Rare Earth Complexes with Imine Type Ligands

1 Rare Earth Complexes with Imine Type Ligands 

By using the template directed cyclization between 2,6-pyridinedicarbaldehyde and ethyl-diamine in the presence of rare earth nitrate salts, a series of corresponding complexes 

According to the structure determination results, it is presumed that the reversion from the carbinolamine form to the tetraimine one exists probably because of the optimal cation-cavity criteria and the fact that the samarium ion can be accommodated by either form of the two macrocycles. Carbinolamine, acting as the intermediate of the tetraimine Schiff base 27, is the kinetically favored product. In contrast, the latter species is the thermodynamically favored product. On dissolution and recrystallization in water, a higher temperature is reached than in the original reaction in alcohol, which facilitates completion of the reaction. Furthermore, 

Associated with the ramifying applications of rare earth elements, a series of rare earth complexes with macroacyclic imine type Schiff bases have been prepared, among which ligands 28 and 29 are two representative compounds. 

2 Rare Earth Complexes with HaSalen (30) Type Ligands 

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