Construction and property investigation of inorganic-organic hybrid materials based on metal-salens and Keggin polyoxometalates

摘要

Four hybrid materials based on the Keggin polyanions and metal-salens, namely, [Mn(salen)(CH _3OH) _2] _4[SiW _(12)O _(40)] (1), [Mn(salen)(H _2O)] _2[Mn(salen)(H _2O)][PW _(12)O _(40)] (2), [NH(CH _2CH _3) _3] _2[Mn(salen)(CH _3OH)] _2[SiW _(12)O _(40)]·2CH _3OH (3), and [(Cu(salen)) _2Cu(H _2O)] _2[SiW _(12)O _(40)] (4) (H _2salen = N,N′-ethylenebis(salicylideneimine)) have been successfully synthesized. All the compounds are characterized by X-ray single-crystal diffractions, elemental analyses, IR spectra, and thermogravimetric analyses (TGA). Crystal structure analysis reveals that compound 1 exhibits a supramolecular structure containing one Keggin-type [SiW _(12)O _(40)] ~(4-) heteropolyanion and four Mn III-salen units. In compound 2, the [PW _(12)O _(40)] ~(3-) polyoxoanions and Mn III-salen complex cations are regularly arranged along the c-axis showing an alternating packing arrangement of anionic and cationic layers. While in compound 3, the polyoxoanion [SiW _(12)O _(40)] ~(4-) is covalently decorated by two [Mn(salen)(CH _3OH)] ~+ fragments via two terminal oxygen atoms in the opposite sites, giving birth to an unusual Keggin anion supporting transition metal-salen complexes. Compound 4 represents the first example that POM supports trinuclear copper-salen complexes. Photocatalytic experiments of 1-4 indicate that they possess high catalytic activity for photodegradation of RhB under UV irradiation. In addition, the electrochemical behaviors of 1 and 2 are well investigated.