Enhanced Acidity, Photophysical Properties and Liposome Binding of Perfluoroalkylated Phthalocyanines Lacking C‐H Bonds

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.

Singlet oxygen-based electrosensing by molecular photosensitizers

“…3). The photocurrents were completely suppressed on N 2 purges, whether HQ was present or not, but recovered completely on admission of air, consistent with a Type II mechanism and the high 1 O 2 quantum yield ( Φ Δ ∼0.6 in acetone, methanol) previously reported for F 64 PcZn23242532. Intriguingly, for SPE|F 64 PcZn the anaerobic photocurrent (under N 2 ) exhibits a sign reversal in the presence of HQ, suggesting a direct electron transfer from HQ to F 64 PcZn and, eventually to the electrode, in agreement with a recent report on the direct photoreduction of F 64 PcZn by an electron donor in strictly oxygen-free conditions30.…”

“…The essential role of O 2 for substrate detection using the photodynamic effect observed for F 64 PcZn in solution2425 and ex vivo 2332, was confirmed by comparing photocurrents obtained in an air-saturated buffer with those obtained under an inert N 2 atmosphere (Fig. 3).…”

“…2a) produces 1 O 2 in a relatively high quantum yield232425. Unlike the protio phthalocyanine, H 16 PcZn, F 64 PcZn is stable in the presence of 1 O 2 and daughter, oxygen-centered species and other radicals2627.…”

Synthesis of novel azo-bridged phthalocyanines and their toluene vapour sensing properties

“…There is also a set of weaker vibronic satellite bands at shorter wavelengths. On the other hand, the Q band of oxo-H 2 Pc 9 exhibited single band in DMSO, suggesting that deprotonation of the inner pyrrolic H atoms in the Pc core and thus, symmetry change from D 2h to D 4h occurs due to basicity of DMSO [26][27][28]. The results suggest that the inner pyrrolic H atoms in H 2 Pc 9 are more acidic than those in H 2 Pc 4.…”

Synthesis, characterization and properties of 1,11,15,25-tetrahydroxy-4,8,18,22-bis(bridging butanedioic acid)phthalocyanine copper

“…There is also a set of weaker vibronic satellite bands at shorter wavelength. The split Q band became a single band in DMF and CHCl 3 , suggesting deprotonation of the inner pyrrolic H atoms in the Pc core, and thus symmetry change from D 2h to D 4h occurs because of the basicity of these solvents [18][19][20]. The observed Q band at 694 nm could originate from protonation of nitrogen atoms on the phthalocyanine skeleton or formation of J-aggregates between phthalocyanine molecules in DMSO.…”