A reversible fluorescent chemosensor for iron ions based on 1H-imidazo [4,5-b] phenazine derivative

Accepted Manuscript Title: A reversible fluorescent chemosensor for iron ions based on 1H-imidazo [4,5-b] phenazine derivative Author: Guo-ying Gao Wen-juan Qu Bing-bing Shi Qi Lin Hong Yao You-ming zhang Jing Chang Yi Cai Tai-bao wei PII: DOI: Reference:

S0925-4005(15)00251-8 http://dx.doi.org/doi:10.1016/j.snb.2015.02.077 SNB 18141

To appear in:

Sensors and Actuators B

Received date: Revised date: Accepted date:

27-9-2014 19-1-2015 16-2-2015

Please cite this article as: G.-y. Gao, W.-j. Qu, B.-b. Shi, Q. Lin, H. Yao, Y.-m. zhang, J. Chang, Y. Cai, T.-b. wei, A reversible fluorescent chemosensor for iron ions based on 1H-imidazo [4,5-b] phenazine derivative, Sensors and Actuators B: Chemical (2015), http://dx.doi.org/10.1016/j.snb.2015.02.077 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.

A reversible fluorescent chemosensor for iron ions based on 1H-imidazo [4, 5-b] phenazine derivative Guo-ying Gao, Wen-juan Qu, Bing-bing Shi, Qi Lin, Hong Yao, You-ming zhang, Jing Chang,

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Yi Cai, Tai-bao wei*

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------------------------------------------E-mail: [email protected] -------------------------------------------

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Key Laboratory of Eco-Environment-Related Polymer Materials, Ministry of Education of

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China; Key Laboratory of Polymer Materials of Gansu Province; College of Chemistry and

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Chemical Engineering, Northwest Normal University, Lanzhou, Gansu, 730070. P. R. China

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Corresponding author E-mail: [email protected] (Prof. Wei T. B.) Tel: +086 931 7973120; 1

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Abstract: Two kinds of fluorescent sensors (G1 and G2) for Fe3+ bearing 1H-Imidazo [4, 5-b] Phenazine derivatives have been designed and synthesized. G1 can display ON-OFF-type fluorescence charged with high selectivity and sensitivity toward Fe3+

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in DMSO solutions. And other cations, including Hg2+, Ag+, Ca2+, Co2+, Ni2+, Cd2+,

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Pb2+, Zn2+, Cr3+, and Mg2+ had no influence on the probing behavior. The detection limit of the sensor G1 towards Fe3+ is 2.860×10-7 M. Once combined with Fe3+, G1

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displayed high specificity for H2PO4-. Furthermore, in the situ generated G1-Fe3+

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ensemble could recover the enhanced fluorescence upon the addition of H2PO4resulting in an ON-OFF-ON sensing with a detection limit of 1.866×10-7 M in the

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same medium. Notably, this sensor serves as a recyclable component in sensing materials. The reversibility and selectivity of G1/G1+Fe3+ toward Fe3+/ H2PO4− ions as

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a sequence dependent molecular keypad lock using the G1, Fe3+ and H2PO4− as three different chemical inputs. In addition, the test strip based on G1 was fabricated, which

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could act as a convenient and efficient Fe3+ test kit. Keywords: phenazine; iron ion; H2PO4-; fluorescence change; test kit.

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1. Introduction Ferric ion is an essential transition metal ion in the human body involved with the oxygen-transport mechanism and acts as a cofactor in many enzymatic electron

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transfer and oxidation reactions [1]. Deficiency of iron throughout the developmental

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phases may lead to permanent loss of motor skills [2]. While, deposition of iron in the

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central nervous system has been involved in a number of diseases, such as Parkinson’s and Alzheimer’s disease, associated with an increased quantity of iron [3].

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Thereby, it is very important to detect iron ions. Meanwhile, phosphate ions and their derivatives are not only noted for their important roles in signal transduction and

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energy storage in living systems [4] but also responsible for the eutrophication [5]. Accordingly, the development of probes for iron ion has been a subject of intense

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research interest [6-9]. In the last few decades, a number of small molecule based fluorescence chemosensors have been developed and reported in literature [10]. Of all,

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bifunctional probes, which refer to those based on a single host that can independently recognize two guest species with distinct spectra responses by the same or different channels, have already emerged and have gradually become a new research focus in the field of fluorescence sensors [11-16]. Therefore, we expose cation to anion relay recognition of Fe3+ and H2PO4- based on the chemosensor approaches. Phenazine derivatives have been synthesized and been used for organic

electronics for a long time and they are ideal platforms for the development of anion, cation, and neutral molecule recognition, but they have seldom been used in host-guest chemistry. Moreover, among the different fluorogenic units, phenazine is 3

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very sensitive to conformational change. Phenazine-based fluorescent chemosensors are still very scarce, although in principle, well-designed ones should show very good performance [17-21].

