Boronate esters that contain N-donor groups are self-complementary structures, which can assemble by means of dative boron–nitrogen bonds to form macrocycles or polymers. Herein, we describe the synthesis of dioxaborinanes and benzodioxaboroles containing pyridyl side chains. In the solid state, the dioxaborinanes were found to exist predominantly as monomers. Upon crystallization, aggregation into one-dimensional polymers was observed, but only for boronate esters that contained electron-withdrawing groups. The more Lewis acidic benzodioxaboroles, on the other hand, were found to form macrocycles both in solution and in the solid state.