RuII complexes of 1,2,3-triazole appended tertiary phosphines, [P(Ph){(o-C6H4)(1,2,3-N3C(Ph)CH}2] and [P(Ph){o-C6H4(CCH)-(1,2,3-N3-Ph)}2]: highly active catalysts for transfer hydrogenation of carbonyl/nitro compounds and for α-alkylation of ketones

The synthesis of two new 1,2,3-triazole appended monophosphines [P(Ph){(o-C₆H₄)(1,2,3-N₃C(Ph)CH}₂] (1) and [P(Ph){o-C₆H₄(CCH)(1,2,3-N₃-Ph)}₂] (2) and their Ru^II complexes is described. The reactions of 1 and 2 with [Ru(PPh₃)₃Cl₂] in a 1 : 1 molar ratio produced cationic complexes 3 and 4, respectively. Both the complexes showed very high catalytic activity towards transfer hydrogenation, nitro reduction, and α-alkylation reactions and afforded the corresponding products in good to excellent yields. The free energy of β-hydride elimination from the respective Ru-alkoxide intermediates, a key mechanistic step common to all the three catalytic pathways, was calculated to be close to ergoneutral by density functional theory-based calculations, which is posited to rationalize the catalytic activity of 3. The reduction of aromatic nitro compounds was found to be highly chemoselective and produced the corresponding amines as major products even in the presence of a carbonyl group. The triazolyl-N2 coordinated Ru^II-NPN complex 3 showed better catalytic activity compared to the triazolyl-N3 coordinated complex 4.

The Role of the 1,2,3-Triazolyl Heterocycle in the Helical Columnar Assembly and Electric Field Response

Here, we have proven the role of the 1,2,3-triazolyl group in the helical assembly and electric field (E-field) response upon comparing liquid crystal analogs 1 and 2 based on 1,2,3-triazolyl and 1,3,4-oxadiazolyl linkers, respectively. An ordered helical column was only observed in 1, driven by the hydrogen-bonding interactions between the adjacent triazolyl nitrogen and hydrogen atoms. X-ray diffraction and energy simulations indicate that the helical column is a 11₂ helix and the helical axis does not coincide with the center of the molecular long axis. The key for the formation of the helical column is the tilted conformation of 1 originating from the steric repulsion between the triazolyl C-H and C-H of the aromatic core. Analysis of the dynamics in the simple hexagonal columnar phase revealed that the in-plane rotational motion of the triazolyl linker (1) is allowed, while the oxadiazolyl linker of 2 has limited conformational flexibility. A uniform alignment under an E-field only occurs in 1, demonstrating the requirement for conformational flexibility in the polar linker. This alignment enhances the electric conductance of 1 by approximately two-fold.

Ferroelectrically Switchable Axial Polarization in Columnar Liquid Crystalline Phases

Recently, ferroelectrically switchable columnar LCs have drawn a great deal of attention for their generation of rich polarization domains. Because of their unique dielectric and self-assembly properties, they are considered to be a promising material for the design of sensors and ultra-high memory devices. Herein, ferroelectrically switchable LCs by using ester, amide, and 1,2,3-triazole groups are reviewed. Most of them do not exhibit genuine ferroelectricity owing to the low energy barrier between the two polar states. The intermolecular interactions between polar groups strongly affect the switchability and stability of polarization. Therefore, it is challenging to balance these two competing factors to improve the ferroelectric function in columnar LCs. Overall, additional effort, including LC design and device fabrication, should be made to optimize the material performance for practical applications in the future.

Triazole-amide isosteric pyridine-based supramolecular gelators in metal ion and biothiol sensing with excellent performance in adsorption of heavy metal ions and picric acid from water

Pyridine-based gelators 1–4 of triazole-amide isosteric relationship have been considered in metal ion sensing, heavy metal and picric acid adsorption from water. The change from triazole to isosteric amide has marked effect on gelling properties of the gelators.

