Katarzyna Gajda

Dimethyl 4,4'-(diazenedi-yl)dibenzoate at 100 K.

In the asymmetric part of the unit cell of the title compound, C16H14N2O4, there are two chemically equivalent but crystallographic independent half molecules. The geometric centre of each complete molecule lies on a crystallographic inversion centre. Both molecules are almost planar [mean deviations of atoms in the two molecules are 0.032 (2) and 0.044 (2) Å] and their geometries are similar. In the crystal, molecules are arranged in columns along the a axis. There are no intermolecular donor–acceptor distances shorter than 3.4 Å.

Preparation and molecular structures of N′-(2-heteroarylmethylidene)-3-(3-pyridyl)acrylohydrazides

Abstract The crystal and molecular structures of N′-(2-furylmethylidene)-3-(3-pyridyl)acrylohydrazide and N′-(2-thienylmethylidene)-3-(3-pyridyl)acrylohydrazide are reported, and the influence of the type of the heteroatom on the aromaticity of the aromatic rings is discussed. Both molecules are nearly planar. The geometry of the acrylohydrazide arrangement is comparable to that of homologous compounds. Density functional theory (DFT) calculations were performed in order to analyze the changes in the geometry of the studied compounds in the crystalline state and for the isolated molecule. The most significant changes were observed in the values of the N–N and C–N bond lengths. The harmonic oscillator model of aromaticity index, calculated for the furan and thiophene rings, demonstrated a noticeable increase in aromaticity in comparison to isolated rings and their DFT-calculated structures. By contrast, the nucleus independent chemical shift index indicated a decrease in aromatic character of the rings containing heteroatoms.

π-Electron delocalization in 2-benzoyl-5-phenylpyrazolidin-3-one

Abstract The crystal and molecular structures of 2-benzoyl-5-phenylpyrazolidin-3-one have been characterized by X-ray diffraction along with density functional theory studies. Cinnamic acid chloride was reacted with benzhydrazide, yielding 2-benzoyl-5-phenylpyrazolidin-3-one. This product was formed in the transformation comprising the nucleophilic addition of benzhydrazide to the styryl fragment of the α,β-unsaturated arrangement and subsequent cyclization. The molecule contains two benzene rings and one five-membered heterocyclic ring with an N–N single bond. The five-membered ring is composed of three atoms of sp3 hybridization and two atoms of sp2 hybridization, which cause the flattening of the heterocyclic ring. The Harmonic Oscillator Model of Aromaticity and Nucleus-Independent Chemical Shift indexes, calculated for the benzene rings, demonstrate that there are no substantial interactions between the regions of π-electron delocalization in the molecule. In the crystal structure, there are N–H···O hydrogen bonds that link the molecules along the crystallographic c axis and weak intermolecular C–H···O hydrogen bonds.