242 This work is licensed under a Creative Commons Attribution 4.0 International License IHJPAS.37 (2) 2024 Ibn Al-Haitham Journal for Pure and Applied Sciences Journal homepage: jih.uobaghdad.edu.iq PISSN: 1609-4042, EISSN: 2521-3407 Amnah Mahdi Abdullah 1* , Abbas Ali Salih Al-Hamdani 2 and Wail Al Zoubi 3 1,2 Department of Chemistry, College of Science for Women, University of Baghdad, Baghdad, Iraq. 3 School of Materials Science and Engineering,Yeungnam University, Gyeongsan 712-749, South Koria. *Corresponding Author. Abstract Diazotization reaction between 1-(2,4,6-trihydroxy-phenyl)-ethanone and diazonium salts produced the ligand 4-(3-Acetyl-2,4,6-trihydroxy-phenylazo)-N-(5-methyl-isoxazol-3-yl)- benzenesulfonamide, which in turn reacted with the metal ions (Ni 2+ , Zn 2+ , Pd 2+ and Pt 4+ ) forming stable complexes with Octahedral geometry suggest of (Ni 2+ and Pt 4+ ), Zn 2+ complex Tetrahedral and Pd 2+ complex Square planer. The creation of such complexes was detected by employing spectroscopic means involving ultraviolet-visible, which proved the obtained geometries; FT-IR confirmed the formation of the azo group and the coordination with metal ions through it. Thermogravimetric analysis studies demonstrated the coordination of water residues (aqua or hydrate) with metal ions inside the coordination sphere, as well as used curve DSC to calculate the thermodynamic parameters ΔH, ΔS, and ΔG. Moreover, element microanalysis and atomic absorption gave corresponding outcomes with theoretically counting outcomes. Neuclearmagnatic resonances for 1 H and 13 C, chlorine atoms, and magnetic moment quantifications also indicate the formation of azo dye ligand. The ligand and new complexes showed antioxidant abilities to scavenge free radicals. Keywords: Antioxidant, mass spectroscopy, azo dye, 1-(2,4,6-trihydroxy-phenyl)-ethanone, thermal analysis. 1. Introduction Until the middle of the 19 th century, all coloring materials were supplied from natural sources such as inorganic dyes [1]. As for natural organic dyes, they also have an ancient history of use, especially in Tissues dyeing [2]. Heterogeneous azo compounds, in particular, won a wide area in several fields because they contain more than one active group that has the ability to form complexes of colored aggregates, which facilitates the spectroscopic determination of very small concentrations of metal ions using the visible-ultraviolet spectra [3-5]. This led to the emergence of new dyes, and Kekule's discovery of the molecular structure of benzene in 1865 had a great impact on the development of dyes until the beginning of the twentieth century [6,7]. Received:7 February 2023 Accepted:2 April 2023 Published:20 April 2024 Synthesis, Characterization and Determination Antioxidant Activities for New Azo Dyederived from Sulfamethoxazole and Some Metal Ion Complexes doi.org/10.30526/37.2.3279 https://creativecommons.org/licenses/by/4.0/ https://orcid.org/0000-0002-9187-2677 mailto:Amnah.Mahdi.Abdullah@gmail.com https://orcid.org/0000-0002-2506-986X mailto:abbasas_chem@csw.uobaghdad.edu.iq https://orcid.org/0000-0002-9959-1431 mailto:wwailalzoubi@yahoo.com https://orcid.org/0000-0002-9187-2677 mailto:Amnah.Mahdi.Abdullah@gmail.com