Preparation and Spectroscopic Studies of Some Metal Ion Complexes of 2-( ( 4-Formyl-3-Hydroxynaphthalen-2-yl ) Diazenyl ) Benzoic Acid

New azo ligand 2-((4-formyl-3-hydroxynaphthalen-2-yl) diazenyl) benzoic acid (H2L) was synthesized from the reaction of 2-aminobenzoic acid and2-hydroxy1-naphthaldehyde. Monomeric complexes of this ligand, of general formulae [M II (L)(H2O)] with (M II = Mn, Co, Ni, Cu, Zn, Pd, Cd and Hg ) were reported. The compounds were isolated and characterized in solid state by using 1 H-NMR, FT-IR, UV–Vis and mass spectral studies, elemental microanalysis, metal content, magnetic moment measurements, molar conductance and chloride containing. These studies revealed tetrahedral geometries for all complexes except Pd II complex is Square planar. The study of complexes formation via molar ratio of (M:L) as (1:1). Theoretical treatments of compounds in gas phase were studied using Hyper Chem-8 program has.


Introduction:
Azo dyes comprise the largest group of organic reagent used in spectrophotometric analysis.They are found in a variety of industrial applications because of their color fastness.These dyes are characterized by chromophoric azo group (-N=N-) offering a wide range spectrum of colors [1].They are usually strongly coloured compounds, which can be intensily yellow, red, orange, blue or even green, depending on the exact structure of the molecule.Because of their colour, azo compounds are tremendous importance as dyes and as pigments for a long time [2,3].They also used for coloring consumer goods such as leather, clothes, food, toys, plastic and cosmetics [1].Infact, about half of the dyes in industrial use today are azo dyes, which are mostly prepared from diazonium salts [4,5].The azo group possesses excellent donor properties and is important in coordination chemistry [6].Azo compounds are very important class of chemical compounds receiving attention in scientific research [7].The aim of this paper is to synthesized, characterized and study the biological activities of the newtridentateazo ligand [2-((4-formyl-3-hydroxynaphthalen-2yl)diazenyl)benzoic acid] H 2 L and its metal complexes.

Materials and Methods:
All reagents were commercially available and used without further purification.Elemental microanalyses (C.H.N.) were performed by using a flash E A 1112 Series elemental microanalyses.IR spectra were obtained by using Perkin -Elmer FT-IR spectrometer.The electronic spectra were carried out by using a Cary 50 Conc.UV-Visible spectra were recorded using spectrophotometer.Thermal analysis studies of the compounds were performed on Perkin -Elmer pyris Diamond DTA / TG.. Chloride was determined by using a 686-Titro processor -665 Dosimat Metrohm Swiss.Conductivity measurements were made with using a Jenway 4071 digital.Magnetic moments were measured with a magnetic susceptibility balance (Jonson Mattey Catalytic system Division).Mass spectra were obtained by LC-Mass 100 P Shimadzu.NMR spectra ( 1 H-NMR) were acquired in DMSO-d 6 solution by using Brucker AMX 400 MHz spectrometer.Metals were determined by using a Shimadzu (A.A) 680 G. Melting points were obtained on a Buchi SMP -20 capillary.

Preparation of Complexes:
The preparation of all complexes is essentially the same and so a generic description will be presented.To a solution of (H 2 L) (0.006 mole) in ethanol was added slowly to a solution of metal salt (MnCl 2 .4H 2 O, CoCl 2. 6H 2 O, NiCl 2 .6H 2 O, CuCl 2 , ZnCl 2 , PdCl 2 , CdCl 2 and HgCl 2 )in (ethanol and water) ratio (1:1) with stirring the mixture was refluxed for (5hrs).Elemental micro analysis data, color and yield for the complexes are given in Table (1).

Results and Discussion:
The new (ONO) dentate ligand H 2 L was obtained in good yield by the reaction of 2-aminobenzoic acidand2hydroxy-1-naphthaldehyde, Scheme (1).In general the ligand was characterized by elemental microanalysis and physical properties Table (

Complex of ZnL
The electron impact spectrum of [ZnL( m/z may be assigned to various fragments.

Complex of HgL
The electron impact spectrum of [Hg L(H 2 O)] confirms the probable formula by showing a peak at 536.9 m/z, corresponding to complex moiety [(C 18 H 12 N 2 O 5 Hg), calculated atomic mass 536.87].The series of peaks in the range of 518.9, 398.8, 216.6, 184.2 and 122 m/z may be assigned to various fragments.

Complex of MnL
The electron impact spectrum of [MnL(H 2 O)] confirms the probable formula by showing a peak at 391 m/z, corresponding to complex moiety [(C 18 H 12 N 2 O 5 Mn), calculated atomic mass 291.24].The series of peaks in the range of 373.22,218.11 and 155.11 m/z may be assigned to various fragments.

