TY - JOUR
T1 - The effect of N-methylation on the spectroscopical and electrochemical properties of 1,4,8,11-tetraazacyclotetradecane chromium(III) complexes
AU - Guldi, Dirk
AU - Wasgestian, F.
AU - Meyerstein, Dan
PY - 1992/4/1
Y1 - 1992/4/1
N2 - trans-[Cr(tmc)X2] complexes (tmc=1,4,8,11-tetramethyl-1,4,8,11-tetraazacyclotetradecane, XF, Cl, Br, H2O, OH, NO3) have been prepared and spectroscopically characterized. The redox potentials of the tmc complexes and of the analogous cyclam complexes (cyclam=1,4,8,11-tetraazacyclotetradecane) were determined by cyclic voltammetry. The potentials of the tmc complexes are 1.1±0.1 V more positive. Their long wavelength absorption is red-shifted by 50 to 100 nm with respect to that of the analogous cyclam complexes. The shift was consistent with a linear dependence of the polarographic half-wave potentials on the transition energies of the first spin allowed ligand field bands, observed on a series of chromium(III) amine complexes. The reaction entropies for the reduction of trans-[Cr(cyclam)(H2O)2]3+, trans-[Cr(cyclam)(OH)2]+, and trans-[Cr(tmc)(OH)2]+, ΔS=88±2, 200±40 and 53±8 J mol-1 K-1, respectively, were obtained from the temperature dependence of the redox potential. It was shown that trans-[Cr(cyclam)(H2O)2]3+ catalyzes the electroreduction of nitrate.
AB - trans-[Cr(tmc)X2] complexes (tmc=1,4,8,11-tetramethyl-1,4,8,11-tetraazacyclotetradecane, XF, Cl, Br, H2O, OH, NO3) have been prepared and spectroscopically characterized. The redox potentials of the tmc complexes and of the analogous cyclam complexes (cyclam=1,4,8,11-tetraazacyclotetradecane) were determined by cyclic voltammetry. The potentials of the tmc complexes are 1.1±0.1 V more positive. Their long wavelength absorption is red-shifted by 50 to 100 nm with respect to that of the analogous cyclam complexes. The shift was consistent with a linear dependence of the polarographic half-wave potentials on the transition energies of the first spin allowed ligand field bands, observed on a series of chromium(III) amine complexes. The reaction entropies for the reduction of trans-[Cr(cyclam)(H2O)2]3+, trans-[Cr(cyclam)(OH)2]+, and trans-[Cr(tmc)(OH)2]+, ΔS=88±2, 200±40 and 53±8 J mol-1 K-1, respectively, were obtained from the temperature dependence of the redox potential. It was shown that trans-[Cr(cyclam)(H2O)2]3+ catalyzes the electroreduction of nitrate.
UR - http://www.scopus.com/inward/record.url?scp=0009138099&partnerID=8YFLogxK
U2 - 10.1016/S0020-1693(00)85817-X
DO - 10.1016/S0020-1693(00)85817-X
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AN - SCOPUS:0009138099
SN - 0020-1693
VL - 194
SP - 15
EP - 22
JO - Inorganica Chimica Acta
JF - Inorganica Chimica Acta
IS - 1
ER -