Introduction

Schiff base composites are considered with the presence of azomethine group (-CH=N-) as per consequence of reflux among aldehyde or ketone with primary amin [1]. Studies have shown that the azomethine group (-CH=N-) is a donor-acceptor group and is an acceptor through the π-orbital of the double bond, and a doner through the non-acceptor of electrons to the nitrogen atom of this group [2].The Schiff base is derived from benzaldehyde or its derivatives with aniline or its derivatives; the Schiff base molecule is uneven, as the benzene ring attached to the nitrogen atom is outside the level of the rest of the molecule, and it turns out that the compensators on the benzaldehyde molecule are more influential in the electronic distribution than the compensators on aniline cycle [3]. Schiff bases mainly frolic unlike other zones like the pharmacology as anti-fungal, anti-bacterial and anti-cancer agents [4]. Further, they are applied in manufacturing things like thermal Initiations in the Radical Polymerization [5].

Materials and Methods

All composites used were of highest purity (BDH, Fluka).

Instrumentation

TGA-DSC was characterized and analyzed. The FTIR-Spectra were recorded on Shimadzu 8400-s in a range of (400 cm^-1 – 4000 cm^-1) with the use of the KBr disk. ¹H-NMR spectra were characterized and analyzed. CHNS was accomplished on Euro-EA Elemental.

Preparations of facilities

Preparation of New Schiff base ligand (E)-3-hydroxy-4-((3,4,5-trimethoxybenzylidene)amino)naphthalene-1-sulfonic acid

In a round bottom flask, 3,4,5- dimethoxybenzaldehyde (5 mmol, 1 g) in 15 mL ethanol and 1-amino-2-aphthol-4-sulfonic acid (5 mmol, 1.219 g) in 15 ml ethanol was refluxed for 5 h. [6]. Then, the reaction flask was located in a freeze bath for several records, followed by filtering the precipitate and leaving it to dry, giving a pale green precipitate. The groundwork of Schiff base is illustrated in Scheme1.

Scheme 1: Schiff base Ligand preparation

Preparation of metallic complexes [Co(Ⅱ), Cu(Ⅱ), Ni(Ⅱ), Zn(Ⅱ), Mercury] through ligand (L)

The chelate facilities of ligand and metal (1:2) were arranged via the dissolution of 0.95 mmol (0.4 g) of the Schiff base in 10ml of solvent and added to KOH dissolved in 10 ml of absolute solvent. The consistent hydrated metal chloride salt of CoCl₂.6H2O, CuCl₂.2H₂O=0.081 g, NiCl₂.6H₂O=0.114 g, HgCl₂=0.130 g and ZnCl₂=0.060 g was liquefied in absolute ethanol 10 mL varied with solvent of the ligand and refluxed for 3h on contents cooling. The facilities were divided out in every event. The produce was filtered, splashed with solvent then dehydrated below vacuity.

Results and discussion

Elemental analyses

Some of the physical and analytical characteristics of ligand as well as its complexes were examined, aimed at finding the chloride content.

Table 1: Physical characteristics and analytical data of ligands as well as their facilities

FT-IR of ligand and Facilities

The infra-red spectral data of the Schiff base ligands as well as their complexes are listed in Table 2. Infra-red spectra of complexes were equated with those of free ligand for the purpose of regulating sites coordination, which could be complicated in the chelation. The band in infra-red spectrum of the free ligands at 1172 cm^-1 was transferrable to stretching shaking carbonyl group of Schiff base ligand that was lifted to lower frequency in IR spectra of facilities at 1168cm^-1. The appearance of band in the range of 582-489cm^-1 in infra-red spectra of all of the facilities came as a result of the υ(M-O) validates [7]. The band at (1658 cm^-1) in free ligand’s infra-red spectrum might be a result of stretching vibration of the imine group υ(C=N) that was changed to a lower or higher frequency; in infra-red spectra of facilities of Cu(II) and Hg(II) rose in to higher frequency, whereas the facilities of Ni(II), Co(II), and Zn(II) fell to lower frequency designated for the harmonization of ligand with metal ion through the N atom [8]. This was further validated by the presence of a newfangled band in range (613-594 cm^-1) transferrable to υ(M-N) [9,10]. It was established that the ligand acted the role of bidentate ligand harmonized to metal ions through O atom of the carbonyl group of benzaldehyde and N atom of imine group for all facilities.

Table 2: Characteristics of infrared bands of absorption of ligand (L) as well as its facilities in cm^-1

UV-Vis

The UV-Vis of ligand and its Ni(II), Cu(II), Co(II), Zn(II) and Mercury facilities were deliberate and spectra1 data were registered as displayed in Table 3. UV-Vis of Schiff base ligands has been described mostly by three absorption top at (235 nm) consigned to (π→π*), at (345nm) that has been allocated to (n→π*) and at (470nm) allocated to Charge transfer [11]. Those electronic transitions were lifted near lower or higher frequency in electronic spectra of all of the set facilities [12-14].

