Photophysical and photochemical properties of non-peripheral butoxy-substituted phthalocyanines with absorption in NIR range

Tuning Photochemical and Photophysical Properties of P(V) Phthalocyanines

The ability of P(V) phthalocyanines (Pcs) for efficient singlet oxygen (SO) generation was demonstrated for the first time by the example of unsubstituted and α- and β-octabutoxy-substituted P(V)Pcs with hydroxy, methoxy and phenoxy ligands in the apical positions of the octahedral P centre. Variation of substituents in Pc ring and P(V) axial ligands allows careful tuning of photophysical and photochemical properties. Indeed, a combination of BuO groups in the β-positions of the Pc ring and PhO groups as axial ligands provides significant SO generation quantum yields up to 90%; meanwhile, the values of SO generation quantum yields for others investigated compounds vary from 27 to 55%. All the complexes, except α-substituted P(V)Pc, demonstrate fluorescence with moderate quantum yields (10-16%). The introduction of electron-donating butoxy groups, especially in the α-position, increases the photostability of P(V)Pcs. Moreover, it has been shown in the example of β-BuO-substituted P(V) that the photostability depends on the nature of axial ligands and increases in the next row: OPh < OMe < OH. The presence of oxy/hydroxy axial ligands on the P(V) atom makes it possible to switch the photochemical and photophysical properties of P(V)Pcs by changing the acidity of the media.

Non-peripherally alkylamino-substituted phthalocyanines: Synthesis, spectral, photophysical and acid-base properties

Non-peripherally substituted metal-free and zinc phthalocyanines (Pcs) bearing four diethylamino groups and four Br atoms were prepared. Optimal conditions for synthesis of corresponding precursor ([Formula: see text] 3-bromo-6-(diethylamino)phthalonitrile) either by nucleophilic substitution or by Buchwald–Hartwig coupling were studied. Noteworthy, 3,6-bis(diethylamino)phthalonitrile was also formed, nevertheless only at low yield (typically below 1%) and all attempts for its cyclotetramerization failed. Q bands of prepared Pcs were strongly red shifted up to the near-IR region (769 and 800 nm in THF for zinc and metal-free Pc, respectively). Unusually large hypsochromic shifts of the Q bands, 130 and 80 nm for metal-free and zinc Pc, respectively, were observed upon treating these Pcs with trifluoroacetic acid, which was attributed to the protonation of non-peripheral amines. Treatment with sulfuric acid led to subsequent protonation on the azomethine nitrogens as well. Photophysical study revealed low fluorescence emission of both derivatives ([Formula: see text] <0.03, in THF) and efficient singlet oxygen production only for zinc Pc ([Formula: see text] 0.77 in THF and 0.60 in DMF).

Crown-substituted naphthalocyanines: synthesis and supramolecular control over aggregation and photophysical properties

Tetra-15-crown-5-naphthalocyanines as first representatives of crown-substituted π-extended phthalocyanines were synthesized and characterized. The possibility to control their aggregation and photophysical properties by reversible formation of supramolecular assemblies in the presence of KOAc was demonstrated.