Octadentate Ligand Research Articles

Derivate des Hydrazins als Liganden in Vanadium(IV)- und -(V)-Komplexen. Darstellung und Struktur dreier dimerer Verbindungen mit Hydrazido- und Hydrazonato-Liganden / D erivatives of H ydrazine as Ligands in V anadium (IV ) and -(V) Complexes. Synthesis and Crystal Structures of Three D im eric C om plexes with H ydrazido and H ydrazonato Ligands

Abstract The complexes [(μ-PhCONNCOPh){VOCl(NHNHCOPh)}2 ·5CH3CN, (1), [(μ-PhCONNCOPh){V(dbh)}2]-2CH3CN, (2) and [{VO}2(tbh)], (3) have been prepared by reaction of VCl2(acac)2, acac = acetylaceto n a to (l-), and VCl2(acpn), acpn = propylendiim ino-bis(acetylacetonato(2-)), with benzoylhydrazine. The structures of the centrosymmetric dimeric molecules 1 -3 have been determined by single crystal X-ray diffraction. 1 and 2 contain both doubly deprotonated N,N′-dibenzoylhydrazine as bridging, doubly N,O chelating ligand. In 1 the two remaining coordination sites at the VOCl group are occupied by the hydrazid o(1-) ligand [NHNHCOPh]- . 2 is a non-oxo vanadium(IV) complex. The coordination geometry is approximately trigonal prismatic. The π-back donating effect of the oxo function is substituted by back donation from three negatively charged enolic oxygen atoms. The V - O bond lengths range from 192.0(2) to 193.7(2) pm. 3 contains a unique highly symmetrical octadentate ligand, formed during the synthesis. It is coordinated to two oxovanadin(IV) centers by N,O chelation. The coordination geometry is square pyramidal.

Polyamine synthesis and co-ordination: structural characterisation of cobalt(III) complexes from an octadentate ligand preparation

The nature of the two principal products of the reaction between pentaerythritol [2,2-bis(hydroxymethyl)propane-1,3-diol] tetrabenzenesulfonate and ethane-1,2-diamine (en) has been confirmed by crystal-structure determinations on their cobalt(III) complexes, the less abundant species, 5,5-bis(4-amino-2-azabutyl)-3,7-diazanonane-1,9-diamine, L1, being characterised in its bis(quadridentate) form in a green, tetrachloro, binuclear complex, and the more abundant 6,6-bis(4-amino-2-azabutyl)-1,4-diazacycloheptane, L2, in a form where the ring nitrogen atoms are uncoordinated, as a green, mononuclear trans dichlorotetramine complex. Compounds L1 and L2 have also been characterised in various forms produced when these dichloro complexes are treated with en. In green [trans-Cl2CoL1CoCl2-trans]CI2·4H2O 1, the binuclear cation has quasi-2 symmetry about the central carbon atom of the ligand which embraces the two cobalt atoms each bound equatorially by four N atoms; Co–Cl(trans) 2.234(8)–2.251(7) and Co–N 1.92(2)–1.99(2)A. In one isomer of the mixed-ligand complexes of L1 and en, structurally characterised both as the chloride [(en)CoL1Co(en)]Cl6·≈ 7H2O 2a, and as the nitrate [(en)CoL1Co(en)][NO3]6·6H2O 2b, the cation also has approximate 2 symmetry, broken significantly only by differing conformations of the two en ligands in 2a; Co–N 1.957(7)–1.986(4)A. Another product of the reaction of 1 with en was the known mononuclear, orange complex [Co(H2L1)]Cl5·≈ 2.3H2O 3, where the ligand is disposed about the cobalt in a half cage, with the fourth diprotonated arm pendant from the cap; Co–N at the open end 1.977A(mean) nearer the cap 1.964A, the difference being significant. In green trans-[CoCl2(H2L2)]Cl3·≈ 3.45H2O 4, the bicyclic ligand co-ordinates the cobalt equatorially through four N atoms; Co–Cl(trans) 2.259(1) and 2.263(1)A, and Co–N (pairwise) 1.946(2), 1.948(3)A for the ‘inner’ nitrogens and 1.960(2), 1.971(2)A for the outer/terminal nitrogens. One of the immediate products of the reaction of en with 4 was [Co(en)(H2L2)]Cl5·≈ 0.6EtOH 5. In this cation the cobalt is co-ordinated by the en and both arms of ligand L2, the seven-membered ring nitrogen atoms being unco-ordinated and protonated after isolation from acidic solution; Co–N 1.95(1)–1.986(5)A. One of the products of more extended reaction between en and 4 was red [Co(en)(H2L2)]Cl5·3H2O 6, in which the ligand is diprotonated on the two nitrogen atoms of one of the ‘arms’; it co-ordinates through both nitrogen atoms of the seven-membered ring, cis in the co-ordination sphere [Co–N 1.986(4) and 2.012(4)A], the two nitrogen atoms of the other ligand arm occupying a further cis pair of sites [Co–N 1.966(4) and 1.972(4)A], with the cis pair of Co–N(en) distances being 1.975(4) and 1.981(4)A.

