Structure of the copper(II) complex of 1,4,10,13-tetraoxa-7,16-diazacyclooctadecane-7,16-diacetic acid

Uechi, Tetsuo; Ueda, I.; Tazaki, Masato; Takagi, Masaaki; Ueno, Keiji

doi:10.1107/s0567740882003124

Cited by 24 publications

(8 citation statements)

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“…[17] In this type of coordination, the metal-macrocycle binding gives rise to the formation of three five-membered rings and one 11-membered chelate ring (the corresponding number is shown in black on Scheme 2) in addition to the two five-membered chelate rings with the pendant sidearms (the corresponding number in red on Scheme 2). In contrast, the complexes formed by L5 [4,16] [15] (L1, Scheme 1) with Cu 2+ ions display symmetric structures. In this case, the metal-macrocycle binding gives rise to the forScheme 2.…”

Section: +mentioning

confidence: 84%

“…For instance, in the case of disubstituted diaza [18]crown-6 ethers, the six-membered chelate rings (and beyond) tend to form binuclear complexes, [6,7] whereas the five-membered chelate rings lead to mononuclear complexes in the presence of non-coordinating counterion. [4,[15][16][17][18] In the present study, we focus on mononuclear complexes formed by the N,NЈ-disubstituted diaza [18]crown-6 and diaza [15]crown-5 macrocyclic compounds with first-row transition-metal ions (Cu 2+ , Ni 2+ , Zn 2+ ) and, specifically, [4,16] Zn 2+ acetate / L5 / N 2 O 4 octahedral / asymmetric [17] Cu 2+ / ClO 4 -(1-benzyl-1H-1,2,3-triazol-4-yl)methyl / L1 / N 4 O 2 octahedral / symmetric [15] N,NЈ-Disubstituted diaza [15]crown-5…”

Section: Introductionmentioning

confidence: 97%

“…[3] Moreover, selective coordination of particular cations depends on the dimension of the macrocyclic ring (type, number, and position of complexing heteroatoms, and so on) and the stereochemistry imposed by the arms. In previous works, it has been shown that the diaza [18]crown-6 ether is a versatile receptor that is able to adapt to the coordination preferences of the particular metal cation, [4][5][6][7][8][9] whereas the diaza [15]crown-5 ether has been revealed to be a receptor that imposes seven-coordination around the metal ion. [8,[10][11][12][13][14] The size of chelate rings formed upon coordination of the pendant arms to the metal ion influences the nuclearity of the complexes.…”

Section: Introductionmentioning

confidence: 99%

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Evolution of the Coordination‐Sphere Symmetry in Copper(II), Nickel(II), and Zinc(II) Complexes with N,N′‐Double‐Armed Diaza‐Crown Ethers: Experimental and Theoretical Approaches

et al. 2014

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crown-6 ligand were determined by means of X-ray crystallography. The Ni II complex is centrosymmetric; the geometry around the metal ion is slightly distorted octahedral whereby the equatorial sites were occupied by four N atoms, and the axial positions by two O atoms that come from the crown moiety. For the Zn IIdiaza[18]crown-6 complex, an irregular octahedral coordination was observed whereby the metal ion is asymmetrically placed in the macrocyclic cavity. The equatorial plane is occupied by two N and two O atoms of the crown moiety, and two N atoms of the triazolyl motifs on the pendant arms occupy the axial positions. The diamagnetic character of the Zn II ion allows its structural study in solution by NMR spectroscopy. A dynamic behavior was observed at room tem-

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Section: +mentioning

confidence: 84%

Section: Introductionmentioning

confidence: 97%

Section: Introductionmentioning

confidence: 99%

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Evolution of the Coordination‐Sphere Symmetry in Copper(II), Nickel(II), and Zinc(II) Complexes with N,N′‐Double‐Armed Diaza‐Crown Ethers: Experimental and Theoretical Approaches

et al. 2014

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“…This implies that the ion binding process ignores whether the donor comes from the tartro units or the N-acetates. Cooperative chelate interactions are also a dominant feature in the solid state chemistry of the oxa crown ethers (38), and can be seen in the published structures of 2.2D2 copper complexes (18)(19)(20). We are therefore tempted to ascribe the energy differences noted above to the difference between five-membered chelate rings containing 0 vs. N as donors in the unit X-C-C02-.…”

