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XAFS investigations of copper(II) complexes with tetradentate Schiff base ligands
Author(s) -
Gaur Abhijeet,
Shrivastava B. D.,
Srivastava K.,
Prasad J.,
Singh Sandeep K.
Publication year - 2012
Publication title -
x‐ray spectrometry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.447
H-Index - 45
eISSN - 1097-4539
pISSN - 0049-8246
DOI - 10.1002/xrs.2418
Subject(s) - copper , extended x ray absorption fine structure , crystallography , chemistry , schiff base , coordination geometry , crystal structure , x ray absorption fine structure , coordination sphere , absorption spectroscopy , molecule , spectroscopy , hydrogen bond , physics , organic chemistry , quantum mechanics
X‐ray absorption fine structure spectra have been investigated at the K‐edge of copper in copper(II) salen/salophen complexes: [Cu(salen)] (1), [Cu(salen)CuCl 2 ].H 2 O (2), [Cu(salophen)] (3) and [Cu(salophen) CuCl 2 ].H 2 O (4), where salen 2− = N , N ′‐ethylenebis (salicylidenaminato); salophen 2− = o ‐phenylenediaminebis(salicylidenaminato). Complexes 1 and 3 are supposed to have one type of copper centers (called (Cu1)) and complexes 2 and 4 two types of copper centers (called (Cu1) and (Cu2)) having different coordination environments and geometries. A theoretical model has been generated using the available crystallographic data of complex 1 and it has been used for analysis of the extended X‐ray absorption fine structure (EXAFS) data of the four complexes to obtain the structural parameters for (Cu1) center. For this center, the obtained Cu–Cu distance (3.2 Å) verifies the binuclear nature of all the complexes. For determining the coordination geometry around (Cu2) center in 2 and 4, a theoretical model has been generated using the crystal structure of a Cu(II) complex, [Cu(C 16 H 12 N 2 O 2 Cl 2 )]. This theoretical model has been fitted to the EXAFS data of 2 and 4 to obtain the structural parameters for (Cu2) center. The present analysis shows that (Cu1) center has square pyramidal geometry involving 2N and 3O donor atoms, whereas (Cu2) center has distorted tetrahedral geometry with 2O and 2Cl donor atoms. The values of the chemical shifts and presence of typical Cu(II) X‐ray absorption near‐edge spectroscopy features suggest that copper is in the +2 oxidation state in all these complexes. The intensity of ls → 3d pre‐edge feature has been used to investigate the geometry and binuclear nature of the complexes. Copyright © 2012 John Wiley & Sons, Ltd.