Catalyst Deactivation Processes During 1-Hexene Polymerization

<p>The catalyst [Cp₂Zr(<i>μ</i>-Me)₂AlMe₂]⁺[B(C₆F₅)₄]⁻ (<b>1</b>) has been studied by electrospray ionisation mass spectrometry (ESI-MS) in order to better understand the complexities of catalyst deactivation in the polymerisation of 1-hexene. Using offline, online and flow-based methods, we observe that zirconium π-allyl species are unstable in solution and previously unobserved dimethylalane complexes are more stable. The dimethylalane complexes are resistant to further 1-hexene additions and their formation represent a new pathway for catalyst deactivation.</p>

Catalyst Deactivation Processes During 1-Hexene Polymerization

<p>The catalyst [Cp₂Zr(<i>μ</i>-Me)₂AlMe₂]⁺[B(C₆F₅)₄]⁻ (<b>1</b>) has been studied by electrospray ionisation mass spectrometry (ESI-MS) in order to better understand the complexities of catalyst deactivation in the polymerisation of 1-hexene. Using offline, online and flow-based methods, we observe that zirconium π-allyl species are unstable in solution and previously unobserved dimethylalane complexes are more stable. The dimethylalane complexes are resistant to further 1-hexene additions and their formation represent a new pathway for catalyst deactivation.</p>

Visible-light reversible photopolymerisation: insights via online photoflow – electrospray ionisation – mass spectrometry

Herein, we introduce a scalable photopolyaddition polymerisations using the pyrene-chalcone [2+2]-cycloaddition and monitor the photodepolymerisation process via an online photoflow – electrospray ionisation mass spectrometry setup.

Cytotoxic and anti-inflammatory resorcinol and alkylbenzoquinone derivatives from the leaves of Ardisia sieboldii

Medicinal plants belonging to the genus Ardisia are traditionally used to cure various human diseases including inflammation and cancer. This study aimed to purify and characterize cytotoxic and anti-inflammatory compounds from Ardisia sieboldii leaves. Bioassay-guided chromatographic analyses yielded three compounds, 2-methyl-5-(8Z-heptadecenyl) resorcinol (1), 5-(8Z-heptadecenyl) resorcinol (2), and ardisiaquinone A (3), whereas liquid chromatography–electrospray ionisation–mass spectrometry chemical profiling revealed the presence of diverse resorcinol and alkylbenzoquinone derivatives in cytotoxic 70% methanol extracts. Chemical structures of 1–3 were confirmed by spectroscopic methods including 1H NMR (nuclear magnetic resonance), 13C NMR, and electrospray ionisation–mass spectrometry. Compounds 1 and 2 were purified from A. sieboldii for the first time, and all three compounds showed cytotoxicity against a panel of cancer cell lines and brine shrimps in a dose-response manner. Among them, compound 2 exhibited the highest cytotoxicity on cancer cells (IC50 values of 8.8–25.7 μM) as well as on brine shrimps (IC50 value of 5.1 μM). Compounds 1–3 exhibited anti-inflammatory effects through inhibiting protein denaturation (IC50 values of 5.8–9.6 μM), cyclooxygenase-2 activity (IC50 values of 34.5–60.1 μM), and nitrite formation in RAW 264.7 cells. Cytotoxic and anti-inflammatory activities of 1–3 demonstrated in this study deserve further investigation for considering their suitability as candidates or leads to develop anticancer and anti-inflammatory drugs.