Construction of Cooperative and Responsive Supramolecular Systems for Molecular Functional Modulation

The transfer and modulation of the molecular information are necessary processes for cooperative and responsive molecular functions. When functional molecules are responsive to external (intermolecular) as well as internal (intramolecular) stimuli, the molecules exhibit cooperative functions in principle. We have developed a variety of cooperative and responsive supramolecular systems created on the basis of new concepts for the molecular design of sophisticated functional systems. The first uses pseudomacrocycles including pseudocrown ether, pseudocryptands, and pseudocyclophanes as novel frameworks for response functions by utilizing a metal ion as an effector. The second utilizes a molecular gate responding to an external signal. The gate is opened and closed by a signal achieving perfect on off switching for guest recognition. The next exploits metal-accumulated molecular systems bearing oligo C=N moieties as a binding site for metal ions. This strategy is remarkably useful for producing new binding sites by structural fixation of multi-metal complexes and to modulate properties of metal ions. Other cooperative molecular assembling systems for host generation are also demonstrated in this account. Metallo-frameworks and self-assembled metallo-systems recently developed in our laboratories, which have high potential for synergistic molecular functions, are discussed. Future cooperative functional systems will be widely applicable as multi-responsive multi-functional supramolecules, molecular functional cascades for successive molecular functions and function amplification. Study of cooperative and responsive molecular systems may lead to more general fields such as complex systems science, which is at the interface of chemistry, physics, biology, and mathematics.