Sesquiterpene lactones (SL) have been reported with various biological effects.Among the described SL skeletons, hirsutinolide and glaucolide have not been extensively studied by mass spectrometry (MS), especially how to distinguish them in organic matrices. Thus, this paper reports (1) a strategy of their differentiation based on MS behavior during the ionization and (2) a proposal of the fragmentation pattern for both SL-subtypes. ESI(+)-HRMS data of four isolated SL (hirsutinolides 1 and 3; glaucolides 2 and 4) were recorded by direct and UPLC water-sample combined injections. These analyses revealed that hirsutinolides and glaucolides formed [M+Na] + ion during the operation of the direct MS injection, and ([M+Na] + and [M+H-H 2 O] + ) and[M+H] + ions were respectively observed for hirsutinolides and glaucolides during the operation of combined UPLC water and sample MS injection. Computational simulations showed that the complex hirsutinolide (1)-Na + formed with a lower preparation energy compared with the complex glaucolide (2)-Na + . However, despite their different behavior during the ionization process, ESI(+)-HRMS/MS analyses of 1-4 gave similar fragmentation patterns at m/z 277, 259, 241, and 231 that can be used as diagnostic ions for both skeletons. Moreover, the differentiation strategy based on the nature of the complex SL-adducts and their MS/MS fragmentation pattern were successfully applied for the chemical characterization of the extract from Vernonanthura tweedieana using UPLC-ESI-HRMS/MS. Among the characterized metabolites, SL with hirsutinolide and glaucolide skeletons showed the aforementioned diagnostic fragments and an ionization behavior that was similar to those observed during the water-sample combined injection. KEYWORDShirsutinolides and glaucolides, ESI-QTofMS n analysis, ESI adducts interaction, fragmentation mechanism, computational study Correction added on 22 May 2020, after online publication: the data in Tables 1, 2, 3, 5 and the citation numbering throughout the article were corrected post publication. /journal/jms 915 916 DA SILVA ET AL. Journal of MASS SPECTROMETRY RESULTS AND DISCUSSION ESI-HRMS/MS analysis of pure compoundsAs depicted in Table 1, ESI(+)-HRMS analysis by direct injection indicated that the SL 1-4 afforded as base peak the ions at m/z 445.1473 (1), m/z 487.1570 (2), m/z 419.1327 (3), and m/z 461.1422 (4), corresponding to [M+Na] + and suggesting a strong affinity for Na + . Moreover, protonated ions [M+H] + were not detected for the hirsutinolide skeletons ( compounds 1 and 3), whereas [M+H] + ions were observed in extremely low abundance for glaucolides 2 (m/z 465.1740, 15%) and 4 (m/z 439.1620, 2%).DA SILVA ET AL.

Cation−π interactions in a set of ruthenophanes [Ru(η 6 -C n H n )(NH 3 ) 3 ] 2+ (n = 16, 18, 20, 22, and 24) (1−9), containing multibridged cyclophanes as ligands, including [2.2]paracyclophane and its multibridged analogs, [2 n ]cyclophanes, are analyzed in terms of SAPT0/TZP and Su−Li EDA analyses. The calculations reveal that the coordination with cation [Ru(NH 3 ) 3 ] 2+ affects the structures of [2 n ]ciclophane ligands, mainly the planarity of the coordinating ring. The EDA results show that the gradual addition of ethano bridges in [2 n ]cyclophanes tends to strengthen the cation−π interaction between [Ru(NH 3 ) 3 ] 2+ and [2 n ]cyclophane. Both Su−Li EDA and SAPT0 are in line, suggesting that the cation−π interactions present a predominant covalent character in complexes 1−9.

The adsorption of linear, monobranched and dibranched saturated hydrocarbons in the gasoline range has been studied on pure silica STW zeolite (Si-STW) by using pentane, hexane, and heptane isomers as model adsorbates. Experimental single-component adsorption isotherms and kinetic measurements together with configurational bias Monte Carlo (CBMC) and molecular dynamics (MD) simulations were carried out. Significant differences in both the equilibrium adsorption and especially the adsorption kinetics were found, which suggests that the separation of the quaternary-carbon dibranched isomer is feasible. The adsorption capacities and selectivities surpass those of pure silica MFI (Si-MFI), considered as reference. Altogether, Si-STW is presented as a promising adsorbent for increasing the octane number (ON) of the hydroisomerization product by selectively excluding quaternary-carbon dibranched hydrocarbons.

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