Fig. 1. The molecular structure (a), molecular arrangements of MH2 (b) and MH3 (c)

Fig. 2. The Powder XRD pattern (a) and the data previously published (b) of MH2 and MH3

Fig. 3. The experimental THz spectra of MH2 and MH3

Fig. 4. The experimental and calculated spectra of MH2 and MH3

Fig. 5. The experimental THz spectra of MH3 and Qingxiansu (b)