Synthesis and supramolecular self-assembly of glutamic acid-based squaramides

We describe the preparation and characterization of two new unsymmetrical squaramide-based organogelators. The synthesis of the compounds was carried out by subsequent amine condensations starting from dimethyl squarate. The design of the gelators involved a squaramide core connected on one side to a long aliphatic chain and on the other side to a glutamic acid residue. The gelator bearing the free carboxylic groups showed a lower gelation capacity than its precursor diester derivative. Some selected gels were further studied by infrared spectroscopy, rheology and electron microscopy. Critical gelation concentrations and gel-to-sol transition temperatures were also determined for each case. In addition, the superior squaramide diester gelator was compared with an analogue triazole-based gelator in terms of critical gelation concentration, gelation kinetics and thermal phase transition.

Tailored Modification of Thioacrylates in a Versatile, Sequence-Defined Procedure

A strategy for the synthesis of sequence-defined oligomers using a selective side-group insertion approach making use of thiophenol-catalyzed amidation reactions is herein reported. In this context, a new thiolactone-based, multistep, iterative protocol is designed, utilizing thioacrylates in combination with solid-phase synthesis for step-by-step growth, resulting in sequence-defined oligomers. Sequence definition and structure variation are introduced by substituting the thioacrylate side groups with a wide variety of amines. The step-by-step growth of the oligomers is followed by liquid chromatography-mass spectrometry and high-resolution mass spectroscopy to determine both conversion and purity.

Click and Click-Inspired Chemistry for the Design of Sequence-Controlled Polymers

During the previous decade, many popular chemical reactions used in the area of "click" chemistry and similarly efficient "click-inspired" reactions have been applied for the design of sequence-defined and, more generally, sequence-controlled structures. This combination of topics has already made quite a significant impact on scientific research to date and has enabled the synthesis of highly functionalized and complex oligomeric and polymeric structures, which offer the prospect of many exciting further developments and applications in the near future. This minireview highlights the fruitful combination of these two topics for the preparation of sequence-controlled oligomeric and macromolecular structures and showcases the vast number of publications in this field within a relatively short span of time. It is divided into three sections according to the click-(inspired) reaction that has been applied: copper-catalyzed azide-alkyne cycloaddition, thiol-X, and related thiolactone-based reactions, and finally Diels-Alder-chemistry-based routes are outlined, respectively.

Two Triazole-Based Phosphine Ligands Prepared via Temperature-Mediated Li/H Exchange: Cu(I) and Au(I) Complexes and Structural Studies

The kinetically favored triazole-based phosphine 1-(2-(diphenylphosphino)phenyl)-4-phenyl-1H-1,2,3-triazole (2, L1) and its thermodynamically preferred isomer, 5-(diphenylphosphino)-1,4-diphenyl-1H-1,2,3-triazole (3, L2), were obtained by the temperature-controlled lithiation of 2-bromotriazole followed by the reaction with chlorodiphenylphosphine. The structures of phosphines 2 and 3 were determined by X-ray diffraction. Upon reaction with late transition-metal derivatives (Cu(I), Ag(I), and Au(I)), phosphines 2 and 3 form complexes with monodentate (Cu(I), Ag(I), and Au(I); κ(1)-P), chelate (Cu(I); κ(2)-P,N), bridged bidentate (Cu(I); μ(2)-P,N), and tridentate (Cu(I); μ(2),κ(2)-P,N,N) modes of coordination. Reactions with copper(I) halides produced mono-, di-, and tetranuclear complexes, whereas the reaction of 2 with [Cu(NCCH3)4]BF4 yielded the binuclear complex [Cu2(CH3CN)2{o-Ph2P(C6H4){1,2,3-N3C(Ph)C(H)}-μ-(κ-P,κ-N),κ-N}2](BF4)2 (10) with the ligand acting as a six-electron donor involving phosphorus and two triazole nitrogen atoms. The copper complexes of 2 and 3 containing rhomboid Cu2X2 units, [(Cu)2(μ-X)2{o-Ph2P(C6H4){1,2,3-N3C(Ph)C(H)}-κ-P}2] (4, X = Cl; 5, X = Br), on treatment with 1,10-phenanthroline and 2,2'-bipyridine gave mixed-ligand complexes of the type [(CuX)(N∩N-κ(2)-N,N){o-Ph2P(C6H4){1,2,3-N3C(Ph)C(H)}-κ-P}] (N∩N = 1,10-phen and 2,2'-bipy; X = Cl, Br, and I).

