A. D. Dubonosov

Photochromic Cation Sensors

ABSTRACT Novel photochromic chemosensors for alkali-, alkali-earth and d-metal cations were synthesized and their photochemical and complexing properties investigated with the use of UV/vis, IR, 1H/7Li NMR spectroscopy and quantum chemical calculations – DFT(B3LYP/6-31G).

Synthesis of Novel Iono- and Photochromic Spiropyrans Derived from 6,7-Dihydroxy-8-Formyl-4-Methyl-2H-Chromene-2-One

�-hydroxy group were synthesized and their spectral properties as well as abilities for complexation with metal ions studied. In solutions they exist as equilibrium mixture of spirocyclic (A) and merocyanine (B) isomers. The largest content of merocyanine form was found for the derivative with an electron-donating methyl group in position 5 of hetaryl fragment. The irradiation of SPPs in acetonitrile shifts the equilibrium to the B form. Similar effect causes the addition of metal cations due to formation of colored complexes with merocyanine isomers.

Synthesis and photochromic properties of spiropyrans containing a fused benzopyranone fragment

New spiro compounds of the indole, phthalazine, isobenzofuran, and benzopyran series, containing a fused benzopyranone fragment in the chromene moiety, were synthesized. Indole derivatives were found to exhibit photochromic properties under stationary conditions at 293 K. The thermal stability of merocyanine isomers sharply decreases upon introduction of electron-withdrawing nitro group into the indole fragment and fusion of a benzene ring to the chromene fragment.

Chemosensors based on N -(9-anthrylmethyl)-benzene-1,2-diamine

A number of N-(9-antrylmethyl)-N′-arylmethylidenebenzene-1,2-diamines and 1-(9-anthrylmethyl)-2-aryl-1H-benzimidazoles were synthesized by condensation of N-(9-anthrylmethyl)benzene-1,2-diamine with aromatic and heterocyclic aldehydes. Study on their luminescent properties and complexing ability showed that 2-{[2-(9-anthrylmethylamino)phenylimino]methyl}-5-methylphenol, 2-{[2-(9-anthrylmethylamino)phenylimino] methyl}-4-methoxyphenol, and 2-{[2-(9-anthrylmethylamino)phenylimino]methyl}-6-methoxy-4-nitrophenol are effective and highly selective chemosensors for H+ and Hg2+ ions.

Complexing properties of ambidentate benzo-15-crown-5-substituted azomethine ligands

Crown-containing azomethines and their zinc complexes were prepared. Examination of their structure by 1H and 7Li NMR and electronic spectroscopy showed that, in accordance with the concept of hard and soft acids and bases, the hard lithium cation coordinates to the crown ether fragment with the formation of mono-(Li) and binuclear (Li, Zn) complexes.

Acylotropic intramolecular rearrangements of keto enamines of benzo[b]-annelated heterocycles

A review is devoted to N → O-acylotropic rearrangements of acylated keto enamines of benzo[b]furan, benzo[b]thiophene, benzo[b]selenophene, and benzo[b]tellurophene series. The mechanism of the photoinitiated migration of the acyl group and effect of the substituents in the migrating group and N-aryl fragment were examined. The compounds studied may be used as light energy accumulators, optical signal molecular switches, fluorescent sensors for measuring pH, and chemosensors for the determination of metal cations.

Benzoid-quinoid tautomerism of schiff bases and their structural analogs: LIII. Schiff bases derived from 5-hydroxy- and 5-hydroxy-6-nitro-2,3-diphenyl-1-benzofuran-4-carbaldehydes

Abstract4-Aryl(alkyl)iminomethyl-5-hydroxy-and 4-aryl(alkyl)iminomethyl-5-hydroxy-6-nitro-2,3-diphenyl-1-benzofurans were synthesized and were shown to exist in solution as equilibrium mixtures of benzoid and quinoid tautomers. The fraction of the quinoid form increases with rise in the solvent polarity and in going from N-aryl to N-alkyl derivatives; introduction of an electron-acceptor substituent (nitro group) into the 6-position of the benzofuran system also favors formation of the quinoid tautomer. Complex formation of alkali and alkaline-earth metal cations with the 5-hydroxy-6-nitro-2,3-diphenyl-1-benzofuran-4-carbaldehyde imine having a benzo-15-crown-5 fragment on the nitrogen atom is accompanied by specific changes in the luminescence spectrum and in the state of tautomeric equilibrium, so that this system may be regarded as tautomeric fluorogenic chemosensor for metal cations.

Inverse photochromic systems based on ketoenamine derivatives

The results of studies into inverse photochromic systems (systems with negative photochromism) based on ketoenamines and ketoenehydrazines of benzo [b]annelated heterocycles and their acylated derivatives carried out at the Institute of Physical and Organic Chemistry at the Rostov State University in the last two decades are summarized.

Synthesis and properties of photoacylotropic (2Z)-2-(N-acyl-N-arylaminomethylidene)benzo[b]thiophen-3(2H)-ones with a chiral migrating group

New photochromic (2Z)-2-(N-acyl-N-arylaminomethylidene)benzo[b]thiophen-3(2H)-ones containing L-amino acid derivatives as migrating groups were synthesized. Light irradiation of their solutions at 436 nm leads to the photoinduced acylotropic rearrangement N → O accompanied by migration of the chiral fragment. The bulky N-acyl group causes steric strain thus destabilizing the amide form of compounds and facilitating the photorearrangement.

Biphotochromic norbornadiene systems

Abstract Novel biphotochromic systems containing two norbornadiene moieties in one molecule or one norbornadienyl group in 2-N-(3-phenylnorbornadiene-2-carbonyl)]-N-arylaminomethylene-(2H) benzo[b]thiophenones have been prepared. Under UV/VIS irradiation the latter compounds undergo Z/E-isomerktion acompanied by N → O acyl rearrangement and valence isomerization in the norbornadiene fragment. Bis-norbornadienyl derivatives upon irradiation convert through stepwise isomerization into corresponding quadricyclanes. The back reactions are catalyzed with trifluoroacetic acid at room temperature.