A New Colorimetric Sensor Responding CN- Anion based on

Hydrazone Compound in Acetonitrile Solution

S. Suharman

and Siti Utari Rahayu

Department of Chemistry, Universitas Sumatera Utara, Jl. Dr. T. Mansyur No. 9, Medan, Indonesia

Department of Physics, Universitas Sumatera Utara, Jl. Dr. T. Mansyur No. 9, Medan, Indonesia

Keywords: Chemosensor, Colorimetric, Cyanide, Hydrazone, Vanillin.

Abstract: A new hydrazone compound 2-methoxy-6-((E)-phenyldiazenyl)-4-((E)-(2-phenylhydrazineylidene)

methyl)phenol (receptor R) based on vanillin has been synthesized and applied to cyanide anion detection in

acetonitrile solvent. Color of the receptor solution turned from yellow to purple in the presence of cyanide

anion and other anions like H

, Br

, CN

, SO

, Cl

, I

, CH

COO

and F

could not effect color of

receptor. Changing in the maximum wavelength of the receptor after addition of cyanide anion was

confirmed by UV-Vis spectrophotometer. In the presence of cyanide, wavelength of the receptor changed

from 347 nm to 510 nm. Detection limit of the receptor were also observed by UV-Vis spectrophotometer.

Based on the UV-Vis titration, the receptor detected cyanide anions with limit of detection 4mM in the

acetonitrile solvent.

1 INTRODUCTION

The anion waste produced from natural processes or

industries like gold mining, electroplating, metal and

pesticides industries cause health and environmental

problems (Ghanavati et al., 2014). Some anions

waste like cyanide have toxic properties and a lethal

effect (Mourzinaet al., 2003;Nezamzadeh-ejhieh and

Esmaeilian, 2012) even exposure to large amount of

cyanide through both Inhalation or oral exposure

cause death and systemic effect (respiratory,

cardiovascular, gastrointestinal, neurological,

haematological) on living organisms (Research

Triangle Institute, 1997). WHO has established level

of cyanide in drinking-water 0.5 mg/L (WHO,

2011). The toxic effect of cyanide can be described

from its ability to inhibit enzyme cytochrome

oxidase on step of oxidative phosphorylation of

respiration process (Gupta, 2009). Cyanide anion

can form complex phenomenon with a part of

enzymatic structure that can inhibit function and

cellular growth (Mekuto et al., 2016).

Severalmethods have been widely used to detect

the presence of anions waste in the environment

including potentiometric (Mourzinaet al.,

2003;Nezamzadeh-ejhieh & Esmaeilian, 2012;

Cuartero et al., 2013), ion chromatography (Silveira

et al., 2014) and electrochemical analysis (Pulkkaet

al., 2014). They are less practical methods that

sample preparation is required. In addition, the

analysis of anion by the methods require high cost

and a long time for analysis. Therefore we need

more practical method for detecting these anions.

Colorimetric chemosensor method, a method

developed for the detection of anions, is more

efficient method which is not require sample

preparation and the specific instrument.

Furthermore, analysis with this method is directly

observed by naked eye. It uses sensor compounds

called chemosensor which generally consists of two

parts: The binding site like -NH or -OH groups plays

as fragment that can interact with anions and

signaling subunit like chromophore groups is act as

a signal transducer (Martinez-Manez & Sancenon,

2003). Both binding site and signaling sub unit are

important part in the colorimetric sensor which gives

effect to its selectivity and sensitivity to anion.

Organic materials have been widely used as

chemosensor. Recently, researcher have been

reported the colorimetric anion based chalcone, azo

and hydrazone derivatives. Azo derivative was used

as sensor of H

, F

and acetate anion with the

amine group as the binding site (Shao et al, 2009).

Hydrazone derivative was also used as sensor of

acetate anion by amine group on the synthesized

314

Suharman, S. and Rahayu, S.

A New Colorimetric Sensor Responding CN- Anion based on Hydrazone Compound in Acetonitrile Solution.

DOI: 10.5220/0010163400002775

In Proceedings of the 1st International MIPAnet Conference on Science and Mathematics (IMC-SciMath 2019), pages 314-318

ISBN: 978-989-758-556-2

compound as binding site that interact with the

acetate anion through hydrogen bonds (Qiao, 2009).

