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Linfeng Rao - One of the best experts on this subject based on the ideXlab platform.
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interactions of bis 2 4 4 trimethylpentyl dithiophosphinate with trivalent lanthanides in a homogeneous medium thermodynamics and coordination modes
Inorganic Chemistry, 2017Co-Authors: Taoxiang Sun, Linfeng RaoAbstract:Complexation of trivalent lanthanides with a sulfur-bearing ligand, bis(2,4,4-trimethylpentyl) dithiophosphinate, was studied in ethanol under identical conditions by optical spectroscopy, microcalorimetry, luminescence lifetime measurement, and extended X-ray absorption fine structure (EXAFS). Three successive complexes, LnL2+, LnL2+, and LnL3, where Ln and L denote the trivalent lanthanide and the dithiophosphinate ligand, respectively, formed in the solution. In contrast to the general findings that heavier lanthanides form stronger complexes due to the lanthanide contraction effect, the Complexation strength between Ln(III) and dithiophosphinate first increases from La(III) to Nd(III) and then decreases gradually toward heavier Ln(III) across the lanthanide series. This trend agrees well with the results of solvent extraction using the same ligand as an extractant. The Complexation is driven by highly positive entropies and opposed by endothermic enthalpies. The enthalpies of Complexation become less ...
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interactions of bis 2 4 4 trimethylpentyl dithiophosphinate with ndiii and cmiii in a homogeneous medium a comparative study of thermodynamics and coordination modes
Chemistry: A European Journal, 2014Co-Authors: Linfeng RaoAbstract:Complexation of Nd(III) and Cm(III) with purified Cyanex301 (ammonium bis(2,4,4-trimethylpentyl)dithiophosphinate, denoted as HL) was studied in 1 % v/v water/ethanol under identical conditions by spectrophotometry and microcalorimetry. For Nd(III) , three successive complexes, NdL(2+) , NdL2 (+) , and NdL3 , formed in the solution. In contrast, four complexes, CmL(2+) , CmL2 (+) , CmL3 , and CmL4 (-) formed during the titration with Cm. Fluorescence lifetime measurements provided additional insight into the Complexation of Cm(III) with Cyanex301. The stepwise stability constants for the CmLj ((3-j)+) (j=1-3) complexes are about one order of magnitude higher than the corresponding NdLj ((3-j)+) complexes. The enthalpies of Complexation are endothermic for both Nd(III) and Cm(III) , suggesting that the energy required for desolvation exceeds the energy gained from the cation/ligand combination. Specifically, the enthalpy of Complexation for CmL(2+) is 3.5 kJ mol(-1) less endothermic than that of NdL(2+) , implying stronger covalent interaction in CmL(2+) than NdL(2+) . However, the enthalpies of Complexation for CmL2 (+) and NdL2 (+) are nearly identical, and the enthalpy of Complexation for CmL3 (aq) becomes more endothermic than that for NdL3 (aq). The observations suggest that, in the ethanol/water media, the overall energetics of the Cm(III) /Nd(III) Complexation with Cyanex301 could depend on a number of factors, including the extent of covalency, the degree of desolvation, and the coordination modes.
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Complexation of u vi with dipicolinic acid thermodynamics and coordination modes
Inorganic Chemistry, 2013Co-Authors: Guoxin Tian, Simon J Teat, Linfeng RaoAbstract:Complexation of UO2(2+) with dipicolinic acid (DPA) has been investigated in 0.1 M NaClO4. The stability constants (log β1 and log β2) for two successive complexes, UO2L and UO2L2(2-) where L(2-) stands for the deprotonated dipicolinate anion, were determined to be 10.7 ± 0.1 and 16.3 ± 0.1 by spectrophotometry. The enthalpies of Complexation (ΔH1 and ΔH2) were measured to be -(6.9 ± 0.2) and -(28.9 ± 0.5) kJ·mol(-1) by microcalorimetry. The entropies of Complexation (ΔS1 and ΔS2) were calculated accordingly to be (181 ± 3) and (215 ± 4) J·K(-1)·mol(-1). The strong Complexation of UO2(2+) with DPA is driven by positive entropies as well as exothermic enthalpies. The crystal structure of Na2UO2L2(H2O)8(s) shows that, in the 1:2 UO2(2+)/DPA complex, the U atom sits at a center of inversion and the two DPA ligands symmetrically coordinate to UO2(2+) via its equatorial plane in a tridentate mode. The structural information suggests that, due to the conjugated planar structure of DPA with the donor atoms (the pyridine nitrogen and two carboxylate oxygen atoms) arranged at optimal positions to coordinate with UO2(2+), little energy is required for the preorganization of the ligand, resulting in strong UO2(2+)/DPA Complexation.
