Comparison of the Optical and Electrochemical Properties of Bi(perylene diimide)s Linked through Ortho and Bay Positions

摘要

The Ullmann homocoupling of 2-bromo-perylene diimides (PDIs) gave [2,2′-biperylene]-3,4:9,10:3′,4′:9′,10′-tetrakis(dicarboximide)s, 2,2′-bi(PDI)s, and the Suzuki coupling of a PDI-2-boronic ester and a 1-bromo-PDI gave a [1,2′-biperylene]-3,4:9,10:3′,4′:9′,10′-tetrakis(dicarboximide), 1,2′-bi(PDI). These were compared with [1,1′-biperylene]-3,4:9,10:3′,4′:9′,10′-tetrakis(dicarboximide)s, 1,1′-bi(PDI)s. Solution absorption spectra suggest that the PDIs in 2,2′-bi(PDI)s are more planar and less strongly coupled than those in 1,1′-bi(PDI)s, which is consistent with density functional theory calculations. 2,2′-Bi(PDI)s are less easily reduced than 1,1′- and 1,2′-bi(PDI)s by ca. 70–90 mV. Bulk heterojunction organic solar cells incorporating a 2,2′-bi(PDI) acceptor behaved similarly to those employing its 1,1′-bi(PDI) analogue.