Synthesis and characterization of (R)-miniPEG-containing chiral γ-peptide nucleic acids using the Fmoc strategy

Diethylene glycol (miniPEG)-containing chiral γPNA is considered to be one of the best PNA derivatives. Its preparation is mainly based on the Boc strategy for solid phase peptide synthesis (SPPS), requiring the repeated use of trifluoroacetic acid TFA, which is not suitable for the in situ synthesis of PNA arrays and some other applications under mild conditions. Herein, Fmoc/Cbz orthogonal protected miniPEG-containing chiral γPNA monomers were synthesized, and a 15mer γPNA was prepared using the Fmoc strategy under mild conditions.     

Synthesis,characterization and biological activity of copper(II) complexes with ligands derived from β-amino acids

Transition Metal Chemistry - Two copper(II) complexes with ligands derived from β-amino acids, 2-(1-aminocyclohexyl)acetic acid L1 and 2-(1-amino-4-(tert-butyl)cyclohexyl)acetic acid L2, were...     

Synthesis,characterization and photophysical properties of homoleptic platinum(II) complexes with 2,2′-biimidazole-based ligands

Eight pairs of cis–trans isomeric homoleptic platinum(II) complexes based on N-alkyl- or aryl-substituted 2,2′-biimidazole ligands were synthesized, and their photophysical properties were investigated. The cis and trans isomers readily interconvert at slightly elevated temperature, implying that the activation barrier for this process is low. Single crystal X-ray diffraction analysis revealed that the complexes have an ideal square-planar geometry. Their UV–Vis spectra showed lower energy absorption bands in the range of 345–378 nm, which are assigned to the typical MLCT mixed with LC transitions. In frozen glass solution at 77 K and also in the powder state, these complexes exhibit green emission ranging from 440 to 540 nm with photoluminescence quantum yields of 3.3–24.4%. The emitting excited state is dominated by ³ππ* character with some contributions from ³MLCT according to the excitation spectra.     

Synthesis, characterization, and supercapacitive properties of β-Co(OH)2 leaf-like nanostructures

Leaf-like nanostructures of ??-Co(OH)₂ were successfully prepared via galvanostatically cathodic electrodeposition at the current density of 1?mA?cm^?2 from an aqueous 0.005?M Co(NO₃)₂ bath. The bath temperature was fixed at 60?°C. The XRD and FTIR results revealed that the prepared sample has a single phase of the hexagonal brucite-like ??-Co(OH)₂. Morphological characterization by SEM showed that the prepared ??-Co(OH)₂ was composed of discrete leaf-like nanostructures with edge lengths ranging from 250 to 450?nm. The electrochemical performance of the prepared ??-Co(OH)₂ was evaluated using cyclic voltammetry and charge?Cdischarge tests. A maximum specific capacitance of 772.8?F?g^?1 was obtained in aqueous 1?M KOH with the potential range of ?0.3?C0.5?V (vs. Ag/AgCl) at scan rate of 10?mV?s^?1, suggesting the potential application of the prepared nanostructures in electrochemical supercapacitors. Result of this work showed that cathodic electrodeposition can be recognized as a facile method for the preparation of cobalt hydroxide.     

Synthesis,characterization, and photoluminescence properties of difluoroboron complexes with bis-β-diketone ligands

Some novel difluoroboron bis-β-diketonates containing a pyridyl moiety were synthesized from diethyl 2,6-pyridinedicarboxylate via Claisen condensation with the corresponding aryl methyl ketones and followed by complexation with boron trifluoride etherate. Their spectroscopic behaviors were studied by FTIR, ¹H NMR, UV–Vis, and fluorescence spectroscopic techniques. The results indicated that difluoroboron bis-β-diketonates exhibited violet or blue fluorescence emission at 428–454 nm under UV illumination in DMSO and possessed high extinction coefficients. It was found that the nature of the substituents at benzene ring in bis-β-diketone ligands had a significant impact on the photoluminescence behaviors of difluoroboron complexes. The complex 5b exhibited the strongest photoluminescence intensity and highest quantum yield (Φ _u = 0.93), due to two strong electron-donating methoxyl moieties in molecule and the compound 4b displayed the lowest photoluminescence intensity and quantum yield, assigned to the heavy atom effect of the chlorine atom in its molecule. The photoluminescence intensity and quantum yield of these difluoroboron complexes decreased in the sequence, 5b > 2b > 1b > 3b > 4b.     

