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A series of complexes of metal halides with unreduced quinone-type ligands have been synthesized and characterized in detail. The 3,6-di-tert-butyl-o-benzoquinone (1) and 4,6-di-tert-butyl-N-aryl-substituted o-iminobenzoquinones (2-5) (aryl is 2,6-dimethylphenyl in 2, 2-methyl-6-ethylphenyl in 3, 2,6-diethylphenyl in 4, and 2,6-diisopropylphenyl in 5) 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. The spectral data, electrochemical measurements, and DFT calculations indicate the significant transformations of the molecular orbitals of 1-5 upon complexation with Lewis acids. The reduction potentials of o-(imino)quinones in complexes with metal halides shift into the anodic region versus uncoordinated ones. The choice of metal halide allows varying the shift magnitude up to 1.7 V in 2·CdI2. The change of the oxidizing ability of the 1-5 upon coordination with Lewis acids enables the oxidation of mercury and ferrocene, infeasible for free ligands.

Abstract Poorly soluble in the most part of organic solvents dimeric complexes $${\text{M}}{{{\text{g}}}_{{\text{2}}}}{\text{L}}_{2}^{2}$$·4DMF (I) and $${\text{N}}{{{\text{i}}}_{{\text{2}}}}{\text{L}}_{2}^{2}$$·4DMF (II) (L is 4,4'-(1,4-phenylenebis(azanylylidene))bis(3,6-di-tert-butyl-2-hydroxycyclohexa-2,5-dien-1-one dianion)) are synthesized by the reactions of magnesium and nickel acetates with the ditopic redox-active ligand of the hydroxy-para-iminoquinone type in a DMF solution. The molecular and crystal structures of the synthesized compounds are determined by X-ray diffraction analysis (CIF files CCDC nos. 2045665 (I) and 2045666 (II·3DMF)). The thermal stability is studied by thermogravimetry. The redox-active character of the organic bridging ligand in the dimeric complexes $${\text{M}}{{{\text{g}}}_{{\text{2}}}}{\text{L}}_{2}^{2}$$·4DMF and $${\text{N}}{{{\text{i}}}_{{\text{2}}}}{\text{L}}_{2}^{2}$$·4DMF is confirmed by the data of solid-phase electrochemistry.

We report a comparative analysis of experimental and theoretical vibrational spectra recorded in the frequency region of 700-100 cm–1 for mono-o-iminosemiquinone tin(IV) complexes with general formulas LSnR2Cl (1-5) and LSnR3 (6, 7) (L is the 4,6-di-tert-butyl-N-(2,6-di-iso-propylphenyl)-o-iminobenzoquinone radical anion, R = Me (1, 6), Et (2), n-Bu (3), t-Bu (4), Ph (5, 7)). It is established that absorption bands of ν(Sn–O) and ν(Sn–N) stretching vibrations in the studied compounds occur at 460-360 cm–1 and 340-350 cm–1, respectively. The position of the ν(Sn–O) absorption band correlates with the Sn–O bond length. In particular, the band is redshifted by 20 cm–1 in complex 6, where this bond is 0.2 A longer than in other compounds. It is shown that parameters ν(Sn–O), a(117, 119Sn) and bond lengths d(Sn–O), d(Sn–N), and d(Sn–C) in the complexes depend on four (inductive, resonance, polarization, and steric) effects of tin-bonded substituents.

N-Heterocyclic carbene is a versatile ligand for the preparation of copper( i ) and silver( i ) derivatives bearing the radical anion forms of redox active o-benzoquinone and o-iminobenzoquinone. The paramagnetic three-coordinated copper( i ) and silver( i ) o-benzosemiquinone and o-iminobenzosemiquinone complexes were prepared and characterized by EPR spectroscopy and X-ray diffraction analysis.

New bis-p-iminobenzoquinone ligands, in which two hydroxy-p-iminobenzoquinone moieties are bridged by various functionalized linkers, were synthesized by 1,4-addition of aromatic diamines to 3,6-di-tert-butyl-o-benzoquinone. The exchange reaction between potassium salts of new ligands and ethylmercury(ii) chloride produces the corresponding mono- and binuclear metal complexes. In these complexes, the mercury atoms exhibit T-shaped trigonal geometry characteristic of three-coordinate mercury(ii) derivatives. The structures of the new ligands and the mercury complexes with these ligands were determined by IR, UV, and NMR spectroscopy and X-ray diffraction.

