Phenyl Ligands Research Articles

Salt-independent hydrophobic displacement chromatography for antibody purification using cyclodextrin as supermolecular displacer

Hydrophobic interaction chromatography (HIC) offers an orthogonal selectivity to ion exchange chromatography and the combination of the two processes can provide a potential cost-effective alternative to protein A chromatography in industrial antibody purification. However, the application of HIC is limited by its close dependence on high concentrations of kosmotropic salts to achieve desired separation. These salts can cause antibody precipitation and induce the corrosion of manufacturing facilities. Here, we report a new strategy of salt-independent HIC, which can capture antibody at the physiological salt concentration and allow the recovery of bound proteins through cyclodextrin (CD)-based displacement elution. Hydrophobicity-intensified HIC media with different coupling amount of phenyl ligands were prepared and assessed for their antibody binding capacity and selectivity. β-CD was investigated for its supermolecular interaction with phenyl ligands and elution capacity as a displacer. The results clarified a nearly linear correlation between binding capacity of human immunoglobulin G (IgG) and phenyl coupling density in the range of 44–159μmol/mL. The host–guest interaction between β-CD and the phenyl ligands revealed a modest binding strength (Ka=4.1×103M−1), and 15mM β-CD solution showed a general effectiveness as displacement eluent for these HIC media, with IgG recovery varying with the ligand density. This strategy allowed the direct purification of human IgG from serum with satisfactory purity. The whole procedure of this method, including loading and elution, can be performed under physiological conditions. We expect such a salt-independent mode of HIC could be used as a capture or intermediate step in industrial antibody purification.

Mesomeric metallosupramolecular grid architectures

We describe herein the self-assembly processes as well as the structural properties of metallosupramolecular grid-architectures, involving bis-bidentate ligand 1, based on imino-pyridine complexation subunits and tetrahedrally (Cu+, Ag+) and octahedrally (Co2+, Zn2+, Fe2+) coordinated metal ions. The NMR, electrospray ionisation mass spectrometry data and X-ray crystal structure results suggest that in solution corner- and grid-type compounds are present, while in the solid state they adopt very compact and stable [2 × 2] grids arrays. Despite the variable binding behaviours of tetrahedrally coordinated cations (Cu+, Ag+) and the four coordination (lower) number of octahedrally coordinated cations (Co2+, Zn2+, Fe2+), the flexibility of the ligand 1 induce a perfect arrangement of these components, resulting in the formation of metallosupramolecular grids. Examination of such structures suggests that simple conformational rotation around the central phenyl of ligand 1 results in the self-assembly of chiral ligands. This allows the formation of mesomeric grid-type superstructures containing an inversion centre with half-superior and -inferior inner surfaces of opposite chirality.

Semi-Automated Hydrophobic Interaction Chromatography Column Scouting Used in the Two-Step Purification of Recombinant Green Fluorescent Protein

BackgroundHydrophobic interaction chromatography (HIC) most commonly requires experimental determination (i.e., scouting) in order to select an optimal chromatographic medium for purifying a given target protein. Neither a two-step purification of untagged green fluorescent protein (GFP) from crude bacterial lysate using sequential HIC and size exclusion chromatography (SEC), nor HIC column scouting elution profiles of GFP, have been previously reported.Methods and ResultsBacterial lysate expressing recombinant GFP was sequentially adsorbed to commercially available HIC columns containing butyl, octyl, and phenyl-based HIC ligands coupled to matrices of varying bead size. The lysate was fractionated using a linear ammonium phosphate salt gradient at constant pH. Collected HIC eluate fractions containing retained GFP were then pooled and further purified using high-resolution preparative SEC. Significant differences in presumptive GFP elution profiles were observed using in-line absorption spectrophotometry (A395) and post-run fluorimetry. SDS-PAGE and western blot demonstrated that fluorometric detection was the more accurate indicator of GFP elution in both HIC and SEC purification steps. Comparison of composite HIC column scouting data indicated that a phenyl ligand coupled to a 34 µm matrix produced the highest degree of target protein capture and separation.ConclusionsConducting two-step protein purification using the preferred HIC medium followed by SEC resulted in a final, concentrated product with >98% protein purity. In-line absorbance spectrophotometry was not as precise of an indicator of GFP elution as post-run fluorimetry. These findings demonstrate the importance of utilizing a combination of detection methods when evaluating purification strategies. GFP is a well-characterized model protein, used heavily in educational settings and by researchers with limited protein purification experience, and the data and strategies presented here may aid in development other of HIC-compatible protein purification schemes.

