A Family of Heterocyclic Naphthalene Diimide (NDI) Analogues: Comparing Parent Isoquinoline Diimides and Phthalazine Diimides with NDI

Parent isoquinoline diimide (IQDI) and phthalazine diimide (PTDI), as two new heterocyclic analogues of naphthalene diimides (NDIs), have been synthesized through an oxidative strategy in 35-79 % yield. X-ray crystallography has been used to support the formation of IQDI, which also show fluorescence quantum yields of 3.5 %. The electrochemical and electrical properties of these molecules have been studied. The electrochemical results show an interesting trend in first reduction potential PTDI<IQDI<NDI and 0.1 eV changes in the optical band gap (E-g) leading to the trend IQDI<NDI<PTDI, as supported by DFT calculations. While initial top gate OFET devices yield charge mobilities less than NDIs, the basis of this study intimates that IQDIs and PTDIs hold promise for applications commensurate with NDIs.