MOLECULAR ELECTRONIC-PROPERTIES OF FUSED RIGID PORPHYRIN-OLIGOMER MOLECULAR WIRES

Porphyrin-derived materials may be linked together by fusion to rigid coplanar aromatic bridges such as substituted anthracenes to form line ar or branched oligomers. Here, we consider linear oligomers of free-b ase porphyrin and meso-tetra-aryl derivatives, such as the tetramer. P reviously, a number of semi-empirical quantum-chemical methods have be en used to determine the geometries and electronic structures of the g round and excited electronic states. Here, the inter-ring coupling res ponsible for electron or hole conduction is discussed as a function of oligomer size and the predicted molecular-wire characteristics outlin ed. Comparisons with properties of other linear molecular wires are su mmarized, and possibilities of introducing switching capacity are indi cated. It should be noted that the edge-to-edge length of the tetramer is ca, 56 Angstrom, sufficient for trans-membrane spanning, while the length of the octamer, ca. 110 Angstrom, is sufficient for nano-elect rode spanning.