Ivan V. Glukhov

“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.

Carboranes: chemical concepts derived from the AIM study of the experimental and theoretical electron density distribution functions

On the basis of high-resolution X-ray diffraction studies as well as quantum-chemical calculations of five carborane derivatives the peculiarities of electron density distribution functions have been analyzed. The data obtained permitted a deeper insight into the nature of unusual properties of the C-C bond in o-carborane and investigating intermolecular H ... H interactions in crystal. It was shown that such an approach allows estimating the values of lattice energy for the crystals of carboranes.

New carborane-containing amino acids and their derivatives. Crystal structures of n-protected carboranylalaninates

New alanine derivatives containing both the carboranyl and trifluoromethyl groups were synthesized by the reaction of organometallic derivatives of o-carborane with methyl trifluoropyruvate imines. When using the 1R-(−)-menthoxycarbonyl protecting group at the nitrogen atom, one of diastereomers was isolated and characterized. Trifluoromethyl-carboranylalanine methyl esters containing different protecting groups at the nitrogen atom were studied by X-ray diffraction. Both complete and partial deprotection of the amino and carboxy groups was performed.

Polyphenylcyclopentadienyl complexes of rare earth elements

Reaction of LnCl3(thf)x (Ln = Y, La, Yb, Lu) with NaCpPhn (CpPhn = 1,3-Ph2C5H3, 1,2,4-Ph3C5H2, Ph4C5H) leads to formation of monocyclopentadienyl dichloride complexes Yb(Ph2C5H3)Cl2(thf)3 (1), Ln(Ph3C5H2)Cl2(thf)3 (Ln = Y (2), Lu (3)), La(Ph4C5H)Cl2(thf)3 (4). Molecular structures of 1, 2 and the polynuclear complex [(Ph3C5H2)3Lu4(Cl)7(O)(thf)3] (5), which is a partial hydrolysis product of 3, have been established by the X-ray method.

Analysis of strong and weak inter- and intramolecular interactions in the crystals of carborane derivatives

Organic compounds exhibiting photoor thermochromicity are of considerable interest owing to their properties and possible applications. The photochromism of salicylideneaniline (SA) was discovered by Senier et al. at the beginning of last century, and in 1964, Cohen et al. [1] observed its polymorphism. It is generally accepted that the stable form of SA in the ground state is the enol form, with an intramolecular hydrogen bond between the hydroxyl proton and the nitrogen atom. Upon photoexcitation of this enol form with UV light, it undergoes an ultrafast proton transfer from the hydroxyl group to the nitrogen, due to the electronic redistribution in the excited state. The proton transfer generates a keto tautomer in the excited state. We report on the alpha-2-polymorph structure of SA in the ground state [2].We also describe a new polymorph, beta, which features a planar SA molecule and is therefore thermochromic. We did also revisit the alpha-1-polymorph structure of SA described by Destro et al. [3], but reconsidering their hypothesis. We suggest a lowering of the symmetry with the aim to improve the structure solution.