Synthesis and near infrared luminescence properties of a series of lanthanide complexes with POSS modified ligands

Article abstract of DOI:10.3390/molecules24071253

A polyhedral oligomeric silsesquioxanes (POSS) modified 8-hydroxyquinoline derivative (denoted as Q-POSS) was synthesized and used as a ligand to coordinate with lanthanide ions to obtain a series of lanthanide complexes Ln(Q-POSS)₃ (Ln = Er³⁺, Yb³⁺, Nd³⁺). The as-prepared lanthanide complexes have been characterized by FT-IR, UV–Vis, and elemental analysis. All these complexes showed the characteristic near-infrared (NIR) luminescence originated from the corresponding lanthanide ions under excitation. Compared with the unmodified counterparts LnQ₃ (HQ = 8-hydroxyquinoline), the Ln(Q-POSS)₃ complexes showed obviously increased emission intensity, which was ascribed mainly to the steric-hindrance effects of the POSS moiety in the ligands. It is believed that the POSS group could suppress undesired excimer formation and intermolecular aggregation, thus decreasing the concentration quenching effect of the corresponding lanthanide complexes.

Full text of DOI:10.3390/molecules24071253

molecules
Article
Synthesis and Near Infrared Luminescence Properties
of a Series of Lanthanide Complexes with POSS
Modified Ligands
Qingrui Zhang 1,2, Xiuyun Yang 1,*, Ruiping Deng 2,*, Liang Zhou 2,*, Yang Yu 2 and Yunhui Li 1
1
School of Chemistry and Environmental Engineering, Changchun University of Science and Technology,
Changchun 130000, China; qrzhang784783@126.com (Q.Z.); liyh@cust.edu.cn (Y.L.)
Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun 130022, China;
2
yuy@ciac.ac.cn
*
Correspondence: yangxiuyun@cust.edu.cn (X.Y.); dengrp@ciac.ac.cn (R.D.); zhoul@ciac.ac.cn (L.Z.);
Tel.: +86-431-85262135 (R.D. & L.Z.)
ꢀꢁꢂꢀꢃꢄꢅꢆꢇ
Academic Editor: Lianshe Fu
Received: 17 January 2019; Accepted: 27 March 2019; Published: 30 March 2019
ꢀꢁꢂꢃꢄꢅꢆ
Abstract: A polyhedral oligomeric silsesquioxanes (POSS) modified 8-hydroxyquinoline derivative
(denoted as Q-POSS) was synthesized and used as a ligand to coordinate with lanthanide ions to
obtain a series of lanthanide complexes Ln(Q-POSS)3 (Ln = Er3+, Yb3+, Nd3+). The as-prepared
lanthanide complexes have been characterized by FT-IR, UV–Vis, and elemental analysis. All these
complexes showed the characteristic near-infrared (NIR) luminescence originated from the
corresponding lanthanide ions under excitation. Compared with the unmodified counterparts LnQ3
(HQ = 8-hydroxyquinoline), the Ln(Q-POSS)3 complexes showed obviously increased emission
intensity, which was ascribed mainly to the steric-hindrance effects of the POSS moiety in the
ligands. It is believed that the POSS group could suppress undesired excimer formation and
intermolecular aggregation, thus decreasing the concentration quenching effect of the corresponding
lanthanide complexes.
Keywords: lanthanide complexes; polyhedral oligomeric silsesquioxanes; near-infrared luminescence
1. Introduction
Luminescent lanthanide (Ln) ions have attracted scientific and technological interest due to their
unique photophysical properties and potential applications in the fields of cell imaging [
amplification [ ], light-emitting diodes [ ], luminescent probes [ ], etc. However, there are still some
challenges for the application of the Ln complexes. Resulting from the weak absorption efficiency
of f–f transitions in Ln3+ ions [
], designing efficient sensitization systems for lanthanide-based NIR
1], optical
2
3
4
5
emitters remains a challenge. Moreover, many Ln complexes suffer from the poor thermal stability.
To resolve the as-mentioned problems, many efforts have been devoted to the design and synthesis
of lanthanide complexes with efficient energy transfer ligands. Quinoline is one of the most popular
ligands for lanthanide ions, thanks to the excellent complexation properties of the quinoline molecule,
which has been selected for NIR luminescent studies as well [6–8]. In addition, the introduction of Ln
complexes into the inorganic matrix, either the fabrication of the organic/inorganic hybrid materials by
chemical bonds or by physical interaction, has been proved to be a highly effective method to improve
the thermal stability of Ln complexes [9,10].
