Highly efficient and selective probes based on polycyclic aromatic hydrocarbons with trimethylsilylethynyl groups for fluoride anion detection

Article abstract of DOI:10.1016/j.tet.2015.04.016

Two polycyclic aromatic hydrocarbons bearing trimethylsilylethynyl groups were designed and synthesized as new colorimetric and ratiometric fluorescent probes for fluoride anion. Both probes exhibit high specific selectivity and sensitivity for F^- compared to other anions. When F^- is added to the solution of the probe, the trimethylsilyl substituents can be removed immediately, and the color of the solution changes from yellow to colorless under ambient light. Moreover, test papers based on the probes are prepared, which could be applied to detect F^- in organic phase.

Full text of DOI:10.1016/j.tet.2015.04.016

Accepted Manuscript
Highly efficient and selective probes based on polycyclic aromatic hydrocarbons with
trimethylsilylethynyl groups for fluoride anion detection
Jinyang Hu, Prof. Rui Liu, Xiao Cai, Mingliang Shu, Prof. Hongjun Zhu
PII:
S0040-4020(15)00492-5
10.1016/j.tet.2015.04.016
TET 26619
DOI:
Reference:
To appear in: Tetrahedron
Received Date: 23 January 2015
Revised Date: 24 March 2015
Accepted Date: 7 April 2015
Please cite this article as: Hu J, Liu R, Cai X, Shu M, Zhu H, Highly efficient and selective probes based
on polycyclic aromatic hydrocarbons with trimethylsilylethynyl groups for fluoride anion detection,
Tetrahedron (2015), doi: 10.1016/j.tet.2015.04.016.
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1
ACCEPTED MANUSCRIPT
Tetrahedron
journal homepage: www.elsevier.com
Highly efficient and selective probes based on polycyclic aromatic hydrocarbons with
trimethylsilylethynyl groups for fluoride anion detection
Jinyang Hu , Rui Liu , Xiao Cai, Mingliang Shu, Hongjun Zhu*1
Department of Applied Chemistry, College of Sciences, Nanjing Tech University, Nanjing 211816, China
ARTICLE INFO
ABSTRACT
Article history:
Received
Received in revised form
Accepted
Two polycyclic aromatic hydrocarbons bearing trimethylsilylethynyl groups were designed
and synthesized as new colorimetric and ratiometric fluorescent probes for fluoride anion.
Both probes exhibit high specific selectivity and sensitivity for F- compared to other
anions. When F- is added to the solution of the probe, the trimethylsilyl substituents can be
removed immediately, and the color of the solution changes from yellow to colorless under
ambient light. Moreover, test papers based on the probes are prepared, which could be
applied to detect F- in organic phase.
Available online
Keywords:
Polycyclic aromatic hydrocarbons
Trimethylsilylethynyl group
Fluoride anion probe
Naked-eye detection
2009 Elsevier Ltd. All rights reserved.
1. Introduction
The development of chemosensors to recognize and sense biologically and environmentally important anions has attracted
considerable attention in recent years due to their importance in chemistry and biotechnology.[1−2] Among these anions, fluoride,
having the smallest ionic radius and highest charge density, has arisen as an intriguing target because fluoride plays an essential
role in a broad range of biological, medical, and technological processes.[3] As is well known, fluoride has been used in
preventing dental caries, and treatment of osteoporosis.[4] Nevertheless, excess F− released from a variety of sources can lead to
human pathologies, such as osteoporosis, fluorosis and other diseases.[5-7] Therefore, research on sensitive and selective probes
for F− detection becomes more and more crucial.
Although considerable progress has been made in sensing of F− by using various chemosensors based on hydrogen bonding [8-9]
or Lewis acid coordination[10-11]. The chemodosimeter method,[12-13] which utilizes target anions to induce specific chemical
reactions, received much less attention comparatively. This approach often displays high selectivity when proper fluorophores
and reactive groups are introduced into the probes.[14] To date, several fluorophore-based probes attached trimethylsilylethynyl
groups has been developed to detect F−, such as boron-dipyrromethene (BODIPY) derivatives,[15-16] naphthalene diimide
derivatives[17], and pyrene derivatives.[18] The research results all prove that the fluoride-triggered cleavage of C-Si is a very
promising method for F− detection.
In the past few decades, great attention has been devoted into large polycyclic aromatic hydrocarbons (PAHs), because they
have been widely employed as active layers inorganic electronics and optoelectronics.[19-21] However, the chemosensors based on
PAHs as core structure are very limited, particularly in detecting F−. Only in 2013, Zhang group[22] reported two novel larger
-
azaacenes, which act as an efficient anion probe for the naked-eye detection of F- and H2PO4 through anion-π interactions. To
the best of our knowledge, no PAHs based probes have been used for the F− detection via the fluoride-triggered cleavage of C-Si.
We envision that new probes containing PAHs core and trimethylsilylethynyl groups can recognize F- efficiently and selectively.
———
1 Corresponding author. Prof. Rui Liu; Prof. Hongjun Zhu
E-mail address: rui.liu@njtech.edu.cn (R. Liu); zhuhj@njtech.edu.cn (H.Zhu)

