INTRODUCTION:

Complex formation with Schiff base, semicarbazone, thiosemicarbazones, triazoles, amino acids, are largely studied for quantitative estimation of metal ions by coupling with various instrumental techniques. Literature survey reveals that there are large number of research papers on complex formation and characterization^2,3. Several complexes are applied for the biological activity studies by examining for antibacterial, antimicrobial, antiviral etc. activities. Some authors studied the coordination chemistry of the complex and its application as biological active complex. Here we present a unique application for metal ligand complex by using it as a precursor for synthesis of nano crystalline Copper (II) oxide⁴.

MATERIALS AND METHODOLOGY:

All the chemicals and solvents used for the synthesis are analytical grade. semicarbazide hydrochloride, 2’,4’-dihydroxy acetophenone and other chemicals were purchased from sigma Aldrich or Merck. The FTIR spectra were recorded using KBr discs on a Perkin-Elmer spectrum FTIR system. The NMR spectra were recorded in Bruker Ultra shield 300 spectrophotometer. The electronic spectra in the range 200–1000 nm was obtained in acetonitrile on a UV-1800 Shimadzu spectrophotometer. Thermogravimetric measurements were carried out on a Mettler Toledo TGA/DSC instrument.

The synthesis of complex was done in two steps, 1) the synthesis of ligand 2) the synthesis of the complex.

1) The synthesis of ligand¹ was done by equimolar mixture of sodium acetate and semicarbazide hydrochloride is dissolved in minimum quantity of water and then it is added to methanolic solution of 2’,4’-Dihydroxy acetophenone. After addition warm the solution and stir the solution about one hour. The light pink colored compound is precipitate out, which is washed and then recrystallized by using 50% ethyl alcohol as solvent.

Fig. No. 1. Synthesis of Ligand (Reagent)

2) The synthesis of complex was done by direct reaction of ligand (Reagent)^5,6 with Copper (II) sulphate. The light-yellow colored complex^12,13is precipitate out, which is washed and then recrystallized by using 50% ethyl alcohol as solvent. The powdered complex was then dried and used for further studies.

Fig. No. 2. Synthesis of Copper complex preparation of Cu-(2, 4-DHA) semicarbazone

RESULT AND DISCUSSIONS:

In order to find application of metal ligand complex as a precursor for synthesis of nanocrystalline Copper the synthesis of different semicarbazone complex were done. The synthesised of Ligand (reagent) 2,4 dihydroxy acetophenone semicarbazone^19,20was first characterised by obtaining IR and NMR^7,8 and the synthesised complex was then characterised and compared with IR^9,10. The interpretation of data is shown in table no 1, 2 and 3 which confirms the formation of a ligand(reagent), Cu (II) complex respectively. The correspond figures of the interpreted results are also included as figure no 3, 4, 5, 6 and 7 for different instrumental techniques^14,15.

Fig. No. 3. IR of Semicarbazone derivative(ligand)

Table No. 1 IR Spectral Studies of Ligand (Reagent)

Frequency (cm^-1)	Functional group
3483	ν_(O-H) stretching
3095	ν_(CH)aromatic stretching
1593	ν_(C=N) stretching
1520	ν_(C=C)stretching
1680	ν_(C=O) stretching
1458	C-O-H bending
1323	Ph-C-O stretching
1284	C-N stretching
1375	In plane bonds due to aromatic substituted benzene ring
1173
1155
1116
854	Substituted benzene ring
758	ν_(C-H)stretching due to substituted benzene ring
538	Benzene ring deformation
1375	(CH₃-C) bending

Fig. No. 4. HNMR of Semicarbazone derivative

Table No. 2. ¹H NMR Spectral Studies of Ligand (Reagent)

Solvent	No. of protons	δ in ppm	Assignment
d⁶- DMSO	s, 3H	3.39	CH₃-C=N
	s,2H	2.14	-NH₂
	s,1H	2.48	-NH-
	two d, 2H s,1H	6.1 to 7.3	Aromatic Proton
	d, 2H	12.98	-OH

Fig. No. 5. IR of Cu (II) Complex

Table No. 3. IR Spectral Studies of Cu (II) Complex

Frequency (cm^-1)	Functional group
3046	ν_(C-H)aromatic stretching
1585	ν_(C=N)stretching
1486	ν_(C=C)stretching
1660	ν_(C=O)stretching
1375	Ph-C-O- stretching
1170	C-N stretching
538	ν_(M-N)stretching
476	ν_(M-O)stretching

Decomposition Studies TGA Studies:

The decomposition studies^16,17 of the complexes were done by means of Thermogravimetric analysis¹¹. The decomposition of the complex was studied at different temperature in the range 28°C to 900°C. Thermogravimetric (TG) weight loss curves and the corresponding differential thermogravimetric (DTG) curves for the complex are shown in Figure no 3. The complex showed three well-defined steps at 170°C, 270°C and 413°C together with final steps above 413°C. The loss in weight in the first step is 7.358% which should be due to the two co-ordinated water molecules. The second, and third weight losses are 29.211% and 46.858%, respectively, totalling 72.46%. This large weight drop can be explained by considering that the residue is a C₈H₆N₂ and CuO (calculated weight loss 72.46%). The table no 4 shows the details of the decomposition studies.

Fig No. 6. TGA for Metal Complex

Table No. 4. Thermo Gravimetric Analytical Data for Metal Complex

Molecule	Temperature (^oC)		Weight loss In %
Molecule	Commencement of decomposition	Completion of decomposition	Observed
H₂O	28	170	7.358
NH₃	170	270	29.211
CO₂	270	413	46.858
C₈H₆N₂	413	900	72.46

XRD STUDIES:

Particle size of the copper oxide was determined by using Scherrer’s formula given below. Average particle size of the CuO was found to be 35nm size.

0.89 λ

D =--------

β Cos θ

Where, λ = 1.54060 A⁰ (Cu K_α)

β = Full width half maxima in radian.

Fig No. 7. XRD of Copper oxide

CONCLUSION:

From the above studies it can be seen that the compounds containing Copper chalcogen bond can be used for the preparation of Copper chalcogenide nanoparticles¹⁸. It is found that the semicarbazone derivative result in Copper oxide. In conclusion, the presence of direct Copper-chalcogen bond is important in getting these materials. Also, it is evident that the simple decomposition technique can lead to Copper oxide nano crystallites. As these nano crystallites have wide range of applications still some are awaiting which are to be finding out.

ACKNOWLEDGEMENT:

The authors wish to thank the Department of Chemistry, University of Mumbai, Mumbai. The Institute of Chemical technology, Matunga, Mumbai. The authors wish to thank IIT Bombay for extending the instrumental facility for the above said project. The author wants to thank Rohit Patil for assisting in the laboratory work.

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Received on 06.02.2021 Modified on 17.03.2021

Asian Journal of Research in Chemistry. 2021; 14(4):255-258.

DOI: 10.52711/0974-4150.2021.00043