Imidazoles, molecular structures

Fig. 45. Molecular structure of the anhydrous imidazole associate of / 1111 (H atoms of the carboxyl groups indicate putative atomic positions only O atoms dotted N atoms hatched)...

Guillaume et al. [69] presented a high performance liquid chromatographic method for an association study of miconazole and other imidazole derivatives in surfactant micellar using a hydrophilic reagent, Montanox DF 80. The thermodynamic results obtained showed that imidazole association in the surfactant micelles was effective over a concentration of surfactant equal to 0.4 pM. In addition, an enthalpy-entropy compensation study revealed that the type of interaction between the solute and the RP-18 stationary phase was independent of the molecular structure. The thermodynamic variations observed were considered the result of equilibrium displacement between the solute and free ethanol (respectively free surfactant) and its clusters (respective to micelles) created in the mobile phase. 

With iodine, the imidazol-2-ylidenes (IV) form stable adducts (Scheme 8.22), in which the carbene clearly acts as a basic a donor, just like a tertiary phosphine. Interestingly, the molecular structure of this adduct may be considered as an isolated transition state that models the nucleophilic attack of the carbene on the iodine molecule. 

The crystal molecular structure of /V1-hydroxylophine A -oxide (= I -hydroxy-2,4,5-triphenyl-17/-imidazole 3-oxide) (59) has been determined [72], This compound presents a case of degenerate or autotrope tautomerism (59a and 59b are identical), which is very common in annular tautomerism of NH-azoles but very rare in functional tautomerism [40], In the solid state, the tautomeric proton is in the middle between two consecutive monomers of the catemer [59]n [72],... 

In the present study, the complex, tetra(imidazole)chlorocopper(II) chloride, [Cu(imidazole)4Cl]Cl, has been synthesized, and the structure has been determined at the Small Crystal X-ray Crystallography Beamline (11.3.1) of the Advanced Light Source (ALS) at Lawrence Berkeley National Laboratory (LBNL)(Fig.l)[7]. Structural parameters are compared to similar compounds previously reported in the literature. The particles in the present study can be used to prepare nanoparticle materials, or the crystals can be grown under conditions to form nanoparticles or nanoparticle clusters. The molecular structure of the complex here can be used as a model to correlate with its magnetic and electronic properties. Structural parameters for the present complex of copper(II) are compared to similar compounds previously reported in the literature. With the data accumulated here, some previously unexplained bioinorganic chemistry and related phenomena may be explained in the context of the compounds molecular and electronic properties. 

The crystal structure of 4(5)-nitro-5(4)-methoxyimidazole contains a 1 1 mixture of two tautomers, 4-nitro-5-methoxy- and 5-nitro-4-methoxyimidazole [55], This is one of the very few cases of 4,5-disubstituted imidazoles for which there are two annular tautomers in the crystal. The molecular structure is the superposition of these tautomer forms. The structure is centrosymmetric and the N-H hydrogen atoms are disordered over two ring N atoms. Owing to the hydrogen-bond pattern, the values of their site occupation factors have to be exactly equal to 1/2. The molecules are connected into a three-dimensional network by means of N-H... N and C-H... 0 hydrogen bonds [55],... 

Molecular structures of solid Np(V) complexes with neutral heterocyclic N-donor ligands, 2,2 -bipyridine (Bipy), 2,2 ,6 ,2 -terpyridine (Terpy), 1,10-phenanthroline (Phen), 2,4,6-tri(pyridin-2-yl)-l,3,5-triazine (TPTZ), imidazole (Im) were determined using X-ray single crystal diffractometry. 

Figure 7.12. Molecular structure of a hairpin pyrrole-imidazole tetramer.

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