Host-Guest-Induced Environment Tuning of 3d Ions in a Polyoxopalladate Matrix

A series of unprecedented supramolecular associates of phenylarsonate-capped {M^II Pd^II ₁₂ O₈ }-type (M=Co, Ni and Zn) polyoxopalladates with α-cyclodextrins (α-CD) was obtained and characterized in the solid state (single-crystal X-ray diffraction (XRD), FT-IR spectroscopy, elemental and thermogravimetric (TGA) analyses), in aqueous solution (¹ H and ¹³ C NMR) and in the gas phase (ESI-MS). The non-covalent host-guest interactions between the organopolyoxoanions and α-CD rings alter the O₈ coordination environment of a 3d transition metal ion (M^II ) situated at the center of a cuboid polyoxododecapalladate shell. This synthetically controlled "chemical pressure" effectively induces axial distortion of the otherwise cubic polyoxopalladate environment between two trans-positioned α-CD moieties. Its effect on the magnetic properties and the electronic structure of the Co^II derivative was assessed in a combined SQUID magnetometry, EPR, X-ray magnetic circular/linear dichroism (XMCD/XMLD), and X-ray absorption near-edge structure (XANES) spectroscopy study.