POLARIZED OPTICAL ABSORPTION AND EMISSION SPECTRA AND THE ELECTRONIC ENERGY-LEVEL STRUCTURE OF TB(DPA)(3)(3-) COMPLEXES IN NA-3[YB0.95TB0.05(DPA)(3)]CENTER-DOT-NACLO4-CENTER-DOT-10H(2)O

摘要

Polarized optical absorption and emission measurements are used to locate and assign 60 crystal-field energy levels split out of the 4f(8) electronic configuration of Tb3+ in single crystals of Na-3[Yb0.95Tb0.05(dpa)(3)]. NaClO4 . 10H(2)O (where dpa drop dipicolinate dianion drop 2,6-pyridinedicarboxylate). In these crystals, each Tb3+ ion is coordinated to three dipicolinate (dpa) ligands, and the tris-terdentate Tb(dpa)(3)(3-) chelate structures have trigonal-dihedral (D-3) symmetry. The combined optical absorption and emission measurements provide access to the energy-level structures of the 17 lowest-energy 4f(8)[SL]J multiplet manifolds of Tb3+, and all of these multiplet manifolds are represented among the 60 crystal-field levels that are characterized with respect to both location (energy) and symmetry properties. The energy-level data obtained from experiment are analyzed in terms of a model Hamiltonian that includes consideration of both isotropic and nonisotropic 4f-electron/crystal-field interactions. A parametrized form of this Hamiltonian is used to perform parametric fits of calculated-to-experimental energy-level data, and the results obtained from these data fits show a root mean square (rms) deviation of 10 cm(-1) between calculated and observed energies. The Hamiltonian parameters evaluated from the energy-level analyses provide information about both the anisotropies and the overall strength of the 4f-electron/crystal-field interactions that contribute to the energy-level structure of Tb(dpa)(3)(3-) complexes. In addition to energy-level data, the polarized emission measurements performed in this study yield information about the relative electric- and magnetic-dipole mechanistic contributions to emission line intensities in the F-7(J)(J=0-6)<--D-5(3)(4) transition regions of Tb(dpa)(3)(3-), and this information is used to help rationalize the observed chiroptical luminescence properties of enantiomerically resolved Tb(dpa)(3)(3-) complexes in solution. [References: 25]