FT-IR spectra were recorded on a SpectrumTwo FT-IR Spectrometer (Perkin-Elmer); samples were applied as KBr pellets. High-resolution electrospray mass spectra (HR-ESI-MS) were recorded on a timsTOF Pro TIMS-QTOF-MS instrument (Bruker Daltonics GmbH, Bremen, Germany). The samples were dissolved in MeOH at a ca. 50 µg mL -1 concentration and analyzed via continuous flow injection (2 µL min -1 ). The mass spectrometer was operated in the positive or negative electrospray ionization mode at 4'000 V (-4'000 V) capillary voltage and -500 V (500 V) endplate offset with an N2 nebulizer pressure of 0.4 bar and a dry gas flow of 4 L min -1 at 180 °C.