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The significant attention drawn to IrIII-complexes in recent years has boosted the development of new compounds with advantageous photophysical features. However, obtaining IrIII deep-red-emitting complexes with long lived excited state, high colour purity and high quantum yield (Φ) remains a challenging task. To address this issue, this study reports the synthesis and photophysical investigation of three novel zwitterionic complexes, [Ir(C^N)2bqdc] (C^N = ppy, phq, and bzq), with ppy = 2-phenylpyridine (Ir-pb), phq = 2-phenylquinoline (Ir-qb), bzq = benzo[h]quinoline (Ir-bb), and bqdc = potassium 2,2′-biquinoline-4,4′-dicarboxylate. These complexes exhibit high quantum yields and long emission lifetimes with high colour purity in the deep-red region. The structural characterisation carried out by usual spectroscopic measurements supports the proposed structures, while the photophysical study unveiled the high contribution of the 3MLCT state to the hybrid emitter state, as endorsed by theoretical investigations. The desired correspondence between the calculations and the experimental data set affirmed the accuracy of the theoretical analysis, which enabled us to establish a relationship between the ground-to-excited-state geometry distortion and the lifetime through the nonradiative decay (knr). Furthermore, these newly synthesized complexes exhibit quenching in the presence of molecular oxygen. In deoxygenated DMSO solution the knr values halve, increasing the quantum yields (34.0, 10.6, and 26.6%) and the lifetimes (1.13, 1.11, and 1.72 μs), while leading to quite pure deep-red emission – CIE coordinates: (0.67, 0.33), (0.60, 0.40;), (0.65, 0.35) for Ir-pb, Ir-qb, and Ir-bb, respectively. These complexes display considerable potential for a wide range of applications, such as photodynamic therapy, due to their attractive photophysical properties, and are among the deep-red-emitting complexes reported in the literature with longer lifetimes and higher Φ. [ABSTRACT FROM AUTHOR]

Tailoring the opto-structural properties of lanthanide (LnIII)-doped phosphors dispersed in polymeric matrices through classical spectroscopic characterization is challenging due to their composite nature. To overcome this issue, a combination of experimental and theoretical methods can bring additional opportunities to understand the interactions at the phosphor–polymer interface at the molecular level. In this scenario, the SrY2O4:CeIII/IV,EuIII/PMMA (poly(methyl)methacrylate – PMMA) red-emitting film is deeply investigated by combining experimental spectroscopic measurements with an adapted low-cost computational approach. This theoretical methodology is based on (i) structural optimization using a quantum chemical tight-binding model, (ii) obtention of the force constants applying the Hellmann–Feynman theorem, and (iii) calculation of the LnIII photophysical properties using the simple overlap and bond overlap model using the force constants while fitting the effective polarizability. As a result, the theoretical analysis elucidated the phosphor/polymer surface interactions, illustrating the polymer groups (methyl and ester) in the EuIII surroundings, and the structural deformities in the composite moieties. These distortions led to changes in the photophysical parameters by varying the phosphor/PMMA proportion. Therefore, this protocol contributes to a better understanding of the opto-structural features of LnIII-based films, bridging the gap between the experimental results and the strategies to enhance their performance. [ABSTRACT FROM AUTHOR]

UV-to-red downshifting phosphors such as BaAl2O4:Eu3+ find broad range of application in sensors, displays, and in solid-state lighting, yet new synthetic routes to improve their luminescence are envisaged. In this regard, herein, it is introduced two new methods to synthesize this environmentally friendly BaAl2O4:Eu3+, by an adapted sol–gel route and a modified Pechini synthesis. Additionally, a systematic study was carried out about the Eu3+ doping concentration and charge compensation effects on the structural, morphological and spectroscopic features. Both routes enabled high-crystalline and nanostructured phosphors displaying optic bandgap near to 4.4 eV, although the sol–gel route also led to low amounts of BaCO3 spurious phase. Upon UV (250 nm) excitation, all Eu3+-doped samples emit red light displaying high emission color purity, characteristic of the 5D0 → 7F0-4 electronic transitions of Eu3+. The Pechini method led to the highest intrinsic emission quantum yield (85% for the 3%-doped sample). Eu3+ replaces Ba2+ within the BaAl2O4 lattice, but in the sol–gel-derived samples, the dopant may also replace Ba2+ into the BaCO3 spurious phase, confirming that the Pechini route is the best one to optimize the luminescence and structure of the phosphor. [ABSTRACT FROM AUTHOR]

Eu3+–β‐diketonate complexes are used, for example, in solid‐state lighting (SSL) or light‐converting molecular devices. However, their low emission quantum efficiency due to water molecules coordinated to Eu3+ and low photostability are still problems to be addressed. To overcome such challenges, we synthesized Eu3+ tetrakis complexes based on [Q][Eu(tfaa)4] and [Q][Eu(dbm)4] (Q1 = C26H56N+, Q2 = C19H42N+, and Q3 = C17H38N+), replacing the water molecules in the tris stoichiometry. The tetrakis β‐diketonates showed desirable thermal stability for SSL and, under excitation at 390 nm, they displayed the characteristic Eu3+ emission in the red spectral region. The quantum efficiencies of the dbm complexes achieved values as high as 51%, while the tfaa complexes exhibited lower quantum efficiencies (28–33%), but which were superior to those reported for the tris complexes. The structures were evaluated using the Sparkle/PM7 model and comparing the theoretical and the experimental Judd–Ofelt parameters. [Q1][Eu(dbm)4] was used to coat a near‐UV light‐emitting diode (LED), producing a red‐emitting LED prototype that featured the characteristic emission spectrum of [Q1][Eu(dbm)4]. The emission intensity of this prototype decreased only 7% after 30 h, confirming its high photostability, which is a notable result considering Eu3+ complexes, making it a potential candidate for SSL. [ABSTRACT FROM AUTHOR]