Mimicking the Reactivity of LPMOs with a Mononuclear Cu Complex

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Mimicking the Reactivity of LPMOs with a Mononuclear Cu Complex

Lytic polysaccharide monoxygenase are Cu-dependent metalloenzymes that catalyze the hydroxylation of strong C−H bonds using O2 and/or H2O2 as oxidants. In this article, we analyze the oxidation chemistry of an unusual mononuclear Cu complex bound by a podal ligand that can act as a H-bond/proton donor. Our results suggest that LPMOs react with O2 to produce H2O2 (oxidase-like chemistry), which is used to promote C−H hydroxylation via a Fenton-like mechanism.


Abstract

Lytic polysaccharide monooxygenases (LPMOs) are Cu-dependent metalloenzymes that catalyze the hydroxylation of strong C−H bonds in polysaccharides using O2 or H2O2 as oxidants (monooxygenase/peroxygenase). In the absence of C−H substrate, LPMOs reduce O2 to H2O2 (oxidase) and H2O2 to H2O (peroxidase) using proton/electron donors. This rich oxidative reactivity is promoted by a mononuclear Cu center in which some of the amino acid residues surrounding the metal might accept and donate protons and/or electrons during O2 and H2O2 reduction. Herein, we utilize a podal ligand containing H-bond/proton donors (LH2) to analyze the reactivity of mononuclear Cu species towards O2 and H2O2. [(LH2)CuI]1+ (1), [(LH2)CuII]2+ (2), [(LH−)CuII]1+ (3), [(LH2)CuII(OH)]1+ (4), and [(LH2)CuII(OOH)]1+ (5) were synthesized and characterized by structural and spectroscopic means. Complex 1 reacts with O2 to produce 5, which releases H2O2 to generate 3, suggesting that O2 is used by LPMOs to generate H2O2. The reaction of 1 with H2O2 produces 4 and hydroxyl radical, which reacts with C−H substrates in a Fenton-like fashion. Complex 3, which can generate 1 via a reversible protonation/reduction, binds H2O and H2O2 to produce 4 and 5, respectively, a mechanism that could be used by LPMOs to control oxidative reactivity.

Structural, stability and relaxation features of lanthanide‐complexes designed for multimodal imaging detection of enzyme activities

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Structural, stability and relaxation features of lanthanide-complexes designed for multimodal imaging detection of enzyme activities

Lanthanide complexes of DO3A-derivative ligands bearing a pyridine-carbamate or pyridine-amine pendant have potential interest in the design of enzymatically activated imaging probes. They are stable and inert, with an exceptionally high kinetic inertness for the carbamate analogue (estimated dissociation half-life ~108 h at pH 7.4).


Abstract

Lanthanide complexes of DO3A-derivative ligands bearing a pyridine-carbamate (L1) or pyridine-amine (L2) arm have potential interest in the design of enzymatically activated imaging probes. Solid-state X-ray structures for CeL1 and YbL2 both demonstrate twisted square antiprismatic geometry, with the metal ion in a nine- or an eight-coordinate environment, respectively. As assessed by pH-potentiometry, in solution lanthanide ions form more stable complexes with the nonadentate L1 than with the octadentate L2 ligand (logK ML=18.7–21.1 vs. 16.7–18.6, respectively), while stability constants are similar for L1 and L2 chelates of Mg2+, Ca2+, Zn2+ or Cu2+. The kinetic inertness of GdL1 is exceptionally high, with an estimated dissociation half-life of ~108 h at pH 7.4, while LnL2 (Ln=Ce, Gd, Yb) complexes have 3–4 orders of magnitude faster dissociation, related to the presence of the protonatable, non-coordinating amine function. The water exchange rate determined for the monohydrated GdL2 (k ex 298=1.3×106 s−1) shows a threefold decrease with respect to GdDOTA, as a consequence of a reduction in the negative charge and in the steric crowding around the water binding site, both important in dissociatively activated water exchange processes.

