First synthesis of symmetrical and unsymmetrical conjugated trinuclear phthalocyanines covalently linked by ethynyl bridges

For the first time, symmetrical and unsymmetrical pi-electron-conjugated trinuclear phthalocyanines (Pcs) were synthesized with the Pc units connected directly by ethynyl linkages. Symmetrically alkoxy-substituted bridged ethynylphthalocyaninatozinc(II) triad was prepared by direct Sonogashira cross-coupling reaction between suitable diiodo Pc and alkynyl Pc derivatives. Nevertheless, the synthesis of the Pe-based triad having a donor-acceptor electron character was carried out by means of co-cyclotetramerization of two different phthalonitriles, namely 4,5-bis(propylsulfonyl)phthalonitrile and 4,5-[hexa(butoxy)ethynylphthalocyaninatozine(II)]phthalonitrile in the presence of a eobalt(II) salt.