Group In Axial Position Research Articles

Low-dimensional compounds containing bioactive ligands. Part XVI: Halogenated derivatives of 8-quinolinol N-oxides and their copper(II) complexes

Four N-oxides, 8-quinolinol N-oxide (8-HQNO), 5,7-dichloro-8-quinolinol N-oxide (HdClQNO), 5,7-dibromo-8-quinolinol N-oxide (HdBrQNO) and 7-iodo-8-quinolinol N-oxide (HIQNO) as well as their six copper complexes, CuCl2(8-HQNO)2(H2O) (1), CuCl2(HdClQNO)2(H2O)2 (2), Cu(dClQNO)2(CHCl3) (3), Cu(dClQNO)2(H2O) (4), {[Cu(dBrQNO)2]•2H2O}n (5) and CuCl2(HIQNO)2(H2O)4 (6) were synthesised as possible anticancer agents. Crystal structures of N-oxides contain planar molecules held together via hydrogen bonds involving oxygen atoms of N-oxide groups as acceptors. Crystal structure of 5 represents the first structure of a copper(II) complex with an N-oxide ligand derived from 8-HQNO and is formed by infinite chains. In the chain, the Cu(II) atom coordinates to six oxygen atoms from two bidentate chelating dBrQNO ligands occupying apexes of elongated tetragonal bipyramid with bridging oxygen atoms of N-oxide groups in axial positions. Antiproliferative activity of prepared N-oxides as well as their complexes was studied using in vitro MTT assay against the MDA-MB-231, HCT-116 and A549 cancer cell lines and their selectivity was verified on MSCs cells. Among the tested cancer cell lines, A549 and MDA-MB-231 cells were the most sensitive to the tested complexes. Complex 1 showed the highest cytotoxicity against both tumor cell lines. At concentration, which could be tested in animal models, 1 induced cell death in more than 50% of cancer cells and in 20% of MSCs indicating its selectivity.

Structural Characterization of β-Glycolaldehyde Dimer

Structural characterization of the β-polymorph of glycolaldehyde dimer by powder X-ray diffraction, Raman and infrared spectroscopies is described. The previously described α-polymorph and the β-polymorph both crystallize in the monoclinic crystal system, space group P21/c, but with different cell parameters. There are no significant differences in the glycolaldehyde dimer molecular structure, the molecules in both polymorphs are trans-isomers with the hydroxyl groups in axial positions. The two polymorphs have a different arrangement of the glycolaldehyde dimer molecules. In the previously reported α-polymorph the molecules are arranged in hydrogen bonded layers parallel to (100) while in the β-polymorph the hydrogen bonded molecules are arranged in a three-dimensional network. Theoretically calculated Gibbs free energy as well as differential scanning calorimetry indicate β-polymorph to be the stable crystal phase of glycolaldehyde.

Synthesis, structural characterization, electronic structure calculation, molecular docking study and biological activity of triorganotin(IV) complexes of schiff base (E)-4-amino-3-(2-(2-hydroxybenzylidene)hydrazinyl)-1H-1,2,4-triazole-5(4H)-thione)

Two new triorganotin(IV) complexes of Schiff base, Bu3SnL (1) and Ph3SnL (2) (where, L is the monoanion of Schiff base (HL= (E)-4-amino-3-(2-(2-hydroxybenzylidene) hydrazinyl)-1H-1,2,4-triazole-5(4H)-thione)) have been synthesized and thoroughly characterized by elemental analysis, IR, NMR (1H, 13C, 119Sn), ESI-MS and UV–Vis studies. The spectroscopic evidences suggest that both complexes adopt distorted trigonal bipyramidal geometry around tin atom with Ophenolic and two organic groups in equatorial plane and the Nazomethine and the third organic group in axial position in which Schiff base ligand acts as monoanionic bidentate coordinating through the Ophenolic and Nazomethine. DFT based quantum chemical calculation have been performed at B3LYP/6-31G(d,p)/Def2-SVP(Sn) level of theory, in order to get optimized geometry and electronic structure of the studied complexes. A comparative analysis of the experimental vibrational frequencies and simulated harmonic frequencies indicates good correlation between them. The assignment and the nature of the electronic transitions observed in the UV–visible spectra were analysed using time-dependent (TD-DFT) calculations. NBO analysis has also been performed to analyse the intra and inter-molecular interactions that leads stabilization in the studied systems. The topological and energetic properties of the electron density distribution for the tin-ligand interaction in studied system have been calculated in terms of atoms-in-molecules (AIM) theory using AIMAll. The synthesized complexes were screened for their in vitro antifungal activity against chosen fungal strains. The studied complexes were exhibited significant antifungal activity against all the chosen strains. In silico, docking experiment has also been carried out on the active site of the cytochrome P450 14-α-demethylase (CYP-51).

