The unique properties of polynuclear cluster-aggregates have long been staples in the molecular magnetism community. The initial success observed in high nuclearity transition metal complexes for generating exciting magnetic behaviors however, has not yet fully been extended to lanthanide-based clusters. This is in part due to the challenges related to promoting non-negligible magnetic interactions between two lanthanide ions. One promising route towards improving magnetic communication involves the incorporation of radical species. Here, we describe the preparation of tetranuclear [Dy 4 (μ 3-OH) 4 ] 8+ core structures that allow the incorporation of air-stable radical ligands. This combination paves the way for magnetically relevant lanthanide cubane cluster-aggregates capable of strong magnetic communication and improved spin-reversal barriers. Moreover, we show that the addition of electron donating groups lead to non-negligible antiferromagnetic coupling between the Dy III centers and the BPyTz •− ligands, while also simultaneously improving the slow magnetic relaxation dynamics in the absence of an applied field.

The first example of unique coordination induced intramolecular pancake bonding was achieved through the reduction of two bis(pyrazolyl)-tetrazine ligands.

A planar tetradentate 3,6-bis(2-pyrimidyl)-1,2,4,5-tetrazine (BpymTz) templating chelate affords the formation of an unprecedented BpymTz˙ radical anion bridged {Ni} complex. Detailed magnetic measurements performed on the isolated air stable [Ni(BpymTz˙)Cl(DMF)]Cl·0.5(HO) compound reveal strong ferromagnetic Ni-BpymTz˙ interactions with a coupling constant of J = 98.84 cm.

The reaction of aqueous solutions of EuIII, TbIII, and GdIII ions with Na2Hpcpa [H3pcpa = N-(4-carboxyphenyl)­oxamic acid] afforded three new isostructural oxamate-containing lanthanide­(III) coordination polymers of general formula {LnIII 2(Hpcpa)3(H2O)5·H2O} n [Ln = Eu (1),Tb (2), and Gd­(3)]. Their structure is made up of neutral zigzag chains running parallel to the [101] direction where double syn–syn carboxylate­(oxamate)-bridged dilanthanide­(III) pairs (Ln1 and Ln2) are linked by three Hpcpa2– ligands, one of them with the μ–κ2 O,O′:κO″ coordination mode and the other two with the μ3-κ2 O,O′:κO″:κO′′′. Additionally, two of those chains are interlinked through hydrogen bonding and π–π type interactions, resulting in a porous structure with channels where water molecules are hosted. The emission properties of 1 and 2 are evaluated as a function of the temperature, exhibiting an emission in red and green, respectively. The external quantum yield for 2 is approximately 7 times that obtained for 1, indicating that the oxamate ligand is a better sensitizer for TbIII ions. The temperature dependence of the dc magnetic properties of 1–3 reveals a different magnetic behavior depending on the nature of the LnIII ion. A continuous decrease of χM T occurs for 1 upon cooling, and finally χM T tends to vanish, as expected for the thermal depopulation of the six magnetic 7F J excited states (J = 1–6) of the EuIII ion with a nonmagnetic 7F0 ground state. χM T for 2 decreases sharply with decreasing the temperature due to the depopulation of the splitted m J levels of the 7F7 ground state of the magnetically anisotropic TbIII ion. A very weak antiferromagnetic interaction between the magnetically isotropic GdIII ions across the double carboxylate­(oxamate) bridge is responsible for the small decrease of χM T at low temperatures for 3. The dynamic (ac) magnetic properties of 2 and 3 reveal a slow magnetic relaxation with very incipient frequency-dependent χM″ signals below 6.0 K (2) and frequency-dependent χM″ peaks below 10.0 K (3) under nonzero applied dc magnetic fields, being thus new examples of field-induced single molecule magnets (SMMs).

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