Mary R. Truter

Alkali metal tetraphenylborate complexes with some macrocyclic, “Crown”, polyethers

Abstract Complexes of sodium, potassium and caesium with a range of cyclic polyethers have been synthesised using tetraphenylborate as the counterion. While some complexes are found to have similar metal co-ordination to compounds studied previously, the non co-ordination of the tetraphenylborate anion enables new products to be obtained when reaction conditions are varied. Thus, the sandwich compound Na(benzo-15- crown-5) 2 BPh 4 crystallises in high yield when appropriate reactant ratios are empoyed, and dibenzo-30-crown-10 is found to co-ordinate either one or two sodium ions depending on the solvent conditions used.

Methyl substituted macrocyclic ‘crown’ polyethers and their complexation

Abstract In an attempt to produce ligands selective for sodium a series of compounds having two methyl groups substituted in 15 or 18 membered cyclic polyethers have been synthesised. E.m.f. and NMR solution studies show that 1:1 species are present for both sodium and pottasium with the 18 membered series, whereas 1:2 potassium:ligand and 1:1 sodium:ligand are the major species for the 15 membered rings. This is supported by the isolation of crystalline complexes.

Specificities of cation permeabilities induced by some crown ethers in mitochondria

Abstract A series of macrocyclic crown ethers have been assayed as ionophores using respiring rat liver mitochondria, and the same compounds have been subjected to physicochemical investigation. Association constants and stoichiometries for the complexes with potassium, rubidium, and cesium were measured in methanol. Rates of transport of potassium bromide through aqueous/organic/aqueous systems and the partition coefficient from water into the organic phase were also measured and found to be in the same rank order as the association constants. Effective uptake by the mitochondria was clearly correlated with the complexing by the cation by one or more molecules of ionophore. Thus, for all three cations the most effective compound was the largest, i.e., di-t-butyldibenzo-30-crown-10, capable of wrapping around the cation. Other compounds giving measurable uptake were those which form sandwich complexes, one cation to two crown molecules; those containing five oxygen atoms induced greater uptake of potassium than of the other two alkali metals, while compounds containing six or seven oxygen atoms had greater effects on cesium or rubidium than on potassium. Within a structurally similar series of compounds the rank orders for uptake differed from those for the association constants; in particular, compounds having one benzene ring on an 18-membered crown compound were ineffective on all cations studied; effective compounds contained two benzene rings. In contrast to X-537A and A23187, none of the compounds caused release of magnesium from the mitochondria.

Crystal structure of a polyether dicarboxylic acid complex with potassium picrate, 2, 2′-di-o-carboxymethoxyphenoxydiethyletherpotassium picrate

Abstract X-ray crystal structure analysis has been carried out on the title compound. In a triclinic unit cell having a = 9.292(9), b = 11.224(3), 3 = 15.000(4)A, α = 95.4592), β = 99.22(4), γ = 108.15(4)° and space group P 1 , there are two units of formula {K[HOOC CH 2 O C 6 H 4 Oue5f8 CH 2 CH 2 ] 2 O} − . Least squares refinement reduced R to 0.0655 for 2210 photographic observations. The hydrogen atoms of the dicarboxylic acid were located unequivocally; one is involved in hydrogen bonding to a centrosymmetrically related carboxylic acid, the other hydrogen bonds the phenolic oxygen of a picrate anion. A centrosymmetrical bridge formed by a carbonyl oxygen atom holds the complex cation in a dimeric form. The eight coordinating oxygen atoms form a shallow helix round each potassium ion with Kue5f8 O distances 2.729–2.903 A; there are no intramolecular hydrogen bonds within the helix.

Crystal structures of complexes between alkali-metal salts and cyclic polyethers. Part V. The 1 : 2 complex formed between potassium iodide and 2,3,5,6,8,9,11,12-octahydro-1,4,7,10,13-benzopentaoxacyclopentadecin (benzo-15-crown-5)

Potassium iodide forms a 1 : 2 complex with the cyclic polyether ‘benzo-15-crown-5’. The crystals are tetragonal with a=b= 17·84(1), c= 9·750(6)A, Z= 4, space group P4/n. The crystal structure has been determined by the heavy-atom method and refined by full-matrix least-squares to a final R of 0·09 on 1603 diffractometer data. The complex cation has crystallographic symmetry , the potassium being ‘sandwiched’ between two centro-symmetrically related ligand molecules. In each of these the five ether-oxygen atoms are approximately coplanar, the cation lying 1·67 A away from this plane, so that the ten-co-ordination is an irregular pentagonal antiprism. The K–O distances range from 2·777(7) to 2·955(8)A. Iodide ions occupy two sets of positions with 4 or symmetry and the arrangement of complex cations and anions resembles the caesium chloride structure; there is no interaction between the anions and the metal.

