Molecular motion of guests trapped in N-methyl-1,3-diaminopropanecadmium(II) tetracyanonickelate(II) host lattices

Abstract

The molecular motion of guest molecules in Cd(mtn)Ni(CN)4•0.5G clathrates (mtn = N-methyl-1,3-diaminopropane, G = toluene, nitrobenzene, dichloromethane, and chloroform) were studied by using CP/MAS 13C and 2H NMR techniques. At room temperature, application of 13C CP/MAS NMR with dipolar dephasing showed the presence of large amplitude molecular motion in all cases. Temperature dependent 2H NMR spectra for the toluene-d8 clathrate shows that the methyl group rotated at all temperatures down to 77 K. Also, a 2-site in-plane reorientation process of the entire molecule is activated above 180 K, which goes over into axially symmetric in-plane rotation around 450 K. Severely restricted motions were also observed for the nitrobenzene and haloalkane guests. The rather complicated dynamic behaviour of the guest molecules at low and room temperatures can be attributed to the presence of static disorders which disappear at higher temperatures due to time averaging.