Copper(II) Complexes of Oxyphosphonates: Synthesis, Spectroscopic Characterization and Plant Growth-Stimulating Activity

Abstract

Coordination compounds of Cu(II) ions with some oxyphosphonates were synthesized in ethanol using ultrasonic activation. The complexes were isolated as blue crystalline powders in yields of 72–87%. Complex formation was confirmed by IR spectroscopy and thermal analysis. The shift of the ν(P=O) band to lower frequencies indicates the involvement of the phosphoryl oxygen in coordination with the Cu(II) ion. Changes in melting points compared to the initial ligands indicates a rearrangement of the crystal structure. For the piperidine based complex, the N,O coordination type was observed by the appearance of a Cu–N absorption band at 661 cm⁻¹. The biological activity of the synthesized compounds was evaluated using a wheat seed germination model. It was found that the oxyphosphonates and their complexes stimulate seedling development, leading to increased shoot and root lengths compared to the control. The most pronounced effect was observed for compounds containing phenyl and piperidine moieties, with root length increases reaching 74.8% and shoot length by 18.7%, relative to the control. In addition, the copper complexes suppressed the growth of mold microflora on treated seeds, exhibiting antimicrobial activity. These results demonstrate the potential of phosphorus-containing Cu(II) coordination compounds as potential agrochemicals with growth-promoting and antimicrobial properties.