Among the hybrid material families, polyhedral oligomeric silsesquioxanes (POSS), a class of
inorganic/organic hybrids at the molecular level, has gained many interests in the materials field due to
its well-defined 3D structures, good biocompatibility [11], and good solubility in organic solvents [12].
Molecules 2019, 24, 1253; doi:10.3390/molecules24071253
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With a generic empirical formula (RSiO1.5)n (where n is commonly 6, 7, 8, 10, or 12), it is comprised of
an inner inorganic core and external substituent groups, and the sizes of the building blocks range from
1 to 3 nm, which can be considered as a class of sphere-like nanomaterials [13]. When POSS units were
introduced into organic or polymeric materials, glass transition temperature, mechanical strength, and
thermal stability of the corresponding materials were enhanced as well [14,15]. POSS have shown a
great potential in the Ln-complexes-based hybrid materials recently, and Li and Sun et al. had reported
excellent luminescent POSS modified Ln complexes [16,17].
Here, we designed a novel ligand using POSS to modify the 8-hydroxyquinoline core to prepare
the hybrid lanthanide complexes. Detailed NIR luminescent properties of these hybrid materials were
investigated. It has been found that the Ln(Q-POSS)3 complexes show obviously enhanced emission
intensity when they are compared with their counterparts LnQ3, which is discussed in the steric
hindrance effects of the POSS and the change of the energy level of the modified ligand.
2. Results
The synthetical procedure of the ligand Q-POSS and the Ln complexes Ln(Q-POSS)3 (Ln = Er3+
Nd3+, Yb3+) is depicted in Scheme 1. The structure characterization of the ligand and complexes were
carried out by 1HNMR, MS, elemental analysis and FT-IR methods. The 1HNMR and MS spectra
(Figures S1 and S2) proved that the ligand Q-POSS was synthesized successfully.
,
Scheme 1. The synthetical procedure of ligands POSS modified 8-hydroxyquinoline derivative
(Q-POSS) and Ln complexes Ln(Q-POSS)3.
2.1. FT-IR Analysis
The FT-IR spectra of Yb(Q-POSS)3, Nd(Q-POSS)3, Er(Q-POSS)3, and Q-POSS are shown in Figure 1.
−1
The absorption peak at around 1100 cm for Yb(Q-POSS)3, Nd(Q-POSS)3, Er(Q-POSS)3, and Q-POSS,
respectively, represents the vibrations of the siloxane Si-O-Si groups and is a general feature of POSS
derivatives [18]. The characteristic bands at 2870–2954 cm−1 were clearly observed, which represent
the vibrations of
−
−
CH3 and
−
CH2. In Yb(Q-POSS)3, Nd(Q-POSS)3, and Er(Q-POSS)3, the peak for
OH group at 3326 cm−1 disappeared completely, and the stretching vibration peak of C=N bond
shifted from 1615 to 1595 cm−1, indicating that the nitrogen and oxygen atom in quinoline moiety
participates in coordination with Ln ions [19].

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Figure 1. The FT-IR spectra of Yb(Q-POSS)3, Nd(Q-POSS)3, Er(Q-POSS)3, and Q-POSS.
2.2. UV–Vis Analysis
Figure 2 displays the UV
−
Visible (UV
−
Vis) absorption spectra of the solutions of Q-POSS,
Er(Q-POSS)3, Nd(Q-POSS)3, and Yb(Q-POSS)3 dissolved in dichloromethane (1
The absorption peaks for Q-POSS appeared at 246 and 334 nm, respectively, which can be attributed to
the * transitions of quinoline moiety. For Er(Q-POSS)3, Nd(Q-POSS)3, and Yb(Q-POSS)3 complexes,
×
10−5 M), respectively.
π–π
they show a strong absorption band at about 241 nm and two weak absorption bands at around 330
and 409 nm, in which the absorption bands at 241 nm and 330 nm can be ascribed to the spin-allowed
π
–
π
* transitions of the ligands, and the band at 409 nm can be assigned to both spin–orbit coupling
enhanced ( *) and spin-forbidden LMCT transitions [20]. The UV–Vis absorption spectra of Q,
ErQ3, NdQ3, and YbQ3 in dichloromethane solutions (1
10−5 M) at room temperature are shown
π–π
×
in Figure S3. They show similar absorption behaviors with that of the Q-POSS and Ln(Q-POSS)3.
