Solid Eu(III) complexes studied by positron annihilation, optical and Mössbauer spectroscopies: Insights on the positronium formation mechanism

Evidence of the participation of electronic excited states in the mechanism of positronium formation in substitutional Tb1−xEux(dpm)3 solid solutions studied by optical and positron annihilation spectroscopies

“…6(a). These results show that this system behaves similarly to those involving the same dpm ligand and acetylacetonate-acac ligand previously studied: [13][14][15]18,38,39 Ps formation is completely inhibited as a function of guest concentration. The experimental data obey the Stern-Volmer expression satisfactorily, I o 3 /I 3 = 1 + kx, where I 3 and I o 3 stand for the o-Ps formation relative intensities of the solid solutions and Tb(dpm) 3 matrix compound, respectively, x represents the solid solution composition in terms of fraction, and k is the total inhibition constant.…”

“…38 However, the increasing value of the full width at half maximum of the annihilation radiation ray, measured at 295 K by Doppler broadening spectroscopy with increasing Eu complex concentration is inconsistent with this hypothesis. 39 Note that none of the five hypotheses raised above interfere with the light excitation and luminescence of the Eu(dpm) 3 complex observed at 77 K. This means that not all luminescent complexes needs to necessarily form Ps, as implicitly considered in our previous publication. 22 The complete solution of the proposed kinetic mechanism is only possible by a numerical solution of a system of four non linear equations for the four unknown probabilities of formation:…”

Thermosensitive Seven‐Coordinate TbIII Complexes with LLCT Transitions

“…Seven‐coordinate [Tb(tmh) 3 (PEB)] (Tb‐PEB) and [Tb 2 (tmh) 6 ( m ‐BPEB)] (Tb‐BPEB) were synthesized by the complexation of phosphine oxide ligands (PEB and m ‐BPEB) with precursor [Tb 2 (tmh) 6 ] in methanol for 12 h (see Supporting Information, Scheme S1). [Tb(tmh) 3 (TPPO)] (Tb‐TPPO) was also synthesized by the same method for comparison with Tb III complexes using ethynyl groups.…”

“…Preparation of [Tb(tmh) 3 (TPPO)] (Tb‐TPPO), [Tb(tmh) 3 (PEB)] (Tb‐PEB), and [Tb 2 (tmh) 6 ( m ‐BPEB)] (Tb‐BPEB): The precursor complex, [Tb 2 (tmh) 6 ], was synthesized as described in previous report . [Tb 2 (tmh) 6 ] (0.87 g, 0.6 mmol), and phosphine oxide ligands (TPPO: 0.33 g, 1.2 mmol; PEB: 0.36 g, 1.2 mmol; m ‐BPEB: 0.32 g, 0.6 mmol) were dissolved in methanol.…”

Evidence of the Participation of Electronic Excited States in the Mechanism of Positronium Formation in Substitutional Tb_1-<i>x</i>Eu_<i>x</i>(dpm)₃ Solid Solutions Studied by Optical and Positron Annihilation Spectroscopies

“…38 However, the increasing value of the full width at half maximum of the annihilation radiation ray, measured at 295 K by Doppler broadening spectroscopy with increasing Eu complex concentration is inconsistent with this hypothesis. 39 Note that none of the five hypotheses raised above interfere with the light excitation and luminescence of the Eu(dpm) 3 complex observed at 77 K. This means that not all luminescent complexes needs to necessarily form Ps, as implicitly considered in our previous publication. …”