ABSTRACT
The subject of this work was the study of thermally and photochemically stimulated Z « E isomerization and hydrazo « azo tautomerism of Z- and E-isomers of isatin arylhydrazones and ((arylamino)methylene)indolin-2-ones and their anions. Using NMR, UV-Vis spectroscopy, kinetic measurements, and HPLC, we studied the relationship of structure, (Z- and E-isomers), of these compounds and hydrazo=azo tautomerism. The ON/OFF functionality of these compounds and their anions using light to stimulate switching between ON and OFF states was investigated. We pointed out the characterization of the effect of =N- and =CH- structural fragments and aryl structure on ON and OFF states of isatin arylhydrazones and ((arylamino)methylene)indolin-2-ones.
Subject(s)
Anions/chemistry , Hydrazones/chemistry , Indoles/chemistry , Isatin/chemistry , Chromatography, High Pressure Liquid , Hydrazones/chemical synthesis , Magnetic Resonance Spectroscopy , Molecular Structure , Photochemistry , Spectrophotometry, Ultraviolet , StereoisomerismABSTRACT
Five novel hydrazones derived from substituted isatins were synthesized as potential anion sensors. Using UV-VIS, FTIR, NMR and fluorescence spectroscopy, these compounds' tautomeric equilibrium and Z-E photoisomerization were studied in DMF and CHCl3, depending on the hydrazone concentrations, the presence of basic anions and light stimulation. Anion recognition aspects (PF6-, HSO4-, Br-, Cl-, NO3-, F- and CH3COO-) and these receptors' detection limits were also studied. We also tested the light-stimulated ON-OFF functionality of these compounds in the presence or absence of these anions.
Subject(s)
Hydrazones/chemistry , Isatin/chemistry , Naphthalimides/chemistry , Anions/chemistry , Isomerism , Molecular Structure , Spectrum Analysis/methodsABSTRACT
Four novel isatin hydrazones containing bipyridyl fragments were synthesized as potential ON/OFF switches. Hydrazone Z-isomers exhibit high thermal stability. The characteristic photochemical reaction for all studied hydrazones is the Z-E isomerization in CHCl3. After irradiation of hydrazones 1 and 2 in dimethylformamide (DMF), the photoreaction products are tautomers. When using light with the appropriate wavelength, the photo-tautomerization reaction is reversible. In these conditions, studied hydrazones have ON/OFF switch properties. In the case of hydrazones 1 and 2, by alternating heat and light stimulation it is possible to control the isomerization process reversibly. In the presence of fluoride ions, NH hydrogen from the studied hydrazones is cleaved, and the corresponding anions are formed. The resulting anions of Z-isomers are changed to the corresponding E-isomer at room temperature.
Subject(s)
2,2'-Dipyridyl/chemistry , Hydrazones/chemistry , Isatin/chemistry , Chloroform/chemistry , Dimethylformamide/chemistry , Hydrogen Bonding , Light , Photochemical Processes , Quantum Theory , Stereoisomerism , TemperatureABSTRACT
Five isatin anions were prepared by deprotonation of initial isatins in aprotic solvents using basic fluoride and acetate anions (F- and CH3COO-). The F- basicity is sufficient to deprotonate isatin NH hydrogen from all the studied compounds. This process is reversible. In the presence of proton donor solvents, the anions form the corresponding isatins. The isatin hydrogen acidity depends on the overall structure of the isatin derivatives. The anions were characterized by ultraviolet-visible (UV-Vis), Fourier transform infrared (FTIR) and nuclear magnetic resonance (NMR) spectroscopy. Interestingly, the anions form aggregates at concentrations above 10-3 mol·dm-3. Further, the effect of cations on the UV-Vis spectra of the studied anions was studied. Charge transfer and its distribution in the anion depends on the radius and the cation electron configuration. The alkali metal cations, tetrabutylammonium (TBAâº), Mg2+ and Agâº, interact with the C-2 carbonyl oxygen of the isatin anion. The interaction has a coulombic character. On the other hand, Cd2+, Zn2+, Hg2+, Co2+, and Cu⺠cations form a coordinate bond with the isatin nitrogen.
Subject(s)
Anions/chemistry , Isatin/chemistry , Magnetic Resonance Spectroscopy , Models, Chemical , Molecular Structure , Spectrophotometry, Ultraviolet , Spectroscopy, Fourier Transform InfraredABSTRACT
Organocatalytic SOMO reactions can provide access to various α-functionalized carbonyl compounds. Chiral imidazolidinones catalysed the organo-SOMO reactions of aldehydes and ketones with cyclic and acyclic enol silanes. The resulting chiral dicarbonyl compounds were obtained in yields of up to 80% and enantiomeric purities of up to 90% ee. Under the SOMO conditions, silyl ketene acetals did not afford the desired products. However, silyl ketene thioacetal could be employed, and the corresponding product was isolated with useful enantiomeric purity of 82% ee.
ABSTRACT
The photoswitching properties of two easily synthesized isatin 4-nitrophenylhydrazones were investigated. Although the parent isatin 4-nitrophenylhydrazones exhibit low addressability which hampers their photochromic applications, the addition of strongly basic anions to phenylhydrazone solutions creates a new Vis-Vis photochromic system with the unusual azo/azine-to-hydrazone photo-tautomerization process as the photoswitching mechanism. To the best of our knowledge, this is the first report related to the anion-assisted azo/azine-to-hydrazone photo-tautomerism.