Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 151 (2015) 785–789

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A novel colorimetric probe derived from isonicotic acid hydrazide for copper (II) determination based on internal charge transfer (ICT) Qing Liu a, Qiang Fei a, Yanqun Fei b, Qian Fan c, Hongyan Shan a, Guodong Feng a, Yanfu Huan a,⇑ a

College of Chemistry, Jilin University, Changchun 130023, PR China Changchun Weiersai Biotec Pharmaceutical Co., Ltd., Changchun 130616, PR China c Changchun Vocational Institute of Technology, Changchun 130033, PR China b

h i g h l i g h t s

g r a p h i c a l a b s t r a c t

 A novel isonicotic acid hydrazide

1.0 0.8

Absorbance

Schiff base was discovered as colorimetric probe for Cu (II) detection. 2+  Addition of Cu to the solution of DHIH resulted in a rapid color change from colorless to yellow.  An obvious new absorption band appeared at the range of 400–440 nm.  The chemosensor was selective and sensitive for Cu (II) determination.

Cu2+

0.6 0.4 0.2 0.0 380

400

420

440

460

480

500

Wavelength (nm)

a r t i c l e

i n f o

Article history: Received 8 March 2015 Received in revised form 18 June 2015 Accepted 7 July 2015 Available online 8 July 2015 Keywords: Isonicotic acid hydrazide Colorimetric probe Internal charge transfer (ICT) Copper determination

a b s t r a c t A novel isonicotic acid hydrazide Schiff base derivative N0 -(3,5-di-tert-butyl-2-hydroxy-benzylidene) isonicotinohydrazide (DHIH) has been synthesized and developed as a high selective and sensitive colorimetric probe for Cu2+ determination. Addition of Cu2+ to the solution of DHIH resulted in a rapid color change from colorless to yellow together with an obvious new absorption band appeared at the range of 400–440 nm by forming a 1:1 complex. Experimental results indicated that the DHIH could provide absorption response to Cu2+ with a linear dynamic range from 1.0  105 to 1.0  104 mol/L. The detection limit of Cu2+ was 5.24  107 mol/L with good tolerance of other metal ions. Ó 2015 Elsevier B.V. All rights reserved.

1. Introduction As is well-known, copper, following zinc and iron, is the third most abundant transition metal in human body, plays an important role in many fundamental physiological processes, such as bone formation, hematopoietic function, cellular respiration, prevention of cardiovascular diseases and connective tissue development [1,2]. Thus, daily ingestion of copper is indispensable for good health [3]. There commended daily allowance of copper, as ⇑ Corresponding author. E-mail address: [email protected] (Y. Huan). http://dx.doi.org/10.1016/j.saa.2015.07.043 1386-1425/Ó 2015 Elsevier B.V. All rights reserved.

suggested by the National Research Council is ranges from 0.4 to 0.6 mg for infants, 1.5 to 2.5 mg for children and 1.5 to 3.0 mg for adults [4]. Copper deficiency might increase the risk of suffering from coronary heart disease [5]. Typically, Cu2+ in low-dose is an indispensable trace nutrient, but short-time challenged with high-dose of Cu2+ can pose harm to the health [6]. When in vivo concentrations of copper exceed the normal range, the redox active metal becomes a biological hazard via the generation of reactive oxygen species (ROS) [7], which can cause severe oxidative stress and disorders associated with neurodegenerative disease such as cardiovascular disorders, Menkes, Wilson diseases Alzheimer’s, Parkinson’s and prion diseases [8,9]. Hence, in this regard,