Synthesis and characterization of α-, β- and γ-cyclodextrin-nicotinamide

Abstract

α-, β- and γ-cyclodextrin-nicotinamide (α-, β- and γ-CDNA) were synthesized as NADH coenzyme models, and the binding abilities were investigated. CDNA binds a negatively charged guest stronger than unmodified cyclodextrin because of the electrostatic interaction between the nicotinamide residue and the guest molecule. Different binding abilities were measured and were dependent on cavity size.     

Synthesis, characterization and magnetic properties of μ-iodanilato dinuclear oxovanadium (Ⅳ) complexes

Five oxovanadium(Ⅳ) dinuclear complexes described by the overall formula [(VO)2(IA)L2]-SO4, where IA represents the dianion of iodanilic acid and L denotes 2,2'-bipyridine (bpy) ; 4,4'-dimethyl-2,2'-bipyridine (Me2-bpy); 1,10-phenanthroline (phen); 4,7-diphenyl-1, 10-phenanthroline (Ph2-phen) and 5-nitro-l, 10-phenanthroline (NO2-phen) , have been synthesized and characterized by elemental analyses, molar conductivity and room-temperature magnetic moment measurements, IR and electronic spectral studies. It is proposed that these complexes have IA-bridged structures and consist of two oxovanadium(Ⅳ) ions each in a square- pyramidal environment. The complexes [ ( VO)2 (IA) (bpy )2 ] SO4 (1) and [ ( VO )2 ( IA) ( phen)2 ] -SO4 (2) were further characterized by variable temperature (4.2-300 K) magnetic susceptibility measurements and the observed data were fitted to the modified Bleaney-Bowers equation by the least-squares method, giving the exchange integral J = -2.15 cm-1 for 1 and J = - 9.88 cm-1 for 2     

Structural characterization of folded pentapeptides containing centrally positioned β(R)Val, γ(R)Val and γ(S)Val residues

A cylindrical pore of ～7.5 Å diameter containing a one-dimensional water wire, within the confines of a hydrophobic channel lined with the valine side chain, has been observed in crystals of the peptide Boc–d-Pro-Aib-Val-Aib-Val–OMe (1) (Raghavender et al., 2009, 2010). The synthesis and structural characterization in crystals of three backbone homologated analogues Boc–d-Pro-Aib-β³(R)Val-Aib-Val–OMe (2), Boc–d-Pro-Aib-γ⁴(R)Val-Aib-Val–OMe (3), Boc–d-Pro-Aib-γ⁴(S)Val-Aib-Val–OMe (4) are described. Crystal structures of peptides 2, 3 and 4 reveal close-packed arrangements in which no pore was formed. In peptides 2 and 3 the N-terminus d-Pro-Aib segment adopted conformations closely related to Type II′ β-turns, while residues 2–4 form one turn of an αβ right-handed C₁₁ helix in 2 and an αγ C₁₂ helix in 3. In peptide 4, a continuous left-handed helical structure was observed with the d-Pro-Aib segment forming a Type III′ β-turn, followed by one turn of a left-handed αγ C₁₂ helix.     

Synthesis and structural characterization of heteroleptic Cu(I) complexes with α-diimines derived from pyridinyliminobenzoic acids

The synthesis and molecular and electronic structure of heteroleptic univalent copper compounds [Cu(L)(PPh₃)X] are reported where X is a halide and L represents 3-pyridinylimino, 4-pyridinylimino or 3,5-dipyridinylimino-substituted benzoic acid, hereafter abbreviated as L1, L2, and L3, respectively. The crystal structures of two iodide and one bromide complexes are described. All compounds are hydrogen-bonded dimers. The electronic excitation spectra of the compounds are dominated by intraligand bands of ligands while characteristic MLCT transitions are observed at 430–480?nm. No emission is observed from the compounds either in the solid state or in solution; on the contrary a photodecomposition is observed resulting in triphenylphosphane ligand elimination and formation of halogen-bridged dimmers.     

