O. S. Popova

New ionochromic azomethinimine chemosensors

A reaction of 5-phenylpyrazolidin-3-one with hydroxy-substituted aromatic aldehydes led to azomethinimines, the representatives of a new class of chemosensors exhibiting ionochromic properties. Electron spectroscopy was used to identify efficient chemosensors toward Cu2+ cations and F– anions.

IONOACTIVE IMINES - 1-R-BENZIMIDAZOL- 2-AMINE DERIVATIVES

Novel ionoactive imines possessing potent chromogenic and fluorogenic properties were accessed by condensation of 1-R-benzimidazol-2-amines with trans-5-[2-(anthracen-9-yl)vinyl]-2-hydroxybenz-aldehyde. These sensors exhibit ability for an intramolecular proton transfer in the excited state and could find use as selective analytical reagents for fluoride ions.

Synthesis and structure of 1-[(3-hydroxybenzo[b]thiophen-2-yl)methylidene]-3-oxo-5-phenyl-1-pyrazolidinium-2-ide

Potentially tautomeric azomethine imine, 1-[(3-hydroxybenzo[b]thiophen-2-yl)methylidene]-3-oxo-5-phenyl-1-pyrazolidinium-2-ide has been prepared. According to X-ray diffraction, 1H, 13C, and 15N NMR and electronic spectroscopy, the compound exists as 3-hydroxybenzothiophene structure containing intermolecular hydrogen bond between the hydroxy group and the carbonyl oxygen of the pyrazolidone ring in crystal state. Quantum chemical calculations predict the possibility of OH and NH tautomeric forms.

Synthesis, structure, and properties of new spirooxindolodibenzodiazepine derivatives

An acid-catalyzed reaction of 3-(2-aminophenylamino)-5,5-dimethylcyclohexen-1-one with isatines leads to the formation of the earlier undescribed 3,3-dimethyl-2,3,4,5,10,11-hexahydrospiro[1H-dibenzo[b,e][1,4]diazepine-11,3′-2H-indole]-1,2′-dione derivatives (6). Spiranes 6 upon heating undergo auto-redox rearrangement with disintegration to 3,3-dimethyl-1,2,3,4-tetrahydrophenazine and the corresponding oxindole. Crystals of four derivatives of compound 6 were studied by X-ray diffraction method.

Benzenoid-quinoid tautomerism of azomethines and their structural analogs 56. Azomethine imines, derivatives of salicylic and 2-hydroxynaphthoic aldehydes

A study by IR, electronic and NMR (1Н and 13С) spectroscopy together with X-ray structure analysis and quantum chemical calculations using DFT B3LYP/6-31G(d,p) determined N,N´-cyclic azomethine imines — 1-(2-hydroxyphenylmethylidene)-3-oxo-5-phenylpyrazolydin-1-ium-2-yde (1) и 1-[(2-hydroxynaphthalene-1-yl)methylidene]-3-oxo-5-phenylpyrazolydin-1-ium-2-yde (2) — to exist in solutions as isomers with an intramolecular hydrogen bond between the hydroxyl group and the nitrogen of the pyrazolidone ring. Compound 1 undergoes photoexcitation in the wavelength range 363—320 nm followed by luminescence with an anomalous Stokes shift that is caused by the intramolecular excited state proton transfer mechanism (ESIPT effect).

Fluorescent chemosensors based on N-aminoimidazole and N-aminobenzimidazole

Nowadays chemosensors are widely used in express determination of ions and neutral compounds in various samples [1, 2]. Ion-sensitive compounds have found application not only in analytical and environmental chemistry but also in biology. It is very important to design efficient and selective chemosensors for the determination and biovisualization of ions (cations and anions) involved in biological cell processes [3, 4]. We previously demonstrated the possibility of using anthracen-9-ylmethyl-substituted benzimidazol-2amines as efficient pH sensors [5, 6]. In continuation of these studies we have synthesized N-amino derivatives of imidazole and benzimidazole containing an anthracene fluorophore group linked to the NNH group. By reaction of benzimidazole-1,2-diamine (I) and 1-amino-4-phenyl-1H-imidazole-2-thiol (II) with anthracene-9-carbaldehyde in acetic acid we synthesized the corresponding Schiff bases which were reduced to diamines III and IV with sodium tetrahydridoborate. In the reaction with diamine I, only the N–NH2 amino group was involved in the condensation. The H NMR spectrum of III contained signals typical of protons in the NH2, NH, and CH2 groups. Amines III and IV showed anthracene-like fluorescence with an emission maximum at λ 414 (415) nm. Their chemosensor properties were studied in acetonitrile (c = 5 × 10 M) by comparing the fluorescence spectra before and after addition of cations (H, Zn, Cd, Ni, Cu, Pb, Hg) and anions (AcO, CN, NO3, F, Cl, see table). The results revealed different selectivities of III and IV toward ionic species. The fluorescence intensity of compound III considerably increased in the presence of H, Zn, and Cd ions and decreased on addition of Cu and Hg. Aminothiol IV turned out to be more sensitive in the determination of anions. It displayed selective increase in the fluorescence intensity in the presence of acetate ions. In all cases, addition of ions to solutions of III and IV did not induce appreciable change in the position of absorption and emission maxima.

