engleski

Magneto-Structural Characterization of Oxalamide Dihalo-Bridged Copper Dimers : Intra- and Interdimer Interactions Studied by Single Crystal ESR Spectroscopy

The detailed single crystal electron spin resonance (ESR) analysis of oxalamide complexes with halogen-bridged copper dimers, supported by X-ray, magnetic susceptibility and powder ESR studies, is reported. Four complexes with two different ligands were synthesized: [CuLA(μ-X)]2 and [CuLV(μ-X)]2, where LA = N-(L-alanine methyl ester)-N’-((2-pyridine-2-yl)methyl)oxalamide and LV=N-(L-valine methyl ester)-N’-((2-pyridine- 2-yl)methyl)oxalamide, while X=Cl or Br. X-ray analysis shows that geometry at each copper(II) ion is square pyramidal while two pyramids share one base-to-apex edge with parallel basal planes. The complexes are linked by hydrogen bonds into infinite chains and further into a 3D network. Susceptibility measurements show that coppers in dimers are weakly antiferromagnetically coupled (|J| = 1 − 2 cm−1). From powder ESR, g-values and dx2−y2 orbital as the ground state of unpaired electron are determined. The complexes show unusual anisotropic splitting and merging of ESR lines when their single crystals rotate in magnetic field. The observation of this partially resolved intradimer dipolar splitting enabled estimation of weak interdimer exchange interaction parameter |J0| = 0.001 cm−1.

copper ; dipolar splitting ; EPR spectroscopy ; magnetic properties ; single crystal

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