IR spectra
The IR spectra bands of the ligand(H 2 L) and its compnelexes were characterized at3076, 2889,3341, 1605 and 1569cm -1   due to the ν(CH) aromatic, ν(CH) aldehyde,ν(O-H) phenol, υ(COOH) carbonyl and υ(N=N) azo,functional groups, respectively, for the ligand [9].The IR spectraof the complexes exhibited ligand bands with the appropriate shifts due complexes formation [10].On complex formation the bands of ν(N=N) and ν(COO) are shifted to lower frequencies by (11 to 77) and (19 to 41) cm-1respectively; these shifts confirm the coordination of the ligand through the nitrogen of the azo group and the carboxylate ion with the metal ions.The presence of coordination water in the spectra of all complexes were suggested by the very broad absorption around (3513 to 3393) and (910 to 870) cm -1 .This indicates that the ligand was coordinated with the metal ions through the (O) carbonyl group, (O) phenol groupand (N)azo group atoms.At lower frequency the complexes exhibited new bands around (588-480), and (450-412) cm -1 assigned to the υ(M-N)and υ(M-O), respectively [11,12].

Electronic spectral, magnetic moments
The electronic spectrum of the ligand exhibit intense absorption at 273, 278 and 315 nm attributed to π→ π* and n→π* respectively.The electronic spectrum of Ni(II) complex showed three broad peaks at 488, 867 and 873 nm assigned to 3 T 1(F) → 3 A 2(F) , 3 T 1(F) → 3 T 1(P) and 3 T 1(F) → 3 T 2(F) respectively, suggesting an tetrahedral geometry.The electronic spectrum of Pd(II) complex showed two broad peaks at 493 and 765 nm assigned to 1 A 1 g→ 1 B 1 g and 1 A 1 g→ 1 A 2 g, suggesting an square planar geometry, the electronic spectrum of Mn(II) complex showed two broad peaks at 418 and 568 nm assigned to 6 A 1 → 4 T 2 (G) and 6 A 1 → 4 T 1 (G) respectively, suggesting an tetrahedral geometry [9,13].The Co(II) complex, there are three absorption bands, two in the visible region at 431 and 604 nm which are attributed to the 4 A 2(F) → 4 T 1(F) and 4 A 2(F) → 4 T 2(F) respectively, suggesting an tetrahedral geometry .The yellow greenish of the Cu(II) complex show only band in the visible region of the lower energy was attributed to 2 T 2 (D) → 2 E(D).In fact, it is difficult to recognize between a square planer and tetrahedral Cu(II) complex because it occurs in the same region for both geometries [14][15][16].In this case the magnetic moment for Cu(II) complex is 1.901 B.M which confirmed the tetrahedral geometry for the[CuHL(H 2 O)] complex.Finally, the absorption bands of the Zn(II), Cd(II) and Hg(II) complexes exhibited charge transfer at 335, 299 and 300 nm respectively.This is because of the electronic configuration and the diamagnetic of these complexes which confirmed the absence of any d-d electronic transition [16].All the absorption bands were fully assigned in Table (3).

Theoretical study
The vibration spectra of the ligand and complexes were calculated by using a semi-empirical (PM3) method.The results obtained for wave numbers are presented in, Figure (1) and the comparison with the experimental values indicates some deviations.These deviations may be due to the harmonic oscillator approximation and lack of electron correlation.It was reported [16] that frequencies coupled with Hartree-Fock Theory (HFT) approximation and a quantum harmonic oscillator approximation tends to be 10% too high.

Electrostatic Potential (E.P)
Electron distribution governs the electrostic potential of molecules [17] and describes the interaction of energy of the molecular system with a positive point charge, so it is useful for finding sites of reaction in a molecular positive charged species tend to attack a molecule where the E.P. is strongly negative electrophilic attach.The E.P of free ligand were calculated and plotted as D contour to investigate the reactive sites of the molecules, and one can interpret the stereochemistry and rates of many reactive in volving soft electrophiles and nuclophiles in terms of the properties of frontier orbitals (HOMO and LUMO).Overlap between the HOMO and LUMO values were plotted as D contour to get more information about these molecules Figure (1).The results of calculation showed that the LUMO of metal ions prefers to react with the HOMO of nitrogen atoms of ligand.

Optimized Geometries Energy of Compounds
A theoretically probable structure of a metal complexes with ligand were calculated to search for the most probable model building stable structure, these shapes, show the calculated optima geometries for ligand.The results of PM3 and ZINDO method of calculation in gas phase for the binding energies and heat of formation of complexes are described in Table 4.The conformation structures and bond lengths of the ligand and its complexes showed in Figure (1).The molar conductivity of the complexes in DMSO solution was nonelectrolyte for all complexes, and the configurations were performed to coordinate the azo through the nitrogen and oxygen atoms.Therefore, from the presented results the complexes have tetrahedral for all complexes except Pd 2+ is Square Planar.Theoretically probable structures of metal complexes with azo have been calculated, these shapes shows the calculated optima geometries for H 2 L and its metal complexes.
H 2 O)] confirms the probable formula by showing a peak at 401.7 m/z, corresponding to complex moiety [(C 18 H 12 N 2 O 5 Zn), calculated atomic mass 401].The series of peaks in the range of 383.7, 280, 170, 114 and 106

Synthesis of the Ligand Table (1): Analytical and Physical Data of the Ligand and its Complexes
1), FT.IR Table (2), UV-Vis Table (3), mass spectroscopy.