Each sample was scanned with the scan number of at least 32 over the spectral range 4000–400 cm−1 at a resolution of 4 cm−1. Data were obtained at 25 ◦C. 3.7. NMR Spectroscopy 1H-NMR and two-dimensional (2D) NMR spectra were acquired on a 400 MHz Bruker Avance-III ...