Synthesis, characterization and magnetic properties of novel μ-isophthalato oxovanadium(IV) binuclear complexes

Four novel oxovanadium(IV) binuclear complexes have been synthesized, namely [(VO)₂(IPHTA) (L)₂SO₄ (L denotes 2,2′-bipyridine (bpy); 1,10-phenanthroline (phen); 4,4′-dimethyl-2,2′-bipyridine (Me₂bpy) and 5-nitro-1,10-phenanthroline (NO₂-phen)), where IPHTA is the isophthalate dianon. Based on elemental analyses, molar conductivity measurements, IR and electronic spectra studies, it is proposed that these complexes have IPHTA-bridged structures and consist of two vanadium(IV) atoms in a square-pyramidal environment. The complexes [(VO)₂(IPHTA)(Me₂bpy)₂]SO₄ (1) and [(VO)₂(IPHTA)(bpy)₂]SO₄ (2) were characterized by variable temperature magnetic susceptibility (4–300 K) and the data could be well fitted by the least-squares method to a susceptibility equation derived from the spin Hamiltonian operator, . The exchange integral, J, was found to be −26.8 cm⁻¹ for (1) and −31.0 cm⁻¹ for (2). These results are commensurate with antifferomagnetic interactions between two oxovanadium(IV) ions within each molecule. The influence of different terminal ligands on magnetic interactions between the metals of this kind of complexes is also discussed.     

Synthesis,characterization and DNA-binding properties of mixed porphyrin–polypyridyl ruthenium(II) complexes

Two mixed porphyrin–polypyridyl Ru^II complexes [Ru(bpy)₂(MPyTPP)Cl]Cl (1) and [Ru(phen)₂(MPyTPP)Cl]Cl ( 2 ) (bpy=2,2-bipyridine; phen=1,10-phenanthroline; MPyTPP=5-monopyridyl-10,15,20–triphenylporphyrin) have been synthesized and characterized by elementary analysis, e.s.–m.s., cyclic voltammetry and u.v.–vis. spectroscopy. The DNA-binding properties of these complexes were investigated by electronic spectra, c.d. spectra and viscosity experiments. The results suggested that both complexes (1) and (2) bind to DNA in an outside binding mode. At the same time, theoretical calculations applying the ab initio and the density functional theory (DFT) methods were also performed, and the results showed that there is no good planarity on the main ligand MPyTPP of these complexes, and there are rather great distortion angles (dihedral angles ca. 72°) between the porphrin ring and each of the 10-, 15-, 20-phenyl groups. This may be the reason why the complexes bind to DNA in an outside mode, instead of an intercalative mode.     

Synthesis,characterization and properties of 3,3′-diethyl-1,1′-oxydiethylenedicarbonyl bis(thiourea)

In this paper, 3,3′-diethyl-1,1′-oxydiethylenedicarbonyl bis(thiourea) (DEOECTU), was synthesized by phase transfer catalysis and then characterized by UV, elemental analysis, infrared spectra, mass spectrum, ¹H NMR and TGA. DEOECTU properties, such as response to metal ions, adsorption on sulfide mineral surfaces, and hydrometallurgical performance as flotation collectors, were also investigated. The results indicated that DEOECTU reacted chemically with Cu²⁺ ions through its S and N atoms in the C(=S)–NH–C(=O) group to form a new chelate compound, but no reaction of DEOECTU with Zn²⁺, Pb²⁺, Fe³⁺ or Fe²⁺ ions was observed. The results of adsorption and flotation experiments demonstrated, that compared to pyrite, sphalerite and galena, DEOECTU exhibited a superior collecting power for chalcopyrite and might attach on chalcopyrite surface by chemisorption. The further theoretical analysis from Pearson’s HSAB view point briefly explained the experimental results of the selective response of DEOECTU to Cu²⁺ ions and chalcopyrite.     

Synthesis,characterization and magnetic properties of γ-Fe2O3 nanoparticles via a non-aqueous medium

Acicular shaped γ-Fe₂O₃ nanoparticles (major axis: 17±2 nm; minor axis: 1.7±1 nm) have been prepared using lauric acid as a non-aqueous medium. The products were investigated by IR, TG-DTA, XRD, Raman, SEM, TEM and magnetization measurements. For the preparation of pure γ-Fe₂O₃ nanoparticles, the suitable condition of the molar ratio of lauric acid to iron nitrate is set 2:1 and the appropriate temperature lies in the range 573–673 K. Besides, either pure α-Fe₂O₃ or a mixture of γ-Fe₂O₃ and α-Fe₂O₃ can also be obtained with the change of the molar ratio of lauric acid to iron nitrate. The experimental results indicate that the particle sizes, thermal stability and magnetic properties of the iron oxide strongly depend on the conditions in the preparation.     