Bridging phenyl ligands. Unsaturated mercury-triosmium carbonyl cluster complexes containing bridging phenyl ligands

The gold phosphine group in the complex Os3(CO)10(μ-η1-Ph)(μ-AuPPh3), 1 can be replaced by mercury halide groups by reactions with mercury halides. The reaction of 1 with HgI2 yielded the new compound [Os3(CO)10(μ-η1-Ph)(μ-HgI)]4, 2 in 19% yield. The reaction of 1 with HgCl2 yielded the new compound Os4(CO)13(μ-η1-Ph)(μ-Cl)3, 3 in 18% yield. When heated to reflux in cyclohexane solvent, compound 2 was converted into the compound [Os3(CO)9(μ3-C6H4)(μ-H)(μ3-Hg)]2Os(CO)4, 4 in 11% yield. All new compounds were characterized by single-crystal X-ray diffraction analyses. Compound 2 is a tetramer of the unit “Os3(CO)10(μ-η1-Ph)(μ-HgI)” that is held together by a cubane-like Hg4I4 core having D2 symmetry. Each triosmium cluster is formally electronically unsaturated and contains one edge-bridging phenyl ligand. Compound 3 contains a Os3(CO)10(μ-η1-Ph)(μ-Hg) cluster, but in this case the Hg atom bridges to an additional Os(CO)3 group via three bridging chloride ligands. Compound 4 contains two Os3(CO)9(μ3-C6H4)(μ-H)(μ3-Hg) clusters that are linked by a bridging Os(CO)4 group. Each Os3 cluster in 4 contains a triply bridging C6H4 benzyne ligand and one bridging hydrido ligand.

Understanding the two-photon absorption spectrum of PE2 platinum acetylide complex.

Herein, we report on the two-absorption cross-section spectrum of trans-Pt(PBu3)2 (C≡C-C6H4-C≡C-C6H5)2 (PE2) platinum acetylide complex employing the femtosecond wavelength-tunable Z-scan technique. The PE2 complex can be visualized as two branches containing two phenylacetylene units, each one linked by a platinum center, completely transparent in the visible region. Because of this structure, large delocalization of π-electrons allied to the strong intramolecular interaction between the branches is expected. The 2PA absorption spectrum was measured using the femtosecond wavelength-tunable Z-scan technique with low repetition rate (1 kHz), in order to obtain the 2PA spectrum without excited-state contributions. Our results reveal that PE2 in dichloromethane solution presents two 2PA allowed bands located at 570 and 710 nm, with cross section of about 320 and 45 GM, respectively. The first one is related to the strong intramolecular interaction between the molecule's branches due to the presence of platinum atom, while the second one is associated with the breaking of symmetry of the chromophore in solution due, most probably to a large twisting angle of the ligand's phenyl rings relative to the Pt core.

Theoretical study of new blue iridium complexes comprising a bipyridine derivative and various ancillary ligands.

New blue emitting ligand Iridium(III) complexes with two phosphines trans to each other and two ancillary ligands, such as Ir(dfpypy)(PPh3)2(H)(CI) and Ir(dfpypy)(PPh3)2(H)(CN), [dfpypy = 2,6-difluoro-3-(pyridin-2-yl)pyridine] were designed and studied to tune the phosphorescence wavelength to the deep blue region and to enhance the luminescence efficiencies. To gain insight into the factors responsible for the emission color change and the different luminescence efficiency, we performed the DFT and TD-DFT calculations on the ground and excited states of these phosphors. (1) The fluorine-substituted dfpypy ligand lower the HOMO energy levels because a N of the pyridyl ligand is more electronegative than a C of the nonsubstituted phenyl ligand and also (2) mono-cyclometalated Iridium(III) complexes using two phosphines trans to each other increased HOMO-LUMO gap by strong field effects of ancillary ligands. From these results, we discuss how the dfpypy ligand and the ancillary ligand influences the emission peak as well as the metal to ligand charge transfer (MLCT) transition efficiency. As the maximum emission spectra of FIrpic known as blue phosphorescence material is about 475 nm. The resulting Iridium(III) complexes, Ir(dfpypy)(PPh3)2(H)(CN), would appear pure blue region about 415 nm with more intensified efficiency.

