Quantum magnetism of spin qubits in S = 1/2 Cu(II) systems in discrete complexes, chains, and metal-organic frameworks

In the last decade, S = 1/2 systems of Cu(II) complexes and Cu(II) ions in the solid state have been found to exhibit slow magnetic relaxations. The mechanism driving this magnetic behavior is different from that of high spin single-molecule magnets and that of bulk/nanoparticle magnets. This behavior is related to spin qubits and is considered to be a new type of quantum magnetism. This review focuses on the magnetic relaxation (tau), spin-lattice relaxation (T-1), and spin-spin relaxation (T-2 or T-m) of isolated Cu(II) complexes, Cu(II) 1D-chains, and Cu(II)-doped metal-organic frameworks. Although these properties have been well studied in isolated Cu(II) systems, studies on systems that exhibit magnetic interactions are still elusive. With the aim of progressing toward the entanglement of spin states and quantum computing using spin qubits, a greater number of studies on molecule-based spin qubits that exhibit magnetic interactions will be conducted and will be of increasing importance from now on.