O12 nanocrystals: toward rational design of
434
highly-sensitive luminescent nanothermometers. Phys Chem Chem Phys 2016;18:15584– 22
ACCEPTED MANUSCRIPT 435 436 437
15592. [45] Auzel F. Upconversion and Anti-Stokes Processes with f and d Ions in Solids. Chem Rev 2004; 104:139−173. [46] Rodrigues M O, Dutra JDL, Nunes LAO, de Sá GF, de Azevedo WM, Silva P, et al. Tb3+→
439
Eu3+ Energy Transfer in Mixed-Lanthanide-Organic Frameworks. J Phys Chem C 2012;116:
440
19951−19957.
RI PT
438
AC C
EP
TE D
M AN U
SC
441
23
ACCEPTED MANUSCRIPT Highlights
EP
TE D
M AN U
SC
RI PT
{[Ln(DCPTP)(NO3)](H2O)}n and {[Tb0.9064Eu0.0936(DCPTP)(NO3)](H2O)}n were presented. The H2-DCPTP ligand is a light-harvesting ligand for efficiently sensitizing of Tb3+ and Eu3+. Tb0.9064Eu0.0936-DCPTP behaves as a high-performance luminescent thermometer. Luminescent thermometer with a high relative thermal sensitivity of Sm up to 21.5 % K‒1.
AC C
• • • •