In order to investigate the self-association of asymmetric glycoluril clips, compounds 1-7 with a common p-dimethoxy-o-xylylene ring sidewall were synthesized and their structures were analyzed by X-ray crystallography. As expected, the clip molecules formed dimers promoted by π-π interactions between their aromatic sidewalls. Interestingly, the nature of the substitutents on the differentially substituted sidewall caused appreciable differences in the observed dimerization motifs in the crystalline state. For example, 1 and 2 adopted the out-out dimeric motif with its diaromatic-vinyl-o-xylylene rings bound in the cleft of the neighboring molecular clip by π–π stacking interactions. In contrast, compounds 3 – 7 adopted the in-in dimeric motif in the solid state, in which the p-dimethoxy-o-xylylene rings were sandwiched by the adjacent clip driven by π–π and OCH3•••O=C H-bonding interactions. X-ray crystallographic analysis of compounds 1 – 7 indicates that the conformational preferences induced by the linking group between the o-xylylene sidewalls and the terminal aromatic rings plays a critical role in determining which mode of dimerization (in-in versus out-out) and three dimensional packing predominates. The ability to control the selective dimerization of asymmetric glycoluril derived molecular clips via π−π interactions promises to expand the use of these building blocks to design complex and functional solid state architectures.