NMR RELAXIVITY AND IMAGING OF NEUTRAL MACROMOLECULAR POLYESTER GADOLINIUM(Ⅲ)COMPLEXES*

Five neutral macromolecular polyester gadolinium (Ⅲ) complexes with pendant hydrophobic alkyland aromatic functional groups were prepared. The longitudinal relaxation rates of these complexes weremeasured. One of these Gd (Ⅲ) complexes was chosen for the acute toxicity test and T_1-weighted imagingmeasurement. Preliminary results showed that. compared with Gd-DTPA. the neutral macromoleculargadolinium (Ⅲ) complexes provide higher T_1 relaxivity enhancement and longer function duration.     

Synthesis and magnetism of μ-isophthalato dinuclear lanthanide(Ⅲ) complexes

Seven new μ-isophthalato dinuclear lanthanide(Ⅲ) complexes, namely [Ln2(IPHTA)(Me2-phen)4-(ClO4)2](ClO4)2 (Ln = La, Nd, Sm, Eu, Gd, Ho, Er), where Me2-phen denotes 2,9-dimethyl-1, 10-phenanthroline (Me2-phen) , IPHTA represents isophthalate dianion, have been synthesized and characterized by elemental analyses, molar conductance measurements, IR, ESR and electronic spectra. The variable-temperature magnetic susceptibilities of [Gd2( IPHTA) (Mez-phen)4 (ClO4)2] (ClO4)2 complex were measured in the temperature range of 4-300 K and the observed data were successfully simulated by the equation based on the spin Hamiltonian operator, H = - 2JS1 · S2, giving the exchange parameter J =- 0.19 cm-1 . This result is commensurate with a weak antiferromagnetic spin-exchange interaction between Gd(Ⅲ)-Gd(Ⅲ) ions within the complex.     

Synthesis and catalytic activity of novel heteronuclear Ln(Ⅲ)-Cu(Ⅱ) complexes with noncyclic polyether-amino acid Schiff base

A series of novel heteronuclear Ln(Ⅲ)-Cu(Ⅱ) complexes with noncyclic polyether-amino acid Schiff base were synthesized. The general formula is [LnCu_2(H_2TALY)(NO_3)_5](NO_3)_2' nH_2O(Ln=La, Nd, Sm, Gd, n= 4; Ln=Yb, Y, n=3), where H_2TALY = tetraglycol aldehyde bis-lysine Schiff base. It is the first time to report the synthetic method for this new Cu(Ⅱ) complexes and Ln(Ⅲ)-Cu(Ⅱ) heteronuclear complexes. The complexes were characterized by elemental analysis, IR spectra, TG-DTA, magnetic susceptibility, and especially by a 500 MHz NMR spectrometer for 2D-COSY NMR. Coordination mechanism and structures of complexes have been suggested as well. Of particular interest is the potential that the novel complexes obtained may be used as a catalyst, which prompted us to investigate them. It shows 100% conversion with the viscosity-average molecular weight 120 000 for the polymerization of methyl methacrylate (MMA) without addition of any cocatalyst. Furthermore, the complexes with such aliphatic Schiff bas     

Bond Valence Sum Analysis of Tl（Ⅰ） and Tl（Ⅲ） Complexes with O and N Donors

The influence of the lone pair of electrons in thallium complexes is analyzed using the bond valence sum method.Bond length data for metal-organic Tl complexes were obtained from the Cambridge Structural Database(CSD),and problems with searching the CSD file for Tl complexes are discussed.The recommended R0 values for Tl(Ⅰ)-O of 2.162 ,Tl(Ⅲ)-O of 2.016 ,Tl(Ⅰ)-N of 2.286 ?,and for Tl(Ⅲ)-N of 2.014  used with b = 0.37 were derived from analyses of homoleptic Tl-O,Tl-N,and heteroleptic Tl-O and-N metal organic complexes.These R0 values can be used to assign correctly the oxidation state of Tl in complexes containing any combination of Tl-O or Tl-N bonds.Examples of questionable oxidation states for Tl complexes are given.The R0 value for Tl(Ⅲ)-Cl of 2.300  was also determined.     

