Heteroatom-Modulated Assembly of Hexalanthanoid-Containing Polyoxometalate-Based Coordination Networks.

Two series of lanthanoid (Ln)-containing polyoxometalates (POMs) {[Ln 6 (ampH) 4 (H 2 O) 24- n (ampH 2 ) n (PW 11 O 39 ) 2 ]·21H 2 O (Ln = Tb, n = 0 ( 1 ), Ln = Er, n = 1 ( 2 )) and K 2 [Ln 6 (ampH) 4 (H 2 O) 22 (SiW 11 O 39 ) 2 ]·23H 2 O (Ln = Tb ( 3 ), Er ( 4 )) (ampH 2 = (aminomethyl) phosphonic acid)} have been synthesized with tri-lacunary Keggin-type POMs containing different types of heteroatoms. Compounds 1 and 2 display neutral organic-inorganic hybrid POM molecules containing {Ln 6 (ampH) 4 } ({Ln 6 }) cores sandwiched by two {PW 11 O 39 } units. By changing the heteroatoms from P V to Si IV , the extended 2D networks of 3 and 4 were successfully isolated where the adjacent {Ln 6 } clusters were connected by {SiW 11 O 39 } moieties. Luminescence performances and magnetic properties of 1-4 have been systematically surveyed. The solid-state fluorescence spectra of 1-4 display characteristic emissions of Ln components resulting from the 4f-4f transitions, and energy transfer from the POM segments to Ln 3+ centers in 1 and 3 has been observed based on the lifetime decay behaviors. Furthermore, all compounds can be utilized as electrocatalysts toward reduction of nitrite with high stability.