Sb Ligands Research Articles

New tetradentate long chain Schiff base and its cadmium(II) complexes: Antimicrobial, antioxidant and anticancer activities

In the current study, a new long chain tetra-nitrogen donor Schiff base ligand (SB) entitled as N1,N2-bis(2-(((1E,2E)-3-(4-(dimethylamino)phenyl)allylidene)amino)ethyl)ethane-1,2-diamine and some its molecular cadmium (II) complexes formulated as Cd(SB)X2 (X = halide/pseudohalide) were prepared and characterized by various physicochemical and spectral methods such as melting point, micro-analytical data, thermal analysis (TG/DTG/DTA), molar conductivity and UV–Visible, FT-IR, 1H, and 13C NMR spectroscopies. Also nanostructured cadmium chloride and iodide chelate complexes approved by PXRD SEM and EDX techniques were synthesized to use as precursor to prepare nanostructure cadmium oxide. The particle sizes about 2–10 nm were estimated for nanostructured cadmium complexes and oxide. Thermo-gravimetric plots showed the compounds are decomposed via 2–4 steps with weight loss of 69–100% to leave out metallic Cd or cadmium salt as final residue. Thermo-kinetic activation parameters calculated based on TG plots suggested non-spontaneous thermal decomposition with activation Ea*, ΔH* and ΔG* parameters in the ranges of (13.54–160.48 kJ.mol−1), (8.22–155.95 kJ.mol−1) and (1.59 × 102-4.1 × 102 kJ.mol−1) respectively. Moreover, the pharmacological activities of the compounds were investigated against some pathogenic fungi and bacteria. According to screening data, the SB ligand showed lower antimicrobial activities than its complexes toward selected microbes so that the cadmium(II) nitrate, thiocyanate and azide were found the most active against B. subtilis, S. aureus, P. aeruginosa and E. coli respectively. The evaluation of DNA cleavage potency using the agarose gel electrophoresis technique suggested Cd(SB)Cl2 as the most destructive compound. Furthermore, the antioxidant assessment of the compounds as compared with the standard references by DPPH and FRAP methods proposed Cd(SB)Cl2 and Cd(SB)Br2 as the best antioxidant. In final, the cytotoxicity of the synthesized compounds was appraised toward human breast cancer (MCF-7) and prostate cancer (PC3) cell lines employing MTT and nitric oxide level assays. The results suggested Cd(SB)Br2 as more cytotoxic than other complexes against two studied cancer cell lines.

Synthesis and crystal structures of new mixed-ligand schiff base complexes containing N-donor heterocyclic co-ligands: Molecular docking and pharmacophore modeling studies on the main proteases of SARS-CoV-2 virus (COVID-19 disease)

Three new mixed-ligand copper(II) complexes (1–3) with NN'O type unsymmetrical tridentate Schiff base ligands (SB) and N-donor heterocyclic co-ligands, with general formula [Cu(SB)(L)]ClO4, were synthesized and characterized using single crystal x-ray diffraction (SCXRD), FT-IR and UV–Vis spectroscopy and elemental analyses. The SB ligand is the half-unit form of the condensation of 1,3-propanediamine with 5-methoxysalicylaldehyde and the co-ligands (L) are pyridine (py in (1)), 2,2′-bipyridine (bpy in (2)) and 1,10-phenanthroline (phen in (3)). Crystal structures of (2) and (3) were obtained by SCXRD. Molecular docking and pharmacophore studies were performed to study the interactions between the synthesized complexes and SARS-CoV-2 virus main proteases (PDB IDs: 6LU7, 6WQF and 6W9C). Results revealed that complex (3) with phen co-ligand showed better docking scores with the three receptors, i.e. 6LU7 (−8.05 kcal.mol−1), 6W9C (−7.70 kcal.mol−1) and 6WQF (−7.75 kcal.mol−1). The order of the binding best energies for (3) was also as follows: 6LU7 > 6WQF > 6W9C. All of the studied complexes showed considerable performance, comparable to the standard drug, Favipiravir.

Synthesis and characterization of two new mixed-ligand Cu(II) complexes of a tridentate NN'O type Schiff base ligand and N-donor heterocyclic co-ligands: In vitro anticancer assay, DNA/human leukemia/COVID-19 molecular docking studies, and pharmacophore modeling.

