Ionothermal syntheses, crystal structures and properties of three-dimensional rare earth metal-organic frameworks with 1,4-naphthalenedicarboxylic acid

Twelve isostructural rare earth metal-organic frameworks, namely, [Hmim][RE2Cl(1,4-NDC)(3)] (RE = La (1), Ce (2), Pr (3), Nd (4), Sm (5), Eu (6), Gd (7), Tb (8), Dy (9), Ho (10), Er (11), Y (12), Hmim = 1-hexyl-3-methylimidazolium, 1,4-NDCH2 = 1,4-naphthalenedicarboxylic acid), have been ionothermally synthesized and structurally characterized. The structures feature three-dimensionally anionic frameworks of [RE2Cl(1,4-NDC)(3)](n)(n-) with channels in which the Hmim(+) cations are located. The current results are the first ionothermal synthesis of rare earth metal-organic frameworks based on 1,4-NDCH2 which possess a previously unknown (4,7)-connected 3-nodal network with the Schlafli symbol of (3(2).4(2).5(2))-(3(2).4(9).5(2).6())(8)2(4(3).6(3))(2). Luminescent and magnetic properties of some of the title compounds have been studied. Thermogravimetric analyses indicated that all these compounds were thermally stable up to ca. 250 degrees C.