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This study is aimed to explore the properties of cellulose nanocrystals (CNC)/polyvinyl alcohol (PVA) composite films with and without 1,2,3,4-butane tetracarboxylic acid (BTCA), a nontoxic crosslinker. CNC and CNC-PVA nanocomposite films are prepared using solution-casting technique. Differential scanning calorimetry (DSC) analyses show that crosslinking increased the glass transition temperature but reduced the melting temperature and crystallinity. Furthermore, high CNC concentrations in the PVA matrix interfere with PVA crystallinity, whereas in specific ratio between CNC and PVA, two different crystalline structures are observed within the PVA matrix. Film surfaces and fracture topographies characterized using scanning electron microscope indicate that at certain CNC-PVA ratios, micron-sized needle-like crystals have formed. These crystalline structures correlate with the remarkable improvement in mechanical properties of the CNC-PVA nanocomposite films, that is, enhanced tensile strain and toughness to 570% and 202 MJ m-3 , respectively, as compared to pristine PVA. BTCA enhances the tensile strain, ultimate tensile stress, toughness, and modulus of CNC films compared to pristine CNC films. Water absorption of crosslinked CNC and CNC-PVA nanocomposite films is significantly reduced, while film transparency is significantly improved as a function of PVA and crosslinker content. The presented results indicate that CNC-PVA nanocomposite films may find applications in packaging, and though materials applications.

A hydrogen transfer mechanism catalyzed by an IrIII PC(sp3)P pincer complex was studied by using DFT, and its efficiency was estimated by using the energetic span model. With the pristine complex, a hydrogen abstraction pathway could not be found, since a ligand dissociation to generate a vacant site is energetically costly. However, a nucleophilic attack of an alkoxide base (present in the reaction mixture) on the carbonyl ligand to form a carboalkoxy ligand generated an anionic catalyst that could easily provide the free site. From there, a hydride abstraction from an isopropyl ion (iPrO−) followed by a hydride transfer to acetophenone resulted in an efficient catalytic cycle.

Transfer dehydrogenation of ketones was efficiently carried out in acetone under air by means of a new Ir(III)-cyclometalated pincer type catalyst bearing a robust triptycene-based ligand.

Trans-chelating bis(diisopropylphosphino)triptycene (1) was employed as a platform for the construction of a new class of C(sp3)-metalated pincer complexes via C−H activation. We synthesized and fully characterized platinum(II), ruthenium(II), and iridium(III) compounds bearing this tridentate ligand. In contrast to the known all-aliphatic C(sp3)-metalated compounds, the new complexes exhibit excellent thermal and conformational stability even under very harsh and noninert conditions, likely due to the lack of labile α- or β-hydrogens. In addition, the three-dimensional barrelene-based scaffold represents a unique structural motif for the design of PC(sp3)P-based compounds with unexplored steric and electronic features.

The manuscript describes the synthesis and full characterization of a new PC(sp(3))P-based cyclometalated Ir(III) complex that manifests an exceptional thermal stability, as well as outstanding reactivity in hydrogen transfer reactions. The described compound represents the first example of a new family of stable C(sp(3))-metalated compounds.

trans -[1,8-Bis(diisopropylphosphino)triptycene]nickel (II) dichloride, trans -[1,8-bis(diisopropylphosphino)triptycene]carbonylrhodium (I) chloride and cis -[1,8-bis(diisopropyl-phosphino)triptycene] platinum (II) dichloride have been prepared and fully characterized in order to evaluate the coordination diversity of triptycene-based bidentate ligands. Their structural features and coordination preferences were studied and compared to the previously reported palladium complexes. The comparative structural analysis revealed that 1,8-bis(diisopropylphosphino)triptycene is able to access a variety of bite angles and to stabilize metal centers in different geometries. In addition, intramolecular weak C–H⋯Cl–Pt hydrogen bonding interactions which stabilize [1,8-bis(diisopropyl-phosphino)triptycene] platinum (II) dichloride in a constrained cis form are discussed.

The new air-stable chelating diphosphine ligands 1,8-bis(diisopropylphosphino)triptycene (2) and 1-(diisopropylphosphino)-8-(diphenylphosphino)triptycene (3) were synthesized in 51−73% yield from readily available starting materials. The examination of their coordination modes in the palladium(II) complexes [PdCl2(2)] (4) and [PdCl2(3)] (5) by means of 1H, 13C, and 31P NMR is consistent with the formation of trans-spanned complexes. X-ray analysis of 4 and 5 confirmed the structure but disclosed a strong distortion of the palladium centers from the expected square-planar geometry toward a butterfly-like environment. Further investigation revealed that 2 can also behave as a binucleating ligand, forming the quasi-closed halogen-bridged dipalladium complex 6, featuring an unusual nonplanar Pd2(μ-Cl)2Cl2 core. The catalytic activity of the new ligands and complexes was tested in palladium-catalyzed cross-coupling reactions of aryl chlorides with phenylboronic acid.

Ligand-metal cooperation in iridium and platinum complexes bearing tricyclic dibenzobarrelene-based PC(sp(3))P pincer ligands is discussed. We demonstrated that the carbon-metal bond in these complexes may be efficiently cleaved and regenerated via 1,2-addition/elimination reactions.

A straightforward synthetic route toward a new family of dibenzobarrelene-based cyclometalated compounds is described.