14 research outputs found
Metal Ion Complexes of N,Nâ˛-Bis(2-Pyridylmethyl)-trans-1,2-Diaminocyclohexane-N,Nâ˛-Diacetic Acid, H2bpcd: Lanthanide(III)âbpcd2â Cationic Complexes
The synthesis and characterization of N,Nâ˛-bis(2-pyridylmethyl)-trans-1,2-diaminocyclohexane-N,Nâ˛-diacetic acid (H2bpcd) cationic complexes of La(III), Nd(III), and Sm(III) are reported. The Ln(III)âbpcd2â complex ions, where bpcd2â stands for N,Nâ˛-bis(2-pyridylmethyl)-trans-1,2-diaminocyclohexane-N,Nâ˛-diacetate, were isolated as PF6â salts. These salts were characterized by elemental analysis, X-ray crystallography, IR, and 1H and 13C NMR spectroscopy. Binuclear [La2(bpcd)2(H2O)2]2+ crystallized from an aqueous solution in the monoclinic P21/c space group as a cocrystallate with Na2bpcd and NaPF6, nominally Na2.34[La1.22(C22H26N4O4)2(H2O)2][PF6]2¡2H2O, with a = 11.3343(6) Ă
, b = 17.7090(9) Ă
, c = 15.0567(8) Ă
, β = 110.632(3)°, and Z = 4 (ZⲠ= 2). La is eight-coordinate with distorted dodecahedral coordination geometry provided by a N4O4 donor atom set. In addition to four N atoms from the bpcd2â ligand, Laâs coordination sphere includes O atoms from a water molecule and three acetate groups (one O atom from singly bound acetate and two O atoms from acetate groups that bridge the La centers). The 1H and 13C assignments for H2bpcd and the metalâbpcd2â complexes were made on the basis of 2D COSY and HSQC experiments, which established 1Hâ1H and 1Hâ13C correlations. The NMR spectral data were used to establish the symmetry of the cationic complexes present in aqueous solution. The data indicate that the La(III)âbpcd2â and Sm(III)âbpcd2â complexes are present in solution as a single species with C2 symmetry. The 1H NMR spectrum of [Nd(bpcd)]PF6 in D2O consists of eight considerably line-broadened, paramagnetic-shifted singlets. The ab initio quantum mechanical calculations at the PCM/MP2/SDD//HF/SDD level, which were established previously for determining isomerization energies for octahedral M(III)âbpad2â complex ions, were used to determine the relative free energies of the geometric isomers possible for eight- and nine-coordinate La(III)âbpcd2â cationic aqua complexes in aqueous solution, i.e., [La(bpcd)(H2O)2]+ and La(bpcd)(H2O)3]+
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Supercritical Carbon Dioxide Ligands for Extracting Actinide Metal Ions from Porous Solids
Numerous types of actinide-bearing waste materials are found throughout the DOE complex. Most of these wastes consist of large volumes of non-hazardous materials contaminated with relatively small quantities of actinide elements. Separation of these wastes into their inert and radioactive components would dramatically reduce the costs of stabilization and disposal. For example, the DOE is responsible for decontaminating concrete within 7000 surplus contaminated buildings. The best technology now available for removing surface contamination from concrete involves removing the surface layer by grit blasting, which produces a large volume of blasting residue containing a small amount of radioactive material. Disposal of this residue is expensive because of its large volume and fine particulate nature. Considerable cost savings would result from separation of the radioactive constituents and stabilization of the concrete dust. Similarly, gas diffusion plants for uranium enrichment contain valuable high-purity nickel in the form of diffusion barriers. Decontamination is complicated by the extremely fine pores in these barriers, which are not readily accessible by most cleaning techniques. A cost-effective method for the removal of radioactive contaminants would release this valuable material for salvage
