Neutral Ligand (neutral + ligand)

Distribution by Scientific Domains


Selected Abstracts


Use of chemometric methodology in optimizing conditions for competitive binding partial filling affinity capillary electrophoresis

ELECTROPHORESIS, Issue 16 2008
Ruth E. Montes
Abstract This work expands the knowledge of the use of chemometric response surface methodology (RSM) in optimizing conditions for competitive binding partial filling ACE (PFACE). Specifically, RSM in the form of a Box,Behnken design was implemented in flow-through PFACE (FTPFACE) to effectively predict the significance of injection time, voltage, and neutral ligand (neutral arylsulfonamide) concentration, [Lo], on protein,neutral ligand binding. Statistical analysis results were used to create a model for response surface prediction via contour and surface plots at a given maximum response (,RMTR) to reach a targeted Kb,=,2.50×106,M,1. The adequacy of the model was then validated by experimental runs at the optimal predicted solution (injection time,=,2.3,min, voltage,=,11.6,kV, [Lo],=,1.4,,M). The achieved results greatly extend the usefulness of chemometrics in ACE and provide a valuable statistical tool for the study of other receptor,ligand combinations. [source]


Flow-through partial-filling affinity capillary electrophoresis can estimate binding constants of neutral ligands to receptors via a competitive assay technique

ELECTROPHORESIS, Issue 6 2003
John Kaddis
Abstract This work evaluates the use of a competitive binding assay using flow-through partial-filling affinity capillary electrophoresis (FTPFACE) to estimate binding constants of neutral ligands to a receptor. We demonstrate this technique using, as a model system, carbonic anhydrase B (CAB, EC 4.2.1.1) and arylsulfonamides. In this technique, the capillary is first partially filled with a negatively charged ligand, a sample containing CAB and two noninteracting standards, and a neutral ligand, then electrophoresed. Upon application of a voltage the sample plug migrates into the plug of negatively charged ligand (L,) resulting in the formation of a CAB-L, complex. Continued electrophoresis results in mixing between the neutral ligand (L0) and the CAB-L, complex. L0 successfully competes out L, to form the new CAB-L0 complex. Analysis of the change in the relative migration time ratio (RMTR) of CAB relative to the noninteracting standards, as a function of neutral ligand concentration, yields a value for the binding constant. These values are in agreement with those estimated using other binding and ACE techniques. Data demonstrating the quantitative potential of this method is presented. [source]


Ketiminate-Supported LiCl Cages and Group 13 Complexes

EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 13 2010
Audra F. Lugo (née Gushwa)
Abstract The coordination preferences of the ketiminato ligands L1H, {[RN(H)(C(Me))2C(Me)=O], R = 2,6-diisopropylphenyl (Dipp) or 2,6-dimethylphenyl (Dmp)} and L2H {[RN(H)C(Me)CHC(Me)=O], R = C2H4NEt2} with group 13 elements were investigated. The expected N,O -chelated products [DmpL1BF2] (1), [L2Al(Me)Cl] (2A and 2B), and [L2InMe2] (6), were obtained from reactions with BF3·OEt2, AlMe2Cl and InMe3 respectively, but the reaction of DippL1 with GaCl3 afforded a metal-halide, neutral ligand adduct, [GaCl3·DippL1H] (3). More interestingly the reactions of DippL1 with InMe3, formed in situ from InCl3 and MeLi, led to the isolation of two ketiminate-supported LiCl cages[InMe2Li7Cl5(DippL1,)2(DippL1)(THF)3] (4) and [Li5(Cl)(DippL1)4]·2PhMe (5). The lithium cage 4 features reaction of InMe3 with one backbone methyl group from each of two DippL1 ligands, to afford a tetraalkylindate moiety in the framework of two doubly deprotonated ligands (L,). [source]


New Coordination Modes of L -Ascorbic Acid and Dehydro- L -ascorbic Acid as Dianionic Chelating Ligand for Platinum

EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 4 2008
Paola Bergamini
Abstract A variety of coordination modes of L -ascorbic acid as an anionic bidentate ligand has been exploited to prepare platinum(II) complexes 1,7 that contain phosphanes or R,R -dach (1R,2R -diaminocyclohexane) as neutral ligands in which O2, O3, O5, O6 and C2 act as anionic donating functionalities. An alternative synthetic route to known O2,O3 complexes is proposed, and their solubility in water has been enhanced by introducing PTA (1,3,5-triaza-7-phosphaadamantane) as a neutral ligand. A new coordination mode of ascorbic acid (O2 and O3 protected) as an O5,O6-diolate chelating ligand has been characterised in solution by NMR spectroscopy and in the solid state by X-ray crystallography. The first example of a platinum complex that contains dehydroascorbic acid, 7, has also been prepared and its X-ray crystal structure has been determined. The antiproliferative activity in vitro of complexes 1,7 has been tested, and the best values were obtained for the DHA complex 7, which was found to be more active than cisplatin on both a cisplatin-sensitive and a cisplatin-resistant cell line.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008) [source]


Reaction of Mercury(0) with the I2 Adduct of Tetraphenyldithioimidodiphosphinic Acid (SPPh2)2NH (HL) , Crystal Structures of [Hg(HL)I2] and HgL2

EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 23 2004
M. Carla Aragoni
Abstract The complex [Hg(HL)I2] (1) has been synthesised by reacting liquid Hg(0) in Et2O under mild reaction conditions with the I2 adduct of HL, HL·I2, while HgL2 (2) has been obtained from the reaction of compound 1 with HL in CH3CN. A single-crystal X-ray investigation of 1 shows four independent molecules in the asymmetric unit, each of which contains an HgII ion coordinated to two iodine atoms and two sulfur atoms of one bidentate neutral ligand in a distorted tetrahedral coordination geometry. Compound 2 consists of two anionic ligands coordinated to an HgII ion, which again displays a distorted tetrahedral coordination sphere. The reaction of 2 with HI (55 wt.-% in water) affords [Hg(HL)2](I)2 (3). Compounds 1, 2, and 3 have been characterised by FT-IR and 31P NMR spectroscopy. Density functional calculations suggest that compound 3 should feature a distorted tetrahedral coordination around the metal centre, with unequal Hg,S bond lengths. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004) [source]


2-(Diphenylphosphinoylmethyl)pyrrole,2-(diphenylphosphinomethyl)pyrrole (0.43/0.57) and tetrachlorido(5-diphenylphosphinomethyl-2H -pyrrole-,2N,P)titanium(IV)

ACTA CRYSTALLOGRAPHICA SECTION C, Issue 3 2010
Lewis M. Broomfield
The title phosphine oxide,phosphine, 0.43C17H16NOP·0.57C17H16NP, (I)/(II), was obtained as a 0.861,(6):1.139,(6) cocrystallized mixture. Hydrogen bonding between the two constituents leads to the formation of 2:2 solid-state assemblies. Instead of forming the expected simple N,P -chelated system via loss of the N-bound H atom, reaction of 2-(diphenylphosphinomethyl)pyrrole, (II), with TiCl4 leads to the formation of the title titanium(IV) complex, [TiCl4(C17H16NP)], (IV), containing a rearranged neutral ligand in which the N-bound H atom moves to one of the pyrrole C atoms, giving a partially unsaturated ring. [source]


[cis -{,2 -(Ph3PAu)2}Ph3PCr(CO)4]·THF, featuring the shortest known separation between two Au metal centres in a heteronuclear Au2M cluster

