jp7b03889_si_001.pdf (14.13 MB)
Charge-Gating Dibenzothiophene‑S,S‑dioxide Bridges in Electron Donor–Bridge–Acceptor Conjugates
journal contribution
posted on 2017-06-19, 13:50 authored by Gilles Yzambart, Anna Zieleniewska, Stefan Bauroth, Timothy Clark, Martin R. Bryce, Dirk M. GuldiThe
synthesis of a series of new electron donor–bridge–acceptor
(D–B–A) conjugates (18–20) comprising electron-donating zinc(II) porphyrins (ZnPs) and electron-accepting
fullerenes (C60s) connected through various co-oligomer
bridges containing both dibenzothiophene-S,S-dioxide and fluorene units is reported. Detailed investigations
using cyclic voltammetry, absorption, fluorescence, and femto/nanosecond
transient absorption spectroscopy in combination with quantum chemical
calculations have enabled us to develop a detailed mechanistic view
of the charge-transfer processes that follow photoexcitation of ZnP,
the bridge, or C60. Variations in the dynamics of charge
separation, charge recombination, and charge-transfer gating are primarily
consequences of the electronic properties of the co-oligomer bridges,
including their electron affinity and the energy levels of the excited
states. In particular, placing one dibenzothiophene-S,S-dioxide building block at the center of the molecular
bridge flanked by two fluorene building blocks, as in 20, favors hole rather than electron transfer between the remote electron
donors and acceptors, as demonstrated by exciting C60 rather
than ZnP. In 18 and 19, in which one dibenzothiophene-S,S-dioxide and one fluorene building block
constitute the molecular bridge, photoexcitation of either ZnP or
C60 results in both hole and electron transfer. Dibenzothiophene-S,S-dioxide is thus shown to be an excellent
building block for probing how subtle structural and electronic variations
in the bridge affect unidirectional charge transport in D–B–A
conjugates. The experimental results are supported by computational
calculations.