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@article{483378,
author = {Kotek, Jan and Lubal, Přemysl and Hermann, Petr and Císařová, Ivana and Lukeš, Ivan and Godula, Tomáš and Svobodová, Ivona and Táborský, Petr and Havel, Josef},
article_location = {Weinheim},
article_number = {1},
keywords = {cyclam derivatives; kinetics ; macrocyclic ligands ; phosphonate ligands ; stability constants},
language = {eng},
issn = {0947-6539},
journal = {Chemistry - A European Journal},
title = {High Thermodynamic Stability and Extraordinary Kinetic Inertness of Cu(II) Complexes with 1,4,8,11-Tetraazacyclotetradecane-1,8-bis(methylphosphonic acid): Example of a Rare Isomerism between Kinetically Inert Penta- and Hexacoordinated Cu(II) Complexes},
url = {http://www3.interscience.wiley.com/cgi-bin/abstract/102521424/START},
volume = {9},
year = {2003}
}
TY - JOUR
ID - 483378
AU - Kotek, Jan - Lubal, Přemysl - Hermann, Petr - Císařová, Ivana - Lukeš, Ivan - Godula, Tomáš - Svobodová, Ivona - Táborský, Petr - Havel, Josef
PY - 2003
TI - High Thermodynamic Stability and Extraordinary Kinetic Inertness of Cu(II) Complexes with 1,4,8,11-Tetraazacyclotetradecane-1,8-bis(methylphosphonic acid): Example of a Rare Isomerism between Kinetically Inert Penta- and Hexacoordinated Cu(II) Complexes
JF - Chemistry - A European Journal
VL - 9
IS - 1
SP - 233
EP - 233
PB - WILEY-VCH Verlag
SN - 09476539
KW - cyclam derivatives
KW - kinetics
KW - macrocyclic ligands
KW - phosphonate ligands
KW - stability constants
UR - http://www3.interscience.wiley.com/cgi-bin/abstract/102521424/START
N2 - In an aqueous solution at room temperature, 1,4,8,11-tetraazacyclotetradecane-1,8-bis(methylphosphonic acid) (H4L1) and CuII form a pentacoordinated (pc) complex, pc-[Cu(L1)]2-, exhibiting conformation I of the cyclam ring. At high temperature, the complex isomerises to a hexacoordinated isomer, trans-O,O-[Cu(L1)]2-, with a trans-III[Note ] conformation of the cyclam ring. In pc-[Cu(L1)]2-, four ring nitrogen atoms and one phosphonate oxygen atom are arranged around CuII in a structure that is half-way between a trigonal bipyramid and a tetragonal pyramid, with one phosphonic acid group uncoordinated. In the trans-O,O-[Cu(L1)]2- isomer, the nitrogen atoms form a plane and the phosphonic acid groups are in a mutually trans configuration. A structurally very similar ligand, 4-methyl-1,4,8,11-tetraazacyclotetradecane-1,8-bis(methylphosphonic acid) (H4L2), forms an analogous pentacoordinated complex, pc-[Cu(L2)]2-, at room temperature. However, the complex does not isomerise to the octahedral complex analogous to trans-O,O-[Cu(L1)]2-. Because of the high thermodynamic stability of pc-[Cu(L1)]2-, (log =25.40(4), 25 degrees of Celsius, I=0.1 mol dm-3 KNO3) and the formation of protonated species, CuII is fully complexed in acidic solution (-log [H+] ~ 3). Acid-assisted decomplexation of both of the isomers of [Cu(H2L1)] takes place only after protonation of both uncoordinated oxygen atoms of each phosphonate moiety and at least one nitrogen atom of the cycle. The exceptional kinetic inertness of both isomers is illustrated by their half-lives 1/2=19.7 min for pc-[Cu(H2L1)] and about seven months for trans-O,O-[Cu(H2L1)] for decomplexation in 5 M HClO4 at 25 degrees of Celsius. The mechanism of formation of pc-[Cu(L1)]2- is similar to those observed for other macrocyclic complexes.
ER -
KOTEK, Jan, Přemysl LUBAL, Petr HERMANN, Ivana CÍSAŘOVÁ, Ivan LUKEŠ, Tomáš GODULA, Ivona SVOBODOVÁ, Petr TÁBORSKÝ and Josef HAVEL. High Thermodynamic Stability and Extraordinary Kinetic Inertness of Cu(II) Complexes with 1,4,8,11-Tetraazacyclotetradecane-1,8-bis(methylphosphonic acid): Example of a Rare Isomerism between Kinetically Inert Penta- and Hexacoordinated Cu(II) Complexes. \textit{Chemistry - A European Journal}. Weinheim: WILEY-VCH Verlag, 2003, vol.~9, No~1, p.~233-248. ISSN~0947-6539.
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