https://orcid.org/0000-0002-2506-986X mailto:abbasas_chem@csw.uobaghdad.edu.iq https://orcid.org/0000-0002-9959-1431 mailto:wwailalzoubi@yahoo.com https://orcid.org/0000-0002-9187-2677 mailto:Amnah.Mahdi.Abdullah@gmail.com https://orcid.org/0000-0002-2506-986X mailto:abbasas_chem@csw.uobaghdad.edu.iq https://orcid.org/0000-0002-9959-1431 mailto:wwailalzoubi@yahoo.com https://jih.uobaghdad.edu.iq/index.php/j/index#1609-4042 https://jih.uobaghdad.edu.iq/index.php/j/index#2521-3407 https://orcid.org/0000-0002-9187-2677 mailto:Amnah.Mahdi.Abdullah@gmail.com https://orcid.org/0000-0002-2506-986X mailto:abbasas_chem@csw.uobaghdad.edu.iq https://orcid.org/0000-0002-9959-1431 mailto:wwailalzoubi@yahoo.com https://orcid.org/0000-0002-9187-2677 mailto:Amnah.Mahdi.Abdullah@gmail.com https://orcid.org/0000-0002-2506-986X mailto:abbasas_chem@csw.uobaghdad.edu.iq https://orcid.org/0000-0002-9959-1431 mailto:wwailalzoubi@yahoo.com https://orcid.org/0000-0002-9187-2677 mailto:Amnah.Mahdi.Abdullah@gmail.com https://orcid.org/0000-0002-2506-986X mailto:abbasas_chem@csw.uobaghdad.edu.iq https://orcid.org/0000-0002-9959-1431 mailto:wwailalzoubi@yahoo.com https://orcid.org/0000-0002-9187-2677 mailto:Amnah.Mahdi.Abdullah@gmail.com https://orcid.org/0000-0002-2506-986X mailto:abbasas_chem@csw.uobaghdad.edu.iq https://orcid.org/0000-0002-9959-1431 mailto:wwailalzoubi@yahoo.com https://orcid.org/0000-0002-9187-2677 mailto:Amnah.Mahdi.Abdullah@gmail.com https://orcid.org/0000-0002-2506-986X mailto:abbasas_chem@csw.uobaghdad.edu.iq https://orcid.org/0000-0002-9959-1431 mailto:wwailalzoubi@yahoo.com https://orcid.org/0000-0002-9187-2677 mailto:Amnah.Mahdi.Abdullah@gmail.com https://orcid.org/0000-0002-2506-986X mailto:abbasas_chem@csw.uobaghdad.edu.iq https://orcid.org/0000-0002-9959-1431 mailto:wwailalzoubi@yahoo.com https://orcid.org/0000-0002-9187-2677 mailto:Amnah.Mahdi.Abdullah@gmail.com https://orcid.org/0000-0002-2506-986X mailto:abbasas_chem@csw.uobaghdad.edu.iq https://orcid.org/0000-0002-9959-1431 mailto:wwailalzoubi@yahoo.com https://orcid.org/0000-0002-9187-2677 mailto:Amnah.Mahdi.Abdullah@gmail.com https://orcid.org/0000-0002-2506-986X mailto:abbasas_chem@csw.uobaghdad.edu.iq https://orcid.org/0000-0002-9959-1431 mailto:wwailalzoubi@yahoo.com https://orcid.org/0000-0002-9187-2677 mailto:Amnah.Mahdi.Abdullah@gmail.com https://orcid.org/0000-0002-2506-986X mailto:abbasas_chem@csw.uobaghdad.edu.iq https://orcid.org/0000-0002-9959-1431 mailto:wwailalzoubi@yahoo.com https://orcid.org/0000-0002-9187-2677 mailto:Amnah.Mahdi.Abdullah@gmail.com https://orcid.org/0000-0002-2506-986X mailto:abbasas_chem@csw.uobaghdad.edu.iq https://orcid.org/0000-0002-9959-1431 mailto:wwailalzoubi@yahoo.com https://orcid.org/0000-0002-9187-2677 mailto:Amnah.Mahdi.Abdullah@gmail.com https://orcid.org/0000-0002-2506-986X mailto:abbasas_chem@csw.uobaghdad.edu.iq https://orcid.org/0000-0002-9959-1431 mailto:wwailalzoubi@yahoo.com https://orcid.org/0000-0002-9187-2677 mailto:Amnah.Mahdi.Abdullah@gmail.com https://orcid.org/0000-0002-2506-986X mailto:abbasas_chem@csw.uobaghdad.edu.iq https://orcid.org/0000-0002-9959-1431 mailto:wwailalzoubi@yahoo.com IHJPAS.37 (2) 2024 244 Thus, natural dyes were replaced by synthetic dyes [8]. Azo dyes are