Complexes of sodium and lithium borohydrides with macrocyclic polyethers

A method for the synthesis of complexes of sodium and lithium borohydrides with crown ethers is proposed. The complexes of sodium borohydride with benzo-15-crown-5, 4′-aminobenzo-15-crown-5, dibenzo-18-crown-6, and diaza-18-crown-6 and the complexes of lithium borohydride with benzo-15-crown-5 and dibenzo-18-crown-6 are synthesized. These complexes can be used for the preparation of hydrogen in their reactions with methanol. The complex formation does not affect the purity of hydrogen formed.     

Complexes of dibenzo-24-crown-8 with some sodium monoalkyl benzeneazophosphonates

Syntheses and properties of complexes of dibenzo-24-crown-8 with the sodium monoethyl ester and the sodium monobutyl ester of [α-(4-benzeneazoanilino)-N-benzyl]phosphonic acid, [α-(4-benzeneazoanilino)-N-4-hydroxybenzyl]phosphonic acid and [α-(4-benzeneazoanilino)-N-4-methoxybenzyl]phosphonic acid have been studied. The crystalline complexes formed were found to depend not only on the size of the cation and the crown ether cavity but also on the choice of anion and the reaction solvent. It was shown that the molecular structure and electronic configuration of the anion are important factors in a salt-ligand system which influence the case of solubilization and charge separation in solution. The complexes obtained were characterized on the basis of conductance measurements and UV, IR and ¹H NMR spectra.     

Interphase transfer of potassium and silver picrates with the participation of macrocyclic polyethers

The transfer of potassium and silver picrates through a liquid membrane in the presence of macrocyclic ligands containing donor atoms of oxygen, nitrogen, and sulfur, and thiophosphonyl groups in the ring has been studied. An interrelationship has been established between the rate of interphase transfer and the size of the constant of the extraction of the salt from an aqueous phase into an organic phase with the aid of macrocyclic polyethers.Translated from Teoreticheskaya i Éksperimental'naya Khimiya, Vol. 21, No. 5, pp. 600–604, September–October, 1985.     

Ultraviolet-visible spectroscopic study of ion-pairs of sodium and potassium monoethyl benzeneazophosphonates and their crown ether complexes in acetonitrile

The u.v.-vis spectroscopic study of ion-pairs of the sodium and potassium monoethyl ester of [α-(4-benzeneazoanilino)-N-benzyl] phosphoric acid, [α-(4-benzeneazoanilino)-N-4-hydroxybenzyl] phosphonic acid and [α-(4-benzeneazoanilino)-N-4-methoxybenzyl] phosphonic acid and their complexes with dibenzo-18-crown-6 and dibenzo-24-crown-8 is described. While the free sodium salts of monoethyl benzeneazophosphonic acids, with an extremely low solubility in acetonitrile, may be classified as tight ion-pair salts, the correspondingly more soluble potassium salts exist as solvated loose ion-pairs in acetonitrile solutions. The interaction of crown ether either with sodium or potassium monoethyl benzeneazophosphonates produces crown separated ion-pairs.     

New macrocyclic polyethers with remote binding sites

The synthesis and binding properties of new macrocyclic polyethers are described. These systems incorporate 2,2′-bipyridyl functions in such a fashion that binding of metal nuclei can occur at either the macro-cycle or the bipyridyl function. Evidence is presented that binding of alkali metals occurs at the crown ether cavity while binding of transition metals occurs at the bipyridyl function. Simultaneous binding of two different metals is interpreted in terms of electronic and allosteric effects.     

Complexation of iodine with macrocyclic polyethers and sulfides

The complexation of iodine with 12-, 15-, and 18-membered crown ethers containing two sulfur atoms in the macrocyclic ring was studied by the spectrophotometric method. It was shown that, in CCl₄, the stability constants of complexes with a 11 composition have a value of the order of magnitude of 10². The enthalpies of complexation are (22–34) kJ/mole, which is practically not different from the parameters of complexes of iodine with simple sulfides.Translated from Teoreticheskaya i Éksperimental'naya Khimiya, Vol. 24, No. 6, pp. 747–750, November–December, 1988.     

Synthesis of macrocyclic polyethers with partially fluorinated side arms

Different types of macrocyclic polyethers with partially fluorinated side arms are prepared. These new macrocyclic ligands are based on sym‐dibenzo‐16‐crown‐5 and sym‐dicyclohexano‐16‐crown‐5 scaffolds.     

Cesium fluoride assisted synthesis of macrocyclic polyethers with aromatic subunits

Several features of the synthesis of crown ethers with aromatic subunits by reactions of dihydroxyaromatic or bis(hydroxyaromatic) compounds with cesium fluoride and polyethylene glycol tosylates are explored. The method is utilized to prepare several new crown ethers and to synthesize known crown compounds in improved yields.     

