Cjc-2017-0741.Pdf

Canadian Journal of Chemistry

Synthesis and fluorescence spectral studies of novel quinolylbenzothiazole-based sensors for selective detection of Fe3+ ion

Journal: Canadian Journal of Chemistry

Manuscript ID cjc-2017-0741.R1

Manuscript Type: Article

Date Submitted by the Author: 22-Feb-2018

Complete List of Authors: Wang, Peng ; Insititute of Fine Chemistry and Chemical Engineering Liu, Xiao-yan ; Insititute of Fine Chemistry and Chemical Engineering Fu, Jia-xin;Draft Insititute of Fine Chemistry and Chemical Engineering Chang, Yong-xin ; Insititute of Fine Chemistry and Chemical Engineering Yang, Li; Insititute of Fine Chemistry and Chemical Engineering Xu, Kuoxi; Insititute of Fine Chemistry and Chemical Engineering

fluorescence sensor, Fe3+ detection, fluorescence imaging, Keyword: Qquinolylbenzothiazole

Is the invited manuscript for consideration in a Special N/A Issue?:

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Synthesis and fluorescence spectral studies of novel quinolylbenzothiazole-based

sensors for selective detection of Fe3+ ion

Peng Wang, Xiaoyan Liu, Jiaxin Fu, Yongxin Chang, Li Yang, Kuoxi Xu

Abstract: Four novel fluorescence sensors bearing quinolylbenzothiazole platform were synthesized and characterized. The sensors displayed excellent selectivity, high 3+ sensitive fluorescence response to Fe ion in H2O/DMSO buffer solution (1:4, volume ratio, TrisHCl 0.01 M, pH = 7.40) at 500 nm originating from quinolylbenzothiazole fluorophore group. Other cations viz. Li+, Na+, K+, Mg2+, Ca2+, Co2+, Ni2+, Cd2+, Cu2+, Zn2+, Mn2+, Ba2+, Pb2+, Hg2+, Al3+, Eu3+ ions showed no appreciable change in fluorescence spectrum. The binding stoichiometry between sensors L1, L2, L3 or L4 and Fe3+ were observed to be 1:1 based on fluorescence titration and Job’s plot analysis. The detection limits of L1, L2, L3 or L4 for Fe3+ were found to be 0.155, 0.362, 0.249, 0.517 M, respectively. Further, possible utilization of sensors as bioimaging fluorescence to detect Fe3+ in living HeLa cells were also investigated by confocalDraft fluorescence microscopy. Keywords: Fluorescence sensor, Qquinolylbenzothiazole, Fe3+ detection,

Fluorescence imaging

Introduction

Molecular sensors are highly valuable tools for the selective recognition of

chemical and biological species. A fluorescent sensor commonly contains at least two

parts, receptor unit and fluorophore unit.13 It is well recognized that for the design of

selective and sensitive sensors to detect analytes, conjugation of a wellestablished

and efficient recognition site (receptor) with a suitable fluorophore (signaling moiety)

is the most rewarding approach. Among many of the efforts, functional

P. Wang, X. Liu, J. Fu, Y. Chang, L. Yang, K. Xu. Institute of Functional Organic Molecular Engineering, College of Chemistry and

Chemical Engineering, Henan University, Kaifeng, 475004, China; Engineering Laboratory for Flame Retardant and Functional Materials

of Hennan Province, College of Chemistry and Chemical Engineering, Henan University, Kaifeng, 475004, China;

Corresponding author: Kuoxi Xu (email: [email protected]). 1

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transformations of 8aminoquinoline, which exhibited good photostability, high affinity to metal ions and satisfactory membrane permeability,4 was plausible for the construction of more elaborate functional sensors. Such as

2methoxy6((quinolin8ylimino)methyl)phenol,5, 6 as well as

N((1Himidazol2yl)methylene)quinolin8amine7 and 2((quinolin8ylimino) methyl)phenol or 1[(quinolin8ylimino)methyl]naphthalene2ol.8 One of these sensors, 1(8quinolyliminomethyl)2naphtholato can detect intracellular Fe3+ ions.9