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Generally, the structural and geometrical flexibility of metal-ligand complexes

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can provide an excellent way of organizing anion binding groups for optimal

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host-guest interactions, even in the presence of a competitive aqueous solution [22]. Therefore, fluorescent sensors for anions based on metal-ligand complexes have

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appeared particularly attractive for supramolecular chemists because of their simplicity, high sensitivity, and high detection limits for trace chemical detection [23].

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In view of this requirement and as part of our research effort devoted into ion recognition [24-28]. Recently, we reported the cation selective properties of a simple

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phenazine derivative 2-(2-hydroxyphenyl)-1H-imidazo [4, 5-b] phenazine [29]. In continuation of this work, in the present manuscript, we have now developed two

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ensemble system based on 2 - (2-hydroxynaphthyl) - 1H - imidazo [4, 5-b] phenazine (G1) and 2 - naphthyl - 1H - imidazo [4,5-b] phenazine (G2) (Scheme 1) for the selective detection of Fe3+. In order to establish the hydroxy contribution to the sensor’s fluorescent sensing abilities for Fe3+, compound G2, which without

containing the hydroxy was synthesized. Sensor G1 showed fluorescent selectivity for Fe3+ in DMSO solutions over other common physiologically important metal ions. In addition, comparing with 2-(2-hydroxyphenyl)-1H-imidazo [4, 5-b] phenazine, G1 has the larger conjugated system, which results red shift about 10 nm of the fluorescence emission spectrum of G1 that identify with iron ion. As practical applications, we also 4

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utilized the G1 coated test strip for trace detection of Fe3+ and H2PO4- ions which provides a simple, portable and low cost method for the detection of Fe3+ and H2PO4-

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in DMSO solution.

2. Experimental

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2.1. Materials and physical methods

All reagents and solvents were commercially available at analytical grade and

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were used without further purification. 1H NMR spectra were recorded on a

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Mercury-400BB spectrometer at 400 MHz and 13C NMR spectra were recorded on a Mercury-600BB spectrometer at 150 MHz. Chemical shifts are reported in ppm down

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field from tetramethylsilane (TMS, δ scale with solvent resonances as internal standards). The fluorescence spectra were recorded with a Shimadzu RF-5301

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spectrofluorimeter. Melting points were measured on an X-4 digital melting-point apparatus (uncorrected). Infrared spectra were performed on a Digilab FTS-3000

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FT-IR spectrophotometer. Massspectra was recorded on an esquire6000 MS instrument equipped with an electrospray (ESI) ion source and version 3.4 of Bruker Daltonics Data Analysis as the data collection system. 2.2 Synthesis of 2-(2-hydroxynaphthyl)-1H-imidazo [4, 5-b] phenazine (G1) 2, 3-diamino-phenazine was prepared following the reported procedure [30-31]. 2,3-diamino-phenazine (0.42g, 2.0mmol), 2-hydroxyl-1-naphthaldehyde (0.38g, 2.2mmol) and catalytic amount of acetic acid (AcOH) were combined in hot absolute DMF (20 mL) (Scheme 1). The solution was stirred under reflux conditions for 8 hours, after cooling to room temperature, the brown precipitate was filtrated, washed 5

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with hot absolute ethanol three times, then recrystallized with DMF-H2O to get brown powdery product G1. The other compound G2 was prepared by similar procedures. G1: yield: 43%; m.p. >300℃; 1H NMR (DMSO-d6, 600 MHz) δ 13.11 (s 1H,

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NH), δ 11.59 (s 1H, OH), δ 8.53 (d 1H ArH), 8.51~8.28 (m 2H, ArH) 8.27~8.09 (m

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4H, ArH) 8.07 (m 1H, ArH) 7.97~7.91 (m 4H, ArH). 13C NMR (DMSO-d6, 150 MHz) δ 158.17, 156.47, 141.80, 139.92, 133.29, 132.15, 129.63, 128.96, 128.46, 127.93,

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127.77, 124.35, 123.54, 118.43, 107.86. IR (KBr, cm-1) v: 3404.70 (O-H), 3052.32

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(N-H), 1661.20 (C=N), 1613.04 (Ar, C=C), 1528.76 (Ar, C=C), 1488.12 (Ar, C=C). ESI-MS m/z: (M+H)+ Calcd for C23H14N4O 363.1; Found 363.1; Anal. Calcd. for

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C23H14N4O: C 76.23, H 3.89, N 15.46; Found C 76.20, H 3.86, N 15.50.

phenazine (G2).

