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Phosphole‐Fused Dehydropurpurins via Titanium‐Mediated [2+2+1] Cyclization Strategy
Author(s) -
Higashino Tomohiro,
Nishimura Issei,
Imahori Hiroshi
Publication year - 2019
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.201903269
Subject(s) - phosphole , antiaromaticity , lone pair , phosphorus , atom (system on chip) , chemistry , titanium , oxidation state , porphyrin , electrochemistry , photochemistry , stereochemistry , aromaticity , molecule , organic chemistry , metal , computer science , electrode , embedded system
A [2+2+1] cyclization strategy of bis(alkynyl)porphyrin using low‐valent titanium species, generated in situ, afforded phosphole‐fused dehydropurpurins for the first time. The systematic investigations on the electronic properties of the dehydropurpurins revealed their unique features owing to the oxidation states of the phosphorus atom on the fused phosphole ring. The phosphole P=O and P=S derivatives were found to possess high electron‐accepting character derived from phosphorus(V) centers without the contribution of 24π antiaromatic character, suggesting their potential utility as electron‐accepting materials. In contrast, the phosphorus(III) derivatives revealed different optical and electrochemical properties arising from both 18π aromatic and 24π antiaromatic networks including the lone pair of the phosphorus(III) atom. Overall, the oxidation state of the phosphorus atom has a clear impact on the whole electronic properties, demonstrating the advantages of chemical modifications of the phosphorus center for creating an exotic π‐system. The application of titanium‐mediated [2+2+1] cyclization to porphyrins is highly promising for expanding a world of heterole‐fused porphyrinoids.