Benzeneseleninic Acids Research Articles

Benzeneseleninic Acids (BSA) and Photocatalysis: An Alternative Duo for the Synthesis of 3‐Selanylindoles

AbstractA novel eco‐friendly methodology for the synthesis of 3‐selanylindoles has been established, circumventing the requirement for transition metal catalysis, strong oxidants and elevated reaction temperatures. In the present protocol a photocatalytic strategy was elegantly developed for the use of benzeneseleninic acid (BSA) derivatives as a selenium‐source reagent, reacting with indole derivatives, to access 3‐selanylindoles in moderate to good yields. A total of fourteen derivatives were selectively prepared, which among three are unprecedented. In addition to the synthetic advantages, this study gives significant insights into the use of BSA derivatives as reagent to construct Se(II)‐decorated products.

Benzeneseleninic Acid Promoting the Selenofunctionalization of 2- Naphthol Derivatives: Synthesis and Antioxidant Activity of 1- Organoselanyl-naphthalen-2-ols

Background: We report the synthesis and antioxidant evaluation of 1-organoselanyl-naphthalen-2-ols. The title compounds were selectively prepared through the selenofunctionalization of 2-naphthol derivatives using benzeneseleninic acids as a selenium source. Objective: We aimed at synthesizing 1-organoselanyl-naphthalen-2-ol by functionalizing 2-naphthol with arylseleninic acids using glycerol as the solvent and further evaluating the pharmacological activity. Methods: The products were synthesized at 70 °C using glycerol as a solvent in an oil bath. Reactive species (RS) tests, DPPH radical scavenging activity assay, and ABTS+ radical scavenging activity assay were performed. A statistical analysis of the data was performed. Results and Discussion: A total of fifteen 1-organoselanyl-naphthalen-2-ols were selectively obtained in yields of 58-95% in 0.25-48 h of reaction. Additionally, all the synthesized seleno-derivatives exhibited antioxidant activity, as revealed by their ability to scavenge DPPH and ABTS+ radicals and reduce the reactive species (RS) levels. Conclusion: The synthesis of 1-arylselanyl-naphthalen-2-ols was developed under mild reaction conditions using benzeneseleninic acid derivatives in reactions with 2-naphthol. All synthesized 2-naphthol derivatives exhibited antioxidant activity, as revealed by their DPPH and ABTS+ radical scavenging activity and reduced RS levels.

Seleninic Acid Potassium Salts as Water-Soluble Biocatalysts with Enhanced Bioavailability.

Organoselenium compounds are well-known glutathione peroxidase (GPx) mimetics that possess antioxidants/prooxidant properties and are able to modulate the concentration of reactive oxygen species (ROS), preventing oxidative stress in normal cells or inducing ROS formation in cancer cells leading to apoptosis. The purpose of this study was the synthesis of potent GPx mimics with antioxidant and anticancer activity along with improved bioavailability, as a result of good solubility in protic solvents. As a result of our research, glutathione peroxidase (GPx) mimetics in the form of water-soluble benzeneseleninic acid salts were obtained. The procedure was based on the synthesis of 2-(N-alkylcarboxyamido)benzeneselenenic acids, through the oxidation of benzisoselenazol-3(2H)-ones or analogous arenediselenides with an amido group, which were further converted to corresponding potassium salts by the treatment with potassium tert-butanolate. All derivatives were tested as potential antioxidants and anticancer agents. The areneseleninic acid salts were significantly better peroxide scavengers than analogous acids and the well-known organoselenium antioxidant ebselen. The highest activity was observed for the 2-(N-ethylcarboxyamido)benzeneselenenic acid potassium salt. The strongest cytotoxic effect against breast cancer (MCF-7) and human promyelocytic leukemia (HL-60) cell lines was found for 2-(N-cyclohexylcarboxyamido)benzeneselenenic acid potassium salt and the 2-(N-ethylcarboxyamido)benzeneselenenic acid, respectively. The structure–activity correlations, including the differences in reactivity of benzeneseleninic acids and corresponding salts were evaluated.

Molecular acidity: An accurate description with information-theoretic approach in density functional reactivity theory.

