Quantum Mechanical Design of Molecular Electronics Logical Machines.

There are presented several two and three variable gates of molecular electronics digital computers. Maximal length of these molecular electronics digital logic gates are no more than four nanometers and maximal width 2.5 nm. The results of light induced internal molecular motions in azo-dyes molecules [1-3] have been used for the design of light driven logically controlled (OR, AND, NOR, NAND) molecular machines composed from organic photoactive electron donor dithieno[3,2-b:2',3'-d]- thiophene, tetrathiofulvalene (TTF) or ferrocene molecules and electron accepting 4,5-dinitro-9-(dicyanomethylidene)-fluorene (DN9(CN)2F), tetracyano-indane, and moving azo-benzene fragment. Density functional theory (DFT) B3PW91/6-311G model calculations were performed for the geometry optimization of these molecular electronics logical gates. Applied DFT time dependent (DFT-TD/B3PW91) method and our visualization program give absorption spectra of designed molecular gates and show from which fragments electrons are hopping in various excited states. There are designed set of single supermolecule fluorescencing devices containing OR and AND logic functions. [ABSTRACT FROM AUTHOR]