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Extended X‐ray Absorption Fine Structure Study of Copper( I ) and Copper( II ) Complexes in Atom Transfer Radical Polymerization
Author(s) -
Pintauer Tomislav,
Reinöhl Ulrich,
Feth Martin,
Bertagnolli Helmut,
Matyjaszewski Krzysztof
Publication year - 2003
Publication title -
european journal of inorganic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.667
H-Index - 136
eISSN - 1099-0682
pISSN - 1434-1948
DOI - 10.1002/ejic.200200503
Subject(s) - chemistry , cyclam , copper , extended x ray absorption fine structure , tetracoordinate , crystallography , square pyramidal molecular geometry , x ray absorption fine structure , ligand (biochemistry) , amine gas treating , inorganic chemistry , absorption spectroscopy , crystal structure , metal , spectroscopy , organic chemistry , biochemistry , physics , computer graphics (images) , receptor , quantum mechanics , computer science , planar
Extended X‐ray Absorption Fine Structure (EXAFS) spectroscopy has been used to investigate structural features of Cu I Br and Cu II Br 2 complexes with dNbpy, PMDETA, Me 6 TREN, tNtpy, and Me 4 CYCLAM in various solvents {dNbpy = 4,4′‐bis(5‐nonyl)‐2,2′‐bipyridine, PMDETA = N , N , N′ , N′′ , N′′ ‐pentamethyldiethylenetriamine, Me 6 TREN = tris[2‐(dimethylamino)ethyl]amine, tNtpy = 4,4′,4′′‐tris(5‐nonyl)‐2,2′:6′,2′′‐terpyridine, Me 4 CYCLAM = 1,4,8,11‐tetramethyl‐1,4,8,11‐tetraazacyclotetradecane}. The structures of the Cu I and Cu II complexes were found to depend on the solvent polarity and the number of nitrogen atoms in the ligand. Generally, in non‐polar media and with monomers typically used in ATRP, Cu I complexes preferred a tetracoordinate geometry, and were either ionic as observed in [Cu I (dNbpy) 2 ] + [Cu I Br 2 ] − (Cu I −N AV = 2.00 Å, Cu I −Br AV = 2.25 Å) and [Cu I (Me 4 CYCLAM)] + [Cu I Br 2 ] − (Cu I −N AV = 2.06 Å, Cu I −Br AV = 2.23 Å), or neutral as in [Cu I (PMDETA)Br] (Cu I −N AV = 2.12 Å, Cu I −Br AV = 2.33 Å), and [Cu I (tNtpy)Br] (Cu I −N AV = 2.03 Å, Cu I −Br AV = 2.29 Å). The EXAFS analysis of Cu II Br 2 complexes indicated a preference for a coordination number of five, such as in [Cu II (dNbpy) 2 Br] + [Br] − (Cu II −N AV = 2.03 Å, Cu II −Br AV = 2.43 Å), [Cu II (PMDETA)Br 2 ] (Cu II −N AV = 2.03 Å, Cu II −Br 1,AV = 2.44 Å, Cu II −Br 2,AV = 2.64 Å) and [Cu II (Me 6 TREN)Br] + [Br] − (Cu II −N AV = 2.09 Å, Cu II ‐Br AV = 2.39 Å), with the exception of the neutral tetracoordinate [Cu II (dNbpy)Br 2 ] (Cu II −N AV = 2.02 Å, Cu II −Br AV = 2.36 Å), which has been observed in non‐polar media. Additionally, polar media were found to favor bromide dissociation in [Cu II (Me 6 TREN)Br] + [Br] − and [Cu II (PMDETA)Br 2 ], as indicated by a decrease in the Br and Cu coordination numbers at the Cu‐ and Br‐ K ‐edges, respectively. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)