Visual detection of triethylamine and a dual input/output logic gate based on a EU3+-complex

Article abstract of DOI:10.3390/molecules26113244

A series of Ln³⁺-metal centered complexes, Ln(TTA)3(DPPI) (Ln = La, 1; Ln = Eu, 2; Ln = Tb, 3; or Ln = Gd, 4) [(DPPI = N-(4-(1H-imidazo [4,5-f][1,10]phenanthrolin-2-yl)phenyl)-Nphenylbenzenamine) and (TTA = 2-Thenoyltrifluoroacetone)] have been

Full text of DOI:10.3390/molecules26113244

molecules
Article
Visual Detection of Triethylamine and a Dual Input/Output
3
+
Logic Gate Based on a Eu -Complex
Bao-Ning Li, Yuan-Yuan Liu, Ya-Ping Wang and Mei Pan *
MOE Laboratory of Bioinorganic and Synthetic Chemistry, Lehn Institute of Functional Materials, School of
Chemistry, Sun Yat-sen University, 135 West Xingang Road, Guangzhou 510275, China;
libn7@mail2.sysu.edu.cn (B.-N.L.); liuyy253@mail2.sysu.edu.cn (Y.-Y.L.); yapingwang0393@163.com (Y.-P.W.)
*
Correspondence: panm@mail.sysu.edu.cn
Abstract: A series of Ln3+-metal centered complexes, Ln(TTA) (DPPI) (Ln = La,
1; Ln = Eu,
2;
3
Ln = Tb, 3; or Ln = Gd, 4) [(DPPI = N-(4-(1H-imidazo [4,5-f][1,10]phenanthrolin-2-yl)phenyl)-N-
phenylbenzenamine) and (TTA = 2-Thenoyltrifluoroacetone)] have been synthesized and character-
ized. Among which, the Eu3+-complex shows efficient purity red luminescence in dimethylsulfoxide
(
DMSO) solution, with a Commission International De L’ Eclairage (CIE) coordinate at x = 0.638,
L
y = 0.323 and
Φ
= 38.9%. Interestingly, increasing the amounts of triethylamine (TEA) in the
Eu
solution regulates the energy transfer between the ligand and the Eu3+-metal center, which further
leads to the luminescence color changing from red to white, and then bluish-green depending on the
different excitation wavelengths. Based on this, we have designed the IMPLICATION logic gate for
TEA recognition by applying the amounts of TEA and the excitation wavelengths as the dual input
signal, which makes this Eu3+-complex a promising candidate for TEA-sensing optical sensors.
ꢀ
ꢁꢂꢀꢃꢄꢅꢆꢇ
ꢀ
ꢁꢂꢃꢄꢅꢆ
Keywords: Eu3+-complex; TEA detection; logic gate
Citation: Li, B.-N.; Liu, Y.-Y.; Wang,
Y.-P.; Pan, M. Visual Detection of
Triethylamine and a Dual
Input/Output Logic Gate Based on a
Eu3+-Complex. Molecules 2021, 26,
1. Introduction
Stimulus-response materials, which are new types of intelligent materials, have re-
ceived widespread attention [1–4]. Molecular systems capable of exhibiting color-tunable
luminescence in suitable substrates or under specific acid or base conditions are highly
3
244. https://doi.org/10.3390/
molecules26113244
appreciated, since they favor sensors [
meters, etc. [ ]. Among which, lanthanide-based complexes are of particular interest
owing to their specific luminescent properties, which can be applied in various areas,
such as pure red organic light-emitting diodes [ ], cellular recognition [ ], fluorescence
sensors [ 11], magnetic materials and catalysis [12]. As to the potential applications of
stimulus-responsive luminescent complexes [13 15], there has been an unremitting pursuit
of new organo-Eu3+ complexes to achieve desirable fluorescence responses for micro-
environment detection [16 18]. Owing to the unique f-f radiative transitions, lanthanide
based emitters show sharp and narrow emission bands, which usually have stability to-
wards the surrounding environments [19]. In suitable cases, by regulating the energy of
the ligand and the outer stimulations, the energy transfer between the ligands and the
Ln-metal centers can be controlled, leading the emission to be “Off-On”, or leading to
a change in color and intensity [20], which leads to the emission becoming a favorable
5,6], molecular logic gates and fluorescence ratio
Academic Editor: Elena Cariati
7
Received: 24 April 2021
Accepted: 25 May 2021
Published: 28 May 2021
8
5
9
–
–
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and promising candidate for visual detection [21,22]. Furthermore, the detection of toxic
Copyright: © 2021 by the authors.
