Charge-Gating Dibenzothiophene‑<i>S</i>,<i>S</i>‑dioxide Bridges in Electron Donor<b>–</b>Bridge<b>–</b>Acceptor Conjugates
Gilles Yzambart
Anna Zieleniewska
Stefan Bauroth
Timothy Clark
Martin R. Bryce
Dirk M. Guldi
10.1021/acs.jpcc.7b03889.s001
https://acs.figshare.com/articles/journal_contribution/Charge-Gating_Dibenzothiophene_i_S_i_i_S_i_dioxide_Bridges_in_Electron_Donor_b_b_Bridge_b_b_Acceptor_Conjugates/5117704
The
synthesis of a series of new electron donor–bridge–acceptor
(D–B–A) conjugates (<b>18</b>–<b>20</b>) comprising electron-donating zinc(II) porphyrins (ZnPs) and electron-accepting
fullerenes (C<sub>60</sub>s) connected through various co-oligomer
bridges containing both dibenzothiophene-<i>S</i>,<i>S</i>-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 C<sub>60</sub>. 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-<i>S</i>,<i>S</i>-dioxide building block at the center of the molecular
bridge flanked by two fluorene building blocks, as in <b>20</b>, favors hole rather than electron transfer between the remote electron
donors and acceptors, as demonstrated by exciting C<sub>60</sub> rather
than ZnP. In <b>18</b> and <b>19</b>, in which one dibenzothiophene-<i>S</i>,<i>S</i>-dioxide and one fluorene building block
constitute the molecular bridge, photoexcitation of either ZnP or
C<sub>60</sub> results in both hole and electron transfer. Dibenzothiophene-<i>S</i>,<i>S</i>-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.
2017-06-19 13:50:31
charge
fluorene building blocks
co-oligomer bridges
electron transfer
ZnP
dibenzothiophene
quantum chemical calculations
C 60 results
fluorene building block
C 60
dioxide building block