Ionic liquid forms of clopyralid with increased efficacy against weeds and reduced leaching from soils

• New HILs based on clopyralid with multifunction were synthesized and characterized.
• The physicochemical property of clopyralid can be regulated using different cations.
• HILs with great adsorption capacity and low leaching characteristic were achieved.
• New HILs reduced the risk to aquatic environment.
• Clopyralid ionic liquids showed a higher herbicidal activity.

The excessive application of water-soluble pesticides poses enormous potential risks to groundwater by leaching or in runoff. Ionic liquids can regulate the physicochemical properties of pesticides and surmount their disadvantages. In this study, five herbicidal ionic liquids (HILs) based on clopyralid have been synthesized and characterized to reduce the risks to the aquatic environment and improve the herbicidal activity. The new HILs are prepared by pairing isopropylamine, 1-dodecylamine, 2-benzothiazolamine, 1-methylimidazole, benzyltriethylammonium chloride respectively. The results of the solubility, soil adsorption, surface activity, leaching characteristic and herbicidal activity of HILs show that the physicochemical properties can be optimized by selecting different counter cations. Compared with clopyralid potassium, HILs have better herbicidal activity, greater adsorption capacity and lower leaching characteristic. The HILs of clopyralid can reduce its hazardous impacts on the aquatic environment, suggesting a desirable candidate in clopyralid application in the future.