Synthesis, characterization and biological evaluation of thiazolyl azo ligand complexes with some metal ions

(E)-2-(benzo[d]thiazol-2-yliazenyl)-4-methoxyaniline was synthesized by reaction the diazonium salt of 2-aminobenzothiazole with 4-methoxyaniline. Identified of the ligand by spectral techniques (UV-Vis, FTIR, 1HNMR and LC-Mass) and microelemental analysis (C.H.N.S.O) are used to produce of the azo ligand. Complexes of (Co2+, Ni2+, Cu2+ and Zn2+) were synthesized and identified using atomic absorption of flame, elemental analysis, infrared and UV-Vis spectral process as well conductivity and magnetic quantifications. Nature of compounds produced have been studied followed the mole ratio and continuous contrast methods, Beer’s law followed during a concentration scope (1×10−4-3×10−4 mole/L). height molar absorptivity of compound solutions have been noticed. Analytical data showed that all the complexes out to 1:2 metal-ligand ratio. At the radix for physicochemical datum an octahedral structure have been described at compounds. other than the biological studies of all produced compounds was evaluation against different kinds of antimicrobial strains.


1-Introduction
Derivatives heterocyclic azo compounds have been used for dyeing industry, electrochromism, nonlinear optical elements and printing system (1) . Thiazolyl azo and their derivatives are very importance uses in different fields (2,3) , it's have been made to determination for many metal ions (4) . Thiazole azo dyes have been used for many applications such as, biological activity, analytical reagents, clinical field and many drugs including antigrowth of germs (5) . Because of presses interesting biological activity, many studies have been done on heterocyclic azo dyes and their metal chelates (6) . Metal chelates of azo dye have been interested for uses to store molecular memory, nonlinear visual elements and printing systems (7) . Recently metal chelates containing azo dyes have attracted increasing attention into increasing electronic and structural features in connection with their application for molecular memory storage (8) . At that work, synthesis, identification and chelating of some metal complexes containing thiazolyl azo dye as a ligand, as well biological studies of all produced compounds was evaluation against different kinds of antimicrobial strains.

2-1-Instrumentation
Microelemental analysis (C.H.N.S.O) have been done in Dimashq University, Syria, employing Euro vector EA 3000, single V.3.Osingle. Conductivity for the compounds resolved at ethanol (10 -3 mol/L) was recorded at 25 о C utilizing Philips PW-Digital Conductimeter. UV-Vis spectrum have been registered at a Shimadzu UV-160A Ultra Violet-Visible Spectrophotometer. Magnetic properties have been completed through utilizing Auto Magnetic Susceptibility Balance Sherwood Scientific instrument at 25C o . Atomic absorption has been recorded by employing a Shimadzu A.A-160A Atomic Absorption/Flame Emission Spectrophotometer. 1 H-NMR spectrum have been noted at a Brucker-400 MHz Ultra Shield spectrometer on Cairo University utilizing dimethylsulfoxide like the solvent also tetramethylsaline like the reference. IR-spectrum have been taken at a Shimadzu, FTIR-8400S Fourier Transform Infrared Spectrophotometer at the 4000-400 cm -1 spectrum areas for models produced like KBr discs. Other than, melting points have been performed utilizing Stuart Melting Point Apparatus.

2-3-Preparation of the ligand
2-aminobenzothiazole (9) (0.335 gm,1mmole) melted in mixture (10ml ethanol, 2ml conc. HCl), and diazotized at 5 o C with 10% solution of NaNO 2 . Diazotized solution has been added collyrium wise for stirring into a cooled ethanolic solution at (0.307 gm, 1mmole) for 4-aminoaniline. Then 25 ml at (1M, NaOH) solution has been followed into dusky colored mix and precipitation for azo ligand has been noticed. This deposit have been filtrated, washed number ounces for (1:1) C 2 H 5 OH: H 2 O, mixture subsequently left into dry. The reaction is appear at scheme 1.

2-4-Buffer solution
(0.01mol/L, 0.771 gm) for ammonium acetate was melted at one liter for doubly deionized water. For only pH scope (4-9) was the use of CH 3 COOH or NH 3 solution.

