π-Conjugated macrocycles from thiophenes and benzenes

Abstract

pi-Conjugated macrocycles consisting of thiophenes and benzenes exhibit benzenoid features for 4npi macrocycles, whereas (4n + 2)pi macrocycles are annulenoid due to rapid interconversion between quinoid and Kekule canonical forms in the benzene units.

Kinetic versus Thermodynamic Control Over Multiple Conformations of Di‐2,7‐naphthihexaphyrin(1.1.1.1.1.1)

“…[23] Many of the expanded carbaporphyrinoids share structural features of an archetypical hexaphyrin [24,25] framework. Thus av ariety of hexaphyrinoids incorporating different carbocyclic subunits,for example,cyclohexene, [26] hexahydronaphthalene, [27] meta-, [13,[28][29][30][31][32][33] and para-phenylene, [33][34][35][36][37][38][39] biphenylene, [14] N-confused-, [40][41][42][43] and neo-confused pyrrole, [44,45] indene, [46] azulene, [47] pyridine, [48] phenanthrene, [22] and triphenylene were synthesized and studied. [49] Thenaphthiporphyrins,that is,carbaporphyrinoids incorporating an aphthalene ring, formally share attributes of both-regular size,a nd expanded porphyrinoids (Scheme 1).…”

Expanded Carbaporphyrinoids

“…In this case, the inversion of the pyrrole rings can be attributed to structure stabilization through formation of hydrogen bonds between the NH groups and the carbonyl oxygen atoms of the indanedione substituents at the meso positions. The heteroporphyrin analogue of 145 , namely tetrathia‐di‐ p ‐benzihexaphyrin 147 , was synthesized by Sreedhar Reddy and Anand . The aromaticity of 147 is consistent with the presence of a 30 π‐electron conjugation pathway.…”

“…Further modification of 121 by the introduction of two alkylidene meso substituents surrounding the benzene subunit ( 124 ) effectively prohibited the overall macrocyclic π‐delocalization . Reddy and Anand synthesized 23,24,25‐trithia‐ p ‐benziporphyrin 125 . Interestingly, this macrocycle demonstrated no macrocyclic ring current, as evidenced by the chemical shifts of the p ‐phenylene protons (7.53 ppm), and β‐thiophenic signals ranging from 6.47 to 6.69 ppm.…”

Expandierte Carbaporphyrinoide

“…[107] Anand und Reddy stellten das 23,24,25-Trithia-pbenziporphyrin 125 her. [118] Interessanterweise zeigte dieser Makrocyclus keinen makrocyclischen Ringstrom, wie mit den chemischen Verschiebungen der p-Phenylen-Protonen (7.53 ppm) und den b-Thiophen-Signalen, die zwischen 6.47 und 6.69 ppm liegen, nachgewiesen wurde.…”

“…Das Heteroporphyrin-Analogon von 145 -Te trathiadi-p-benzihexaphyrin 147 -w urde von Anand und Sreedhar Reddy synthetisiert. [118] (ein Analogon von 145,w enngleich die sperrigen meso-Substituenten fehlen) die Konformation in Form einer Acht ein, mit Kante-zu-Fläche-ausgerichteten p-Phenylenringen, ähnlich dem Mçbius-Konformer 145-A (Schema 25). [126] Tr otz der konformativen ¾hnlichkeit zeigte 148 nicht den makrocyclischen Ringstrom, der für 145-A charakteristisch ist.…”