Synthesis and characterization of metal complexes with N, N″-bis(2-hydroxybenzyl)-diethylenetriamine- N, N′, N″-triacetic acid and the stabilities of its complexes with divalent and trivalent metal ions

The synthesis, characterization and metal ion affinities of a new multidentate ligand, N, N″-bis(2-hydroxybenzyl)-diethyl- enetriamine - N, N′, N″-triacetic acid (HBDT) are described. Protonation constants of the ligand and stability constants of its 1:1 complexes with trivalent and divalent metal ions are determined by potentiometric, spectrophotometric methods and by potentiometric determination of ligand-ligand competition. The stabilities of complexes formed by the trivalent ions Fe 3+, Ga 3+ and In 3+ with HBDT are compared with those of structurally related ligands. While this new octadentate ligand, which contains two phenolate donor groups, forms stable complexes with trivalent metal ions its stability constants are significantly lower than those of hexadentate N, N′-bis(2-hydroxybenzyl)-ethylenediamine- N, N′-diacetic acid (HBED) which also contains two phenolate donor groups. The difference is rationalized on the basis of ligand structure and the probable arrangement of donor groups around the metal center.

Aromatic polyaminocarboxylate ligands for energy transfer luminescence measurements of lanthanide ions in aqueous solutions

The promising ligand candidates for the energy transfer luminescence measurements of lanthanide (Ln) chelates on aqueous matrices are first proposed. The ligands are; 2[(2-amino-5-methyl-phenoxy)methyl]-6-methoxy-8-aminoquinoline- N,N,N′, N′-tetraacetate (Quin 2), 1,2-bis(2-amino-phenoxy)ethane- N,N,N′, N′-tetraacetate (BAPTA), and 1,2-bis(2-amino-5-fluoro-phenoxy)ethane- N,N,N′, N′-tetraacetate (F-BAPTA). The Ln-chelates of these aromatic polyaminocarboxylates show the sensitized emission which results from efficient ligand-centered light absorption, and the interesting selectivity is seen; BAPTA and F-BAPTA form the luminescent chelates only with Tb(III) and Dy(III) ions, whereas the emission from Sm(III) and Eu(III) ions is greatly sensitized with Quin 2. The sufficient emission intensity can be obtained even in slightly alkaline aqueous solutions without any addition of surfactants or organic solvents. These octadentate ligands are fairly capable of shielding central Ln ions from quenching by surrounding water molecules. The luminescence enhancement factors are 1600 for Tb(III) ion with BAPTA (em.544 nm) and 1380 for Eu(III) ion with Quin 2 (em. 615 nm), respectively, being relative to their aqueous chloride solutions.

