Structural comparisons between methylated and unmethylated nitrophenyl lophines

Abstract

The lophine derivative 2-(2-nitrophenyl)-4,5-diphenyl-1H-imidazole, C21H15N3O2, (I), crystallized from ethanol as a solvent-free crystal and from acetonitrile as the monosolvate, C21H15N3O2.C2H3N, (II). Crystallization of 2-(4-nitrophenyl)-4,5-diphenyl-1H-imidazole from methanol yielded the methanol monosolvate, C21H15N3O2.CH4O, (III). Three lophine derivatives of methylated imidazole, namely, 1-methyl-2-(2-nitrophenyl)-4,5-diphenyl-1H-imidazole methanol solvate, C22H17N3O2.CH4O, (IV), 1-methyl-2-(3-nitrophenyl)-4,5-diphenyl-1H-imidazole, C22H17N3O2, (V), and 1-methyl-2-(4-nitrophenyl)-4,5-diphenyl-1H-imidazole, C22H17N3O2, (VI), were recrystallized from methanol, acetonitrile and ethanol, respectively, but only (IV) produced a solvate. Compounds (III) and (IV) each crystallize with two independent molecules in the asymmetric unit. Five imidazole molecules in the six crystals differ in their molecular conformations by rotation of the aromatic rings with respect to the central imidazole ring. In the absence of a methyl group on the imidazole [compounds (I)-(III)], the rotation angles are not strongly affected by the position of the nitro group [44.8 (2) and 45.5 (1) degrees in (I) and (II), respectively, and 15.7 (2) and 31.5 (1) degrees in the two molecules of (III)]. However, the rotation angle is strongly affected by the presence of a methyl group on the imidazole [compounds (IV)-(VI)], and the position of the nitro group (ortho, meta or para) on a neighbouring benzene ring; values of the rotation angle range from 26.0 (1) [in (VI)] to 85.2 (1) degrees [in (IV)]. This group repulsion also affects the outer N-C-N bond angle. The packing of the molecules in (I), (II) and (III) is determined by hydrogen bonding. In (I) and (II), molecules form extended chains through N-H...N hydrogen bonds [with an N...N distance of 2.944 (5) A in (I) and 2.920 (3) A in (II)], while in (III) the chain is formed with a methanol solvent molecule as the mediator between two imidazole rings, with O...N distances of 2.788 (4)-2.819 (4) A. In the absence of the imidazole N-H H-atom donor, the packing of molecules (IV)-(VI) is determined by weaker intermolecular interactions. The methanol solvent molecule in (IV) is hydrogen bonded to imidazole [O...N = 2.823 (4) A] but has no effect on the packing of molecules in the unit cell.

Aryl, bi-functionalised imidazo[4,5-f]-1,10-phenanthroline ligands and their luminescent rhenium(I) complexes

“…For example, an anilino azobenzene, the highly lipophilic 4-tritylaniline, and 4-([2,2 ′ :6 ′ ,2 ′ '-terpyridin]-4 ′ -yl)aniline were all compatible with this synthetic approach, thus yielding highly functionalised ligands; 5 was isolated from 4-(benzoyloxy)benzaldehyde. In general, the substituted imidazo [4,5-f]-1,10-phenanthroline ligands (1)(2)(3)(4)(5) were typically isolated as off-white solids, with the exception of the azobenzene derivatives (2,3), which were obtained as light orange powders. All species displayed poor solubility in water, but good solubility in a range of common organic solvents.…”

“…The coordination chemistry of the ligands (1)(2)(3)(4)(5) was investigated by reaction with [ReBr(CO) 5 ] using standard conditions (toluene, heat, hr) to yield the expected complexes, fac-[ReBr(CO) 3 (1)(2)(3)(4)(5)], as air-stable, yellow-orange coloured solids. All isolated compounds (Scheme 2) were initially investigated by 1 H and 13 C{ 1 H} NMR spectroscopies (where solubility permitted).…”

“…The R ′ group, 3,5-dimethylphenyl, displays a torsion angle of 71.69 (12) • . In the case of fac-[ReBr(CO) 3 (1)] no significant contacts were observed in the packing diagram whilst with fac-[ReBr(CO) 3 (5)] an approximately graphitic slipped π-stacking interaction (3.558(10) Å) was observed between adjacent 4-substituted aryl groups of the 4-benzoyloxyphenyl moieties.…”

“…2,4,5-triphenylimidazole [1] (lophine) based chromophores are a very well-known class of molecule [2] which are of interest in several areas of application due to their fluorescence and chemiluminescence properties [3]. Various synthetic approaches have been described [4] and the fluorescent properties of these species can be altered via the addition of different groups to the imidazole core [5].…”

Synthesis and Structure of 1-Ethyl-2,4,5-triphenyl-1H-imidazole (Ethyl-Lophine)

“…Widely used are combinations of small inorganic or organic anions with large organic cations like N-alkylpyridinum, tetraalkylammonium, tetraalkyl-or tetraarylphosphonium, and especially the cations resulting from the alkylation/arylation of N-alkylimidazole. Examples of such imidazole derivatives with alkyl and aryl substituents include 2,4-di-t-butyl-2-(1-methyl- [20] and 2,2 -(1,4-phenylene)bis(4,5-diphenyl-1-methyl-1H -imidazole) [21].…”