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In this work, we report the design, synthesis and characterization of two novel PAHs based probes, which exhibits high
sensitivity, rapid response and naked-eye recognition for F−. The detection limits for two probes towards F- are 48 nM and 50 nM
in THF, respectively, which are lower than the F- probes reported previously. [10,16,23-35 ]
2. Results and discussion
2.1. Synthesis
4,7-Dibromobenzo[c][1,2,5]-thiadiazole, 3,6-dibromobenzene-1,2-diamine, and 3,6-ditrimethyl-silylethynylbenzene-1,2-
diamine were prepared from the starting material benzene-1,2-diamine according to the literature procedure.[36] Two synthetic
routes were designed and employed to obtain the target compounds. First, PAHs were prepared through the cyclization of
compound 4 with different ketones, and then reacted with trimethylsilylacetylene to afford the compound 1 and 2. However, the
target compounds were obtained in low yields due to the poor solubility of PAHs (33% for 1 and 21% for 2). Secondly, as shown
in Scheme 1, compound 3 was prepared by compound 4 and trimethylsilylacetylene via Sonogashira reaction (55% yield). Then
probes 1 and 2 were synthesized by the cyclization of compound 3 and corresponding ketones in relative high yields (92.8% for
1 and 90.2% for 2).[37] It is also noted that compound 3 was unstable in air and need to be used immediately for the next step
synthesis. The synthesized target compounds were characterized by FT-IR, 1H NMR, 13C NMR, MS and elemental analyses.
Br
Br2 ,HBr
NH2
N
N
SOCl2 ,Et3N
NaBH4
S
S
reflux,2.5h
87%
reflux,24h
95%
N
N
DCM,rt,12h
57%
NH2
Br
5
7
6
O
X
O
X
Si
Si
Br
Br
4
Pd(PPh3)2Cl2,
CuI,TMSA
NH2
NH2
N
X
X
NH2
NH2
N
THF, Et3N
reflux , 24h
75%
EtOH,reflux ,4h
1
:92.8%
2:90.2%
Si
Si
1:X=C
2:X=N
3
Scheme 1 Synthesis of probes1 and 2
2.2. Selectivity studies
The selectivity of probes 1 and 2 towards F- was firstly evaluated by using tetrabutylammonium fluoride (TBAF) as fluoride
-
-
-
source. Various anions including F-, Cl-, Br-, I-, OAc-, H2PO4 , HSO4 and ClO4 were investigated by UV-vis absorption and
fluorescence spectra.[38-39] As shown in Fig. 1, notable changes in the absorption and fluorescence spectra upon the addition of 5
equiv. F- were observed. When F- was added to the solution of 1, the absorption peak blue-shifted, leading to a color changing
from yellow to colorless and could be easily recognized by the naked-eye. Meanwhile, the intensity of original emission at 447
nm decreased and a new emission centered at 427 nm appeared, which resulted in a significant color changing from cyan to blue
under the 365 nm UV-lamp (Fig. 1(c)). In comparison, minor changes were observed in both absorption and fluorescence when
other anions were introduced into the solutions of probes. Again, the highly selective sensing ability of probe 1 for F- could be
-
-
-
demonstrated in the presence of Cl-, Br-, I-, OAc-, H2PO4 , HSO4 and ClO4 (Fig. 1(d)). Namely, the fluorescent response of probe
1 to F- could be hardly interfered by other anions. Most results of probe 2 for recognizing F- are similar with probe 1 except the
absorption peak (λabs = 408 nm), which exhibits 15 nm blue-shift compared to that of probe 1 (ESI, Fig. S9).