Tris(3-Fluorophenyl)antimony Derivatives (3-FC6H4)3Sb(OC6H3Br2-2,4)2, (3-FC6H4)3Sb(OC6Cl5-2,3,4,5,6)2, and (3-FC6H4)3Sb[OC(O)C6H4(NO2-2)]2: Synthesis and Structure

Tris(3-fluorophenyl)antimony bis(2,4-dibromophenoxide) (I), tris(3-fluorophenyl)antimony bis(pentachlorophenoxide) (II), and tris(3-fluorophenyl)antimony bis(2-nitrobenzoate) (III) have been synthesized by the reaction of tris(3-fluorophenyl)antimony with 2,4-dibromo- and 2,3,4,5,6-pentacholophenols and 2-nitrobenzoic acid in the presence of tert-butylperoxide. The antimony atoms in complexes I–III have a distorted trigonal bipyramidal coordination with aroxides (carboxyl) groups in axial positions (OSbO angles, 176.0(2)° (I), 174.89(7)° (II), 173.04(8)° (III); Sb–O distances, 2.057(5), 2.048(5) A (I); 2.098(2), 2.106(2) A (II); 2.120(6), 2.090(6) A (III)).

Synthesis, structure and property of diorganotin complexes with chiral N-(5-chlorosalicylidene)valinate ligand

Six new diorganotin N-[(5-chloro-2-oxyphenyl)methylene]valinates, R2SnL (R = Me, 1; Et, 2; L = 5-Cl-2-OC6H3CH = NCH(i-Pr)COO: (S)-, a; (R)-, b; (RS)-, c), have been synthesized from the reaction of R2SnCl2 with the chiral ligand KHL (potassium salt of HL) in different solvents and characterized by elemental analysis, IR, NMR (1H, 13C and 119Sn) spectra. In benzene, the configuration of the chiral ligand was retained. (S)-Enantiomers (1a and 2a) and (R)-enantiomers (1b and 2b) display discrete molecular structures with distorted trigonal bipyramidal geometries in which two C atoms of organic groups (R) and the imino N atom occupy the equatorial positions and a phenoxide O and an unidentate carboxylate group O atom are in the axial orientation. In the methanol, the chiral ligand was racemized. 1c⋅MeOH is a centrosymmetric dimers formed by (R)- and (S)- enantiomers through two SnO⋅⋅⋅Sn bridges. The coordination geometry of the Sn atom can be described as a distorted pentagonal bipyramid with two methyl groups in axial positions. The crystal of 2c is composed of two threefold symmetric trimers, a [Et2SnL-(R)]3 and a [Et2SnL-(S)]3, with a macrocyclic 12-membered ring structure formed by the bidenate bridging coordination of carboxylate group to tin atoms. Each tin atom is six-coordinated in distorted [SnC2NO3] octahedron geometry. The fluorescence properties of ligand KHL and complexes 1 (1a-1c) and 2 (2a-2c) have been measured. The results show the complexes may be explored for potential luminescent materials.

Tetra-para-tolylantimony derivatives (4-MeC6H4)4SbX, X = OC(O)C6H4(NO2-2), OC(O)C≡CPh, ON=CHC6H4(NMe2-4): Synthesis and structure

Tetra-para-tolylantimony derivatives (4-MeC6H4)4SbX, X = OC(O)C6H4(NO2-2) (I), OC(O)C≡CPh (II), ON=CHC6H4(NMe2-4) (III)) have been synthesized by the reaction between penta-para-tolylantimony and 2-nitrobenzoic and phenylpropiolic acids and 4-dimethylaminobenzaldoxime in benzene. Using X-ray diffraction, it has been established that the Sb atoms in molecules of complexes I–III are in distorted trigonal bipyramidal coordination to X groups in axial positions. The Sb–O bond lengths are 2.2797(16) (I), 2.2925(17) (II), and 2.1357(17) A (III). The CSbO axial angles are 178.28(7)° (I), 178.57(9)° (II), 176.09(8)° (III).

