Preparation-and Spectroscopic Characterization of Transition Metal Complexes with Schiff base 2-[1-(1 H -indol-3-yl)ethylimino) methyl]naphthalene-1-ol

: The ligand 2-[1-(1H-indol-3-yl)ethylimino) methyl]naphthalene-1-ol, derived from 1-hydroxy-2-naphthaldehyde and 2-(1H-indol-3-yl)ethylamine, was used to produce a new sequence of metal ions complexes. Thus ligand reactions with NiCl 2 .6H 2 O, PdCl 2 , FeCl 3. 6H 2 O and H 2 PtCl 6 .6H 2 O were sequentially made to collect mono-nuclear Ni(II), Pd(II), Fe (III), and Pt(IV). (IR or FTIR), Ultraviolet Reflective (UV– visible), Mass Spectra analysis, Bohr-magnetic (B.M.), metal content, chloride content and molar conductivity have been the defining features of the composites. The Fe(III) and Pt(IV) complexes have octahedral geometries, while the Ni(II) complex has tetrahedral geometry and the Pd (II) complex has square planer geometry, according to these findings.


Introduction:
Indole compounds can be present in a variety of natural sources, including fungal metabolites, Indole alkaloids, and aquatic organisms 1 .The inclusion of the (-N=CH-) group, denotes antibacterial, antifungal, antimalarial, antiviral, and antipyretic properties. [1][2][3] and multifaceted applications such as organic synthesis intermediates, rewards, polymer stabilizers, coordination chemistry ligands, and dyes or colorants. Due to their ease of synthesis, structural variability, and broad range of applications, Schiff bases are regarded as important ligands for metal ion coordination complexes 2 . Schiff bases are important in coordination chemistry because they shape stable complexes with the largest transition metal ions with ease. Numerous biologically important Schiff bases and their mineral complexes have been identified in the paper, with significant roles in anticorrosion, soil treatment factors, and medicinal factors, as well as agricultural, analytical, biological, therapeutic, biochemical, antimicrobial, anticancer, antibacterial, antitumor activity, and antifungal activity 3 . Schiff bases undergo chelation with oxygen, nitrogen, and other elements. Collections of imine or azomethine can be used in a variety of natural, derivative, and non-natural compounds. Some compounds' biological activities are based on the existence of an amine group 3 . These ligands were mostly used as polydentate ligands, and they showed excellent steric properties as well as electronic smooth tuning of their metal complexes 2 . Schiff base complexes with two or three metal centers are ideal catalysts. It is also understood that ligand-metal ion coordination enhances the biological function of the ligand thus reducing the cytotoxic effects of the metal atom and ligand 3 . Schiff bases are polydentate ligands and their complexes designed by chemists, and they have been used in a variety of applications 2 . This ligand has never been seen in this type before, according to the analysis [4][5][6][7][8][9] . This work investigates the synthesis and characterization of a new Schiff base ligand from the reaction of 2-(1H-indol-3-yl) ethylamine with 1-hydroxy-2-naphthaldehyde and their metal complexes. The consequences proposed that Schiff base acts like a bidentate ligand for all the prepared complexes.

Materials and Methods: Chemicals and Measurements
Chemicals were obtained from industrial sources (Sigma-Aldrich, Merck) and were not filtered prior to usage. Eurovector EA 3000A was used to conduct elemental microanalysis. Metal ions were calculated as metal oxides using a gravimetric method. The following instruments were used to calculate the molar conductivity (units) of metal complexes 10 -3 M in DMSO at room temperature: Conduct meter (WTW). The chloride content of complexes was calculated using Mohr's method in the presence of potassium chromate and silver nitrate as a titrating agent. At 25°C in England, the magnetic study was calculated by the Balance of Johnson Matthey catalytic device division. MS QP50A: DI Analysis. The Shimadzu QP-2010-Plus (E170Ev) spectrometer was used to interpret mass spectra for ligands and complexes. The SHIMADZU 1800 Double Beam UV-Visible spectrophotometer was used to record electronic spectra for compounds in the (UV-Visible) range 200-1100 nm. Bruker Ultra Sheild 300 MHz NMR was used to produce H-NMR spectra. Fourier Transform Infrared (FTIR) spectra were obtained using SHIMADZU FT-IR 8400S Fourier transforms and KBr and CsI discs in the wavenumber range of 4000 to 200 cm -1 .

Synthesis of complexes
Metals of Schiff base were made by refluxing a 2:1 molar rate ethanolic solution of Schiff base and equivalent metal salts at 250mL in two necked flasks for three hours. Chloride salts of Pt(IV), Pd(II), Ni(II), and Fe (III) were included in the current analysis. Filtration was used to remove the strong precipitate that had accumulated in the reduced amount of origin oil. The raw material was recrystallized with ethanol, then dried and stored in vacuum desiccators scheme 1. Results and Discussion:

Scheme 1. synthesis of ligand 2-{[1(1h-indol-3-yl)-ethylamine]-methyl}-naphthalene-1-ol and its complexes
C.H.N. Analysis was conducted and it was found that the practical results match the theory as shown in the Tab.1 Metal salts were used with ratio 2: 1 reaction of ligand and metal, and the molar conductivity showed that all the complexes were of equal charge, except for the iron complex, had an ionic ratio of 1: 1.

Table 1. Results of the Elemental microanalysis as well some physical characteristic for ligand LH as well metal complexes
Electronic absorption spectra, magnetic moments, and conductivity measurements: The ligand's electronic range (LH) shows acute absorption at (364 nm, 27473cm -1 ), which is assigned to n→π*, and (322 nm, 31056 cm -1 ) which is assigned to π→ π* (Fig. 2). The electronic spectrum of the Ni (II) Complex with ligand displays many absorption bands at 262, 290, 330, 563, and 784nm, respectively, which are allocated to π→π*, π→π*, n→π*, 3 T 1(F) → 3 T 2(F) 3 T 1(F) → 3 T 1(P) respectively (Fig. 3). The magnetic moment of the Ni (II) (d 8 ) complex has also been estimated to be 2.82B.M. All of the information presented above of the Ni(II) complex is consistent with tetrahedral geometry. The diamagnetic Pd (II) d 8 low spin complex has absorption peaks at 248, 347, and 643 nm, which correspond to π→ π*, n→ π*and 1 A 1 g→ 1 A 2 g sequentially, and another band at 572nm, which can be chosen as 1 A 1 g → 1 B 1 g (Fig.  4). The square planer Pd (II) complex is responsible for these assignments. The spectrum of Pt(IV) complex Tab.2 shows peaks at 320,386,466 and 542nm, which are due to π→ π*, n→ π*, 1 A 1 g → 1 T 2 g, and 1 A 1 g → 1 T 1 g transitions (Fig. 5), sequentially, and suggest octahedral symmetry around Pt(IV) complex. The electrical spectrum of the Fe complex reported four peaks at 337,376,460 and one at 652nm, which were attributed to the π→ π*, n→ π*, 6 A 1 g → 4 T 2 g (G) and 6 A 1 g → 4 T 1 g (G) transitions, respectively (Fig. 6); the observed magnetic moment of this complex is compatible with the octahedral geometry structure 13-16 .

Infrared Spectra
The structural features of the Schiff base and its metal complexes, as shown in Figs