Metallophthalocyanines as Catalysts in Aerobic Oxidation

Quantum-Classical Protocol for Efficient Characterization of Absorption Lineshape and Fluorescence Quenching upon Aggregation: The Case of Zinc Phthalocyanine Dyes

A quantum-classical protocol that incorporates Jahn-Teller vibronic coupling effects and cluster analysis of molecular dynamics simulations is reported, providing a tool for simulations of absorption spectra and ultrafast nonadiabatic dynamics in large molecular photosystems undergoing aggregation in solution. Employing zinc phthalocyanine dyes as target systems, we demonstrated that the proposed protocol provided fundamental information on vibronic, electronic couplings and thermal dynamical effects that mostly contribute to the absorption spectra lineshape and the fluorescence quenching processes upon dye aggregation. Decomposing the various effects arising upon dimer formation, the structure-property relations associated with their optical responses have been deciphered at atomistic resolution.

Manganese-Based Antioxidase-Inspired Biocatalysts with Axial Mn-N5 Sites and 2D d-π-Conjugated Networks for Rescuing Stem Cell Fate

Constructing highly effective biocatalysts with controllable coordination geometry for eliminating reactive oxygen species (ROS) to address the current bottlenecks in stem-cell-based therapeutics remains challenging. Herein, inspired by the coordination structure of manganese-based antioxidase, we report a manganese-coordinated polyphthalocyanine-based biocatalyst (Mn-PcBC) with axial Mn-N5 sites and 2D d-π-conjugated networks that serves as an artificial antioxidase to rescue stem cell fate. Owing to the unique chemical and electronic structures, Mn-PcBC displays efficient, multifaceted, and robust ROS-scavenging activities, including elimination of H2 O2 and O2 ⋅- . Consequently, Mn-PcBC efficiently rescues the bioactivity and functionality of stem cells in high-ROS-level microenvironments by protecting the transcription of osteogenesis-related genes. This study offers essential insight into the crucial functions of axially coordinated Mn-N5 sites in ROS scavenging and suggests new strategies to create efficient artificial antioxidases for stem-cell therapies.

Doped Graphene To Mimic the Bacterial NADH Oxidase for One-Step NAD+ Supplementation in Mammals

Nicotinamide adenine dinucleotide (NAD) is a critical regulator of metabolic networks, and declining levels of its oxidized form, NAD⁺, are closely associated with numerous diseases. While supplementing cells with precursors needed for NAD⁺ synthesis has shown poor efficacy in combatting NAD⁺ decline, an alternative strategy is the development of synthetic materials that catalyze the oxidation of NADH into NAD⁺, thereby taking over the natural role of the NADH oxidase (NOX) present in bacteria. Herein, we discovered that metal-nitrogen-doped graphene (MNGR) materials can catalyze the oxidation of NADH into NAD⁺. Among MNGR materials with different transition metals, Fe-, Co-, and Cu-NGR displayed strong catalytic activity combined with >80% conversion of NADH into NAD⁺, similar specificity to NOX for abstracting hydrogen from the pyridine ring of nicotinamide, and higher selectivity than 51 other nanomaterials. The NOX-like activity of FeNGR functioned well in diverse cell lines. As a proof of concept of the in vivo application, we showed that FeNGR could specifically target the liver and remedy the metabolic flux anomaly in obesity mice with NAD⁺-deficient cells. Overall, our study provides a distinct insight for exploration of drug candidates by design of synthetic materials to mimic the functions of unique enzymes (e.g., NOX) in bacteria.

The regioselective Wacker oxidation of internal allylamines: synthesis of functionalized and challenging β-amino ketones

A convenient and general protocol for the palladium-catalysed oxidation of internal allylamine derivatives to β-amino ketones is reported. The transformation occurs at room temperature and shows a wide substrate scope as well as high functional group and N-protecting group tolerance. We also describe potential applications of the method, e.g., the synthesis of bioactive molecules or simple transformations of selected β-amino ketones into other interesting building blocks.

