Molecular Design and Crystal Chemistry of Polyfluorinated Naphthalene-bis-phenylhydrazimides with Superior Thermal and Polymorphic Stability and High Solution Processability.

Naphthalene tetracarboxylic diimides (NDIs) are highly promising air-stable n-type molecular semiconductor candidates for flexible and cost-effective organic solar cells and thermoelectrics. Nonetheless, thermal and polymorphic stabilities of environmentally stable NDIs in the low-to-medium temperature regime (<300 °C) remain challenging properties. Structural, thermal, spectroscopic, and computational features of polyfluorinated NDI-based molecular solids (with up to 14 F atoms per NDI molecule) are discussed upon increasing the fluorination level. Slip-stacked arrangement of the NDI cores with suitable π-π stacking and systematically short interplanar distances (<3.2 Å) are found. All these materials exhibit superior thermal stability (up to 260 °C or above) and thermal expansion coefficients indicating a response compatible with flexible polymeric substrates. Optical bandgaps increase from 2.78 to 2.93 eV with fluorination, while LUMO energy levels decrease down to -4.37 eV, as shown per DFT calculations. The compounds exhibit excellent solubility of 30 mg mL-1 in 1,4-dioxane and DMF.

Modeling bismuth insertion in 1D hybrid lead halide TMSO(PbxBiy)I3pseudo-perovskites.

The structures of the disordered 1D (pseudo-)perovskites of general TMSO(PbxBiy)I3formulation [TMSO = (CH3)3SO+], obtained by doping the TMSOPbI3species with Bi3+ions, are investigated through the formulation of a statistical model of correlated disorder, which addresses the sequences of differently occupied BI6face-sharing octahedra (B = Pb, Bi or vacant site) within ideally infinite [(BI3)-]nchains. The x-ray diffraction patterns simulated on the basis of the model are matched to the experimental traces, which show many broad peaks with awkward (nearly trapezoidal) shapes, under the assumption that the charge balance is fully accomplished within each chain. The analysis allowed to establish a definite tendency of the metal species to cluster as pure Pb and Bi sequences. The application of the model is discussed critically, in particular as what concerns the possibility that further B-site neighbors beyond the second may influence the overall B-site occupancies.

Modelling the structural disorder in trigonal-prismatic coordinated transition metal dichalcogenides.

Trigonal-prismatic coordinated transition metal dichalcogenides (TMDCs) are formed from stacked (chalcogen)-(transition metal)-(chalcogen) triple layers, where the chemical bond is covalent within the triple layers and van der Waals (vdW) forces are effective between the layers. Bonding is at the origin of the great interest in these compounds, which are used as 2D materials in applications such as catalysis, electronics, photoelectronics, sensors, batteries and thermoelectricity. This paper addresses the issue of modelling the structural disorder in multilayer TMDCs. The structural model takes into account stacking faults, correlated displacement of atoms and average crystallite size/shape, and is assessed by simulation of the X-ray diffraction pattern and fitting to the experimental data relative to a powdered sample of MoS2 exfoliated and restacked via lithiation. From fitting, an average crystallite size of about 50 Å, nearly spherical crystallites and a definite probability of deviation from the fully eclipsed atomic arrangement present in the ordered structure are determined. The increased interlayer distance and correlated intralayer and interlayer atomic displacement are attributed to the presence of lithium intercalated in the vdW gap between triple layers (Li/Mo molar ratio of about 0.06). The model holds for the whole class of trigonal-prismatic coordinated TMDCs, and is suitably flexible to take into account different preparation routes.

Salphen metal complexes as potential anticancer agents: interaction profile and selectivity studies toward the three G-quadruplex units in the KIT promoter.

DNA G-rich sequences can organize in four-stranded structures called G-quadruplexes (G4s). These motifs are enriched in significant sites within the human genomes, including telomeres and promoters of cancer related genes. For instance, KIT proto-oncogene promoter, associated with diverse cancers, contains three adjacent G4 units, namely Kit2, SP, and Kit1. Aiming at finding new and selective G-quadruplex binders, we have synthesized and characterized five non-charged metal complexes of Pt(II), Pd(II), Ni(II), Cu(II) and Zn(II) of a chlorine substituted Salphen ligand. The crystal structure of the Pt(II) and Pd(II) complexes was determined by XRPD. FRET measurements indicated that Pt(II) and Pd(II) compounds stabilize Kit1 and Kit2 G4s but not SP, telomeric and double stranded DNA. Spectroscopic investigations (UV-Vis, circular dichroism and fluorescence) suggested the Cu(II) complex as the most G4-selective compound. Interestingly, docking simulations indicate that the synthesized compounds fit groove binding pockets of both Kit1 and Kit2 G4s. Moreover, they exhibited dose-dependent cytotoxic activity in MCF-7, HepG2 and HeLa cancer cells.

Interface Diffusion and Compatibility of (Ba,La)FeO3-δ Perovskite Electrodes in Contact with Barium Zirconate and Ceria.