Investigating retention characteristics of a mixed-mode stationary phase and the enhancement of monolith selectivity for high-performance liquid chromatography.

The synthesis and chromatographic behavior of an analytical size mixed-mode bonded silica monolith was investigated. The monolith was functionalized by an in situ modification process of a bare silica rod with chloro(3-cyanopropyl)dimethyl silane and chlorodimethyl propyl phenyl silane solutions. These ligands were selected in order to combine both resonance and nonresonance π-type bonding within a single separation environment. Selectivity studies were undertaken using n-alkyl benzenes and polycyclic aromatic hydrocarbons in aqueous methanol and acetonitrile mobile phases to assess the methylene and aromatic selectivities of the column. The results fit with the linear solvent strength theory suggesting excellent selectivity of the column was achieved. Comparison studies were performed on monolithic columns that were functionalized separately with cyano and phenyl ligands, suggesting highly conjugated molecules were able to successfully exploit both of the π-type selectivities afforded by the two different ligands on the mixed-mode column.

Surfaces Energies of Monoliths by Inverse Liquid Chromatography and Contact Angles

Seven porous chromatographic columns, termed monoliths, and seven nonporous sheets were produced from polymethacrylates. Their surfaces were activated by different densities of butyl and phenyl ligands. We determined the retention times of highly dilute molecular probes in monoliths and accessed contact angles of pure molecular probes of sheets. We calculated surface energies for both systems. We applied theories of Young, Dupré, and van Oss and compared the results of both types of experiments with respect to Lifshitz-van der Waals and Lewis acid and Lewis base contributions and find agreement but an additive constant.

Nearly perfect spin filter, spin valve and negative differential resistance effects in a Fe4-based single-molecule junction.

The spin-polarized transport in a single-molecule magnet Fe4 sandwiched between two gold electrodes is studied, using nonequilibrium Green's functions in combination with the density-functional theory. We predict that the device possesses spin filter effect (SFE), spin valve effect (SVE), and negative differential resistance (NDR) behavior. Moreover, we also find that the appropriate chemical ligand, coupling the single molecule to leads, is a key factor for manipulating spin-dependent transport. The device containing the methyl ligand behaves as a nearly perfect spin filter with efficiency approaching 100%, and the transport is dominated by transmission through the Fe4 metal center. However, in the case of phenyl ligand, the spin filter effect seems to be reduced, but the spin valve effect is significantly enhanced with a large magnetoresistance ratio, reaching 1800%. This may be attributed to the blocking effect of the phenyl ligands in mediating transport. Our findings suggest that such a multifunctional molecular device, possessing SVE, NDR and high SFE simultaneously, would be an excellent candidate for spintronics of molecular devices.

Neutral Hexacoordinate Silicon(IV) Complexes with a Tridentate Dianionic O,N,X Ligand (X = O, N, S), Bidentate Monoanionic X,N Ligand (X = O, S), and Phenyl Ligand: Compounds with a SiO3N2C, SiSO2N2C, SiO2N3C, SiSON3C, or SiS2ON2C Skeleton

AbstractA series of neutral hexacoordinate silicon(IV) complexes (4a, 4b, 5a, 5b, 6a, and 6b) with a SiO3N2C, SiSO2N2C, SiO2N3C, SiSON3C, or SiS2ON2C skeleton have been synthesized and structurally characterized by solid‐state and solution NMR spectroscopy and single‐crystal X‐ray diffraction. These studies were performed with a special emphasis on comparing the respective O/NMe/S analogues 4a/5a/6a and 4b/5b/6b and the O/S pairs 4a/4b, 5a/5b, and 6a/6b with respect to their structures and NMR spectroscopic parameters.