The color change of the synthesized compound

solution in DMSO solvent from yellow to green was

occurred after addition of acetate anion. In addition,

azo-hydrazone derivative such as 4-phenylazo-2-

hydroxy-benzaldehydephenylhydrazone compound

from salicylaldehyde was used as compound sensor

by the change of color from yellow to red after the

addition of acetate, F- and H

anions (Li et al.,

2010).

In this study, we synthesized receptors 2-

methoxy-6-((E)-phenyldiazenyl)-4-((E)-(2-

phenylhydrazineylidene)methyl)phenol (receptor R).

We also present the solvent (solvatochromic) and

electron-withdrawing group like azo effect to UV-

Vis electronic absorption and sensitivity of receptors

R to cyanide anion.

2 EXPERIMENTAL SECTION

2.1 General

Vanillin, NaOH, methanol, acetic acid, H

98% ,

ethanol, NaNO

, CHCl

, phenylhydrazine, DMSO,

acetonitrile, acetone, silica gel 60 (0.040-0.063 mm),

NaF, NaCl, NaI, NaBr, Na

, Na

, NaH

COONa, NaCN. All materialswere purchased

from Merck.Infrared spectra were recorded using

Shimadzu Prestige-21 FT-IR Spectrophotometer.

The spectra of

H-NMR and

C-NMR were

evaluated on JEOL JNM ECA-500, Mass spectra

were performed on Shimadzu QP-QP-5000 and

2010. Melting point was measured using uncorrected

Electrothermal-9100

2.2 Synthetic Procedure of 4-hydroxy-

3-methoxy-5-

(phenyldiazenyl)benzeldehyde

Solution I (aniline0.03 mol, water (7.5 mL) and

H2SO4 7.5 mL) was addedinto sodium nitrite

solution (0.03 mol, water 12 mL) and stirred for 1 h.

Solution II (NaOH 3.6 g in water 90 mL and vanillin

0.03 mol, 0-5

C)was dropwised into the solution I.

The solution was stirred for 3 at temperature 0-5

The precipitate was filtered (Radchatawedchakoon

et al., 2014). Product was obtained as dark red solid

and yield 72%. IR cm-1: 3425 (O-H); 3062 (Csp

H), 2931 and 2864 (Csp

-H); 1681 (C=O); 1604

(C=C aromatic); 1458 (N=N); 1411(-CH

); 1280 (C-

N); 1141 and 1072 (C-O-C).

H-NMR (CDCl

δ/ppm 14.23 (O-H, s, 1H); 9.94 (CHO, s, 1H); 7.88

(m, 2H); 7.56-7.52 (m, 3H); 7.48 (s, 1H), 4.00

(OCH

, s, 3H). EI-MS (m/z): 256.

2.3 Synthetic Procedure of Receptor R

The compound of 4-hydroxy-3-methoxy-5-

(phenyldiazenyl)benzaldehyde (1mmol) in ethanol

(100 mL) was introduced into the base-round three

neck flask capacity 250 mL with a condenser.

Phenylhidrazine (1 mmol) and four drop of acetic

acid were dropwised into the solution. The solution

stirred and refluxed for 3 h. The precipitate was

filtered. Product was produced as dark brown solid,

yield 81%, m.p. 141-141.8

C. IR (cm

-1

): 3425 (O-

H); 3309 (N-H); 3055 (Csp

-H); 2931 and 2854

(Csp

-H); 1597 (C=N); 1496 (N=N); 1265 (C-N);

1149 and 1072 (C-O-C).

H-NMR (DMSO-

d6;δ/ppm): 13.66 (NH, s, 1H); 7.78 (aromatic, d, J =

1.95 Hz, 2H); 7.74 (CH=N, s, 1H; 7.63 (OH, s, 1H);

7.56-7.48 (m, 5H); 7.3-7.28 (m, 2H); 7.14 (s, 2H);

6.88 ( s, 1H); 4.03 (-OCH

, s, 3H).

C-NMR

(DMSO-d6;δ/ppm): 149.9; 149.6; 145.4; 136.8;

131.4; 129.7; 129.6; 129.5; 127.0; 123.6; 122.5;

122.2; 120.3; 112.9; 110.5; 56.6. EI-MS (m/z): 346

(M+).

