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Two series of binary halogen-bonded co-crystals involving perfluorinated di- and triiodobenzene (1,2-ditfb, 1,4-ditfb and 1,3,5-titfb) and 1,3-azulenedicarboxaldehyde (azdicho) 1 and 1,3-bis(4-pyridyl)azulene (azbbpy) 2 are reported. The crystal structures of the six new co-crystals show primarily O⋯I or N⋯I interactions, and the subsidiary weak C–H⋯F and π–π interactions of the aromatic units. Because the halogen-bond acceptors contain different heteroatoms and length size, the supramolecular recognition in the co-crystal is quite different. Besides novel structural features formed via halogen-bonding interactions, our results showed that the azulene moiety plays a unique organizing role in the formation and stabilization of supramolecular aggregates through π–π stacking interactions. These non-covalent interactions are investigated by theoretical studies through Hirshfeld surface analysis and DFT calculations followed by topological analysis of the electron density distribution within the QTAIM approach. The co-crystals were also investigated in solution by NMR spectroscopy through 19F-NMR and 1H,15N-HMBC experiments. [ABSTRACT FROM AUTHOR]

The availability of post-verbal subjects in non-canonical sentences is one of the properties which distinguish between non null-subject languages, like English, and consistent null-subject languages, like Romanian. L2 learning studies provide conflicting results with respect to whether native speakers of a null-subject language can fully eliminate ungrammatical postverbal subjects from their L2 English. The aim of this paper is to investigate if postverbal subjects are difficult to eliminate from the L2 English of L1 speakers of Romanian. The main results show that postverbal subjects are no longer accepted by L1 Romanian advanced and proficient learners of L2 English. However, intermediate learners accept significantly more postverbal subjects with unaccusative verbs than the other two groups. These results are in line with the Interface Hypothesis and the Full Transfer/Full Access Model. [ABSTRACT FROM AUTHOR]

The present paper investigates the learning of subjects in L2 English by Romanian learners with a view to identifying possible developmental differences between referential and non-referential subjects. The main question targets the role that feature interpretability plays in the acquisition process in a context in which the learners’ L1 allows null subjects. The main results reveal relatively early acquisition of subjects in L2 English. In line with the view that narrow syntax is acquirable in L2, the results show that proficient learners have native-like knowledge of subjects. A higher acceptance rate of null expletive subjects even at an advanced proficiency level indicates that non-referential subjects are vulnerable in L2 English. I account for these findings in terms of the Feature Interpretability Hypothesis. [ABSTRACT FROM AUTHOR]

A novel 3D coordination polymer, ∞3[{Cu3(felden)}4(btec)3]·17H2O, has been assembled using cationic trigonal nodes, [CuII3(felden)]3+, generated by a tricompartmental ligand, H3felden, which results from the Schiff condensation reaction between 2,4,6-triformylphloroglucinol and N,N-dimethylethylenediamine. The tetraanion of the 1,2,4,5-benzenetetracaboxylic acid (H4btec) was employed as a spacer. The structure of 1 shows large icosahedral cavities and channels and the magnetic interaction between the copper(II) ions within the triangles is weak and antiferromagnetic. [ABSTRACT FROM AUTHOR]

The supramolecular interactions between 1,3-bis(4-pyridyl)azulene (azbbpy) as a hydrogen bond acceptor and a variety of aromatic hydrogen-bond donors produced new binary molecular co-crystals and a salt. All crystal structures display extensive and very complex hydrogen bond networks containing both homo- and heterosynthons formed through robust O–H…N and OH…O hydrogen bonds. The binary co-crystals of azbbpy with 4,4′-biphenol and 4,4′-oxo-bis-benzoic acid in a 1 : 1 ratio revealed that the recognition process differs. While 4,4′-biphenol acts both as a donor and an acceptor of protons, generating a two-dimensional supramolecular network in which azbbpy interacts with only one pyridine moiety, the co-crystallization with 4,4′-oxo-bis-benzoic acid yielded zig-zag chains formed by alternating acid–pyridine supramolecular heterosynthons. Co-crystallization with isophthalic acid yields a 2 : 1 system, 4, as hydrogen-bonded zig-zag supramolecular chains containing a R44(36) graph set organized through strong OH…N and weak C–H…N hydrogen bonds. Co-crystallization of azbbpy with trimesic acid in different ratios yielded two distinct systems: co-crystal 5 and salt 6. In 5, the trimesic acid molecules are assembled in supramolecular helical chains which are further connected by azbbpy through hydrogen bonding and π–π interactions into a 3D architecture with channels that host water molecules. A complicated supramolecular 3D architecture is also established between trimesic anions and azbbpyH+ cations in crystal 6, resulting in channels filled with disordered solvent molecules. These types of interactions were also evidenced in a quantitative way and confirmed on grounds of the Hirshfeld surface mapped with geometrical parameters that characterize close contacts in co-crystals. The optical properties of these supramolecular systems showed strong absorption bands in the visible region due to the azulene fragment. [ABSTRACT FROM AUTHOR]

Here in, we describe an ultrafast, single-step microwave irradiation route (MW) to prepare graphene supported Pt nanoparticles, during which the small Pt nanoparticles are distributed uniformly on a reduced graphene oxide surface. This route provides evident advantages namely low cost, easiness, low time consuming and high yield in comparison to actual chemical methods to develop efficient Pt/rGO catalyst with Pt content close to state-of-the-art commercial composition. The structure and composition of prepared samples have been studied by specific techniques, while the electrocatalytic stability has been studied using ex-situ and in-situ measurements. High performance and electrochemically stable catalyst for PEM fuel cells was developed using the sample with highest loading and good dispersion. The fabricated Pt-rGO-based MEA was investigated for durability under fuel starvation in comparison with commercial Pt/C-based MEA. The electrocatalytic activity was investigated and the electrochemical response revealed the higher stability during accelerated degradation test under fuel starvation in comparison with commercial Pt/C. This study promotes the applicability of described preparation method to noble or transition metal nanoparticles embedded on graphene-based materials. • Pt/rGOs samples were prepared using the eco-friendly microwave-assisted process. • High platinum loading with good dispersion was prepared. • The electrochemical stability was investigated using the accelerated stress test. • The excellent stability under fuel starvation was demonstrated. [ABSTRACT FROM AUTHOR]