A novel 3d-4f two dimensional molecular assembly: synthesis, structure, magnetic, thermal and Hirshfeld surface studies

A novel 3d-4f framework has been synthesized with the formula, [Cu₂Gd₂(L)₄(HL)₂(H₂O)₄]_n (where, H₂L = 3-hydroxypicolinic acid) (1). Compound 1 was characterized by single crystal X-ray diffraction. The structure analysis reveals that the compound possesses 2D network structure. In the structure Gd ions are in square antiprism geometry whereas the copper ions adopt distorted octahedral geometry. The Gd ions are forming a Gd₂-dimeric unit (Gd1-Gd1) bridging by the carboxylate oxygen atoms. These units are further bonded by the octahedral copper centers alternately forming a one dimensional zig-zag chain motif. A better overview of the crystal structure of 1 shows that dimeric unit formulated as {Gd₂} forms a 1D chain which are linked through the Cu(L) unit and the monoprotonated ligand forming a two dimensional network and this propagates along the crystallographic bc-plane. Compound 1 was subjected for variable temperature magnetic susceptibility measurement. Magnetic study reveals that compound 1 possesses weak ferromagnetic interaction basically due to 3d-4f exchange interaction. In-situ variable temperature PXRD measurement was also carried. PXRD patterns clearly reveal the formation of bimetallic mixed-oxide at higher temperature with particular stoichiometry. Hirshfeld surface (HS) analysis was done to explore the intermolecular contacts present within the molecular crystal.