Coordination control of intramolecular electron transfer in boronate ester-bridged donor–acceptor molecules

Abstract

Acid–base reaction at the bridge in a donor–acceptor molecule can influence intramolecular electron-transfer reactions; this has been demonstrated in boronate ester bridged zinc porphyrin–diimide dyads in which intramolecular electron transfer reaction has been completely suppressed by coordination of F^– on the bridge boron.

References

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7. The transient absorption spectra indicate that the S₁ state of the ZP does not undergo any ET and is converted to the T₁ state absorbing at 455 nm.
8. The one-electron redox potentials of the donor and the acceptor moieties have been measured in DMF by cyclic voltammetry: E_ox(ZP)= 0.22, E_red(PI)=–1.24 and E_ox(NI)=–0.98 V for 1a–c, and E_ox(ZP)= 0.22, E_red(PI)=–1.18 and E_red(NI)=–0.94 V for 2a–cvs. ferrocene–ferrocenium ion.
9. Estimated distance between the ZP and the boron is 9.4 Å and those between the boron and the diimide are 7.6 and 7.8 Å in 1b and 1c, respectively.
10. MO calculations were performed using MacSpartan Plus (ab initio, 3-21G basis set). Calculated LUMO energies are 3.4, 8.2, and 4.1 eV for neutral 9, F^–-coordinated 9, and an acetal reference bridge, respectively.