Twisted BODIPY derivative: intersystem crossing, electron spin polarization and application as a novel photodynamic therapy reagent

Yu Dong, Prashant Kumar, Partha Maity, Ivan Kurganskii, Shujing Li, Ayhan Elmali, Jianzhang Zhao, Daniel Escudero, Huijian Wu, Ahmet Karatay, Omar F. Mohammed, Matvey Fedin

Research output: Contribution to journalArticlepeer-review

2 Citations (Scopus)

Abstract

The photophysical properties of a heavy atom-free BODIPY derivative with a twisted p-conjugated framework were studied. Efficient intersystem crossing (ISC quantum yield: 56%) and an exceptionally long-lived triplet state were observed (4.5 ms in solid polymer film matrix and 197.5 µs in solution). Time-resolved electron paramagnetic resonance (TREPR) spectroscopy and DFT computations confirmed the delocalization of the triplet state on the whole twisted p-conjugated framework and the zero-field-splitting (ZFS)Dparameter ofD= -69.5 mT, which is smaller than that of 2,6-diiodoBODIPY (D= -104.6 mT). The electron spin polarization (ESP) phase pattern of the triplet state TREPR spectrum of the twisted BODIPY is (a, a, e, a, e, e), which is different from that of 2,6-diiodo BODIPY (e, e, e, a, a, a), indicating that the electron spin selectivity of the ISC of the twisted structure is different from that of the spin orbital coupling effect. According to the computed spin-orbit coupling matrix elements (0.154-1.964 cm-1), together with the matched energy of the S1/Tnstates, ISC was proposed to occurviaS1?T2/T3. The computational results were consistent with TREPR results on the electron spin selectivity (the overpopulation of the TYsublevel of the T1state). The advantage of the long-lived triplet state of the twisted BODIPY was demonstrated by its efficient singlet oxygen (1O2) photosensitizing (F?= 50.0%) even under a severe hypoxia atmosphere (pO2= 0.2%, v/v). A high light toxicity (EC50= 1.0 µM) and low dark toxicity (EC50= 78.5 µM) were observed for the twisted BODIPY, and thus the cellular studies demonstrate its potential as a novel potent heavy atom-free photodynamic therapy (PDT) agent.

Original languageEnglish
Pages (from-to)8641-8652
Number of pages12
JournalPhysical Chemistry Chemical Physics
Volume23
Issue number14
DOIs
Publication statusPublished - 14 Apr 2021

OECD FOS+WOS

  • 1.03 PHYSICAL SCIENCES AND ASTRONOMY
  • 1.04 CHEMICAL SCIENCES
  • 1.04.EI CHEMISTRY, PHYSICAL
  • 1.03.UH PHYSICS, ATOMIC, MOLECULAR & CHEMICAL

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