Prof. Dr.Sajid Hassan Guzar
Hussain Majeed Mahdi
Department of chemistry, College of Education for Pure Sciences,
Azo compounds contain the functional group (-N=N-) and it is called the azo group[1]. The azo group (-N = N-) is a type of chromophore group, and this color-bearing group is responsible for the coloring of azo compounds, Azo compounds may contain one or more active groups called auxochromic groups, which increase color, such as (-COOH, -OH, -SH, -Br, -NH2)[2]. Azo compounds and their complexes have been widely used due to their importance in the field of inorganic chemistry as well as their spectroscopic applications in analytical chemistry. Heterocyclic azo compounds, in particular, have gained a wide area in the aforementioned fields because they contain more than one active group that has the ability to form colored chelating complexes, which facilitates the process of spectroscopic determination of very small concentrations of metal ions using ultraviolet–visible spectroscopy[3, 4].
Azo compounds can be prepared in two steps. The first step is the formation of the diazonium salt, by reacting aromatic amines with a solution of nitrous acid (HNO2), which is prepared by reacting a mineral acid such as hydrochloric acid (HCl) with a solution of sodium nitrite (NaNO2) at low temperatures(0-5)°C[5].
The second step is the coupling step: coupling the resulting diazonium salt with an electron-rich nucleophilic compound such as phenols in an alkaline medium to give azo compounds, as coupling reactions usually occur at the site para relative to the phenol group[6].
Azo compounds have many applications. Synthetic azo compounds have shown antibacterial[7], antifungal, anticancer, antioxidant, antitumor[8], antidiabetic[9], and anti HIV properties in the human body, as well as in printing and in photosensitive solar cells[10]. In the field of medicine, it has been used as an important medicine because of its role in inhibiting bacteria[11], In medicine, compound Prontosil is the first azo dye used as an antibacterial[12].
References:
[1] S. A. A. Jawad and I. K. Kareem, “Synthesis, characterization of new azo-Schiff ligand type N2O2 and metal complexes with Di valance nickel, palladium and tetra valance platinum,” NeuroQuantology, vol. 20, no. 1, p. 62, 2022.
[2] N. M. Aljamali and H. S. Hassen, “Review on azo-compounds and their applications,” Journal of Catalyst & Catalysis, vol. 8, no. 2, pp. 8-16p, 2021.
[3] M. W. Taher, S. H. Guzar, and H. Hanoon, “Simple, selective, and sensitive spectrophotometric method for determination of trace a mount of cobalt (II), cadmium (II), lead (II), with a new reagent 1-[(3-methylthiophen-2-yl) methylene]-2-phenylhydrazine,” in AIP Conference Proceedings, 2023, vol. 2830, no. 1: AIP Publishing.
[4] S. H. Guzar and Q.-h. JIN, “Simple, selective, and sensitive spectrophotometric method for determination of trace amounts of nickel (II), copper (II), cobalt (II), and iron (III) with a novel reagent 2-pyridine carboxaldehyde isonicotinyl hydrazone,” Chemical Research in Chinese Universities, vol. 24, no. 2, pp. 143-147, 2008.
[5] M. Q. Abdulridha, A. A. S. Al-Hamdani, and I. A. Hussein, “Synthesis, Characterization and Antioxidant Activity of New Azo Ligand and Some Metal Complexes of Tryptamine Derivatives,” Baghdad Science Journal, vol. 20, no. 3 (Suppl.), pp. 1046-1046, 2023.
[6] M.-Y. Zhao, Y.-F. Tang, and G.-Z. Han, “Recent Advances in the Synthesis of Azo Compounds,” 2023.
[7] W. A. Ali, H. H. Mihsen, and S. H. Guzar, “Novel Derivative for Dithiocarbamite Containing a New Sulphur-Azo Linkage and Its Complexes with Sn (II), Sn (IV), Co (II), Ni (II) and Cu (II) Ions; Synthesis, Characterization and Antibacterial Activity,” Al-Bahir Journal for Engineering and Pure Sciences, vol. 2, no. 1, p. 3, 2023.
[8] N. A. Hussein and A. K. Abbas, “Synthesis, spectroscopic characterization and thermal study of some transition metal complexes derived from caffeine azo ligand with some of their applications,” Eurasian Chem Commun, vol. 4, no. 1, pp. 67-93, 2022.
[9] T. Aziz et al., “Rational synthesis, biological screening of azo derivatives of chloro-phenylcarbonyl diazenyl hydroxy dipyrimidines/thioxotetrahydropyrimidines and their metal complexes,” Heliyon, vol. 9, no. 1, 2023.
[10] R. Khanum, S. A. RA, H. Rangaswamy, S. S. Kumar, A. P. Kumar, and A. Jagadisha, “Recent Review on Synthesis, Spectral Studies, Versatile Applications of Azo Dyes and its Metal Complexes,” Results in Chemistry, p. 100890, 2023.
[11] S. H. Guzar and J. Qin-Han, “Synthesis, characterization and spectral studies of new cobalt (II) and copper (II) complexes of pyrrolyl-2-carboxaldehyde isonicotinoylhydrazone,” Journal of Applied Sciences, vol. 8, no. 13, pp. 2480-2485, 2008.
[12] H. A. Abd El Salam, M. S. Abdel-Aziz, E. R. El-Sawy, and E. Shaban, “Synthesis and Antibacterial Activity of Azo-Sulfa-Based Disperse Dyes and Their Application in Polyester Printing,” Fibers and Polymers, vol. 24, no. 8, pp. 2751-2760, 2023.
