Dually directional glycosylated phthalocyanines as extracellular red-emitting fluorescent probes

The development of new non-aggregated phthalocyanines bearing multivalent saccharide moieties on their macrocyclic rims is of great interest. Many characteristics, including water-solubility, non-toxicity and others, can be feasibly obtained by these amphiphiles which can be considered as a key solution for demonstrating highly efficient photoactive materials in water. Herein, a family of five newly prepared dually directional Zn(ii) containing phthalocyanines (PcG1-4) and azaphthalocyanine (AzaPcG1) glycoconjugates is described. The unique spatial arrangement of the glucoside units based on peripherally hexadeca-(PcG1) and nonperipherally octa-(PcG4) macrocycles provides a fully monomeric behaviour along with a high fluorescence (Φ_F∼ 0.21) in aqueous solution. These amphiphiles were characterized by low toxicity, and an extremely low cellular uptake was obtained due to the highly polar nature of the glucoside substituents. Accordingly, their potential as suitable photoactive chromophores for red-emitting extracellular fluorescent probes has been confirmed upon the evaluation of paracellular transport using a layer of MDCKII cells with the permeability coefficient fully comparable with an established evaluator of the integrity of the monolayer.

Methodological Survey of Simplified TD-DFT Methods for Fast and Accurate Interpretation of UV-Vis-NIR Spectra of Phthalocyanines

A methodological survey of density functional theory (DFT) methods for the prediction of UV-visible (vis)-near-infrared (NIR) spectra of phthalocyanines is reported. Four methods, namely, full time-dependent (TD)-DFT and its Tamm-Dancoff approximation (TDA), together with their simplified modifications (sTD-DFT and sTDA, respectively), were tested by using the examples of unsubstituted and alkoxy-substituted metal-free ligands and zinc complexes. The theoretical results were compared with experimental data derived from UV-visible absorption and magnetic circular dichroism spectroscopy. Seven popular exchange-correlation functionals (BP86, B3LYP, TPSSh, M06, CAM-B3LYP, LC-BLYP, and ωB97X) were tested within these four approaches starting at a relatively modest level using 6-31G(d) basis sets and gas-phase BP86/def2-SVP optimized geometries. A gradual augmentation of the computational levels was used to identify the influence of starting geometry, solvation effects, and basis sets on the results of TD-DFT and sTD-DFT calculations. It was found that although these factors do influence the predicted energies of the vertical excitations, they do not affect the trends predicted in the spectral properties across series of structurally related substituted free bases and metallophthalocyanines. The best accuracy for the gas-phase vertical excitations was observed in the lower-energy Q-band region for calculations that made use of range-separated hybrids for both full and simplified TD-DFT approaches. The CAM-B3LYP functional provided particularly accurate results in the context of the sTD-DFT approach. The description of the higher-energy B-band region is considerably less accurate, and this demonstrates the need for further advances in the accuracy of theoretical calculations. Together with a general increase in accuracy, the application of simplified TD-DFT methods affords a 2-3 orders of magnitude speedup of the calculations in comparison to the full TD-DFT approach. It is anticipated that this approach will be widely used on desktop computers during the interpretation of UV-vis-NIR spectra of phthalocyanines and related macrocycles in the years ahead.

Effect of the Substitution Pattern (Peripheral vs Non-Peripheral) on the Spectroscopic, Electrochemical, and Magnetic Properties of Octahexylsulfanyl Copper Phthalocyanines

In order to investigate the substitution position effect on the spectroscopic, electrochemical, and magnetic properties of copper phthalocyanines, a detailed structure-property analysis has been performed by examining two copper phthalocyanines that are octasubstituted by hexylsulfanyl chains respectively in the peripheral (Cu-P) and non-peripheral (Cu-NP) positions. Cu-NP showed a marked near-IR maximum absorption compared to Cu-P and, accordingly, a smaller HOMO-LUMO energy gap, calculated via the electrochemical results and simulations in the gas phase, as well as for Cu-NP from its crystallographic data. An electron-spin resonance (ESR) technique is used to extract the g values from the powder spectra that are taken at room temperature. The g values were determined to be g_∥ = 2.160 and g_⊥ = 2.045 for Cu-P and g_∥ = 2.150 and g_⊥ = 2.050 for Cu-NP. These values indicate that the paramagnetic copper center in both phthalocyanines has axial symmetry with a planar anisotropy ( g_∥ > g_⊥). The ESR spectra in solution could be obtained only for Cu-P. Curie law is used to fit the experimental data of the magnetic susceptibility versus temperature graphs, and the Curie constant ( C) and diamagnetic/temperature-independent paramagnetic (α) contributions are deduced as 0.37598 (0.39576) cm³·K/mol and -23 × 10^-5 (25 × 10^-5) cm³/mol respectively for Cu-P and Cu-NP. The room temperature magnetic moment value (1.70 μ_B) is close to the spin-only value (1.73 μ_B) for the peripheral complex, showing that there is no orbital contribution to μ_eff. In contrast, at room temperature, the value of the magnetic moment (1.77 μ_B) is above the spin-only value, showing an orbital contribution to the magnetic moment. Cu-NP's room temperature magnetic moment value is larger than the value for Cu-P, demonstrating that the orbital contribution to the magnetic moment depends upon the substituent position. The magnitudes of the effective magnetic moment values also support that both Cu-P and Cu-NP complexes have square-planar coordination. This result is consistent with the determined g values. The spin densities were determined experimentally, and the results suggest that the positions of the substituents affect these values (0.469 for Cu-P and 0.490 for Cu-NP).

Subphthalocyanine basicity: reversible protonation at the azomethine bridge

Protonation of subphthalocyanine azomethine bridges is reversible and was evidenced by UV/Vis, ¹H-NMR and IR.

Assessment of the relevance of GaPc substituted with azido-polyethylene glycol chains for photodynamic therapy. Design, synthetic strategy, fluorescence, singlet oxygen generation, and pH-dependent spectroscopic behaviour

New synthetic route and PDT potential of symmetrically and asymmetrically substituted Ga(iii)Pcs with terminal azides.