BENZO-9-CROWN-3 ETHER - X-RAY CRYSTAL-STRUCTURE, NMR-STUDIES IN SOLUTION AND THE SOLID-PHASE, AND AB-INITIO CALCULATIONS OF ISOTROPIC C-13 CHEMICAL-SHIFTS USING LORG WITH A D95V BASIS-SET

Using the X-ray crystal geometry as input, the C-13 NMR chemical shifts of benzo-9-crown-3 ether have been calculated via ab initio methods using a localized orbital local origin (LORG) approach. Reasonable agreement is found between the calculated values for an isolated molecule in the gas phase and those obtained in the C-13 CPMAS NMR spectrum. Solid phase C-13 spectra of the C7,10-d(4), derivative confirm the existence of a 7.9 ppm shift difference between these sites in the solid, whereas in solution they are conformationally averaged to one resonance. The effects of C-H bond length variation on calculated C-13 shifts have been explored.