Thermal polymerization improved the adhesion properties of softwood kraft lignin, making polymerized softwood kraft lignin a viable and sustainable partial substitute for phenol-formaldehyde resins used in engineered wood panels. This was confirmed by the increased shear strengths observed after pressing hardwood veneers with either alkaline aqueous lignin solutions or their blends with commercial phenol-formaldehyde resins. Plywood panels bonded with blends of polymerized kraft lignin and phenol-formaldehyde resins exhibited higher wood failure values compared with those bonded with phenol-formaldehyde resins alone. Extensive polymerization was achieved solely via nonoxidative thermal treatments. The impact of temperature and time on average molar mass, dispersity, and intrinsic viscosity was investigated by size-exclusion chromatography, revealing that the average molar mass of kraft lignin can be increased by more than 40 times its original value. Other critical parameters affecting the polymerization process such as pH and water content were identified, and their influence quantified. Hydroxyl content measured by 31P NMR before and after polymerization suggests that the formation of ethers between phenols and benzylic hydroxyl groups is mainly responsible for the observed increase in molar mass.

This study explores copper-catalyzed oxidative depolymerization (CCOD) of enzymatic hydrolysis lignins derived from aspen thermomechanical pulp (HW-EHL) and ball-milled softwood mechanical pulp (SW-EHL). Reaction conditions for HW-EHL depolymerization were optimized using a design of experiments (DOE) approach and subsequently applied to SW-EHL. Overall, the ideal conditions were temperatures of 160-180 degrees C, reaction durations of 0.75-1.25 h, and oxygen pressures of 135-240 kPa. Under these conditions, high monomer yields were achieved-up to 37% for HW-EHL and 23% for SW-EHL based on their respective lignin content-comparable to those obtained from milled wood, highlighting the strong potential of EHLs as feedstocks for aromatic monomer production. The process was successfully scaled up, and a protocol for the isolation of crystalline vanillin from the CCOD reaction mixture is provided. These findings underscore the value of integrating enzymatic hydrolysis with mechanical pretreatments for woody biomass valorization.

Industrial kraft lignins are mixtures of macromolecular components variable in both structure and composition. To maximize their value in commercial applications, they often need to be homogenized and purified. Several fractionation methods have been reported to improve the properties of kraft lignins, but these reports have been mostly limited to kraft lignins of single origins. In this study, the physicochemical properties of fractions from four industrial kraft lignins were compared. Fractionation was performed on both softwood and hardwood lignins by partial dissolution in aqueous ethanol followed by precipitation with water. The yields of each fraction varied greatly between the lignins, with differences reaching up to 35% for a single fraction. All fractions were characterized which showed that fractions having remarkably similar properties and compositions can be obtained from different lignins. Organic and inorganic impurities were found to concentrate in specific fractions which allowed the isolation of highly purified fractions of kraft lignin. These results highlight the importance of matching individual kraft lignins with suitable applications.

A green methodology for the methylation of kraft lignins with chloromethane has been developed.

Conjugated polymers are widely used in thin-film organic photovoltaic devices to absorb light and serve as electron donors or acceptors. Small molecular analogues are attractive substitutes because they have fully defined structures, can be purified rigorously, and are typically more soluble and volatile. However, producing active films composed primarily of small molecules remains challenging. We have devised bulk heterojunction solar cells in which poly(3-hexylthiophene-2,5-diyl) and poly[[9-(1-octylnonyl)-9H-carbazole-2,7-diyl]-2,5-thiophenediyl-2,1,3-benzothiadiazole-4,7-diyl-2,5-thiophenediyl] are used as matrices to prepare films containing low-bandgap push–pull molecules as electron donors and (6,6)-phenyl-C61-butyric acid methyl ester or (6,6)-phenyl-C71-butyric acid methyl ester as electron acceptors. Compared with reference devices devoid of push–pull molecular additives, increases in power conversion efficiencies up to 30.4% were measured.

An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.

Predictably ordered materials can be constructed by a modular strategy in which properly designed molecular components are positioned in space by reliable interactions. In principle, this approach can be used to control the arrangement of adjacent systems of π-conjugation, thereby creating molecular materials with valuable optoelectronic properties. To explore this possibility, we have synthesized compounds in which 2,4-diamino-1,3,5-triazinyl groups are attached to derivatives of 6,12-dihydroindeno[1,2-b]fluorene to produce molecules with well-defined cruciform topologies, extended π-conjugated aromatic cores, and an ability to form multiple hydrogen bonds. These compounds crystallize to form robust open hydrogen-bonded networks with parallel indenofluorenyl cores, significant volume (64-70%) available for accommodating guests, and characteristic luminescence. Our results will help permit the rational design of complex new molecular materials in which multiple optoelectronically active components are arranged in productive ways.

