Synthesis, electrochemical properties, and antioxidant activity of sterically hindered catechols with 1,3,4-oxadiazole, 1,2,4-triazole, thiazole or pyridine fragments.

A series of new RS-, RS-CH- and RN-CH-functionalized сatechols with heterocyclic fragments such as 1,3,4-oxadiazole, 1,2,4-triazole, thiazole, or pyridine were synthesized by the reaction of 3,5-di--butyl--benzoquinone or 3,5-di--butyl-6-methoxymethylcatechol with different heterocyclic thiols. The S-functionalized catechols were prepared by the Michael reaction from 3,5-di--butyl--benzoquinone and the corresponding thiols. The starting reagents such as substituted 1,3,4-oxadiazole-2-thiols and 4-triazole-3-thiols are characterized by thiol-thione tautomerism, therefore their reactions with 3,5-di--butyl-6-methoxymethylcatechol can proceed at the sulfur or nitrogen atom.

Synthesis, Structure, Electrochemical Properties, and Antioxidant Activity of Organogermanium(IV) Catecholate Complexes.

A series of novel organogermanium(IV) catecholates - of the general formula R'Ge(Cat), where R' = Ph, Et, have been synthesized. Compounds were characterized by H, C NMR, IR spectroscopy, and elemental analysis. The molecular structures of -, , and in crystal state were established using single-crystal X-ray analysis.

α-Diimine Cisplatin Derivatives: Synthesis, Structure, Cyclic Voltammetry and Cytotoxicity.

Three new Pt(II) complexes [(dpp-DAD)PtCl] (), [(Mes-DAD(Me))PtCl] () and [(dpp-DAD(Me))PtCl] () were synthesized by the direct reaction of [(CHCN)PtCl] and corresponding redox-active 1,4-diaza-1,3-butadienes (DAD). The compounds were isolated in a single crystal form and their molecular structures were determined by X-ray diffraction. The purity of the complexes and their stability in solution was confirmed by NMR analysis.

Heteroligand α-Diimine-Zn(II) Complexes with O,N,O'- and O,N,S-Donor Redox-Active Schiff Bases: Synthesis, Structure and Electrochemical Properties.

A number of novel heteroligand Zn(II) complexes (-) of the general type (L)Zn(NN) containing O,N,O'-, O,N,S-donor redox-active Schiff bases and neutral N,N'-chelating ligands (NN) were synthesized. The target Schiff bases LH were obtained as a result of the condensation of 3,5-di--butyl-2-hydroxybenzaldehyde with substituted -aminophenols or -aminothiophenol. These ligands with combination with 2,2'-bipyridine, 1,10-phenanthroline, and neocuproine are able to form stable complexes upon coordination with zinc(II) ion.

Binuclear Triphenylantimony(V) Catecholates through N-Donor Linkers: Structural Features and Redox Properties.

A series of binuclear triphenylantimony(V) bis-catecholato complexes - of the type (Cat)PhSb-linker-SbPh(Cat) was prepared by a reaction of the corresponding mononuclear catecholates (Cat)SbPh with a neutral bidentate donor linker ligands pyrazine (Pyr), 4,4'-dipyridyl (Bipy), bis-(pyridine-4-yl)-disulfide (PySSPy), and diazobicyclo[2,2,2]octane (DABCO) in a dry toluene: Cat = 3,6-di-tert-butyl-catecholate (3,6-DBCat), linker = Pyr (); PySSPy (); Bipy (); DABCO (); Cat = 3,5-di-tert-butyl-catecholate (3,5-DBCat), linker = Bipy (); DABCO (); Cat = 4,5-(piperazine-1,4-diyl)-3,6-di-tert-butylcatecholate (pip-3,6-DBCat), linker = Bipy (); DABCO (); Cat = 4,5-dichloro-3,6-di-tert-butylcatecholate (4,5-Cl-3,6-DBCat), linker = Bipy (); DABCO (); and Cat = 4,5-dimethoxy-3,6-di-tert-butylcatecholate (4,5-(MeO)-3,6-DBCat), linker = Bipy (). The same reaction of (4,5-Cl-3,6-DBCat)SbPh with DABCO in an open atmosphere results in a formation of 1D coordination polymer {[(4,5-Cl-3,6-DBCat)SbPh·HO]·DABCO} (). Bis-catecholate complex PhSb(Cat-Spiro-Cat)SbPh reacts with Bipy as 1:1 yielding a rare macrocyclic tetranuclear compound {PhSb(Cat-Spiro-Cat)SbPh∙(Bipy)} ().

