Search results for "Substituent"
showing 10 items of 353 documents
2-(3-Methyl-2-oxo-1,2-dihydroquinoxalin-1-yl)acetic acid dihydrate
2018
In the title compound, C11H10N2O3·2H2O, the constituent atoms of the dihydroquinoxaline moiety deviate from the mean plane of the unit by +0.0572 (8) to −0.0874 (8) Å while the acetic acid substituent is nearly orthogonal to this plane. The crystal packing consists of corrugated layers constructed by O—H...O, O—H...N and C—H...O hydrogen bonds, which also involve the lattice water molecules. O—H...O hydrogen bonds and π–π stacking interactions hold these layers together.
Substituent effects in nitro derivatives of carbazoles investigated by comparison of low-temperature crystallographic studies with density functional…
2014
The crystal structure of 9H-carbazole, C12H9N, (I), has been redetermined at low temperature for use as a reference structure in a comparative study with the structures of 1-nitro-9H-carbazole, C12H8N2O2, (II), and 9-nitrocarbazole, C12H8N2O2, (III). The molecule of (I) has crystallographically imposed mirror symmetry (Z′ = 0.5). All three solid-state structures are slightly nonplanar, the dihedral angles between the planes of the arene and pyrrole rings ranging from 0.40 (7)° in (III) to 1.82 (18)° in (II). Nevertheless, a density functional theory (DFT) study predicts completely planar conformations for the isolated molecules. To estimate the influence of nitro-group substitution on aroma…
Crystal structure of two N′-(1-phenylbenzylidene)-2-(thiophen-3-yl)acetohydrazides
2019
Two N′-(1-(phenylethylidene)-2-(thiophen-3-yl)acetohydrazides containing –OH and –OCH3 at the para-position of the phenyl ring have been synthesized and their molecular and crystal structures are reported.
Non-linear optical, electrochemical and spectroelectrochemical properties of amphiphilic inner salt porphyrinic systems
2016
Three zwitterionic meso-substituted A3B- and AB2C-porphyrins containing one sulfonato alkylpyridinium substituent and three or two alkoxy-substituted phenyl groups were synthesized in good yield and fully characterized as to their physicochemical properties by a variety of techniques. This new series of inner salt donor-acceptor meso-substituted porphyrin derivatives were prepared for possible application as amphiphilic probes for membrane insertion in the area of combined second-harmonic and two-photon fluorescence cellular microscopy. To this end, the linear and nonlinear optical properties of the compounds were characterized, together with their electrochemical and spectroelectrochemica…
Substituent effects of nitro group in cyclic compounds
2020
AbstractNumerous studies on nitro group properties are associated with its high electron-withdrawing ability, by means of both resonance and inductive effect. The substituent effect of the nitro group may be well described using either traditional substituent constants or characteristics based on quantum chemistry, i.e., cSAR, SESE, and pEDA/sEDA models. Interestingly, the cSAR descriptor allows to describe the electron-attracting properties of the nitro group regardless of the position and the type of system. Analysis of classical and reverse substituent effects of the nitro group in various systems indicates strong pi-electron interactions with electron-donating substituents due to the re…
Syntheses of Trifluoroethylated N-Heterocycles from Vinyl Azides and Togni’s Reagent Involving 1,n-Hydrogen-Atom Transfer Reactions
2020
2,2,2-Trifluoroethyl-substituted 3-oxazolines, 3-thiazolines, and 5,6-dihydro-2H-1,3-oxazines have been obtained by reacting substituted vinyl azides with a combination of Togni’s reagent and substoichiometric amounts of iron(II) chloride. The results of density functional theory calculations support the proposed mechanism involving 1,n-hydrogen-atom transfer reactions. peerReviewed
Gene delivery agents possessing antiradical activity: self-assembling cationic amphiphilic 1,4-dihydropyridine derivatives
2013
Seventeen 1,4-dihydropyridine (1,4-DHP) amphiphiles including differently substituted pyridinium, pyrazinium, N-methyl piperidinium or N-methyl morpholinium moieties as the cationic head-group of the molecule have been designed and synthesised. 1,4-DHP amphiphiles have been earlier proposed as a promising tool for plasmid DNA (pDNA) delivery in vitro. In this work the ability of the 1,4-DHP amphiphiles to self-assemble, to bind pDNA and to transfer it into the cells as well as the cytotoxicity of 1,4-DHP amphiphiles–pDNA complexes was studied. Furthermore, antiradical activity (ARA) of the 1,4-DHP derivatives was determined. We have revealed that all new 1,4-DHP amphiphiles possessed self-a…
Substituent Effects on the [N-I-N](+) Halogen Bond
2016
We have investigated the influence of electron density on the three-center [N-I-N](+) halogen bond. A series of [bis(pyri din e) io dine](+) and [1,2-bis ( (pyridin e-2-71 ethynyl)b e nze n e)io dine](+) BF4- complexes substituted with electron withdrawing and donating functionalities in the para-position of their pyridine nitrogen were synthesized and studied by spectroscopic and computational methods. The systematic change of electron density of the pyridine nitrogens upon alteration of the para-substituent (NO2, CF3, H, F, Me, OMe, NMe2) was confirmed by N-15 NMR and by computation of the natural atomic population and the pi electron population of the nitrogen atoms. Formation of the [N-…
Tailoring polymers through interplay of ligands within precatalysts: 8-(Nitro/benzhydryl-arylimino)-7,7-dimethyl-5,6-dihydroquinolylnickel halides in…
2017
A series of 8-(nitro/benzhydryl-substituted arylimino)-7,7-dimethyl-5,6-dihydroquinolines and the corresponding nickel halide complexes were synthesized and characterized. Molecular structures of representative nickel complexes were determined by single crystal X-ray diffraction, showing the dinuclear dimers with distorted square-pyramidal geometry around the nickel center. The binding energies determined by X-ray photoelectron spectroscopy (XPS) indicate the effective coordination between the sp2-nitrogen and nickel atoms as well as the influence of both the halogen ligands and the substituents within dihydroquinolines on the strength of the NiN bond. Ethylene polymerization with the nicke…
Structure-based evaluation of the resonance interactions and effectiveness of the charge transfer in nitroamines
2011
Structural data for five nitroamines of general formula Me2N–G–NO2 show effectiveness of the ground-state charge transfer to be most and least efficient in N,N-dimethylnitramine and in 4-N,N-dimethylamino-β-nitrostyrene, respectively. Electron-donor power of the amino nitrogen atom in the latter compound is less than that in 4-nitro-β-N,N-dimethylaminostyrene (these two compounds are isomers). Natural population analysis shows that the charge transfer from the amino to the nitro oxygen atoms is most effective in N,N-dimethylnitramine, Me2N–NO2. The nitro oxygen atoms are not the only acceptors of the negative charge lost by the amino nitrogen atom. The nitro group in two substituted nitrobe…