SYNTHESIS AND BIOLOGICAL ACTIVITY OF 3d-­METAL COMPLEXES WITH BIS(PHOSPHONOMETHYL)AMINOSUNRIC ACID

Abstract

New complexes of 3d-metals (Co2+, Ni2+, Zn2+) with bis(phosphonomethyl)aminosuccinic acid (H6BPMAS) have been synthesized. The complexes were studied in aqueous solutions at ratios M2+:H6BPMAS = 1:1 in a wide pH range (1÷10). Regardless of the nature of the metal, the formation of complexes of the general composition [M(HnBPMAS)(OH)m] (n= 4÷0, m=1÷0) is shown. The stability constants of the formed differently protonated complexes are calculated and diagrams of their distribution are plotted. It is shown that the process of complexation takes place most completely in the region of pH>4. For all bis(phosphonomethyl)aminosuccinates of 3d metals, the dominance of the complex with one form of the ligand occurs in approximately the same pH ranges. A close order of change in the values of lgKst. complexes testifies to the same type of structure of their internal coordination sphere.
 Solid complexes of the composition Na4[MBPMAS]⋅4H2O were synthesized. Their composition, structure, and thermal characteristics were determined by the set of me­thods such as diffuse reflectance spectroscopy, IR spectroscopy, DTA and non-quantitative mass spectrometry. It is proved that the complexes have the structure of a distorted octahedron, in which the 3-d metal ions are bound to the oxygen atoms of the carboxyl and phosphonic groups and the tertiary nitrogen atom of the ligand. At the same time, two 5-membered (aminomethylenephosphonic and glycine) and one 6-membered (β-alanine) metallocycles are formed in bis(phosphonomethyl)aminosuccinates.
 The biological activity of H6BPMAS and its complexes with Ni(II) and Co(II) against non-pathogenic bacterial species of microorganisms Pseudomonas fluorescens and Pseudomonas aureofaciens was studied. The study of the activity of substances was carried out in a liquid sterile Hiss medium. The maxi­mum stimulating effect on the growth of bacterial cultures for the studied compounds was recorded at a concentration of 1 µM in 24 hours after the start of cultivation of mic­ro­organisms. The highest growth of microorganisms was recorded for metal complexes (50% Na4[CoBPMAS]·4H2O and 35% Na4[NiBPMAS]·4H2O). The maximum stimulating effect on the growth of bacterial cultures is shown by the Co(II) complex, which is able to initiate the synthesis of one of the most important growth hormones - heteroauxin.