organic substances consisting of two organic groups linked through coupling reactions with an azo group to give colored compounds that are absorbed in the visible and ultraviolet regions [9-12]. Azo dyes are considered the most significant group within organic dyes, which are prepared industrially and can add colors to fibers [13]. They contain an azo group – N = N – as nitrogen atoms are linked to carbon atoms with Sphybridization and at least one carbon atom is connected to a ring (usually benzene or naphthalene derivatives) or polycyclic such as (Pyrazolone or Thiazole) [14]. Studies have shown that these compounds represent essential drugs, as they were found to have properties that inhibit the growth of bacteria [15-17]. Due to the importance of these compounds, the current research included the preparation and identification of a new azo dye derived from 1- (2,4,6-Trihydroxy-phenyl)-ethanone and sulfamethoxazole. This work aims to synthesize new metal ions complexes (Ni 2+ , Zn 2+ , Pd 2+ and Pt 4+ ) from azo ligand H3L as well as characterization with spectroscopic analysis and studying thermal decomposition and thermal stability by using DSC and TGA curve. This study uses curve DSC to calculate the thermodynamic parameters ∆H, ∆S and ∆G then antioxidant activity of these compounds against the DPPH radicals and compare to those of the natural antioxidant gallic acid. 2. Materials and Methods Materials have been obtained from the trading suppliers (Sigma Aldrich, Merck, and others). The eurovectormodel EA/3000, singleV3O, has been employed to achieve (C.H.N.S and O). Mineral-ions have determined as M-O using a gravimetric-approaches. Molar conductivity has been estimated by operating Conduct meter W-T-W, at room temperature, 1×10-3 M. DMSO has been employed as solvent. Mass spectra for substances have been collected using mass spectrometry (MS) Q-P-50-A-D-I Analysis Shimadzu QP (E170Ev) -2010-Pluss spectrometer. The UV-visible absorption spectra were obtained using a UV-1800 Shimadzu spectrophotometer. The Brucker (400 MHz) spectrometer was used to obtain the 1 H and 13 C NMR spectra. The IR Prestige-21 was used to investigate the Fourier transform infrared (FTIR) spectra, where the device was used Shimadzu 4000-200 cm -1 by CsI and Bruker 4000- 500 cm -1 by KBr. The F.A.A. determined the metal percentage. The balancing susceptibility model MSR-MKI utilized magnetic characteristics. Perkin-Elmer Pyris Diamond DSC/TGA was used for all prior sorts of thermal analysis. The chlorine content of the prepared complexes was measured using Moore's method 686-titro processor-665. The magnetic sensitivity was also measured using the Magnetic Susceptibility Balance Model (MSB-MKI) device. 2.1 Synthesis of azo dye ligand [4-(3-Acetyl-2,4,6-trihydroxy-phenylazo)-N-(5-methyl– isoxazol-3-yl)–benzenesulfonamide] Sulfamethoxazole (1 g, 3.948 mmol) was dissolved in (2 mL of HCl and 10 mL of ethanol) at 0-5°C, gradually added (10%, 1 g, 14.49 mmol) NaNO2 stirred for approximately 45 minutes, then, the (0.663 g, 3.948 mmol) of 1-(2,4,6-Trihydroxy-phenyl)-ethanone dissolved in 15 mL of ethanol was added. The change to a dark-colored solution was observed after stirring for 30 minutes. This product is collected after being filtered and dried. Its melting point was (146- 148)°C and the color of precipitate was orange, its yield was 93%. Scheme 1 shows the formation of the ligand azo dye. The ligand showed bands at 3503, 3281,3014, 2979, 1635 and (1088-1015) cm -1 that were ascribed to the ν (OH) phenolic, ν (NH), ν (C-H) aromatic,ν (C-H) aliphatic,ν (C=O) and ν (SO2). The infrared spectrum of the ligand showed a medium-intensity IHJPAS. 