Synthesis and Spectral Properties Studies of Novel Hetrocyclic Mono Azo dye Derived from Thiazole and Pyridine with Some Transition Complexes KHALID

A novel hetrocyclic mono azo dye ligand 5-[2-(5-nitro thiazolyl)azo]-2-amino-4-methyl pyridine (NTAPy) was prepared by coupling reaction between 5-nitro thiazole diazonium chloride with 2-amino-4-methyl pyridine in alkaline alcoholic solution . Anew series of some transition metal complexes of Cr(III) , Mn(II) , Fe(III) , Co(II) , Ni(II) , Cu(II) and Zn(II) ions were prepared forming seven chelate complexes . The prepared hetrocyclic mono azo dye ligand and its metal complexes were checked by different spectral technique such as 1H-NMR , 13C-NMR ,FT-IR , electronic spectra , mass spectrum , C.H.N analysis , magnetic susceptibility , atomic absorption and molar conductivity. The analytical data show that the metal to ligand ratio [M:L] in all complexes are[1:2] and the mono azo ligand behavior as a bidentate chelating agent. The coordination number of all metal ions is found to be six in coordination through the nitrogen atom of azo group (N3) farthest of thiazole ring and nitrogen atom (N3) of thiazole molecule forming five member metlo –ring. All metal complexes of nonelectrolytic and no conductive species exist excepted the Cr(III)and Fe(III)complexes are 1:1 electrolyte.


INTRODUCTION
Azo dyes of thiazole and pyridine compounds are very important class of chemical constituents having enormous applications in multiple fields such as polymer ,paper , paint and coating industries as a dyeing pigments [1][2][3][4] .Thiazolyl azo and pyridyl azo compounds are important in intermediates for the preparation of some applications such as biological activity 5,6 , clinical fields 7,8 , analytical reagents 9,10 and some drugs including discouraging the growth of germs 11,12 .Most hetrocyclic azo dyes such as pyridyl azo and thiazolylazo compounds of technical interest for application to textiles are derived from mono and diazo components consisting of five -membered metallo ring consisting of one sulphur or nitrogen hetero atom and to which a diazotisable amino group is directly attached ,the ring may also possess one or two nitrogen hetro atoms such as pyridyl azo, imidazolylazo and benzimidazolyl azo [13][14][15] , or one nitrogen and one sulpher hetro atoms such as thiazolylazo and benzothiazolylazo and be fused to another aromatic ring 16,17 .The thiazolylazo and pyridyl azo reagents have an important role in spectral determination field to determine metal ions because of high sensitivity and selectivity 18,19 .Thus azo dyes compounds from this intermediate have achieved significant commercial success for the dyeing of cellulose acetate fibers in which gas fastness is a higher priority than light fastness.In the present study, the synthesis of mono azo dye ligand (NTAPy) which contains two hetrocyclic ring thiazole and pyridine and its metal complexes with Cr(III) , Mn(II) , Fe(III) , Co(II) , Ni(II) , Cu(II), and Zn(II) ions are reported.Moreover spectral and analytical identification studies have been investigated for comparative purposes .

MATERIALS AND METHODS
2-Amino-4-methyl pyridine, 2-amino-5-nitro thiazole and other chemicals were equipped from Aldrich, BDH and sigma chemical companies and used without further purification .All chemicals and solvents used in the preparation and characterization were of analytical grade. 1 H-NMR and 13 C-NMR spectra were obtained with a model Bruker AM(400MHz)spectrometer for using DMSO-d6 solution in an appropriate deuterated solvent .The chemical shift are reported in ppm using tetra methyl silane(TMS)as the internal reference.Mass spectrum of azo ligand (NTAPy)were recovrded on a Shimadzu Agilent Technologies 5975 o C at 70ev and MSD energy using a direct insertion probe (Acqmethod low energy) at 90-110 o C temperature .Elemental analysis (C.H.N.S) was carried out using a C.H.N EA-99 mth instrument.The metal contents of metal complexes were measured by using atomic absorption technique by Shimadzu AA-6300.IR spectra were recorded as KBr discs in range (4000-400)cm -1 on a Shimadzu 8400FT-IR spectrophotometer .The electronic spectra were measured in 1cm quartz cells on a spectraphotometer a UV-Visible T80-PG by using 10 -3 M solution absolute ethanol at room temperature in the rang (200-1100) nm.Magnetic susceptibility measurements of the metal complexes in powder form were carried out on Balance Magnetic (MSB-MKi) apparatus by using farady method at room temperature Diamagnetic correction for the metal complexes was calculated using pascals constant.Molar conductivity measurements were recorded at room temperature in DMF solution (10 -3 M) by using a 31 A digital conductivity meter .Melting points of azo dye ligand and its metal complexes are un corrected and were determined using open capillary tube method which uses Electrothermal melting point 9300 apparatus .The purity of the azo dya ligand was assessed by thin layer chromatography (TLC) using whatman 250 m silicegel plates as the stationary phase and methanol as developing solvent .

