Synthesis of Vanadium (III) Schiff Base Complex and its Electrocatalytic Sensing Application

Mechanics, Materials Science & Engineering, May 2017

ISSN 2412-5954

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P. Supriya Prasad1, Praveen Kumar2, K. Bharathi1, V. Narayanan1,a 1

Department of Chemistry, DKM College for Women, Vellore, India

2

Department of Inorganic Chemistry, University of Madras, Guindy Campus, Chennai, India

a

vnnara@yahoo.co.in DOI 10.2412/mmse.47.57.91 provided by Seo4U.link

Keywords: Vanadium (III) Schiff base complex, microwave irradiation, Vitamin-B6, differential pulse voltammetry, electrochemical polymerization.

ABSTRACT. The coordination chemistry of vanadium complexes have been focused more than half a century because of its interesting structural and chemical activities. The vanadium complexes are wide used in biological and industrial fields. The vanadium Schiff base complex was synthesized by simple and green chemical microwave irradiation synthetic process. The Schiff base ligand was synthesized by condensation reaction between 5bis (3-aminopropyl)ethylenediamine, with this Schiff base ligand vanadium(III) chloride was added for the formation of vanadium(III) Schiff base complex. The Schiff base ligand provide a tetradentate planar structure to vanadium (III) center metal for the formation of stable complex. It was characterized by FT-IR, UV-Visible, Raman and fluorescence spectral techniques. The electrochemical redox activity of vanadium (III) Schiff base complex was studied by cyclic voltammetry with three electrode system. The synthesized vanadium complex was utilized for the electrocatalytic sensing of vitamin B6. The vanadium (III) Schiff base complex was electrochemically polymerized, the polymer Schiff base vanadium complex was deposited on the surface of GCE. The modified GCE was exhibits an anodic peak for vitamin B6 at 1.25 V result we can conclude that the vanadium(III) Schiff base complex modified GCE has better electrocatalytic sensing activity for the determination of vitamin B6 and it can be used for real sample analysis.

Introduction. Schiff base ligands have considerable attention, because of its facile synthesis and wide range of applications in different fields. Schiff bases are privileged ligands due to their ligating behavior towards metal ions. The Schiff bases are synthesized by a simple one-pot condensation between a carbonyl group of ketone or aldehyde with amine, the carbonyl groups are replaced by an imine group in an alcoholic solvent [1]. More than a century, the Schiff base metal complexes have be materials, non-linear optics, electrocataytic sensors, catalyst in synthetic chemistry and photo physical studies. The Schiff base metal complexes have high stability in different oxidation states, hence these complexes have wide range of application. Among the various Schiff base metal complexes, the vanadium (III) have great interest in fast few decades due to its catalytic and medicinal importance. Vanadium is an important trace bio-element, it plays a vital role in many metabolic and mitogenic processes. To know the role of vanadium in biological process, it is necessity to carry out the studies in model vanadium complexes. The interactions of amino acids and peptides with vanadium complexes are better example for biological studies. The studies of vanadium (III) complexes have been investigated less than the corresponding chemistry of vanadium (IV or V) complexes. However, the vamadium (III) complexes can play important role in biochemical redox processes and there are organisms, such as ascidians in which the principal oxidation state of vanadium is +3. Even though the inorganic vanadium salts have less biological activities and toxicity, the complexation with organic ligands of vanadium leads to minimize the adverse effects. The 23

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vanadium compounds have different physiological roles, such as insulin-mimetic action, antihypertension, anti-hyperlipidemia, antin ascidians sequester have vanadium (III) complexes in their blood cells, it spurred the interest of chemists to investigated vanadium (III) complexes [2]. However, the investigation of structures and activities of vanadium (III) complexes in biological process may give some understanding the puzzling role of vanadium (III) in ascidians. In addition, complexes of vanadium (III) with organic ligands like Schiff base can explains, the efficiency of vanadium (III) complexes in catalytic process and other biological active process. In the present work the vanadium (III) Schiff base complex was synthesized by microwave irradiation method and it was characterized by several spectral techniques. The synthesized vanadium complex was electrochemically polymerized and utilized for the sensing of vitamin B6. Vitamin B6 (pyridoxine) is an important vitamin for both mental and physical health process. Vitamin B6 (V-B6) is much essential for the formation of red blood cells. It takes wide variety of functions in human body for maintaining good health. The conversion of tryptophan amino acid to niacin vitamin needs the V-B6. V-B6 is an important vitamin for the nervous and immune systems function. V-B6 is an essential vitamin for the better healthy condition of human body.

-B6 can causes a simple, selective and sensitive method for the analysis of V-B6. There are so many analytical methods were available for the quantification of V-B6, but the electrochemical method gives better results for the V-B6 determination. Hence, the electrocatalytic determination was used for the V-B6 quantification, it gives low detection limits, simple experimental procedure, cost effective and better sensitivity. This vanadium complex has good electrocatalytic sensing ability for V-B6 determination.