Design of ligands containing the o-hydroxybenzyl group. Metal-complexing properties of N,N″-bis(2-hydroxybenzyl)diethylenetriamine-N,N′,N″-triacetic acid

The ligand N,N″-bis(2-hydroxybenzyl)diethylenetriamine-N,N′,N″-triacetic acid (H5L) has been synthesised and the protonation constants for L determined by potentiometric methods in 0.5 mol dm–3 NaNO3, and spectrophotometric methods in 0.5 and 0.1 mol dm–3 NaCl, all at 25 °C. The sites of protonation have been inferred from 1H NMR studies in D2O. The complex formation constants of CaII, ZnII CdII, CuII, PbII and BiIII have been determined at 25 °C by potentiometric methods in 0.5 mol dm–3 NaNO3, and spectrophotometric methods in 0.5 mol dm–3 NaCl. The results show that at biological pH the hydroxybenzyl groups tend to remain protonated, and over most of the pH range protonated complexes dominate, with fully deprotonated complexes occurring only at pH values above 9 or 10. The ligand L is, compared to some of its analogues, effectively a weak complexing agent. This is rationalised in terms of the six-membered chelate rings formed in the complex, which include the hydroxybenzyl group. The six-membered chelate rings destabilize complexes of the larger metal ions with which the octadentate ligand should prefer to co-ordinate.

An eight-coordinate cage: synthesis and structure of the first macrotricyclic tetraterephthalamide ligand

One side effect of nuclear technology is possible actinide element dispersal, which has raised concerns about low-level nuclear contamination of humans. The synthesis of a macrotricyclic tetraterephthalmide Pu(IV) sequestering agent has been prepared by high-yield tetrapod-tetrapod cyclization. The structural characterization of the methyl-protected compound, Me[sub 8]BH(2,2)CAM, is the first example of an octadentate macrotricyclic ligand. The Ce(IV) complex of the ligand has been characterized in solution by NMR. The octadentate cage ligand H[sub 8]BH(2,2)-CAM can remove 56% of Pu(IV) in contaminated mice, while its nonmacrocyclic analogue H(2,2)-MeTAM can remove up to 77% Pu(IV). These results indicate that these tetraterephthalamide ligands are potent sequestering agents for Pu(IV). The macrocyclic ligand is found to react more slowly than the open octadentate ligand; this may explain the relatively poor efficacy of H[sub 8]BH(2,2)CAM.

Short syntheses of rigid acyclic or macrocyclic poly-imine ligands and their use in Ru(II), Fe(III), and alkali metal complexation

Lipophilic derivatives of 2,6-bis(3-pyrazolyl)pyridine and 1,3-bis (3-pyrazolyl)benzene were obtained in acceptable yields by Stork reactions and transformed by N-alkylations into three pentadentates, three bis(bidentates), and one macrocyclic octadentate ligand. The parent bis(pyrazolyl) pyridine constituted a terpyridine analogue and readily formed a Ru(II) complex. By comparison of 1H nuclear magnetic resonance patterns, it was found that the alkylations in the bis(pyrazolyl)pyridine series conferred an anti,anti conformation of the imino nitrogens. The pentadentates were then able to extract alkali metal ions into CHCl3 with only modest strength and selectivity, but the preferred extraction of Li+ by one of these was notable. By variation of the reaction conditions, a tri-iron(III) and a di-iron(III) complex were obtained from a bis(bidentate).

Eight-co-ordination in manganese(II) and iron(II) complexes with a pyrazole-functionalised tetraazamacrocycle

The potentially octadentate ligand 1,4,7,10-tetrakis(pyrazol-1-ylmethyl)-1,4,7,10-tetraazacyclododecane (L) gives with manganese(II) the complex [MnL][PF6]2·(CH3)2CO and with iron(II) species of formula [FeLxL'1–x][PF6]2·solvent where the ligand L' originates from L by substitution of an ethoxy group for a pyrazolyl group in one of the pendant arms of the macrocycle. The crystal structure of [MnL][PF6]2·(CH3)2CO has been determined by X-ray diffraction: orthorhombic, space group Pcab, with a= 15.801(6), b= 17.973(4), c= 26.793(3)Å and Z= 8. The manganese(II) atom is co-ordinated by the eight nitrogen atoms of the L ligand. X-Ray analyses on the isomorphous crystals of the iron(II) species have shown that these contain both eight- and seven-co-ordinate iron(II) in complex cations respectively formed by the L and L' ligands.