Synthesis and Antioxidant Activity of New Catechol Thioethers with the Methylene Linker.

Novel catechol thio-ethers with different heterocyclic substituents at sulfur atom were prepared by reacting 3,5-di--butyl-6-methoxymethylcatechol with functionalized thiols under acidic conditions. A common feature of compounds is a methylene bridge between the catechol ring and thioether group. Two catechols with the thio-ether group, bound directly to the catechol ring, were also considered to assess the effect of the methylene linker on the antioxidant properties.

Complexes of Metal Halides with Unreduced -(Imino)quinones.

A series of complexes of metal halides with unreduced quinone-type ligands have been synthesized and characterized in detail. The 3,6-di--butyl--benzoquinone () and 4,6-di--butyl--aryl-substituted -iminobenzoquinones (-) (aryl is 2,6-dimethylphenyl in , 2-methyl-6-ethylphenyl in , 2,6-diethylphenyl in , and 2,6-diisopropylphenyl in ) were used to obtain the molecular complexes with metal 12 group halides as well as with indium(III) iodide. The molecular structures of five complexes, bearing an unreduced form of redox-active ligand, have been established by single-crystal X-ray analysis.

Triphenylantimony(V) Catecholates of the Type (3-RS-4,6-DBCat)SbPh-Catechol Thioether Derivatives: Structure, Electrochemical Properties, and Antiradical Activity.

A new series of triphenylantimony(V) 3-alkylthio/arylthio-substituted 4,6-di-tert-butylcatecholates of the type (3-RS-4,6-DBCat)SbPh, where R = n-butyl (), n-hexyl (), n-octyl (), cyclopentyl (), cyclohexyl (), benzyl (), phenyl (), and naphthyl-2 (), were synthesized from the corresponding catechol thioethers and PhSbBr in the presence of a base. The crystal structures of , , , and were determined by single-crystal X-ray analysis. The coordination polyhedron of - is better described as a tetragonal pyramid with a different degree of distortion, while that for - was a distorted trigonal bipyramid ( = 0.

Ferrocene-Containing Tin(IV) Complexes Based on -Benzoquinone and -Iminobenzoquinone Ligands. Synthesis, Molecular Structure, and Electrochemical Properties.

The addition of different substituted -benzoquinones and -iminobenzoquinones to tin(II) bis(-iminophenolates) of the types (Fc-IP)Sn and (Fc-4,6-IP)Sn (where Fc-IP is anion 2-(ferrocenylmethyleneamino)phenolate [Fc-C(H)═N(CH)O] and Fc-4,6-IP is anion 2-(ferrocenylmethyleneamino)-4,6-di--butylphenolate [Fc-C(H)═N(4,6-tBu-CH)O]) in tetrahydrofuran leads to the oxidation of Sn(II) to Sn(IV) with formation of the corresponding tin(IV) catecholates (Fc-4,6-IP)Sn(3,6-Cat) (), (Fc-IP)Sn(3,6-Cat) (), (Fc-4,6-IP)Sn(4-Cl-3,6-Cat) (), (Fc-IP)Sn(4-Cl-3,6-Cat) (), (Fc-4,6-IP)Sn(4,5-Cl-3,6-Cat) (), and (Fc-IP)Sn(4,5-Cl-3,6-Cat) () or the -amidophenolates (Fc-4,6-IP)Sn(AP-Me) (), (Fc-IP)Sn(AP-iPr) (), and (Fc-4,6-IP)Sn(AP-iPr) (). Here ligands 3,6-Cat, 4-Cl-3,6-Cat, and 4,5-Cl-3,6-Cat are dianions 3,6-di--butyl-, 4-chloro-3,6-di--butyl-, and 4,5-dichloro-3,6-di--butylcatecholates, respectively, and AP-Me and AP-iPr are dianions 4,6-di--butyl--(2,6-dimethylphenyl)--amidophenolate and 4,6-di--butyl--(2,6-diisopropylphenyl)--amidophenolate, respectively. Complexes - have been characterized in detail by IR spectroscopy, cyclic voltammetry, and H, C, and Sn NMR spectroscopy.

