Lanthanide Anionic Metal-Organic Frameworks Containing Semirigid Tetracarboxylate Ligands: Structure, Photoluminescence, and Magnetism

A series of lanthanide anionic metal-organic frameworks, [NH2(CH3)(2)][Ln(MDIP)(H2O)] (Ln = Pr (1), Nd (2), Sm (3), Eu (4), Gd (5), Tb (6), Dy (7); H4MDIP = methylenediisophthalic acid) and [NH2(CH3)(2)][Ln(MDIP)(H2O)]center dot 0.5NH(CH3)(2) (Ln = Er (8), Tm (9), Yb (10)), have been synthesized and characterized. In compounds 1-7, the adjacent Ln(3+) ions are intraconnected to form infinite metal-carboxylate oxygen chain-shaped building blocks along the [001] direction. In compounds 8-10, MDIP ligands bridge dinuclear lanthanide centers to form three-dimensional frameworks which can be rationalized as a (4,8)-connected topological net with the Schlafli symbol of (4(10).6(14).8(4))(4(5).6)(2). Dimethylamine cations occupy the vacancy of all the compounds as counterions. The photophysical properties of trivalent Pr, Nd, Sm, Eu, Tb, Dy, Er, Yb compounds at temperature were investigated and showed that MDIP is an efficient sensitizer of the luminescence of both the Tb3+ ion emitting visible light and the Yb3+. ion emitting in the near-IR Antiferromagnetic interactions between Gd3+ ions were observed from magnetic susceptibility data.