Spectrophotometometric and potentiometric studies on cr [lll], Mn [ll], Fe[III], Co [ll] and Ni [ll] complexes with 5,7-dinitroso-6-hydroxy-4-methylcoumarin

The composition, stability constants and optimal formation conditions of the complexes of Cr3+, Mn2+, Fe3+, Co2+ and Ni2+ with 5, 7-dinitroso-6-hydroxy-4-methylcoumarin have been studied spectrophotometrically. The stoichiometries of the complexes showed that 1: 1 and 1: 2 [M: L] species were formed and the influence of foreign ions was investigated. The ionization constants [pKa] of the investigated ligand and stability constants of the metal ions complexes were determined, potentiometrically, in 40% ethanolic solution