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triethylamine (TEA) [23] possesses a direct relevance to the quality of the environment and
our lives and is highly demanding [24]. However, the development of stimuli-responsive
systems that show a wide range of luminescent color changes for sensitive and eye-catching
observations upon TEA stimulations are still worth studying [17,25,26].
Herein, we developed a series of organo-Ln3+ (Ln = La, Eu, Tb, Gd) complexes
coordinated with the donor-acceptor structured DPPI ligand (Scheme 1), which possesses
an ILCT (intra-ligand charge transfer) potential due to the combination of phenanthroline,
4
.0/).
Molecules 2021, 26, 3244. https://doi.org/10.3390/molecules26113244
https://www.mdpi.com/journal/molecules

Molecules 2021, 26, 3244
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3
+
imidazole and triphenylamine groups, which can serve as sensitizers for the Eu -centered
3
+
emission and also stimulation sites for the detection of TEA. As a result, the molecular Eu
-
complex showed good photophysical responses to both TEA concentrations and excitation
wavelengths, and was applied well within the dual input/output logic gate design.
Scheme 1. Reaction procedure for the synthesis of DPPI, and complexes 1–4.
2. Results and Discussion
2.1. Synthesis and Photophysical Properties of the Ln-Complexes
The ligand DPPI was synthesized according to the typical reaction [27], as shown in
Scheme 1. Further into its self-assembly with a deprotonated TTA ligand and LnCl3 6H O
·
2
(
Ln = La, Eu, Tb, or Gd), a series of Ln (TTA) (DPPI) complexes (Ln = La,
1
; Ln = Eu,
2;
3
1
Ln = Tb, 3; or Ln = Gd,
4
) were obtained and well-characterized by EA, FT-IR, H NMR and
ESI-MS, respectively (Figures S1–S5). In particular, the H NMR spectra of complex
1
1 and
−
3+
the DPPI ligand reveals that the TTA ligand and the rare earth ion [Ln ] are in a stipulated
molar ratio of 3:1. In addition, the characteristic proton resonances (δ = 13.68 ppm) of the
typical group ‘-NH’ relative to the DPPI ligand moved 0.11 ppm to the higher field of
complex
effects [28
1 (δ
= 13.59 ppm), due to the coordination of the La3+ ion by the metal-atomic
,29]. Moreover, the ESI-MS spectra of these typically binary tris-
β-diketonate-
3+
Ln -complexes show standard molecular ion peaks at 1288.97, 1302.03, 1308.99, and
1307.32, respectively (Ln = La, 1; Ln = Eu, 2; Ln = Tb, 3; or Ln = Gd, 4) [30–32].
The photophysical properties of the complexes were examined in dilute DMSO so-
lution at RT or 77 K, and are summarized in Figure 1, Figures S6 and S7 and Table S1. In
Figure S6, the similar solution absorption spectra at the ranges of 245–247, 286–288 and
3
25–380 nm of Ln(TTA) (DPPI) (Ln = Eu,
2
; Ln = Tb,
π-π
3
; or Ln = Gd,
* transitions and the intra-ligand charge
transfer (ILCT) bands of the TTA and DPPI ligands, simultaneously [33,34].