trans-1,3-Bis(Anthracen-9-Ylmethyl)Octahydro-Benzimidazoles: Synthesis and Study of Spectral Properties

The reaction between (±)-trans-cyclohexane-1,2-diamine and anthracene-9-carbaldehyde with a subsequent reduction of the condensation product gave N,N-bis(anthracen-9-ylmethyl)cyclohexane-1,2-diamine. The interaction of this diamine with aldehydes was shown to produce octahydrobenz-imidazoles. The chemosensor properties of the obtained compounds were investigated, and a high affinity to Zn2+ cations was identified.

Carbamides as chemosensors for cations Eu 3

Nowadays chromogenic and fl uorogenic chemosensors containing an anthracene fragment as a luminophore are generally recognized as fi ne and reliable tool for the investigation of abiotic and biologic objects [1, 2]. Numerous sensor systems in the form of organic ligand complexes with cations of lanthanide metals (e.g., Eu3+) are used in determining both cations and anions [3]. Yet the range of optical sensors for the proper europium(III) cations is considerably limited [4, 5]. We attempted to synthesize fl uorescent chemosensors based on carbamides for the determination of europium(III) ions. The reaction of amine I [6] with excess N,N-dimethylcarbamoyl chloride in toluene in the presence of NEt3 afforded a bisacylation product III. In the 1Н NMR spectrum a signal of methyl group protons appears at 2.72 ppm and the signal of methylene protons of the group directly linked to the aromatic framework undergoes a downfi eld shift by ~0.6 ppm with respect to the spectrum of the unsubstituted amine. However in the case of N,N′-bis(9-anthranylmethyl) ethane-1,2-diamine (II) [6] instead of a bisurea imidazolidone IV was isolated in a 44% yield. The latter apparently formed as a result of the N,N-dimethylurea cyclization with the elimination of dimethylamine. In the 1Н NMR spectra of compound IV the signals of the NMe2 are lacking while downfi eld shifts are observed of the pro-

Benzoid–Quinoid tautomerism of schiff bases and their structural analogs: LVII. 2-[(3-oxo-5-phenylpyrazolidin-1-yl)methylidene]-1H-indene-1,3(2H)-dione

Potentially tautomeric azomethine imide, 2-[(3-oxo-5-phenylpyrazolidin-1-yl)methylidene]-1H-indene- 1,3(2H)-dione, has been synthesized by condensation of 5-phenylpyrazolidin-3-one with 2-(hydroxymethylidene)-1H-indene-1,3(2H)-dione. According to the IR, 1H and 13C NMR, and electronic absorption spectroscopy data and DFT B3LYP/6-311++G(d,p) quantum chemical calculations, the title compound in solution exists as planar tricarbonyl tautomer stabilized by intramolecular hydrogen bond between the NH proton of the pyrazolidine fragment and carbonyl oxygen atom of the indene fragment. Its crystal structure was determined by X-ray analysis.

Azomethine imines of pyrazolidone series and their bis-chelate Ni(II), Zn(II), Cd(II) complexes. Quantum chemical simulation

Prototropic processes in the molecules of azomethine imines with 2-pyrrolylmethylidene fragment were studied by the density functional theory (DFT) method and the most stable by energy isomers with the intramolecular hydrogen bond between the nitrogen atoms of the pyrrole and the pyrazole rings were found. The energy barriers of the reactions of intramolecular proton transfer were estimated. Based on quantum chemical calculations of the molecular structure of azomethine imine bis-chelates ML2 [M = Ni(II), Zn(II), Cd(II)] with the coordination unit MN2N2 the most stable configurations of the complexes were determined.