Synthesis and characterization of copper(II), nickel(II), and cobalt(II) binuclear complexes with a new tricyclic octadentate ligand, 1,5,8,12,15,19,22,26-octaazatricyclo[17.9.2.25,15]dotriacontane (tcoa): trapping of carbon dioxide in a neutral aqueous solution

Synthesis and characterization of copper(II), nickel(II), and cobalt(II) binuclear complexes with a new tricyclic octadentate ligand, 1,5,8,12,15,19,22,26-octaazatricyclo[17.9.2.25,15]dotriacontane (tcoa): trapping of carbon dioxide in a neutral aqueous solution

Structure and solution stability of indium and gallium complexes of 1,4,7-triazacyclononanetriacetate and of yttrium complexes of 1,4,7,10-tetraazacyclododecanetetraacetate and related ligands: kinetically stable complexes for use in imaging and radioimmunotherapy. X-Ray molecular structure of the indium and gallium complexes of 1,4,7-triazacyclononane-1,4,7-triacetic acid

Of the four triazacycloalkanetriacetic acids screened for their ability to bind 111ln, triazacyclononanetriacetate bound indium most quickly and formed a complex whose dissociation as a function of pD was monitored by 13C NMR spectrometry using a labelled ligand (k296 1.8 × 10–1 dm3 mol–1 s–1) in the pD range 0 to –0.6. The corresponding gallium complex is even more stable with respect to acid dissociation and may be observed by 71Ga NMR spectrometry both in vitro(δGa+ 171 ppm) and in vivo. Crystal structures of the neutral gallium and of the protonated indium complexes are reported. The syntheses of a series of octadentate ligands are described and their relative efficiency to bind 90Y reported. Ligands based on tetraazacyclododecane bind 90Y most rapidly, and tetraazacyclododecanetetraacetate forms a strong complex with yttrium (log Ks 24.9, 298 K) which dissociates at low pH (< 2) as measured by HPLC and 13C NMR spectrometry.

ChemInform Abstract: A Tetraazamacrocycle Functionalized with Pendant Pyrazole Groups: Synthesis of the Octadentate Ligand 1,4,7,10‐Tetrakis(1‐pyrazolylmethyl)‐1,4,7,10‐tetraazacyclododecane (L) and Its Transformation to the Ligand 1,4,7‐Tris(1‐pyrazolylmethyl)‐10‐((ethyloxy)methyl)‐1,4,7,10‐tetraazacyclododecane (L′). Structural Characterizations of the Complexes (NiL)I2, (NiL′)(BPh4)2·2(CH3)2CO, and (ZnL′)(BPh4)2·(CH3)2CO.

AbstractThe potentially octadentate ligand (III) reacts with NiI2 to give (VIb), crystallizing in C2/c with Z=4.

Tetraazamacrocycle functionalized with pendant pyrazole groups: synthesis of the octadentate ligand 1,4,7,10-tetrakis(1-pyrazolylmethyl)-1,4,7,10-tetraazacyclododecane (L) and its transformation to the ligand 1,4,7-tris(1-pyrazolylmethyl)-10-((ethyloxy)methyl)-1,4,7,10-tetraazacyclododecane (L'). Structural characterizations of the complexes [NiL]I2, [NiL'](BPh4)2.cntdot.2(CH3)2CO, and [ZnL'](BPh4)2.cntdot.(CH3)2CO

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTTetraazamacrocycle functionalized with pendant pyrazole groups: synthesis of the octadentate ligand 1,4,7,10-tetrakis(1-pyrazolylmethyl)-1,4,7,10-tetraazacyclododecane (L) and its transformation to the ligand 1,4,7-tris(1-pyrazolylmethyl)-10-((ethyloxy)methyl)-1,4,7,10-tetraazacyclododecane (L'). Structural characterizations of the complexes [NiL]I2, [NiL'](BPh4)2.cntdot.2(CH3)2CO, and [ZnL'](BPh4)2.cntdot.(CH3)2COGuia De Martino Norante, Massimo Di Vaira, Fabrizio Mani, Stefania Mazzi, and Piero StoppioniCite this: Inorg. Chem. 1990, 29, 15, 2822–2829Publication Date (Print):July 1, 1990Publication History Published online1 May 2002Published inissue 1 July 1990https://doi.org/10.1021/ic00340a021RIGHTS & PERMISSIONSArticle Views159Altmetric-Citations32LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (997 KB) Get e-AlertsSupporting Info (1)»Supporting Information Supporting Information Get e-Alerts

ChemInform Abstract: Synthesis, Crystal Structure, and Electrochemical Properties of μ‐(2,5‐Bis(N,N‐bis(2′‐pyridylmethyl)aminomethyl)pyrazine)‐bis(chlorocopper(I# I)) Perchlorate.