3
1.0
0.8
0.6
0.4
0.2
0.0
a
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Blank
-
b
1400
1200
1000
800
600
400
200
0
Blank
Cl
-
Cl
-
Br
-
Br
-
I
-
I
-
AcO
HSO
-
ClO
4
-
4
-
HSO
4
-
H PO
2
4
-
H PO
2
4
-
ClO
4
-
AcO
-
F
-
F
330
360
390
420
450
480
400
500
600
700
800
Wavelength/nm
Wavelength/nm
Competing anions+F-
Competing anions
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0.0
d
H2PO4-
-
Br-
ClO4-
I-
AcO-
Cl-
-
HSO
-
4
Fig. 1 (a).Absorption and (b).fluorescent spectra of probe
1
(1×
10-5 M) in the presence of F- (5 equiv.), Cl-, Br-, I-, CH3COO-, HSO4 , H2PO4 , ClO4- (20 equiv.)
in THF.(c). Color changes observed upon the addition of various anions (20 equiv.) to the solutions of probe
1
(1×
10-5 M) under ambient light and 365 nm UV-
lamp. (d). Fluorescent response of probe
1
(1
×
10-5 M) to F- (5 equiv.) in the presence of various anions (20 equiv.) in THF (
λex=393 nm).
2.3. Response time
To evaluate response time of probe 1 (1×10-5M) towards F- (5 equiv.) by fluorescence method, [34] fluorescence spectra were
recorded in THF at 0-60 seconds after F- was introduced to the probes. As shown in Fig. 2, a saturation of fluorescence intensity
appeared after 10 seconds for probe 1, which is consistent with the response time of the probes containing the CꢀC—SiMe3
groups.[15-18] The interaction between probe 2 and F- was also completed within 10 seconds (ESI, Fig. S10). Moreover, the
response time of the probes attached CꢀC—SiMe3 substituent is much shorter than those probes with Si–O bonds, which
usually exhibits response times in the minutes range . [10,16,23-35 ]
1400
1400
1300
1200
1000
800
600
400
200
0
1200
1100
1000
900
800
0
10
30
50 60
20Time/s40
0-60s
400 450 500 550 600 650 700
Wavelength/nm
Fig. 2. Time-dependent fluorescence spectra of probe
1 (1×
10-5 M) in the presence of 5 equiv. F-.
2.4. Titration experiment
The results of the absorption and fluorescence titrations of probe 1 with F- are shown in Fig. 3.[40] When the concentration of F-
increases, the original bands of absorption and fluorescence display obvious blue-shift. In absorption titration spectra of probe 1
(Fig. 3a), the absorption peaks at 393 and 374 nm gradually decreased and blue-shifted to 386 and 367 nm. The two well-defined
isosbestic points appeared at 389 and 370 nm, indicating the formation of alkyne compound upon treatment of probe 1 with F-.