Iron is one of the indispensable trace elements in biological systems, which plays indispensable role in growth process of live systems and for the most part of biochemical processes at the cellularDraft level,1012 such as oxygenuptake, cellular metabolism, enzymecatalys.1316 Too much iron ion content in the human body will lead to various diseases (Parkinson's diseases, Alzheimer's and Huntington's diseases).17, 18 Therefore, it is important to develop sensors that detect Fe3+ in biological and environmental analyzes. Despite the availability of some commercial fluorescent sensors for Fe3+ ion, the design of lowtoxicity, extremely high affinity for

Fe3+ ions and good selectivity over other relevant metal ions is still a challenging task.

Herein, we introduced benzothiazole equipped with 8aminoquinoline moiety for sensitive and selective recognition of Fe3+ ion in mixed organoaqua solution. It was looking quite interesting that our synthesized fluorescent sensor fulfill almost all the crucial characteristic that a intracellular fluorescent sensor should have excitation wavelengths exceeding 340 nm to prevent UV–induced cell damage and emission wavelength approaching 500 nm to avoid auto fluorescence from species native to the

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cell and to facilitate use with typical fluorescence microscopy optical filter sets.19

However to the best of our knowledge, application of 2quinolylbenzothiazole

fluorescent sensors for Fe3+ ion are still unexplored.

Experimental Section

Materials and general methods

All reagents are analytical grades and used without further purification. The metal

ion salts in stock solutions used its nitrates. 1H NMR spectra were recorded on a

BrukerAV400 NMR spectrometer using tetramethylsilane(TMS) as an internal

standard and DMSOd6 or CDClDraft3 as solvent. Electrospray ionization mass spectrometry (ESIMS) spectra were collected on a Bruker amaZon SL mass

instrument. Infrared measurements with the KBr pellet technique were performed

within the 4000–400 cm−1 region on a Nicolet 670 FTIR spectrophotometer.

Elemental analyses were performed by the Vario Elemental CHSNO microanalyzer.

The absorption spectra were recorded on a PerkinElmer Lamda25 UVvis

spectrophotometer in the range 200700 nm wavelengths. Fluorescence spectra were

obtained with F7000 FL Spectrophotometer. Compounds

8hydroxy2hydroxymethylquinoline and 2hydroxymethylphenol were synthesized

according to literature methods20, 21.

Synthesis

Synthesis of compound 1

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Chloroacetyl chloride (0.40 g, 3.6 mmol) was added to a solution of

8aminoquinaldine (0.47 g, 3 mmol) and DIPEA (0.46, 3.6 mmol) in anhydrous

CHCl3 (20 mL) and the reaction mixture stirred for 16 h under N2. The reaction mixture was neutralised with saturated sodium Na2CO3 and the product extracted into

CHCl3 (20 mL) then washed with water (40 mL) and brine (40 mL) and dried over anhydrous Na2SO4. The solvent was removed under vacuum. After filtration, the filtrate was concentrated to give the crude product. The crude residue was purified by column chromatography (silica gel, chloroform / methanol =20/1, v/v) to give compound 1, as a white solid (0.69 g, 97.6 %)(Scheme 1). m.p.103.3–104.5 °C. 1H

NMR (400 MHz, CDCl3) δ 10.82Draft (s, 1H), 8.52 (d, J = 8.0 Hz, 1H), 7.85 (d, J = 12.0 Hz, 1H), 7.31 (t, J = 8.0 Hz, 2H), 7.15 (d, J = 12.0 Hz, 1H), 4.14 (s, 2H), 2.58 (s, 3H).

IR (KBr): 3327.28, 1682.99, 1603.77, 1537.79, 1498.34, 1473.16, 1338.21, 1271.84,

834.80, 761.83, 724.89 cm1; MS: calcd for: [M + H]+: 235.06; found: 235.10.

