In recent years there has been a considerable upsurge in the synthesis of covalently linked multiporphyrin arrays. These compounds are interesting in light of their unique photoelectronic properties and potential applications as mimics of light-harvesting systems in photosynthesis, and as electronenergy transfer moieties in molecular wires. [1] Among these, fused oligoporphyrins sharing a common extended p-electron network are of particular interest because of their remarkable red-shifted absorption bands as well as their extremely enhanced electronic communications that are favorable for molecular wires. [2, 3] Indeed, several fused diporphyrins and oligoporphyrins exhibit significantly red-shifted Soret bands and intense Q-bands, [2, 3] which demonstrates the promising potential of fused multiporphyrins. Here we report a facile synthesis of other fused diporphyrins that contain two meso-b direct linkages.
Recently we found that the one-electron oxidation of 5,15diaryl-substituted metalloporphyrins bearing sterically uncongested meso-positions led to the formation of directly linked porphyrin dimers. The Zn II complex gave a meso ± meso-linked diporphyrin by oxidation with a Ag I salt or by
Experimental Section
The starting materials 3 and 4 used in the preparation of compounds of type 2 were known or could be prepared by literature methods. [7, 8, 11] Previously unknown sulfur-or selenium-containing reagents of type 3 with X S or Se and Y CH were obtained by reaction of the corresponding 3-chloro-3dialkylaminopropeniminium salts [12] with sodium sulfide or selenide [13] in ethanol. [14] 3-Chloro-3-morpholinopropenylidene dimethyliminium perchorate was prepared according to the literature method: [12a] M.p. 177 ± 180 8C;