Crystal structure and luminescence of Na[Eu(DCTA)·H2O]·4H2O (DCTA = trans-cyclohexane-1,2-diyldinitrilotetraacetate)
Abstract
The crystal structure and the luminescence of the complex Na[Eu(DCTA)·H2O]·4H2O (DCTA = trans-cyclohexane-1,2-diyldinitrilotetraacetate) have been determined. In the structure the EuIII is co-ordinated by two nitrogen atoms and four terminal oxygen atoms of two iminodiacetate groups, and two water oxygen atoms which bridge two adjacent EuIII. When the crystals are excited by UV light they produce a very characteristic luminescence responsible for the 5D0 → 7FJ (J = 0, 1, 2, 3, 4) transitions. The energy-level scheme of the 7FJ states and detailed assignments for the observed luminescence lines have been proposed by phenomenological simulation in the framework of the free-ion and crystal-field Hamiltonians. Although an additional correction to the free-ion model is needed for the barycenter shifting due to the complexation, the set of refined crystal-field parameters under C2v site symmetry satisfactorily reproduces the fine splitting of the luminescence lines in the 5D0 → 7FJ (J = 0, 1, 2, 3, 4) transitions. The behavior of the maximum splitting of the 7F1 manifold is also discussed in terms of a scalar crystal-field strength parameter.