Molecular acidity is one of the important physiochemical properties of a molecular system, yet its accurate calculation and prediction are still an unresolved problem in the literature. In this work, we propose to make use of the quantities from the information-theoretic (IT) approach in density functional reactivity theory and provide an accurate description of molecular acidity from a completely new perspective. To illustrate our point, five different categories of acidic series, singly and doubly substituted benzoic acids, singly substituted benzenesulfinic acids, benzeneseleninic acids, phenols, and alkyl carboxylic acids, have been thoroughly examined. We show that using IT quantities such as Shannon entropy, Fisher information, Ghosh-Berkowitz-Parr entropy, information gain, Onicescu information energy, and relative Rényi entropy, one is able to simultaneously predict experimental pKa values of these different categories of compounds. Because of the universality of the quantities employed in this work, which are all density dependent, our approach should be general and be applicable to other systems as well. © 2017 Wiley Periodicals, Inc.

Triorganotin(IV) complexes with substituted benzeneseleninic acids: syntheses, characterization, crystal structures, and antitumor activity

Nine new organotin(IV) selenites have been prepared by the reaction of 2-methylbenzeneseleninic acid, 2-methoxybenzeneseleninic acid, 4-isopropylbenzeneseleninic acid, and the corresponding triorganotin(IV) chloride with sodium ethoxide in methanol. The complexes have been characterized by elemental analysis, FT-IR, (1H, 13C, and 119Sn) NMR spectroscopy, and thermogravimetric analysis. Except for 3, 6, and 9, all of the complexes were also characterized by X-ray crystallography diffraction analyses. The structural analyses reveal that 1, 2, 4, 5, 7, and 8 exhibit 1-D infinite chain structures which are generated by bidentate oxygen atoms and five-coordinated tin. Complex 5 forms a 2-D organotin framework linked by intermolecular C–H ··· O interactions. Additionally, 1 and 2 were tested for antitumor activity in vitro.

Photoluminescence study of new lanthanide complexes with benzeneseleninic acids

New lanthanide complexes with benzeneseleninic (ABSe) and 4-chloro-benzeneseleninic (ABSeCl) acids have been synthesized and characterized by elemental analysis, infrared and UV–visible spectroscopies. The emission spectra of the trivalent europium complexes presented the typical electronic 5D 0→ 7F J transitions of the ion ( J=0–4). The ground-state geometries of the europium complexes have been calculated by using the Sparkle/AM1 model. From these results, the 4f–4f intensity parameters and energies of the ligand singlet and triplet excited states have been obtained. The lower emission quantum yield for the [Eu(ABSe) 3(H 2O) 2](H 2O) 2 compound, as compared to the [Eu(ABSeCl) 3(H 2O) 2] one, can be associated to the higher numbers of water molecules, in the first and second coordination spheres, that contribute to the luminescence quenching. The [Eu(ABSe) 3(H 2O) 2](H 2O) 2 complex presents an intermediate state whose energy difference with respect to the first excited singlet state is resonant with three phonons from the water molecules, favouring a multiphonon relaxation process from the singlet state followed by a fast internal conversion process; this effect is less pronounced in the complex with the ABSeCl ligand. The luminescence decay curves of the gadolinium complexes indicate that the level responsible for the intramolecular energy transfer process has a triplet character for both compounds. The nephelauxetic effect in these compounds was investigated under the light of a recently proposed covalency scale based on the concept of overlap polarizability of the chemical bond.

Synthesis and Characterization of Lanthanide Complexes. Lanthanum(III), Cerium(III) and Europium(III) Derivatives withPara- andMeta-Substituted Benzeneseleninic Acids

Abstract New complexes of lanthanum(III), cerium(III) and europium(III) with para- and meta-substituted benzeneseleninic acids of the type XC6H4SeO2H (X = H, m-Cl, p-Br, p-Me) are reported. The compounds Ln(XC6H4SeO2)3, Ln(XC6H4SeO2)2Cl, Ln(XC6H4SeO2)Cl2 and Ln2(XC6H4SeO2)3Cl3, where Ln denotes trivalent La, Ce, and Eu, have been studied using spectroscopic techniques (ir, far-ir and electronic spectra), magnetic susceptibility, thermogravimetric and conductivity measurements. The electronic spectra of the 1 : 3 derivatives have been analysed and spectral parameters are calculated and discussed for the europium complexes. The ir data point to a seleninato-O,O' coordination for all the complexes; in particular, the presence of three SeO bands with irreducible representation A 2 + 2E in the ir spectra of the tris derivatives suggests an octahedral configuration with D 3 symmetry. All the halo derivatives are polymeric and octahedral in nature with bridging halide atoms. The magnetic moment values lie in the...

