Iodine-Catalyzed Radical C-H Amination of Nonaromatic Imidazole Oxides: Access to Cyclic α-Aminonitrones.

A straightforward cross-dehydrogenative coupling approach to incorporate alicyclic amino residues into the structure of model cyclic aldonitrones, 2-imidazole oxides, is reported. The elaborated C(sp)-H functionalization is achieved by employing cyclic amines in the presence of the I--butyl hydroperoxide (TBHP) reagent system. As a result, a series of 19 novel heterocyclic derivatives were obtained in yields of up to 97%.

Spin Crossover and Thermochromism in Iron(II) Complexes with 2,6-Bis(1-imidazol-2-yl)-4-methoxypyridine.

New iron(II) complexes with 2,6-bis(1-imidazol-2-yl)-4-methoxypyridine () of the composition [FeL]A∙mHO (A = SO, n = 1, m = 2 (); A = ReO, n = 2, m = 1 (); A = Br, n = 2, m = 2 ()) have been synthesized and investigated. To determine the coordination ability of the ligand, a single crystal of a copper(II) complex of the composition [CuLCl] () was obtained and studied by X-ray technique. Compounds - were studied using methods of X-ray phase analysis, electron (diffuse reflection spectra), infrared and Mössbauer spectroscopy, static magnetic susceptibility.

Luminescence of ESIPT-capable zinc(II) complexes with a 1-hydroxy-1-imidazole-based ligand: exploring the impact of substitution in the proton-donating moiety.

The rational design of ESIPT-capable metal complexes (ESIPT - Excited State Intramolecular Proton Transfer) requires two sites, namely, an ESIPT site and a metal binding site, to be spatially separated into the ligand core. Ligands featuring such sites are able to bind metal ions without being deprotonated upon their coordination. The use of ESIPT-capable ligands for the synthesis of metal complexes paves the way toward the exploration of ESIPT in the field of coordination chemistry.

ESIPT-Capable 4-(2-Hydroxyphenyl)-2-(Pyridin-2-yl)-1-Imidazoles with Single and Double Proton Transfer: Synthesis, Selective Reduction of the Imidazolic OH Group and Luminescence.

1-Imidazole derivatives establish one of the iconic classes of ESIPT-capable compounds (ESIPT = excited state intramolecular proton transfer). This work presents the synthesis of 1-hydroxy-4-(2-hydroxyphenyl)-5-methyl-2-(pyridin-2-yl)-1-imidazole () as the first example of ESIPT-capable imidazole derivatives wherein the imidazole moiety simultaneously acts as a proton acceptor and a proton donor. The reaction of with chloroacetone leads to the selective reduction of the imidazolic OH group (whereas the phenolic OH group remains unaffected) and to the isolation of 4-(2-hydroxyphenyl)-5-methyl-2-(pyridin-2-yl)-1-imidazole (), a monohydroxy congener of .

Tuning ESIPT-coupled luminescence by expanding π-conjugation of a proton acceptor moiety in ESIPT-capable zinc(II) complexes with 1-hydroxy-1-imidazole-based ligands.

The emission of ESIPT-fluorophores is known to be sensitive to various external and internal stimuli and can be fine-tuned through substitution in the proton-donating and proton-accepting groups. The incorporation of metal ions in the molecules of ESIPT fluorophores without their deprotonation is an emerging area of research in coordination chemistry which provides chemists with a new factor affecting the ESIPT reaction and ESIPT-coupled luminescence. In this paper we present 1-hydroxy-5-methyl-4-(pyridin-2-yl)-2-(quinolin-2-yl)-1-imidazole (HLq) as a new ESIPT-capable ligand.

High-Temperature Spin Crossover in Iron(II) Complexes with 2,6-Bis(1-imidazol-2-yl)pyridine.

Novel iron(II) coordination compounds containing a ligand 2,6-bis(1-imidazol-2-yl)pyridine (L), having such a composition as [FeL]SO·0.5HO, [FeL]Br·HO, [FeL](ReO), [FeL]BH∙HO, [FeL]BH∙1.5HO had been synthesized and studied using UV-Vis (diffuse reflectance), infrared, extended X-ray absorption fine structure (EXAFS), and Mössbauer spectroscopy methods, as well as X-ray diffraction and static magnetic susceptibility methods.

-Hydroxy--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)-1-imidazole ESIPT-ligand.

The ability of 1-hydroxy-1-imidazoles to undergo proton transfer processes and to exist in -hydroxy and -oxide tautomeric forms can be used in coordination chemistry for the design of ESIPT-capable complexes. A series of ESIPT-capable zinc(II) complexes [Zn(HL)Hal2] (Hal = Cl, Br, I) with a rationally designed ESIPT-ligand 1-hydroxy-5-methyl-2,4-di(pyridin-2-yl)-1-imidazole (HL) featuring spatially separated metal binding and ESIPT sites have been synthesized and characterized. Crystals of these compounds consist of a mixture of two isomers of [Zn(HL)Hal2].

A 1-Hydroxy-1H-imidazole ESIPT Emitter Demonstrating anti-Kasha Fluorescence and Direct Excitation of a Tautomeric Form.

The ability of 1-hydroxy-1H-imidazoles to exist in the form of two prototropic tautomers, the N-hydroxy and the N-oxide forms, can be utilized in the design of new types of ESIPT-fluorophores (ESIPT=excited state intramolecular proton transfer). Here we report the first example of 1-hydroxy-1H-imidazole-based ESIPT-fluorophores, 1-hydroxy-5-methyl-2,4-di(pyridin-2-yl)-1H-imidazole (HL), featuring a short intramolecular hydrogen bond O-H⋅⋅⋅N (O⋅⋅⋅N 2.56 Å) as a pre-requisite for ESIPT.

Stable Bicyclic Functionalized Nitroxides: The Synthesis of Derivatives of Aza-nortropinone-5-Methyl-3-oxo-6,8-diazabicyclo[3.2.1]-6-octene 8-oxyls.

In recent decades, bicyclic nitroxyl radicals have caught chemists' attention as selective catalysts for the oxidation of alcohols and amines and as additives and mediators in directed C-H oxidative transformations. In this regard, the design and development of synthetic approaches to new functional bicyclic nitroxides is a relevant and important issue. It has been reported that imidazo[1,2-]isoxazoles formed during the condensation of acetylacetone with 2-hydroxyaminooximes having a secondary hydroxyamino group are recyclized under mild basic catalyzed conditions to 8-hydroxy-5-methyl-3-oxo-6,8-diazabicyclo[3.