STUDY ON SYNTHESIS AND RELAXIVITY OF PARAMAGNETIC POLYESTER METAL COMPLEXES FOR MRI

Fifteen new polyester ligands were prepared by copolymerization of EDTA (ethylenediaminetertraacetic acid)dianhydride or DTPA (diethylenetriamine pentaacetic acid) dianhydride and dihydric alcohol or dihydric phenol.Their paramagnetic metal complexes were also synthesized.All polyester ligands and metal complexes were characterized by ^1HNMR,IR spectra and elemental analyses.Preliminary study showed that the polyester metal complexes had higher relaxation effectiveness as compared to corresponding small molecular metal complexes.     

Cysteine and Methionine Derivatives of Aminophenol Ligands: Synthesis,Iron Complexation,Magnetic, Electronic and Redox Investigation

Two new Cysteine and Methionine derivatives of aminophenol ligands (HL^Cys and HL^Met) were synthesized by a convenient procedure. The ligands were characterized by ¹H NMR, ¹³C NMR and IR spectroscopies, ESI‐MS, elemental analysis and optical activity measurements. Iron(III) complexes (FeL^Cys and FeL^Met) of these ligands were synthesized and characterized by spectroscopic, magnetic susceptibility studies and cyclic voltammetry techniques. The molecular structure of FeL^Cys and FeL^Met determined by ESI‐MS consist of two ligands coordinated to Fe(III) centers. The magnetic susceptibility measurement indicates the monomeric complexes with paramagnetic properties. Both complexes undergo metal‐centred reduction, and ligand‐centred oxidation.     

顺磁性聚酯金属配合物的合成及其驰豫性能的研究

本文通过二乙三胺五乙酸（ＤＴＰＡ）或乙二胺四乙酸（ＥＤＴＡ）的双酸酐与二元醇或二元酚进行聚合反应，制备了两个系列共１５种新的聚酯型大分子配体及其顺磁性金属配合物，用核磁、红外光谱以及元素分析表征了配体和配合物的结构。初步试验结果表明，与相应的小分子金属配合物相比，聚酯金属配合物具有较高的弛豫性能。     

STUDY ON SYNTHESIS AND RELAXIVITY OF PARAMAGNETIC POLYESTER METAL COMPLEXES FOR MRI

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Ru(III), Cr(III), Fe(III) complexes of Schiff base ligands bearing phenoxy Groups: Application as catalysts in the synthesis of vitamin K3

Two polydentade Schiff base ligands and their Ru(III), Cr(III) and Fe(III) complexes were synthesized and characterized by elemental analysis (C, H, N), UV/Vis, FT IR, ¹H and ¹³C NMR, LC–MS/MS, molar conductivity and magnetic susceptibility techniques. The absorption bands in the electronic spectra and magnetic moment measurements verified an octahedral environment around the metal ions in the complexes. The thermal stabilities were investigated using TGA. The synthesized complexes were used in the catalytic oxidation of 2-methyl naphthalene (2MN) to 2-methyl-1,4-naphthoquinone; vitamin K₃, menadione, 2MNQ; using hydrogen peroxide, acetic acid and sulfuric acid. L₁-Fe(III) complex showed very efficient catalytic activity with 58.54% selectivity in the conversions of 79.11%.     

Structural,spectroscopic, and biological aspects of S∩N donor Schiff-base ligands and their chromium(III) complexes

New chromium(III) complexes are synthesized by classical thermal and microwave (MW)-irradiated techniques. The Schiff bases 2-acetylfuran-S-benzyldithiocarbazate (L¹H), 2-acetylthiophene-S-benzyldithiocarbazate (L²H), 2-acetylpyridine-S-benzyldithiocarbazate (L³H), and 2-acetylnaphthalene-S-benzyldithiocarbazate (L⁴H) were prepared by condensation of -S-benzyldithiocarbazate in ethanol with the respective ketones by using MW as well as conventional methods. The chromium(III) complexes have been prepared by mixing CrCl₃ · 6H₂O in 1 : 1 and 1 : 2 molar ratios with monofunctional bidentate ketimines. The structure of the ligands and their transition metal complexes were confirmed by elemental analysis, melting point determinations, molecular weight determinations, infrared (IR), electronic and electron paramagnetic resonance (EPR) spectral, and X-ray powder diffraction studies. On the basis of these studies it is clear that the ligands coordinated to the metal atom in a monobasic bidentate mode by S∩N donors. Thus, an octahedral environment around the chromium(III) has been proposed. The growth inhibiting potential of the ligands and complexes has been assessed against a variety of fungal and bacterial strains.     

