A procedure has been developed for the annulation of a 2-(thi)oxo-1,3-dithiole-4,5-dithiolate fragment to 3,6-di-
tert
-butyl-
o
-benzoquinone. The resulting
o
-quinones have a significant asymmetry ...with respect to the plane of the chelate dioxolene site, which can be used in the targeted design of the coordination environment of metal ions in complexes. Isomeric manganese adducts containing dioxolene, carbonyl, and phosphine ligands, which differ in the location of the asymmetric
o
-quinone ligand, have been characterized by EPR spectroscopy.
Electrochemical transformations and antioxidant activity of some Schiff bases 1–5 containing ferrocenyl group and (thio‐)phenol, catechol fragments were investigated. Compounds under investigation ...are: 2‐(ferrocenylmethylene)amino)phenol (1), 2‐((ferrocenylmethylene)amino)‐4,6‐di‐tert‐butylphenol (2), 2‐((ferrocenylmethylene)amino)‐thiophenol (3), 3‐((ferrocenylmethylene)hydrazonomethyl)‐4,6‐di‐tert‐butylcatechol (4) and 2‐((3,5‐di‐tert‐butyl‐4‐hydroxybenzylidene)amino)thiophenol (5).
In a case of compounds 1–3 it has shown that the sequence of electrochemical transformations leads to the products of intramolecular cyclization – 2‐ferrocenylbenzoxazole (benzothiazole). o‐Quinone formation occurs during the electrochemical oxidation of catechol‐ferrocene 4 at the first anode stage. Electrochemical oxidation of the redox‐active fragments in Schiff bases 1–4 can be achieved indirectly at a lower potential corresponding to the oxidation of ferrocenyl moiety, consequently these substances can reveal more pronounced antioxidant properties. The antioxidant activities of the compounds were evaluated using 2,2′‐diphenyl‐1‐picrylhydrazyl radical (DPPH) assay, the reaction of 2,2′‐azobis(2‐amidinopropane hydrochloride) (AAPH) induced glutathione depletion (GSH), the oxidative damage of the DNA, the process of lipid peroxidation of rat (Wistar) brain homogenates in vitro. The compounds 1–4 in the antioxidant assays show effectiveness comparable with standard antioxidants (vitamin E, Trolox) and in some parameters superior to them. In the reaction of AAPH with the glutathione compounds 2–5 have a more pronounced protective activity than Trolox. Compounds 1–5 inhibit AAPH induced oxidation damage of the DNA. The more effective inhibitors of the lipid peroxidation process in vitro are molecules containing the bulky tert‐butyl groups: 2 and 4 and Schiff base 3.
Electrochemical oxidation of the redox‐active fragments can be achieved indirectly at a low potential corresponding to the oxidation of ferrocenyl moiety. The Schiff bases can be activated at lower redox potentials and show pronounced antioxidant activity in comparison with the compounds containing phenolic or catecholic groups only.
A synthetic procedure was developed for the preparation of sterically hindered di- and trisubstituted catechols and
o
-quinones by the reaction of catechol with isopropanol. Compared to sterically ...more hindered analogs,
o
-quinones bearing isopropyl substituents exhibit a higher reactivity toward the formation of oxanthrenequinone derivatives.
A series of
o
-benzoquinones containing 2,4,4-trimethyl-2-pentyl (
tert
-octyl) substituents were synthesized. The stability of the reduced forms of the synthesized
o
-quinones and the electron ...density distribution in the corresponding radical anion species were studied by cyclic voltammetry and EPR spectroscopy.
A novel sterically hindered
o
-benzoquinone 4,6-di-
tert-
butyl-3-(5,7-di-
tert-
butylbenzooxazole-2-yl)-
o
-benzoquinone containing a benzoxazole moiety is prepared. The interaction of this quinone ...with Cu(0) yielded a cubane copper(II) complex with a Cu
4
O
4
core. Molecular and crystal structures of the
o
-quinone (CCDC 2269708) and the copper complex (CCDC 2269709) are determined by XRD.
The technology is based on recording the focal activity (FA) of the olfactory bulb (OB) of rats upon the exposure rats to trinitrotoluene (TNT) vapors in the concentration 4.7 × 10
–15
g/cm
3
, ...separately and in a mixture with saturated vapors of a complex interference composed of spices. The focal activity of the rat olfactory bulb was recorded using an array of 16 special electrodes implanted in the dorsal part of the rat olfactory bulb. The setup contained a box with a rat, sources of vapors (odorants), a multichannel digital system for recording electrical signals from an electrode array, and software performing algorithms for recognizing and classifying odorants presented to the rat. One source of TNT vapors was a device for batch volumetric preparation with a concentration of about 10
–15
g/cm
3
, and another source was a source with a concentration of 4.7 × 10
–15
g/cm
3
in an air flow presented to rats. Data from 25 tests showed a 100% probability of detecting TNT vapors of the specified concentrations in pure air and also in the presence of a complex odor interference in the form of vapors from a mixture of red pepper, coriander, tobacco, etc., which, as a rule, mask the smell of TNT for animals.
New tri- and tetraalkyl-substituted
o
-benzoquinones were synthesized based on 5,5,8,8-tetramethyl-5,6,7,8-tetrahydronaphthalene-2,3-diol derivatives. The new compounds were characterized by ...spectroscopic and electrochemical methods. The reactivity of
o
-benzoquinones was evaluated in the photoreduction and initiation of photopolymerization of oligocarbonate dimethacrylate (OCM-2) in the presence of
N,N
-dimethylcyclohexylamine and in the inhibition of MMA polymerization. The introduction of the methyl substituent into the benzene ring has a weak effect on the inhibitory activity of
o
-benzoquinone, whereas the (3,5-dimethylpyrazol-1-yl)methyl substituent enhances the inhibitory effect of 4,5-di-
tert
-alkyl-substituted
o
-benzoquinone.
New 1-hexadecyl derivatives of isatin containing substituents of various natures in the 5-position have been synthesized and characterized. The kinetics of their photoreduction by visible radiation ...in the presence of 4-methyl-
N
,
N
-dimethylaniline and triethylamine has been studied. It has been found that the photoreduction rate constant increases in the following order of substituted isatins: CH
3
< H < Cl < Br. It is shown that the isatin–amine system initiates photopolymerization of oligocarbonate dimethacrylate OKM-2 by visible light. The efficiency of photoinitiation correlates with the activity of isatins in the photoreduction reaction.
Two new photoinitiators of the α,α-bis(arylidene)cyclopentanone series having an unsymmetrical structure and containing two methacrylate units have been synthesized. The electrochemical and ...photoluminescent properties of the initiators have been studied. In the presence of the initiators, photopolymerization of pentaerythritol triacrylate was carried using radiation at λ = 365/405 nm (one-photon process) and focused femtosecond laser radiation with a wavelength of 780 nm (two-photon process). For each initiator, “fabrication windows” were determined and 3D microstructures of complex architecture were fabricated by DLW nanolithography.
Free-radical photopolymerization has been widely used in additive technologies, in particular, stereolithography using single- and two-photon initiated polymerization. The single-photon ...stereolithography affords the objects with about 100 μm resolution. The two-photon stereolithography initiated with a femtosecond near-infrared laser can afford arbitrary 3D microstructures with ultrahigh resolution at micro- and nanoscale level (~100 nm). Herein each of the mentioned method and the mechanisms of single- and two-photon excitation are reviewed. The recent results on the components of the photopolymerizable resin as well as the approaches to decrease the size of the elements of objects and accelerate their formation have been generalizated and systematized.
