Ann M. Chippindale

Materials utilized for impact protection must be capable of effective absorption and dissipation of external impact forces as well as being lightweight, flexible, and comfortable. One strategy to meet these stringent criteria is through the exploitation of adaptive dynamic networks. Herein, we report a series of chain-extended supramolecular polyurethane and poly(urethane–urea) elastomers, which utilize both hydrogen bonding interactions and disulfide units to impart structural stability, reprocessability, and reversible adaptability. The key design element of these phase-separated materials is the use of two distinct dynamic bonding mechanisms within the hard domains, which serve to efficiently reinforce the elastomeric assemblies. The optimum elastomer exhibited excellent self-recoverability (91% and 99%) after relaxing for 30 and 60 s, respectively, at 20% compression. During loading–unloading compression cycles, the elastic recovery ratios of this elastomer reached 77 ± 0.3% with dissipated energies of 235,000 J m^–3 at a deformation of 80%. This study highlights how the combination of noncovalent interactions and dynamic covalent bonding can be utilized to generate elastomers capable of rapid autonomous healing and property recovery while simultaneously providing exceptional energy dissipation, paving the way for the impact-resistant systems.

To address the current needs of the pharmaceutical industry, this study demonstrates how the design of LMWGs can be exploited to tune self-assembled nanostructured gel morphologies to enable the selective crystallisation of polymorphous APIs.

A series of novel chain-extended polyurethanes (CEPUs) featuring degradable sulfonyl ethyl urethane chain-extenders that permit degradation under base-triggered conditions to afford "debond-on-demand" elastomeric adhesives are reported. Exposure of the CEPUs to tetra-butylammonium fluoride (TBAF) triggered the degradation of the sulfonyl ethyl urethane chain-extenders. Lap shear adhesion tests of the CEPUs exposed to TBAF revealed reductions in shear strength of up to 65% for both aluminum and glass substrates, from 2.18 to 0.76 MPa and from 1.13 to 0.52 MPa, respectively. The selective depolymerization of these polymers makes them suitable candidates as debondable binders for inkjet inks and coatings, enabling removal of inks and adhesive residues from substrates before they enter the recycling process, to prevent surface contaminants decreasing the quality of the recycled material.

This paper describes the synthesis, characterization, and supramolecular assembly of polyurethane elastomers. Bis-aromatic urea hydrogen-bonding motifs have been used to promote the self-assembly of the materials. The materials described comprise a soft block, namely, polytetramethylene ether glycol (PTMG), as a telechelic diol and hard crystalline domains that feature a bis-aromatic urea hydrogen bonding motif as a chain extender. Two diols were polymerized (one featuring the bis-aromatic urea hydrogen bonding motif) with a PTMG diisocyanate prepolymer to yield supramolecular polyurethanes with molecular weights ca. 185000 with polydispersities ca. 2.0. The mechanical properties and processing temperatures of the polyurethanes were shown to be tunable by controlling the feed ratio of the supramolecular chain extenders. These supramolecular polyurethanes were found to be healable in nature, offering a useful property for use of these elastomers in applications such as cable coatings.

Hepatocellular carcinoma is the most common type of primary liver cancer. However, multidrug resistance (MDR) is a major obstacle to the effective chemotherapy of cancer cells. This report documents the rational design, synthesis, and biological evaluation of a novel series of triazolotriazines substituted with CH₂NH‐linked pyridine for use as dual c‐Met/MDR inhibitors. Compound 12g with IC₅₀ of 3.06 μM on HepG2 cells showed more potency than crizotinib (IC₅₀ = 5.15 μM) in the MTT assay. In addition, 12g inhibited c‐Met kinase at a low micromolar level (IC₅₀ = 0.052 μM). 12g significantly inhibited P‐gp and MRP1/2 efflux pumps in both cancerous HepG2 and BxPC3 cells starting from the lower concentrations of 3 and 0.3 µM, respectively. 12g did not inhibit MDR1 and MRP1/2 in noncancerous H69 cholangiocytes up to the concentration of 30 and 60 µM, respectively. Current results highlighted that cancerous cells were more susceptible to the effect of 12g than normal cells, in which the inhibition occurred only at the highest concentrations, suggesting a further interest in 12g as a selective anticancer agent. Overall, 12g, as a dual c‐Met and P‐gp/MRP inhibitor, is a promising lead compound for developing a new generation of anticancer agents.