PURIFICATION OF RECOMBINANT GREEN FLUORESCENT PROTEIN FROM ESCHERICHIA COLI USING HYDROPHOBIC INTERACTION CHROMATOGRAPHY

□ In this study, an efficient purification system was developed using a packed-bed column for the purification of recombinant green fluorescent protein (GFP) from clarified feedstock. A series of hydrophobic ligands [phenyl (low sub), phenyl (high sub), butyl, and octyl] was screened at bench scale and the optimum concentration of salt in binding buffer was determined by precipitating the sample with (NH4)2SO4. The optimum salt concentration used in binding buffer is 30%(w/v) (NH4)2SO4 in 20 mM sodium phosphate buffer at pH 8.0. Phenyl (high sub) ligand showed the best result of GFP purification in terms of yield and purity. Maximum recovery (82%) of recombinant GFP was achieved with phenyl (high sub) ligand. The optimum elution buffer for scaled-up process was determined by conducting a stepwise elution with 0–15%(w/v) (NH4)2SO4 salt solution and the result showed that the GFP absorbed at the ligand was mostly eluted by using a buffer with the absence of (NH4)2SO4. The effect of GFP concentration in initial sample on the dynamic binding capacity was also studied by running a scaled-up hydrophobic interaction chromatography using HiPrep™ HIC Phenyl (high sub) 16/10 20mL packed-bed column connected to Äkta FPLC.

Enantioselective Hydrophosphination of Enones with Diphenylphosphine Catalyzed by Bis(imidazoline) NCN Pincer Palladium(II) Complexes

A series of chiral NCN pincer Pd(II) complexes with 1,3-bis(2′-imidazolinyl)phenyl (Phebim) ligands were synthesized via the C–H activation or oxidative addition method. A dinuclear macrocyclic Pd(II) complex was also prepared by reaction of the Phebim-H ligand with PdCl2. All of the new compounds were fully characterized, and X-ray single-crystal structures were obtained for two of the complexes. The Pd(II) complexes were successfully applied to enantioselective hydrophosphination of various enones with diphenylphosphine, providing optically active phosphine derivatives in good yields with enantioselectivities of up to 94% ee.

Crystal Structure and Spectroscopic Studies of a Dimeric Europium(III) β‐Diketonate Complex Containing [3‐(2‐Pyridyl)‐1‐pyrazolyl]acetate

The homodinuclear europium(III) β-diketonate complex [Eu2(bta)4(pypzCH2COO)2] (1) {bta = 1-benzoyl-3,3,3-trifluoroacetonate, pypzCH2COO = [3-(2-pyridyl)-1-pyrazolyl]acetate} was isolated after recrystallization of the crude product obtained from the reaction of [Eu(bta)3(H2O)2] with one equivalent of the ligand phenyl[3-(2-pyridyl)-1-pyrazolyl]acetate (pypzCH2CO2C6H5). A single-crystal X-ray diffraction study confirmed that during the recrystallization the hydrolysis of the ester group in pypzCH2CO2C6H5 took place to give pypzCH2COO–, which culminated in the crystallization of dinuclear complex 1 in which each Eu3+ ion is coordinated to two O,O′-chelated bta– groups and one N,N′-chelated pyrazolylpyridine ligand, and the two metal centers are linked by tridentate chelating–bridging (μ2-η2,η1) carboxylate groups. The luminescence properties of 1 were investigated by steady-state photoluminescence (PL), PL excitation, and time-resolved PL.