Structures and Spectroscopic Properties of(1)Dipyridine Quinoxaline with Hg(Ⅱ), Cu(Ⅰ) and Ag(Ⅰ)

The interaction of Hg(Ⅱ), Cu(Ⅰ) and Ag(Ⅰ) with dipyridine quinoxaline ligand 2,3-bis(2-pyridyl)quinoxaline(DPQ) were investigated, and three new complexes have been synthesized and characterized. Complex 1 exhibits a 0D dual-core structure, complex 2 is a 0D tetra nuclear case based on a dual-core Cu unit, and complex 3 shows a one-dimensional pipeline structure. Furthermore, the optical properties of complex and DPQ were also investigated, and the results showed that the fluorescence intensity of complexes was weaker than that of ligand DPQ.     

Study on EPR Spectra of Three Gadolinium Complexes With Noncyclic Polyether Schiff Bases

The EPR spectra of three new gadolinium complexes with noncyclic polyether Schiff bases in powder and those of these complexes in organic solvents were investigated at different temperatures. It was observed that EPR spectra of nine and four peaks of Gd(Ⅲ) complexes in polycrystalline powder and freezing samples appeared at low temperature respectively for the first time. The interpretations of these results obtained on the basis of spin Hamiltonian of s = 7/2 system are satisfactory. The correlations of EPR feature between crystal-field strength in complexes and local symmetry around Gd3+ ions were revealed. The crystal-field parameters b20 and the asymmetry parameters λ' of complexes were estimated. A series of interesting regularity and new results were obtained.     

~1H and ~(13)C NMR studies of TTHA complexes with diamagnetic rare earth ions

TTHA complexes with diamagnetic rare earth ions (La3+, Y3+ and Lu3+) were studied by 1H and 13C NMR spectroscopy. A symmetric structural model was suggested for La(TTHA) complex and an asymmetric model for Y(TTHA) and Lu(TTHA) complexes. The complex formation was dependent on the pH value of the solution. The interactions of La(TTHA) with the additional metal ions (La3+, Y3+ and Ca2+) were relatively weak, but relatively strong for that of Lu(TTHA) with the additional Lu3+.     

Studies on Insoluble Species of Gd(Ⅲ)in Human Blood Plasma by Computer Simulation

The insoluble species of Gd ( Ⅲ ) in human blood plasma were investigated by computer simulation. The distribution of the Gd(Ⅲ ) species was obtained. It was found that most of the Gd( Ⅲ ) ions were bound to phosphate to form precipitate GdPO4 at the concentration of 1. 000 10-7 mol/L and when the concentration of the Gd (Ⅲ ) increased to 3. 750 X 10-4 mol/L, in excess of the concentration of phosphate, the Gd ( Ⅲ ) ions were bound to carbonate to form another kind of precipitate, Gd2(CO3)3.     

Preparation,Characterization and Properties of Two New Lanthanide(Ⅲ)-5-(2-pyridyl)tetrazolate Complexes

Two new mononuclear lanthanide(Ⅲ) complexes Ln(pytz)3(H2O)3·(H2O)3.5[Ln=Tb(1);Eu(2);Hpytz=5-(2-pyridyl)tetrazole] were synthesized by reacting Hpytz with the corresponding lanthanide(Ⅲ) ions and characterized.The single crystal X-ray diffraction analysis reveals that complexes 1 and 2 are isostructural and the lanthanide(Ⅲ) ions in both complexes 1 and 2 are nine-coordinated,with three oxygen atoms of three coordination water molecules and six nitrogen atoms of three pytz ligands,forming a monocapped square antiprism.Extensive hydrogen bonds exist,resulting in a three-dimensional supramolecular network structure by hydrogen-bonds in both complexes 1 and 2,respectively.Complex 1 exhibits typical green fluorescence of Tb(Ⅲ) ion and complex 2 red fluorescence of Eu(Ⅲ) ion,in solid state at room temperature.     