Synthesis of Metal Complexes
The metal complexes of mono azo dye ligand (NTAPy)were synthesized by adding 0.528 g (0.002 mol) of ligand dissolved in 50 ml hot ethanol in the form of drop-wise with stirring stoichiometric amount of 1:2, [M:L] mole ratio (0.001mol) for Cr(III), Mn(II) , Fe(III) , Co(II) , Ni(II) , Cu(II) and Zn(II) Chloride salts which dissolved in 30 ml hot buffer solution (ammonium acetate) at pH,6-7.5 for each metal ions .The reaction mixture was heated and stirred for another 40 minutes at (60-70) o C until the precipitated product ,than left over night,

NTAPy=L
The crude precipitate was filitered off and washed several time with distilled water, then washed by 10 ml absolute ethanol to remove any trace of unreacted organic material to get crystals product purple, orange, green and red solids, dried and preserved in desiccators over anhydrous CaCl 2 .The yields, melting points, color and analytical data are collected in Table 1

Mass Spectrum of the Novel Azo dye Ligand (NTAPy)
The mass spectrum fragmentation of novel azo dye ligand (NTAPy) shown in scheme-2 and Figure 1.The base peak of azo dye ligand at m/Z + =264.0 is a ttributed to the original molecular weight of ligand [C 9   20,22,23 .

Infrared Spectral Studies
The IR spectral data of the prepared azo dye ligand (NTAPy) and their Cr(III) ,Mn(II) ,Fe(III) ,Co(II), Ni(II) , Cu(II) and Zn(II) complexes (KBr disc) are presented in Table 2.The IR spectrum of the free azo dye ligand exhibited a band at 3402 cm -1 which is assigned to υ(-NH 2 ) group in the ligand (NTAPy) .This band does not change in position in all metal complexes because of non coordination with metal ion 26 .The IR spectrum of azo dye ligand shows characteristic bands at 3263 cm -1 and 3101 cm -1 was attributed to υ(-CH 3 ) and υ(-CH) pyridine ring respectively 27 .This band did not show any frequency shift in IR spectra of all metal complexes 20,27,28 .The spectra of all metal complexes show a broad band around at(3440-3496) cm -1 indicated the presence of water molecule υ(H 2 O) in these complexes 14,15 .The strong band observed at 1628 cm -1 in the free azo dye ligand was attributed to υ(-C=N) stretching of the thizole ring 30 .This band shifted to a lower wave number side (1605-1620) cm -1 in all metal complexes suggesting the participation of the υ(-C=N-) of thiazole ring in bonding with metal ions 15,31 .A strong to medium in tensity band at 1512 cm -1 in free ligand and 1512-1519 cm -1 in all metal complexes which is assigned to υ(-NO 2 ) group 16 .A medium intensity band at 1473 cm -1 in the free ligand was attributed to υ(-N=N) stretch of the azo group 32,33 .The band shifts to lower wave number side (458-1434 cm -1 in all metal complexes indicating the coordination with metal ions 34 .Another bands appeared at 1257 cm -1 in free ligand spectrum.attributed to ²(-C-S) of the thiazole ring 15,20,27,35 .The existence of this band in all metal complexes means that the suphur atom of thiazole ring does not participate in coordination 36 .New absorption the range of 512-493 cm -1 which are not present in the spectrum of the free ligand are due to υ(M-N) band vibrate ion 37 .IR spectra data lead to suggest that the ligand behaves as a bidentate chelating agent coordination through the nitrogen atom of thiazole ring nitrogen of azo group nearest to pyridine ring to give five membred metalo ring .Some representative spectra are given in Figures 4,5 and 6 .

