Karina S. Tikhomirova

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.

New fluorogenic chemosensors derived from benzimidazole

We report the synthesis of new 1-substituted N-(anthracen-9-ylmethyl)-1H-benzimidazol-2-amines and 1,2,3-trisubstituted 1H-benzimidazolium chlorides containing anthracene fluorophores. Benzimidazol-2-amine derivatives exhibited high chemosensing activity toward H+ cations, but in neutral media – toward Zn2+ and Cd2+ cations. The quinoline-containing benzimidazolium chloride showed fluorogenic sensor properties toward F− and CN− anions.

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.

Photochromic benzo[g]indolyl fulgimide with modulated fluorescence

A new photochromic fulgimide, (E)-1-(anthracen-9-ylmethyl)-3-[1-(5-methoxy-2-methyl-1-phenyl-1H-benzo[g]indol-3-yl)ethylidene]-4-(propan-2-ylidene)pyrrolidine-2,5-dione, has been synthesized and found to exhibit fluorescence. The structure of this compound and intermediate fulgenates and amidofulgenic and fulgenic acids has been determined by electronic and vibrational spectroscopy, 1H and 13C NMR, and mass spectrometry. The amidofulgenic and fulgenic acids are capable of undergoing photoinduced reversible Z/E isomerization with respect to the C=C bond without subsequent cyclization, whereas fulgenates are converted to the corresponding cyclic structures. The new fluorescent fulgimide is transformed into the colored nonfluorescing cyclic isomer under UV irradiation. The reverse ring opening under visible light irradiation restores the fluorescence properties, which makes this compound a molecular fluorescence switch.

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).

Cation-active photochromic molecular swithches based on acylated enamino ketones of benzo[b]thiophene series

Benzo-12-crown-4-containing 2-(N-acyl-N-arylaminomethylidene)benzo[b]thiophene-3(2H)-ones possess the properties of molecular switches based on the photo-initiated Z/E-isomerization with respect to the exocyclic C=C bond followed by a fast thermal N→O migration of the acyl groups (φ 0.19–0.22). In the presence of lithium cation whose diameter suits the best the cavity of 12-crown-4 ether an efficient complex formation is observed resulting in essential growth of the quantum yields of the N→O migration of the acyl groups (φ 0.58–0.63).

Synthesis and Photo- and Ionochromic and Spectral-Luminescent Properties of 5-Phenylpyrazolidin-3-one Azomethine Imines

Photochromic 5-phenylpyrazolidin-3-one-based azomethine imines containing 2-((1H-imidazol-2-yl)methylene) 1, 2-(pyridin-2-ylmethylene) 2, 2-(quinolin-2-ylmethylene) 3, and 2-((8-hydroxyquinolin-2-yl)methylene) 4 substituents were synthesized. All the compounds exist in the ring-opened O forms. Under irradiation with light of 365 nm, compounds 1–4 undergo thermally reversible isomerization into ring-closed bicyclic diaziridine isomers C. Azomethine imines 1–3 exhibit properties of ion-active molecular “off-on” switches of fluorescence when interacting with F− or AcO− anions. Compound 4 represents a bifunctional chemosensor demonstrating a colorimetric “naked-eye” effect for Ni2+ cation and complete fluorescence quenching in the presence of H+, F−, and CN− ions.

Photo- and Ionochromic Spiroindoline-2,2′-pyrano[2,3-f]chromenecarbohydrazides—Chemosensors for Lanthanide Cations

Photochromic indoline spiropyrans with carbohydrazide substituents in the pyrano[2,3-f]chromene moiety of the molecule have been synthesized. These compounds exhibit inochromic properties and are chromogenic (“naked-eye”) and fluorogenic chemosensors for lanthanide cations.

Photo- and ionochromic indolyl(thienyl)maleimides containing naphthalimide linkers

Newly synthesized indolyl(thienyl)maleimides containing naphthalimide linkers were found to exhibit weak fluorescence due to PET effect. Irradiation at 436 nm wavelength led to the formation of their cyclic isomers. The obtained compounds showed the properties of chromogenic and fluorogenic chemosensors for F– ions.

Photochromic fluorescent indol-3-yl-substituted maleimides

New hetarylethenes, 3-(indol-3-yl)-4-thienyl(but-1-en-1-yl)-substituted pyrrole-2,5-diones containing coumarin or fluorene substituents on the pyrrole nitrogen atom, were synthesized by reactions of furan-2,5-diones with 9H-fluoren-2-amine and 6-amino-2H-chromen-2-one. Acyclic maleimide isomers showed fluorescence with quantum yields of 0.002 to 0.072. Their irradiation with UV light generates non-fluorescing cyclic isomer. The reverse ring opening occurs in the excited state.