Construction of cooperative and responsive supramolecular systems for molecular functional modulation

Abstract

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 inprinciple. 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 novelframeworks for response functions by utilizing a metalion as an effector. The second utilizes amolecular 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=Nmoieties as a binding site for metalions. This strategy is remarkably usefulfor producing new binding sites by structuralfixation of multi-metal complexes and to modulate properties of metalions. Other cooperative molecular assembling systems for host generation are also demonstrated inthis 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 asmulti- 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. © 2010 The Chemical Society of Japan.