Asymmetric ZnPc-TEG photosensitizers: the effect of Pc substitution on phototoxicity

Dominic K. Muli, Pallavi Rajaputra, Youngjae You, Dominic V Mcgrath

Research output: Contribution to journalArticlepeer-review

3 Scopus citations


Asymmetric zinc phthalocyanine (ZnPc) isomers with triethylene glycol (TEG) moieties in the peripheral (1a) and non-peripheral (1b) substitution were designed, synthesized, characterized, and their phototoxicity on colon-26 cells evaluated. TEG moieties as water solubilizing groups were incorporated at peripheral or non-peripheral positions to investigate the effect of their position on the Pc on the photodynamic activity. UV/vis analyses indicated a small red-shifting of the Q band of the non-peripheral ZnPc-TEG 1b (ca. 4 nm) relative to 1a in dichloromethane and THF. n-Octanol/pH 7.4 buffer partition coefficients revealed that 1b was marginally more hydrophilic than 1a with log D7.4 values of 2.44 and 2.46, respectively. Fluorescence emission aggregation studies indicate that 1b is ca. 61% (DMSO) and 32% (phosphate buffer) less aggregated than the peripherally substituted ZnPc 1a suggesting that non-peripheral substitution decreased overall aggregation of the photosensitizers. Singlet oxygen generation studies are reported. Both ZnPc-TEGs showed negligible dark toxicity on colon 26 cells with 10 μM 1a and 1b. Irradiation (690 nm, 45 J/cm2) of the cells produced an IC50 value >25 μM for 1a and an IC50 value between 1 and 5 μM for 1b. Overall, the non-peripheral isomer 1b was found to be more photodynamically active.

Original languageEnglish (US)
Pages (from-to)6236-6239
Number of pages4
JournalTetrahedron Letters
Issue number45
StatePublished - Sep 23 2015


  • Asymmetric ZnPc
  • Peripheral and non-peripheral substitution
  • Photodynamic therapy
  • Phthalocyanine
  • Water solubility

ASJC Scopus subject areas

  • Biochemistry
  • Drug Discovery
  • Organic Chemistry


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