Optical and Chromaticity Characteristics of Ethylenediaminetetraacetates of 3d-Block Elements

Optimum conditions for the formation of mono- and mixed-ligand Cr(III), Mn(II), Fe(III), Co(II, III), Ni(II), and Cu(II) ethylenediaminetetraacetates were found. The optical and chromaticity characteristics of these complexes were determined. The prospects of using chromaticity characteristics of the studied complexes of 3d-block elements in optical methods were shown.     

Mononuclear and Dinuclear Cobalt Complexes and its Dioxygen Adduct with a New 24-membered Hexaaza Macrocyclic Ligand

Abstract

Dinucleating 24-membered hexaazadiphenol macrocyclic ligand 3,6,9,17,20,23-hexaaza-29,30-dihydroxy-13,27-dimethyl-tricyclo[23,3,1,1^11,15] triaconta-1(29), 11,13,15(30),25,27-hexaene (L or BDBPH), is prepared by the NaBH₄ reduction of the Schiff base obtained from [2+2] template condensation of 2,6-diformyl-p-cresol with diethylenetriamine. The ligand maintains dinuclear integrity for cobalt (II) while facilitating the formation of bridging phenolate dicobalt cores. Potentiometric equilibrium studies indicate that a variety of protonated, mononuclear and dinuclear cobalt (II) complexes form from p[H] 2 through 11 in aqueous solution. The protonation constants of this ligand and stability constants of the 1:1, 1:2 ligand: cobalt(II) complexes were determined in KCl supporting electrolyte (μ = 0.100 M) at 25°C. The mechanism for the formation of dinuclear dioxygen cobalt(II) complexes is also described. The stability constants of mononuclear and dinuclear cobalt complexes were determined under nitrogen. Preliminary results show that the dinuclear dioxygen cobalt (II) complexes do not catalyze hydroxylation of adamantane in the presence of H₂S as two-electron reductant.     

Dinuclear Cobalt Complexes with a Decadentate Ligand Scaffold: Hydrogen Evolution and Oxygen Reduction Catalysis

A new decadentate dinucleating ligand containing a pyridazine bridging group and pyridylic arms has been synthesized and characterized by analytical and spectroscopic techniques. Four new dinuclear cobalt complexes featuring this ligand have been prepared and thoroughly characterized both in the solid state (X‐ray diffraction) and in solution (1D and 2D NMR spectroscopy, ESI‐MS, and electrochemical techniques). The flexible but stable coordination environment provided by the ligand scaffold when coordinating Co in different oxidation states is shown to play a crucial role in the performance of the set of complexes when tested as catalysts for the photochemical hydrogen evolution reaction (HER) and chemical oxygen reduction reaction (ORR).     

New Palladium(II) Complexes with a Tridentate PNO Ligand

The synthesis of neutral and cationic palladium complexes containing the tridentate monoanionic ligand [2-(2-Ph₂PC₆H₄-CH=N)C₆H₄O]^? is described. Deprotonation of the Schiff base formed by condensation of 2-(diphenylphosphino)benzaldehyde with 2-aminophenol in the presence of the appropriate palladium precursor ([Pd(AcO)₂] or [PdCl₂(PhCN)₂]) form the corresponding neutral complexes [Pd{2-(2-Ph₂PC₆H₄-CH=N)C₆H₄O}(AcO)] (1) or [Pd{2-(2-Ph₂PC₆H₄-CH=N)C₆H₄O}(Cl)] (2) in good yield. The first reacts smoothly with thiols and activated phenols to give complexes of general formula [Pd{2-(2-Ph₂PC₆H₄-CH=N)C₆H₄O}(X)] (X = OC₆F₅ (3), SEt (4), S^tBu (5), SC₆H₅ (6), SC₆H₄-4Me (7), SC₆H₄-4NO₂ (8)). When the chloro complex is treated with silver perchlorate and tertiary phosphines (L) the cationic derivatives [Pd{2-(2-Ph₂PC₆H₄-CH=N)C₆H₄O}(L)][ClO₄] (L = PPh₃ (9), PMePh₂ (10), PMe₂Ph (11), PEt₃ (12)) were obtained. The new complexes were characterized by partial elemental analyses and spectroscopic methods (IR, ¹H, ¹⁹F and ³¹P NMR).     