PMR investigation of the hydration of macrocyclic polyethers

PMR was used to investigate the reaction of water dissolved in chloroform with ten macrocyclic polyethers, differing from each other by the kind of donor atoms, the size of the cavity, and the character of the substituants in the macrocycle. The curves representing the shift of the proton signal of water as function of the concentration of the macrocyclic polyether in chloroform were used to calculate the stability constants of the associates of the macrocyclic polyethers with water with the composiiton 11. The analysis of the association constants obtained showed that, according to their ability to coordinating water, the investigated macrocyclic polyethers can be placed into the following order: diaza-18-crown-6 > dicyclohexyl-18-crown-6 > kryptand(2.2.2) > 18-crown-6 > dibenzo-18-crown-6 > dibenzo-24-crown-8 > 15-crown-6 > benzo-15-crown-5 > dithio-18-crown-6 > benzo-12-crown-4.Translated from Teoreticheskaya i Eksperimental'naya Khimiya, Vol. 21, No. 2, pp. 248–252, March–April, 1985.     

Complexation of protons by macrocyclic polyethers in acetonitrile

The complexation of H⁺ by different macrocyclic polyethers in acetonitrile solutions has been studied by means of calorimetric titrations. The most stable complex is observed with 18-crown-6. The measured stability constants decrease when the number of benzo substituents of 18C6 are increased. The stability of the complexes formed with larger macrocyclic polyethers is also smaller in comparison with 18C6. Unfavourable entropic changes during the reaction are responsible. Compared with noncyclic polyethers all ligands studied form more stable complexes. Favourable entropic contributions are mainly responsible.     

新型大环聚醚的合成及配位性能

本文报道一类新型大环聚醚的合成.在以1,7-二氧杂-4,10-二氮杂环十二烷(1a)及1,7,10,16-四氧杂-4,13-二氮杂环十八烷(1b)中的两个仲胺上进行含醚键的卤代烷取代反应,获得一批带有两个含有侧链醚键的新型冠醚.以碳酸钾为缩合剂,所得冠醚碱金属配合物经酸分解及四甲基氢氧化铵处理后,得游离的大环聚醚. 用溶解度法初步测定了这类冠醚对碱金属的配位性能.结果指出,其母环及侧链上氧原子数的多少及碱金属离子半径的大小均影响配合物的稳定性,其中有些冠醚对碱金属有良好的配位能力,有的还具有优异的选择性,例如N,N′-β-甲氧基乙基-1,7-二氧杂-4,10-二氮杂环十二烷(13a)对钾及钠离子的选择比大于18-c-β,并比4,4′(5′)-二甲基苯并-30-c-10还高.     

The synthesis and coordination properties of new macrocyclic polyethers

A new type of macrocyclic polyethers has been synthesized. It consists of an azacrown ether as mother ring, e.g. 1,7-dioxa-4,10-diaza-cyclododecane (1a) or 1,7,10,16-tetraoxa-4,13-diazacycloocatadecane (1b), and two side chains attached on the two nitrogen atoms of 1a or 1b. A number of these new crown ethers are obtained by alkylation of the two secondary amino groups of 1a or 1b with corresponding halides, BrCH₂(CH₂OCH₂)_nCH₂OR, in the presence of potassium carbonate. The crown-alkali metal complex thus obtained is hydrolyzed by acid. In order to obtain pure crown ether the reaction mixture is treated with tetramethylammonium hydroxide and followed by solvent extraction. The ability of complexing alkali cations of macrocyclic polyethers in terms of the equilibrium constant have been studied by the method of solubilities of salts in chloroform. It is shown that the size of the mother ring, the number of oxygen atoms either in the ring or in the side-chains, and the ionic radius of the alkali metal are the factors governing the stability of the metal complexes. Most of these new crown ethers possess high ability for alkali metal complexation some of them, such as N,N′- di-β-methoxyethyl-1,7-dioxa-4,10-diaza-cyclododecanc (13a), possesses higher selectivity for Na+ and K+ ions than 18-crown-6- and 4,4′(5′)-dimethylbenz-30-crown-10.     

The synthesis of deuterium labeled macrocyclic polyethers (crown ethers)

Five tetradeuterated analogues ( 1a, 1b, 1c, 1d , and 1e ) of 3,6,9,12,15-pentaoxa-21-aza-bicyclo[15.3.1]heneicosa-1(21),17,19-triene (pyridyl-18-crown-6, 1 ) have been prepared corresponding to the five unique protonated carbon atoms of the polyether cycle. Deuterium labeling was ≥ 99% for four of the compounds and ≥ 97% for the other (1a ).     

Primary amine drug sensitive electrodes based on macrocyclic polyethers with 2,2′-dinaphthyl subunits

Dinaphthyl macrocyclic polyethers were synthesized and used as neutral carriers for preparing primary amine drug sensitive PVC membrane electrodes. Contrary to the ion-associate based electrodes, which show an excellent potentiometric response to quaternary ammonium ions and the like, but a very poor response to primary amines, the macrocyclic polyether-based electrodes showed potentiometric response characteristics with primary amines preferred. Dinaphthyl macrocyclic polyether-based electrodes are superior to those based on common macrocyclic polyethers for their potentiometric selectivity coefficients much lower than those of the latter. The main characteristics of a dinaphthyl-20-crown-6-based benzyl amine sensitive electrode are as follows: linear response range, 4.2 × 10^–5 – 1.0 ×10^–1 M; slope, 51.3 mV/decade; and detection limit, 4.6 × 10^–6 M. A mexiletine sensitive electrode was prepared using dinaphthyl-23-crown-7 with following performance features: linear response range, 2.0 × 10^–5 – 1.0 ×10^–1 M; slope, 52.1mV/decade; and detection limit, 5.0 × 10^–6 M.