The Schiff base compounds 2-((4-amino-1,2,5-oxadiazol-3-ylimino)methyl)-4-(phenyldiazenyl) phenol (2a–e) were prepared from the reaction of 3,4-diamino-1,2,5-oxadiazole with 2-hydroxy-5-[(E)-(aryldiazenyl)]benzaldehyde (1a–e) in methanol. The structures of all compounds were then characterized by elemental analysis, mass, IR, UV–Vis, ¹H and ¹³C NMR spectroscopy. UV–Vis absorption spectra indicated enol–keto tautomeric and positive solvatochromism in compound 2a–e which is dependent on the substitution, nature of solvent, pH and environment temperature. The Quantum chemical calculations and UV–Vis absorption spectra data show that positive solvatochromism behavior of compounds 2a–e, which could be due to intramolecular hydrogen bond in enol–keto tautomeric and dipole moment changes. The antibacterial activities of compounds were evaluated against both gram-positive and gram-negative bacteria. All the compounds were found to be active against Staphylococcus aureus and Bacillus cereuss. Among them, compound 2b exhibited the most potent antibacterial activity.

席夫碱化合物2-（（4-氨基-1,2,5-恶二唑-3-ylimino）甲基）-4-（苯基二氮烯基）苯酚（2a – e）由3,4-二氨基- 1,2,5-恶二唑与2-羟基-5-[（E）-（芳基二氮烯基）]苯甲醛（1a – e）的甲醇溶液。然后通过元素分析，质量，IR，UV-Vis，¹ H和¹³ C NMR光谱对所有化合物的结构进行表征。UV-Vis吸收光谱表明化合物2a - e中的烯醇-酮互变异构和正溶剂变色这取决于取代基，溶剂的性质，pH值和环境温度。量子化学计算和UV-Vis吸收光谱数据表明，化合物2a - e的正溶剂变色行为是由于烯醇-酮互变异构体中的分子内氢键和偶极矩变化引起的。评价了化合物对革兰氏阳性和革兰氏阴性细菌的抗菌活性。发现所有化合物对金黄色葡萄球菌和蜡状芽孢杆菌均具有活性。其中，化合物2b表现出最强的抗菌活性。