Search results for "Cyclophane"

Photochemical Generation of Cyclophanes from 1,3,5-Trisubstituted Benzenes with Chalcone Chromophores

2007

(E,E,E)-1,3,5-Tricinnamoylbenzene (7a) photodimerizes in solution to the [4.4.4](1,3,5)cyclophane 8a. The process consists of three consecutive steps in which cisoid enone conformations of 7a react in regio- and stereoselective anti-head-to-head cycloadditions. (E,E,E)-1,3,5-Tris(3-oxo-3-phenylpropenyl)benzene (13a), an isomer of 7 with reversed enone units, shows a single [2π+2π] cycloaddition of the same type. Due to steric reasons, it is afterwards not capable of intramolecular processes and oligomerizes by intermolecular photocycloadditions. Photolyses in the crystalline state yield dimers by topochemically controlled syn-head-to-tail processes (7a → 10a, 13a → 15a). An efficient dimeri…

Polyether-bridged cyclophanes incorporating bisphenol A units as neutral receptors for quats: synthesis, molecular structure and binding properties

2001

Two novel neutral polyoxyethylene bridged cyclophanes (2a and 2b) incorporating bisphenol A units were synthesized and characterized by means of x-ray crystal structure determination. The binding properties of 2a and 2b toward tetramethylammonium, N-methylpyridinium, and acetylcholine cations were evaluated by means of 1H NMR spectroscopy. Consistent with indications provided by the molecular structure, the cavity in the basket-like cyclophanes is large enough to accommodate the given guest cations conveniently. Circumstantial evidence was obtained that 1,1,2,2-tetrachloroethane is too large to enter the cavity of the smaller cyclophane 2a, but can be included in the cavity of the larger cy…

Makrobicyclische Endorezeptoren: Synthese, Kristallstruktur und Einschluß organischer Gastmoleküle

1992

Macrobicyclic Endoreceptors: Synthesis, Crystal Structure, and Inclusion of Organic Guests The macrobicyclic ligand 2 is synthesized in a one-step cyclization procedure. According to an X-ray structure analysis three dichloromethane guest molecules are included inside the cavity, whereas water and methanol are found outside the cavity. The rigid endo preorganization of the nitrogen donors allows the complexation of three 2,9-disubstituted 1,10-phenanthrolines inside the cavity.

Double and triple calix[4]arenis connected via the oxygen functions

1990

New macrocyclic molecules are described containing two or three p-tert-butylcalix[4]arene subunits connected via their oxygen atoms. These macrocycles are available by two general methods which are capable of producing assemblies with bridges of varying rigidity and length.

Synthesis and protonation behaviour of the macrocycle 2,6,10,13,17,21-hexaaza[22]metacyclophane. Thermodynamic and NMR studies on the interaction of …

1996

Abstract The novel cyclophane receptor 2,6,10,13,17,21-hexaaza[22]metacyclophane (L) has been synthesised and characterised. The acid-base behaviour and interaction with ATP, ADP and AMP have been studied by potentiometry in 0.15 mol dm−3 at 298.1 K and multinuclear NMR. L presents in its protonated forms a molecular organization which enables its multipoint binding with nucleotides. Salt-bridge formation occur between the polyammonium sites of L and the phosphate chain of the nucleotides while π-stacking between the meta-phenylene subunit incorporated in the receptor and the adenine ring of the nucleotides.

Synthesis, Protonation and Cu II Complexes of Two Novel Isomeric Pentaazacyclophane Ligands: Potentiometric, DFT, Kinetic and AMP Recognition Studies

2008

The synthesis and coordination chemistry of two novel ligands, 2,6,9,12,16-pentaaza[17]metacyclophane (L1) and 2,6,9,12,16-pentaaza[17]paracyclophane (L2), is described. Potentiometric studies indicate that L1 and L2 form a variety of mononuclear complexes the stability constants of which reveal a change in the denticity of the ligand when moving from L1 to L2, a behaviour that can be qualitatively explained by the inability of the paracyclophanes to simultaneously use both benzylic nitrogen atoms for coordination to a single metal centre. In contrast, the formation of dinuclear hydroxylated complexes is more favoured for the paraL2 ligand. DFT calculations have been carried out to compare …

Concave π-prismand hydrocarbon [2.2.2]cyclophanes and their crystalline Ag-triflate complexes

1999

New small concave hydrocarbon cyclophanes were prepared via the well-known HD-2SO2-method. The cyclophanes obtained are isomers of the very well-known [2.2.2]p,p,p-cyclophane, C24H24, a π-prismand efficiently complexing Ag+-ion. X-ray crystal structure determinations showed the bis-sulfide 7 (1,10-dithia[3.3.2]m,p,p-cyclophane) to be helically chiral and that the conformation of the parent hydrocarbon cyclophane 13 ([2.2.2]m,p,p-cyclophane) does not change dramatically upon complexation with the Ag+-ion. The 16- and 17-membered [2.2.2]m,m,p- and [2.2.2]m,p,p-cyclophane (15 and 16) also act as π-prismands and form surprisingly similar crystalline 1:1 Ag-triflate complexes (π-prismates) as th…

Das erste verklammerte und stark deformierte Adamantan

1990

Calix[4]arenes with resorcinol units incorporated in 2,6-position

1990

Abstract Calix[4]arenes containing one or two resorcinol units incorporated via their 2,6-positions were prepared by fragment condensation. Due to the cyclic array of intramolecular hydrogen bonds these molecules assume the cone-conformation.

New molecular catalysts for ATP cleavage. Criteria of size complementarity

2000

The interaction of the cyclophane receptor 2,5,8,11,14,17-hexaaza[18]metacyclophane (L) with the nucleotides ATP, ADP and AMP is described. L yields one of the largest rate enhancements for hydrolytic ATP cleavage observed in macrocyclic polyamines. The process is specific for the formation of ADP and involves a high degree of geometrical complementarity between host and guest species. The analogue compound 24-hydroxy-2,5,8,11,14,17-hexaaza[18]metacyclophane (L11) shows also a high degree of ATP activation. However, in this case deprotonation of the hydroxy group results in almost complete quenching of the ATPase activity above pH 7.0.