New bis(azobenzocrown)s with dodecylmethylmalonyl linkers as ionophores for sodium selective potentiometric sensors

Abstract

Novel biscrowns 1 and 2 were synthesized from 13-membered azobenzocrown ethers containing bromoalkylenoxy chains in para position relative to the azo group. The synthesized diester molecules are dodecylmethylmalonic acid derivatives differing by the linker length. The synthesized compounds have the potential of being used as sodium ionophores in ion-selective electrodes. They were characterized and used as ionophores in classic and miniature, solid contact (screen-printed and glassy carbon) membrane ion-selective electrodes. Compound 3, a similar monoester derivative of 13-membered azobenzocrown, was synthesized and used in membrane electrodes for comparison. Lipophilicity of new ionophores was determined by TLC. Lipophilicity of bis(azobenzocrown)s was found to be within the range of logPTLC = 12–13. It was observed that the particularly important selectivity coefficients logK Na,K determined for new electrodes, being logK Na,K = −2.5 and −2.6 (SSM, 0.1 M), are better than those of the electrodes featuring seven out of the nine commercially available sodium ionophores. It was concluded that the ionophore 1 creates, in acetone, with sodium iodide, complex of 1:1 stoichiometry (sandwich complex) with stability constant (logK) ca. 3.0.

Azo group(s) in selected macrocyclic compounds

“…Another example of biscrowns are diester derivatives of dodecylmethylmalonic acid joining two 13-membered azobenzocrown moieties obtained in Luboch group [ 163 ] (compounds 49 and 50 , Scheme 5 ). Biscrowns were obtained using bromoalkoxy derivatives of azobenzocrowns [ 164 ] and potassium salt of dodecylmethylmalonic acid in ~ 40% yield.…”

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Scheme 5 Synthesis of bis-(azobenzocrown)s 49 and 50 , diesters of dodecylmethylmalonic acid and monoazobenzocrown 51 [ 163 ]

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“…26 Proposed organization of biscrown 49 sodium cation complex. Reprinted without changes from [ 163 ]. Copyright 2016 with permission from Springer Publishing Company ( http://creativecommons.org/licenses/by/4.0/ ) …”

“…27 a Selectivity coefficients (SSM, 0.1M) and b potentiometric response characteristics: LDL [loga] and slope [mV/dec] for glassy carbon sodium selective electrodes based on 49 as ionophore. UV-electrode upon irradiation with UV light (9W) [ 163 ]. (Color figure online) …”

A Newly Synthesized Tris(crown ether) Ionophore for Assisted Ion Transfer at NanoITIES Electrodes

“…[9,15,16,[18][19][20][21][38][39][40][41][42][43] A commonly used ionophore in ITIES is dibenzo-18-crown-6 (DB18C6). [9,18,[23][24][25][26]40,41,43] Although great progress has been made in synthesizing ionophores with multiple crown either moieties for ion selective electrodes, [44][45][46][47] such ionophores have yet to be tested for amperometric ion detection at ITIES electrodes. Additionally, it is unknown how the thermodynamics of the ionic complexation change when facilitated by tris(crown ether) ionophore compared to mono(crown ether) ionophore.…”