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Thiophene, a key building block for the construction of conjugated materials, has been scarcely studied in halogen bonding (XB)-driven self-assemblies. In the present study, two thiophene derivatives modified at position 3 were (co-)crystallized using complementary XB donor/acceptor functional groups. Single-crystal X-ray diffraction analysis confirmed the presence of halogen and chalcogen bonding acting, in most cases, concomitantly. While the majority of the structures are governed by the conventional N···I motif, additional S···N and S···S contacts encouraged the cohesion of the supramolecular architectures. Density functional theory calculations shed the light on interaction energy, their respective contributions of the motifs to these non-covalent bonds, and the overall stability of these assemblies. To gain further insight into the formation and evidence of XB interactions, solution and mechanochemical syntheses of polymorphic adducts were performed, followed by 13C solid-state NMR analysis. Further, 1H and 19F{1H} solution-state NMR spectroscopy studies were carried out to highlight these interactions in the solution phase. The strength and directionality of halogen bonding thus reaffirm its role as a structure-directing agent for designing functional materials. The evidence of N···S chalcogen bonds in thiophene derivatives also broadens up the horizon of supramolecular chemistry in S-heterocycles, while necessitating further investigation for rational application in materials science.

The synthesis and catalytic activity of novel phosphine palladium PEPPSI and dimer complexes bearing RuPhos, SPhos and XPhos phosphines is reported.

Bipyridine covalent triazine framework (bpyCTF) was used as a support material for the development of a highly efficient Rh catalyst. The heterogeneous catalyst was applied for both batch and flow transfer hydrogenation of various N-heteroarenes.

In this study, the preparation of 4-imidoyl-, 4-oxiranyl-, and 4-propargyloxyphenyl-substituted beta-lactams as versatile building blocks in heterocyclic chemistry was realized. Efforts were made to deploy these polyvalent compounds for ensuing cyclization reactions en route to new bi- or polycyclic frameworks, which, in the case of a 3-chloro-4-propargyloxyphenyl-beta-lactam substrate, enabled the preparation of an unprecedented beta-lactam-fused benzotriazolo-oxazocane scaffold. The chemical structure of the latter polyheterocycle was unequivocally secured by means of X-ray analysis.

A supramolecular self-assembly of semiconducting polymers and small molecules plays an important role in charge transportation, performance, and lifetime of an optoelectronic device. Tremendous efforts have been put into the strategies to self-organize these materials. In this regard, here, we present the self-organization of terthiophene and its methyl alcohol derivative with 4,4′-bipyridine (44BiPy). An unexpected 2D layered organization of 5,5″-dimethyl-2,2′:5′,2″-terthiophene (DM3T) and 44BiPy was obtained and analyzed. Single-crystal X-ray diffraction analysis revealed that DM3T and 44BiPy consist of stacked, almost independent, infinite 2D layers while held together by weak hydrogen bonds. In addition to this peculiar supramolecular arrangement of these compounds, the investigation of their photophysical properties showed strong fluorescence quenching of DM3T by 44BiPy in the solid state, suggesting an efficient charge transfer. On the other hand, the methyl alcohol derivative of terthiophene, DM3TMeOH, organized in a closed cyclic motif with 44BiPy via hydrogen bonds.

The (3 + 2) cycloaddition of various indoles with a dithioallyl cation affords dearomatized cyclopentannulated adducts, with complete control of regioselectivity and excellent chemo- and diastereoselectivity. The success of the reaction critically relies on the use of an excess of very strong Brønsted acid, which paradoxically prevents carbocationic side reactions. The reaction tolerates sensitive functionalities such as basic amines or free hydroxyls, and we demonstrate its use in late stage derivatization of highly functionalized, unprotected indoles.

A simple and efficient method for the oxidative coupling of terminal alkynes is reported for the first time, making use of imidazol(in)ium aurates as pre-catalysts. This approach displays high functional group tolerance and leads to a broad range of 1,3-diyne compounds in moderate to excellent yields using low catalyst loading and is performed in air under mild and sustainable conditions.

