Thermodynamic Study of Ion-Pairing Effects between Reduced Double-Decker Lutetium(III) Phthalocyanines and a Cationic Matrix

Takashi Nakanishi, Ismail Yilmaz, Naotoshi Nakashima, Karl M. Kadish

Research output: Contribution to journalArticle

42 Citations (Scopus)

Abstract

The thermodynamics of ion paring between electrochemically reduced [(C 6H 13S) 8Pc] 2Lu or [(C 12H 25S) 4Pc] 2Lu and a cationic tetra-n-octylphosphonium bromide (4C 8P +Br -) matrix that was deposited in a gel-like cast film on a basal plane pyrolytic graphite electrode was investigated in an aqueous KC1 solution that varied in concentration from 0.005 to 1.0 M. The purpose of this study was to elucidate ion-pairing effects between reduced double-decker lutetium(III) phthalocyanines with charges of -1 to -5 and cationic sites of the 4C 8P +Br - matrix. Both phthalocyanines undergo five one-electron reductions in the film, and a linear relationship was observed between the measured half-wave potentials (E 1/2) for these processes and the Cl - concentration of the electrolyte in the film. The apparent number of electrons transferred in each reduction step was obtained from plots of E 1/2 versus ln[Cl -], which gave Nernstian slopes of -23.5 ± 2.3 mV (or -54.1 ± 5.3 mV from plots of E 1/2 vs log[Cl -]) over a chloride concentration range of 0.005 to 1.0 M. The E 1/2 versus ln[Cl -] plots indicate that the stepwise addition of electrons to the phthalocyanines in the film is accompanied by a stepwise unit increase in the number of associated 4C 8P + cations. Thus, the ratio of phthalocyanine molecules to monocations increases from 1:1 for the singly reduced derivative to 1:5 in the case of {[(C 6H 13S) 8Pc] 2Lu} 5- or {[(C 12H 25S) 4Pc] 2Lu} 5-. This result leads to the conclusion that a binding of reduced [(C 5H 13S) 8Pc] 2Lu or [(C 12H 25S) 4Pc] 2 to the cationic sites of the 4C 8P + matrix is responsible for the experimentally observed positive shift of the measured half-wave potentials as compared to E 1/2 values for the same electrode reactions in nonaqueous media. The changes in E 1/2 upon changing the electrolyte counter cation and/or the charge of the matrix are also described, and these results further support the observed ion-pairing effects that were examined by means of electrochemical and spectroscopic techniques.

Original languageEnglish
Pages (from-to)12789-12796
Number of pages8
JournalJournal of Physical Chemistry B
Volume107
Issue number46
Publication statusPublished - Nov 20 2003

Fingerprint

Lutetium
lutetium
Thermodynamics
Ions
thermodynamics
plots
Electrons
matrices
Electrolytes
Cations
Electrodes
ions
Positive ions
Electrochemical Techniques
electrolytes
cations
Graphite electrodes
electrons
electrodes
Graphite

All Science Journal Classification (ASJC) codes

  • Physical and Theoretical Chemistry
  • Surfaces, Coatings and Films
  • Materials Chemistry

Cite this

Thermodynamic Study of Ion-Pairing Effects between Reduced Double-Decker Lutetium(III) Phthalocyanines and a Cationic Matrix. / Nakanishi, Takashi; Yilmaz, Ismail; Nakashima, Naotoshi; Kadish, Karl M.

In: Journal of Physical Chemistry B, Vol. 107, No. 46, 20.11.2003, p. 12789-12796.