The synthesis, crystal structure, thermal stability, porosity and magnetic properties of three new layered coordination polymers [(M2(pQ)3)·4DMAA]n (M3+ = La3+ (1), Pr3+ (2), Nd3+ (3); pQ2− – the dianionic form of 2,5-dihydroxy-3,6-di-tert-butyl-para-quinone; DMAA = N,N′-dimethylacetamide) are reported. The coordination polymers obtained were investigated by solid-state electrochemistry which demonstrates multistep one-electron transformations caused by the presence of redox-active dioxolene ligands.

By the metal salt metathesis reaction between tin(IV) bis-o-iminobenzosemiquinonates imSQi−Pr2SnCl2 (1) or imSQMe2SnCl2 (2) (where imSQi-Pr – radical-anion of N-2,6-di-iso-propylphenylsubstituted o-iminobenzoquinone, imSQMe - radical-anion of N-2,6-dimethylphenylsubstituted o-iminobenzoquinone) and an excess of sodium azide, potassium isocyanate or potassium thiocyanate new hexacoordinated tin(IV) bis-o-iminobenzosemiquinonates imSQi−Pr2SnX2 (3, 5 and 7) and imSQMe2SnX2 (4, 6 and 8) (where X - azide, isocyanate or thioisocyanate group) were synthesized and characterized including X-ray diffraction analysis. The magnetic susceptibility measurements for new compounds 2–8 and related previously known complexes imSQi−Pr2SnX2 (X = Me (9), Br (11), I (12)) were performed. All tin(IV) bis-o-iminobenzosemiquinonates were found to be characterized by antiferromagnetic exchange interaction between unpaired electrons of two imSQ ligands independently on the X substituent nature. However known tin(IV) complexes imSQi−Pr2Sn(Me)2 (9) and imSQi−Pr2Sn(Ph)2 (10) containing organic ligands bonded to the metal atom demonstrate quite strong magnetic interaction compared with complexes including halide or pseudohalide substituents. Due to their great kinetic stability the diradical tin(IV) derivatives obtained have a possible application as potential components for molecular electronics and spintronics, lithium batteries, nonlinear optics and magnetic materials.

Two synthetic approaches were used for the synthesis of 3,6-di-tert-butylcatecholate derivatives of titanium(iv). These approaches are based on the exchange reaction between sodium catecholate and titanium(iv) chloride and the reaction of 3,6-di-tert-butylpyrocatechol with titanium tetrabutoxide. Depending on the reaction conditions, the former method allows the synthesis of the titanium monocatecholate complex 3,6-CatTiCl2(THF)2 (3,6-Cat is doubly deprotonated 3,6-di-tert-butylpyrocatechol) or bimetallic sodium titanium catecholate derivatives. Using the latter method, it is possible to synthesize six-coordinate titanium(iv) bis-cate-cholate complexes in high yields after the introduction of neutral bidentate donor ligands (TMEDA, DME, 2,2′-bipyridyl) to the reaction mixture.

New catecholate complexes of triphenylantimony(V), (Etgly-3,6-DBCat)SbPh3 (I), (Propgly-3,6-DBCat)SbPh3 (II), and (Cat-3,6-DBCat)SbPh3 (III), based on analogs of sterically hindered 3,6-di-tert-butyl-o-benzoquinone, 5,8-di-tert-butyl-2,3-dihydrobenzo[b][1,4]dioxine-6,7-dione (L1), 6,9-di-tert-butyl-2,3-dihydrobenzo[b][1,4]dioxepine-7,8-dione (L2), and 1,4-di-tert-butyl-dibenzo[b,e][1,4]dioxine-2,3-dione (L3), which are the 2,3-dihydrobenzo[b][1,4]dioxine, 2,3-dihydrobenzo[b][1,4]dioxepine, and dibenzo[1,4]dioxine derivatives, respectively, have been synthesized. At room temperature catecholates I and II react with molecular oxygen adding an O2 molecule to form the corresponding spiroendoperoxides IV and V. Catecholate III reacts with oxygen with the deep oxidation of the complex and formation of neutral o-benzoquinone. The molecular structures of complexes I and III are determined by X-ray diffraction analysis (CIF files CCDC nos. 1840299 (I · toluene) and 1840300 (III)).

