Guest Molecular Motion of [N(CH3)4][Cd3(CN)7] Benzene, Toluene, and Ethylbenzene Clathrates As Studied by2H NMR

2 H NMR powder patterns of [N(CH 3 ) 4 ][Cd 3 (CN) 7 ]· n G type benzene ( n = 1.5, G = C 6 D 6 ), toluene ( n = 1, G = C 6 D 5 CD 3 and C 6 D 5 CH 3 ), and ethylbenzene ( n = 1, G = C 6 D 5 CD 2 CD 3, C 6 D 6 CH 2 CH 3, and C 6 H 5 CD 2 CH 3 ) clathrates have been measured between 128 and 468 K and analyzed in order to obtain information about motional behavior of the guest molecules before and during their thermal decomposition. (1) Benzene clathrate: below ca. 300 K the benzene molecule undergoes an ordinary in-plane rotational motion. Above 300 K, a sign of an out-of-plane motion like a precessional motion, which comes from the benzene escaping from the clathrate host owing to its thermal decomposition, was observed. (2) Toluene clathrate: below ca. 320 K the main motion is a 180° flip motion of the aromatic ring and its activation energy is estimated to be 33(1) kJ/mol. Above 320 K, in its thermal decomposition process, an in-plane two-site reorientational motion of the whole toluene molecule takes place. (3) Ethylbenzene clathrate: below ca. 350 K the main motion is a 180° flip motion of the aromatic ring whose activation energy is estimated to be 36(4) kJ/mol, and the ethyl group is undergoing a fast two-site reorientational motion within a restricted space even at 133 K. In a higher temperature region, the reorientational motion of the ethyl group changes to a rotational motion. Detailed motional models for each case have been constructed with several simple motions based on their molecular and crystal structures.