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The same method is used for the synthesis of 2-naphthyl-1H-imidazo [4, 5-b]

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G2: yield: 75%; m.p.>300
; 1H NMR (DMSO-d6, 600 MHz) δ 13.49 (s 1H), δ

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9.33 (s 1H), 9.31~8.65 (d 2H), 8.32~8.26 (d 4H), 8.24~8.14 (d 2H), 8.12~7.90 (d 4H). 13

C NMR (DMSO-d6, 150 MHz) δ 159.94, 148.96, 141.97, 141.67, 140.23, 139.81,

139.74, 133.61, 131.92, 130.47, 129.89, 129.53, 129.26, 129.05, 128.84, 128.61, 127.66, 126.62, 126.17, 125.99, 125.27, 115.25, 105.91; IR (KBr, cm-1) v: 3208 (NH),

1650 (C=N); ESI-MS m/z: (M+H)+ Calcd for C23H14N4 347.1; Found 347.1; Anal. Calcd. For C23H14N4: C 79.75; H 4.07; N 16.17; Found C 79.70; H, 4.05; N, 16.18. Scheme 1 2.3. General procedure for fluorescence experiments All fluorescence spectra were recorded on a Shimadzu RF–5301 fluorescence 6

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spectrometer after the addition of perchlorate metal salts in DMSO, while keeping the ligand concentration constant (2.0×10-5M). The excitation wavelength was 445 nm. Solutions of metal ions were prepared from the perchlorate salts of Fe3+, Hg2+, Ag+,

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Ca2+ , Co2+, Ni2+, Cd2+, Pb2+, Zn2+, Cr3+, and Mg2+.

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2.4 General procedure for 1H NMR experiments

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For 1H NMR titrations, one stock solution was prepared in DMSO-d6 which containing the sensor only. Aliquots of the solution were mixed directly in NMR

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tubes.

3. Results and discussion

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The recognition profiles of compound G1 and G2 were investigated by measuring the fluorescence emission spectra against different metal ions (Fe3+, Hg2+, Ag+, Ca2+,

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Co2+, Ni2+, Cd2+, Pb2+, Zn2+, Cr3+, and Mg2+) in DMSO solution. As shown in Fig. 1, in the fluorescence spectrum, the emission of G1 appeared at the maximum emission

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wavelength was 540 nm in DMSO solution when excited at λex=445 nm. When 20 equivalents of Fe3+ (4×10-4M) was added to the DMSO solution of sensor G1,

dramatic fluorescent quenching was observed, the apparent fluorescence emission color change from light green to colorless could be distinguished by naked-eyes through UV lamp.

Fig. 1 To validate the selectivity of sensor G1, the same tests were also applied using Hg2+, Ag+, Ca2+, Co2+, Ni2+, Cd2+, Pb2+, Zn2+, Cr3+, and Mg2+ ions, Fig. 2 and Fig. S1 shows clearly a very little change in fluorescence intensity resulted by the addition of different metal ions in case of Fe3+. These data explicitly showed the selectivity of 7

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compound G1 toward Fe3+ (λex= 445 nm and λem= 540 nm). Fig. 2 The same tests were applied to G2 as shown in Fig. 3. In this case, when various

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cations (Fe3+, Hg2+, Ag+, Ca2+, Co2+, Ni2+, Cd2+, Pb2+, Zn2+, Cr3+, and Mg2+) were

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added to the DMSO solutions of G2, no obvious changes were observed. In corresponding fluorescent spectrum of G2, there is no selectivity for the recognition of

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Fig. 3

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Fe3+, which indicated that G2 couldn’t sense selectively Fe3+ under these conditions.

Therefore, according to these results we can find that the hydroxyl group acted as

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a functional group and played a crucial role in the process of colorimetric recognition. The sensor G1 employs hydroxyl group as functional group, which possess fluorescent

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response abilities for Fe3+. At the same time, because the G2 has no hydroxyl unit as functional group, it has no fluorescent capability to fluorescent recognize any cations.

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To further evaluate the Fe3+-responsive nature of G1, fluorescence titration with

Fe3+ in varying concentrations was conducted. As shown in Fig. 4, the addition of

increasing concentrations of Fe3+, the emission peak at 540 nm gradually diminished intensity, and the fluorescence of G1 was essentially quenched by 2.0 equiv. of Fe3+ ion. The fluorescence quantum yield (Φ) of sensor G1 in DMSO is 0.69, whereas it

drops 0.02 when sensor G1 reacts with Fe3+. Moreover, the association constant (Ka) for G1with Fe3+ was found to be 1.47×104 M−1, obtained by a nonlinear curve fitting of the fluorescence titration results (Fig. S2, Supporting Information). And the detection limit of the G1 for the determination of Fe3+ was estimated to be 8

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2.860×10−7M (Fig. S3). Simultaneously, which point to the high detection sensitivity. With such a high selectivity and sensitivity, G1 could serve as a fluorescent sensor for

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Fe3+ (see supporting information). Fig. 4

