New Series of Layered Vanadyl Phosphates with Varied Polyamine Templates

Abstract

Four two-dimensional vanadyl phosphates, (H 3 dien)[(VOPO 4 ) 2 (OH)]·H 2 O (dien = diethylenetriamine) ( 1 ), (H 2 dach) 1.5 [(VOPO 4 ) 2 (OH)]·2H 2 O (dach = 1,4-diaminocyclohexane) ( 2 ), (H 2 tmdpp)[V 3 O 4 (OH)(PO 4 ) 2 ]·3H 2 O (tmdpp = 4,4‘-trimethylenedipiperidine) ( 3 ), and (H 2 tmdpp)(H 1.5 tmdpp)K 0.5 [V 5 O 7 (H 2 O) 2 (PO 4 ) 4 ]·H 2 O ( 4 ), with clearly distinct but orderly increasing layer separations from 7.75 to 18.07 Å, have been prepared via hydrothermal routes and characterized by single-crystal X-ray diffraction, thermogravimetric analysis, and magnetic susceptibility or ion-exchange studies. The series possesses three unique layer topologies, but all contain V IV O 5 square pyramid, PO 4 tetrahedron, discrete dimers of V−O polyhedra, and 3-, 4-, 5-, and 8-membered rings. Structures 1 and 2 are V IV species, having the same layer topology but different amine cations. Compounds 3 and 4 are V IV /V V mixed valent, holding the same amine templates in varied inclined angles. Being similar to 1 and 2, the layer of 3 contains extra vanadate groups. In contrast, the layers in 4 are distinct and contain V V O 6 and V IV O 6 octahedra besides V IV O 5 square pyramid. It exhibits an interlayer d -spacing of 18.07 Å, the largest propped up by noncovalent intermediates between VPO layers. With an extremely low density of 1.71 g·cm - 3, compound 4 also demonstrates the lightest layered material ever prepared in the V/P/O system. Structural relationship, template effect, factors controlling layer gaps, ion exchange, thermal stability, and magnetic properties are discussed.