Synthesis of Metal Complexes of Acetylacetone Electrolytically

 

Sneha Kumari Agarwal, M. Alam*

Department of Chemistry, Ranchi University, Ranchi-834008

*Corresponding Author E-mail: malamgold@gmail.com

The interaction of ligand, acetylacetone with elemental zinc and copper leads to the formation of chelates ML_n or ML_n.mH₂0 through electrochemical synthesis. On the basis of elemental analysis, IR spectroscopy and TGA , the structures are discussed.

 

 

 

1. INTRODUCTION:

The metal is oxidized at the anode and substrate is reduced at the cathode by applying a voltage.^(1,2) Electrons are transfered from anode to the reaction mixture and from the reaction mixture to the cathode and this allows an electric current to pass through the cell.^(3-7)

 

At Anode:                   

M            à         Mⁿ⁺    +    ne-

 

At Cathode:                

nL      +   ne-      à    (L_n)^n-

 

Overall:                    

Mⁿ⁺      +    (L_n)^n-    à    ML_n

 

The oxidized metal reacts with the ligand to form complexes by using suitable ligating species derived from potentially chelating organic reagents.^(8-13)

 

In the present work, we have used Zn electrode and Cu electrode as anodes to form complexes with acetylacetone.^(14,15) Pt electrode was used as cathode. Acetone was used as solvent and lithium perchlorate  as electrolyte with 3v DC supply under atmospheric condition. The solids formed were isolated in the pure form and characterized on the basis of elemental analysis, FTIR spectra studies and thermal analysis.

 

Chemical used:- LiClO₄, acetylacetone, acetone. (The chemicals used were of A.R. grade).

 

EXPERIMENTAL PROCEDURES:

(a) Anodic metal: Zinc:

0.5g LiClO₄ was dissolved in 30ml of acetone in a 100ml beaker. 2ml acetylacetone was added, .Sodium acetate solution was prepared dissolving 1g sodium acetate to 1ml acetone and water (1:1),mixed with glass rod and the solution was subjected  to electrolysis  using Pt electrode as cathode and Zn electrode as sacrificial anode under 3v DC supply. The electrolytic process going on can be confirmed through the bubbles emerging out of Pt electrode. After 4 hr the white powder  deposited at the bottom of the cell was collected. It  was dried and bottled as sample SAZ1.Percentage of zinc was obtained by EDTA titration method.

 

(b) Anodic metal: Copper:

Solution was prepared dissolving 0.5g KClO₄ in 30ml of DMF. 2ml acetylacetone was added in the solution. 1:1 sodium acetate solution was prepared dissolving 1g sodium acetate to 1ml acetone and water .poured in the parent solution. The solution turned to light yellow. It  was electrolysed using Pt electrode as cathode and Cu electrode as sacrificial anode under 3v DC supply. The electrolytic process going on could be confirmed through the bubbles emerging out of Pt electrode. After 4 hr, blue solution was filtered giving blue solid as filtrate. It was purified, dried and collected as SAC1.Percentage of copper was obtained titrimetrically. 

 

 

 

 

 

Elemental analysis and related data

No.	Colour	C%	H%	O%	M%	Empirical formula
SAZ1	White	f: 43.40 c:42.63	f:6.034 c:5.68	C:28.42	C:23.27	C10H16O5Zn
SAC1	Shining blue	f:45.57 c:45.89	f:6.235 C:5.35	C:24.47	C:24.28	C10H14O4Cu

 

 

FTIR RESULT SAZ-1

Table-1-FTIR Results (sample SAZ1)

Peaks	Nature of peaks	Group assignment
3379.29	Broad	O-H stretching(H-bonded)
2989.66	Strong	C-H; CH3
2449.60	weak	overtone
1944.25	Weak	overtone
1593.20	Sharp	C=O stretching
1516.05	Sharp	C=O
1408.04	Sharp	CH3
1257.59	Sharp	C-C,C-CH3
1195.87	medium	C-H, in plane bending
1014.56	Sharp	CH3 rocking
918.12	Sharp	C-CH3+C-O
771.53	Sharp	C-H, out of plane bending
655.80	Medium	C-CH3 bend + Zn-O
547.78	Sharp	Zn-O

 

 

Thermogravimetric results:

 

Table-2

Temperature	Formulation sequence	Experimental loss	Theoretical loss
24-5000C	Zn.(CH3COCHCOCH3)2.H2O   ↓ - (CH3COCHCOCH3)2   ZnO	69%	70%

 

 

FTIR RESULT SAC -1

Table-3-FTIR Results sample SAC1

Peaks	Nature of peaks	Group assignment
2997.38	Medium	C-H;CH3
2920.23	Medium	C-H;CH3
2627.05	M	Overtone
2368.50	M	Overtone
2121.70	M	Overtone
1959.68	M	Overtone
1573.91	S	C=O
1535.34	S	C=C
1419.61	S	CH3
1357.89	S
1273.02	S	C-C;C-CH3
1188.15	M	C-H, in plane bend
1018.41	S	CH3,rock
937.40	S	C-CH3+C-O
738.10	S	C-H, out of plane bend
682.80	M	Ring deformation + M-O
651.04	M	C-CH3 ;bend + M-O
613.36	S	C-CH3 ;bend + M-O
455.20	S	Ring def.+ M-O skeletal vib.

 

Proposed formulation:

SAZ1:

 

 

SAC1 :

 

RESULTS AND DISCUSSION:

The FTIR curves (Table-1) of sample SAZ1 contain almost all the peaks which are expected for the formulation. A very broad band appeared in the 3200-3300 cm^-1 region resulting due to stretching of OH bond  of water  due to H bonding. The bands at 1593 cm^-1 and 1516cm^-1 were assigned to C=O and C=C vibrational modes. The bands near 544cm^-1 is due to M-O stretching vibration for Zn acetylacetonate ^(16-19). Thus ,the FTIR curves strongly support the proposed formulation of SAZ1.Also in the TGA-DTA curves, the water of hydration is lost between 24-170⁰C and further decomposition (loss of acac) occurs until 300⁰C. A small amount of mass is additionally lost upto 500⁰c with Zn oxide as ultimate product.⁽²⁰⁾

 

Similarly,the proposed formulation of SAC1,on the basis of empirical formulation is strongly supported by FTIR curves as well as TGA analysis., i.e. the expected broad peaks for C=O and C=C vibrational modes  appeared in the region 1573.91 and 1535.34 . The band due to H-bonded acetyl carbonyl at 1630cm^-1 of ligands disappeared and a new strong band assignable to the stretching of a metal bonded carbonyl group appeared at 1570 cm^-1. The bands due to C-H vibrations appeared. This supports the replacement of chelated proton of the ligands by a metal ion. The IR spectrum of SAC1 had no band in the region 1650-1800cm^-1 which is for free carbonyl group. The band near 400cm^-1 due to M-O stretching vibration for Cu- acetylacetonates is present in the curve.⁽²¹⁾

 

 

Similarly, the loss pattern in TGA-DTA curve is just what we expect for the formulation. The total loss of Cu(acac)₂ almost takes place in the range 175-500⁰C (96%)and it reveals that it is a volatile compound leaving almost nothing behind at temperature above 500⁰C.^(22-24)

 

ACKNOWLEDGEMENT:

The author is grateful to Dr. M. Alam for improvement of paper. The author is thankful to the CIF, BIT Mesra, for providing useful data of elemental analysis. This work was supported by chemistry laboratory, Department of Chemistry, Faculty of Science, Ranchi University.

 

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Received on 18.04.2015         Modified on 28.04.2015

Accepted on 11.05.2015         © AJRC All right reserved