Regulating competing supramolecular interactions using Ligand concentration.

The complexity of biomol. systems inevitably leads to a degree of competition between the noncovalent interactions involved. However, the outcome of biol. processes is generally very well-defined often due to the competition of these interactions. In contrast, specificity in synthetic supramol. systems is usually based on the presence of a min. set of alternative assembly pathways. While the latter might simplify the system, it prevents the selection of specific structures and thereby limits the adaptivity of the system. Therefore, artificial systems contg. competing interactions are vital to stimulate the development of more adaptive and lifelike synthetic systems. Here, we present a detailed study on the self-assembly behavior of a C2v-sym. tritopic mol., functionalized with three self-complementary ureidopyrimidinone (UPy) motifs. Due to a shorter linker connecting one of these UPys, two types of cycles with different stabilities can be formed, which subsequently dimerize intermolecularly via the third UPy. The UPy complementary 2,7-diamido-1,8-naphthyridine (NaPy) motif was gradually added to this mixt. in order to examine its effect on the cycle distribution. As a result of the C2v-symmetry of the tritopic UPy, together with small differences in binding strength, the cycle ratio can be regulated by altering the concn. of NaPy. We show that this ratio can be increased to an extent where one type of cycle is formed almost exclusively.