X. Wang, H. Song, C. Fan et al.
Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 250 (2021) 119373
coordinated by white blood cells, causing DNA damage [12], induc-
ing accumulation of tin in the conductor, which is harmful to res-
piratory, nervous and digestive systems [11,12]. On the other hand,
copper plays an important role in the fields of chemical, biological
and environmental systems [13,14]. The transition metal Cu2+ ion
takes part in various fundamental physiological and pathological
processes in biological systems [15–17], such as it acts as a vital
catalytic cofactor for the synthesis of collagen, elastin and hemo-
globin. However, excessive Cu2+ ion in individual body will induce
toxicity, cell death, kidney damage and neurodegenerative dis-
eases, such as Menkes and Wilson’s disease and so on [18–21].
Based on the harmfulness of Cu2+ ions, the World Health Organiza-
tion (WHO) and the United States Environmental Protection
Agency (U.S. EPA) have regulated the permissible concentration
of Cu2+ in drinking water to be 1.0 and 1.3 ppm, respectively
[22,23]. Therefore, the concentration of the Sn2+ and Cu2+ ions in
the living environment or human body have attracted more and
more people’s attention.
-resulted from single crystal X-ray diffraction, 1H NMR, 13C NMR
and HRMS. Its multifunctional properties of the recognition of
Sn2+ and Cu2+ have been studied in deionized water at room tem-
perature. The synthetic procedure of 1a is depicted in Scheme 1.
2. Experimental
2.1. General methods
All reagents were of analytical reagent grade that were
purchased from commercial suppliers. These reagents were used
without further purification during the process of experiment. All
the metal ions are in the form of nitrate, except for Mn2+ and
Hg2 +, K+, Ba2+ in the form of halide. 1H and 13C NMR spectra of
compounds were performed on a Bruker AVANCENEO 500 MHz
FT-NMR spectrometer in DMSO d6 at room temperature with
tetramethylsilane (TMS) as internal norms. Elemental analysis,
low resolution mass spectrum (LRMS) and melting point were car-
ried out on PE CHN 2400 analyzer, AB SCIEX Triple TOF 4600 and
WRS-1B melting point apparatus, respectively. UV–vis spectra
and fluorescence spectra were tested in Agilent 8454 UV/vis spec-
trophotometer and Hitachi F-4500, respectively. FLS 1000 facilities
were used to measure Fluorescence quantum yields and fluores-
cence lifetimes. The single-crystal data of 1a were collected on a
Bruker Smart Apex II CCD diffractometer which equipped with
Due to Sn2+ and Cu2+ ions play the critical roles in environmen-
tal and biological systems, which make us to monitor the concen-
tration by the detection of Sn2+ and Cu2+ ions [24]. The reported
methods for detecting Sn2+ and Cu2+ ions include spectrophotom-
etry, voltammetry, atomic absorption spectroscopy, and atomic
fluorescence spectroscopy [25–28]. However, these reported meth-
ods whether showing interference by some other metal ions, or the
methods mentioned above required more complicated pretreat-
ment process and more sophisticated instrumentation, longer
response time and inferior sensitivity [29]. Therefore, developing
new methods for detecting Sn2+ and Cu2+ ions are urgently dis-
played for us. Fortunately, chemosensors have aroused much
attentions in recent years with the advantages of fast response
time, simplicity, low background, and real-time detection [30].
With the development of the society, more and more fluores-
cent sensors have been used in the fields of chemical analysis for
human beings. Especially, the fluorescent sensors that have
recently attracted increasing attention in the fields of life and envi-
ronmental sciences, were used as special spectra for the detection
of Sn2+ and Cu2+ ions [11,31–34]. For example, Lan et al. investi-
gated a fluorescence sensor for the detection of Sn2+ ions in live
eukaryotic and prokaryotic cells [35]. Xu et al. used the
rhodamine-triazolepyridine derivative as a sensor for the detection
of Sn2+ ions [36]. Pu et al. reported a fluorescent sensor for Sn2+ and
Cu2+ ions based on a diarylethene which contained a carbazole unit
[37]. However, a great number of the reported sensors for detect-
ing Sn2+ or Cu2+ ions either have high limit of detection, or can only
respond to single metal ion. In addition, the reported Sn2+ or Cu2+
ions sensors showed low quantum yield and short lifetime. There-
fore, developing novel sensors capable of simultaneously detecting
Sn2+ and Cu2+ ions becomes an interesting research topic for us.
