Tetracyanoethylene substituted triphenylamine analogues

A set of tetracyanoethylene (TCNE) substituted triphenylamine analogues (4–6) exhibiting strong intramolecular charge transfer (ICT) were designed and synthesized by the [2+2] cycloaddition–retroelectrocyclization reaction of 3 (tris-(4-phenylethynyl-phenyl)-amine) with TCNE. The reaction was found to be temperature dependent. The blue shift in the π → π∗ transition and intramolecular charge transfer (ICT) in amines 4–6 were found to be directly proportional to the number of TCNE units. The computational study shows good agreement with the experimental results and reveals that as the number of TCNE units in amine increases, HOMO–LUMO gap increases.