Efficient Radical-Enhanced Intersystem Crossing in an NDI-TEMPO Dyad: Photophysics, Electron Spin Polarization, and Application in Photodynamic Therapy

Wang Z., Gao Y., Hussain M., Kundu S., Rane V., HAYVALI M., ...Daha Fazla

CHEMISTRY-A EUROPEAN JOURNAL, cilt.24, sa.70, ss.18663-18675, 2018 (SCI-Expanded) identifier identifier identifier

  • Yayın Türü: Makale / Tam Makale
  • Cilt numarası: 24 Sayı: 70
  • Basım Tarihi: 2018
  • Doi Numarası: 10.1002/chem.201804212
  • Dergi Adı: CHEMISTRY-A EUROPEAN JOURNAL
  • Derginin Tarandığı İndeksler: Science Citation Index Expanded (SCI-EXPANDED), Scopus
  • Sayfa Sayıları: ss.18663-18675
  • Anahtar Kelimeler: electron spin polarization, EPR spectroscopy, intersystem crossing, photodynamic therapy, photophysics, photosensitizers, TRIPLET-TRIPLET ANNIHILATION, TIME-RESOLVED EPR, PHOTOINDUCED CHARGE SEPARATION, PHOTON UP-CONVERSION, STATE FORMATION, SYNTHETIC APPLICATIONS, PHOTOREDOX CATALYSIS, ENERGY-TRANSFER, EXCITED-STATE, PI-TOPOLOGY
  • Ankara Üniversitesi Adresli: Evet

Özet

A compact naphthalenediimide (NDI)-2,2,6,6-tetramethylpiperidinyloxy (TEMPO) dyad has been prepared with the aim of studying radical-enhanced intersystem crossing (EISC) and the formation of high spin states as well as electron spin polarization (ESP) dynamics. Compared with the previously reported radical-chromophore dyads, the present system shows a very high triplet state quantum yield (phi(T)=74 %), a long-lived triplet state (tau(T)=8.7 mu s), fast EISC (1/k(EISC)=338 ps), and absorption in the red spectral region. Time-resolved electron paramagnetic resonance (TREPR) spectroscopy showed that, upon photoexcitation in fluid solution at room temperature, the D-0 state of the TEMPO moiety produces strong emissive (E) polarization owing to the quenching of the excited singlet state of NDI by the radical moiety (electron exchange J>0). The emissive polarization then inverts into absorptive (A) polarization within about 3 mu s, and then relaxes to a thermal equilibrium while quenching the triplet state of NDI. The formation and decay of the quartet state were also observed. The dyad was used as a three-spin triplet photosensitizer for triplet-triplet annihilation upconversion (quantum yield phi(UC)=2.6 %). Remarkably, when encapsulated into liposomes, the red-light-absorbing dyad-liposomes show good biocompatibility and excellent photodynamic therapy efficiency (phototoxicity EC50=3.22 mu m), and therefore is a promising candidate for future less toxic and multifunctional photodynamic therapeutic reagents.