scholarly journals Helicate-to-tetrahedron transformation of chiral lanthanide supramolecular complexes induced by ionic radii effect and linker length

2021 ◽  
Vol 4 (1) ◽  
Author(s):  
King-Him Yim ◽  
Chi-Tung Yeung ◽  
Michael R. Probert ◽  
Wesley Ting Kwok Chan ◽  
Lewis E. Mackenzie ◽  
...  
Keyword(s):  
Ligand Design ◽  
Lanthanide Ions ◽  
Supramolecular Complexes ◽  
Special Focus ◽  
Coordination Geometry ◽  
Ionic Radii ◽  
Tetrahedral Structure ◽  
Linker Length ◽  
Species Formation ◽  
Polarized Luminescence

AbstractControlled formation of desired lanthanide supramolecular complexes is challenging because of the difficulties in predicting coordination geometry, as well as a labile coordination number. Herein, we explore the effect of ionic radii and linker length on supramolecular species formation. A helicate-to-tetrahedron transformation occurred between [Ln2L13] and [Ln4L16] (Ln = La, Sm, Eu, Gd, Tb and Lu). For six lanthanide ions, the unfavored tetrahedron [La4L16] can only be observed in a concentrated mixture with the helicate [La2L13] where no pure [La4L16] species was isolated via crystallization. For Sm, Eu, Gd, Tb, the [Ln4L16] supramolecular tetrahedron can be isolated via crystallization from diisopropyl ether. A similar result was also observed for Lu, but the tetrahedral structure was found to be relatively stable and transformed back to [Lu2L13] much slower upon dissolution.  No tetrahedron formation was observed with L3 giving rise to only [Ln2L33] species, in which L3 contains a longer and more flexible linker compared with that of L1. Results show that the supramolecular transformation in these systems is governed by both the ionic radii as well as the ligand design. Special focus is on both [Eu2L13] and [Eu4L16] which form chiral entities and exhibit interesting circular polarized luminescence.

scholarly journals Interactions of tervalent lanthanide ions with bacterial collagenase (clostridiopeptidase A)

1981 ◽  
Vol 195 (3) ◽  
pp. 677-684 ◽  
Author(s):  
Christopher H. Evans
Keyword(s):  
Ionic Radius ◽  
Substrate Inhibition ◽  
Volume Ratio ◽  
Binding Pocket ◽  
Lanthanide Ions ◽  
Ionic Radii ◽  
Apparent Dissociation Constant ◽  
Substrate Complex ◽  
Bacterial Collagenase ◽  
Hydrolysis Of

Tervalent cations of the lanthanide (rare-earth) elements reversibly inhibit bacterial collagenase (clostridiopeptidase A; EC 3.4.24.3). Sm3+, whose ionic radius is closest to that of Ca2+, is the most effective inhibitor, completely suppressing clostridiopeptidase activity at a concentration of 100μm in the presence of 5mm-Ca2+. Er3+ and Lu3+, which both have ionic radii smaller than either Ca2+ or Sm3+, inhibit less efficiently, and La3+, which is slightly larger than Ca2+ or Sm3+, inhibits only weakly. These findings indicate a closely fitting, stereospecific, Ca2+-binding pocket in clostridiopeptidase, which excludes ions that are only slightly larger than Ca2+ [ionic radius 0.099nm (0.99 Ȧ)]. By contrast, trypsin, an enzyme whose activity does not depend on Ca2+, requires lanthanide concentrations 50–100-fold greater for inhibition. Furthermore, the relative efficiency of inhibition of trypsin by lanthanides increases as the lanthanide ions become smaller and the charge/volume ratio increases. At a concentration of 50μm, Sm3+ lowers the apparent Km for the hydrolysis of Pz-peptide by clostridiopeptidase from 5.4mm to 0.37mm and the apparent Vmax. from 0.29 Wünsch–Heidrich unit to 0.018 unit. Thus Sm3+ enhances the affinity of this enzyme for its substrate; inhibition of hydrolysis of Pz-peptide may result from the excessive stability of the enzyme–Sm3+–substrate complex. Inhibition by Sm3+ is competitive with regard to Ca2+. The apparent dissociation constant, Kd, of Ca2+ is 0.27mm, where the Ki for Sm3+ is 12μm. Clostridiopeptidase is more thermolabile in the absence of Ca2+. With Sm3+, thermoinactivation of the enzyme at 53°C or 60°C is initially accelerated, but then becomes retarded as heating continues. Lanthanide ions bind to gelatin and collagen. In so doing, they appear to protect these substrates from lysis by clostridiopeptidase through mechanisms additional to supplanting Ca2+ at its binding site on the enzyme. Collagen and gelatin sequester sufficient lanthanide ions to gain partial protection from clostridiopeptidase in the absence of an extraneous source of these inhibitors.

