meso-Aryl Core-Modified Fused Sapphyrins: Syntheses and Structural Diversity

Abstract

Two new, fused core-modified expanded porphyrins, sapphyrins 3 and 4, were synthesized by a simple acid-catalyzed condensation of electron-rich and rigid precursor, dithienothiophene (DTT) diol, and core-modified tripyrrane. These sapphyrins exhibit structural diversity depending upon the heteroatom present in the macrocyclic framework, where the thiophene ring is inverted in 3, while the selenophene ring in 4 exists in normal and inverted form in the free base and addition of two protons shifts the equilibrium to inverted form.

24π Core‐Modified Nonfused Pentaphyrin with Möbius Aromaticity

“…The pyrrolic nitrogen atoms of the tripyrrene unit are separated by a distance of 7.17 Å. This distance is slightly larger than those of the pyrrole nitrogen atoms (6.5 Å) observed for sapphyrin upon protonation, reported earlier by our group . The increased distance is able to accommodate both β‐CH protons of the inverted thiophene ring inside the cavity without many repulsions.…”

“…The pyrrolic nitrogen atoms of the tripyrrene unit are separatedb yadistance of 7.17 .T hisd istance is slightly larger than those of the pyrrole nitrogen atoms (6.5 )o bserved for sapphyrin upon protonation, reported earlier by our group. [22] The increased distance is able to accommodate both b-CH protons of the invertedt hiophener ing inside the cavity without many repulsions. The twisted Mçbiust opology with distinct aromatic character is reflected in the substantial distortion of the macrocyclic framework tilted from the meanp lane defined by 31 inner core atoms.…”

Fused core-modified planar antiaromatic 32π heptaphyrins: unusual synthesis and structural diversity

“…We adopted the [2 + 3] acid-catalyzed condensation reaction of DTT-diol 10 5 with thia-tripyrrane 13 6 followed by oxidation which afforded mono-fused sapphyrin 8 in 4% yield. 24 To our surprise, along with 8, the hitherto unknown heptaphyrin 3 was also formed in 6% yield. Under the similar reaction conditions, the acid-catalyzed condensation of 5 with selena-tripyrrane 7 afforded 9 in 3% yield and 4 in 4% yield, respectively.…”

The development of artificial porphyrinoids embedded with functional building blocks

“…Structural diversity was found for 99, in which the selenophene ring switched between the normal and inverted form in the free base and protonated conditions, respectively. 72 Due to the structural flexibility of the dipyrin linkage in the same macrocyclic networks, 36p nonaromatic 97 73 adopted a figure-eight twisty conformation in the solid state. Upon stepwise protonation by TFA, monoprotonated 97 showed a Soret-like band at 568 and weak Q bands at 816 and 1136 nm.…”

“…69,70 As a condensed and fused structure of thiophene, DTT can be introduced into porphyrin skeletons of various ring sizes via its diol compound 93 (Scheme 17). Four, five and six-unit heteroporphyrins 96, 98-102 71,72 embedded with a rigid DTT moiety exhibited more planar and rigid conformations and enhanced aromaticity compared with their bithiophene congeners. Structural diversity was found for 99, in which the selenophene ring switched between the normal and inverted form in the free base and protonated conditions, respectively.…”