同、异双核卟啉-Salen型金属配合物的合成及非线性光学性质

设计合成了两种新型卟啉-Salen 型配体5-（3-氨基-4-（3,5-二叔丁基水杨醛基）-氨基苯基）-10,15,20-三苯基卟啉（1）和5-（N,N’-二（3,5-二叔丁基水杨醛基）-3,4-二氨基苯基）-10,15,20-三苯基卟啉（2）及其同、异双核金属配合物和单金属核配合物. 采用氢核磁共振（1H NHR）谱、电喷雾质谱（ESI-MS）、傅里叶变换红外（FTIR）光谱和紫外-可见（UV-Vis）光谱等手段对各目标化合物进行了表征. 用Z扫描技术研究了配体及其金属配合物的三阶非线性光学性质. 实验结果表明：配体1和配体2具有相似的光学特征,均具有反饱和吸收的特性和自散焦效应;当不同的金属离子嵌入配体形成单、双核金属配合物后,分子的极性发生改变,他们的光学特性均受到影响.     

The synthesis and characterization of single substitute melamine cored Schiff bases and their [Fe(III) and Cr(III)] complexes

In this study, firstly, two single substitute novel ligands have been synthesized by reacting melamine with 3,4,-dihydroxybenzaldeyhde or 4-carboxybenzaldehyde. Then, eight new mono nuclear single substitute [Salen/Salophen Fe(III) and Cr(III)] complexes have been synthesized by reacting the ligands [2-(3,4-dihydroxybenzimino)-4,6-diamimo-1,3,5-triazine and 2-(4-carboxybenzimino)-4,6-diamimo-1,3,5-triazine)] with tetradentate Schiff bases N,N′-bis(salicylidene)ethylenediamine-(salenH₂) or bis(salicylidene)-o-phenylenediamine-(salophen H₂). And then, all ligands and complexes have been characterized by means of elementel analysis, FT-IR spectroscopy, ¹H NMR, LC–MS, thermal analyses and magnetic suscebtibility measurements. Finally, metal ratios of the prepared complexes were determined using AAS. The complexes have also been characterized as disorted octahedral low-spin Fe(III) and Cr(III) bridged by catechol and COO^? groups.     

DNA interaction and cytotoxicity studies of ruthenium(III) complexes containing 3-(benzothiazol-2-yliminomethyl)-naphthalen-2-ol ligand

A new Schiff base, 3-(benzothiazol-2-yliminomethyl)-naphthalen-2-ol, has been synthesized and characterized by elemental analysis, Fourier transform infrared spectroscopy (FT-IR), UV–vis, nuclear magnetic resonance, and single-crystal X-ray diffraction. Ruthenium(III) complexes of the Schiff base were synthesized and characterized by analytical and spectroscopic (FT-IR, UV–vis, and electron paramagnetic resonance) data as well as magnetic susceptibility measurements. DNA-binding properties of the ligand and its ruthenium(III) complexes have been investigated by electronic absorption spectroscopy. The three ruthenium(III) complexes were tested for DNA cleavage. Further in vitro study of the cytotoxity of the ligand and the complexes on human cervical cancer cell line and human laryngeal epithelial carcinoma cell line were carried out.     