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[15-18] The results of the fluorescence titrations of probe 1 with F- are shown in Fig. 3b. With the concentration of F- boosting, the
original fluorescent peak at 448 nm decreased gradually while a new fluorescent band centered at 427 nm appeared. The results
obtained were in good agreement with those of UV–vis absorption spectroscopy. In addition, the near-linear correlation curves of
probe 1 at 448 and 427 nm (vs F- concentration in THF) demonstrated that the potential utility of probe 1 for quantitative
determination of F-. The detection limit of probe 1 for F- was about 48 nM (calculated from Fig. 4). Similarly, the detection limit
of probe 2 for F- was evaluated as about 50 nM (ESI, Fig. S12), which is lower than the probes reported in the literatures
previously. [10,16,23-35 ]
1.0
1400
0.96
a
1400
1300
1200
1100
1000
900
b
1200
1000
800
600
400
200
0
0.8
0.6
0.4
0.2
0.0
0.90
0.84
0.78
386 nm
393 nm
427 nm
448 nm
0
1
2
3
4
[F]/[1]
800
0
1
2
3
4
[F]/[1]
400 450 500 550 600 650 700 750 800
330
390 420
3W60avelength/n4m50
480
Wavelength/nm
Fig. 3.Absorption and fluorescent titration spectra of probe
of probe monitored at 386/427 nm (black) and 393/448 nm (red) versus fluoride equiv..
1 (1× λex = 393 nm. Inset: linear correlation curve
10-5 M) in THF upon the addition of F-(0 -4 equiv.),
1
500
400
300
200
100
_
ꢁ I = 153.85C -17.774
F
2
R
= 0.9976
0.5 1.0 1.5 2.0 2.5 3.0
-
-5
10 M
Concentration of F
(
)
Fig. 4. Linear region of fluorescence intensity of probe
1
(10 µM) in THF upon addition of F- (5
‒
30 µM) in THF at λem = 427 nm.
2.5. 1H NMR titration experiment
1H NMR titration experiments in CDCl3 were conducted to look into the nature of the new peak formed in absorption and
fluorescence titration spectra.[41] Fig. 5 depicts the changes in the chemical shifts of probe 1 in the absence and presence of 3
1
equiv. of F-. H NMR spectra of the probe 1 show the complete disappearance of the trimethylsilyl signal at δ = 0.45 ppm and
appearance at δ = 0.0 ppm as the free TMS moieties. Meanwhile, the new peak at 3.44 is originated from the terminal alkyne
protons. A similar observation was reported earlier which confirmed that the shifts in the NMR signals of probe 1 only occurred
due to cleavage of the TMS moieties with F-.[17] In addition, the slight variation of chemical shifts in fluorophore was also
observed. The peaks of δ = 9.465 and δ = 8.57 ppm down-shifted to δ = 9.40 and δ = 8.50 ppm, respectively. Although the
changes in chemical shifts are relatively small, it is enough to demonstrate the progress of the reaction and the mechanism of
probe detecting F-. However, the aryl protons of probe 2 up-shifted from 9.56 and 7.95 ppm to 9.60 and 7.99 ppm respectively,
which could be associated with the introduction of the nitrogen atoms in probe 2 (ESI, Fig. S13).