Two new mixed‐ligand complexes with general formula [Cu(SB)(L')]ClO4 (1 and 2) were synthesized and characterized by different spectroscopic and analytical techniques including Fourier transform infrared (FT‐IR) and UV–Vis spectroscopy and elemental analyses. The SB ligand is an unsymmetrical tridentate NN'O type Schiff base ligand that was derived from the condensation of 1,2‐ethylenediamine and 5‐bromo‐2‐hydroxy‐3‐nitrobenzaldehyde. The L' ligand is pyridine in (1) and 2,2′‐dimethyl‐4,4′‐bithiazole (BTZ) in (2). Crystal structure of (2) was also obtained. The two complexes were used as anticancer agents against leukemia cancer cell line HL‐60 and showed considerable anticancer activity. The anticancer activity of these complexes was comparable with the standard drug 5‐fluorouracil (5‐FU). Molecular docking and pharmacophore studies were also performed on DNA (PDB:1BNA) and leukemia inhibitor factor (LIF) (PDB:1EMR) to further investigate the anticancer and anti‐COVID activity of these complexes. The molecular docking results against DNA revealed that (1) preferentially binds to the major groove of DNA receptor whereas (2) binds to the minor groove. Complex (2) performed better with 1EMR. The experimental and theoretical results showed good correlation. Molecular docking and pharmacophore studies were also applied to study the interactions between the synthesized complexes and SARS‐CoV‐2 virus receptor protein (PDB ID:6LU7). The results revealed that complex (2) had better interaction than (1), the free ligands (SB and BTZ), and the standard drug favipiravir.

Spectral characterization and biological studies of some ternary complexes with molecular docking investigations against MERS and SARS type coronaviruses

ABSTRACT. A series of ternary complexes with a Schiff base (HL1) derived from 2-hydrazinobenzimidazole and o-hydroxybenzophenone (primary ligand) have been prepared. Here, 1,10-phenanthroline acts as secondary ligand (L2). These metal complexes were investigated by UV-Vis, IR, 1H NMR and thermal techniques. The spectral data confirmed tridentate nature of the SB ligand with NNO type coordination, whereas the secondary ligand L2 (1,10-phenanthroline) coordinated through its two nitrogen atoms (NN type). These compounds possess distorted octahedral geometry. Moreover, these compounds were screened against B. subtilis and E. coli to evaluate their antibacterial activity. In addition, molecular docking studies were performed against MERS-CoV and SARS-CoV-2 main protease (Mpro). Moreover, DFT calculations and QSAR studies of the SB ligand were also performed.
 
 KEY WORDS: Ternary complexes, Spectral, Antibacterial, DFT, QSAR, Molecular docking studies
 
 Bull. Chem. Soc. Ethiop. 2021, 35(3), 525-535.
 DOI: https://dx.doi.org/10.4314/bcse.v35i3.5

Trivalent Antimony as L-, X-, and Z-Type Ligand: The Full Set of Possible Coordination Modes in Pt-Sb Bonds.

In the course of our investigations of the coordination chemistry of trivalent antimony (Sb) compounds, we studied heteronuclear complexes formed in reactions of the compounds RSb(pyS)2 (R = pyS, Ph; pyS- = pyridine-2-thiolate) with [Pt(PPh3)4], i.e., complexes [(R)Sb(μ-pyS)2Pt(PPh3)] (R = pyS, 1; R = Ph, 2). The reaction of 1 with o-chloranil proceeds cleanly with elimination of 2,2'-dipyridyl disulfide and formation of the salt [(PPh3)Pt(μ-pyS)2Sb(μ-pyS)2Pt(PPh3)]+[Sb(C6Cl4O2)2]- (3III), which features the cation 3+. The charge-neutral, unsymmetrically substituted compound [(PPh3)Pt(μ-pyS)2Sb(μ-pyS)2Pt(κS-pyS)] (4) can be accessed by the reaction of 3+ with LipyS. The oxidation of 2 with o-chloranil furnishes the complex [(κ-O,O-C6Cl4O2)PhSb(μ-pyS)2Pt(PPh3)] (5). The oxidation of 1 with PhICl2 afforded the paddlewheel-shaped complex [Sb(μ-pyS)4PtCl] (6). Moreover, compound 6 was obtained by the reaction of Sb(pyS)3 with [PtCl(pyS)(PPh3)]. The polarization of Pt-Sb bonds of compounds 1-6 was investigated by natural localized molecular orbital (NLMO) calculations, which suggest X-type ligand character (covalent Pt-Sb bonds) for 1 and 2, whereas the Sb ligand of 6 reflects Z-type character (dative Pt→Sb bonds). In 3+, 4, and 5, high contributions of the reverse, i.e., L-type (dative Pt←Sb bonds), were observed. In conjunction with the results of NLMO analyses, 121Sb Mössbauer spectroscopy proves that complexes 1-6 represent essentially trivalent Sb complexes with either a free lone pair (LP) at the Sb atom (1, 2, and 6) or LP character involved in L-type Pt←Sb coordination (3+, 4, and 5).

