Lanthanide complexes with polyaminopolycarboxylates as prospective NMR/MRI diagnostic probes: peculiarities of molecular structure, dynamics and paramagnetic properties.

The paramagnetic lanthanide complexes with polyaminopolycarboxylate (PAPC) ligands attract considerable attention from the standpoint of potential applications thereof as relaxation agents used in medical magnetic resonance imaging (MRI) and in luminescent materials, as well as owing to promising use thereof as paramagnetic labels for studying the properties of biopolymers since they exhibit thermodynamic stability, good solubility in aqueous media and moderate toxicity. For the last decades, the NMR methods have been used to determine the physical and chemical properties of paramagnetic Ln compounds. The studies concerning paramagnetic NMR lanthanide-induced shifts (LISs) in dissolved Ln complexes, as well as the analysis of band shape as a function of temperature make it possible to obtain valuable information on the structure, intra- and intermolecular dynamics and paramagnetic properties thereof. This review is devoted solely to the following features: firstly, the processes of intramolecular dynamics of lanthanide complexes with polyamino-polycarboxylate ligands such as DOTA, EDTA and DTPA and their derivatives studied by NMR; secondly, the LISs of lanthanide complexes with EDTA, DOTA, DTPA and some of their derivatives depending on temperature and pH. Moreover, in this review, for the first time, the dependence of the activation energy of molecular dynamics in complexes with polydentate ligands on the atomic number of the lanthanide cation is analyzed and a monotonic change in energy is detected, which is due to the effect of lanthanide contraction. It should be noted that this phenomenon is quite general and may also appear in the future in many other series of lanthanide complexes with both other multidentate ligands and with bidentate and monodentate ligands. In the future, it is possible to predict the dependence of the properties of certain lanthanide complexes on the ionic radius of the lanthanide cation based on the approaches presented in the review. In this review, we have also presented the dynamic NMR as the main research method widely used to analyze the processes of molecular dynamics, and the structural studies based on the NMR relaxation spectroscopy and LIS analysis.

Synthesis of 1-Amino-2,4-Dinitroimidazole Optimized by Online Infrared Spectroscopy and its Energetic Properties.

The optimization of the reaction conditions (solvent, reaction time, and aminating agent) for the synthesis of 1-amino-2,4-dinitroimidazole (3) by monitoring the reaction with online infrared spectroscopy is reported in this study. First, the thermal characteristics of 3 were studied by using differential scanning calorimetry (DSC; using heating rates of 2.5, 5, 10, and 20 K min-1 ), thermogravimetric analysis (TG), and the thermal explosion method. The Kissinger and Ozawa methods were used to calculate the average activation energy for the formation of 3; with logarithmic frequency factors (ln A) of 21.04 and 9.62, and activation energies (Ea ) of 98.68 and 102.28 kJ mol-1 , respectively. Compound 3 and its reaction precursors 2,4-dinitroimidazole (1) and 1,4-dinitroimidazole were characterized by single-crystal X-ray diffraction. Compound 3 is shown to have good energetic properties, as determined through EXPLO5 v6.02 and actual measurement. Furthermore, this energetic material is found to have low impact sensitivity (IS>40 J) and friction sensitivity (FS>360 N).

Furazans with Azo Linkages: Stable CHNO Energetic Materials with High Densities, Highly Energetic Performance, and Low Impact and Friction Sensitivities.

Various highly energetic azofurazan derivatives were synthesized by simple and efficient chemical routes. These nitrogen-rich materials were fully characterized by FTIR spectroscopy, elemental analysis, multinuclear NMR spectroscopy, and high-resolution mass spectrometry. Four of them were further confirmed structurally by single-crystal X-ray diffraction. These compounds exhibit high densities, ranging from 1.62 g cm(-3) up to a remarkably high 2.12 g cm(-3) for nitramine-substituted azofurazan DDAzF (2), which is the highest yet reported for an azofurazan-based CHNO energetic compound and is a consequence of the formation of strong intermolecular hydrogen-bonding networks. From the heats of formation, calculated with Gaussian 09, and the experimentally determined densities, the energetic performances (detonation pressure and velocities) of the materials were ascertained with EXPLO5 v6.02. The results suggest that azofurazan derivatives exhibit excellent detonation properties (detonation pressures of 21.8-46.1 GPa and detonation velocities of 6602-10 114 m s(-1) ) and relatively low impact and friction sensitivities (6.0-80 J and 80-360 N, respectively). In particular, they have low electrostatic spark sensitivities (0.13-1.05 J). These properties, together with their high nitrogen contents, make them potential candidates as mechanically insensitive energetic materials with high-explosive performance.

Synthesis of 3-indole derivatives by copper sulfonato Salen catalyzed three-component reactions in water.

An efficient three-component reaction of indole, aldehyde, and malononitrile in water catalyzed by a copper(II) sulfonato Salen complex afforded 3-indole derivatives in good to excellent yields up to 97%.

An efficient copper-catalyzed carbon-sulfur bond formation protocol in water.

An efficient protocol of copper-catalyzed C-S bond formation between aryl halides and potassium thiocyanate leading to diaryl sulfides is reported. A variety of diaryl sulfides can be synthesized in good to excellent yields up to 94%.