4) complexes are
3
1
observed, which were contributed to by the
3+
For complex
2
, the luminescent emission (Figure 1) shows the Eu -centered char-
5
7
acteristic peaks ( D – F , J = 0–4) with the maximum at 612 nm [26], giving the pure
red-light CIE coordinate of (x = 0.638, y = 0.323) and a quantum yield of (
0
J
L
Φ
= 38.9%).
Eu
3+
For complex
emission at 545 nm, while a strong and wide residual emission (λem = 506 nm) assigned
to the DPPI ligand was observed [35]. However, in contrast to complexes and at RT,
complex shows that the 0-0 transition phosphorescence (λem = 519 nm,
was under 77 K (Figure S7), assigned to the (
3, photoexcitation (λex = 406 nm) gave a weak Tb -centered characteristic
2
3
4
τ
= 11.3
µs)
3
−1
π-
π
*) triplet energy level (20198 cm ) of
the ligand. Meanwhile, the (1
the lowest wavelength of the UV-visible edge. As a result, an energy gap of
π
-
π*) singlet energy level (25313 cm ) was obtained by
−1
1
∆
E (
π-
π
*
3
−1 −1
→
π-π* = 5115 cm ) greater than 5000 cm was obtained [36], as shown in Figure S8,
which enabled an effective ISC (intersystem crossing) according to Reinhouldt’s empirical
rule [37]. Furthermore, through the check of the energy level match between the ligand
5
−1
3+
and the first excited state level of D (17286 cm ) of the Eu ion, the suitable energy gap
0

Molecules 2021, 26, 3244
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∆
E of 2912 cm 1 within a 2500–4500 cm range from Latva’s empirical rule confirmed the
− −1
3+
effective sensitization of Eu . However, the triplet energy level of the ligand was lower
than D (20545 cm ) of Tb , and the excessive nonradiative transitions resulted in the
quenching of the Tb -centered effective emission [20]. The Eu -based (λem = 612 nm)
lifetime of
5
−1
3+
3+
4
3+
L
2
was found to be
τ
= 217
µs, and a high overall quantum yield (
Φ
= 38.9%)
obs
Eu
was obtained, further manifesting the efficient energy transfer from the ligand. Noticeably,
the Gd-complex also gave an attractive quantum yield (Φem = 8.9%) of blue light emission
x = 0.211 and y = 0.219) from the organic ligands TTA and DPPI. Moreover, the TG analysis
4
(
◦
of the Ln-complex revealed good thermal stability to be about 300 C (Figure S9).
Figure 1.
(
a
) Emission and excitation spectra of complexes
2
–
4
and DPPI and (
b
) CIE coordinates of complex
2
in DMSO
−
5
solution (10 M) at room temperature (at around λex = 400 nm, and λem = 612 nm for complex
complex 3, λem = 495 nm for complex 4 and DPPI).
2, λem = 545 nm for
2
.2. Adjustable Color Emission of Complex 2 with TEA Stimulate
3+
As shown in Figure 2a,b, the Eu -centered red-luminescence intensity of complex
in a DMSO solution gradually decreased when TEA is added dropwisely. Noticeably,
2
a new broad blue-emission peak (λem = 500 nm) appeared that was dependent on the
different excitations and ranged from 315–420 nm. Near white light emission (x = 0.381,
y = 0.382) was successfully constructed through the two emission color components (red
and bluish green) at the excitation of 385 nm, and the white light emission index parameters
are summarized in Table S2. In addition, the fluorescence photographs record the process of
the emitting color change upon the addition of different amounts of TEA under ultraviolet
light (365 nm), which is shown in Figure S10. As the amounts of TEA increased, the emis-
sion intensity of complex
meanwhile, the blueish green light emission intensity at around 500 nm gradually increased.
When the content of TEA reached 10 L, it is recorded that the intensity of the residual
ligand fluorescence at around 495 nm became the main emission in the whole spectra, and
2 at 613 nm gradually weakened and disappeared (Figure 2c–f);
µ
3+
the Eu -centered emission was very weak and even non-observable.