5
-
Fig. 5. Changes in partial 1H NMR spectra of probe
1
upon addition of F [TBA salt] in CDCl3 solvent, ●
ACCEPTED MANUSCRIPTindicates signals of the TBA salt and THF.
2.6. DFT calculations
To gain insight into the optical response of these probes to F-, compounds 1 and 2 and the corresponding removed TMS species were
examined by density function theory (DFT) calculations at the B3LYP/6-31 G(d) level of the Guassian 09 program.[42] As shown in Fig.
6, for probe 1, the whole probe was almost planar. Both the HOMO and LUMO are distributed at the dibenzo[a,c]phenazine
components due to the electron-donating properties of the trimethylsilylethynyl substituents. The energy of LUMO and HOMO is each
-2.47 and -5.70 eV. Though the HOMO and LUMO are located a total molecular after removing trimethylsilyl species, the energy of
LUMO and HOMO decreases to -2.49 and-5.86 eV, respectively. Furthermore, the energy gap between the HOMO and LUMO of the
deprotonated product is larger than that of probe 1, which is in good agreement with the blue-shift in the absorption and fluorescence
spectra observed upon the treatment of probe 1 with F-.
Fig. 6. Calculated (DFT B3LYP/6-31 G(d)) geometry and HOMO-LUMO energy levels and the interfacial plots of the orbitals for probe
1 and the removed
TMS species .
2.7. Test papers
So far, most of probes reported in literatures have focused on detection for F- in the organic/organic-water phase, which is
inconvenient for achieving real-time monitoring.[43] In order to utilize probe 1 more conveniently, test trips were prepared by
immersing filter papers into THF solution of probe 1 (1× 10-4 M) and then dried in air .The fluorescence image changes of the test
paper under 365 nm UV light in various concentrations of F- are illustrated in Fig. 7, which shows cyan colour when the
concentration of F- is 100 ꢀM. After adding F- on the test paper, the color changing from cyan to blue could be observed clearly
under the 365 nm UV lamp compared with other anions (2 mM). Although the probes cannot detect F− in the aqueous solution,
the test strips of the probes could conveniently sense F- in water-solvent solutions. Obvious color change of the test papers can be
observed when the volume ratio of water to THF is lower than 1:20 (Fig. S15). Consequently, test paper could be potential
employed to detect and estimate the concentration of F- in environment.
Fig. 7. Fluorescence images of test papers after immersing them in THF solutions containing fluoride anions of different concentration.(a) :100 ꢀM (b):10
-
-
ꢀ
M ,From fourth to tenth: Cl-, Br-, I-,OAc-,H2PO4 , HSO4- and ClO4 (excited at 365 nm using a UV lamp).
3. Conclusions
In conclusion, two new simple ratiometric fluorescent probes for F- based on polycyclic aromatic hydrocarbons (PAHs)
containing two trimethylsilylethynyl substituents were designed and synthesized. These probes show high sensitivity, short
response time and high selectivity for F-. The drastic color and fluorescence change upon the addition of F- is attributed to the
1
elimination of the trimethylsilyl substituents through a strong interaction between the F- and Si atoms, which is proved by H
NMR spectra. DFT calculations were conducted to rationalize the optical response of the probes. Both two probes exhibit very
low detection limits, which reach up to 48 nM for probe 1 and 50 nM for probe 2, respectively. Furthermore, test papers have
established the utility of probes in monitoring F- in solutions, indicating its potential application to detect and estimate the
concentration of F-.
4.Experimental
4.1. Materials and methods

