Efficient red emission from poly(vinyl butyral) films doped with a novel europium complex based on a terpyridyl ancillary ligand: synthesis, structural elucidation by Sparkle/RM1 calculation, and photophysical properties

Abstract

A novel efficient antenna Eu-complex Eu(TTA)₂Tpy-OCH₃·2H₂O, based on the terpyridyl derivative 4′-(4-methoxyphenyl)-2,2′:6′,2′′-terpyridine(Tpy-OCH₃) as the ancillary ligand, has been synthesized, structurally characterized, and its photophysical properties have been examined. Upon irradiation at the ligand-centered band in the range of 200–450 nm, the new Eu-complex displays bright red luminescence, irrespective of the medium. A Sparkle/RM1 calculation was utilized for predicting the ground-state geometries of this complex. Theoretical Judd–Ofelt and photoluminescence parameters, including quantum efficiency, as predicted from this model are in good agreement with the experimental values, proving the efficiency of this theoretical approach as implemented in the LUMPAC software (http://lumpac.pro.br). The kinetic scheme for modelling energy transfer processes shows that the main donor state is the ligand triplet state and that energy transfer occurs on both the ⁵D₁ (20.7%) and ⁵D₀ (79.3%) levels. As an integral part of this work, the synthesis, characterization, and luminescence properties of poly(vinyl butyral) (PVB) polymer films doped with the Eu-complex are also reported. After the Eu-complex Eu(TTA)₂Tpy-OCH₃·2H₂O was doped into the PVB matrix to form the films, the PVB polymer matrix, acting as a co-sensitizer for Eu³⁺ ions, enhances the luminescence lifetimes and quantum efficiencies of the complex in comparison with its precursor complex. The new luminescent Eu/PVB films therefore show considerable promise for polymer light-emitting diode and active polymer optical fiber applications. To the best of our knowledge, this is the first report which studies in detail the photophysical properties of doped europium fluorescent films based on PVB as the polymer matrix.