A Versatile Strategy to Synthesize Perfluoropolyether-Based Thermoplastic Fluoropolymers by Alkyne-Azide Step-Growth Polymerization

Perfluoropolyether (PFPE)-based thermoplastic fluoropolymers are synthesized by A2 + B2 step-growth polymerization between PFPE-diyne and fluorinated diazides. This versatile method allows synthesizing PFPE-based materials with tunable physicochemical properties depending on the exact nature of the fluorinated segment of the diazide precursor. Semicrystalline or amorphous materials endowed with high thermostability (≈300 °C under air) and low glass transition temperature (≈-100 °C) are obtained, as confirmed by differential scanning calorimetry, thermogravimetry, and rheometry. Step-growth polymerizations can be copper-catalyzed but also thermally activated in some cases, thus avoiding the presence of copper residues in the final materials. This strategy opens up new opportunities to easily access PFPE-based materials on an industrial scale. Furthermore, a plethora of developments can be envisioned (e.g., by adding a third trifunctional component to the formulations for the synthesis of PFPE-based elastomers).

Poly(1,2,3-triazolium)s: a new class of functional polymer electrolytes

Poly(1,2,3-triazolium)s are tunable and highly functional ion conducting materials that stretch out the actual boundaries of PILs macromolecular design.

Amide–triazole isosteric substitution for tuning self-assembly and incorporating new functions into soft supramolecular materials

We report the proof-of-concept demonstration for the synthesis of novel supramolecular soft gel materials based on amide–triazole isometric substitution.

Systematic study of the synthesis and coordination of 2-(1,2,3-triazol-4-yl)-pyridine to Fe(ii), Ni(ii) and Zn(ii); ion-induced folding into helicates, mesocates and larger architectures, and application to magnetism and self-selection

The 2-pyridyl–1,2,3-triazole chelate was found to display unique coordination properties.

Primary Structure Control of Oligomers Based on Natural and Synthetic Building Blocks

Solid-phase synthesis was exploited for the preparation of oligomers constructed from natural and synthetic building blocks by combining the formation of amide bonds and copper-assisted alkyne-azide cycloaddition reactions extending the variety of oligomers with well-defined primary structures accessible through this technique and providing control over the spacing between amino acids.

Stereospecific generation of homochiral helices in coordination polymers built from enantiopure binaphthyl-based ligands

The novel enantiopure spacer 2,2′-dimethoxy-1,1′-binaphthyl-3,3′-bis(4-pyridyl-amido) has been designed to prepare helical coordination polymers here investigated by means of experimental and theoretical data.

1,4:3,6-Dianhydrohexitols: Original platform for the design of biobased polymers using robust, efficient, and orthogonal chemistry

1,4:3,6-Dianhydrohexitols (DAHs) are nontoxic and sustainable diols that have been extensively applied as monomers for the preparation of polymer materials by step-growth polymerization processes. The presence of two reactive alcohol groups was exploited to design a library of symmetric and asymmetric stereocontrolled alkyne- and/or azide-functionalized AA/BB and AB monomers suitable for thermal or copper(I)-catalyzed azide-alkyne cycloaddition (TAAC and CuAAC). Step-growth polymerization of these monomers yielded a series of linear polytriazoles as well as partially biosourced networks using a combination of AB + A2B2 derivatives. Characterization of the resulting materials allowed for the establishment of a thorough structure–property relationship emphasizing the impact of monomer stereochemistry and cycloaddition regioselectivity on materials properties.