Macro- and nanosized core, as well as core-shell, gamma-cyclodextrin metal-organic frameworks (gamma-CD-MOFs) have been designed and used as platforms for the encapsulation of dye molecules to develop the first CD-MOF-based ratiometric optical thermometer materials. A novel dye combination was employed for this purpose, i.e., the duo rhodamine B (RhB) and fluorescein (FL). RhB is highly temperature-sensitive, whereas FL is less temperature-sensitive, and its luminescence emission peak is used as a reference. Promising results in terms of thermometric properties were obtained for a series of dye-encapsulated gamma-CD-MOF materials based on this dye combination, with high relative sensitivities, even up to 5%K-1, for the dye-encapsulated 75%RhB-25%FL nanosized gamma-CD-MOF, among the highest performance values reported so far for luminescent dual thermometers. In our study, we have additionally developed a simple yet effective preparation method for core-shell gamma-CD-MOFs, allowing effective manipulation of the gamma-CD-MOF shell growth. The proposed method allows incorporation of the FL and RhB dyes in the gamma-CD-MOFs in a more controlled manner, enhancing the efficiency of the developed ratiometric (macro) gamma-CD-MOF thermometers.

A new Cd(ii) MOF was used as a fluorometric sensor for ascorbic acid in water, fruits, vegetables and human urine.

We report the mechanochemical synthesis of five single-crystalline phenylboroxine and 1,4-diazabicyclo[2.2.2]octane (DABCO) ligand-based adducts, directed by boron-nitrogen dative bonds. By tuning the electronic features of the phenylboroxines by chemical modifications (-H/-OMe/-F/-Cl/-Br) at the para-position, the formation of the resulting bicomponent adducts can be controlled to obtain molecular to 1D polymeric crystalline materials. The electrostatic and quantum topological aspects of the B

Hollow Y2O3 and Y2O2SO4 materials doped with Er3+ and Yb3+ can be successfully used for simultaneous luminescence thermometry and drug delivery applications.

A simple synthetic pathway to new families of Au–NHC amido complexes under mild reaction conditions is described. Their in vitro anticancer activity was investigated on three human cell lines, showing comparable or even better results than cisplatin.

We present the use of gold sensitizers [Au(SIPr)(Cbz)] (PhotAu 1) and [Au(IPr)(Cbz)] (PhotAu 2) as attractive alternatives to state-of-the-art iridium-based systems. These novel photocatalysts are deployed in [2 + 2] cycloadditions of diallyl ethers and N-tosylamides. The reactions proceed in short reaction times and in environmentally friendly solvents. [Au(SIPr)Cbz] and [Au(IPr)(Cbz)] have higher triplet energy (E-T) values (66.6 and 66.3 kcal mol(-1), respectively) compared to commonly used iridium photosensitizers. These E-T values permit the use of these gold complexes as sensitizers enabling energy transfer catalysis involving unprotected indole derivatives, a substrate class previously inaccessible with state-of-the-art Ir photocatalysts. The photosynthesis of unprotected tetracyclic spiroindolines via intramolecular [2 + 2] cycloaddition using our simple mononuclear gold sensitizer is readily achieved. Mechanistic studies support the involvement of triplet-triplet energy transfer (TTEnT) for both [2 + 2] photocycloadditions.

A synthetic route making use of a weak inorganic base has been developed to easily access [M(diketonato)(NHC)] complexes.

The synthetic access to monomeric copper-alkynyl and copper-thiolato complexes of the type [(NHC)Cu(R)] (R = alkynyl or thiolato) using a weak base approach is reported. All reported reactions proceed under mild conditions in air and in environmentally acceptable solvents. The novel complexes are fully characterized and single crystal X-ray analyses unambiguously establish the atom connectivity in these mononuclear complexes. The importance of the supporting NHC ligand steric properties in stabilizing mononuclear complexes is discussed.

The peculiar isomer-selective reduction of (α)-hydroxyiminophosphonates (oxime isomers) into (α)-hydroxyaminophosphonate (hydroxylamine) derivatives is presented. A library of 16 (α)-hydroxyiminophosphonates is prepared and studied via a unique multifaceted approach involving the interplay of NMR, XRD, MS, IM-MS and computational chemistry techniques. The combination of NMR, XRD and HPLC enables the seamless separation, identification and quantification of the oxime isomers (E/Z). Tandem MS (MS/MS) enables the determination of the fragmentation patterns for both isomers. Collision energy breakdown curves highlight the order of apparition of the fragments as well as their related energy of fragmentation, demonstrating that the strength of the C–P bond in the Z isomers is much weaker than in the E isomers. Computational chemistry demonstrates that favorable protonation site is isomer-dependent with the phosphonate moiety being the favorable protonation site for the E isomers, while protonation occurs preferentially on the amino moiety for Z isomers regardless of the phosphite source. The combination of these various methods led an unprecedented level of characterization of oxime isomers, providing a better uderstanding of the isomer-dependent behavior of (α)-hydroxyiminophosphonates.