Nuclear magnetic resonance relaxometry as a spectroscopic probe of the coordination sphere of a paramagnetic metal bound to a humic acid mixture

Protons on water molecules are strongly affected by paramagnetic ions. Since the acid-base properties of water facilitate rapid proton exchange, a single proton nuclear magnetic resonance (NMR) signal is seen in aqueous solutions of paramagnetic ions. Proton relaxation times are significantly affected by paramagnetic species and the readily detectable single signal serves as a powerful amplifier of the information contained concerning the protons in the paramagnetic environment. Where water molecules coordinated to free paramagnetic ions and to metal complexes of ligands that form non-labile (on the NMR time scale) complexes, the effects on water in the two environments can be distinguished. This can provide information on the nature of the ligand binding sites. The example of Cu²⁺ bound to the Laurentian humic acid mixture reported here using convenient low field NMR relaxometers shows that the information can enrich our understanding of complexation and speciation in the presence of complex mixture ligands characteristic of natural water systems. In this case, the data underline the role of aggregation and conformation in defining the complexation sites.     

Synthesis of Star-Shaped Macromolecular Schiff Base Complexes Having Melamine Cores and Their Magnetic and Thermal Behaviors

Abstract

We aim to study magnetic and thermal behaviors of some melamine cored macromolecular Schiff base complexes. In this context, tripodal ligands were synthesized by reacting melamine with 4-carboxybenzaldehyde or 4-hydroxybenzaldehyde. Then, 16 new trinuclear Fe(III), Cr(III), Mn(III), and Al(III) complexes were synthesized by reacting the ligands [tris-(4-carboxybenzimino)-1,3,5-triazine) or tris-(4-hydroxybenzimino)-1,3,5-triazine)] with pentadentate Schiff bases N,N′-bis(1-hydroxy-2-benzyliden)-1,7-diamino-4-azaheptane or N,N′-bis(salicylidene)pyridine-2,6-diamine. Later, ligands and complexes were characterized by means of elemental analysis, infrared spectroscopy, ¹H NMR, liquid chromatography–mass spectrometry, thermal analyses, and magnetic susceptibility measurements. Finally, metal ratios of the prepared complexes were determined by using atomic adsorption spectrometry. The complexes were also characterized as distorted octahedral high-spin d ³ (S = 3 × 1/2) Cr(III), high-spin d ⁵ (S = 5 × 1/2) Fe(III), low-spin d ⁴ (S = 2 × 1/2) Mn(III), and diamagnetic Al(III) bridged by ?OH group of COO^? or OH group of phenol.     

Study on the nematicidal activity and chemical structure of NO bidentate Schiff base some metal complexes

A series of Co(II), Cu(II), Y(III), Zr(IV), La(III), and U(VI) complexes derived from 2-(2-hydroxybenzylidinemine)-benzoic acid (L) ligand were synthesized. The mode of bonding of L and the structure of its metal complexes were investigated using different analytical and spectral tools (FT-IR, UV–Vis, ¹H NMR, mass, and XRD). The ligand chelated with the metal ions as a neutral bidentate through oxygen and azomethine nitrogen atoms. All metal complexes adopted octahedral geometry with characteristic color for metal ions. The results of magnetic moment measurements supported paramagnetic for some complexes (Co(II) and Cu(II)) and diamagnetic phenomena for the other complexes. The thermal decomposition of the ligand along with its metal complexes was explained. The molar conductance values of all complexes in (DMF) were found in the range 154.50 to 250.20 S cm² mol⁻¹ at room temperature. The activation thermodynamic parameters, such as E*, ΔH*, ΔS* and ΔG*, were calculated from the DTG curves using Coats–Redfern (CR) and Horowitz–Metzeger (HM) methods at n = 1 or n ≠ 1. The nematicidal activity of the synthesized L and their metal complexes was screened.     