To probe the origins of the above emission responses, we speculate that as the TEA ra-
tio in the solution increased, the electronic distribution and intra-ligand charge transfer state
between the donor-acceptor groups on the DPPI ligand was changing gradually, accompa-
3+
nying the changes of energy transfer from the DPPI to the Eu metal centers [38]. Basically,
due to the stimulation of TEA, the energy level of DPPI was elevated (Figures S10–S12, as
confirmed by the UV-visible absorption titration tests discussed below), and this caused an
incomplete energy transfer to the Eu3+ center. Furthermore, the energy transfer processes
are sensitive to the excitations. As discussed before, the DPPI ligand absorbs the UV
light by either
π-π* and/or ILCT singlet states. After transitioning to the triplet states via
intersystem crossing (ISC), the energy can be further transferred to the metal centers and
3+
can generate the red Eu -emissions. However, the bluish green emission of the DPPI

Molecules 2021, 26, 3244
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ligand can only be excited by the ILCT spectral region (see Figure 1a)
in the emission spectra of complex
basically only the Eu3+-centered emissions were observed, manifesting that the emission of
the DPPI ligand itself in complex was hampered due to the total energy transfer to the
[
39
,40]. As shown
2
at different excitations without TEA (Figure S13),
2
3+
metal center. After the addition of TEA, both the ligand and the Eu -centered emissions
appeared due to the changes in the ligand electronic states and energy transfer processes
to the Eu3 center. However, according to Figure S14, it is clear that the Eu -centered
+
3+
emission (recorded at 613 nm) can be excited by both the π-π* and ILCT states (show-
ing two excitation peaks), while the ligand-centered emission can only be excited by the
ILCT states (basically only one excitation peak is observed). As a result, the alternative
3+
intensity between the Eu -centered and residual fluorescence of the DPPI ligand can be
tuned by applying different excitation wavelengths in complex after the addition of TEA,
accompanying with various color emissions as a whole (Figure 3).
2
−
5
Figure 2. Emission spectra of complex
) and 10 L TEA (0.1 mM) ( ) dependent on the excitations (λex = 315–425 nm, each interval of
0 nm) at RT. (b,d,f) corresponding CIE graph dependent on the excitations.
2
in DMSO solution (1
×
10 M) stimulated by 2 µL (a), 5 µL
(
1
c
µ
e

Molecules 2021, 26, 3244
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Figure 3. Schematic representation of the energy states and emission processes in the Eu3+-complex with the simulation
of TEA or not. (* excited state; ’ differentiate the energy states before and after added TEA; LC, ligand-centered; MC,
metal-centered; ILCT, intra-ligand charge transfer; S, singlet state; T, triplet state, ET, energy transfer).
As shown in Figures S11–S14, in order to further verify the mechanism of the fluores-
cence changes, the UV-visible absorption titration of 2 upon TEA addition was taken. It can
be seen that the absorbance intensity at 230, 270, 285 and 340 nm was obviously enhanced.
At the same time, comparing the spectra before and after titration, there was a significant
blue shift for the long wavelength absorption peak of nearly 20 nm after the addition of
TEA, which shifted from 369 to 349 nm. For comparison, a red-shift tendency was observed
upon the addition of acetic acid into the DMSO solution of complex 2. Such phenomena
further confirms that the basic-attributed TEA can cause electronic redistribution in the
ligand DPPI, increase its energy levels and regulate the energy transfer from the ligand to
3+
the Eu -metal centers [41].
