Koordinationschemie makrocyklischer liganden—I

Kinetics of reaction of benzyl chloride with sodium acetate/benzoate: phase transfer catalysis in solid-liquid system

“…Many tertiary amines, quaternary ammonium salts, crown ethers, cryptates, open-chain polyethers (glymes, polypodes), diamines, and polyamines are used as S-L PT catalysts (Hennis andco-workers, 1967,1968;Knóchel et al, 1975;Normant et al, 1975;Dehmlow, 1977).…”

“…However, the cyanide anion was found to react at least 100 times faster when catalyzed by crown ether relative to Aliquat 336. Knóchel et al (1975) have investigated the effect of a wide variety of macrocyclic polydentate ligands on the reaction of benzyl chloride with solid potassium acetate in acetonitrile. The characteristics of the ligand, which influence the reaction rate, were shown to be the stability of the metal-ligand complex, the lipophilicity of the ligand, the rigidity of the ligand, and the reactivity of the ligand toward the substrate (the aza crowns).…”

“…The characteristics of the ligand, which influence the reaction rate, were shown to be the stability of the metal-ligand complex, the lipophilicity of the ligand, the rigidity of the ligand, and the reactivity of the ligand toward the substrate (the aza crowns). Toke and Szabo' (1977) and Lehmkuhl et al (1977) have used polyethylene glycol ether as a catalyst for the reaction of benzyl chloride with potassium/ sodium acetate in acetonitrile. Dehmlow and Slopianka (1980) have reported that the reaction of benzyl bromide with aqueous potassium acetate was catalyzed by tetrabutylammonium bromide (TBAB).…”

New Fluorescent Chemosensors for Heavy Metal Ions Based on Functionalized Pendant Arm Derivatives of 7-Anthracenylmethyl-1,4,10-trioxa-7,13-diazacyclopentadecane

“…1,4,10-trioxa-7,13-diazacyclopentadecane ( L 1 ) is commercially available, and because of its marked tendency to bind different metal ions (alkali and alkaline earths, transition metals and lanthanides) − it has already been used as a receptor unit in redox and fluorescent conjugated chemosensors. − Normally, fluorescent conjugated chemosensors based on polyaza or aza−oxa macrocyclic receptors such as L 1 feature, for obvious synthetic reasons, all of the nitrogen donor atoms belonging to the macrocyclic framework functionalized with the same type of signaling fluorogenic unit ( L 2 in Figure reported by Martínez-Máñez and co-workers, which features two anthracenylmethyl units attached to the secondary nitrogen atoms of L 1 ; the emission intensity of L 2 is selectively enhanced in the presence of Hg II at basic pH in 1,4-dioxane/H 2 O, 70:30 v/v). − Martínez-Máñez and co-workers have also reported difunctionalized polyaza or aza−oxa macrocyclic receptors that contain more than one type of signaling unit; these systems can be considered as multiple-sensing chemosensors capable of displaying two or more macroscopic observable events upon the addition of a certain analyte …”

Application of macrocyclic compounds in chemical analysis

“…Another factor connected with solvent effects is the topology (conformation) of complexand, this effect, in a given solvent, being different in the cation complex than in the uncomplexed ligand. Using high resolution NMR spectroscopy, Knóckel et al (103) showed that the structure of the monocyclic 18-crown-4-oxa-2-aza ligand was much more affected by the solvent than that of cryptand 2.2.2. This is partly accounted for by the fact that the intramolecular hydrogen bonding between the two -NH groups, and of the latter with -CH2 groups, is different and is also solvent dependent.…”