Series Of Bis Research Articles

Modulation of Reduction Potentials of Bis(pyridinium)alkane Dications through Encapsulation within Cucurbit[7]uril

Supramolecular modulation of reduction potentials of two series of bis(pyridinium)alkane salts is described. Study of the encapsulation of bis(pyridinium)alkane guests within the CB[7] cavity revealed the critical influence of the linker length and the position of the heteroatom on the reduction potentials of encapsulated guests. CB[7] complexation of pyridinium salts induced reduction potential changes ranging between +50 and -430 mV. Noncovalent modulation of the electron-accepting ability of organic cations can be utilized in electron-transfer-initiated reactions.

First Bis(σ)-borane Complexes of Group 6 Transition Metals: Experimental and Theoretical Studies.

A series of bis(σ)-borane complexes of Group 6 transition metals were prepared by direct dihydroborane coordination to the metal center. Reaction of [M(CO)3 (PCy3 )2 ] and two dihydroboranes [DurBH2 ] and [(Me3 Si)2 NBH2 ] (Dur=2,3,5,6-Me4 C6 H) yielded bis(σ)-borane complexes fac-[M(CO)3 (PCy3 ){η2 -(H2 BR)}] (R=Dur; 1: M=Cr, 2: M=W; R=N(SiMe3 )2 ; 3: M=Cr, 4: M=W). In the case of molybdenum, we have isolated an arene complex (5) with [DurBH2 ] in which the Dur group acts as a η6 -bound ligand, and with [(Me3 Si)2 NBH2 ] a similar bis(σ)-borane complex was isolated, cis,trans-[Mo(CO)2 (PCy3 )2 {η2 -(H2 BN(SiMe3 )2 }] (6), with a different pattern of auxiliary ligands. The complexes were investigated by multinuclear NMR spectroscopy, mass spectrometry, X-ray diffraction analysis, and computational methods. Quantum theory of atoms in molecules (QTAIM) calculations demonstrated that the borane complexes may be described as pure bis(σ)-borane complexes rather than elongated or stretched examples given that the calculations do not show the presence of a ring-critical point (RCP) at the ring formed by the interactions of the B-H with metal center.

Design, Synthesis, and Anti-HBV Activity of New Bis(l-amino acid) Ester Tenofovir Prodrugs.

A series of bis(l-amino acid) ester prodrugs of tenofovir (TFV) were designed and synthesized as new anti-HBV agents in this work. Four compounds 11, 12a, 12d, and 13b displayed better anti-HBV activity (IC50: 0.71-4.22 μM) than the parent drug TFV. The most active compound 11 (IC50: 0.71 μM), a bis(l-valine) ester prodrug of TFV, was found to have obviously greater AUC0-∞, C max, and F% than tenofovir disoproxil fumarate (TDF), and potent in vivo efficacy which is not inferior to TDF in a duck HBV (DHBV) model and a HBV DNA hydrodynamic mouse model, and it may serve as a promising lead compound for further anti-HBV drug discovery.

Terminal Carboxylate Effects on the Thermodynamics and Kinetics of Cucurbit[7]uril Binding to Guests Containing a Central Bis(Pyridinium)-Xylylene Site.

A series of bis(pyridinium)-xylylene derivatives bearing carboxylate terminal groups were investigated as guests for the cucurbit[7]uril host in aqueous solution. While the presence of the terminal carboxylates has a modest effect on the thermodynamic stability of the complexes, the kinetics of complex association/dissociation is strongly affected. The relative position ( meta, para) of the carboxylate group in relation to the pyridinium nitrogen also exerts a considerable effect on the binding kinetics.

Construction of functional coordination polymers derived from designed flexible bis(4-carboxybenzyl)amine

A series of coordination polymers (CPs) have been constructed from bis(4-carboxybenzyl)amine and a series of bis(imidazole) linkers. Luminescence sensing measurements indicate that two zinc-based CPs both show highly selective and sensitive sensing for acetone and Cr2O72−/CrO42−.

