Two newly synthesized ligands based on 1,3,4-thiadiazolethiosemicarbazone have been isolated by the condensation reaction of 2,3-disubstituted-5-acetyl-1,3,4-thiadiazole derivatives with thiosemicarbazide in acidic medium in addition to their Co(II) chelates. The synthesized cobalt chelates that have been obtained by the reaction of each ligand with cobalt acetate were confirmed to have the formulae [(LM)Co(OAc)(H₂O)₂]H₂O (LM–Co) and [(LN)Co(OAc)(H₂O)₂]0.5CH₃OH (LN–Co); where LM and LN are 1,3,4-thiadiazolethiosemicarbazone ligands with methyl and nitro substituents, respectively. Comparison of the IR spectrum of each ligand with that of its cobalt complex implied that both ligands acted as monobasic tridentate connecting to the cobalt ion through N atoms of both azomethine group and thiadiazole ring and S atom of deprotonated SH group as well. The two complexes have been proved to have octahedral geometrical structures. The synthesized compounds were studied as corrosion inhibitors for carbon steel in molar hydrochloric acid solution using several chemical and electrochemical techniques. The investigational outcomes displayed that the inhibition efficiencies of the examined compounds were found to augment as the concentrations of such compounds raised. At comparable inhibitors concentration, the inhibition efficiency was a little increased following the order: LM > LM–Co > LN > LN–Co. The acquired high inhibition efficiencies of the explored compounds were ascribed to the potent adsorption of the molecules on the steel surface and construction of adherent layers. Such adsorption was found to accord with Langmuir adsorption isotherm. There is a good correlation in the results obtained from the different measurements used.

中文翻译：

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新型1,3,4-噻二唑硫代半咔唑酮衍生物及其二价钴配合物：碳钢的酸性腐蚀抑制作用的合成，表征及其功效

通过在酸性介质中将2,3-二取代的-5-乙酰基-1,3,4-噻二唑衍生物与thiosemicarbazide在酸性介质中进行缩合反应，分离出两个新合成的基于1,3,4-噻二唑硫代半脲的配体。 II）螯合物。通过每个配体与乙酸钴反应制得的合成钴螯合物被证实具有式[（LM）Co（OAc）（H ₂ O）₂ ] H ₂ O（LM–Co）和[（LN）Co（OAc）（H ₂ O）₂ ] 0.5CH ₃ OH（LN–Co）；其中，LM和LN是分别具有甲基和硝基取代基的1,3,4-噻二唑硫代半碳酮配体。每种配体的红外光谱与其钴配合物的红外光谱的比较表明，两个配体都通过偶氮甲碱基团和噻二唑环的N原子以及去质子化的SH基团的S原子与钴离子连接成一元三齿。已经证明这两个复合物具有八面体的几何结构。使用几种化学和电化学技术，对合成的化合物作为碳钢在盐酸盐酸溶液中的腐蚀抑制剂进行了研究。研究结果表明，发现所检查化合物的抑制效率随着此类化合物浓度的升高而提高。在抑制剂浓度相当的情况下，LM  >  LM–Co  >  LN  >  LN–Co。探索性化合物获得的高抑制效率归因于分子在钢表面上的强力吸附和粘附层的构造。发现这种吸附符合朗缪尔吸附等温线。从使用的不同测量结果中可以得出很好的相关性。