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Structure, Magnetic Properties, Polarized Neutron Diffraction, and Theoretical Study of a Copper(II) Cubane
Author(s) -
Aronica Christophe,
Chumakov Yurii,
Jeanneau Erwann,
Luneau Dominique,
Neugebauer Petr,
Barra AnneLaure,
Gillon Béatrice,
Goujon Antoine,
Cousson Alain,
Tercero Javier,
Ruiz Eliseo
Publication year - 2008
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.200800557
Subject(s) - cubane , antiferromagnetism , neutron diffraction , electron paramagnetic resonance , crystallography , ground state , ferromagnetism , chemistry , magnetization , magnetic structure , condensed matter physics , ion , copper , single crystal , crystal structure , magnetic field , atomic physics , physics , nuclear magnetic resonance , organic chemistry , quantum mechanics
The paper reports the synthesis, X‐ray and neutron diffraction crystal structures, magnetic properties, high field–high frequency EPR (HF‐EPR), spin density and theoretical description of the tetranuclear Cu II complex [Cu 4 L 4 ] with cubane‐like structure (LH 2 =1,1,1‐trifluoro‐7‐hydroxy‐4‐methyl‐5‐aza‐hept‐3‐en‐2‐one). The simulation of the magnetic behavior gives a predominant ferromagnetic interaction J 1 (+30.5 cm −1 ) and a weak antiferromagnetic interaction J 2 (−5.5 cm −1 ), which correspond to short and long Cu–Cu distances, respectively, as evidence from the crystal structure (ℋ=− ${{{}\mathrel{\mathop{\sum{}}\limits_{i\char62 j}}{}}}$ 2 J ij Ŝ i Ŝ j ). It is in agreement with DFT calculations and with the saturation magnetization value of an S=2 ground spin state. HF‐EPR measurements at low temperatures (5 to 30 K) provide evidence for a negative axial zero‐field splitting parameter D (−0.25±0.01 cm −1 ) plus a small rhombic term E (0.025±0.001 cm −1 , E/D = 0.1). The experimental spin distribution from polarized neutron diffraction is mainly located in the basal plane of the Cu II ion with a distortion of yz ‐type for one Cu II ion. Delocalization on the ligand (L) is observed but to a smaller extent than expected from DFT calculations.