title: Core-modified, meso-alkylidenyl porphyrins and their expanded analogues: a new family of nonplanar porphyrinoids.
abstract: New core-modified, meso-alkylidenyl porphyrinoids bearing multiple exocyclic double bonds were synthesized and characterized. The synthesis was accomplished using a typical "3 + 1"-type condensation approach. Stable exocyclic tautomers bearing double bonds at the meso positions, as well the corresponding endocyclic tautomers, were isolated in the case of both thiabenziporphyrin and thiapyriporphyrin products prepared in the course of this study. On the other hand, only the exocyclic tautomer was isolated in the case of the congeneric oxapyriporphyrin and oxabenziporphyrin. Expanded analogues of the exocyclic forms of oxabenziporphyrin and thiabenziporphyrin were also isolated as minor products. A single-crystal X-ray diffraction analysis of the expanded thiabenziporphyrin (20) revealed that all four pyrrole rings displayed an inverted geometry, presumably reflecting the strong hydrogen-bonding extant between the pyrrole N-H proton and the carbonyl group of the malonate moiety in the solid state. On the other hand, the expanded oxabenziporphyrin (14) was found to possess a severely distorted geometry with only one pyrrole ring being inverted. Careful analysis of the structure revealed that the solid-state geometry of the expanded macrocycles correlates well with the internal angle defined by the 2- and 5 substituents and the centers of the furan (14) or thiophene (20) subunits.
authors.affiliation: Department of Chemistry and Institute of Basic Science, Kangwon National University, Chun-Chon 200-701, Korea.
authors.forename: Seung-Doo
authors.initials: SD
authors.lastname: Jeong
authors.forename: Seong-Jin
authors.initials: SJ
authors.lastname: Hong
authors.forename: Kee Jong
authors.initials: KJ
authors.lastname: Park
authors.forename: Sihyun
authors.initials: S
authors.lastname: Ham
authors.forename: Jonathan L
authors.initials: JL
authors.lastname: Sessler
authors.forename: Vincent
authors.initials: V
authors.lastname: Lynch
authors.forename: Chang-Hee
authors.initials: CH
authors.lastname: Lee
mesh_terms: D002384:Catalysis; D002625:Chemistry, Organic / Q000379:methods*; D009682:Magnetic Resonance Spectroscopy; D008956:Models, Chemical; D008968:Molecular Conformation; D011166:Porphyrins / Q000737:chemistry*; D013876:Thiophenes / Q000737:chemistry
chemical_list: D011166:Porphyrins; D013876:Thiophenes