Structure‐Property Relationships for Potential Inversion From Electron Acceptors Based on Thiophene‐Fused Triptycene Quinones, 1,4‐Diketones and Their Malononitrile Adducts

The synthesis and properties of a series of 11,11,12,12‐tetracyano‐9,10‐anthraquinodimethane (TCAQ) inspired electron acceptors based on thiophene‐fused quinone and triptycene motifs is presented. This has yielded insights into structure‐property relationships for establishing and modulating simultaneous two‐electron reduction processes in TCAQ analogues. These new compounds were synthesised using a Friedel‐Crafts acylation between triptycene and thiophene‐3,4‐dicarbonyl chloride. Isomeric para‐quinones featuring a [c]‐fused thiophene on one side and a β,β‐ or α,β‐fused triptycene on the other were isolated alongside a thiophene‐3,4‐diketone which bears two triptycene fragments. Knoevenagel condensation of these products with malononitrile produced a quinoidal bis(dicyanomethylene), an oxo‐dicyanomethylene and an acyclic bis(dicyanomethylene). This series of new electron accepting molecules has been studied using X‐ray crystallography and the implications of their 3D structures on NMR and UV/vis absorbance spectroscopy and cyclic voltammetry results have been ascertained with conclusions underpinned by computational methods. The products of two isomeric thiophene/triptycene para‐quinones with malononitrile provide insights into modulating potential inversion in 11,11,12,12‐tetracyano‐9,10‐anthraquinodimethane type electron‐acceptors. Intramolecular hydrogen bonding influences both the product distribution of the reaction to make the quinones, and the NMR chemical shift of the bridgehead hydrogens involved.