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Open AccessArticle

Simple One–Pot Synthesis of Hexakis(2-alkoxy-1,5-phenyleneimine) Macrocycles by Precipitation–Driven Cyclization

by Toshihiko Matsumoto

Macromol 2024, 4(1), 1-22; https://doi.org/10.3390/macromol4010001 - 3 Jan 2024

Cited by 1 | Viewed by 1929

Hexakis(2-alkoxy-1,5-phenyleneimine) macrocycles were synthesized using a simple one-pot procedure through precipitation-driven cyclization. The acetal-protected AB–type monomers, 2-alkoxy-5-aminobenzaldehyde diethyl acetals, underwent polycondensation in water or acid-containing tetrahydrofuran. The precipitation–driven cyclization, based on imine dynamic covalent chemistry and π–stacked columnar aggregation, played a decisive role in the one–pot synthesis. The progress of the reaction was analyzed using MALDI–TOF mass spectrometry. The macrocycles with alkoxy chains were soluble in specific organic solvents, such as chloroform, allowing their structures to be analyzed using NMR. The shape-anisotropic, nearly planar, and shape-persistent macrocycles aggregated into columnar assemblies in polymerization solvents, driven by aromatic π-stacking. The octyloxylated macrocycle OcO–Cm6 exhibited an enantiotropic columnar liquid crystal-like mesophase between 165 °C and 197 °C. In the SEM image of (S)-(–)-3,7-dimethyloctyloxylated macrocycle (–)BCO–Cm6, columnar substances with a diameter of 200–300 nm were observed. The polymerization solution for the 2-(2-methoxyethoxy)ethoxy)ethoxylated macrocycle (TEGO–Cm6) gelled, and showed thixotropic properties by forming a hydrogen bond network. Full article

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17 pages, 6074 KB

Open AccessArticle

Highly Efficient One-Pot Synthesis of Hexakis(m-phenyleneimine) Macrocyle Cm6 and the Thermostimulated Self-Healing Property through Dynamic Covalent Chemistry

by Toshihiko Matsumoto

Polymers 2023, 15(17), 3542; https://doi.org/10.3390/polym15173542 - 25 Aug 2023

Cited by 2 | Viewed by 1850

Abstract

Highly efficient one-pot synthesis of hexakis(m-phenyleneimine) macrocycle Cm6 from acetalprotected AB-type monomer, m-aminobenzaldehyde diethylacetal, was successfully achieved based on imine dynamic covalent chemistry and precipitation-driven cyclization. The structure of Cm6 in the solid state was determined using CP/MAS NMR, X-ray single crystallographic analysis, and WAXD. Macrocycle Cm6 is composed of six phenylene and imine bonds facing the same direction, with nitrogen atoms arranged on the outside of the ring, and has a chair conformation, as predicted from DFT calculation. The macrocycle forms π-stacked columnar aggregates and hexagonally closest-packed structure. The cyclization process was investigated using MALDI-TOF MS and NMR. A mechanism of precipitation-driven cyclization based on imine dynamic covalent chemistry and π-stacked columnar aggregation is proposed. Both the nature of imine linkage and the shape anisotropy of the macrocycle played an important role in the single one-pot synthesis. The water-mediated mutual conversion between macrocycle Cm6 and linear oligomers driven by thermal stimulation was analyzed using MALDI-TOF MS and GPC methods. Macrocycle Cm6 with a dynamic covalent imine bond exhibited self-healing properties when stimulated using heat. Full article

(This article belongs to the Special Issue Dynamic Covalent Polymers: Synthesis, Characterization, and Applications)

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28 pages, 13783 KB

Open AccessReview

Imine- and Amine-Type Macrocycles Derived from Chiral Diamines and Aromatic Dialdehydes

by Jerzy Lisowski

Molecules 2022, 27(13), 4097; https://doi.org/10.3390/molecules27134097 - 25 Jun 2022

Cited by 26 | Viewed by 5234

Abstract

The condensation of aromatic dialdehydes with chiral diamines, such as 1,2-trans-diaminocyclohexane, leads to various enantiopure or meso-type macrocyclic Schiff bases, including [2 + 2], [3 + 3], [4 + 4], [6 + 6] and [8 + 8] condensation products. Unlike most cases of macrocycle synthesis, the [3 + 3] macrocycles of this type are sometimes obtained in high yields by direct condensation without a metal template. Macrocycles of other sizes from this family can often be selectively obtained in high yields by a suitable choice of metal template, solvent, or chirality of the building blocks. In particular, the application of a cadmium(II) template results in the expansion of the [2 + 2] macrocycles into giant [6 + 6] and [8 + 8] macrocycles. These imine macrocycles can be reduced to the corresponding macrocyclic amines which can act as hosts for the binding of multiple cations or multiple anions. Full article

(This article belongs to the Special Issue Design and Synthesis of Macrocyclic Compounds)

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13 pages, 5579 KB

Open AccessFeature PaperArticle

Solvent-Free Visible Light Photocatalytic Oxidation Processes Mediated by Transparent Films of an Imine-Based Organic Polymer

by Miguel Sánchez-Fuente, Alicia Jimenez-Almarza, José Alemán and Rubén Mas-Ballesté

Catalysts 2021, 11(12), 1426; https://doi.org/10.3390/catal11121426 - 24 Nov 2021

