The synthesis, complexation properties and catalytic activities under phase-transfer (PT) conditions of differently substituted cyclohexapeptoids are reported. Association constants, for small cationic alkali, and catalytic performances, in a model nucleophilic substitution, are comparable to those of representative crown ethers. Noteworthy, the N-[2-(2-methoxyethoxy)ethyl] side chain derivative presents a catalytic efficiency comparable to that of crypt-222, and higher than some commonly used quaternary ammonium salts and crown ethers. Moreover its association constant for Na+ complexation proved to be higher when compared with dicyclohexyl-18-crown-6. The synthesized cyclohexapeptoids represent the first example of these peptidomimetics in PT catalysis, anticipating interesting applications in biphasic PT methodology.

Cyclopeptoids: a novel class of phase-transfer catalysts

The effects of substituents and cavity size on catalytic efficiency of proline-rich cyclopeptoids under phase-transfer conditions were studied. High affinity constants (Ka) for the sodium and potassium cations, comparable to those reported for crown ethers, were observed for an alternated N-benzylglycine/l-proline hexameric cyclopeptoid. This compound was found to catalyze the alkylation of N-(diphenylmethylene)glycine cumyl ester in values of enantioselectivities comparable with those reported for the Cinchona alkaloid ammonium salts derivatives (83–96% ee), and with lower catalyst loading (1–2.5% mol), in the presence of a broad range of benzyl, allyl and alkyl halides.

Enantioselective Alkylation of Amino Acid Derivatives Promoted by Cyclic Peptoids under Phase-Transfer Conditions.

Synthetic ionophores for the separation of Li+, Na+, K+, Ca2+, Mg2+ metal ions using liquid membrane technology

The selectivity of the cryptands [22bpy] and [2bpybpy] for the endohedral complexation of alkali, alkaline-earth and earth metal ions was predicted on the basis of the DFT (B3LYP/LANL2DZp) calculated structures and complex-formation energies The cavity size in both cryptands lay between that for [222] and [bpybpybpy], such that the complexation of K+, Sr2+ and Tl3+ is most favorable While the [22bpy] is moderately larger, preferring Rb+ complexation and demonstrating equal priority for Sr2+ and Ba2+, the slightly smaller [2bpybpy] yields more stable cryptates with Na+ and Ca2+ Although the CH2-units containing molecular bars fixed at the bridgehead nitrogen atoms determine the flexibility of the cryptands, the twist angles associated with the bipyridine and glycol building blocks also contribute considerably

https://www.beilstein-journals.org/bjoc/content/pdf/1860-5397-9-142.pdf

Host-guest complexes of mixed glycol-bipyridine cryptands: prediction of ion selectivity by quantum chemical calculations, part V.

A new class of redox-switched anthraquinone derived lariat ethers 1-(1-anthraquinonyloxy) 3, 6, 9 trioxaundecane 11-ol (M1), 1-(1-anthraquinonyloxy) 3, 6 dioxaoctane 9-ol (M2), 1-(1-anthraquinonyloxy) 3 oxapentane 5-ol (M3), 1-(1-anthraquinonyloxy) 3 oxapentane 5-butane (M4), 1-(1-anthraquinonyloxy) 3, 6 dioxaoctane 9-methane (M5) and 1-(1-anthraquinonyloxy) 3 oxapentane 5-methane (M6) have been synthesized and characterized by spectral analysis. These ionophores were used in liquid membrane carrier facilitated transport of main group metal cations across supported liquid membrane (SLM). Cellulose nitrate membrane was used as membrane support. Effect of various parameters such as variation in concentration of metal as well as ionophore, effect of chain length and end group of ionophore have been studied. The sequence of metal ions transported by ionophore M1 is Na

https://downloads.hindawi.com/journals/bca/2006/097141.pdf

Design and Synthesis of Redox-Switched Lariat Ethers and Their Application for Transport of Alkali and Alkaline-Earth Metal Cations Across Supported Liquid Membrane

The interest in understanding the interactions in living systems has made supra-molecular chemistry one of the fastest-growing and most active fields of chemistry. Supra-molecular chemistry has evolved from efforts to mimic the weak noncovalent interactions and the phenomenon of molecular recognition in biological systems. A series of redox-switched anthraquinone derived lariat ethers, l-(l-anthraquinonyloxy) 3, 6, 9 trioxaundecane ll-ol (MO, l-(l-anthraquinonyloxy) 3, 6 dioxaoctane 9-ol (M2), l-(l-anthraquinonyloxy) 3 oxapentane5-ol (M3), l-(l-anthraquinonyloxy) 3 oxapentane 5-butane (M4) have been synthesized and characterized by spectral analysis. These redox-switched ionophores were used as carrier in liquid membrane extraction and transport studies of alkali and alkaline earth metal ions. Effect of various parameters such as variation in concentration of metal as well as ionophore, effect of chain length and end group of ionophore have been studied. All ionophores show higher extraction with Li in reduced state of the carrier because Li has large binding efficiency for most of the redox polyethers. Ionophore Mh having a tetraethylene glycol + side chain with anthraquinone, shows maximum extraction for Κ ion in both oxidized and reduced state. Altering the structure of ionophores can be correlated to quantitative structure property relationship (QSPR), which helps in fabrication of ion selective electrode, redox switchable devices and sensors.

Redox Chemical Switching of Cation Transport in Liquid Membrane System

Stoichiometric Complexes of Some Main Group Metal Ions (Li+, Na+, K+, Ca++) with Redox -switched Lariat Ethers

Synthesis of redox switched ionophores 1-[1-anthraquinonyloxy] 3, 6 dioxaoctane-8-methane (A 1 ) and 1-[1-anthraquinonyloxy] 3 oxapentane-5-methane (A 2 ) has been reported. These ionophores have been used as carriers in liquid membrane transport and extraction studies of alkali and alkaline earth metal ions. The sequence of metal ions extracted and transported in oxidised and reduced state by ionophore A 1 is: Ca 2+ >K + >Li + >Mg 2+ and Li + >K + >Ca 2+ >Mg 2+ respectively. The order of extraction and transport of metal ions with respect to ionophore A 2 is Li + >K + >Ca + and Ca 2+ >K + >Li + respectively. Ionophore A 1 is selective for Ca 2+ while ionophore A 2 is selective for Li + ions. This selectivity may be used in ion selective electrode and redox switchable devices.

http://nopr.niscair.res.in/bitstream/123456789/19991/1/IJCA%2045A%285%29%201170-1172.pdf

Mamta Bhatnagar

Papers

Design and Synthesis of Redox-Switched Lariat Ethers and Their Application for Transport of Alkali and Alkaline-Earth Metal Cations Across Supported Liquid Membrane

Redox Chemical Switching of Cation Transport in Liquid Membrane System

Stoichiometric Complexes of Some Main Group Metal Ions (Li+, Na+, K+, Ca++) with Redox -switched Lariat Ethers

Effect of side arm chain length of redox ionophores on uptake of some metal ions