scholarly journals The origins of binding specificity of a lanthanide ion binding peptide

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
Takaaki Hatanaka ◽  
Nobuaki Kikkawa ◽  
Akimasa Matsugami ◽  
Yoichi Hosokawa ◽  
Fumiaki Hayashi ◽  
...  
Keyword(s):  
Water Molecule ◽  
Ionic Radius ◽  
Binding Specificity ◽  
Lanthanide Ions ◽  
Ion Binding ◽  
Deep Insight ◽  
Ionic Radii ◽  
Linear Peptide ◽  
High Affinity ◽  
Insight Into

Abstract Lanthanide ions (Ln3+) show similar physicochemical properties in aqueous solutions, wherein they exist as + 3 cations and exhibit ionic radii differences of less than 0.26 Å. A flexible linear peptide lanthanide binding tag (LBT), which recognizes a series of 15 Ln3+, shows an interesting characteristic in binding specificity, i.e., binding affinity biphasically changes with an increase in the atomic number, and shows a greater than 60-fold affinity difference between the highest and lowest values. Herein, by combining experimental and computational investigations, we gain deep insight into the reaction mechanism underlying the specificity of LBT3, an LBT mutant, toward Ln3+. Our results clearly show that LBT3-Ln3+ binding can be divided into three, and the large affinity difference is based on the ability of Ln3+ in a complex to be directly coordinated with a water molecule. When the LBT3 recognizes a Ln3+ with a larger ionic radius (La3+ to  Sm3+), a water molecule can interact with Ln3+ directly. This extra water molecule infiltrates the complex and induces dissociation of the Asn5 sidechain (one of the coordinates) from Ln3+, resulting in a destabilizing complex and low affinity. Conversely, with recognition of smaller Ln3+ (Sm3+ to Yb3+), the LBT3 completely surrounds the ions and constructs a stable high affinity complex. Moreover, when the LBT3 recognizes the smallest Ln3+, namely Lu3+, although it completely surrounds Lu3+, an entropically unfavorable phenomenon specifically occurs, resulting in lower affinity than that of Yb3+. Our findings will be useful for the design of molecules that enable the distinction of sub-angstrom size differences.

Heterobimetallische 3d-4f-Komplexe mit Bis(1,2-dithiooxalato)nickelat(II) als planarem Brückenbaustein / Heterobimetallic 3d-4f-Complexes with Bis(1,2-dithiooxalato)nickelate(II) as Planar Bridging Block

2005 ◽  
Vol 60 (11) ◽  
pp. 1149-1157 ◽  
Author(s):  
Matthias Siebold ◽  
Alexandra Kelling ◽  
Uwe Schilde ◽  
Peter Strauch
Keyword(s):  
Room Temperature ◽  
Magnetic Moments ◽  
Lanthanide Ions ◽  
Water Molecules ◽  
Unit Cell Parameters ◽  
Ionic Radii ◽  
X Ray ◽  
Cell Parameters ◽  
Heterobimetallic Complexes ◽  
The Individual