Lanthanide complexes are favored because of their long life-
time, peak emission, and large Stokes shift [38,39]. In particular,
the excellent optical properties of the lanthanide complexes have
the practical application prospects, which have been widely used
in the fields of fluorescent probes and luminescence bioassays
[34]. The sensors for better application, the fast response and the
feasibility of fluorescence change have attracted many analysts to
research. 1,10-Phenanthroline derivatives has the advantages of
easy to synthesize and quick response to metal ions with obvious
fluorescence change which usually be used as sensors for metal
ions [40]. For example, Satheesh Kumar et al. have synthesized a
novel 1,10-phenanthroline derivative probe for recognizing Zn2+
and Cd2+ ions [41]. However, the sensor based on europium(III)
complexes with a 1,10-phenanthroline ligand for the fluorescent
detection of Sn2+ and Cu2+ has not been reported so far. In this
work, we designed and synthesized one europium(III) complex
with a 1,10-phenanthroline ligand. The structural characterization
graphite-mono-chromatized MoKa radiation at 100(2) K. The crys-
tallographic data were deposited in the Cambridge Crystallo-
graphic Data Center as CCDC No. 2047136.
2.2. Synthesis of ligand L1
3,8-Dibromo-1,10-phenanthroline (0.338 g, 1.0 mmol), phenyl-
boronic acid (0.244 g, 2.0 mmol) and Pd(PPh3)4 (0.050 g) were
added in THF solution. Then, Na2CO3 (3.00 g, 28.0 mmol) was dis-
solved in 15 mL of water, which was added to the mixed solution,
and stirring was continued at 90 °C for 12 h. Then the mixture was
cooled to room temperature, and the THF solvent was evaporated
under vacuum to obtain the resulting solution which was extracted
with dichloromethane. MgSO4 was used to dry over the organic
layer. And the crude product was gotten by filtering and concen-
trating the solvent. At last, the crude product was purified by col-
umn chromatography on SiO2 with dichloromethane and ethanol
as eluent to obtained 0.218 g L1 3,8-dipheny-1,10-phenanthroline
as white solid in 65.7% yield. M.p. 453–454 K. 1H NMR(500 MHz,
DMSO, ppm) d 7.51 (t, 2H, J = 17.5 Hz), 7.61 (t, 4H, J = 20 Hz),
7.99 (d, 4H, J = 25 Hz), 8.11 (s, 2H), 8.81 (d, 2H, J = 15 Hz), 9.46
(d, 2H, J = 20 Hz). 13C NMR (126 MHz, DMSO, ppm) d 127.80,
127.86, 128.94, 128.97, 129.71, 133.78, 134.99, 137.24, 144.90,
149.07. LRMS: m/z = 333.1 [M + H+]+ (calcd 333.1) (Figs. S1–S3).
2.3. Synthesis of europium(III) complex 1a
Under an argon atmosphere, 3.0 mmol tta and 1.0 mmol ligand
L1 were added to a 100 mL three-necked flask, using ethanol as sol-
vent. During the reaction, 1.0 mmol EuCl3Á6H2O in 10 mL ethanol
solution was added dropwise to the mixed solution. Then, 3.0 mmol
triethylamine was added to neutralize pH to 7 under stirring. After
the solution was stirred for 40 min, the mixture was stirred at 60 °C
over the night and then set them to the flask without stirring for
one day. The precipitates were collected by filtration and cleaned
with absolute ethanol for three times. Finally, the precipitates were
kept in vacuum for three days and gained white powder product
(1a) (0.945 g). Yield 82.3%. M.p. 563–564 K. 1H NMR(500 MHz,
DMSO, ppm) d: 3.67 (s, 2H), 6.4 (d, J = 95 Hz, 6H), 7.47 (s, 4H),
7.63 (d, J = 90 Hz, 6H), 7.89–8.21 (m, 6H), 8.83 (s, 2H), 9.47(s,
2