Abstract
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 13C NMR of the labeled guests. Large 1H-13C dipolar splittings for 13CHCl3 guests indicated significantly enhanced (∼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 13C chemical shift anisotropy (CSA) shifts (via the gradient method) and the restored 1H-13C 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.
Original language | English (US) |
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Pages (from-to) | 104-112 |
Number of pages | 9 |
Journal | Solid State Nuclear Magnetic Resonance |
Volume | 29 |
Issue number | 1-3 |
DOIs | |
State | Published - Feb 1 2006 |
Keywords
- Chloroform
- Cryptophane-A
- Dipolar couplings
- Dynamic coupling
- Gradient method
- Inclusion complexes
- Liquid crystals
- NMR
- ZLI 1132
- bis-cryptophane