Near-infrared spectra were acquired on a Bruker FTIR Tensor 27 spectrometer in the 4000-400 cm -1 range with a 2 cm -1 resolution. The sample (~1 mg) was mixed with FTIRgrade KBr (100-110 mg) in the drybox, homogenized, pressed in a threaded-hole press to form a semi-transparent window, and measured within 20 min. A short exposition to ambient air (<30 s) was inevitable and therefore, even though the samples do not contain any -OH groups, the spectra always contain the corresponding vibration bands (1636 cm -1 , 3435 cm - 1 ) with variable intensity.