Planar bis(1,2-dithiooxalato)nickelates(II) react in aqueous solutions of lanthanide ions to form pentanuclear, heterobimetallic complexes of the general composition [{Ln(H2O)n}2- {Ni(dto)2}3]・xH2O (Ln = Y3+, La3+, Ce3+, Pr3+, Nd3+, Sm3+, Eu3+, Gd3+, Tb3+, Dy3+, Ho3+, Er3+, Tm3+, Yb3+, Lu3+; n = 4 or 5; x = 9 - 12). With [{Nd(H2O)5}2{Ni(S2C2O2)2}3]・xH2O (x = 10 - 12) (1) and [{Er(H2O)4}2{Ni(S2C2O2)2}3]・xH2O (x = 9 - 10) (2) we were able to isolate two complexes of this series as single crystals, which were characterized by X-ray structure analysis. Depending on the individual ionic radii of the lanthanide ions, the compounds crystallize in two different crystal systems with the following unit cell parameters: 1, monoclinic in P21/c with a = 11.3987(13), b = 11.4878(8), c = 20.823(2) Å , β = 98.907(9)° and Z = 2; 2, triclinic in P1̅ with a = 10.5091(6), b = 11.0604(6), c = 11.2823(6) Å , α = 107.899(4)°, β = 91.436(4)°, γ = 112.918(4)° and Z = 1. The channels and cavities appearing in the packing of the molecules are occupied by uncoordinated water molecules. High magnetic moments up to 14.65 BM./f.u. have been observed at room temperature due to the combined moments of the individual lanthanide ions.

Superoonductivity in the R3CaBa3Cu7Oy System with R = Lanthanide

1992 ◽  
Vol 275 ◽  
Author(s):  
H. -C. I. Kao ◽  
J. L. Wang ◽  
R. J. Huang ◽  
C. M. Wang ◽  
M. K. Wu
Keyword(s):  
Single Phase ◽  
Perovskite Phase ◽  
Hole Concentration ◽  
Residual Resistivity ◽  
Lanthanide Ions ◽  
Similar Process ◽  
Oxygen Stoichiometry ◽  
Nominal Composition ◽  
Second Phase ◽  
Ionic Radii

ABSTRACTA series of samples with a nominal composition of R3CaBa3Cu7Oy (abbreviated as R3137), where R = Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er and Tm, was prepared by a similar process as for an 80-K superconductor, La3CaBa3Cu7Oy. Most of the R3137 (except for R = Ce, Tb) had a tetragonal triple-perovskite phase like La3137 identified from the XRD patterns, and they were superconducting except Pr3137. For R3+ radius larger than Dy3+ (0.908 Å), a single phase R3137 was observed, and their Tc(zero)' probably related to the rCu-o distance in the copper-oxygen layer, was spread from 85 to 76 K with a maximum for the Eu3137. Oxygen stoichiometry of these R3137 was slightly decreased with decreasing lanthanide radii. The hole concentration, (Cu-O), was found between 0.47 and 0.38/unit cell. For Smaller R3+ ions, residual resistivity was found in the superconducting samples due to the existence of second phase. From the structural study of La3137, it was known that part of the lanthanide ions had to be fitted into the bigger Ba-site. Because ionic radii of the heavy lanthanides (R3+ < Ho3+ = 0.894 Å) were too small to be located at the Ba-site, it was rather difficult to prepare these single phase R3137.

Lanthanide-Induced Shifts in the 13C N.M.R. Spectra of epi-Inositol and Some Anhydrohexoses. The Anomalous Behaviour of the Heavy Lanthanides

1985 ◽  
Vol 38 (3) ◽  
pp. 411 ◽  
Author(s):  
SJ Angyal ◽  
L Littlemore ◽  
PAJ Gorin
Keyword(s):  
Anomalous Behaviour ◽  
Lanthanide Ions ◽  
Ionic Radii ◽  
Lanthanide Induced Shifts ◽  
Heavy Lanthanides

The shifts induced in the 13C n.m.r . spectrum of epi-inositol by the addition of various lanthanide ions have been determined and have been analysed in terms of contact and pseudocontact interactions. The behaviour of the three heavy lanthanides was found to be anomalous, probably owing to their smaller ionic radii and their lesser extent of hydration. Similar measurements have also been carried out on four 1,6- anhydro-β-D-hexopyranoses.

scholarly journals Crystal structures of two isotypic lanthanide(III) complexes: triaqua[2,6-diacetylpyridine bis(benzoylhydrazone)]methanollanthanide(III) trichloride methanol disolvates (Ln III = Tb and Dy)