Polyfunctional Sterically Hindered Catechols with Additional Phenolic Group and Their Triphenylantimony(V) Catecholates: Synthesis, Structure, and Redox Properties.

New polyfunctional sterically hindered 3,5-di--butylcatechols with an additional phenolic group in the sixth position connected by a bridging sulfur atom-(6-(CH-S-tBuPhenol)-3,5-DBCat)H (), (6-(S-tBuPhenol)-3,5-DBCat)H (), and (6-(S-Phenol)-3,5-DBCat)H () (3,5-DBCat is dianion 3,5-di--butylcatecolate)-were synthesized and characterized in detail. The exchange reaction between catechols and with triphenylantimony(V) dibromide in the presence of triethylamine leads to the corresponding triphenylantimony(V) catecholates (6-(CH-S-tBuPhenol)-3,5-DBCat)SbPh () and (6-(S-Phenol)-3,5-DBCat)SbPh (). The electrochemical properties of catechols - and catecholates and were investigated using cyclic voltammetry.

Tetrahedral nickel(ii) and cobalt(ii) bis-o-iminobenzosemiquinonates.

The new bis-o-iminobenzosemiquinonate nickel and cobalt complexes (imSQt-Bu)2M (M = Ni (1), Co (2)), where imSQ is a radical anion of 4,6-di-tert-butyl-N-(tert-butyl)-o-iminobenzoquinone, were synthesized and characterized in detail. The molecular structures of 1 and 2 have been established by single-crystal X-ray analysis. The metal atoms in 1 and 2 have a distorted tetrahedral environment, and the dihedral angles between the planes of two radical imSQ ligands are approximately 80° in both complexes.

Catechol thioethers with physiologically active fragments: Electrochemistry, antioxidant and cryoprotective activities.

A number of asymmetrical thioethers based on 3,5-di-tert-butylcatechol containing sulfur atom bonding with physiologically active groups in the sixth position of aromatic ring have been synthesized and the electrochemical properties, antioxidant, cryoprotective activities of new thioethers have been evaluated. Cyclic voltammetry was used to estimate the oxidation potentials of thioethers in acetonitrile. The electrooxidation of compounds at the first stage leads to the formation of o-benzoquinones.

Cobalt complexes with hemilabile o-iminobenzoquinonate ligands: a novel example of redox-induced electron transfer.

The tetracoordinated square-planar CoIII complex (imSQC(O)Ph)CoIII(APC(O)Ph) (1) bearing a radical anion and the closed-shell o-amidophenolate forms of the functionalized o-aminophenol H2LC(O)Ph were synthesized. The intermediate spin state (SCo = 1) CoIII center was found for compound 1. The cyclic voltammogram of derivative 1 contains two oxidative processes and one reductive redox process as well as an additional multi-electron wave at high negative potentials above -2 V, which can involve both the ligand and metal center.

Tin(IV) and lead(IV) complexes with a tetradentate redox-active ligand.

The coordination chemistry of a tetradentate redox-active ligand, glyoxal-bis(2-hydroxy-3,5-di-tert-butylanil) (H(2)L), was investigated with the diorganotin(IV) and diphenyllead(IV) moieties. Complexes R(2)SnL (R = Me (1), Et (2), (t)Bu (3), Ph (4)) and Ph(2)PbL (5) have been prepared and characterized. The molecular structures of compounds 1, 3, and 5 have been determined by single crystal X-ray diffraction.