Impact of Redox Stimuli on Ferrocene–Buckybowl Complexes: Switchable Optoelectronic and Nonlinear Optical Properties

A series of redox-active complexes 1–3 (1,1′-diquadrannulenylferrocene, 1,1′-dicorannulenylferrocene, 1,1′-disumanenylferrocene) and their corresponding conformational isomers that are composed of ferrocene donor and various acceptors of different buckybowl (open bowl-shaped polyaromatic hydrocarbon) subunits have been investigated by density functional theory. The nature of the redox property makes it possible to develop novel examples of chromophores that are amenable to molecular switches, which can therefore be used in optical devices. The complexes 1–3, with high thermal and chemical stabilities, show π–π stacking interaction between two buckybowl subunits, and support for the presence of significant donor–acceptor interaction was obtained from the employment of the natural bond orbital charge and charge decomposition analysis. Both one-electron oxidation and one- and two-electron reduction have been considered. The results show some important electronic structure changes upon oxidation/reduction that are accompanied by significant differences in the corresponding absorption spectra and second-order nonlinear optical properties. These differences are due to a change in the charge transfer pattern. The redox switch ability suggests that these ferrocene–buckybowl complexes can be viewed as redox-triggered nonlinear optical switches with one of the complexes having an on/off ratio of 100.2 for the hyperpolarizability values. Thus, our work has helped to establish ferrocene–buckybowl complexes as versatile and fascinating nonlinear optical switching compounds with a promising future.