37(2)2024 245 stretch band at a frequency of 1485 cm -1 , which was attributed to the vibrational frequencies of the double bond N=N. The UV-Vis spectrum exhibits strong absorbance at (286 nm, 34965.04 cm -1 ), ascribed to the π ⟶ π* transition and peak at (392 nm, 25510.20 cm -1 ) attributed to the n⟶π* transition peak [18]. The 1 H-NMR and 13 C-NMR spectra of Newazo, which can be seen in Figure 1, demonstrate the chemical shifts of these spectra. 1 H-NMR (DMSO-d6, ppm):1.92 ppm (3H,s, CH3), 2.08 ppm (3H,s, CH3CO), CH3,6.43 ppm, (1H, s, C-H) isoxazole ring [The rest of the 1 HNMR signals are arranged in this manner, 6.77 ppm, (1H,s, CH aromatic) beside OH, (7.26-8.1) ppm (4H, dd, aromatic), 8.11 ppm (1H,s, NH ), 8.74 ppm (1H)S, (OH) phenolic beside (N=N), 8.75 ppm, (1H)S (OH) phenolic beside (N=N) and it belongs to NH, (OH) phenolic beside COCH3. 13 C-NMR: 33.62(C1), 49.71(C18), 106.90(C13), 118.20(C3), 127.48(C15), 132.21(C11), 137.27(C9), 145.00(C7), 148.96(C10), 155.15(C6), 157.23(C5), 165.30(C4), 169.75(C16), 172.24(C8), 178.10(C12), 181.97(C2), 189.75(C14) and 196.20 (C17) [19,20]. LC- Mass spectrum was tested using an LC-Mass device; this approach is one of the most essential approaches in characterization and complementary to the rest of the approaches by which the molecular weight of the compound is estimated according to the relation (m/z). Mass information of the ligand in Scheme 1 shows the fragmentation pattern and the extracted mass for each pattern. It can be clearly observed the molecular ion peak [M] + for the fragment C14H10N2O6S•+ and its relative abundance of about 66% in Figure 2, in addition to other abundances for the rest of peaks including C8H8N2O4 •+ , C6H4O2S •+ and C4H4N2O •+ , corresponded the next abundances: 47%, 33% and 79% respectively [21]. Figure 1. The 1 H and 13 C-NMR spectra of ligand (H3L). IHJPAS. 37(2)2024 246 Figure 2. Mass spectrum of ligand. Scheme 1. Pattern of fragmentation of ligand. 2.2 General approach for complexes synthesis The metal salt (1 mmol) of [0.1979 g NiCl2.6H2O, 0.1364 g ZnCl2, 0.17742 g PdCl2 and 0.5178 g H2PtCl6.6H2O] was dissolved in 15 mL of hot ethanol. Then (0.432 g, 1 mmol) of azo dye in 15 mL of hot ethanol was added drop by drop. The mixture washeated under reflux for 6 hours up to 40-50 °C. The solid complexes were separated and any non-apostate ingredients are removed by immersing them shortly in the hot ethanol. The complexes were collected, dried and weighed. Schem 2 shows the formation of the metal ions complexes. IHJPAS. 37(2)2024 247 Scheme 2. Formation for ligand and their metal complexes. 