Complexation of neutral 1,4-dihalobutanes with simple pillar[5]arenes that is dominated by dispersion forces

The complexation of neutral 1,4-dihalobutanes with simple pillar[5]arenes was investigated. The results indicate the formation of interpenetrated complexes, where the dispersive interactions dominate the complex stability. Typically, 1,4-diiodobutane displays the strongest binding strength with ethylpillar[5]arene [K-a = (1.0 + 0.1) x 10(4) M-1], up to 120 fold as compared with 1,4-difluorobutane.