The absorption peaks for the unmodified ligand 8-hydroxyquinoline (HQ) appeared at 241 and 317
nm, respectively. Besides the π–π* transitions of the ligands, occurring at 242 and 317 nm, respectively,
the LnQ3 complexes show weak bands at about 385 nm, which are also the spin–orbit coupling
enhanced (π–π*) and spin-forbidden LMCT transitions, as mentioned in the cases of Ln(Q-POSS)3.
Figure 2. UV–Vis absorption spec−tr5a of Q-POSS, Er(Q-POSS)3, Nd(Q-POSS)3, and Yb(Q-POSS)3 in
dichloromethane solutions (1 × 10 M) at room temperature.

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2.3. Luminescent Properties
The Luminescent properties of the Ln(Q-POSS)3 (Ln = Nd3+, Yb3+, Er3+) complexes in the solid
state were investigated. Figure 3 displays their excitation and emission spectra. All these complexes
exhibit similar excitation bands, with a broad band ranging from 250 to 560 nm, which arise from the
8-hydroxyquinolinate ligand related transitions and the LMCT from the complexes according to the
UV–Vis absorption spectra as mentioned above. And the main excitation peak occurs at about 469 nm.
For the case of Nd(Q-POSS)3, the excitation band is superimposed with the characteristic absorption
4
transition I9/2
→
2G7/2 (585 nm) of the Nd3+ ion as well. After excitation, all the Ln(Q-POSS)3
(Ln = Nd3+
The emission spectrum of Nd(Q-POSS)3 consists of three narrow bands from the f–f transitions of the
Nd3+ ion in the range of 800–1700 nm, with the main band occurring at 1068 nm (4F3/2 4I11/2), and
two other bands at 904 nm (4F3/2 4I9/2) and 1333 nm (4F3/2 4I13/2), respectively. The Yb(Q-POSS)3
complex emits in the range of 910–1100 nm, with a sharp band at around 980 nm assigned to the
2F5/2 2F7/2 transition of the Yb3+ ion and a broader vibronic component at a longer wavelength.
,
Yb3+, Er3+) complexes show the characteristic transitions of the corresponding Ln3+ ion.
→
→
→
→
The emission spectrum of Er(Q-POSS)3 is comprised of two bands from the Er3+ ion, which are assigned
to the 4I11/2→ I15/2 (980 nm) and 4I13/2→ I15/2 (1536 nm) transitions, respectively.
4
4
Figure 3. Excitation and emission spectra of Ln(Q-POSS)3.
(A) Nd (Q-POSS)3
(λ
ex
= 469 nm,
λmonitor = 1068 nm),
(B
) Yb (Q-POSS)3
(
λ
ex
= 469 nm, λmonitor = 980 nm), and (C) Er(Q-POSS)3
(λ = 471 nm, λ
= 1536 nm).
ex
monitor
To further investigate the luminescent properties of the Ln(Q-POSS)3 complexes, the complexes
LnQ3 without POSS modification were also prepared to be used as the counterparts of the Ln(Q-POSS)3
complexes. We have measured the excitation spectra (Figure S4, S5, and S6 in Supporting Information)
and emission spectra of the Ln(Q-POSS)3/LnQ3 couples in the solid state under the same condition.
The comparison results of the emission spectra of Ln(Q-POSS)3/LnQ3 (Ln = Nd3+, Yb3+, Er3+)

Molecules 2019, 24, 1253
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are displayed in Figure 4. In comparison with the complexes LnQ3 with unmodified ligand,
the corresponding Ln(Q-POSS)3 (Ln = Er3+, Yb3+, Nd3+) complexes show obviously enhanced
luminescence intensity.
Figure 4. Emission spectra of the Ln(Q-POSS)3/LnQ3 couples. ( ) Nd(Q-POSS)3 and NdQ3
A
(λ = 469 nm), ) Yb(Q-POSS)3 and YbQ3 = 469 nm), and (C) Er(Q-POSS)3 and ErQ3
(
B
(
λ
ex
ex
(λ = 471 nm).
ex
3. Discussion
Ln complexes with emissions in the NIR region such as Nd3+, Yb3+, and Er3+ have been intensely
studied in the past decades on account of their attractive features, such as large stock shift, emission
line spectrum, ideal excitation and emission wavelengths, long fluorescence lifetime, and small external
influence [21
etc. For example, the 1.5
–
23]. They showed special importance in the field of optical amplifier, laser, night vision,
m emission of Er3+ ion has been widely used in the IR laser operating at
µ
eye-safe wavelengths and in the fabrication of optical amplifiers [24]. The 1333 nm emission band of
the Nd3+ ion also occurs at the second window of the optical amplifier. Therefore, it is significant for
improving NIR luminescence of Ln complexes [25].