Palladacyclic architectures have been shown as versatile motifs in cross-coupling reactions. NHC-ligated palladacycles possessing unique electronic and steric properties have helped to stabilize the catalytically active species and provide additional control over reaction selectivity. Here, we report on a synthetic protocol leading to palladacycle complexes using a mild base and an environmentally desirable solvent, with a focus on complexes bearing backbone-substituted N-heterocyclic carbene ligands. The readily accessible complexes exhibit high catalytic activity in the Buchwald–Hartwig amination. This is achieved using low catalyst loading and mild reaction conditions in a green solvent.

Paving the way towards new functional materials relies increasingly on the challenging task of forming organic-inorganic hybrid compounds. In that regard, discrete atomically-precise metal-oxo nanoclusters have received increasing attention due to the wide range of organic moieties that can be grafted onto them through functionalization reactions. The Lindqvist hexavanadate family of clusters, such as [V6O13{(OCH2)3C-R}2]2- (V6-R), is particularly interesting due to the magnetic, redox, and catalytic properties of these clusters. However, compared to other metal-oxo cluster types, V6-R clusters have been less extensively explored, which is mainly due to poorly understood synthetic challenges and the limited number of viable post-functionalization strategies. In this work, we present an in-depth investigation of the factors that influence the formation of hybrid hexavanadates (V6-R HPOMs) and leverage this knowledge to develop [V6O13{(OCH2)3CNHCOCH2Cl}2]2- (V6-Cl) as a new and tunable platform for the facile formation of discrete hybrid structures based on metal-oxo clusters in relatively high yields. Moreover, we showcase the versatility of the V6-Cl platform through its post-functionalization via nucleophilic substitution with various carboxylic acids of differing complexity and with functionalities that are relevant in multiple disciplines, such as supramolecular chemistry and biochemistry. Hence, V6-Cl was shown to be a straightforward and versatile starting point for the formation of functional supramolecular structures or other hybrid materials, thereby enabling their exploration in various fields. ispartof: CHEMICAL SCIENCE vol:14 issue:20 pages:5405-5414 ispartof: location:England status: published

Three highly crystalline and porous COFs with promising photoredox properties have been prepared. Via a post-sulfurization process, the imine-linked COFs were converted into thiazole-linked COFs, generating a highly conjugated and ultrastable photocatalyst for H2O2 production.

Green and sustainable access to chiral and achiral gold-IBiox complexes is reported. The gold complexes were synthesized using a simple, air-tolerant, weak base protocol carried out in a green solvent. Their catalytic activity was examined in the hydroamination of alkynes. The steric protection afforded the gold center by these ligands was quantified using the %; V; bur; model and compared with the most commonly encountered NHCs.

Photoluminescent molecular crystals integrated with the ability to transform light energy into macroscopic mechanical motions are a promising choice of materials for both actuating and photonic devices. However, such dynamic photomechanical effects, based on molecular organoboron compounds as well as phosphorescent crystalline materials, are not yet known. Here we present an intriguing example of photomechanical molecular single crystals of a newly synthesized organoboron containing Lewis acid-base molecular adduct (BN1, substituted triphenylboroxine and 1,2-di(4-pyridyl)ethylene) having a capsule shape molecular geometry. The single crystals of BN1 under UV light exhibit controllable rapid bending-shape recovery, delamination, violent splitting-jumping, and expanding features. The detailed structural investigation by single-crystal X-ray diffraction and 1H NMR spectroscopy reveals that the photosalient behavior of the BN1 single crystals is driven by a crystal-to-crystal [2 + 2] cycloaddition reaction, supported by four donor-acceptor type B-N bonds. The instant photomechanical reaction in the BN1 crystals occurs under UV on account of sudden release of stress associated with the strained molecular geometry, significant solid-state molecular movements (supramolecular change), and cleavage of half intermolecular B-N linkages to result in a complete photodimerized single-crystalline product via the existence of two other intermediate photoproducts. In addition, the BN1 crystals display short-lived room temperature phosphorescence, and the photodynamic events are accompanied by the enhancement of their phosphorescence intensity to yield the photoproduct. Interestingly, the molecular crystals of the final photoproduct polymerize at ambient conditions when recrystallized from the solution forming a 2D supramolecular crystalline polymer stabilized by the retention of all B-N coordination modes.

