Synthesis And Electronic Properties Of Tris(4-Formylbiphenyl-4-Yl) Amine As A Building Block For Covalent Organic Frameworks And For Optoelectronic Devices.

Herein is reported the preparation of a new triphenylamine derivative, the tris(´4-formylbiphenyl- 4-yl) amine (TFBA). This compound exhibits optoelectronic properties suitable for its use in Dye-Sensitized Solar Cells (DSSCs) and light emitting diodes. The electrochemical properties were studied by cyclic voltammetry (CV) and square wave voltammetry (SWV). At the same time, the symmetrical chemical structure of TFBA allows its utilization as a building block in Covalent Organic Frameworks (COFs) bringing additional properties and a wide range of applications to such materials

Breaking the photoswitch speed limit

The forthcoming generation of materials, including artificial muscles, recyclable and healable systems, photochromic heterogeneous catalysts, or tailorable supercapacitors, relies on the fundamental concept of rapid switching between two or more discrete forms in the solid state. Herein, we report a breakthrough in the “speed limit” of photochromic molecules on the example of sterically-demanding spiropyran derivatives through their integration within solvent-free confined space, allowing for engineering of the photoresponsive moiety environment and tailoring their photoisomerization rates. The presented conceptual approach realized through construction of the spiropyran environment results in ~1000 times switching enhancement even in the solid state compared to its behavior in solution, setting a record in the field of photochromic compounds. Moreover, integration of two distinct photochromic moieties in the same framework provided access to a dynamic range of rates as well as complementary switching in the material’s optical profile, uncovering a previously inaccessible pathway for interstate rapid photoisomerization.</p

Praseodymium Nitride Endohedral Metallofullerene as Donor in Photovoltaic Cells

Trimetallic nitride template endohedral metallofullerenes (TNT EMFs) have been found to have structures and electronic properties that make them suitable for fields like molecular electronics. The particular compounds synthesized were the family of TNT EMFs Pr3N@C2n due to the relatively high yield of Pr3N@C­88 and even more due to its low first oxidation potential (0.06 V) and therefore this compound has the ability to act as a capable electron donor in a multilayer organic photovoltaic cell. The compound was synthesized through the use of a Kratschmer-Huffman arc reactor. A mixture of Praseodymium Oxide and graphite with a ratio of 3:7 respectively was made and then the powder was packed into graphite rods that were then arced inside the reactor. After it was arced, the soot that is created as a product of the arcing was dissolved in carbon disulfide and characterized by mass spectroscopy. The obtained metallofullerenes were isolated by HPLC with a one-stage separation, and then again the purified solution was passed under a two-stage HPLC separation

Electrochemical studies of grid and linear type M2+ (M=Zn, Cd and Pb) complexes of a bis-(hydrazone) bearing two symmetric carboxylic groups.

Herein we present the preparation of a bis-(hydrazone) containing a pyridine-pyrimidinepyridine framework. This compound can be visualized as a double arm system able of coordinating two metal ions in a terpyridine-like manner. By NMR (1D and 2D) it was determined a transoid conformation and an E configuration around the two imine double bonds. Complexation with M2+ (M = Zn, Cd, and Pb) ions resulted in grid and linear type structures which were studied by cyclic and squared wave voltammetry at different temperatures. No linear correlations of the redox potentials as a function of temperature were observed. The latter is likely due to rearrangements in the structure or to spin crossover events. The present results deserve further studies on the electronic properties of these types of compounds for the development of smart materials

Preparation of Novel Endohedral Metallofullerenes by the Krätschmer-Hoffman Arc Reactor Method

Since the discovery of C60 fullerene 25 years ago, the pursuit of encapsulating different metals, metallic clusters, and small molecules have attracted the attention of the scientific community due to the possibility of tuning the electronic and chemical properties of these compounds. As of today various metal-non-metal combinations have been obtained such as metallic nitrides, sulfides, metal carbides and metal oxides, however, none of them (except for Sc3N@C80) has been prepared in high yields. In this work we study the preparation process of different metallofullerenes and the dependence of the fullerene yield on various parameters such as plasma temperature, gas atmosphere and rods composition. Each of the resulting samples was analyzed by mass spectrometry (MALDI-TOF) and liquid chromatography (HPLC)

Photochemical and electrochemical studies on lanthanide complexes of 6-(hydroxymethyl)pyridine- 2-carboxaldehyde[2- methyl-pyrimidine-4,6-diyl] bis-hydrazone

Herein we report the synthesis of the 6-(hydroxymethyl)pyridine-2- carboxaldehyde[2-methyl-pyrimidine- 4,6-diyl]bis-hydrazone by a condensation reaction between 6-(hydroxymethyl) picolinaldehyde with 4,6-(bis-hydrazino)-2- methylpyrimidine. This bis-hydrazone can be visualized as a two-arm system which exhibits photochemical induced [E,E]/[E,Z]/[Z,Z’] isomerizations and double coordination to metal centers. Configurational changes, upon UV light irradiation, were followed over time by 1 H NMR, establishing that isomerization, in both arms, is a consecutive reaction that follows first-order kinetics (k1 = 4.06 x 10-4 s-1 and k2 = 2.80 x 10-4 s-1). Furthermore, the synthesis of bis-hydrazone metal complexes with La (III) and Sm (III) ions was achieved; subsequently, the absorption and emission properties of these complexes were studied, determining the fluorescence quantum yields, La= 0.2024 and Sm= 0.1413. Electrochemical studies of the complexes were conducted by square wave voltammetry, demonstrating that the bis-hydrazone and its complexes are electroactive species between +1.5 and -2.5 V

Evaluation of the Covalent Functionalization of Carbon Nano-Onions with Pyrene Moieties for Supercapacitor Applications

Herein, we report the surface functionalization of carbon nano-onions (CNOs) through an amidation reaction that occurs between the oxidized CNOs and 4-(pyren-4-yl)butanehydrazide. Raman and Fourier transform infrared spectroscopy methods were used to confirm the covalent functionalization. The percentage or number of groups in the outer shell was estimated with thermal gravimetric analysis. Finally, the potential applications of the functionalized CNOs as electrode materials in supercapacitors were evaluated by cyclic voltammetry and electrochemical impedance spectroscopy. Functionalization increased the specific capacitance by approximately 138% in comparison to that of the pristine CNOs, while acid-mediated oxidation reduced the specific capacitance of the nanomaterial by 24%