Chelation of Ce-III and Pr-III by N,N '-Bis(pyridoxylideneiminato)ethylene, a Schiff Base Ligand Derived from Vitamin B6: Synthesis, Structural Features and TGA Evaluations of [M(Hpyr(2)en)(pyr(2)en)]center dot nH(2)O (M = Ce-III, n=2; Pr-III, n=8)

摘要

The neutral Schiff base N,N'-bis(pyridoxylideneiminato)ethylene (H(2)pyr(2)en) reacts with CeCl3 center dot 4H(2)O and PrCl3 center dot 4H(2)O to give [Ce(Hpyr(2)en)(pyr(2)en)]center dot 2H(2)O. (1) and [Pr(Hpyr(2)en)(pyr(2)en)]center dot 8H(2)O (2). In the two bimolecular chelate systems, the endo hydroxyl groups of the rings undergo deprotonation by transferring one proton to the pyridinic nitrogen atoms. This confirms the ability of the pyridoxal containing ligand H(2)pyr(2)en to form stable heavy metal chelates with unusual coordination polyhedra. Complexes 1 and 2 show coordination number 8, and represent a distorted quadratic antiprismatic arrangement. To date no other references have been made to the complexation of Ce and Pr by any vitamin B6 derivative. The synthesis and the structure elucidation of 1 and 2 represent a contribution to the research on prevention and therapy of damages caused by heavy elements.