The design of small molecules that can target the aggregation of A beta as potential therapeutic agents for Alzheimer's disease is an area of study that has attracted a lot of attention recently. The novel ligand methyl 1-butyl-2-pyridyl-benzimidazole carboxylate was prepared for the synthesis of a series of new iridium(III), ruthenium(II), and platinum(II) 2-pyridyl-benzimidazole complexes. The crystal structure of the half-sandwich iridium(III) complex was established by X-ray diffraction. An arrangement of two cationic complexes in the unit cell is observed, and it seems to be organized by weak pi...pi interactions that are taking place between two symmetry-related benzimidazole ring systems. All new compounds inhibited aggregation of A beta 1-42 in vitro as shown by both thioflavin T fluorescence assay and transmission electron microscopy. Among them the Ir compound rescued the toxicity of A beta 1-42 in primary cortical neurons effectively.