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Complexation of lactate with neodymium iii and europium iii at variable temperatures studies by potentiometry microcalorimetry optical absorption and luminescence spectroscopy
Inorganic Chemistry, 2010Co-Authors: Guoxin Tian, Leigh R Martin, Linfeng RaoAbstract:Complexation of Lactate with Nd(III) and Eu(III) at Variable Temperatures: Studies by Potentiometry, Microcalorimetry, Optical Absorption and Luminescence Spectroscopy Guoxin Tian, 1 Leigh R. Martin, 2 Linfeng Rao *,1 Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA Aqueous Separations and Radiochemistry Department, Idaho National Laboratory, PO Box 1625, Idaho Falls, ID 83415, USA Abstract Complexation of neodymium(III) and europium(III) with lactate was studied at variable temperatures by potentiometry, absorption spectrophotometry, luminescence spectroscopy and microcalorimetry. Stability constants of three successive lactate complexes (ML 2+ , ML 2+ and ML 3 (aq), where M stands for Nd and Eu, and L stands for lactate) at 10, 25, 40, 55 and 70oC were determined. The enthalpies of Complexation at 25oC were determined by microcalorimetry. Thermodynamic data show that the Complexation of trivalent lanthanides (Nd 3+ and Eu 3+ ) with lactate is exothermic, and the Complexation becomes weaker at higher temperatures. Results from optical absorption and luminescence spectroscopy suggest that the complexes are inner-sphere chelate complexes in which the protonated α-hydroxyl group of lactate participates in the Complexation. Key Words: Neodymium, Europium, Lactate, Complexation, Temperature effect To whom correspondence should be addressed. E-mail: LRao@lbl.gov
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thermodynamic study of the Complexation of uranium vi with nitrate at variable temperatures
The Journal of Chemical Thermodynamics, 2008Co-Authors: Linfeng Rao, Guoxin TianAbstract:Abstract Complexation of uranium(VI) with nitrate was studied at variable temperatures by spectrophotometry and microcalorimetry. The Complexation is weak and the stability constant of a 1:1 complex, UO 2 NO 3 + , was found to slightly increase as the temperature was increased from 25 to 70 °C. The molar enthalpy of Complexation at 25 °C was determined by microcalorimetry to be small and positive, (3.9 ± 0.5) kJ · mol−1, in good agreement with the trend in the stability constant at different temperatures. Discussions were made on topics including weak Complexation vs. ionic medium effect and outer sphere vs. inner sphere complexes. Specific ion interaction (SIT) approach was used to obtain the stability constants at infinite dilution and variable temperatures.
Marcus E Brewster - One of the best experts on this subject based on the ideXlab platform.
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characterization of the interaction of 2 hydroxypropyl β cyclodextrin with itraconazole at ph 2 4 and 7
Journal of Pharmaceutical Sciences, 2002Co-Authors: Jef Peeters, Peter Neeskens, Jan P Tollenaere, Pieter Van Remoortere, Marcus E BrewsterAbstract:Abstract Phase‐solubility techniques were used to assess the effect of pH on itraconazole Complexation with 2‐hydroxypropyl‐β‐cyclodextrin (HPβCD). In addition, molecular modeling using β‐cyclodextrin as a surrogate for HPβCD was completed. Data suggested A p ‐type solubility relationships, indicating higher order Complexation at higher HPβCD concentrations. Stability constants were derived from the solubility isotherms using a simplex optimization procedure. At pH 2 (2 units below the p K a4 ), a 1:2 complex formation was observed, whereas at pH 4 (i.e., the p K a4 for itraconazole) and at pH 7, 1:3 Complexation occurred. The lower order of Complexation observed at lower pH may be related to substructure protonation which reduced HPβCD interaction. Molecular mechanics also suggest 1:3 complex formation for the neutral species, indicating that possible interaction sites may include (in order of binding) triazole > 1,4‐diaminophenyl > 2‐butyl ≊ piperazine.