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Achieving high selectivity for the analyte of interest over a complex background

of potentially competing species is a challenging task in sensor development. Fig. 5

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illustrates the fluorescence response of compound G1 to Fe3+ in the presence of other

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metal ions (Hg2+, Ag+, Ca2+, Co2+, Ni2+, Cd2+, Pb2+, Zn2+, Cr3+, and Mg2+) in DMSO solution. A background of most selected metals does not interfere with Fe3+

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coordination to G1. In the presence of these cations, the Fe3+ still produced similar emission changes. These results show that the selectivity of sensor G1 toward Fe3+

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was no influence in the presence of other cations and suggest that it could be used as a

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fluorescent chemosensor for Fe3+ in DMSO solution. Fig. 5

Corresponding, the X-ray diffraction (XRD) of G1 was determined. We obtained

a d-spacing of 3.50Å by 2θ =25.5°, it suggested that it was π-π stacking between aromatic nucleus. (Fig. S4)

The recognition profiles of chemosensor G1-Fe3+ (15 equiv.) toward various

anions, H2PO4−, F−, Cl−, Br−, I−, AcO−, HSO4−, ClO4−, CN−, were primarily investigated by Fluorescence spectroscopy in DMSO solution. The completely quenched fluorescence of G1 in DMSO solutions by Fe3+ was turned on after addition of H2PO4-. To evaluate the dihydrogen phosphate ion -selective nature of G1-Fe3+ 9

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complex, the influence of other anions such as F-, Cl-, Br-, I-, AcO-, HSO4-, ClO4-, CNwas investigated and interestingly, no significant change in fluorescence emission was observed with other anions. These results suggested that probe G1 displayed an

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excellent selectivity toward Fe3+ in DMSO solution, and the resulting G1-Fe3+ system

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showed high selectivity for H2PO4- in the same media as well (Fig. 6). Fig. 6

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The addition of H2PO4- to the G1-Fe3+ complex shows that the process of titrating

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sensor G1 with Fe3+ is reversible, and the reversible process could be repeated at several times (Fig. 7).

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Fig. 7

Because the optical signal changes relied on the chemical reaction between G1

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and Fe3+, G1-Fe3+ and H2PO4-, the reaction rate might affect the experimental results. We investigated the influence of the reaction time on the sensing results, with the

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obtained results summarized in Fig. 8 and 9. When the concentration of Fe3+ was 2.0

equiv of G1 and H2PO4- was 23 equiv of G1-Fe3+, a plateau of fluorescent intensity could be achieved after 20 min and 3 s, respectively. So, in the titration experiment, we measured the optical intensity changes of the G1 solutions 20 min later after Fe3+ were added and the G1-Fe3+ solutions 3 s later after H2PO4- were added. Fig.8, Fig. 9 At the same time, fluorescence emission spectral variation of sensor G1-Fe3+ in

DMSO solution was monitored during titration with different concentrations of H2PO4− from 0 to 28 equiv. As shown in Fig. 10, the addition of increasing 10

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concentrations of H2PO4−, the emission peak at 540 nm gradually enhanced intensity and the fluorescence of G1-Fe3+ was essentially quenched by 23 equiv. of H2PO4− ion. The detection limit of the G1-Fe3+ for the determination of H2PO4− was estimated to

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be 1.866×10−7 M (Fig. S5) pointing to the high detection sensitivity. With such a high

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selectivity and sensitivity, G1-Fe3+ could serve as a fluorescent sensor for H2PO4−. Fig. 10

H NMR (Fig. S6; Fig. S7) and 13C NMR (Fig. S8; Fig. S9) spectra were further

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1

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confirmed that the structure of G1 and G2. In good agreement with this finding, the product G1, G2, G1 with Fe3+ and G1-Fe3+ with H2PO4- was subjected to mass spectral

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analyses. The ion peaks were detected at m/z 363.1 (Fig. S10) and 347.1 (Fig. S11), which are corresponding to [G1+H]+ and [G2+H]+. The ion peak at m/z 778.1

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demonstrated the presence of [2G1+Fe3+] (Fig. S12). The peak at m/z 363.1

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demonstrated the presence of [A+H]+ (Fig. S13). The A was indicated G1 as a final

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product after TBAH2PO4 were added to the solution of G1-Fe3+. Based on the above findings, we propose that the reaction mechanism in this system may proceed through the route depicted in Scheme 2: The presence of Fe3+ leads to the formation of

2G1+Fe3+, which is then converted to a structural change, the phenol O-H of G1 appeared tautomerism to C=O [32], producing the MS signals at m/z 778.1 showing the formation of a 2:1 bonding mode between G1 and Fe3+ ion. After TBAH2PO4 were added to the solution of G1-Fe3+, G1-Fe3+ complex was decomposed and inorganic iron phosphate was formed. Scheme 2 11