Synthesis of compound 2

To a solution of compound 1 (0.23 g, 1 mmol) in 1,4dioxane (15 mL), SeO2

(0.17 g, 1.5 mmol) was added and reaction mixture was stirred at 105 ºC for 12 h.

After which deposited selenium was filtered off and the solution was evaporated under reduced pressure. Purification by column chromatography(acetidine/petroleum ether=1:15) yielded product 2, as a yellow solid(0.16 g, 65%). m.p.147.3–148.1 °C.

1 H NMR (CDCl3) δ 10.99 (s, 1H), 10.24(s, 1H), 8.86 (d, J = 12.0 Hz, 1H), 8.37 (d, J =

12.0 Hz, 1H), 8.11 (d, J = 12.0 Hz, 1H), 7.75–7.65(m, 2H), 4.37 (s, 2H); IR (KBr):

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3337.75, 1711.06, 1688.21, 1591.73, 1551.37, 1492.10, 1432.24, 1336.29, 843.07,

765.12, 709.01 cm1; MS: calcd for: [M + Na]+: 271.02; found: 271.07.

Synthesis of compound 3

2Aminothiophenol (0.15g, 1.2 mmol) was added to the solution of compound 2

(0.25 g, 1 mmol) in anhydrous CH3OH(10 mL), the reaction was refluxed at 65 ºC for

8 h. The solution was then filtered, and the filter cake was washed three times with

1 hot CH3OH to afford yellowish product 3(0.26 g, 75 %). m.p.245.2–246.5 °C. H

NMR(DMSOd6) δ 10.76(s, 1H), 8.65(t, J = 12.0 Hz, 2H), 8.52 (d, J = 12.0 Hz, 1H),

8.26 (d, J = 12.0 Hz, 1H), 8.16 (d, J = 12.0 Hz, 1H), 7.84 (t, J = 12.0 Hz, 1H), 7.71 (t, J = 12.0 Hz, 1H), 7.637.52(m,Draft 2H), 4.68(s, 2H); IR (KBr): 3317.21, 1679.64, 1626.45, 1567.37, 1540.72, 1490.56, 1387, 1431.3, 1345.6, 843.13, 763.32, 742.63,

716.03 cm1; MS: calcd for: [M + Na]+: 376.03; found: 376.13.

General procedure for the synthesis of compounds L1, L2, L3 and L4

Compound 3(0.35 g, 1 mmol) and anhydrous K2CO3 (0.27 g, 2.0 mmol) were

added to a solution of 1.0 mmol phenol in anhydrous CH3CN (20 mL) and anhydrous

DMF (5 mL). The solution mixture was refluxed at 85 ℃ for 16h. After the reaction

was cooled down to room temperature and concentrated by evaporation under reduced

pressure. The residue was washed with water three times. The crude residue was

purified by chromatography (acetidine/petroleum ether = 1:15), obtained yellow solid.

1 L1: 0.4 g, 55 %. M.p. 206.5207.3 °C. H NMR(CDCl3) δ 11.04 (s, 1H), 10.19(s, 1H),

8.96(d, J = 8.0 Hz, 1H), 8.47 (d, J = 8.0 Hz, 1H), 8.37 (d, J = 8.0 Hz, 1H), 8.30 (d, J =

8.0 Hz, 1H), 8.10(d, J = 8.0 Hz, 1H), 8.03 (d, J = 8.0 Hz, 1H), 7.697.63(m, 4H),

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7.48(dd, J = 8.0, 4.0 Hz, 2H), 7.33 (q, J = 8.0, 4.0 Hz, 2H), 5.17 (s, 2H), 4.74 (s, 2H);

IR (KBr): 3421.85, 3349.05, 1676.81, 1600.17, 1570.15, 1540.58, 1504.47, 1468.91,

1340.54, 1263.22, 1079.56, 840.33, 756.15, 749.66, 727.06 cm1; Elemental analysis calcd C 68.28, H 4.09, N 11.37; Found C 68.22, H 4.11, N 11.34; MS: calcd for: [M +

Na]+: 515.11; found: 515.14.