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establishing a rapid, simple and reliable method for Cu2+ determination is very important, necessary and still in high demand. So far, many methods have been described for the detection of Cu2+, including atomic absorption spectrometry [10,11], inductively coupled plasma-mass spectrometry (ICP-MS) [12–14], inductively coupled plasma atomic emission spectrometry (ICP-AES) [15,16], voltammetry [17,18], capillary electrophoresis [19]. Although each method has its own advantages, these methods are limited in their use for in situ and on-line monitoring because of their size, expensive instruments, tedious separation and analysis time for laboratories operating in routine with large amount of samples to be analyzed [20–22]. In recent years, Ultraviolet–visible and fluorescence spectroscopy have been paid widespread attention in the majority of researchers by virtue of its apparatus less expensive and easy to be popular. Small-molecule (both colorimetric and fluorescence) sensors possessing a sight of merits like high sensitivity, simplicity and tunability have sprung up as a powerful tool for conquering the drawbacks of above-mentioned methods [23]. Compared with fluorescence, the importance of the colorimetric sensors is closely related to their ability to allow the so-called ‘naked-eye’ detection in a straightforward and inexpensive manner, offering qualitative and quantitative information [3]. As is known to all, Schiff bases have been made as one of the most widely explored molecular chemosensors for selective sensing of metal ions due to the ease of synthesis coupled with synthetic tailorability, good biological activities, strong photophysical properties and coordination ability with metal ions [24]. From previous reports we can learn, many Schiff base molecules used as fluorescence chemosensors have been developed for various cations determination, for example Al3+ [25], Ag+ [26], Zn2+ [27], Fe3+ [28], and Cu2+ [29]. Meanwhile, many copper ion colorimetric probes have been reported. For example, Kim [30] found a new Cu2+-selective chromogenic probe system based on the oxidative coupling of phenols with 4-aminoantipyrine by prominent color change from colorless to pink with a detection limit of 8.5  107 M. Ekmekci [31] developed monostyryl and distyryl-boradiazaindacene (BODIPY) derivatives as fluorescence and colorimetric ‘‘turn-off’’ sensors for Cu2+. A novel rhodamine derivative 3-bromo-5-methylsalicylaldehyde rhodamine B hydrazone (BMSRH) has been synthesized by Zhang [32]. Addition of Cu2+ to the solution of BMSRH results in a rapid color change from colorless to red together with an obvious new band appeared at 552 nm in the UV–vis absorption spectra with a detection limit of 6.67  107 mol/L. Na [33] synthesized colorimetric and fluorescent receptor 1, based on 4-diethylaminosalicylaldehyde moieties with a detection limit of 12 lM for Cu2+ determination. In the present study, we designed and synthesized a novel isonicotic acid hydrazide Schiff base derivative N0 -(3,5-di-t ert-butyl-2-hydroxy-benzylidene) isonicotinohydrazide (DHIH), for rapid selective and sensitive response to Cu2+ in acetonitrile and water media. Addition of Cu2+ to the solution of DHIH resulted in a rapid color change from colorless to yellow together with an obvious new band appeared at 408 nm in the UV–vis absorption spectra with a detection limit of 5.24  107 mol/L which is lower than above-mentioned. Moreover, DHIH showed excellent selectivity and sensitivity toward Cu2+ over other competing ions including alkaline metals, alkaline-earth metals, transition metals, halogens, etc.

measurements were made with a Sartorius PB-10 digital pH meter. NMR spectra were performed on a Varian Mercury YH-300 spectrometer operated at 400 MHz. ESI Mass spectrum was obtained using a Q-Trap2000 (Applied Biosystems Corporation, American) without using the LC part. All reagents and the materials for synthesis were purchased from commercial suppliers and used without further purification. Distilled water was used throughout all experiments. 2.2. Synthesis of N0 -(3,5-di-tert-butyl-2-hydroxy-benzylidene) isonicotinohydrazide (DHIH) Compound DHIH was synthesized according to the literature [34] with small modification. A solution of 3,5-di-tert-butyl-2-hy droxybenzaldehyde (0.003 M, 0.412 g) in anhydrous ethanol (20 ml) was added drop wise to a solution of isonicotic acid hydrazide (0.003 M, 0.703 g) in anhydrous ethanol (20 mL). After being stirred and refluxed for 5 h, the mixture was cooled to room temperature and the solvent was removed under reduced pressure to give DHIH (Scheme 1) as white solid with purification by alumina column chromatography (ethyl acetate/petroleum ether = 2:1). Yield: 70%. 1H NMR (400 MHz, DMSO) d 12.39 (s, 1H), 12.20 (s, 1H), 9.10 (d, J = 1.6 Hz, 1H), 8.80 (d, J = 3.6 Hz, 1H), 8.57 (s, 1H), 8.28 (d, J = 8.0 Hz, 1H), 7.61 (dd, J = 7.9, 4.9 Hz, 1H), 7.29 (dd, J = 31.3, 2.1 Hz, 2H), 1.42 (s, 9H), 1.29 (s, 9H). ESI-MS: m/z (M + H)+ calc. for C21H28N3O2, 354.3, found 354.2; (M + Na)+ calc. for C21H27N3O2Na 376.2, found 376.2. 2.3. UV–visible spectral measurements A stock standard solution of DHIH (10.0 mM) was prepared by dissolving the corresponding amount of DHIH powder in acetonitrile and diluting it to the mark in a 50 ml volumetric flask, which was stored in the dark. The solutions of cations (10.0 mM) were prepared from the corresponding chloride or nitrate salts and the solutions of anions were prepared from the corresponding sodium or potassium salts. The solutions were added in the following sequence with total volume 3 mL: 30 lL DHIH (10 mM), acetonitrile, 30 lL Cu (10 mM), Hepes buffer solution (water/acetonitrile, 3:7 v/v; Hepes 0.1 mol/L; pH = 7.0). And then the mixture was shook for UV spectrum determination immediately. All measurements were performed in quartz cell of 1 cm path length at room temperature (298 K). 3. Results and discussion 3.1. UV–vis absorption spectra The UV–visible absorption spectra of DHIH in the absence and presence of Cu2+ in a water/acetonitrile mixture (3:7, v/v; Hepes 0.1 mol/L; pH = 7.0) were displayed in Fig. 1. The UV–vis absorption spectrum of DHIH exhibited two major peaks at 294 and 343 nm and nearly no absorption over 400 nm region. When Cu2+ was added into the solution of DHIH, it could chelate with DHIH caused a decrease of absorption intensity to some extent at 294 and 343 nm and accompanied by a new absorption peak appeared obviously at the range of 400–440 nm. Correspondingly, the solution of DHIH changed from colorless to yellow.