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To establish the selectivity of G1 toward Fe3+ and H2PO4− over a range of various solvents ((CH3)2CO, CH3CN, DMF, CH3CH2OH, CH3OH, CH3COOCH2CH3, CH2Cl2, CHCl3, THF), we carried out the parallel reaction recognition studies where the other

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solvents were used in same concentrations (Table 1, Fig. S14), no obvious changes

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were observed. In corresponding different solvents of G1, there is no selectivity for

the recognition of Fe3+ and H2PO4−. Therefore, the receptor G1 only displayed

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ON-OFF-ON type fluorescence charged with high selectivity toward Fe3+ and H2PO4−

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in DMSO medium. Table 1

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The reversibility and selectivity of G1/G1+Fe3+ toward Fe3+/H2PO4− ions prompted us to consider the present system as a sequence dependent molecular

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keypad lock using the G1, Fe3+ and H2PO4− as three different chemical inputs. These chemical inputs designated as ‘G’, ‘I’, and ‘P’, respectively. Among the possible six

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input combinations, PGI, IGP, IPG, PIG, GPI and GIP, the combination GIP gave maximum fluorogenic output, whereas minimum output signaling was displayed by PIG (Fig. 11). The keypad contains various keys, like that in the electronic keypad (containing A to Z) and follows correct password order (GIP). Fig. 11

To investigate the practical application of chemosensor G1, test strips were prepared by immersing filter papers into a DMSO solution of G1 (2×10−5 mol/L) and then drying in air. The test strips containing G1 was utilized to sense Fe3+ first. As shown in Fig.12, when Fe3+ (2×10−5 mol/L) were added on the test kits, the obvious 12

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color change from light green to colorless was observed under the 365 nm UV lamp. The same procedures were done for H2PO4- and different anions. The colorless of the test strips turn to light green when the H2PO4- (2×10−5 mol/L) were added. The

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immersion of these test strips in the solution mixture of other anions (2.0×10-5 mol/L),

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did not cause any color change. Therefore, the test strips could conveniently detect

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4. Conclusion

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Fe3+ and H2PO4- in DMSO solutions.

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We have constructed a fluorescent sensor 1H-imidazo [4, 5-b] Phenazine

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derivatives G1 or G2 for sequential recognition of two ions (Fe3+ and H2PO4-) based on the displacement approach. The sensor G1 displayed high selectivity and sensitivity

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for iron ions in DMSO solution. The presence of Fe3+ leads to the formation of

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2G1+Fe3+, which is then converted to a structural change, the phenol O-H of G1

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appeared tautomerism to C=O, and the fluorescence quenching. Consequently, the product of the G1-Fe3+ ensemble was an excellent indicator for H2PO4- over other

common ions in the same media without interference, constituting an ON-OFF-ON type fluorescence recognition system. In addition, test strips were prepared by immersing filter papers (3×1 cm2) into the DMSO solution of G1 which exhibits a

good selectivity to Fe3+ and H2PO4-. The present approach can be further extended to yield a new class of chemosensors with potential applications.

Acknowledgment This work was supported by the National Natural Science Foundation of China (No. 21064006, 21262032 and 21161018), the Program for Changjiang Scholars and 13

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Innovative Research Team in University of Ministry of Education of China (No. IRT1177), the Natural Science Foundation of Gansu Province (No. 1010RJZA018), the

Youth

Foundation

of

Gansu

Province

(No.

and

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NWNU-LKQN-11-32.

2011GS04735)

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Monatshefte fÜr Chemie, 130 (1999) 1217-1225. [22] E. J. O’Neil, B. D. Smith, Anion recognition using dimetallic coordination complexes, Coord. Chem. Rev. 250 (2006) 3068-3080.

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[23] A. W. Czarnik, Fluorescent Chemosensors for Ion and Molecule Recognition;

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American Chemical Society: Washington, DC, 1993

[24] T. B. Wei, P. Zhang, B. B. Shi, P. Chen, Q. Lin, J. Liu, Y. M. Zhang, A highly

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selective chemosen sor for colorimet ric detection of Fe3+ and fluorescence turn-on

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response of Zn2+, Dyes and Pigments 97 (2013) 297-302.

[25] Q. Lin; P. Chen; J. Liu; Y. P. Fu; Y. M. Zhang and T. B. Wei, Colorimetric

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chemosensor and test kit for detection copper (II) cations in aqueous solution with specific selectivity and high sensitivity, Dyes. Pigm. 98 (2013) 100-105.