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characterization of the interaction of 2 hydroxypropyl β cyclodextrin with itraconazole at ph 2 4 and 7
Journal of Pharmaceutical Sciences, 2002Co-Authors: Jef Peeters, Peter Neeskens, Jan P Tollenaere, Pieter Van Remoortere, Marcus E BrewsterAbstract:Phase-solubility techniques were used to assess the effect of pH on itraconazole Complexation with 2-hydroxypropyl-beta-cyclodextrin (HPbetaCD). In addition, molecular modeling using beta-cyclodextrin as a surrogate for HPbetaCD was completed. Data suggested A(p)-type solubility relationships, indicating higher order Complexation at higher HPbetaCD concentrations. Stability constants were derived from the solubility isotherms using a simplex optimization procedure. At pH 2 (2 units below the pK(a4)), a 1:2 complex formation was observed, whereas at pH 4 (i.e., the pK(a4) for itraconazole) and at pH 7, 1:3 Complexation occurred. The lower order of Complexation observed at lower pH may be related to substructure protonation which reduced HPbetaCD interaction. Molecular mechanics also suggest 1:3 complex formation for the neutral species, indicating that possible interaction sites may include (in order of binding) triazole > 1,4-diaminophenyl > 2-butyl approximate, equals piperazine.
Vladislav Tomišić - One of the best experts on this subject based on the ideXlab platform.
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solvation effect on Complexation of alkali metal cations by a calix 4 arene ketone derivative
Journal of Physical Chemistry B, 2017Co-Authors: Josip Požar, Ivana Niksicfranjic, Marija Cvetnic, Katarina Leko, Ivana Borilovic, Nikola Cindro, Leo Frkanec, Katarina Pičuljan, Vladislav TomišićAbstract:The medium effect on the Complexation of alkali metal cations with a calix[4]arene ketone derivative (L) was systematically examined in methanol, ethanol, N-methylformamide, N,N-dimethylformamide, dimethyl sulfoxide, and acetonitrile. In all solvents the binding of Na+ cation by L was rather efficient, whereas the Complexation of other alkali metal cations was observed only in methanol and acetonitrile. Complexation reactions were enthalpically controlled, while ligand dissolution was endothermic in all cases. A notable influence of the solvent on NaL+ complex stability could be mainly attributed to the differences in Complexation entropies. The higher NaL+ stability in comparison to complexes with other alkali metal cations in acetonitrile was predominantly due to a more favorable Complexation enthalpy. The 1H NMR investigations revealed a relatively low affinity of the calixarene sodium complex for inclusion of the solvent molecule in the calixarene hydrophobic cavity, with the exception of acetonitrile...
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Synthesis of Fluorescent Diphenylanthracene-Based Calix[4]arene Derivatives and their Complexation with Alkali Metal Cations
'Croatian Chemical Society', 2017Co-Authors: Marina Tranfić Bakić, Katarina Leko, Nikola Cindro, Josip Požar, Leo Frkanec, Tomislav Portada, Tomica Hrenar, Gordan Horvat, Vladislav TomišićAbstract:Two novel fluorescent calix[4]arenes comprising diphenylanthracene moiety at the lower rim were synthetized and their Complexation with alkali metal cations in acetonitrile/dichloromethane and methanol/dichloromethane mixtures (φ = 0.5) was studied experimentally and by classical molecular dynamics and quantum chemical calculations. The monosubstituted calixarene derivative (L1) proved to be a poor cation receptor, whereas the ester-based macrocycle (L2) exhibited rather high affinity towards lithium, sodium and potassium cations, particularly in MeCN/CH2Cl2. All Complexation reactions were enthalpically controlled, whereby the overall stability was the largest in the case of sodium complex. The computational investigations provided an additional insight into the Complexation properties and structures of complex species. The molecular dynamics simulations indicated the occurrence of inclusion of solvent molecules in the calixarene hydrophobic cavity of the free and complexed ligand, which was found to significantly affect the Complexation equilibria. This work is licensed under a Creative Commons Attribution 4.0 International License
Taoxiang Sun - One of the best experts on this subject based on the ideXlab platform.