Ising spins on frustrated bronze‐mean hexagonal quasicrystal

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Ising spins on frustrated bronze-mean hexagonal quasicrystal


Abstract

We investigate the Ising model on the Bronze-mean hexagonal quasicrystal (BMH QC), an aperiodic tiling with geometric frustration. Our extensive Monte Carlo simulations explore the model's rich phase diagram, revealing six distinct phases with diverse magnetic properties and degrees of frustration. We uncover exotic spin glass phases, signaled by the replica symmetry breaking and slow relaxation dynamics. We shed light on the intriguing magnetic properties of frustrated quasicrystals and open new avenues for studying exotic phases in condensed matter physics.

Access to Versatile Functionalized Cu(III) Complexes Enabled by Direct Transmetalation to Well‐Defined Copper(III) Fluoride Complex Me4N+[Cu(CF3)3F]‐

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Access to Versatile Functionalized Cu(III) Complexes Enabled by Direct Transmetalation to Well-Defined Copper(III) Fluoride Complex Me4N+[Cu(CF3)3F]-

The invention of a well-defined Cu(III) fluoride complex Me4N+[Cu(CF3)3(F)]- 1 enabled to access a versatile of functionalized Cu(III) complexes [Me4N]+[Cu(X)(CF3)3]- (X = C6F5, C6F5C≡C, CN, Cl, N3, t BuOO, SCN, OAc, SAr), many of them for the first time. The availability of these complexes allowed us to evaluate the the trans-influence order of ligand in Cu(III) complexes: Bn > CF3 – > C6F5 – > N3 – > py ~ CH3 – ~ C6F5C≡C > NO2PhO– ~ t BuOO– ~ CH3COO– > F–.


Comprehensive Summary

The invention of a well-defined Cu(III) fluoride complex Me4N+[Cu(CF3)3(F)]- 1 enabled to access a versatile of functionalized Cu(III) complexes [Me4N]+[Cu(X)(CF3)3]- (X = C6F5, C6F5C≡C, CN, Cl, N3, t BuOO, SCN, OAc, SAr), many of them for the first time. The availability of these complexes allowed us to evaluate the trans-influence order of ligand in Cu(III) complexes: Bn > CF3 – > C6F5 – > N3 – > py ~ CH3 – ~ C6F5C≡C > NO2PhO– ~ t BuOO– ~ CH3COO– > F–.

Revisiting the Chemistry and Photophysics of 3‐(N‐Methylpyridinium‐4‐yl)Coumarins for Designing “Covalent‐Assembly” and “Molecular Disassembly” Fluorescent Probes

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Revisiting the Chemistry and Photophysics of 3-(N-Methylpyridinium-4-yl)Coumarins for Designing “Covalent-Assembly” and “Molecular Disassembly” Fluorescent Probes**

The double face of N -methylpyridinium moiety!!! Synthesis and photophysics of 7-(diethylamino)/7-hydroxycoumarins bearing N-methylpyridinium-4-yl group as C3 substituent were studied for identifying novel fluorophores usable in activity-based sensing approaches. The unexpected weak emissive properties of the 7-hydroxycoumarin derivative in neutral aqueous media was rationalized. Superior fluorescence performances observed with 7-(diethylamino) counterpart and ortho-formylated derivative led us to consider the design of two novel reaction-based fluorescent probes responsive to alkaline phosphatase enzyme and pyrophosphate ions respectively.