Crystal structure of {2,2â˛-[N,Nâ˛-bis(pyridin-2-ylmethyl)cyclohexane-trans-1,2-diyldi(nitrilo)]diacetato}cobalt(III) hexafluoridophosphate
The title compound [Co(C22H26N4O4)]PF6, commonly known as [Co(bpcd)]PF6, where bpcd2â is derived from the historical ligand name N,Nâ˛-bis(2-pyridylmethyl)-trans-1,2-diaminocyclohexane-N,Nâ˛-diacetate, crystallized by slow evaporation of a saturated acetonitrile solution in air. The cation of the hexafluoridophosphate salt has the CoIII atom in a distorted octahedral coordination geometry provided by an N4O2 donor atom set. The acetate groups, which are oriented trans with respect to each other, exhibit monodentate coordination whereas the pyridyl N atoms are coordinating in a cis configuration. The geometry of the cation is compared to the geometries of other diamino diacetate complexes with CoIII
{2,2\u27-[N,N\u27-Bis(pyridin-2-ylmethÂyl)propane-1,3-diyldi(nitrilo)]diÂacetato}Âcobalt(III) hexaÂfluoridophosphate acetoÂnitrile 0.064-solvate
In the title compound, [Co(C19H22N4O4)]PF6¡0.064CH3CN, commonly known as [Co(bppd)]PF6¡0.064CH3CN, where bppd represents the historical ligand name N,N\u27-bis(2-pyridylmethyl)-1,3-diaminopropane-N,N\u27-diacetate, the CoIII atom is coordinated in a distorted octaÂhedral geometry with an N4O2 donor atom set. The acetate O atoms, which exhibit monodentate coordination, are oriented in a trans configuration with respect to each other, whereas the pyridyl N atoms are coordinated in a cis configuration. The compound crystallizes with two crystallographically unique cations and two anions per asymmetric unit along with a disordered, partially occupied (occupancy = 0.128) acetoÂnitrile solvent molÂecule. Crystals of the title complex were found to be twinned by pseudomerohedry with a 180° rotation around [10-1] and a refined contribution of 90.5 (3)% of the major twin component
Metal Ion Complexes of <i>N,N</i>â˛âBis(2-Pyridylmethyl)-1,3-Diaminopropane-<i>N,N</i>â˛âDiacetic Acid, H<sub>2</sub>bppd
A higher yield synthesis of <i>N,N</i>â˛-bisÂ(2-pyridylmethyl)-1,3-diaminopropane-<i>N,N</i>â˛-diacetic acid (H<sub>2</sub>bppd) and its complexation
of trivalent metal ions (AlÂ(III), GaÂ(III), InÂ(III)) and selected lanthanides
(LnÂ(III)) are reported. H<sub>2</sub>bppd and the metalâbppd<sup>2â</sup> complexes, isolated as hexafluorophosphate salts,
were characterized by elemental analysis, mass spectrometry, IR, and <sup>1</sup>H and <sup>13</sup>C NMR spectroscopy. [GaÂ(bppd)]ÂPF<sub>6</sub>, [GaÂ(C<sub>19</sub>H<sub>22</sub>N<sub>4</sub>O<sub>4</sub>)]ÂPF<sub>6</sub>, was crystallized as colorless needles by slow evaporation
from anhydrous methanol; its molecular structure was solved by direct
X-ray crystallography methods. The compound crystallized in the monoclinic
space group <i>P</i>2<sub>1</sub>/<i>c</i>, with <i>a</i> = 9.6134(2) Ă
, <i>b</i> = 20.2505(4) Ă
, <i>c</i> = 11.6483(3) Ă
, β = 97.520(1)<sup>o</sup>,
and <i>Z</i> = 4. Ga is coordinated in a distorted octahedral
geometry provided by a N<sub>4</sub>O<sub>2</sub> donor atom set with
cis-monodentate acetate groups and <i>cis</i>-2-pyridylmethyl
N atoms. Quantum mechanical calculations were performed for the three
possible geometric isomers of a pseudo-octahedral metalâbppd<sup>2â</sup> complex with five different metal ions. The results
