Complexes of the Lighter Lanthanoid Nitrates with 15‐crown‐5 and 18‐crown‐6 ethers: Synthesis and characterization

Complexes of lanthanoid trinitrates Ln(NO3)3 with 15‐crown‐5 ether 1 (Ln = La, Ce, Pr, Nd, Sm, Eu, Gd) and with 18‐crown‐6 ether 2 (Ln = La, Ce, Pr, Nd) having a 1:1 stoichiometry as well as 4:3 complexes with 2 (Ln = La, Ce, Pr, Nd, Sm, Eu, Gd) have been synthesized and characterized. All the isolated complexes are solvent free. At 170–220° the 1:1 complexes of 2 are quantitatively transformed into 4:3 complexes. X‐Ray powder diagrams of the neodymium complexes with 2 indicate that both the 1:1 and 4:3 complexes are genuine compounds. All the 1:1 complexes show a characteristic IR. absorption band at 875–880 cm−1 absent from both the spectra of the free ligands and of the 4:3 complexes. The spectroscopic properties (IR. and electronic spectra, fluorescence lifetimes) of the complexes and the low magnetic moments of the Ln(III) ions in the complexes with Ln = Ce‐Eu are indicative of a strong interaction between the lanthanoid ions and the crown ethers 1 and 2.