Imine N Atom (imine + n_atom)

Distribution by Scientific Domains

Selected Abstracts

Cocrystallization of two tautomers: 4-(1-{[4-(dimethylamino)benzylidene]hydrazono}ethyl)benzene-1,3-diol and 6-[(E)-1-{[4-(dimethylamino)benzylidene]hydrazino}ethylidene]-3-hydroxycyclohexa-2,4-dien-1-one (1/1)

Zhen-Hua Wu
Two different tautomeric forms of a new Schiff base, C17H19N3O2ĚC17H19N3O2, are present in the crystal in a 1:1 ratio, namely the enol,imine form 4-(1-{[4-(dimethylamino)benzylidene]hydrazono}ethyl)benzene-1,3-diol and the keto,amine form 6-[(E)-1-{[4-(dimethylamino)benzylidene]hydrazino}ethylidene]-3-hydroxycyclohexa-2,4-dien-1-one. The tautomers are formed by proton transfer between the hydroxy O atom and the imine N atom and are hydrogen bonded to each other to form a one-dimensional zigzag chain along the crystallographic b axis via intermolecular hydrogen bonds. [source]

The zwitterion of 4-nitro-2-{(E)-[2-(piperidin-1-yl)ethyl]iminomethyl}phenol

Rocio J. Santos-Contreras
The title Schiff base compound, 4-nitro-1-oxo-2-{(E)-[2-(piperidin-1-yl)ethyl]iminiomethyl}cyclohexadienide, C14H19N3O3, exists as a zwitterion, with the H atom of the phenol group being transferred to the imine N atom. The C=O, CAr,CAr and C,N bond lengths are in agreement with the oxocyclohexadienide,iminium zwitterionic form. The iminium H atom is engaged in a strong intramolecular hydrogen bond with the O atom of the keto group (N+,H...O) to form an S(6) motif. Soft C,H...O interactions in the ac plane lead to the development of hydrogen-bonded tapes, which are ,-stacked through the oxocyclohexadienide ring and iminium group. The significance of this study is in providing crystallographic evidence, supported by NMR and IR data, of the predominance of the oxocyclohexadienide,iminium zwitterion form over the noncharged canonical form in the title Schiff base. [source]

Conformational polymorphism in a Schiff-base macrocyclic organic ligand: an experimental and theoretical study

Leonardo Lo Presti
Polymorphism in the highly flexible organic Schiff-base macrocycle ligand 3,6,9,17,20,23-hexa-azapentacyclo(,15.02,6.016,20)triaconta-1(29),9,11,13,15(30),23,25,27-octaene (DIEN, C24H30N6) has been studied by single-crystal X-ray diffraction and both solid-state and gas-phase density functional theory (DFT) calculations. In the literature, only solvated structures of the title compound are known. Two new polymorphs and a new solvated form of DIEN, all obtained from the same solvent with different crystallization conditions, are presented for the first time. They all have symmetry, with the macrocycle positioned on inversion centres. The two unsolvated polymorphic forms differ in the number of molecules in the asymmetric unit Z,, density and cohesive energy. Theoretical results confirm that the most stable form is (II░), with Z, = 1.5. Two distinct molecular conformations have been found, named `endo' or `exo' according to the orientation of the imine N atoms, which can be directed towards the interior or the exterior of the macrocycle. The endo arrangement is ubiquitous in the solid state and is shared by two independent molecules which constitute an invariant supramolecular synthon in all the known crystal forms of DIEN. It is also the most stable arrangement in the gas phase. The exo form, on the other hand, appears only in phase (II░), which contains both the conformers. Similarities and differences among the occurring packing motifs, as well as solvent effects, are discussed with the aid of Hirshfeld surface fingerprint plots and correlated to the results of the energy analysis. A possible interconversion path in the gas phase between the endo and the exo conformers has been found by DFT calculations; it consists of a two-step mechanism with activation energies of the order of 30,40,kJ,mol,1. These findings have been related to the empirical evidence that the most stable phase (II░) is also the last appearing one, in accordance with Ostwald's rule. [source]

4-(9,10-Dihydroacridin-9-ylidene)thiosemicarbazide and its five-membered thiazole and six-membered thiazine derivatives

Ivan Poto
Two methyl derivatives, five-membered methyl 2-{2-[2-(9,10-dihydroacridin-9-ylidene)-1-methylhydrazinyl]-4-oxo-4,5-dihydro-1,3-thiazol-5-ylidene}acetate, C20H16N4O3S, (I), and six-membered 2-[2-(9,10-dihydroacridin-9-ylidene)-1-methylhydrazinyl]-4H -1,3-thiazin-4-one, C18H14N4OS, (II), were prepared by the reaction of the N -methyl derivative of 4-(9,10-dihydroacridin-9-ylidene)thiosemicarbazide, C14H12N4S, (III), with dimethyl acetylenedicarboxylate and methyl propiolate, respectively. The crystal structures of (I), (II) and (III) are molecular and can be considered in two parts: (i) the nearly planar acridine moiety and (ii) the singular heterocyclic ring portion [thiazolidine for (I) and thiazine for (II)] including the linking amine and imine N atoms and the methyl C atom, or the full side chain in the case of (III). The structures of (I) and (II) are stabilized by N,H...O hydrogen bonds and different ,,, interactions between acridine moieties and thiazolidine and thiazine rings, respectively. [source]