AbstractThe octadentate ligand (IV) produces the complex (VI) which crystallizes in a green bis‐methanol‐solvated form (space group Pcab, Z=4) and a blue unsolvated form (P1, Z=1).

Synthesis, crystal structure, and electrochemical properties of µ-{2,5-bis[N,N-bis(2′-pyridylmethyl)aminomethyl]pyrazine}-bis[chlorocopper(II)] perchlorate

Reaction of the octadentate ligand 2,5-bis[N,N-bis(2′-pyridylmethyl)aminomethyl]pyrazine (L1) and copper(II) chloride produces a binuclear complex, which crystallized in green (1) and blue (2) forms, [Cu2L1Cl2][ClO4]2·nCH3OH [n= 2 for (1) and 0 for (2)]. The structures of the two complexes have been determined by X-ray analysis. Complex (1) crystallizes in the orthorhombic space group Pcab with a= 14.895(2), b= 19.559(3), c= 13.263(2)A, and Z= 4, and complex (2) crystallizes in the triclinic space group P with a= 10.004(1), b= 12.212(2), c= 7.791(1)A, α= 100.99(1), β= 86.26(1), γ= 111.76(1)°, and Z= 1. The complex cations in (1) and (2) have centrosymmetric binuclear structures with copper atoms in distorted trigonal-bipyramidal and square-pyramidal geometries, respectively. The electronic spectrum in acetonitrile solution revealed that the structure in solution is the same as in complex (1). E.s.r. and magnetic susceptibility data for (1) and (2) show the absence of a strong magnetic interaction between the copper atoms. The compound in acetonitrile shows a quasi-reversible cyclic voltammogram which has Epc and Epa at –0.29 and –0.13 V vs. Ag–AgCl with shoulders observable. Controlled-potential electrolysis demonstrates that the process involves the transfer of two electrons. The two-step reduction potentials leading to CuII–CuI and CuI–CuI from CuII–CuII were estimated to be –0.14 and –0.26 V, respectively, by using the width method for the ΔEp and Ep–Ep½ values.

Highly polydentate ligands. Part 4. Crystal structures of neodymium(III) and erbium(III) complexes of 3,12-bis(carboxymethyl)-6,9-dioxa-3,12-diazatetradecanedioate(4–)

The structures of calcium salts of the erbium(III) and neodymium(III) chelates of the calcium-selective octadentate ligand egta4–[H4egta = 3,12-bis(carboxymethyl)-6,9-dioxa-3,12-diazatetradecanedioic acid] have been determined, in order to identify the structural changes that occur in a calcium-selective binding site when lanthanides are substituted for calcium. Ca[Er(egta)(OH2)]2·12H2O·(CH3)2CO (1) crystallizes in the monoclinic space group P21(Z= 2), with a= 12.710(2), b= 12.157(2), c= 17.765(3)A, and β= 105.79(1)°R= 0.027, R′= 0.035. Ca[Nd(egta)(OH2)]2·9H2O (2) crystallizes in the monoclinic space group P21/c(Z= 2), with a= 10.776(2), b= 18.218(4), c= 12.560(2)A, and β= 112.14(1)°; R= 0.028, R′= 0.040. The full octadentate chelating capability of egta4– is utilized in both chelates. In contrast to the eight-co-ordinate calcium ions in [Ca(egta)]2–, the ErIII ions in (1) are nine-co-ordinate; the ninth co-ordination site is occupied by a water molecule. Of the three ligand atom types, the carboxylate oxygen atoms are bound at the shortest distance [Er–O(carboxylate)av= 2.31(3)A], followed by the ether oxygen atoms [Er–O(ether)av= 2.42(5)A], and the amine nitrogen atoms [Er–Nav= 2.57(4)A]. The NdIII ions in (2) are ten-co-ordinate; ten-co-ordination is achieved in the solid state by binding a water molecule, as well as a carboxylate oxygen atom from an adjacent complex ion The order of metal–Iigand bond distances observed for NdIII is the same as that observed for ErIII Nd–O(carboxylate)av= 2.46(1), Nd–O(ether)av= 2.67(3), Nd–Nav= 2.81(7)A.