Abstract

The constant need for high-performance aniline- or phenol-based fluorophores suitable for the construction of activity-based fluorescent probes, led us to study both synthesis and photophysics of C3-N-methylpyridinium-4-yl substituted 7-(dialkylamino)/7-hydroxycoumarins. Indeed, in the field of photoactive organic molecules, the positively charged N-alkylpyridinium-4-yl groups are often used as acceptor units to dramatically impact spectral features through promoting intramolecular charge transfer (ICT) processes. They are also known as effective water-solubilizing and mitochondria targeting moieties. The poor fluorescence efficiency of cationic 7-hydroxycoumarin derivatives in aqueous physiological conditions was highlighted and rationalized by the predominance of a neutral quinonoid form in such buffer medium. The ability of the excited singlet state (S1) of this neutral species to undergo intersystem crossing (ISC) to triplet state (T1) was partly supported by phosphorescence measurements of singlet oxygen. We also took advantage of green-emissive properties of 7-(diethylamino)-3-(N-methylpyridinium-4-yl)coumarin to successfully design and validate a novel small-molecule fluorescent probe for the detection of alkaline phosphatase (ALP), based on the “covalent-assembly” principle. A practical use of ortho-formylated 7-hydroxy-3-(N-methylpyridinium-4-yl)coumarin was next considered with the synthesis of a Fe(III)-salen complex whose the potential as a “molecular disassembly” probe for fluorogenic sensing of pyrophosphate (PPi) anion was assessed.

Homochirality in Ferroelectrochemistry

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Homochirality in Ferroelectrochemistry

Introducing homochirality provides an effective and universal strategy to precisely design molecular ferroelectrics. This review summarizes the recent progress on the chemical design of molecular ferroelectrics through the strategy of introducing homochirality.


What is the most favorite and original chemistry developed in your research group?

We originally proposed the design principle for molecular ferroelectrics: ferroelectrochemistry, including quasi-spherical theory, the introduction of homochirality, and H/F substitution. Ferroelectrochemistry changed the blind search for molecular ferroelectrics into targeted chemical design, which will develop into a new discipline.

How do you get into this specific field? Could you please share some experiences with our readers?

I have been devoted to the field of molecular ferroelectrics for more than 20 years. In the early stage, I worked on non-centrosymmetric metal-organic complexes, which are potential molecular ferroelectrics. This laid a foundation for my further study of molecular ferroelectrics. Non-centrosymmetric crystal symmetry is only one of the necessary requirements for ferroelectrics, which must adopt one of the 10 polar crystallographic point groups and should also generally undergo symmetry-breaking phase transitions. Due to the lack of a feasible method, the discovery of molecular ferroelectrics has long depended on blindly searching. This process is like finding a needle in a haystack. After years of exploration in this field, I fully understood the Landau phase transition phenomenological theory, Curie symmetry, and Neumann principle from a chemical perspective, and proposed the design principle for molecular ferroelectrics: ferroelectrochemistry, transforming the discovery of molecular ferroelectrics from blind search to targeted chemical design. Never give up no matter how much difficulty you have met, because maybe there is an opportunity the next second.

What is the most important personality for scientific research?

Curiosity, divergent thinking, perseverance, team spirit, and gratitude.

How do you supervise your students?

Emphasis on independent problem-solving abilities. Encourage students to read professional books frequently while doing research.

What are your hobbies? What’s your favorite book(s)?

Jogging, reading, and swimming. My favorite book is The Journey to the West.

Comprehensive Summary

Molecular ferroelectrics have attracted tremendous attention in the past decades due to their excellent ferroelectric performance and superiorities of easy processability, mechanical flexibility, and good biocompatibility. However, the discovery of molecular ferroelectrics is a great challenge and has long relied on blind search. This situation changed recently, with the development of ferroelectrochemistry proposed by our group. As a major design approach in ferroelectrochemistry, introducing homochirality, which facilitates the crystallization of materials in polar crystallographic point groups, greatly improves the probability of being ferroelectrics. Various new molecular ferroelectrics with splendid properties have been precisely synthesized by using this efficient and universal strategy. In this review, we summarize the advances in the chemical design of molecular ferroelectrics through the strategy of introducing homochirality.