Three novel rhenium N−heterocyclic carbene complexes, [Re]−NHC−1−3 ([Re] = fac−Re(CO)₃Br), were synthesized and characterized using a range of spectroscopic techniques. Photophysical, electrochemical and spectroelectrochemical studies were carried out to probe the properties of these organometallic compounds. Re−NHC−1 and Re−NHC−2 bear a phenanthrene backbone on an imidazole (NHC) ring, coordinating to Re by both the carbene C and a pyridyl group attached to one of the imidazole nitrogen atoms. Re−NHC−2 differs from Re−NHC−1 by replacing N−H with an N−benzyl group as the second substituent on imidazole. The replacement of the phenanthrene backbone in Re−NHC−2 with the larger pyrene gives Re−NHC−3. The two−electron electrochemical reductions of Re−NHC−2 and Re−NHC−3 result in the formation of the five−coordinate anions that are capable of electrocatalytic CO₂ reduction. These catalysts are formed first at the initial cathodic wave R1, and then, ultimately, via the reduction of Re−Re bound dimer intermediates at the second cathodic wave R2. All three Re−NHC−1−3 complexes are active photocatalysts for the transformation of CO₂ to CO, with the most photostable complex, Re−NHC−3, being the most effective for this conversion. Re−NHC−1 and Re−NHC−2 afforded modest CO turnover numbers (TONs), following irradiation at 355 nm, but were inactive at the longer irradiation wavelength of 470 nm. In contrast, Re−NHC−3, when photoexcited at 470 nm, yielded the highest TON in this study, but remained inactive at 355 nm. The luminescence spectrum of Re−NHC−3 is red−shifted compared to those of Re−NHC−1 and Re−NHC−2, and previously reported similar [Re]−NHC complexes. This observation, together with TD−DFT calculations, suggests that the nature of the lowest−energy optical excitation for Re−NHC−3 has π→π*(NHC−pyrene) and d_π(Re)→π*(pyridine) (IL/MLCT) character. The stability and superior photocatalytic performance of Re−NHC−3 are attributed to the extended conjugation of the π−electron system, leading to the beneficial modulation of the strongly electron−donating tendency of the NHC group.

Two new hybrid iodobismuthates, [C₈H₁₇N₂][C₁₀H₂₂N₂][BiI₆] (1) and [C₆H₁₂N₂]_0.5[C₁₀H₂₂N₂]_3.5[Bi₂I₁₀][Bi₂I₉] (2), have been prepared by solvothermal synthesis in the presence of 1,4-diazabicyclo[2.2.2]octane (DABCO) and ethanol. Both compounds have been characterized by single-crystal and powder X-ray diffraction, infrared and UV–Vis spectroscopies and thermogravimetric analysis. Structure determination reveals that the crystal structure of 1 contains mononuclear [BiI₆]³⁻ anions, whilst 2 contains an unusual combination of dinuclear anions, [Bi₂I₉]³⁻ and [Bi₂I₁₀]⁴⁻, consisting of two edge- and two face-sharing [BiI₆]³⁻ octahedra, respectively. Mono- and diethylated derivatives of DABCO, which are formed in situ under solvothermal conditions, act as countercations and are located between the discrete anions. The optical band gaps of 1 and 2, which are 2.29(1) and 2.03(2) eV respectively, are consistent with the red color of these compounds, and are comparable to the band gaps measured for other iodobismuthates containing discrete anions. Graphical Two new iodobismuthates, [C₈H₁₇N₂][C₁₀H₂₂N₂][BiI₆] (1) and [C₆H₁₂N₂]_0.5[C₁₀H₂₂N₂]_3.5[Bi₂I₁₀][Bi₂I₉] (2), have been synthesized under solvothermal conditions, and their crystal structures determined by single-crystal X-ray diffraction.

Herein, we report a new method of synthesis of N-acylureas (E1–5) via reaction of dibenzoylhydrazine carboxamide (N,2-bis(4-methoxybenzoyl)hydrazine-1-carboxamide) (C) and various benzylamines. Preparation of dibenzoylhydrazine carboxamide (C) was performed by the treatment of 5,6-diaryl-3-methylthio-1,2,4-triazine (B) with Oxone which leads to oxidation and triazine ring cleavage in high yield (82%). Five benzylamine derivatives containing different electron donating and withdrawing substituents were used in this study. Yields for the conversion of dibenzoylhydrazine carboxamide (C) to N-acylureas (E1–5) were in the range of 40–55%. The structures of the intermediates and final products were characterized and confirmed by NMR, mass spectrometry and single-crystal X-ray crystallography. Graphical Abstract