The structure and photophysical properties of the luminophore 4′-butyl-4-propyloxysalicylideneaniline (1) were studied by X-ray diffraction analysis and differential scanning calorimetry. At room temperature, compound 1 does not luminesce. According to the DSC data, compound 1 undergoes a crystal—mesophase phase transition at 54.1 °C and it melts at 68.4 °C, being transformed into an isotropic melt. When cooled to 67.9 °C, the isotropic melt becomes turbid due to the formation of a mesophase. A yellow fluorescence of the sample is achieved under UV irradiation, it intensifies on further cooling, persists at room temperature for about a week, and then fades. The mechanical action triggers the growth of luminescent crystals (1′). The X-ray diffraction study of original non-luminescent crystal 1 and luminescent crystal 1′ demonstrated that they are structurally identical. The possible cause of the difference in the photophysical properties of crystals 1 and 1′ is discussed. It is based on dynamic processes leading to a shift of the prototropic equilibrium toward either the benzenoid or quinoid configuration of the bonds in the azomethine moiety.

The thermal properties of a series of substituted alkoxyaryls 1–5 and N-(n-butyloxybenzylidene)-p-propiophenone (6) were studied by differential scanning calorimetry. The phase transition temperatures and heats were determined. Compounds 1–5 do not form a mesophase during the melting process, unlike compound 6, which sbows several liquid-crystalline transitions. To explain the thermal properties, crystals of compound 4, containing sulfonyl fluoride and amino groups, and compound 6 were studied by X-ray diffraction at different temperatures. The crystal packing of 4 consists of dimers connected by weak hydrogen bonds and is composed of alternating aliphatic and aromatic regions. The absence of mesomorphism in compounds 1–5 can be attributed to the dominant role of a long (C14—C18) alkyl substituent in the formation of the packing. In the crystal packing of 6, there are clearly distinguished loose aliphatic and dense aromatic regions. Along with the stabilizing C—H⋯π and C—O⋯H interactions, this packing allows the existence of several liquid-crystalline phases on heating.

Uranium is a key element in nuclear power. Developing new extraction systems for its purification and concentration is an important task for improving the nuclear fuel cycle. In this work solvent extraction and uranyl complexes with tri-dentate pyridine-based and tetra-dentate phenanthroline-based diphosphonates were studied in thorough detail, both in the organic phase and the solid state. A combination of experimental methods (loading isotherms and conductivity measurements), spectroscopic techniques (UV–vis, EXAFS, 31P NMR, and Raman spectroscopy) and theoretical calculations were used to disclose the mechanism of U(VI) solvent extraction. We demonstrated that with tetradentate phenanthroline-based ligands, tight ion pairs ([UO2LNO3]+[UO2(NO3)3]−) are formed. With tridentate ligands, U(VI) forms a mixture of complexes with different stoichiometries. Significant differences in the structure of complexes with tridentate ligands in the solid state compared to complexes in the organic solution were also shown.

In this work, we studied the extraction systems for the separation f-elements based on the tetradentate N,O-donor ligand di(N-ethyl-4-ethylanilide) 2,2'-dipyridyl-6,6'-dicarboxylic acid (L). The organic phase of these systems was perspective fluorine-containing organic solvents-metanitrobenzotrifluoride (F-3), ionic liquid C4mimNTf2 (IL), and their mixture. The increase of Am(III) selectivity in the presence of Ln(III) in cases of the diluent mixture was shown. The mechanism of the f-element complexation leading to the improved properties of the extraction systems was studied by UV-visible, Raman-spectroscopy, XRD-study, and density functional theory calculations.

New zwitterionic bisulfite compounds of aldehydes, such as pyridine-2-carbaldehyde (1) and qunoline-2-carbaldehydes (2) , were for the first time spectroscopically characterized and structurally studied. In the crystal structures, molecules 1 and 2 are connected via intermolecular OH⋯−O 3 S and NH + ⋯−O 3 S interactions to form hydrogen-bonded chains. The oxidation of a solution of 2 in dimethyl sulfoxide with atmospheric air afforded quinaldil (3) and quinaldoin (4). In the crystalline state, compound 4 exists as the enediol tautomer formed by strong intramolecular hydrogen bonds.

Two series of bis-2,5-diphenyloxazolato cyclometalated iridium(III) complexes with substituted 2,2′-bipyridine or dipyridophenazine as the ancillary ligand have been prepared and characterized by X-ray structural analysis, 1 H NMR, and high resolution mass spectrometry. Bipyridine-based complexes exhibited bright emission in the yellow-orange region in solution, whereas their dipyridophenazine analogues demonstrated low quantum yields in the same spectral area. Varying the substituents in the ancillary ligand (CH 3 , H, COOH) caused noticeable shifts of the long-wavelength absorption bands retaining the redox potentials of the complexes practically unchanged. Crystallization of the complexes with iodine species gave interesting salts containing infinite polyiodide chains forming intermolecular contacts with the π-system of the ligands. Complexes bearing “anchoring” COOH-groups were used in sensitization of titania photoanodes followed by their study under the AM 1.5 G condition.

The crystal structure of N -(4-hexyloxybenzylidene)- p -toluidine ( 1 ) was determined at 150, 273, 295, and 320 K. Compound 1 was studied by differential scanning calorimetry (DSC). According to the DSC analysis, compound 1 exhibits monotropic mesomorphism associated with Cr-Iso-N-S-Cr phase transitions. The crystal packing is built up from alternating loosely packed aliphatic and closely packed aromatic regions, which is typical of enantiotropic mesomorphic compounds. In the closely packed regions, there are two types of weak directional interactions, such as π⋯π stacking interactions and weak C-H O hydrogen bonds, which link the molecules into centrosymmetric dimers. The thermal behavior of compound 1 and its relation to the crystal packing are discussed.

Potentially mesomorphic 4-[4-octyloxy-2-hydroxybenzylidene)]cyanoaniline C8H17OC6H3(OH)–CH=N–C6H4CN (I) has been studied by X-ray diffraction analysis and differential scanning calorimetry. The crystal packing of this compound does not exhibit any featurestypical of mesomorphic crystals. This fact is in agreement with the calorimetry data on the absence of mesomorphic properties for compound I.

The structure and thermal properties of mesomorphic phenyl benzoate CH 3 –C(O)–C 6 H 4 –OC(O)–C 6 H 4 –OC 9 H 19 ( I ) were studied by differential scanning calorimetry (DSC) and X-ray diffraction. The crystal packing of I is typical of mesomorphic crystals. It consists of alternating loosely packed aliphatic and closely packed aromatic regions, the latter regions being stabilized by weak directional C–H···π interactions. According to the DSC data, compound I does not form a mesophase upon melting. The latter was observed only upon cooling of the isotropic melt. The lack of enantiotropic mesomorphism in the crystal of I is attributed to the fact that C–H···π non-covalent interactions, which could ensure the structuring of the melt, are broken at the melting point.

New cyclometalated neutral iridium(III) complexes [Ir(L) 2 (dbm)] have been synthesized, where L is 2-arylphenanthroimidazoles with various electron-donor or acceptor substituents, dbm is dibenzoyl-methane. The compositions and structures of the ligands and complexes have been studied by X-ray diffraction and high-resolution mass spectrometry. In the absorption spectra of the complexes, a bathochromic shift of the absorption maxima is observed with an increase in the electron donor properties of the ligands. All the complexes show the reversible redox behavior; redox potentials fall in the range of 0.8–1.6 V. The combination of the obtained results allows us to consider the synthesized compounds as potential photosensitizers in solar cells.