腙型双冠醚对碱金属的配位性能

本文报道了五个腙型双冠醚的合成。电导测定结果表明含苯并-15-冠-5单元的双冠醚与四苯基硼酸钾、铷、铯,含苯并-18-冠-6单元的双冠醚与四苯基硼酸铯生成2:1夹心型配合物(冠醚单元:金属离子)。并用这些双冠醚的氯仿溶液萃取苦味酸碱金属盐水溶液,测定了萃取百分率和计算了萃取平衡常数,结果表明腙型双冠醚的萃取能力及选择性优于相应的单冠醚。     

Potentiometric and AM1d studies of the equilibria between silver(I) and diaza-15-crown and diaza-18-crown ethers with nitrogen in different positions in various solvents

Abstract

Complex formation and stability constants between typical and atypical diaza-15-crown and diaza-18-crown ethers with silver(I) were determined in methanol, acetonitrile and propylene carbonate by the potentiometric method. In two of the diaza crown ethers, AA-diaza-15 and AA-diaza-18-crown, two nitrogens in the macrocyclic ring replaced two consecutive oxygens instead of two opposite ones in the two other diaza crown ethers. It was found that complexes of 1:1 and 1:2 metal-to-ligand stoichiometry were formed. The solvent composition and cavity size of crown ethers significantly influences the stability constants of complexes. AA-diaza-15 and AA-diaza-18-crown ethers were examined for comparison with diaza-15-crown and diaza-18-crown ethers. AA-diaza crown ethers formed less stable 1:1 metal-to-ligand complexes with silver(I) than typical diaza crown ethers but their ability to form 1:2 metal-to-ligand complexes was stronger. The energetically most favorable structures of the 1:1 metal-to-ligand complexes were calculated and visualized by the AM1d method at the semiempirical level of theory.     

Schiff碱型和仲胺型双冠醚的合成和配位性能

由水杨醛与α,ω-二溴代烷或二(对-甲苯磺酸)三甘醇酯反应,制成相应的二醛化合物。再与4′-氨基苯并-15-冠-5反应生成5种Schiff碱型双冠醚,经LiAlH_4还原可生成5种仲胺型双冠醚。电导率测量结果表明可与KCl(Rb)盐生成2:1(冠醚单元:金属离子)的夹心型配合物。而与钠离子形成1:1配合物。用双冠醚制成PVC膜钾离子选择电极,并测量了电极的线性范围和选择系数。     

Dissociation of polyether-transition metal ion dimer complexes in a quadrupole ion trap

The formation and dissociation of dimer complexes consisting of a transition metal ion and two polyether ligands is examined in a quadrupole ion trap mass spectrometer. Reactions of three transition metals (Ni, Cu, Co) with three crown ethers and four acyclic ethers (glymes) are studied. Singly charged species are created from ion-molecule reactions between laser-desorbed monopositive metal ions and the neutral polyethers. Doubly charged complexes are generated from electrospray ionization of solutions containing metal salts and polyethers. For the singly charged complexes, the capability for dimer formation by the ethers is dependent on the number of available coordination sites on the ligand and its ability to fully coordinate the metal ion. For example, 18-crown-6 never forms dimer complexes, but 12-crown-4 readily forms dimers. For the more flexible acyclic ethers, the ligands that have four or more oxygen atoms do not form dimer complexes because the acyclic ligands have sufficient flexibility to wrap around the metal ion and prevent attachment of a second ligand. For the doubly charged complexes, dimers are observed for all of the crown ethers and glymes, thus showing no dependence on the flexibility or number of coordination sites of the polyether. The nonselectivity of dimer formation is attributed to the higher charge density of the doubly charged metal center, resulting in stronger coordination abilities. Collisionally activated dissociation is used to evaluate the structures of the metal-polyether dimer complexes. Radical fragmentation processes are observed for some of the singly charged dimer complexes because these pathways allow the monopositive metal ion to attain a more favorable 2 + oxidation state. These radical losses are observed for the dimer complexes but not for the monomer complexes because the dimer structures have two independent ligands, a feature that enhances the coordination geometry of the complex and allows more flexibility for the rearrangements necessary for loss of radical species. Dissociation of the doubly charged complexes generated by electrospray ionization does not result in losses of radical neutrals because the metal ions already exist in favorable 2+ oxidation states.     

