Synthesis and Photophysical Properties of Hexaphenylbenzene–Pyrrolo[3,2-b]pyrroles

Abstract

Methods for the synthesis of pyrrolo[3,2-b]pyrroles containing hexaphenylbenzene moieties at the 2- and 5-positions or the 1- and 4-positions have been developed. It was shown that placing a hexaphenylbenzene moiety at the 2- and 5-positions requires a Diels–Alder reaction between an alkyne-substituted pyrrolopyrrole core and a 2,3,4,5-tetraphenylcyclopenta-2,4-dien-1-one. The resulting dyes show a strong blue fluorescence that was hypsochromically shifted by chlorination at the 3- and 6-positions. The overall conjugation between the hexaphenylbenzene moieties and the pyrrolopyrrole core is limited, as evident from their photophysical properties. The hexaphenylbenzene moieties attached to the pyrrolo[3,2-b]pyrrole core could not be transformed into hexa-peri-hexabenzocoronenes through intramolecular oxidative aromatic coupling.

Relating Design and Optoelectronic Properties of 1,4-Dihydropyrrolo[3,2-b]pyrroles Bearing Biphenyl Substituents

“…The para -substituted chromophores, including methyl (DHPP 3 ), methoxy (DHPP 4 ), trifluoromethyl (DHPP 5 ), and cyano (DHPP 6 ) substituents, were synthesized in addition to chromophores with substituents at various positions around the benzene ring or alternative aromatics (DHPPs 7 – 12 , Scheme S2). After workup and purification, the π-extended DHPPs were obtained in moderate-to-high yields that were consistent with previous reports involving Pd-catalyzed reactions of DHPPs. ,,,,, The structure and purity of the DHPPs were confirmed via 1 H and 13 C NMR in tandem with melting point experiments, all of which can be found in the Supporting Information as Figures S1–24 and Table S1. Overall, these efforts represent a robust route to achieving π-extension through the 2,5-positions of DHPP chromophores as an additional strategy for tailoring DHPP dyes.…”

“…After workup and purification, the π-extended DHPPs were obtained in moderate-to-high yields that were consistent with previous reports involving Pd-catalyzed reactions of DHPPs. 25 , 26 , 32 , 35 , 39 , 40 The structure and purity of the DHPPs were confirmed via 1 H and 13 C NMR in tandem with melting point experiments, all of which can be found in the Supporting Information as Figures S1–24 and Table S1. Overall, these efforts represent a robust route to achieving π-extension through the 2,5-positions of DHPP chromophores as an additional strategy for tailoring DHPP dyes.…”