Yulia V. Nelyubina

A Trigonal Prismatic Mononuclear Cobalt(II) Complex Showing Single-Molecule Magnet Behavior.

Single-molecule magnets (SMMs) with one transition-metal ion often rely on unusual geometry as a source of magnetically anisotropic ground state. Here we report a cobalt(II) cage complex with a trigonal prism geometry showing single ion magnet behavior with very high Orbach relaxation barrier of 152 cm(-1). This, to our knowledge, is the largest reported relaxation barrier for a cobalt-based mononuclear SMM. The trigonal prismatic coordination provided by the macrocyclic ligand gives intrinsically more stable molecular species than previously reported SMMs, thus making this type of cage complexes more amendable to possible functionalization that will boost their magnetic anisotropy even further.

“Higher density does not mean higher stability” mystery of paracetamol finally unraveled

Topological analysis of the experimental electron density distribution functions for two polymorphs of paracetamol showed that strong H-bonds are responsible for the higher stability of crystal phase I, weak interactions for the higher density of phase II. This made it possible to finally resolve the contradiction between the relative stabilities and the densities of the two paracetamol polymorphs.

Six-Membered Cyclic Nitronates as 1,3-Dipoles in Formal [3 + 3]-Cycloaddition with Donor–Acceptor Cyclopropanes. Synthesis of New Type of Bicyclic Nitrosoacetals

The first formal [3 + 3]-cycloaddition of nitronates with donor-acceptor cyclopropanes is reported. The reaction is catalyzed by ytterbium trifluoromethanesulfonate and leads to hitherto unknown bicyclic nitrosoacetals, possessing two annelated six-membered rings.

Simple Synthesis of Ruthenium π Complexes of Aromatic Amino Acids and Small Peptides

The interaction of [Ru(eta(6)-C(10)H(8))(Cp)](+) (Cp=C(5)H(5)) with aromatic amino acids (L-phenylalanine, L-tyrosine, L-tryptophane, D-phenylglycine, and L-threo-3-phenylserine) under visible-light irradiation gives the corresponding [Ru(eta(6)-amino acid)(Cp)](+) complexes in near-quantitative yield. The reaction proceeds in air at room temperature in water and tolerates the presence of non-aromatic amino acids (except those which are sulfur containing), monosaccharides, and nucleotides. The complex [Ru(eta(6)-C(10)H(8))(Cp)](+) was also used for selective labeling of Tyr and Phe residues of small peptides, namely, angiotensin I and II derivatives.

Pseudosymmetry as viewed using charge density analysis

Peculiarities of chemical bonding in crystalline 3-isopropyl-4-thiomethyl-N6-benzoylsidnone imine with four independent molecules were investigated by means of R. Baders “Atoms in Molecule” theory. For the fist time the pseudosymmetry phenomenon was explored at both the molecular (charge density within the molecular species) and supramolecular (network of intermolecular interactions) level.

From “Loose” to “Dense” Crystalline Phases of Calcium Carbonate through “Repulsive” Interactions: An Experimental Charge-Density Study

Anion-anion interactions in an eggshell: experimental electron density analysis for two polymorphs of calcium carbonate revealed why the less stable form, aragonite, has higher density than the most stable form, calcite. Although believed to be exclusively repulsive, the interactions between anions cause them to bind more tightly in a crystal and thus make the aragonite phase denser than its calcite counterpart.

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.

Hydrogen bonds between zwitterions: intermediate between classical and charge-assisted ones. A case study.

Detailed investigation of the electron density distribution function of N-succinopyridine in the crystal and in isolated state within Baders Atoms in Molecules theory has been carried out to analyze the charge density and energetical aspects of zwitterionic H-bonding. By means of comparative analysis of H-bonds formed between molecular, zwitterionic, and likely charged species, it was shown that, according to the criteria of H-bonding, all these interactions do not differ from each other.

A New Volume-Based Approach for Predicting Thermophysical Behavior of Ionic Liquids and Ionic Liquid Crystals

Volume-based prediction of melting points and other properties of ionic liquids (ILs) relies on empirical relations with volumes of ions in these low-melting organic salts. Here we report an accurate way to ionic volumes by Baders partitioning of electron densities from X-ray diffraction obtained via a simple database approach. For a series of 1-tetradecyl-3-methylimidazolium salts, the volumes of different anions are found to correlate linearly with melting points; larger anions giving lower-melting ILs. The volume-based concept is transferred to ionic liquid crystals (ILs that adopt liquid crystalline mesophases, ILCs) for predicting the domain of their existence from the knowledge of their constituents. For 1-alkyl-3-methylimidazolium ILCs, linear correlations of ionic volumes with the occurrence of LC mesophase and its stability are revealed, thus paving the way to rational design of ILCs by combining suitably sized ions.

NO3−⋯NO3− and NO3−⋯π interactions in the crystal of urea nitrate

The geometrical and energy aspects of the NO3−⋯NO3− and NO3−⋯π-system interactions were analyzed in the framework of the charge density investigation in crystalline urea nitrate. The results obtained have revealed that relatively weak anion–anion and anion–π (cation) contacts contribute greatly to the stabilization of the layered structure for this particular ionic material.