Potentiometeric Study of New Schiff Base Complexes Bearing Morpholine in Ethanol-water Medium with some Metal Ions

摘要

Acid dissociation constants of 2-[(4-morpholinobenzylidene)amino]phenol (HL) and the equilibriumconstants of their metal complexes with Cu 2+ , Zn 2+ , Sr 2+ , Cd 2+ , Ba 2+ and Hg 2+ ions were investigatedusing a pH metric titration technique in 40 % (v/v) ethanol-water medium and μ = 0.5 M NaClO 4 . Τhedissociation constants (pK a ) of HL ligand and the stability constants of the respective complexes (logK i ) were calculated at 298, 308 and 318 K. The values of dissociation constants (pK OH and pK NH ) ofmonoprotic HL were found as 10.36 and 2.95, respectively. The formation constants of the complexesincrease in the arrangement of Sr 2+ < Zn 2+ < Cd 2+ < Hg 2+ < Ba 2+ < Cu 2+ ions. The thermodynamicfunctions for the protonation and the deprotonation process of HL and their metal complex equilibria arederived and discussed. The formation metal complexes of Cu 2+ , Zn 2+ , Sr 2+ , Cd 2+ , Ba 2+ and Hg 2+ h asbeen found to be endothermic and spontaneous processed. Furthermore, the geometric parameters of themetal-HL complexes were studied according to the density functional theory (DFT) method.