ChemInform Abstract: A Fluorescence Stopped‐Flow Kinetic Study of the Displacement of 2‐((2‐Bis(carboxymethyl)amino‐5‐methylphenoxy)methyl)‐6‐methoxy‐8‐bis(carboxymethyl)aminoquinoline(quin 2) from Its Ca2+, Pr3+, Tb3+, Dy3+, and Yb3+ Complexes by Ethylenedinitrilotetraacetate (edta) in Aqueous Solution.

AbstractThe origins in the lability differences in the title complexes of the octadentate ligand (I) are discussed and mechanistic interpretations of the data are presented.

Transition metal complexes of ligands containing 3,5-dimethylpyrazolyl groups and thioether functions. The crystal and molecular structure of (1,12-bis(3,5-dimethylpyrazol-1-yl)-2,11-diaza-5,8-dithiadodecane)nickel(II)-bis(tetrafluoroborate)

The hexadentate (N 4S 2) ligand 1,12-bis(3,5-dimethylpyrazol-1-yl)-2,11-diaza-5,8-dithiadodecane (dsbd) forms compounds M(dsbd)A 2 where M is Co, Ni or Cd and A is ClO 4 − or BF 4 −. The compound Ni-(dsbd)(BF 4) 2 crystallizes in the monoclinic space group P 1/ n, Z = 4, a = 1.2817(4), b = 1.5512(3), c = 1.3366(4) nm, β = 94.11(1)°. The structure was refined to a final R w value of 0.032 for 2181 observed reflections. The nickel ion is octahedrally chelated by two sulfur atoms, two amine nitrogens and two pyrazole nitrogens. NiN amounts to 210–212 pm, NiS distances are 243.5 pm. The other dsbd compounds have very similar structures as is concluded from their spectroscopic properties. The octadentate (N 6S 2) ligand 1,1,10,10-tetrakis(3,5-dimethyl-pyrazol-1-ylmethyl)-1,10-diaza-4,7-dithiadecane (dstd) forms compounds M 2(dstd)A 4(H 2O) n, where M is Mn, Fe, Co, Ni, Cu, Zn or Cd; A is ClO 4 − and n is 4; where M is Co, Ni or Zn, A is BF 4 − and n = 4; and where M is Co or Ni, A is NCS − and n = 0. In all compounds the metal ions are six-coordinated, as deduced from their spectroscopic properties.

Coordination chemistry of lanthanide catecholates

The solution complexation chemistry of Eu(III) and Lu(III) with several monocatecholates [1,2- dihydroxy(3,5-disulfo)benzene (tiron); 4-nitrocatechol (n-cat); catechol; 5-sulfo-2,3-dihydroxy- N, N- dimethylbenzamide (DMBS)], and a tetracatecholate (3,4,3-LICAMS) has been investigated using potentiometric and spectrophotometric methods. These two trivalent lanthanides form complexes of the same composition with those of Lu(III) more stable. At pH 8 only 1:1 complexes of Eu(III) and Lu(III)with tiron are formed, regardless of the amount of excess ligand present. Complexes of Eu(III) with catechol of 1:1, 1:2 and 1:3 are formed at pH 8.0, 10.0 and 12.0, respectively. The octadentate ligand 3,4,3-LICAMS and the simple catechols 4-nitrocatechol and DMBS form complexes with 1.5 catechol groups per Eu(III) or Lu(III). The formation constants of these complexes have been determined. Discussion of these differences in catecholate coordination chemistry with lanthanides, as well as comparison of these results with those obtained for trivalent and tetravalent transition metals and actinides, are presented.

Specific sequestering agents for the actinides. 16. Synthesis and initial biological testing of polydentate oxohydroxypyridinecarboxylate ligands.

