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Symmetry controlled photo-selection and charge separation in butadiyne-bridged donor-bridge-acceptor compounds.

Publication ,  Journal Article
Li, X; Valdiviezo, J; Banziger, SD; Zhang, P; Ren, T; Beratan, DN; Rubtsov, IV
Published in: Physical chemistry chemical physics : PCCP
May 2020

Electron transfer (ET) in donor-bridge-acceptor (DBA) compounds depends strongly on the structural and electronic properties of the bridge. Among the bridges that support donor-acceptor conjugation, alkyne bridges have attractive and unique properties: they are compact, possess linear structure permitting access to high symmetry DBA molecules, and allow torsional motion of D and A, especially for longer bridges. We report conformation dependent electron transfer dynamics in a set of novel DBA compounds featuring butadiyne (C4) bridge, N-isopropyl-1,8-napthalimide (NAP) acceptors, and donors that span a range of reduction potentials (trimethyl silane (Si-C4-NAP), phenyl (Ph-C4-NAP), and dimethyl aniline (D-C4-NAP)). Transient mid-IR absorption spectra of the C[triple bond, length as m-dash]C bridge stretching modes, transient spectra in the visible range, and TD-DFT calculations were used to decipher the ET mechanisms. We found that the electronic excited state energies and, especially, the transition dipoles (S0 → Sn) depend strongly on the dihedral angle (θ) between D and A and the frontier orbital symmetry, offering an opportunity to photo-select particular excited states with specific ranges of dihedral angles by exciting at chosen wavelengths. For example, excitation of D-C4-NAP at 400 nm predominantly prepares an S1 excited state in the planar conformations (θ ∼ 0) but selects an S2 state with θ ∼ 90°, indicating the dominant role of the molecular symmetry in the photophysics. Moreover, the symmetry of the frontier orbitals of such DBA compounds not only defines the photo-selection outcome, but also determines the rate of the S2 → S1 charge separation reaction. Unprecedented variation of the S2-S1 electronic coupling with θ by over four orders of magnitude results in slow ET at θ ca. 0° and 90° but extremely fast ET at θ of 20-60°. The unique features of high-symmetry alkyne bridged DBA structures enable frequency dependent ET rate selection and make this family of compounds promising targets for the vibrational excitation control of ET kinetics.

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Published In

Physical chemistry chemical physics : PCCP

DOI

EISSN

1463-9084

ISSN

1463-9076

Publication Date

May 2020

Volume

22

Issue

17

Start / End Page

9664 / 9676

Related Subject Headings

  • Chemical Physics
  • 51 Physical sciences
  • 40 Engineering
  • 34 Chemical sciences
  • 09 Engineering
  • 03 Chemical Sciences
  • 02 Physical Sciences
 

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Li, X., Valdiviezo, J., Banziger, S. D., Zhang, P., Ren, T., Beratan, D. N., & Rubtsov, I. V. (2020). Symmetry controlled photo-selection and charge separation in butadiyne-bridged donor-bridge-acceptor compounds. Physical Chemistry Chemical Physics : PCCP, 22(17), 9664–9676. https://doi.org/10.1039/d0cp01235a
Li, Xiao, Jesús Valdiviezo, Susannah D. Banziger, Peng Zhang, Tong Ren, David N. Beratan, and Igor V. Rubtsov. “Symmetry controlled photo-selection and charge separation in butadiyne-bridged donor-bridge-acceptor compounds.Physical Chemistry Chemical Physics : PCCP 22, no. 17 (May 2020): 9664–76. https://doi.org/10.1039/d0cp01235a.
Li X, Valdiviezo J, Banziger SD, Zhang P, Ren T, Beratan DN, et al. Symmetry controlled photo-selection and charge separation in butadiyne-bridged donor-bridge-acceptor compounds. Physical chemistry chemical physics : PCCP. 2020 May;22(17):9664–76.
Li, Xiao, et al. “Symmetry controlled photo-selection and charge separation in butadiyne-bridged donor-bridge-acceptor compounds.Physical Chemistry Chemical Physics : PCCP, vol. 22, no. 17, May 2020, pp. 9664–76. Epmc, doi:10.1039/d0cp01235a.
Li X, Valdiviezo J, Banziger SD, Zhang P, Ren T, Beratan DN, Rubtsov IV. Symmetry controlled photo-selection and charge separation in butadiyne-bridged donor-bridge-acceptor compounds. Physical chemistry chemical physics : PCCP. 2020 May;22(17):9664–9676.
Journal cover image

Published In

Physical chemistry chemical physics : PCCP

DOI

EISSN

1463-9084

ISSN

1463-9076

Publication Date

May 2020

Volume

22

Issue

17

Start / End Page

9664 / 9676

Related Subject Headings

  • Chemical Physics
  • 51 Physical sciences
  • 40 Engineering
  • 34 Chemical sciences
  • 09 Engineering
  • 03 Chemical Sciences
  • 02 Physical Sciences