Intramolecular N–H...O hydrogen bonding assisted by resonance. III. Structural studies of 1-ketone-2-arylhydrazone derivatives

Physical Properties of E143 Food Dye as a New Organic Semiconductor Nanomaterial

Organic semiconductors (OSCs) have attracted considerable attention for many promising applications, such as organic light-emitting diodes (OLEDs), organic field-effect transistors (OFETs), and organic photovoltaics (OPVs). The present work introduced E143 food dye as a new nanostructured organic semiconductor that has several advantages, such as low cost, easy fabrication, biocompatibility, and unique physical properties. The material was characterized using a transmission electron microscope (TEM), Fourier transform infrared (FT-IR) spectroscopy, thermogravimetric analysis (TGA), and optical absorption spectroscopy. The study of X-ray diffraction (XRD) showed that E143 dye has a monoclinic polycrystalline structure. Electrical and dielectric properties were performed by impedance spectroscopy at frequencies (20 Hz-1 MHz) in the temperature range (303-473 K). The values of interband transitions and activation energy recommended the application of E143 dye as a new organic semiconductor material with promising stability, especially in the range of hot climates such as KSA.

Resonance-Assisted Hydrogen Bond-Revisiting the Original Concept in the Context of Its Criticism in the Literature

In the presented research, we address the original concept of resonance-assisted hydrogen bonding (RAHB) by means of the many-body interaction approach and electron density delocalization analysis. The investigated molecular patterns of RAHBs are open chains consisting of two to six molecules in which the intermolecular hydrogen bond stabilizes the complex. Non-RAHB counterparts are considered to be reference systems. The results show the influence of the neighbour monomers on the unsaturated chains in terms of the many-body interaction energy contribution. Exploring the relation between the energy parameters and the growing number of molecules in the chain, we give an explicit extrapolation of the interaction energy and its components in the infinite chain. Electron delocalization within chain motifs has been analysed from three different points of view: three-body delocalization between C=C-C, two-body hydrogen bond delocalization indices and also between fragments (monomers). A many-body contribution to the interaction energy as well as electron density helps to establish the assistance of resonance in the strength of hydrogen bonds upon the formation of the present molecular chains. The direct relation between interaction energy and delocalization supports the original concept, and refutes some of the criticisms of the RAHB idea.

Tautomeric transformations and electronic structures of azopyrazolone dyes and their metal complexes

The features of molecular and electronic structures of complex compounds derived from azopyrazolone derivatives are reviewed. Despite the wide use of metal-containing azopyrazolone dyes for more than 1.5 centuries, little information on their molecular structure is found. Our recent researches allowed the introduction of new coordination modes of azopyrazolone derivatives at complexation with metals. Together with traditional bi- and tridentate coordination, the possibility of an N pyrazolone atom to be involved in coordination was also found. As a result, polymeric or polynuclear complexes were isolated and described by X-ray analysis, NMR, EPR, IR, and UV spectroscopy. The analysis of the interatomic distances in the organic anions indicated that azopyrazolone derivatives do not undergo significant azo-hydrazo tautomeric transformations at ionization and complexation despite strong shifts of the absorption bands in their IR and UV-VIS spectra.

A family of substituted hydrazonoisoxazolones with potential biological properties

The synthesis and characterization of a family of isoxazolones were performed. X-Ray diffraction over three structures was performed. All the compounds showed antineoplastic activity.

A structural framework of biologically active coumarin derivatives: crystal structure and Hirshfeld surface analysis

The relation between the lipophilicity parameter (log P) and the contribution of C–H⋯π interactions to the Hirshfeld surface has been investigated.

2-[2-(4-Nitrophenyl)hydrazinylidene]-1,3-diphenylpropane-1,3-dione

In the mol­ecular structure of the title compound, C₂₁H₁₅N₃O₄, the inter­planar angle between the benzoyl units is 89.7 (1)°. The corresponding angles between the phenyl­hydrazono and the benzoyl groups are 31.4 (3) and 60.8 (2)°, respectively. In the crystal, a strong resonance-assisted intra­molecular hydrogen bond (N—H⋯O) and a weak intra­molecular hydrogen bond (C—H⋯N) strongly affect the observed conformation of the mol­ecule. The crystal packing is determined by a strong inter­molecular hydrogen bond (N—H⋯O), giving rise to a helical chain along the a axis. In addition, two weak inter­molecular contacts (C—H⋯O) are observed.

