Molecular logic systems

G. Ashkenazy, Biochemical molecular logic systems structure and function, M.Sc. thesis, Technion (Israel Instimte of Technology), Haifa, Israel, 1992. 

ND McClenaghan. Molecular Logic Systems. PhD thesis, Queen s University of Belfast, Northern Ireland, 1999. 

A very good example is the conductance of a dianthra[a,c]naphtacene starphenelike molecule presented in Fig. 20, interacting with three metallic nano-pads. The EHMO-NESQC T(E) transmission spectrum per tunnel junction looks like a standard conjugated molecule T(E) with well-identified molecular orbitals and their resonances. For the Fig. 20 case all the T(E) are the same. One can note a small deviation after the LUMO resonance, due to a little asymmetry in the adsorption site between the three branches on the nano-pads [127]. A lot of asymmetric star-like three-molecular-branches system can be constructed, in particular in reference to chemical composition of the central node. This had been analyzed in detail [60]. But in this case, each molecule becomes a peculiar case. The next section presents one application of this central-node case to construct molecule OR and molecule XOR logic gates. 

It is very important that such molecular-level motions are accompanied by changes of some chemical or physical property of the system, resulting in a readout signal that can be used to monitor the operation of the machine. The reversibility of the movement ie, the possibility to restore the initial situation by means of an opposite stimulus, is an essential feature of a molecular machine. Since such induced motions correspond to a binary logic systems of this kind could also prove useful for information processing. 

MOLECULAR LOGIC GATES BASED ON ELECTROACTIVE SYSTEMS... 

In the preceding chapters, reference has often been made to biological molecules and processes, for both biomimetic and abiotic purposes. The emphasis on molecular information in supramolecular chemistry finds its response in the operation of biological systems. There is a molecular logic of living organisms [10.24]. 

---