Reaction of α,β-unsaturated aldehydes with hydrogen peroxide catalysed by benzeneseleninic acids and their precursors

Oxidation of α,β-unsaturated aldehydes with hydrogen peroxide catalysed by benzeneseleninic acids and their precursors has been investigated. Bis 2-nitrophenyl diselenide has proved to be the most effective catalyst. The major products resulting from the oxidation are vinyl formates ( a ) which on hydrolysis give saturated aldehydes or ketones ( g ) having the carbon chain shortened by one carbon atom, compared with the starting alde-hydes. The minor products are formyloxyoxiranes ( b ), α-hydroxy-carbonyl ( e ) and α-formyloxycarbonyl ( f ) compounds with the carbon chain shortened by one carbon atom. Carbonyl compounds d , formally derived from an oxidative fission of the carbon-carbon double bond, have been also isolated. Diformyloxy ( 4c ) and formy-loxyacetoxy phenylmethane ( 5c ) have been isolated when cinnamaldehyde ( 4 ) or 1-phenyl-2-formyloxypropane ( 5a ) were oxidized, respectively. Possible mechanisms of formation of these products are discussed. Similar products resulted when α, β -unsaturated aldehydes were oxidized with organic peroxy acids.

Osmium(III) Halide Complexes with para-and meta-Substituted Benzeneseleninato Ligands

New complexes of osmium(III) with para - and meta-substituted benzeneseleninic acids of the type XC6H4SeO2H (X = H, p- Cl , m- Cl , p-Br, m-Br, p-Me) are reported. The compounds, of the type Os(XC6H4SeO2)3, Os(XC6H4SeO2)2Y, Os(XC6H4SeO2)Y2 and Os2(XC6H4SeO2)3Y3 (Y = Cl , Br), have been studied through spectroscopic techniques ( i.r ., far- i.r .and electronic spectra), magnetic susceptibility measurements, thermogravimetric studies and conductivity measurements. The wavelengths of the principal electronic absorption peaks have been accounted for quantitatively in terms of the crystal-field theory; the nephelauxetic parameter is indicative of an appreciable metal- ligand covalency. It is worth noting that among the present complexes the highest q values are related to the Os(XC6H4SeO2)3 derivatives in which OsO6 chromophores are present; the Dq values decrease on passing to the 1 : 2, 1 : 1.5 and 1 : 1 metal/ ligand molar ratio complexes according to the presence of chlorine- and bromine-containing chromophores . The i.r . data point to a seleninato -O,O′ coordination for all the complexes; in particular, the presence of three SeO bands with the irreducible representation A2 + 2E in the i.r . spectra of the tris derivatives suggests an octahedral configuration with D3 symmetry. All the halo complexes are polymeric octahedral with bridging halide atoms. The magnetic moment values lie in the expected range for the trisbenzeneseleninato derivatives, and they decrease on passing to the halo complexes.

Synthesis and characterization of ruthenium (III) complexes with para- and meta-substituted benzeneseleninic acids as ligands

A number of complexes of ruthenium(III) with para- and meta-substituted benzeneseleninic acids, XC 6H 4SeO 2H (X = H, m-Br, p-Br, p-CH 3, m-Cl, p-Cl) are reported. The recently prepared compounds are characterized through elemental analyses, near and far i.r. spectroscopy, electronic spectra, conductivity measurements, thermal analyses (TG and DTG) and magnetic susceptibility measurements. The wavelengths of the principal electronic absorption peaks have been accounted for quantitatively in terms of the crystal field theory; the nephelauxetic parameters are all indicative of an appreciable metal-ligand covalency. The i.r. results point to a O, O′-seleninato coordination for all the complexes; in particular the presence of three SeO bands with the irreducible representation A 2 + 2 E in the i.r. spectra of the trisderivatives of the type Ru (XC 6H 4SeO 2) 3 suggests an octahedral configuration with D 3 symmetry. The complexes of the type Ru (XC 6H 4SeO 2) 2 Y (Y = Cl, Br) are polymeric octahedral with bridging halides.

