Search results for " COMPLEXES"
showing 10 items of 818 documents
Coexistence of long-range antiferromagnetic order and slow relaxation of the magnetization in the first lanthanide complex of a 1,2,4-benzotriazinyl …
2017
The first lanthanide complex of a 1,2,4-benzotriazinyl radical (1), Dy(1)(tbacac)3 (2, tbacac = 2,2,6,6-tetramethyl-3,5-heptane-dionato), was synthesised and found to have an antiferromagnetically ordered ground state with a metamagnetic phase diagram and a critical field of 0.91 T at 1.85 K. The application of a small dc field revealed the single-molecule magnet behaviour of 2, illustrating the coexistence of long-range antiferromagnetic order and slow relaxation of the magnetization. peerReviewed
Extended dipyrrin ligands : candidates for optical metal ion detection under competitive conditions
2017
Acylhydrazone based extended dipyrrins L1-H and L2-H are introduced as complexometric ppb sensitive metal ion detectors. The binding of lanthanide, transition as well as post-transition metal ions is followed by UV-Vis measurements. The carbohydrate based ligand L2 is water soluble and thus can act as a metal ion sensor in this medium.
Lanthanide complexation with CMPO and CMPO-calix[4]arenes in solution: spectrophotometric and electrospray mass spectrometric approaches.
2007
The binding of lanthanide(III) cations with organophosphorous ligands like CMPO and related calix[4]arene-based derivatives have been investigated using two experimental methods. The stability constants of the lanthanum, europium and ytterbium complexes were first determined in methanol by UV absorption spectrophotometry in the presence of nitrate or chloride anions. The results showed that the stoichiometry and the stability of the complexes formed depend on the position of the CMPO moieties either on the wide or the narrow rim of the calixarene scaffold, the nature of the medium, the conformational mobility of the ligands. Complexation of lanthanum was also followed by ESI-mass spectromet…
Thermal expansion and magnetic properties of benzoquinone-bridged dinuclear rare-earth complexes.
2017
The synthesis and structural characterization of two benzoquinone-bridged dinuclear rare-earth complexes [BQ(MCl2·THF3)2] (BQ = 2,5-bisoxide-1,4-benzoquinone; M = Y (1), Dy (2)) are described. Of these reported metal complexes, the dysprosium analogue 2 is the first discrete bridged dinuclear lanthanide complex in which both metal centres reside in pentagonal bipyramidal environments. Interestingly, both complexes undergo significant thermal expansion upon heating from 120 K to 293 K as illustrated by single-crystal X-ray and powder diffraction experiments. AC magnetic susceptibility measurements reveal that 2 does not show the slow relation of magnetization in zero dc field. The absent of …
Guidelines to design new spin crossover materials
2010
International audience; This review focuses on new families of spin crossover (SCO) complexes based on polynitrile anions as new anionic ligands or on polyazamacrocycles as neutral macrocyclic ligands. We have shown that the structural and electronic characteristics (original coordination modes and high electronic delocalization) of the polynitrile anions can be tuned by slight chemical modifications such as substitution of functional groups or variation of the negative charge to design new discrete or polymeric SCO systems.In our ongoing work on the design of new molecular systems based on new ligands that can be fine-tuned via chemical modifications, another promising way which has been r…
An unprecedented hetero-bimetallic three-dimensional spin crossover coordination polymer based on the tetrahedral [Hg(SeCN)4]2− building block
2019
[EN] Self-assembly of octahedral FeII ions, trans-1,2-bis(4-pyridyl) ethane (bpe) bridging ligands and [Hg(XCN)(4)](2-) (X = S (1), Se (2)) tetrahedral building blocks has afforded a new type of hetero-bimetallic Hg-II-Fe-II spin-crossover (SCO) 3D 6,4-connected coordination polymer (CP) formulated {Fe(bpe)[Hg(XCN)(4)]}(n). For X = S (1), the ligand field is close to the crossing point but 1 remains paramagnetic over all temperatures. In contrast, for X = Se (2) the complex undergoes complete thermal induced SCO behaviour centred at T-1/2 = 107.8 K and complete photoconversion of the low spin state into a metastable high-spin state (LIESST effect) with T-LIESST = 66.7 K. The current results…
Nonheme Fe(IV) Oxo Complexes of Two New Pentadentate Ligands and Their Hydrogen-Atom and Oxygen-Atom Transfer Reactions.
