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Phenoxo- and azido-bridged complexes with N2OS2 Schiffbase ligand; synthesis, spectral investigation and bacterial activity

Talib H.Mawat, Mohamad J.Al-Jeboori

Aseries of phenoxo- and azido-bridged complexes with potentially binucleating N2OS2 multidentate Schiff-base ligand (HL) are reported. The condensation reaction of 2,6-diformyl-4-methylphenol with 2-(4-amino-5-mercapto-4H-1,2,4- triazol-3-yl)phenol in a 1:2 mole ratio afforded the preparation of the new Schiff-base ligand 4'- ( ( ( 1 E , 1 Â’ E ) - ( 2 - h y d r o x y - 5 -me t h y l - 1 , 3 - phenylene)bis(methanylylidene))bis(azanylylidene))bis(5- (2-hydroxyphenyl)-2,4-dihydro-3H-1,2,4-tr- iazole- 3-thione. The reaction of the ligand with Cr(III), Mn(II), Fe(II) Co(II), Ni(II), Cu(II), Zn(II), Cd(II) and Hg(II) metal ions resulted in the formation of binucleating phenoxo-bridged complexes, of general formula [Cr2L(H2O)2Cl4]Cl, [M2L(H2O)4Cl2]Cl, K[Cu2L(H2O)2Cl4], [M‘2LCl2]Cl(H2O) and K[Zn2LCl4] (M= Mn(II), Co(II) and Ni(II); M‘= Fe(II) or Cd(II); M‘= Hg(II), H2O= 0). The reactivity studies of the phenoxo-bridged binucleating complexes toward azido moiety were also investigated, which gave tetranuclear µ-1,1-azido-bridged complexes of the general formula [Cr2L(N3)4]Cl(H2O)2 andNa[M2L(N3)4](H2O)2 (M=Mn(II), Fe(II), Co(II), Ni(II), Cu(II), Zn(II), Cd(II) andHg(II). Themode of bonding and predicted geometry of complexes were determinedthroughphysico-chemical andspectroscopic methods. These analytical and physical studies for the phenoxo-bridged binucleatingcomplexes revealed octahedral and tetrahedral geometries about (Mn(II), Co(II) andNi(II)) and (Fe(II),Cd(II) andHg(II)) ions, respectively.However, a five-coordinate structure is proposed for the Zn(II) complex. The formation of octahedral geometries aboutmetal centre has been suggested for the tetranuclear azido-bridged complexes. The ligand and its metal complexes were screened againstGramnegative bacterial strainsEscherichiacoli (E. coli), Pseudomonas aeruginosa and Bacillus sabtuius and Gram positive bacterial strain Staphylococcus aureus that revealed the metal complexes become more potentially resistive to the microbial activities as compared to the free ligand.