2-5-Standard solution
Several standard solutions of the metal salts were made in varying concentration (10 -5 -10 -3 mole/L) at pH scope (4-9). At the same time a bulk of ethanolic solutions of ligand within the extent of concentrations (10 -5 -10 -3 mole/L) was also produced.

2-7-Antimicrobial activity
The ligand and all the synthesized compounds were evaluated to examine their in vitro antibacterial activities against (Staphyl-ococcus aureus, Staphyloco-ccus epidermidis andPsedomonas Aeruginaso) as gram positive bacteria and (Steptococcus sp., Escherichia coli and Klebsiella sp.) as gram negative bacteria and antifungal activity such as Candida albicans (Yeast) by employing disk diffusion method (10) . The solvent utilized for working exam samples and level was DMSO and sample of (1-200 μg/ml) were utilized. Antibacterial and antifungal activity of any compound were estimated by means of the well-diffusion method. 1cm 3 at a 24h broth the culture including 106CFU/cm 3 was placed in sterilized Petri-dishes.Molten nutritio us agar (15cm 3 ) was kept in ca.45 o C and teeming in the Petri-dishes and pliable into stiffen. Other holes of 6mm diameter were punctured accurately employing a sterilized cork borer and these were perfectly stuffed for the exam solutions. The dishes were brood into 24h. within 37 o C.

3-Results and Discussion
Rudy for azo ligand (L) a joined of 4-methoxyaniline with the suitable diazotized in alkaline solution was performance.

3.2.Mass spectra
Mass spectrum for azo ligand (L) showed peak centered at m/z = 284 due to the formula C 14 H 12 N 4 OS. The general pattern of fragmentation are summarized in Scheme-3, see Fig. 2. Mass spectrum for Co 2+ complex displays peak centered at m/z = 698 due to the formulas C 28 H 24 N 8 O 2 S 2 Cl 2 Co. The general pattern of fragmentation are summarized in Schemes-4, see Fig. 3.

3-3 Calibration curve
Varied molar concentration (10 -5 -10 -3 M/L) for mixed aqueous-ethanol ligand and metal ions, only reach (1-3×10 -4 M/L) concentration followed Beer's law as well showed obvious intensive color. The best straight lines fit have been taken for correlation factor R>0.9980 like assigned at Fig. 4.

3-4-Model conditions
For search out interaction between produced ligand and metal ions beneath education at the preparation of compounds, the spectrum from combining solutions at ligand and metal ions into attain for optimum pH and concentration, as well firm wave length (O max ) were the first studies .As well as mole ratio metal to ligand (M:L) has been defined into prepare compounds. Perfect concentration was option of compound solution based on that solution gives highest absorbance in fixed (O max ) with various pH, and outcomes are described at Table 3. Trial outcomes proof such the absorbance for all prepared compounds are extreme and steady at a buffer solution from NH 4 OOCCH 3 at the pH extent (4-9).All prepared compounds were found to have a perfect pH like is shown at Fig. 5.

3-5. Metal to ligand ratio
Appoint for the complexes in solutions have been tested by mole ratio and job techniques. At both situations outcomes spread 1:2 (metal to ligand) ratio. Picked plot is shown at Fig. 6. Table 3 synopsizes outcomes gated, and specification into making compounds .

3-6-Physical estates
Interaction of the ligand melted in ethanol with the metal ions melted in perfect pH and in a (Metal:Ligand) ratio of (1:2) have been produced to solid complexes. The outcome of elemental analysis and the metal import from compounds were in real identical as well calculated values. Conductivity from ligand and metal chelates melted at ethanol (10 -3 mole / L) display electrolytic type (13) ratio (1:2), data are recorded at Table 3.

3-7-Determination of stability constant and gibbs free energy
The constant (K) of stability to the (1:2) metal to ligand compound can be computed according to the equations.
Where c = condensation to the compound solution at mole/ L α = degree for dissociation, As = Absorption in solution containing same amount of ligand and metal ion and Am= the absorption of solution containing the selfsame quantities for metal and surplus for ligand. High values for (K) refers to high constancy for produced complexes (14) . Thermodynamic parameters of Gibbs free energy ('G) were also studied. The 'G data have been reckoned from the equation (15) .