2018 ◽  
Vol 74 (4) ◽  
pp. 535-538 ◽  
Author(s):  
Chihiro Kachi-Terajima ◽  
Norihisa Kimura
Keyword(s):  
Hydrogen Bonds ◽  
Crystal Structures ◽  
Lanthanide Complexes ◽  
Three Dimensional ◽  
Lanthanide Ions ◽  
Water Molecules ◽  
Coordination Geometry ◽  
Lanthanide Ion ◽  
Π Interactions ◽  
Coordinated Water

The title lanthanide complexes, [Ln(DAPBH2)(CH3OH)(H2O)3]Cl3·2CH3OH [Ln III = Tb and Dy; DAPBH2 = 2,6-diacetylpyridine bis(benzoylhydrazone), C23H21N5O2], are isotypic. The central lanthanide ions are nine-coordinate, being ligated by three N and two O atoms from the pentadentate DAPBH2 ligand, and four O atoms from the coordinated methanol molecule and three coordinated water molecules. The coordination geometry of the lanthanide ion is a distorted capped square antiprism. In the crystals, the various components are linked by O—H...Cl, N—H...Cl and O—H...O hydrogen bonds, forming three-dimensional supramolecular frameworks. Within the frameworks, there are C—H...Cl and C—H...O hydrogen bonds and offset π–π interactions (intercentroid distance ca 3.81 Å).

Study ofAandBsites order in lanthanide-doped lead titanate ferroelectric system

2016 ◽  
Vol 31 (1) ◽  
pp. 23-30
Author(s):  
A. Pentón-Madrigal ◽  
Y. Mendez-González ◽  
A. Peláiz-Barranco ◽  
F. Calderón-Piñar ◽  
L. A. S. de Oliveira ◽  
...  
Keyword(s):  
Lead Titanate ◽  
Perovskite Structure ◽  
Ionic Radius ◽  
Phonon Mode ◽  
Lanthanide Ions ◽  
X Ray Diffraction ◽  
Ionic Radii ◽  
Optical Phonon Mode ◽  
Rietveld Refinements ◽  
X Ray

Pb0.88Ln0.08TiO3ferroelectric system, whereLn= La, Sm, Eu, and Dy, has been characterized using Scanning Electron Microscopy, Raman spectroscopy, and X-ray diffraction experiments. Softening of the lowest transverse optical phonon modeE(1TO) was evaluated as a function of the rare earths’ ionic radius suggesting partial occupation of lanthanide ions at theAandBsites of the perovskite structure. Using Rietveld refinements, it has been established a higher incorporation of Ln3+ions into theAsites of the perovskite structure than that of theBsites for the studied ceramics. The occupation atBsites increases slightly with the decreases of the ionic radii of the lanthanides.

Alginate Polyelectrolyte Ionotropic Gels-XVI. Kinetics and Chemical Equilibria Studies for Heterogeneous Ion Exchange of Polyvalent Metal Ions in Alginate Gel Complexes

1992 ◽  
Vol 4 (3) ◽  
pp. 173-179 ◽  
Author(s):  
S. A. El-Shatoury ◽  
R. M. Hassan ◽  
A. A. Said
Keyword(s):  
Ionic Strength ◽  
Ion Exchange ◽  
Metal Ions ◽  
Thermodynamic Parameters ◽  
Coordination Geometry ◽  
Ionic Radii ◽  
Chemical Equilibria ◽  
Polyvalent Metal ◽  
Alginate Gel ◽  
Counter Ions

The kinetics or chemical equilibria of exchange of Ca(II), Sr(II), Ba(I), Zn(II), Cd(II), Al(III), Fe(III), Se(IV), Ce(IV) and Th(IV) counter ions in alginate gel complexes by H+ ions have been investigated titrimetrically and conductimetrically at a constant ionic strength of 0.1 mol/dm3. The thermodynamic parameters have been evaluated and are discussed in terms of ionic radii and polarizability of the metal ions, coordination geometry, and stability of the gel complexes.

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