Semiempirical Study of the Electronic and Optical Properties of the Er(8-hydroxyquinolinate)₃ Complex

Abstract

We use a simple quantum chemical semiempirical procedure to study the electronic properties of organic-lanthanide complexes, taking as a model system Er(8-hydroxyquinolinate)3. Among the problems inherent to such a study is the fact that the lanthanide ion has never been parametrized in any of the standard semiempirical Hamiltonians. To overcome this difficulty, the lanthanide ion is replaced by a different but somewhat similar parametrized ion, or merely by a point charge. Good agreement with experiment, where available, is obtained, particularly in the former case. In fact, the electronic properties of the complex (apart from the emission properties) are seen to be scarcely affected by the nature of the lanthanide ion itself, but the core interactions between the metal ion and the ligand units play a relevant role, also in the calculation of the excitation energies. In particular, the ordering and separation of both singlet and triplet excited states are affected. The main conclusion is that to describe in detail the mechanism of the energy-transfer process occurring in the complex it is essential to take into account the geometry relaxation effects in the excited states.

New Insights on Near‐Infrared Emitters Based on Er‐quinolinolate Complexes: Synthesis, Characterization, Structural, and Photophysical Properties

“…The large Stokes-shift from the absorption maximum at 370-400 nm arises from the fast geometrical relaxation following excitation of the S 1 state. [38] In crystals with tetrakis molecular arrangement, the emission is shifted to longer wavelength (620 nm) with respect to the tris complex 2′. This finding confirms the redshift observed in the DR spectra, which was ascribed to the peculiar p-p intermolecular interactions of the tetrakis crystal structure.…”

New erbium complexes emitting in infrared region based on oligothiophene and thiophenefluorene carboxylate

“…In order to avoid the coordination of DMSO the emission measurements were carried out immediately after solution preparation. However, these arguments are in favour of the trend of Table 2, which otherwise would be hardly justified by the effective matching between a triplet state of the organic sensitizer and the excited 2 H 11/2 erbium level [18].…”

Photophysical analysis of the organic complex [Eu(C12H8N2)2](NO3)3

“…A more general discussion and comparison between the two approaches can be found in Refs. [11,14]. Here, we use the PCC approach in the quantum chemical study of the [Eu(-C 12 H 8 N 2 ) 2 ](NO 3 ) 3 , since in the description of the electronic properties, it takes into account the electron back-transfer processes [11,12].…”

“…1 is shown a sketch of the complex structure obtained from the geometry optimization performed with the PM3 Hamiltonian [11,12], where the pseudocoordination centre used (X) was the Al 3+ ion. Furthermore, we used the SMLC method (MOPAC2007 James Stewart, Stewart Computational Chemistry, Version 8.211W) as a comparison.…”

“…In the present paper, the applicability of Judd-Ofelt theory to the luminescence of Eu 3+ ion in a widely used luminescent complex is investigated by comparing measured emission spectra and decay rates of excited levels with calculations made by the ligand-field approach. The pseudocoordination centre method (PCC) [11,12] will be used for model the geometry and the electronic properties of the complex.…”