'G = -R T Ln k
Where; R = gas constant = 8.314 J.mol -1 .K, T = absolute temperature (Kelvin). Negative value of ('G) due to the reaction between azo dye ligand (L) and metal ions understudy are spontaneous, see Table 2. UV-Vis spectra to the produced compounds melted at ethanol (10 -3 M/L) were gauged as well the datum formed are listed at Table 3. UV-Vis spectrum for azo ligand shows peaks in 240 and 354 nm were appointed into mild energy (π-π * ) transition and peak in 412 nm due to (n-π * ) transition (16) . Co II spectrum appears three peaks at 245, 352 and 457 nm caused by intra ligand and charge transfer, peaks at 632, 730 and 868 nm described to electronic transition type 4 T 1g(F) → 4 T 1g(P) , 4 T 1g(F) → 4 A 2g and 4 T 1g(F) → 4 T 2g(F) respectively, also the value of the magnetic moment at 4.85 B.M may be taken as additional evidence for octahedral geometry (17) . Ni II complex exhibited three absorption peaks at 244, 355 and 457 nm which were assigned to intra ligand and charge transfer. Other peaks at 624, 688 and 724 nm were assigned to electronic transition type 3 A 2g → 3 T 1g(P) , 3 A 2g → 3 T 1g(F) and 3 A 2g → 3 T 2g(F) respectively. Magnetic moment of this complex was found at 2.96 B.M which was very close to the octahedral environment (18) . Cu II complex shows peaks at 245, 353 and 480 nm due to intra ligand and charge transfer, while peak at 680 nm described to electronic transition type 2 E g → 2 T 2g , the magnetic moment of this complex was found at 1.73 B.M which was very close to the octahedral environment (19) . Zn II complex show the charge transfer, and the magnetic susceptibility shows that the complex has diamagnetic moments, because d-d transition are not possible hence electronic spectra did not give any fruitful information, in fact this result is a good agreement with previous work of octahedral geometry (20) .

3-9-FTIR spectra
FTIR spectra to the azo ligand and their metal chelates have been collated, and the data was scheduled in Table 4. Spectrum of the ligand exhibited bands at 3441 and 3387 cm -1 which were assigned to stretching vibration of υ(NH 2 ), at the spectra of all produced compounds these bands has been removed to lower frequency implying the coordination with metal ion (21) . Strong band at 1604 cm -1 described to υ(C=N) of thiazole ring, at the spectra of metal chelates this band has been removed to lower frequency implying the coordination with metal ion (22) . Bands at 1568 and 1535 cm -1 attributed to υ(C=C), and the bands at (1404, 1387 and 1309) cm -1 lead to bending vibration of δ(CH 3 ) group (23) . Band of the azo group at 1504 cm -1 displaced into lower wave number for change during shape at spectra for all produced compounds (24) . Stretching frequency bands to metal-nitrogen more (25,26) assured by the existence to the bands at rate 432-536 cm -1 . Pursuant to the results protected, an octahedral geometry has been offered for the produced metal chelates. As = asymmetry, s = symmetry, sh = sharp, s = strong, w = weak, sho =shoulder

3-10-Antimicrobial screening result
Azo ligand (L) and its complexes reported here were evaluated for antibacterial activity against (Staphyl-ococcus aureus, Staphyloco-ccus epidermidis and Psedomonas Aeruginaso), (G+ev) and (Steptococcus sp., Escherichia coli and Klebsiella sp. ), (G-ev) and antifungal activity such as Candida albicans (Yeast) by employing disk diffusion method . The data of antibacterial and antifungal activities of zone inhibition were measured in millimeter of ligand and its complexes with are given in Table(5). As can be seen from the antibacterial activity and antifungal activity of ligand and metal complexes, among all these complexes the Zn II complex showed the higher antibacterial activity with inhibition zone of 15 mm against Staphyloco-ccus epidermidis, Steptococcus sp. and Escherichia coli compared with ligand and other metal complexes .In case of Zn II compound the antifungal activity of Candida albicans shows higher inhibition area of 18 mm is higher activity from ligand and rest metal complexes.  16 In this work, the metal chelates complexes have been readied with the ligand. The willing compounds are described by melting point, atomic absorption of flame, IR and UV-visible spectral, as well conductivity quantifications. Exploration of antimicrobial activities was lifted out opposite the experimented organism. According result data an octahedral structure suggested for readied complexes.