Molecular spin qubits are chemical nanoobjects with promising applications that are so far hampered by the rapid loss of quantum information, a process known as decoherence. A strategy to improve this situation involves employing so-called Clock Transitions (CTs), which arise at anticrossings between spin energy levels. At CTs, the spin states are protected from magnetic noise and present an enhanced quantum coherence. Unfortunately, these optimal points are intrinsically hard to control since their transition energy cannot be tuned by an external magnetic field; moreover, their resilience towards geometric distortions has not yet been analyzed. Here we employ a python-based computational tool for the systematic theoretical analysis and chemical optimization of CTs. We compare three relevant case studies with increasingly complex ground states. First, we start with vanadium(IV)-based spin qubits, where the avoided crossings are controlled by hyperfine interaction and find that these S = 1/2 systems are very promising, in particular in the case of vanadyl complexes in an L-band pulsed EPR setup. Second, we proceed with a study of the effect of symmetry distortions in a holmium polyoxotungstate of formula [Ho(W₅O₁₈)₂]⁹⁻ where CTs had already been experimentally demonstrated. Here we determine the relative importance of the different structural distortions that causes the anticrossings. Third, we study the most complicated case, a polyoxopalladate cube [HoPd₁₂(AsPh)₈O₃₂]⁵⁻ which presents an unusually rich ground spin multiplet. This system allows us to find uniquely favorable CTs that could nevertheless be accessible with standard pulsed EPR equipment (X-band or Q-band) after a suitable chemical distortion to break the perfect cubic symmetry. Since anticrossings and CTs constitute a rich source of physical phenomena in very different kinds of quantum systems, the generalization of this study is expected to have impact not only in molecular spin science but also in other related fields such as molecular photophysics and photochemistry.

The postharvest life of most fruit, vegetables and cereals is limited by fungal proliferation. The chemical composition of Mentha piperita, M. spicata and M. suaveolens essential oils (EO), and the antifungal activity against four pathogenic and post-harvest fungi isolated from food, were herein investigated to evaluate their potential as natural food preservatives. The EO were obtained by hydrodistillation of aerial parts leaves, stems and inflorescences (except for peppermint oil, which was purchased in a specialized store) and submitted to GC-MS and GC-FID analysis. Regarding the EO composition, carvone (41.1%) and limonene (14.1%) were the major compounds in M. spicata, menthol (47.0%) and menthone (23.1%), as well as other menthol derivatives (neomenthol -3.6%- and menthofurane -3.7%-) in M. piperita, and piperitone oxide (40.2%) and piperitenone oxide (31.4%) in M. suaveolens. Botryotinia fuckeliana was the most sensitive fungus. The three studied EO inhibited growth by 92–100%. The highest dose of M. suaveolens EO, 400 µg/mL, produced 100% MGI in all the studied fungi, except Fusarium oxysporum with 94.21%. The M. suaveolens EO can be considered to develop a low-risk enviro-friendly botanical biofungicide. GRAPHICAL ABSTRACT

The European Union is promoting regulatory changes to ban fungicides because of the impact their use has on the ecosystem and the adverse effects they can pose for humans. An ecofriendly alternative to these chemicals to fight against fungal species with low toxicity is essential oils and their compounds extracted from aromatic plants. The purpose of this study was to evaluate the in vitro antifungal capacity of the botanical compounds eugenol, carvacrol, thymol, and cinnamaldehyde, and the synergy or antagonism of their mixtures, against Botryotinia fuckeliana and Rhizoctonia solani. Different bioassays were performed at doses of 300, 200, 150, and 100 µg/mL using pure commercial compounds and their combination in potato dextrose agar culture medium. Growth rate and the mycelium growth inhibition parameters were calculated. Phenolic compounds and their combination inhibited the development of species at the different concentrations, with fungicidal or fungistatic activity shown under almost all the tested conditions. When comparing the growth rates of the species in the control plates and treatments, the statistical analysis showed that there were statistically significant differences. The mixture of compounds improved fungicidal activity against the studied species and at a lower concentration of monoterpenes.