To further strengthen the reason for the fluorescence alternating processes, dynamic
1
H NMR spectra were performed for complex
1
(Figure S15). The results recorded that
= 13.59 ppm)
were gradually widened or weakened. Meanwhile, the whole chemical shift peaks shifted
slightly, due to the intermolecular forces between the Ln-complexes and TEA [42 43].
with the addition of TEA, the proton resonances of the typical group ‘-NH’ (
δ
,
These observations can be attributed to the unique structure of DPPI with imidazole and
triphenylamine groups, which are sensitive to the micro-environments changed by the
addition of TEA [44–46]. On one hand, TEA provides active hydrogen protons that result
in acid-base interactions; on the other hand, it causes the electronic distribution and energy
state changes in the ILCT-structured DPPI ligand due to molecular interactions [47], and
3
+
leads to the color emission variations and the TEA detecting capabilities of the Eu -
complex [48,49].
2.3. Potential Application in IMPLICATION Logic Gate
As discussed above, by increasing the amounts of TEA into the solution of complex
2
at the same excitation wavelength (λex = 365 nm), the color tunable emission can be
obtained, which can range from a red emission with a CIE chromatic coordinate of (x = 0.638,
y = 0.323), to a white light emission (x = 0.366, y = 0.372), then to a green emission (x = 0.280,
y = 0.420) (Figures 3 and 4). The amounts of TEA may affect the rate and degree of the
molecular interaction between the TEA molecule and the DPPI ligand, further leading
the emission color to change, combined with the results in Figures 2 and 3 and Figures
S11 and S12. This is a key factor in determining the fold of the ratio metric enhancement

Molecules 2021, 26, 3244
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between the two emission peaks at 613 nm and 500 nm of complex
fluorescence intensity for Eu3+ at 613 nm of
2
. The strongest
2
was achieved without the addition of TEA
under λex = 365 nm. With the addition of TEA, the emission intensity at 613 nm decreased,
while the fluorescence intensity at 500 nm assigned to the ligand was gradually enhanced.
The corresponding histograms of ratiometric signals vs. various excitations and TEA values
3
+
are displayed in Figure 4c,d. To this end, the intensity ratio (R = I613/I500) between the Eu
emission at 613 nm and the metal disturbed ligand emission at 500 nm is set as the standard,
with a threshold of 2.5. If the luminescence ratio value is higher than the default threshold,
the ratiometric signals show turn-on. When the ratio is smaller than the threshold, it can
be described as the turn-off state.
Figure 4. Visible emission spectra (
a
), and corresponding CIE graph (
b
) of complex
) corresponding histograms of the fluorescence
L TEA at different excitation. ( ) corresponding histograms
at 613 and 500 nm (R = I500/I613) with different amounts of TEA at λex = 365 nm.
) The IMPLICATION logic gate dependent on the excitation and amounts of TEA as input signals, and the color of the
emission and the ratio intensity as dual output signals.
2 in DMSO solution stimulated by
−
5
different amounts of TEA at 1
intensity ratio (R) of
of the fluorescence intensity ratio (R’) of
×
10 M at RT with the excitation 365 nm. (
at 613 and 500 nm (R = I613/I500) with 2
c
2
µ
d
2
(
e

Molecules 2021, 26, 3244
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It is noted that such color tunable changes of fluorescence intensity are dependent both
on the excitation wavelength and amounts of TEA, which are conducive to the construction
of the logic gate as illustrated in Figure 4e. The following interpretation of two input
modes and two output modes can be applied: for input modes, (a) changing the amounts
of TEA, and (b) changing the excitation wavelengths. In addition, for output modes: (a)
viewing the overall emission color, and (b) detecting the readout ratios for comparing the
relative intensities at 613 and 500 nm. As we can see, with different input signals, the
output 1 signals (overall emission color) can be red, yellowish pink, white, or blueish green,
while the output 2 signals will change from ON (I613/I500 > 2.5) to OFF (I613/I500 < 2.5).
Therefore, we can design a dual-input/dual-output color IMPLICATION logic gate.
