Spectrophotometric and potentiometric study on iron(II) complexes with some macrocyclic ligands

One new macrocycle. 4,10-bis(2-hydroxy-5-nitrobenzyl)-4,10-diaza-1.7,-dioxa dodecanc (LO) has been synthesised and characterised. Its basicity behaviou r, as well as that of the two related azamacrocycles 1,7-bis(2-hydroxy-5-ni trobenzyl)-4,10-dimethyl-1,4,7,10-tetraazadodecane (L1) and 1,13-bis(2-hydr oxy-5-nitrobenzyl)-4,10-dimethyl-4,7,10,16-tetramethyt-1.4,7,10,13,16-hexaa zaoctadecane (L2), was studied by potentiometry in 0.1 M N(CH3)(4)Cl at 25 degreesC, characterising moreover the ionisation processes related to macro cyclic nitrogens and to nitrophenolic moieties on the base of spectral vari ations. The equilibria of the three ligands with iron(II) were studied. 1:1 complexation models with different protonation degrees were found for the three ligands and the related formation constants were estimated from poten tiometric results. The pH distribution curves are discussed on the basis of spectrophotometric findings. (C) 2001 Elsevier Science B.V. All rights res erved.