2.1. Apparatus and materials Absorption spectra were recorded using an UV-2550 spectrophotometer (Shimadzu Corporation, Japan). All pH

O

O

2. Experimental

N H N

+

O H

NH2 OH

N H

EtOH reflux

N

N

Scheme 1. Synthesis route of the probe DHIH.

HO

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1.0

DHIH DHIH+Cu

2.8

0.8

2.4

Absorbance

2.0

Absorbance

(a)

1.6 1.2 0.8

0.6 0.4 0.2

0.4 0.0

0.0 280

320

360

400

440

480

380

400

420

440

460

480

500

Wavelength (nm)

Wavelength (nm) Fig. 1. The UV–visible absorption spectra of DHIH (1.0  104 M) and DHIH upon additions of Cu2+ (1.0  104 M) in the Hepes buffer solution.

0.9

(b)

0.8 3.2. Effects of experimental conditions

3.3. Titration for Cu2+ Under the optimum conditions, the absorption spectra of DHIH in the presence of different concentrations of Cu2+ were recorded in Fig. 2a. The absorbance of DHIH at 407 nm was linearly increased with the concentration increase of Cu2+ in the range of 1.0  105–1.0  104 M. There was a good linear relationship with a correlation coefficient of 0.9996 (R2 = 0.9992) (Fig. 2b). The limit of detection [35] was estimated to be 5.24  107 mol/L (based on S/N = 3), which could illustrate that DHIH was a high sensitive probe for Cu2+ determination. 3.4. Interference of common ions on Cu2+ detection The selectivity is one of the significant features of chemosensors to signal a specific species in a complex system. The effect of a wide range of environmentally and physiologically active metal ions

0.7

Absorbance

For the sake of a steadier as well as a higher level of absorbance, several conditions such as solvents, solvent composition, pH values and buffer solutions were investigated. First of all, four common laboratory organic solvents were explored for the absorption response of DHIH to Cu2+ (Fig. S1). Only in the acetonitrile system, the increase of absorbance of DHIH was most obvious, which was benefit for Cu2+ determination. So, it was necessary to investigate the effect of different ratios between acetonitrile and water on the absorbance of the system. Fig. S2 illustrated that DHIH showed the best absorption response to Cu2+ in mixed solvent of acetonitrile/H2O 7:3. DHIH displayed weak signals with small change over the range of pH 2.0–9.0 (mediated by NaOH and a mixture of acid comprising of H3PO4, CH3COOH, H3BO3) and high absorption at pH 10.0 (Fig. S3). Addition of Cu2+ ion results in enhanced absorption and DHIH–Cu did not have any significant change at pH range from 2.0 to 8.0. Hence, for the convenience of measurement and practicability, pH = 7.0 was chose for all subsequent measurements. In addition, the effect of the following buffer solution media on the absorbance was determined and compared: Na2HPO4–NaH2PO4, KH2PO4–NaOH, Hepes (Fig. S4). It was found that Hepes buffer solution could fostered the highest absorbance at pH 7.0. In summary, by comprehensive consideration of the absorption determination of every factor, acetonitrile– Hepes buffer solution (7:3, v/v; Hepes 0.1 mol/L; PH = 7.0) was exploited for the following Cu2+ determinations.

