Three heterobimetallic complexes of formula [Ca₂Cu₃(mpyba)₂(2-apyma)(H₂O)₇]·8.3H₂O (1), [Sr₂Cu₃(mpyba)₂(2-apyma)(H₂O)₈]·11.6H₂O (2) and [Sr_4.5Cu₄(mpyba)₄(ox)(H₂O)₂₀]·8.5H₂O (3) [H₄mpyba = N,N′-2,6-pyridinebis(oxamic acid), 2-apyma = 2-(6-aminopyridinyl)oxamate and ox = oxalate] have been synthesized and structurally characterized. Complexes 1 and 2 are isostructural compounds, with tricopper(II) units having mpyba and its hydrolytic product (2-apyma) as ligands. They are interlinked through strontium(II) (1) and calcium(II) (2) ions to afford neutral two-dimensional networks. Two of the copper(II) ions are five-coordinate in distorted square pyramidal (Cu3) and trigonal bipyramidal (Cu1) surroundings, whereas the other (Cu2) is six-coordinate in an elongated octahedral environment. The main difference between their structures, apart from the number of water molecules, resides in the nature of the alkaline earth cation coordinated to the oxamate fragments, Sr²⁺ (1)/Ca²⁺ (2), which exhibit eight and seven coordination, respectively. The π–π interactions and an extensive network of hydrogen bonds in 1 and 2 lead to supramolecular 3D structures. The relatively small size of their cavities, in the micropore domain, hinders the inclusion of N₂ but allows CO₂ adsorption (0.45 and 0.52 mmol g⁻¹ for 1 and 2, respectively). The structure of 3 is made up of [3,3] metallacyclophane-type motifs, having the formula [Cu₂(mpyba)₂(H₂O)₂]⁴⁻. These act as tetrakis(bidentate) ligands towards the strontium(II) ions (Sr1, Sr2 and Sr3), leading to a sheet-like polymer growing in the bc plane, which extends further along the crystallographic a axis by a bis(chelating) oxalate between the Sr1 atoms. The investigation of the magnetic properties of 1–3 in the temperature range 1.9–300 K shows the occurrence of an overall antiferromagnetic behaviour for 1 and 2 [J₁₂ = J₂₃ = −9.71(2) (1) and −10.81(5) cm⁻¹ (2), with the Hamiltonian being defined as H = −J₁₂S₁·S₂ − J₂₃S₂·S₃ + gβH[S₁ + S₂ + S₃], and a ferromagnetic coupling within the dicopper(II) metallacylophane unit of 3 [J = +1.86(1) cm⁻¹ through the Hamiltonian H = −JS₁·S₂ + gβH(S₁ + S₂)]. Simple orbital symmetry considerations (1–3) and the spin polarization mechanism (3) account for the observed magnetic properties.

Molecular magnetism has made a long journey, from the fundamental studies on through-ligand electron exchange magnetic interactions in dinuclear metal complexes with extended organic bridges to the more recent exploration of their electron spin transport and quantum coherence properties. Such a field has witnessed a renaissance of dinuclear metallacyclic systems as new experimental and theoretical models for single-molecule spintronics and quantum computing, due to the intercrossing between molecular magnetism and metallosupramolecular chemistry. The present review reports a state-of-the-art overview as well as future perspectives on the use of oxamato-based dicopper(II) metallacyclophanes as promising candidates to make multifunctional and multiresponsive, single-molecule magnetic (nano)devices for the physical implementation of quantum information processing (QIP). They incorporate molecular magnetic couplers, transformers, and wires, controlling and facilitating the spin communication, as well as molecular magnetic rectifiers, transistors, and switches, exhibiting a bistable (ON/OFF) spin behavior under external stimuli (chemical, electronic, or photonic). Special focus is placed on the extensive research work done by Professor Francesc Lloret, an outstanding chemist, excellent teacher, best friend, and colleague, in recognition of his invaluable contributions to molecular magnetism on the occasion of his 65th birthday.