3. Results and Discussion 3.1 Physical and analytical data for ligand and the synthesized complexes Reactions of metal salts with ligands gave the synthetic complexes, as shown in Scheme 1. The results of the elemental analysis demonstrate 1:1 M: L stoichiometry for all complexes. The elemental analysis results were compatible with the theoretical calculated results, as denoted in Table 1. Table 1. Some physical propertiesand element micro analysis studies of ligand and complexes. Micro elemental analysis (Found) and Calculated % Compounds formula M.wt m.p °C Color Cl M S O N H C 146- 148 Orange -- -- (6.70) 7.42 (25.10) 25.90 (14.00) 12.96 (4.01) 3.72 (50.55) 50.00 H3L= C18H16N4O7S 432 = 196 d Brown (7.03) 6.33 (11.09) 10.46 (6.05) 5.70 (26.01) 25.66 (10.96) 9.98 (4.09) 3.38 (37.77) 38.49 C18H19N4O9SClN i = 561.1934 259 d Brown (6.00) 6.46 (11.10) 11.89 (5.62) 5.82 (22.66) 23.28 (11.61) 10.18 (3.00) 3.09 (40.01) 39.28 C18H17N4O8SClZ n= 549.909 220 d Light Brown (7.08) 6.19 (16.69) 18.58 (6.09) 5.60 (18.91) 19.54 (10.67) 9.77 (2.09) 2.64 (38.65) 37.68 C18H15N4O7SClP 572.92=d 186 d Dark Brown (13.69) 14.54 (25.67) 26.63 (5.05) 4.37 (15.21) 15.29 (8.01) 7.64 (2.41) 2.05 (30.01) 29.48 C18H15N4O7SCl3 Pt = 732.578 d=decompose. 3.2 The UV-Vis studies of the complexes The UV-Vis spectrum exhibits the electronic transition of Pt 4+ complex show in Figure 4 depicts a peak of (288, 375, 615, 632 and 680) nm assigned to π→ π*, n→ π*, 1 A1g→ 1 T1g, 1 A1g→ 1 T2g and 1 A1g→ 3 T2g respectively which indicative of a Octahedral geometry, it has a magnetic moment of diamagnatic. The Ni 2+ complex show in Figure 3 exhibited peaks of (220, 270, 418, 614, 730 and IHJPAS. 37(2)2024 248 840) nm ascribed to the π→π*, n→π*, C.T M→L, 3 A1g→ 3 T2g(F), 3 A1g→ 3 T1g(F) and 3 A2g→ 3 T1g(P) respectively is in good agreement with prior work on octahedral geometry, it has a magnetic moment of 2.13 [22]. The electronic absorption of Zn 2+ complexe exhibited peaks of (263, 368 and 447) nm ascribed to the π →π*,n→π* and C.TM→L respectively which is indicative of a Tetrahedral geometry, it has a magnetic moment of diamagnetic [23]. The Pd 2+ complexe exhibited peaks at (262, 363, 421, 700 and 804) nm ascribed to the π→ π*, n→ π*, C.TM→L, 1 A1g→ 1 B1g and 1 A1g→ 1 A2g respectively is in good agreement with prior work on Squar planer geometry it has a magnetic moment of diamagnetic [24]. Table 2 displays the electronic assignmentfor metal complexes. Figure 3. The UV-Vis spectrum of Ni-complex. Figure 4. The UV-Vis spectrum of Pt-complex. Table 2. The UV-Vis spectra, magnetic moments and molar conductivity for metal complexes. ɅmS. cm 2 . Mol -1 µeff (B.M) Assignment Ɛmax L mol - 1 cm -1 Abs ύ cm -1 λ nm Compound 13 2.13 π→π* n→π* C.T M→L 3 A1g→ 3 T2g(F) 3 A1g→ 3 T1g(F) 3 A2g→ 3 T1g(P) 4000 9500 12380 5500 4850 3800 0.400 0.950 1.238 0.550 0.485 0.380 45454.55 37037.04 23923.45 16286.65 13698.63 11904.76 220 270 418 614 730 840 [Ni(H2L)(H2O)2Cl] Octahedral 16 diamagnatic π→π* n→π* C.T M→L 14000 10630 15810 1.400 1.063 1.581 38022.81 27173.91 22371.36 263 368 447 [Zn(H2L)(H2O)Cl] Tetrahedral 13 diamagnatic π→π* n→π* C.T M→L 1 A1g→ 1 B1g 1 A1g→ 1 A2g 5400 3550 6100 380 400 0.540 0.355 0.610 0.038 0.040 38167.942 7548.2123 752.97142 85.711243 7.81 262 363 421 700 804 [Pd(H2L)Cl] Square planer 20 diamagnatic π→π* n→π* 1 A1g→ 1 T1g 1 A1g→ 1 T2g 1 A1g→ 3 T2g 3400 4850 1440 1600 1800 0.340 0.485 0.144 0.160 0.180 34722.22 26666.66 16260.16 15822.78 14705.88 288 375 615 632 680 [Pt(H2L)Cl3]O Octahedral IHJPAS. 