Tetradentate Schiff-base ruthenium(III) complexes containing triphenylphosphine/arsine as coligands: study of physico-chemical,spectrometric, catalytic,and biocidal activities

A series of air-stable, low-spin Ru(III) octahedral complexes [RuX(EPh₃)L] (where X = Cl/Br; E = P/As; and L = dibasic tetradentate Schiff base derived by condensation of ethylenediamine with acetoacetanilide/acetoacetotoluidide/ethylacetoacetate in 1 : 2 molar ratio in ethanol) have been synthesized from RuX₃(EPh₃)₃ (where X = Cl/Br and E = P/As) with Schiff bases in 1 : 1 molar ratio in benzene for 6 h. These complexes were characterized by elemental analysis, spectral methods (Fourier transform infrared (FT-IR), UV-Vis, ¹H- and ¹³C-nuclear magnetic resonance (NMR) for the ligands, and electron paramagnetic resonance (EPR)), and are examined electrochemically. The complexes were efficient catalysts for oxidation of primary and secondary alcohols in their corresponding aldehydes and ketones in the presence of molecular oxygen. These complexes were also tested for their antibacterial and antifungal activities.     

The (salophen)-bridged Fe/Cr (III) capped complexes with triphenylene core: Synthesis and characterization

This article describes synthesis of the difference carboxylic acid derivatives of triphenylene and its complexation properties with Fe/Cr (III)-salophen. For this purpose, the carboxylic acid derivatives of 2,3,6,7,10,11-hexahydroxytriphenylene were synthesized and then reacted with four new Fe(III) and Cr(III) complexes involving tetradenta Schiff bases bis(salicylidene)-o-phenylenediamine-(salophenH₂). The prepared compounds were characterized by means of elemental analysis carrying out infrared spectroscopy (IR), thermogravimetric analysis (TG), nuclear magnetic resonance (¹H NMR), elemental analysis and magnetic susceptibility measurement. The complexes can also be characterized as low-spin distorted octahedral Fe(III) and Cr (III) bridged by carboxylic acids.     

含末端炔基的Salen型金属配合物的合成、表征及性质

设计合成了新型含有末端炔基的Salen型配体H2Ln及其系列金属配合物MLn(n=1,2;M=Ni,Cu,Mn),并用氢核磁共振(1H NHR)谱、电喷雾质谱(ESI-MS)、元素分析(EA)、傅里叶变换红外(FT-IR)光谱和紫外-可见(UV-Vis)光谱等对各目标化合物进行了表征.采用循环伏安法研究了配体及其金属配合物的电化学氧化还原性质.研究发现,配体除H2L1外均在测试范围内出现特征的亚胺氧化还原峰.镍和铜的配合物均经历了两个单电子的氧化还原过程;锰的配合物均出现由Mn(III)/Mn(II)产生的一对氧化还原峰,该过程为准可逆的单电子过程.H2Ln及MLn的溶液摩尔电导率数据显示,各目标化合物为弱电解质,具有一定的导电性.     

Synthesis and characterization of two binuclear iron(III) complexes of aminoethanol derivatives of aminophenol as models for non-heme iron enzymes active sites

Two aminoethanol derivatives of aminophenol ligands were synthesized and characterized by IR and ¹H NMR spectroscopies. The binuclear iron(III) complexes of these ligands have been prepared and characterized by IR, ¹H NMR and UV-Vis spectroscopic techniques, cyclic voltammetry, single crystal X-ray diffraction and magnetic susceptibility studies. X-ray analysis revealed binuclear complexes, Fe₂(L₂), in which Fe(III) centers are surrounded by two phenolate and hydroxyl oxygen atoms, and amine nitrogens of the ligands. The metal active sites of both complexes are held together by the two above mentioned hydroxyl bridges. Variable temperature magnetic susceptibility indicates antiferromagnetic coupling between the iron centers of both complexes. This exchange coupling is stronger for Fe₂(L^ae)₂, such that it shows a room temperature strong coupling between the two iron centers. The investigated complexes undergo irreversible electrochemical oxidation and reduction.     

