ABSTRACT
The non-metal cation pentaborate(1-) salt [p-H2NC6H4CH2NH3][B5O6(OH)4]·1/2H2O (1) was synthesised from B(OH)3 and p-H2NC6H4CH2NH2 and crystallized from aqueous solution. Compound 1 was characterized by thermal (TGA/DSC), spectroscopic (IR, NMR) and single-crystal X-ray diffraction methods and it was found to crystallize in the non-centrosymmetric point group P21. Powder SHG measurements on 1 and some related alkylammonium pentaborate salts, [NH3CMe2(CH2OH)][B5O6(OH)4], [NH3CMe(CH2OH)2][B5O6(OH)4] and [NH3CHMeCH2OH][B5O6(OH)4], a substituted imidazolium salt, [1,2,3-Me3C3H2N2][B5O6(OH)4], a substituted piperidinium salt, [(CH2)5NH(CH2CH2OH)][B5O6(OH)4], and a substituted pyrrolidinium salt, [S-(+)-2-(HOCH2)C4H7NH2][B5O6(OH)4], were determined. Compound 1 and all compounds, except [1,2,3-Me3C3H2N2][B5O6(OH)4], showed some weak SHG activity with SHG efficiencies of 0.1-0.2 relative to that of KH2PO4 (KDP).
ABSTRACT
RATIONALE: Traditional investigation of bacteriohopanepolyols (BHPs) has relied on derivatisation by acetylation prior to gas chromatography/mass spectrometry (GC/MS) or liquid chromatography/MS (LC/MS) analysis. Here, modern chromatographic techniques (ultrahigh-performance liquid chromatography (UPLC)) and new column chemistries were tested to develop a method for BHP analysis without the need for derivatisation. METHODS: Bacterial culture and sedimentary lipid extracts were analysed using a Waters Acquity Xevo TQ-S triple quadrupole mass spectrometer in positive ion atmospheric pressure chemical ionisation (APCI) mode. Waters BEH C18 and ACE Excel C18 were the central columns evaluated using a binary solvent gradient with 0.1% formic acid in the polar solvent phase in order to optimise performance and selectivity. RESULTS: Non-amine BHPs and adenosylhopane showed similar performance on each C18 column; however, BHP-containing terminal amines were only identified eluting from the ultra-inert ACE Excel C18 column. APCI-MS/MS product ion scans revealed significant differences in fragmentation pathways from previous methods for acetylated compounds. The product ions used for targeted multiple reaction monitoring (MRM) are summarised. CONCLUSIONS: UPLC/MS/MS analysis using an ACE Excel C18 column produced superior separation for amine-containing BHPs and reduced run times from 60 to 9 min compared with previous methods. Unexpected variations in fragmentation pathways between structural subgroups must be taken into account when optimising MRM transitions for future quantitative studies. Copyright © 2016 John Wiley & Sons, Ltd.
Subject(s)
Chromatography, High Pressure Liquid/methods , Membrane Lipids/chemistry , Methylococcus capsulatus/chemistry , Methylosinus trichosporium/chemistry , Tandem Mass Spectrometry/methods , Membrane Lipids/metabolism , Methylococcus capsulatus/metabolism , Methylosinus trichosporium/metabolism , Molecular StructureABSTRACT
The synthesis and characterization of a series of pentaborate(1-) salts of substituted pyrrolidinium cations [C4H8NH2][B5O6(OH)4] (), [C4H8NMe2][B5O6(OH)4] () [C4H8NMeH][B5O6(OH)4] (), [(2-CH2OH)C4H7NH2][B5O6(OH)4] () is reported. All compounds were characterized by single-crystal XRD studies with (1/2CH3COCH3) and (1/2H2O) solvated. TGA/DSC analysis of the pentaborates showed that they thermally decomposed in air at 800 °C to 2.5 B2O3, in a 2 step process involving dehydration (<250 °C) and oxidative decomposition (250-600 °C). BET analysis of materials derived thermally from the pentaborates and had internal porosities of <1 m(2) g(-1), indicating they were non-porous. All compounds show extensive supramolecular H-bonded anionic lattices. H-bond interactions are described in detail and motifs found in these and in other pentaborate structures have been examined and modelled by DFT calculations. These calculations confirm that H-bonds interactions in pentaborates are moderately strong (ca. -10 to -21 kJ mol(-1)) and are likely to dominate the energetics of their templated syntheses.
