We present a comprehensive description of the unique properties of newly developed phthalocyanines (Pcs) containing main-group elements that absorb and emit in the near-IR region. Group 16 (S, Se, and Te) elements and group 15 (P, As, and Sb) elements were used as peripheral and central (core) substituents. With the introduction of group 16 elements into free-base Pc, a red-shift of the Q-band was observed, as a result of the electron-donating ability of group 16 elements particularly at the α positions. An X-ray crystallographic analysis of α-ArS-, ArSe-, and ArTe-linked free-base Pcs was also successfully performed, and the relationship between structure and optical properties was clarified. When a group 15 element ion was introduced into the center of the Pc ring, the resulting Pcs showed a single Q-band peak beyond 1000 nm (up to 1056 nm in CH2Cl2). In particular, [(ArS)8PcP(OMe)2]+ and [(ArS)8PcAs(OMe)2]+ exhibited a distinct fluorescence in the 960–1400 nm region with moderate quantum yields. The at...

Design, synthesis, and properties of phthalocyanine complexes with main-group elements showing main absorption and fluorescence beyond 1000 nm.

Novel zinc, magnesium, and metal-free octasubstituted phthalocyanine photosensitizers bearing [(triethylammonio)ethyl]sulfanyl substituents in the peripheral or nonperipheral positions were synthesized and investigated for their photophysical properties (ΦΔ value up to 0.91, λmax up to 750 nm) and photodynamic anticancer activity. The photodynamic treatment of 3T3, HeLa, SK-MEL-28, and HCT 116 cancer cells revealed that the magnesium complexes were not active (IC50 > 100 μM), whereas the IC50 values of the zinc complexes typically reached values in the submicromolar range with low toxicity in the dark (TC50 ≈ 1500 μM). The subcellular changes upon photodynamic treatment of the HeLa cells indicated that the studied photosensitizers induced damage primarily to the lysosomes, which was followed by a relocalization and damage to other organelles. The time-lapse morphological changes along with the flow cytometry and caspase activity measurements indicated a predominant involvement of necrosis-like cell death.

Far-red-absorbing cationic phthalocyanine photosensitizers: synthesis and evaluation of the photodynamic anticancer activity and the mode of cell death induction.

Tetrapyrazinoporphyrazines and their metal derivatives. Part I: Synthesis and basic structural information

Tetrapyrazinoporphyrazines and their metal derivatives. Part II: Electronic structure, electrochemical, spectral, photophysical and other application related properties

Despite the manifold use of heterocyclic fluorophores, only a fraction of the desired dye diversity can be accessed by contemporary synthetic approaches. Herein, we describe a modular method that converts various carboxylic acid esters directly into a broad spectrum of heteroanthrylium fluorophores. The double addition of heteroatom-bridged 1,5-bifunctional organomagnesium reagents to esters leads to the formation of acridinium, xanthylium, and SiR fluorophores after dehydrative acidic work-up. This one-step synthetic method provides access to organophotoredox catalysts for dual catalysis with nickel and dyes amenable to fluorescence enhancement.

Direct Transformation of Esters into Heterocyclic Fluorophores.

Magnesium(II), zinc(II), and metal-free phthalocyanines (Pcs) and azaphthalocyanines (AzaPcs) containing alkylsulfanyl, aryloxy, and dialkylamino peripheral substituents have been synthesized. The complexation of magnesium(II) by metal-free Pcs and AzaPcs has been studied in detail to determine the optimal reaction conditions necessary to ensure a complete conversion. Photophysical and photochemical measurements in tetrahydrofuran showed that magnesium(II) AzaPcs with aryloxy and alkylsulfanyl substituents have excellent fluorescent properties (Φ(F) up to 0.73) and that the corresponding zinc(II) Pcs are efficient singlet oxygen producers (Φ(Δ) up to 0.68). The presence of dialkylamino substituents causes intramolecular charge transfer within the molecule that competes with fluorescence and singlet oxygen formation. Alkylsulfanyl MgAzaPc and ZnAzaPc were the most photostable compounds among the series of studied derivatives. In addition, high molar absorption coefficients (e ∼ 300,000 M(-1) cm(-1)), absorption (λ(max) ∼ 650 nm), and emission (λ(em) ∼ 660 nm, high Φ(F)) in the red region suggest that these molecules are potential fluorescent probes that are superior to the commercial red cyanine dye Cy5. MgAzaPc, when incorporated into lipidic bilayers of liposomes, maintains excellent fluorescence properties (Φ(F) = 0.64). Water-soluble MgAzaPc with quaternary ammonium peripheral substituents retained a high fluorescence quantum yield even in water (Φ(F) = 0.25). The described properties show that magnesium(II) AzaPcs are excellent red-emitting fluorophores with potential applications as fluorescent probes in sensing or in vitro imaging applications.

Eva Svandrlikova

Papers

Magnesium azaphthalocyanines: an emerging family of excellent red-emitting fluorophores.