Ferrocenyl substituted triphenylamine based donor-acceptor molecular systems; synthesis, photophysical, electrochemical, and theoretical studies

A series of push-pull molecular systems 5-14 were designed, and synthesized by the Sonogashira cross-coupling, Knoevenagel condensation, and cycloaddition reactions. The donor 'ferrocenyl substituted triphenylamine' was kept constant, whereas the acceptors were varied (malononitrile, indanone, and tetralone). The electronic absorption spectra of the ferrocenyl substituted triphenylamine based donor-acceptor (D-A) compounds 5-9 exhibit intense intramolecular charge transfer (ICT) band in the visible region (415-502 nm). The incorporation of the tetracyanoethylene (TCNE) group in compounds 5-9 results in new D-A system 10-14, which exhibits the ICT band in the region 630-700 nm. The electrochemical studies suggest considerable donor-acceptor interaction. The computational studies reveal strong D-A interaction, and show good agreement with the experimental results.