Chemical and biological similarities of plutonium(IV) and iron(III) suggested that octadentate ligands containing hydroxamate or catecholate functional groups, which are found in microbial iron chelating agents (siderophores), would be effective and relatively selective complexing agents for actinide(IV) ions. However, their usefulness for in vivo chelation of actinide(IV) is limited, because catechol and hydroxamate are such weak acids that the potential for octadentate binding of actinide(IV) cannot be achieved at physiological pH. The structurally similar monoprotic and more acidic 1-hydroxy-2(1H)-pyridinone (1,2-HOPO) group was, therefore, incorporated into multidentate ligands. Treatment of 1,2-dihydro-1-hydroxy-2-oxopyridine-6-carboxylic acid (5) with phosgene in THF solution gives the active ester poly[1,2-dihydro-1,2-dioxopyridine-6-carboxylate], which upon treatment with excess anhydrous dimethylamine gave a 60% yield of N,N-dimethyl-1,2-dihydro-1-hydroxy-2-oxopyridine-6-carboxamide (6). A similarly reactive intermediate was prepared from 5 and an equimolar amount of phosgene in N,N-dimethylacetamide. Combined in situ with 1,3-propanediamine, benzylamine, spermine, spermidine, 1,3,5-tris(aminomethyl)benzene, or desferrioxamine B and excess triethylamine, the latter intermediate gave the corresponding amides in isolated yields ranging from 16% to 60%. The free ligands, their Zn(II) complexes, and the ferric complex of 3,4,3-LIHOPO were administered to mice [30 mumol/kg intraperitoneally 1 h after Pu(IV)-238 citrate, kill at 24 h]. Net Pu removal [Pu excretion (treated)-PU excretion (control)], expressed as percent of injected Pu, was as follows: Na salts and Zn(II) complexes, respectively, of 3-LIHOPO (54, 56), 3,4-LIHOPO (58, 60), 3,4,3-LIHOPO (73, 76); Na salts of MEHOPO (46), DFO-HOPO (78); Fe(III) complex of 3,4,3-LIHOPO (79). DFO-HOPO and 3,4,3-LIHOPO and its Zn(II) and Fe(III) complexes promoted significantly more Pu excretion than CaNa3-DTPA (61% of injected Pu). Preliminary findings on the acute toxicity of the poly(HOPO) ligands and HOPO monomers are presented in an appendix. The biological data indicate strongly that the aqueous solubility and relatively high acidity of the octadentate HOPO ligands, 3,4,3-LIHOPO and DFO-HOPO allow them to form complete eight-coordinate complexes with Pu(IV) ion.

Dinuclear transition metal compounds of a decadentate pyrazole-containing chelating ligand. X-ray crystal structure of Co 2(tthd)(ClO 4) 4(H 2O) 2(MeOH) 1.75

A potentially decadentate ligand, 1,1,4,7,10,10-hexakis(3,5-dimethyl-1-pyrazolylmethyl)-1,4,7,10-tetraazadecane (tthd), has been synthesized from the reaction of tri-ethylenetetramine with six equivalents of N-hydroxymethyl-3,5-dimethylpyrazole. The tthd ligand forms coordination compounds, M 2(tthd)(ClO 4) 4(H 2O) x , when M is Co, Ni, Cu, Zn and Cd and x = 4–8; and M 2(tthd)(A) 2(ClO 4) 2(H 2O) x when M is Co and Ni, A is NCS or Cl, and x = 4–8. The cobalt compound, Co 2(tthd)(ClO 4) 2(H 2O) 2(MeOH) 1.75, crystallizes in the triclinic space group P1, a = 1.959(2), b = 1.5657(3), c = 2.1244(3) nm, α = 105.5(1), β = 96.9(1), γ = 112.1(1). Due to severe disorder of the anions the structure could only be refined to an R w, value of 0.099. The ligand acts as a decadentate, dinucleating ligand. The cobalt ions are distorted octahedrally surrounded by five N-atoms of the tthd ligand and an O-atom of water occupying the sixth coordination place. The other perchlorate compounds have very similar structures, as can be concluded from spectroscopic data. In the thiocyanate and chloride compounds the anions have replaced the coordinated water molecules, resulting in octahedral Ni compounds. With Co thiocyanate, however, tthd acts as an octadentate ligand, resulting only in five-coordinated compounds.