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1
All reagents were obtained from commercial suppliers and used without further purification, unless otherwise indicated. H
NMR (400 MHz) and 13C NMR (100 MHz) spectra were recorded in CDCl3-d6 at room temperature using a Bruker Ultra Shield
Plus 400 MHz instrument with reference tetramethylsilane (TMS). Melting points (m.p.) were taken on a Gal-lenkamp apparatus.
FTIR spectra were measured using a Germany Bruker Vertex 80v FT-IR spectrometer by incorporating samples in KBr disks.
High resolution mass (HRMS) analyses were performed at an Auto Spec Premier mass spectrometer (Waters). Optical absorption
spectra were obtained by using a Cary 5000UV/Spectrophotometer (Varian). PL spectra were carried out on a LS-55
spectrofluorometer (Perkin-Elmer). Elemental analyses were performed using a Vario EL cube elemental analyzer.
4.2. General procedure for the synthesis of compound 1 and 2
Synthesis of probe 1: 3,6-ditrimethylsilylethynylbenzene-1,2-diamine(0.30 g, 1 mmol) and phenanthrene-9,10-dione (0.208 g,
1 mmol) were dissolved in ethanol and under reflux condition for 4 h. After cooling to room temperature, the precipitate was
filtrated to get yellow powdery product 1 (0.438 g, 92.8% yield). M.p. 235.3-236.5ꢂ, 1H NMR (CDCl3-d6, 400 MHz) δ = 9.465
(q, J = 4.0 Hz, 2H), 8.57 (d, J = 8.0 Hz, 2H), 7.96 (sꢃ2H), 7.82 (m, J = 4.0 Hz, 2H)ꢃ7.75 (t, J = 8.0 Hz, 2H), 0.45 (s, 18H).13C
NMR (CDCl3-d6, 100 MHz) δ =142.62, 142.11, 133.10, 132.28, 131.78, 129.77, 127.62, 126.44, 123.97, 122.76, 103.29, 101.30,
0.98. ESI-MS m/z: (M+1)+, calcd. for C30H28N2Si2, Exact Mass: 472.18; found :473.1865.Anal. Calcd (%) for C30H28N2Si2, C,
76.22; H, 5.97; N, 5.93; Found: C, 76.25; H, 5.96; N, 5.94.
Probe 2: Yield: 90.2%. M.p. 278.4-279.6ꢂ, 1H NMR (CDCl3-d6, 400 MHz) δ = 9.56 (d, J = 8.0 Hz, 2H), 9.205(d, J = 4.0 Hz,
2H), 7.735 (q, J = 4.0Hz, J = 8.0 Hz,2H), 0.38 (s, 18H). 13C NMR (CDCl3-d6, 100 MHz)δ=152.96, 148.64, 142.28, 140.97,
134.34, 127.31, 124.21, 123.90, 103.99, 100.68, 0.99. ESI-MS m/z: (M+1)+, calcd. for C28H26N4Si2, Exact Mass: 474.17; found
:475.1773. Anal. Calcd (%) for C28H26N4Si2, C, 70.84; H, 5.52; N, 11.80; Found: C, 70.81; H, 5.50; N, 11.83.
Acknowledgements
The authors greatly acknowledge the financial support in part by Natural Science Foundation of Jiangsu Province
(BK20130926), Natural Science Foundation of the Jiangsu Higher Education Institutions of China (13KJB150018), Jiangsu
Planned Projects for Postdoctoral Research Funds (1302089C) and Scientific Research Foundation for the Returned Overseas
Chinese Scholars, State Education Ministry.
Supplementary data1H NMR,13C NMR, MS and FT-IR spectra of probe 1 and 2, UV-vis absorption and fluorescence spectra and
DFT calculations for probe 2 as well as comparison of detection limit with reported probes are provided.
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Supporting information
Highly efficient and selective probes based on polycyclic aromatic hydrocarbons with
trimethylsilylethynyl groups for fluoride ion detection
a
Jinyang Hua , Rui Liu , Xiao Caia, Mingliang Shua, Hongjun Zhu*a
Department of Applied Chemistry, College of Sciences, Nanjing Tech University, Nanjing 211816, China
1. 1H NMR, 13C NMR , MS and FT-IR spectra
Fig. S1. 1H NMR spectrum of probe 1 in CDCl3

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Fig. S2. 1H NMR spectrum of probe 2 in CDCl3
Fig. S3. 13C NMR spectrum of probe 1 in CDCl3

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Fig. S4. 13C NMR spectrum of probe 2 in CDCl3
Fig. S5. Mass spectrum of probe 1
Fig. S6. Mass spectrum of probe 2

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100
80
1623
2158
3075
2976
1505
1359
742
60
860
4000 3500 3000 2500 2000 1500 1000
Wavelength/nm
Fig. S7. FT-IR of probe 1
100
80
60
40
20
1596
1486
2140
3030
2967
624
1341
760
851
4000 3500 3000 2500 2000 1500 1000
Wavelength/nm
Fig. S8. FT-IR of probe 2
2. Selectivity studies for probe 2
1.0
1400
a
0.9
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0.0
b
1200
1000
800
600
400
200
0
390
420
450
480
400
500
600
700
800
Wavelength/nm
Wavelength/nm
Competing anions+F-
Competing anions
d
0.6
0.5
0.4
0.3
0.2
0.1
0.0
H2PO4-
Br-
ClO4-
I-
AcO-
HSO
Cl-
-
4