A New Class of Lanthanide Complexes with Three Ligand Centered Radicals: NMR Evaluation of Ligand Field Energy Splitting and Magnetic Coupling

Combination of three radical anionic Ph-BIAN ligands (Ph-BIAN=bis-(phenylimino)-acenaphthenequinone) with lanthanoid ions leads to a series of homoleptic, six-coordinate complexes of the type Ln(Ph-BIAN)₃. Magnetic coupling data were measured by paramagnetic solution NMR spectroscopy. Combining ¹H NMR with ²H NMR of partially deuterated compounds allowed a detailed study of the magnetic susceptibility anisotropies over a large temperature range. The observed chemical shifts were separated into ligand- and metal-centered contributions by comparison with the Y analogue (diamagnetic at the metal). The metal-centered contributions of the complexes with the paramagnetic ions could then be separated into pseudocontact and Fermi contact shifts. The latter is large within the Ph-BIAN scaffold, which shows that magnetic coupling is significant between the lanthanide ion and the radical ligand. Pseudocontact shifts were further correlated to structural data obtained from X-ray diffraction experiments. Ligand-field parameters were determined by fitting the temperature dependence of the observed magnetic susceptibility anisotropies. The electronic structure determined by this approach shows, that the Er and Tm analogues are candidates for single molecule magnets (SMM). These results demonstrate the possibilities for the application of NMR spectroscopy in investigations of paramagnetic systems in general and single molecule magnets in particular.     

New Complexes of Rare Earth Elements with 3-Methyladipic Acid

Rare earth element 3-methyladipates were prepared as crystalline solids with general formula Ln₂(C₇H₁₀O₄)₃⋅nH₂O, where n=6 for La, n=4 for Ce,Sm–Lu, n=5 for Pr, Nd and n=5.5 for Y. Their solubilities in water at 293 K were determined (2⋅10^–3–1.5⋅10^–4 mol dm^–3). The IR spectra of the prepared complexes suggest that the carboxylate groups are bidentate chelating. During heating the hydrated 3-methyladipates lose all crystallization water molecules in one (Ce–Lu) or two steps (Y) (except of La(III) complex which undergoes tomonohydrate) and then decompose directly to oxides (Y, Ce) or with intermediate formation of oxocarbonates Ln₂O₂CO₃ (Pr–Tb) or Ln₂O(CO₃)₂ (Gd–Lu). Only La(III) complex decomposes in four steps forming additionally unstable La₂(C₇H₁₀O₄)(CO₃)₂. This revised version was published online in August 2006 with corrections to the Cover Date.     

一种含磷三足体衍生物及其铕配合物的合成及性能表征

设计合成了一种新型含磷的水溶性三足体衍生物[L:N-二(吡啶-二氨基乙酰基)甲基磷酸]及其Eu(Ⅲ)的配合物,用红外吸收光谱、元素分析、差热-热重和紫外光谱法等技术手段对该配合物进行了表征,用荧光光谱法研究了室温下该配合物和牛血清白蛋白(BSA)的相互作用。 结果表明,配体与苦味酸铕形成1:1型配合物Eu(pic)₃L;配合物与BSA之间有很强的结合作用;配合物对BSA内源荧光的猝灭方式为静态猝灭;配合物与BSA的作用力为分子间氢键和范德华力。 分别考察了Fe³⁺和Cu²⁺对配合物与BSA结合作用的影响,证明Fe³⁺和Cu²⁺能够以金属离子桥键与配合物结合使配合物-BSA的稳定性增强。 根据Foster型偶极-偶极无辐射能量转移机理可知,配合物可以和BSA以偶极-偶极无辐射进行能量传递。     

Mixed Ligand Complexes of Palladium (II) with Diethylenetriamine as Primary Ligand and Peptides as Secondary Ligand

Solution equilibria of the system palladium (II)-diethylenetriamine (dien) and peptides have been studied. The pH-metric titration of the reaction mixture containing equimolar solutions of palladium (II), dien and peptide have shown the formation of 1:1:1 mixed ligand complex. The pK_e of the peptides studied and formation constants of the resulting complexes have been determined at 25°C. The mode of chelation has been deduced from the conductivity measurements.     

Synthesis and Pyrolytical Studies of New Oxorhenium(V) Complexes with a Tetraaza Macrocyclic Ligand

5,12-dioxa-7,14-dimethyl-1,4,8,11-tetraazacyclotetradeca-1,8-diene (N₄L) reacts with the starting oxorhenium(V) complex, H₂[ReOCl₅], to yield either mononuclear [ReO(N₄L)(OH₂)]Cl₃, or dinuclear [Re₂O₃(N₄L)₂]Cl₄·2H₂O depending on the concentration of hydrochloric acid in rhenium complex. The reaction of (N₄L) mixed with KSCN or PPh₃ with the oxorhenium(V) complex in 6N HCl, yielded the mononuclear complexes [ReO(N₄L)(SCN)]Cl₂·H₂O and [ReO(N₄L)(PPh₃)]Cl₃·H₂O respectively. Both complexes have an octahedral configuration. These complexes decompose through several isolable, as well as non-isolable, intermediates during heating. [Re₂O₃(N₄L\)₂] (N₄L\ = dianionic tetradentate ions), [ReO(N₄L)Cl]Cl₂ and [ReO(N₄L\)(SCN)], were synthesized pyrolytically in the solid state from the corresponding rhenium(V) complexes. All have octahedral configurations. The ligand (N₄L) behaves in these complexes either as a neutral tetradentate or dianionic tetradentate ligand towards the oxorhenium ions. All complexes and the corresponding thermal products were isolated and their structures were elucidated by elemental analyses, conductance, IR and electronic absorption spectra, magnetic moments, ¹H NMR and TG-DSC measurements as well as by mass spectroscopy.     