Ba1-xLaxFeO3-δ perovskites (BLF) capable of conducting electrons, protons, and oxygen ions are promising oxygen electrodes for efficient solid oxide cells (fuel cells or electrolyzers), an integral part of prospected large-scale power-to-gas energy storage systems. We investigated the compatibility of BLF with lanthanum content between 5 and 50%, in contact with oxide-ion-conducting Ce0.8Gd0.2O2-δ and proton-conducting BaZr0.825Y0.175O3-δ electrolytes, annealing the electrode-electrolyte bilayers at high temperature to simulate thermal stresses of fabrication and prolonged operation. By employing both bulk X-ray diffraction and synchrotron X-ray microspectroscopy, we present a space-resolved picture of the interaction between electrode and electrolyte as what concerns cation interdiffusion, exsolution, and phase stability. We found that the phase stability of BLF in contact with other phases is correlated with the Goldschmidt tolerance factor, in turn determined by the La/Ba ratio, and appropriate doping strategies with oversized cations (Zn2+, Y3+) could improve structural stability. While extensive reactivity and/or interdiffusion was often observed, we put forward that most products of interfacial reactions, including proton-conducting Ba(Ce,Gd)O3-δ and mixed-conducting (Ba,La)(Fe,Zr,Y)O3-δ, may not be very detrimental for practical cell operation.

Polyfluorinated Naphthalene-bis-hydrazimide for Solution-Grown n-Type Semiconducting Films.

Naphthalene tetracarboxylic diimides (NDIs), possessing low-lying and tunable LUMO levels, are of wide interest for their aptitude to provide cost-effective, flexible, and environmentally stable n-type organic semiconductors through simple solution processing. NDI-based aromatic hydrazidimides are herein studied in relation to their chemical and environmental stability and as spin-coated stable thin films. In the case of the pentafluorinated residue, these were found to be crystalline, highly oriented, and molecularly flat (roughness = 0.3 nm), based on optical and atomic force microscopy, X-ray diffraction in specular and grazing incidence geometry, and X-ray reflectivity measurements. A new polymorph, previously undetected during the isolation of bulk powders or in their controlled thermal treatments, is found in the thin film and was metrically and structurally characterized from 2D GIWAXS patterns (monoclinic, P2/c, a = 17.50; b = 4.56; c = 14.24 Å; ß = 84.8°). This new thin-film phase, TF-F5, is formed no matter whether silicon, glass, or polymethylmethacrylate substrates are used, thus opening the way to the preparation of solution-grown flexible semiconducting films. The TF-F5 films exhibit a systematic and rigorous molecular alignment with both orientation and packing favorable to electron mobility (µ = 0.02 cm2 V-1 s-1). Structural and morphological differences are deemed responsible for the absence of measurable conductivity in thin films of polyfluorinated analogues bearing -CF3 residues on the hydrazidimide aromatic rings.

Highly Stable Thin Films Based on Novel Hybrid 1D (PRSH)PbX3 Pseudo-Perovskites.

In this study, the structure and morphology, as well as time, ultraviolet radiation, and humidity stability of thin films based on newly developed 1D (PRSH)PbX3 (X = Br, I) pseudo-perovskite materials, containing 1D chains of face-sharing haloplumbate octahedra, are investigated. All films are strongly crystalline already at room temperature, and annealing does not promote further crystallization or film reorganization. The film microstructure is found to be strongly influenced by the anion type and, to a lesser extent, by the DMF/DMSO solvent volume ratio used during film deposition by spin-coating. Comparison of specular X-ray diffraction and complementary grazing incidence X-ray diffraction analysis indicates that the use of DMF/DMSO mixed solvents promotes the strengthening of a dominant 100 or 210 texturing, as compared the case of pure DMF, and that the haloplumbate chains always lie in a plane parallel to the substrate. Under specific DMF/DMSO solvent volume ratios, the prepared films are found to be highly stable in time (up to seven months under fluxing N2 and in the dark) and to highly moist conditions (up to 25 days at 78% relative humidity). Furthermore, for representative (PRSH)PbX3 films, resistance against ultraviolet exposure (λ = 380 nm) is investigated, showing complete stability after irradiation for up to 15 h at a power density of 600 mW/cm2. These results make such thin films interesting for highly stable perovskite-based (opto)electronic devices.

Solid-Solid Interfaces in Protonic Ceramic Devices: A Critical Review.

The literature concerning protonic ceramic devices is critically reviewed focusing the reader's attention on the structure, composition, and phenomena taking place at solid-solid interfaces. These interfaces play a crucial role in the overall device performance, and the relevance of understanding the phenomena taking place at the interfaces for the further improvement of electrochemical protonic ceramic devices is therefore stressed. The grain boundaries and heterostructures in electrolytic membranes, the electrode-electrolyte contacts, and the interfaces within composite anode and cathode materials are all considered, with specific concern to advanced techniques of characterization and to computational modeling by ab initio approaches. An outlook about future developments and improvements highlights the necessity of a deeper insight into the advanced analysis of what happens at the solid-solid interfaces and of in situ/operando investigations that are presently sporadic in the literature on protonic ceramic devices.