indicate, that in aqueous solution, the stability of the <i>trans</i>-O,O isomer is similar to that of the <i>cis</i>-O,O; <i>cis</i>-N<sub>py</sub>,N<sub>py</sub> isomer but is greater
than that of the <i>trans</i>-N<sub>py</sub>,N<sub>py</sub> isomer. Calculations for a six-coordinate LaÂ(III)-bppd<sup>2â</sup> complex converge to a structure with a very large N<sub>py</sub>âLaâN<sub>py</sub> bond angle (146.4°), a high
metal charge (2.28 au), and a high solvation free energy (â79.4
kcal/mol). The most stable geometric arrangement for bppd<sup>2â</sup> around the larger LaÂ(III) is best described as an open nestlike
structure with space available for additional ligands. IR spectroscopy
was used to investigate the nature of the H<sub>2</sub>bppdâmetal
complexes isolated in the solid state and the binding modes of the
carboxylate functionalities. The spectra indicate that fully deprotonated
[MÂ(bppd)]<sup>+</sup> complexes as well as partially protonated complexes
[MÂ(Hbppd)ÂCl]<sup>+</sup> were isolated. The <sup>1</sup>H and <sup>13</sup>C assignments for H<sub>2</sub>bppd and metalâbppd<sup>2â</sup> complexes were made on the basis of 2D COSY, NOESY,
and <sup>1</sup>Hâ<sup>13</sup>C HSQC experiments, which were
used to differentiate among the cis (<i>C</i><sub>1</sub> symmetry) and the two trans (<i>C</i><sub>2</sub> symmetry)
isomers
Metal Ion Complexes of <i>N,N</i>â˛âBis(2-Pyridylmethyl)-<i>trans</i>-1,2-Diaminocyclohexane-<i>N,N</i>â˛âDiacetic Acid, H<sub>2</sub>bpcd: Lanthanide(III)âbpcd<sup>2â</sup> Cationic Complexes
The synthesis and
characterization of <i>N,N</i>â˛-bisÂ(2-pyridylmethyl)-<i>trans</i>-1,2-diaminocyclohexane-<i>N,N</i>â˛-diacetic
acid (H<sub>2</sub>bpcd) cationic complexes of LaÂ(III), NdÂ(III), and
SmÂ(III) are reported. The LnÂ(III)âbpcd<sup>2â</sup> complex
ions, where bpcd<sup>2â</sup> stands for <i>N,N</i>â˛-bisÂ(2-pyridylmethyl)-<i>trans</i>-1,2-diaminocyclohexane-<i>N,N</i>â˛-diacetate, were isolated as PF<sub>6</sub><sup>â</sup> salts. These salts were characterized by elemental
analysis, X-ray crystallography, IR, and <sup>1</sup>H and <sup>13</sup>C NMR spectroscopy. Binuclear [La<sub>2</sub>(bpcd)<sub>2</sub>(H<sub>2</sub>O)<sub>2</sub>]<sup>2+</sup> crystallized from an aqueous
solution in the monoclinic <i>P</i>2<sub>1</sub>/<i>c</i> space group as a cocrystallate with Na<sub>2</sub>bpcd
and NaPF<sub>6</sub>, nominally Na<sub>2.34</sub>[La<sub>1.22</sub>(C<sub>22</sub>H<sub>26</sub>N<sub>4</sub>O<sub>4</sub>)<sub>2</sub>(H<sub>2</sub>O)<sub>2</sub>]Â[PF<sub>6</sub>]<sub>2</sub>¡2H<sub>2</sub>O, with <i>a</i> = 11.3343(6) Ă
, <i>b</i> = 17.7090(9) Ă
, <i>c</i> = 15.0567(8) Ă
, β
= 110.632(3)°, and <i>Z</i> = 4 (<i>Z</i>Ⲡ= 2). La is eight-coordinate with distorted dodecahedral
coordination geometry provided by a N<sub>4</sub>O<sub>4</sub> donor
atom set. In addition to four N atoms from the bpcd<sup>2â</sup> ligand, Laâs coordination sphere includes O atoms from a
water molecule and three acetate groups (one O atom from singly bound
acetate and two O atoms from acetate groups that bridge the La centers).
The <sup>1</sup>H and <sup>13</sup>C assignments for H<sub>2</sub>bpcd and the metalâbpcd<sup>2â</sup> complexes were
made on the basis of 2D COSY and HSQC experiments, which established <sup>1</sup>Hâ<sup>1</sup>H and <sup>1</sup>Hâ<sup>13</sup>C correlations. The NMR spectral data were used to establish the
symmetry of the cationic complexes present in aqueous solution. The
data indicate that the LaÂ(III)âbpcd<sup>2â</sup> and
SmÂ(III)âbpcd<sup>2â</sup> complexes are present in solution
as a single species with <i>C</i><sub>2</sub> symmetry.
