pπ-molecular orbitals of conjugated linear polyene molecules as molecular orbital functional groups in the design of near-infrared dyes

While reviewing molecular orbital models for the ppi-electronic system of conjugated polyene molecules new examples on embedding of higher linear polyenes will be presented. It is shown that embedding (Hall subgraphs) and right-hand mirror-plane (McClelland subgraphs) fragments are MO functional groups of importance in molecular modeling of near IR absorbing pigments. The major new result reported in this paper is the recognition that the HOMO/LUMO gap for perylene-3,4:9,10-bis(carboximide) and poly(perinaphthalene) related materials is determined by the embedding fragment which circumvents the need to do a full molecule calculation.