Theoretical Study on the Ligand Exchange Reactions of Hypervalent Antimony and Tellurium Compounds

The ligand exchange reactions (LERs) of hypervalent compounds of antimony (R5Sb: R = Me, Ph) and tellurium (R4Te: R = Me, Ph) were analyzed via dispersion corrected density functional theory (DFT) and coupled cluster calculations. The dispersion force plays a key role in forming reactant/product complexes. For the phenyl ligand compounds, the pathway of the LER was predicted as being stepwise, while that for the methyl ligand compounds was predicted to be concerted. From the natural localized molecular orbital analysis for the reaction of Me4Te, it was found that the lone pair electrons of tellurium do not participate in LER. The LER of antimony compounds was elucidated to proceed along the mechanism similar to that of Me4Te. LER of a mixture of Me4Te and Me5Sb was shown to proceed more easily than that of each component.

High Nuclearity (Octa-, Dodeca-, and Pentadecanuclear) Metal (M = CoII, NiII) Phosphonate Cages: Synthesis, Structure, and Magnetic Behavior

The synthesis, structural characterization, and magnetic property studies of five new transition metal (M = Co, Ni) phosphonate-based cages are reported. Three substituted phenyl and benzyl phosphonate ligands [RPO3H2; R1 = p-tert-butylbenzyl, R2 = p-tert-butylphenyl, R3 = 3-chlorobenzyl] were synthesized and employed to seek out high-nuclearity cages. Complexes 1-3 are quasi-isostructural and feature a dodecanuclear metal-oxo core having the general molecular formula of [M12(μ3-OH)4 (O3PR)4(O2C(t)Bu)6 (HO2C(t)Bu)6(HCO3)6] {M = Co, Ni and R = R1 for 1 (Co12), R2 for 2, 3 (Co12, Ni12)}. The twelve metal centers are arranged at the vertices of a truncated tetrahedron in a manner similar to Keggin ion. Complex 4 is an octanuclear nickel phosphonate cage [Ni8(μ3-OH)4 (OMe)2(O3PR1)2 (O2C(t)Bu)6(HO2C(t)Bu)8], and complex 5 represents a pentadecanuclear cobalt phosphonate cage, [Co15(chp)8(chpH) (O3PR3)8(O2C(t)Bu)6], where chpH = 6-chloro-2-hydroxypyridine. Structural investigation reveals some interesting geometrical features in the molecular cores, which may provide new models in single molecular magnetic materials. Magnetic property measurements of compounds 1-5 indicate the coexistence of both antiferromagnetic and ferromagnetic interactions between magnetic centers for all cages.

ChemInform Abstract: Chiral Bis(imidazolinyl)phenyl NCN Pincer Rhodium(III) Catalysts for Enantioselective Allylation of Aldehydes and Carbonyl—Ene Reaction of Trifluoropyruvates.

Chiral NCN pincer rhodium(III) complexes with bis(imidazolinyl)phenyl ligands were found to be effective catalysts for the allylation of a variety of electronically and structurally diverse aldehydes with allyltributyltin, giving the corresponding optically active homoallylic alcohols in high yields with enantioselectivities of up to 97% ee. These complexes were also applied in the carbonyl–ene reaction of ethyl or methyl trifluoropyruvate with various 2-arylpropenes. With the aid of silver trifluoromethanesulfonate, the pincer rhodium(III) catalysts could catalyze the reaction to provide the corresponding chiral α-hydroxy-α-trifluoromethyl esters in good yields with high stereoselectivities (up to 95% ee).

Neutral Hexacoordinate Silicon(IV) Complexes with a SiO4NC or SiO3N2C Skeleton and Neutral Pentacoordinate Silicon(IV) Complexes Containing a Trianionic Tetradentate O,N,O,O Ligand

AbstractA series of neutral hexacoordinate silicon(IV) complexes with a SiO4NC or SiO3N2C skeleton was synthesized. Additionally, two neutral pentacoordinate silicon(IV) complexes with a SiO3NC skeleton were synthesized. All compounds studied were structurally characterized by multinuclear NMR spectroscopy in the solid state and in solution and by single‐crystal X‐ray diffraction. The hexacoordinate compounds studied contain a tridentate dianionic O,N,O or N,N,O ligand, a phenyl ligand, and a symmetrically substituted derivative of an acetylacetonato ligand of the formula type RC(O)–CH=C(OSiMe3)R (R = Me, Ph, CF3). The two pentacoordinate complexes contain a tetradentate trianionic O,N,O,O ligand and a phenyl ligand.