Electronic Effects of the Backbone on Bis(imino)pyridyliron(II)‐Catalyzed Ethylene Polymerization

A series of bis(imino)pyridyl iron(II) complexes 1–5 with electron‐donating and ‐withdrawing substituents on the backbone of the ligand have been synthesized and characterized. Activated with methylaluminoxane (MAO), ethylene polymerization by these iron(II) complexes was investigated in detail, involving the electronic effect and influence of reaction conditions on catalyst activity and polymer molecular weight. The electronic perturbations exert great influence on the catalytic activity of ethylene polymerization. Complexes bearing electron‐withdrawing substituents in the 4‐position of the pyridine ring showed the better activity than analogues bearing electron‐donating substituents. However, no clear trend was observed for the dependence of polymer molecular weight on these substituents. In particular, the binuclear iron(III) complex 2′ we obtained by accident displayed a similar catalytic behavior compared to its iron(II) analogue complex 2.

Stable cycling of NaFePO4 cathodes in high salt concentration ionic liquid electrolytes

Highly concentrated solutions of sodium bis(fluorosulfonyl)imide (NaFSI) with a series of bis(fluorosulfonyl)imide-based ionic liquids incorporating either alkyl phosphonium or alkoxy ammonium cations (P111i4FSI:NaFSI, P1i4i4i4FSI:NaFSI), N2(2O2O1)3FSI:NaFSI) are combined with NaFePO4 cathodes to demonstrate excellent cycling performance with respect to potential range, rate capability, cycle life and elevated temperature stability. With a capacity of 85 mAhg−1 and a capacity retention of 95% over 100 cycles (50 °C, C/2) P111i4FSI:NaFSI matches or outperforms conventional organic solvent based electrolytes as well as other ionic liquid electrolytes in terms of capacity, elevated temperature performance and cycle stability. The electrolyte conductivity does not correlate with the capacity, suggesting that this is not the primary factor determining the cell performance. The solid electrolyte interphase determines the cycle stability with SEM and XPS techniques suggesting the presence of NaOH, Na2S and NaF on the Na metal surface post cycling.

Synthesis of Novel Bis(thiazolylchromen‐2‐one) Derivatives Linked to Alkyl Spacer via Phenoxy Group

A novel series of bis(thiazolylchromen‐2‐one) derivatives 8 were prepared in good yields by the reaction of the appropriate bis(α‐bromoketones) 7 with 2‐(1‐(2‐oxo‐2H‐chromen‐3‐yl)ethylidene) hydrazinecarbothioamide (6) in refluxing EtOH in the presence of few drops of TEA. Some other isomeric derivatives of bis(thiazolylchromen‐2‐one) 11 and 13 were also successfully obtained by the reaction of bromoacetylcoumarin 9 with the corresponding bis(ethan‐1‐yl‐1‐ylidene))bis(hydrazinecarbothioamides) 10 and 12. The structures of the new compounds were established based on elemental analyses as well as spectral data.

Highly Recoverable Pd(II) Catalysts for the Mizoroki–Heck Reaction Based on N-Heterocyclic Carbenes and Poly(benzyl ether) Dendrons

Two series of bis(imidazolylidene)palladium complexes of general formula [PdBr2(NHC)2] have been prepared. The molecular weight of the complexes was enlarged by bonding poly(benzyl ether) dendrons of increasing size (G0 to G3) at the nitrogen atom of the NHC ligands. Complexes 1–4 contain monodentate NHC ligands coordinated in a trans mode, whereas complexes 9–12 contain a chelating ethylene-bridged bis(NHC) ligand. The complexes were recovered from the product stream of a Mizoroki–Heck reaction by nanofiltration through thermally and chemically stable ceramic membranes. The recoverability is better for larger complexes and chelate ligands. In particular, chelate G3 complex 12 maintained a constant activity during the 13 recovery cycles performed, affording an accumulated turnover number (TON) of 13 000. On average, around 99.5% of the metal is recovered in each recovery cycle, and contamination by palladium is only 3 mg per kg of product. Several models to explain the efficiency of the recovery are discu...