The <sup>1</sup>H NMR spectrum of [NdÂ(bpcd)]ÂPF<sub>6</sub> in D<sub>2</sub>O consists of eight considerably line-broadened, paramagnetic-shifted
singlets. The ab initio quantum mechanical calculations at the PCM/MP2/SDD//HF/SDD
level, which were established previously for determining isomerization
energies for octahedral MÂ(III)âbp<i>a</i>d<sup>2â</sup> complex ions, were used to determine the relative free energies
of the geometric isomers possible for eight- and nine-coordinate LaÂ(III)âbpcd<sup>2â</sup> cationic aqua complexes in aqueous solution, i.e.,
[LaÂ(bpcd)Â(H<sub>2</sub>O)<sub>2</sub>]<sup>+</sup> and LaÂ(bpcd)Â(H<sub>2</sub>O)<sub>3</sub>]<sup>+</sup>
Metal Ion Complexes of <i>N,N</i>â˛âBis(2-Pyridylmethyl)-<i>trans</i>-1,2-Diaminocyclohexane-<i>N,N</i>â˛âDiacetic Acid, H<sub>2</sub>bpcd: Lanthanide(III)âbpcd<sup>2â</sup> Cationic Complexes
The synthesis and
characterization of <i>N,N</i>â˛-bisÂ(2-pyridylmethyl)-<i>trans</i>-1,2-diaminocyclohexane-<i>N,N</i>â˛-diacetic
acid (H<sub>2</sub>bpcd) cationic complexes of LaÂ(III), NdÂ(III), and
SmÂ(III) are reported. The LnÂ(III)âbpcd<sup>2â</sup> complex
ions, where bpcd<sup>2â</sup> stands for <i>N,N</i>â˛-bisÂ(2-pyridylmethyl)-<i>trans</i>-1,2-diaminocyclohexane-<i>N,N</i>â˛-diacetate, were isolated as PF<sub>6</sub><sup>â</sup> salts. These salts were characterized by elemental
analysis, X-ray crystallography, IR, and <sup>1</sup>H and <sup>13</sup>C NMR spectroscopy. Binuclear [La<sub>2</sub>(bpcd)<sub>2</sub>(H<sub>2</sub>O)<sub>2</sub>]<sup>2+</sup> crystallized from an aqueous
solution in the monoclinic <i>P</i>2<sub>1</sub>/<i>c</i> space group as a cocrystallate with Na<sub>2</sub>bpcd
and NaPF<sub>6</sub>, nominally Na<sub>2.34</sub>[La<sub>1.22</sub>(C<sub>22</sub>H<sub>26</sub>N<sub>4</sub>O<sub>4</sub>)<sub>2</sub>(H<sub>2</sub>O)<sub>2</sub>]Â[PF<sub>6</sub>]<sub>2</sub>¡2H<sub>2</sub>O, with <i>a</i> = 11.3343(6) Ă
, <i>b</i> = 17.7090(9) Ă
, <i>c</i> = 15.0567(8) Ă
, β
= 110.632(3)°, and <i>Z</i> = 4 (<i>Z</i>Ⲡ= 2). La is eight-coordinate with distorted dodecahedral
coordination geometry provided by a N<sub>4</sub>O<sub>4</sub> donor
atom set. In addition to four N atoms from the bpcd<sup>2â</sup> ligand, Laâs coordination sphere includes O atoms from a
water molecule and three acetate groups (one O atom from singly bound
acetate and two O atoms from acetate groups that bridge the La centers).
The <sup>1</sup>H and <sup>13</sup>C assignments for H<sub>2</sub>bpcd and the metalâbpcd<sup>2â</sup> complexes were
made on the basis of 2D COSY and HSQC experiments, which established <sup>1</sup>Hâ<sup>1</sup>H and <sup>1</sup>Hâ<sup>13</sup>C correlations. The NMR spectral data were used to establish the
symmetry of the cationic complexes present in aqueous solution. The
data indicate that the LaÂ(III)âbpcd<sup>2â</sup> and
SmÂ(III)âbpcd<sup>2â</sup> complexes are present in solution
as a single species with <i>C</i><sub>2</sub> symmetry.
