Spectroscopic properties of lanthanide based metal-organic framework [Nd(C4H5O6)(C4H4O6)][3H2O]: Theoretical and experimental approaches

The spectroscopic properties of a lanthanide based MOF, [Nd(C4H5O6)(C4H4O6)][3H2O] have been discussed in detail. Semiempirical quantum methods are used to calculate the singlet and triplet excited states, and Uv and IR spectra of the organic part of the MOF. The experimental absorption and luminescent spectra of the MOF are also reported. The experimental absorption spectrum shows the characteristic transition of Nd(III) ion as well as the transitions of the ligands. The experimental line strengths of all the observed transition are calculated. The standard Judd-Ofelt theory is used to calculate intensity parameters, transition probabilities, branching ratios, and radiative lifetimes for [Nd(C4H5O6)(C4H4O6)][3H2O] MOF. The JO parameters are used to calculate various excited state properties. Upon excitation by ultraviolet and visible photons, the complex emits in blue and green regions respectively. The blue emission is ligand (tartrate) based assigned to S1→ S0 transition whereas green emission is metal based assigned to 4G9/2 + 4G7/2 → 4I11/2 transitions. No antenna effect is observed in NTT-MOF. It is because of the large gap between the triplet energy level of the tartrate ligand and the resonance energy level 4F3/2 of the Nd(III) ion.