Computer-aided design, synthesis, and biological studies of anticological nitrogen-containing tetraphosphonic acids against melanoma

As a part of our quest to develop new bioactive bisphosphonic acids, we synthesized a series of bis(α-aminobisphosphonic acids) in good yields (66–78%) as new entities for treating malignant melanoma. The reaction of the Schiff bases, 1,4-pheneylenediimines with the Horner–Emmons–Wadsworth reagent, tetraethyl methylene-1,1-bisphosphonate in DMF/LiOH (aq) solution led exclusively to a meso form of nitrogen-containing tetraphosphonates (NTPs) (bis(α-aminobisphosphonates)). Next, hydrolysis of the ester moieties of the tetraphosphonate products yielded the corresponding tetraphosphonic acids, which treated with MeOH/KOH (aq, 20%) to give the respective NTP-tetrapotassium salts. Prior to synthesis, the suggested structures (and others) were applied to the computer-assisted molecular modeling, PASS program to investigate their prospective biological properties. Cytotoxic properties were later evaluated against five malignant melanoma cell lines that originated from different categories of malignant melanoma primary stage (I/II), histologically advanced stage (III/IV), and metastasized malignancy. Almost all tested compounds showed antitumor activity though on different levels. Three NTP salts were found to have activity in the range of GI50 0.650–5.73 μM vs. control reference GI50: 1.745–6.50 μM. Structure activity relationship is also discussed.

Absorption of n-butane in imidazolium and phosphonium ionic liquids and application to separation of hydrocarbon gases

In this report, the density, viscosity, and heat capacity of the tetraalkylphosphonium ionic liquids, containing newly synthesized trihexyltetradecylphosphonium p-dodecylbenzenesulfonate and bis(2-ethylhexyl)sulfobutanedioate, were measured at atmospheric pressure. Then, the n-butane absorption in the dialkylimidazolium and tetraalkylphosphonium ionic liquids were investigated at the n-butane pressure of 0.101 MPa and the temperatures of (298.15–353.15) K. In a series of bis(trifluoromethanesulfonyl)amide ionic liquids, the trihexyltetradecylphosphonium salt absorbed the largest amount of n-butane, followed by the triethyloctylphosphonium, 1-methyl-3-octylimidazolium, and 1-butyl-3-methylimidazolium salts. On the other hand, in the trihexyltetradecylphosphonium ionic liquids, the bis(2-ethylhexyl)sulfobutanedioate and p-dodecylbenzenesulfonate salts had the higher solubilities of n-butane than the bis(trifluoromethanesulfonyl)amide salt. In addition, the solubilities of water vapor in the trihexyltetradecylphosphonium salt were measured at 298.2 K and atmospheric pressure. Trihexyltetradecylphosphonium bis(trifluoromethanesulfonyl)amide was the most free from the moisture. We further performed the continuous gas absorption experiments of n-heptane and toluene using the present tetraalkylphosphonium ionic liquids. They removed successfully the vapors of hydrocarbons despite the very dilute concentrations of hydrocarbons, less than 1500 ppm. The initial absorption rates were calculated to discuss the absorption kinetics in the tetraalkylphosphonium ionic liquids.

H–bonded mesogenic unsymmetric bis-heterocycles

Five new series of bis−heterocycles containing isoxazole and pyrazole were reported, and their mesomorphic properties were investigated. A polar phenolic−OH group incorporated in compounds 1b–c and 1e is to probe the possible H−bonds induced. Two single crystals of mesogenic compounds 1a and 1b (all n=8) were obtained, and their single crystal and molecular structure were resolved. Intra− and intermolecular H−bonds observed in both crystal lattices were probably attributed to the formation of mesophases in these bis−heterocyclic structures. The CH−π interaction was also found to be important. All the precursors 2a−d were mesogenic, giving N, SmA, or/and SmC phases, however, other compounds 2e were not mesogenic. On the other hand, bis−heterocyclic compounds 1a−c were mesogenic, exhibiting SmC or SmA phases, and other compounds 1d−e were not mesogenic. The shape effect and H−bonds induced inherently from the core might be attributed to the formation of the mesophases in these bis−heterocycles. All derivatives showed good stabilities at temperature below T=299−327°C on TGA. The PL spectra of all compounds 1a−e showed one intense peak at λmax=317−386 nm, and these photoluminescent emissions originated from heterocyclic core.

Electrochemistry of Bis(pyridine)cobalt (Nitrophenyl)corroles in Nonaqueous Media.

