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

J 2019

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

VĚŽNÍK, Jakub, Martin KONHEFR, Libuše TRNKOVÁ, Petr SKLÁDAL, Karel LACINA et. al.

Basic information

Original name

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

Authors

VĚŽNÍK, Jakub (203 Czech Republic, belonging to the institution), Martin KONHEFR (203 Czech Republic, belonging to the institution), Libuše TRNKOVÁ (203 Czech Republic, belonging to the institution), Petr SKLÁDAL (203 Czech Republic, belonging to the institution) and Karel LACINA (203 Czech Republic, guarantor, belonging to the institution)

Edition

Electrochimica Acta, Elsevier, 2019, 0013-4686

Other information

Language

English

Type of outcome

Článek v odborném periodiku

Field of Study

10403 Physical chemistry

Country of publisher

Netherlands

Confidentiality degree

není předmětem státního či obchodního tajemství

References:

URL

Impact factor

Impact factor: 6.215

RIV identification code

RIV/00216224:14310/19:00107678

Organization unit

Faculty of Science

DOI

http://dx.doi.org/10.1016/j.electacta.2019.05.113

UT WoS

000478969600057

Keywords in English

Ferrocene; Aminoferrocene; Protein labels; pH; Unbuffered solution; Electrochemical determination of pKa’

Abstract

V originále

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.

Links

GJ19-16273Y, research and development project

Name: ROS-indukované uvolňování léčiv založené na interakcích ferocenylboronátů

Investor: Czech Science Foundation, ROS-Induced Drug Release Based on Interactions of Ferrocenylboronates

LQ1601, research and development project

Name: CEITEC 2020 (Acronym: CEITEC2020)

Investor: Ministry of Education, Youth and Sports of the CR

MUNI/A/1359/2018, interní kód MU

Name: Vývoj metod a instrumentace pro analýzu biologicky významných látek 2019

Investor: Masaryk University, Category A

MUNI/A/1575/2018, interní kód MU

Name: Podpora biochemického výzkumu v roce 2019

Investor: Masaryk University, Category A

90043, large research infrastructures

Name: CIISB

Citovat

VĚŽNÍK, Jakub, Martin KONHEFR, Libuše TRNKOVÁ, Petr SKLÁDAL and Karel LACINA. Elusive pKa’ of aminoferrocene determined with voltammetric methods in buffered and unbuffered systems and practical aspects of such experiments. Electrochimica Acta. Elsevier, 2019, vol. 318, SEP, p. 534-541. ISSN 0013-4686. Available from: https://dx.doi.org/10.1016/j.electacta.2019.05.113.

@article{1561958,
   author = {Věžník, Jakub and Konhefr, Martin and Trnková, Libuše and Skládal, Petr and Lacina, Karel},
   article_number = {SEP},
   doi = {http://dx.doi.org/10.1016/j.electacta.2019.05.113},
   keywords = {Ferrocene; Aminoferrocene; Protein labels; pH; Unbuffered solution; Electrochemical determination of pKa’},
   language = {eng},
   issn = {0013-4686},
   journal = {Electrochimica Acta},
   title = {Elusive pKa’ of aminoferrocene determined with voltammetric methods in buffered and unbuffered systems and practical aspects of such experiments},
   url = {https://www.sciencedirect.com/science/article/pii/S0013468619310461},
   volume = {318},
   year = {2019}
}

TY  - JOUR
ID  - 1561958
AU  - Věžník, Jakub - Konhefr, Martin - Trnková, Libuše - Skládal, Petr - Lacina, Karel
PY  - 2019
TI  - Elusive pKa’ of aminoferrocene determined with voltammetric methods in buffered and unbuffered systems and practical aspects of such experiments
JF  - Electrochimica Acta
VL  - 318
IS  - SEP
SP  - 534-541
EP  - 534-541
PB  - Elsevier
SN  - 00134686
KW  - Ferrocene
KW  - Aminoferrocene
KW  - Protein labels
KW  - pH
KW  - Unbuffered solution
KW  - Electrochemical determination of pKa’
UR  - https://www.sciencedirect.com/science/article/pii/S0013468619310461
L2  - https://www.sciencedirect.com/science/article/pii/S0013468619310461
N2  - 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.
ER  -

VĚŽNÍK, Jakub, Martin KONHEFR, Libuše TRNKOVÁ, Petr SKLÁDAL and Karel LACINA. Elusive pKa’ of aminoferrocene determined with voltammetric methods in buffered and unbuffered systems and practical aspects of such experiments. \textit{Electrochimica Acta}. Elsevier, 2019, vol.~318, SEP, p.~534-541. ISSN~0013-4686. Available from: https://dx.doi.org/10.1016/j.electacta.2019.05.113.

Detailed Information on Publication Record