The pincer ligand H3L3N, bis(2‐amino‐3,5‐di‐tert‐butylphenyl)amine}, was chelated to NiII, PdII, and PtII. Square‐planar complexes of stoichiometry 2:1 (ligand/metal) formed, wherein the ligand coordinates in a bidentate fashion. By X‐ray diffraction we established that each ligand molecule coordinates in its diiminosemiquinone radical form in the neutral NiII, PdII, and PtII complexes (1, 2, and 3, respectively). The resulting systems are singlet diradical species, with a predicted J value in the range –1062 to –1764 cm–1. These diradicals display an intense LLCT transition involving the diiminosemiquinone moieties: 860, 852, and 760 nm for 1, 2, and 3, respectively. Complex 1, 2, and 3 exhibit reversible oxidation waves in their CV curves. Cations 1+, 2+, and 3+ are (S = 1/2) systems with g values close to 2. The increase in the intensity of the resonance in the order 1+ < 2+, 3+ is consistent with the easy comproportionation of 1+. X‐ray diffraction analysis discloses that 3+ is a mixed‐valent radical mononuclear complex. An intense IVCT is observed at low energy (1536, 1656, and 1256 nm for 1+, 2+, and 3+, respectively), confirming that this classification applies to all the cations. Dications 12+, 22+, and 32+ are closed‐shell bis(diiminobenzoquinone) species. The crystal structure of 32+ shows that this complex exhibits the shortest mean C–N bond lengths within the series.

Wine oxidation and ageing involve many complex chemical pathways and reaction mechanisms. The purpose of this study is to set up new and reproducible accelerated red wine ageing tests and identify chemical oxidation or ageing molecular markers. Three accelerated and reproducible ageing tests were developed: a heat test (60 °C); an enzymatic test (laccase test; a chemical test (hydrogen peroxide test). Depending on the test, oxygen consumption was significantly different. For a young wine (2018), the oxygen consumption rate moved from 2.40 ppm·h−1 for the heat test to 3.33 ppm·h−1 for the enzymatic test and 2.86 ppm·h−1 for the chemical test. Once applied to two other vintages (2010 and 2014) from the same winery, the tests revealed different comportments corresponding to wine natural evolution. High resolution UPLC-MS was performed on forced ageing samples and compared to naturally aged red wines. Specific oxidation or ageing ion markers were found with significant differences between tests, revealing the specificity of each test and different possible molecular pathways involved. The hydrogen peroxide test seems to be closer to natural oxidation with an important decrease in absorbance at 520 nm and similar molecular ion variations for [M+H]+ = 291, 331, 347, 493, 535, 581, 639 Da.

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