1 L2: 0.24 g, 50 %. M.p. 187.8188.5 °C. H NMR (CDCl3) δ 11.06 (s, 1H), 8.92(d, J =

12.0 Hz, 1H), 8.40 (d, J = 12.0 Hz, 1H), 8.22 (d, J = 12.0 Hz, 1H), 8.08 (d, J = 12.0

Hz, 1H), 8.01 (d, J = 8.0 Hz, 1H), 7.62(d, J = 12.0 Hz, 1H), 7.57 (d, J = 12.0 Hz, 1H),

7.50 (d, J = 8.0 Hz, 1H), 7.457.30 (m, 6H), 5.18(s, 2H), 2.66(s, 3H). IR (KBr): 3349.50, 1688.82, 1600.01, 1570.59,Draft 1542.33, 1491.24, 1469.19, 1429.18, 1341.39, 1230.01, 1096.31, 839.50,775.49, 726.66 cm1; Elemental analysis calcd C 70.57, H

4.23, N 11.76; Found C 70.51, H 4.25, N 11.79; MS: calcd for: [M+H]+: 477.14; found: 477.07.

1 L3: 0.45 g, 60 %. M.p. 165.01166.4 °C. H NMR (CDCl3) δ 10.56(s, 1H), 8.84(d, J =

8.0, 1H), 8.40(d, J = 12.0 Hz, 1H), 8.21(d, J = 12. Hz, 1H), 8.06 (d, J = 8.0 Hz, 1H),

7.87(d, J = 8.0 Hz, 1H), 7.607.52(m, 3H), 7.46(t, J = 6.0 Hz, 1H), 7.40(d, J = 6.0 Hz,

1H), 7.29(t, J = 6.0, 1H), 7.10(t, J = 6.0 Hz, 1H), 7.03(d, J = 8.0 Hz, 1H), 5.06 (s, 2H),

4.87 (s, 2H); IR (KBr): 3380.61, 3059.91, 1683.52, 1601.67, 1591.77,

1563.39,1531.03, 1489.24, 1455.90, 1435.93, 1372.23, 1336.80, 1272.81, 1089.48,

850.89, 771.88, 762.04, 745.18 cm1; Elemental analysis calcd C 68.01, H 4.34, N

9.52; Found C 67.99, H 4.36, N 9.49; MS: calcd for: [M + Na]+: 515.11; found:

515.14.

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1 L4: 0.2g, 40 %. M.p. 193.6194.3 °C. H NMR(400 MHz, CDCl3) δ 10.17(s, 1H),

8.87(q, J = 8.0, 4.0Hz, 1H), 8.50(d, J = 8.0 Hz, 1H), 8.31(d, J = 8.0 Hz, 1H), 8.13(d, J

= 8.0 Hz, 1H), 7.96(d, J = 8.0 Hz, 1H), 7.60 (t, J = 8.0 Hz, 2H), 7.55(t, J = 8.0 Hz,

1H), 7.49(t, J = 8.0 Hz, 1H), 7.23(dd, J = 8.0,4.0 Hz, 1H), 7.167.05(m, 3H), 5.94(s,

2H), 4.89(s, 2H); IR (KBr): 3436.72, 3306.30, 1691.10, 1551.29, 1503.41, 1489.86,

1399.18, 1338.10, 1260.20, 1055.48, 852.75, 747.49, 682.26 cm1; Elemental analysis

calcd C 67.59, H 4.25, N 13.14; Found C 67.56, H 4.27, N 13.09; MS: calcd for: [M +

Na]+: 449.10; found: 449.07.

Draft

Scheme 1 The synthetic route of sensors L1, L2, L3 and L4.

