The Photophysics and Photochemistry of a series of Phthalocyanines as Potential Photosensitisers in Photodynamic Therapy

Abstract The photophysical and photochemical measurements have been made on 3 series of novel alpha octa(alkyl-substituted) phthalocyanines. Each series is defined by the distinct non-metal or metal ion centre, silicon hydroxide, zinc(II) and palladium(II). It is well documented that the phthalocyanine molecule possesses several distinct properties, including absorption in the red, low fluorescence and high triplet quantum yields that make it an ideal candidate as a potential photosensitiser in photodynamic therapy. Photodynamic therapy is an alternative treatment to cancer using a photosensitiser, which is preferentially absorbed by malignant cells and remains dormant until activated by red light. This results in the formation of singlet delta oxygen via the excited state of the photosensitiser. The generation of singlet oxygen leads to cell death. Fluorescence quantum yields and lifetimes, triplet quantum yields, lifetimes and energies and singlet delta oxygen quantum yields were measured in 1% v/v pyridine in toluene. The effects of alkyl substitution, with increasing chain length, variation of metal ion centre and the core modification of the phthalocyanine unit are investigated and compared relative to the unsubstituted parent molecules, SiPc, ZnPc and PdPc. All substituted phthalocyanines exhibited a typical phthalocyanine absorption spectrum with significant red-shift of the Q-band maxima. Q-band maxima for all compounds ranged between 660 – 712 nm and extinction coefficients of the Q-band between 10-4 – 10-5 M-1 cm-1. All compounds also exhibited triplet quantum yields in the range 0.52 – iii 0.96 and singlet delta oxygen quantum yields of 0.49 – 0.94, illustrating promising photophysical and photochemical properties for photodynamic therapy.

Name dc:type.qualificationname

phd

Level dc:type.qualificationlevel

doctoral

Grantor dc:publisher.institution

University of East Anglia

Year dc:date.issued

2013

Author dc:creator

• Van Leeuwen, Magda

Language dc:language

en