Building molecular wires from the colours of life: conjugated porphyrin oligomers Harry L. Anderson Department of Chemistry, University of Oxford, Dyson Perrins Laboratory, South Parks Road, Oxford, UK OX1 3QY. E-mail:
[email protected] Received (in Cambridge, UK) 25th May 1999, Accepted 13th July 1999 Conjugated porphyrin polymers are giant supramolecular gomers derived from small heterocycles, such as thiophene, are chromophores with extraordinary electrooptical and nonlinear useful semiconductors,15 so it is interesting to compare optical properties. Close collaboration between synthetic or- conjugated oligomers derived from larger, more polarisable, ganic chemists, chemical physicists and theoreticians has aromatic units such as porphyrins. This Feature Article yielded new insights into the electronic structure of these highlights the emerging design principles, and structure– remarkable materials. Alkyne-linked oligomers have been most property relationships, for materials of this type, and focuses on intensively investigated. Several strands of independent work interporphyrin conjugation: how to maximise it, how to show that the unusual electronic behaviour of these materials measure it, and how to use it to make advanced optoelectronic can be attributed to strong ground state interporphyrin materials. conjugation, which is amplified in the excited states, and in the oxidised and reduced forms. Porphyrins as building blocks for electronic Many porphyrin oligomers have been studied as models for materials natural photosynthetic systems1 and as enzyme mimics.2 Most of them are not conjugated; that is to say there is no significant The word porphyrin is derived from the Greek porphura p-overlap between the macrocycles, and their electronic meaning purple, and all porphyrins are intensely coloured.16 absorption spectra resemble those of their components.