TY - JOUR
T1 - Electrochemistry of a double-decker lutetium(III) phthalocyanine in aqueous media. The first evidence for five reductions
AU - Kadish, Karl M.
AU - Nakanishi, Takashi
AU - Gürek, Aysegül
AU - Ahsen, Vefa
AU - Yilmaz, Ismail
PY - 2001/10/11
Y1 - 2001/10/11
N2 - The double-decker lutetium(III) phthalocyanine, Lu[(RS)4Pc]2, where R = C12H25, was synthesized and electrochemically characterized under several solution conditions. The neutral complex undergoes a single reversible one-electron oxidation and up to four reversible one-electron reductions in nonaqueous solutions of CH2Cl2 or benzonitrile containing 0.1 M tetra-n-butylammonium perchlorate (TBAP), while one oxidation and five reductions are seen in aqueous 0.5 M KCl for a gel-like cast film membrane of Lu[(RS)4Pc]2 in a tetraoctylphosphonium bromide (4C8P+Br-) matrix at a basal plane pyrolytic graphite electrode. The halfwave potentials for reduction of Lu[(RS)4Pc]2 in CH2Cl2, 0.1 M TBAP are located at E1/2 = 0.04, -1.03, -1.36 and -1.73 V, while the single oxidation is located at E1/2 = 0.43 V vs SCE. These potentials, when measured vs Fc/Fc+, are negatively shifted by 0.20-0.46 V from the E1/2 values obtained in the 0.5 M KCl solution where the electrogenerated anions of the double-decker complex are stabilized by the cations of the 4C8P+Br- matrix and five reductions are seen at E1/2 = 0.29, -0.66, -0.94, -1.22, and -1.41 V vs SCE. The fifth reduction has been theoretically predicted but had never before been observed for any doubledecker lutetium(III) phthalocyanine or related complex. A cast film of Lu[(RS)4Pc]2 displays only one oxidation in the 0.5 M KCl solution (at E1/2 = 0.78 V vs SCE), and no reductions at all are seen in the absence of a matrix. An almost identical oxidation potential of E1/2 = 0.80 V is seen for oxidation of Lu[(RS)4Pc]2 in KCl when dissolved in the cationic matrix. These half-wave potentials for oxidation in the cationic film, when measured vs Fc/Fc+, are thus more positive by more than 0.27-0.32 V than E1/2 values measured in CH2Cl2 or PhCN and this is consistent with a decreased degree of solvent or anion binding to {Lu[(RS)4Pc]2}+ in the 4C8P+Br- matrix, as compared to what is observed in solution.
AB - The double-decker lutetium(III) phthalocyanine, Lu[(RS)4Pc]2, where R = C12H25, was synthesized and electrochemically characterized under several solution conditions. The neutral complex undergoes a single reversible one-electron oxidation and up to four reversible one-electron reductions in nonaqueous solutions of CH2Cl2 or benzonitrile containing 0.1 M tetra-n-butylammonium perchlorate (TBAP), while one oxidation and five reductions are seen in aqueous 0.5 M KCl for a gel-like cast film membrane of Lu[(RS)4Pc]2 in a tetraoctylphosphonium bromide (4C8P+Br-) matrix at a basal plane pyrolytic graphite electrode. The halfwave potentials for reduction of Lu[(RS)4Pc]2 in CH2Cl2, 0.1 M TBAP are located at E1/2 = 0.04, -1.03, -1.36 and -1.73 V, while the single oxidation is located at E1/2 = 0.43 V vs SCE. These potentials, when measured vs Fc/Fc+, are negatively shifted by 0.20-0.46 V from the E1/2 values obtained in the 0.5 M KCl solution where the electrogenerated anions of the double-decker complex are stabilized by the cations of the 4C8P+Br- matrix and five reductions are seen at E1/2 = 0.29, -0.66, -0.94, -1.22, and -1.41 V vs SCE. The fifth reduction has been theoretically predicted but had never before been observed for any doubledecker lutetium(III) phthalocyanine or related complex. A cast film of Lu[(RS)4Pc]2 displays only one oxidation in the 0.5 M KCl solution (at E1/2 = 0.78 V vs SCE), and no reductions at all are seen in the absence of a matrix. An almost identical oxidation potential of E1/2 = 0.80 V is seen for oxidation of Lu[(RS)4Pc]2 in KCl when dissolved in the cationic matrix. These half-wave potentials for oxidation in the cationic film, when measured vs Fc/Fc+, are thus more positive by more than 0.27-0.32 V than E1/2 values measured in CH2Cl2 or PhCN and this is consistent with a decreased degree of solvent or anion binding to {Lu[(RS)4Pc]2}+ in the 4C8P+Br- matrix, as compared to what is observed in solution.
UR - http://www.scopus.com/inward/record.url?scp=0035846386&partnerID=8YFLogxK
U2 - 10.1021/jp012636y
DO - 10.1021/jp012636y
M3 - Article
AN - SCOPUS:0035846386
SN - 1089-5647
VL - 105
SP - 9817
EP - 9821
JO - Journal of Physical Chemistry B
JF - Journal of Physical Chemistry B
IS - 40
ER -