Table 5: UV-Vis spectra of ligand as well as its chelate facilities

Magnetic measurement

µ_S+L=         B.M

µ             B.M,            S=n/ 2               

µ             B.M                                    

X_M=X_g×M_wt                                                                    (1)

X_A =X_M – D                                                                     (2)

µ _eff= 2.82      (3)                     B.M             

Co(II) composite displays magnetic moment µ eff (4.82BM) that is consistent with 3 unpaired electrons. This significance submits octahedral environment around ion of Co (II) [15]. Ni(II) complex displays magnetic moment µeff. (2.80 BM) at room temperature that is resultant to 2 unpaired electrons. This significance directs octahedral geometry about Nickel(II) ion [16]. Cu(II) complex indications µeff (1.75 BM) conform to unpaired electrons. This value suggests octahedral environment around ion of Cu(II) [17]. The value of the magnetic moment µeff of Zn(II) associates with Mercury composite (0.00 B.M) for the reason of being diamagnetic in nature (d¹⁰) [17].

¹HNMR

In mixture, as in solid state, this marvel was set by infra-red and NMR spectra.¹HNMR ligand spectrum in the DMSO-d₆ revealed signal at chemical shift (δH =9.6 ppm, s) credited to the one proton of the hydroxyl group phenol δ(OH) [18], and at (8.7 ppm, s) credited to the proton of the hydroxyl group sulfonic δ(OH)). Resonance values at the chemical shifting (δH = 6.7 -7.6 ppm, m) are flexible to the aromatic ring protons and at (3.0, 3.2 ppm, s) official to nine protons of (-OCH₃).

GC-mass of ligand and complexes

Electro-spray mass spectrum of ligand displays parent ion top at (M/Z)=(417) that agrees with [M⁺], other rubbles as well as their comparative abundance and disintegration pattern has been presented. Electro-spray mass spectrum of Co(II) complexes illustrates parent ion top at (M/Z)=(928) that agrees with [M⁺], other fragments as well as their comparative abundance and disintegration configuration is exposed. Electro-spray mass spectrum of Ni(II)complexes confirm the parent ion top at (M/Z)=(927), corresponding to [M⁺], other fragments as well as their comparative abundance and disintegration patterns having been illustrated.

Thermal decomposition of ligands and Cu(II), Zn(II) Complexes

The thermogram of prepared ligand (C₂₀H₁₉NO₁₇S) was carried out by thermogravimetric analysis (TGA) and differential calorimetry (DSC), in an inert atmosphere using argon gas at an average temperature of 10°Cmin^-1 and a weight of (26mg) of the sample. The TGA curve of the prepared ligand (L) shows that it undergoes one phase of weight loss [19,20]. Thermal study of the complex CuC₄₀H₄₂N₂O₁₇S₂ was carried out in an inert atmosphere of argon at an average temperature of 10°Cmin^-1 with a weight of (21 mg). The TGA curve shows the complex going through four stages of weight loss.

Thermal study of the complex ZnC₄₀H₄₂N₂O₁₇S₂ was carried out in an inert atmosphere of argon at an average temperature of 10 °Cmin^-1 by the weight of 17mg [21]. The TGA curve shows that the complex had one phase of weight loss.

Table4: Thermal analysis of the ligand as well as its complexes

Conclusion

The aim of this research was to create a new ligand containing the azomethine group (-CH=N-) as a donor-acceptor group countered with around transition metal ions in Ni(II), Co(II), Cu(II), Zn(II) and mercury to offer a series of new metal complexes of the common molecular formulation [M(L)₂(H₂O)₂].H₂O. The metal complexes were proved to have an octahedral formula.

Acknowledgments

The authors extend sincere thanks and appreciation to the reviewers for their appreciable comments.

Funding

This research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors.

Authors' contributions

All authors contributed toward data analysis, drafting, and revising the paper and agreed to be responsible for all the aspects of this work.

Conflict of Interest

We have no conflicts of interest to disclose.

ORCID:

Wurood Ali Jaafar

https://www.orcid.org/0000-0002-9705-7622

HOW TO CITE THIS ARTICLE

Majida Ibrahim Obaid, Wurood Ali Jaafar. Formation, Characterization and Thermal Study of Novel Schiff Base Ligand From Sulfonic Acid and Its Complexes with Co(II), Ni(II), Cu(II), Zn(II) and Hg(II) Type NO. Chem. Methodol., 2022, 6(6) 457-462

https://doi.org/10.22034/CHEMM.2022.335650.

URL: http://www.chemmethod.com/article_148341.html