engleski

EXTRACTION OF METAL CATIONS WITH POROUS OXO-AZA MACROCYCLIC COMPOUNDS

Removal of highly toxic air, water and soil pollutants from the environment is a major scientific topic. Macrocycles are organic compounds that can bind toxic species and be designed for extraction of specific metal cations [1, 2. Macrocycles containing oxygen and nitrogen donor atoms in the inner macrocyclic ring (oxa-aza macrocycles) have been studied for that purpose [1. The affinity of an oxa-aza macrocycle towards specific cations can be designed by changing several factors: ring size (cavity size), HSAB principle, donor atom properties, planarity of the system (puckering) and orientation of donor atoms (exodentate or endodentate) [1, 2. In this work we have synthesized a novel N4O4 -donor macrocycle (2) by reduction of previously prepared [2 porous macrocyclic Schiff base (1). Compounds were characterized by elemental and thermal analysis, FT-IR and NMR spectroscopy. Picrate extraction studies were performed following modified Pedersen’s procedure [3 for Ni2+, Cd2+, Zn2+, Ag+, Co2+, Hg2+, Cu2+, Fe3+, Mn3+, Au3+ and Cr3+. The composition of extracted species and extraction constant (Kex) were calculated using dependance of the distribution ratio (D) on macrocycle concentration (logD-logL plot) for Cu2+, Au3+ and Ag+. Metal extraction experiments indicate that highest extraction is achieved for Cu2+ (87%) in the case of compound 1 and for Au3+ (100%), Cu2+ (100%) and Fe3+ (100%) in the case of compound 2. The composition of extracted species in case of 1 and Cu2+ is 1:1 (ligand:metal ratio, Kex = 11.062), and 1:1 ratio for 2 and Ag+ and Au3+ (Kex = 8.7107 and 17.667, respectively).

oxa-aza macrocycles, metal extraction

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