Eight lanthanide compounds [Ln(H2O)9](m-BDTH)3·9(H2O) where Ln = Pr (1), Nd (2) and Sm (3) and [Ln(H2O)8](m-BDTH)3·9(H2O) where Ln = Eu (4), Gd (5), Tb (6), Dy (7) and Tm (8) have been synthesized at room temperature. In these compounds a new class of pillared layer framework is exemplified in which 2-D hydrophobic organic layers of π-stacked and hydrogen-bonded (m-BDTH)− are separated by hydrophilic [Ln(H2O)n]3+ cationic pillars. The thermal stability, reversible solvent uptake, photoluminescence properties and magnetic studies of these compounds were carried out. In addition, theoretical investigations were carried out in compound 1 for the existence of a near-planar pentamer water cluster.