Covalent triazine frameworks (CTFs) based on polydentate ligands are highly promising supports to anchor catalytic metal complexes. The modular nature of CTFs allows to tailor the composition, structure, and function to its specific application. Access to a broad range of chelating building blocks is therefore essential. In this respect, we extended the current available set of CTF building blocks with new nitrile-functionalized N-heterocyclic ligands. This paper presents the synthesis of the six ligands which vary in the extent of the aromatic system and the denticity. The new building blocks may help in a rational design of enhanced support materials in catalysis.

The crystal structures of three N-(pyridine-2-carbon­yl)pyridine-2-carboxamide ligands, with or without F atoms on the 3-position of the pyridine ring, with potential use in supra­molecular chemistry are reported., The synthesis and single-crystal X-ray structures of three N-(pyridine-2-carbon­yl)pyridine-2-carboxamide imides, with or without F atoms on the 3-position of the pyridine rings are reported, namely, N-(pyridine-2-carbon­yl)pyridine-2-carboxamide, C12H9N3O2 (1), N-(3-fluoro­pyridine-2-carbon­yl)pyridine-2-carboxamide, C12H8FN3O2 (2), and 3-fluoro-N-(3-fluoro­pyridine-2-carbon­yl)pyridine-2-carboxamide, C12H7F2N3O2 (3). The above-mentioned compounds were synthesized by a mild, general procedure with an excellent yield, providing straightforward access to symmetrical and/or asymmetrical heterocyclic ureas. The crystal structures of 1 and 2 are isomorphous, showing similar packing arrangements, i.e. double layers of parallel (face-to-face) mol­ecules alternating with analogous, but perpendicularly oriented, double layers. In contrast, the crystal structure of 3, containing a fluoro- group at the 3-position of both pyridine rings, shows mol­ecular arrangements in a longitudinal, tubular manner along the c axis, with the aromatic pyridine and carbon­yl/fluorine moieties facing towards each other.

The use of weak and inexpensive bases has recently opened promising perspectives towards the simpler and more sustainable synthesis of Au(I)-aryl complexes with valuable applications in catalysis, medicinal chemistry, and materials science. In recent years, continuous manufacturing has shown to be a reliable partner in establishing sustainable and controlled process scalability. Herein, the first continuous flow synthesis of a range of Au(I)-aryl starting from widely available boronic acids and various [Au(NHC)Cl] (NHC=N-heterocyclic carbene) complexes in unprecedentedly short reaction times and high yields is reported. Successful synthesis of previously non- or poorly accessible complexes exposed fascinating reactivity patterns. Via a gram-scale synthesis, convenient process scalability of the developed protocol was showcased.

Gold catalysis has witnessed immense evolution in recent years, yet it still requires the use of activators to render the common [AuCl(L)] complexes catalytically active. Herein, the H-bonding donor properties of hexafluoroisopropanol (HFIP) are utilized for Au-Cl bond activation and the ancillary ligand and counteranion effects on cycloisomerization reactions are showcased in HFIP as solvent.

At present, two-dimensional (2D) hybrid organic-inorganic perovskites (HOIPs) are drawing significant interest because of their potential use in different optoelectronic applications, that is, photovoltaics and photodetectors. Here, we report on a series of 2D layered HOIPs (Bit-C3)(2)PbX4 (with X = Cl, Br, and I) containing a 2,2'-bithiophene chromophore functionalized with a propylammonium tethering chain as a model molecule. The optical properties, crystal structure, and phase behavior of the 2D layered HOIPs are studied in depth. The crystal structures with the chemical formula (Bit-C3)(2)PbX4 (with X = Cl, and Br) are successfully obtained. Contrastingly, different crystal structures with an inorganic framework containing face- and corner-sharing octahedra were identified for the iodide-based HOIP. The phase diversity and thermal stability of the (Bit-C3)(2)PbX4 (with X = Cl, Br, and I) thin films were investigated via in situ measurements. Here, the presence of lower-dimensional hybrids with reduced electronic dimensionality within the iodide-based thin film is demonstrated. Additionally, we show that the 2D hybrid thermal stability is dependent on the type of lead(II)halide framework employed. We suggest that, via halide substitution from iodide to bromide and chloride, the molecular degrees of freedom of the Bit-C3 ammonium cations are reduced by spatial confinement of a smaller inorganic framework, therefore, limiting the formation of lower-dimensional hybrids besides the targeted 2D layered HOIP. This study illustrates the importance of efficiently utilizing the space supplied by the inorganic framework in which the organic ammonium cations can reside within a 2D layered HOIP. This, in turn, dictates how the organic ammonium cations arrange themselves within the organic layer and influences the adopted crystal structure of the hybrid.