General method for the fluorescence experiments

The stock solutions of metal ions (0.1 M, Li+, Na+, K+, Ag+, Zn2+, Mg2+, Ba2+,

Ca2+, Mn2+, Pb2+, Hg2+, Ni2+, Cd2+, Co2+, Cu2+, Fe2+, Cr3+, Fe3+, Al3+and Eu3+) in

water and sensors L1, L2, L3 and L4 (0.01 M) in DMSO were prepared. The study

solution of sensors were then diluted with water or different buffer (pH = 7.4) solution

to a desired concentration (3.33×105 M), and solutions of metal ions was added 7

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according to need. The resulting solutions were kept at room temperature for more than 2 h, and then the absorption or fluorescence spectra were recorded. In order to ensure the reproducibility of the experimental data, all experiments were test at least three times. For fluorescence emission experiment, excitation was sited at 350 nm, and emission was collected from 330 to 600 nm. In pH affect experiments, the pH values of TrisHCl buffer were adjusted with 1.0 M NaOH or HCl aqueous solution.

All the experiments performed at room temperature.

Results and discussion Synthesis Draft Four novel quinolylbenzothiazolebased sensors were prepared in fourstep procedure (Scheme 1) starting from 8aminoquinaldine precursors. 8aminoquinoline was firstly treated with chloroacetyl chloride, followed by oxidate of –CH3 using

SeO2 to give the aldehyde intermediate 2, then was treated with 2aminothiophenol to afford compound 3 as a yellowish powder. Compound 3 was dissolved in anhydrous

CH3CN and DMF and then treated with different kinds of phenol to afford pure target molecules L1, L2, L3 or L4, after purification by chromatography. The structures of

L1, L2, L3 or L4 were characterized by IR, ESIMS, 1 H NMR techniques and elemental analysis, and the results are in good agreement with the structure presented.

Moreover, the chemical shift value corresponding to the OH proton, δ = 10.19 ppm of compound L1, is relatively high for an alcohol OH group, indicating that the proton is deshielded by formation of a hydrogen bond. Due to the presence of the

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intramolecular hydrogen bonds, the proton signals of the neighboring –CH2 were

involved in too, and presented upfield shifts to 2.13 ppm of compound L1, comparing

to the precursor compound L3 (4.87 ppm) or the compound

8hydroxy2hydroxymethylquinoline.

Spectral characteristics

Preliminary fluorescence spectra studies showed that sensor L1 exhibited a good

3+ selectivity to Fe in H2O/DMSO (1:4 volume ratio, pH=7.4 of TrisHCl) solution.

The fluorescence response of L1 solution toward various metal ions was conducted

and the results were shown in Figure 1 (L2, L3 and L4 see Figure S13). Free sensor L1 showed a weak emission at 500Draft nm in the buffered solution. Upon addition of 10.0 equiv. of Fe3+ into the solution of L1, a significant fluorescence quench at 500 nm

was observed. Other metal ions (10.0 equiv. of each) did not induce significant

fluorescence emission changes under the identical conditions. These observations

indicated that sensors L1, L2, L3 and L4 had an excellent selectivity to Fe3+ ion in

aqueous media.

Figure. 1 insert here

The high selectivitiy of sensors L1, L2, L3 and L4 toward Fe3+ were further

confirmed by the competition experiments (L1 see Figure. 2; L2, L3 and L4 see

Figure S46). The fluorescence changes of the sensors solution were measured by the

treatment of 10.0 equiv. Fe3+ ion in the presence of 100.0 equiv. aforementioned other

competitive metal ions. No obvious changes in the emission ratio were observed with

the detection of Fe3+ ion. 9

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Figure.2 insert here

To elucidate the sensing properties of sensors L1, L2, L3 and L4 toward Fe3+, fluorescence titration experiment were carried out. As shown in Figure. 3a (L2, L3 and L4 see Figure S79), a gradually decrease in fluorescence intensity of L1 solution could be observed upon incremental addition of Fe3+. The association constants of sensor L1 toward Fe3+ ion were found to be 4.26×103 M1 by BenesiHildebrand equation (R2=0.9954) (Figure.3b) (L2, L3 and L4 see Figure S1012 and Table 1),22, 23 these results suggested formation of the 1:1 complex between sensors L1 and Fe3+ ion.