Kinetics of chromium(V)-oxo and chromium(IV)-oxo porphyrins: Reactivity and mechanism for sulfoxidation reactions

In this work, chromium(IV)-oxo porphyrins [Cr^IV(Por)(O)] (2) (Por = porphyrin) were produced either by oxidation of [Cr^III(Por)Cl] (1) with iodobenzene diacetate or visible light photolysis of porphyrin‑chromium(III) chlorates. Subsequent oxidation of 2 with silver perchlorate gave chromium(V)-oxo porphyrins [Cr^V(Por)(O)](ClO₄) (3) in three porphyrin ligands, including 5,10,15,20-tetramesitylporphyrin(TMP, a), 5,10,15,20-tetrakis(2,6-difluorophenyl)porphyrin(TDFPP, b), and 5,10,15,20-tetrakis(pentafluorophenyl)porphyrin (TPFPP, c). Complexes 2 and 3 reacted with thioanisoles to produce the corresponding sulfoxides, and their kinetics of sulfoxidation reactions with a series of aryl methyl sulfides(thioanisoles) were studied in organic solutions. Chromium(V)-oxo porphyrins are several orders of magnitudes more reactive than chromium(IV)-oxo species, and representative second-order rate constants (k_ox) for the oxidation of thioansole are (0.40 ± 0.01) M^-1 s^-1 (3a), and (2.82 ± 0.20) × 10² M^-1 s^-1 (3b), and (2.20 ± 0.01) × 10³ M^-1 s^-1 (3c). The order of reactivity for 2 and 3 follows TPFPP > TDFPP > TMP, in agreement with the electrophilic nature of metal-oxo complexes. Hammett analyses indicate significant charge transfer in the transition states for oxidation of para-substituted thioanisoles by [Cr^V(Por)(O)]⁺. The ρ⁺ constants are -1.69 for 3a, -2.63 for 3b, and - 2.89 for 3c, respectively, mirror values found previously for related metal-oxo species. A mechanism involving the electrophilic attack of the Cr^V-oxo at sulfides to form a sulfur cation intermediate in the rate-determining step is suggested. Competition studies with chromium(III) porphyrin chloride and PhI(OAc)₂ gave relative rate constants for oxidations of competing thioanisoles that closely match ratios of absolute rate constants from chromium(V)-oxo species, which are true oxidants under catalytic conditions.

Synthesis, Characterization, and Physicochemical Studies Of Orientation-Controlled Multi-Arm PEG Zn(II)/Mg(II) (Aza)Phthalocyanines

Tuning the amphiphilicity of (aza)phthalocyanine hydrophobic cores by introducing multiple polyethylene glycol (PEG) moieties with controlled orientations of their (non)peripheral positions is an innovative approach to fabricating water-soluble macrocyclic materials. Although many water-soluble PEGylated macrocycles have been produced in this way, the ability to generate substances with PEG tails oriented outward from the macrocyclic plane in order to obtain non-aggregated, water soluble forms remains a challenge. In this study, we resolved this issue by developing a methods for the synthesis of four new dual directional PEG containing Zn(II)/Mg(II) amphiphiles (ZnPc-PEG, MgPc-PEG, ZnAzaPc-PEG and MgAzaPc-PEG). In addition, the non-aggregating behaviour, and photophysical and photochemical properties of these PEG-complexes were elucidated.

A Janus-Type Phthalocyanine for the Assembly of Photoactive DNA Origami Coatings

Design and synthesis of novel photosensitizer architectures is a key step toward new multifunctional molecular materials. Photoactive Janus-type molecules provide interesting building blocks for such systems by presenting two well-defined chemical functionalities that can be utilized orthogonally. Herein a multifunctional phthalocyanine is reported, bearing a bulky and positively charged moiety that hinders their aggregation while providing the ability to adhere on DNA origami nanostructures via reversible electrostatic interactions. On the other hand, triethylene glycol moieties render a water-soluble and chemically inert corona that can stabilize the structures. This approach provides insight into the molecular design and synthesis of Janus-type sensitizers that can be combined with biomolecules, rendering optically active biohybrids.