title: Investigation of chloromethane complexes of cryptophane-A analogue with butoxy groups using ¹³C NMR in the solid state and solution along with single crystal X-ray diffraction.
abstract: Host-guest complexes between cryptophane-A analogue with butoxy groups (cryptophane-But) and chloromethanes (chloroform, dichloromethane) were investigated in the solid state by means of magic-angle spinning (13)C NMR spectroscopy. The separated local fields method with (13)C-(1)H dipolar recoupling was used to determine the residual dipolar coupling for the guest molecules encaged in the host cavity. In the case of chloroform guest, the residual dipolar interaction was estimated to be about 19 kHz, consistent with a strongly restricted mobility of the guest in the cavity, while no residual interaction was observed for encaged dichloromethane. In order to rationalize this unexpected result, we performed single crystal X-ray diffraction studies, which confirmed that both guest molecules indeed were present inside the cryptophane cavity, with a certain level of disorder. To improve the insight in the dynamics, we performed a (13)C NMR spin-lattice relaxation study for the dichloromethane guest in solution. The system was characterized by chemical exchange, which was slow on the chemical shift time scale but fast with respect to the relaxation rates. Despite these disadvantageous conditions, we demonstrated that the data could be analyzed and that the results were consistent with an isotropic reorientation of dichloromethane within the cryptophane cavity.
authors.affiliation: Department of Materials and Environmental Chemistry, Arrhenius Laboratory, Stockholm University, SE-106 91, Stockholm, Sweden.
authors.forename: Emilie
authors.initials: E
authors.lastname: Steiner
authors.affiliation: Department of Materials and Environmental Chemistry, Arrhenius Laboratory, Stockholm University, SE-106 91, Stockholm, Sweden.
authors.forename: Renny
authors.initials: R
authors.lastname: Mathew
authors.affiliation: Department of Materials and Environmental Chemistry, Arrhenius Laboratory, Stockholm University, SE-106 91, Stockholm, Sweden.
authors.forename: Iwan
authors.initials: I
authors.lastname: Zimmermann
authors.affiliation: Laboratoire de Chimie, (CNRS-UMR 5182) Ecole Normale Supérieure de Lyon, 46 Allée d' Italie, F-69364, Lyon Cedex 07, France.
authors.forename: Thierry
authors.initials: T
authors.lastname: Brotin
authors.affiliation: Department of Materials and Environmental Chemistry, Arrhenius Laboratory, Stockholm University, SE-106 91, Stockholm, Sweden.
authors.forename: Mattias
authors.initials: M
authors.lastname: Edén
authors.affiliation: Department of Materials and Environmental Chemistry, Arrhenius Laboratory, Stockholm University, SE-106 91, Stockholm, Sweden.
authors.forename: Jozef
authors.initials: J
authors.lastname: Kowalewski
keywords: 13C NMR; X-ray diffraction; dipolar couplings; relaxation