2.4 Solvatochromic Study of Receptor

Solvatochromic studies of receptors R were used

various solvent such as ethanol, DMSO, acetonitrile

and acetone. 4.0 mg of Receptor was dissolved in

solvents. The color change and the UV-Vis

absorptions were recorded.

2.5 Selectivity Study of Receptor R

Selectivity studies of receptor R were carried out in

acetonitrile solution at concentration level 2 x 10

-5

M. The solution of receptor was added by 10 µL of

NaF, NaCl, NaBr, NaI, NaCN, Na

, Na

COONa and NaH

solution, respectively.

The color change and the UV-Vis absorption were

recorded.

2.6 UV-Vis Titration of Receptor R

with CN

The titration of UV-Vis was carried out in

acetonitrile solution at concentration level of 5 x 10

-5

M for receptor R and (1-10) x 10

-2

and (1-10) x 10

-3

M for CN

. The solution of receptor was added by 50

µL of CN

solution. The UV-Vis absorptions were

A New Colorimetric Sensor Responding CN- Anion based on Hydrazone Compound in Acetonitrile Solution

315

recorded by spectrophotometer UV-Vis at 200-700

nm.

3 RESULT AND DISCUSSION

The receptor R was synthesized by condensation

reaction between 1 mmol of 4-hydroxy-3-methoxy-

5-(phenyldiazenyl) benzaldehyde and I mmol of

Phenylhidrazinein 100 mL ethanol solvent (Fig. 1).

The chemical structure of receptor Rwere confirmed

byGC-MS, FT-IR,

C-NMR and

H-NMR.

Figure 1: Synthesis of receptor R.

3.1 Solvatochromic Study

Solvatochromic studies of receptor R carried out

with variety of protic and non-protic solvents. Table

1 shows the maximum wavelength of receptor R in

various solvents and Fig. 2 shows solvatochromic

absorbance spectra of receptor.

Table 1: λmax values of receptor 1, 2 and 3 in various

solvents.

Receptor λmax (nm)

DMSO acetonitrile Acetone Ethanol

R 355 347 348 351

Table 2: ET(30) and normalized EN/T value.

Solvent ET (30)

(Kcal mol-1)

Ethanol 51.9 0.654

DMSO 45.1 0.444

Acetonitrile 45.6 0.460

Acetone 42.2 0.355

Based on Table 1 showed that polar solvent such

as DMSO and ethanol caused bathochromic shift

compared to less polar solvent such as acetonitrile

and acetone. Solvent polarity causes the different of

maximum wavelength of receptor R. Based on the

UV-Vis electronic absorption, maximum wavelength

of receptor in DMSO solvent was 355 nm, while in

acetonitrile solvent was 390 nm. Hypsochromic shift

occurred at acetone (λmax 348 nm and acetonitrile

(λmax 347 nm) solvent. The difference of solvent

polarity affects electronic transition energy of the

ground state to the excited state. More polar solvents

such as DMSO stabilizes the electron in the excited

state (π*) that causes the transition energy becomes

smaller so maximum wavelength will be greater. In

addition, protic (DMSO) and aprotic (ethanol)

solvent affect maximum wavelength of receptor.

Based on normalized

and ET (30) value, ethanol

solvent is more polar than solvent DMSO (see Table

2). However, maximum wavelength of receptor in

ethanol solvent is smaller than the DMSO solvent.

Transition energy of the ground state to the excited

stateis influenced by the ability of the solvent to

form hydrogen bond with receptor. Protic solvent

such as ethanol can form hydrogen bonds with the

receptor that causes free electrons in the ground state

is more stabilized than the excited state. Therefore,

the energy transition will be greater and maximum

wavelength will be smaller (Reichardt, 1994).

Figure 2: Solvatochromic UV-Vis spectra of receptor R.

Figure 2 shows the UV-Vis spectra of receptors

R. Table 1 and Fig. 2 shows that the substituent at

aromatic ring affect the λmax value between

receptor R. Electron-withdrawing group such as azo

group increases delocalization of electron which it

caused the electron more conjugated and

bathochromic shift (Huang et al., 2012). It is attested

by the presences of azo group at receptor increased

the intensity of color change and wavelength shift of

receptor.

