Dissociation kinetics study of Ce(III) complexes with H8dotp (H8dotp=1,4,7, 10-tetraazacyclododecane-1,4,7,10-tetrakis (methylphosphonic acid))

Abstract

Rate of decomplexation of phosphonic acid DOTA analog Ce(III) complex was investigated in strongly acidic solutions. Complex is highly kinetically inert.

The dissociation kinetics of cerium(III) complexes with H(8)dotp (I = 3.0 mol dm(-3) (Na,H)ClO4, t = 25-60 °C) was studied by means of molecular absorption spectroscopy in the UV region. The mechanism of the proton-assisted reaction was proposed, and the activation parameters (E(a) = 111 +- 20 kJ mol(-1), ΔH≠ = 108 +- 20 kJ mol(-1), ΔS≠ = 32 +- 62 J K(-1) mol(-1)) for the rate-determining step were calculated.

Keywords

• macrocyclic complexes
• cyclen derivatives
• phosphonate complexes
• lanthanide(III) complexes
• cerium(III)
• dissociation kinetics