Thermal decomposition (TD) products of the ionic liquids (ILs) [CnC1Im][BF4] and [CnC1Im][PF6] ([CnC1Im]+ = 1-alkyl-3-methylimidazolium, [BF4]- = tetrafluoroborate, and [PF6]- = hexafluorophosphate) were prepared, ex situ, by bulk heating experiments in a bespoke setup. The respective products, CnC1(C3N2H2)BF3 and CnC1(C3N2H2)PF5 (1-alkyl-3-methylimidazolium-2-trifluoroborate and 1-alkyl-3-methylimidazolium-2-pentafluorophosphate), were then vaporized and analyzed by direct insertion mass spectrometry (DIMS) in order to identify their characteristic MS signals. During IL DIMS experiments we were subsequently able, in situ, to identify and monitor signals due to both IL vaporization and IL thermal decomposition. These decomposition products have not been observed in situ during previous analytical vaporization studies of similar ILs. The ex situ preparation of TD products is therefore perfectly complimentary to in situ thermal stability measurements. Experimental parameters such as sample surface area to volume ratios are consequently very important for ILs that show competitive vaporization and thermal decomposition. We have explained these experimental factors in terms of Langmuir evaporation and Knudsen effusion-like conditions, allowing us to draw together observations from previous studies to make sense of the literature on IL thermal stability. Hence, the design of experimental setups are crucial and previously overlooked experimental factors.

A novel ciprofloxacin–siderophore Trojan Horse antimicrobial was prepared by incorporating key design features of salmochelin, a stealth siderophore that evades mammalian siderocalin capture via its glycosylated catechol units. Assessment of the antimicrobial activity of the conjugate revealed that attachment of the salmochelin mimic resulted in decreased potency, compared to ciprofloxacin, against two Escherichia coli strains, K12 and Nissle 1917, in both iron replete and deplete conditions. This observation could be attributed to a combination of reduced DNA gyrase inhibition, as confirmed by in vitro DNA gyrase assays, and reduced bacterial uptake. Uptake was monitored using radiolabeling with iron-mimetic 67Ga3+, which revealed limited cellular uptake in E. coli K12. In contrast, previously reported staphyloferrin-based conjugates displayed a measurable uptake in analogous 67Ga3+ labeling studies. These results suggest that, in the design of Trojan Horse antimicrobials, the choice of siderophore and the nature and length of the linker remain a significant challenge.

, https://www.york.ac.uk/chemistry/ Dedicated to Prof. Bernt Krebs on the occasion of his 80 th birthday Highlights  Synthesis of a mimic of the tetradentate stealth siderophore salmochelin S1  The periplasmic binding protein of Vibrio cholerae (VctP) binds the mimic strongly  VctP selects for-configured Fe(III) complexes of the mimic  VctP displays a preference for bis(catecholate) over tris(catecholate) siderophores  The role of salmochelin in iron uptake by pathogens merits further investigation

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