Molecular engineering. Part 5. Tuning the constrictive binding of container host by the atomic order of portal pillars

Two D-4h container hosts 12 and 13 with 4(CH2-O-bridge-O-CH2) portal pillar s were obtained in good yields by stepwise synthetic routes and showed comp lementary complexation behaviors to their analogues with (O-CH2-bridge-CH2- O)(4) portal pillars. H-1 NMR spectral chemical shifts of host's inward-tur ned OCH2O protons were sensitive to guest change. The stability orders of h emicarceplexes were 12-p-(CH3CH2)(2)C6H4 > 12-p-(CH3O)(2)C6H4 much greater than 12-o-(CH3O)(2)C6H4 > 12-m-(CH3O)(2)C6H4 and 13-CH3COCH2CH3 > 13-CH3COC H2CH(CH3)(2) > 13-CH3CON(CH3)(2) > 13-CH3COOCH2CH3 > 13-CH3CH2CON(CH3)(2) i n terms of the activation energy barrier for decomplexation. Large solvent effects on the activation energy for decomplexation of hemicarceplexes were observed.