Titanocene as a New Acceptor (A) for Arylamine Donors (D) in D-π-A Chromophores
Pienkos, J. A.; Agakidou, D. A.; Trindle, C. O.; Herwald, D. W.; Altun, Z.; Wagenknecht, P. S. "Titanocene as a New Acceptor (A) for Arylamine Donors (D) in D-π-A Chromophores", Organometallics, 2016, 35, 2575–2578.
Charge transfer (CT) transitions are relevant in the fields of solar energy conversion and non-linear optical materials. Herein, a series of complexes with an alkynyl linkage between an aryl amine donor and a TiIV (titanocene) acceptoris reported. Each complex displays a strong (15,000 < ε < 24,000 M-1cm-1), low energy (520 < l < 560 nm) absorption ascribed to an amine to TiIV ligand-to-metal CT. This characterization is supported by UV-Vis spectroscopy, cyclic voltammetry, and TD-DFT calculations. These complexes are not photostable so an alternate architecture, wherein the amine donor is appended to the titanocene cyclopentadienyl ligand, has been designed. The molar absorptivity of the amine to TiIV CT in this latter architecture is lower (2100 M-1cm-1), indicating weaker donor-acceptor coupling. This architecture is indeed much more photostable.