Titanocene as a New Acceptor (A) for Arylamine Donors (D) in D-pi-A Chromophores

Abstract

Charge transfer (CT) transitions are relevant in the fields of solar energy conversion and nonlinear optical materials. Herein, a series of complexes with an alkynyl linkage between an aryl amine donor and a Ti-IV (titanocene) acceptor is reported. Each complex displays a strong (15000 < epsilon < 24,000 M(-1)cm(-1)), low-energy (520 < lambda < 560 nm) absorption ascribed to an amine to Ti-IV ligand-to-metal CT. This characterization is supported by UV-vis spectroscopy, cyclic voltammetry, and TD-DFT calculations. These complexes are not photostable; therefore, an alternate architecture, wherein the amine donor is appended to the titanocene cyclopentadienyl ligand, has been designed. The molar absorptivity of the amine to Ti-IV CT in this latter architecture is lower (2100 M-1 cm(-1)), indicating weaker donor-acceptor coupling. This architecture is indeed much more photostable.