Substituted benzeneseleninic acids as bidentate ligands. Synthesis and spectroscopic studies of manganese(II) and iron(II) complexes

The para- and meta-substituted seleninato anion, XC 6H 4SeO − 2, forms complexes with manganese(II) and iron(II) of the type [M(XC 6H 4SeO 2) 2(H 2O) 2], which have been shown to contain the bidentate ligand in seleninato- O, O′ derivatives, the water molecules being coordinated to the metals. From the electronic absorption spectra and from the magnetic susceptibility data we have proposed for all the complexes a distorted octahedral D 4 h symmetry. The structure of the anhydrous para- and meta-substituted benzeneseleninato complexes of manganese(II) and iron(II) have been investigated by means of electrical conductance measurements, spectral (electronic and i.r.) studies and magnetic susceptibility measurements. The anhydrous complexes are always of the seleninato- O, O′ type with the ligands tetrahedrally coordinated to the central atom. The wavelengths of the principal absorption peaks have been accounted for quantitatively in terms of the crystal field theory for manganese(II) derivatives. The nephelauxetic parameters are all indicative of an appreciable metal-ligand covalency.

Mass spectral investigations on selenium compounds. II. The behaviour of meta-and para-substituted benzeneseleninic acids and of meta-nitrophenyl selenocyanate under electron impact

Substituted benzeneseleninic acids of the type XC6H4SeO2H (X = m-Cl, p-Cl, m-Br, p-Br, p-Me, m-NO2, p-NO2) have been investigated by mass spectrometry. The fragmentation modes and the fragment ions are discussed and compared with those obtained from the mass spectrum of m-nitro-phenyl selenocyanate, O2NC6H4SeCN. Generally, as regards the acids, besides very weak peaks due to the molecular ions, a number of peaks at higher mass numbers and of greater intensity is observed; these peaks are in multiplets typical of the presence of two selenium atoms, and they correspond to the disubstituted diphenyl diselenides of the type XC6H4SeSeC6H4X. m-Nitrophenyl selenocyanate shows an intense molecular ion peak and the relative fragmentation, while the peak due to the diselenide is of very low intensity.

ChemInform Abstract: SYNTHESIS AND CHARACTERIZATION OF PARA‐ AND META‐SUBSTITUTED BENZENESELENINATO COMPLEXES OF TIN(II), SILVER(I) AND IRON(II)

AbstractDie Benzolseleninato‐Komplexe (I), (II) und (III) werden durch die Reaktion von Sn‐dichloriddihydrat, Ag‐nitrat oder F e‐diammoniumdisulfat‐hexahydrat mit den entsprechenden Na‐arenseleninaten in Ethanol dargestellt (keine Ausb.‐Angabe).

Metal-ligand bonding in benzeneseleninato complexes of p- and d-block metals

New complexes of lead(II) and zirconium(IV) withmeta-andpara-substituted benzeneseleninic acids are reported and characterized by chemical analyses, spectroscopic methods and conductivity and magnetic measurements. The complexes are of the Pb(XC6H4SeO2)2 and ZrO(XC6H4SeO2)2 type; for zirconium(IV), working with a 1:4 metal:ligand stoichiometrical ratio, invariably the oxy derivative was obtained. The i.r. spectral data suggest that the complexes contain RSeO2− ligands acting as bidentate in O,O′-seleninato complexes, Where possible, a tentative stereochemistry for the complexes is discussed on the basis of the results obtained.

