Influence of outer-sphere anions in europium tetrahydrofuran-2-carboxylates on the Eu3+ luminescence center, analyzed by methods of X-ray diffraction and optical spectroscopy

Crystal structures for four new Eu and Tb compounds. An increase of the distortions of the Eu coordination polyhedron with the size of the counterion. An extra splitting of the 7FJ states under distortions of the Eu3+ nearest surroundings. A growing influence of the crystal field components of the second and fourth ranks.