Tetraphenylantimony aroxides Ph4SbOAr (Ar = C6H4C6H7, C6H2(Br2-2,6)(tert-Bu-4), C6H3(NO2)2-2,4, C6H2(Br2-2,6)(NO2-4)): Synthesis and structure

Tetraphenylantimony aroxides Ph4SbOAr, where Ar = C6H4C6H7 (I), C6H2(Br2-2,6)(tert-Bu-4) (II), C6H2(Br2-2,6)(NO2-4) (III), and C6H3(NO2)2-2,4 (IV), have been synthesized by the reaction of pentaphenylantimony with 4-cyclohexadienylphenol, 2,6-dibromo-4-tert-butylphenol, 2,6-dibromo-4-nitrophenol, and 2,4-dinitrophenol. The antimony atoms in molecules of complexes I–IV have a differently distorted trigonal bipyramidal coordination to the oxygen atoms of aroxy groups in axial positions. The OSbС angles are 177.63(13)° (I), 174.29(7)° (II), 177.8(6)° (III), and 174.01(7)° (IV). The Sb–O bond length is 2.117(3) A (I), 2.2613(15) A (II), 2.409(11) A (III), and 2.4296(15) A (IV).

Synthesis, structure and cytotoxic activity of diethyltin N‐[(2‐oxyphenyl)methylene]phenylalaninates

Four new diethyltin N‐[(2‐oxyphenyl)methylene]phenylalaninates, (CH3CH2)2Sn[2‐O‐3‐X‐5‐YC6H2CHNCH(CH2Ph)COO] (X, Y = H, H, 1; H, Br, 2; H, OCH3, 3; Br, Br, 4), have been synthesized and characterized using elemental analysis and infrared and NMR (1H, 13C and 119Sn) spectra. The crystal structures of 1, 2, 3, 4 have been determined. Compounds 1 and 2 have a 12‐membered macrocyclic structure with a trimeric [Sn3O6C3] core. Each tin atom is six‐coordinated in distorted [SnC2NO3] octahedral geometry. Compound 3 is a centrosymmetric weak dimer in which the two tin centers are linked by two asymmetric SnO⋅⋅⋅Sn bridges involving the phenolic oxygen of the ligand and two Sn⋅⋅⋅O interactions from ether oxygen of the adjacent ligand. The coordination geometry of the tin atom can be described as a distorted pentagonal bipyramid with two ethyl groups in axial positions. Compound 4 is a novel binuclear tin complex, formed by the carboxylate of a ligand asymmetrically bridging two tin atoms, which contains a five‐coordinated tin and a six‐coordinated tin. Bioassay results have shown that the compounds have weak in vitro activity against two human tumor cell lines, A549 and CoLo205. Copyright © 2016 John Wiley & Sons, Ltd.

Синтез и строение ароксида тетра-пара-толилсурьмы (4-MeC6H4)4SbOC6H2Br2-2,6-(t-Bu)-4

Penta- p -tolylantimony interaction with 2,6-dibromo(4- tert -butyl)phenol has led to synthesis of the complex tetra- p -tolylantimony 2,6-dibromo(4- tert -butyl)phenoxide, whose structure has been established by X-ray diffraction. The antimony atom in the molecule (4-MeC 6 H 4 ) 4 SbOC 6 H 2 Br 2 -2,6-( t -Bu)-4 has distorted trigonal-bipyramidal coordination with the aroxy group in axial position. The bond Sb-O is 2.229(2) Å, the axial angle CSbO is 176.82(10)°

Синтез и строение бис(4-бромфенокси)трифенилсурьмы

Interaction of triphenylantimony with 4-bromophenol in the presence of tert-butylhydroperoxide in ether has led to the synthesis of bis(4-bromophenoxy)triphenylantimony, whose structure has been established by X-ray diffraction analysis. The antimony atom has distorted trigonal-bipyramidal coordination with aroxy groups in axial positions. The bond lengths equal: 2.094(4), 2.108(5), 2.109(5) A for Sb–C; 2.062(4) and 2.066(3) A for Sb-O. The axial angle OSbO equals 172.41(1)°.

Cytotoxicity-boosting of kiteplatin by Pt(IV) prodrugs with axial benzoate ligands

Kiteplatin, the neglected drug analogous of cisplatin but containing cis-1,4-DACH in place of the two ammines, has been recently reevaluated for its activity against cisplatin- and oxaliplatin-resistant tumors, in particular colo-rectal cancer. With the aim of further improving the pharmacological activity of this drug, Pt(IV) prodrugs were derived by addition of two, differently substituted, benzoate groups in axial positions (X-ray structure). The cytotoxic activity of both compounds resulted markedly potentiated reaching nanomolar concentration against a wide panel of human cancer cells. The ability of benzoate ligands to enhance the activity of kiteplatin most likely originates from their lipophilicity promoting a higher drug accumulation in cancer cells; however, it is to be noted that the increase in pharmacological effect is far greater than the increase in cellular uptake. Overcoming cisplatin- and oxaliplatin-resistance by kiteplatin derivatives appears to relate to the inability of membrane extrusion pumps to remove active Pt species from tumor cells.

