Search results for "Cyclophane"

Silver Ion-Selective Electrodes Based on π-Coordinating Ionophores Without Heteroatoms

2002

Ion-selective electrodes (ISEs) were constructed by using spherical hydrocarbons (cyclophanes) as π-coordinating ionophores in solvent polymeric membranes. Four structurally similar cyclophanes, i. e., [2.2.2]p,p,p-cyclophane, [2.2.2]m,p,p-cyclophane, [2.2.1]p,p,p-cyclophane and [2.2.1]m,p,p-cyclophane were studied as ionophores for Ag+. The ion-selective membranes were composed of the corresponding ionophore (1%), potassium tetrakis(4-chlorophenyl)borate (0.5%), 2-nitrophenyl octyl ether (65–66%) and PVC (32–33%). The ion-selective membrane was placed on top of a layer of the conducting polymer, poly(3,4-ethylenedioxythiophene) (PEDOT), working as ion-to-electron transducer. The selectivit…

Nitrate Encapsulation within the Cavity of Polyazapyridinophane. Considerations on Nitrate−Pyridine Interactions

2010

Interaction of nitrate anions with a cyclophane (L) containing two pyridine units connected to two diethylenetriamine bridges through methylene positions is reported both in pure water and in the solid state. The crystal structure of [H4L](NO3)4 shows that one of the nitrate anions resides in the macrocyclic cavity forming two sets of bifurcated hydrogen bonds with the four protonated amino groups of the macrocycle. This anion is symmetrically placed in the middle of the pyridine rings with distances between its nitrogen atom and the centroids of the ring of 3.58 A. Despite this location, calculations by theoretical analysis were carried out to confirm whether the stabilizing effect is due …

Stability and kinetics of the acid-promoted decomposition of Cu(II) complexes with hexaazacyclophanes: kinetic studies as a probe to detect changes i…

2004

The synthesis, protonation and Cu(II) coordination features of the novel azacyclophane type receptors 2,6,10,13,17,21-hexaza[22]-(2,6)-pyridinophane (L2), 2,6,9,12,15,19-hexaza[20]-(2,6)-pyridinophane (L5) and 2,6,9,12,15,19-hexaza[20]metacyclophane (L6) are presented. The protonation and Cu(II) constants are analysed and compared with the previously reported open-chain polyamines 4,8,11,15-tetrazaoctadecane-1,18-diamine (L1) and 4,7,10,13-tetraazahexadecane-1,16-diamine (L4) and of the cyclophane 2,6,10,13,17,21-hexaaza[22]paracyclophane (L3). All the systems form mono- and dinuclear complexes whose stability and pH range of existence depend on the type of hydrocarbon chains and molecular …

Dithiametacyclophane mit Dreifachbindungen

1994

Dithiametacyclophanes with Triple Bonds Schemes 1 and 2 show the syntheses of dithia[8]metacyclo-phanes 4a-d and tetrathia[m.n]metacyclophanes 9, 10 by cyclization reactions applying the cesium effect. All these cyclophanes contain C—C triple bonds which influence the molecular dynamics; especially the halogen substituents in 4b-d obstruct the topomerization.

[3.3]Metacyclophane mit anti ‐Konformation

1992

[3.3]Metacyclophanes with anti Conformation The [3.3]metacyclophanes 5 and 9 with prevailing anti conformation were prepared by using different cyclisation techniques. 1H-NMR studies and X-ray structure analyses of both phanes 5 and 9 prove their unprecedented conformations.

Photochemie des 1,3,5‐Tristyrylbenzols

1984

In Abhangigkeit von den Reaktionsbedingungen erhalt man bei der Belichtung der Titelverbindung 1 das Cyclophan 5, das Pyrenderivat 6 oder das polykondensierte aromatische System 9. Fur den neuen Cyclophantyp 5, bei dem zwei Benzolringe selbst wieder durch Ringe verbruckt sind, wurde eine Rontgenstrukturanalyse durchgefuhrt. Photochemistry of 1,3,5-Tristyrylbenzene Depending on the reaction conditions the irradiation of the title compound 1 yields the cyclophane 5, the pyrene derivative 6, or the polycondensed aromatic system 9. An X-ray analysis was performed for 5, representing a new type of cyclophane in which two benzene rings are bridged again by rings.

Equilibrium and Kinetic Properties of Cu II Cyclophane Complexes: The Effect of Changes in the Macrocyclic Cavity Caused by Changes in the Substituti…

2008

The o-B232, m-B232 and p-B232 cyclophanes result from attaching the terminal amine groups of 1,4,8,11-tetraazaundecane (232) to the benzylic carbons of the corresponding o-, m- or p-xylanes. The cavity size of these cyclophanes changes moderately as a consequence of the substitution at the aromatic ring. The effects caused by these changes on the equilibrium constants for protonation and CuII complex formation of the cyclophanes are analyzed and compared with those of the noncyclic 232 polyamine. All three cyclophanes form mononuclear complexes, but only o-B232 is able to coordinate to CuII through the four amine groups simultaneously, whereas m-B232 and p-B232 can only use three nitrogen d…

1,2,3,4,5‐[1′,8′] Anthra‐8,9;10,11‐dibenzo[13]annulene and 1,8‐Distyrylanthracene as Models for Phenylenevinylene Species. Syntheses, Structures, and…

1987

The synthesis of the title compound 4, formally a [13] perimeter, and of its acyclic model system, 1,8-distyrylanthracene (6) is described. The crystal structure of 4 reveals the configuration of the double bonds and the conformation of the macrocycle. Related findings come from the 1H-NMR spectroscopic characterization of 4 and 6 in solution. The spin density distribution of the radical anions 4−· and 6−· is interpretet in terms of the singly occupied molecular orbital and of the prevailing geometry. In contrast to 4, compund 6 proves to be an efficient electron acceptor since it can even be reduced to a tetraanion salt. The complete redox sequence is characterized by NMR and ESR spectrosc…

Photochemie des 1,3‐Distyrylbenzols — Ein neuer Weg zu syn ‐[2.2](1,3)Cyclophanen

1986

Adamantan als Baustein neuer Araliphane Synthese, Spektroskopie und Kristallstrukturen

1991

Adamantane as a Building Block of New Araliphanes – Synthesis, Spectroscopy, and Crystal Structures Exchange of benzene units for aliphatic building blocks in cyclophanes leads to new molecules of the “araliphane” type. With adamantane the araliphanes 2 – 4 are synthesized. Their stereochemical behavior as shown by NMR studies and X-ray crystallographic analyses differs significantly from that of their aromatic counterparts. The signals of the intraannular adamantane hydrogens are strongly shifted upfield up to δ=– 2.18 (in 2). 4 is obtained as a racemic mixture of enantiomers (in the crystalline state) and shows a boat-like deformation of the benzene moiety.