In this study, POSS modified ligand Q-POSS and unmodified ligand HQ were used to synthesize
a series of Ln complexes. Nd(Q-POSS)3/NdQ3, Yb(Q-POSS)3/YbQ3, and Er(Q-POSS)3/ErQ3 exhibit
similar band location in their excitation spectra (Figure S4, S5, and S6 in Supporting Information,
respectively) and emission spectra (Figure 4), which are related to the 8-hydroxyquinolinate based
excitation and the f–f transitions from the center Ln3+ ions, respectively. But tiny differences between
the emission spectra of the Ln(Q-POSS)3/LnQ3 could still be observed; for example, the shapes of
the peaks of the Nd3+ ion at 1068 nm (4F3/2
→
4I11/2), which may be because that the tiny difference of
the coordination environments differs from the Ln3+ ion when it is coordinated with the ligands of
Q-POSS and Q. What should be noted is that the excitation and emission intensity of the Ln(Q-POSS)3
are higher than that of the LnQ3, which reveals that the introduction of the POSS moiety into the

Molecules 2019, 24, 1253
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ligand could provide better luminescent properties for the resulted complexes. It is believed that the
enhancement of the luminescence intensity is related to the steric-hindrance effects of the POSS moiety
in the ligands. The large volume of the POSS group in the Ln(Q-POSS)3 will decrease the concentration
quenching effect of the corresponding Ln complexes, and suppress undesired excimer formation and
intermolecular aggregation [26].
Another possible factor for the emission intensity enhancement is the change of energy levels of
the ligands, which will affect the energy transfer efficiency from the ligand to the center Ln3+ ion, and,
accordingly, the overall photoluminescence performance. In order to investigate the energy transfer
from the Q-POSS ligands to the lanthanide ions, Gd complex Gd(Q-POSS)3 was prepared and used to
study the triplet energy level of the ligand since Gd has no energy levels below 312 nm (32000 cm−1
)
and it cannot accept energy from the ligands. The phosphorescence spectrum of the Gd(Q-POSS)3
complex (Figure S7 in Supporting Information) at 77 K under UV excitation was obtained. The first
phosphorescence peak occurred at 469 nm; thus, the triplet energy level of the Q-POSS was calculated
to be 21322 cm−1. According to the reported literature, the triplet energy level of GdQ3 was located
at 21830 cm−1
lower than that of the ligand HQ. As there is no conjugation effect between the POSS cage and the core
ligand 8-hydroxyquinoline, the C=N group at 5-position of 8-hydroxyquinoline moiety is ascribed to
[19]. In other words, the triplet energy level of our modified ligand Q-POSS is a bit
−
the reduction of the energy level of the Q-POSS. As shown in Scheme 2, compared with that of the
ligand HQ, the energy level of the Q-POSS is closer to the 4f excited state energy level of the lanthanide
ions (Er3+, Nd3+, Er3+), indicating a possible more efficient energy transfer between the ligand and the
lanthanide ions, thus a better performance in the characteristic emission of lanthanide ions. However,
the difference between the energy levels of the Q-POSS and HQ is not that large, which could also be
verified from the small differences of the absorption peaks originated from the ligands of the Q-POSS
and HQ (246 and 334 nm for Q-POSS and 241 and 317 nm for HQ, respectively); thus, such small
change of electronic energy level can’t be the main cause of the enhanced emission intensity of the
Ln(Q-POSS)3. We believe that the luminescence optimization in the Ln(Q-POSS)3 comes mainly from
the POSS moiety itself.
30
S (HQ)
1
25
ISC
T (HQ)
S1(Q-POSS)
1
T1(Q-POSS)
20
15
10
5
ET
Ex
Ln3+
4F3/2
4I11/2
4I13/2
2F5/2
EM
4I13/2
4I11/2
4I
4I15/2
0
S0
2F7/2
Ln3+
Ligands
9/2
Er
Nd
Yb
Lanthanide
Scheme 2. Schematic energy level diagram of the emissive states of the Ln ions (Ln = Er3+, Nd3+, and
Yb3+) compared with the triplet states of the Q-POSS and 8-hydroxyquinoline (HQ).
