Lanthanide sulfate frameworks: synthesis, structure, and optical properties

Abstract

Layered lanthanide sulfate compounds with three different structures have been prepared and characterized. The compounds [C(10)H(10)N(2)] [La(SO(4))(2)]center dot 2H(2)O (I), [C(10)H(10)N(2)] [La(SO(4))(2)(H(2)O)(2)](2) (Ha), [C(10)H(10)N(2)][Pr(SO(4))(2)(H(2)O)(2)](2) (IIb), [C(10)H(10)N(2)][Nd(2)(SO(4))(4)(H(2)O)(2)](2) (IIIa), [C(10)H(10)N(2)][Sm(2)(SO(4))(4)(H(2)O)(2)](2) (IIIb), and [C(10)H(10)N(2)][Eu(2)(SO(4))(4)(H(2)O)(2)] 2 (IIIC) have anionic lanthanide sulfate layers separated by protonated bipyridine molecules. The layers are formed by the connectivity between the lanthanide polyhedra and sulfate tetrahedra. The formation of a two-dimensional La-O-La layer (la), Pr-O-Pr chains (IIb), and a tetramer cluster (IIIa) is noteworthy. The compounds exhibit honeycomb (I), square (IIa, IIb), and honeycomb (IIIa-IIIc) net arrangements, when the connectivity between the lanthanide ions is considered. Optical studies indicate the observation of characteristic metal-centered emission at room temperature. The Nd compound (IIIa) exhibits a two-photon upconversion behavior.