Research output: Contribution to journalArticle

Nakanishi, Takashi ; Yilmaz, Ismail ; Nakashima, Naotoshi ; Kadish, Karl M. / Thermodynamic Study of Ion-Pairing Effects between Reduced Double-Decker Lutetium(III) Phthalocyanines and a Cationic Matrix. In: Journal of Physical Chemistry B. 2003 ; Vol. 107, No. 46. pp. 12789-12796.
@article{8cc93cdf12a142b583dc5ffbb83223ad,
title = "Thermodynamic Study of Ion-Pairing Effects between Reduced Double-Decker Lutetium(III) Phthalocyanines and a Cationic Matrix",
abstract = "The thermodynamics of ion paring between electrochemically reduced [(C 6H 13S) 8Pc] 2Lu or [(C 12H 25S) 4Pc] 2Lu and a cationic tetra-n-octylphosphonium bromide (4C 8P +Br -) matrix that was deposited in a gel-like cast film on a basal plane pyrolytic graphite electrode was investigated in an aqueous KC1 solution that varied in concentration from 0.005 to 1.0 M. The purpose of this study was to elucidate ion-pairing effects between reduced double-decker lutetium(III) phthalocyanines with charges of -1 to -5 and cationic sites of the 4C 8P +Br - matrix. Both phthalocyanines undergo five one-electron reductions in the film, and a linear relationship was observed between the measured half-wave potentials (E 1/2) for these processes and the Cl - concentration of the electrolyte in the film. The apparent number of electrons transferred in each reduction step was obtained from plots of E 1/2 versus ln[Cl -], which gave Nernstian slopes of -23.5 ± 2.3 mV (or -54.1 ± 5.3 mV from plots of E 1/2 vs log[Cl -]) over a chloride concentration range of 0.005 to 1.0 M. The E 1/2 versus ln[Cl -] plots indicate that the stepwise addition of electrons to the phthalocyanines in the film is accompanied by a stepwise unit increase in the number of associated 4C 8P + cations. Thus, the ratio of phthalocyanine molecules to monocations increases from 1:1 for the singly reduced derivative to 1:5 in the case of {[(C 6H 13S) 8Pc] 2Lu} 5- or {[(C 12H 25S) 4Pc] 2Lu} 5-. This result leads to the conclusion that a binding of reduced [(C 5H 13S) 8Pc] 2Lu or [(C 12H 25S) 4Pc] 2 to the cationic sites of the 4C 8P + matrix is responsible for the experimentally observed positive shift of the measured half-wave potentials as compared to E 1/2 values for the same electrode reactions in nonaqueous media. The changes in E 1/2 upon changing the electrolyte counter cation and/or the charge of the matrix are also described, and these results further support the observed ion-pairing effects that were examined by means of electrochemical and spectroscopic techniques.",
author = "Takashi Nakanishi and Ismail Yilmaz and Naotoshi Nakashima and Kadish, {Karl M.}",
year = "2003",
month = "11",
day = "20",
language = "English",
volume = "107",
pages = "12789--12796",
journal = "Journal of Physical Chemistry B",
issn = "1520-6106",
number = "46",

}

TY - JOUR

T1 - Thermodynamic Study of Ion-Pairing Effects between Reduced Double-Decker Lutetium(III) Phthalocyanines and a Cationic Matrix

AU - Nakanishi, Takashi

AU - Yilmaz, Ismail

AU - Nakashima, Naotoshi

AU - Kadish, Karl M.