Complex formation between guanidinium nitrate and 1,4,7,10,13,16-hexaoxacyclo-octadecane (18-crown-6). Crystal structure of the hydrogen-bonded 2 : 1 complex

Reaction between guanidinium nitrate and 18-crown-6 in ethanol yielded a crystalline complex of 2 : 1 stoicheiometry. Three-dimensional X-ray crystal structure analysis has shown the monoclinic unit cell, a= 8.969(1), b= 10.278(2), c= 14.253(1)A, β= 102.682(8)°, space group P21/c, to contain two centrosymmetrical entities, nitrate–guanidinium–18-crown-6-guanidinium–nitrate, the linkages being via a guanidinium hydrogen atom, H … O 1.91(13)A, to one oxygen atom of the ether, and from a second guanidinium hydrogen atom to one oxygen atom of the nitrate ion, H … O 2.08(18)A. Full-matrix least-squares refinement gave an R value of 0.083 for 711 reflections measured on a CAD-4 diffractometer. While the crystalline product isolated from an ethanol solution of guanidinium chloride and 18-crown-6 also has 2 : 1 stoicheiometry, calorimetric measurements establish that in methanol solution the interaction ratio is 1 : 1 even when the concentration of guanidinium chloride exceeds that of 18-crown-6 by a ratio of 4 : 1.

Crystal structures of complexes between alkali-metal salts and cyclic polyethers. Part IV. The crystal structures of dibenzo-30-crown-10 (2,3:17,18-dibenzo-1,4,7,10,13,16,19,22,25,28-decaoxacyclotriaconta-2,17-diene) and of its complex with potassium iodide

The crystal structures of the title compounds have been determined from X-ray diffractometer observations. The molecules of the cyclic ether are centrosymmetric with Z= 2 in a monoclinic unit cell having a= 16·960, b= 8·920, c= 9·096 A, β= 90·03°, and space group P21/c. They form loops approximately parallel to the a axis. The structure was solved by the iterative application of Sayres equation, and refined by least-squares methods to R 0·056 for 1414 independent observations.In the complex Z= 4 in an orthorhombic unit cell having a= 19·576, b= 12·405, and c= 12·965 A with space group Pnna. The structure was solved by conventional Patterson and Fourier methods and refined by least-squares techniques to R 0·046 for 1102 independent observations. Each potassium ion lies on a two-fold axis, and is enclosed by a ligand molecule wrapped round to give ten K–O distances in the range 2·850(6)–2·931(6)A. The iodide ions also lie on two-fold axes and are not in contact with potassium. The packing of the complex cations and the iodide ions is a distorted sodium chloride structure.Bond lengths and angles in the complexed and free molecules are the same; the conformations and different. Four of the C–C–O–C angles change from trans in the free molecule to gauche in the complex; the remaining torsion angles are of the same type in both forms but corresponding ones differ by as much as 30° and the sign may be reversed.

The synthesis and complexation of open chain polyethers having various end groups

Abstract The syntheses of a series of oxygen containing ligands of general formula o -ROC 6 H 4 O(CH 2 CH 2 O) n o C 6 H 4 OR′ are described; the complex formation of these ligands with alkali and alkaline earth metal cations has been investigated. Stability constants for sodium and potassium increase as n is increased from 1 to 3, as R is varied through the series, H, CH 2 C 6 H 5 , CH 2 CH 2 OH, CH 2 CO 2 C 2 H 5 , CH 2 CO 2 H. When R and R′ are different, the stability constant is intermediate between that found when both end groups are R and that when both are R′. In these compounds there is no evidence for the presence of internal hydrogen bonding contributing to the stability of the complexes.