Facile synthesis, crystal structure and bioactivity evaluation of two novel barium complexes based on 2,4,6-trichlorophenoxyacetic acid and o-ferrocenylcarbonyl benzoic acid

Abstract

Two novel Ba(II) complexes [Ba(TCPA)₂(H₂O)₄] 1 and [Ba(H₂O)₈]·2(o-FcCOC₆H₄COO)·6H₂O 2 [HTCPA = 2,4,6-trichlorophenoxyacetic acid and o-HOOCC₆H₄-COFc = o-ferrocenylcarbonyl benzoic acid] have been synthesized by a facile microwave method. The solid-state structures were well established by means of X-ray crystallography as well as routine analysis of the infrared spectrum (FTIR), elemental analysis, field emission scanning electron microscopy (FESEM) and thermogravimetric analysis (TG). Different polyhedra of tricapped triangular prisms for 1 and dodecahedra for 2 were present. It is worth noting that the central Ba(II) ion in 1 is nine-coordinated by two carboxylate oxygen atoms from TCPA ligands and seven oxygen atoms from coordinated water molecules. By contrast, the eight-coordinated Ba(II) in 2 forms barium-water clusters assembled by O–H⋯O hydrogen-bonds contributed by coordinated water molecules. The uncoordinated o-OOCC₆H₄-COFc ligands in 2 play a key role in the process of charge balance. FESEM images exhibited different surface appearances between the ligand and barium complexes, that is: flower-like HTCPA, branch-like o-HOOCC₆H₄-COFc, block-like complex 1 and corner-truncated cubes for complex 2. The allelopathic activity of the complexes and their corresponding ligands was evaluated against two herbaceous plants of barnyard grass and turnip (Raphanus sativus). All the tested compounds showed certain activity with good RI values. An antifungal bioassay was also carried out in vitro on three strains of Botrytis cinerea Pers., Glomerella cingulata Schr and Cytospora sp. Complex 1 and HTCPA can work against all three tested fungi, whereas o-HOOCC₆H₄-COFc and 2 only worked for Botrytis cinerea Pers. The complex presented in this paper has potential applications in weed control, and this work provides an experimental basis for future studies on Ba-based pesticides.