Molecular and Electronic Structures of Model Compounds of Doped Polyacetylene

Abstract

Abstract Using the ab initio HF SCF MO method optimized molecular structures were calculated on twenty five model compounds of doped polyacetylene, which were charge-transfer complexes between dopants (Na, Li, and Cl atoms) and trans-polyenes (C6H8, C8H10, C12H14, C14H16, and C16H18) or trans-odd polyene radicals (C3H5·, C5H7·, C7H9·, C9H11·, C11H13·, and C13H15·). In alkali metal-doped complexes, each alkali atom is located at the vertex of the trigonal pyramid, whose basal triangle consists of an allylic group, (CH)3. On the other hand, each chlorine atom is coplanar with the (CH)n chain and is connected with an allylic group by hydrogen bonding. The allylic group acts as a bidentate or tridentate ligand, forming an ionic closed-shell structure with the dopants. The molecular orbitals of the singly doped complexes are correlated with those of parent trans-polyene or odd polyene radical chains. The molecular orbitals of doubly doped complexes are analyzed on the basis of those of singly doped complexes. The molecular structure of the polson unit is presented, which is important for heavily doped polyacetylene to be metallic.