Synthesis,structural characterization,and in vitro antimicrobial properties of salicylate and pyrazoline complexes of bismuth(III)

Displacement reactions of dichlorobismuth(III)pyrazolinates with oxygen donors such as sodium salicylate and acetate in 1?:?1 and 1?:?2 molar ratio in refluxing anhydrous benzene yields (C₁₂H₁₅N₂OX)Bi(C₆H₄O₃), (CH₃COO)BiCl(C₁₅H₁₂N₂OX), and (CH₃COO)₂Bi(C₁₅H₁₂N₂OX) [C₁₂H₁₅N₂OX?=?3(2′-hydroxyphenyl)-5-(4-X-substituted phenyl) pyrazoline X?=?H in 1,5,9, CH₃ in 2,6,10, OCH₃ in 3,7,11, and Cl in 4,8,12, respectively, (C₆H₄O₃)?=?salicylate and (CH₃COO)?=?acetate]. Newly synthesized derivatives are brown solids, soluble in organic solvents like benzene, chloroform, and acetone. The compounds have been characterized by elemental analyses (C, H, N, Cl, and Bi), molecular weight measurements, and spectral (IR, ¹H NMR, ¹³C NMR) studies. The (C₁₂H₁₅N₂OX) and (C₆H₄O₃) are bidentate while (CH₃COO) is monodentate to bismuth(III), leading to a distorted trigonal bipyramidal structure. The complexes were screened against different bacteria and fungi showing potential antibacterial and antifungal activities.     

Synthesis of novel non-natural spiro[2.3]hexane amino acids,the conformationally restricted analogs of γ-aminobutyric acid

3-Methylenecyclobutanecarboxylic acid and its methyl ester were used as the starting compounds for the synthesis of new spiro[2.3]hexane amino acids, the conformationally rigid analogs of γ-aminobutyric acid, namely, 5-aminospiro[2.3]hexanecarboxylic and 5-amino-spiro[2.3]hexanephosphonic acids, promising modulators of GABAergic cascades in the human central nervous system. The methods developed for the synthesis of the target amino acids are based on the reactions of catalytic [1+2] cycloaddition of diazoacetic and diazophosphonic esters to 3-substituted methylenecyclobutanes, as well as on a modified Curtius reaction for the transformation of a carboxy group to the amine one.     

Synthesis and characterization of allyl functionalized poly(α-hydroxy)acids and their further dihydroxylation and epoxidation

In this study, the synthesis of an allyl functionalized aliphatic polyester and the subsequent oxidation of the double bonds was investigated. Allylglycolide (3-allyl-1,4-dioxane-2,5-dione) was synthesized and its homopolymer and copolymers with l-lactide were prepared by ring opening polymerization in the melt using benzyl alcohol and SnOct₂ as initiator and catalyst, respectively. The polymerizations proceeded with high yields and conversions and good control over molecular weights and copolymer composition. The obtained polymers were amorphous materials and their T_g increased with increasing lactide content. Dihydroxylation of the double bonds in poly(allylglycolide) and copolymers with lactide was attempted with osmiumtetroxide/4-methylmorpholine-4-oxide (OsO₄/NMO). However, particularly the polymers rich in allylglycolide could not be isolated after dihydroxylation because they likely underwent degradation during workup. Optimizing the reaction conditions gave partially dihydroxylated copolymers only for copolymers with high lactide content (50 and 75 mol%) with a conversion of the double bonds of only ∼60%. GPC analysis showed that chain scission had occurred during the dihydroxylation reaction and/or workup.The allyl groups of poly(allylglycolide) homopolymers and copolymers with lactide were oxidized using m-chloroperoxy benzoic acid (mCPBA) to yield the corresponding epoxidated polymers in high yield. NMR analysis showed that conversion of the double bonds to epoxides was quantitative, whereas GPC analysis showed that the epoxidation was not associated with chain scission. All epoxidated polymers were amorphous materials with a T_g depending on the composition.     