Experimental Procedure. Vanadium (III) Schiff base complex was synthesized by the following procedure. An absolute 2 mM [0.313 g] of methanolic solution of 5-chlorosalicyaldehyde was taken -bis(3aminopropyl)ethylenediamine in methanol was added drop wise with the aid of burette under stirring condition. A yellow colour solution was obtained. The yellow coloured reaction mixture was employed for microwave irradiation at 320 W, 2-3 min. After that, the reaction mixture was cooled to room temperature and kept for 12 hr. A yellow solid product was obtained it was collected and recrystallized using 1:1 methanol in hot condition and dichloromethane. The synthesized Schiff base ligand was used for the vanadium Schiff base complex synthesis. 1 mM of the Schiff base ligand was taken and 1 mM of vanadium (III) chloride was added to Schiff base ligand under stirring using in methanol medium. A brown colour solution was obtained and it was subjected to microwave irradiation at 320 W, for 5 min. The reaction mixture was cooled to room temperature and kept in 24 hr. A brown vanadium (III) Schiff base complex was obtained. The vanadium (III) Schiff base complex was collected and recrystallized by using hot ethanol solution.

Cl

NH2

Cl NH

+

2

NH O

Microwave Irradiation

NH2

320 W, 2-3 min

N

OH

NH NH

Cl

N

VCl3 N

OH

OH

Microwave Irradiation

NH NH

N

O OH2 V OH 2 O

320 W, 5 min Cl

Fig. 1. Synthesis of Vanadium(III) Schiff basecomplex.

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Cl

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Result and discussion FT-IR spectral analysis. The FT-IR spectrum of vanadium (III) Schiff base complex was shown exhibits a band at 1625 cm-1, it appeared at lower frequency when compare to the free Schiff base ligand C=N, due to the bond formation between the imine group nitrogen with the vanadium metal ion. The free C=N in Schiff base ligand exhibits its vibrational frequency peak around 1650 cm-1. It indicates that bond formation of the nitrogen atom with the vanadium metal ion. In addition the complex formation was confirmed by two other characteristic peaks in the region of 400 600 cm-1, these peak suggest the bond formation between the vanadium metal ion with the oxygen and nitrogen atoms. The van -O) at 496 cm-1 and the -1 nitrogen vanadium bond appeared at 595 cm , these three peaks confirms the complex formation.

Besides with few characteristic peaks were appeared, a peak at 3326 cm-1 shows the presence of solvated water molecules in the metal complex, the C-C shows a peak at 2936 cm-1, a peak observed at 1358 cm-1 due to aromatic C=C and the C-N bond exhibits a peak at 1455 cm-1 in the complex.

The phenyl ring shows its vibrational frequency at 820 cm-1. All these vibrational peaks are confirmed the formation of vanadium (III) Schiff base complex.

Electronic spectral analysis. The electronic spectrum of vanadium (III) Schiff base complex was recorded in the range of 200-800 nm, in the methanol solution and it was shown in Fig. 1b. In the

in the azomethane group. The band at 410 nm is due to charge transfer (LMCT) transitions. The weak band at about 650 nm corresponds to d-d transition of vanadium (III) ion, which can be assigned as 3 3 T2g T1g in octahedral geometry. The electronic transitions in the absorption study suggests that the vanadium (III) Schiff base complex in octahedral geometry [3].

Raman spectral analysis. Raman spectrum of vanadium (III) Schiff base complex was given in Fig. 1, c. In the Raman spectrum the imine group, metal nitrogen and metal oxygen bond vibrational peaks was consider for confirms complex formation. The imine C=N group exhibits a sharp peak at 1525 cm-1, which is lower region when compare to that of free ligand imine group Raman spectral analysis was carried out using laser Raman microscope in the range of 200 2500 cm-1 for vanadium (III) Schiff base complex, which is shown in Fig. 1, c. We can observe the characteristic vibrational bands of the complex in the expected region. In the Raman spectra the azomethine group -C=Nvibrational frequency was observed in the range of 1525 cm-1. The C=N- peak appears at lower frequency in V (III) Schiff base complex than the free ligand, it indicates that the nitrogen atom in azomethane group has coordination with vanadium metal ion. In the spectrum a sharp peak appeared around 810 cm-1 corresponds to vibrations frequency of phenyl ring in the V(III) Schiff base complex. The metal nitrogen and metal oxygen bonds were exhibited around 551 and 480 cm-1 in the Raman spectra which confirms the complex formation between Schiff base ligand and vanadium formation is confirmed by shift in a number of stretching frequency to lower than free Schiff base ligand.