In summary, a novel ligand based on 8-hydroxyquinoline derivative modified by POSS has been
synthesized, and a series of molecular hybrid NIR luminescent complexes Ln(Q-POSS)3 (Ln = Er3+
Yb3+, Nd3+) have been prepared. The optical properties of the as-prepared complexes have been
investigated. After ligand-mediated excitation, all of the Ln(Q-POSS)3 (Ln = Er3+, Yb3+, Nd3+)
complexes exhibited the characteristic NIR luminescence of the corresponding lanthanide ions.
,

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Compared with the complexes LnQ3 with unmodified ligand, the corresponding Ln(Q-POSS)3
(Ln = Er3+ Yb3+, Nd3+) have showed enhanced luminescence performances, which is mainly ascribed
,
to the steric-hindrance effects of the POSS on the complexes. It is believed that the POSS modification
will benefit for the preparation of the potential excellent lanthanide-based luminescent materials.
4. Materials and Methods
4.1. Drugs and Reagents
Aminopropylisobutyl POSS (Hybrid Plastics Co., Hattiesburg, MS, USA); 5-formyl-
8-hydroxyquinoline (Shanghai SHUYA Co., Shanghai, China); toluene; methanol; erbium(III)
chloride hexahydrate; ytterbium(III) chloride and neodymium(III) chloride (Aladdin Co., China);
8-hydroxyquinoline (Tianjin Chemical Reagent Research Institute, Tianjin, China); All the chemicals
were analytical grade reagent.
4.2. Instruments
Excitation and emission spectra were measured with an Edinburgh FLSP 920 fluorescence
spectrophotometer. FT-IR spectra were measured within a 4000–400 cm−1 region on an American
BIO-RAD Company model FTS135 infrared spectrophotometer (Philadelphia, PA, USA) with the KBr
1
pellet technique. HNMR spectra were obtained on the Avance III 400MHz. UV–Vis absorption was
recorded on a Shimadzu UV-2550 spectrometer (Kyoto, Japan). The low temperature phosphorescence
spectra of the Gd(Q-POSS)3 complexes were measured on a Hitachi F-4500 spectrophotometer at
liquid nitrogen temperature (77 K). Elemental analysis was carried out on a Vario MICRO cube
Elemental Analyzer. MALDI-TOF mass spectrum was obtained from Bruker microTOF Electro-spray
Mass Spectrometry.
4.3. Synthesis of Aminopropylisobutyl POSS Modified 8-Hydroxyquinoline Hybrid Ligand (Q-POSS)
The 5-formyl-8-hydroxyquinoline and aminopropylisobutyl POSS were dissolved in a suitable
round bottom flask of toluene with a molar ratio of 1:2, and then refluxed for 12 h under stirring in a
◦
nitrogen atmosphere at 90 C. After that, the solvent was distilled off under reduced pressure, yielding
the aminopropylisobutyl POSS modified 8-hydroxyquinoline: yellow solid (Q-POSS) in 53.1% yield
1
(0.95 g). HNMR (CDCl3,
δ, ppm): 9.78 (1H, d, J = 8.5 Hz), 8.83 (1H, d, J = 4.1 Hz), 8.60(1H, d), 7.70 (1H,
d, J = 7.9 Hz), 7.56 (1H, dd), 7.19 (1H, d, J = 8.0 Hz), 3.65 (2H, t,
(42H, m, CH3), 0.74 (2H, m,
1029.73; found, 1029.54. Elemental analysis—calculated: C, 47.8%; H, 7.44%; N, 2.72%. Found: C,
48.1%; H, 7.56%; N, 2.29%.
−
N-CH2−), 1.87 (7H, m, CH ), 0.98
−
−
−
−CH2−), 0.62 (16H, m, Si-CH2−). MS—calculated for C41H76N2O13Si8,
4.4. Synthesis of Ln(Q-POSS)3 (Ln = Er3+, Nd3+, Yb3+) Hybrid Material
The lanthanide trichloride methanol solution was added dropwise to a Q-POSS toluene solution.
The molar ratio of Ln3+/Q-POSS was 1:3. The mixture was heated under reflux at 90 ◦C for 12 h and
then cooled to room temperature. The toluene was evapora◦ted in vacuo, and then those complexes
were washed with cold methanol for 3 times and dried at 100 C under vacuum for 12 h. Nd(Q-POSS)3
in 58.6% yield (0.12 g), Yb(Q-POSS)3 in 53.7% yield (0.11 g), and Er(Q-POSS)3 in 60.7% yield (0.13 g).