含三嗪环的双冠醚——Ⅱ.电导行为及其在离子选择电极上的应用

用电导法研究了五种三嗪环双冠醚与碱金属盐的配合物的组成,报导了用这些双冠醚制备的PVC膜钾离子选择性电极的性能。     

Schiff碱型双冠醚的合成及性质

用脂链或芳环桥联两个苯并—15—冠—5单元的双冠醚报道较多,而桥联苯并-18-冠-6或苯并-12-冠-4单元的双冠醚报道较少。本文报道以α,ω-二卤代烷或二(对甲苯磺酸)二甘醇酯与邻羟基苯甲醛反应,制成相应的二醛化合物1_(α-∫)后使它们分别与4′-氨基苯并-18-冠-6或4′-氨基苯并-12-冠-4反应,得到脂芳混合桥联的schiff碱型双冠醚2_(b-∫)或3_(?)。     

双冠醚研究(Ⅴ)——Schiff碱型和仲胺型双-(苯并-18-冠-6)对碱金属苦味酸盐的萃取性质

用两类结构不同的Schiff碱型、仲胺型双-(苯并-18-冠-6)在氯仿-水体系中对碱金属苦味酸盐进行萃取,测量了配合物组成比和萃取平衡常数。     

Formation Constants of Complexes of Monovalent Cations with Benzocrown Ethers in Nitromethane

The complexation reactions between the macrocyclic polyethers dibenzo-18-crown-6, benzo-18-crown-6, benzo-15-crown-5 and polyethers bearing a stilbene unit with alkali metal and silver cations have been studied conductometrically in nitromethane. The formation constants of 1 : 1 and 1 : 2 (metal : ligand) complexes were determined and found to decrease with increasing cation diameter. The stability of the stilbene crown – metal cation complexes is lower than for complexes of other investigated crown ethers with analogous cations. There seem to be some effects of double bond-silver ion interactions.     

Computerized conductometric determination of stability constants of complexes of crown ethers with alkali metal salts and with neutral molecules in polar solvents

A computerized conductometric procedure for the determination of stability constants of the complexes of crown ethers (15-crown-5, benzo-15-crown-5 and 12-crown-4) with alkali metal salts in polar solvents is described, based on a microcomputer-controlled titration system. For the control of the experiments from software, a modular computer program was written in FORTH computer language. The procedure is especially suitable for the study of 1:2 metal ion/ligand complexes, which occur frequently with the compounds used. For the study of the interaction between crown ethers and neutral molecules, an indirect procedure is outlined.     

Solvent Effect upon Ion-pair Extraction of Different Sodium Dyes Using Some Crown Ethers

Liquid-liquid extractive-spectrophotometric studies of sodium ion complexes of 18-crown-6(18C6), dibenzo-18-crown-6(DB18C6), 15-crown-5(15C5), and 12-crown-4(12C4) and anionic dyes [4-(2-pyridylazo)-resorcinol monosodium salt monohydrate (PAR), Eriochrom Black T (EBT), and methyl orange (MOR)] and sodium picrate (PICRAT) as the counter ion are described. The overall extraction equilibrium constants for the 1 : 1 complexes of the above crown ethers with sodium dyes between different organic solvents and water have been determined at 25deg;C. They were conducted in various solvent-water systems maintaining an identical initial cation concentration in water, [M0+]w, and macrocyclic ligand concentration in the organic phase, [L0]org}, so that in all extractions [M0+]w : [L0]org ratios were 1 : 1, 1 : 10, 1 : 20, 1 : 50, and 1 : 62.5. An ion association complex formed between the sodium-crown ether complex ion and a dye anion was extracted into the organic solvent, and then the dye concentration of the separated aqueous phase was measured with an ultraviolet-visible spectrophotometer. PAR was the best associated dye with all crown ethers sodium-dyes and the extracted dye occurs as the ion-pair complex. Methylene chloride was found to be better than other extractive solvents used in this study.     