Synthesis, characterization and antibacterial properties of multifunctional hindered amine light stabilizers

A series of novel hindered amine light stabilizers containing an N-halamine moiety were designed and synthesized. Their structures were characterized by FT-IR, 1H NMR, and MS. The compounds were tested for antibacterial activity against Candida albicans, Staphylococcus aureus, and Escherichia coll. At a concentration of 0.5 mmol/L, these compounds all exhibited satisfactory antibacterial activity against all the three types of bacteria.     

Synthesis, and characterization of ruthenium(II) polypyridyl complexes containing α-amino acids and its DNA binding behavior

Reactivity of the ruthenium complexes [Ru(κ³-tptz)(PPh₃)Cl₂] (1) and [Ru(κ³-tpy)(PPh₃)Cl₂] (2) [tptz = 2,4,6-tris(2-pyridyl)-1,3,5-triazine; tpy = 2,2′:6′,2″-terpyridine] with several α-amino acids [glycine (gly); leucine (leu); isoleucine (isoleu); valine (val); tyrosine (tyr); proline (pro) and phenylalanine (phe)] have been investigated. Cationic complexes with the general formulations [Ru(κ³-L)(κ²-L″)(PPh₃)]⁺ (L = tptz or tpy; L″ = gly, leu, isoleu, val, tyr, pro, and phe] have been isolated as tetrafluoroborate salts. The resulting complexes have been thoroughly characterized by analytical, spectral and electrochemical studies. Molecular structures of the representative complexes [Ru(κ³-tptz)(val)(PPh₃)]BF₄ (6)_, [Ru(κ³-tpy)(leu)(PPh₃)]BF₄ (10) and [Ru(κ³-tpy)(tyr)(PPh₃)]BF₄ (13) have been determined crystallographically. The complexes [Ru(κ³-tptz)(leu)(PPh₃)]BF₄ (4), [Ru(κ³-tptz)(val)(PPh₃)]BF₄ (6), [Ru(κ³-tpy)(leu)(PPh₃)]BF₄ (10) [Ru(κ³-tpy)(tyr)(PPh₃)] BF₄·3H₂O (13) exhibited DNA binding behavior and acted as mild Topo II inhibitors (10-40%). The complexes also inhibited heme polymerase activity of the malarial parasite Plasmodium yoelii lysate.     

Synthesis and characterization of lead(II) complexes with substituted 2,2′-bipyridines,trifluoroacetate, and furoyltrifluoroacetonate

Two substituted 2,2′-bipyridine lead(II) complexes, [Pb(5,5′-dm-2,2′-bpy)(tfac)₂] _n (1) (5,5′-dm-2,2′-bpy?=?5,5′-dimethyl-2,2′-bipyridine and tfac?=?trifluoroacetate) and [Pb₂(4,4′-dmo-2,2′-bpy)₂(ftfa)₄] (2) (4,4′-dmo-2,2′-bpy?=?4,4′-dimethoxy-2,2′-bipyridine and ftfa?=?furoyltrifluoroacetonate), have been synthesized and characterized by elemental analysis, IR, ¹H NMR, and ¹³C NMR spectroscopies, thermal behavior, and X-ray crystallography. Complexes 1 and 2 are 1D coordination polymer and dinuclear complex, respectively. The supramolecular features in these complexes are guided by weak directional intermolecular interactions.     

Synthesis,characterization, and cytotoxicity of complexes of platinum(II) with 2,2′-bipyridine and N-benzoyl-L-amino acid dianion

Four new platinum(II) complexes (1–4) with N-benzoyl-L-amino acid and bipy were synthesized and characterized by elemental analysis, IR, UV, ¹H NMR, and mass spectra. The crystal structure of 1 was determined by X-ray diffraction analysis. Cytotoxicities were measured by MTT and SRB assays. Complexes 1–4 exert cytotoxicity with selectivity against HL-60, Bel-7402, BGC-823, and KB cell lines. This suggests that amino acids and acylated groups have important effects on cytotoxicity; the cytotoxicity is also related to the species of tumor cells, but the IC₅₀ values do not show definite correlation with the variation of amino acids and acylated groups.