-
Fig.S9. Fig.1(a)(b).Absorption and fluorescent spectra of probe 2 (1×10-5 M) in the presence of F-(5 equiv.), Cl-, Br-, I-, CH3COO- ,HSO4 , H2PO4- , ClO4-,(20
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equiv.) in THF.(c). Color changes observed upon the addition of various anions (20 equiv.) to the solutions of probe 2 (1×10-5 M) under daylight and hand-held
UV-lamp (365 nm).(d). Fluorescent response of probe 2 (1×10-5 M) to F- (5 equiv.) in the presence of various anions (20 equiv.) in THF (λex=408 nm).
3. Response time for probe 2
1400
1400
1300
1200
1200
1100
1000
1000
800
900
800
0
10 20 30 40 50 60
600
400
200
0
Time/s
0-60s
400
500
600
700
Wavelength/nm
Fig.S10. Fluorescence spectra of probe 2 (1×10-5 M) in the presence of 5 equiv. F-.
4. Titration experiment for probe 2
1.0
1400
1300
1200
1100
1000
900
1.00
427 nm
448 nm
402 nm
408 nm
0.98
0.96
0.94
0.92
0.90
0.88
0.86
0.84
0.82
0.80
0.78
0.76
1400
1200
1000
800
600
400
200
0
0.9
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0.0
0
1
2
3
4
0
1
2
3
4
[F]/[2]
[F]/[2]
360
390
420
450
480
400
500
600
700
Wavelength/nm
Wavelength/nm
Fig.S11. Absorption and fluorescent titration spectra of probe 2 (1×10-5 M) in THF upon the addition of F- (0-4 equiv.).λex = 408nm.
500
_
ꢀ I = 148.98C -0.47937
400
300
200
100
F
2
R
= 0.9897
0.5
1.0
1.5
2.0
2.5
-5
3.0
-
Concentration of F (10 M)
Fig.S12. Linear region of fluorescence intensity of probe 2 (10 µM) in THF upon addition of F- (5 ‒ 30 µM) in THF at λem = 427 nm
The detection limit (DL) of probe 1 for F− were determined from the following equation:
DL = K* Sb1/S
Where K = 2 or 3 (we take 3 in this case); Sb1 is the standard deviation of the blank solution; S is the slope of the calibration
curve. From the graph we get slope = 148.98.Thus using the formula we get the Detection Limit = 50nM.
5. 1H NMR titration experiment for probe
2

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Fig.S13. Changes in partial 1H NMR spectra of probe 2 upon addition of F- in CDCl3 solvent.
6. DFT calculations for probe 2
Fig.14. Calculated (DFT B3LYP/6-31 G(d)) geometry and HOMO-LUMO energy levels and the interfacial plots of the orbitals for probe 2 and the removed
TMS species .
7. Test papers in an organic solvent-water system
Fig.15. Color change of probe 1 on test papers under the 365nm UV lamp after immersion into solutions with different volume ratio of water and THF, and the
concentration of F- is 100 ꢀM.
8. Detection to different fluoride source
Fig.16. Color change of probe 1 in THF solutions after addition of different fluoride salts.
9.Comparison of detection limit with reported probes:
Table S1. Comparison of detection limit and response time of probe 1 and 2 with reported probes.

No.
1
Chemical structure
Solvent(v/v)
Response Ref.
Time
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limit
Ethanol : water =3 : 7
80 ꢀM
50 min
[1]
2
HEPES: CH3CN =7:3
5.4ꢀM
10 min
[2]
Si
O
N
N
NC CN
3
4
HEPES: CH3CN =8:2
210 ꢀM
0.12 ꢀM
60 min
ND
[3]
[4]
DMSO

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5
6
Acetone
0.0674ꢀM
1 ꢀM
ND
[5]
[6]
THF
10 s
7
ACN
6.73 ꢀM
ND
[7]
NC
H
N
O
N
O
8
9
THF
1.86 ꢀM
ND
30s
[8]
[9]
CH2Cl2
0.118 ꢀM
N
N
B
F
F
O
Si
10
11
12
13
CH3CN
DMF-H2O
0.05 ꢀM
0.19ꢀM
0.093 ꢀM
1.21ꢀM
ND
40 min
ND
[10]
[11]
[12]
[13]
CH3CN
CH3CN : H2O=7 :3
ND

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14
15
DMSO:water=1:1
0.01ꢀM
ND
[14]
[15]
THF-Water
THF
0.06ꢀM
10 min
10s
Present
work
0.048ꢀM,
THF
0.05ꢀM
10s
Si
Si
N
N
N
N
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