Molecular wire

Molecular wires (or sometimes called molecular nanowires) are molecular chains that conduct electric current. They are the proposed building blocks for molecular electronic devices. Their typical diameters are less than three nanometers, while their lengths may be macroscopic, extending to centimeters or more. Most types of molecular wires are derived from organic molecules. One naturally occurring molecular wire is DNA. Prominent inorganic examples include polymeric materials such as Li2Mo6Se6 and Mo6S9−xIx, [Pd4(CO)4(OAc)4Pd(acac)2], and single-molecule extended metal atom chains (EMACs) which comprise strings of transition metal atoms directly bonded to each other. Molecular wires containing paramagnetic inorganic moieties can exhibit Kondo peaks. Molecular wires conduct electricity. They typically have non-linear current-voltage characteristics, and do not behave as simple ohmic conductors. The conductance follows typical power law behavior as a function of temperature or electric field, whichever is the greater, arising from their strong one-dimensional character. Numerous theoretical ideas have been used in an attempt to understand the conductivity of one-dimensional systems, where strong interactions between electrons lead to departures from normal metallic (Fermi liquid) behavior. Important concepts are those introduced by Tomonaga, Luttinger and Wigner. Effects caused by classical Coulomb repulsion (called Coulomb blockade), interactions with vibrational degrees of freedom (called phonons) and Quantum Decoherence have also been found to be important in determining the properties of molecular wires. Methods have been developed for the synthesis of diverse types of molecular wires (e.g. organic molecular wires and inorganic molecular wires). The basic principle is to assemble repeating modules. Organic molecular wires are usually synthesized via transition metal-mediated cross-coupling reactions. Organic molecular wires usually consist aromatic rings connected by ethylene group or acetylene groups.