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The reaction of 1,l'-ferrocenylene-bis(methy1enepyridinium) tosylate chloride (1) with aza-x-crown-y (x/y = 1214; 1515; 181 6) gives the three novel ferrocene biscrown ethers 1,l'-ferrocenylene-bis(methy1ene-aza-x-crown-y) (x/y = 1214, 2; 1515, 3; 1816, 4). The reaction of 1 with diaza-18-crown-6 represents a new and simple route to the known ferrocene cryptands 1,l'-ferrocenylene-[bis-?,16-methylene( 1,4,10,13-tetraoxa-?,16-diazacyclooctadecane)] (5) and 1,l" : l',l"'-bisferrocenylene-bis- [bis-?,16-methylene( 1,4,10,13-tetraoxa-?,16-diazacyclooctadecane)] (6). The solid-state structure of 5 is described. The ferrocene bridge compresses the diaza crown ether leading to an internitrogen distance of 458 pm. The stoichiometry of Na+ and K' complexes with 2 and 3 in CD,CN determined in NMR titration experiments suggests the formation of Na' and K+ One of the most prominent molecules of organometallic chemistry is ferrocene, whose most characteristic features are the sandwich structure and its redox chemistry[''. Crown ether ligands on the other hand are modern representatives of classic coordination chemistry, which are known to form exceptionally stable complexes with alkali metal ionsL2'.Chemically linking ferrocene and crown ethers combines their specific properties. Thus, the reversibility of the ferrocene/ferrocenium redox couple and the high stability of crown ether metal complexes can cooperate within one molecule[''. This synergetic relation creates a switch on a molecular level, which allows the complexing ability to be turned off (i.e. drastic decrease of the complexation stability constant) of the macrocyclic subcomponent, once a positive charge within the ferrocene moiety is generated. Upon reduction the ability for cation complexation is restored; consequently, the combination of ferrocene and crown ether produces a redox-switched crown ethert4].Ferrocene macrocycles with a Fc(C0N) amide structure were synthesized by Beer ['] and Hall [']. The weak redox switching effect upon addition of monovalent cations suggested that coordination of metal ions does not occur within the macrocycle but rather on the periphery at the amide oxygen1']. This was confirmed recently by the solid-state structure of a ferrocene cryptand with Dy3+ in which five of the seven coordination sites at dysprosium are occupied by four amide oxygen atoms and one water molecule[81. Our target therefore was to synthesize ferrocene-containing macrocycles without the disadvantages of an amide structure. In this paper we report on a simple synthesis of new ferrocene biscrown ethers, an improved synthesis of ferrocene cryptands, and an investigation of the effects of H + , Li+, Na+, and K + complexation on NMR spectra and the electrochemical behavior. Results and DiscussionThe salt 1,l '-ferrocenylene-bis(methy1enepyridinium) tosylate chloride (1) is easily available from ferrocene in two steps" ' via l,l'-Fc(CH,OH),. This compound is the ideal starting material for the synthesis of ferrocene-biscrown ethers and ferrocene cryptands. The rea...

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Functionalized multi-walled carbon nanotubes (f-MWCNT) with open ends, small diameters and functional groups at defect sites along their sidewalls were obtained by simple acid oxidation of pristine MWCNTs. The carboxylic acid functionalization of MWCNTs was confirmed using FTIR spectroscopy. f-MWCNTs show a considerably higher BET surface area with respect to pristine MWCNTs. Mebeverine Hydrochloride (MV.HCl) was determined based on functionalized multi-wall carbon nanotubes modified carbon paste electrode (f-MWCNT/CPE) as a sensor. The electrochemical properties of the modified CPEs were characterized using electrochemical impedance spectra (EIS), scan electron microscopy (SEM), and cyclic voltammetry. The modified electrode exhibited higher electrocatalytic activities toward determination of MV.HCl. f-MWCNTs lead to enrichment the electrode surface properties and decreases the charge transfer resistances of the modified electrode facilitating the electron transfer process. The modified electrode was successfully applied for trace determination of MV.HCl in different pharmaceutical preparations; "Coloverin A", "Colona" and "Colofac" tablets without interferences from excipients and co-formulated drugs. The achieved detection limit in human serum was 2.0 × 10 −10 M. The described adsorptive anodic stripping voltammetric method is reliable, simple and sensitive enough for assay of MV. HCl in real plasma samples, pharmacokinetic studies, quality control and assurance of the drug in industry and in clinical laboratories.