37(2)2024 249 3.3 The LC-Mass spectrum of complexes The LC-Mass spectrum of the products were tested using LC-Mass device, this approach is one of the most essential approaches in characterization and complementary for the rest approaches by which the molecular weight of the compound is estimated according to the relation (m/z). For [Ni(H2L)(H2O)2Cl], Figure 5 and Scheme 3, it can also be detected the molecular ion peak (M + ) at 559.99 m/z with the relative abundance of 10% and following patterns: C18H15ClN4NiO7S + , C14H10ClN2NiO4 •+ , C6H6ClN2NiO2 •+ , C4H4N2O3S •+ and C8H7O2 + , which corresponded to 523.97 m/z, 362.97 m/z, 230.95 m/z, 159.99 m/z and 135.04 m/z respectively [25]. For [Pd(H2L) Cl] complex in Figure 6 and Scheme 4 illustrate the following fragments: (M + ) at 571.94 m/z with the relative abundance of 21%, C18H15N4O7PdS •+ , C5H6O3Pd •+ , C6H5NO2S •+ , C3H4N2O •+ , and C4H4NO + that correspond to 536.97 m/z, 219.93 m/z, 155.00 m/z, 84.03 m/z and 82.03 m/z respectively [26]. Finally, [Pt(H2L)Cl3] complex in Figure 7 and Scheme 5 illustrate the following fragments: (M + ) at 730.94 m/z with the relative abundance of 29%, C18H15N4O7PtS + , C5H6O3Pt •+ , C6H5NO2S •+ , C3H4N2O •+ and C4H4NO + that correspond to 626.03 m/z, 309.00 m/z, 155.00 m/z, 84.03 m/z and 82.03 m/z respectively [27]. Figure 5. Mass spectrum of Ni-complex. Figure 6. Mass spectrum of Pd-complex. IHJPAS. 37(2)2024 250 Figue 7. Mass spectrum of Pt-complex. Scheme 3. Pattern of fragmentation of Ni-complex. Scheme 5. Pattern of fragmentation of Pt-complex. Scheme 4. Pattern of fragmentation of Pd-complex. IHJPAS. 37(2)2024 251 Table 3. The LC-Mass spectral data for complexes. Relative Abundance (%) m/z Exact mass Fragment 10 559.99 [C18H19ClN4NiO9S] 47 523.97 [C18H15ClN4NiO7S] + 65 362.97 [C14H10ClN2NiO4] •+ 48 79 34 230.95 159.99 135.04 [C6H6ClN2NiO2] •+ [C4H4N2O3S] •+ [C8H7O2] + 21 571.94 [C18H15ClN4O7PdS] 11 536.97 [C18H15N4O7PdS] •+ 40 219.93 [C5H6O3Pd] •+ 48 155.00 [C6H5NO2S] •+ 35 84.03 [C3H4N2O] •+ 34 82.03 [C4H4NO] + 29 730.94 [C18H15Cl3N4O7PtS] 36 626.03 [C18H15N4O7PtS] + 35 309.00 [C5H6O3Pt] •+ 77 155.00 [C6H5NO2S] •+ 76 84.03 [C3H4N2O] •+ 87 82.03 [C4H4NO] + 3.4 Infrared spectra measurements The infrared spectra of metal complexes were recorded with Ni 2+ , Zn 2+ , Pd 2+ and Pt 4+ have been compiled, show in Figure 8 for Zn complex, Figure 9 for Pd complex and the data has been organized in Table 4. The infrared spectrum of metal complexes showed the vibration frequencies of the double bond N=N; this band suffered a remarkable change in shape, intensity, and position in the spectra of the chelate complexes, which indicates the intercalation of the electron pair of the nitrogen atom of the azo bridge group in the coordination process where N=N and C=O shift, OH disappears and OH water bands appear in addition to the emergence of new packages called the coordination process, which are M-N, M-O and M-Cl. After this, the IR spectra of all produced compounds revealed that the azo-dye ligand connected to metal ions through two sites: the azo group's nitrogen site, and oxygen site via deprotonation of of one of the hydroxyl groups of the aromatic ring [28]. IHJPAS. 