Spectroscopic Investigation of Anhydrous Solutions of Europium Perchlorate and Europium Nitrate in N , N ‐Dimethylformamide

Anhydrous solutions of Eu(ClO 4 ) 3 and Eu (NO 3 ) 3 0.05m in N , N ‐dimethyl formamide (DMF) are investigated by means of conductometric measurements, vibrational spectroscopy, electronic absorption and emission spectra, and fluorescence lifetime determinations. Eu (ClO 4 ) 3 is completely dissociated and no inner‐sphere interaction takes place between ClO 4 and Eu 3+ ions. The solvated species Eu (DMF)   x 3+has a C 2v ‐symmetry and x is probably equal to 8. A more complicated situation occurs for Eu (NO 3 ) 3 , the solutions of which contain at least three different solvates; the predominant species is [Eu (NO 3 ) 2 (DMF) x−4 ]+ (≈80% of the total Eu‐concentration) and it is more stable than the mononitrato complex [Eu (NO 3 ) (DMF) X−2 ] 2+ ; the neutral complex Eu (NO 3 ) 3 (DMF) x−6 is also present, as can be inferred from a high‐resolution analysis of the 5 D 0 → 7 F 0 emission band. The absence of emission from the excited 5 D 1 ‐level can be rationalized in terms of an efficient non‐radiative deexcitation path through a vibrational mode of the DMF‐molecules bonded to the central metal ion.