NMR studies of chloroform@cryptophane-A and chloroform@bis-cryptophane inclusion complexes oriented in thermotropic liquid crystals.
Oriented inclusion complexes of chloroform@cryptophane-A and chloroform@bis-cryptophane were prepared using a nematic thermotropic liquid crystal (ZLI 1132), and the alignment and magnetic resonance properties of these host-guest systems were studied via (13)C NMR of the labeled guests. Large (1)H-(13)C dipolar splittings for (13)CHCl(3) guests indicated significantly enhanced (approximately 2-fold) ordering for the trapped vs. free ligands under all conditions studied, with similar ordering observed for the two complexes-despite significant differences in size and motional freedom between the hosts. For each environment, variable-temperature studies permitted the sign and magnitude of the order parameter for chloroform's C-H bond to be independently determined from the (13)C chemical shift anisotropy (CSA) shifts (via the gradient method) and the restored (1)H-(13)C dipolar couplings. In both systems, the results are consistent with overall alignment of the complexes such that the cage principal axis lies roughly perpendicular to the LC director.
Chaffee
Kathleen E
KE
Department of Chemistry and Biochemistry, 113 Neckers Hall, Southern Illinois University, Carbondale, IL 62901, USA.
Marjanska
Malgorzata
M
Goodson
Boyd M
BM
D001665:Binding Sites; D002250:Carbon Radioisotopes; D002725:Chloroform / Q000032:analysis* / Q000737:chemistry*; D003461:Crystallography / Q000379:methods*; D050866:Liquid Crystals / Q000032:analysis* / Q000737:chemistry*; D046911:Macromolecular Substances / Q000032:analysis / Q000737:chemistry; D009682:Magnetic Resonance Spectroscopy / Q000379:methods*; D008422:Materials Testing; D008968:Molecular Conformation; D044367:Phase Transition; D013696:Temperature
D002250:Carbon Radioisotopes; D046911:Macromolecular Substances; D002725:Chloroform