Phase controlled colour tuning of samarium and europium complexes and excellent photostability of their PVA encapsulated materials. Structural elucidation, photophysical parameters and the energy transfer mechanism in the Eu3+ complex by Sparkle/PM3 calculations

Abstract

Luminescent [Sm(acac)₃(pyz)₂] (1) and [Eu(acac)₃(pyz)₂] (2) complexes (acac is the anion of acetylacetone and pyz is pyrazine) have been synthesized and thoroughly characterized by microanalyses, TGA, DTA, IR, ESI-MS⁺ and NMR spectroscopy. The photophysical properties of these complexes have been investigated. The Sparkle/PM3 model was utilized for predicting the ground-state geometry of (2). The Judd–Ofelt intensity parameters, radiative parameters, intramolecular energy transfer rates and quantum efficiency are calculated and discussed. The intramolecular energy transfer rates predict that the major energy transfer (96%) is from the ligand triplet state to the levels ⁵D₁ (74.53%) and ⁵D₀ (21.87%) of the Eu³⁺ ion, in the complex. Complexes (1) and (2) were analysed for colour tuning properties and these show varying colours upon changing phases. This property would possibly allow the use of these complexes as ‘colour indicators’. The photoluminescence and photostability of the thin hybrid films of both complexes (1) and (2) in polyvinyl alcohol (PVA) are investigated and discussed. The hybrid films of (1) and (2) are quite robust due to their higher photostability. An important feature of complex (2) is that the excitation window extends close to the visible range (393 nm). The lasing property of the Eu³⁺ complex in various phases is also presented.