An experimental and computational study on isomerically pure, soluble azaphthalocyanines and their complexes and boron azasubphthalocyanines of a varying number of aza units

Synthesis, Optical Properties, and Fluorescence Cell Imaging of Novel Mixed Fluorinated Subphthalocyanines

Subphthalocyanines (SubPcs) are a kind of tripyrrolic macrocycle with a boron atom at their core. Incorporating different units onto the SubPc periphery can endow them with various unique properties. Herein, a series of novel fluorinated low-symmetry SubPc derivatives containing chlorine groups (F₈-Cl₄-SubPc, F₄-Cl₈-SubPc) and methoxy groups (F₈-(OCH₃)₂-SubPc) were synthesized and characterized by spectral methods (MS, FT-IR, ¹H, ¹³C, ¹¹B, and ¹⁹F NMR spectroscopy), and the effect of the peripheral substituents on their electronic structure of low-symmetry macrocycle was investigated by cyclic voltammetry, theoretical calculation, electronic absorption, and emission spectroscopy. In contrast to perfluorinated SubPcs, these low-symmetry SubPcs revealed non-degenerate LUMO and LUMO + 1 orbitals, especially F₈-(OCH₃)₂-SubPc, which was consistent with the split Q-band absorptions. The cyclic voltammetry revealed that these SubPcs exhibited two or three reduction waves and one oxidation wave, which is consistent with the reported SubPcs. Finally, an intracellular fluorescence imaging study of these compounds revealed that these compounds could enter cancer cells and be entrapped in the lysosomes, which provides a possibility of future applications in lysosome fluorescence imaging and targeting.

Recent advances in subphthalocyanines and related subporphyrinoids

Subporphyrinoids constitute a class of extremely versatile and attractive compounds. Herein, a comprehensive review of the most recent advances in the fundamentals and applications of these cone-shaped aromatic macrocycles is presented.

Analysis of the Solvent Effects on the Crystal Growth of Peripherally Chlorinated Boron Subphthalocyanines

We report the characterization of the crystal/nano-structures for hexachloro-boron subphthalocyanines (Cl6BsubPc) grown via a variety of solvent diffusion methods and also with having axial substitutions variants: chloride; phenoxy; naphthoxy and...

Subphthalocyanines as Efficient Photosensitizers with Nanomolar Photodynamic Activity against Cancer Cells

Because cancer is the second leading cause of death globally, investigation of new photosensitizers for photodynamic therapy is highly desirable. In this work, different peripherally substituted subphthalocyanines (SubPcs) with either a benzocrown moiety (CE-) or a tyrosine methyl ester (Tyr-) as the axial ligand have been prepared. Target SubPcs showed high Φ_Δ values, >0.50 in EtOH. Both CE- and Tyr- moieties increased substantially the hydrophilicity of the compounds (log P = 1.79-2.63, n-octanol/PBS). Uptake to cells, subcellular localization, and monitoring of the progression of cell death over time are described. Improved spectroscopic behavior of the CE- series in cell culture medium resulted in higher photodynamic activity versus that of the Tyr- series. In particular, the peripherally triethylsulfanyl SubPc-CE exhibited extraordinarily low EC₅₀ values of 2.3 and 4.4 nM after light activation and high TC₅₀ values of 14.49 and 5.25 μM (i.e., dark toxicity without activation) on SK-MEL-28 and HeLa cells, respectively, which rank it among the best photosensitizers ever.

tert-Butyl substituted hexaazasubphthalocyanine: Synthesis, isolation of C1 and C3 regioisomers and their spectral-luminescence study