Synthesis,characterization and magnetism of copper(Ⅱ)-lan-thanide(Ⅲ) heterobimetalic complexes with N,N'-oxamidobis-(benzoato) cuprate (Ⅱ)

Seven new μ-oxamido copper(Ⅱ)-lanthanide(Ⅲ)hetero-bitnetalic complexes described by the fonnula Cu(obbz)Ln-(Ph-phen)2NO3(Ln=La,Nd,Eu,Gd,Tb,Ho,Er),where obbz denotes the oxamidobis(benzoato)and Ph-phen represents 5-phenyl-1,10-phenanthroline,have been synthesized and characterized by the elemental analyses,spectro-scopic(IR,UV,ESR)studies,magnetic moments(at room temperature)and molar conductivity measurement.The temperature dependence of the magnetic susceptibility of Cu(obbz)Gd(Ph-phen)2NO3 complex has been measured over the range 4.2-300 K.The least-squares fit of the experimental susceptibilities based on the spin Hamiltonian operator,H=-2JS1 S2,yielded J= 1.28 cm-1,a weak ferromagnetic coupling.A plausible mechanism for a ferromagnetic coupling between Gd(Ⅲ)-Cu(Ⅱ)is discussed in terms of spin-polarization.     

Syntheses,Crystal Structures and Anticancer Activities of Dithiocarbamate Bismuth(Ⅲ) Complexes

Two novel complexes, [Bi(III)(S2CNBn Et)3] 1 and [Bi(III)(S2CNPPPy-2)3] 2, were synthesized and characterized by elemental analysis, IR, 1H NMR, 13 C NMR, TG-DTG and X-ray single-crystal diffraction. The structure reveals that complex 1 belongs to the monoclinic system, space group P21/c with a = 11.457(5), b = 17.437(8), c = 33.439(14), β= 98.499(8)o, Z = 4, V = 6607(5)3, Dc = 1.689 g·cm-3, F(000) = 3328, μ= 5.742 mm-1, the final R = 0.0906, w R = 0.1678 and S = 1.032. The structure indicates that complex 2 belongs to the triclinic system, space group P1 with a = 12.608(9), b = 12.622(8), c = 12.49(6), α = 102.652(15), β = 103.013(14), γ = 109.698(10)o, Z = 1, V = 1762.3(19)3, Dc = 1.741 g·cm-3, F(000) = 916, μ = 5.395 mm-1, the final R = 0.048 2, w R = 0.1206 and S =1.046. In the two complexes, each six-coordinated Bi(III) atom adopts a pentagonal pyramidal configuration with six sulfur atoms from three ligands, and the dimmer structures are formed by weak interactions of Bi···S between two molecules. The anticancer activities of the two complexes were studied by evaluating their cytotoxicities against several human cancer cell lines using the MTT assay. Results indicated complex 2 showed moderate cytotoxic effects on the selected cancer cells.     

Theoretical Study on the Inclusion Complex of β-Cyclodextrin and Nitrobenzene

Quantum chemical calculations were carried out to investigate the structures and properties for the inclusion complexes of nitrobenzene (NB) into β-cyclodextrin. Two low-energy conformations of β-cyclodextrin (A and B) in the gas phase were initially investigated by the PM3 and B3LYP/6-31+G(d,p) calculations, respectively. Three different orientations were considered in the inclusion process of A and B with NB to form 1:1 complexes. Potential energy scan by PM3 calculations indicated that the phenyl orientation Ab for conformation A and the equator orientation Bc for conformation B are more favorable in energy, respectively. We also considered the 2:1 inclusion complexes of host A or B with guest NB in the gas phase. PM3 calculation indicated that the host-guest interaction energies to form 1:1 complexes are more negative than those to form 2:1 NB/B complexes. Finally, we studied the solvent effect of NB/CD complex, and PM3 results show that the influence of water molecules on the inclusion process is very important. The driving forces for the inclusion process and the geometries of complexes were discussed in detail.     

Studies on synthesis and magnetic resonance of lanthanide complexes with novel Schiff base derived from noncyclic polyether and P-diketone

Nine Ln( Ⅲ ) complexes with a novel Schiff base derived from diglycolamine and benzoylacetone (BZDA) have been synthesized and characterized. They can be formulated as [Ln2(BZDA)3(NO3)3](NO3)3· nH2O(Ln=La, Pr, Nd, Sm, n = 4; Ln=Gd, Tb, Er, Yb, Y, n = l). Enamic form mechanism in this β-diketone Schiff base and its complexes were suggested and proved by IR, UV and NMR methods. The 13C spin-lattice relaxation time T1 and the ratios of r(ci-Ln)/r(cj-Ln) were measured by a 500 MHz NMR instrument for elucidating the formation of the stable sk-membered chelate ring structure in these complexes. The EPR spectrum of the Gd( Ⅲ ) complex exhibits the "U" spectral feature and "zero field effect". On the basis of them, the crystal field strength and the local symmetry around Gd3 in the complex have been discussed.     

