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Enhanced Acidity, Photophysical Properties and Liposome Binding of Perfluoroalkylated Phthalocyanines Lacking C‐H Bonds
Author(s) -
Minnes Refael,
Weitman Hana,
Lee HyunJin,
Gorun Sergiu M.,
Ehrenberg Benjamin
Publication year - 2006
Publication title -
photochemistry and photobiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.818
H-Index - 131
eISSN - 1751-1097
pISSN - 0031-8655
DOI - 10.1562/2005-11-08-ra-732
Subject(s) - protonation , liposome , lipophilicity , chemistry , hydrogen bond , phthalocyanine , binding constant , base (topology) , quantum yield , free base , medicinal chemistry , hydrophobic effect , stereochemistry , molecule , photochemistry , binding site , organic chemistry , ion , fluorescence , biochemistry , mathematical analysis , physics , salt (chemistry) , mathematics , quantum mechanics
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(isopropy1) phthalocyanine, F 64 PcH 2 , are reported. The perfluoroalkylation of the phthalocyanine core renders the hydrogen atoms acidic, with a pK a = 6. The F 64 Pc ‐2 dianion is detected already at pH 3, by singular‐value decomposition analysis of electronic spectra. F 64 Pc ‐2 generates 1 O 2 with quantum yields Φ Δ = 0.252 (in MeOH) and 0.019 in liposomes. Metallation of the Pc macrocycle to yield F 64 PcZn increases Φ Δ to 0.606 and 0.126 in MeOH and liposomes, respectively. Surprisingly, F 64 Pc ‐2 (but not F 64 PcH 2 or F 64 PcZn) binds strongly to liposomes, with a binding constant K b = 25 (mg/mL) ‐1 . The fully protonated F 64 PcH 2 , but not the zwitterionic F 64 Pc ‐2 , might favor hydrogen bonding, thus reducing its lipophilicity. Similarly, the Lewis acidity of Zn in F 64 PcZn, and thus its ability to bind water within a hydrophobic perfluoroalkyl pocket, is significantly enhanced by the fluorinated substituents.