The preparation and properties of two new series of rare-earth organic frameworks, [Ln2(cam)2(NO3)2(MeOH)4]n (Ln = Gd (1·Gd), Tb (1·Tb), Dy (1·Dy), Ho (1·Ho) and Er (1·Er)) and [Ln(D-cam)(O2CH)]n (Ln = Tb (2·Tb), Dy (2·Dy), Ho (2·Ho) and Er (2·Er); D-H2cam = (+) D-camphoric acid) under solvothermal conditions is described. Single-crystal X-ray diffraction analyses revealed that the 1·Gd–1·Er compounds are isostructural and crystallize in the monoclinic space group P21/n with the chiral D-camphorate ligand racemized, while the 2·Tb–2·Er compounds are isostructural and crystallize as orthorhombic with the chiral space group P21212121. The structures of the 1·Gd–1·Er compounds consist of a dimeric sub-building unit (SUB) of [Ln2(O2CR)4(NO3)2(MeOH)4], which is covalently-linked by cam2− to a 2D grid layer and the layer is extended into a 3D supramolecular network by hydrogen bonding. Compounds 2·Tb–2·Er feature a three-dimensional homochiral framework involving one-dimensional lanthanide–carboxylate chains that are aligned parallel to the [100] direction. Direct current (dc) magnetic susceptibility data were collected for these two series of compounds. The findings indicate that compound 1·Gd shows a Gd⋯Gd antiferromagnetic interaction through carboxylate bridges, with a coupling constant of J = −0.034 cm−1. Compounds 1·Tb–1·Er, and 2·Dy–2·Er are dominated by the depopulation of Stark levels, while 2·Tb exhibits ferromagnetic interaction between the Tb3+ ions. Interestingly, compounds 1·Dy and 2·Dy exhibit frequency-dependent out-of-phase signals in alternating current (ac) magnetic susceptibility measurements indicating their slow magnetic relaxation characteristics.
You have access to this article
Please wait while we load your content...
Something went wrong. Try again?