Effects of linkage between donors on photoinduced charge transfer in one-photon and two-photon absorption of Donor-π-Donor-π-Acceptor conjugates

Photoinduced charge transfer (CT) mechanisms of two Donor-pi-Donor-pi-Acceptor conjugates composed of ferrocene (Fc), zinc-porphyrin (ZnP), and fullerene (C-60) linked by phenylene-acetylene/acetylene during the one- (OPA) and the two-photon absorption (TPA) processes are analyzed theoretically based on the density functional theory calculations and visualization methods to study the effects of linkage between the two donors on the excitation characteristics. The change of bridge affects the efficiency of superexchange CT from Fc to ZnP in the OPA process. The one-photon excitations are dominated by local transitions of ZnP and Fc, and there is almost no efficient CT from the donors to the acceptor for both the two researched structures. In contrast, the advantage of superexchange CT from ZnP to C-60 becomes much larger than the other transition forms during the TPA process when the linkage between ZnP and Fc is changed from acetylene to phenylene-acetylene. This linkage effect in TPA would have great significance in designing novel optoelectronic devices. (C) 2022 Elsevier B.V. All rights reserved.