Electrochemical studies. The redox behaviour of vanadium(III) Schiff base complex was examined by cyclic voltammetry, in three electrode system. The glassy carbon electrode utilized as working electrode, silver and silver chloride (Ag/AgCl) as reference electrode and platinum wire was counter electrode. Voltammetry measurement was carried in 0.1 M acetonitrile solution, in the presence of tetrabutylammonium perchlorate (TBAP) as supporting electrolyte. The obtained cyclic voltammogram explains the electrochemical redox properties of the vanadium metal ion, it was show in Fig. 1d. The positive potential of metal ion shows that vanadium ion has lower oxidation state and strongly binds with Schiff base ligand. The vanadium Schiff base complex shows an oxidation peak and its corresponding reduction peak. The anodic peak appeared at 0.345 V due to the oxidation process of V(III) to V(V). The cathodic peak exhibits at -0.282 V for the reduction process of V (V) to V(III). The electrons were transferred between two stable oxidation states, when the potential was MMSE Journal. Open Access www.mmse.xyz

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applied. The electrochemical studies show that vanadium (III) Schiff base complex has good electrochemical redox behaviour [4].

Fig. 2. (a) FTIR spectrum, (b) UV-Visible spectrum, (c) Raman spectrum and (d) Cyclic voltammogram in 0.1 M TBAP at the scan rate of 50 mVs-1 of vanadium(III) complex.

Electrochemical polymerization. The vanadium (III) Schiff base complex was electrochemically polymerized and used for the sensing of vitamin B6. The glassy carbon electrode (GCE) was modified by the electrochemical polymerization of 0.1 M vanadium (III) Schiff base complex in acetonitrile solution, at -0.5 to 0.5 V working potential. The polymerized vanadium (III) complex was deposited on the surface of GCE. The electrochemical polymerization was occurred due to the vanadium (III) redox process i.e., {V (III) to V (V)} and {V (V) to V (III)}.

Electrocatalytic Sensing of vitamin B6. The electrocatalytic sensing of vitamin B6 (V-B6) using vanadium (III) Schiff base complex modified GCE and bare GCE was investigated with the aid of cyclic voltammetry in phosphate buffer as background electrolyte. Cyclic voltammograms of V-B6 at bare GCE and poly-V-SBC/GCE as working electrodes are shown in Fig. 2b. V-B6 exhibits an anodic peak only for both the electrodes. The oxidation of V-B6 at bare GCE is 1.277 V, with the peak current of 7.97 A. The poly-V-SBC/GCE shows the V- B6 anodic peak at 1.264 V, with peak current is 8.95 A. The modified GCE shows lower anodic potential with higher peak current when compare with bare GCE. These results clearly explains that the vanadium Schiff base complex modified GCE has better electrocatalytic sensing ability for vitamin B6 determination. The enhanced sensing activity was attributed by the vanadium (III) Schiff base complex [5, 6].

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Fig. 3. (a) electrochemical ploymerization of vanadium(III) Schiff base complex in 0.1 M TBAP, (b) Sensing of vitamin B6 in PBS at the scan rate of 50 mVs-1.

Summary. Microwave irradiation method was utilized for synthesis of Vanadium (III) Schiff base complex and characterized by FT-IR, UV-Vis. and Raman spectral techniques. The electrochemical redox property of V (III) Schiff base complex was studied by cyclic voltammetry. The vanadium Schiff base complex was electrochemically polymerized on the GCE surface and the modified electrode was successfully used for the detection of vitamin B6. The modified electrode shows a better result than bare GCE. References [1] Plass W. Chiral and Supramolecular Model Complexes for Vanadium Haloperoxidases:HostGuest Systems and Hydrogen Bonding Relays for Vanadate Species J. Coord Chem Rev, 2011, Vol. 255(19/20):2378-2387, DOI 10.1016/j.ccr.2011.04.014.

[2] Kanamori K. Structures and properties of multinuclear vanadium (III) complexes: seeking a clue to understand the role of vanadium (III) in ascidians. Coord. Chem. Rev. 2003; 237:147 161, DOI 10.1016/S0010-8545(02)00279-5.

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DOI

10.1016/j.poly.2009.03.015.

[4] T.L. Riechel, L. J. D. Hayes, D. T. Sawyer, Inorg. Chem., Vol. 15, 1976, 1900-1904.

[5] B. Brunetti, E. Desimoni, J. Food Comp. Anal., Vol. 33, 2014, 155 160. DOI 10.1016/j.jfca.2013.12.008.

[6] W. Qu, K. Wu, S. Hu, Voltammetric determination of pyridoxine (Vitamin B 6) by use of a chemically-modified glassy carbon electrodeJ. Pharm. Biomed. Anal., Vol. 36, 2004, 631-635.

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