Dalton Transactions

Osawa, Masahisa

doi: 10.1039/d4dt03047hpmid: 39652361

White organic light-emitting diodes (WOLEDs) are promising light-emitting devices. A typical method for generating white light is to superimpose the three primary colours of light – red, green, and blue – or the two colours of light – blue and yellow. These colours are generated from each emitting material doped into the emission layers of the device. To achieve high-quality white light, the emission colours and intensities should be properly adjusted in the device. Apart from the superimposition of colours of light, white light can also be generated by doping with a single molecule that emits visible light in the wavelength range of 380–780 nm. In this review, we have listed some white-light-emitting complexes that are expected to drastically simplify the device fabrication process for OLEDs. We have shed light on these metal complexes and outlined the current status of their synthesis and device applications, looking toward promising future prospects.

Rudolf, Richard; Todorovski, Andrej; Schubert, Hartmut; Sarkar, Biprajit

doi: 10.1039/d4dt02317jpmid: 39831464

In this work, we show two synthetic routes to substitute the Nexo position of mesoionic imines (MIIs). By Buchwald–Hartwig amination, 5-amino-1,2,3-triazoles can be arylated at the said position, showing the versatility of amino-triazoles as building blocks for MIIs. The reaction of MIIs with electrophiles (MeI, fluoro-arenes) highlights the nucleophilic nature of MIIs as even at room temperature aromatic C–F bonds can be activated with MIIs. By combining experimental methods such as Tolman/Huynh-electronic-parameter and crystallographic interpretations with theoretical calculations, we establish that MIIs expand the nucleophilicity scale of N-donors. Contrary to the flanking substituents on the triazole scaffold, the Nexo substituent heavily influences the donating ability of MIIs: electron-withdrawing substituents will dramatically decrease the donor strength of the MII ligand. We have now established ways to functionalise not only the triazole backbone but also the Nexo position. More importantly, we show here how the substitution pattern influences the electronic structure of MIIs. Such electronic tunability should make MIIs suitable for use in various fields of chemistry.

Wang, Jihua; Li, Hui; Gong, Lige; Dong, Limin; Gu, Yunhao; Wang, Meijia; Yang, BingHe

doi: 10.1039/d4dt02612hpmid: 39846244

In this work, we successfully prepared four POM-based organic–inorganic hybrids, namely, [(C5H6N)2(C4H5N2)][PMo12O40] (1), [(C5H6N)3(C5H5N)][PMo12O40] (2), [(C3H6N8)3][PMo12O40]·4H2O (3), and [(C2H5N4)3][PMo12O40] (4) (where C5H6N = pyridine, C4H5N2 = pyrazine, C3H6N8 = 2,7-diamino-1,3,4,6,8,9-hexaazaspiro[4.4] nonane, and C2H5N4 = 3-amino-1,2,4-triazole), using a hydrothermal method. Compounds 1 and 2 exhibited a lamellar three-dimensional structure. Compared to compound 1, compound 2 contained only one ligand, pyridine, which formed a pyridine polymer tubular structure that was further connected to a [PMo12O40]3− anion, creating a pyridine-PMo12-pyridine stacking-like structure. Compounds 3 and 4 showed a stereostructure, where organic ligands were wrapped around polyacid spheres. Unlike compound 3, compound 4 maintained a similar three-dimensional structure but had a hexagonal astral ligand configuration. However, ligands formed hexagonal boxes that were smaller than those in compound 3, with shorter distances between the ligands. The overpotential values for compound 2 were 143 mV (HER) and 136 mV (OER) at 10 mA cm−2, which were significantly lower than those of the other compounds, the H3[PMo12O40] precursor, and the organic ligands. Given the relatively outstanding HER/OER catalytic properties of compound 2, a dual-electrode water-splitting device was assembled. The compound 2/CC∥compound 2/NF system achieved a low cell voltage of 1.48 V at 10 mA cm−2, which was significantly lower than that of the commercial Pt/C/CC∥RuO2/NF setup (1.5 V). In addition, compound 2/CC∥compound 2/NF exhibited rapid response capabilities and showed no significant increase in voltage after 6000 s of operation.