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interactions of bis 2 4 4 trimethylpentyl dithiophosphinate with trivalent lanthanides in a homogeneous medium thermodynamics and coordination modes
Inorganic Chemistry, 2017Co-Authors: Taoxiang Sun, Linfeng RaoAbstract:Complexation of trivalent lanthanides with a sulfur-bearing ligand, bis(2,4,4-trimethylpentyl) dithiophosphinate, was studied in ethanol under identical conditions by optical spectroscopy, microcalorimetry, luminescence lifetime measurement, and extended X-ray absorption fine structure (EXAFS). Three successive complexes, LnL2+, LnL2+, and LnL3, where Ln and L denote the trivalent lanthanide and the dithiophosphinate ligand, respectively, formed in the solution. In contrast to the general findings that heavier lanthanides form stronger complexes due to the lanthanide contraction effect, the Complexation strength between Ln(III) and dithiophosphinate first increases from La(III) to Nd(III) and then decreases gradually toward heavier Ln(III) across the lanthanide series. This trend agrees well with the results of solvent extraction using the same ligand as an extractant. The Complexation is driven by highly positive entropies and opposed by endothermic enthalpies. The enthalpies of Complexation become less ...
Jef Peeters - One of the best experts on this subject based on the ideXlab platform.
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characterization of the interaction of 2 hydroxypropyl β cyclodextrin with itraconazole at ph 2 4 and 7
Journal of Pharmaceutical Sciences, 2002Co-Authors: Jef Peeters, Peter Neeskens, Jan P Tollenaere, Pieter Van Remoortere, Marcus E BrewsterAbstract:Abstract Phase‐solubility techniques were used to assess the effect of pH on itraconazole Complexation with 2‐hydroxypropyl‐β‐cyclodextrin (HPβCD). In addition, molecular modeling using β‐cyclodextrin as a surrogate for HPβCD was completed. Data suggested A p ‐type solubility relationships, indicating higher order Complexation at higher HPβCD concentrations. Stability constants were derived from the solubility isotherms using a simplex optimization procedure. At pH 2 (2 units below the p K a4 ), a 1:2 complex formation was observed, whereas at pH 4 (i.e., the p K a4 for itraconazole) and at pH 7, 1:3 Complexation occurred. The lower order of Complexation observed at lower pH may be related to substructure protonation which reduced HPβCD interaction. Molecular mechanics also suggest 1:3 complex formation for the neutral species, indicating that possible interaction sites may include (in order of binding) triazole > 1,4‐diaminophenyl > 2‐butyl ≊ piperazine.
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characterization of the interaction of 2 hydroxypropyl β cyclodextrin with itraconazole at ph 2 4 and 7
Journal of Pharmaceutical Sciences, 2002Co-Authors: Jef Peeters, Peter Neeskens, Jan P Tollenaere, Pieter Van Remoortere, Marcus E BrewsterAbstract:Phase-solubility techniques were used to assess the effect of pH on itraconazole Complexation with 2-hydroxypropyl-beta-cyclodextrin (HPbetaCD). In addition, molecular modeling using beta-cyclodextrin as a surrogate for HPbetaCD was completed. Data suggested A(p)-type solubility relationships, indicating higher order Complexation at higher HPbetaCD concentrations. Stability constants were derived from the solubility isotherms using a simplex optimization procedure. At pH 2 (2 units below the pK(a4)), a 1:2 complex formation was observed, whereas at pH 4 (i.e., the pK(a4) for itraconazole) and at pH 7, 1:3 Complexation occurred. The lower order of Complexation observed at lower pH may be related to substructure protonation which reduced HPbetaCD interaction. Molecular mechanics also suggest 1:3 complex formation for the neutral species, indicating that possible interaction sites may include (in order of binding) triazole > 1,4-diaminophenyl > 2-butyl approximate, equals piperazine.