Chiral CNN Pincer Palladium(II) Complexes with 2-Aryl-6-(oxazolinyl)pyridine Ligands: Synthesis, Characterization, and Application to Enantioselective Allylation of Isatins and Suzuki–Miyaura Coupling Reaction

A series of chiral 2-aryl-6-(oxazolinyl)pyridine (aryl = phenyl or 1-naphthyl) ligands 2a–f were conveniently prepared from commercially available 6-bromo-2-picolinaldehyde in two steps. Reaction of 2a–f with PdCl2 in toluene in the presence of sodium bicarbonate afforded the corresponding CNN pincer Pd(II) complexes 3a–f via aryl C–H bond activation of the related ligands. All of the new compounds have been fully characterized by elemental analysis (MS for ligands), 1H and 13C NMR, and IR spectra. In addition, the molecular structures of Pd(II) complexes 3c–f have been determined by X-ray single-crystal diffraction. The obtained chiral pincer catalysts were successfully used in the asymmetric allylation of isatins with allyltributyltin, giving the corresponding 3-allyl-3-hydroxyoxindoles in high yields with enantioselectivities of up to 86% ee. These pincers could also catalyze the asymmetric Suzuki–Miyaura coupling reaction to provide the axially chiral biaryl products in good yields with good stereoselectivities (up to 68% ee).

MOLECULAR STRUCTURE, NATURAL BOND ORBITAL, SUBSTITUENT EFFECT AND CHEMICAL REACTIVITY ANALYSIS OF TERMINAL BORYLENE RUTHENIUM COMPLEXES: Ru(PH3)2HCl(BC6H4X)

The structure and properties of a terminal borylene ruthenium complexes Ru ( PH 3)2 HCl ( BC 6 H 4X) have been investigated using theoretical methods. Frontier orbital analysis indicates the HOMO is distributed on the Ru and Cl ligand. On the other hand, LUMO is distributed on the Ru and phenyl ligand. The influence of solvent on the structure and properties of X = H structure has been studied. Time-dependent density functional theory (TD-DFT) is used to calculate the energy, oscillatory strength and wavelength absorption maxima (λmax) of various electronic transitions and their nature within molecules. Nonlinear optical (NLO) behavior of title compounds is investigated by the computed value of first hyperpolarizability (βtotal).

Synthesis, structure and theoretical investigation into a homoleptic tris(dithiolene) tungsten

A new homoleptic dithiolene tungsten complex, tris-{1,2-bis(3,5-dimethoxyphenyl)-1,2-ethylenodithiolene-S,S′}tungsten, was successfully synthesized via a reaction of the thiophosphate ester and sodium tungstate. The thiophosphate ester was prepared from 3,5-dimethoxybenzaldehyde via benzoin condensation to produce the intermediate 1,2-bis-(3,5-dimethoxyphenyl)-2-hydroxy-ethanone compound, followed by a reaction of the intermediate with phosphorus pentasulfide. FTIR, UV–Vis spectroscopy, 1H NMR and 13C NMR and elemental analysis confirmed the product as tris{1,2-bis-(3,5-dimethoxyphenyl)-1,2-ethylenodithiolene-S,S′}tungsten with the molecular formula of C54H54O12S6W. Crystals of the product adopted a monoclinic system with space group of P2(1)/n, where a=12.756(2)Å, b=21.560(3)Å, c=24.980(4)Å and β=103.998(3)°. Three thioester ligands were attached to the tungsten as bidentate chelates to form a distorted octahedral geometry. Density functional theory calculations were performed to investigate the molecular properties in a generalized-gradient approximation framework system using Perdew–Burke–Ernzerhof functions and a double numeric plus polarization basis set. The HOMO was concentrated on the phenyl ligands, while the LUMO was found along the W(S2C2)3 rings. The theoretical optical properties showed a slight blue shift in several low dielectric solvents. The solvatochromism effect was insignificant for high polar solvents.