SYNTHESIS AND SELF-ASSEMBLY OF PSEUDO-SPHERICAL HOMODIMERIC AND HETERODIMERIC CAPSULES

Experimental details are given for the synthesis and characterization of several new molecules capable of self-assembly. The new molecules f eature glycoluril subunits held apart by various rigid spacers, ethyle ne (2), naphthalene (3), and ethenoanthracene (4), and assemble throug h hydrogen bonds into pseudo-spherical dimeric capsules. The nature of their assembly is demonstrated by the X-ray crystal structure of caps ules 1.1. The capsules are shown to enclose smaller guest molecules in a reversible manner. Direct evidence of the guest molecules inside th e capsules from NMR is presented. In addition to self-assembling dimer ically, these new molecules are shown to disproportionate into hybrid species or heterodimers. The resulting new capsules feature internal c avities of varying sizes and shapes. Formation of hybrid dimers 1.2, 1 .4, and 3.4 is observed in solutions containing mixtures of two homodi mers. The dispropoaionation equilibria could be manipulated by the add ition of appropriately sized solvents as guests. Even the energeticall y unlikely hybrids 1.4 and 3.4 are found to be the dominant species wh en suitable guests such as CDBr3 are present. Evidence of the existenc e of the heterodimers is presented from NOE measurements. Factors cont rolling the heterodimerization are discussed.