3.2 Selectivity Study of Receptor R

The selectivity of receptor was evaluated by adding

anions likeH

, CO

, Br

, CN

, SO

, Cl

, I

COO

and F

to acetonitrile solution of receptors

R. It was observed that the addition of CO

and

anions to receptor solution, the receptor solution

color changed from bright yellow to purple (Fig. 3).

Other anions such as H

, Br

, SO

, Cl

, I

IMC-SciMath 2019 - The International MIPAnet Conference on Science and Mathematics (IMC-SciMath)

316

COO

did not provide color change of receptor

solution. In addition, the absorbance spectra were

determined by UV-Vis spectrophotometer. Out of all

anions examined, the presence of CN

in solution

appeared new band at 510 nm. New band appeared

at 522 nm after addition CO

but the absorbance

intensity of CN

were greater than CO

(Fig. 4).

Based on the study, we concluded that the receptor

could be used as a colorimetric sensor for CN

acetonitrile solvent.

Figure 3: The color change of receptor 3 in CH

CN after

addition of anions: 1) Receptor, 2) F

, 3) Cl

, 4) Br

, 5) I

6) H

, 7) CH

COO

, 8) SO

, 9) CO

, 10) CN

Figure 4: Titration of UV-Vis of receptor R with Cyanide.

The color change caused by the presence of CN

in solution proves that there is an interaction

between receptor and CN

. We suggested three

possible mechanisms. The first interaction is the

hydrogen bond between CN

with O-H or N-H

group. The second interaction is deprotonation of H

atom at hydroxyl or amine group (Mondal et al.,

2018). The last possible mechanism is

chomodisimeter: CN

, which is a strong nucleophile,

attacks C=N to form a new C-C bond (Cao & Wang,

2013).

3.3 UV-Vis Titration of Receptor R

with CN

UV-Vis titration receptors R were carried out in

acetonitrile solution at a concentration level 2 x 10

-5

M. the ability of anion to form bond with receptor R

was evaluated by adding solution of sodium cyanide

salt. The addition of CN

anion also affected UV-Vis

spectra of receptor 3 (Fig. 5). The addition of CN-

anion to receptor caused absorbance at 347 nm

decreased gradually and new band appeared at 510

nm. In addition, the change of color from yellow to

purple occurred after addition of cyanide anion to

receptor (Fig. 3). The color change and wavelength

shift after the addition of CN

anion indicated that

the receptors reacted with CN

anion. We concluded

that receptor could be used to cyanide detection by

naked eye.

Figure 5: UV-Vis titration of R with Cyanide.

Receptor R have two active sites part i.e. amine

and hydroxyl groups. However, the ability of amine

group to form hydrogen bond with cyanide anion

was better than hydroxyl group. The presence of azo

group on the receptor caused the proton on the

amine group is more acid than the hydroxyl group

(Shang and Xu, 2009). Thus, Interaction occurs

between -NH at receptor with CN

anion. The

presence of chromophore group such as azo group

affect the sensitivity of the receptor to the CN

anion. It is attested by detection limit of receptor.

Based on Fig. 5, the color change at receptor

occurred after the addition of 4 mM of CN

anion.

4 CONCLUSIONS

Receptor R show the solvatochromic properties in

protic and aprotic solvents. In aprotic solvents,

bathochromic shift of receptors occur in more polar

solvents, while protic solvent such as ethanol can

form H-bonds with binding site of receptor that can

stabilize the electron in the ground state. It causes

the λmax value of receptor in ethanol is smaller than

the DMSO. The presence of electron withdrawing-

group like azo group can increase sensitivity of

receptor to cyanide anion. It is evidenced by the

limit of detection of receptor was 4 mM.

A New Colorimetric Sensor Responding CN- Anion based on Hydrazone Compound in Acetonitrile Solution

317

ACKNOWLEDGEMENTS

This research was funded by Universitas Sumatera

Utara with research implementation contract number

in fiscal year 2019 Number:

4167/UN5.1.R/PPM/2019 dated April 1

,2019.

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