Job’s plots were used to determine the binding stoichiometry of L1, L2, L3 and L4 and Fe3+. The total concentrationDraft of L1 and Fe3+ ion was held as 1.0×10−4 M while altering the mole fraction of Fe3+ ions. The fluorescence exhibited a maximum when the molar fraction of Fe3+ ion was 0.50 (L1 see Figure. 4; L2, L3 and L4 see Figure

S1315 and Table 1), which also demonstrated the 1:1 binding stoichiometry were adopted between sensors and Fe3+.24

Figure.3 insert here Figure. 4 insert here

In addition, the fluorescent detection limit of L1 for Fe3+ was also evaluated

(Figure. 5, L2, L3 and L4 see Figure S1618 and Table 1). The DL calculated to be

0.155 M for L1, which was below the maximum permissive level of Fe3+in drinking water (5.37 M) set by the U. S. Environmental Protection Agency.25 These results indicated that sensor L1, L2, L3 and L4 were sensitive enough to monitor Fe3+ 10

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concentration in drinking water. To observe the stability of sensor complex at varied

pH, fluorescence spectra were recorded in aqueous medium (H2O: DMSO =1:4

volume ratio, pH=7.4 of TrisHCl) by adjusting pH using NaOH and HCl.

Figure. 5 insert here

Table 1. Association constants (Kass), correlation coefficients (R2) and detection limit (DL) for the sensors L1, L2, 3+ L3 and L4 with Fe in DMSOH2O (4:1, v/v, pH=7.4 of TrisHCl) at 25 °C. Entry sensor Kass (M –1 ) a,b R2 DL(M) 1 L1 4.26×103 0.9954 0.155 2 L2 1.80×103 0.9935 0.362 3 L3 2.98×103 0.9930 0.249 4 L4 3.42×103 0.9935 0.517

a. The data were calculated from the results of fluorescence titrations in DMSOH2O (4:1, v/v, pH=7.4 of TrisHCl). b. All error values were obtained from nonlinearDraft curve fitting.

Experimental results showed that the free sensor, the fluorescence intensities of

L1 L2, L3 or L4 are stronger in the pH range of 2.0–11. However, in the presence of

Fe3+ the fluorescence intensities decrease steadily (Figure. 6 and Figure S1921). In

acidic medium, fluorescence intensity of the sensors quenched maybe due to

formation of cationic salt. So, the TrisHCl buffer solution at pH physiological

conditions 7.4 was suggested to be suitable for sensor’s sensing toward Fe3+.

Figure. 6insert here

Plausible Mechanism of Sensing of Fe3+ Ions

To get further insight into the binding between L1 with Fe3+, the FTIR spectra

of L1 and L1Fe3+ complex were carried out (Figure. 7). The FTIR spectrum of

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sensor L1 exhibited stretching vibration bands assignable to NH, NHC=O, C=N and

CO functions at 3349, 1677, 1540 and 1080 cm−1, respectively. Upon complexation with Fe3+, the vibration bands of NHC=O, C=N and CO functions shifted to reappear at 1635, 1384 and 1020 cm−1, respectively. These substantial red shifts revealed that the coordination of Fe3+ ions with N atoms of NHC=O, C=N and ether O atom of sensor L1. Meanwhile, the –NH peak at 3449 cm−1 was disappeared, indicating the coordination through NH nitrogen atom in the complex.26, 27 Based on above experiments and some reports, we proposed a possible complexation mechanism between sensor and Fe3+ in Scheme 2. After Fe3+ ion was added to the aqueous solution, the excitedstate intramolecularDraft proton transfer (ESIPT) process was efficiently inhibited and fluorescence quenching was discovered owing to the fact that the complex was formed.28, 29 Furthermore, the paramagnetic nature of Fe3+ commonly leads to fluorescence quenching.