3. Experimental Section
3.1. Synthesis of 1,10-Phenanthroline-5,6-Dione (PHD)
The general procedure for the synthesis of PHD followed the methods in the litera-
ture [50]. An ice-cooled mixture solution of 20 mL H SO and 10 mL HNO was added
2
4
3
by (11.0 mmol, 2.0 g) 1,10-phenanthroline and (16.8 mmol, 2.0 g) KBr, stirred at room
◦
temperature for 20 min. After this procedure, the mixture was stirred at 130 C for another
3
h. Then the hot yellow solution was poured into 500 mL of ice water and neutralized
by a saturated Na CO aqueous solution until pH = 7–8. The solution was then extracted
2
3
with CHCl , dried with anhydrous Mg SO and the solvent was removed. There was a
3
2
4
1
yield of 98%. H NMR (400 MHz, DMSO-d ):
δ
9.05 (d, 2H, -pyridyl), 8.56 (d, 2H, -pyridyl),
.84 (t, 2H, -pyridyl). FT-IR (KBr, cm ): 1684 (s), 1560 (m), 1459 (w), 1414 (s), 1313 (w),
293 (s), 1205 (w), 1115 (w), 1010 (w), 925 (w), 807 (m), 736 (vs), 668 (w), 613 (w), 540 (w).
The elemental analysis calculated (%) for C H N O was C, 68.57; H, 2.88; N, 13.33. C,
6
−
1
7
1
1
2
6
2
2
+
+
6
8.49; H, 2.77; N, 13.21. MS (ESI ): m/z: 211.04(100%), [M − H] was found.
3.2. Synthesis of DPPI
The DPPI was synthesized by refluxing a mixture of 1,10-phenanthroline-5,6-dione
(
0,21 g, 1 mmol), 4-(diphenylamino)-benzaldehyde (0.27 g, 1 mmol), NaH PO (0.012 g,
2 4
0
.1 mmol) and ammonium acetate (1.54 g, 20 mmol) in glacial acid (40 mL) for 6 h under a
N atmosphere, according to the literature [51]. After being stirred overnight, the mixture
2
was cooled to room temperature, and then the aiming compound was obtained by the
addition of a K CO solution to the mixture filtration and from washing with enough water.
2
3
The crude product was further extracted by CHCl and vacuum dried. There was a yield
3
1
of 46%. H NMR (400 MHz, DMSO-d ):
δ 13.68 (s, 1H, -NH), 9.04 (d, 2H, -pyridyl), 8.91
6
(
7
d, 2H, -pyridyl), 8.17 (t, 2H, -pyridyl), 7.83 (m, 2H, -phenyl), 7.45–7.36 (m, 4H, -phenyl),
.25–7.07 (m, 8H, -phenyl). FT-IR (KBr, cm ): 3060 (w), 1590(m), 1521 (w), 1480 (s), 1450
−
1
(w), 1397 (w), 1317 (w), 1280 (m), 1190 (w), 1126 (w), 1069 (w), 1029 (w), 952 (w), 840 (w),
8
04 (w), 740 (s), 694 (vs), 636 (w), 619 (w), 530 (w). The elemental analysis calculated (%)
+
for C H N was C, 85.87; H, 5.02; N, 9.10. C, 86.06; H, 5.18; N, 9.37. MS (ESI ): m/z:
25
23
3
+
486.17(100%), [M − H] was found.
3
.3. Synthesis and Characterization of Ln(TTA) (DPPI) (Ln = La, 1; Ln = Eu, 2; Ln = Tb, 3;
3
Ln = Gd, 4)
A solution of 2-Thenoyltrifuoroacetone (HTTA) (0.20 g, 0.9 mmol), and sodium hy-
droxide (0.36 g, 0.9 mmol) was added in 5 mL of mixed solvent (MeOH/chloroform =
3
: 5) and stirred for 30 min. Then DPPI (0.13 g, 0.3 mmol) was added, and then heated
◦
at 50 C for 30 min with stirring. Following this, the solution of LnCl -6H O (0.3 mmol;
3
2
Ln = La, 0.10 g; Ln = Eu, 0.11 g; Ln = Tb, 0.12 g or Ln = Gd, 0.11 g) was dissolved in 2 mL
◦
of MeOH and added dropwise and stirred at 50 C for 12 h. The light yellow product was
◦
isolated by precipitation in ice-cold n-hexane and dried for 24 h in a vacuum oven at 30 C
to obtain a milk-white powder. The detailed process is shown in Scheme 1. The series of
complexes Ln(TTA) (DPPI) (Ln = La,
and well-characterized by EA, FT-IR, H NMR and ESI-MS, respectively.
