Molecular structure regulation and herbicidal activity of dibutyltin aryloxyacetate complexes

Abstract

Six dibutyltin aryloxyacetate complexes [(X-C6H4OCH2COO)(SnBu2)2(μ3O)(OMe)]2 (A1, B1), [(X-C6H4OCH2COO)2(SnBu2)2(μ3O)]2 (A2, B2), and [(X-C6H4OCH2COO)2SnBu2] (A3, B3) were synthesized and characterized by IR, NMR, HRMS, and TGA techniques. The molecular structure of complexes A1, A3 and B1-B3 was confirmed by single-crystal X-ray crystallography. Complexes A1, B1, A2, and B2 are dimeric carboxylate tetraorganodistannoxanes, displaying a "ladder-like" molecular arrangement. The aryloxyacetate ligands in A1 and B1 adopt a monodentate mode, while they function as bridging coordination ligands in A2 and B2. Complexes A3 and B3 represent dibutyltin carboxylates with crystallographically imposed two-fold symmetry, with the aryloxyacetate ligands adopting a bidentate mode. Aryloxyacetic acids demonstrate a propensity for assuming various coordination modes, leading to the formation of diverse molecular architectures in organotin carboxylates. In addition, complex B1 exhibits polymorphism. Echinochloa crus-galli and Portulaca oleracea L. were used as target organisms for herbicidal activity testing using a petri dish method. It was found that they have a significant inhibitory effect on weed roots and stems at 200 μmol/L, and the structure-activity relationship analysis revealed the important influence of substituent types and complex structures on their activity.