High‐Affinity Anion Binding by Steroidal Squaramide Receptors

AbstractExceptionally powerful anion receptors have been constructed by placing squaramide groups in axial positions on a steroidal framework. The steroid preorganizes the squaramide NH groups such that they can act cooperatively on a bound anion, while maintaining solubility in nonpolar media. The acidic NH groups confer higher affinities than previously‐used ureas or thioureas. Binding constants exceeding 1014 M−1 have been measured for tetraethylammonium salts in chloroform by employing a variation of Cram’s extraction procedure. The receptors have also been studied as transmembrane anion carriers in unilamellar vesicles. Unusually their activities do not correlate with anion affinities, thus suggesting an upper limit for binding strength in the design of anion carriers.

High-affinity anion binding by steroidal squaramide receptors.

Exceptionally powerful anion receptors have been constructed by placing squaramide groups in axial positions on a steroidal framework. The steroid preorganizes the squaramide NH groups such that they can act cooperatively on a bound anion, while maintaining solubility in nonpolar media. The acidic NH groups confer higher affinities than previously-used ureas or thioureas. Binding constants exceeding 1014 m−1 have been measured for tetraethylammonium salts in chloroform by employing a variation of Cram’s extraction procedure. The receptors have also been studied as transmembrane anion carriers in unilamellar vesicles. Unusually their activities do not correlate with anion affinities, thus suggesting an upper limit for binding strength in the design of anion carriers.

(−)‐R‐Mevalonolactone Studied by ROA and SERS Spectroscopy

Here we present for the first time the experimental and theoretical (DFT/B3LYP/6-311++G**) Raman optical activity (ROA) spectra of (-)-R-mevalonic acid as the δ-lactone form in neat liquid and in the aqueous solution. Quantum chemical calculations show the conformational diversity of (-)-R-mevalonolactone originated from small energy differences between the various conformation of the six-membered ring and the arrangement of the hydroxyl group. According to calculations, the investigated compound takes predominantly the chair conformation with the hydroxyl group in axial position, but the contribution of the other chair and boat conformers in the equilibrium at room temperature is not negligible. Additionally, we present normal Raman and the surface enhanced Raman (SERS) spectra of (-)-R-mevalonolactone adsorbed on the colloidal silver.

Glycolaldehyde dimer in the stable crystal phase has axial OH groups: Raman, infrared and X-ray data analysis

Although a small molecule and a simple 1,4-dioxane derivative, 2,5-dihydroxy-1,4-dioxane or glycolaldehyde dimer has a crystal structure that has eluded researchers so far, chief reason lying presumably in substance polymorphism. Here we report for the first time on the stable crystal structure of the glycolaldehyde dimer characterized by the X-ray powder diffraction method at room temperature. It crystallizes in the monoclinic system, space group P21/c, with unit cell parameters a=5.9473(1)Å, b=8.3997(1)Å, c=5.61953(8)Å and β=114.8814(9)°. The glycolaldehyde dimer molecules are the trans-isomers with the electronegative hydroxyl groups in axial positions and molecules are arranged in hydrogen bonded layers parallel to (100). Each layer is stabilized by intermolecular medium strong O–H⋯O hydrogen bonds. The 1,4-dioxane ring of the molecule adopts a chair conformation.Raman and infrared spectra were re-examined and assigned with the help of ab initio calculation followed by a normal modes analysis modes most sensitive to crystal packing were identified as the C–OH deformations which were assigned to the IR and Raman bands at 1239 and 1237cm−1, respectively; the two O–C–O deformation modes, both associated with the Raman and IR bands at 561 and 535cm−1 and, the two OH torsion modes assigned to the IR bands at 630 and 604cm−1.

Vibrational spectra of an RDX film over an aluminum substrate from molecular dynamics simulations and density functional theory

We report calculated vibrational spectra in the range of 0-3,500 cm(-1) of RDX (hexahydro-1,3,5-trinitro-1,3,5-triazine) molecules adsorbed on a model aluminum surface. A molecular film was modeled using two approaches: (1) density functional theory (DFT) was used to optimize a single RDX molecule interacting with its periodic images, and (2) a group of nine molecules extracted from the crystal structure was deposited on the surface and interacted with its periodic images via molecular dynamics (MD) simulations. In both cases, the molecule was initialized in the AAA conformer geometry having the three nitro groups in axial positions, and kept that conformation in the DFT examination, but some molecules were found to change to the AAE conformer (two nitro groups in axial and one in equatorial position) in the MD analysis. The vibrational spectra obtained from both methods are similar to each other, except in the regions where collective RDX intermolecular interactions (captured by MD simulations) are important, and compare fairly well with experimental findings.

