Elusive pKa’ of aminoferrocene determined with voltammetric methods in buffered and unbuffered systems and practical aspects of such experiments

Kód výsledku v IS VaVaI

<a href="https://www.isvavai.cz/riv?ss=detail&h=RIV%2F00216224%3A14310%2F19%3A00107678" target="_blank" >RIV/00216224:14310/19:00107678 - isvavai.cz</a>

Výsledek na webu

<a href="https://www.sciencedirect.com/science/article/pii/S0013468619310461" target="_blank" >https://www.sciencedirect.com/science/article/pii/S0013468619310461</a>

DOI - Digital Object Identifier

<a href="http://dx.doi.org/10.1016/j.electacta.2019.05.113" target="_blank" >10.1016/j.electacta.2019.05.113</a>

Jazyk výsledku

angličtina

Název v původním jazyce

Elusive pKa’ of aminoferrocene determined with voltammetric methods in buffered and unbuffered systems and practical aspects of such experiments

Popis výsledku v původním jazyce

Redox behaviour of aminoferrocene (FcNH2) in buffered and unbuffered systems has been studied. In unbuffered solutions with background electrolyte only, two discrete redox pairs of unprotonated and protonated forms were evident. On the other hand, in buffered systems only one redox centre was visible continuously shifting with pH. If one wants to determine the apparent acid dissociation constant pKa’ of ferrocene with protonatable side group, buffered environment will be the first choice. Throughout the electrochemical experiments at such conditions, the most limiting factor was the type of the electrode – gold, platinum, glassy carbon and boron-doped diamond electrodes were probed. We found that the influence of the surface of the electrode was so significant that either the determination of pKa’ was not possible at aqueous conditions or observed differences among the determined values were up to five units. In that case, elusive constants were determined. On the other hand, titrations performed in unbuffered systems appeared to be useable despite inconsistences and deficiencies that can be expected. Determined pKa's agreed well with that quantified using spectrophotometry. Although, experimental work at unbuffered conditions can be considered as incorrect or misleading at the first sight, interesting facts and unexpected mechanisms can be revealed. Especially, when one is aware of the possible risks, and the measurement in different (even unbuffered) media and with different tools are done simultaneously. Finally, a method for estimation of pKa’ of unstable compounds without their separation and isolation was introduced.

Název v anglickém jazyce

Elusive pKa’ of aminoferrocene determined with voltammetric methods in buffered and unbuffered systems and practical aspects of such experiments

Popis výsledku anglicky

Redox behaviour of aminoferrocene (FcNH2) in buffered and unbuffered systems has been studied. In unbuffered solutions with background electrolyte only, two discrete redox pairs of unprotonated and protonated forms were evident. On the other hand, in buffered systems only one redox centre was visible continuously shifting with pH. If one wants to determine the apparent acid dissociation constant pKa’ of ferrocene with protonatable side group, buffered environment will be the first choice. Throughout the electrochemical experiments at such conditions, the most limiting factor was the type of the electrode – gold, platinum, glassy carbon and boron-doped diamond electrodes were probed. We found that the influence of the surface of the electrode was so significant that either the determination of pKa’ was not possible at aqueous conditions or observed differences among the determined values were up to five units. In that case, elusive constants were determined. On the other hand, titrations performed in unbuffered systems appeared to be useable despite inconsistences and deficiencies that can be expected. Determined pKa's agreed well with that quantified using spectrophotometry. Although, experimental work at unbuffered conditions can be considered as incorrect or misleading at the first sight, interesting facts and unexpected mechanisms can be revealed. Especially, when one is aware of the possible risks, and the measurement in different (even unbuffered) media and with different tools are done simultaneously. Finally, a method for estimation of pKa’ of unstable compounds without their separation and isolation was introduced.

Druh

J_imp - Článek v periodiku v databázi Web of Science

CEP obor

—

OECD FORD obor

10403 - Physical chemistry

Projekt

Výsledek vznikl pri realizaci vícero projektů. Více informací v záložce Projekty.

Návaznosti

P - Projekt vyzkumu a vyvoje financovany z verejnych zdroju (s odkazem do CEP)<br>S - Specificky vyzkum na vysokych skolach

Rok uplatnění

2019

Kód důvěrnosti údajů

S - Úplné a pravdivé údaje o projektu nepodléhají ochraně podle zvláštních právních předpisů

Název periodika

Electrochimica Acta

ISSN

0013-4686

e-ISSN

—

Svazek periodika

318

Číslo periodika v rámci svazku

SEP

Stát vydavatele periodika

NL - Nizozemsko

Počet stran výsledku

8

Strana od-do

534-541

Kód UT WoS článku

000478969600057

EID výsledku v databázi Scopus

2-s2.0-85067667920