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[26] Y. M. Zhang, B. B. Shi, P. Zhang, P. Chen, Q. Lin, T. B. Wei, A highly selective

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dual-channel Hg2+ chemosensor based on an easy to prepare double naphthalene

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Schiff base, Science China Chemisty 56 (2013) 612-618. [27] B. B. Shi, Y. M. Zhang, T. B. Wei, Q. Lin, H. Yao, P. Zhang, X. M. You, A fluorescent and colorimetric chemosensor for dihydrogen phosphate ions based on 2-pyridine-1H-imidazo [4, 5-b] phenazine-zinc ensemble, Sensors and Actuators B 190 (2014) 555-561.

[28] T. B. Wei, J. Liu, H. Yao, Q. Lin, Y. Q Xie, B. B. Shi, P. Zhang, X. M. You, Y. M. Zhang, Selective Chemosensor of Fe3+ Based on Fluorescence Quenching by 2, 2′-Bisbenzimidazole Derivative in Aqueous Media, Chinese Journal of Chemistry 31 (2013) 515-519. 18

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[29] G. Y. Gao, W. J. Qu, B. B. Shi, P. Zhang, Q. Lin, H. Yao, W. L. Yang, Y. M. Zhang, T. B. Wei, A highly selective fluorescent chemosensor for iron ion based on 1H-imidazo [4,5-b] phenazine derivative, Spectrochimica Acta Part A: Molecular and

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Biomolecular Spectroscopy 121 (2014) 514-519.

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[30] A. B. Korzhenevskii, L. V. Markova, S. V. Efimova, O. I. Koifman, E. V. Krylova,

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Metal Complexes of a Hexameric Network Tetrapyrazinoporpyrazine: I. Synthesis and Identification, Russian Journal of General Chemistry 75 (2005) 980-984.

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[31] A. M. Amer1, A. A. Bahnasawi1, M. R. H. Mahran, M. Lapib, On the Synthesis of Pyrazino [2, 3-b] phenazine and 1H-Imidazo [4, 5-b] phenazine Derivatives

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Monatshefte fÜr Chemie, 130 (1999) 1217-1225.

[32] K. Benelhadj, J. Massue, P. Retailleau, G. Ulrich, R. Ziessel, 2-

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(2ˊ-Hydroxyphenyl) benzimidazole and 9,10-Phenanthroimidazole Chelates and

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Borate Complexes: Solution-and Solid-State Emitters, Org. Lett. 15(2013) 2918-2921.

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Biographies TaiBao Wei is a professor of Key Laboratory of Eco-Environment-Related Polymer Materials, Ministry of Education of China; Key Laboratory of Polymer Materials of

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Gansu Province; College of Chemistry and Chemical Engineering,; Department of

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Chemistry, Northwest Normal University, China.

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GuoYing Gao is currently a graduate student in Northwest Normal University. Her major is organic chemistry.

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WenJuan Qu is currently a graduate student in Northwest Normal University. Her major is inorganic chemistry.

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Qi Lin is an associate professor of Department of Chemistry, Northwest Normal University, China.

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Hong Yao is currently a PhD in Northwest Normal University, China. Her research interests focus mainly on supramolecular chemistry.

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YouMing Zhang is a professor of Key Laboratory of Eco-Environment-Related

Polymer Materials, Ministry of Education of China; Key Laboratory of Polymer Materials of Gansu Province; College of Chemistry and Chemical Engineering,; Department of Chemistry, Northwest Normal University, China.

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List of Figures, Table and schemes: Fig. 1 Fluorescence spectra of G1 (20μM) upon an excitation at 445 nm in DMSO in the presence of Fe3+ (20 equiv.). Inset: photograph from left to right shows the change in the fluorescence of G1,

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G1+Fe3+ (20 equiv.) in DMSO.

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Fig. 2 Visual fluorescence emissions of sensor G1 after the addition of Fe3+, Hg2+, Ag+, Ca2+, Co2+,

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Ni2+, Cd2+, Pb2+, Zn2+, Cr3+ and Mg2+ (20 equiv.) in DMSO on excitation at 365 nm using UV lamp at room temperature.

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Fig. 3 Fluorescence emission data for G2 (20μM) and different metal ions (20 equiv.): 1)only G2, 2) Fe3+, 3) Hg2+, 4) Ag+, 5) Ca2+, 6) Co2+, 7) Ni2+, 8) Cd2+, 9) Pb2+, 10) Zn2+, 11) Cr3+ and 12) Mg2+;

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as their perchlorate salts, in DMSO solution. (excitation wavelength = 445 nm). Fig. 4 (a) Fluorescence spectra of G1 (20μM) in the presence of different concentration of Fe3+

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(0-2.48 equiv.) in DMSO. (b) Fluorescence change at 540 nm as a function of Fe3+ ions.