y=0.0817x+0.0061 R=0.9996

0.6 0.5 0.4 0.3 0.2 0.1 0.0 0

1

2

3

4

5

6

7

8

9

10

[Cu2+](×10-5 mol/L) Fig. 2. (a) Absorption spectrum of DHIH (1.0  104 M) with the addition of increasing concentrations of Cu2+ (1.0  105–1.0  104 M) in Hepes/acetonitrile (3:7 v/v; Hepes 0.1 mol/L; pH = 7.0); (b) the linearity of the absorbance versus the concentration of Cu2+.

such as Li+, Na+, K+, Rb+, Cs+, Be2+, Mg2+, Ca2+, Sr2+, Ba2+, Cd2+, Pb2+, Mn2+, Zn2+, Ni2+, Pt2+, Hg2+, Al3+, Fe3+, Cr6+, Mo6+, and Cu2+ (104 M) was investigated on UV–vis spectrophotometer (Fig. S5). It was observed that the absorption spectra of DHIH did not undergo any significant change, except in the case of Cu2+. Meanwhile, Fig. 3 shows that only the color of Cu2+ solution changes from colorless to yellow in the Hepes/acetonitrile mixture, the colors of other metal ion solutions did not change except for Fe3+. Interference experiments were carried out by mixing DHIH (104 M) with 1 equiv. of above-mentioned cations respectively before Cu2+ (104 M) was added (Fig. 4). It was noticeable that absorbance remained almost unchanged before and after addition of other potentially contaminating ions except for Ni2+. As for the interference caused by the addition of Ni2+, EDTA was used to mask Ni2+. Hence, the detection of Cu2+ was hardly affected by these coexistent common metal ions. Further to investigate the role of different anions, we carried out a series of experiments using anions like CH3COO, Cl, Br, F,  2 NO and SO2 (104 M) as interference respectively 3 , SCN , CO3 4 (Fig. S6). The absorption signals were hardly changed. In the competition experiments, Cu2+ (104 M) was added to the mixing solution containing the aforementioned anions under the identical conditions (Fig. 5). Similarly, miscellaneous competitive anions did not lead to significant interference. In summary, these experimental phenomena demonstrated that DHIH showed excellent selectivity and sensitivity to Cu2+ over other competitive cations and anions.

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DHIH+XnDHIH+Xn-+Cu2+

Absorbance

0.8

0.6

0.4

0.2

0.0

D

3.5. Job’s plot analyses Job’s method [32] for the absorbance intensity was applied to determine the stoichiometry of DHIH–Cu2+ complex by keeping the sum of the initial concentration of Cu2+ and DHIH at 10 lM and the molar ratio of Cu2+ changing from 0.1 to 0.9. A plot of absorbance versus the molecular fraction of [Cu2+]/([DHIH]+[Cu2+]) was provided in Fig. 6. The results exhibited that the absorbance went through a maximum when the molecular fraction was close to 0.5, which indicated a 1:1 stoichiometry of the DHIH to Cu2+ in the complex. According to the formula as follows [36], the association constant Ka used to estimate the stability of the complex could be calculated.

1 1 1 ¼ þ A  A0 K a ðAmax  A0 Þ  ½Cu2þ  Amax  A0

2+

Cu

2-

-

-

-

SCN Ac NO3 F

Br CO3

2SO4 Cl

Fig. 5. Absorbance of DHIH (1.0  104 M) upon the addition of different anions (10 lM) (black bars) and the addition of Cu2+ (10 lM) in the buffer solution–CH3CN (3:7, v/v) (red bars). (For interpretation of the references to color in this figure legend, the reader is referred to the web version of this article.).

0.40 0.35 0.30

Absorbance

Fig. 3. Color change of the buffer solution–CH3CN (3:7, v/v) system. (For interpretation of the references to color in this figure legend, the reader is referred to the web version of this article.).

0.25 0.20 0.15 0.10 0.05 0.1

0.2

0.3

0.4 2+

here A0 and A are the corresponding absorbance of DHIH in the absence and presence of metal ion solution of a given concentration. Amax is the absorbance completely complexed with cations. A plot of 1/(A  A0) versus 1/[Cu2+] was obtained (Fig. 7). From the slop of the Benesi–Hildebrand plot, the association constant Ka was calculated to be 1.0  104 M1.

