Unorthodox Interactions at Work
For the construction of functional systems, a surprising limited number of primary interactions between molecules is available. Hydrogen bonds, hydrophobic interactions, ion pairing, aromatic (π, π) interactions and cation-π interactions can be named as basic set, comparable to notes to compose music, letters to write or colors to paint. The addition of more colors to the chemist's palette is of fundamental importance. We entered this field when we discovered that synthetic transport systems can serve as unique analytical tools to elaborate on interactions that are otherwise difficult to detect. With this approach, experimental evidence for the functional relevance of anion-π interactions, halogen bonds and chalcogen bonds was secured. These interactions are the underrecognized counterparts of cation-π interactions and hydrogen bonds.
Evidence for ground-state stabilization of anions during transport called the stabilization of anionic transition states by these unorthodox interactions. Current emphasis is on non-covalent catalysis with anion-π interactions and chalcogen bonds, both unprecedented.
Other less explored "interactions" of interest on functional systems include repulsion-driven ion-pairing interactions and strained disulfide bonds under high ring tension for cellular uptake, mechanosensitive bonds for the creation of fluorescent probes, ionpair-π interactions, aromatic donor-acceptor interactions, orthogonal dynamic covalent bonds, and remote control by voltage, macrodipoles, and the like.