A Novel Bicyclophosphite Ligand Directly Yields Rhodium Hydride Complexes

Summary.  Complexation of Rh(I) with o, o′-dimethylene-(tris-p-cresyl)-bicyclophosphite (BCP, 1) has been investigated in solution by NMR, semi-empirical quantum mechanical, and molecular mechanics calculations. ¹H and ³¹P NMR spectroscopic data show that when the BCP/Rh ratio exceeds 2, Rh hydride complexes of the composition RhH(BCP)₃ and RhH(BCP)₄ are formed. The source of the hydride ion is the ligand itself; most probably, H⁻ originates from the bridging CH₂ groups of BCP. The chemical shifts of these protons are sensitive to complexation due to the considerable electron density of HOMO and LUMO at one of the bridging CH₂ moieties. Molecular mechanics simulations of the molecular structure of these complexes show that two cavities are formed in [Rh(BCP)₃]⁺ by the aromatic rings of the ligands. These cavities may alternatively open and close, thus providing for a flexibly shielded catalytic site which explains the unusual catalytic behaviour of Rh complexes with BCP in hydrogenation and hydroformylation reactions. Received February 15, 2001. Accepted (revised) April 23, 2001     

A Novel Bicyclophosphite Ligand Directly Yields Rhodium Hydride Complexes

 Complexation of Rh(I) with o, o′-dimethylene-(tris-p-cresyl)-bicyclophosphite (BCP, 1) has been investigated in solution by NMR, semi-empirical quantum mechanical, and molecular mechanics calculations. ¹H and ³¹P NMR spectroscopic data show that when the BCP/Rh ratio exceeds 2, Rh hydride complexes of the composition RhH(BCP)₃ and RhH(BCP)₄ are formed. The source of the hydride ion is the ligand itself; most probably, H⁻ originates from the bridging CH₂ groups of BCP. The chemical shifts of these protons are sensitive to complexation due to the considerable electron density of HOMO and LUMO at one of the bridging CH₂ moieties. Molecular mechanics simulations of the molecular structure of these complexes show that two cavities are formed in [Rh(BCP)₃]⁺ by the aromatic rings of the ligands. These cavities may alternatively open and close, thus providing for a flexibly shielded catalytic site which explains the unusual catalytic behaviour of Rh complexes with BCP in hydrogenation and hydroformylation reactions.     

Anion Effect on Structure of Silver(I) Complexes with New Unsymmetrical Tripodal Ligand

Reactions of new unsymmetrical pyridyl‐ and imidazoyl‐containing tripodal ligand, 3‐(1H‐imidazol‐1‐yl)‐N,N‐bis(2‐pyridylmethyl)propan‐1‐amine ( L ), with varied silver(I) salts result in formation of three supramolecular architectures [Ag₂L₂](BF₄)₂·H₂O ( 1 ), [Ag₂L₂](ClO₄)₂·H₂O ( 2 ) and [Ag₃L₂](CF₃SO₃)₃ ( 3 ). All the structures were established by single‐crystal X‐ray diffraction analysis. In the solid state, three complexes consist of one‐dimensional infinite chains, in which the conformation and the bridging mode of L for complexes 1 and 2 are the same but 3 different. There are Ag···Ag and π‐π interactions in 3 . The results imply that the shape and size of the anion have great impact on the structure of the complexes. The complexes were also characterized by electrospray mass spectrometry.     

Metal Complexes with a New Tetrapyridyl Pendant Armed Macrocyclic Ligand. X‐ray Crystal Structures of CuII and NiII Complexes

A new pendant‐armed macrocyclic ligand, L¹, bearing four pyridyl pendant groups has been synthesized by N‐alkylation of the tetraazamacrocyclic precursor L with 2‐picolyl chloride hydrochloride. Metal complexes of L¹ have been synthesized and characterized by microanalysis, MS‐FAB, conductivity measurements, IR, UV‐Vis, ¹H and ¹³C NMR spectroscopy and magnetic studies. Crystal structures of the ligand L¹ as well as of the complexes [Ni₂L¹](ClO₄)₄·5CH₃CN and [Cu₂L¹](ClO₄)₄·4.5CH₃CN have been determined by single crystal X‐ray crystallography. The X ray studies show the presence of two metal atoms within the macrocyclic ligand in both metal complexes showing five coordination arrangement for the metal ions.