Electronic Spectral Studies
The electronic absorption spectra of the novel azo dye ligand (NTAPy) and its prepared metal complexes with some metal ions such as of Cr(III) , Mn(II) , Fe(III) , Co(II) , Ni(II) ,Cu(II) and Zn(II) ions were recorded in freshly absolute ethanol(10 -3 M) at room temperature .The spectral data are summarized in Table (3) and show the spectra in Figures 7,8,9 and 10.
The electronic spectrum of the free ligand (NTAPY) exhibited two absorption bands at 384 nm (26042 cm -1 ) and 239nm (41841 cm -1 ) assignable to p→*p and n→*p transition respectively due to the azo group (-N=N-) and (C=C) groups of thiazole and pyridine rings 20,38 .The absorption band of azo group showed a red shift because of coordination between ligand and metal ion 15,39 .The electronic spectrium of the Cr(III) complex displayed three bands at 532 nm (18797 cm -1 ), 412 nm (24272 cm -1 )and 349 nm(28653 cm -1 ) which may be d-d transitions of Cr(lll)ion, these bands are assignable to 4 A 2 g → 4 T 2 g(F), 4 A 2 g→ 4 T 1 g(F) and 4 A 2 g → 4 T 1 g(p) transitions respectively 27 .The electronic absorption    spectrum of Mn(II)-complex(d 5 ) exhibited one term apree ion ( 6 s) in addition to several times dubline and quarter there for any transition between the crystal field cases will be prohibited multplicity ,and as a result the spectra of ions(d 5 ) are very weak and the colors are faint 40 .The Mn(II)-complex where showed two absorption bands at 907 nm (11025 cm -1 ) and 537nm (18622 cm -1 ) which may be attributed to 6 A 1 g→4 T 2 g and 6 A 1 g→ 4 Eg, 4 A I g(G) transitions respectivel 41 .The absorption band at 238 nm(42017 cm -1 ) is attributed to center ligand transition.The electronic spectrum of Fe(III)-complex showed three absorption band at 963 nm (10384 cm -1 ), 468nm(21367 cm -1 ) and 317 nm(31546 cm -1 ) attributed to 2 A 2 g→ 4 T 1 g(G), 2 A 2 g→ 4 Eg, 4 A 1 g(G) and 2 A 2 g→ 4 T 1 g(p) transitions respectively 27 .The Co(II)-complex exhibited three absorption band at 637 nm(1569 8 cm -1 ), 500 nm (20000 cm -1 ) and 402 nm (24876 cm -1 ) assignable to band due to 2 B 2 g→ 2 A 2 g transition.The broadness of the band may be attributed to dynamic Jahn-Teller distortion 20,23 .The electronic spectrum of the Zn(II)complex did not show any d-d transition because it is saturated with electron (d 10 ).The absorption band at longer wavelength 416 nm (24038 cm -1 ) is due to a charge transfer (M→L,CT) transition.This transition where d p(Zn +2 )→ *p(L)is belived to be primarily dominated by the LUMO of the azoimine chromophory 44,45 .

Magnetic Moments Studies
T h e m a g n e t i c m o m e n t s o b t a i n e d at room temperature for Cr(III),Mn(II),Fe(III), Co(II),Ni(II), Cu(II) and Zn(II) complexes are listed in table 3. The Cr(III)-Complex exhibited the magnetic moment value of 3.78 B.M, this value is too close to the theoretical of magnetic moment for the Cr(III) ion ( 3 t 2 g eg 0 ), (M eff =3.87B.M) which indicates an octahedral geometry and d 2 sp 3 hybridization 27 .The magnetic moment value of Mn(II)-complex has been found 5.63 B.M. The larger variation in the magnetice moment for a high spin has a d 5 , (t 2 g 3 eg 2 ) configuration depends on the magnituede of the orbital contribution.The high value of magnetic moment is because of five electrons unpaired which may suggest a regular octahedral geometry and sp 3 d 2 hybridization 27,46 .The Fe(III)-complex showed the magnetic moment value of 1.84 B.M due presence of one electron unpaired for alow spin has a d 5 (t 2 g 5 eg 0 ) configuration which indicates a distorted octahedral geometry (Z-out) and d 2 sp 3 hybridization 47 .The Co(II)complex exhibited three absorption bands at 637 nm (15698 cm -1 ), 500 nm (20000 cm -1 ) and 402 nm (24876 cm -1 ) assignable to 4 T 1 g(F) → 4 T 2 g(F), 4 T 1 g→ 4 A 2 g and 4 T 1 g(F)→ 4 T 2 g(p) transitions respectively 40,42 , while the absorption bands a t 2 9 6 n m ( 3 3 7 8 4 c m -1 ) a n d 2 5 1 n m (39841 cm -1 ) is attributed to center ligand transition.The Ni(II)-complex showed the magnetic moment value of 3.04 B.M with the range of 2.8-3.5B.M for high spin (t 2 g 6 eg 2 ) configuration suggesting a regular octahedral geometry and sp 3 d 2 hybridization 50,51 .The Cu(II)-complex has a d(t 2 g 6 eg 3 ) configuration show magnetic moment of 1.83 B.M is slightly higher than the spin -only value of 1.73 B.M which offers possibility of an octahedral geometry because of the presence of one electron unpaired and sp 3 d 2 hybridization 52 .The magnetic moment value of Zn(II)-complex is diamagnetic consistent d 10 ,(t 2 g 6 eg 4 ) configuration which indicates an octahedral geometry with sp 3 d 2 hybridization 53 .

