One of the distinguishing features of living organisms is their proclivity to employ molecular machinery on a grand scale to power their metabolic processes. Recently, an artificial system that can transport molecules unidirectionally and autonomously, using light as the only energy source, has been developed in our laboratory. An improved system (Figure 1) has been designed to pump the CBPQT  4+ rings from bulk solution onto a long chain repetitively and progressively. We have named it a molecular pump. The prototypical molecular pump consists of a dumbbell containing a 3,5-dimethylpyridinium (Py  +), a 4,4'-bipyridinium (BIPY  2+), an isopropylphenyl (IPP  ) and a long chain terminated by a bulky stopper.The CBPQT  4+ ring is repelled by the Py  + and BIPY  2+ initially, upon reduction with activated zinc dust, and the Coulombic repulsion between Py  + and the CBPQT  2(+�) ring decreases dramatically, forming a thermodynamically stable trisradical complex BIPY  +�� CBPQT  2(+�) within seconds. When re-oxidized to the fully charged state, the electrostatic Py  + barrier is recovered, forcing the CBPQT  4+ ring to jump over the steric barrier (IPP  ) onto the long chain, trapping them there. When the redox process is repeated, a second CBPQT  4+ ring can be pumped onto the long chain. It is anticipated that the molecular pumps can pump multiple CBPQT  4+ rings if the chain is long enough. 

Artificial molecular pumps

248th National Meeting (2014)

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