Dicyanopentafulvene-fused perylene diimide and its stable radical anion

Abstract

A novel PDI-based electron acceptor, namely dicyanopentafulvene-fused PDI (3) is presented via Knoevenagel condensation with malononitrile in a simple and efficient way from the key intermediate cyclopentadienone-annulated PDI (2). The resulting degenerated LUMO level of approximately −4.29 eV is based on the fusion of multiple cyano groups and delocalization of π-electrons across the molecular skeleton. A stable radical anion is thus produced between 3 and cobaltocene (CoCp2) in 1:1 ratio, which was unambiguously confirmed by spectroscopic characterization and structural elucidation. The broad NIR band from 900 nm to 1300 nm is characteristic of delocalized unpaired electron in CT complex 3·CoCp2. Single crystal X-ray diffraction analyses revealed distinction in the molecular shape and packing arrangement before and after forming radical anion. Remarkably, the presence of intensive π···π interactions endow them good electron transporting characteristics, signifying the prospects in the organic electronic or spintronic devices.