3, 3'-Diisoviolanthronyl (6) which is expected to have high electronic semiconductivity was prepared in 90% yield by ring closure of isomeric quarterbenzanthrones (4) and (5) in ethanolic potassium hydoroxide solutions at 120°C.
The dimer of 3, 4'-dibenzanthrone (isoviolanthrone) which has C-C linkage at the 3 positions of both isoviolanthrone nuclei, has electronic conductivity as much as 30 times of its monomer isoviolanthrone. The λ max of uv spectra in 98% sulfuric acid shifted by 20 nm to longer region than its monomer.
Two isomeric quarterbenzanthrones (4) and (5) were synthesized by the Ullmann reaction in pyrene with Cu powder from 9-iodo- (2) and 9'-iodo-4, 3'-dibenzanthronyl (3) respectively (yield of (4) 19%, (5) 24%). The structure of these quarterbenzanthrone (4) or (5) was identified on the bases of elemental analyses, the additivity of their uv and visible spectra to 9, 9'-and 3, 4'-dibenzanthronyl, and the similarity of ir spectra of quarterbenzanthrone (4) and (5) corresponding to their intermediates (2) and (3).
On the other hand, direct iodination of 3, 4'-dibenzanthronyl (1) with periodic acid and iodine gave the mixture of monoiodo derivative of (1) in 38% yield. By-product diiodo derivative of (1) was proved to be identical with those obtained by iodination of (2) or (3).
Therefore it was concluded that those diiodo derivative of (1) have the same structure, not 9, 3'-but 9, 9'-diiodo-3, 4'-dibenzanthronyl (7). This evidence shows that the above mixture of monoiodo-3, 4'-dibenzanthronyl, prepared by direct iodination of (1), is composed only of (2) and (3), and this was supported by ir spectra.
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