A series of bis(pyridine)cobalt corroles with one or three nitrophenyl groups on the meso positions of the corrole macrocycle were synthesized and characterized as to their electrochemical and spectroscopic properties in dichloromethane, benzonitrile, and pyridine. The potentials for each electrode reaction were measured by cyclic voltammetry and the electron-transfer mechanisms evaluated by analysis of the electrochemical data combined with UV-visible spectra of the neutral, electroreduced, and electroxidized forms of the corroles. The proposed electronic configurations of the initial compounds and the prevailing redox reactions involving the electroactive central cobalt ion, the electroactive conjugated macrocycle, and the electroactive meso-nitrophenyl groups are all discussed in terms of solvent binding and the number of the nitrophenyl groups and other substituents on the meso-nitrophenyl rings of the compounds.

A method for dyeing polyester fibres with quinone derivatives and evaluation of their antioxidant activity

In this study, a series of bis(thio)substituted-1,4-naphthoquinone compounds (4a-j) were synthesized via Michael addition reaction and their structures were determined by infrared spectrometry, 1H and 13C nuclear magnetic resonance spectroscopy, mass spectrometry and elemental analysis. The synthesized substances were applied to polyester fibers and the dyeing properties were investigated. The rubbing fastness, wash fastness and optical properties of synthesized compounds were also studied. The color change and staining test results were found to be ?4? to ?4-5? for the most of the dyed samples. There is only a small number of previous studies interested with dyeing properties of synthetic derivatives of heteroatom-substituted-1,4-naphthoquinone compounds in existing literature. The synthesized dyes were screened for their antioxidant activity, using the CUPRAC method against trolox (TR) as the standard reference compound at room temperature. The aims of this study were the synthesis of the quinone compounds, the investigation of the capability of dyeing polyester fibers and the evaluation of their antioxidant capacity, using the CUPRAC method. The dyed polyester fibers are promising candidates for biologically active fabrics to be used in various ways. We were encouraged to do this study in order to determine the dying properties and antioxidant activities of the quinone compounds.

Excimer‐Based On‐Off Bis(pyreneamide) Macrocyclic Chemosensors

A series of bis(pyreneamide) macrocycles, synthesized in two steps from THF, THP, oxepane and 1,4‐dioxane, are tested as chemosensors for a large range of mono‐, di‐ and trivalent cations. In their native states, these macrocycles exhibit a strong excimer fluorescence that is quenched upon the addition of the metal ions (alkaline, alkaline earth, p‐, d‐, and f‐block metals). UV‐Vis spectrophotometric titrations, cyclic voltammetry, excimer fluorescence quenching, and transient absorption spectroscopy experiments helped characterize the On‐Off changes occurring upon binding and demonstrate that the highest stability constants are obtained with divalent cations Ca2+ and Ba2+ specifically.

Bis- and Tris(2-oxobenzimidazolyl)hydroborato Complexes of Sodium and Thallium: New Classes of Bidentate and Tridentate Oxygen Donor Ligands.

A series of bis- and tris(oxobenzimidazolyl)hydroborato compounds, namely, [BoRBenz]Na and [ToRBenz]-Na (R = Me, But, Ad), which feature uncommon sterically demanding LX [O2] and L2X [O3] donor ligands, have been obtained via the reactions of NaBH4 with 1-R-1,3-dihydro-2H-benzimidazol-2-ones. Evidence that the alkyl substituents are suitably located to have a significant impact on the coordination environment is provided by the observation that the methyl derivative [ToMeBenz]Na(κ3-diglyme) exhibits κ3-coordination of the diglyme, whereas the t-butyl and adamantyl derivatives, [ToButBenz]Na(κ2-diglyme) and [ToAdBenz]Na(κ2-diglyme), exhibit κ2-coordination. The [BoRBenz] and [ToRBenz] ligands also allow for isolation of discrete mononuclear thallium compounds, [BoRBenz]Tl and [ToRBenz]Tl, for which the steric demands of the ligands have been quantified in terms of both cone angle and buried volume concepts.