PY - 2003/11/20

Y1 - 2003/11/20

N2 - The thermodynamics of ion paring between electrochemically reduced [(C 6H 13S) 8Pc] 2Lu or [(C 12H 25S) 4Pc] 2Lu and a cationic tetra-n-octylphosphonium bromide (4C 8P +Br -) matrix that was deposited in a gel-like cast film on a basal plane pyrolytic graphite electrode was investigated in an aqueous KC1 solution that varied in concentration from 0.005 to 1.0 M. The purpose of this study was to elucidate ion-pairing effects between reduced double-decker lutetium(III) phthalocyanines with charges of -1 to -5 and cationic sites of the 4C 8P +Br - matrix. Both phthalocyanines undergo five one-electron reductions in the film, and a linear relationship was observed between the measured half-wave potentials (E 1/2) for these processes and the Cl - concentration of the electrolyte in the film. The apparent number of electrons transferred in each reduction step was obtained from plots of E 1/2 versus ln[Cl -], which gave Nernstian slopes of -23.5 ± 2.3 mV (or -54.1 ± 5.3 mV from plots of E 1/2 vs log[Cl -]) over a chloride concentration range of 0.005 to 1.0 M. The E 1/2 versus ln[Cl -] plots indicate that the stepwise addition of electrons to the phthalocyanines in the film is accompanied by a stepwise unit increase in the number of associated 4C 8P + cations. Thus, the ratio of phthalocyanine molecules to monocations increases from 1:1 for the singly reduced derivative to 1:5 in the case of {[(C 6H 13S) 8Pc] 2Lu} 5- or {[(C 12H 25S) 4Pc] 2Lu} 5-. This result leads to the conclusion that a binding of reduced [(C 5H 13S) 8Pc] 2Lu or [(C 12H 25S) 4Pc] 2 to the cationic sites of the 4C 8P + matrix is responsible for the experimentally observed positive shift of the measured half-wave potentials as compared to E 1/2 values for the same electrode reactions in nonaqueous media. The changes in E 1/2 upon changing the electrolyte counter cation and/or the charge of the matrix are also described, and these results further support the observed ion-pairing effects that were examined by means of electrochemical and spectroscopic techniques.

AB - The thermodynamics of ion paring between electrochemically reduced [(C 6H 13S) 8Pc] 2Lu or [(C 12H 25S) 4Pc] 2Lu and a cationic tetra-n-octylphosphonium bromide (4C 8P +Br -) matrix that was deposited in a gel-like cast film on a basal plane pyrolytic graphite electrode was investigated in an aqueous KC1 solution that varied in concentration from 0.005 to 1.0 M. The purpose of this study was to elucidate ion-pairing effects between reduced double-decker lutetium(III) phthalocyanines with charges of -1 to -5 and cationic sites of the 4C 8P +Br - matrix. Both phthalocyanines undergo five one-electron reductions in the film, and a linear relationship was observed between the measured half-wave potentials (E 1/2) for these processes and the Cl - concentration of the electrolyte in the film. The apparent number of electrons transferred in each reduction step was obtained from plots of E 1/2 versus ln[Cl -], which gave Nernstian slopes of -23.5 ± 2.3 mV (or -54.1 ± 5.3 mV from plots of E 1/2 vs log[Cl -]) over a chloride concentration range of 0.005 to 1.0 M. The E 1/2 versus ln[Cl -] plots indicate that the stepwise addition of electrons to the phthalocyanines in the film is accompanied by a stepwise unit increase in the number of associated 4C 8P + cations. Thus, the ratio of phthalocyanine molecules to monocations increases from 1:1 for the singly reduced derivative to 1:5 in the case of {[(C 6H 13S) 8Pc] 2Lu} 5- or {[(C 12H 25S) 4Pc] 2Lu} 5-. This result leads to the conclusion that a binding of reduced [(C 5H 13S) 8Pc] 2Lu or [(C 12H 25S) 4Pc] 2 to the cationic sites of the 4C 8P + matrix is responsible for the experimentally observed positive shift of the measured half-wave potentials as compared to E 1/2 values for the same electrode reactions in nonaqueous media. The changes in E 1/2 upon changing the electrolyte counter cation and/or the charge of the matrix are also described, and these results further support the observed ion-pairing effects that were examined by means of electrochemical and spectroscopic techniques.

UR - http://www.scopus.com/inward/record.url?scp=0344531053&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=0344531053&partnerID=8YFLogxK

M3 - Article

AN - SCOPUS:0344531053

VL - 107

SP - 12789

EP - 12796

JO - Journal of Physical Chemistry B

JF - Journal of Physical Chemistry B

SN - 1520-6106

IS - 46

ER -