Copper-mediated synthesis of phthalocyanino-fused dehydro[12]- and [18]annulenes

Cyclooligomeric phthalocyanines with the special feature of having a dehydr oannulene core are described. Compounds 4a,b and 5a,b were prepared by an o xidative coupling mediated by copper from the corresponding diethynyl unsym metrically substituted phthalocyanines 8a,b, which are easily accessible fr om the corresponding diiodo compounds 6a,b by a palladium-copper-catalyzed coupling. Appropriate conditions to Selectively form cyclodimers and cyclot rimers using Glaser and Eglinton methodologies have been attempted. In this way, two Compounds, 4a and 5b, each representative of a kind of oligomers, could be appropriately isolated and characterized by MALDI-MS. The W-vis s pectra of compounds 4a and 5b show a split Q-band shifted to the red with r espect to the corresponding precursor 8a,b. This can be interpreted,;in lig ht of previous results, as a consequence of intramolecular electronic coupl ing between the Pc subunits. Extensive formation of aggregates in chlorofor m can be also inferred from the spectra. No significant differences could b e observed in the spectra by comparison with that of the open-chain analogu e II, most probably due to a saturation phenomenon of the optical propertie s already pointed out in the literature for other alkynyl-linked open-chain dimers.