Low-dimensional (2D or 1D) hybrid perovskites are receiving increased attention due to their structural flexibility and enhanced stability compared to their 3D counterparts. Understanding the phase formation and degradation behavior of these materials is crucial towards their use in optoelectronic devices, since different crystal phases possess different optical and electronic properties. In this communication, we study the phase formation and degradation of a series of hybrids containing bithiophene, terthiophene and quaterthiophene derivatives. We show that two crystal phases can be formed for each of these systems, depending on the processing conditions. One phase corresponds to a 2D layered perovskite and the other phase has optical properties corresponding to a dimensionality intermediate between a 2D and a 1D hybrid.

2H-Benzotriazol-2-ylethylammonium bromide and iodide and its difluorinated derivatives are synthesized and employed as interlayers for passivation of formamidinium lead triiodide (FAPbI3) solar cells. In combination with PbI2 and PbBr2, these benzotriazole derivatives form two-dimensional (2D) Ruddlesden-Popper perovskites (RPPs) as evidenced by their crystal structures and thin film characteristics. When used to passivate n-i-p FAPbI3 solar cells, the power conversion efficiency improves from 20% to close to 22% by enhancing the open-circuit voltage. Quasi-Fermi level splitting experiments and scanning electron microscopy cathodoluminescence hyperspectral imaging reveal that passivation provides a reduced nonradiative recombi-nation at the interface between the perovskite and hole transport layer. Photoluminescence spectroscopy, angle-resolved grazing-incidence wide-angle X-ray scattering, and depth profiling X-ray photoelectron spectroscopy studies of the 2D/three-dimensional (3D) interface between the benzotriazole RPP and FAPbI3 show that a nonuniform layer of 2D perovskites is enough to passivate defects, enhance charge extraction, and decrease nonradiative recombination. The research has received funding from the Ministry of Education, Culture, and Science (Gravity program 024.001.035) and the Netherlands Organization for Scientific Research via a Spinoza grant. This work of B.T.v.G. is part of the Advanced Research Center for Chemical Building Blocks, ARC CBBC, which is cofounded and cofinanced by the Netherlands Organization for Scientific Research (NWO) and the Netherlands Ministry of Economic Affairs (project 2016.03.Tue). W.T.M.v.G., K.V.H., L.L., and D.V. acknowledge the Research Foundation Flanders (FWO) for the funding of the SBO project PROCEED (S002019N) and the senior FWO research projects G043320N and G0A8723N. A.M. acknowledges the FWO for the funding of his FWO fundamental research PhD grant (1115721N). This study was supported by the Special Research Fund (BOF) of Hasselt University (BOF22PD01). J.F.O. acknowledges funding from the Engineering and Physical Sciences Research Council (EPSRC) Nano Doctoral Training Centre (EP/L015978/1).

In recent years, luminescent materials doped with Ln3+ ions have attracted much attention for their application as optical thermometers based on both downshifting and upconversion processes. This study presents research done on the development of highly sensitive optical thermometers in the physiological temperature range based on poly(methyl methacrylate) (PMMA) films doped with two series of visible Ln3+ complexes (Ln3+ =Tb3+ , Eu3+ , and Sm3+ ) and SiO2 nanoparticles (NPs) coated with these PMMA films. The best performing PMMA film doped with Tb3+ and Eu3+ complexes was the PMMA[TbEuL1 tppo]1 film (L1 =4,4,4-trifluoro-1-phenyl-1,3-butadionate; tppo=triphenylphosphine oxide), which showed good temperature sensing of Sr =4.21 % K-1 at 313 K, whereas for the PMMA films doped with Tb3+ and Sm3+ complexes the best performing was the PMMA[TbSmL2 tppo]3 film (L2 =4,4,4-trifluoro-1-(4-chlorophenyl)-1,3-butadionate), with Sr =3.64 % K-1 at 313 K. Additionally, SiO2 NPs coated with the best performing films from each of the series of PMMA films (Tb-Eu and Tb-Sm) and their temperature-sensing properties were studied in water, showing excellent performance in the physiological temperature range (PMMA[TbEuL1 tppo]1@SiO2 : Sr =3.84 % °C at 20 °C; PMMA[TbSmL2 tppo]3@SiO2 : Sr =3.27 % °C at 20 °C) and the toxicity of these nanoparticles on human cells was studied, showing that they were nontoxic. ispartof: CHEMISTRY-A EUROPEAN JOURNAL vol:27 issue:21 pages:6479-6488 ispartof: location:Germany status: published

