Study on Triflumezopyrim Solid Forms: Crystal Structure Analysis and Suspension Concentrate Application Insights

Polymorphism in solid molecules is increasingly recognized in the field of agriculture. Triflumezopyrim (TFM) is a pioneering mesoionic insecticide that has played a pivotal role in the control of resistant rice hoppers, yet studies of its polymorphs are scarce. This study systematically investigated the polymorphism of Triflumezopyrim, identifying four new polymorphs (Forms II–V), a hydrate (Form H), and an amorphous form. The crystal structures of Forms III, V, and H were identified by single-crystal X-ray diffraction analysis for the first time. Solubility, dissolution, and stability tests were conducted. Thermal analysis, solvent-mediated transformation experiments, and lattice energy calculations clarified the transformation relationships among the different forms, identifying Form V as the most thermodynamically stable polymorph with the lowest solubility. Furthermore, Forms I, II, V, and H were formulated as suspension concentrates, and their formulation capabilities and bioactivity were tested. Moreover, the fluorescence change of different solid polymorphs was observed. The analysis of the weak interaction in the single-crystal structure revealed that the change in the π–π packing pattern was the possible reason for the observed fluorescence change. These findings significantly enrich our understanding of the solid-state properties of Triflumezopyrim and provide substantial guidance for future processing and formulation selection.