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Fig. 5 Fluorescence intensity changes of the G1 (20μM) to Fe3+ (20 equiv.) in the presence of

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various test cations (20 equiv.) in DMSO solution. Key: left to right, (1) only G1, G1+Fe3+, (2)

G1+Hg2+, G1+Fe3++Hg2+, (3) G1+Ag+, G1+Fe3++Ag+, (4) G1+Ca2+, G1+Fe3++Ca2+, (5) G1+Co2+, G1+Fe3++Co2+, (6) G1+Ni2+, G1+Fe3++Ni2+, (7) G1+Cd2+, G1+Fe3++Cd2+, (8) G1+Pb2+, G1+Fe3++Pb2+, (9) G1+Zn2+, G1+Fe3++Zn2+, (10) G1+Cr3+, G1+Fe3++Cr3+, (11) G1+Mg2+, G1+Fe3++Mg2+.

Fig. 6 (a)Fluorescence changes of G1-Fe3+ (20μM) system in the presence of various anions (20equiv.) for F-, Cl-, Br-, I−, AcO−, H2PO4−, HSO4-, ClO4-, CN- in DMSO solution. (excitation wavelength = 445 nm). (b) Visual fluorescence emissions of sensor G1-Fe3+ after the addition of F-, Cl-, Br-, I−, AcO−, H2PO4−, HSO4-, ClO4-, CN- (20 equiv.) in DMSO on excitation at 365 nm 21

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using UV lamp at room temperature. Fig. 7 Emission spectra showing the reversible complexation between G1 and Fe3+ (20.0 equiv.) by introduction of H2PO4- (50.0 equiv.).

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Fig. 8 Time-dependent of G1 (20μM) upon addition of Fe3+ in DMSO. Fluorescence intensity

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changes: each spectrum was recorded after 0, 2, 4, 6, 8, 10, 12, 14, 16, 18, 20, 22 and 23 min. Inset shows a plot of fluorescence intensity that is estimated as the peak height at 540 nm.

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Fig. 9 Time-dependent of G1-Fe3+ (20μM) upon addition of H2PO4- in DMSO. Fluorescence

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intensity changes: each spectrum was recorded after 0, 1, 2, 3, 4, 5 and 6 s. Inset shows a plot of fluorescence intensity that is estimated as the peak height at 540 nm.

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Fig. 10 Fluorescence spectra of G1-Fe3+ (20μM) in the presence of different concentration of H2PO4- (0-28 equiv.) in DMSO solution. Inset shows fluorescence change at 540 nm as a function

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of H2PO4- ions.

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Table 1 ON-OFF-ON type fluorescence charge of G1 (20μM) with Fe3+ and H2PO4- (20 equiv.) in

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different solvents (λex= 445 nm).

Fig. 11 Output for G1, corresponding to six possible input combinations at 543 nm. Inset shows a

molecular keypad lock generating emission at 543 nm when a correct password, namely, GIP, is entered keys G, I, and P hold the relevant inputs G1, Fe3+, and H2PO4-, respectively. Fig.12 Photographs of G1 and G1-Fe3+ on test papers after immersion into DMSO solution. Left to

right: (1) only G1, (2) G1 with Fe3+, (3) G1-Fe3+ with H2PO4- under irradiation at 365 nm on UV lamp. Scheme 1 Synthetic procedures for sensor G1 and G2 Scheme 2 The proposed structures of G1 for Fe3+ and G1-Fe3+ for H2PO4− anions. 22

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Figures, Table and schemes:

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Fig. 1 Fluorescence spectra of G1 (20μM) upon an excitation at 445 nm in DMSO in the presence

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G1+Fe3+ (20 equiv.) in DMSO.

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of Fe3+ (20 equiv.). Inset: photograph from left to right shows the change in the fluorescence of G1,

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Fig. 2 Visual fluorescence emissions of sensor G1 after the addition of Fe3+, Hg2+, Ag+, Ca2+, Co2+,

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Ni2+, Cd2+, Pb2+, Zn2+, Cr3+ and Mg2+ (20 equiv.) in DMSO on excitation at 365 nm using UV

Ac ce p

te

d

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lamp at room temperature.

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Fig. 3 Fluorescence emission data for G2 (20μM) and different metal ions (20 equiv.): 1)only G2, 2)

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Fe3+, 3) Hg2+, 4) Ag+, 5) Ca2+, 6) Co2+, 7) Ni2+, 8) Cd2+, 9) Pb2+, 10) Zn2+, 11) Cr3+ and 12) Mg2+;

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as their perchlorate salts, in DMSO solution. (Excitation wavelength = 445 nm).

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Fig. 4 (a) Fluorescence spectra of G1 (20μM) in the presence of different concentration of Fe3+ (0-2.48 equiv.) in DMSO. (b) Fluorescence change at 540 nm as a function of Fe3+ ions.