The <sup>1</sup>H NMR spectrum of [NdÂ(bpcd)]ÂPF<sub>6</sub> in D<sub>2</sub>O consists of eight considerably line-broadened, paramagnetic-shifted
singlets. The ab initio quantum mechanical calculations at the PCM/MP2/SDD//HF/SDD
level, which were established previously for determining isomerization
energies for octahedral MÂ(III)âbp<i>a</i>d<sup>2â</sup> complex ions, were used to determine the relative free energies
of the geometric isomers possible for eight- and nine-coordinate LaÂ(III)âbpcd<sup>2â</sup> cationic aqua complexes in aqueous solution, i.e.,
[LaÂ(bpcd)Â(H<sub>2</sub>O)<sub>2</sub>]<sup>+</sup> and LaÂ(bpcd)Â(H<sub>2</sub>O)<sub>3</sub>]<sup>+</sup>
Metal Ion Complexes of <i>N,N</i>â˛âBis(2-Pyridylmethyl)-<i>trans</i>-1,2-Diaminocyclohexane-<i>N,N</i>â˛âDiacetic Acid, H<sub>2</sub>bpcd: Cis/Trans Isomerization Equilibria
The
synthesis of <i>N,N</i>â˛-bisÂ(2-pyridylmethyl)-<i>trans</i>-1,2-diaminocyclohexane-<i>N,N</i>â˛-diacetic
acid (H<sub>2</sub>bpcd) and its complexation of GaÂ(III) and CoÂ(III)
are reported. H<sub>2</sub>bpcd and the metalâbpcd<sup>2â</sup> complexes, isolated as hexafluorophosphate salts, were characterized
by elemental analysis, X-ray crystallography, IR spectroscopy, and <sup>1</sup>H and <sup>13</sup>C NMR spectroscopy. [GaÂ(bpcd)]ÂPF<sub>6</sub>, [GaÂ(C<sub>22</sub>H<sub>26</sub>N<sub>4</sub>O<sub>4</sub>)]ÂPF<sub>6</sub>, crystallized in the orthorhombic space group <i>Ibca</i>, with <i>a</i> = 13.8975(7) Ă
, <i>b</i> = 15.0872(7) Ă
, <i>c</i> = 22.2418(10) Ă
, and <i>Z</i> = 8. Ga is coordinated in a distorted octahedral geometry
provided by a N<sub>4</sub>O<sub>2</sub> donor atom set with <i>trans</i>-monodentate acetate groups and <i>cis</i>-2-pyridylmethyl N atoms, i.e., the <i>trans</i>-O,O isomer.
The diamagnetic [CoÂ(bpcd)]ÂPF<sub>6</sub>, [CoÂ(C<sub>22</sub>H<sub>26</sub>N<sub>4</sub>O<sub>4</sub>)]ÂPF<sub>6</sub>, also crystallized
from solution in the <i>Ibca</i> space group as the <i>trans</i>-O,O isomer. The <sup>1</sup>H and <sup>13</sup>C assignments
for H<sub>2</sub>bpcd and metalâbpcd<sup>2â</sup> complexes
were made on the basis of 2D COSY and HSQC experiments, which were
used to differentiate among three possible isomers, i.e., one cis
(<i>C</i><sub>1</sub> symmetry) and two trans (<i>C</i><sub>2</sub> symmetry). NMR results indicate that the [GaÂ(bpcd)]<sup>+</sup>, [CoÂ(bpcd)]<sup>+</sup>, and <i>cis</i>-O,O, <i>cis</i>-N<sub>py</sub>,N<sub>py</sub>-[GaÂ(bppd)]<sup>+</sup> cations, where bppd<sup>2â</sup> stands for bisÂ(2-pyridylmethyl)-1,3-diaminopropane
diacetate, are present in solution as isomers with the same symmetry
as observed in the solid state. The crystallographic data and the
dramatic shift that occurs in the position of the cis/trans isomerization
equilibria for the [GaÂ(bpad)]<sup>+</sup> cations simply by increasing
the number of bridging CH<sub>2</sub> groups in the ligandâs
diamine backbone represent a unique opportunity to assess the accuracy
of modern computational methods. The performance of several local
density functionals using a pseudopotential-based SDD basis set was
compared with the more rigorous HF and MP2 ab initio calculations.
The SVWN5 and SV5LYP functionals provide significantly better GaâO
and GaâN distances than the HF method or the nonlocal BLYP
functional. However, to provide proper isomerization energies the
pseudopotential-DFT calculations must be augmented by MP2 single-point
energies and calculations of solvation free energies