冠醚配合物的研究XV．若干席夫碱及仲胺型双冠醚和碱金属离子的配位反应

本文运用微量电导滴定及计算机拟合技术，研究了若干席夫碱及仲胺型双冠醚和减金属离子的配位反应，测定了配合物的组成及稳定常数，并对实验结果进行了讨论．     

冠醚配合物的研究XV.若干席夫碱及仲胺型双冠醚和碱金属离子的配位反应

本文运用微量电导滴定及计算机拟合技术，研究了若干席夫碱及仲胺型双冠醚和碱金属离子的配位反应，测定了配合物的组成及稳定常数，并对实验结果进行了讨论。     

A comparison of complexation of Li+ ion with macrocyclic ligands 15-crown-5 and 12-crown-4 in binary nitromethane-acetonitrile mixtures by using lithium-7 NMR technique and ab initio calculation

Lithium-7 NMR measurements were used to investigate the stoichiometry and stability of Li+ complexes with 15-crown-5 (15C5), benzo-15-crown-5 (B15C5), dibenzo-15-crown-5 (DB15C5) and 12-crown-4 (12C4) in a number of nitromethane (NM)-acetonitrile (AN) binary mixtures. In all cases, the exchange between the free and complexed lithium ion was fast on the NMR time scale and a single population average resonance was observed. While all crown ethers form 1:1 complexes with Li+ ion in the binary mixtures used, both 1:1 and 2:1 (sandwich) complexes were observed between lithium ion and 12C4 in pure nitromethane solution. Stepwise formation constants of the 1:1 and 2:1 (ligand/metal) complexes were evaluated from computer fitting of the NMR-mole ratio data to equations which relate the observed metal ion chemical shifts to formation constants. There is an inverse linear relationship between the logarithms of the stability constants and the mole fraction of acetonitrile in the solvent mixtures. The stability order of the 1:1 complexes was found to be 15C5·Li+>B15C5·Li+>DB15C5·Li+>12C4·Li+. The optimized structures of the free ligands and their 1:1 and 2:1 complexes with Li+ ion were predicted by ab initio theoretical calculations using the Gaussian 98 software, and the results are discussed.     

A fast atom bombardment mass spectrometric analysis of crown ether complexes [1]

Analyses of crown ether complexes of alkali metal ions and characterization of the complexes formed inm-nitrobenzyl alcohol have been carried out by fast atom bombardment (FAB) mass spectrometry. By using m-nitrobenzyl alcohol as a matrix for measurements, the stoichiometry of the complexes was assessed on the basis of the observed FAB peaks. In addition, the formation of crown ether-alkali metal complexes at a 2 : 1 molar ratio was enhanced by increasing the ionic radius of the metal ion in agreement with previous observations. On these grounds, FAB mass spectrometry may provide a rapid means for investigation of the complexation behavior of crown ethers and the stoichiometry of the complexes.     

Ion pairing in metal nitrate complexes of optically active crown ethers detected by circular dichroism

The detection by circular dichroism of ion pair formation in the lithium nitrate complexes of two new optically active crown ethers is described.     

Lithium-7 nuclear magnetic resonance and calorimetric study of lithium crown complexes in various solvents

Lithium-7 NMR studies have been carried out on lithium ion complexes with crown ethers 12C4, 15C5, and 18C6 in water and in several nonaqueous solvents. In all cases the exchange between the free and complexed lithium ion was fast on the NMR time scale, and a single, population average, resonance was observed. Both 1:1 and 2:1 (sandwich) complexes were observed between lithium ion and 12C4 in nitromethane solution. The stability of the complexes varied very significantly with the solvent. With the exception of pyridine, the stability varies inversely with the Gutmann donor number of the solvent. In general, the stability order of the complexes was found to be 15C5·Li⁺>12C4·Li⁺>18C6·Li⁺. Calorimetric studies on these complexes show that, in most cases, the complexes are both enthalpy and entropy stabilized.     

The complexation of the ammonium ion by 18-crown-6 in different solvents and by noncyclic ligands,crown ethers and cryptands in methanol

The complexation of the ammonium ion with the macrocyclic ligand 18-crown-6 was studied using calorimetric and potentiometric titrations in different solvents. In water and dimethyl sulphoxide the stability constants had the lowest values compared with all other solvents examined. No specific interactions between the ammonium ion and solvent molecules were observed. Crown ethers formed more stable complexes in methanol with the ammonium ion than diaza crown ethers. The most stable complexes were formed with cryptands. The highest values of the stability constants for the reaction with macrocyclic and macrobicyclic ligands were measured if the dimensions of the ammonium ion and of the cavities were nearly identical.     

High energy collision-induced dissociation of alkali-metal ion adducts of crown ethers and acyclic analogs.