Cited by 4 | Viewed by 3401

Abstract

Reaction between concentrated solutions of phenotiazine containing trialdehyde building block 4,4′,4″-(10-phenothiazine-3,7,10-triyl)tribenzaldehyde and (1R,2R)-cyclohexane-1,2-diamine results in the formation of a yellow transparent film. Exhaustive characterization of this material indicates that it is the result of the assembly of a linear polymer resulting from the linking of imine-based macrocycles. Phenotiazine units confer to this plastic the optical properties characteristic of photocatalytic materials. The transparency of the obtained material enabled the performance of solvent-free photocatalytic processes. This concept is illustrated by the oxidation of liquid organic sulfides, which can be performed in a recyclable manner. According to selective quenching experiments, such processes are the result of the energy transfer to oxygen molecule, generating singlet oxygen that is able to activate the sulfide molecules directly. Full article

(This article belongs to the Special Issue Catalytic Applications of Porous Organic Materials (Covalent Organic Frameworks, Porous Organic Polymers and Related Materials))

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9 pages, 3341 KB

Open AccessArticle

π-Stacking Stopper-Macrocycle Stabilized Dynamically Interlocked [2]Rotaxanes

by Sing-Ming Chan, Fung-Kit Tang, Ching-Yau Lam, Chak-Shing Kwan, Sam C. K. Hau and Ken Cham-Fai Leung

Molecules 2021, 26(15), 4704; https://doi.org/10.3390/molecules26154704 - 3 Aug 2021

Cited by 3 | Viewed by 4207

Abstract

The synthesis of mechanically interlocked molecules is valuable due to their unique topologies. With π-stacking intercomponent interaction, e.g., phenanthroline and anthracene, novel [2]rotaxanes have been synthesized by dynamic imine clipping reaction. Their X-ray crystal structures indicate the π-stackings between the anthracene moiety (stopper) on the thread and the (hetero)aromatic rings at the macrocycle of the rotaxanes. Moreover, the length of glycol chains affects the extra π-stacking intercomponent interactions between the phenyl groups and the dimethoxy phenyl groups on the thread. Dynamic combinatorial library has shown at best 84% distribution of anthracene-threaded phenanthroline-based rotaxane, coinciding with the crystallography in that the additional π-stacking intercomponent interactions could increase the thermodynamic stability and selectivity of the rotaxanes. Full article

(This article belongs to the Special Issue Synthesis and Properties of Macrocyclic Compound)

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28 pages, 6960 KB

Open AccessReview

Homo- and Hetero-Oligonuclear Complexes of Platinum Group Metals (PGM) Coordinated by Imine Schiff Base Ligands

by Barbara Miroslaw

Int. J. Mol. Sci. 2020, 21(10), 3493; https://doi.org/10.3390/ijms21103493 - 15 May 2020

Cited by 36 | Viewed by 6615

Abstract

Chemistry of Schiff base (SB) ligands began in 1864 due to the discovery made by Hugo Schiff (Schiff, H., Justus Liebigs Ann. der Chemie 1864, 131 (1), 118–119). However, there is still a vivid interest in coordination compounds based on imine ligands. The aim of this paper is to review the most recent concepts on construction of homo- and hetero-oligonuclear Schiff base coordination compounds narrowed down to the less frequently considered complexes of platinum group metals (PGM). The combination of SB and PGM in oligonuclear entities has several advantages over mononuclear or polynuclear species. Such complexes usually exhibit better electroluminescent, magnetic and/or catalytic properties than mononuclear ones due to intermetallic interactions and frequently have better solubility than polymers. Various construction strategies of oligodentate imine ligands for coordination of PGM are surveyed including simple imine ligands, non-innocent 1,2-diimines, chelating imine systems with additional N/O/S atoms, classic N₂O₂-compartmental Schiff bases and their modifications resulting in acyclic fused ligands, macrocycles such as calixsalens, metallohelical structures, nano-sized molecular wheels and hybrid materials incorporating mesoionic species. Co-crystallization and formation of metallophilic interactions to extend the mononuclear entities up to oligonuclear coordination species are also discussed. Full article

(This article belongs to the Special Issue Oligonuclear Metal Complexes with Schiff Base Ligands)

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16 pages, 3436 KB

Open AccessArticle

DNA-Polylactide Modified Biosensor for Electrochemical Determination of the DNA-Drugs and Aptamer-Aflatoxin M1 Interactions

by Veronika Stepanova, Vladimir Smolko, Vladimir Gorbatchuk, Ivan Stoikov, Gennady Evtugyn and Tibor Hianik

Sensors 2019, 19(22), 4962; https://doi.org/10.3390/s19224962 - 14 Nov 2019

Cited by 19 | Viewed by 3490

Abstract

DNA sensors were assembled by consecutive deposition of thiacalix[4]arenes bearing oligolactic fragments, poly(ethylene imine), and DNA onto the glassy carbon electrode. The assembling of the layers was monitored with scanning electron microscopy, cyclic voltammetry and electrochemical impedance spectroscopy. The configuration of the thiacalix[4]arene core determined self-assembling of the polymeric species to the nano/micro particles with a size of 70–350 nm. Depending on the granulation, the coatings show the accumulation of a variety of DNA quantities, charges, and internal pore volumes. These parameters were used to optimize the DNA sensors based on these coatings. Thus, doxorubicin was determined to have limits of detection of 0.01 nM (cone configuration), 0.05 nM (partial cone configuration), and 0.10 nM (1,3-alternate configuration of the macrocycle core). Substitution of native DNA with aptamer specific to aflatoxin M1 resulted in the detection of the toxin in the range of 20 to 200 ng/L (limit of detection 5 ng/L). The aptasensor was tested in spiked milk samples and showed a recovery of 80 and 85% for 20 and 50 ng/L of the aflatoxin M1, respectively. Full article

(This article belongs to the Special Issue Electrochemical DNA Sensors)

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