Solvent‐free synthesis by using a vibratory ball mill (VBM) offers the chance to access new chemical reactivity, whilst reducing solvent waste and minimising reaction times. Herein, we report the core functionalisation of N,N’‐bis(2‐ethylhexyl)‐2,6‐dibromo‐1,4,5,8‐naphthalenetetracarboxylic acid (Br2‐NDI) by using Suzuki, Sonogashira and Buchwald–Hartwig coupling reactions. The products of these reactions are important building blocks in many areas of organic electronics including organic light‐emitting diodes (OLEDs), organic field‐effect transistors (OFETs) and organic photovoltaic cells (OPVCs). The reactions proceed in as little as 1 h, use commercially available palladium sources (frequently Pd(OAc)2) and are tolerant to air and atmospheric moisture. Furthermore, the real‐world potential of this green VBM protocol is demonstrated by the double Suzuki coupling of a monobromo(NDI) residue to a bis(thiophene) pinacol ester. The resulting dimeric NDI species has been demonstrated to behave as an electron acceptor in functioning OPVCs.
Tweezer‐type receptors that form π−π stacked supramolecular complexes are important components in functional polymeric materials and molecular machines. Herein, we study how varying specific structural components of tweezer‐receptors impacts their binding. A library of tweezer receptors, each containing two π‐electron poor receptor residues and differing by the nature of the linking unit which was either a flexible 2,2′‐(ethylenedioxy)bis(ethylamine) residue or a rigid 3,3’’‐diamino‐m‐terphenyl diamine structure, were synthesised. Each tweezer formed 1 : 1 supramolecular complexes with π‐electron rich residues (1,5‐dihydroxynapthalene and pyrene) as confirmed by UV/Vis and 1H NMR spectroscopic studies. Binding constants were determined to be between 2.3×10−5 and 71 M−1 in organic solvents and were one magnitude greater in aqueous solvents for water soluble systems. The nature of the linker had variable effects on the binding constants, showing the design of tweezer type supramolecular receptors with targeted Ka values is non‐trivial and requires structural optimisation supported by binding constant determination studies.
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