Knowledge Bank

While liquid solution complexes between many cations and crown ethers have been reported, very few studies have been made which involve rare earth ions. In this paper we will present spectral data fro trivalent neodymium ($Nd+3$) and trivalent europium ($Eu+3$) complexes with the crown ethers 15-crown-5 and benzo-15-crown-5. In contrast to previous reports, we find significant effects of these pentagonally symmetrical crown ethers on the electric dipole forbidden f to f transitions of the rare earth ions. At least one transition which is both electric quadrupole and magnetic dipole forbidden; the $\mathrm{<mrow\; data-mjx-texclass="ORD">5</mrow>}Da\leftarrow 7F0$, transition in $Eu+3$ is enhanced, and many transition probabilities in $Nd+3$ are altered. Crystal field effects are also observed on several transitions in both earth ions. The fluorescence both of $Eu+3$ and benzene in the benzo 15-crown-5 are strongly quenched in the complex. A new, braod absorption band which is characteristic of the complex, is found for $Eu+3$ -benzo-crown-5.