De novo design approach based on nanorecognition toward development of functional molecules/materials and nanosensors/nanodevices

For the design of functional molecules and nanodevices, it is very useful to utilize nanorecognition (which is governed mainly by interaction forces such as hydrogen bonding, ionic interaction, π-H/π-π interactions, and metallic interactions) and nanodynamics (involving capture, transport, and release of electrons, photons, or protons). The manifestation of these interaction forces has led us to the design and realization of diverse ionophores/receptors, organic nanotubes, nanowires, molecular mechanical devices, molecular switches, enzyme mimetics, protein folding/unfolding, etc. In this review, we begin with a brief discussion of the interaction forces, followed by some of our representative applications. We discuss ionophores with chemo-sensing capability for biologically important cations and anions and explain how the understanding of hydrogen bonding and π-interactions has led to the design of self-assembled nanotubes from calix[4]hydroquinone (CHQ). The binding study of neutral and cationic transition metals with the redox system of hydroquinone (HQ) and quinone (Q) predicts what kind of nanostructures would form. Finally, we look into the conformational changes between stacked and edge-to-face conformers in π-benzoquinone-benzene complexes controlled by alternating electrochemical potential. The resulting flapping motion illustrates a promising pathway toward the design of mobile nanomechanical devices.