Enhanced acidity, photophysical properties and liposome binding of perfluoroalkylated phthalocyanines lacking C-H bonds

Photochemistry and Photobiology
Refael MinnesBenjamin Ehrenberg

Abstract

The acid-base, spectroscopic, photophysical and liposome-binding properties of the recently synthesized free base, 29H,31H,1,4,8,11,15,18,22,25-octafluoro-2,3,9,10,16,17,23, 24-octakisperfluoro(isopropyl) phthalocyanine, F64PcH2, are reported. The perfluoroalkylation of the phthalocyanine core renders the hydrogen atoms acidic, with a pK(a) = 6. The F64Pc(-2) dianion is detected already at pH 3, by singular-value decomposition analysis of electronic spectra. F64Pc(-2) generates 1O2 with quantum yields phi(delta) = 0.252 (in MeOH) and 0.019 in liposomes. Metallation of the Pc macrocycle to yield F64PcZn increases phi(delta) to 0.606 and 0.126 in MeOH and liposomes, respectively. Surprisingly, F64Pc(-2) (but not F64PcH2 or F64PcZn) binds strongly to liposomes, with a binding constant K(b) = 25 (mg/mL)(-1). The fully protonated F64PcH2, but not the zwitterionic F64Pc(-2), might favor hydrogen bonding, thus reducing its lipophilicity. Similarly, the Lewis acidity of Zn in F64PcZn, and thus its ability to bind water within a hydrophobic perfluoroalkyl pocket, is significantly enhanced by the fluorinated substituents.

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Citations

Jul 9, 2008·Chemistry and Physics of Lipids·Refael MinnesBenjamin Ehrenberg
Jan 29, 2016·Chemphyschem : a European Journal of Chemical Physics and Physical Chemistry·Łukasz ŁapokMaria Nowakowska
Jul 10, 2013·Dalton Transactions : an International Journal of Inorganic Chemistry·Sevinc Zehra TopalCatherine Hirel
May 21, 2014·Dalton Transactions : an International Journal of Inorganic Chemistry·Hans MoonsSabine Van Doorslaer
Jul 10, 2019·Analytical Chemistry·Liselotte NevenKarolien De Wael

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electron microscopy
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