Synthesis and characterization ofpara- andmeta-substituted benzeneseleninato complexes of tin(II), silver(I) and iron(II)

New complexes of tin(II), silver([) and iron(II) withpara- andmeta-substituted benzeneseleninic acids are reported and studied by chemical analyses, spectroscopic methods, conductivity and magnetic measurements. The complexes, of the type Sn(XC6H4SeO2)2, Ag(XC6H4SeO2) and Fe(H2O)2(XC6H4SeO2)2, were obtained by reaction of SnCl2, · 2 H2O. AgNO3 and Fe(NH4)2(SO4)2·6 H2O with the sodium benzeneseleninates, XC6H4SeO2Na (X = H.p-Cl,m-Cl,p-Br,m-Br orp-Me). The i.r. spectral data suggest that the silver and iron complexes contain RSeO 2 − ligands which act as bidentates in O,O′-seleninato complexes. All the iron complexes have a distorted octahedralD 4h symmetry. The number of bands in the i.r. spectra of the tin derivatives indicates that there is no equivalence in the manner in which the two seleninato ligands are bonded. We could suggest that the tin atoms are intermolecularly O.O′-bonded via one RSeO 2 − group, whereas the second ligand is coordinated to the metal via one oxygen atom forming polymeric Ψ-tetrahedral derivatives.

Chromium(III), manganese(II) and iron(III) O,O'-bonded complexes of the para- and meta-substituted benzeneseleninic acids

A number of complexes of chromium(III), manganese(II) and iron(III) with para- and meta-substituted benzeneseleninic acids, XC6H4SeO2H (X = H, p-Cl, m-Cl, p-Br, m-Br, p-Me), are reported. The newly prepared compounds are characterized on the basis of near-i.r. and far-i.r. spectroscopy, electronic spectra and conductivity measurements, as well as by magnetochemical evidence. The wavelengths of the principal absorption peaks have been accounted for quantitatively in terms of the crystal field theory for chromium(III) and manganese(II) derivatives. The nephelauxetic parameters are all indicative of an appreciable metal-ligand covalency. The i.r. spectral data suggest that the ligands act as bidentate in seleninato-O,O' complexes and we can propose octahedral geometries with D3 symmetry for the chromium(III) and iron(III) derivatives and octahedral geometries, distorted towards D4h, for the manganese(II) complexes, in which the water has been shown to be coordinated to the metal.

Para and Meta-Substituted Benzeneseleninic Acids Interactions with Cr(III), Mn(II), Fe(II), Fe(III), Sn(II) and Ag(I)

Working on the study of the chemical reactivity and linkage isomers of the coordination compounds of the para- and meta-substituted benzeneseleninic acids as ligands, we report the interaction of Cr(III), Mn(II), Fe(II), Fe(III), Sn(II) and Ag(I) with XC 6H 4- SeO − 2 (X = H, p-Cl, m-Cl, p-Br, m-Br, p-Me). The seleninato ion is well known for its capability to coordinate to a metal ion as unidentate or bidentate ligand either inter- or intra-molecularly through the two oxygen and the selenium atoms. I.r. spectroscopy provides a convenient means of distinguishing between the different possibilities. All these possible types of binding have been reported in previous papers [1], and the chemical reactivity of some of the obtained complexes, of the type [M(H 2O) 2(XCH 4SeO 2) 2] (M = Co, Ni, Zn), towards N donor ligands has been described in other works [2–4]. In the present work we have obtained complexes of general formula Cr(L) 3, Mn(H 2O) 2(L) 2,Fe(H 2O) 2(L) 2, Fe(L) 3, Sn(L) 2 and Ag(L); the compounds are microcrystalline or powder-like and with the exception of the tin derivatives, whose limited solubility prohibits conductance measurements, all are non-conducting in nitromethane, indicating the covalent nature of the compounds. Infrared spectra. The bands due to the substituent X and all the band assigned to fundamentals of the benzene ring appear in the complexes at the same wavenumbers as in the starting ligands. In the Mn(II), Fe(II) and Ag(I) derivatives the bands due to the sym. and asym. v(SeO) are shifted towards lower energies in comparison with the stretching values of the free anions. This fact and the small frequency differences between these modes point to a O,O′-seleninato coordination. Three SeO bands with the irreducible representations A 2 + 2E are observed in the i.r. spectra of all the Cr(III) and Fe(III) trisderivatives, suggesting an octahedral configuration with D 3 symmetry. The i.r. spectra of the tin(II) derivatives show a more complex profile, significantly different from those above discussed. The number of the bands, in the v(SeO 2) region, is indicative of the non-equivalence in the manner in which the two areneseleninato ligands are coordinated. We could suggest that one group is O,O′-bonded intermolecularly to the tin atoms in linear chains, whereas the second group is seleninato-O bonded. Taking into account the lone pair of electrons, the tin atom has a ψ-tetrahedral environment. The vibrational spectra of the Mn(II) and Fe(II) complexes show meaningful differences with the spectra of the other water-containing derivatives as regards the related-water bands; the spectra of these compounds show the absorptions characteristic of the coordinated water, and the complexes can be regarded as distorted octahedral. In the far-i.r. region the v(MO) vibrational modes have been assigned and discussed. It is noteworthy that v(FeO) in the iron(II) derivatives is at lower wavenumbers than in the corresponding iron(III) complexes, in very good agreement with the fact that, in a change of oxidation number, the metal-ligand vibration increases in frequency with an increase of the oxidation number. Electronic spectra and magnetic moments. For the chromium(III) derivatives the calculated Dq and B′ parameters suggest the presence of CrO 6 chromophores, thus confirming the conclusions reached from the i.r. studies. As for the manganese(II) derivatives the value of B, C and 10 Dq have been calculated by the method already reported, together with the energies of the bands arising from the transitions 6A 1 → 4T 1g( 4G), → 4T 1g(P), and → 4T 1g( 4F). Inthis way good agreement between calculated and observed energies has been found for all the states. The iron(II) derivatives exhibit an absorption band clearly split into two components, which represents the transition 5T 2g → 5E g for octahedral iron(II) complexes. The room temperature magnetic moment values are in agreement with the literature data.