ACTA CRYSTALLOGRAPHICA SECTION C, Issue 7 2003
Mat­thias W. Esterhuysen
The title compound, tetra­carbonyl-1,4C -tris­(tri­phenyl­phos­phino)-1,P,2,P,3,P - triangulo -chromiumdigold(Au,Au)(2 Cr,Au) tetra­hydro­furan solvate, [Au2Cr(C18H15P)3(CO)4]·C4H8O, is a stable isolobal analogue of the extremely labile [(,2 -H2)CrLn,1] molecular hydrogen complex (n = 6; L is a neutral ligand, e.g. CO or PPh3), and features the shortest known separation [2.6937,(2),Å] between two Au atoms in a triangular heteronuclear metal-cluster framework. [source]


Flow-through partial-filling affinity capillary electrophoresis can estimate binding constants of neutral ligands to receptors via a competitive assay technique

ELECTROPHORESIS, Issue 6 2003
John Kaddis
Abstract This work evaluates the use of a competitive binding assay using flow-through partial-filling affinity capillary electrophoresis (FTPFACE) to estimate binding constants of neutral ligands to a receptor. We demonstrate this technique using, as a model system, carbonic anhydrase B (CAB, EC 4.2.1.1) and arylsulfonamides. In this technique, the capillary is first partially filled with a negatively charged ligand, a sample containing CAB and two noninteracting standards, and a neutral ligand, then electrophoresed. Upon application of a voltage the sample plug migrates into the plug of negatively charged ligand (L,) resulting in the formation of a CAB-L, complex. Continued electrophoresis results in mixing between the neutral ligand (L0) and the CAB-L, complex. L0 successfully competes out L, to form the new CAB-L0 complex. Analysis of the change in the relative migration time ratio (RMTR) of CAB relative to the noninteracting standards, as a function of neutral ligand concentration, yields a value for the binding constant. These values are in agreement with those estimated using other binding and ACE techniques. Data demonstrating the quantitative potential of this method is presented. [source]


New Coordination Modes of L -Ascorbic Acid and Dehydro- L -ascorbic Acid as Dianionic Chelating Ligand for Platinum

EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 4 2008
Paola Bergamini
Abstract A variety of coordination modes of L -ascorbic acid as an anionic bidentate ligand has been exploited to prepare platinum(II) complexes 1,7 that contain phosphanes or R,R -dach (1R,2R -diaminocyclohexane) as neutral ligands in which O2, O3, O5, O6 and C2 act as anionic donating functionalities. An alternative synthetic route to known O2,O3 complexes is proposed, and their solubility in water has been enhanced by introducing PTA (1,3,5-triaza-7-phosphaadamantane) as a neutral ligand. A new coordination mode of ascorbic acid (O2 and O3 protected) as an O5,O6-diolate chelating ligand has been characterised in solution by NMR spectroscopy and in the solid state by X-ray crystallography. The first example of a platinum complex that contains dehydroascorbic acid, 7, has also been prepared and its X-ray crystal structure has been determined. The antiproliferative activity in vitro of complexes 1,7 has been tested, and the best values were obtained for the DHA complex 7, which was found to be more active than cisplatin on both a cisplatin-sensitive and a cisplatin-resistant cell line.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008) [source]


Tetrahedral CoII Complexes with CoI2O2 and CoO2S2 Cores , Crystal Structures of [Co{HN(OPPh2)(SPPh2)- O}2I2] and [Co{N(OPPh2)(SPPh2)- O,S}2]

EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 29 2007
M. Carla Aragoni
Abstract The compound [CoII{HN(OPPh2)(SPPh2)- O}2I2] (1) was synthesised by the reaction of cobalt in powder with the iodine adduct of tetraphenylthiooxoimidodiphosphinic acid, HN(OPPh2)(SPPh2), in Et2O; treatment of compound 1 with NaOH resulted in deprotonation of the ligands bound to the metal ion and a separation of [CoII{N(OPPh2)(SPPh2)- O,S}2] (2). Molecular structures of complexes 1 and 2 were elucidated by X-ray diffraction analysis, which revealed a CoI2O2 tetrahedral core for compound 1 in which two neutral ligands bind through the oxygen atoms the CoII ion, and a tetrahedral CoO2S2 core for compound 2 with the oxygen and sulfur atoms of each anionic ligand chelating a CoII centre. Variable-temperature magnetic susceptibility measurements are consistent with tetrahedral high-spin (S = 3/2) CoII that possesses a 4A2 ground state with best fit parameters g = 2.25, |D| = 12.0 cm,1 and g = 2.37, |D| = 11.9 cm,1 for complexes 1 and 2, respectively. The compounds were further characterised by UV/Vis and IR spectroscopy. DFT calculations were performed on model complexes [CoII{N(OPH2)(SPH2)- O,S}2] (3) and [CoII{N(SPH2)2 - S,S,}2] (4) to compare the electronic properties of the CoO2S2 and CoS4 cores. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007) [source]


A New Synthesis of Charge-Neutral Tris-Pyrazolyl and -Methimazolyl Borate Ligands

CHEMISTRY - A EUROPEAN JOURNAL, Issue 9 2010
Philip
Abstract The dimethylamine in the adducts [(HNMe2)B(azolyl)3] (azolyl=methimazolyl, pyrazolyl), obtained by reaction of the azole with B(NMe2)3, can readily be substituted with a range of nitrogen donors to provide new charge-neutral, tripodal ligands in high yield. This observation has led to a revision of an earlier interpretation of the mechanism of the formation of these species. The donor properties of the ligands [(nmi)B(azolyl)3] (nmi=N -methylimidazole) have been compared with their anionic analogues [HB(azolyl)3], by synthesis of their manganese(I),tricarbonyl complexes and comparison of their infrared ,CO energies. This comparison indicates that the new neutral ligands are only marginally weaker donors than the corresponding anionic hydrotris(azolyl)borate ligands. This may be explained by the ability of the attached nmi ring to stabilize a positive charge remotely from the coordinated metal, which may also account for the fact that the [(nmi)B(pyrazolyl)3] ligand is a substantially stronger donor than the similarly neutral tris(pyrazolyl)methane ligand. [source]


Electrophilic Attack on Sulfur,Sulfur Bonds: Coordination of Lithium Cations to Sulfur-Rich Molecules Studied by Ab Initio MO Methods

CHEMISTRY - A EUROPEAN JOURNAL, Issue 4 2005
Yana Steudel Dr.
Abstract Complex formation between gaseous Li+ ions and sulfur-containing neutral ligands, such as H2S, Me2Sn (n = 1,5; Me = CH3) and various isomers of hexasulfur (S6), has been studied by ab initio MO calculations at the G3X(MP2) level of theory. Generally, the formation of LiSn heterocycles and clusters is preferred in these reactions. The binding energies of the cation in the 29 complexes investigated range from ,88 kJ,mol,1 for [H2SLi]+ to ,189 kJ,mol,1 for the most stable isomer of [Me2S5Li]+ which contains three-coordinate Li+. Of the various S6 ligands (chair, boat, prism, branched ring, and triplet chain structures), two isomeric complexes containing the S5S ligand have the highest binding energies (,163±1 kJ,mol,1). However, the global minimum structure of [LiS6]+ is of C3v symmetry with the six-membered S6 homocycle in the well-known chair conformation and three LiS bonds with a length of 256 pm (binding energy: ,134 kJ,mol,1). Relatively unstable isomers of S6 are stabilized by complex formation with Li+. The interaction between the cation and the S6 ligands is mainly attributed to ion,dipole attraction with a little charge transfer, except in cations containing the six sulfur atoms in the form of separated neutral S2, S3, or S4 units, as in [Li(S3)2]+ and [Li(S2)(S4)]+. In the two most stable isomers of the [LiS6]+ complexes, the number of SS bonds is at maximum and the coordination number of Li+ is either 3 or 4. A topological analysis of all investigated complexes revealed that the LiS bonds of lengths below 280 pm are characterized by a maximum electron-density path and closed-shell interaction. [source]