Synthesis and Characterization of Binuclear Lanthanide Complexes with Macrocyclic Schiff Base Derived From 2,6-Diacetylpyridine and 1,3-Diamino-2-hydroxypropane

Nine homobinuclear lanthanide complexes with macrocyclic Schiff base were prepared by condensing 2, 6-diacetylpyridine and 1, 3-diamino-2-hydroxypropane in the presence of template lanthanide metal ions. These complexes were characterized by elemental analysis, IR, molar conductance and magnetic susceptibility. The variable-temperature magnetic susceptibility (4-300 K) of complexes of Gd( Ⅲ ) and Dy( Ⅲ ) was determined. A satisfactory fit to theoretical curve derived from spin Hamiltonian operator was obtained using least-squares method. The exchange interaction parameters are J=-0.26 cm-1, g=1.98 and △=0.06 cm-1, Z.J'=-0. 21 cm-1,g'=1.33 for Gd( Ⅲ ) and Dy( Ⅲ ), respectively. The results indicate a very week antiferromagnetic interaction between Gd( Ⅲ )-Gd( Ⅲ ) and Dy( Ⅲ )-Dy( Ⅲ ) ions.     

Synthesis,DNA binding and cleavage studies of the copper(Ⅱ) complexes of PNA-cyclen conjugates

Two dinucleotide PNA-cyclen copper(II) complexes with α-PNA (P1) and classical PNA (P2) backbones were synthesized and characterized.The interactions between title complexes and DNA were investigated under physiological conditions.Fluorescence studies indicate that the binding ability of complex P1 to CT-DNA is as twice as that of P2.DNA melting experiments were also carried out and the results show that ΔTm caused by P1 is higher than that caused by P2.Agarose gel electrophoresis experiments demonstrate th...     

Synthesis of New Ruthenium（Ⅱ）Bipyridyl Complexes and Studies on Their Photophysical and Photoelectrochemical Properties

Two new mixed-ligand ruthenium(Ⅱ） complexes,Ru(dcbpy)-(LL)NCS)2[where dcbpy=4,4‘-dicarboxyl-2,2‘‘-bipyridine,LL=4,4‘-bis(N-methyl-anilinomethyl)-2,2‘‘-bipyridine(2)],were synthesized,and the tphotophysical properties of these complexes were studied.The metal-to-ligand charge transfer (MLCT) transitions of these complexes exhibited solvatochromic effect due to the existence of NCS ligands.The MLCT energies also strongly depend on the pH values of the solutions because of protonation and deprotonation of the carboxyl groups.The pKa values of the ground state,4.0 for 1 and 3.8 for 2,were obtained from the titration curves.The photoelectrochemical properties of 1 and 2 as sensitizers in sandwich-type solar cells have been studied.Complex 1 exhibited better photoelectrochemical behavior than complex 2 as expected.It was proved that the design of mixed-ligand complex by introducing electron donating group in one of the ligands should be a promising approach.     

Synthesis and Characterization of 2-DecyI-DTPA and Its Gd （Ⅲ） Chelate

The present paper covers the synthesis and the characterization of ligand 2-decyl-3, 6, 9-tris (car-boxymethyl)-3,6,9-triazaundecan-1,11-dioic acid, HsL, and its Gd (Ⅲ) chelate. The protonation constantsfor HsL(IgKi^H= 10. 90, 8.50, 4.55, 2.92., 2.20) and the stability constant for GdL^2- (lgKGdL^2- = 2.2.80)were determined by means of potentiometric titration. They are similar to the corresponding values of DTPAand Gd-DTPA, respectively. The results obtained show that the basicity of the ligand and the stability con-stant of its Gd (Ⅲ) chelate are not obviously altered after the introduction of a linear chain decyl group intothe terminal acetic acid residue of DTPA. The Gd(Ⅲ) chelate may be a potential contrast agent with liver-specificity for magnetic resonance imaging(MRI).     