Elemental analysis for Yb(Q-POSS)3, calculated: C, 45.3%; H, 6.95%; N, 2.95%. Found: C, 46.4%; H,
6.35%; N, 2.57%; Er(Q-POSS)3, calculated: C, 47.8%; H, 7.35%; N, 2.72%. Found: C, 47.0%; H, 7.21%; N,
2.42%; Nd(Q-POSS)3, calculated: C, 48.2%; H, 7.42%; N, 2.74%. Found: C, 47.5%; H, 7.36%; N, 2.53%.
4.5. Synthesis of the LnQ3 Complexes (Ln = Er3+, Nd3+, Yb3+
)
The synthesis procedure was according to the procedure described in the literature [27].
The lanthanide trichloride methanol solution was added dropwise to 8-hydroxyquinoline (HQ)
methanol solution. The molar ratio of Ln3+/Q was 1:3. Upon addition of the chloride to the quinoline

Molecules 2019, 24, 1253
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solution, the solution became an orange color. The mixture was heated under reflux at 55 ◦C for 10 h
and then cooled to room temperature. After an appropriate amount of water was added, plenty of
precipitates appeared and were collected by filtration and washed with cold methanol. Then these
complexes were dried at 80 ◦C under vacuum for 12 h. NdQ3 in 31.2% yield (0.18 g), ErQ3 in 36.3%
yield (0.22g), YbQ3 in 53.3% yield (0.32g). Elemental analysis for YbQ3, calculated: C, 53.56%; H, 3.00%;
N, 6.94%. Found: C, 51.3%; H, 2.93%; N, 6.29%; ErQ3, calculated: C, 54.1%; H, 3.03%; N, 7.01%. Found:
C, 53.3%; H, 3.03%; N, 6.07%; NdQ3, calculated: C, 56.2%; H, 3.15%; N, 7.29%. Found: C, 53.5%; H,
3.34%; N, 7.12%.
4.6. Synthesis of Gd(Q-POSS)3 Complex
The synthesis procedure was according to the procedure described in the literature [19].
The powder GdCl3 was added to Q-POSS toluene solution with a molar ratio of 1:3 (GdCl3: Q-POSS),
and then the mixture was kept stirring at 90 ◦C for 12 h in a nitrogen atmosphere. The precipitates
were collected by filtration, washed with anhydrous ethanol, and dried at room temperature under
vacuum overnight. Gd(Q-POSS)3 in 40.3% yield (0.25 g).
1
Supplementary Materials: The following are available online, Figure S1: HNMR spectrum of the Q-POSS ligand.
Figure S2: MALDI-TOF mass spectrum of the Q-POSS ligand. Figure S3: UV–Vis absorption spectra of HQ, ErQ3,
−5
NdQ3, and YbQ3 in dichloromethane solutions (1
×
10 M) at room temperature. Figure S4: Excitation spectra
of NdQ3 and Nd(Q-POSS)3 Figure S5: Excitation spectra of YbQ3 and Yb(Q-POSS)3. Figure S6: Excitation spectra
of ErQ and Er(Q-POSS) . Figure S7: Emission spectrum of the Gd(Q-POSS) (λ = 302 nm) complex at 77 K.
ex
3
3
3
Author Contributions: Experiment design, R.D.; experiment implementation, L.Z., Q.Z.; writing—original draft
preparation, R.D., Q.Z. and X.Y.; characterization, L.Z., X.Y., Y.Y. and Y.L.; data analysis, R.D., Q.Z.; manuscript
revision/review, X.Y., R.D., and L.Z.; manuscript final version approval, X.Y., R.D., and L.Z.
Funding: This research was funded by the National Natural Science Foundation of China (No.51502285) and
National Basic Research Program of China (No.21521092).
Acknowledgments: We thank the National Natural Science Foundation of China (No.51502285) and National
Basic Research Program of China (No.21521092) supported this study.
Conflicts of Interest: The authors declare no conflict of interest.
References
1.
Gao, N.; Zhang, Y.F.; Huang, P.C.; Xiang, Z.H.; Wu, F.Y.; Mao, L.Q. Perturbing tandem energy transfer in
luminescent heterobinuclear lanthanide coordination polymer nanoparticles enables real-time monitoring
of release of the anthrax biomarker from bacterial spores. Anal. Chem. 2018, 90, 7004–7011. [CrossRef]
[PubMed]
2.
Kim, H.K.; Baek, N.S.; Oh, J.B.; Ka, J.W.; Roh, S.G.; Kim, Y.H.; Nah, M.K.; Hong, K.S.; Song, B.J.; Zhou, G.J.
