Understanding the Photophysical Properties of the Polyoxotitanates Ln2Ti4O6(phen)2(met)10
Rosa Müller1, Alasdair Tew2, Andrew D Bond1
1Yusuf Hamied Department of Chemistry, Cambridge University, Cambridge CB2 1EW, U.K.
Abstract:
Understanding and tuning the luminescent properties of lanthanide(III) ions is of great interest for a range of optical applications, for example photo down-shifters for photovoltaics. In this work a series of isostructural polyoxotitanates (POTs) of general formula Ln2Ti4O6(phen)2(met)10 (Ln2Ti4, Ln = Nd, Sm-Er, Yb, met = methacrylate) was synthesized, where the lanthanide is coordinated to a titanium-oxo core and the antenna ligand 1,10-phenanthroline (phen). The energies of the ligand S1 and T1 states in the Ln2Ti4 series were determined, which, together with the luminescence spectra of the Ln2Ti4 compounds, gave new insights into the intramolecular energy-transfer mechanism and efficiencies between the ligand periphery and the Ln3+ ions. The effect of the rigidity of the Ti4O6-core on the coordination environment of a lanthanide was quantified for the first time using lifetime measurements, which shows a significant increase of Δτ = 1.1 ms for Eu2Ti4 compared to the reference Eu2(phen)2(met)6 (Eu2), in which no metal-oxo core is present. This key finding illustrates the advantage in designing lanthanide-based lumiphores containing rigid metal-oxide cores.
Related Concept Videos
02:27Predicting Molecular Geometry
02:46Crystal Field Theory - Tetrahedral and Square Planar Complexes
Crystal field theory (CFT) is applicable to molecules in geometries other than octahedral. In octahedral complexes, the lobes of the dx2−y2 and dz2 orbitals point directly at the ligands. For tetrahedral complexes, the d orbitals remain in place, but with only four ligands located between the axes. None of the orbitals points directly at the tetrahedral ligands. However, the dx2−y2 and dz2 orbitals (along the Cartesian axes) overlap with the ligands less than the dxy,...
02:42Valence Bond Theory
01:14Photoluminescence: Applications
01:26Thermal and Photochemical Electrocyclic Reactions: Overview
02:58Crystal Field Theory - Octahedral Complexes
To explain the observed behavior of transition metal complexes (such as colors), a model involving electrostatic interactions between the electrons from the ligands and the electrons in the unhybridized d orbitals of the central metal atom has been developed. This electrostatic model is crystal field theory (CFT). It helps to understand, interpret, and predict the colors, magnetic behavior, and some structures of coordination compounds of transition metals.
CFT focuses on...