These results indicated that L1, L2, L3 and L4 were good ﬂuorescent sensors toward Fe3+ over other metal ions and could serve as the sensitive ﬂuorescent sensors for Fe3+ in aqueous solution.

Figure. 7 insert here

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Scheme 2 The illustration of fluorescence turnoff of L1 for selective detection of Fe3+.

Intracellular

We investigated the utility of L1 (20 M) for monitoring the intracellular Fe3+ ion.

HeLa cells were cultured and stained with L1 within 30 min and washed by PBS

buffer and then treated with Fe3+ ion (20 M) another 30 min. As shown in Figure. 8,

before addition of Fe3+ ion, the optical window showed blue fluorescence, this

indicated that L1 was cellpermeable. After Fe3+ ion addition, the fluorescence of the

optical window significantly decreased. The fluorescence images generated from the

above optical windows demonstrated that the great potential of the sensor system for

fundamental biology research. Draft Figure. 8 insert here

Conclusion

In this paper, we report on the synthesis and the fluorescence response properties

of a series of novel 8aminoquinoline derivatives L1, L2, L3 and L4, which having

extra binding sites of benzothiazole and aminoquinoline groups. The synthesized

compounds showed a remarkably sensitive Fe3+selective fluorescence response,

which could be used for the analysis of Fe3+ ions in an aqueous environment. This

work also described fluorescence strategy for sensing and in vivo imaging of Fe3+ ion

that was important in physiological and pathological events.

Acknowledgements

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We thank the National Natural Science Foundation of China (No. U1404207) for financial support.

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(26) Lan, L.; Niu, Q.; Guo, Z.; Liu, H.; Li, T. Sens. Actuators B. 2014, 244, 500.

(27) Zhang, S.S.; Sun, T.; Xiao, D.J.; Yuan, F.; Li,T.D.; Wang, E.H.; Liu, H.X.; Niu,

Q.F. Spectrochim. Acta A. 2018, 189, 594.

(28) Forés, M.; Duran, M.; Solà, M.; Orozco, M.; Luque, F. J. J. Phys. Chem. A 1999,

103, 4525.

(29) Das, K.; Sarkar, N.; Ghosh, A.K.; Majumdar, D.; Nath, D.N.; Bhattacharyya, K.

J. Phys. Chem.1994, 98, 9126. Draft

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L1, L1+ Li+, Na+, K+, Ag+, Zn2+, 350 Mg2+, Ba2+, Ca2+, Mn2+, Pb2+, Hg2+, Ni2+, Cd2+, Cu2+, Co2+, 300 Al3+, Cr3+, Eu3+ 250

200 L1+Fe2+ 150

100 L1+Fe3+ 50 FluorescenceIntensity (a.u.) 0 350 400 450 500 550 600 650 Wavelength(nm) + Figure 1. Changes in fluorescent intensity (λex=350 nm) of sensor L1 upon the addition of different metal ions Li , Na+, K+, Ag+, Zn2+, Mg2+, Ba2+, Ca2+, Mn2+, Pb2+, Hg2+, Ni2+, Cd2+, Co2+, Al3+, Cr3+, Cu2+ , Fe3+, Al3+and Eu3+ (10 equiv.) in H2O/DMSO (1:4 volume ratio, pH=7.4Draft of TrisHCl).

