Crystal structures of 1-hydroxylimidazole and imidazole 1-oxide derivatives

Abstract

The N-oxide or 1-hydroxy forms of four solid 1-hydroxy-5-(4-methyl-2-nitroimidazol-2-yl)-4-phenyl-2-(Xphenyl)-imidazole derivatives, 6, have been studied by X-ray crystallography. Compounds, (6: X = 4-Br) and (6: X = 2-O 2 N), both recrystallized from EtOH, and (6: X = 4-F), recrystallized from EtOCH 2 CH 2 OH, were isolated in the 1-hydroxyimidazole form. In contrast, (6: X = H), recrystallized from EtOCH-2 CH 2 OH, was obtained in the imidazole N-oxide form. Two independent molecules, Mol A and Mol B, rotamers, are present in the asymmetric unit of the imidazole N-oxide compound, (6: X = H) and are linked into chains of alternating compounds, mainly by N-H···O hydrogen bonds, but also by N-H···N and C-H···O hydrogen bonds and π···π interactions. These chains are linked by other C-H···O and C-H···N hydrogen bonds and π···π interactions into a 3-D arrangement. In the 1-hydroxyimidazole compound, (6: X = 2-O 2 N), classical hydrogen bonds, O1-H1···N3, are the major interactions linking molecules into C(5) chains: weak π···π stacking interactions also link the molecules within the chains. These chains are linked by C-H···O and hydrogen bonds and by N-O···π interactions into a three-dimensional array. The other 1-hydroxyimidazole compounds, (6: X = 4-Br) and(6: X = 4-F), have similar structures, which differ from that of (6: X = 2-O 2 N). In (6: X = 4-Br) and (6: X = 4-F), pairs of classical O-H···N hydrogen bonds link molecules into symmetric dimers: these dimers are further stabilized by π···π interactions. Other intermolecular interactions found in both (6: X = 4-Br) and (6: X = 4-F) are C-H···O hydrogen bond and N-O···π interactions, which link the O-H···N hydrogen bonded dimers into a 3-dimensional array.

Synthesis and study of prototropic tautomerism of 2-(2-hydroxyphenyl)-1-hydroxyimidazoles

“…18 Unambiguous evidence for the occurence of the Nhydroxyimidazole tautomeric form in the solid state may be obtained from the X-ray structural analysis data (see, e.g., papers). [19][20][21][22][23][24][25] In the report 24 the X-ray data for 1-hydroxyimidazole derivatives were considered with regard to their tautomeric form stabilization.…”

“…One of the most widespread and convenient methods to synthesize 1-hydroxyimidazoles is a cyclization of starting aldehydes with α-hydroxyiminoketones and ammonium acetate 1,2,4,7,23,24,[26][27][28][29][30] in alcohols or glacial acetic acid. Scheme 2.…”

“…1,[10][11][12][13][14][15][23][24][25] ) that 1-hydroxyimidazoles may exist in the two tautomeric forms (Scheme 1). Taking into consideration possible hydrogen M A N U S C R I P T A C C E P T E D ACCEPTED MANUSCRIPT Tetrahedron 4 bonding in the molecules under study, the following utmost forms of the prototropic tautomers of 2-(2-hydroxyphenyl)substituted 1-hydroxyimidazoles 2-4 could be proposed: Scheme 7.…”

N-Hydroxy–N-oxide photoinduced tautomerization and excitation wavelength dependent luminescence of ESIPT-capable zinc(ii) complexes with a rationally designed 1-hydroxy-2,4-di(pyridin-2-yl)-1H-imidazole ESIPT-ligand

“…The predominant form of 1-hydroxy-1 H -imidazoles, N -hydroxyl or N -oxide, depends on the proton-donating or proton-accepting properties of the media, substituents in the imidazole ring and packing of the molecules in the solid state. 90–98…”

“…The predominant form of 1-hydroxy-1H-imidazoles, N-hydroxyl or N-oxide, depends on the proton-donating or proton-accepting properties of the media, substituents in the imidazole ring and packing of the molecules in the solid state. [90][91][92][93][94][95][96][97][98] In the case of 1-hydroxy-1H-imidazoles, this strategy can purposedly be interwoven with the strategy of the rational design of ESIPT-ligands for the synthesis of ESIPT-capable metal complexes. We suggested that coupled with the ease of the deprotonation of the hydroxy group, the introduction of a suitable proton accepting moiety in position 2 or 5 of the imidazole cycle could promote not only the intramolecular proton transfer from the 1-hydroxy group to this nearby proton accepting group, but also leave the N 3 imidazolic atom free for metal coordination.…”