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Fig. 5 Fluorescence intensity changes of the G1 (20μM) to Fe3+ (20 equiv.) in the presence of various test cations (20 equiv.) in DMSO solution. Key: left to right, (1) only G1, G1+Fe3+, (2)

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G1+Hg2+, G1+Fe3++Hg2+, (3) G1+Ag+, G1+Fe3++Ag+, (4) G1+Ca2+, G1+Fe3++Ca2+, (5) G1+Co2+,

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G1+Fe3++Co2+, (6) G1+Ni2+, G1+Fe3++Ni2+, (7) G1+Cd2+, G1+Fe3++Cd2+, (8) G1+Pb2+,

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G1+Fe3++Pb2+, (9) G1+Zn2+, G1+Fe3++Zn2+, (10) G1+Cr3+, G1+Fe3++Cr3+, (11) G1+Mg2+, G1+Fe3++Mg2+.

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Fig. 6 (a)Fluorescence changes of G1-Fe3+ (20μM) system in the presence of various anions (20equiv.) for F-, Cl-, Br-, I−, AcO−, H2PO4−, HSO4-, ClO4-, CN- in DMSO solution. (excitation

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wavelength = 445 nm). (b) Visual fluorescence emissions of sensor G1-Fe3+ after the addition of

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F-, Cl-, Br-, I−, AcO−, H2PO4−, HSO4-, ClO4-, CN- (20 equiv.) in DMSO on excitation at 365 nm

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using UV lamp at room temperature.

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Fig. 7 Emission spectra showing the reversible complexation between G1 and Fe3+ (20.0 equiv.) by

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introduction of H2PO4- (50.0 equiv.).

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Fig. 8 Time-dependent of G1 (20μM) upon addition of Fe3+ in DMSO. Fluorescence intensity changes: each spectrum was recorded after 0, 2, 4, 6, 8, 10, 12, 14, 16, 18, 20, 22 and 23 min.

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Inset shows a plot of fluorescence intensity that is estimated as the peak height at 540 nm.

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Fig. 9 Time-dependent of G1-Fe3+ (20μM) upon addition of H2PO4- in DMSO. Fluorescence intensity changes: each spectrum was recorded after 0, 1, 2, 3, 4, 5 and 6 s. Inset shows a plot of

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fluorescence intensity that is estimated as the peak height at 540 nm.

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Fig. 10 Fluorescence spectra of G1-Fe3+ (20μM) in the presence of different concentration of H2PO4- (0-28 equiv.) in DMSO solution. Inset shows fluorescence change at 540 nm as a function

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of H2PO4- ions.

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Solvent

G1

Fe3+

H2PO4-

1

DMSO

ON

OFF

ON

2

CH3COCH3

ON

OFF

OFF

3

CH3CN

OFF

-

-

4

DMF

ON

OFF

OFF

5

CH3CH2OH

ON

OFF

OFF

6

CH3OH

ON

OFF

7

CH3COOCH2CH3

-

-

8

CH2Cl2

OFF

OFF

OFF

9

CHCl3

OFF

OFF

OFF

10

THF

ON

ON

ON

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Entry

OFF

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Table 1 ON-OFF-ON type fluorescence charge of G1 (20μM) with Fe3+ and H2PO4- (20 equiv.) in

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different solvents (λex= 445 nm).

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Fig. 11 Output for G1, corresponding to six possible input combinations at 543 nm. Inset shows a molecular keypad lock generating emission at 543 nm when a correct password, namely, GIP, is

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entered keys G, I, and P hold the relevant inputs G1, Fe3+, and H2PO4-, respectively.

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Fig.12 Photographs of G1 and G1-Fe3+ on test papers after immersion into DMSO solution. Left to

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right: (1) only G1, (2) G1 with Fe3+, (3) G1-Fe3+ with H2PO4- under irradiation at 365 nm on UV

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lamp.

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Scheme 1 Synthetic procedures for sensor G1 and G2

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Scheme 2 The proposed structures of G1 for Fe3+ and G1-Fe3+ for H2PO4− anions.

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Graphical abstract: A new fluorescent molecular sensor G1 was designed and

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synthesized by a cheap sensitive method and exhibited single selectivity by

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naked-eyes under the 365 nm UV lamp on recognition for Fe3+ and H2PO4- in DMSO

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solution.

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Highlights 1. We synthesized a novel sensor was never reported and explored the interaction of the sensor and Fe3+ by MS, and fluorescence spectra.

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2. The fluorescence revealed that receptor G1 is an excellent sensor in the

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recognition to Fe3+ and H2PO4- selectively.

3. The reversibility and selectivity of G1/G1+Fe3+ toward Fe3+/ H2PO4− ions as a

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sequence dependent molecular keypad lock using the G1, Fe3+ and H2PO4− as three

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different chemical inputs.

sensitively to Fe3+ and H2PO4-.

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4. The test strips were containing G1 were fabricated, which also shows a highly

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5. The sensor G1 serves as a recyclable component in sensing materials.

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