Synthesis and Spectral Properties of Terbium(III) and Gadolinium(III) Complexes with Hydroxybenzoic Acids

Russian Journal of General Chemistry - Coordination compounds of terbium(III) and gadolinium(III) with some hydroxybenzoic acids were electrochemically synthesized. Structure and spectral...     

Physicochemical Characterization of Four Gadolinium(III) DTPA‐like Complexes

The analysis of ¹⁷O NMR transverse relaxation rates and EPR transverse electronic relaxation rates for aqueous solutions of the four DTPA‐like (DTPA = diethylenetriamine‐N,N,N′,N″,N″‐pentaacetic acid) complexes, [Gd(DTPA‐PY)(H₂O)]^? (DTPA‐PY = N′‐(2‐pyridylmethyl)), [Gd(DTPA‐HP)(H₂O)₂]^? (DTPA‐HP = N′‐(2‐hydroxypropyl)), [Gd(DTPA‐H1P)(H₂O)₂]^? (DTPA‐H1P = N′‐(2‐hydroxy‐1‐phenylethyl)) and [Gd(DTPA‐H2P)(H₂O)₂] (DTPA‐H2P = N′‐(2‐hydroxy‐2‐phenylethyl)), at various temperatures allows us to understand the water exchange dynamics of these four complexes. The water‐exchange lifetime (τM) parameters for [Gd(DTPA‐PY)(H₂O)]^?, [Gd(DTPA‐HP)(H₂O)₂]^?, [Gd(DTPA‐H1P)(H₂O)₂]^? and [Gd(DTPA‐H2P)(H₂O)₂] are of 585, 98, 163, and 69 ns, respectively. Compared with [Gd(DTPA)(H₂O)]^2? (τM = 303 ns), the τM value of [Gd(DTPA‐PY)(H₂O)]^? is slightly higher, but the other three complexes values are significantly lower than those of [Gd(DTPA)(H₂O)]^2?. This difference is explained by the fact that the gadolinium(III) complexes of DTPA‐HP, DTPA‐H1P, and DTPA‐H2P have two inner‐sphere waters. The ²H longitudinal relaxation rates of the labeled diamagnetic lanthanum complex allow the calculation of its rotational correlation time (τR). The τR values calculated for DTPA‐PY, DTPA‐HP, DTPA‐H1P, and DTPA‐H2P are of 127, 110, 142 and 147 ps, respectively. These four values are higher than the value of [La(DTPA)]^2? (τR = 103 ps), because the rotational correlation time is related to the magnitude of its molecular weight.     

Platinum(II)–Gadolinium(III) Complexes as Potential Single‐Molecular Theranostic Agents for Cancer Treatment

Theranostic agents are emerging multifunctional molecules capable of simultaneous therapy and diagnosis of diseases. We found that platinum(II)–gadolinium(III) complexes with the formula [{Pt(NH₃)₂Cl}₂GdL](NO₃)₂ possess such properties. The Gd center is stable in solution and the cytoplasm, whereas the Pt centers undergo ligand substitution in cancer cells. The Pt units interact with DNA and significantly promote the cellular uptake of Gd complexes. The cytotoxicity of the Pt–Gd complexes is comparable to that of cisplatin at high concentrations (≥0.1 mM ), and their proton relaxivity is higher than that of the commercial magnetic resonance imaging (MRI) contrast agent Gd–DTPA. T₁‐weighted MRI on B6 mice demonstrated that these complexes can reveal the accumulation of platinum drugs in vivo. Their cytotoxicity and imaging capabilities make the Pt–Gd complexes promising theranostic agents for cancer treatment.     

Investigation of 5-chloro-2-methoxybenzoates of La(III), Gd(III) and Lu(III) Complexes

5-Chloro-2-methoxybenzoates of La(III), Gd(III) and Lu(III) were synthesized as penta-, mono- and tetrahydrates with a metal to ligand ratio of 1:3 and with white colour typical of La(III), Gd(III) and Lu(III) ions. The complexes were characterized by elemental analysis, IR and FIR spectra, thermogravimetric and diffractometric studies. The carboxylate group appears to be a symmetrical, bidentate, chelating ligand. The complexes are polycrystalline compounds. Their thermal stabilities were studied in air and inert atmospheres. When heated they dehydrate to form anhydrous salts which next in air are decomposed through oxychlorides to the oxides of the respective metals while in inert atmosphere to the mixture of oxides, oxychlorides of lanthanides and carbon. The most thermally stable in air, nitrogen and argon atmospheres is 5-chloro-2-methoxybenzoate of Gd(III). This revised version was published online in August 2006 with corrections to the Cover Date.     

Interaction of Gadolinium(III) with Nitrilotrimethylenephosphonic Acid

Interaction of gadolinium(III) with nitrilotrimethylenephosphonic acid is studied by potentiometry in wide range of concentration ratios and pH at 298.15 K and ionic strength of 0.1 (KNO₃). Logarithmic constants of protonation (logK _pr) are 7.88 ± 0.08 and 4.93 ± 0.05 for GdL^3– and GdHL^2–, respectively.     

