Mohamed Gehad G, Omar M M, Hindy Ahmed M M
Chemistry Department, Faculty of Science, Cairo University, Giza, Egypt.
Spectrochim Acta A Mol Biomol Spectrosc. 2005 Dec;62(4-5):1140-50. doi: 10.1016/j.saa.2005.03.031. Epub 2005 Jun 13.
Metal complexes of Schiff base derived from 2-thiophene carboxaldehyde and 2-aminobenzoic acid (HL) are reported and characterized based on elemental analyses, IR, 1H NMR, solid reflectance, magnetic moment, molar conductance and thermal analysis (TGA). The ligand dissociation as well as the metal-ligand stability constants were calculated pH metrically at 25 degrees C and ionic strength mu=0.1 (1M NaCl). The complexes are found to have the formulae M(HL)2n.yH2O (where M=Fe(III) (X=Cl, n=3, y=3), Co(II) (X=Cl, n=2, y=1.5), Ni(II) (X=Cl, n=2, y=1) and UO2(II) (X=NO3, n=2, y=0)) and [M(L)2] (where M=Cu(II) (X=Cl) and Zn(II) (X=AcO)). The molar conductance data reveal that Fe(III) and Co(II), Ni(II) and UO2(II) chelates are ionic in nature and are of the type 3:1 and 2:1 electrolytes, respectively, while Cu(II) and Zn(II) complexes are non-electrolytes. IR spectra show that HL is coordinated to the metal ions in a terdentate manner with ONS donor sites of the carboxylate O, azomethine N and thiophene S. From the magnetic and solid reflectance spectra, it is found that the geometrical structure of these complexes are octahedral. The thermal behaviour of these chelates shows that the hydrated complexes losses water molecules of hydration in the first step followed immediately by decomposition of the anions and ligand molecules in the subsequent steps. The activation thermodynamic parameters, such as, E*, DeltaH*, DeltaS* and DeltaG* are calculated from the DrTG curves using Coats-Redfern method. The synthesized ligands, in comparison to their metal complexes also were screened for their antibacterial activity against bacterial species, Escherichia coli, Pseudomonas aeruginosa, Staphylococcus pyogones and Fungi (Candida). The activity data show that the metal complexes to be more potent/antibacterial than the parent Schiff base ligand against one or more bacterial species.
报道了由2-噻吩甲醛和2-氨基苯甲酸衍生的席夫碱的金属配合物，并通过元素分析、红外光谱、核磁共振氢谱、固体反射光谱、磁矩、摩尔电导率和热分析（热重分析）对其进行了表征。在25℃和离子强度μ=0.1（1M氯化钠）条件下，通过pH滴定法计算了配体解离常数以及金属-配体稳定常数。发现这些配合物具有通式M(HL)2n·yH2O（其中M = Fe(III)（X = Cl，n = 3，y = 3）、Co(II)（X = Cl，n = 2，y = 1.5）、Ni(II)（X = Cl，n = 2，y = 1）和UO2(II)（X = NO3，n = 2，y = 0））以及[M(L)2]（其中M = Cu(II)（X = Cl）和Zn(II)（X = AcO））。摩尔电导率数据表明，Fe(III)、Co(II)、Ni(II)和UO2(II)螯合物本质上是离子型的，分别为3:1和2:1电解质类型，而Cu(II)和Zn(II)配合物是非电解质。红外光谱表明，HL以三齿方式通过羧酸根的O、偶氮甲碱的N和噻吩的S的ONS供体位点与金属离子配位。从磁性和固体反射光谱发现，这些配合物的几何结构为八面体。这些螯合物的热行为表明，水合配合物在第一步失去水分子，随后在后续步骤中阴离子和配体分子分解。使用Coats-Redfern方法从热重曲线计算活化热力学参数，如E*、ΔH*、ΔS和ΔG。还对合成的配体及其金属配合物针对细菌物种大肠杆菌、铜绿假单胞菌、化脓性葡萄球菌和真菌（白色念珠菌）的抗菌活性进行了筛选。活性数据表明，金属配合物对一种或多种细菌物种比母体席夫碱配体更具效力/抗菌性。
