Synthesis and properties of benzannulenes and their metal complexes




Chen, Yongsheng

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A series of bis [e] and [a] fused dibenzannulenes/cyclophanes have been synthesized for the first time using benzyne-like intermediates (annulynes). These include the dibenzannulene trans-2,9-di-t-butyl-14c, 14d-dihydro-14c-14d-dimethyldibenzo[fg,op]naphthacene 82b, and the metacyclophanedienes anti-[1,2;9,10]- dibenzo-5, 13-di-t-butyl-8,16-dimethyl[2.2]metacyclophane 82a, and anti-[1,2-b; 9,10-b]- dinaphtho-5,13-di-t-butyl-8,16-dimethyl[2.2]metacyclophane 85a. From these compounds several metal complexes including trans-{μ- [( 1,2,3,4,4a, 14b-η:8a,9,10,11,12,12a-η)-12c, 12d-dihydro-12c-12d-dimethylbenzo[ rst]pentaphene]]hexacarbonyldichromium 100, have been synthesized. Among the bis [e] fused compounds, pairs 82a/82b and 95a/95b show reversible and repeatable photo-switching properties both in solution and in the solid state. The pyrene forms 82b and 95b are characterized at low temperature and they thermally return to their cyclophane forms 82a and 95a at room temperature. A polystyrene based film of 82 shows a much better bistability required for photo-switching units. These properties make them potential candidates for optical memory units. For the similar naphtho[e] fused compound 95a, no pyrene isomer 95b was detected upon irradiation with UV light. Based on the NMR data, relative bond fixing abilities (RBFA) of several species are measured. The order is: [special characters omitted] > Benzene > Oxanorbomadiene > lU Norbomadiene The reduced species, oxanorbomene and norbomene, do not induce any significant bond localization on the [14] annulene ring.



Metal complexes, Metal ions