2015
Two new pentadentate {N5} donor ligands based on the N4Py (N4Py = N,N-bis(2-pyridylmethyl)-N-bis(2-pyridyl)methylamine) framework have been synthesized, viz. [N-(1-methyl-2-benzimidazolyl)methyl-N-(2-pyridyl)methyl-N-(bis-2-pyridyl methyl)amine] (L1) and [N-bis(1-methyl-2-benzimidazolyl)methyl-N-(bis-2-pyridylmethyl)amine] (L2), where one or two pyridyl arms of N4Py have been replaced by corresponding (N-methyl)benzimidazolyl-containing arms. The complexes [FeII(CH3CN)(L)]2+ (L = L1 (1); L2 (2)) were synthesized, and reaction of these ferrous complexes with iodosylbenzene led to the formation of the ferryl complexes [FeIV(O)(L)]2+ (L = L1 (3); L2 (4)), which were characterized by UV–vis spe…
Dimer complexes of 2,4-toluenediamine-N,N,N′,N′-tetraacetic acid (2,4-TDTA) with copper(II), nickel(II), cobalt(II), zinc(II) and manganese(II). Stud…
1997
Abstract Potentiometric investigations in aqueous solution at 25°C and ionic strength 0.1 mol dm−3 KCl show that 2 2,4-toluenediamine-N,N,N′N′-tetraacetic acid (2,4-TDTA) forms with Cu(II), Ni(II), Co(II), Zn(II) and Mn(II) the following complexes (ligand, H4L): monomers [MH2L], [MHL]− and [ML]2−; dimers [M2HL2]3− and [M2L2]4−; with excess of ligand [MH2L2]4−, [MHL2]5− and [ML2]6− (Cu(II), Ni(II) and Zn(II)) and with excess of metal [M2HL]+ (Ni(II), Co(II)and Mn(II) and [M2L] (Cu(II)). The formation constants of the complexes have been determined. The species distribution diagrams indicate that a concentrated solution with a ligand:metal ratio 1:1 at pH 6 is suitable for the synthesis of cr…
Potentiometric and spectroscopic studies of transition-metal ions complexes with a quinolone derivative (cinoxacin). Crystal structures of new Cu(II)…
1997
Abstract The interaction of cobalt(II), nickel(II), copper(II), and zinc(II) with Cinoxacin (HCx = 1-ethyl-1,4-dihydro-4-oxo(1,3)dioxolo(4,5-g)cinnoline-3-carboxylic acid), a 4-quinolone derivative, has been studied at metal/ligand ratios of 1:1-1:3 by means of pH-metric, spectrophotometric, and ESR methods. The formation constants have been determined and the stereochemistry for the metal ions in the species present in aqueous solutions (at 37 ± 0.1°C and I = 0.1 mol dm −3 NaCl) is discussed. In all the studied systems, complexes with different stoichiometric ratios, in which cinoxacin acts both as neutral and deprotonated ligand, are formed. The anomalous sequence of the stepwise stabilit…
Evaluation of the sequestering ability of different complexones towards Ag+ ion
2014
Abstract The interaction between Ag+ cation and different ligands was evaluated as a function of temperature and ionic strength by means of potentiometric techniques. Six aminopolycarboxylic (APCs) and aminopolyphosphonic (APPs) ligands were chosen, namely four APCs: nitrilotriacetic acid (NTA), ethylene-glycol-bis(2-aminoethylether)-N,N,N’,N’-tetraacetic acid (EGTA), ethylenediamine-N,N,N’,N’-tetraacetate (EDTA) and diethylenetriamine-N,N,N’,N”,N”-pentaacetic acid (DTPA)] and two APPs: [(1-hydroxyethane-1,1-diyl)bis(phosphonic acid) (HEDP) and [[(Phosphonomethyl)imino]bis[2,1-ethanediylnitrilobis(methylene)]] tetrakis-phosphonic acid (DTPP). Different mononuclear species with general formu…