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Cu(I) carbene complexes are common emitters of current emerging interest for next-generation OLED technology based on their encountered thermally activated delayed fluorescence (TADF) properties. However, general molecular design principles for successfully observable TADF properties of such complexes usually rely on π-acidic N-heterocyclic carbene (NHC) ligands, while Cu(I) carbene complexes with purely σ-donating NHC ligands are still scarce. Based on a simple synthetic approach reported by us earlier that offers large-scale access to this class of Cu(I) carbene complexes, we aim to elucidate design principles to enhance their TADF properties. In this work, we combined temperature-dependent time-resolved luminescence spectroscopy on different time scales (ns, μs, ms) with high-level DFT/MRCI calculations on a number of representative Cu(I) NHC complexes with the anionic carbene An6DAC and additional pyridine-derived ligands. Good agreement between experiment and theory related to the electronic nature of the optical transitions, the energy levels of the electronic states and the kinetics of interconversion controlled by the respective energy gaps was found. We conclude that both the electron-rich or electron-poor nature of the pyridine ligands and the coordination geometry (linear, trigonal planar) play a significant role in the outcome of the optical properties of these complexes. While electron-rich pyridine moieties induce decoupled prompt fluorescence and phosphorescence with connected low photoluminescence quantum yields, electron-poor pyridine moieties enhance a "push–pull" effect mediated by Cu(I) that favours TADF properties so that the luminescence intensity is increased by 1–2 orders of magnitude if the complex is trigonal. In the trigonal formyl pyridine complex, theory predicts high MLCT contributions to the electronic wavefunctions, so that the T1 states should exhibit large spin–orbit coupling matrix elements (SOCMEs) with several excited singlet states. Indeed, in temperature dependent luminescence measurements, the electronic states behave as an intimately coupled ensemble. At 270 K, 56% of its luminescence can be attributed to TADF. However, while the luminescence of the trigonal complexes is brighter, their chemical Cu–pyridine bond is more labile. Overall, this study provides a detailed overview of the possibilities of targeted molecular design to selectively address desirable optical properties in organometallic compounds for potential applications in lighting. [ABSTRACT FROM AUTHOR]

AlB4O6N, Al0.97Cr0.03B4O6N, and Al0.83Cr0.17B4O6N are the first representatives of the recently established structure‐family of oxonitridoborates containing Al3+. These compounds are isotypic to CrB4O6N and are synthesized in a multi‐anvil press under high‐pressure/high‐temperature conditions of 7.0 GPa/1350 °C. Structural refinement by single‐crystal X‐ray diffraction shows that they crystallize in the space group P63mc (no. 186) with two formula units per cell. Detailed characterization including high‐temperature X‐ray powder diffraction (HT‐XRD), electron probe microanalysis (EPMA), measurements of second harmonic generation (SHG), hardness, photoluminescence properties, vibrational spectroscopy, and band structure calculations reveal intriguing physicochemical properties that strongly resemble the famous material ruby. [ABSTRACT FROM AUTHOR]

Two new isostructural semiconducting metal‐phosphonate frameworks are reported. Co2[1,4‐NDPA] and Zn2[1,4‐NDPA] (1,4‐NDPA4− is 1,4‐naphthalenediphosphonate) have optical bandgaps of 1.7 eV and 2.5 eV, respectively. The electrocatalyst derived from Co2[1,4‐NPDA] as a precatalyst generated a low overpotential of 374 mV in the oxygen evolution reaction (OER) with a Tafel slope of 43 mV dec−1 at a current density of 10 mA cm−2 in alkaline electrolyte (1 mol L−1 KOH), which is indicative of remarkably superior reaction kinetics. Benchmarking of the OER of Co2[1,4‐NPDA] material as a precatalyst coupled with nickel foam (NF) showed exceptional long‐term stability at a current density of 50 mA cm−2 for water splitting compared to the state‐of‐the‐art Pt/C/RuO2@NF after 30 h in 1 mol L−1 KOH. In order to further understand the OER mechanism, the transformation of Co2[1,4‐NPDA] into its electrocatalytically active species was investigated. [ABSTRACT FROM AUTHOR]

Correction for 'How to tune luminescent Cu(I) complexes with strong donor carbenes towards TADF?' by Jasper Guhl et al., J. Mater. Chem. C, 2024, https://doi.org/10.1039/D4TC01487A. [ABSTRACT FROM AUTHOR]

In an article published in Advanced Functional Materials, Markus Suta, Hubert Huppertz, and their colleagues introduce a new oxonitridoborate compound called AlB4O6N:Cr3+. This compound exhibits a highly efficient red line emission and has the potential to serve as an alternative luminescent pressure sensor. The researchers suggest that AlB4O6N:Cr3+ could offer more precise pressure calibration in diamond anvil cells compared to the current standard, ruby. The authors express gratitude to Abraham Siedler and Marie-Theres Wildauer for their contributions to the design of the inside back cover. [Extracted from the article]

The new microporous metal organic framework [La2(H2O)5(H2TPPE)]·3H2O (CAU‐54), is obtained in a hydrothermal reaction of the linker 1,1,2,2‐tetrakis(4′‐phosphonophenyl)ethylene (H8TPPE) and La3+ ions. The extensive characterization including temperature‐dependent crystal structures and spectroscopic properties allowed to understand the unique, multi‐responsive material properties. CAU‐54 exhibits rarely observed reversible photochromism as well as turn‐on photoluminescence by various external chemical or physical stimuli including change of pressure, solvent exchange, and temperature variation. These properties can be unequivocally assigned to the presence of tetraphenylethylene (TPE) moieties of the linker molecules within the MOF, i.e., the ordered spatial arrangement of the linker molecules, the presence of accessible pores as well as the coordination flexibility of the phosphonate groups and the rotational freedom of the linker. By temperature‐dependent steady‐state and time‐resolved luminescence studies, it is shown that this compound exhibits a) blue fluorescence that becomes effectively quenched at room temperature, b) green efficient luminescence with thermal stability up to 400 K, and c) red phosphorescence correlated to the observed photochromism. In addition, CAU‐54 shows unusual thermal expansion properties as shown by temperature‐dependent powder X‐ray diffraction measurements with identified transition points that correlate with the observed temperature‐dependent changes in the photoluminescence. [ABSTRACT FROM AUTHOR]

Two new isostructural semiconducting metal-phosphonate frameworks are reported. Co 2 [1,4-NDPA] and Zn 2 [1,4-NDPA] (1,4-NDPA 4- is 1,4-naphthalenediphosphonate) have optical bandgaps of 1.7 eV and 2.5 eV, respectively. The electrocatalyst derived from Co 2 [1,4-NPDA] as a precatalyst generated a low overpotential of 374 mV in the oxygen evolution reaction (OER) with a Tafel slope of 43 mV dec -1 at a current density of 10 mA cm -2 in alkaline electrolyte (1 mol L -1 KOH), which is indicative of remarkably superior reaction kinetics. Benchmarking of the OER of Co 2 [1,4-NPDA] material as a precatalyst coupled with nickel foam (NF) showed exceptional long-term stability at a current density of 50 mA cm -2 for water splitting compared to the state-of-the-art Pt/C/RuO 2 @NF after 30 h in 1 mol L -1 KOH. In order to further understand the OER mechanism, the transformation of Co 2 [1,4-NPDA] into its electrocatalytically active species was investigated., (© 2023 The Authors. Chemistry - A European Journal published by Wiley-VCH GmbH.)