1
; Ln = Eu,
2
; Ln = Tb,
3; Ln = Gd, 4) were obtained
3
1

Molecules 2021, 26, 3244
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1
For
1
(C H F O N S La), H NMR (400 MHz, DMSO-d ):
δ
13.59 (s, 1H, -NH),
55
33
9
6
5
3
6
9.05–8.91 (t, 4H, -phenyl, and -pyridyl), 8.17 (d, 2H, -phenyl), 7.83 (m, 8H, -phenyl, -thienyl
and -pyridyl), 7.38 (m, 4H, -phenyl, -thienyl and -pyridyl), 7.15–7.12 (m, 11H, -phenyl,
−
1
-
1
9
5
5
thienyl and -pyridyl), 6.17 (s, 3H, -CH=C-). FT-IR (KBr, cm ): 1599 (s), 1536 (s), 1481(m),
454(m), 1411 (s),1355 (w),1298 (vs), 1246 (w),1229 (w), 1186 (s), 1137 (s), 1078 (w), 1061 (w),
33 (w), 859 (w), 842 (w), 786 (m), 767 (w), 718 (w), 696 (m), 680 (w), 640 (m), 604 (w),
79 (m), 520 (w). The elemental analysis (%) calculated for C H F O N S La was C,
55
33
9
6
5 3
+
+
2.18; H, 2.63; N, 5.53. C, 52.21; H, 2.49; N, 5.60. MS (ESI ): m/z: 1288.97(100%), [M + Na]
was found. The yield was 60%.
For
(C H F O N S Eu), FT-IR (KBr, cm 1): 1594 (s), 1537 (s), 1505 (m), 1454 (m),
410 (s),1354 (w),1306 (vs), 1247 (w),1229 (w), 1181(s), 1135 (s), 1076 (w), 1062 (w), 933 (w),
60 (w), 842 (w), 788 (m), 768 (w), 719 (w), 696 (m), 683 (w), 640 (m), 605 (w), 579 (m),
21 (w). The elemental analysis (%) calculated for C H F O N S Eu was C, 51.65; H,
−
2
55
33
9
6
5 3
1
8
5
2
5
5
33
9
6
5 3
+
+
.60; N, 5.48. C, 51.62; H, 2.59; N, 5.46. MS (ESI ): m/z: 1302.05(100%), [M + Na] was
found. The yield was 63%.
For
(C H F O N S Tb), FT-IR (KBr, cm 1): 1594 (s), 1537 (s), 1505 (m), 1454 (m),
410 (s),1354 (w),1306 (vs), 1247 (w),1229 (w), 1181(s), 1135 (s), 1076 (w), 1062 (w), 933 (w),
60 (w), 842 (w), 788 (m), 768 (w), 719 (w), 696 (m), 683 (w), 640 (m), 605 (w), 579 (m),
21 (w). The elemental analysis (%) calculated for C H F O N S Tb was C, 51.37; H,
−
3
55
33
9
6
5 3
1
8
5
2
5
5
33
9
6
5 3
+
+
.59; N, 5.45. C, 51.29; H, 2.52; N, 5.39. MS (ESI ): m/z: 1308.99(100%), [M + Na] was
found. The yield was 65%.
