Intersystem Crossing and Electron Spin Selectivity in Anthracene-Naphthalimide Compact Electron Donor-Acceptor Dyads Showing Different Geometry and Electronic Coupling Magnitudes

Kepeng Chen, Ivan V. Kurganskii, Xue Zhang, Ayhan Elmali, Jianzhang Zhao, Ahmet Karatay, Matvey V. Fedin

Research output: Contribution to journalArticlepeer-review

1 Citation (Scopus)

Abstract

Anthracene-naphthalimide (An-NI) compact electron donor-acceptor dyads were prepared, in which the orientation and distance between the two subunits were varied by direct connection or with intervening phenyl linker. Efficient intersystem crossing (ISC) and long triplet state lifetime (ΦΔ=92 %, τT=438 μs) were observed for the directly connected dyads showing a perpendicular geometry (81°). This efficient spin-orbit charge transfer ISC (SOCT-ISC) takes 376 fs, inhibits the direct charge recombination (CR) to ground state (1CT→S0, takes 3.04 ns). Interestingly, efficient SOCT-ISC for dyads with intervening phenyl linker (ΦΔ=40 % in DCM) was also observed, although the electron donor and acceptor adopt almost coplanar geometry (dihedral angle: 15°). Time-resolved electron paramagnetic resonance (TREPR) spectroscopy shows that the electron spin polarization of the triplet state, i. e. the electron spin selectivity of ISC, is highly dependent on the dihedral angle and the linker. For the dyads showing weaker coupling between the donor and acceptors, the charge separation and the intramolecular triplet energy transfer are inhibited at 80 K (frozen solution), because both the 3An and 3NI states were observed and the ESP are same as compared to the native anthracene and naphthalimide, which unravel their origin. The dyads were used as triplet photosensitizers for triplet−triplet annihilation upconversion (TTA UC). High UC quantum yield (ΦUC=12.9 %) as well as a large anti-Stokes shift (0.72 eV) was attained by excitation into the CT absorption band.

Original languageEnglish
Pages (from-to)7572-7587
Number of pages16
JournalChemistry - A European Journal
Volume27
Issue number27
DOIs
Publication statusPublished - 12 May 2021

Keywords

  • anthracene
  • charge transfer
  • electron spin polarization
  • intersystem crossing
  • upconversion

OECD FOS+WOS

  • 2.04 CHEMICAL ENGINEERING
  • 1.04 CHEMICAL SCIENCES
  • 1.04.DY CHEMISTRY, MULTIDISCIPLINARY

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