In this study we demonstrated that exposure of Escherichia coli (E. coli) to terahertz (THz) radiation resulted in a change in the activities of the tdcABCDEFGR and matA–F genes (signs of cell aggregation), gene yjjQ (signs of suppression of cell motility), dicABCF, FtsZ, and minCDE genes (signs of suppression of cell division), sfmACDHF genes (signs of adhesin synthesis), yjbEFGH and gfcA genes (signs of cell envelope stabilization). Moreover, THz radiation induced E. coli csg operon genes of amyloid biosynthesis. Electron microscopy revealed that the irradiated bacteria underwent increased aggregation; 20% of them formed bundle-like structures consisting of two to four pili clumped together. This could be the result of changes in the adhesive properties of the pili. We also found aberrations in cell wall structure in the middle part of the bacterial cell; these aberrations impaired the cell at the initial stages of division and resulted in accumulation of long rod-like cells. Overall, THz radiation was shown to have adverse effects on bacterial populations resulting in cells with abnormal morphology.

A series of the new tin(IV) complexes based on the 2-hydroxy-4-N-(phenyl)-3,6-di-tert-butyl-p-iminobenzoquinone ligand (LH) containing various hydrocarbon substituents R at the metal atom (R = Me, Et, n Bu, t Bu, and Ph) is synthesized. The structures of the synthesized compounds were determined by elemental analysis, IR spectroscopy, and 1H and 119Sn NMR spectroscopy. The X-ray diffraction analyses are carried out for the LSnPh3 (I) and L2SnEt2 (IV) complexes (CIF files CCDC no. 1557840 (I) and 1557839 (IV)). The main electrochemical characteristics in a solution are obtained for the whole series by cyclic voltammetry.

Raman spectra of tin 2-hydroxy-3,6-di-tert-butyl-para-benzoquianone complexes L2SnX2 and LSnX3 (L is 2-oxy-3,6-di-tert-butyl-para-benzoquianone; X = CH3, C2H5, n-C4H9, and C6H5) are studied. A comparative analysis of the experimental and calculated spectra is carried out and the vibrational frequencies are conventionally assigned. A new tin(IV) complex based on 2,5-dihydroxy-3,6-di-tert-butyl-para-benzoquianone (L′H2) containing phenyl substituents at the metal atom is synthesized. Absorption bands of the complexes are interpreted in the low-frequency range of the infrared spectrum that was not considered previously.

New tris-o-benzosemiquinonato complexes of Al, Ga, and In based on the sterically hindered o-benzoquinone 5,8-di-tert-butyl-2,3-dihydro-1,4-ethanoquinoxaline-6,7-dione (NN-3,6-Q) were synthesized. The structures of the hexacoordinate metal compounds were investigated by X-ray diffraction. The magnetic properties of the complexes obtained were found to be strongly dependent on their molecular geometry. The octahedral Al and Ga derivatives demonstrate ferromagnetic exchange between the magnetic centers, whereas the trigonal-prismatic In complex shows an antiferromagnetic coupling.

Heat-induced transformations of N-[2,6-diisopropylphenyl]-3,5-di(tert-butyl)-, N-[2,6-diethylphenyl]-3,5-di(tert-butyl)-, and N-[2-methyl-6-ethylphenyl]-3,5-di(tert-butyl)-o-benzoquinonimines in nonane follow the first-order rate equation, whereas that of N-[2,5-di(tert-butyl)phenyl]-3,5-di(tert-butyl-o-benzoquinonimine obey the second-order rate equation. Kinetic parameters of these reactions have been determined. 4aH-Phenoxazine derivatives of quinonimines are intermediates of the heat-induced transformations following the first-order kinetics; under the irradiation with 405 nm light they undergo the ring opening to give the starting compounds with quantum yield close to unity.

