Yoshiko Sakaino

Chromotropism of imidazole derivatives. Part 1. 4,5-Bis-(4-methoxyphenyl)-2-(4-nitrophenyl)imidazolium acetate dihydrate

4,5-Bis-(4-methoxyphenyl)-2-(4-nitrophenyl)imidazolium acetate dihydrate (1) in the crystalline state exhibits a sensitive colour change from orange-yellow to red on treatment by various methods (drying, trituration, or heating). The colour change was reversible below 70 °C but above 70 °C the change was irreversible and the colour deepened. Compound (1) was deprotonated with the loss of one mole of water of crystallization under treatment and can revert to the original by absorption of one mole of water. On heating to 100 °C, (1) lost all solvent of crystallization to give a deep red material (2). (2) Was considered to be 4,5-bis-(4-methoxyphenyl)-2-(4-nitrophenyl)imidazole which was linked by hydrogen bond from the imino group in one molecule to the nitro oxygen in another. Compound (2) reverted to (1) in saturated AcOH–H2O vapour.

Inclusion complexes of a new host, 4,5-bis(4-methoxyphenyl)-2-(4-nitrophenyl)-1H-imidazole, with various guests

The title host compound forms crystalline inclusion complexes, the colour of which depend on the guest. It forms a complex with 2-phenylethanol (6), which when heated changes colour and emits the characteristic fragrance of the latter. The complex formed with trichloroacetic acid shows solid-state fluorescence.

Structures and chromotropic properties of imidazole derivatives produced from 3,6-bis(4,5-diphenyl-2H-imidazol-2-ylidene)cyclohexa-1,4-diene

Addition of acetic acid to 3,6-bis (4,5-diphenyl-2H-imidazol-2-ylidene) cyclohexa-1,4-diene (1) afforded 2-[4-(4-acetoxy-4,5-diphenyl-4H-imidazol-2-yl) phenyl]-4,5-diphenyl-1H-imidazole (2). Lead dioxide oxidation of (2) in acetic acid yielded 1,4-bis(4-acetoxy-4,5-diphenyl-4H-imidazol-2-yl)-benzene (13) but hexacyanoferrate(III) oxidation in alkaline solution gave a 2,2′-imidazolyl dimer (7) derived via 2-[4-(5-oxo-4,4-diphenyl-4,5-dihydro-1H-imidazol-2-yl)phenyl]-4,5-diphenyl-1H-imidazole (4).Irradiation of compounds (2) and (13) with u.v. light resulted in the formation of the starting quinonoid compound (1) as indicated by its deep blue colour. However, the dimeric compound (7) shows chromotropism caused by radical dissociation of the dimer during irradiation, heating, or grinding. Particularly rapid reversible photochromic behaviour was observed for (7).

Polymorphisms and Colourations of 4,5,-Bis(4-Methoxyphenyl)-2-(3-Nitrophenyl0–1H-Imidazole

Abstract 4,5-Bis(4-methoxyphenyl)-2-(3-nitrophenyl)-1H-imidazole [I] crystallized in several coloured states such as red, orange, yellow, by changing solvents. From X-ray powder diffraction, d.s.c. thermograms and I.R. spectra, the red and the two yellow crystals were found to be polymorphic forms of [I]. The polymorphisms are based on differencies in the hydrogen bonds. The red crystals have a hydrogen bond of the type ‒NH—O˭. The NH hydrogen of one molecule bonds to the nitro oxygen of another. One of the two yellow crystals has hydrogen bonds of the type -NH—N =. The NH of one molecule bonds to the nitrogen on the others imidazole ring. Another yellow crystal has two kinds of hydrogen bonds, -NH—N= and -NH—OMe-, the NH of one molecule with the methoxy oxygen of another molecule. On the other hand, the orange crystals have solvent of crystallization. The solvent was connected with the imidazole ring and hinders direct hydrogen bonding between two imidazole rings. Colouration of the red crystals is due ...

Simple and Excellent Preparation of Polymorphic Crystals of 4,5-Bis(4-Methoxyphenyl)-2-(3-Nitrophenyl)-1H-Imidazole

Abstract The title imidazole 1 forms inclusion complexes with ethyl acetate, tert-BuOH, and benzene. The complexes lost their guest molecule to give polymorphic crystals A, B, C and D in a pure state. A is red plates, B is yellow needles, C is pale yellow silky needles and D is light yellow cottony needles. The polymorphic crystal turns to the other one when the crystal contacts with organic vapor. The reactivity decreased with B>D>C>A. Structure and reactivity of the polymorphic crystals are discussed on the type of hydrogen bonding and on molecular arrangements in crystals.

POLYMORPHISMS OF 4,5-BIS(4-METHOXYPHENYL)-2-(3-NITROPHENYL)-1H-IMIDAZOLE AS STUDIED BY SOLID STATE NMR

Abstract Solid state NMR measurements are carried out for polymorphs and inclusion complexes of 4,5-bis(4-methoxyphenyl)-2-(3-nitrophenyl)-1H-imidazole. Observed 13C and 15N chemical shifts are characteristic of each polymorph A, B, C and D. In addition, 15N chemical shift was a good index for understanding hydrogen bond. VT measurements revealed that B transforms to C between 93 and 113°C. From PSTMAS and 1H solid echo measurements for AcOET inclusion complex, host molecules have almost same structure as B and guest molecules have the highest mobility of all inclusion complexes.

Structure of the chromotropic dimers produced from 2-arylphenanthro-[9,10-d]imidazoles

The dimer produced from 2-phenylphenanthro[9,10-d]imidazole by oxidation with hexacyanoferrate(III) is shown to be 2,2′-diphenyl-1H,2′H-1,2′-biphenanthro[9,10-d]imidazolyl (23). Derivatives of this dimer substituted in the phenyl rings have been obtained similarly, and their chromotropic properties are reported.

Friedel-Crafts Reaction of Toluene with Oxalyl Chloride

Abstract By the Friedel-Crafts reaction of toluene with oxalyl chloride, three kinds of fluorene derivatives (c, d, e), naphthalene derivative f, fluorenone derivative g, were obtained in addition to 4,4′-dimethyl benzophenone b. In the compounds (c, d, e, f, g), c shows thermochromism above 135°C in solution, while e emits phosphorescence and f exhibits fluorescence at room temperature in the solid states.

Reaction product of TCNQ with p-phenylenedimalononitrile and the chromic phenomena

Complex formation of 7,7,8,8-Tetracyanoquinodimethane (TCNQ) with p-phenylenedimalononitrile (molr ratio 1 :2) was assumed by DSC and IR spectral measurements. The complex shows very sensitive chromic phenomena when it contacts with moist air or with metal carbonates due to formation of TCNQ anion radical or formation of the anion radical salts.

Complex Formation of Imidazole Derivatives and Properties of the Products

Abstract A thermochromic complex which gives out rose fragrance with the color change, and inclusion complexes which emit intense solid state fluorescence, were obtained by grinding of imidazole derivatives with 2-phenylethanol and carboxylic acid. Preparation and properties of these complexes are described.