For
(C H F O N S Gd), FT-IR (KBr, cm 1): 1598 (s), 1538 (s), 1480 (m), 1454 (m),
411 (s),1355 (w), 1304 (vs), 1247 (w),1230 (w), 1188 (s), 1137 (s), 1078 (w), 1062 (w), 934 (w),
60 (w), 842 (w), 787 (m), 768 (w), 718 (w), 695 (m), 681 (w), 641 (m), 605 (w), 581 (m),
21 (w). The elemental analysis (%) calculated for C H F O N S Gd was C, 51.44; H,
−
4
55
33
9
6
5 3
1
8
5
2
5
5
33
9
6
5 3
+
+
.59; N, 5.45. C, 51.42; H, 2.53; N, 5.39. MS (ESI ): m/z: 1307.32 (100%), [M + Na] was
found. The yield was 61%.
4
. Conclusions
L
3+
In summary, a purity-red emitter (x = 0.638, y = 0.323;
Φ
= 38.9%) of Eu -complex
Eu
was synthesized, which showed color tunable emissions that ranged from red, white,
to bluish green under the different excitation wavelengths and various amounts of TEA
stimulations. Relying on the changeable color emission, we successfully designed the
dual-input/dual-output logic gate for the visual detection of toxic TEA in a solution, which
expands the research applications of lanthanide Eu3+ luminescent materials.
1
Supplementary Materials: The following are available online. Figure S1 Partial H NMR spectra of
PHD, DPPI and complex 1. Figure S2 FT-IR spectrum of DPPI. Figure S3 FT-IR spectra of complexes
1–4. Figure S4 ESI mass spectrum of DPPI. Figure S5 ESI mass spectrum of complex 2. Figure S6
UV-visible absorption spectra of complexes 2–4, the ligand HTTA and DPPI. Figure S7 Emission and
3
+
excitation spectra of complex 4 at 77 K. Figure S8 Energy transfer process from DPPI ligand to Eu
or Tb3+ in complexes 2–3. Figure S9 TG curves of 2 and DPPI. Figure S10 Fluorescent photographs of
complex 2 under Sunlight and UV light. Figure S11 UV-visible absorption spectra changes of complex
2
. Figure S12 UV-visible absorption spectra changes of complex 2 with the stimulation of acetic acid
−
5
(
0.1 mM) in DMSO solution (10 M) at RT. Figure S13 Emission spectra of complex 2 by different
excitation wavelengths (λex = 290 to 410 nm) in DMSO solution without TEA. Figure S14 Excitation
spectra of complex 2 monitored at 495 nm and 613 nm with the simulation of TEA in solution at
1
room temperature. Figure S15 H NMR (400 MHz, DMSO-d ) of complex 1 with the addition of TEA
6
(
0.1 mM). Table S1 Photophysical properties of complex monomers 2–4, HTTA and DPPI. Table S2
White light emission index parameters.
Author Contributions: Contributions: B.-N.L.; data curation, B.-N.L. and M.P.; formal analysis,
M.P.; funding acquisition, Y.-Y.L. and Y.-P.W.; investigation, B.-N.L.; methodology, M.P.; project
administration, M.P.; supervision, B.-N.L.; Y.-Y.L.; Y.-P.W.; M.P.; validation, B.-N.L.; visualization,
B.-N.L. and M.P.; writing—original draft, B.-N.L. and Y.-Y.L.; writing—review and editing. All
authors have read and agreed to the published version of the manuscript.

Molecules 2021, 26, 3244
9 of 11
Funding: This research was funded by NSFC grant number (21771197, 21720102007, 21821003,
21890380) And Local Innovative and Research Teams Project of Guangdong Pearl River Talents
Program (2017BT01C161), and FRF for the Central Universities.
Institutional Review Board Statement: Not applicable.
Informed Consent Statement: Not applicable.
Data Availability Statement: All data are included in the article.
Conflicts of Interest: The authors declare no conflict of interest.
Sample Availability: Samples of the compounds DPPI and complex
2
are available from the authors.
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