Lanthanide(III)-cored supramolecular complexes with light-harvesting dendritic arrays for advanced
photonics applications. J. Nonlinear. Opt. Phys. 2005, 14, 555–564. [CrossRef]
3.
4.
Kim, H.K.; Oh, J.B.; Baek, N.S.; Roh, S.G.; Nah, M.K.; Kim, Y.H. Humidity sensing properties of nanoporous
TiO2-SnO2 ceramic sensors. Bull Korean Chem. Soc. 2005, 26, 201–214. [CrossRef]
Ning, Y.Y.; Liu, Y.W.; Meng, Y.S.; Zhang, J.L. Design of near-infrared luminescent lanthanide complexes
sensitive to environmental stimulus through rationally tuning the secondary coordination sphere.
Inorg. Chem. 2018, 57, 1332–1341. [CrossRef]
5.
6.
7.
Hatanaka, M.; Yabushita, S. Mechanisms of f-f hypersensitive transition intensities of lanthanide trihalide
molecules: A spin-orbit configuration interaction study. Theor. Chem. Acc. 2014, 133, 219–233. [CrossRef]
Imbert, D.; Comby, S.; Chauvin, A.S.; Bunzli, J.C.G. Lanthanide 8-hydroxyquinoline-based podates with
efficient emission in the NIR range. Chem. Commun. 2005, 11, 1432–1434. [CrossRef] [PubMed]
Rizzo, F.; Meinardi, F.; Tubino, R.; Pagliarin, R.; Dellepiane, G.; Papagni, A. Synthesis of 8-hydroxyquinoline
functionalised DO3A ligand and Eu(III) and Er(III) complexes: Luminescence properties. Synth. Met. 2009
159, 356–360. [CrossRef]
,

Molecules 2019, 24, 1253
9 of 10
8.
9.
Sun, L.N.; Dang, S.; Yu, J.B.; Feng, J.; Shi, L.Y.; Zhang, H.J. Near-Infrared Luminescence from
Visible-Light-Sensitized Hybrid Materials Covalently Linked with Tris(8-hydroxyquinolinate)-lanthanide
[Er(III), Nd(III), and Yb(III)] Derivatives. J. Phys. Chem. B. 2010, 114, 16393–16397. [CrossRef]
Pelle, F.; Surble, S.; Serre, C.; Millange, F.; Ferey, G. Enhanced Eu3+ luminescence in a new hybrid material
with an open-framework structure. J. Lumin. 2007, 122, 492–495. [CrossRef]
10. Yan, B.; Zhao, L.M.; Wang, X.L.; Zhao, Y. Sol-gel preparation, microstructure and luminescence of rare
earth/silica/polyacrylamide hybrids through double functionalized covalent Si-O linkage. Rsc. Adv. 2011, 1,
1064–1071. [CrossRef]
11. Solouk, A.; Cousins, B.G.; Mirahmadi, F.; Mirzadeh, H.; Nadoushan, M.R.J.; Shokrgozar, M.A.; Seifalian, A.M.
Biomimetic modified clinical-grade POSS-PCU nanocomposite polymer for bypass graft applications:
A preliminary assessment of endothelial cell adhesion and haemocompatibility. Mat. Sci. Eng. C Mater. 2015
46, 400–408. [CrossRef]
,
12. Liu, L.; Ming, T.; Liang, G.H.; Chen, W.Q.; Zhang, L.Q.; Mark, J.E. Polyhedral oligomeric silsesquioxane (POSS)
particles in a polysiloxane melt and elastomer. Dependence of the dispersion of the POSS on its dissolution
and the constraining effects of a network structure. J. Macromol. Sci. A 2007, 44, 659–664. [CrossRef]
13. Rahimifard, M.; Ziarani, G.M.; Badiei, A.; Yazdian, F. Synthesis of Polyhedral Oligomeric Silsesquioxane
(POSS) with Multifunctional Sulfonamide Groups Through Click Chemistry. J. Inorg. Organomet Polym. Mater.