Section: Electrostatic Ion Binding and Chelate Interactionsmentioning

confidence: 99%

“…At least one of the parent ligands, 2.2D2, is capable of achieving a chelate geometry similar to that found in simple aminopolycarboxylate complexones. The crystal structures of two copper complexes of 2.2D2 (18)(19)(20) show encapsulated Cu2+ held in a geometry similar to a glycinate or EDTA complex. The ligand is relatively undistorted and the majority of the torsion angles are close to normal values for crown ether complexes, Moreover, the units which would be occupied by carboxylates from the tartaric acid residues are in open positions about the complex.…”

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confidence: 99%

Polycarboxylate diaza crown ethers derived from R,R-(+)-tartaric acid: synthesis and complexation of metal ions

Anantanarayan¹,

Fyles²

1990

Can. J. Chem.

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ASHOK ANANTANARAYAN and THOMAS M. FYLES. Can. J. Chem. 68, 1338 (1990.The synthesis and complexation properties of polycarboxylate diaza crown ethers based on R,R-(+)-tartaric acid are described. Cesium carbonate mediated macrocyclization of a bis-tosylamide precursor with a bis-tosylate precursor provided the protected crown ethers. Photochemical deprotection of the tosylamides and hydrolysis of the carboxamides yielded dicarboxylic and tetracarboxylic acid derivatives of 1, lO-diaza-18-crown-6. N-Methylenecarboxylate (N-acetate) derivatives were prepared by N-alkylation with bromoacetic acid. The synthetic and purification procedures developed provide samples of the ligands in a metal-free form. Acidity and stability constants for complexation of alkali metal, alkaline earth, late-and post-transition metal cations were determined by potentiometric titration. The ligands form complexes which show enhancement of stability by charge-charge and chelate interaction with the carboxylates. In comparison with crown ether polycarboxylates these aza crown ethers showed a selectivity for softer metal ions relative to alkali and alkaline earth metal ions. N-Methylenecarboxylate chelate ligands were found to bind almost all types of metal ions, due to a highly co-operative array of charge-charge, chelate and crown ether interactions. Metal ion recognition by synthetic and naturally occurring ligands is a complex process involving a cooperative match of the complementary properties of the host and the guest. A key factor in the design of new ligands with unique complexation behaviors is the choice of ligand donor sites (1). Within a class of ligands, such as the crown ethers or cryptands, clear changes in selectivity of cation binding are provoked by substitution of the oxygen donors of a parent ring system for nitrogen or sulfur donor sites (2). Such substitutions alter the primary character of the donor (Lewis basicity) as well as the geometrical and conformational properties of the ligand (3). Thus in a system involving highly cooperative binding interactions, donor atom substitution can profoundly influence binding selectivity.Our interest in ligand design has centered on crown ethers derived from R,R-(+)-tartaric acid: the di-, tetra-, and hexaacids illustrated at the top of Fig. 1 (4-6). The tartarate derived units impart rigidity to the ligands, leading to well defined conformations, and the carboxylates, when ionized, provide a strong electrostatic field which greatly enhances complex stability for alkali metal and alkaline earth cations. Despite the favorable Coulombic interactions, binding of heavy metal cations occurs only to a limited extent due to a mismatch of the hard oxygen donor set and the softer guest cations (6). An obvious ligand modification which might lead to stabilized crown ether type complexes of heavier cations would be the substitution of some of the donor atoms for N or S. We have previously reported dithia crown ethers bearing four carboxylates (7); the purpose of this report is to describe th...

