Gennadii S. Borodkin

The novel azomethine ligands for binuclear copper(II) complexes with ferro- and antiferromagnetic properties

A series of novel binuclear ferro- and antiferromagnetic Cu(2+) chelates of structurally broadly varied Schiff bases (derived from o-tosylamino(hydroxyl)benzaldehydes and monoalkylated o-phenylenediamine, o-aminophenol, o-aminothiophenol, 1,2-diaminobenzimidazole, 1-aminobenzimidazoline-2-thione) and β-diketimines (derived from 2,6-di-i-Pr-aniline) has been prepared. The tautomerism of the ligands and structureof their copper complexes have been studied with the use of IR, 1H NMR EPR and EXAFS spectroscopy. Molecular and crystal structure of a β-diketimine copper dimer has been determined by X-ray crystallography. The magnetic measurements (2–300 K) performed for all the complexes showed that the ferro- and antiferromagnetic character of the exchange interaction depends both on the structure of the coordination site (origin of the ligating centers) and the structure of the ligands (in particular, on the type of the cycle annelated to the bridging fragment). Whereas S-binding metal chelates 13 (X = NTs, Y = S, R = H) are diamagnetic, the complexes 15 with annelated azole moieties are ferromagnetic.

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.

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.

Photoinitiated rearrangements of 3-phenylnorbornadiene with conjugated substituents in 2-position

Abstract A series of novel 3-phenyhorbornadienes with conjugated substituents in 2- position (carbaldimine, carbaldoxime, amide, aroylvinyl and heterocyclic groups) have been synthesized. All the compounds obtained absorb in the 310-420 nm spectral region and under UV-Vis-irradiation form corresponding quadricyclanes with quantum yields in the range of 0.1-0.7. The back reaction proceeds almost quantitative yield under homogeneous and heterogeneous catalysis or on heating.

Direct chemical and electrochemical syntheses of coordination compounds of benzazolyl azo ligands

The chelates of 2-hydroxy(aminophenylnaphthyl)-azo-1-alkylbenzimidazoles were obtained from electrochemical (anodic dissolution of zero-valent d-metals) and chemical (from acetates of the same metals) syntheses in methanol. The EXAFS and X-ray single crystal diffraction data revealed the existence of octahedral nickel, zinc, and cadmium complexes containing four five-membered metallocycles with the N4О2 or N6 ligand environments. The formation of five-membered coordination units, non-typical for azo ligands, is explained on the basis of inner-chelate competitive metal binding of ambidentate ligand systems.

METAL CHELATES OF NEW LIGANDS: 1,2-BENZOTHIAZINE-1,1-DIOXIDE DERIVATIVES

Abstract The novel chelates ML2 (M = Co, Ni, Cu, Zn) were obtained by the interaction of 3-benzoyl-4-hydroxy-1,2-benzothiazine-4(3H)-on-1,1-dioxide and 2-methyl-3-benzoyl-4-hydroxy-1,2-benzo-thiazine-4(3H)-on-1,1-dioxide with elemental metals (direct electrochemical synthesis) or their acetates (chemical synthesis) in methanol. The tetrahedral or polymeric-octahedral structures with a β-diketonate fragment are assigned based on IR and 1H NMR spectra. The studied ligands and their complexes are model compounds of molecules used as anti-inflammatory drugs.

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.

Photochemical generation, photochromism and photocyclization of 2-norbornadienyl substituted benzo-1,3-oxazoles

Abstract Under UV-irradiation (365 nm) of their solutions Schiff bases (I) undergo the oxidative photocyctization to give 2-(3′-aryl-norbomadien-2-yl)-benzo-1,3-oxazoles (II) (λmax = 337 nm, hexane), which then convert to the quadricyclane isomers (III) (λmax = 287 nm). The back thermal reaction proceeds on heating the solution (τ1/2 70°C = 2340 s). Under prolonged UV-irradiation a further (2π+2π+2π) photocyctization of the triene moiety of (II) followed by 1,5-sigmatropic migration of a hydrogen atom occurs. The resulting photoproduct (IV) possesses by an intense horescence (λII max=390nm).

Tautomeric and non-tautomeric N-substituted 2-iminobenzimidazolines as new lead compounds for the design of anti-influenza drugs: An in vitro study

A series of 1,3-disubstituted 2-iminobenzimidazolines as well as a number of their tautomeric analogs were synthesized. The synthesized compounds were tested for their cytotoxicity against MDCK cells and for inhibiting activity against influenza virus A/California/07/09 (H1N1)pdm09. Based on the results obtained, 50% cytotoxic concentration (CC50), 50% inhibiting concentration (IC50) and selectivity index (SI) were calculated for each compound. It was found that some of synthesized benzimidazole derivatives (7 of 22, 32%) possess strong virus-inhibiting activity against pandemic influenza virus (IC50s in low micromolar range) with quite moderate cytotoxicity (CC50 in the range of thousands micromoles). Due to their high selectivity (highest SIs=50-83) these compounds are of significant interest for further in vivo experiments as well as for further structural optimization and drug development.