Mohamed Gehad G, Abd El-Wahab Zeinab H
Chemistry Department, Faculty of Science, Cairo University, Giza, Egypt.
Spectrochim Acta A Mol Biomol Spectrosc. 2005 Apr;61(6):1059-68. doi: 10.1016/j.saa.2004.06.021.
The synthesis and structural characterization of mixed ligand complexes derived from 2,6-pyridinedicarboxaldehydebis(o-hydroxyphenylimine), 2,6-pyridinedicarboxaldehydebis(p-hydroxyphenylimine) (1(ry) ligands) and 2-aminopyridne (2(ry) ligand) are reported. The ligands and their transition metal complexes were characterized on the bases of their elemental analyses, IR, solid reflectance, magnetic moment, molar conductance and thermal analysis (TGA). The mixed ligand complexes are formed in the 1:1:1 (M:L(1) or L(2):L') ratio as found from the elemental analyses and found to have the formulae [MX(2)(L(1) or L(2))(L')].nH(2)O where M = Co(II), Ni(II), Cu(II) and Zn(II), L(1) = 2,6-pyridinedicarboxaldehydebis(p-hydroxyphenylimine), L(2) = 2,6-pyridine dicarboxaldehydebis(o-hydroxyphenylimine), L' = 2-aminopyridine, X = Cl(-) in case of Cu(II) complex and Br(-) in case of Co(II), Ni(II) and Zn(II) complexes and y = 0-3. The molar conductance data reveal that the chelates are non-electrolytes. IR spectra show that the Schiff bases are coordinated to the metal ions in a terdentate manner with NNN donor sites of the pyridine-N and two azomethine-N. While 2-aminopyridine coordinated to the metal ions via its pyridine-N. Magnetic and solid reflectance spectra are used to infer the coordinating capacity of the ligand and the geometrical structure of these complexes are found to be octahedral. The thermal behaviour of these chelates shows that the hydrated water molecules and the anions are removed in a successive two steps followed immediately by decomposition of the ligands (L(1), L(2) and L') in the subsequent steps. The activation thermodynamic parameters, such as, E*, DeltaH*, DeltaS* and DeltaG* are calculated from the TG curves and discussed. The ligands and their metal chelates have been screened for their antimicrobial activities and the findings have been reported, explained and compared with some known antibiotics.
报道了由2,6 - 吡啶二甲醛双（邻羟基苯基亚胺）、2,6 - 吡啶二甲醛双（对羟基苯基亚胺）（1(ry)配体）和2 - 氨基吡啶（2(ry)配体）衍生的混合配体配合物的合成及结构表征。基于元素分析、红外光谱、固体反射光谱、磁矩、摩尔电导率和热分析（热重分析）对配体及其过渡金属配合物进行了表征。从元素分析可知，混合配体配合物以1:1:1（M:L(1)或L(2):L'）的比例形成，其化学式为[MX₂(L(1)或L(2))(L')].nH₂O，其中M = Co(II)、Ni(II)、Cu(II)和Zn(II)，L(1) = 2,6 - 吡啶二甲醛双（对羟基苯基亚胺），L(2) = 2,6 - 吡啶二甲醛双（邻羟基苯基亚胺），L' = 2 - 氨基吡啶，对于Cu(II)配合物X = Cl⁻，对于Co(II)、Ni(II)和Zn(II)配合物X = Br⁻，且y = 0 - 3。摩尔电导率数据表明螯合物为非电解质。红外光谱显示席夫碱以三齿方式与金属离子配位，通过吡啶 - N的NNN供体位点和两个甲亚胺 - N。而2 - 氨基吡啶通过其吡啶 - N与金属离子配位。利用磁光谱和固体反射光谱推断配体的配位能力，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，结晶水分子和阴离子分两步相继去除，随后在后续步骤中配体（L(1)、L(2)和L'）分解。根据热重曲线计算并讨论了活化热力学参数，如E*、ΔH*、ΔS和ΔG。对配体及其金属螯合物的抗菌活性进行了筛选，并报告、解释了研究结果，并与一些已知抗生素进行了比较。