Key Scientists

Synthesis of novel [1,2,3]triazolo[4′,5′:3,4]pyrrolo[1,2‐a]thieno[2,3‐d] pyrimidines: Potent EGFR targeting anti‐breast cancer agents

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Synthesis of novel [1,2,3]triazolo[4′,5′:3,4]pyrrolo[1,2-a]thieno[2,3-d] pyrimidines: Potent EGFR targeting anti-breast cancer agents

Synthesis of fused [1,2,3]triazolo [4′,5′:3,4]pyrrolo[1,2-a]thieno[2,3-d]pyrimidines using [3 + 2] reaction cycloaddition followed by C-C bond coupling in a PEG-400 medium. Anti-breast cancer activity against two breast cancer cell lines, MDA-MB-231 and MCF-7. The most promising compounds, 5g and 5i, demonstrated excellent anticancer activity against both cancer cell lines, with IC50 values ranging from 04.17 ± 0.55 to 8.65 ± 0.89 μM, respectively, as well as excellent kinase inhibitory activities (EGFR: IC50 = 0.467 ± 0.063 and 0.412 ± 0.081 μM).


Abstract

In this study, we designed and synthesized several novel fused [1,2,3]triazolo [4′,5′:3,4]pyrrolo[1,2-a]thieno[2,3-d]pyrimidine derivatives using in a single [3 + 2] reaction cycloaddition reaction of 3-(3-iodoprop-2-yn-1-yl)thieno[2,3-d]pyrimidin-4(3H)-one (4) followed by C-C bond coupling with various aryl azides in a PEG-400 medium. All of the newly synthesized compounds were evaluated in vitro for EGFR kinase inhibitory action as well as anti-breast cancer activity against MDA-MB-231 and MCF-7 breast cancer cell lines. When compared to the reference molecule, erlotinib, the majority of the compounds demonstrated adequate efficacy. The most promising compounds, 5g and 5i, demonstrated excellent anticancer activity against both cancer cell lines, with IC50 values ranging from 04.17 ± 0.55 to 8.65 ± 0.89 μM, respectively, as well as excellent kinase inhibitory activities (EGFR: IC50 = 0.467 ± 0.063 and 0.412 ± 0.081 μM). The in silico studies of five potent compounds 5f, 5g, 5h, 5i, and 5k were also carried out to identify the interactions against the EGFR receptor and found that the energy calculations were covenant with the obtained IC50 values.

A Guide to Chemical Reactions Design in Carbon Nitride Photocatalysis

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A Guide to Chemical Reactions Design in Carbon Nitride Photocatalysis

This article provides general guidelines, which are used to design photocatalytic organic transformations using graphitic carbon nitrides. It includes discussion of the local chemical structure of carbon nitride excited state, its redox potentials and the redox potentials of the reagents, and the chemical reactivity of the open-shell intermediates.


Abstract

Graphitic carbon nitride semiconductors are inexpensive and reusable photocatalysts, which are actively studied in organic synthesis. Successful design of photocatalytic reactions is based on the next considerations. i) Thermodynamic feasibility of photoinduced processes, which involve transfer of electrons or electron-proton couples. ii) Redox activity of reagents. iii) Reactivity of the open-shell intermediates generated from the reagents. Herein, we summarize current understanding of how local chemical structure of graphitic carbon nitrides and their redox potentials are used to design photocatalytic reactions. This work intends to serve as a guideline for materials scientists, who are willing to apply their carbon nitride semiconductors in reactions involving organic substrates, and for organic chemists, who are interested to dive into heterogeneous carbon nitride photocatalysis.

Selective O‐Acylation of Enol Silyl Ethers with Acyl Fluorides Catalyzed by Fluoride Ions Derived from Potassium Fluoride and 18‐Crown‐6

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Selective O-Acylation of Enol Silyl Ethers with Acyl Fluorides Catalyzed by Fluoride Ions Derived from Potassium Fluoride and 18-Crown-6

Fluoride ions derived from potassium fluoride and 18-crown-6 efficiently catalyzed the selective O-acylation of a variety of enol silyl ethers with aromatic and aliphatic acyl fluorides to produce unique enol ester derivatives.


Abstract

The fluoride ion-catalyzed selective O-acylation of enol silyl ethers with acyl fluorides using KF and 18-Crown-6 is described herein. This catalytic system facilitated the practical and facile reaction of a variety of enol silyl ethers derived from aromatic/aliphatic ketones and aldehydes with acyl fluorides to afford useful and valuable enol esters.