Synthesis and Relaxometric Properties of Gadolinium(III) Complexes of New Triazine‐Based Polydentate Ligands

Two new derivatives based on an s‐triazine structural motif were synthesized by attaching two 2,2′‐hydrazinylidenebis[acetic acid] moieties to the triazine ring to reach an overall heptadenticity for the complexation of lanthanide(III) cations. The remaining reactive site was exploited for the substitution with a functionizable amino group (see H₄ L1 ) and a lipophilic moiety (see H₄ L2 ). Luminescence‐lifetime determinations revealed the presence of a single H₂O molecule coordinated for [Eu( L1 )]. A complete ¹H‐NMR relaxometric study was carried out for the octacoordinated [Gd( L1 )] and [Gd( L2 )] complexes. A remarkably long H₂O residence lifetime (²⁹⁸τ_M =5.2 μs) was found by ¹⁷O‐NMR in the case of [Gd( L1 )]. Micelle formation of the lipophilic complex [Gd( L2 )] was evidenced, the critical micellization concentration (cmc) determined, and relaxometric properties of the system investigated.     

Solid Solutions of Europium(III) and Gadolinium(III) Trifluoroacetate Trihydrates as Precursors of Solid Solutions of Europium and Gadolinium Trifluorides

The system Eu(CF₃CO₂)₃-Gd(CF₃CO₂)₃-H₂O, which forms solid solutions Eu_xGd₁-x(CF₃CO₂)₃ · 3H₂O, was studied. The thermolysis of these solutions at 350-360°C yields solid solutions of lanthanide trifluorides. X-ray examination showed that these solid solutions are formed on the basis of the predominantly rhombic phase of Eu(III) and Gd(III) trifluorides.     

Slow Magnetic Relaxation of Ni(III) Complexes toward Molecular Spin Qubits

Molecule-based magnetic materials are promising candidates for molecular spin qubits, which utilize spin relaxation behavior. Various kinds of transition metal complexes with S=1/2 have been reported to act as spin qubits with long spin-spin relaxation times (T₂). However, the spin qubit properties of low-spin Ni(III) complexes are not as well known since Ni(III) compounds are often unstable. We report here the slow magnetic relaxation behavior and T₂ values for three kinds of low-spin Ni(III) based complexes with S=1/2 under magnetically diluted conditions. [Ni(cyclam)X₂]Y (cyclam=1,4,8,11-tetraazacyclotetradecane) with octahedral structures and [Ni(mnt)₂]⁻ (mnt=maleonitriledithiolate) with a square-planar structure underwent slow magnetic relaxations in the presence of a dc magnetic bias field. From electron spin resonance (ESR) spectroscopy, the Ni(III) complexes exhibited observable T₂, indicating that Ni(III) complexes are promising candidates for use as molecule-based spin qubits.     

三价金配合物抗肿瘤活性研究*

三价金配合物具有潜在的抗肿瘤活性,是目前金属药物领域的研究热点。本文按配位原子的不同总结了稳定三价金配合物的结构特征,按其生物活性的构效关系、生物靶点和作用机制综述了三价金配合物抗肿瘤活性研究的最新成果：配体的结构特点以及离去基团对三价金配合物的体外细胞毒性影响较大;介绍了用于检测三价金配合物与可能的生物靶分子之间的相互作用的多种物理和生物学方法,重点关注了相互作用的模式,如嵌入/静电吸引/共价结合等,并解释了三价金配合物抗肿瘤活性的原因。最后提出了一些研究新思路,以期有助于设计得到靶标明确的具有良好药理活性的抗肿瘤药物。     

Antiferromagnetic Coupling in a Gadolinium(III) Semiquinonato Complex

The strongest antiferromagnetic coupling to Gd(III) so far reported was found for the complex [Gd(Hbpz(3))(2)(dtbsq)] small middle dot2 CHCl(3) (1; Hbpz(3)=hydrotris(pyrazolyl)borate; dtbsq=3,5-di-tert-butylsemiquinonato; see structure). At 245 K the magnetic susceptibility of 1 is lower than expected for two uncorrelated spins of 7/2 and 1/2, and the lowering of chiT with increasing temperature suggests that this is due to antiferromagnetic interaction between Gd(III) and the radical.     

Chirality and Order in Binary Molecular Crystals of Inert Cobalt(III) Complexes

Starting from the enantiomerically pure and racemic chiral Lewis bases 1‐phenylethylamine and 1‐(1‐naphthyl)ethylamine inert cobalt(III) complexes of the general composition Co(Hdmg)₂(lig)X (Hdmg = dimethylglyoximate; lig = Lewis base; X = CN, NCO, NO₂) were synthesized and characterized by single crystal X‐ray diffraction. The enantiopure complexes were used as building blocks for the synthesis of binary crystals. Solid solutions resulted from cocrystallizing isomorphous compounds of equal chirality whereas complexes of opposite chirality formed well‐ordered heterochiral solids with efficient packing. Two binary crystals of the latter type could be studied by X‐ray diffraction: Cocrystallization of two isomorphous phenylethylamine derivatives gave a quasiracemic solid. Starting from two non‐isomorphous naphthylethylamine complexes of opposite chirality cocrystals with an unexpected composition were obtained: Their asymmetric unit comprises four independent complex molecules in a 3:1 ratio between the constituents.     

