Artem O. Dmitrienko

Polymorphism in a Cobalt-Based Single-Ion Magnet Tuning Its Barrier to Magnetization Relaxation

A large barrier to magnetization reversal, a signature of a good single-molecule magnet (SMM), strongly depends on the structural environment of a paramagnetic metal ion. In a crystalline state, where SMM properties are usually measured, this environment is influenced by crystal packing, which may be different for the same chemical compound, as in polymorphs. Here we show that polymorphism can dramatically change the magnetic behavior of an SMM even with a very rigid coordination geometry. For a cobalt(II) clathrochelate, it results in an increase of the effective barrier from 109 to 180 cm-1, the latter value being the largest one reported to date for cobalt-based SMMs. Our finding thus highlights the importance of identifying possible polymorphic phases in search of new, even more efficient SMMs.

Electronic structure of cesium butyratouranylate(VI) as derived from DFT-assisted powder X-ray diffraction data.

Investigation of chemical bonding and electronic structure of coordination polymers that do not form high-quality single crystals requires special techniques. Here, we report the molecular and electronic structure of the first cesium butyratouranylate, Cs[UO(2)(n-C(3)H(7)COO)(3)][UO(2)(n-C(3)H(7)COO)(OH)(H2O)], as obtained from DFT-assisted powder X-ray diffraction data because of the low quality of crystalline sample. The topological analysis of the charge distribution within the quantum theory of atoms-in-molecules (QTAIM) space partitioning and the distribution of electron localization function (ELF) is reported. The constancy of atomic domain of the uranium(VI) atom at different coordination numbers (7 and 8) and the presence of three ELF maxima in equatorial plane of an uranyl cation attributed to the 6s and 6p electrons were demonstrated for the first time. Details of methodologies applied for additional verification of the correctness of powder XRD refinement (Voronoi atomic descriptors and the Morse restraints) are discussed.

Toward a Rigorous Definition of a Strength of Any Interaction Between Bader’s Atomic Basins

Strength of interaction between Baders atomic basins, enclosed by zero-flux surfaces of electron distribution, was proposed to be a measure of elastic deformation of an interaction. The set containing 53 atomic aggregate and covering all range of interaction strength (from van der Waals interactions to triple covalent bonds) was calculated by DFT and perturbation theory methods. Further analysis was performed to seek correlations between various local quantities based on electron density and effective force constants of stretching diatomic vibrations. The linear trend between effective force constants and the potential energy density at the (3, -1) critical point of electron distribution was found. This correlation was improved by the integration of the potential energy density over an interbasin zero-flux surface of electron density. Simple mechanical explanation of established trends is presented. The correlations can be further used to at least semiquantitatively compare any pair of interactions between Baders atomic basins.

The influence of halogen type on structural features of compounds containing α-halo-α,α-dinitroethyl moieties

We report the synthesis, as well as the molecular and crystal structures of N-(2-halo-2,2-dinitroethyl)pyrrolidine-2,5-diones (Hal = F, Cl, Br). A combination of X-ray structural analysis and quantum chemistry calculations was used for comparative analysis of molecular packing in the crystals of the synthesized compounds. It was shown that the fluorinated derivative contained a shortened F···F halogen bond of the first type, and in the bromo derivative the bromine atoms formed a relatively strong Br···O=C halogen bond of the second type, while the chlorine atom in the structure of chloro derivative interacted with a nitro group oxygen atom, also forming a weak Cl···O2N halogen bond of the second type. These variations in the “preferences” of different halogen atoms resulted in observable differences in the crystal structures of the studied compounds.

Solid‐State Reactions of Eicosaborate [B20H18]2− Salts and Complexes

A series of salts and complexes containing trans- and iso-isomers of octadecahydro-eicosaborate [B20 H18 ]2- dianion is synthesized and characterized using FTIR and 11 B NMR spectroscopies and X-ray diffraction techniques. Both isomers are found to act as four-, bi-, or zero-dentate ligands in reactions with copper(II), silver(I), and lead(II) through apical and/or equatorial boron atoms. Solid-state photo- and thermoinitiated reactions of octadecahydro-eicosaborate isomerization and solvent cleavage occurring in these compounds in a single-crystal-to-single-crystal manner are studied in situ. In contrast with solutions, in solids the reaction of boron cluster transformation occurs rarely, thus, analysis of crystal packing allowed us to suggest some criteria of isomerization of macropolyhedral boranes in crystals. X-ray diffraction data are used to confirm reaction path of isomerization of the [B20 H18 ]2- dianion.

The structure and phase transitions of crystalline polydimethylsilane (Me 2 Si) n revisited

The results of vibrational spectroscopy and X-ray diffraction obtained at the present level of the methods confirm the planar trans (all-A) conformation of the polydimethylsilane chain recently called in question. The differential scanning calorimetry data also verify the first order phase transitions at about –35 and 145 °C which proceed with retention of the all-A chain conformation and are of order-disorder type.

Synthesis of [1,2]dithiolo[3,4-b]pyridines via the reaction of dithiomalondianilide with arylmethylidenemalononitriles

6-Amino-4-aryl-7-phenyl-3-(phenylamino)-4,7-dihydro-3Н-[1,2]dithiolo[3,4-b]pyridine-5-carbonitriles were synthesized via the reaction of arylmethylidenemalononitriles with dithiomalonic acid dianilide in the presence of an excess of morpholine. The structure of 6-amino-4-(3,4-dimethoxyphenyl)-7-phenyl-3-(phenylamino)-4,7-dihydro-3Н-[1,2]dithiolo[3,4-b]pyridine-5-carbonitrile was studied by X-ray structural analysis.