Synthesis and spectroscopic studies of new binuclear transition metal complexes of Schiff bases derived from 4,6-diacetylresorcinol

Two new series of copper(II), nickel(II), cobalt(II), zinc(II), iron(III), chromium(III), vanadyl(IV) and uranyl(VI) complexes with two bifunctional tridentate Schiff base, H₄L¹ and H₂L² ligands have been prepared. The Schiff base, H₄L¹ and H₂L², ligands were synthesized by the condensation of 4,6-diacetylresorcinol with o-aminophenol or o-phenylenediamine. The ligands are either di- or tetra-basic with two symmetrical sets of either OON or NNO tridentate chelating sites. The ligands and their metal complexes have been characterized by elemental analysis, ¹H-n.m.r., FT-IR, mass, electronic, esr spectra and thermal gravimetric analysis and magnetic susceptibility. With the exception of Co^II ion with H₂L² which afforded a trinuclear complex, a variety of binuclear complexes for the rest of the metal complexes were obtained with the ligands in its di- or tetra-deprotonated forms. The bonding sites are the azomethine and amino nitrogen atoms, and phenolic oxygen atoms. The metal complexes exhibit different geometrical arrangements such as square planar, tetrahedral, square pyramid and octahedral arrangement.     

Synthesis of Two N,N′-bis(N,N-dialkylamide) Derivatives of Diethylenetriaminepentaacetic Acid and the Stabilities of Their Complexes with Gd3+, Ca2+, Cu2+, and Zn2+

Two bis(N,N-dialkylamide) derivatives of DTPA [(carboxymethyl)iminobis (ethylenenitrilo) tetraacetic acid], DTPA-BDMA = the bis(N,N-dimethylamide) and DTPA-BDEA = the bis(N,N-diethylamide) were synthesized. Their protonation constants were determined by potentiometric titration in 0.10 M Me₄NNO₃ and by NMR pH titration at 25.0 ± 0.1 °C. Stability and selectivity constants were measured to evaluate the possibility of using the corresponding gadolinium(III) complexes for magnetic resonance imaging contrast agents. The stability constants of gadolinium(III), copper(II), zinc(II), and calcium(II) complexes with DTPA-BDMA and DTPA-BDEA were investigated quantitatively by potentiometry. The stability constant for gadolinium(III) complexes is larger than those for Ca(II), Zn(II), and Cu(II) complexes. The selectivity constants and modified selectivity constants of the amides for Gd³⁺ over endogenously available metal ions were calculated. Effectiveness of these two ligands in binding divalent and trivalent metal ions in biological media is assessed by comparing pM values at physiological pH 7.4. Spin-lattice relaxivity values R₁ for Gd(III) complexes were also determined. The observed relaxivity values were found to decrease with increasing pH in the acid range below pH 4 and relaxivity values became invariant with respect to pH changes over the range of 4–10. ¹⁷O NMR shifts showed that the [Dy(DTPA-BDMA)] and [Dy(DTPA-BDEA)] complexes had one inner-sphere water molecule. Water proton spin-lattice relaxation rates for the [Gd(DTPA-BDMA)] and [Gd(DTPA-BDEA)] complexes were also consistent with one inner-sphere gadolinium(III) coordination position.     

具有π共轭骨架的Salen-卟啉型同、异双核配合物的合成及谱学性质

设计合成了两类具有π共轭骨架的Salen-卟啉型配体及金属配合物. 以Salen-卟啉半体及相应的醛为原料, 运用金属模板法合成了单核镍和双核镍Salen-卟啉型金属配合物. 在单核镍的基础上可得到异双核镍、锌Salen-卟啉型金属配合物. 通过核磁共振氢谱(¹H NMR)、紫外-可见(UV-Vis)光谱、傅里叶变换红外(FTIR)光谱、电喷雾质谱(ESI-MS)和荧光光谱等多种谱学手段对其结构进行了表征. 研究表明, 单核镍及异双核镍、锌配合物中, 镍离子落入Salen 部分的配位空腔, 而锌离子则是与卟啉部分形成锌卟啉大环结构。由于卟啉环流效应及分子π共轭结构的影响, 导致配体上的氢原子的化学位移向高场或低场移动. 当金属离子与配体配位之后,卟啉部分的紫外-可见光谱的Soret带和Q带均发生显著变化, 而荧光则出现猝灭现象.