37(2)2024 252 Figure 8. The FT-IR spectrum of Zn-complex. Figure 9. The FT-IR spectrum of Pd-complex. Table 4. The IR spectral data (cm -1 ) of complexes. M-N M-O M-Cl ν (SO2) ν (N=N) Ν (C=O) ν (C-H) aromatic aliphatic ν (NH) ν (OH) phenolic ν (H2O) aqua Compounds 507 459 369 1088 1008 1471 1612 3067 2980 3287 3506 3757 Ni(H2L)(H2O)2Cl]] 528 403 331 1088 1015 1467 1633 3061 2979 3281 3503 3739 Zn(H2L)(H2O)Cl]] 510 433 370 1087 1470 1607 3063 2983 3284 3514 _ [Pd(H2L)Cl] 514 405 324 1094 1009 1470 1608 3057 2978 3289 3489 _ [Pt(H2L)Cl3] IHJPAS. 37(2)2024 253 3.5 Thermalstudy data The results obtained for the thermal analysis for ligand (H3L) and their synthesized complexes were displayed in Tables 5 and 6, and Figures 10-13 respectively. Tentative decomposition reaction of metal complexes summarize in Schemes 6. Decomposition stages, temperature ranges, decomposition products, and weight loss complex percentages were computed based on the thermograms, and they showed agreement. Between their thermal decomposition results and calculated values, that validates elemental analysis results and suggested equations [29]. In this work, it was noted that the remaining ligand was carbon and the remaining metal oxide in the ligand and metal complexes of Ni 2+ , Pd 2+ and Pt 4+ . According to the results of the thermo gravimetric tests, the complexes and the ligand decompose in (1 to 4) phases. The thermodynamic parameters ΔH, ΔS and ΔG were computed using the DCS curve. Figure 10. The TGA and DSC curve of ligand (H3L). Figure 11. The TGA and DSC curve of Ni-complex. IHJPAS. 37(2)2024 254 Figure 12. The TGA and DSC curve of Pd-complex Figure 13. The TGA and DSC curve of Pt-complex. Scheme 6. Tentative decomposition reaction of ligand and metal complexes. IHJPAS. 37(2)2024 255 Table 5. The TGA data of the ligand H3L and some complexes. Reaction Weight mass loss% Tmax Tf/°C Ti/°C Step Complexes Found Calc -C17H16N4O7S 97.7560 97.2248 347.362 597.747 111.021 1 Ligand C Calculated:97.2248%final=2.7752%;Estimated97.7560%final=2.244% -2H2O 5.5804 6.4286 76.362 100.044 32.102 1 Ni-complex -Cl, -SO2 17.1778 17.7681 149.952 207.473 100.011 2 -C8H6N2O 27.5320 26.0718 288.764 349.75 208.223 3 -C10H9N2O3 35.7711 36.6077 480.362 593.805 350.412 4 ONi Calculated:86.8762% final =13.1238%;Estimated 86.0613% final =13.9387% -Cl,-2CO2,- CO,N2O 33.7361 34.1819 301.762 393.362 268.200 1 Pd-complex -C15H15N2S 43.3984 42.8366 476.453 593.384 402.998 2 OPd Calculated:77.0185% final =22.9815%;Estimated 77.1345% final =22.8655% -Cl3,-SO2,- 2CO2, -C7H6N2 49.8662 51.5090 207.936 331.868 132.111 1 Pt-complex -C9H9N2 20.5410 19.8374 461.395 590.862 331.001 2 OPt Calculated:71.3464% final =28.6536%;Estimated 70.4072% final =29.5928% Table 6. Thermal decomposition DSC of ligand and some complexes. Type ΔG J/mol ΔS J/K.mol ΔH J/mol Maximum temperature point °C Tf/°C Ti/°C Compound endothermic 694.399 -1.804 -13.49 392.40 395.13 387.65 L3H endothermic 38.6225 -0.8431 -3.17 49.57 49.99 46.23 [Ni(H2L)(H2O)2Cl] endothermic 115.3452 -1.5844 -39.72 97.87 108.46 83.39 endothermic endothermic exothermic exothermic 39.6314 316.6206 -545.504 - 2608.568 -0.2647 -1.3381 1.9843 8.7952 -3.61 -40.05 42.96 616.28 163.36 