2-[2-(3-Chloro-phen-yl)hydrazinyl-idene]-1,3-diphenyl-propane-1,3-dione

The mol-ecular structure of the title compound, C(21)H(15)ClN(2)O(2), features one strong intra-molecular N-H⋯O resonance-assisted hydrogen bond (RAHB). In the crystal, mol-ecules form inversion-related dimers via pairs of weak inter-molecular N-H⋯O contacts. These dimers are further stabilized via three weak C-H⋯O contacts, developing the three-dimensional structure.

2-[2-(4-Bromo-phen-yl)hydrazinyl-idene]-1,3-diphenyl-propane-1,3-dione

The conformation of the title mol­ecule, C₂₁H₁₅BrN₂O₂, is stabilized by a weak intra­molecular C—H⋯N hydrogen bond and a strong resonance-assisted N—H⋯O intra­molecular hydrogen bond. In the crystal, the mol­ecules are linked by weak inter­molecular C—H⋯O inter­actions, forming zigzag chains along the b axis.

Synthesis and structure of some azo coupled cyclic beta-enaminones

The reaction of 3-phenylaminocyclopent-2-en-1-one with 4-methyl, 4-methoxy and 4-chlorobenzenediazonium tetrafluoroborates was used to prepare the azo coupling products 3a-c. It was found that these compounds are present in both CDCl(3) solution and solid phase practically exclusively as (E)-3-phenylamino-2-(4-subst.phenyldiazenyl)cyclopent-2-en-1-ones with N--H...N intramolecular hydrogen bond. The substitution of the phenyl residue of the diazonium salt has no effect on the position of the tautomeric equilibrium. On the other hand, the compounds 4a, b formed by the reaction of 3-phenylamino-1H-inden-1-one with 4-methylbenzene- or benzenediazonium tetrafluoroborates exist in CDCl(3) solution and in solid phase as hydrazone compounds. In the solution they occur as a mixture of three forms, out of which two were identified as E/Z isomers with different types of hydrogen bonds. Compound 5 formed by the reaction of 3-amino-5,5-dimethylcyclohex-2-en-1-one with 4-methoxybenzenediazonium tetrafluoroborate is converted into a stable hydrochloride 5.HCl on standing in CHCl(3) solution; this product exhibits a high degree of delocalization of the positive charge. Its structure was studied by means of X-ray.

Waste-free chemistry of diazonium salts and benign separation of coupling products in solid salt reactions

Gas-solid and solid-solid techniques allow for waste-free and quantitative syntheses in the chemistry of diazonium salts. Five techniques for diazotations with the reactive gases NO(2), NO and NOCl are studied. Two types are mechanistically investigated with atomic force microscopy (AFM) and are interpreted on the basis of known crystal packings. The same principles apply to the cascade reactions that had been derived from one-step reactions. Solid diazonium salts couple quantitatively with solid diphenylamine and anilines to give the triazenes. Azo couplings are achieved with quantitative yields by cautious co-grinding of solid diazonium salts with beta-naphthol and C-H acidic heterocycles, such as barbituric acids or pyrazolinones. Solid diazonium salts may be more easily applied in a stoichiometric ratio for couplings in solution. Co-grinding of solid diazonium salts with KI gives quantitative yields of various solid aryl iodides. The unavoidable coupling products in salt reactions are completely separated from the insoluble products in a highly benign manner. The solid-state reactions compare favourably with similar solution reactions that produce much waste. The structures of the products are elucidated with IR and NMR spectroscopy and mass spectrometry, while the tautomeric properties of the compounds are studied with density functional calculations at the B3LYP/6-31G* and BLYP/6-31G** levels.