Magnetic Properties and Photoluminescence of Lanthanide Coordination Polymers Constructed with Conformation-Flexible Cyclohexane-Tetracarboxylate Ligands

To investigate the effects on the physical properties of complexes with different conformations of flexible ligands, four lanthanide (Ln) coordination polymers with flexible ligand cyclohexane-1e,2a,4a,5e-tetracarboxylic acid (H₄L^I), [Ln­(HL^II)­(H₂O)₂]·1.5H₂O (Ln = Dy, 1; Tb, 2) and [Ln₂(H₂L^IV)­(L^IV)­(H₂O)₄]·1.5H₂O (Ln = Dy, 3; Tb, 4), have been synthesized and characterized. Complexes 1 and 2 are 2D layers composed of L^II ligands and [Ln₂O₂] dinuclear units whereas complexes 3 and 4 are 3D coordination frameworks constructed with L^IV ligands and two kinds of dinuclear units, [Ln₂O₂] and [Ln₂(COO)₂]. Notably, the conformations of ligands in two structures, which were different and changed from the original L^I conformation to L^II (e,a,e,e) and L^IV (e,e,e,e) conformations, impact the construction of different structures and the magnetic properties. Complex 1 shows antiferromagnetic interactions whereas complex 3 exhibits weak ferromagnetic interactions and slow magnetic relaxation properties. Additionally, the photoluminescence of complexes 2 and 4 have been investigated.