TY  - JOUR
A1  - Kozlevcar, Bojan
A1  - Golobic, Amalija
A1  - Strauch, Peter
T1  - Dynamic pseudo Jahn-Teller distortion in a compressed octahedral CuO6 complex
JF  - Polyhedron : the international journal of inorganic and organometallic chemistry
N2  - The crystal structure of cis-[Cu(C8H7O3)(2)(H2O)(2)] (115 K data) reveals bidentate vanillinate ions coordinated via methoxy and deprotonated hydroxy oxygen atoms and water molecules in a distorted octahedral CuO6 chromophore. A cis orientation of the ligands enables two non-identical O(methoxy)-Cu-O(water) coordination axes (2.354(l) + 2.163(1); 2.151(1) + 2.020(1) angstrom), and the third shortest O(hydroxy)-Cu-O(hydroxy) axis (1.919(1) + 1.914(1) angstrom). This 115 K coordination sphere differs importantly to the one obtained from the 293 K data of the same compound, where two long 0(methoxy)-Cu-O(water) axes are of the same length, and only minor changes at the short 0(hydroxy)-Cu-O(hydroxy) axis are noticed. An axial symmetry of the complex with an inverse g(1.2)(g(perpendicular to)) > g(3)(g(parallel to)) pattern is observed in the temperature range from 298 to 180 K. A further decrease of temperature reveals gradual changes from axial to rhombic symmetry (g(1) > g(2) > g(3)) that is reversible. A mean-square displacement amplitude (MDSA) analysis reveals a disorder in the Cu-O(methoxy) bonds, but not in the other metal-ligand Cu-O(hydroxy) and Cu-O(water) bonds at 293 and 115 K. The disorder is significantly weaker in the 115 K structure. The MSDA analysis and the structural-EPR agreement show vibrational disorder in two coordination axes, due to the cis conformation of the complex with two 0(methoxy)-Cu-O(water) axes.
KW  - copper
KW  - vanillin
KW  - Jahn-Teller distortion
KW  - MSDA
KW  - cis
KW  - EPR
Y1  - 2006
U6  - https://doi.org/10.1016/j.poly.2006.04.009
SN  - 0277-5387
VL  - 25
IS  - 15
SP  - 2824
EP  - 2828
PB  - Elsevier
CY  - Oxford
ER  - 
TY  - JOUR
A1  - Kozlevcar, Bojan
A1  - Odlazek, Darja
A1  - Golobic, Amalija
A1  - Pevec, Andrej
A1  - Strauch, Peter
A1  - Segedin, Primoz
T1  - Complexes with lignin model compound vanillic acid : two different carboxylate ligands in the same dinuclear tetracarboxylate complex [Cu-2(C8H7O4)(2)(O2CCH3)(2)(CH3OH)(2)]
N2  - Two copper(II) coordination compounds with vanillic acid C8H8O4 (1), namely [Cu- 2(C8H7O4)(2)(O2CCH3)(2)(CH3OH)(2)] (2) and [Cu-2(C8H7O4)(4)(H2O2)(2)] (3), were synthesized and characterized. Single crystals of 1-3 were obtained and their crystal structures determined. The structure of 2 shows dinuclear cage structure of copper acetate hydrate type, however with two different carboxylates, acetates and vanillic acid anions,. respectively. Both bridging anions are in pairs in trans orientation. Methanol molecules are apically coordinated (Cu-O7 2.160(2) angstrom), fulfilling square-pyramidal coordination sphere around both copper ions. The compound 2 decomposes outside mother-liquid (yielding [Cu-2(C8H7O4)(2)(O2CCH3)(2)(H2O)(2)] (2a)) with the removal of methanol, but without significant change of the dicopper tetracarboxylate cage structure, as noticed by mu(eff) 1.48 BM for 2a. Similar was found also in the X-band EPR spectra with three signals H-z1, H-perpendicular to 2 and H-z2 in the region from 0 to 600 mT. The structure of free vanillic acid 1 is composed of dimeric units of two molecules, connected by two parallel hydrogen bonds between carboxylate group of each other (O1-H(...)O2 2.642(3) angstrom), while the structure of 3 is of [Cu-2(O2CCH3)(4)(H2O)(2)] type. Interestingly, an additional signal in the EPR spectra of 3 is found at 80 mT (H- perpendicular to 1) at 298 and at 116 K, next to three signals H-z1, H-perpendicular to 2 and H-z2.
Y1  - 2006
UR  - http://www.sciencedirect.com/science/journal/02775387
U6  - https://doi.org/10.1016/j.poly.2005.08.031
SN  - 0277-5387
ER  -