The source voltage and temperature were fixed at 3 kV and 250 °C. NMR spectra were recorded on a Bruker Avance DMX400 FT-NMR spectrometer operating at 400 MHz for 1 H and 100 MHz for 13C at room temperature. Signals were referred to an internal standard TMS. Chemical shifts were reported in δ units and coupling constants (J) in Hz.