Structure and Dynamics of Chlorocyclohexane/Thiourea Inclusion Compound C₆H₁₁Cl/SC(NH₂)₂Studied by X-ray Diffraction and¹H-NMR

Abstract

Structure and dynamics of chlorocyclohexane/thiourea inclusion compound C 6 H 11 Cl/SC(NH 2 ) 2 have been studied by single crystal X-ray structure analysis and 1 H-NMR. The structure analysis at room temperature disclosed hydrogen bonds in host subunit and molecular arrangement of chlorocyclohexane guest molecule. In the host subunit, thiourea molecule has fairly good planarity and its N and S atoms are bounded by two and four hydrogen bonds grouped into two types, respectively. Inside the thiourea channel, the guest molecules are disordered among six orientations around the special positions with site symmetry D 3d . Proton second moments of C 6 H 11 Cl/SC(NH 2 ) 2 and C 6 H 11 Cl/SC(ND 2 ) 2 gave the following results about the dynamics of the host subunit in the high-temperature phase stable above 197 K. In C 6 H 11 Cl/SC(NH 2 ) 2 , amino group undergoes a uniaxial rotation about its C-N bond, and this rotation begins to freeze at 240 K. For C 6 H 11 Cl/SC(ND 2 ) 2 , the freezing temperature of this rotation is found to elevate by 30 K. This phenomenon can be understood by the isotope effect on the NH 2 rotation, hindered by the hydrogen bonds. The both moments exhibit slightly discontinuous changes in the phase transition and increase with decreasing temperature even in the low-temperature phase.

X-ray Birefringence: A New Strategy for Determining Molecular Orientation in Materials

“…Structural and dynamic properties of the BrCH/thiourea inclusion compound have been studied previously by singlecrystal and powder XRD, 9,10 solid-state NMR, 11−15 and other techniques. 16,17 At ambient temperature, BrCH/thiourea has the "conventional" rhombohedral host structure of thiourea inclusion compounds 18−21 (Figure 1a), comprising tunnels within which the BrCH guest molecules are located.…”

“…Structural and dynamic properties of the BrCH/thiourea inclusion compound have been studied previously by single-crystal and powder XRD, , solid-state NMR, − and other techniques. , At ambient temperature, BrCH/thiourea has the “conventional” rhombohedral host structure of thiourea inclusion compounds − (Figure a), comprising tunnels within which the BrCH guest molecules are located. At ambient temperature, the BrCH guest molecules (and thus the C–Br bonds) undergo unrestricted reorientation within the tunnel, giving rise to essentially isotropic disorder.…”