Modulating Magnetic and Photoluminescence Properties in 2‐Aminonicotinate‐Based Bifunctional Coordination Polymers by Merging 3d Metal Ions

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Abstract
Herein, the synthesis and study of bifunctional coordination polymers (CPs) with both magnetic and photoluminescence properties, derived from a heterometallic environment, are reported. As a starting point, three isostructural monometallic CPs with the formula [M(μ‐2ani)2]n (MII=Mn (1Mn), Co (3Co) and Ni (4Ni); 2ani=2‐aminonicotinate), crystallise as chiral 2D‐layered structures stacked by means of supramolecular interactions. These compounds show high thermal stability in the solid state (above 350 °C), despite which, in aqueous solution, compound 1Mn is shown to partially transform into a novel 1D chain CP with the formula [Mn(2ani)2(μ‐H2O)2]n (2Mn). A study of the direct current (dc) magnetic properties of 1Mn, 3Co and 4Ni reveals a spin‐canted structure derived from antisymmetric antiferromagnetic weak exchanges along the chiral network (as confirmed by DFT calculations) and magnetic anisotropy of the ions, in such a way that long‐range ordering is observed with variable magnitude for the spin carriers. Moreover, compounds 3Co and 4Ni show no frequency‐dependent alternating current (ac) susceptibility curves under zero dc field; this is characteristic behaviour of a glassy state that may be partially supressed for 3Co by applying an external dc field. To overcome long‐range magnetic ordering, CoII ions are diluted in a diamagnetic ZnII‐based matrix, which enables single‐molecule magnet behaviour. Interestingly, this strategy allows a bifunctional CoxZn1−x2ani material, which is imbued with a strong photoluminescent emitting capacity, as characterised by an intense blue light followed by a green afterglow, to be obtained.
Funding Information
  • Euskal Herriko Unibertsitatea (GIU 17/13)
  • Eusko Jaurlaritza (IT1005-16, IT1310-19)
  • Ministerio de Ciencia, Innovación y Universidades (PGC2018-102052-A-C22, PGC2018-102052-B-C21)

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