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Solution and Solid-State Characterization of EuII Chelates: A Possible Route Towards Redox Responsive MRI Contrast Agents

et al. 2000

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We report the first solid state X-ray crystal structure for a Eu(II) chelate, [C(NH2)3]3[Eu(II)(DTPA)(H2O)].8H2O, in comparison with those for the corresponding Sr analogue, [C(NH2)3]3[Sr(DTPA)(H2O).8H2O and for [Sr(ODDA)].8H2O (DTPA5 = diethylenetriamine-N,N,N',N",N"-pentaacetate, ODDA2- =1,4,10,13-tetraoxa-7,16-diazacyclooctadecane-7,16-diacetate ). The two DTPA complexes are isostructural due to the similar ionic size and charge of Sr(2+) and Eu(2+). The redox stability of [Eu(II)(ODDA)(H2O)] and [Eu(II)(ODDM)]2- complexes has been investigated by cyclovoltammetry and UV/Vis spectrophotometry (ODDM4- =1,4,10,13-tetraoxa-7,16-diaza-cyclooctadecane-7,16-++ +dimalonate). The macrocyclic complexes are much more stable against oxidation than [Eu(II)(DTPA)(H2O)]3- (the redox potentials are E1/2 =-0.82 V, -0.92 V, and -1.35 V versus Ag/AgCl electrode for [Eu(III/II)(ODDA)(H2O)],[Eu(III/II)(ODDM)], and [Eu(III/II)(DTPA)(H2O)], respectively, compared with -0.63 V for Eu(III/II) aqua). The thermodynamic stability constants of [Eu(II)(ODDA)(H2O)], [Eu(II)(ODDM)]2-, [Sr(ODDA)(H2O)], and [Sr(ODDM)]2- were also determined by pH potentiometry. They are slightly higher for the EuII complexes than those for the corresponding Sr analogues (logK(ML)=9.85, 13.07, 8.66, and 11.34 for [Eu(II)(ODDA)(H2O)], [Eu(II)(ODDM)]2-, [Sr(ODDA)(H2O)], and [Sr(ODDM)]2-, respectively, 0.1M (CH3)4NCl). The increased thermodynamic and redox stability of the Eu(II) complex formed with ODDA as compared with the traditional ligand DTPA can be of importance when biomedical application is concerned. A variable-temperature 17O-NMR and 1H-nuclear magnetic relaxation dispersion (NMRD) study has been performed on [Eu(II)(ODDA)(H2O)] and [Eu(II)(ODDM)]2- in aqueous solution. [Eu(II)(ODDM)]2- has no inner-sphere water molecule which allowed us to use it as an outer-sphere model for [Eu(II)(ODDA)(H2O)]. The water exchange rate (k298(ex)= 0.43 x 10(9)s(-1)) is one third of that obtained for [Eu(II)(DTPA)(H2O)]3-. The variable pressure 17O-NMR study yielded a negative activation volume, deltaV (not=) = -3.9cm3mol(-1); this indicates associatively activated water exchange. This water exchange rate is in the optimal range to attain maximum proton relaxivities, which are, however, strongly limited by the fast rotation of the small molecular weight complex.

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Structure of the copper(II) complex of 1,4,10,13-tetraoxa-7,16-diazacyclooctadecane-7,16-diacetic acid

Cited by 24 publications

References 4 publications

Evolution of the Coordination‐Sphere Symmetry in Copper(II), Nickel(II), and Zinc(II) Complexes with N,N′‐Double‐Armed Diaza‐Crown Ethers: Experimental and Theoretical Approaches

Evolution of the Coordination‐Sphere Symmetry in Copper(II), Nickel(II), and Zinc(II) Complexes with N,N′‐Double‐Armed Diaza‐Crown Ethers: Experimental and Theoretical Approaches

Polycarboxylate diaza crown ethers derived from R,R-(+)-tartaric acid: synthesis and complexation of metal ions

Solution and Solid-State Characterization of EuII Chelates: A Possible Route Towards Redox Responsive MRI Contrast Agents

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