Theoretical studies on the complexation of Eu(Ⅲ) and Am(Ⅲ) with HDEHP: structure,bonding nature and stability

Separation of trivalent lanthanides(Ln(Ⅲ)) and actinides(An(Ⅲ)) is a key issue in the advanced spent nuclear fuel reprocessing. In the well-known trivalent actinide lanthanide separation by phosphorus reagent extraction from aqueous komplexes(TALSPEAK) process, the organophosphorus ligand HDEHP(di-(2-ethylhexyl) phosphoric acid) has been used as an efficient reagent for the partitioning of Ln(Ⅲ) from An(Ⅲ) with the combination of a holdback reagent in aqueous lactate buffer solution. In this work, the structural and electronic properties of Eu~(3+) and Am~(3+) complexes with HDEHP in nitric acid solution have been systematically explored by using scalar-relativistic density functional theory(DFT). It was found that HDEHP can coordinate with M(Ⅲ)(M=Eu, Am) cations in the form of hydrogen-bonded dimers HL_2~-(L=DEHP), and the metal ions prefer to coordinate with the phosphoryl oxygen atom of the ligand. For all the extraction complexes, the metal-ligand bonds are mainly ionic in nature. Although Eu(Ⅲ) complexes have higher interaction energies, the HL_2~- dimer shows comparable affinity for Eu(Ⅲ) and Am(Ⅲ) according to thermodynamic analysis, which may be attributed to the higher stabilities of Eu(Ⅲ) nonahydrate. It is expected that this work could provide insightful information on the complexation of An(Ⅲ) and Ln(Ⅲ) with HDEHP at the molecular level.     

Synthesis and Structure of Dibenzoyl-bissemicarbazone Neodymium(Ⅲ) Perchlorate

A new Schiff base Dibenzoyl-bissemicarbazone C15H16N6O2(L) and its complex with neodymium(Ⅲ ) perchlorate [NdL2(H2O)2](ClO4)3 were synthesized. The crystal and molecular structure of the title complex were determined by single crystal X-ray diffraction. The crystal is monoclinic and conforms to space group P. with cell constants a=10. 893(2) A, b= 12. 118(3) A , c=22. 494(5) A , β=89. 86(3)% V = 2969.19A3. The final standard deviation R=0. 0919. In the complex Nd is coordinated by four nitrogen and six oxygen atoms, of which four nitrogen and four oxygen atoms are provided by two neutral ligands L, and the other two oxygen atoms are provided by two water molecules, forming a ten-coordinated complex cation, which the perchlorate groups exist in the outer sphere. The coordination polyhedron takes a bicapped anti-square prism arrangement. That the average bond length of Nd-N is 2. 735 A indicates that the coordination of N in groups to Nd( Ⅲ ) is very weak.     

Structure and magnetic properties of homobinuclear gadolinium (Ⅲ) complex of isonicotinoyl hydrazone

The crystal structure of [Gd2(μ-L)3(H2O)2].1.5(NO3).1.5 (OH)-5H2O (where L is an-ion of N, N'-Diisonicotinoyl-2-hydroxy-5-methyl-isophthalaIdehyde dihydrazone) has been determined by X-ray diffraction method. The complex crystallizes in the monoclinic system, space group P21/c with a=1.6654(3), b=1.6904(3), c=2.8039(6) nmβ=91.30(3)°, final R factor is 6.3%. The structrue consists of [Gd2(μ-L)3(H2O)2]3+ cation, one and a half nitrate and 1.5 hydroxyl anions and five water molecules. Within dinuclear cation, Gd(Ⅲ)-Gd(Ⅲ) is bridged by oxygen and nitrogen atoms of the three ligands, resulting in Gd...Gd distance of 0.36353(2) nm. Gd(Ⅲ) exhibits a distorted 1333 stack coordination environment. Magnetic susceptibility measurements in the temperature range 300-4 K revealed the occurrence of weak antiferromagnetic exchange interaction between two Gd(Ⅲ) ions with a J value of -0.22, and g of 1.93.