The synthesis and chiral resolution of a C-3-symmetric triaminotribenzotriquinacene is reported. Both enantiomers were obtained in good yields and excellent enantiomeric purity by selective precipitation of their monodibenzoyltartrate salts. Conversion of the enantiopure (M)-triaminotribenzotriquinacene into a C-3-symmetric triiodide highlights the usefulness of this compound as a starting point for the preparation of other enantiopure C-3-symmetric tribenzotriquinacene derivatives, which may find application as building blocks for the preparation of chiral molecules in the nanosize regime.

We describe a simple way to build giant macrocyclic hydrocarbons by the reversible formation of carbon-carbon bonds. Specifically, extended spirobifluorene-substituted derivatives of Wittig's hydrocarbon were synthesized and found to undergo oligomerization, giving the largest hydrocarbon that has been crystallized and characterized by X-ray diffraction to date.

The strategy of chirality-assisted synthesis, which makes use of enantiomerically pure building blocks that are designed to associate in a single geometric orientation, was applied to synthesize an octameric hydrogen-bonded capsule with a cavity volume of 2300 Å3 . This cube-shaped capsule forms even host-guest complexes with tetraalkylammonium ions, and accommodates the large tetrahexadecylammonium cation in its cavity. The use of an enantiopure building block was shown to be highly beneficial for capsule formation, whereas its racemate also generates a large amount of ill-defined aggregates in solution and crystallizes as a hydrogen-bonded network.

Aromatic C-nitroso compounds (Ar-N═O) and related species have a rich chemical history, and they continue to interest researchers in many fields. Among the most distinctive and puzzling properties of these compounds is their ability to dimerize reversibly to form azodioxy compounds. The present review subjects this intriguing phenomenon to comprehensive analysis. All aspects of the subject are examined in detail, including the structures of monomeric and dimeric forms, the mechanism of dimerization, features that favor or disfavor dimerization, thermodynamic and kinetic factors, dimerization under specific conditions (including in solution, in the solid state, and on surfaces), and the special associative behavior of dinitroso and polynitroso compounds. By summarizing the current state of knowledge, the review promises to spur further advances in the evergreen field of C-nitroso chemistry, including the discovery of new ways to exploit the reversible dimerization of nitrosoarenes.

An inherently chiral C3 -symmetric triaminotribenzotriquinacene was condensed in racemic and enantiomerically pure form with a bis(salicylaldehyde) to form [2+3] salicylimine cage compounds. Investigations on the chiral self-sorting revealed that while entropy favors narcissistic self-sorting in solution, selective social self-sorting can be achieved by exploiting the difference in solubility between the homochiral and heterochiral cages. Gas sorption measurements further showed that seemingly small structural differences can have a significant impact on the surface area of microporous covalent cage compounds.

A new synthetic procedure for the synthesis of 1,4,7-tribromo-10-methyltribenzotriquinacene on multigram scale is reported. Its conversion into 1,4,7-trimethoxy-10-methyltribenzotriquinacene is also described. Both procedures are simpler and greener alternatives to the known ones, and the crystal structures of both compounds are disclosed.

Amidines can be protonated by carboxylic acids to give amidinium carboxylates, and the ions can associate by forming multiple charge-assisted hydrogen bonds according to reliable motifs. Extended hydrogen-bonded networks can be constructed by treating suitable bis(amidines) with acids containing multiple carboxyl groups. To further explore the potential of this strategy, we have determined the structures of salts produced by treating 2,2'-bi-2-imidazoline, a cyclic bis(amidine), with oxalic, fumaric, terephthalic, and trimesic acids. The structures of the salts proved to incorporate features resulting predictably from the geometry of the ions and their ability to engage in charge-assisted hydrogen bonds.

An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.

An emerging strategy for making ordered materials is modular construction, which connects preformed molecular subunits to neighbours through interactions of properly selected reactive sites. This strategy has yielded remarkable materials, including metal–organic frameworks joined by coordinative bonds, supramolecular networks linked by strong non-covalent interactions, and covalent organic frameworks in which atoms of carbon and other light elements are bonded covalently. However, the strategy has not yet produced covalently bonded organic materials in the form of large single crystals. Here we show that such materials can result from reversible self-addition polymerizations of suitably designed monomers. In particular, monomers with four tetrahedrally oriented nitroso groups polymerize to form diamondoid azodioxy networks that can be fully characterized by single-crystal X-ray diffraction. This work forges a strong new link between polymer science and supramolecular chemistry by showing how predictably ordered covalent or non-covalent structures can both be built using a single modular strategy. Modular construction using connectable molecular subunits is a powerful strategy for making new carbon-based materials. So far, large crystals have been produced only from subunits linked by weak interactions. Covalently bonded analogues have now been prepared by reversible self-addition polymerization of suitable monomers and structurally characterized by single-crystal X-ray diffraction.

Pd-catalyzed coupling of aryl halides with TeocNHOTBS, followed by treatment of the products with TBAF, provides effective access to a wide range of N-arylhydroxylamines by a route that produces stable doubly-protected intermediates and allows the protective groups to be removed under mild conditions that do not cause extensive degradation of the final product.