Synthesis, crystal structures, computational studies and antimicrobial activity of new designed bis((5-aryl-1,3,4-oxadiazol-2-yl)thio)alkanes

A new series of bis((5-aryl-1,3,4-oxadiazol-2-yl)thio)alkanes 4–14 have been synthesized via nucleophilic substitution reaction of dihaloalkanes with respective 1,3,4-oxadiazole-2-thiols 3a-f, and characterized by spectroscopic techniques. The structures of 4 and 12 were unambiguously confirmed by single-crystal X-ray diffraction analysis. Density functional theory calculations at B3LYP/6-31 + G(d) level of theory were performed for comparison of X-ray geometric parameters, molecular electrostatic potential (MEP) and frontier molecular orbital analyses of synthesized compounds. MEP analysis revealed that these compounds are nucleophilic in nature. Frontier molecular orbitals (FMOs) analysis of 4–14 was performed for evaluation of kinetic stability. All synthesized compounds were screened in vitro for antimicrobial activity against three bacterial and three fungal strains and showed promising results.

Regioselective synthesis and theoretical studies of novel bis(tetrahydro[1,2,4]triazolo[5,1-b]quinazolin-8(4H)-ones) catalyzed by ZnO nanoparticles

A novel series of bis(tetrahydro[1,2,4]triazolo[5,1-b]quinazolin-8(4H)-ones) were prepared in a regioselective manner via a three component reaction of bis-aldehydes with 5-amino-1,2,4-triazole and dimedone under microwave irradiation as well as under conventional heating. The reactions were carried out in the absence as well as in the presence of ZnO nanoparticles as a heterogeneous catalyst. Best results were achieved when these reactions were carried out under MW heating. The presence of ZnO nanoparticles was found to improve the yields of the reactions but did not change the regioselectivity the products. The reaction mechanism and the unambiguous structural elucidation of the expected regioisomers were studied using DFT calculations as well as 2D-HMBC spectroscopy.

Structure and spectroscopic properties of porphyrinato group 14 derivatives: Part I – Phenylacetylido ligands

AbstractA series of bis(phenylacetylido)(porphyrinato) E(IV) (E=Si, Ge, Sn) derivatives were obtained by reacting lithium phenylacetylide with the corresponding bis(chlorido)(porphyrinato) E(IV) precursors. Crystal structure determinations demonstrated that thetrans-coordinated acetylide ligands deviate from their expected ideal geometry. Density functional theory calculations and comparison of the packing of the molecules among the homologous series of Si(IV), Ge(IV) and Sn(IV) revealed causes for the deviation from the simple valence shell electron pair repulsion model. Fluorescence and phosphorescence of these organometallic group 14 derivatives were studied and the results are compared to the literature-known properties of the related bis(chlorido)(porphyrinato) E(IV) compounds (E=Si, Ge, Sn). The first crystal structure of a porphyrinato Ge(IV) compound with σ-bonded acetylide ligands is reported.

Structures and biochemical evaluation of silver(I) 5,5-diethylbarbiturate complexes with bis(diphenylphosphino)alkanes as potential antimicrobial and anticancer agents

New silver(I) 5,5-diethylbarbiturate (barb) complexes with a series of bis(diphenylphosphino)alkanes such as 1,1-bis(diphenylphosphino)methane (dppm), 1,2-bis(diphenylphosphino)ethane (dppe), 1,3-bis(diphenylphosphino)propane (dppp) and 1,4-bis(diphenylphosphino)butane (dppb) were synthesized and characterized. [Ag2(barb)2(μ-dppm)2] (1), [Ag2(barb)2(μ-dppe)(DMSO)2] (2) and [Ag2(barb)2(μ-dppp)2] (3) were binuclear, while [Ag(barb)(μ-dppb)]n (4) was a coordination polymer. 1–4 effectively bind to the G/C rich region of the major groove of DNA and interact with BSA via hydrophobic interactions in accordance with molecular docking studies. All complexes displayed significant DNA cleavage in the presence of H2O2. 1–4 exhibited more specificity against Gram-positive bacteria than Gram-negative bacteria, but 2 targets both bacterial strains, being comparable to AgNO3 and silver sulfadiazine. Complex 1 has a strong growth inhibitory effect on A549 cells, while 2 and 3 exhibit considerable cytotoxicity against MCF-7 cells. The complexes showed high accumulation in the cytosol fraction of the cells. Mechanistic studies showed that 1 and 2 display effective cell growth inhibition by triggering S and G2/M phase arrest, induce apoptosis via mitochondrial pathways and also damage to DNA due to the overproduction of ROS.