NMR-Relaxometric Investigation of Mn(II)-Doped Polyoxometalates in Aqueous Solutions.

Solution behavior of K; 5 [(Mn(H 2 O))PW 11 O 39 ]·7H 2 O ( 1 ), Na 3.66 (NH 4 ) 4.74 H 3.1 [(Mn II (H 2 O)) 2.75 (WO(H 2 O)) 0.25 (α-B-SbW 9 O 33 ) 2 ]·27H 2 O ( 2 ), and Na 4.6 H 3.4 [(Mn II (H 2 O) 3 ) 2 (WO 2 ) 2 (β-B-TeW 9 O 33 ) 2 ]·19H 2 O ( 3 ) was studied with NMR-relaxometry and HPLC-ICP-AES (High Performance Liquid Chromatography coupled with Inductively Coupled Plasma Atomic Emission Spectroscopy). According to the data, the [(Mn(H 2 O))PW 11 O 39 ] 5- Keggin-type anion is the most stable in water among the tested complexes, even in the presence of ethylenediaminetetraacetic acid (EDTA) or diethylenetriaminepentaacetic acid (DTPA). Aqueous solutions of 2 and 3 anions are less stable and contain other species resulting from dissociation of Mn 2+ . Quantum chemical calculations show the change in Mn 2+ electronic state between [Mn(H 2 O) 6 ] 2+ and [(Mn(H 2 O))PW 11 O 39 ] 5- .