2017, 27, 1037–1044. [CrossRef]
14. Loh, T.C.; Ng, C.M.; Kumar, R.N.; Ismail, H.; Ahmad, Z. Improvement of thermal ageing and transparency
of methacrylate based poly(siloxane-silsesquioxane) for optoelectronic application. J. Appl. Polym. Sci. 2017
134, 45285. [CrossRef]
,
15. Yang, X.M.; Wang, Y.L.; Li, Y.Y.; Li, Z.P.; Song, T.Y.; Liu, X.J.; Hao, W. Thermal stability and mechanical
properties of hybrid materials based on nitrocellulose grafted by aminopropylisobutyl polyhedral oligomeric
silsesquioxane. Polimery-W 2017, 62, 576–587. [CrossRef]
16. Chen, X.F.; Zhang, P.N.; Wang, T.R.; Li, H.R. The First Europium(II) b- Diketonate Complex Functionalized
Polyhedral Oligomeric Silsesquioxane. Chem. Eur. J. 2014, 20, 2551–2556. [CrossRef] [PubMed]
17. Sun, L.N.; Liu, Y.; Dang, S.; Wang, Z.Y.; Liu, J.L.; Fu, J.F.; Shi, L.Y. Lanthanide complex-functionalized
polyhedral oligomeric silsesquioxane with multicolor emission covered from 450 nm to 1700 nm. New. J.
Chem. 2016, 40, 209–216. [CrossRef]
18. Zhao, Y.L.; Qiu, X.L.; Yu, T.Z.; Shi, Y.L.; Zhang, H.; Xu, Z.X.; Li, J.F. Synthesis and characterization
of 8-hydroxyquinolinolato-iridium(III) complex grafted on polyhedral oligomeric silsesquioxane core.
Inorg. Chim. Acta. 2016, 445, 134–139. [CrossRef]
19. Sun, L.N.; Zhang, H.J.; Yu, J.B.S.; Yu, Y.; Peng, C.Y.; Dang, S.; Guo, X.M.; Feng, J. Near-infrared emission from
novel tris(8-hydroxyquinolinate)lanthanide(III) complexes-functionalized mesoporous SBA-15. Langmuir
2008, 24, 5500–5507. [CrossRef] [PubMed]
20. Ilichev, V.A.; Rozhkov, A.V.; Rumyantcev, R.V.; Fukin, G.K.; Grishin, I.D.; Dmitriev, A.V.; Lypenko, D.A.;
Maltsev, E.I.; Yablonskiy, A.N.; Andreev, B.A.; et al. LMCT facilitated room temperature phosphorescence
and energy transfer in substituted thiophenolates of Gd and Yb. Dalton Trans. 2017, 46, 3041–3050. [CrossRef]
[PubMed]
21. Magennis, S.W.; Ferguson, A.J.; Bryden, T.; Jones, T.S.; Beeby, A.; Samuel, I.D.W. Time-dependence
of erbium(III) tris(8-hydroxyquinolate) near-infrared photoluminescence: Implications for organic
light-emitting diode efficiency. Synth. Met. 2003, 138, 463–469. [CrossRef]
22. Salley, G.M.; Valiente, R.; Gudel, H.U. Cooperative Yb3+-Tb3+ dimer excitations and upconversion in
Cs3Tb2Br9: Yb3+. Phys. Rev. B 2003, 67, 134111. [CrossRef]
23. He, H.S.; Zhao, Z.X.; Wong, W.K.; Li, K.F.; Meng, J.X.; Cheah, K.W. Synthesis, characterization and
near-infrared photoluminescent studies of diethyl malonate appended mono-porphyrinate lanthanide
complexes. Dalton Trans. 2003, 980–986. [CrossRef]
24. Li, Z.F.; Yu, J.B.; Zhou, L.; Zhang, H.J.; Deng, R.P.; Guo, Z.Y. 1.54 mu m near-infrared photoluminescent
and electroluminescent properties of a new Erbium (111) organic complex. Org. Electron. 2008, 9, 487–494.
[CrossRef]
25. Demirbas, U.; Kurt, A.; Sennaroglu, A.; Yilgor, E.; Yilgor, I. Luminescent Nd3+ doped silicone-urea
copolymers. Polymer 2006, 47, 982–990. [CrossRef]

Molecules 2019, 24, 1253
10 of 10
26. Li, J.; Xie, B.; Xia, K.; Zhao, C.M.; Li, Y.C.; Hu, S.L. Enhanced PL and EL properties of Alq3/nano-TiO2 with
the modification of 8-vinyl POSS. Opt. Mater. 2018, 78, 279–284. [CrossRef]
27. Thompson, J.; Blyth, R.I.R.; Gigli, G.; Cingolani, R. Obtaining characteristic 4f-4f luminescence from rare
earth organic chelates. Adv. Funct. Mater. 2004, 14, 979–984. [CrossRef]
Sample Availability: Samples of the synthetic compounds are available from the authors.
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