Syntheses, Structural, and Spectroscopic Properties of Copper(II) Complexes of Constrained Macrocyclic Ligands

AbstractThe complexes [Cu(L1)(H2O)2](BF4)2·2H2O (1) [L1 = 5, 16‐dimethyl‐2, 6, 13, 17‐tetraazatricyclo(14, 4, 01.18,07.12)docosane] and 0.5[Cu(L2)(NO3)2][Cu(L2)](NO3)2 (2) [L2 = dibenzyl‐5, 16‐dimethyl‐2, 6, 13, 17‐tetraazatricyclo(14, 4, 01.18,07.12)docosane] were synthesized and characterized by single crystal X‐ray analyses. In these constrained macrocycles, the central copper(II) atoms are in a tetragonally distorted octahedral environment with four nitrogen atoms of the macrocyclic ligands in equatorial positions and oxygen atoms from either water molecules or nitrato groups in axial positions. The macrocyclic ligands in both complexes adopt the most stable trans‐III conformation. The Cu–N distances [1.999(7)–2.095(7) Å] are typical for such complexes, but the axial ligands are weakly coordinating Cu–OH2 bonds [2.693(3) Å] and Cu–ONO2 bonds [2.873(7) Å] due to the combination of the pseudo Jahn–Teller effect and strong in‐plane ligand field. The crystals are stabilized by a three‐dimensional network by hydrogen bonds that are formed among the secondary nitrogen hydrogen atoms, oxygen atoms of water molecules, fluorine atoms of BF4–, and oxygen atoms of NO3–. The electronic absorption and IR spectroscopic properties are also discussed.

Synthesis of Glycosylthiols and Reactivity Studies

The acid-catalyzed reaction of 1,2-anhydro-3,4,6-tri-O-benzyl-α-d-glucopyranose (7) as glycosyl donor with bis-trimethylsilyl sulfide as acceptor affords the α-thiol. Hence, this sterically hindered S-nucleophile as acceptor should provide with O-glycosyl trichloroacetimidates as glycosyl donors that have nonparticipating groups at C-2, glycosylthiols with the thiol group in axial position. This was confirmed for various donors (4, 16-19) with the exception of the corresponding mannosyl donor (20). However, powerful participating groups at C-2 of the donor (23-28) governed the anomeric selectivity.

Cis,cis-1,3,5-Trihydroxynonamethylcyclohexasilane: A Cyclopolysilane with Unusual Properties

cis,cis-Trihydroxynonamethylcyclohexasilane (2) is easily accessible by the controlled hydrolysis of Cl3Si6Me9 in the presence of Et3N as an auxiliary base. The crystal structure of 2, as determined by single-crystal X-ray crystallography, exhibits “barrel-type” face-to-face dimeric aggregates held together by six intermolecular hydrogen bonds. NMR and IR spectra suggest that these OH-bonded aggregates are also present in nonpolar solutions. Full geometry optimization (B3LYP/TZVP) of the gas-phase structure of 2 further reveals unusually high energy differences between different conformers and a considerable stabilization of the molecule upon dimerization due to O−H hydrogen bonding. Time-dependent DFT B3LYP/TZVP calculations allow for a detailed interpretation of the UV absorption spectra of 2. The electronic transitions occur between occupied molecular orbitals with predominant σ(Si−Si) character and a small contribution of the oxygen lone pairs, and virtual MOs with contributions from σ*(Si−C), σ*(Si−O), and σ*(Si−Si) type orbitals. If 2 is reacted with MeSiCl3/Et3N, the adamantane-like cage MeSi(O3Si6Me9) (4) is obtained without the formation of considerable amounts of polymeric material, which is most likely a consequence of the preferred conformation of 2 with three adjacent OH groups in axial positions.

(1R,4aS,10aR)-1,4a-Dimethyl-N-[(morpholin-4-yl)carbothioyl]-7-(propan-2-yl)-1,2,3,4,4a,9,10,10a-octahydrophenanthrene-1-carboxamide

In the title compound, C25H36N2O2S, the cyclo­hexane and morpholine rings adopt chair conformations. The cyclo­hexene and cyclo­hexane rings form a trans ring junction with the two methyl groups in axial positions. The N—H and C=O bonds in the urea group are anti to each other. The crystal structure is stabilized by inter­molecular N—H⋯O hydrogen bonds.