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−).