Molar Conductivity Studies
The molar conductance( Λ m ) studies of the metal complexes were measured in DMF solvent in 10 -3 M concentration at room temperature.The high values of molar conductivity of the Cr(III)-complex and Fe (III)-complex give 73.85 S.mol -1 .cm 2 and 79.37 S.mol -1 .cm 2 respectively which indicates that the complexes are 1:1 electrolyte with ionic nature because of the presence of the chloride ion (Cl -)which is located outside the coordination sphere 20,27 , but showed the values of molar conductivity of the Mn(II), Co(II), Ni(II), Cu(II) and Zn(II) complexes ranged between (16.08-24.17)S.mol -1 cm 2 , this indicates that non -electrolyte and no conductive species exist because of the chloride ions (2Cl -)which are located in side the coordination sphere 14,32,42,54 The values of molar conductivity of this metal complexes are listed in Table 4.

Metal: Ligand Ratio
The metal : ligand ratio [M:L]of metal complexes were determined by molar ratio method at fixed concentration at wavelength maximum absorption (λ max ).The solution of prepared metal complexes increase the intensity of the colors as approach point of intersection ratio and color continus constant at passing the point which indicates that the metal complexes formed 15,20,32,39 .The azo dye ligand (NTAPY)which was found to form 1:2 [M:L] mole ratio with all metal ions suggested the formation of metal complexes to give two five-membered chelate rings.

Calculation of Metal Complexes Stability Constant
The stability constant(b and logb) of metal complexes are determined spectrophotometrically by measure the absorbance of mixture of solution of azo dye ligand (NTAPY) and metal ions at fixed wavelength (λ max )and optimum concentration values .The degree of formation of metal complexes are calculated depending on the relation-ship b=1-a/4a 3 c 2 and a= Am-As/Am, (where....... r e s p e c t i v e l y.T h e c a l c u l a t e d b a n d log b values for prepared metal complexes are listed in Table 4 .The listed stability constant follows the arrangement Cu(II) >Ni(II) >Co(II) >Zn(II) >Mn(II) >Cr(III) >Fe(III) the sequence of metal ions of the first row transition metals agree with Irving-Williams of stability constant 55,56 .

The Proposed Structures of Metal Complexes
Acoording to the results and discussion through different techniques, the proposed structures of the prepared metal complexes are suggested and shown in Figure 11.Depending on the analytical and spectral data, the novel azo dye ligand (NTAPy) behaves as a bidentate chelating agent coordination through the nitrogen atom (N 3 )of azo group nearest to pyridine ring and nitrogen atom (N 3 ) of thiazole ring to give one-five membered chelate ring .

CONCLUSION
In this paper we report the synthesis and spectral properties studies of a bidentate azo dye ligand derived from thiazole and pyridine ring (NTAPy) and its metal complexes with Cr(III), Mn(II), Fe(III), Co(II), Ni(II), Cu(II) and Zn(II) ions.The azo dye ligand and its metal complexes were characterized by using several physical techniques such as elemental analysis, 1 H-NMR . 13C-NMR, Mass spectroscopy, IR, UV-Vis.and molar conductivity.The geometry proposed for all metal complexes were octahedral stereo chemistry.All metal complexes are not effected by air, light and a moisture, suggesting high stability plus degrees of melting point that give another evidence of the stability of the prepared metal complexes .

Table 1 : physical and analytical data of novel azo dye of ligand (NTAPy) and its metal complexes Compound pH color
m.p Yield Molecular Found (cacld) % H 8 N 6 O 2 S] , 264.29.The peak at m/Z + = 234.0 is due to loss of methyl and amine groups [C 8 H 4 N 5 O 2 S] + ion, while a peak at m/Z + =188.0 is attributed to the loss of nitro group(NO 2 ) to give groups [C 8 H 4 N 4 S] + .The loss of azo group give a peak at m/Z + =160.0 [C 8 H 4 N 2 S] + .The peak at m/Z + =84.0 is analogous to the loss of [C 5 H 4 N] + (pyridine ring) and gives thiazole molecule[C 3 H 2 NS] + , 20,21 .

Table 2 : Selected IR data (KBr disc, υ cm -1 ) for novel azo dye ligand (NTAPy) and their metal complexes
This band attributed to υ(NH 2 ) and υ(H 2 O) molecule because of interference between this bands in this reagan ; w=weak , m=medium , s=strong , sh=sholder , b=broad . *