Nephelauxetic effect in the lanthanide complexes with methyl acetoacetate

The complexation between methyl acetoacetate and certain lanthanides was studied in the mixed ethanol–water solvent (90% ethanol) using electronic absorption spectroscopy. The formation of the cationic 1:2 type complexes was shown at alkalescent medium. Based on the energy of the f–f transitions, the interelectronic repulsion parameters (Slater integrals) were determined by a least-square fit using effective Hamiltonian comprised of electrostatic and spin–orbit components and the nephelauxetic ratio was calculated as a ratio of the second-order Slater integrals. The nephelauxetic ratio was found to be proportional to the relative shortening of the lanthanide–oxygen bond length when the geometry of the complexes was optimized by semiempirical Sparkle/Parametric Method 7.