Spectroscopic Studies and Thermal Analysis of New Azo Dyes Ligands and their Complexes with some Transition of Metal Ions

New Azo ligands HL1 [2-Hydroxy-3-((5-mercapto-1,3,4-thiadiazol-2-yl)diazenyl)-1naphth aldehyde] and HL2 [3-((1,5-Dimethyl-3-oxo-2-phenyl-2,3-dihydro-1Hpyrazol-4-yl)diazenyl)-2-hydroxy-1-naphthaldehyde] have been synthesized from reaction (2-hydroxy-1-naphthaldehyde) and (5-amino-1,3,4-thiadiazole-2-thiol) for HL1 and (4-amino-1,5-dimethyl-2-phenyl-1H-pyrazol-3(2H)-one) for HL2. Then, its metal ions complexes are synthesized with the general formula; [CrHL1Cl3(H2O)], [VOHL1(SO4)] [ML1Cl(H2O)] where M = Mn(II), Co(II), Ni(II) and Cu(II), and general formula; [Cr(L2)2 ]Cl and [M(L2)2] where M = VO(II), Mn(II), Co(II), Ni(II) and Cu(II) are reported. The ligands and their metal complexes are characterized by phiscochemical spectroscopic techniques (FT.IR, Mass, UV-Vis, 1 H and 13 C-NMR, TGA, (C.H.N.), molar conductivity, Atomic Absorbance, Chloride containing magnetic susceptibility). The spectral data suggest that the (HL1) behaves as a bidentate ligand in all complexes, whereas (HL2) behaves as a tridentate ligand for all complexes; bidentate ligand in Vanadium complex is coordinated with the metal ions through azo nitrogen and oxygen atoms. Theoretical studies of these ligands and their metal complexes in gas phase using Hyper chem.8. Studies of these compounds are prepared for their bacterial activity


Materials and Methods:
All the following chemicals and reagents are of an analytical grade and used as supplied without any further purification (BDH) sigma Aldrich, and (Fluka).

Results and Discussion:
Elemental microanalysis and some physical properties of the (HL 1 and HL 2 ) and their prepared complexes are shown in Table (1), The composition of the complexes formed in solution has been established by the mole ratio method.In both cases, the result reveals (1:1) metal to ligand for HL 1 but (1:2) metal to ligand for HL 2 respectively (Figure -2).