Hard x-ray spectroscopy of the itinerant magnets RFe4Sb12 (R=Na, K, Ca, Sr, Ba)

Ordered states in itinerant magnets may be related to magnetic moments displaying some weak local moment characteristics, as in intermetallic compounds hosting transition metal coordination complexes. In this paper, we report on the Fe $K$-edge X-ray absorption spectroscopy (XAS) of the itinerant magnets $R$Fe$_{4}$Sb$_{12}$ ($R=$ Na, K, Ca, Sr, Ba), aiming at exploring the electronic and structural properties of the octahedral building block formed by Fe and the Sb ligands. We find evidence for strong hybridization between the Fe $3d$ and Sb $5p$ states at the Fermi level, giving experimental support to previous electronic structure calculations of the $R$Fe$_{4}$Sb$_{12}$ skutterudites. The electronic states derived from Fe 3$d$ Sb $5p$ mixing are shown to be either more occupied and/or less localized in the cases of the magnetically ordered systems, for which $R=$ Na or K, connecting the local Fe electronic structure to the itinerant magnetic properties. Moreover, the analysis of the extended region of the XAS spectra (EXAFS) suggests that bond disorder may be a more relevant parameter to explain the suppression of the ferromagnetic ordered state in CaFe$_{4}$Sb$_{12}$ than the decrease of the density of states.

Synthesis and Oxidation of a Paddlewheel-Shaped Rhodium/Antimony Complex Featuring Pyridine-2-Thiolate Ligands.

The paddlewheel-shaped complex [Sb(μ-pyS)4 Rh]2 (1) (pyS- = 2-S-C5 H4 N- ) was synthesized from [Rh(pyS)(cod)]2 (cod=1,5-cyclooctadiene) and Sb(pyS)3 . Upon oxidation with ONMe3 , the complex [(μ-O)Sb(μ-pyS)3 Rh(κ2 -pyS)]2 (2) is formed. Both 1 and 2 form dimers and feature short Rh-Sb bonds and bridging pyS ligands. 121 Sb Mössbauer spectro- scopy and computational studies were employed to elucidate the Rh-Sb bonding in 1 and 2. Both covalent (Rh-Sb, X-type Sb ligand) and dative (Rh→Sb, Z-type; Rh←Sb L-type Sb ligand) interactions have to be considered for the description of their bonding situations.

First examples of neutral and cationic indenyl nickel(II) complexes bearing arsine or stibine ligands: highly active catalysts for the oligomerisation of styrene.

New indenyl nickel(ii) complexes bearing arsine or stibine ligands synthesised by a new methodology exhibit very high catalytic activities for the oligomerisation of styrene.

Synthesis and characterization of mercury(II) complexes with 2-styryl-1,3-benzothiazole (sb). Presence of two differently coordinated Hg(II) ions in the dinuclear complex Hg 2Cl 4(sb) 3. Structural characterization of 2-styryl-1,3-benzothiazole and some of its derivatives

The molecular and crystal structures of the following compounds 2-styryl-1,3-benzothiazole, sb, ( 1), Hg 2Cl 4(sb) 3 ( 2), 1,3-bis(1,3-benzothiazol-2-yl)-2,4-diphenylcyclobutane ( 3) 1,3-bis(1,3-benzothiazol-2-yl)-2,4-bis(4-chlorophenyl)cyclobutane ( 4) and HgBr 2(sb) 2 ( 5) were determined by single-crystal X-ray diffractometry. The crystal structure of 1 consists of discrete sb molecules which are essentially planar. The dimeric molecules of 3 and 4 are characterized by a cyclobutane ring. In both isolated complexes 2 and 5, sb acts as a neutral monodentate ligand coordinated to the mercury atom through the thiazolyl nitrogen atom. The dinuclear complex 2 is characterized by the unique example of two differently coordinated Hg(II) ions bridged via a non-symmetrical linear Cl − bridge. The first one is coordinated by one terminal and one bridging Cl − ion and two thiazolyl nitrogen atoms in the form of distorted tetrahedron. The second one is bonded to two terminal Cl − ions and the bridging Cl − ion and one thiazolyl nitrogen atom in a 2+2 manner. In complex 5 the Hg(II) ion, which is situated on a crystallographic twofold axis, is tetrahedrally coordinated by two Br − ions and two thiazolyl nitrogen atoms. Both complexes are characterized by stronger mercury-to-halide covalent bonds than mercury-to-nitrogen bonds, which are regarded as contacts shorter than the van der Waals radii sum of the corresponding atoms. The geometry of the sb ligand in both complexes 2 and 5 has not been changed remarkably from that one in the uncoordinated state due to not so strong bonds formation with the Hg(II) ion.