Cluster and Molecular Mechanical Analysis of Cobalt(III) 14-Membered Macrocyclic Complexes

The configurational distribution of all the cobalt(III) complexes containing a 14-membered tetra-aza macrocyclic backbone in the Cambridge Structural Database was determined by cluster analysis, and the reason for some of the complexes adopting their configuration was established by molecular mechanics.     

Hydroxide complexes of lanthanides-III Gadolinium(III) in perchlorate medium

From the precipitation borderline in the pM′—pH diagram, determined experimentally under CO₂-free conditions, the stability constants of the mononuclear and polynuclear species of gadolinium hydroxide have been established. The values found are log*β₁ = −7.3, log*β₂ = −14.6, log*β₃ = −21.9, log*β_4,3 = −19.0 and log *K_s0 = 17.0. They refer to fresh precipitates, prepared at room temperature in sodium perchlorate medium with an ionic strength of 1.     

Sulfitoamine Complexes of Cobalt(III)

Abstract

Monosulfito and bis(hydrogensulfito) cobalt(III) complexes were prepared using sodium sulfite and sodium metabisulfite salts respectively. The two types of products showed different and characterizing patterns of IR and UV-visible spectra. They both contain Co-SO₃ linkages and the sulfite groups have similar or different site symmetries in the same compound.     

Isosaccharinate Complexes of Fe(III)

Prior to this study there were no thermodynamic data for isosaccharinate (ISA) complexes of Fe(III) in the environmental range of pH (>~4.5). This study was undertaken to obtain such data in order to predict Fe(III) behavior in the presence of ISA. The solubility of Fe(OH)₃(2-line ferrihydrite), referred to as Fe(OH)₃(s), was studied at 22?±?2?°C in: (1) very acidic (0.01?mol·dm^?3 H⁺) to highly alkaline conditions (3?mol·dm^?3 NaOH) as a function of time (11?C421?days), and fixed concentrations of 0.01 or 0.001?mol·dm^?3 NaISA; and (2) as a function of NaISA concentrations ranging from approximately 0.0001 to 0.256?mol·dm^?3 and at fixed pH values of approximately 4.5 and 11.6 to determine the ISA complexes of Fe(III). The data were interpreted using the SIT model that included previously reported stability constants for $ {{\text{Fe(ISA}})_{n}}^{3 - n} $ (with n varying from 1 to 4) and Fe(III)?COH complexes, and the solubility product for Fe(OH)₃(s) along with the values for two additional complexes (Fe(OH)₂(ISA)(aq) and $ {\text{Fe(OH)}}_{ 3} ( {{\text{ISA}})_{2}}^{2 - } $ ) determined in this study. These extensive data provided a log₁₀ K ⁰ value of 1.55?±?0.38 for the reaction $ ({\text{Fe}}^{ 3+ } + {\text{ISA}}^{-} + 2 {\text{H}}_{ 2} {\text{O}} \rightleftarrows {\text{Fe(OH}})_{ 2} {\text{ISA(aq}}) + 2 {\text{H}}^{ + } ) $ and a value of ?3.27?±?0.32 for the reaction $ ({\text{Fe}}^{ 3+ } + 2 {\text{ISA}}^{-} + 3 {\text{H}}_{ 2} {\text{O}} \rightleftarrows {\text{Fe(OH)}}_{ 3} ( {\text{ISA}})_{2}^{2 - } + 3 {\text{H}}^{ + } ) $ and show that ISA forms strong complexes with Fe(III) which significantly increase the Fe(OH)₃(s) solubility at pH?<~12. Thermodynamic calculations show that competition of Fe(III) with tetravalent ions for ISA does not significantly affect the solubilities of tetravalent hydrous oxides (e.g., Th and Np(IV)) in ISA solutions.     

Dihaloperhaloaryl(triphenylarsine)gold(III) Complexes

When C₆Cl₅AuAsPh₃ reacts with halogens, oxidation of the gold(I) complex and formation of X₂Au(C₆Cl₅)AsPh₃ (X = Cl, Br, I) take place. However, when C₆F₅AuAsPh₃ reacts with halogens, oxidation is only observed in the case of Cl₂, whilst I₂ (totally) and Br₂ (partially) split the AuC bond. This behaviour is contrary to that observed with C₆F₅AuPPh₃ and halogens, where the tendency to split the AuC bond decreases in the sequence Cl>B>I.     

Dithiocarbamate Iridium(III) Hydride Complexes

Complexes of IrH₃(PPh₃)₂ and IrH₃(AsPh₃)₂ with piperidinedithiocarbamate (Pipdtc), piperazinedithiocarbamate (Pzdtc), N-methylpiperazinedithiocarbamate (CH₃—Pzdtc), morpholinedithiocarbamate (Morphdtc) and thiomorpholinedithiocarbamate (Timdtc) have been prepared and characterized by infrared and nuclear magnetic resonance techniques and vapor phase osmometric molecular weight determinations. The possible stereochemistry of the complexes is discussed based upon the obtained results.