By cyclotrimerization of tert-butyl substituted pyrazine-2,3-dicarbonitrile in the presence of boron trichloride, two positional isomers ([Formula: see text] and [Formula: see text] symmetry) of the corresponding boron(III) tripyrazinosubporphyrazines were first obtained and efficiently separated by column chromatography. The new compounds were characterized by MALDI mass-spectrometry, UV-visible and 1H NMR spectroscopy. A Q-band in the electronic absorption spectra for both fractions was observed at [Formula: see text]530 nm, which is typical for tripyrazinosubporphyrazines. The fluorescence quantum yield for the regioisomer with lower symmetry ([Formula: see text] is 1.5 times higher than for the more symmerical [Formula: see text] species ([Formula: see text] = 0.37 and 0.28, respectively). Comparative spectrophotometric study of the basic properies reveals that hexaaza substitution in benzene rings of tert-butyl substituted subphthalocyanine decreases the basic properties of meso-nitrogen atoms.

Reductive O-triflylation of naphthalene diimide: access to alkyne- and amine-functionalized 2,7-diazapyrenes

A reductive one-pot triflylation and silylation of naphthalene diimide is presented. Post-functionalization of the 1,3,6,8-tetratriflato key compound leads to so far non-accessible UHV processable tetraalkynyl and tetraaminyl 2,7-diazapyrenes.

pH-Sensitive subphthalocyanines and subazaphthalocyanines

Although subphthalocyanines (SubPcs) possess advantageous fluorescence properties and serve as an amazing tool to attach a recognition sensor moiety to the axial position, a limited number of switchable SubPcs have been described so far. Isosteric aza-replacement is known to improve sensing properties in closely related phthalocyanine families; however, pyrazino[2,3-b,g,l]subporphyrazines (SubPyzPzs) have not yet been investigated for use in sensing applications. Therefore, this project focuses on the synthesis and sensing abilities of pH-sensitive SubPcs and SubPyzPzs on the principle of photoinduced electron transfer (PET). 4-Dimethylaminophenoxy (for acidic pH) or 4-hydroxyphenoxy (for basic pH) groups were employed as pH-sensitive axial ligands. Electrochemical studies revealed improvements in the electron-accepting properties of SubPyzPzs (E_red-0.56 V vs. SCE) in comparison to those of SubPcs (E_red-1.0 V vs. SCE). Hydroxy groups on the axial phenoxy ligands of SybPyzPzs and SubPcs have been found to act as donors for PET. The sensing properties under basic conditions could not be studied, since all the SubPcs and SubPyzPzs decomposed under basic conditions, SubPyzPzs were more susceptible to this process. On the other hand, compounds with 4-dimethylaminophenoxy groups as axial ligands showed great potential for sensing applications. These compounds were nonfluorescent (Φ_F < 0.01) in acetone due to efficient PET, while their fluorescence steeply increased by two orders of magnitude upon the addition of trifluoroacetic acid, reaching a Φ_F value of up to 0.17 (λ_em range of 563-590 nm). These compounds maintained their sensing properties in aqueous medium after incorporation into microemulsions. The most basic derivative showed pK_A = 2.95 with Φ_F = 0.10 in the ON state (fluorescence enhancement factor = 46, λ_em = 577 nm).

Influence of phenylpropanoid units of lignin and its oxidized derivatives on the stability and βO4 binding properties: DFT and QTAIM approach

Obtaining lignin products is currently one of the great challenges, mainly because of its stable and poorly reactive structure. This work used a DFT and QTAIM approach, seeking to understand the influence of lignin structure on the reactivity and βO4 binding properties of 18 model structures. The computational modeling used confirmed that lignins derived from more oxygenated monomers have a smaller HOMO-LUMO gap, and therefore are less stable. In the developed study, the replacement of alpha hydroxyl with a carbonyl was able to abruptly change the electron topology, reducing binding energy in βO4 indicating which SHOX model is more susceptible to breakage.

Self-assembly of azaphthalocyanine–oligodeoxynucleotide conjugates into J-dimers: towards biomolecular logic gates

Unique spatial self-assembly of azaphthalocyanine–oligonucleotide–fluorescein conjugates can be selectively dissociated by a complementary sequence or coordinating solvent and used for the development of biomolecular logic gates.