Highly Efficient Orange and Green Solid‐State Light‐Emitting Electrochemical Cells Based on Cationic IrIII Complexes with Enhanced Steric Hindrance

AbstractHighly efficient orange and green emission from single‐layered solid‐state light‐emitting electrochemical cells based on cationic transition‐metal complexes [Ir(ppy)2sb]PF6 and [Ir(dFppy)2sb]PF6 (where ppy is 2‐phenylpyridine, dFppy is 2‐(2,4‐difluorophenyl)pyridine, and sb is 4,5‐diaza‐9,9′‐spirobifluorene) is reported. Photoluminescence measurements show highly retained quantum yields for [Ir(ppy)2sb]PF6 and [Ir(dFppy)2 sb]PF6 in neat films (compared with quantum yields of these complexes dispersed in m‐bis(N‐carbazolyl)benzene films). The spiroconfigured sb ligands effectively enhance the steric hindrance of the complexes and reduce the self‐quenching effect. The devices that use single‐layered neat films of [Ir(ppy)2sb]PF6 and [Ir(dFppy)2sb]PF6 achieve high peak external quantum efficiencies and power efficiencies of 7.1 % and 22.6 lm W–1) at 2.5 V, and 7.1 % and 26.2 lm W–1 at 2.8 V, respectively. These efficiencies are among the highest reported for solid‐state light‐emitting electrochemical cells, and indicate that cationic transition‐metal complexes containing ligands with good steric hindrance are excellent candidates for highly efficient solid‐state electrochemical cells.

Poly[(1,10-phenanthroline-κ2N,N′)lead(II) μ4-(4-sulfonatobenzoato-κ4O,O′:O′′,O′′′ hydrate

In the title polymeric compound, [Pb(C12H8N2)(C7H4O5S)]n·nH2O, the seven-coordinate PbII atom is surrounded by one 1,10-phenanthroline (phen) and four 4-sulfonatobenzoate (sb) ligands in a hemidirected coordination geometry. Both the sulfonyl and carboxy groups of the sb ligand bridge the neighboring PbII atoms to form a two-dimensional sheet structure.

Cobalt Schiff Base Complex-Catalyzed Oxidation of Anilines with tert-Butyl Hydroperoxide

Cobalt Schiff base complexes [Co(SB)] catalyze the oxidation of anilines (1) with tert-butyl hydroperoxide to give nitrobenzenes 2 and 4-(tert-butylperoxy)-2,5-cyclohexadien-1-imine derivatives 3 in yield distributions depending on the substitution mode of the substrate. 4-Alkyl- and 4-aryl-2,6-di-tert-butylanilines gave mixtures of 2 and 3, where the higher the bulkiness of the 4-substituent, the higher the yield of 2. With 2,4,6-trimethylaniline, the ratio of oxidations of the nitrogen and C-4 atoms was almost the same; but a hydrolyzed product 5 of the imine was obtained. 2,4,6-Triphenylaniline gave only 2. Nitrobenzene derivatives were also obtained from 2,6-dialkylanilines and 4-substituted anilines. The catalytic activity of Co(SB) depended on the nature of the SB ligand: the formal potential E° and steric factors seem to affect the reaction rate. Kinetic studies showed that the key step may involve hydrogen abstraction from the aniline, presumably by t-BuO• generated from homolytic decomposition o...

ChemInform Abstract: MOESSBAUER STUDY OF STIBONIC AND STIBINIC ACIDS‐ STRUCTURAL IMPLICATIONS FROM ORBITAL POPULATION ANALYSIS

and Ph3Sb0 have been studied by '%b Mossbauer spectroscopy. The isomer shift, 6, decreases almost linearly with increasing number of R groups. Both the stibonic and stibinic acids have appreciable values of 7 as well as quadrupole coupling constants on the order of &lo mm s-'. Using an additive model to obtain orbital populations along the Sb ligand bonds for various assumed geometries, it is concluded that the typical Sb site in the amorphous acids has approximately trigonal-bipyramidal geometry with bridging oxygens in apical positions. The orbital population along the equatorial Sb-OH bond, UOH, is appreciably larger than the apical bOH in Ph,SbOH.

Moessbauer study of stibonic and stibinic acids: structural implications from orbital population analysis

and Ph3Sb0 have been studied by '%b Mossbauer spectroscopy. The isomer shift, 6, decreases almost linearly with increasing number of R groups. Both the stibonic and stibinic acids have appreciable values of 7 as well as quadrupole coupling constants on the order of &lo mm s-'. Using an additive model to obtain orbital populations along the Sb ligand bonds for various assumed geometries, it is concluded that the typical Sb site in the amorphous acids has approximately trigonal-bipyramidal geometry with bridging oxygens in apical positions. The orbital population along the equatorial Sb-OH bond, UOH, is appreciably larger than the apical bOH in Ph,SbOH.