High energy collision-induced dissociation (CID) techniques were applied for structural elucidation of alkali-metal ion adducts of crown ethers. The CID of alkali-metal adducts of tetraglyme and hexaethylene glycol were also evaluated to contrast the fragmentation pathways of the cyclic ethers with those of acyclic analogs. A common fragmentation channel for alkali-metal ion adducts of all the ethers, which results in distonic radical cations, is the homolytic cleavage of carbon-carbon bonds. Additionally, dissociation by carbon-oxygen bond cleavages occurs, and these processes are analogous to the fragmentation pathways observed for simple protonated ethers. The proposed fragmentation pathways for alkali-metal ion adducts of crown ethers result mostly in odd-electron, acyclic product ions. Dissociation of the alkali-metal ion adducts of the acyclic ethers is dominated by losses of various neutral species after an initial hydride or proton transfer. The CID processes for all ethers are independent of the alkali-metal ion sizes; however, the extent of dissociation of the complexes to bare alkali-metal ions increases with the size of the metal.     

Complexing properties of 3′,5′‐disubstituted‐4′‐hydroxybenzyl armed monoaza‐12‐crown‐4 and armed monoaza‐15‐crown‐5 ethers and crystal structures of the alkali metal ion complexes

A series of monoaza‐15‐crown‐5 ethers (2b‐2h) having 4′‐hydroxy‐3′,5′‐disubstituted benzyl groups have been prepared by the Mannich reaction of 2,6‐disubstituted phenols with the corresponding N‐methoxymethylmonoaza‐crown ethers. Competitive transport through a chloroform membrane by 12‐crown‐4 derivatives (lithium, potassium and cesium) and 15‐crown‐5 derivatives (sodium, potassium and cesium) were measured under basic‐source phase and acidic‐receiving phase conditions. All ligands transported size‐matched alkali‐metal cations. Ligands 1h and 2h with two fluorine atoms in the side arm gave higher metal ion transport rates than those of dimethyl‐ (1a and 2a), diisopropyl‐ (1b and 2b), and butylmethyl‐ (1d and 2d) derivatives. X‐ray crystal structures of six alkali metal complexes with monoaza‐12‐crown‐4‐derivatives ( 1b‐LiSCN, 1b‐KSCN, 1c‐NaSCN, 1d‐LiSCN, 1f‐RbSCN and 1h‐LiSCN ) and three alkali metal complexes with 15‐crown‐5 derivatives ( 2b‐KSCN, 2c‐KSCN , and 2e‐KSCN ) along with crystal structures of some new ligands (1b, 1c, 1d, 1f, and 2c) are also reported. These X‐ray analyses indicate that the crystal structures of the alkali metal ion complexes of these new armed‐crown ethers changed depending on the substituents at the 3′‐ and 5′‐positions of the appended hydroxybenzyl arms.     

alpha-Nitration of Ketones via Enol Silyl Ethers. Radical Cations as Reactive Intermediates in Thermal and Photochemical Processes

Highly colored (red) solutions of various enol silyl ethers and tetranitromethane (TNM) are readily bleached to afford good yields of alpha-nitro ketones in the dark at room temperature or below. Spectral analysis show the red colors to be associated with the intermolecular 1:1 electron donor-acceptor (EDA) complexes between the enol silyl ether and TNM. The formation of similar vividly colored EDA complexes with other electron acceptors (such as chloranil, tetracyanobenzene, tetracyanoquinodimethane, etc.) readily establish enol silyl ethers to be excellent electron donors. The deliberate irradiation of the diagnostic (red) charge-transfer absorption bands of the EDA complexes of enol silyl ethers and TNM at -40 degrees C affords directly the same alpha-nitro ketones, under conditions in which the thermal reaction is too slow to compete. A common pathway is discussed in which the electron transfer from the enol silyl ether (ESE) to TNM results in the radical ion triad [ESE(*)(+), NO(2)(*), C(NO(2))(3)(-)]. A subsequent fast homolytic coupling of the cation radical of the enol silyl ether with NO(2)(*)() leads to the alpha-nitro ketones. The use of time-resolved spectroscopy and the disparate behavior of the isomeric enol silyl ethers of alpha- and beta-tetralones as well as of 2-methylcyclohexanone strongly support cation radicals (ESE(*)(+)) as the critical intermediate in thermal and photoinduced electron-transfer as described in Schemes 1 and 2, respectively.