L1+ metal ions L1+ metal ions + Fe3+ 300

250

200

150

100

50 FluorescenceIntensity(a.u.) 0 Li+ Na+ K + Ba2+Cd2+Zn2+Hg2+Ca2+Co2+Al3+Mn2+Pb2+Mg2+Eu3+Ag+Cr3+Cu2+Fe2+

Figure 2. Metalion selectivity of L1 in DMSO/H2O (4:1, volume ratio, pH=7.4 of TrisHCl). The black bars express a solution of L1 (3.33×105 M) and 100.0 equiv. of other metal ions. The red bars express after the addition of 10 equiv. of Fe3+ to the solution containing L1 and different metal ions.

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35 0 F e 3 + 0 -1 5 e q u iv 30 0 ) a.u.

( 25 0

20 0

15 0

10 0

Fluorescence Intensity Fluorescence 5 0

0 350 400 450 500 550 600 650 700 Wavelength(nm)

Y= 0.00217+ 5.09678×107×X K= 4.26×103 Draft 0.03

0.02

Equation y = a + b*x

1/(F0F) Weight No Weightin g Residual Sum 3.13911E-6 of Squares Adj. 0.99549 0.01 R-Square Value Standard Erro r Intercept 0.00217 2.40204E-4 B Slope 5.09678E- 1.08489E-8 7

0.00 0 10000 20000 30000 40000 50000 60000

1/[Fe3+]

Figure 3. A: Fluorescent spectra of sensor L1 (3.33×105 M) with the addition of various concentration of Fe3+ in

H2O/DMSO (1:4 volume ratio, pH=7.4 of TrisHCl) (λex=350 nm). B: Bensei–Hildebrand plot for sensor L1 with Fe3+, considering the 1:1 complexation. The goodness of the fit is shown by the R2 value.

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300

200 I 0 I

100

0 Draft 0.0 0.2 0.4 0.6 0.8 1.0 3+ 3+ [Fe ]/[L1]+[Fe ] 3+ Figure 4. 1:1 Fluorescence job's plot for the determination of stoichiometry of L1Fe in H2O/DMSO (H2O: DMSO =1:4 volume ratio, pH=7.4 of TrisHCl).

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350 Equation y = a + b*x Adj. R-Square 0.99094 Value Standard Error 300 Fluorescence Intensit Intercept 294.05818 4.44763 Fluorescence Intensit Slope -7.16053E6 228140.35697

250

200

150

100 Fluorescence Intensity(a.u.)

0.0 1.0x105 2.0x105 3.0x105 Concentration of Fe3+(M) Draft Figure 5. The detection limit (DL) of sensor L1 for Fe3+ was calculated as 1.55 ×107 M.

L1 L1+Fe3+ 300

250

200

150

100 Fluorescence Intensity (a.u.)

50 2 4 6 8 10 12 14 pH 3+ Figure 6. Fluorescence intensity recorded for L1Fe complex in DMSOH2O (4:1, v/v, pH=7.4 of TrisHCl) at various pH values (λex = 350 nm; λem = 500 nm).

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L1 65 L1+Fe3+ 1019.83

50 1635.36 3422.08 45

40 1384.41 1079.69 Transmittance 35 3421.85 3349.05 1540.30 30 1676.92

25 4000 3500 3000 2500 2000 1500 1000 500 1 Wavelength (cm ) Figure 7. IR spectra of sensor L1 (black) and L1+Fe3+ complex (red) Draft

Figure 8. Fluorescence images of Hela cell incubated with L1 and Fe3+. Cells were incubated with 20 µM L1 for 30 min (a and b) and then further with 20 µM Fe3+ for 30 min (c and d). The left images (a and c) were observed with the light microscope and the right images (b and d) were taken with a ﬂuorescence microscope.

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We report on the synthesis and the fluorescence response properties of a series of novel 8-aminoquinoline derivatives L1, L2, L3 and L4, which having extra binding sites of benzothiazole and aminoquinoline groups. The synthesized compounds showed a remarkably sensitive Fe3+-selective fluorescence response, which could be used for the analysis of Fe3+ ions in an aqueous environment. This work also described fluorescence strategy forDraft sensing and in vivo imaging of Fe3+ ion that was important in physiological and pathological events.

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