266.55 296.56 366.66 170.04 276.99 306.96 396.74 156.40 247.06 285.31 326.67 endothermic 24.0122 -0.2288 -2.19 114.52 115.51 105.94 [Pd(H2L)Cl] endothermic 21.8952 -0.1456 -0.75 155.53 156.31 151.16 endothermic 399.6495 -1.2806 -5.75 316.57 319.54 315.05 endothermic 59.0595 -1.5097 -90.28 98.92 126.07 66.27 [Pt(H2L)Cl3] 3.6 Investigation of antioxidant activity The assay was used to determine how well antioxidants can scavenge it. Antioxidants provide a hydrogen atom to1-(2,4,6-trihydroxy-phenyl)-ethanone, which reduces the single electrons from nitrogen atoms in DPPH. When the DPPH radical solution is combined with the antioxidant, the color of the corresponding hydrazine changes from violet to yellow, which is characterized by an absorption band in an ethanol solution centered at approximately (517 nm). Electron delocalization also produces dark purple [30]. The interaction of [Ni(H2L)(H2O)2Cl], [Zn(H2L)(H2O)Cl],[Pd(H2L)Cl] and [Pt(H2L)Cl3] complexes with DPPH radicals and subsequent hydrogen donation to scavenge the radicals were displayed with Table 7. Effective DPPH radical scavenging is indicated by a lower IC50 value. In the DPPH assay, the practically Pt- complex has more antioxidant activity than the othermetal complexes [31,32]. IHJPAS. 37(2)2024 256 Table 7. Antioxidant activity of azo dye and its complexes. Compounds Compounds Mean Standard deviation Coefficient of variation% Correlation coefficient IC50(M) GA 93.5600 2.0846 12.2281 0.9993 6.1135 H3 L 85.7600 3.0663 13.3521 0.9938 4.6630 [Ni(H2L)(H2O)2Cl] 68.8311 4.2753 13.1762 0.9988 3.1625 [Zn(H2L)(H2O)Cl] 65.4423 3.8123 17.6531 0.9991 4.0109 [Pd(H2L)Cl] 83.1152 3.3796 15.5221 0.9981 3.0025 [Pt(H2L)Cl3] 71.3217 2.2009 14.4119 0.9975 2.704 4. Conclusion In summary, this study has successfully synthesized a new azo ligand derivative of sulfamethoxazole by simple substitution reaction with 1-(2,4,6-trihydroxy-phenyl)-ethanone. Then characterized ligand and metal complexes by various analytical techniques, like elemental microanalysis, metal–chloride containing, electrical conductivity measurement, magnetic susceptibility, 1 H and 13 CNMR, FT-IR,UV-Vis , mass spectroscopy, and thermal analysis (TGA and DSC) curves. The DCS curve was used to calculated the thermodynamic parameters ΔH, ΔS, and ΔG.The yield of the synthesized compounds was found to be in the range from 60-80%.The molar conductivity results showed that none of the produced complexes are electrolytes, and the atomic N, O and O tridentate coordination sites in the ligand were identified by comparing their IR spectra to those of the metal complexes. The M:L ratio in every compound was [1:1]. According to the results, Octahedral geometry suggests ( Ni 2+ and Pt 4+ ), Tetrahedral of Zn 2+ complex, and Square planer of Pd 2+ . The antioxidant activity of the synthetic compounds was evaluated against the DPPH radical (1.1-diphenyl-2-picrylhydrazyl), and the results were contrasted with those of gallic acid, a widely used natural antioxidant. Results show how efficient metal complexes are in scavenging free radicals. Acknowledgment The authors would like to thank everyone who contributed to the success of this review article. 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