Characteristic features of synthesis of various polymers with participation of the tin complex imSQSnBut2Cl, where imSQ is the 4,6-di-tert-butyl-N-(2,6-diisopropylphenyl)-o-iminobenzoquinone radical anion, were studied. It was shown that for a number of monomers, this complex acts as an iniferter, i.e., it can not only initiate the polymerization, but can also regulate the chain growth of macromolecules. The effect of the conditions of the process on the possibility of obtaining macromolecular products with a narrow polydispersity was estimated.

Indium catecholate complexes 3,6-CatInR (3,6-Cat is the 3,6-di-tert-butyl-o-benzoquinone dianion (3,6-Q), R = Me (I) and Et (II)) are synthesized by the exchange reaction between RInI2 and thallium catecholate 3,6-CatTl2. Compounds I and II are trimeric in both the solution and crystalline state. The oxidation of compound I and earlier described complex [3,6-CatInI(THF)]2 (THF is tetrahydrofuran) by various substrates (iodine, 3,6-Q, and tetramethylthiuram disulfide) is studied. Different indium(III) o-semiquinone complexes are the reaction products, depending on the reaction conditions.

A series of stable paramagnetic organomercury compounds containing the 4,6-di-tert-butyl-N-(2,6-diisopropylphenyl)-o-iminobenzosemiquinone ligand (imSQ) with the general formula imSQHgR (R = Ph, Et, Prn, Bun, Pri, Hexc, CH2SiMe3, p-FPh, Fc, p-Me2NPh) were synthesized. The molecular and electronic structures of the synthesized compounds were investigated by EPR spectroscopy and X-ray diffraction. The o-iminosemiquinone ligand shows the unusual amidophenoxy-type coordination mode. In the EPR spectra of the compounds imSQHgR, the hyperfine coupling constant of magnetic mercury isotopes (199,201Hg) depends on the nature of the substituent R, the temperature, and the nature of the solvent. Voltammetric investigations showed that the complex imSQHgFc undergoes three reversible one-electron redox steps related to the redox transformations of both the o-iminoquinone ligand and the metallocene moiety of the molecule.

New tin(iv) mono- and bis-o-iminosemiquinone complexes were obtained by the exchange reaction of radical anion lithium salt of 4,6-di-tert-butyl-N-(2,6-diisopropylphenyl)-o-imino-benzoquinone with tin(iv) organochlorides. The compounds synthesized were characterized by EPR spectroscopy and X-ray diffraction analysis. Substituents on the tin atom were found to affect stability of paramagnetic metal derivatives formed.

The mutagenicity and genotoxicity in bacteria of 2.3THz radiation (THz) produced by a free-electron laser (NovoFEL) were evaluated; exposures were 5, 10, or 15min at average power 1.4W/cm(2). Two Ames mutagenicity test strains of Salmonella typhimurium, TA98 and TA102, were used. For the genotoxicity test, we measured SOS induction in Escherichia coli PQ37. No significant differences were found between exposed and control cells, indicating that THz radiation is neither mutagenic nor genotoxic under these conditions. Nevertheless, a small increase in total cell number of S. typhimurium after 15min exposure, and an increase in β-galactosidase and alkaline phosphatase activities in E.coli PQ37, were observed, indicating some effect of THz radiation on cell metabolism. We also examined the combined effect of 4-NQO (8μM; positive control) and THz exposure (5min) on genotoxicity in E.coli PQ37. Unexpectedly, THz radiation decreased 4-NQO genotoxicity.

We have determined the nucleotide sequence of a flagellin gene locus from the haloalkaliphilic archaeon Natrialba magadii , identified the gene products among proteins forming flagella, and demonstrated cotranscription of the genes. Based on the sequence analysis we suggest that different regions of the genes might have distinct evolutionary histories including possible genetic exchange with bacterial flagellin genes.

The reaction of bis(4,6-di-tert-butyl-N-(2,6-di-iso-propylphenyl)-o-amidophenolato)indium(III) anion with alkyl iodides is reported. This process includes oxidative addition of two RI (R = Me, Et) molecules to the non-transition metal complex and results in an alkyl transfer to ring carbon atoms with the formation of two new C-C bonds. The interaction proceeds at mild conditions and gives new indium(III) derivatives containing iminocyclohexa-1,4-dienolate type ligands.