Spectroscopic study on the nature of the metal—ligand bond in cobalt(II) and nickel(II) para- and meta-substituted areneseleninato complexes

The para- and meta-substituted benzene-seleninato anion forms complexes with cobalt (II) and nickel (II) of the type [M(XPhSeO 2) 2(H 2O) 2]. The i.r. spectra of these compounds suggest that the complexes are seleninato-O, O′ with the ligand acting as bidentate and with the water coordinated to the metals. From the electronic absorption spectra and from the magnetic susceptibility data we have proposed for all the complexes a distorted octahedral D 4 h symmetry. The structures of the para- and meta-substituted benzeneseleninic acids, anhydrous complexes of cobalt (II) and nickel (II) have been investigated by i.r. spectroscopy, electronic spectra and magnetic susceptibility measurements. The anhydrous complexes are always seleninato-O, O′ type with the ligands tetrahedrally coordinated to the central atom. The electronic absorption spectra were studied and the values of the spectral parameters were determined. They are in keeping with the proposed structures confirming the presence of CoO 4 and NiO 4 chromophores.

Study of the nature of metal—ligand bond in zinc, cadmium and mercury areneseleninato complexes

The structures of para- and meta-substituted benzeneseleninic acids complexes of zinc, cadmium and mercury have been investigated by i.r. spectroscopy and it has been shown that the bonding of the areneseleninato ligand to these metals depends on the water content of the compound. The water containing complexes are always seleninato—O,O′-type, while the compounds without water are mainly seleninato—O,O′ in the case of zinc, seleninato—O in the case of cadmium and seleninato—Se in the case of mercury.

Synthesis and characterization of O,O′-bonded benzeneseleninate complexes of rhodium(III) and iridium(III)

A number of complexes of rhodium(III) and iridium(III) with para- and meta-substituted benzeneseleninic acids are reported and characterized by spectroscopic methods. The benzeneseleninate complexes were prepared by the reaction of the sodium aryl-seleninate with RhCl 3 and (NH 4) 3IrCl 6. From the electronic absorption spectra the values of the ligand field parameters were determined. The nephelauxetic parameters are all indicative of appreciable metal-ligand covalency. The i.r. spectral data suggest that the complexes contain RSeO 2 − ligands chelating the metal via the oxygen atoms. A monomeric structure for the tris(benzeneseleninato) complexes is suggested.