0.5

0.6

0.7

0.8

0.9

2+

[Cu ]/([Cu ]+[DHIH]) Fig. 6. Job’s plot for the determination of the stoichiometry of DHIH and Cu2+ in the buffer solution–CH3CN (3:7, v/v); The total concentration of DHIH and Cu2+ was 10 lM.

12

Absorbance

0.8

0.6

10

1/(A-A0)

1.0

n+ DHIH+M n+ 2+ DHIH+M +Cu 2+ 2+ DHIH+Ni +EDTA+Cu

8

y=116.3x+0.053 R=0.9995

6 4 2

0.4

0 0.00 0.2

0.0

0.02

0.04

0.06

0.08

0.10

1/[Cu2+] (μM-1) Fig. 7. Benesi–Hildebrand plot of 1/(A  A0) versus 1/[Cu2+]. 2+ 2+ 2+ 2+ + 2+ 6+ 2+ 2+ 3+ 2+ 3+ 2+ + 6+ + + 2+ 3+ + 2+ D Cu Cd Pt Ba Rb Hg Cr Be Zn Sr2+Fe Mn2+ Mg Al Ca Na Mo Cs Li Pb As K Ni

Fig. 4. Absorbance of DHIH (1.0  104 M) upon the addition of different metal ions (10 lM) (black bars) and the addition of Cu2+ (10 lM) in the buffer solution–CH3CN (3:7, v/v) (red bars). (For interpretation of the references to color in this figure legend, the reader is referred to the web version of this article.).

3.6. Interaction mechanism of DHIH binding to Cu2+ UV–vis absorption spectrum of DHIH (Fig. 1) exhibited two major peaks at 294 and 343 nm, which could be respectively

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789

O

Cu2+

N N H

N

N HO

O

NH

Cu2+ O

N

Scheme 2. Proposed binding mechanism of DHIH with Cu2+ in solutions.

assigned to p–p⁄ and n–p⁄ transition involving molecular orbitals particularly localized on the C@N chromophore and benzene ring [24]. Only with Cu2+ added into the solution of DHIH, absorbance was obviously decreased at 294 and 343 nm and accompanied by a new absorption peak appeared at the range of 400–440 nm. These results suggested the M (Cu2+)–A (acceptor) interaction has been increased due to the recognition of Cu2+ at imine nitrogen, amide carbonyl and hydroxyl groups (Scheme 2) and consequently a red-shift of absorption spectra was observed upon base on the internal charge transfer (ICT) [37,38]. 4. Conclusions In summary, we have developed a new colorimetric probe isonicotic acid hydrazide Schiff base derivative (DHIH). In the presence of Cu2+, the DHIH displayed an obvious color change from colorless to yellow together with UV–vis absorption spectra change in a very short time. The colorimetric probe performs high sensitivity toward Cu2+ with an association constant (Ka) of about 1.0  104 M1 and a detection limit of 5.24  107 mol/L in acetonitrile/Hepes buffered solution. Moreover, the proposed probe exhibits excellent selectivity over other competing common cations and anions, which could make it possible for practical applications. Acknowledgments This work was supported by the National Natural Science Foundation of China (No. 21207047), the State Major Project for Science and Technology Development, China (No. 2013YQ 47078102-3), the Science-Technology Development Project of Jilin Province of China (Nos. 201105008, 20126018, 20130206014GX) and the Program for the State Key Laboratory of Inorganic Synthesis and Preparative Chemistry Open Project, Jilin University, China (No. 2014-07). Appendix A. Supplementary data Supplementary data associated with this article can be found, in the online version, at http://dx.doi.org/10.1016/j.saa.2015.07.043. References [1] J.G. Zhang, L. Zhang, Y.L. Wei, J. Ma, S.M. Shuang, Z.W. Cai, C. Dong, Spectrochim. Acta, Part A 122 (2014) 731–736. [2] F.J. Chen, F.P. Hou, L. Huang, J. Cheng, H.Y. Liu, P.X. Xi, D.C. Bai, Z.Z. Zeng, Dyes Pigm. 98 (2013) 146–152. [3] R. Martinez, A. Espinosa, A. Tarraga, P. Molina, Tetrahedron 66 (2010) 3662– 3667.

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