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ESI IM-MS, additional IM mass spectra, energy-resolved CID experiments, and breakdown representations, 1H and 13C{1H} NMR spectra of compound [(NHC4)(p-cym)RuCl2], and atomic coordinates of [(NHC2)(p-cym)RuCl]+ and [(NHC2 - H)(p-cym)Ru]+.

Plant pathogens are major threats for optimal crop yield and preservation of the harvest. Although plant immune responses are well characterised in isolation, pathogen infections frequently occur in combination with other stress conditions. Importantly, the outcome of plant-pathogen interactions under combinatorial stress is unpredictable as the operating molecular mechanisms difer from those triggered under each individual stressor. Certain abiotic stressors ultimately confer resilience to subsequent pathogen infection, i.e. cross-tolerance, however the network of molecular events involved remains undeciphered. Recent studies suggested that metabolites could retain “stress memory” and modulate combinatorial stress responses, but their potential role in cross-tolerance has been barely investigated. My Marie Skłodowska-Curie project is aimed at identifying changing metabolites after abiotic stress periods that contribute to enhance plant tolerance to pathogens. To this end, comprehensive time-courses for sequential stress were defned to cultivate Arabidopsis plants under nine frequent adverse environmental conditions – namely fuctuations in light intensity, humidity, water availability and temperature - followed by a recovery phase and an eventual pathogen challenge. Metabolome changes of plants were profled on daily basis using untargeted LC-MS and systemically analysed by means of conditional networks. Network analysis and identifcation of signifcantly altered metabolites were used to retrieve central features to cope with abiotic stressors. Complementary, transcriptome analyses were also conducted. Our frst results are consistent with the idea that metabolome changes in response to abiotic stressors are persistent overtime, whereas transcriptome changes are reversible. Further investigation on metabolite composition of plants after abiotic stressors uncovered fuctuations in central groups of compounds. The potential relevance of such candidates to modulate immune

The activation of C–H bonds in a selective manner still constitutes a major challenge from a synthetic point of view; thus, it remains an active area of fundamental and applied research. Herein, we introduce ion mobility spectrometry mass spectrometry-based (IM-MS) approaches to uncover site-selective C–H bond activation in a series of metal complexes of general formula [(NHC)LMCl]+ (NHC = N-heterocyclic carbene; L = pentamethylcyclopentadiene (Cp*) or p-cymene; M = Pd, Ru, and Ir). The C–H bond activation at the N-bound groups of the NHC ligand is promoted upon collision induced dissociation (CID). The identification of the resulting [(NHC-H)LM]+ isomers relies on the distinctive topology that such cyclometalated isomers adopt upon site-selective C–H bond activation. Such topological differences can be reliably evidenced as different mobility peaks in their respective CID-IM mass spectra. Alternative isomers are also identified via dehydrogenation at the Cp*/p-cymene (L) ligands to afford [(NHC)(L-H)M]+. The fragmentation of the ion mobility-resolved peaks is also investigated by CID-IM-CID. It enables the assignment of mobility peaks to the specific isomers formed from C(sp2)–H or C(sp3)–H bond activation and distinguishes them from the Cp*/p-cymene (L) dehydrogenation isomers. The conformational change of the NHC ligands upon C–H bond activation, concomitant with cyclometalation, is also discussed on the basis of the estimated collision cross section (CCS). A unique conformation change of the pyrene-tagged NHC members is identified that involves the reorientation of the NHC ring accompanied by a folding of the pyrene moiety.

Complexation of the glutamic-tyrosine-glutamic tripeptide (EYE) with a series of pseudopeptidic cages has been thoroughly investigated using different analytical techniques. The stoichiometry and affinities of the supramolecular host : guest complexes both in aqueous solution and in the gas-phase were obtained from a suitable combination of fluorescence spectroscopy, NMR, and mass spectrometry (MS) methods. The cages bearing basic groups (lysine, ornitine and histidine) display the tightest EYE binding in aqueous media following the order CyHis > CyLys > CyOrn, thus suggesting that Tyr side chain encapsulation is additionally modulated by the identity of the cage side chains and their ability to be engaged in polar interactions with the EYE peptide. Similarly, binding affinities estimated by MS methods clearly point towards a reduced affinity for the Cy cages with acidic pendant groups and a higher affinity of the CyHis cage over CyLys and CyOrn. Ion mobility spectrometry (IMS)-MS, assisted by molecular modelling, has been used to uncover the structural and conformational characteristics of the pseudopeptidic hosts and their supramolecular adducts with the EYE peptide. The cages display a collisional cross-section increase upon EYE inclusion that is associated with the expansion of the binding pocket of the cage cavity, thus constituting a unique example of conformational pseudopeptidic host adaptation to accommodate the inclusion of the guest.

[EN] We describe an unprecedented catalytic dehydrogenation of glucose by homogeneous catalysts. Iridium(iii) complexes containing the fragment [Cp*Ir(NHC)](2+) (NHC = N-heterocyclic carbene ligand) are shown to be very active and highly selective catalysts for the dehydrogenation of glucose to gluconic acid and molecular hydrogen. Glucose is converted to gluconic acid at a catalyst loading of 2 mol%, at reflux in water, without additives and with a selectivity of over 95%. Experimental evidence obtained by H-1 NMR spectroscopy and mass spectrometry (ESI/MS) reveals the formation of iridium coordinated to glucose and gluconic acid species. A plausible mechanism is proposed, based on the experimental evidence and supported by DFT calculations.

We describe an unprecedented catalytic dehydrogenation of glucose by homogeneous catalysts. Iridium(III) complexes containing the fragment [Cp*Ir(NHC)]2+ (NHC = N-heterocyclic carbene ligand) are shown to be very active and highly selective catalysts for the dehydrogenation of glucose to gluconic acid and molecular hydrogen. Glucose is converted to gluconic acid at a catalyst loading of 2 mol%, at reflux in water, without additives and with a selectivity of over 95%. Experimental evidence obtained by 1H NMR spectroscopy and mass spectrometry (ESI/MS) reveals the formation of iridium coordinated to glucose and gluconic acid species. A plausible mechanism is proposed, based on the experimental evidence and supported by DFT calculations.