Table (1) Analytical and Physical Data of the Ligands and their Complexes
The electronic spectra of the Co(II) complexes with HL 1 and HL 2 ligands exhibit one and three absorption band at 677 nm and (615,678,909) nm which are attributed to 4 A 2 → 4 T 1P and 4 T 1g → 4 T 1g(P) , 4 T 1g → 4 A 2g(F) and 4 T 1g → 4 A 2gF respectively.Furthermore, the magnetic moment of the Co(II)(d7) complexes was found to be 4.1 and 4.8 B.M., All the above mentioned data correspond to an tetrahedral and octahedral geometry respectively [18][19][20].The electronic spectra of the Ni(II) complexes with HL 1 and HL 2 ligands exhibit one and three absorption band at 797 nm and (597, 690, 780) nm which are attributed to 3 T 1 → 3 T 1P and 3 A 2g → 3 T 1gP , 3 A 1g → 3 T 1gF and 3 A 1g → 3 T 2gF respectively.Furthermore , the magnetic moment of the Ni(II) (d8) complexes is found to be 3.9 and 2.80 B.M., All the above mentioned data correspond to an tetrahedral and octahedral geometry respectively [18][19][20].The electronic spectra of the Cu(II) complexes exhibit one and two absorption band with HL 1 and HL 2 ligands at 953 nm and (450 and 540) nm which attributed to 2 T 2 → 2 E and 2 B 1g → 2 A 1g and 2 B 1g → 2 B 2g respectively.Furthermore, the magnetic moment of the Cu(II) (d9) complexes is found to be 2.01 and 1.9 B.M., All the above mentioned data correspond to an tetrahedral and octahedral geometry respectively [18].The electronic spectra of the Cr(III) complexes exhibit three absorption band with HL 1 and HL 2 ligands at (535, 645, 905) nm and (601,736, 864) nm which attributed to 4 A 2g → 3 T 1gP , 4 A 2g → 3 T 1gF and 4 A 2g → 3 T 2gF respectively [20][21][22].Furthermore, the magnetic moment of the Cr(III)(d3) complexes is found to be 3.87 and 3.77 B.M., All the above mentioned data correspond to an octahedral geometry respectively [22].The electronic spectra of the VO(II) complexes exhibit two absorption band with HL 1 and HL 2 ligands at (515 and 618) nm and (815 and 915) nm which are attributed to 2 B 2g → 2 B 1g and 2 B 2g → 2 E g respectively [20][21][22].Furthermore, the magnetic moment of the VO(II) (d1) complexes is found to be 1.81 and 1.86 B.M., All the above mentioned data correspond to an square pyramidal geometry respectively [22].The electronic spectra of the Mn(II) complexes exhibits two and three absorption band with HL 1 and HL 2 ligands at (696 and 850) nm and (540, 650, 905) nm which are attributed to and ( 6 A 1 → 4 T 2 g, 6 A 1 → 4 T 1 g, 6 A 1 → 4 E 1 g) respectively.Furthermore, the magnetic moment of the Mn(II) (d5) complexes is found to be 5.45 and 5.01 B.M., All the above mentioned data correspond to an tetrahedral and octahedral geometry respectively [18].The molar conductivity value of the complexes is consistent with nonelectrolytes for all complexes and 1:1 electrolytes Cr(III) complex with HL 2 .See structure for the complexes Figure (3).4).The thermograms have been carried out in the range of 25-700 °C at a heating rate of 10 °C/min in nitrogen atmosphere.They show an agreement in weight loss between their results obtained from the thermal decomposition and the calculated values, which supports the results of elemental analysis and confirms the suggested formulae.Thus, the ligands and complexes show a common general behavior as show in Scheme (1).Coats-Redfern is the method mentioned in the literature related to decomposition kinetics studies; this method is applied in this study [23,24].Kinetic parameters are calculated by employing the Coats-Redfern equations which are summarized in Table (5).The Coats-Redfern equation may be written as the following:

Table (3) Electronic Data, µ eff and Molar Conductivity for the Complexes
The activation entropy ΔS*, the activation enthalpy ΔH* and the free energy of activation ΔG* were calculated using the following equations: Where K and h are the Boltzmann's and Planck's constants, respectively.The calculated values of ΔE*, ΔS*, ΔH* and ΔG* for the dehydration and the decomposition steps are given in table (5).

Theoretical Study
The vibration spectra Azo dyes ligands are calculated by using a Hyber chem.8 method.The results obtained for wave numbers are presented in Table (6), 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 is reported [25] that frequencies coupled with (HFT) approximation and quantum harmonic oscillator approximations tend to be 10% too high.And structures of ligands are calculated to search for the most probable model building stable structure.These shapes show the calculated optima geometries for compounds prepared as shown in Figure (4).And the ∆E b and ∆H f for compounds in table (7).

Microbiological Investigation
The biological activity of ligands and their metal complexes is tested against bacteria; we use more than one test organism to increase the chance of detecting antibiotic principles in tested materials.The organisms used in the present investigation includes two Gram positive bacteria (B.subtilis and S. aureus) and two Gram negative bacteria (E. coli and P. aeruginosa).The results of the bactericidal screening of the synthesized compounds are recorded in Table (8).An influence of the central ion of the complexes in the antibacterial activity against the tested Gram positive and Gram negative organisms shows that the complexes have an enhanced activity compared to the ligand itself.Key to interpretation: Less than 10 mm=inactive, 10-15 mm=weakly active, 15-20 mm=moderately active, more than 20 mm= highly active.

) The Tentative Decomposition Reaction of the Complexes R
2=correlation coefficient of the linear plot, n = order of reaction, Z = preexponential factor

Table ( 6) Comparison of Experimental and Theoretical Vibration Frequencies for Ligands
Experimental frequency.** Theoretical frequency.*** Error% due to main difference in the experimental measurements and theoretical treatments of vibration spectrum. *