The stereoselective preparation of a novel 4′-spirocyclopropyl nucleoside analogue has been developed by using a semibenzilic Favorskii rearrangement of a 4′-(2-chloro-3-oxocyclobutyl)spirofuranose as a key step. These chiral spirocyclic intermediates, readily obtained on a multigram scale from chiral-pool starting materials, were shown to be highly suitable precursors for achieving full stereoselectivity in the reduction–ring contraction sequence. The downstream introduction of a nucleobase through Vorbrüggen glycosylation successfully resulted in the formation of the corresponding novel 4′-spirocyclic nucleoside analogue in a stereospecific manner.

A simple and efficient synthetic route to [RuCl2(NHC)(p-cymene)] and [Ru(CO3)(NHC)(p-cymene)] complexes making use of a weak base, under aerobic conditions, is reported. This method enables access to a series of NHC-ruthenium compounds with moderate to good yields under mild conditions. The Ru pre-catalysts were successfully used in olefin oxidation catalysis at low catalyst loading and reach complete conversion in short times.

A sustainable and facile weak-base synthetic route to platinum N-heterocyclic carbene (NHC) complexes is disclosed. The mechanism of this reaction is also elucidated

L-ascorbic acid 2-phosphate magnesium (APMg) salt is a vitamin C derivative frequently used as a raw material in cell and tissue therapy. APMg is not only used as a replacement of the unstable ascorbate, but also shows additional cell-biological functionalities. However, its unknown structural characteristics hamper the mechanistic elucidation of its biological role. Therefore, different techniques were applied for APMg structure characterization. Firstly, the stoichiometric composition was characterized by its solvent, ligand and magnesium content. No crystals of APMg could be obtained; however, a single crystal of APNa, the sodium salt of l-ascorbic acid 2-phosphate, was successfully obtained and its crystal structure was elucidated. FT-IR was applied to further clarify the structure of solid APMg. Finally, the structure of APMg in aqueous solution was explored by potentiometric titration as well as FT-IR.

A new stable phosphorus ylide (p-tolyl)3P = CHCOC6H4(p-CN) (Y) was synthesized and a series of novel complexes based on metalated phosphorus ylides were prepared through the reaction of (p-tolyl)3P...

Tri(1-adamantyl)phosphine (PAd3) possesses unique steric and electronic properties positioning it at the border between tertiary phosphines and N-heterocyclic carbenes (NHC). Novel Au-PAd3 complexes were synthesized from the known [Au(PAd3)Cl]. We have optimised reaction conditions for the synthesis of this useful synthon in order to circumvent the formation of the [Au(PAd3)2]Cl. [Au(PAd3)Cl] was used to access a number of derivatives and some were deployed as catalysts. The hydration of alkynes was targeted to gauge the reactivity of Au-PAd3 complexes and permit comparison with NHC and tertiary phosphine congeners.

The present study highlights a straightforward and versatile strategy for the synthesis of strong poly(2-isopropenyl-2-oxazoline) hydrogels with tunable properties by using a bifunctional macrocyclic pillar[5]arene host having two carboxylic acid groups as cross-linker. This new strategy provides access to materials with tailored properties from soft and flexible to rigid and strong. The mechanical properties and water uptake of the hydrogels could be effortlessly controlled during the synthesis step through variation of the cross-linker content and after cross-linking by guest–host interactions. The hydrogels displayed strongly enhanced mechanical properties (i.e., compression and tensile modulus, energy dissipation, stress at break and storage modulus) compared to their counterparts cross-linked with linear dicarboxylic acids. The remarkable properties of the pillar[5]arene cross-linked hydrogels were assigned to the transfer of the external stress to the rigid and bulky pillar[5]arene residues that contribute to the overall dimensional stability of the hydrogels and allow energy dissipation. Moreover, we demonstrate the applicability of these materials for water purification. The hydrogels showed high adsorption performance for phenols and dyes such as methylene blue and methyl red and they could be easily regenerated, by washing with an organic solvent for reuse.

The reaction mechanism leading to the formation of cross-coupling palladium pre-catalysts of the PEPPSI family was investigated. Two intermediates were isolated and proved to be both suitable synthons to the pre-catalysts, with one permitting the design of a novel and greener user-friendly synthetic route. In light of this mechanistic understanding, the traditional one-pot method was shown to be possible using stoichiometric amounts of throw-away ligand, which represents a considerable synthetic improvement over the wasteful "in pyridine" approach.