5,10,20,25,35,40-hexanornonapyrrin: The largest structurally characterized oligopyrrole prepared to date

The synthesis and X-ray diffraction-based characterization of a nonapyrrolic oligomer 2 [5,5 ''-bis((2-(ethoxycarbonyl)-3,4,3',4',3 '',4 ''-hexamethyl-5,2':5',2 ''-terpyrrol-5 ''-yl)vinyl)-3,4,3',4',3 '',4 ''-hexamethyl-2,2':5',2 ''-terpyrrole] is reported. It was prepared by condensing 2 equiv of the 2-(ethoxycarbonyl)-2 ''-formyl-3,4,3',4',3 '',4 ''-hexamethyl-5,2':5',5 ''-terpyrrole (8) with 1 equiv of 3,4,3',4',3 '',4 ''-hexamethyl-2,2':5',2 ''-terpyrrole (9). A similar procedure, involving the condensation of 1 equiv of the 2-(ethoxycarbonyl)-2 ''-formyl-3,4,3',4',3 '',4 ''-hexamethyl-5,2':5',5 ''-terpyrrole (8) with 1 equiv of 2-(ethoxycarbonyl)-3,4,3',4',3 '',4 ''-hexamethyl-5,2':5',2 ''-terpyrrole (10) was found to give rise to the corresponding hexameric system 4 bis(2-(ethoxycarbonyl)-3,3,3',4',3 '',4 ''-hexamethyl-5,2':5',2 ''-terpyrrol-5 ''-yl)methene, a system that was likewise characterized by X-ray diffraction methods. It was also found that replacing the monoformyl terpyrrole 8 by the corresponding bipyrrole, namely 2-(ethoxycarbonyl)-2'-formyl-3,4,3',4'-tetramethyl-5,5'-bipyrrole (13), and condensing 2 equiv of it with 1 equiv of 9 gives rise to the heptapyrrole 5,5 ''-bis((2-(ethoxycarbonyl)-3,4,3',4'-tetramethyl-5,2'-bipyrrol-5'-yl)vinyl)-3,4,3',4',3 '',4 ''-hexamethyl-2,2':5',2 ''-terpyrrole (3).