2.4. Measurement Conditions

Cross-polarization magic-angle spinning NMR spectra were recorded on a Bruker Avance III 300 MHz (Bruker Biospin, Ettlingen, Germany) spectrometer equipped with 4-mm broad band CP-MAS probe head. Approximately 100 mg of the studied material in the form of powder was placed into a 4-mm zirconium oxide rotor. Using a magic angle spinning rate of 10 kHz, ¹³C NMR spectra were acquired with 3072 data points and 5120 scans with a 5 s recovery delay; they were processed using TopSpin (v3.62, Bruker Biospin, Ettlingen, Germany) software. The chemical shifts were referenced to adamantane as an external standard.